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  • 1.
    Abelow, Alexis
    et al.
    University of Utah, Salt Lake City, USA.
    Persson, Kristin
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Jager, Edwin
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biosensorer och bioelektronik. Linköpings universitet, Tekniska högskolan.
    Berggren, Magnus
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Zharov, Ilya
    University of Utah, Salt Lake City, USA.
    Electroresponsive Nanoporous Membranes by Coating Anodized Alumina with Poly(3,4-ethylenedioxythiophone) and Polypyrrole2014Inngår i: Macromolecular materials and engineering (Print), ISSN 1438-7492, E-ISSN 1439-2054, Vol. 299, nr 2, s. 190-197Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Electrically-active nanoporous membranes are prepared by coating the surface of anodized alumina with electroactive polymers using vapor phase polymerization with four combinations of conjugated polymers and doping ions: poly(3,4-ethylenedioxythiophone) and polypyrrole, FeCl3 and FeTs3. The permeability of the polymer-coated membranes is measured as a function of the applied electric potential. A reversible three-fold increase is found in molecular flux of a neutral dye for membranes in oxidized state compared to that in the reduced state. After analyzing various factors that may affect the molecular transport through these membranes, it is concluded that the observed behavior results mostly from swelling/deswelling of the polymers and from the confinement of the polymers inside the nanopores.

  • 2.
    Abrikosov, Igor A.
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    Alling, Björn
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Steneteg, Peter
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Hultberg, Lasse
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska fakulteten.
    Hellman, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    Yu Mosyagin, Igor
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten. Department of Theoretical Physics and Quantum Technologies, National Research, Technological University MISiS, Moscow, Russia.
    Lugovskoy, Andrey V.
    Department of Theoretical Physics and Quantum Technologies, National Research, Technological University MISiS, Russia.
    Barannikova, Svetlana A.
    Institute of Strength Physics and Materials Science, Siberian Branch of Russian Academy of Science, Tomsk, Russia; Department of Physics and Engineering, Tomsk State University, Tomsk, Russia.
    Finite Temperature, Magnetic, and Many-Body Effects in Ab Initio Simulations of Alloy Thermodynamics2013Inngår i: TMS2013 Supplemental Proceedings, John Wiley & Sons, 2013, s. 617-626Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    Ab initio electronic structure theory is known as a useful tool for prediction of materials properties. However, majority of simulations still deal with calculations in the framework of density functional theory with local or semi-local functionals carried out at zero temperature. We present new methodological solution.s, which go beyond this approach and explicitly take finite temperature, magnetic, and many-body effects into account. Considering Ti-based alloys, we discuss !imitations of the quasiharmonic approximation for the treatment of lattice vibrations, and present an accurate and easily extendable method to calculate free ,energies of strongly anharmonic solids. We underline the necessity to going beyond the state-of-the-art techniques for the determination of effective cluster interactions in systems exhibiting mctal-to-insulator transition, and describe a unified cluster expansion approach developed for this class of materials. Finally, we outline a first-principles method, disordered local moments molecular dynamics, for calculations of thermodynamic properties of magnetic alloys, like Cr1-x,.AlxN, in their high-temperature paramagnetic state. Our results unambiguously demonstrate importance of finite temperature effects in theoretical calculations ofthermodynamic properties ofmaterials.

  • 3.
    Abrikosov, Igor
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Knutsson, Axel
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Nanostrukturerade material. Linköpings universitet, Tekniska högskolan.
    Alling, Björn
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Tasnádi, Ferenc
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Lind, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Hultman, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Odén, Magnus
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Nanostrukturerade material. Linköpings universitet, Tekniska högskolan.
    Phase Stability and Elasticity of TiAlN2011Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 4, nr 9, s. 1599-1618Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We review results of recent combined theoretical and experimental studies of Ti1−xAlxN, an archetypical alloy system material for hard-coating applications. Theoretical simulations of lattice parameters, mixing enthalpies, and elastic properties are presented. Calculated phase diagrams at ambient pressure, as well as at pressure of 10 GPa, show a wide miscibility gap and broad region of compositions and temperatures where the spinodal decomposition takes place. The strong dependence of the elastic properties and sound wave anisotropy on the Al-content offers detailed understanding of the spinodal decomposition and age hardening in Ti1−xAlxN alloy films and multilayers. TiAlN/TiN multilayers can further improve the hardness and thermal stability compared to TiAlN since they offer means to influence the kinetics of the favorable spinodal decomposition and suppress the detrimental transformation to w-AlN. Here, we show that a 100 degree improvement in terms of w-AlN suppression can be achieved, which is of importance when the coating is used as a protective coating on metal cutting inserts.

