liu.seSearch for publications in DiVA
Change search
Refine search result
123456 1 - 50 of 269
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the 'Create feeds' function.
  • 1.
    Carvalho Bittencourt, André
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Saarinen, Kari
    ABB Corporate Research, Västerås, Sweden.
    Sander Tavallaey, Shiva
    ABB Corporate Research, Västerås, Sweden.
    Gunnarsson, Svante
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Norrlöf, Mikael
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology. ABB Robotics, Västerås, Sweden.
    A data-driven approach to diagnostics of repetitive processes in the distribution domain: Applications to gearbox diagnosticsin industrial robots and rotating machines2014In: Mechatronics (Oxford), ISSN 0957-4158, Vol. 24, no 8, 1032-1041 p.Article in journal (Refereed)
    Abstract [en]

    This paper presents a data-driven approach to diagnostics of systems that operate in a repetitive manner. Considering that data batches collected from a repetitive operation will be similar unless in the presence of an abnormality, a condition change is inferred by comparing the monitored data against an available nominal batch. The method proposed considers the comparison of data in the distribution domain, which reveals information of the data amplitude. This is achieved with the use of kernel density estimates and the Kullback–Leibler distance. To decrease sensitivity to disturbances while increasing sensitivity to faults, the use of a weighting vector is suggested which is chosen based on a labeled dataset. The framework is simple to implement and can be used without process interruption, in a batch manner. The approach is demonstrated with successful experimental and simulation applications to wear diagnostics in an industrial robot gearbox and for diagnostics of gear faults in a rotating machine.

  • 2.
    Carvalho Bittencourt, André
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Saarinen, Kari
    ABB Corporate Research.
    Sander Tavallaey, Shiva
    ABB Corporate Research.
    Gunnarsson, Svante
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    A Data-Driven Method for Monitoring of Repetitive Systems: Applications to Robust Wear Monitoring of a Robot Joint2013Report (Other academic)
    Abstract [en]

    This paper presents a method for monitoring of systems that operate in a repetitive manner. Considering that data batches collected from a repetitive operation will be similar unless in the presence of an abnormality, a condition change is inferred by comparing the monitored data against a nominal batch. The method proposed considers the comparison of data in the distribution domain, which reveals information of the data amplitude. This is achieved with the use of kernel density estimates and the Kullback-Leibler distance. To decrease sensitivity to unknown disturbances while increasing sensitivity to faults, the use of a weighting vector is suggested which is chosen based on a labeled dataset. The framework is simple to implement and can be used without process interruption, in a batch manner. The method was developed with interests in industrial robotics where a repetitive behavior is commonly found. The problem of wear monitoring in a robot joint is studied based on data collected from a test-cycle. Real data from accelerated wear tests and simulations are considered. Promising results are achieved where the method output shows a clear response to the wear increases.

  • 3.
    Carvalho Bittencourt, André
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Saarinen, Kari
    ABB Corporate Research Västerås, Sweden.
    Sander-Tavallaey, Shiva
    ABB Corporate Research Västerås, Sweden.
    A Data-driven Method for Monitoring Systems that Operate Repetitively: Applications to Robust Wear Monitoring inan Industrial Robot Joint2011Manuscript (preprint) (Other academic)
    Abstract [en]

    This paper presents a method for condition monitoring of systems that operate in a repetitive manner. A data driven method is proposed that considers changes in the distribution of data samples obtained from multiple executions of one or several tasks. This is made possible with the use of kernel density estimators and the Kullback-Leibler distance measure between distributions. To increase robustness to unknown disturbances and sensitivity to faults, the use of a weighting function is suggested which can considerably improve detection performance. The method is very simple to implement, it does not require knowledge about the monitored system and can be used without process interruption, in a batch manner. The method is illustrated with applications to robust wear monitoring in a robot joint. Interesting properties of the application are presented through a real case study and simulations. The achieved results show that robust wear monitoring in industrial robot joints is made possible with the proposed method.

  • 4.
    Carvalho Bittencourt, André
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Saarinen, Kari
    ABB Corporate Research Västerås, Sweden.
    Sander-Tavallaey, Shiva
    ABB Corporate Research Västerås, Sweden.
    A Data-Driven Method for Monitoring Systems that Operate Repetitively: Applications to Robust Wear Monitoring inan Industrial Robot Joint2011Report (Other academic)
    Abstract [en]

    This paper presents a method for condition monitoring of systems that operate in a repetitive manner. A data driven method is proposed that considers changes in the distribution of data samples obtained from multiple executions of one or several tasks. This is made possible with the use of kernel density estimators and the Kullback-Leibler distance measure between distributions. To increase robustness to unknown disturbances and sensitivity to faults, the use of a weighting function is suggested which can considerably improve detection performance. The method is very simple to implement, it does not require knowledge about the monitored system and can be used without process interruption, in a batch manner. The method is illustrated with applications to robust wear monitoring in a robot joint. Interesting properties of the application are presented through a real case study and simulations. The achieved results show that robust wear monitoring in industrial robot joints is made possible with the proposed method.

  • 5.
    Ribeiro, Luis
    et al.
    Faculty of Sciences and Technology, New University of Lisbon, Portugal.
    Barata, José
    Faculty of Sciences and Technology, New University of Lisbon, Portugal.
    Silvério, Nelson
    Faculty of Sciences and Technology, New University of Lisbon, Portugal.
    A high level e-maintenance architecture to support on-site teams2008In: Enterprise and Work Innovation Studies, ISSN 1646-1223, Vol. 4, 129-138 p.Article in journal (Refereed)
    Abstract [en]

    Emergent architectures and paradigms targeting reconfigurable manufacturing systems increasingly rely on intelligent modules to maximize the robustness and responsiveness of modern installations. Although intelligent behaviour significantly minimizes the occurrence of faults and breakdowns it does not exclude them nor can prevent equipment’s normal wear. Adequate maintenance is fundamental to extend equipments’ life cycle. It is of major importance the ability of each intelligent device to take an active role in maintenance support. Further this paradigm shift towards “embedded intelligence”, supported by cross platform technologies, induces relevant organizational and functional changes on local maintenance teams. On the one hand, the possibility of outsourcing maintenance activities, with the warranty of a timely response, through the use of pervasive networking technologies and, on the other hand, the optimization of local maintenance staff are some examples of how IT is changing the scenario in maintenance. The concept of e-maintenance is, in this context, emerging as a new discipline with defined socio-economic challenges. This paper proposes a high level maintenance architecture supporting maintenance teams’ management and offering contextualized operational support. All the functionalities hosted by the architecture are offered to the remaining system as network services. Any intelligent module, implementing the services’ interface, can report diagnostic, prognostic and maintenance recommendations that enable the core of the platform to decide on the best course of action.

  • 6.
    Carvalho Bittencourt, André
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Saarinen, Kari
    ABB, Sweden.
    Sander-Tavallaey, Shiva
    ABB, Sweden.
    A method for Monitoring of Systems that operate in a Repetitive Manner: Application to Wear Monitoring of an Industrial Robot2011In: Proceedings of the 2011 PAPYRUS Workshop on Fault Diagnosis and Fault Tolerand Control in Large Scale Processing Industries, 2011Conference paper (Refereed)
  • 7.
    Strömberg, Niclas
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Mechanics .
    A method for structural dynamic contact problems with friction and wear2003In: International Journal for Numerical Methods in Engineering, ISSN 0029-5981, Vol. 58, no 15, 2371-2385 p.Article in journal (Refereed)
    Abstract [en]

    A method for structural dynamic contact problems with friction and wear is suggested. The method is obtained by including wear in the non-smooth contact dynamics method of Moreau. A comparison of the method to the discrete energy-momentum method of Simo and Tarnow is also outlined briefly. The fully discrete equations are treated using the augmented Lagrangian approach, where a non-smooth Newton method is used as the equation solver. Two two-dimensional examples are solved by the method. It is investigated how solutions of contact, friction and wear are influenced by inertia. It is shown that the quasi-static assumption might be questionable for solving contact problems with friction and wear. © 2003 John Wiley and Sons, Ltd.

  • 8.
    Ireman, Peter
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Mechanics .
    Klarbring, Anders
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Mechanics .
    Strömberg, Niclas
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Mechanics .
    A model of damage coupled to wear2003In: International Journal of Solids and Structures, ISSN 0020-7683, Vol. 40, no 12, 2957-2974 p.Article in journal (Refereed)
    Abstract [en]

    The present paper presents a model of damage coupled to wear. The damage model is based on a continuum model including the gradient of the damage variable. Such a model is non-local in the sense that the evolution of damage is governed by a boundary-value problem instead of a local evolution law. Thereby, the well-known mesh-dependency observed for local damage models is removed. Another feature is that the boundary conditions can be used to introduce couplings between bulk damage and processes at the boundary. In this work such a coupling is suggested between bulk damage and wear at the contact interface. The model is regarded as a first attempt to formulate a continuum damage model for studying crack initiation in fretting fatigue. The model is given within a thermodynamic framework, where it is assured that the principles of thermodynamics are satisfied. Furthermore, two variational formulations of the full initial boundary value problem, serving as starting points for finite element discretization, are presented. Finally, preliminary numerical results for a simple one-dimensional example are presented and discussed. It is qualitatively shown how the evolution of damage may influence the wear behaviour and how damage may be initiated by the wear process. © 2003 Elsevier Science Ltd. All rights reserved.

  • 9.
    Broitman, Esteban
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    A new method for in-situ measurement of nano-friction and nano-wear of thin films by using the Triboindenter TI-9502014In: Nanobrucken 2014, Saarbrucken, Germany: INM - Leibniz Institute for New Materials , 2014, 24- p.Conference paper (Other academic)
    Abstract [en]

    The Triboindenter present many advantages for the measurement of friction and wear at the nanoscale. A reciprocating multi-cycle linear test can be programmed, from where it is possible to obtain simultaneously the friction force and wear rate from the lateral force and vertical displacement sensors, respectively. The friction values have high precision but the wear data is usually wrong in long duration tests because the drift rate is only measured just before the test start. Alternatively, one can program the SPM scanning mode of the instrument with a high load in order to produce the wear of the surface. At the end of the experiment, a squared hole is produced which can be measured using the SPM facility of the system. However, this wear experiment does not allow the simultaneous measurement of the friction coefficient.In this talk I will present a new methodology to measure in-situ the friction and wear of thin films using a Triboindenter TI-950 from Hysitron. I will show how the possible changes of drift rate during long-time tests can be overcome, obtaining simultaneous precise values of friction and wear rate as a function of time. I will discuss how the Triboimage® software can be adapted to this methodology in order to get realistic values of friction and wear. Finally I will show some results for soft (H < 1GPa) Pb films and very hard (H ~ 35 GPa) nitride coatings

  • 10.
    Hammersberg, Peter
    et al.
    Linköping University, Department of Mechanical Engineering. Linköping University, The Institute of Technology.
    Stenström, Mats
    Linköping University, Department of Medicine and Care, Radio Physics. Linköping University, Faculty of Health Sciences.
    Hedtjärn, Håkan
    Linköping University, Department of Medicine and Care, Radio Physics. Linköping University, Faculty of Health Sciences.
    Mångård, Måns
    Linköping University, Department of Mechanical Engineering. Linköping University, The Institute of Technology.
    Absolute energy spectra for an industrial micro focal X-ray source under working conditions measured with a Comptonscattering spectrometer: full spectra data1998Report (Other academic)
    Abstract [en]

    Absolute energy spectra [1/(keV·mAs·sr)] for an industrial micro focal X-ray source has been measured under working conditions, using a Compton scattering spectrometer. The energy spectra were measured as a function of tube potential (30 – 190 kV for every 10th kV) at maximum tube charge of 8 W for the minimum focus (~5 μm diameter). Target material was tungsten. The spectra were measured for a highly focused fresh focal spot. Neither focal spot wear (age) nor defocusing of the focal spot was considered.

    The measured spectra were compared to simulated spectra for the same source supplied by the X-ray source manufacturer. It was found that the measured spectra have slightly different energy distributions with a lower mean energy even though their emitted number of photons were similar. The energy calibration was shown to be accurate compared to the energy resolution, Dhu=0.5 keV, used.

  • 11.
    Migueles, Jairo H.
    et al.
    University of Granada, Spain.
    Cadenas-Sanchez, Cristina
    University of Granada, Spain.
    Ekelund, Ulf
    Norwegian School Sport Science, Norway; University of Cambridge, England.
    Delisle Nystrom, Christine
    Karolinska Institute, Sweden.
    Mora-Gonzalez, Jose
    University of Granada, Spain.
    Löf, Marie
    Linköping University, Department of Clinical and Experimental Medicine, Division of Surgery, Orthopedics and Oncology. Linköping University, Faculty of Medicine and Health Sciences. Karolinska Institute, Sweden.
    Labayen, Idoia
    University of Basque Country, Spain.
    Ruiz, Jonatan R.
    University of Granada, Spain; Karolinska Institute, Sweden.
    Ortega, Francisco B.
    University of Granada, Spain; Karolinska Institute, Sweden.
    Accelerometer Data Collection and Processing Criteria to Assess Physical Activity and Other Outcomes: A Systematic Review and Practical Considerations2017In: Sports Medicine, ISSN 0112-1642, E-ISSN 1179-2035, Vol. 47, no 9, 1821-1845 p.Article, review/survey (Refereed)
    Abstract [en]

    Background Accelerometers are widely used to measure sedentary time, physical activity, physical activity energy expenditure (PAEE), and sleep-related behaviors, with the ActiGraph being the most frequently used brand by researchers. However, data collection and processing criteria have evolved in a myriad of ways out of the need to answer unique research questions; as a result there is no consensus. Objectives The purpose of this review was to: (1) compile and classify existing studies assessing sedentary time, physical activity, energy expenditure, or sleep using the ActiGraph GT3X/+ through data collection and processing criteria to improve data comparability and (2) review data collection and processing criteria when using GT3X/+ and provide age-specific practical considerations based on the validation/calibration studies identified. Methods Two independent researchers conducted the search in PubMed and Web of Science. We included all original studies in which the GT3X/+ was used in laboratory, controlled, or free-living conditions published from 1 January 2010 to the 31 December 2015. Results The present systematic review provides key information about the following data collection and processing criteria: placement, sampling frequency, filter, epoch length, non-wear-time, what constitutes a valid day and a valid week, cut-points for sedentary time and physical activity intensity classification, and algorithms to estimate PAEE and sleep-related behaviors. The information is organized by age group, since criteria are usually age-specific. Conclusion This review will help researchers and practitioners to make better decisions before (i.e., device placement and sampling frequency) and after (i.e., data processing criteria) data collection using the GT3X/? accelerometer, in order to obtain more valid and comparable data.

  • 12.
    Öfjäll, Kristoffer
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, Faculty of Science & Engineering.
    Adaptive Supervision Online Learning for Vision Based Autonomous Systems2016Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Driver assistance systems in modern cars now show clear steps towards autonomous driving and improvements are presented in a steady pace. The total number of sensors has also decreased from the vehicles of the initial DARPA challenge, more resembling a pile of sensors with a car underneath. Still, anyone driving a tele-operated toy using a video link is a demonstration that a single camera provides enough information about the surronding world.  

    Most lane assist systems are developed for highway use and depend on visible lane markers. However, lane markers may not be visible due to snow or wear, and there are roads without lane markers. With a slightly different approach, autonomous road following can be obtained on almost any kind of road. Using realtime online machine learning, a human driver can demonstrate driving on a road type unknown to the system and after some training, the system can seamlessly take over. The demonstrator system presented in this work has shown capability of learning to follow different types of roads as well as learning to follow a person. The system is based solely on vision, mapping camera images directly to control signals.  

    Such systems need the ability to handle multiple-hypothesis outputs as there may be several plausible options in similar situations. If there is an obstacle in the middle of the road, the obstacle can be avoided by going on either side. However the average action, going straight ahead, is not a viable option. Similarly, at an intersection, the system should follow one road, not the average of all roads.  

    To this end, an online machine learning framework is presented where inputs and outputs are represented using the channel representation. The learning system is structurally simple and computationally light, based on neuropsychological ideas presented by Donald Hebb over 60 years ago. Nonetheless the system has shown a cabability to learn advanced tasks. Furthermore, the structure of the system permits a statistical interpretation where a non-parametric representation of the joint distribution of input and output is generated. Prediction generates the conditional distribution of the output, given the input.  

    The statistical interpretation motivates the introduction of priors. In cases with multiple options, such as at intersections, a prior can select one mode in the multimodal distribution of possible actions. In addition to the ability to learn from demonstration, a possibility for immediate reinforcement feedback is presented. This allows for a system where the teacher can choose the most appropriate way of training the system, at any time and at her own discretion.  

    The theoretical contributions include a deeper analysis of the channel representation. A geometrical analysis illustrates the cause of decoding bias commonly present in neurologically inspired representations, and measures to counteract it. Confidence values are analyzed and interpreted as evidence and coherence. Further, the use of the truncated cosine basis function is motivated.  

    Finally, a selection of applications is presented, such as autonomous road following by online learning and head pose estimation. A method founded on the same basic principles is used for visual tracking, where the probabilistic representation of target pixel values allows for changes in target appearance.

  • 13.
    Olsson, Simon
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Al-based Thin Film Quasicrystals and Approximants2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this work, Al-based quasicrystalline and approximant phases have been synthesized in thin films using magnetron sputter deposition. Quasicrystals are structures having long-range order and rotational symmetries which are inconsistent with periodicity. Due to their unusual structure, quasicrystals show many anomalous and unique physical properties, including; high hardness, wear resistance, low friction, and low electrical and thermal conductivities. Approximants are a family of periodic phases that are related to the quasicrystals. These phases share the local atomic arrangement of quasicrystals and have as a result many similar physical properties. Bulk quasicrystals are too brittle for many of the suggested applications, and instead the most important area of applications concerns that of surface  coatings.

    Multilayered Al/Cu/Fe thin films, with a nominal global composition   corresponding to the quasicrystalline phase, have been deposited onto Si and Al2O3 substrates. During isothermal annealing at temperatures up to 700 °C homogeneous thin films were formed. When Si was used as substrate a film-substrate reaction occured already below 390 °C, where Si diffused into the film. This changed the composition, and promoted the formation of the cubic α-approximant phase. Annealing at 600 °C for 4 h the cubic α-approximant phase formed in a polycrystalline state, with a small amount of a second phase, τ7-Al3Fe2Si3. The film was within 1.5 at.% of the ideal composition of the α-approximant phase and contained 8 at.% Si. Continued annealing for 64 h provided for more diffusion of Si to 12 at.%. No degradation of the crystal quality of the remaining α-phase was observed even after as much as 150 h of treatment.

    Nanomechanical and nanotribological properties, including hardness, elastic modulus, friction and toughness, were investigated for the approximant and quasicrystalline samples. The approximant phase, annealed at 600 °C for 4 h, proved to be harder and had higher elastic modulus values than the quasicrystalline phase, about, 15.6 GPa and 258 GPa, respectively. The fracture toughness of the approximant, on the other hand, <0.1 MPa/m½, was inferior to that of the quasicrystals with 1.5 MPa/m½. Low friction coefficients of about 0.13 were measured for both phases.

    When annealing multilayered Al/Cu/Co thin films on Al2O3 the decagonal quasicrystal d-Al-Cu-Co was formed at 500 °C. The XRD peak intensities were rather low, but after raising the temperature to 850 °C a large increase in intensity and a complete texturing with the 10-fold periodic axis aligned with the substrate normal occurred. When annealing the same samples on Si, the decagonal quasicrystal was again found, however, TEM and EDX measurements identified 3-6 at.% Si inside the quasicrystalline grains. Also the decagonal d-Al-Cu-Co-Si quasicrystal was textured with the 10-fold periodic axis aligned with the surface normal. The texture was however not complete as in the thin films grown on Al2O3. Raising the temperature to over 700 °C led to the formation of other crystalline phases in favor of the decagonal d-Al-Cu-Co-Si.

    For the Cu-Al-Sc system quasicrystalline thin films were grown directly from the vapor phase by utilizing ion-assistance during growth at low temperatures, thus eliminating the need for post-annealing. Diffraction experiments revealed that amorphous films were formed at room temperature. The quasicrystalline phase formed at a substrate temperature of 340 °C with an improved quality at higher temperatures up to 460 °C. The quasicrystal film quality was improved by increasing the ion-flux during with ion energies of 26.7 eV. Increasing the ion energy further was however found to cause resputtering and defects in the films. Electron microscopy revealed a polycrystalline microstructure with crystal grains in the shape of thin needles.

    List of papers
    1. Formation of α-approximant and quasicrystalline Al-Cu-Fe thin films
    Open this publication in new window or tab >>Formation of α-approximant and quasicrystalline Al-Cu-Fe thin films
    2012 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 526, 74-80 p.Article in journal (Refereed) Published
    Abstract [en]

    Multilayered Al/Cu/Fe thin films have been deposited by magnetron sputtering onto Si and Al2O3 substrates with a nominal global composition corresponding to the quasicrystalline phase, 5:2:1. Subsequent annealing was performed on the samples up to 710 degrees C. It is found that when using Si as a substrate a film-substrate reaction occurs already below 390 degrees C, where Si diffuses into the film. This changes the composition, promoting the formation of the alpha-approximant Al55Si7Cu25.5Fe12.5 in the temperature range 400 to 650 degrees C over the quasicrystalline psi-phase. When annealing the same Al-Cu-Fe thin film grown on Al2O3 substrates the Al62.5Cu25Fe12.5 icosahedral quasicrystalline phase is formed.

    Place, publisher, year, edition, pages
    Elsevier, 2012
    Keyword
    Quasicrystal, Approximant, Al-Cu-Fe-Si, X-ray diffraction, Annealing, Phase evolution, Multilayer, Sputtering
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-89532 (URN)10.1016/j.tsf.2012.11.009 (DOI)000313703200012 ()
    Note

    Funding Agencies|Swedish Foundation for Strategic Research (SSF) Strategic Research Center in Materials Science for Nanoscale Surface Engineering (MS2E)||

    Available from: 2013-02-26 Created: 2013-02-26 Last updated: 2016-08-31
    2. Structure and Composition of Al(Si)CuFe Approximant Thin Films Formed by Si Substrate Diffusion
    Open this publication in new window or tab >>Structure and Composition of Al(Si)CuFe Approximant Thin Films Formed by Si Substrate Diffusion
    Show others...
    2014 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 550, no 1, 105-109 p.Article in journal (Refereed) Published
    Abstract [en]

    Multilayered Al/Cu/Fe thin films with composition close to the quasicrystalline phase have been prepared by magnetron sputtering. Annealing at 600 °C yields a homogeneous film of the cubic a-approximant phase by Si substrate diffusion, which prevents the formation of the quasicrystalline phase. After 4 h annealing the film contained 8 at.% Si, which corresponds to the expected value of the a-approximant. The amount of Si in the films was found to slowly increase to ~12 at.% during continued annealing (64 h) while the α-approximant phase was retained. The lattice parameter was found to  continuously decrease as Al became substituted with Si. The film is observed to be polycrystalline with individual grains being strained in varying magnitude, and with no preferential orientation relationship to the substrate or each other.

    Place, publisher, year, edition, pages
    Elsevier, 2014
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-96906 (URN)10.1016/j.tsf.2013.10.121 (DOI)000328499700017 ()
    Available from: 2013-08-29 Created: 2013-08-29 Last updated: 2016-08-31Bibliographically approved
    3. Mechanical and Tribological Properties of AlCuFe Quasicrystal and Al(Si)CuFe Approximant Thin Films
    Open this publication in new window or tab >>Mechanical and Tribological Properties of AlCuFe Quasicrystal and Al(Si)CuFe Approximant Thin Films
    Show others...
    2016 (English)In: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 31, no 2, 232-240 p.Article in journal (Refereed) Published
    Abstract [en]

    Multilayered thin films of Al/Cu/Fe have been prepared by magnetron sputtering and annealed into the quasicrystalline or approximant phases, for Al2O3 or Si substrates, respectively. The nanomechanical and nanotribological properties; hardness, elastic modulus, friction and toughness, have been measured using a triboindenter and analytical methods. The approximant phase, annealed at 600 °C for 4 h, proved to be harder and had higher elastic modulus values than the quasicrystalline phase, about, 15.6 GPa and 258 GPa, respectively. The fracture toughness of the approximant, <0.1 MPa/m½, was however inferior to that of the quasicrystals with 1.5 MPa/m½. The friction coefficients were measured in a range of 0.10-0.14 for the quasicrystalline and approximant thin films.

    Place, publisher, year, edition, pages
    Cambridge University Press, 2016
    Keyword
    quasicrystal, approximant, thin film, hardness, elastic modulus, friction, toughness, tribology, TEM, STEM, XRD
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-96907 (URN)10.1557/jmr.2015.384 (DOI)000371704900007 ()
    Note

    Funding agencies:  Knut and Alice Wallenberg Foundation; Swedish Government Strategic Research Area Grant in Materials Science (SFO Mat-LiU) on Advanced Functional Materials

    Available from: 2013-08-29 Created: 2013-08-29 Last updated: 2016-08-31Bibliographically approved
    4. Phase Evolution of Multilayered Al/Cu/Co Thin Films into Decagonal Al-Cu-Co and Al-Cu-Co-Si Quasicrystalline Phases
    Open this publication in new window or tab >>Phase Evolution of Multilayered Al/Cu/Co Thin Films into Decagonal Al-Cu-Co and Al-Cu-Co-Si Quasicrystalline Phases
    Show others...
    2013 (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Multilayered Al/Cu/Co thin films have been prepared by magnetron sputtering on Al2O3(0001) and Si(001) substrates and the phase evolution has been investigated. The decagonal d-Al-Cu-Co and d-Al-Cu-Co-Si phases were found to form at 500 °C, and at 600 °C these were the only phases. At increasing temperatures, the quasicrystals grew larger in size, up to 500 nm, although always smaller for the d-Al-Cu-Co-Si, and obtained a texturing with the 10-fold periodic axis aligned with the substrate normal. The d-Al-Cu-Co phase persisted to more than 850 °C, with a complete texturing, while the d-Al-Cu-Co-Si phase was replaced by other crystalline phases at 800 °C.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-96908 (URN)
    Available from: 2013-08-29 Created: 2013-08-29 Last updated: 2016-08-31Bibliographically approved
    5. Ion-assisted Growth of Quasicrystalline Cu-Al-Sc Directly from the Vapor Phase
    Open this publication in new window or tab >>Ion-assisted Growth of Quasicrystalline Cu-Al-Sc Directly from the Vapor Phase
    Show others...
    2013 (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Ion assisted depositions have been used to grow the Al38Cu46Sc16 quasicrystalline phase directly from the vapor phase in thin film form. Diffraction experiments reveal that amorphous films are formed at room temperature. The quasicrystalline phase formed at a substrate temperature of 340 °C with an improved quality at higher temperatures up to 460 °C. The quasicrystal film quality is improved by increasing the ion flux during ion-assisted growth with ion energies of 26.7 eV. Increasing the ion energy further was however found to cause resputtering and defects in the film. Electron microscopy reveals a polycrystalline microstructure with crystal grains in the shape of thin needles.

    Keyword
    Quasicrystal, thin film, ion-assisted depositions, magnetron sputtering, TEM, XRD
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-96909 (URN)
    Available from: 2013-08-29 Created: 2013-08-29 Last updated: 2016-08-31Bibliographically approved
  • 14.
    Wallin, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics . Linköping University, The Institute of Technology.
    Alumina Thin Films: From Computer Calculations to Cutting Tools2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The work presented in this thesis deals with experimental and theoretical studies related to alumina thin films. Alumina, Al2O3, is a polymorphic material utilized in a variety of applications, e.g., in the form of thin films. However, controlling thin film growth of this material, in particular at low substrate temperatures, is not straightforward. The aim of this work is to increase the understanding of the basic mechanisms governing alumina growth and to investigate novel ways of synthesizing alumina coatings. The thesis can be divided into two main parts, where the first part deals with fundamental studies of mechanisms affecting alumina growth and the second part with more application-oriented studies of high power impulse magnetron sputter (HiPIMS) deposition of the material.

    In the first part, it was shown that the thermodynamically stable α phase, which normally is synthesized at substrate temperatures of around 1000 °C, can be grown using reactive sputtering at a substrate temperature of merely 500 °C by controlling the nucleation surface. This was done by predepositing a Cr2O3 nucleation layer. Moreover, it was found that an additional requirement for the formation of the α phase is that the depositions are carried out at low enough total pressure and high enough oxygen partial pressure. Based on these observations, it was concluded that energetic bombardment, plausibly originating from energetic oxygen, is necessary for the formation of α-alumina (in addition to the effect of the chromia nucleation layer). Moreover, the effects of residual water on the growth of crystalline films were investigated by varying the partial pressure of water in the ultra high vacuum (UHV) chamber. Films deposited onto chromia nucleation layers exhibited a columnar structure and consisted of crystalline α-alumina if deposited under UHV conditions. However, as water to a partial pressure of 1*10-5 Torr was introduced, the columnar α-alumina growth was disrupted. Instead, a microstructure consisting of small, equiaxed grains was formed, and the γ-alumina content was found to increase with increasing film thickness.

    To gain a better understanding of the atomistic processes occurring on the surface, density functional theory based computational studies of adsorption and diffusion of Al, O, AlO, and O2 on different α-alumina (0001) surfaces were also performed. The results give possible reasons for the difficulties in growing the α phase at low temperatures through the identification of several metastable adsorption sites and also show how adsorbed hydrogen might inhibit further growth of α-alumina crystallites. In addition, it was shown that the Al surface diffusion activation energies are unexpectedly low, suggesting that limited surface diffusivity is not the main obstacle for low-temperature α-alumina growth. Instead, it is suggested to be more important to find ways of reducing the amount of impurities, especially hydrogen, in the process and to facilitate α-alumina nucleation when designing new processes for low-temperature deposition of α-alumina.

    In the second part of the thesis, reactive HiPIMS deposition of alumina was studied. In HiPIMS, a high-density plasma is created by applying very high power to the sputtering magnetron at a low duty cycle. It was found, both from experiments and modeling, that the use of HiPIMS drastically influences the characteristics of the reactive sputtering process, causing reduced target poisoning and thereby reduced or eliminated hysteresis effects and relatively high deposition rates of stoichiometric alumina films. This is not only of importance for alumina growth, but for reactive sputter deposition in general, where hysteresis effects and loss of deposition rate pose a substantial problem. Moreover, it was found that the energetic and ionized deposition flux in the HiPIMS discharge can be used to lower the deposition temperature of α-alumina. Coatings predominantly consisting of the α phase were grown at temperatures as low as 650 °C directly onto cemented carbide substrates without the use of nucleation layers. Such coatings were also deposited onto cutting inserts and were tested in a steel turning application. The coatings were found to increase the crater wear resistance compared to a benchmark TiAlN coating, and the process consequently shows great potential for further development towards industrial applications.

    List of papers
    1. Phase control of Al2O3 thin films grown at low temperatures
    Open this publication in new window or tab >>Phase control of Al2O3 thin films grown at low temperatures
    Show others...
    2006 (English)In: Thin Solid Films, ISSN 0040-6090, Vol. 513, no 1-2, 57-59 p.Article in journal (Refereed) Published
    Abstract [en]

    Low-temperature growth (500 °C) of α-Al2O3 thin films by reactive magnetron sputtering was achieved for the first time. The films were grown onto Cr2O3 nucleation layers and the effects of the total and O2 partial pressures were investigated. At 0.33 Pa total pressure and ≥ 16 mPa O2 partial pressure α-Al2O3 films formed, while at lower O2 pressure or higher total pressure (0.67 Pa), only γ phase was detected in the films (which were all stoichiometric). Based on these results we suggest that α phase formation was promoted by a high energetic bombardment of the growth surface. This implies that the phase content of Al2O3 films can be controlled by controlling the energy of the depositing species. The effect of residual H2O (10− 4 Pa) on the films was also studied, showing no change in phase content and no incorporated H (< 0.1%). Overall, these results are of fundamental importance in the further development of low-temperature Al2O3 growth processes.

    Place, publisher, year, edition, pages
    Elsevier, 2006
    Keyword
    Aluminum oxide, Chromium oxide, Sputtering, Ion bombardment, X-ray diffraction
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-14318 (URN)10.1016/j.tsf.2006.01.016 (DOI)
    Note
    Original publication: Andersson, J.M., Wallin, E., Helmersson, U., Kreissig, U. and Münger, E.P., Phase control of Al2O3 thin films grown at low temperatures, 2006, Thin Solid Films, (513), 1-2, 57-59. http://dx.doi.org/10.1016/j.tsf.2006.01.016. Copyright: Elsevier B.V., http://www.elsevier.com/ Available from: 2007-03-02 Created: 2007-03-02 Last updated: 2013-10-30Bibliographically approved
    2. Ab initio studies of Al, O, and O2 adsorption on α-Al2O3 (0001) surfaces
    Open this publication in new window or tab >>Ab initio studies of Al, O, and O2 adsorption on α-Al2O3 (0001) surfaces
    Show others...
    2006 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 74, no 12, 125409-1-125409-9 p.Article in journal (Refereed) Published
    Abstract [en]

    The interactions of Al, O, and O2 with different α- Al2O3 (0001) surfaces have been studied using ab initio density functional theory methods. All three surface terminations obtainable by cleaving the bulk structure [single Al-layer (AlO), double Al-layer (AlAl), and O terminations] have been considered, as well as a completely hydrogenated O-terminated surface. Adsorbed Al shows strong ioniclike interaction with the AlO - and O-terminated surfaces, and several metastable adsorption sites are identified on the O-terminated surface. On the completely hydrogenated surface, however, Al adsorption in the bulk position is found to be unstable or very weak for the studied configurations of surface H atoms. Atomic O is found to interact strongly with the AlAl -terminated surface, where also O2 dissociative adsorption without any appreciable barrier is observed. In contrast, O adsorption on the AlO -terminated surface is metastable relative to molecular O2. On the O-terminated surface, we find the creation of O surface vacancies to be plausible, especially upon exposure to atomic O at elevated temperatures. The results are mainly discussed in the context of alumina thin film growth and provide insight into phenomena related to, e.g., preferred adsorption sites and effects of hydrogen on the growth.

    Place, publisher, year, edition, pages
    College Park, MD, United States: American Physical Society, 2006
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-10427 (URN)10.1103/PhysRevB.74.125409 (DOI)000240872500080 ()
    Note

    Original publication: E. Wallin, J.M. Andersson, E.P. Münger, V. Chirita & U. Helmersson, Ab initio studies of Al, O, and O2 adsorption on α- Al2 O3 (0001) surfaces, 2006, Physical Review B, (74), 125409. http://dx.doi.org/10.1103/PhysRevB.74.125409. Copyright: The America Physical Society, http://prb.aps.org/

    Available from: 2007-12-12 Created: 2007-12-12 Last updated: 2014-06-18Bibliographically approved
    3. Influence of residual water on magnetron sputter deposited crystalline Al2O3 thin films
    Open this publication in new window or tab >>Influence of residual water on magnetron sputter deposited crystalline Al2O3 thin films
    2008 (English)In: Thin Solid Films, ISSN 0040-6090, Vol. 516, no 12, 3877-3883 p.Article in journal (Refereed) Published
    Abstract [en]

    The effects of residual water on the phase formation, composition, and microstructure evolution of magnetron sputter deposited crystalline alumina thin films have been investigated. To mimic different vacuum conditions, depositions have been carried out with varying partial pressures of H2O. Films have been grown both with and without chromia nucleation layers. It is shown that films deposited onto chromia nucleation layers at relatively low temperatures (500 °C) consists of crystalline alpha-alumina if deposited at a low enough total pressure under ultra high vacuum (UHV) conditions. However, as water was introduced a gradual increase of the gamma phase content in the film with increasing film thickness was observed. At the same time, the microstructure changed drastically from a dense columnar structure to a structure with small, equiaxed grains. Based on mass spectrometry measurements and previous ab initio calculations, we suggest that either bombardment of energetic negative (or later neutralized) species being accelerated over the target sheath voltage, adsorbed hydrogen on growth surfaces, or a combination of these effects, is responsible for the change in structure. For films containing the metastable gamma phase under UHV conditions, no influence of residual water on the phase content was observed. The amounts of hydrogen incorporated into the films, as determined by elastic recoil detection analysis, were shown to be low. Overall, the results demonstrate that residual water present during film growth drastically affects film properties, also in cases where the hydrogen incorporation is found to be low.

    Place, publisher, year, edition, pages
    ScienceDirect, 2008
    Keyword
    Aluminum oxide, Phase formation, Sputtering, Water
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-11476 (URN)10.1016/j.tsf.2007.07.135 (DOI)
    Note
    Original publication: E. Wallin, J.M. Andersson, M. Lattemann, and U. Helmersson, Influence of residual water on magnetron sputter deposited crystalline Al2O3 thin films, 2008, Thin Solid Films, (516), 12, 3877-3883. http://dx.doi.org/10.1016/j.tsf.2007.07.135. Copyright: Elsevier B.V., http://www.elsevier.com/Available from: 2008-04-03 Created: 2008-04-03 Last updated: 2013-10-30Bibliographically approved
    4. Low-temperature alpha-alumina thin film growth: ab initio studies of Al adatom surface migration
    Open this publication in new window or tab >>Low-temperature alpha-alumina thin film growth: ab initio studies of Al adatom surface migration
    2009 (English)In: JOURNAL OF PHYSICS D-APPLIED PHYSICS, ISSN 0022-3727, Vol. 42, no 12, 125302- p.Article in journal (Refereed) Published
    Abstract [en]

    Investigations of activation energy barriers for Al surface hopping on alpha-Al2O3 (0 0 0 1) surfaces have been carried out by means of first-principles density functional theory calculations and the nudged elastic band method. Results show that surface diffusion on the (most stable) Al-terminated surface is relatively fast with an energy barrier of 0.75 eV, whereas Al hopping on the O-terminated surface is slower, with barriers for jumps from the two metastable positions existing on this surface to the stable site of 0.31 and 0.99 eV. Based on this study and on the literature, the governing mechanisms during low-temperature alpha-alumina thin film growth are summarized and discussed. Our results support suggestions made in some previous experimental studies, pointing out that limited surface diffusivity is not the main obstacle for alpha-alumina growth at low-to-moderate temperatures, and that other effects should primarily be considered when designing novel processes for low-temperature alpha-alumina deposition.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-19393 (URN)10.1088/0022-3727/42/12/125302 (DOI)
    Note
    Original Publication: Erik Wallin, Peter Münger, Valeriu Chirita and Ulf Helmersson, Low-temperature alpha-alumina thin film growth: ab initio studies of Al adatom surface migration, 2009, JOURNAL OF PHYSICS D-APPLIED PHYSICS, (42), 12, 125302. http://dx.doi.org/10.1088/0022-3727/42/12/125302 Copyright: Iop Publishing Ltd http://www.iop.org/ Available from: 2009-06-29 Created: 2009-06-22 Last updated: 2013-10-30Bibliographically approved
    5. Hysteresis-free reactive high power impulse magnetron sputtering
    Open this publication in new window or tab >>Hysteresis-free reactive high power impulse magnetron sputtering
    2008 (English)In: Thin Solid Films, ISSN 0040-6090, Vol. 516, no 18, 6398-6401 p.Article in journal (Refereed) Published
    Abstract [en]

    High power impulse magnetron sputtering (HIPIMS) of an Al target in Ar/O2 mixtures has been studied. The use of HIPIMS is shown to drastically influence the process characteristics compared to conventional sputtering. Under suitable conditions, oxide formation on the target as the reactive gas flow is increased is suppressed, and the hysteresis effect commonly observed as the gas flow is varied during conventional sputtering can be reduced, or even completely eliminated, using HIPIMS. Consequently, stoichiometric alumina can be deposited under stable process conditions at high rates. Possible explanations for this behavior as well as a model qualitatively describing the process are presented.