  • 4.
    Afshari, Davood
    et al.
    School of Mechanical Engineering, Iran University of Science and Technology, Iran .
    Mohammd, Sedighi
    School of Mechanical Engineering, Iran University of Science and Technology, Iran .
    Zuhier, Barsoum
    Department of Aeronautical and Vehicle Engineering, KTH – Royal Institute of Technology, Sweden .
    Peng, Ru
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    An Approach in Prediction of Failure in Resistance Spot Welded Aluminum 6061-T6 under Quasi-static Tensile Test2012Inngår i: Proceedings of the Institution of mechanical engineers. Part B, journal of engineering manufacture, ISSN 0954-4054, E-ISSN 2041-2975, Vol. 226, nr 6, s. 1026-1032Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this article is to predict the failure load in resistance spot welded aluminum 661-T6 sheets with 2 mm thickness under quasi-static tensile test. Various welding parameters, e.g. welding current, welding time and electrode force are selected to produce welded joints with different quality. The results show that for all the samples in this study only interfacial failure mode was observed in tensile-shear test and no pull-out mode was observed. According to the failure mode, an empirical equation was used for the prediction of failure load based on nugget size and hardness of failure line. Microstructure study has been carried out to investigate microstructural changes in the welded joints. For determination of the minimum hardness, microhardness tests have been carried out to find hardness profiles. The minimum hardness value was observed for a thin layer around the nugget with large and coarse grains. The results show that by using the presented empirical equation, the failure can be predicted with a good agreement only by measuring nugget size.                   .

  • 5. Agmell, Mathias
    et al.
    Ahadi, A
    Zhou, J M
    Peng, Ru
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Bushlya, Volodymyr
    Stahl, J-E
    Modeling Subsurface Deformation Induced by Machining of Inconel 7182017Inngår i: Machining science and technology, ISSN 1091-0344, E-ISSN 1532-2483, Vol. 21, nr 1, s. 103-120Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Traditionally, the development and optimization of the machining process with regards to the subsurface deformation are done through experimental method which is often expensive and time consuming. This article presents the development of a finite element model based on an updated Lagrangian formulation. The numerical model is able to predict the depth of subsurface deformation induced in the high- speed machining of Inconel 718 by use of a whisker-reinforced ceramic tool. The effect that the different cutting parameters and tool microgeometries has on subsurface deformation will be investigated both numerically and experimentally. This research article also addresses the temperature distribution in the workpiece and the connection it could have on the wear of the cutting tool. The correlation of the numerical and experimental investigations for the subsurface deformation has been measured by the use of the coefficient of determination, R2. This confirms that the finite element model developed here is able to simulate this type of machining process with sufficient accuracy.

  • 6.
    Ahmad, Maqsood
    et al.
    Base Engine & Materials Technology, Volvo Group, Gothenburg.
    Peng, Ru
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    König, Mathias
    Materials Technology for Basic Engine, Scania CV, Södertälje.
    Johansson, Sten
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Bending Fatigue Behavior of Blast Cleaned Grey Cast Iron2017Inngår i: Residual Stresses 2016: ICRS-10, Materials Research Proceedings 2 (2016), 2017, Vol. 2, s. 193-198Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents a detailed study on the effect of an industrial blast cleaning process on the fatigue behavior of a grey cast iron with regard to the residual stresses and microstructural changes induced by the process. A comparison was also made to the effect of a machining operation which removed the casting skin layer. The blast cleaning process was found to greatly improve the fatigue resistance in both the low and high cycle regimes with a 75% increase in the fatigue limit. Xray diffraction measurements and scanning electron microscopic analyses showed that the improvement was mainly attributed to compressive residual stresses in a surface layer up to 800 μm in thickness in the blast cleaned specimens. The machining also gave better fatigue performance with a 30% increase in the fatigue limit, which was ascribed to the removal of the weaker casting skin layer.

  • 7.
    Aid, Graham
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Industriell miljöteknik. Ragn-sells, Sweden.
    Kihl, Anders
    Ragn Sells AB.
    Driving forces and inhibitors of secondary stock extraction2014Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Even though it’s well known to mankind that our common resources are limited and that recycling is a key for a sustainable future; in reality we see few examples of true recycling where virgin raw material is substituted by waste. There are endless number of examples where waste is utilized to some extent without solving the core issue: reducing the need of extracting virgin raw materials. This article analyses some of the driving forces and inhibitors that explains why it’s so difficult establish secondary stock extraction although technology is available. The authors discuss and suggest possible ways for reducing the some of the main barriers.

  • 8.
    Akbar, Muhammad
    et al.
    COMSATS Univ Islamabad, Pakistan; Hubei Univ, Peoples R China.
    Alvi, Farah
    COMSATS Univ Islamabad, Pakistan.
    Shakir, Muhammad Imran
    Univ Calif Los Angeles, CA 90095 USA.
    Rehman, Saif Ur
    COMSATS Univ Islamabad, Pakistan.
    Rafique, Asia
    COMSATS Univ Islamabad, Pakistan.
    Mushtaq, Naveed
    COMSATS Univ Islamabad, Pakistan; Hubei Univ, Peoples R China.
    Raza, Rizwan
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten. COMSATS Univ Islamabad, Pakistan.
    Effect of sintering temperature on properties of LiNiCuZn-Oxide: a potential anode for solid oxide fuel cell2019Inngår i: MATERIALS RESEARCH EXPRESS, ISSN 2053-1591, Vol. 6, nr 10, artikkel-id 105505Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Crystal structure and surface morphology play vital role in the performance of Solid Oxide Fuel cells (SOFCs) anode. Sufficient electrocatalytic activity and high conductivity are the key requirements for anode to enhance the electrochemical capability. In current work, sintering temperature effects are investigated on the properties of advanced LiNiCuZn-Oxide based electrode for solid oxide fuel cells (SOFCs). The powders were prepared by simple solid-state reaction method was followed by sintering at different temperatures (700 degrees C-1200 degrees C). Moreover, various characterization techniques have been employed to investigate the sintering temperatures effects on the crystallite size, morphology, particle size, energy band gap and absorption peaks. The energy gap (Eg) was observed to increase from 2.94 eV to 3.32 eV and dc conductivity decreased from 9.084 Scm(-1) to 0.46 Scm(-1) by increasing sintering temperature from 700 degrees C to 1200 degrees C. Additionally, the best fuel cell performance of 0.90 Wcm(-2) was achieved for LiNiCuZn-Oxide sintered at 700 degrees C using H-2/air as a fuel and oxidant and it decreased to 0.17 Wcm(-2) for powders sintered at 1200 degrees C. Based on these results, we can conclude that 700 degrees C is the best optimum temperature for these chemical compositions, where all parameters of electrode are as per SOFCs requirement.