    Keyword
    Reactive Sputtering, High Power Impulse Magnetron Sputtering, Alumina, Process modeling
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-15028 (URN)10.1016/j.tsf.2007.08.123 (DOI)
    Note
    Original publication: E. Wallin and U. Helmersson, Hysteresis-free reactive high power impulse magnetron sputtering, 2008, Thin Solid Films, (516), 18, 6398-6401.http://dx.doi.org/10.1016/j.tsf.2007.08.123. Copyright: Elsevier B.V., http://www.elsevier.com/Available from: 2008-10-10 Created: 2008-10-10 Last updated: 2013-10-30Bibliographically approved
    6. Synthesis of α-Al2O3 thin films using reactive high power impulse magnetron sputtering
    Open this publication in new window or tab >>Synthesis of α-Al2O3 thin films using reactive high power impulse magnetron sputtering
    2008 (English)In: Europhysics letters, ISSN 0295-5075, Vol. 82, no 3, 36002- p.Article in journal (Refereed) Published
    Abstract [en]

    α-alumina coatings have been deposited directly onto cemented-carbide and Mo substrates at a temperature as low as 650 °C using reactive high-power impulse magnetron sputtering (HiPIMS) of Al in an Ar/O2 gas mixture. The coatings consisted of plate-like crystallites, as revealed by scanning electron microscopy. α phase growth was retained over the studied range of substrate bias voltages (from floating potential up to -100 V), with films exhibiting a slightly denser microstructure at higher bias voltages. X-ray diffraction indicated that the α-alumina grains had a preferred orientation of (0001)-planes perpendicular to the substrate surface. X-ray analysis of films deposited at 575 °C indicated the presence of γ-alumina, whereas films grown at 500 °C or lower were X-ray amorphous.

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-15354 (URN)10.1209/0295-5075/82/36002 (DOI)
    Note
    Original Publication: Erik Wallin, T. I. Selinder, M. Elfwing and Ulf Helmersson, Synthesis of α-Al2O3 thin films using reactive high power impulse magnetron sputtering, 2008, Europhysics letters, (82), 36002. http://dx.doi.org/10.1209/0295-5075/82/36002 Copyright: EDP Sciences. http://publications.edpsciences.org/ Available from: 2009-02-22 Created: 2008-11-05 Last updated: 2013-10-30Bibliographically approved
    7. α-alumina coatings on WC/Co substrates by physical vapor deposition
    Open this publication in new window or tab >>α-alumina coatings on WC/Co substrates by physical vapor deposition
    2009 (English)In: International journal of refractory metals & hard materials, ISSN 0958-0611, Vol. 27, no 2, 507-512 p.Article in journal (Refereed) Published
    Abstract [en]

    Physical vapor deposition coatings for cutting tools may be deposited by, e.g. reactive magnetron sputtering. Alumina growth in Ar/O2 gas mixtures gives rise to problems due to insulating layers on targets, and hysteresis effects with respect to oxygen gas flow. In this paper is described a technology for the deposition of crystalline alumina: reactive high power impulse magnetron sputtering. Pure Al was used as target material, and the cemented carbide (WC/Co) substrates were kept at 500-650 ºC. Hysteresis effects with respect to oxygen gas flow were alleviated, which enabled stable growth at a high deposition rate. The high power impulses were helpful in obtaining a crystalline oxide coating. X-ray diffraction and crosssection transmission electron microscopy showed that α-alumina films were formed. Technological testing of these PVD alumina coatings, with state-of-the-art AlTiN as benchmark, showed significantly improved crater wear resistance in steel turning.

    Keyword
    HiPIMS, HPPMS, ionized-PVD, alumina, corundum
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-15359 (URN)10.1016/j.ijrmhm.2008.10.007 (DOI)
    Note
    On the day of defence date the status of article VII was: Accepted. Original Publication: T.I. Selinder, E. Coronel, Erik Wallin and Ulf Helmersson, α-alumina coatings on WC/Co substrates by physical vapor deposition, 2009, International journal of refractory metals & hard materials, (27), 2, 507-512. http://dx.doi.org/10.1016/j.ijrmhm.2008.10.007 Copyright: Elsevier Science B.V., Amsterdam. http://www.elsevier.com/ Available from: 2009-02-23 Created: 2008-11-05 Last updated: 2013-10-30Bibliographically approved
  • 15.
    Isberg, Peter
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Eklund, Per
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Emmerlich, Jens
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Hultman, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Högberg, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Ljungcrantz, Henrik
    Impact Coatings AB.
    Amorphous and nanocomposite MAX compounds for wear protective coatings on components and tools as well as electrical contacts2005Patent (Other (popular science, discussion, etc.))
  • 16.
    Pettersson, Thomas
    Linköping University, Department of Mathematics, Computational Mathematics. Linköping University, Faculty of Science & Engineering.
    Analysis and implementation of the Smooth Discrete Element Method in AgX2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    We encounter granular materials on a daily basis. We walk up a gravel path or we eat our breakfast cereals. When handling granular materials on an industrial scale it is important to do so efficiently, to avoid unnecessary energy losses, wear and tear. To help designing efficient tools for handling these materials engineers uses numerical simulations.

    This project investigates the difference between the two main approaches to simulation of granular materials, the Smooth- and Non-smooth Discrete Element Methods by implementing the Smooth method into AgX dynamics were the Non-smooth method already is implemented, and then setup and execute a range of experiments to investigate their differences.

    The investigation shows both advantages and weaknesses for both methods. The result of simulations with smooth discrete element method are more consistent than with the nonsmooth discrete element method with respect to choice of time step and other parameters that can be chosen for the simulation. Smooth discrete element method have problems when it comes to extreme situations.

    The relative simulation time for system as large as treated by this project (more than1000) can not be shown to depend on the size of the system.

  • 17.
    Kronstrand, Robert
    Linköping University, Department of Biomedicine and Surgery, Clinical Chemistry. Linköping University, Faculty of Health Sciences.
    Analytical and Toxicological Aspects of Drug Incorporation into Human Hair2001Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The overall purpose of this thesis was to develop analytical methods for the determination of drugs and melanin content of human hair for practical use in forensic and clinical toxicology. The thesis consists of five papers, two of which are controlled single dose studies where codeine or selegiline were administered to healthy volunteers. One patient study, looked at the concentrations of selegiline metabolites in both pigmented and senile white hairs as well as plasma. Another study involved forensic autopsy cases where the occurrence of drugs of abuse in post-mortem blood, urine and hair were compared. Finally, one in vitro study investigated the binding of [3H]-flunitrazepam to melanin. To our knowledge, the controlled dosage studies are the first to quantitatively determine the relationship between drug concentration in human hair and melanin content.

    The results demonstrated that pigmentation was an important factor for the incorporation of codeine, methamphetamine, and amphetamine into human hair. The relationships could be described by exponential functions with correlations coefficients r2>0.8. We have shown that the pigmented portion of hair from grey-haired patients incorporated more methamphetamine and amphetamine than the non-pigmented portion. The mean pigmented/white-hair ratios were 3.7±1.9 and 3.0±1.2 for methamphetamine and amphetamine respectively. Segmental hair analysis showed decreasing drug-concentrations over three months as a sign of noncompliance or of instability of the drugs in hair owing to cosmetic treatment of hair or wear. In the controlled studies, we demonstrated that the drug concentration in hair was fairly constant up to one month. In the study on autopsy cases, we found that hair analysis revealed patterns of multi-drug use not found by analysis of a single blood sample. Also, in 6 of 19 cases of heroin overdose, no opiates could be detected in hair. This suggested "first" or only occasional use of heroin, which might have been a contributing factor to the overdose death, because of lack of tolerance. The results from the in vitro study showed that binding of flunitrazepam to eumelanin occurs by two mechanisms, a Langmuir-like binding and a diffusion limited binding. We propose that these are expressions of an initial binding to the melanin surface (surface binding) followed by the diffusion of drug molecules into the melanin granule (bulk binding).

    Hair as a specimen for toxicological analysis has hitherto not been investigated in Sweden. This thesis address questions raised by international research on the incorporation of drugs into hair and its implications for clinical and forensic toxicology.

    Melanin has been established as an important factor for incorporation and binding of certain drugs into human hair and methods that allow correction for this are presented. Together, the results from the various studies provide a framework for both future research and the start of drug analysis in hair for forensic and clinical applications in Sweden.

    List of papers
    1. Incidence of opiates, amphetamines, and cocaine in hair and blood in fatal cases of heroin overdose
    Open this publication in new window or tab >>Incidence of opiates, amphetamines, and cocaine in hair and blood in fatal cases of heroin overdose
    1998 (English)In: Forensic Science International, ISSN 0379-0738, E-ISSN 1872-6283, Vol. 92, no 1, 29-38 p.Article in journal (Refereed) Published
    Abstract [en]

    The purpose of the present study was to investigate the occurrence in hair, of some drugs of abuse in deaths caused by heroin overdose, in comparison to findings in blood. Blood, urine and hair samples were obtained during routine post mortem examinations. Samples were analysed for amphetamines, opiates, and cocaine. Immunometric drug screening was performed in urine and positive results confirmed with gas chromatography–mass spectrometry (GC–MS) of blood samples. All hair samples were analyzed with GC–MS. Hair samples were either incubated with methanol for determination of opiates and cocaine, or dissolved in sodium hydroxide for determination of amphetamines. All 19 blood samples were positive for morphine (0.04–0.4 μg g−1) and ten were also positive for 6-acetylmorphine (0.003–0.02 μg g−1). Thirteen of the hair samples were positive for 6-acetylmorphine and seven of which were positive also for morphine. Concentrations ranged from 0.3–7.4 and 0.3–1.3 (ng mg), respectively. Amphetamine was found in three blood samples (0.04–1.2 μg g−1) and in eleven hair samples (0.4–18.3 ng mg). Cocaine was determined in one blood sample (0.03 μg g−1) and two hair samples (0.7–6.5 ng mg). Out of the nineteen cases studied, eight showed chronic multi drug use on the basis of the results of hair analysis. In six subjects no opiates could be detected in hair, suggesting; “first” or occasional intake of heroin, which could be a contributing factor to the overdose death, because of lack of tolerance. We conclude that analysis of hair can be a useful complement to analysis of more conventional autopsy material, especially when investigating overdose deaths and previous histories of drug use and abuse.

    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-80902 (URN)10.1016/S0379-0738(98)00003-6 (DOI)
    Available from: 2012-09-03 Created: 2012-09-03 Last updated: 2012-09-03Bibliographically approved
    2. Codeine Concentration in Hair after Oral Administration Is Dependent on Melanin Content
    Open this publication in new window or tab >>Codeine Concentration in Hair after Oral Administration Is Dependent on Melanin Content
    Show others...
    1999 (English)In: Clinical Chemistry, ISSN 0009-9147, E-ISSN 1530-8561, Vol. 45, no 9, 1485-1494 p.Article in journal (Refereed) Published
    Abstract [en]

    Background: Analysis of drugs in hair has been used on a qualitative basis to estimate earlier exposure to drugs. Clinical applications are rare because of the lack of dose–response relationships in the studies performed to date, and questions remain regarding the mechanisms of drug incorporation into hair. Several human studies have shown differences in drug accumulation between pigmented and nonpigmented hair. However, the melanin concentration in hair was not determined and correlated to the amount of drug incorporated.

    Methods: Nine human subjects were given codeine as a single oral dose, and plasma codeine concentrations were determined for 24 h, using gas chromatography–mass spectrometry. Hair samples were obtained weekly for a month. Total melanin, eumelanin, and codeine were measured quantitatively in hair samples by spectrophotometry, HPLC, and gas chromatography–mass spectrometry, respectively.

    Results: There was an exponential relationship between codeine and melanin concentrations in hair, (r2 = 0.95 with total melanin and r2 = 0.83 with eumelanin). After normalizing the results by the area under the curve for codeine in plasma, we obtained r2 = 0.86 for codeine vs total melanin and r2 = 0.90 vs eumelanin.

    Conclusions: Our results stress the importance of melanin determination when measuring drugs in hair. We postulate that analysis of drug concentration in hair may be worthwhile in the monitoring of drug compliance if the results are normalized for melanin content.

    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-25184 (URN)9623 (Local ID)9623 (Archive number)9623 (OAI)
    Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2012-09-03Bibliographically approved
    3. Incorporation of Selegiline Metabolites into Hair after Oral Selegiline Intake
    Open this publication in new window or tab >>Incorporation of Selegiline Metabolites into Hair after Oral Selegiline Intake
    2001 (English)In: Journal of Analytical Toxicology, ISSN 0146-4760, Vol. 25, no 7, 594-601 p.Article in journal (Refereed) Published
    Abstract [en]

    We have previously shown that melanin in human hair has a great impact on the incorporation of codeine into hair. The present study on 10 subjects was performed to investigate whether or not these findings could also be extrapolated to other therapeutic drugs. We chose selegiline because it metabolizes to two commonly abused central stimulants, methamphetamine and amphetamine. The results would therefore also be of interest when studying the intake of such drugs and their incorporation into human hair. Selegiline and metabolites were determined by gas chromatography-mass spectrometry, total melanin by spectrophotometry, and pyrroletricarboxylic acid by high-performance liquid chromatography with ultraviolet detection. Our results show strong positive exponential relationships (y = ex) between melanin and the metabolites, which for methamphetamine improved by normalizing for plasma area under the curve. We conclude that the major metabolites of selegiline can be detected in hair up to four weeks after a single oral dose and that the incorporation closely relates to the melanin contents.

    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-25186 (URN)10.1093/jat/25.7.594 (DOI)9625 (Local ID)9625 (Archive number)9625 (OAI)
    Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2012-09-03Bibliographically approved
    4. Quantitative Analysis of Desmethylselegiline, Methamphetamine, and Amphetamine in Hair and Plasma from Parkinson Patients on Long-Term Selegiline Medicatio
    Open this publication in new window or tab >>Quantitative Analysis of Desmethylselegiline, Methamphetamine, and Amphetamine in Hair and Plasma from Parkinson Patients on Long-Term Selegiline Medicatio
    2003 (English)In: Journal of Analytical Toxicology, ISSN 0146-4760, Vol. 27, no 3, 135-141 p.Article in journal (Refereed) Published
    Abstract [en]

    Hair and plasma from patients on long-term selegiline medication were analyzed to evaluate the relationships between plasma and hair melanin concentrations and the incorporation of the selegiline metabolites methamphetamine and amphetamine in hair, and to evaluate hair analyses for determining compliance in medication. Analyses were performed on both the whole hairs, as well as pigmented and non-pigmented hairs from gray-haired patients. Melanin was quantitated by spectrophotometry, and metabolites were quantitated by gas chromatography-mass spectrometry. Concentrations in pigmented and non-pigmented hairs differed significantly for both methamphetamine (p < 0.01) and amphetamine (p < 0.02), with mean concentration ratios being 3.69 ± 1.88 and 2.95 ± 1.16 for methamphetamine and amphetamine, respectively. Segmental analysis indicated that some patients had not been compliant with medication. We concluded that the incorporation of methamphetamine and amphetamine into hair of single individuals shows a preference for pigmented hairs over white hairs and that segmental analysis of hair may he useful when measuring compliance with medication.

    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-26747 (URN)10.1093/jat/27.3.135 (DOI)11342 (Local ID)11342 (Archive number)11342 (OAI)
    Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2012-09-03Bibliographically approved
    5. Characterization of [3H]flunitrazepam binding to melanin
    Open this publication in new window or tab >>Characterization of [3H]flunitrazepam binding to melanin
    Show others...
    2001 (English)In: Analytical Biochemistry, ISSN 0003-2697, E-ISSN 1096-0309, Vol. 298, no 2, 259-264 p.Article in journal (Refereed) Published
    Abstract [en]

    In both clinical and forensic toxicology, the analysis of hair for drugs is an important tool to determine drug use in the past or to verify abstinence from illegal drugs during extended periods. Melanin is proposed as one of the factors that influences drug incorporation to hair and we have characterized the binding of the drug flunitrazepam to melanin in vitro. The drug was 3H labeled and melanin granules from cuttlefish, Sepia officinalis, were used according to the suggested standard for melanin studies. We observed a rapid Langmuir-like binding followed by a slower diffusion-limited binding that may be interpreted as an initial surface binding followed by deeper bulk binding. From three concentrations of melanin, with a 60-min incubation time, a mean saturation value of 180 ± 20 pmol/mg was calculated. The binding of a group of benzodiazepines and tranquilizers was compared to the binding of [3H]flunitrazepam by means of displacement experiments. These drugs showed binding characteristics similar to [3H]flunitrazepam except phenobarbital, which had a lower affinity to melanin. The method presented in this study allowed measurements with low melanin and drug concentrations and it has the strength of directly measuring the amount of drug bound to melanin, in contrast to previous indirect methods.

    Keyword
    Affinity, Benzodiazepines, Binding, Hair, Melanin
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-47156 (URN)10.1006/abio.2001.5364 (DOI)
    Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2013-02-22Bibliographically approved
  • 18.
    Good, Lars
    Linköping University, Department of Neuroscience and Locomotion, Orthopaedics and Sports Medicine. Linköping University, Faculty of Health Sciences.
    Anterior cruciate ligament reconstruction: Anatomic and biomechanical considerations of graft placement and fixation1993Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This study, comprising 7 separate papers, is concerned with the mechanical causes of graft failure after intraarticular reconstruction of the anterior cruciate ligament (ACL). The study is predominantly experimental in design, but a clinical follow-up is also included to test a causal hypothesis of secondary graft elongation.

    Fixations of synthetic ACL substitutes with ligament staples had low security and the maximum tolerance loads were in parity with forces generated during daily activities, while screw fixations of looped ligaments had higher load to failure than a normal ACL.

    A stenosis, caused by osteophyte formation, was found at the intercondylar notch less than 2 years after an ACL tear, strongly suggesting impingement and wear as a possible mechanism of ACL substitute failure. The intercondylar notch was also found to be narrowed in patients with an acute tear of the ACL compared to a normal control group, thus implying causality.