  • 9.
    Albertini, Gianni
    et al.
    Dipartimento di Scienze dei Materiali e della Terra, Universita, Ancona, Italy.
    Peng, Ru
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Manescu, Adrian
    Instituto di Scienze Fisiche, Universita, Ancona, Italy.
    Ponzetti, Araldo
    NUOVA M.A.I.P SpA, Viale Cavalotti n 30, Jesi, Italy.
    Neutron Diffraction Measurement of Residual Stress in a centrifugal Bowl of Duplex Steel2001Inngår i: Journal of Neutron Research, ISSN 1023-8166, E-ISSN 1477-2655, Vol. 9, s. 305-312Artikkel i tidsskrift (Fagfellevurdert)
  • 10.
    Ali, Amjad
    et al.
    COMSATS Univ Islamabad, Pakistan; Univ Okara, Pakistan.
    Raza, Rizwan
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten. COMSATS Univ Islamabad, Pakistan.
    Shakir, Muhammad Imran
    King Saud Univ, Saudi Arabia; Univ Calif Los Angeles, CA 90095 USA.
    Iftikhar, Asia
    COMSATS Univ Islamabad, Pakistan.
    Alvi, Farah
    COMSATS Univ Islamabad, Pakistan.
    Ullah, Muhammad Kaleem
    COMSATS Univ Islamabad, Pakistan.
    Hamid, Abdul
    Univ Okara, Pakistan.
    Kim, Jung-Sik
    Loughborough Univ, England.
    Promising electrochemical study of titanate based anodes in direct carbon fuel cell using walnut and almond shells biochar fuel2019Inngår i: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 434, artikkel-id 126679Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The direct carbon fuel cell (DCFC) is an efficient device that converts the carbon fuel directly into electricity with 100% theoretical efficiency contrary to practical efficiency around 60%. In this paper four perovskite anode materials La0.4Sr0.6M0.09Ti0.91O3-delta (M = Ni, Fe, Co, Zn) have been prepared using sol-gel technique to measure the performance of the device using solid fuel. These materials have shown reasonable stability and conductivity at 700 degrees C. Further structural analysis of as-prepared anode material using XRD technique reveals a single cubic perovskite structure with average crystallite size roughly 47 nm. Walnut and almond shells biochar have also been examined as a fuel in DCFC at the temperature range 400-700 degrees C. In addition, Elemental analysis of walnut and almond shells has shown high carbon content and low nitrogen and sulfur contents in the obtained biochar. Subsequently, the superior stability of as-prepared anode materials is evident by thermogravimetric analysis in pure N-2 gas atmosphere. Conversely, the LSFT anode has shown the highest electronic conductivity of 7.53Scm(-1) at 700 degrees C. The obtained power density for LSFTO3-delta composite anode mixed in sub-bituminous coal, walnut and almond shells biochar is of 68, 55, 48 mWcm(-2) respectively. A significant improvement in performance of DCFC (78 mWcm(-2)) was achieved.

  • 11.
    Alici, Gursel
    et al.
    School of Mechanical, Materials, and Mechatronic Engineering, ARC Centre of Excellence for Electromaterials Science, University of Wollongong, Wollongong, Australia.
    Mutlu, Rahim
    School of Mechanical, Materials, and Mechatronic Engineering, ARC Centre of Excellence for Electromaterials Science, University of Wollongong, Wollongong, Australia.
    Melling, Daniel
    Institute for Medical Science and Technology, University of Dundee, Dundee, UK.
    Jager, Edwin
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Sensor- och aktuatorsystem. Linköpings universitet, Tekniska fakulteten.
    Kaneto, Keiichi
    Kyushu Institute of Technology, Eamex Co. Ltd, Chuoku, Fukuoka, Japan.
    Conducting Polymers as EAPs: Device Configurations2016Inngår i: Electromechanically Active Polymers: A Concise Reference / [ed] Federico Carpi, Cham: Springer, 2016, s. 257-292Kapittel i bok, del av antologi (Annet vitenskapelig)
    Abstract [en]

    This chapter focuses on device configurations based on conjugated polymer transducers. After the actuation and sensing configurations in the literature are presented, some successful device configurations are reviewed, and a detailed account of their operation principles is described. The chapter is concluded with critical research issues. With reference to the significant progress made in the field of EAP transducers in the last two decades, there is an increasing need to change our approach to the establishment of new device configurations, novel device concepts, and cutting-edge applications. To this aim, we should start from the performance specifications and end up with the material synthesis conditions and properties which will meet the performance specifications (top-to-down approach). The question should be “what electroactive material or materials can be used for a specific purpose or application,” rather than looking for an application or a device concept suitable to the unique properties of the EAPs and transducers already made of these materials. The field is mature enough to undertake this paradigm change.