    A standardized technique of graft placement, using a guide to aid bone drilling, was found more accurate and reproducible in achieving desired graft insertions compared to freehand drilling. This was evaluated by a new method for detennining the graft insertion locations on the femur and tibia, using a ratio related to the sagittal depth of the condyles.

    The ability to restore knee kinematics from an ACL deficient state, was evaluated for a drill guided graft route and an over-the-top route. The only effect of both methods, using a dacron graft tensioned in full extension, was restoring or partially restoring the increased anterior -posterior translation.

    A good in vitro and in vivo correlation was found between the patterns of change in dynamic fixation distance, as measured intraoperatively with an isometer, and tension in the fixed ACL substitute. The isometry measurement could not predict the magnitude of the frnal tension due to the biological variability in soft tissue compliance.

    Sagittal knee stability was measured at regular intervals for 2 years on patients who had an intraarticular ACL reconstruction with a patellar tendon substitute. Increasing anterior-posterior displacement was found for all patients as a group, and more for patients with an anterior femoralligament insertion location.

    A standardized treatment including aided bone drilling, notch plasty, isometry measurement, and restricted postoperative rehabilitation is recommended.

  • 19.
    COLBY, J
    et al.
    UNIV NEWCASTLE UPON TYNE,SCH MED,DEPT MICROBIOL,NEWCASTLE TYNE NE1 7RU,TYNE and WEAR,ENGLAND; CRANFIELD INST TECHNOL,CTR BIOTECHNOL,CRANFIELD MK43 0AL,BEDS,ENGLAND; .
    WILLIAMS, E
    UNIV NEWCASTLE UPON TYNE,SCH MED,DEPT MICROBIOL,NEWCASTLE TYNE NE1 7RU,TYNE and WEAR,ENGLAND; CRANFIELD INST TECHNOL,CTR BIOTECHNOL,CRANFIELD MK43 0AL,BEDS,ENGLAND; .
    TURNER, APF
    Cranfield University, UK.
    APPLICATIONS OF CO-UTILIZING MICROORGANISMS1985In: Trends in Biotechnology, ISSN 0167-7799, E-ISSN 1879-3096, Vol. 3, no 1, 12-17 p.Article, review/survey (Refereed)
    Abstract [en]

    n/a

  • 20.
    Sjölén, Jacob
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Arc evaporated wear-resistant nitride coatings for metal cutting tools2008Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This Thesis is dedicated to increase the understanding of arc evaporated PVD coatings as wear resistant layers on metal cutting tools. The approach is to study coatings that have excellent performance in metal cutting applications, specifically (Ti,Al)N and (Ti,Si)N in terms of thermal and mechanical properties, and to correlate this to their microstructure, stress state, and composition. The effect of addition of oxygen into (Ti,Al)N is also evaluated in terms of structure, chemical bonding, and mechanical properties. It is shown that metastable fcc-(Ti,Al)N coatings separate into Ti-rich and Al-rich fcc-(Ti,Al)N zones via spinodal decomposition at 800 - 1000 °C, which acts as a hardening mechanism. This is followed by nucleation and growth into the stable phases fcc-TiN and hex-AlN at T>1000°C, with subsequent loss of hardness. These structural changes are correlated to the cutting performance, showing that the initial spinodal phase separation improves the performance. The success of (Ti,Al)N in metal cutting applications is, hence, due not only to the well documented oxidation resistance, but also to the spinodal decomposition process, which is active at the typical temperatures at the cutting edge of an engaged cutting insert. The potential subsequent renucleation process is, however, detrimental in metal cutting applications. Oxygen is commonly regarded as a contamination in PVD coating processes due to the risk of formation of insulating layers. This study, however, shows that by using arcevaporation, up to 35 at.% O can be incorporated into (Ti,Al)N coatings without altering its NaCl-structure. 1t is inferred that O substitutes for N in the lattice and (Ti,Al)(O,N) is formed. The incorporation of small amounts of oxygen (up to 13 at.%) improves the cutting performance by reducing the risk of chipping. However, at higher oxygen levels, the wear resistant properties are dramatically reduced. Finally, is shown that it is poss ible to replace at least 14 at.% Ti by Si, without altering the NaCl-structure in (Ti,Si)N coatings. The measured hardness of solid solution fcc-(Ti,Si)N is nearly a linear function of Si-content in the coating (from 31 GPa in TiN up to 45 GPa in (Ti0.86Si0.14)N). The hardness is also retained after annealing at 900 oC for 2h.

    List of papers
    1. Thermal stability of arc evaporated high aluminum-content Ti1−xAlxN thin films
    Open this publication in new window or tab >>Thermal stability of arc evaporated high aluminum-content Ti1−xAlxN thin films
    Show others...
    2002 (English)In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 20, no 5, 1815-1823 p.Article in journal (Refereed) Published
    Abstract [en]

    The thermal stability of Ti1−xAlxN films deposited by arc evaporation from Ti–Al cathodes with 67 and 75 at. % aluminum, respectively, has been investigated. The microstructure of as-deposited and isothermally annealed samples were studied using scanning electron microscopy, transmission electron microscopy, and x-ray diffraction. The chemical composition and elemental distribution were determined by energy dispersive x ray (EDX), Rutherford backscattering spectrometry, and EDX mapping. Transmission electron micrographs revealed a dense and columnar microstructure in the as-deposited condition. Films deposited from the 67 at. % cathodes were of cubic NaCl-structure phase, whereas films deposited from the 75 at. % cathodes exhibited nanocrystallites of wurzite-structure hexagonal-phase AlN in a cubic (c)-(Ti,Al)N matrix. Both films were stable during annealing at 900 °C/120 min with respect to phase composition and grain size. Annealing at 1100 °C of films deposited from the 67 at. % cathodes resulted in phase separation of c-TiN and h-AlN, via spinodal decomposition of c-TiN and c-AlN. (Ti,Al)N films undergo extensive stress relaxation and defect annihilation at relatively high temperatures, and aspects of these microstructural transformations are discussed.

    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-18801 (URN)10.1116/1.1503784 (DOI)
    Available from: 2009-06-08 Created: 2009-06-04 Last updated: 2016-08-31Bibliographically approved
    2. Self-organized nanostructures in the Ti-Al-N system
    Open this publication in new window or tab >>Self-organized nanostructures in the Ti-Al-N system
    Show others...
    2003 (English)In: Applied Physics Letters, ISSN 0003-6951, Vol. 83, no 10, 2049-2051 p.Article in journal (Refereed) Published
    Abstract [en]

    The phenomenon of age hardening could be evidenced in thin film applications. A model system, Ti1-xAlxN was chosen as such coatings are known for their excellent wear resistance enabling improved machining processes like high-speed and dry cutting. Here, we show unambiguously that metastable Ti1-xAlxN coatings initially undergo spinodal decomposition into coherent cubic-phase nanometer-size domains, causing an increase in hardness at elevated temperatures. These intermediate metastable domains transform into their stable phases TiN and AlN during further thermal treatment. Activation energies for the processes indicate defect-assisted segregation of Ti and Al. The findings are corroborated by ab initio calculations. A long-standing discussion on the thermal stability of this important class of ceramics is thus resolved.

    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-18822 (URN)10.1063/1.1608464 (DOI)
    Available from: 2009-06-08 Created: 2009-06-05 Last updated: 2016-08-31Bibliographically approved
    3. Mechanical properties and machining performance of Ti1−xAlxN-coated cutting tools
    Open this publication in new window or tab >>Mechanical properties and machining performance of Ti1−xAlxN-coated cutting tools
    Show others...
    2005 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 191, no 2-3, 384-392 p.Article in journal (Refereed) Published
    Abstract [en]

    The mechanical properties and machining performance of Ti1−xAlxN-coated cutting tools have been investigated. Processing by arc evaporation using cathodes with a range of compositions was performed to obtain coatings with compositions x=0, x=0.25, x=0.33, x=0.50, x=0.66 and x=0.74. As-deposited coatings with x≤0.66 had metastable cubic structures, whereas x=0.74 yielded two-phase coatings consisting of cubic and hexagonal structures. The as-deposited and isothermally annealed coatings were characterised by nanoindentation, scanning electron microscopy (SEM) and X-ray diffraction (XRD). Cutting tests revealing tool wear mechanisms were also performed. Results show that the Al content, x, promotes a (200) preferred crystallographic orientation and has a large influence on the hardness of as-deposited coatings. The high hardness (∼37 GPa) and texture of the as-deposited Ti1−xAlxN coatings are retained for annealing temperatures up to 950 °C, which indicates a superior stability of this system compared to TiN and Ti(C,N) coatings. We propose that competing mechanisms are responsible for the effectively constant hardness: softening by residual stress relaxation through lattice defect annihilation is balanced by hardening from formation of a coherent nanocomposite structure of c-TiN and c-AlN domains by spinodal decomposition. This example of secondary-phase transformation (age-) hardening is proposed as a new route for advanced surface engineering, and for the development of future generation hard coatings.

    Keyword
    Hard coatings; TiAlN; Age hardening; Spinodal decomposition; Transition; Metal nitrides
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-18823 (URN)10.1016/j.surfcoat.2004.04.056 (DOI)
    Available from: 2009-06-08 Created: 2009-06-05 Last updated: 2016-08-31Bibliographically approved
    4. Structure and mechanical properties of arc evaporated Ti–Al–O–N thin films
    Open this publication in new window or tab >>Structure and mechanical properties of arc evaporated Ti–Al–O–N thin films
    Show others...
    2007 (English)In: Surface & Coatings Technology, ISSN 0257-8972, Vol. 201, no 14, 6392-6403 p.Article in journal (Refereed) Published
    Abstract [en]

    The structure, mechanical properties, and machining performance of arc evaporated Ti–Al–O–N coatings have been investigated for an Al0.66Ti0.34 target composition and O2/(O2+N2) gas flow-ratio varied between 0 to 24%. The coating structure was analysed using SEM, EDX, XRD, XPS, TEM, and STEM. Mechanical properties were analysed using nanoindentation and the deformation behaviour was analysed by probing the nanoindentation craters. The coatings performances in cutting tests were evaluated in a turning application in low carbon steel (DIN Ck45). It is shown that the addition of oxygen into the arc deposition process leads to the formation of a dual layer structure. It consists of an initial cubic NaCl-structure solid solution phase formed closest to the substrate, containing up to 35 at.% oxygen (O/O+N), followed by steady-state growth of a nanocomposite compound layer comprised of Al2O3, AlN, TiN, and Ti(O,N). The addition of oxygen increases the ductility of the coatings, which improves the performances in cutting tests. At high levels of oxygen, (>13 at.%), however, the performance is dramaticallyreduced as a result of increased crater wear.

    Keyword
    TiAlON; Arc-evaporation; Nanostructure; Mechanical properties
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-18825 (URN)10.1016/j.surfcoat.2006.12.006 (DOI)
    Available from: 2009-06-08 Created: 2009-06-05 Last updated: 2016-08-31Bibliographically approved
    5. Influence of Si on the Microstructure of Arc Evaporated (Ti,Si)N Thin Films: Evidence for Cubic Solid Solutions and their Thermal Stability
    Open this publication in new window or tab >>Influence of Si on the Microstructure of Arc Evaporated (Ti,Si)N Thin Films: Evidence for Cubic Solid Solutions and their Thermal Stability
    Show others...
    2005 (English)In: Surface and Coatings Technology, ISSN 0257-8972, Vol. 200, no 5-6, 1535-1542 p.Article in journal (Refereed) Published
    Abstract [en]

    Ti1−xSixN (0 ≤ x ≤ 0.14) thin solid films were deposited onto cemented carbide (WC-Co) substrates by arc evaporation. X-ray diffraction and transmission electron microscopy showed that all films were of NaCl-structure type phase. The as-deposited films exhibited a competitive columnar growth mode where the structure transits to a feather-like nanostructure with increasing Si content. Films with 0 ≤ x ≤ 0.01 had a 111 crystallographic preferred orientation which changed to an exclusive 200 texture for 0.05 ≤ x ≤ 0.14. X-ray photoelectron spectroscopy revealed the presence of Si–N bonding, but no amorphous Si3N4. Band structure calculations performed using a full potential linear muffin tin orbital method showed that for a given NaCl-structure Ti1−xSixN solid solution, a phase separation into cubic SiN and TiN is energetically favorable. The microstructure was maintained for the Ti0.86Si0.14N film annealed at 900 °C, while recrystallization in the cubic state took place at 1100 °C annealing during 2 h. The Si content influenced the film hardness close to linearly, by combination of solid-solution hardening in the cubic state and defect hardening. For x = 0 and x = 0.14, nanoindentation gave a hardness of 31.3 ± 1.3 GPa and 44.7 ± 1.9 GPa, respectively. The hardness was retained after annealing at 900 °C, while it decreased to below 30 GPa for 1100 °C following recrystallization and W and Co interdiffusion.

    Keyword
    Nitrides; Arc evaporation; Transmission electron microscopy (TEM); Thin films; Solid solution; Microstructure
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-14144 (URN)10.1016/j.surfcoat.2005.08.096 (DOI)
    Available from: 2006-11-15 Created: 2006-11-15 Last updated: 2016-08-31
  • 21.
    Iovino, Maria Rosa
    et al.
    Servizio Archeologico, Soprintendenza ai BB.CC.AA., Catania, Italy.
    Maniscalco, Laura
    Servizio Archeologico, Soprintendenza ai BB.CC.AA., Catania, Italy.
    Pappalardo, Giuseppe
    LANDIS, National Institute of Nuclear Physics (INFN)-LNS, Catania, Italy; University of Catania, Italy.
    Pappalardo, Lighea
    LANDIS, National Institute of Nuclear Physics (INFN)-LNS, Catania, Italy; IBAM-CNR, Catania, Italy.
    Puglisi, Donatella
    University of Catania, Italy.
    Rizzo, Francesca
    LANDIS, National Institute of Nuclear Physics (INFN)-LNS, Catania, Italy; University of Catania, Italy.
    Romano, Francesco Paolo
    LANDIS, National Institute of Nuclear Physics (INFN)-LNS, Catania, Italy; IBAM-CNR, Catania, Italy.
    Archaeological volcanic glass from the site of Rocchicella (Sicily, Italy)2008In: Archaeometry, ISSN 0003-813X, E-ISSN 1475-4754, Vol. 50, no 3, 474-494 p.Article in journal (Refereed)
    Abstract [en]

    The site of Rocchicella, near Catania, in eastern Sicily, has yielded important archaeological evidence from prehistoric times to the Middle Ages. Extensive archaeological investigations of cultural layers dating from the Palaeo-Mesolithic to the Copper Age have recently been undertaken, and volcanic glass, mainly obsidian, has been collected in the course of excavation. To determine the provenance of this volcanic glass, a non-destructive elemental analysis was carried out to measure the concentration of characteristic trace elements. The analysis was carried out using a new XRF spectrometer equipped with a beam stability controller and a quantitative method developed at the LANDIS laboratory of the INFN–CNR Institutes of Catania. In addition to the obsidian, it was demonstrated for the first time that a local vitreous material similar to obsidian, but displaying a completely different composition, was used during all the investigated periods. This material was identified as a basaltic glass, characterized by a superficial product of devitrification called palagonite. Analysis of the obsidians has led to the identification of the island of Lipari as the provenance source. High- and low-power microscopic use-wear analysis on obsidian and basaltic glass artefacts indicated that soft wood and plant matter might have been processed at the site.

  • 22.
    Sandgren, B.
    et al.
    Karolinska Institute, Sweden.
    Skorpil, M.
    Karolinska Institute, Sweden.
    Nowik, P.
    Karolinska Institute, Sweden; Karolinska University Hospital, Sweden.
    Olivecrona, H.
    Karolinska Institute, Sweden.
    Crafoord, J.
    Karolinska Institute, Sweden; Ersta Hospital, Sweden.
    Weidenhielm, L.
    Karolinska Institute, Sweden; Karolinska Institute, Sweden.
    Persson, Anders
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Department of Radiology in Linköping. Linköping University, Center for Medical Image Science and Visualization (CMIV). Karolinska Institute, Sweden.
    Assessment of wear and periacetabular osteolysis using dual energy computed tomography on a pig cadaver to identify the lowest acceptable radiation dose2016In: BONE and JOINT RESEARCH, ISSN 2046-3758, Vol. 5, no 7, 307-313 p.Article in journal (Refereed)
    Abstract [en]

    Objectives Computed tomography (CT) plays an important role in evaluating wear and periacetabular osteolysis (PAO) in total hip replacements. One concern with CT is the high radiation exposure since standard pelvic CT provides approximately 3.5 millisieverts (mSv) of radiation exposure, whereas a planar radiographic examination with three projections totals approximately 0.5 mSv. The objective of this study was to evaluate the lowest acceptable radiation dose for dual-energy CT (DECT) images when measuring wear and periacetabular osteolysis in uncemented metal components. Materials and Methods A porcine pelvis with bilateral uncemented hip prostheses and with known linear wear and acetabular bone defects was examined in a third-generation multidetector DECT scanner. The examinations were performed with four different radiation levels both with and without iterative reconstruction techniques. From the high and low peak kilo voltage acquisitions, polychrmoatic images were created together with virtual monochromatic images of energies 100 kiloelectron volts (keV) and 150 keV. Results We could assess wear and PAO while substantially lowering the effective radiation dose to 0.7 mSv for a total pelvic view with an accuracy of around 0.5 mm for linear wear and 2 mm to 3 mm for PAO. Conclusion CT for detection of prosthetic wear and PAO could be used with clinically acceptable accuracy at a radiation exposure level equal to plain radiographic exposures.

  • 23.
    Engberg, David
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Atom Probe Tomography of TiSiN Thin Films2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis concerns the wear resistant coating TiSiN and the development of the analysis technique atom probe tomography (APT) applied to this materials system. The technique delivers compositional information through time-of-flight mass spectrometry, with sub-nanometer precision in 3D for a small volume of the sample. It is thus a powerful technique for imaging the local distribution of elements in micro and nanostructures. To gain the full benefits of the technique for the materials system in question, I have developed a method that combines APT with isotopic substitution, here demonstrated by substitution of natN with 15N. This alters the time-of-flight of ions with of one or more N and will thereby enable the differentiation of the otherwise inseparable isotopes 14N and 28Si. Signs of small-scale fluctuations in the data led the development of an algorithm needed to properly visualize these fluctuations. A method to identify the best sampling parameter for visualization of small-scale compositional fluctuations was added to an algorithm originally designed to find the best sampling parameters for measuring and visualizing strong compositional variations. With the identified sampling parameters, the nano-scale compositional fluctuations of Si in the metal/metalloid sub-lattice could be visualized. The existence and size of these fluctuations were corroborated by radial distribution functions, a technique independent of the previously determined sampling parameter. The radial distribution function algorithm was also developed further to ease in the interpretation. The number of curves could thereby be reduced by showing elements, rather than single and molecular ions (of which there were several different kinds). The improvement of the algorithm also allowed interpretation of signs regarding the stoichiometry of SiNy. With a combination of analytical transmission electron microscopy and APT we show Si segregation on the nanometer scale in arc-deposited Ti0.92Si0.0815N and Ti0.81Si0.1915N thin films. APT composition maps and proximity histograms generated from Ti-rich domains show that the TiN contain at least ~2 at. % Si for Ti0.92Si0.08N and ~5 at. % Si for Ti0.81Si0.19N, thus confirming the formation of solid solutions. The formation of relatively pure SiNy domains in the Ti0.81Si0.19N films is tied to pockets between microstructured, columnar features in the film. Finer SiNy enrichments seen in APT possibly correspond to tissue layers around TiN crystallites, thus effectively hindering growth of TiN crystallites, causing TiN renucleation and thus explaining the featherlike nanostructure within the columns of these films.

    List of papers
    1. Resolving Mass Spectral Overlaps in Atom Probe Tomography by Isotopic Substitutions: Case of TiSi15N
    Open this publication in new window or tab >>Resolving Mass Spectral Overlaps in Atom Probe Tomography by Isotopic Substitutions: Case of TiSi15N
    Show others...
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Mass spectral overlaps in atom probe tomography (APT) analyses of complex compounds typically limit the identification of elements and microstructural analysis of a material. This study concerns the TiSiN system, chosen because of severe mass-to-charge-state ratio overlaps of the 14N+ and 28Si2+ peaks as well as the 14N and 28Si2+ peaks. By substituting 14N with 15N, mass spectrum peaks generated by ions composed of one or more N atoms will be shifted toward higher mass-to-charge-state ratios, thereby enabling the separation of N from the predominant Si isotope. We thus resolve thermodynamically driven Si segregation on the nanometer scale in cubic phase Ti1-xSix15N thin films for Si contents 0.08 ≤ x ≤ 0.19 by APT, as corroborated by transmission electron microscopy. The APT analysis yields a composition determination that is in good agreement with energy dispersive X-ray spectroscopy and elastic recoil detection analyses. Additionally, a method for determining good voxel sizes for visualizing small-scale fluctuations is presented and demonstrated for the TiSiN system.

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-122721 (URN)
    Available from: 2015-11-18 Created: 2015-11-18 Last updated: 2016-08-31Bibliographically approved
    2. Solid Solution and Segregation Effects in Arc-Deposited Ti1-xSixN Thin Films Resolved on the nanometer scale by 15N Isotopic Substitution in AtomP robe Tomography
    Open this publication in new window or tab >>Solid Solution and Segregation Effects in Arc-Deposited Ti1-xSixN Thin Films Resolved on the nanometer scale by 15N Isotopic Substitution in AtomP robe Tomography
    Show others...
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Nanostructured TiSiN is an important material in wear--‐resistant coatings for extending the lifetime of cutting tools. Yet, the understanding regarding the structure, phase composition, and bonding on the detailed nanometer scale, which determines the properties of TiSiN, is lacking. This limits our understanding of the growth phenomena and eventually a larger exploitation of the material. By substituting natN2 with 15N2 during reactive arc deposition of TiSiN thin films, atom probe tomography (APT) gives elemental sensitivity and sub-nanometer resolution, a finer scale than what can be obtained by commonly employed energy dispersive electron spectroscopy in scanning transmission electron microscopy. Using a combination of analytical transmission electron microscopy and APT we show that arc-deposited Ti0.92Si0.0815N and Ti0.81Si0.1915N exhibit Si segregation on the nanometer scale in the alloy films. APT composition maps and proximity histograms from domains with higher than average Ti content show that the TiN domains contain at least ~2 at. % Si for Ti0.92Si0.08N and ~5 at. % Si for Ti0.81Si0.19N, thus confirming the formation of solid solutions. The formation of relatively pure SiNy domains in the Ti0.81Si0.19N films is tied to pockets between microstructured, columnar features in the film. Finer SiNy enrichments seen in APT possibly correspond to tissue layers around TiN crystallites, thus effectively hindering growth of TiN crystallites, causing TiN renucleation and thus explaining the featherlike nanostructure within the columns of these films. For the stoichiometry of the TiN phase, we establish a global under stoichiometry, in accordance with the tendency for SiNy films to have tetrahedral bonding coordination towards a nominal Si3N4 composition.

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-122722 (URN)
    Available from: 2015-11-18 Created: 2015-11-18 Last updated: 2016-08-31Bibliographically approved
  • 24.
    Pröstl, Susanne
    Linköping University, Department of Science and Technology, Communications and Transport Systems.
    Attitudes and beliefs of students towards wearing bicycle helmets: A study carried out at Linköping University, Sweden2009Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The most common diagnoses after bicycle accidents are head injuries and fractures on arms and legs. At two of three injured cyclists, head injuries are the primary cause of death and bicycle helmets are a good protection against these injuries. Because the brain is very fragile, even a moderate hit can cause a serious injury. Arms and legs can often be treated, while brain damage could be a permanent disability. The main goal of this paper is to find out what makes students at Linköping University wear a bicycle helmet. The specific aim of this paper is to find out why students at Linköping University do not wear a bicycle helmet when they are cycling. The paper is divided into a literature review and a case study. The literature review delivers an insight into the road traffic safety system and the contributing factors that influence road traffic safety. It covers research analysis of experts about human behavior and gives an overview of relevant facts and figures concerning cycling within Sweden as well as within the European Union. The case study is a survey carried out at Linköping University. The method used is paper questionnaire with the target group of students at Linköping University. The result of the questionnaire is that more information regarding bicycle helmets and cycling as such, bicycle helmets for free or at least for reduced prices and to somehow change the attitudes towards bicycle helmets is important to increase the number of students wearing a bicycle helmet at Linköping University. As the most important reasons for not wearing a bicycle helmet, practical problems due to having no opportunity to fix the bicycle helmet secure to the bicycle, the fear of negative appearance and the discomfort of wearing a bicycle helmet have been mentioned. To increase the usage of bicycle helmets measures like increasing the awareness, reducing the helmet price or providing extra features with the helmet, based on the results of the literature review and the questionnaire, are suggested at the end of this paper.

  • 25.
    Ilestrand, Maja
    Linköping University, Department of Electrical Engineering, Computer Vision.
    Automatic Eartag Recognition on Dairy Cows in Real Barn Environment2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    All dairy cows in Europe wear unique identification tags in their ears. These eartags are standardized and contains the cows identification numbers, today only used for visual identification by the farmer. The cow also needs to be identified by an automatic identification system connected to milk machines and other robotics used at the farm. Currently this is solved with a non-standardized radio transmitter which can be placed on different places on the cow and different receivers needs to be used on different farms. Other drawbacks with the currently used identification system are that it is expensive and unreliable. This thesis explores the possibility to replace this non standardized radio frequency based identification system with a standardized computer vision based system. The method proposed in this thesis uses a color threshold approach for detection, a flood fill approach followed by Hough transform and a projection method for segmentation and evaluates template matching, k-nearest neighbour and support vector machines as optical character recognition methods. The result from the thesis shows that the quality of the data used as input to the system is vital. By using good data, k-nearest neighbour, which showed the best results of the three OCR approaches, handles 98 % of the digits.

  • 26.
    Hultman, Lars
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hörling, Anders
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Auto-organized nanostructures in the Ti-Al-N thin film system2004In: SURFACES AND INTERFACES IN NANOSTRUCTURED MATERIALS AND TRENDS IN LIGA, MINIATURIZATION, AND NANOSCALE MATERIALS: Fifth MPMD Global Innovations Symposium / [ed] Mukhopadhyay, SM; Seal, S; Dahotre, N; Agarwal, A; Smugeresky, JE; Moody, N, John Wiley & Sons, 2004, 163-172 p.Conference paper (Refereed)
    Abstract [en]

    Age hardening by spinodal decomposition in ceramic thin film systems is reviewed. This is a new concept for advanced surface engineering with applications for wear-resistant coatings in machining processes like high-speed and dry cutting. The reactive arc deposition method with relatively low substrate temperatures is employed to produce supersaturated solid solutions of the material by ion-bombardment-induced mixing of atoms and kinetic limitation to reduce thermodynamically-driven segregation during synthesis. It is shown using electron microscopy, X-ray diffraction, and nanoindentation techniques that Ti1-xAlxN (0 less than or equal to x less than or equal to 1) coatings with compositions in the miscibility gap undergo spinodal decomposition during annealing at temperatures between similar to900 degreesC and 1100 degreesC. As a result, coherent cubic-phase nanometer-size domains form that cause an increase in hardness. These intermediate metastable domains transform into their stable phases TiN and hexagonal wurtzite-structure AlN during further thermal treatment. The findings are corroborated by Ab initio calculations of phase stability and molar volume for competing phases. Activation energies for the processes indicate defect-assisted segregation of Ti and Al. It is inferred that the success of Ti1-xAlxN coatings is not only based on its superior oxidation resistance, but also on its ability for self-adaptation to the thermal load applied during cutting by age hardening. The findings and experimental approach have implications also for other ternary and multinary ceramic systems including the group-III nitride alloys.

  • 27.
    Nolén, Sixten
    et al.
    Linköping University, Department of Department of Health and Society, Division of Preventive and Social Medicine and Public Health Science. Linköping University, Faculty of Health Sciences.
    Ekman, Robert
    Karolinska Institutet, Department of Public Health Sciences, Division of Social Medicine, Stockholm, Sweden and Swedish Rescue Services Agency, National Centre for Learning from Accidents (NCO), Karlskoga, Sweden .
    Lindqvist, Kent
    Linköping University, Department of Department of Health and Society, Division of Preventive and Social Medicine and Public Health Science. Linköping University, Faculty of Health Sciences.
    Bicycle helmet use in Sweden during the 1990s and in the future2005In: Health Promotion International, ISSN 0957-4824, E-ISSN 1460-2245, Vol. 20, no 1, 33-40 p.Article in journal (Refereed)
    Abstract [en]

    This paper describes how the use of bicycle helmets in Sweden has changed for different categories of cyclists from 1988 to 2002, and it also estimates future trends in voluntary wearing of bicycle helmets up to the year 2010. Observational studies of the use of bicycle helmets were conducted once a year from 1988 to 2002 at 157 sites in 21 cities. The subjects observed were children cycling to school (average n = 5471/year) and in their free time (average n = 2191/year), and adults cycling to workplaces and on public bike paths (average n = 29 368/year). The general trend in helmet use from 1988 to 2002 was determined by linear regression analysis, and the results were also employed to estimate future helmet wearing for the period 2003–2010. Differences in helmet use according to gender and size of city were analysed by chi-square tests. From 1988 to 2002, all categories of cyclists showed an upward trend in helmet use (p < 0.01, p < 0.001). Helmet wearing increased from about 20 to 35% among children (≤10 years) cycling during free time, from approximately 5 to 33% among school children, and from around 2 to 14% in adults. Total average helmet use rose from about 4 to 17%. However, during the last 5 years of the study period (1998–2002), none of the categories of cyclists studied showed an upward trend in helmet wearing. It is estimated that ∼30% of cyclists will wear helmets voluntarily by the year 2010, if helmet promotion activities are continued at the same level as previously. The results suggest that Sweden will probably not reach its official goal of 80% helmet use unless a national bicycle helmet law is passed.

  • 28.
    Skoglund, Björn
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Neuroscience and Locomotion, Orthopaedics and Sports Medicine.
    Larsson, L
    Aspenberg, Per
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Neuroscience and Locomotion, Orthopaedics and Sports Medicine. Östergötlands Läns Landsting, Orthopaedic Centre, Department of Orthopaedics Linköping.
    Bone-resorptive effects of endotoxin-contaminated high-density polyethylene particles spontaneously eliminated in vivo2002In: Journal of Bone and Joint Surgery, ISSN 0301-620X, Vol. 84, no 5, 767-773 p.Article in journal (Refereed)
    Abstract [en]

    Wear particles commonly used for experiments may carry adherent endotoxin on their surfaces, which may be responsible for the observed effects. In this study, we attached titanium plates to the tibiae of 20 rats. After osseointegration, endotoxin-contaminated or uncontaminated high-density-polyethylene (HDPE) particles were applied. Contaminated specimens showed a dramatic resorption of bone after seven days but new bone filled the site again at 21 days. Uncontaminated specimens showed no resorption. In 18 rats we implanted intramuscularly discs of ultra-high-molecular-weight polyethylene (UHMWPE) with baseline or excess contamination of endotoxin. Excess endotoxin disappeared within 24 hours and the amount of endotoxin remained at baseline level (contamination from production). Uncontaminated titanium discs did not adsorb endotoxin in vivo. The endotoxin was measured by analytical chemistry. Locally-applied endotoxin stimulated bone resorption similarly to that in experiments with wear particles. Endotoxin on the surface of implants and particles appeared to be inactivated in situ. A clean implant surface did not adsorb endotoxin. Our results suggest that endotoxin adhering to orthopaedic implants is not a major cause for concern.

  • 29.
    Berntsson, Fredrik
    Linköping University, Department of Mathematics. Linköping University, The Institute of Technology.
    Boundary identification for an elliptic equation2001Report (Other academic)
    Abstract [en]

    We consider an inverse problem for the two dimensional steady state heat equation. More precisely, the heat equation is valid in a domain Ω, that is a subset of the unit square, temperature and heat-flux measurements are available on the line y = 0, and the sides x = 0 and x = 1 are assumed to be insulated. From these we wish to determine the temperature in the domain Ω. Furthermore, a part of the boundry ∂Ω is considered to be unknown, and must also be determined.

    The problem is ill-posed in the sense that the solution does not depend continuously on the data. We stabilize the computations by replacing the x-derivative in the heat equation by an operator, representing differentiation of least squares cubic splines. We discretize in the x-coordinate, and obtain an initial value problem for a system of ordinary differential equation, which can be solved using standard numerical methods.

    The inverse problem, that we consider in this paper, arises in iron production, where the walls of a melting furnace are subject to physical and chemical wear. In order to avoid a situation where molten metal breaks out the remaining thickness of the walls should constantly be monitored. This is done by recording the temperature at several locations inside the walls. The shape of the interface boundary between the molten iron and the walls of the furnace can then be determined by solving an invers heat conduction problem.

  • 30.
    Berntsson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Mathematics, Scientific Computing.
    Boundary identification for an elliptic equation2002In: Inverse Problems, ISSN 0266-5611, Vol. 18, no 6, 1579-1592 p.Article in journal (Refereed)
    Abstract [en]

    We consider an inverse problem for the two-dimensional steady-state heat equation. More precisely, the heat equation is valid in a domain O, that is a subset of the unit square. Temperature and heat-flux measurements are available on the line y = 0, and the sides x = 0 and 1 are assumed to be insulated. From these we wish to determine the temperature in the domain O. Furthermore, a part of the boundary ?O is considered to be unknown, and must also be determined. The problem is ill-posed in the sense that the solution does not depend continuously on the data. We stabilize the computations by replacing the x-derivative in the heat equation by an operator, representing differentiation of least-squares cubic splines. We discretize in the x-coordinate, and obtain an initial value problem for a system of ordinary differential equations, which can be solved using standard numerical methods. The inverse problem that we consider in this paper arises in iron production, where the walls of a melting furnace are subject to physical and chemical wear. In order to avoid a situation where molten metal breaks out the remaining thickness of the walls should constantly be monitored. This is done by recording the temperature at several locations inside the walls. The shape of the interface boundary between the molten iron and the walls of the furnace can then be determined by solving an inverse heat conduction problem.

  • 31.
    Berlind, Torun
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Carbon Nitride: Characterization and Protein Interactions2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis concerns synthesis and characterization of carbon-based materials and theinvestigation of the possible use, of a selection of these materials, in biomedicalapplications. Protein adsorption and blood plasma tests were used for this purposeutilizing a surface sensitive technique called spectroscopic ellipsometry.

    The materials were synthesized by physical vapor deposition and characterizedregarding microstructure, mechanical properties and optical properties. The ternaries BC-N and Si-C-N as well as carbon and carbon nitrides (CNx) of different microstructureshave been examined. In the B-C-N work, the intention was to investigate the possibilityto combine the two materials CNx and BN, interesting on their own regarding highhardness and extreme elasticity, to produce a material with even better properties.Theoretical calculations were performed to elucidate the different element substitutionsand defect arrangements in the basal planes promoting curvature in the fullerene-likemicrostructure. The Si-C-N ternary was investigated with the consideration of finding away to control the surface energy for certain applications. Amorphous carbon and threemicrostructures of CNx were analyzed by spectroscopic ellipsometry in the UV-VIS-NIRand IR spectral ranges in order to get further insight into the bonding structure of thematerial.

    In the second part of this work focus was held on studies of macromolecularinteractions on silicon, carbon and CNx film surfaces using ellipsometry. One purposewas to find relevance (or not) for these materials in biological environments. Materials for bone replacement used today, e.g. stainless steel, cobalt-chromium alloys andtitanium alloys suffer from corrosion in body fluids, generation of wear particles inarticulating systems, infections and blood coagulation and cellular damage leading toimpaired functionality and ultimately to implant failure. Artificial heart valves made ofpyrolytic carbon are used today, with friction and wear problems. Thus, there is still aneed to improve biomaterials. The aim of the fourth paper was to investigate theinteraction between carbon-based materials and proteins. Therefore, amorphous carbon(a-C), amorphous (a), graphitic (g) and fullerene-like (FL) CNx thin films were exposedto human serum albumin and blood plasma and the amount of protein was measured insitu using spectroscopic ellipsometry. Surface located and accessible proteins after blood plasma incubations were eventually identified through incubations in antibody solutions.

    Antibody exposures gave indications of surface response to blood coagulation,complement activation and clotting. The a-C and FL-CNx films might according to theresults have a future in soft tissue applications due to the low immuno-activity, whereasthe g-CNx film possibly might be a candidate for bone replacement applications.

    "Layered" structures of fibrinogen, a fibrous but soft protein involved in manyprocesses in our body, were grown in situ and dynamically monitored by ellipsometry inorder to understand the adsorption process and molecule arrangement onto a siliconsurface.

    In the last paper of this thesis, the effects of ion concentration and proteinconcentration on the refractive index of water-based solutions used in in situ ellipsometrymeasurements were demonstrated and spectral refractive index data for water solutionswith different ionic strengths and protein concentrations have been provided.

    List of papers
    1. Microstructure, mechanical properties, and wetting behaviorof Si-C-N thin films grown by reactive magnetron sputtering
    Open this publication in new window or tab >>Microstructure, mechanical properties, and wetting behaviorof Si-C-N thin films grown by reactive magnetron sputtering
    2001 (English)In: Surface and Coatings Technology, ISSN 0257-8972, Vol. 141, no 2-3, 145-155 p.Article in journal (Refereed) Published
    Abstract [en]

    Silicon–carbon–nitride (Si–C–N) thin films were deposited by reactive magnetron co-sputtering of C and Si targets in a mixed Ar/N2 discharge. Films were grown to a thickness of more than 0.5 μm on graphite and Si(001) substrates held at a negative floating potential of −35 V, and substrate temperature between 100 and 700°C. The total pressure was constant at 0.4 Pa (3 mtorr), and the nitrogen fraction in the gas mixture was varied between 0 and 100%. As-deposited films were analyzed with respect to composition, state of chemical bonding, microstructure, mechanical properties, and wetting behavior by Rutherford backscattering spectroscopy (RBS), energy dispersive spectroscopy (EDS), X-ray photoelectron spectrometry (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), nanoindentation and contact angle measurements, respectively. Depending on the deposition condition, ternary SixCyNz films within the composition range 1≤x≤34 at.%, 34≤y≤81 at.%, and 16.5≤z≤42 at.% were prepared with a textured, amorphous-to-graphite-like microstructure. For Si–C–N films with low Si content, C---C, C---N and Si---C bonds were present. At higher Si content, N preferentially bonds to Si, while less C---N bonds were observed. Films containing more than 12 at.% of Si contained widely dispersed crystallites, 2–20 nm in diameter. Incorporation of a few at.% Si resulted in a dramatic reduction of the film surface energy compared to pure CN films. The measured contact angles using distilled water and glycerol liquids were for some films comparable with those on a polytetrafluoroethylene (PTFE), Teflon® surface. The hardness of Si–C–N films could be varied over the range 9–28 GPa.