  • 12.
    Alimadadi, Majid
    et al.
    Department of Natural Sciences, Mid Sweden University, Sweden.
    Lindström, Stefan B
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Kulachenko, Artem
    Department of Solid Mechanics, Royal Institute of Technology (KTH), Stockholm, Sweden.
    Role of microstructures in the compression response of three-dimensional foam-formed wood fiber networks2018Inngår i: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 14, s. 8945-8955Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    High-porosity, three-dimensional wood fiber networks made by foam forming present experimentally accessible instances of hierarchically structured, athermal fiber networks. We investigate the large deformation compression behavior of these networks using fiber-resolved finite element analyses to elucidate the role of microstructures in the mechanical response to compression. Three-dimensional network structures are acquired using micro-computed tomography and subsequent skeletonization into a Euclidean graph representation. By using a fitting procedure to the geometrical graph data, weare able to identify nine independent statistical parameters needed for the regeneration of artificial networks with the observed statistics. The compression response of these artificially generated networks and the physical network is then investigated using implicit finite element analysis. A direct comparison of the simulation results from the reconstructed and artificial network reveals remarkable differences already in the elastic region. These can neither be fully explained by density scaling, the size effect nor the boundary conditions. The only factor which provides the consistent explanation of the observed difference is the density and fiber orientation nonuniformities; these contribute to strain-localization so that the network becomes more compliant than expected for statistically uniform microstructures. We also demonstrate that the experimentally manifested strain-stiffening of such networks is due to development of new inter-fiber contacts during compression.

  • 13. Alkaisee, Rasha
    et al.
    Peng, Ru
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Influence of Layer Removal Methods in Residual Stress Profiling of a Shot Peened Steel using X-ray Diffraction2014Inngår i: Residual Stresses IX, 2014, Vol. 996, s. 175-180Konferansepaper (Fagfellevurdert)
  • 14.
    Almroth, Per
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik. Linköpings universitet, Tekniska högskolan.
    Constitutive modeling of a nickel base superalloy: with a focus on gas turbine applications2003Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Gas turbines are used where large amounts of energy is needed, typically as engines in aircraft, ferries and power plants. From an efficiency point of view it is desirable to increase the service temperature as much as possible. One of the limiting factors is then the maximum allowable metal temperatures in the turbine stages, primarily in the blades of the first stage, that are exposed to the highest gas temperatures. Specially designed materials are used to cape with these severe conditions, such as the nickel base superalloy IN792. In order to be able to design the components for higher temperatures and tighter tolerances, a detailed understanding and computational models of the material behaviour is needed.

    The models presented in this work have been developed with the objective of being physically well motivated, and with the intention of avoiding excessive numbers of parameters. The influence of the parameters should also be as easy as possible to interpret. The models are to describe the the behaviour of IN792, under conditions typically found for a gas turbine blade. Specifically the high- and intermediate- temperature isothermal modelling of IN792 have been addressed.

    One main issue when characterising the material and calibrating the models is the use of relevant tests, that are representative of component conditions. Therefore isothermal tests with an eye on the typical environment of a turbine blade have been planned and performed.

    Using numerical optimization techniques the material parameters for the isothermal behaviour of IN792 at 650°C and 850°C have been estimated. The good overall calibration results for these specific temperatures, using the presented modeling concept and nonstandard constitutive tests, suggests that the model can describe the behaviour of IN792 in gas turbine hot part applications.

  • 15.
    Almyras, Georgios
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Nanodesign. Linköpings universitet, Tekniska fakulteten.
    Sangiovanni, Davide Giuseppe
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten. Ruhr Univ Bochum, Germany.
    Sarakinos, Kostas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Nanodesign. Linköpings universitet, Tekniska fakulteten.
    Semi-Empirical Force-Field Model For The Ti1-XAlXN (0 ≤ x ≤ 1) System2019Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, nr 2, artikkel-id 215Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a modified embedded atom method (MEAM) semi-empirical force-field model for the Ti1-xAlxN (0 x 1) alloy system. The MEAM parameters, determined via an adaptive simulated-annealing (ASA) minimization scheme, optimize the models predictions with respect to 0 K equilibrium volumes, elastic constants, cohesive energies, enthalpies of mixing, and point-defect formation energies, for a set of approximate to 40 elemental, binary, and ternary Ti-Al-N structures and configurations. Subsequently, the reliability of the model is thoroughly verified against known finite-temperature thermodynamic and kinetic properties of key binary Ti-N and Al-N phases, as well as properties of Ti1-xAlxN (0 amp;lt; x amp;lt; 1) alloys. The successful outcome of the validation underscores the transferability of our model, opening the way for large-scale molecular dynamics simulations of, e.g., phase evolution, interfacial processes, and mechanical response in Ti-Al-N-based alloys, superlattices, and nanostructures.