    Place, publisher, year, edition, pages
    Elsevier, 2001
    Keyword
    Silicon-carbon-nitride thin films; Magnetron sputtering; Properties
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-19703 (URN)10.1016/S0257-8972(01)01236-1 (DOI)
    Available from: 2009-07-16 Created: 2009-07-16 Last updated: 2016-08-31Bibliographically approved
    2. Fullerene-like B C N thin films a computational andexperimental study
    Open this publication in new window or tab >>Fullerene-like B C N thin films a computational andexperimental study
    Show others...
    2004 (English)In: Materials Science and Engineering B, Vol. 113, no 3, 242-247 p.Article in journal (Refereed) Published
    Abstract [en]

    Ab initio calculations show that the energy cost for incorporating lattice defects such as pentagons and heptagons is significantly reduced for BCN compared to BN, thus promoting bending of basal planes in these compounds. Boron–carbon–nitride (Bsingle bondCsingle bondN) thin films with a fullerene-like (FL) microstructure were then deposited by dual cathode magnetron sputtering from C and B4C targets. Up to 1 μm thick films were grown at a total gas pressure of 3 mTorr (0.4 Pa) in varying Ar/N2 ratios, and substrate temperatures between 225 and 350 °C. Compositional and microstructural studies were performed using RBS, SEM and HREM, respectively. Depending on the deposition condition, ternary BxCyNz films with fullerene-like microstructure could be prepared in agreement with the calculations within the composition range 0 ≤ x ≤ 53, 15 ≤ y ≤ 62, and 24 ≤ z ≤ 50 at.%. Fullerene-like structures also tend to form at lower temperatures in the case of BCN compared to CN. Nanoindentation measurements show that all BxCyNz films exhibited a highly elastic response independent of elemental composition. In addition, the calculations suggest a driving force for C and BN phase separation.

    Place, publisher, year, edition, pages
    Elsevier, 2004
    Keyword
    Ab initio calculations; Fullerene-like materials; BCN compounds; Thin films Reactive magnetron sputtering
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-19704 (URN)10.1016/j.mseb.2004.08.013 (DOI)
    Available from: 2009-07-16 Created: 2009-07-16 Last updated: 2016-08-31Bibliographically approved
    3. Spectroscopic ellipsometry characterization of amorphous carbon and amorphous,graphitic and fullerene-like carbon nitride thin films
    Open this publication in new window or tab >>Spectroscopic ellipsometry characterization of amorphous carbon and amorphous,graphitic and fullerene-like carbon nitride thin films
    Show others...
    2009 (English)In: Thin Solid Films, ISSN 0040-6090, Vol. 517, no 24, 6652-6658 p.Article in journal (Refereed) Published
    Abstract [en]

    Carbon nitride (CNx) and amorphous carbon (a-C) thin films are deposited by reactive magnetron sputtering onto silicon (001) wafers under controlled conditions to achieve amorphous, graphitic and fullerene-like microstructures. As-deposited films are analyzed by Spectroscopic Ellipsometry in the UV–VIS–NIR and IR spectral ranges in order to get further insight into the bonding structure of the material. Additional characterization is performed by High Resolution Transmission Electron Microscopy, X-ray Photoelectron Spectroscopy, and Atomic Force Microscopy. Between eight and eleven resonances are observed and modeled in the ellipsometrically determined optical spectra of the films. The largest or the second largest resonance for all films is a feature associated with C–N or C–C modes. This feature is generally associated with sp3 C–N or sp3 C–C bonds, which for the nitrogen-containing films instead should be identified as a three-fold or two-fold sp2 hybridization of N, either substituted in a graphite site or in a pyridine-like configuration, respectively. The π→πlow asterisk electronic transition associated with sp2 C bonds in carbon films and with sp2 N bonds (as N bonded in pyridine-like manner) in CNx films is also present, but not as strong. Another feature present in all CNx films is a resonance associated with nitrile often observed in carbon nitrides. Additional resonances are identified and discussed and moreover, several new, unidentified resonances are observed in the ellipsometric spectra.

    Place, publisher, year, edition, pages
    Elsevier, 2009
    Keyword
    Carbon nitride; Amorphous carbon; Spectroscopic ellipsometry; Spectral decomposition; Fullerene-like; Structural properties; X-ray photoelectron spectroscopy; Transmission electron microscopy
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-19705 (URN)10.1016/j.tsf.2009.04.065 (DOI)
    Note
    Original Publication: Torun Berlind, Andrej Furland, Zs. Czigany, Jörg Neidhardt, Lars Hultman and Hans Arwin, Spectroscopic ellipsometry characterization of amorphous carbon and amorphous,graphitic and fullerene-like carbon nitride thin films, 2009, Thin Solid Films, (517), 24, 6652-6658. http://dx.doi.org/10.1016/j.tsf.2009.04.065 Copyright: Elsevier Science B.V., Amsterdam. http://www.elsevier.com/ Available from: 2009-07-16 Created: 2009-07-16 Last updated: 2016-08-31Bibliographically approved
    4. Protein adsorption on thin films of carbon and carbon nitride monitored with in situ ellipsometry
    Open this publication in new window or tab >>Protein adsorption on thin films of carbon and carbon nitride monitored with in situ ellipsometry
    2011 (English)In: ACTA BIOMATERIALIA, ISSN 1742-7061, Vol. 7, no 3, 1369-1378 p.Article in journal (Refereed) Published
    Abstract [en]

    Amorphous carbon and amorphous, graphitic and fullerene-like carbon nitride thin filmswere deposited by reactive magnetron sputtering and optically characterized withspectroscopic ellipsometry. The films were exposed to human serum albumin and theadsorption was monitored in situ using dynamic ellipsometry. From the ellipsometric data theadsorbed amount of proteins was quantified in terms of surface mass density using de Feijter'smodel. The results indicated larger adsorption of proteins onto the amorphous films comparedto the films with a more ordered microstructure. Complementary studies with labeled HSAusing radioimmunoassay showed up to 6 times higher protein adsorption compared to theellipsometry measurement which partly might be explained by differences in surfaceroughness (from 0.3 to 13 nm) among the films. The elutability of adsorbed labeled HSAusing unlabeled HSA and sodium dodecyl sulphate was low compared to a silicon reference.In addition, the four types of films were incubated in blood plasma followed by antifibrinogen,anti-HMWK or anti-C3c revealing the materials response to complement andcontact activation. Three of the films indicated immunoactivity, whereas the amorphouscarbon showed less immunoactivity compared to a titanium reference. All films showedindications of a stronger ability to initiate the intrinsic pathway of coagulation, compared tothe reference. Finally, the surfaces bone bonding ability was investigated by examination oftheir ability to form calcium phosphate (CaP) crystals in a simulated body fluid, with a-CNxdepositing most CaP after 21 days of incubation.

    Place, publisher, year, edition, pages
    Elsevier Science B.V. Amsterdam, 2011
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-19706 (URN)10.1016/j.actbio.2010.10.024 (DOI)000287643900049 ()
    Note
    Original Publication: Torun Berlind, Pentti Tengvall, Lars Hultman and Hans Arwin, Protein adsorption on thin films of carbon and carbon nitride monitored with in situ ellipsometry, 2011, ACTA BIOMATERIALIA, (7), 3, 1369-1378. http://dx.doi.org/10.1016/j.actbio.2010.10.024 Copyright: Elsevier Science B.V. Amsterdam http://www.elsevier.com/ Available from: 2009-07-16 Created: 2009-07-16 Last updated: 2016-08-31Bibliographically approved
    5. Formation and cross-linking of fibrinogen layers monitored with in situ spectroscopic ellipsometry
    Open this publication in new window or tab >>Formation and cross-linking of fibrinogen layers monitored with in situ spectroscopic ellipsometry
    2010 (English)In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 75, no 2, 410-417 p.Article in journal (Other academic) Published
    Abstract [en]

    Thick matrices of fibrinogen with incorporation of a matrix metalloproteinaseinhibitor were covalently bonded on functionalized silicon surfaces using an ethyl-3-dimethyl-aminopropyl-carbodiimide and N-hydroxy-succinimide affinity ligand couplingchemistry. The growth of the structure was followed in situ using dynamic ellipsometryand characterized at steady-state with spectroscopic ellipsometry. The growth wascompared with earlier work on ex situ growth of fibrinogen layers studied by singlewavelength ellipsometry. It is found that in situ growth and ex situ growth yield differentstructural properties of the formed protein matrix. Fibrinogen matrices with thicknessesup to 58 nm and surface mass densities of 1.6 μg/cm2 have been produced.

    Keyword
    Fibrinogen, ellipsometry, coupling chemistry, protein adsorption
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-19707 (URN)10.1016/j.colsurfb.2009.09.013 (DOI)000276921900004 ()
    Note
    Original Publication: Torun Berlind, Michal Poksinski, Pentti Tengvall and Hans Arwin, Formation and cross-linking of fibrinogen layers monitored with in situ spectroscopic ellipsometry, Colloids and Surfaces B: Biointerfaces, 2010, (75), 2, 410-417. http://dx.doi.org/10.1016/j.colsurfb.2009.09.013 Copyright: Elsevier Science B.V., Amsterdam. http://www.elsevier.com/ Available from: 2009-07-16 Created: 2009-07-16 Last updated: 2013-10-14Bibliographically approved
    6. Effects of ion concentration on refractive indices offluids measured by the minimum deviation technique
    Open this publication in new window or tab >>Effects of ion concentration on refractive indices offluids measured by the minimum deviation technique
    Show others...
    2008 (English)In: Physica Status Solidi. C, Current topics in solid state physics, ISSN 1610-1634, Vol. 5, no 5, 1249-1252 p.Article in journal (Refereed) Published
    Abstract [en]

    The prism minimum deviation technique has been used to measure the fluid dependence of refractive indices. Fluids with varying ion concentration (0 to 1.0 M) and varying protein concentration (0.01-10 mg/ml) have been examined and the measurements show that these parameters influence the refractive index values. Also it is shown by simulations that it is important to take the change of refractive index of the fluid into account when evaluating insitu protein adsorption measurements.

    Place, publisher, year, edition, pages
    Weinheim: WILEY-VCH Verlag GmbH & Co. KGaA, 2008
    Keyword
    07.60.Fs, 78.20.Ci, 87.14.E-
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-19708 (URN)10.1002/pssc.200777897 (DOI)
    Available from: 2009-07-16 Created: 2009-07-16 Last updated: 2013-10-14Bibliographically approved
  • 32.
    Eriksson, Anders
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Cathodic Arc Synthesis of Ti-Si-C-N Thin Films: Plasma Analysis and Microstructure Formation2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This Thesis explores the arc deposition process and films of Ti-Si-C-N, inspired by the two ternary systems Ti-Si-N and Ti-C-N, both successfully applied as corrosion and wear resistant films. The correlation between cathode, plasma, and film properties are studied for a comprehensive view on film formation. Novel approaches to adapt arc deposition to form multi-element films are investigated, concluding that the source of C is not a determining factor for film growth. Thus, cubic-phase films of similar properties can be synthesized from processes with either 1) ternary Ti-Si-C cathodes, including the Ti3SiC2 MAX phase, in N2 atmosphere or 2) Ti-Si cathodes in a mixture of N2 and CH4. With the Ti3SiC2 cathodes, superhard (45-50 GPa) cubic-phase (Ti,Si)(C,N) films can be deposited. The structure is nanocrystalline and feather-like, with high Si and C content of 12 and 16 at%, respectively. To isolate the effects of Si on film structure, magnetron sputtered Ti-Si-N films of comparatively low defect density was studied. These films show a strong preference for {200}  growth orientation, and can be grown as a single phase solid solution on MgO(001) substrates up to ~9 at% Si, i.e. considerably higher than the ~5 at% Si above which a feather-like nanocrystalline structure forms in arc deposited films. On (011) and (111) growth surfaces, the films self-organize into TiN columns separated by segregated crystalline-to-amorphous SiNx. The conditions for film growth by arc were investigated through plasma studies, showing that plasma properties are dependent on cathode composition as well as phase structure. Plasma generation from Ti-Si cathodes, with up to 25 at% Si, show higher average ion charge states of Ti and Si compared to plasma from elemental cathodes, which may be related to TiSix phases of higher cohesive energies. The ion energy distributions range up to 200 eV. Furthermore, compositional discrepancies between plasma ions and film infer significant contributions to film growth from Si rich neutral species. This is further supported by depositions with a macroparticle filter, intended for growth of films with low surface roughness, where Si and C contents lower than the stoichiometry of Ti3SiC2 cathodes was measured in both plasma and films. Also the substrate geometry is critical for the film composition in plasma based film deposition, as evidenced by the formation of artificial layering from rotating substrate fixtures common in high capacity arc deposition systems. The layers are characterized by modulations in composition and crystallinity, primarily attributed to preferential resputtering in high ion incidence angle segments repeated through rotation.

    List of papers
    1. Layer Formation by Resputtering in Ti-Si-C Hard Coatings during Large Scale Cathodic Arc Deposition
    Open this publication in new window or tab >>Layer Formation by Resputtering in Ti-Si-C Hard Coatings during Large Scale Cathodic Arc Deposition
    Show others...
    2011 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 205, no 15, 3923-3930 p.Article in journal (Refereed) Published
    Abstract [en]

    This paper presents the physical mechanism behind the phenomenon of self-layering in thin films made by industrial scale cathodic arc deposition systems using compound cathodes and rotating substrate fixture. For Ti-Si-C films, electron microscopy and energy dispersive x-ray spectrometry reveals a trapezoid modulation in Si content in the substrate normal direction, with a period of 4 to 23 nm dependent on cathode configuration. This is caused by preferential resputtering of Si by the energetic deposition flux incident at high incidence angles when the substrates are facing away from the cathodes. The Ti-rich sub-layers exhibit TiC grains with size up to 5 nm, while layers with high Si-content are less crystalline. The nanoindentation hardness of the films increases with decreasing layer thickness.

    Place, publisher, year, edition, pages
    Elsevier, 2011
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-61991 (URN)10.1016/j.surfcoat.2011.02.007 (DOI)000289606000004 ()
    Note

    Original Publication: Anders Eriksson, Jianqiang Zhu, Naureen Ghafoor, Mats Johansson, Jacob Sjölen, Jens Jensen, Magnus Odén, Lars Hultman and Johanna Rosén, Layer Formation by Resputtering in Ti-Si-C Hard Coatings during Large Scale Cathodic Arc Deposition, 2011, Surface & Coatings Technology, (205), 15, 3923-3930. http://dx.doi.org/10.1016/j.surfcoat.2011.02.007 Copyright: Elsevier Science B.V., Amsterdam. http://www.elsevier.com/

    Available from: 2010-11-18 Created: 2010-11-18 Last updated: 2016-08-31
    2. Ti-Si-C-N Thin Films Grown by Reactive Arc Evaporation from Ti3SiC2 Cathodes
    Open this publication in new window or tab >>Ti-Si-C-N Thin Films Grown by Reactive Arc Evaporation from Ti3SiC2 Cathodes
    Show others...
    2011 (English)In: Journal of Materials Research, ISSN 0884-2914, Vol. 26, 874-881 p.Article in journal (Refereed) Published
    Abstract [en]

    Ti-Si-C-N thin films were deposited onto WC-Co substrates by industrial scale arc evaporation from Ti3SiC2 compound cathodes in N2 gas. Microstructure and hardness were found to be highly dependent on the wide range of film compositions attained, comprising up to 12 at.% Si and 16 at.% C. Nonreactive deposition yielded films consisting of understoichiometric TiCx, Ti and silicide phases with high (27 GPa) hardness. At a nitrogen pressure of 0.25-0.5 Pa, below that required for N saturation, superhard, 45-50 GPa, (Ti,Si)(C,N) films with a nanocrystalline feathered structure were formed. Films grown above 2 Pa displayed crystalline phases of more pronounced nitride character, but with C and Si segregated to grain boundaries to form weak grain boundary phases. In abundance of N, the combined presence of Si and C disturb cubic phase growth severely and compromises the mechanical strength of the films.

    Place, publisher, year, edition, pages
    Cambrdige University Press, 2011
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-61992 (URN)10.1557/jmr.2011.10 (DOI)
    Note

    Original Publication: Anders Eriksson, Jianqiang Zhu, Naureen Ghafoor, Jens Jensen, Grzegorz Greczynski, Mats Johansson, Jacob Sjölen, Magnus Odén, Lars Hultman and Johanna Rosén, Ti-Si-C-N Thin Films Grown by Reactive Arc Evaporation from Ti3SiC2 Cathodes, 2011, Journal of Materials Research, (26), 874-881. http://dx.doi.org/10.1557/jmr.2011.10 Copyright: Mrs Materials Research Society http://www.mrs.org/

    Available from: 2010-11-18 Created: 2010-11-18 Last updated: 2016-08-31
    3. Influence of Ar and N2 Pressure on Plasma Chemistry, Ion Energy, and Thin Film Composition during Filtered Arc Deposition from Ti3SiC2 Cathodes
    Open this publication in new window or tab >>Influence of Ar and N2 Pressure on Plasma Chemistry, Ion Energy, and Thin Film Composition during Filtered Arc Deposition from Ti3SiC2 Cathodes
    Show others...
    2014 (English)In: IEEE Transactions on Plasma Science, ISSN 0093-3813, E-ISSN 1939-9375, Vol. 42, no 11, 3498-3507 p.Article in journal (Refereed) Published
    Abstract [en]

    Arc plasma from Ti3SiC2 compound cathodes used in a filtered dc arc system has been characterized with respect to plasma chemistry and charge-state resolved ion energies. In vacuum, the plasma composition is dominated by Ti ions, with concentrations of 84.3, 9.3, and 6.4 at% for Ti, Si, and C ions, respectively. The reduced amount of Si and most notably C compared with the cathode composition is confirmed by analysis of film composition in corresponding growth experiments. The deposition of light-element deficient films is thus related to plasma generation or filter transport. The ion energy distributions in vacuum range up to 140, 90, and 70 eV for Ti, Si, and C, respectively. Corresponding average ion energies of 48, 36, and 27 eV are reduced upon introduction of gas, down to around 5 eV at 0.6 Pa Ar or 0.3 Pa N2 for all species. In vacuum, the charge state distributions of Si and C are shifted to higher values compared with corresponding elemental cathodes, likely caused by changed effective electron temperature of the plasma stemming from compound cathode material and/or by electron impact ionization in the filter. The average ion charge states are reduced upon addition of Ar, ranging between 1.97 and 1.48 for Ti, 1.91 and 1.46 for Si, and 1.25 and 1.02 for C. Similar effects are observed upon introduction of N2, though with more efficient charge state reduction with pressure. It is conceivable that the pressure-induced changes in ion energy and charge state are crucial for the film synthesis from a microstructure evolution point of view, as they affect the ion-surface interactions through supply of energy, especially when substrate biasing is employed during arc deposition from a compound cathode.