  • 16.
    Altgärde, Noomi
    Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Local release of lithium from sol-gel coated orthopaedic screws: an in vitro and in vivo study2009Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

     

    In orthopaedic practice, fractures are usually stabilised with metal screws or rods. This is done in order to keep the fracture parts in place during the rather slow healing process. The healing time can potentially be reduced by local- or systemic treatment with different bone promoting drugs. In later years, lithium, otherwise used to treat bipolar disease, has shown promise to be such a drug.

     

    The aim of this master thesis was to find a way to coat metal bone screws with lithium and to characterise the coating. The coating was to be designed in such a way that it could release lithium to the surrounding bone tissue.

     

    Lithium chloride was incorporated into a titanate sol-gel and attached to silicon wafers and stainless steel screws by dip coating. Wafers were used for initial in vitro studies of how lithium changed coating characteristics. This was studied using ellipsometry, AFM and SEM. Lithium is most probably physisorbed and not incorporated into the network building up the sol-gel. Coating structure is changed as more lithium is incorporated. For large amounts of lithium, the nanoparticles normally formed when curing the sol-gel are inhibited. One effect of this is reduced bioactivity, seen as a reduced ability for calcium phosphate crystals to nucleate on the coating when immersed in simulated body fluid.

    Lithium release was investigated using AAS. Lithium is released from the coating, showing a burst effect. By changing the number of coating layers used, the release profile can be partly altered. The coating was also applied to screws, showing good attachment, and the lithium release profile was similar to the one seen from wafers.

    Finally, a screw model was used in rats to assess the effect of local lithium treatment from screws and systemic lithium treatment on fracture healing. In the model, a screw was inserted in tibia, mimicking a fracture. When the bone around the screw was healed, a pullout test was performed, giving information about the strength of the bone surrounding the screw. No significant difference could be found for either local- or systemic lithium treatment compared to control. However, when evaluating the strength of intact bone in a similar way, a positive effect of systemic lithium treatment could be seen. Therefore, it is still likely that lithium has a positive effect on bone and further studies are needed to fully evaluate its role in fracture healing.

     

  • 17.
    Anderberg, Elin
    Linköpings universitet, Institutionen för fysik, kemi och biologi.
    LED Array Frequency Dependent Photocurrent Imaging of Organic Solar Cell Modules2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    To mitigate the risk for devastating climate changes, there is an urgent need to change the energy production from the current fossil based to renewable sources. Solar cells will contribute to an increasing share of the future energy systems. Today silicon solar cells dominate the market but printed organic solar cells are promising alternatives in terms of cost, flexibility, possibilities for building integrations and energy payback times. Printing enables roll-to-roll processing that is quick and renders huge volumes. Thus, also characterization and quality control must be fast. Recent tests have been performed showing that a LED array with amplitude modulated LEDs can be used to provide photocurrent images of modules with series connected sub cells in-line during manufacturing. The purpose of this thesis work is to further evaluate and develop this LED array characterization technique focusing on contact methods and signal interpretation. Two modes were examined; a contact mode and a capacitive contact-less mode. Both modes gave comparable results and indicated strong variations in performance of sub cells in the measured modules. Other methods to address individual cells also showed similar behavior. However, by manually adding extra contact points, current-voltage curves could be measured on the individual sub cells in the modules. Extraction of photocurrents were similar, but the parallel resistances varied strongly between the cells in the module. Increasing the frequency of the LEDs resulted in less variations. Calculations indicated that this frequency dependence could be used to separate the photocurrent generation and parallel resistance in the sub cells.

  • 18.
    Andersen Söderbergh, Kim
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Carl Malmsten - furniture studies. Linköpings universitet, Tekniska högskolan.
    Blästring av trä: Ett materialbibliotek av blästrade och ytbehandladeträytor2012Independent thesis Basic level (degree of Bachelor), 10,5 poäng / 16 hpOppgave
    Abstract [en]

    In my thesis I have sand blasted different type of woods - ring-porous and diffuseporous deciduous tree species and conifers - to show different results depending on the species, the direction of the grain and the effects of surface treatment of a blasted surface.