    Place, publisher, year, edition, pages
    IEEE Press, 2014
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-86252 (URN)10.1109/TPS.2014.2361867 (DOI)000345067700008 ()
    Available from: 2012-12-12 Created: 2012-12-12 Last updated: 2016-08-31Bibliographically approved
    4. Arc deposition of Ti–Si–C–N thin films from binary and ternary cathodes — Comparing sources of C
    Open this publication in new window or tab >>Arc deposition of Ti–Si–C–N thin films from binary and ternary cathodes — Comparing sources of C
    Show others...
    2012 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 213, 145-154 p.Article in journal (Refereed) Published
    Abstract [en]

    Ti–Si–C–N thin films with composition of 1–11 at.% Si and 1–20 at.% C have been deposited onto cemented carbide substrates by arcing Ti–Si cathodes in a CH4 + N2 gas mixture and, alternatively, through arcing Ti–Si–C cathodes in N2. Films of comparable compositions from the two types of cathodes have similar structure and properties. Hence, C can be supplied as either plasma ions generated from the cathode or atoms from the gas phase with small influence on the structural evolution. Over the compositional range obtained, the films were dense and cubic-phase nanocrystalline, as characterized by X-ray diffraction, ion beam analysis, and scanning and transmission electron microscopy. The films have high hardness (30–40 GPa by nanoindentation) due to hardening from low-angle grain boundaries on the nanometer scale and lattice defects such as growth-induced vacancies and alloying element interstitials.

    Place, publisher, year, edition, pages
    Elsevier, 2012
    Keyword
    Cathodic arc deposition; Reactive deposition; Hard coatings; Compound cathodes; Ti–Si–C–N
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-86253 (URN)10.1016/j.surfcoat.2012.10.038 (DOI)000314081200020 ()
    Available from: 2012-12-12 Created: 2012-12-12 Last updated: 2016-08-31Bibliographically approved
    5. Characterization of plasma chemistry and ion energy in cathodic arc plasma from Ti-Si cathodes of different compositions
    Open this publication in new window or tab >>Characterization of plasma chemistry and ion energy in cathodic arc plasma from Ti-Si cathodes of different compositions
    Show others...
    2013 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 113, no 16Article in journal (Refereed) Published
    Abstract [en]

    Arc plasma from Ti-Si compound cathodes with up to 25 at. % Si was characterized in a DC arc system with respect to chemistry and charge-state-resolved ion energy. The plasma ion composition showed a lower Si content, diverging up to 12 at. % compared to the cathode composition, yet concurrently deposited films were in accordance with the cathode stoichiometry. Significant contribution to film growth from neutrals is inferred besides ions, since the contribution from macroparticles, estimated by scanning electron microscopy, cannot alone account for the compositional difference between cathode, plasma, and film. The average ion charge states for Ti and Si were higher than reference data for elemental cathodes. This result is likely related to TiSix phases of higher cohesive energies in the compound cathodes and higher effective electron temperature in plasma formation. The ion energy distributions extended up to ∼200 and ∼130 eV for Ti and Si, respectively, with corresponding average energies of ∼60 and ∼30 eV. These averages were, however, not dependent on Si content in the cathode, except for 25 at. % Si where the average energies were increased up to 72 eV for Ti and 47 eV for Si.

    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-91729 (URN)10.1063/1.4802433 (DOI)000318550300012 ()
    Available from: 2013-04-30 Created: 2013-04-30 Last updated: 2017-11-03
    6. Nanocolumnar Epitaxial Ti1-xSixN (0 ≤ x ≤ 0.18) Thin Films Grown by Dual Reactive Magnetron Sputtering on MgO (001), (011), and (111) Substrates
    Open this publication in new window or tab >>Nanocolumnar Epitaxial Ti1-xSixN (0 ≤ x ≤ 0.18) Thin Films Grown by Dual Reactive Magnetron Sputtering on MgO (001), (011), and (111) Substrates
    Show others...
    2012 (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Ti1-xSixNy thin films and multilayers have been grown on single-crystal TiN-templated MgO (001), (011), and (111) substrates kept at 550 °C. Elemental Ti and Si targets were used in UVH reactive dual magnetron sputtering in a mixed Ar/N2 discharge. Composition analysis by time-of-flight energy elastic recoil detection analysis show that the films are close to stoichiometric (0.95 ≤ y ≤ 1.00) with respect to TiN over the wide range of Si concentrations 0 ≤ x ≤ 0.22. High-resolution transmission electron microscopy (TEM) combined with scanning TEM and energy dispersive Xray analysis show that all films grow epitaxially for x ≤ 0.18 and that as much as every fifth Ti atom can be replaced by Si (~10 at.%) in Ti1-xSixN(001). For the (011) and (111)-oriented films, however, only 1-2 at.% Si substitutes for Ti. Instead, Si segregates to form crystalline-to-amorphous SiNz (z ≈ 1) tissue phases, which promote the formation of epitaxial TiN nanocolumns. The nanocolumns have preferred {110} interfaces and {200} top facets and grow several hundreds  of nm in length.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-86256 (URN)
    Available from: 2012-12-12 Created: 2012-12-12 Last updated: 2016-08-31
  • 33.
    Eriksson, Anders
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Cathodic Arc Synthesis of Ti-Si-C-N Thin Films from Ternary Cathodes2010Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Cathodic arc deposition is a powerful technique for thin film synthesis, associated with explosive phase transformations resulting in an energetic and highly ionized plasma. This Thesis presents film growth through arc deposition from compound cathodes of Ti3SiC2, providing source material for plasma and films rich in Si and C. The interest for the resulting Ti-Si-C-N films is inspired by the two ternaries Ti-Si-N and Ti-C-N, both successfully applied as corrosion  and wear resistant films, with a potential for synergistic effects in the quarternary system.

    When using a rotating substrate fixture setup, which is common in high capacity commercial deposition systems, the repeated passage though the plasma zone results in growth layers in the films. This effect has been observed in several coating systems, in deposition of various materials, but has not been explained in detail. The here investigated layers are characterized by a compositional modulation in Si and Ti content, which is attributed primarily to preferential resputtering in segments of rotation when the plasma has high incidence angle towards the substrate normal. For depositions in a non-reactive environment, the films consist of primarily understoichiometric TiCx, Ti, and silicide phases, and display a modest hardness (20-30 GPa) slightly improved by a decreasing layer thickness. Hence, the side effects of artificial layering from substrate rotation in deposition systems should be recognized.

    Adding N2 to the deposition process results in reactive growth of nitride material, formed in a wide range of compositions, and thereby enabling investigation of films in little explored parts of the Ti-Si-C-N system. The structure and properties of such films, comprising up to 12 at% Si and 16 at% C, is highly dependent on the supply of N2 during deposition. Superhard (45-50 GPa) cubic-phase (Ti,Si)(C,N) films with a nanocrystalline feathered structure is formed at N-content of 25-30 at%. At higher N2 deposition pressure, C and Si segregate to column and grain boundaries and the cubic phase assumes a more pronounced nitride character. This transformation is accompanied by substantially reduced film hardness to 20 GPa. Ti-Si-C-N films thus display a rich variety of structures with favorable mechanical properties, but in the regime of high Si and C content, the amount of N must be carefully controlled to avoid undesirable formation of weak grain boundary phases based on Si, C and N.

    List of papers
    1. Layer Formation by Resputtering in Ti-Si-C Hard Coatings during Large Scale Cathodic Arc Deposition
    Open this publication in new window or tab >>Layer Formation by Resputtering in Ti-Si-C Hard Coatings during Large Scale Cathodic Arc Deposition
    Show others...
    2011 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 205, no 15, 3923-3930 p.Article in journal (Refereed) Published
    Abstract [en]

    This paper presents the physical mechanism behind the phenomenon of self-layering in thin films made by industrial scale cathodic arc deposition systems using compound cathodes and rotating substrate fixture. For Ti-Si-C films, electron microscopy and energy dispersive x-ray spectrometry reveals a trapezoid modulation in Si content in the substrate normal direction, with a period of 4 to 23 nm dependent on cathode configuration. This is caused by preferential resputtering of Si by the energetic deposition flux incident at high incidence angles when the substrates are facing away from the cathodes. The Ti-rich sub-layers exhibit TiC grains with size up to 5 nm, while layers with high Si-content are less crystalline. The nanoindentation hardness of the films increases with decreasing layer thickness.

    Place, publisher, year, edition, pages
    Elsevier, 2011
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-61991 (URN)10.1016/j.surfcoat.2011.02.007 (DOI)000289606000004 ()
    Note

    Original Publication: Anders Eriksson, Jianqiang Zhu, Naureen Ghafoor, Mats Johansson, Jacob Sjölen, Jens Jensen, Magnus Odén, Lars Hultman and Johanna Rosén, Layer Formation by Resputtering in Ti-Si-C Hard Coatings during Large Scale Cathodic Arc Deposition, 2011, Surface & Coatings Technology, (205), 15, 3923-3930. http://dx.doi.org/10.1016/j.surfcoat.2011.02.007 Copyright: Elsevier Science B.V., Amsterdam. http://www.elsevier.com/

    Available from: 2010-11-18 Created: 2010-11-18 Last updated: 2016-08-31
    2. Ti-Si-C-N Thin Films Grown by Reactive Arc Evaporation from Ti3SiC2 Cathodes
    Open this publication in new window or tab >>Ti-Si-C-N Thin Films Grown by Reactive Arc Evaporation from Ti3SiC2 Cathodes
    Show others...
    2011 (English)In: Journal of Materials Research, ISSN 0884-2914, Vol. 26, 874-881 p.Article in journal (Refereed) Published
    Abstract [en]

    Ti-Si-C-N thin films were deposited onto WC-Co substrates by industrial scale arc evaporation from Ti3SiC2 compound cathodes in N2 gas. Microstructure and hardness were found to be highly dependent on the wide range of film compositions attained, comprising up to 12 at.% Si and 16 at.% C. Nonreactive deposition yielded films consisting of understoichiometric TiCx, Ti and silicide phases with high (27 GPa) hardness. At a nitrogen pressure of 0.25-0.5 Pa, below that required for N saturation, superhard, 45-50 GPa, (Ti,Si)(C,N) films with a nanocrystalline feathered structure were formed. Films grown above 2 Pa displayed crystalline phases of more pronounced nitride character, but with C and Si segregated to grain boundaries to form weak grain boundary phases. In abundance of N, the combined presence of Si and C disturb cubic phase growth severely and compromises the mechanical strength of the films.

    Place, publisher, year, edition, pages
    Cambrdige University Press, 2011
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-61992 (URN)10.1557/jmr.2011.10 (DOI)
    Note

    Original Publication: Anders Eriksson, Jianqiang Zhu, Naureen Ghafoor, Jens Jensen, Grzegorz Greczynski, Mats Johansson, Jacob Sjölen, Magnus Odén, Lars Hultman and Johanna Rosén, Ti-Si-C-N Thin Films Grown by Reactive Arc Evaporation from Ti3SiC2 Cathodes, 2011, Journal of Materials Research, (26), 874-881. http://dx.doi.org/10.1557/jmr.2011.10 Copyright: Mrs Materials Research Society http://www.mrs.org/

    Available from: 2010-11-18 Created: 2010-11-18 Last updated: 2016-08-31
  • 34.
    Nedfors, Nils
    et al.
    Uppsala University, Sweden.
    Tengstrand, Olof
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Flink, Axel
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Jansson, Ulf
    Uppsala University, Sweden.
    Characterization of amorphous and nanocomposite Nb–Si–C thin films deposited by DC magnetron sputtering2013In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 545, 272-278 p.Article in journal (Refereed)
    Abstract [en]

    Two series of Nb–Si–C thin films of different composition have been deposited using DC magnetron sputtering. In the first series the carbon content was kept at about 55 at.% while the Si/Nb ratio was varied and in the second series the C/Nb ratio was varied instead while the Si content was kept at about 45 at.%. The microstructure is strongly dependent on Si content and Nb–Si–C films containing more than 25 at.% Si exhibit an amorphous structure as determined by X-ray diffraction. Transmission electron microscopy, however, induces crystallisation during analysis, thus obstructing a more detailed analysis of the amorphous structure. X-ray photo-electron spectroscopy suggests that the amorphous films consist of a mixture of chemical bonds such as Nb–Si, Nb–C, and Si–C. The addition of Si results in a hardness decrease from 22 GPa for the binary Nb–C film to 18 – 19 GPa for the Si-containing films, while film resistivity increases from 211 μΩcm to 3215 μΩcm. Comparison with recently published results on DC magnetron sputtered Zr–Si–C films, deposited in the same system using the same Ar-plasma pressure, bias, and a slightly lower substrate temperature (300 °C instead of 350 °C), shows that hardness is primarily dependent on the amount of Si–C bonds rather than type of transition metal. The reduced elastic modulus on the other hand shows a dependency on the type of transition metal for the films. These trends for the mechanical properties suggest that high wear resistant (high H/E and H3/E2 ratio) Me–Si–C films can be achieved by appropriate choice of film composition and transition metal.

  • 35.
    Nedfors, Nils
    et al.
    Uppsala University, Sweden.
    Primetzhofer, Daniel
    Uppsala University, Sweden.
    Wang, Liping
    Chinese Academic Science, Peoples R China.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Jansson, Ulf
    Uppsala University, Sweden.
    Characterization of magnetron sputtered Cr-B and Cr-B-C thin films for electrical contact applications2015In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 266, 167-176 p.Article in journal (Refereed)
    Abstract [en]

    We have deposited Cr-B and Cr-B-C thin films by co-sputtering from chromium boride and carbon targets. The binary Cr-B films consist of nanocrystalline and substoichiometric CrB2 - x grains (B/Cr atomic ratio less than= 1.5) with a (101)-texture, where B segregates to the grain boundaries forming a B-rich tissue phase. A hardness of 25 GPa is measured for these films. They have a low wear resistance, attributed to a (101)-texture and limited adhesion. As a consequence, wear debris in the CrB2 - x wear track from delaminated film and steel-to-steel contact between the exposed substrate and the counter surface result in a high friction (0.52-0.78 against stainless steel) making the Cr-B films unsuitable as sliding electric contacts. Cr-B-C films, on the other hand, form a two phase amorphous structure at greater than17 at.% C consisting of an amorphous Cr-rich phase containing both B and C and an amorphous matrix phase containing mainly B and C. The addition of C improves the adhesion and tribological properties and a coefficient of friction of 0.12 is obtained at 38 at.% C. The improved tribological properties are explained by the formation of the matrix phase, which acts as a solid lubricant forming a graphite-like tribofilm during ball-on-disc test. However, the formation of an amorphous structure is not beneficial for the electrical contact resistance, which increases from 0.5 Omega for the Cr-B film to 1.5 and 2.3 Omega for the Cr-B-C films containing 17 and 26 at% C, respectively. Finally, the importance of a chemical analysis of the chromium boride sputtering target composition is discussed. (C) 2015 Published by Elsevier B.V.

  • 36.
    Frykholm, P.
    et al.
    Uppsala University, Sweden .
    Pikwer, A.
    Lund University, Sweden .
    Hammarskjöld, Fredrik
    Linköping University, Department of Clinical and Experimental Medicine, Division of Microbiology and Molecular Medicine. Linköping University, Faculty of Health Sciences.
    Larsson, A.T.
    Gavle Sandviken County Hospital, Sweden .
    Lindgren, S.
    University of Gothenburg, Sweden .
    Lindwall, R.
    Karolinska Institute, Sweden .
    Taxbro, K.
    Ryhov County Hospital, Sweden .
    Oberg, F.
    Karolinska University Hospital Solna, Sweden .
    Acosta, S.
    Lund University, Sweden .
    Akeson, J.
    Lund University, Sweden .
    Clinical guidelines on central venous catheterisation2014In: Acta Anaesthesiologica Scandinavica, ISSN 0001-5172, E-ISSN 1399-6576, Vol. 58, no 5, 508-524 p.Article, review/survey (Refereed)
    Abstract [en]

    Safe and reliable venous access is mandatory in modern health care, but central venous catheters (CVCs) are associated with significant morbidity and mortality, This paper describes current Swedish guidelines for clinical management of CVCs The guidelines supply updated recommendations that may be useful in other countries as well. Literature retrieval in the Cochrane and Pubmed databases, of papers written in English or Swedish and pertaining to CVC management, was done by members of a task force of the Swedish Society of Anaesthesiology and Intensive Care Medicine. Consensus meetings were held throughout the review process to allow all parts of the guidelines to be embraced by all contributors. All of the content was carefully scored according to criteria by the Oxford Centre for Evidence-Based Medicine. We aimed at producing useful and reliable guidelines on bleeding diathesis, vascular approach, ultrasonic guidance, catheter tip positioning, prevention and management of associated trauma and infection, and specific training and follow-up. A structured patient history focused on bleeding should be taken prior to insertion of a CVCs. The right internal jugular vein should primarily be chosen for insertion of a wide-bore CVC. Catheter tip positioning in the right atrium or lower third of the superior caval vein should be verified for long-term use. Ultrasonic guidance should be used for catheterisation by the internal jugular or femoral veins and may also be used for insertion via the subclavian veins or the veins of the upper limb. The operator inserting a CVC should wear cap, mask, and sterile gown and gloves. For long-term intravenous access, tunnelled CVC or subcutaneous venous ports are preferred. Intravenous position of the catheter tip should be verified by clinical or radiological methods after insertion and before each use. Simulator-assisted training of CVC insertion should precede bedside training in patients. Units inserting and managing CVC should have quality assertion programmes for implementation and follow-up of routines, teaching, training and clinical outcome. Clinical guidelines on a wide range of relevant topics have been introduced, based on extensive literature retrieval, to facilitate effective and safe management of CVCs.

  • 37.
    Rönnberg, Jerker
    et al.
    Linköping University, The Swedish Institute for Disability Research. Linköping University, Department of Behavioural Sciences and Learning, Disability Research. Linköping University, Faculty of Arts and Sciences.
    Rudner, Mary
    Linköping University, The Swedish Institute for Disability Research. Linköping University, Department of Behavioural Sciences and Learning, Disability Research. Linköping University, Faculty of Arts and Sciences.
    Zekveld, Adriana A.
    Linköping University, The Swedish Institute for Disability Research. Linköping University, Department of Behavioural Sciences and Learning, Disability Research. Linköping University, Faculty of Arts and Sciences.
    Cognitive Hearing Science: The role of a working memory system for speech understanding in old age2009In: Hearing care for adults / [ed] L. Hickson, Stäfa: Phonak , 2009Chapter in book (Other academic)
    Abstract [en]

    Many older adults with hearing impairment continue to have substantial communication difficulties after being fitted with hearing aids, and many do not choose to wear hearing aids. Two group communication education programs aimed at such older people are described. The 'Keep on Talking' program has a health promotion focus, and is aimed at maintaining communication for older adults living in the community. An experimental group (n = 120) attended the program, and a control group (n = 130) received a communication assessment but no intervention. Significant improvements were found in the experimental participants in terms of knowledge about communication changes with age and about strategies to maintain communication skills. At the follow-up evaluation at 1 year, 45% of the experimental group, compared to 10% of the control group, had acted to improve their communication skills. The 'Active Communication Education' program focuses on the development of problem-solving strategies to improve communication in everyday life situations. Preliminary outcomes have been assessed on a small scale (n = 14) to date. It is concluded that communication programs represent an important adjunct to, or supplement for, the traditional approach that focuses on hearing aid fitting.