    The results of my tests were sometimes unexpected, such as that the sand from blasting almost completely disappeared, that all wood surfaces after blasting exhibited a much lighter or paler surface than before and that the diffuse-porous tree species showed differences in hardness between the beginning and end of annual rings.

    By creating a library of different kinds of wood and sandblasted surface treatment, I have created a reference bank that I will be able to use me in the manufacturing of interiors, furniture and other objects.

  • 19.
    Andersson, Mike
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad sensorvetenskap. Linköpings universitet, Tekniska högskolan.
    Lloyd Spetz, Anita
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad sensorvetenskap. Linköpings universitet, Tekniska högskolan.
    Technology and application opportunities for SiC-FET gas sensors2012Inngår i: Solid State Gas Sensors - Industrial Application / [ed] Maximilian Fleischer and Mirko Lehmann, Springer Berlin/Heidelberg, 2012, s. 189-214Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    The development of SiC-FET gas sensors has proceeded for about fifteen years. The maturity of the SiC material and a deeper understanding of the transduction mechanisms and sensor surface processes behind the sensitivity to a number of target substances have recently allowed the development of market-ready sensors for certain applications. Some examples presented below are a sensor system for domestic boiler control, an ammonia sensor for control of the SCR (selective catalytic reduction) and SNCR (Selective Non-Catalytic Reduction) NOx abatement processes as well as other more or less market-ready applications. In parallel, the basic research continues in order to reach more demanding markets/new applications and also to possibly lower the production costs of the sensors. Therefore, current research and future challenges are also treated, such as the development of new types of conducting ceramics for ohmic contacts to SiC in order to increase the operation temperature beyond the present state of the art.

  • 20.
    Andersson, Niklas
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling.
    Gesällprovets tillverkningsprocess2008Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Examensarbetet är en beskrivande rapport om tillverkningsprocessen av ett gesällprov. Rapportens syfte är att beakta olika konstruktioner och hur de förvärvade kunskaperna används för att utföra en slutprodukt, i det här fallet ett gesällprov. Rapporten försöker svara på vilka faktorer som varit mest avgörande för ett lyckat resultat.

    Tyngdpunkten i arbetet ligger i att beskriva tillverkningsprocessen. Rapporten beskriver resonemanget kring valet av en möbel. Den presenterar olika träslag och hur de kan påverka möbelns uttryck. Vidare berättar rapporten om olika alternativ på skivmaterial att använda som blindträ. Uttag och hantering av faner och massivträ förklaras. Rapporten visar även olika konstruktioner och sammansättningar.

    I den avslutande delen presenteras resultatet av tillverkningen och granskarnas betygssättning. Ett resonemang förs angående vilka faktorer, så som erfarenheter, förvärvade kunskaper, noggrannhet etc. som påverkat resultatet. Slutligen beskrivs olika svårigheter och vad som skulle kunna göras annorlunda.

  • 21.
    Andric, Jelena
    et al.
    Chalmers University of Technology.
    Fredriksson, Sam T.
    Chalmers University of Technology.
    Lindström, Stefan B
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik. Linköpings universitet, Tekniska högskolan.
    Sasic, Srdjan
    Chalmers University of Technology.
    Nilsson, Håkan
    Chalmers University of Technology.
    A study of a flexible fiber model and its behavior in DNS of turbulent channel flow2013Inngår i: Acta Mechanica, ISSN 0001-5970, E-ISSN 1619-6937, Vol. 224, nr 10, s. 2359-2374Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The dynamics of individual flexible fibers in a turbulent flow field have been analyzed, varying their initial position, density and length. A particle-level fiber model has been integrated into a general-purpose, open source computational fluid dynamics code. The fibers are modeled as chains of cylindrical segments connected by ball and socket joints. The equations of motion of the fibers contain the inertia of the segments, the contributions from hydrodynamic forces and torques, and the connectivity forces at the joints. Direct numerical simulation of the incompressible Navier-Stokes equations is used to describe the fluid flow in a plane channel, and a one-way coupling is considered between the fibers and the fluid phase. We investigate the translational motion of fibers by considering the mean square displacement of their trajectories. We find that the fiber motion is primarily governed by velocity correlations of the flow fluctuations. In addition, we show that there is a clear tendency of the thread-like fibers to evolve into complex geometrical configurations in a turbulent flow field, in fashion similar to random conformations of polymer strands subjected to thermal fluctuations in a suspension. Finally, we show that fiber inertia has a significant impact on reorientation timescales of fibers suspended in a turbulent flow field.