  • 38.
    Merrett, Kimberly
    et al.
    Linköping University, Department of Clinical and Experimental Medicine. Linköping University, Faculty of Health Sciences.
    Kozak Ljunggren, Monika
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Health Sciences.
    Mondal, Debasish
    Linköping University, Department of Clinical and Experimental Medicine. Linköping University, Faculty of Health Sciences.
    Griffith, May
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Health Sciences.
    Rafat, Mehrdad
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Health Sciences.
    Collagen Type I: A Promising Scaffold Material for Tissue Engineering and Regenerative Medicine2012In: Type I collagen: biological functions, synthesis & medicinal applications / [ed] Maria Eduarda Henriques and Marcio Pinto, Nova Science Publishers, Inc., 2012, 1-43 p.Chapter in book (Other academic)
    Abstract [en]

    It is now recognized that biological macromolecules such as components of the extracellular matrix (ECM) are important as instructive templates in Regenerative Medicine applications. They are now increasingly used in the development of a new generation of bio-mimetic materials that allow for restoration of function when the self-renewal capacity of a tissue or organ cannot overcome degeneration caused by disease, injury or age-related wear. For example, macromolecules derived from connective tissue have been isolated, chemically modified, and used in medical applications ranging from tissue repair and reconstruction to drug and cell delivery systems. Common ECM macromolecules of vertebrates include collagen, proteoglycans, elastin, and other cell-interactive proteins such as fibronectin and laminin. Of these, type I collagen is the most abundant ECM macromolecule and is the primary scaffolding material that maintains the 3-dimensional structure of tissues and organs within the body. It also provides the micro-environmental milieu for cellular attachment, migration, and proliferation.

    Animal-derived collagen is frequently used in tissue engineering applications due to its biocompatibility, but there are significant concerns about the immunogenicity of xenogeneic material as well as the possibility of pathogen transmission. Most recently, synthetic collagens and recombinant human collagens have been produced for medical application. Regardless of the source, however, macromolecules require processing and chemical treatment in order to improve their stability both in vitro and in vivo. This is most commonly achieved by cross-linking using a variety of agents. Cross-linking also allows for the development of “tailor-made” collagen-based biomaterials that possess specific properties for tissue engineering. Chemical cross-linkers such as glutaraldehyde and epoxy compounds are frequently used but their cytotoxicities have limited their clinical application. This has led to the use of zero-length cross-linkers such as carbodiimides and naturally derived agents such as genipin. Enzymatic cross-linking is becoming an attractive method to induce in situ biomaterial formation due to the mildness of the reaction. Naturally occurring enzymes such as transglutaminase are now commonly used. Photosensitizers used in combination with ultra-violet light irradiation can be used as exogenous cross-linkers. For example, riboflavin in combination with ultra-violet light is used clinically to augment the properties of collagen-based tissues such as the sclera and the cornea.

    Collagen type I is a good candidate for tissue engineering and in vivo delivery systems for cells, proteins, and drugs. Important to its versatile and functional nature are its chemotactic properties, which promote cellular proliferation and differentiation, richness in cross-linking sites, and biodegradability. Collagen based delivery matrices have been reported to improve the results of cell delivery by improving cell viability.

  • 39.
    Bakoglidis, Konstantinos
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Glenat, Herve
    Technosud, France.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Schmidt, Susann
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Grillo, Stefano
    Technosud, France; University of Perpignan, France.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Broitman, Esteban
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Comparative study of macro- and microtribological properties of carbon nitride thin films deposited by HiPIMS2017In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 370Article in journal (Refereed)
    Abstract [en]

    The macro- and microtribological properties of carbon nitride thin films deposited by high power impulse magnetron sputtering at different substrate bias voltages (V-b) were investigated. V-b of -100, -150, -200, and-300 V were used. A Hysitron Triboindenter TI950 and a reciprocating Tribotechnic tribometer with diamond counterparts were used in order to assess the tribological performance of the films at the micro- and macroscale, respectively. Initial Hertzian contact pressures of 2.5 GPa, 3.3 GPa and 3.9 GPa were chosen for the comparative measurements at both scales. At the macroscale, films with higher initial roughness present an increased wear. Debris creation and asperity deformation takes place causing abrasive wear. At the microscale, compression of the surface material occurs. The run-in friction shows similar trends at both scales; an initial decrease and an increase thereafter. Steady-state friction is not reached at the microscale, attributed to the absence of a graphitic tribolayer in the contact. At the macroscale, all films show abrasive wear and debris creation. Here, the changes in friction coefficients are attributed to the debris loss from the contact during the tribotests. The CN film tested at 2.5 GPa shows a continuous increase of friction, due to the continuous loss of debris from the contact. The other films reach a steady-state friction coefficient, since most of the debris is lost before the end of the tribotests. (C) 2016 Elsevier B.V. All rights reserved.

  • 40.
    Karlsson, Hanna L
    et al.
    Karolinska Institutet, Department of Biosciences and Nutrition at Novum, Unit for Analytical Toxicology, Huddinge, Stockholm, Sweden.
    Ljungman, Anders
    Linköping University, Department of Molecular and Clinical Medicine, Occupational and Environmental Medicine. Linköping University, Faculty of Health Sciences.
    Lindbom, John
    Linköping University, Department of Molecular and Clinical Medicine, Occupational and Environmental Medicine. Linköping University, Faculty of Health Sciences.
    Möller, Lennart
    Karolinska Institutet, Department of Biosciences and Nutrition at Novum, Unit for Analytical Toxicology, Huddinge, Stockholm, Sweden.
    Comparison of genotoxic and inflammatory effects of particles generated by wood combustion, a road simulator and collected from street and subway2006In: Toxicology Letters, ISSN 0378-4274, E-ISSN 1879-3169, Vol. 165, no 3, 203-211 p.Article in journal (Refereed)
    Abstract [en]

    The health effects of exposure to airborne particles are of increasing concern in society. In order to protect public health, a clarification of the toxic properties of particles from different sources is of importance. The aim of this study was to investigate and compare the genotoxicity and the ability to induce inflammatory mediators of nine different particle types from wood and pellets combustion, from tire–road wear and collected from an urban street and a subway station. The comet assay was used to assess genotoxicity after exposure of the human lung cell line A549. Inflammatory effects were measured as induction of IL-6, IL-8 and TNF-α after exposure of human macrophages. We found that all particles tested caused DNA damage and those from the subway caused more damage than the other particles (p < 0.001) likely due to redox-active iron. In contrast, particles collected from an urban street were most potent to induce inflammatory cytokines. Particles from tire–road wear collected using a road simulator were genotoxic and able to induce cytokines. Finally, more effective combustion of wood led to less emission of particles, but those emitted did not show less toxicity in this study.

  • 41.
    Ehiasarian, A. P.
    et al.
    Sheffield Hallam University, Sheffield, UK.
    Hovsepian, P. Eh.
    Sheffield Hallam University, Sheffield, UK.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Helmersson, Ulf
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Comparison of microstructure and mechanical properties of chromium nitride-based coatings deposited by high power impulse magnetron sputtering and by the combined steered cathodic arc/unbalanced magnetron technique2004In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 457, no 2, 270-277 p.Article in journal (Refereed)
    Abstract [en]

    Sliding, abrasive, and impact wear tests were performed on chromium nitride (CrN)-based coatings deposited on mirror-polished M2 high speed steel substrates by the novel high power impulse magnetron sputtering (HIPIMS) utilising high peak cathode powers densities of 3000 W cm−2. The coatings were compared to single layer CrN and multilayer superlattice CrN/NbN coatings deposited by the arc bond sputtering (ABS) technique designed to improve the coating substrate adhesion by a combined steered cathodic arc/unbalanced magnetron (UBM) sputtering process. The substrates were metal ion etched using non-reactive HIPIMS or steered cathodic arc at a substrate bias voltage of −1200 V. Subsequently a 2- to 3-μm thick CrN or CrN/NbN coating was deposited by reactive HIPIMS or UBM. No bias was used during the HIPIMS deposition, while the bias during UBM growth was in the range 75–100 V. The ion saturation current measured by a flat electrostatic probe reached values of 50 mA cm−2 peak for HIPIMS and 1 mA cm−2 continuous during UBM deposition. The microstructure of the HIPIMS coatings observed by transmission electron microscopy was fully dense in contrast to the voided columnar structure observed in conventional UBM sputtered CrN and CrN/NbN. The sliding wear coefficients of the HIPIMS CrN films of 2.3×10−16 m3 N−1 m−1 were lower by a factor of 4 and the roughness of the wear track was significantly reduced compared to the UBM-deposited CrN. The abrasive wear coefficient of the HIPIMS coating was 2.2×10−13 m3 N−1 m−1 representing an improvement by a factor of 3 over UBM deposited CrN and a wear resistance comparable to that of the superlattice CrN/NbN. The adhesion of the HIPIMS deposited CrN was comparable to state-of-the-art ABS technology.

  • 42.
    Oberg, A.
    et al.
    ABB Corp Research.
    Kassman, A.
    Uppsala University.
    Andre, B.
    Uppsala University.
    Wiklund, U.
    Uppsala University.
    Lindquist, M.
    ABB Corp Research.
    Lewin, E.
    Uppsala University.
    Jansson, U.
    Uppsala University.
    Högberg, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Joelsson, T.
    Impact Coatings AB.
    Ljungcrantz, H.
    Impact Coatings AB.
    Conductive nanocomposite ceramics as tribological and electrical contact materials2010In: European Physical Journal: Applied physics, ISSN 1286-0042, E-ISSN 1286-0050, Vol. 49, no 2Article in journal (Refereed)
    Abstract [en]

    Conductive ceramics have widespread use in many industrial applications. One important application for such materials is electrical contact technology. Over the last few years, a new class of nanocomposite ceramic thin film materials has been developed with contact coatings as one key objective. This family of materials has proven to combine the favorable contact properties of metals, such as low electrical and thermal resistivity, and high ductility, with those of ceramics such as low friction and wear rate, high chemical integrity and good high-temperature properties. Furthermore, it is also found that the tribological properties of such materials can be tailored by alloying thus creating a triboactive system. The technology is now industrialized, and a practical example of a contact system utilizing a nanocomposite coating for improved performance is given.

  • 43.
    Lundvall, Olle
    Linköping University, Department of Management and Engineering, Mechanics. Linköping University, The Institute of Technology.
    Contact mechanics and noise in gears2004Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis, recent findings in the area of computational contact mechanics are applied to gear technology. The focus of this application is gear noise. One of the main goals is to calculate the so called transmission error, which is a measure that relates structural properties of a gear to gear noise.

    Computational methodologies are developed in order to analyze different types of gear problems. The finite element method forms the basis for the developed models. In addition to the finite element models of the gear wheels, contact laws are used in order to simulate the contact between the gear flanks. These laws are Signorini's contact law and Coulomb's law of friction and by expressing them as B-differential equations the application of Pang's Newton method for B-differential equations is enabled.

    The transmission error is calculated with good accuracy under both quasi-static and dynamic conditions. By incorporating Archard's wear law into the models, predictions of how wear affects the transmission error are made. It is found that wear can have a significant impact on gear noise.

    It is shown that friction by no means can be neglected when calculating the transmission error. In the dynamic calculations of this thesis, friction always increases the dynamic transmission error. It is also concluded that the effect from friction becomes more significant if shaft and bearing stiffnesses are small.

    List of papers
    1. Simulation of wear by use of a nonsmooth Newton method: a spur gear application
    Open this publication in new window or tab >>Simulation of wear by use of a nonsmooth Newton method: a spur gear application
    2001 (English)In: Mechanics of structures and machines (Print), ISSN 0890-5452, Vol. 29, no 2, 223-238 p.Article in journal (Refereed) Published
    Abstract [en]

    This paper presents a method for calculating wear between two elastic bodies in contact. Discrete representations of the bodies are obtained by the finite element method. Constitutive laws representing the behavior of the interacting surfaces are then added. These are Signorini's contact law, Coulomb's law of friction, and Archard's law of wear. By formulating Signorini's contact law and Coulomb's law of friction by means of projection equations, the complete formulation of a time increment of a quasistatic wear-friction evolution problem becomes a system of nonsmooth equations. A modification of Newton's method is applied to solve this system. The method is applied to a spur gear problem in a heavy truck transmission.

    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-47402 (URN)10.1081/SME-100104481 (DOI)
    Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-05-15
    2. Prediction of transmission error in spur gears as a consequence of wear
    Open this publication in new window or tab >>Prediction of transmission error in spur gears as a consequence of wear
    2001 (English)In: Mechanics of structures and machines (Print), ISSN 0890-5452, Vol. 29, no 4, 431-449 p.Article in journal (Refereed) Published
    Abstract [en]

    The aim of this article is to investigate how the so-called transmission error in a gear develops in a wear process. A finite element procedure for calculating wear between two elastic bodies in contact is developed that includes constitutive laws, representing the behavior of the interacting surfaces. When treating a gear problem, large rotations must be included. This is done by analyzing a sequence of finite-element models along with an interpolation procedure. The constitutive laws of interacting surfaces are Signorini's contact law, Coulomb's law of friction, and Archard's law of wear. By formulating both Signorini's contact law and Coulomb's law of friction by means of projection equations, the complete formulation of a time increment of a quasistatic wear-friction evolution problem becomes a system of nonsmooth equations. Then, a modified Newton method is applied to solve this system. The transmission error can be found from the infinitesimal displacement field superposed on the rigid body configuration. Results from the simulations show that wear will increase the peak-to-peak value of the transmission error. This is most significant in a gear when some kind of modification of the gear flank is applied to minimize the transmission error in an initial state.

    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-47232 (URN)10.1081/SME-100107621 (DOI)
    Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-05-15
    3. A flexible multi-body approach for frictional contact in spur gears
    Open this publication in new window or tab >>A flexible multi-body approach for frictional contact in spur gears
    2004 (English)In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 278, no 3, 479-499 p.Article in journal (Refereed) Published
    Abstract [en]

    In the present paper, a large rotational approach for dynamic contact problems with friction is proposed. The approach is used for modelling a spur gear pair with shafts and bearings. The model is obtained by superposing small displacement elasticity on rigid-body motions, and postulating tribological laws on the gear flanks. The finite element method is used to model the elastic properties of the gear pair. Shafts and bearings are represented by linear springs. The tribological laws of the contact interface are Signorini's contact law and Coulomb's law of friction. An important feature of the approach is that the difficulties of impacting mass nodes are avoided. The governing equations of the model are numerically treated by use of the augmented Lagrangian approach. In such manner the geometry of the gear flanks are well represented in the numerical simulations. It is possible to study accurately the consequences of different types of profile modifications as well as flank errors. In this work, the dynamic transmission error is studied. For instance, it turns out that the effect from profile modification is less significant for the transmission error when frictional effects are included.

    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-22562 (URN)10.1016/j.jsv.2003.10.057 (DOI)1828 (Local ID)1828 (Archive number)1828 (OAI)
    Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2017-05-15
    4. Node-to-target formulation in finite element spur gear problems
    Open this publication in new window or tab >>Node-to-target formulation in finite element spur gear problems
    2005 (English)In: Mechanics based design of structures and machines, ISSN 1539-7734, E-ISSN 1539-7742, Vol. 33, no 1, 31-49 p.Article in journal (Refereed) Published
    Abstract [en]

    In this paper, a quasistatic finite element model of a spur gear pair is developed. A node-to-target contact formulation is given, where calculations of initial gaps are based upon the actual geometry of the gear flanks rather than upon a contact node and a facet or a line segment. By using a special contact search algorithm, profile modifications and mounting errors are easily incorporated in the analysis. The problem, which also includes friction, is solved by using a nonsmooth Newton method. The static transmission error can be calculated with accuracy with a relatively small number of nodes along the gear flanks. Several examples are given in order to demonstrate the model.

    Keyword
    Contact, Finite element, Gears, Static transmission error
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-50338 (URN)10.1081/SME-200045797 (DOI)
    Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2013-01-30
  • 44.
    Abbott, Allan
    et al.
    Karolinska Institutet, Stockholm, Sweden; Karolinska University Hospital, Stockholm, Sweden; Bond University, Gold Coast, Australia.
    Möller, Hans
    Karolinska Institutet, Stockholm, Sweden; Karolinska University Hospital, Stockholm, Sweden.
    Gerdhem, Paul
    Karolinska Institutet, Stockholm, Sweden; Karolinska University Hospital, Stockholm, Sweden.
    CONTRAIS: CONservative TReatment for Adolescent Idiopathic Scoliosis: a randomised controlled trial protocol2013In: BMC Musculoskeletal Disorders, ISSN 1471-2474, E-ISSN 1471-2474, Vol. 14, 261Article in journal (Refereed)
    Abstract [en]

    Background:

    Idiopathic scoliosis is a three-dimensional structural deformity of the spine that occurs in children and adolescents. Recent reviews on bracing and exercise treatment have provided some evidence for effect of these interventions. The purpose of this study is to improve the evidence base regarding the effectiveness of conservative treatments for preventing curve progression in idiopathic scoliosis.

    Methods/design:

    Patients: Previously untreated girls and boys with idiopathic scoliosis, 9 to 17 years of age with at least one year of remaining growth and a curve Cobb angle of 25–40 degrees will be included. A total of 135 participants will be randomly allocated in groups of 45 patients each to receive one of the three interventions.Interventions: All three groups will receive a physical activity prescription according to the World Health Organisation recommendations. One group will additionally wear a hyper-corrective night-time brace. One group will additionally perform postural scoliosis-specific exercises.Outcome: Participation in the study will last until the curve has progressed, or until cessation of skeletal growth. Outcome variables will be measured every 6 months. The primary outcome variable, failure of treatment, is defined as progression of the Cobb angle more than 6 degrees, compared to the primary x-ray, seen on two consecutive spinal standing x-rays taken with 6 months interval. Secondary outcome measures include the SRS-22r and EQ5D-Y quality of life questionnaires, the International Physical Activity Questionnaire (IPAQ) short form, and Cobb angle atend of the study.

    Discussion:This trial will evaluate which of the tested conservative treatment approaches that is the most effective for patients with adolescent idiopathic scoliosis.

    Trial registration: NCT01761305

  • 45.
    Martinsson, Joel
    Linköping University, Department of Electrical Engineering, Vehicular Systems.
    Controlled Start Transmission Wet Clutch Temperature Modeling and Application2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Controlled Start Transmissions (CST) can be described as a mechanical transmission combined with a wet clutch for controlled torque output. CST:s are commonly used to start up heavy loads for example mining conveyors. Several CST:s can work together to share the load. The transferred torque is controlled by a hydraulic wet clutch which is a proven technology for high torque transfer and low wear. This thesis is a part of a project to increase the knowledge and improve the CST design and control performance. The heat generation in the wet clutch is the focus of this thesis. Literature review shows that most research is done in order to get high accuracy for smaller clutches and most of the high torque engagements have very short transients.Models for the CST clutch heat generation together with thermal behavior have been developed and investigated. This includes a temperature model together with a kinetic model of the gearbox and a clutch torque model. Validation of separate model components and sensitivity analysis of the parameters are made. The developed model is then analyzed by comparing measurements from a commission site and simulations to get an idea of how much heat is generated.

  • 46.
    Andersson, Jon Martin
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics . Linköping University, The Institute of Technology.
    Controlling the Formation and Stability of Alumina Phases2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]