  • 22.
    Andric, Jelena
    et al.
    Chalmers University of Technology, Göteborg, Sweden.
    Lindström, Stefan B
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik. Linköpings universitet, Tekniska högskolan.
    Sasic, Srdjan
    Chalmers University of Technology, Göteborg, Sweden.
    Nilsson, Håkan
    Chalmers University of Technology, Göteborg, Sweden.
    Rheological properties of dilute suspensions of rigid and flexible fibers2014Inngår i: Journal of Non-Newtonian Fluid Mechanics, ISSN 0377-0257, E-ISSN 1873-2631, Vol. 212, s. 36-46Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Particle-level simulations are used to study the rheology of monodispersed suspensions of rigid and flexible fibers in a creeping, simple shear flow of a Newtonian fluid. We also investigate the influence of different equilibrium shapes (straight and curved) of the fibers on the behavior of the suspension. A parametric study of the impacts of fiber flexural rigidity and morphology on rheology quantifies the effects of these realistic fiber features on the experimentally accessible rheological properties. A fiber is modeled as a chain of rigid cylindrical segments, interacting through a two-way coupling with the fluid described by the incompressible three-dimensional Navier–Stokes equations. The initial fiber configuration is in the flow–gradient plane. We show that, when the shear rate is increased, straight flexible fibers undergo a buckling transition, leading to the development of finite first and second normal stress differences and a reduction of the viscosity. These effects, triggered by shape fluctuations, are dissimilar to the effects induced by the curvature of stiff, curved fibers, for which the viscosity increases with the curvature of the fiber. An analysis of the orbital drift of fibers initially oriented at an angle to the flow–gradient plane provides an estimate for the time-scale within which the prediction of the rheological behavior is valid. The information obtained in this work can be used in the experimental characterization of fiber morphology and mechanics through rheology.

  • 23.
    Arbring Sjöström, Theresia
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Jonsson, Amanda
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten. Stanford University, CA 94305 USA.
    Gabrielsson, Erik
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Kergoat, Loig
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten. Aix Marseille University, France.
    Tybrandt, Klas
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Berggren, Magnus
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Simon, Daniel
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Cross-Linked Polyelectrolyte for Improved Selectivity and Processability of lontronic Systems2017Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, nr 36, s. 30247-30252Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    On-demand local release of biomolecules enables fine-tuned stimulation for the next generation of neuromodulation therapies. Such chemical stimulation is achievable using iontronic devices based on microfabricated, highly selective ion exchange membranes (IEMs). Current limitations in processability and performance of thin film LEMs hamper future developments of this technology. Here we address this limitation by developing a cationic IEM with excellent processability and ionic selectivity: poly(4-styrenesulfonic acidco-maleic acid) (PSS-co-MA) cross-linked with polyethylene glycol (PEG). This enables new design opportunities and provides enhanced compatibility with in vitro cell studies. PSSA-co-MA/PEG is shown to out-perform the cation selectivity of the previously used iontronic material.

  • 24.
    Armakavicius, Nerijus
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Study of novel electronic materials by mid-infrared and terahertz optical Hall effect2017Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Development of silicon based electronics have revolutionized our every day life during the last three decades. Nowadays Si based devices operate close to their theoretical limits that is becoming a bottleneck for further progress. In particular, for the growing field of high frequency and high power electronics, Si cannot offer the required properties. Development of materials capable of providing high current densities, carrier mobilities and high breakdown fields is crucial for a progress in state of the art electronics.

    Epitaxial graphene grown on semi-insulating silicon carbide substrates has a high potential to be integrated in the current planar device technologies. High electron mobilities and sheet carrier densities make graphene extremely attractive for high frequency analog applications. One of the remaining challenges is the interaction of epitaxial graphene with the substrate. Typically, much lower free charge carrier mobilities, compared to free standing graphene, and doping, due to charge transfer from the substrate, is reported. Thus, a good understanding of the intrinsic free charge carriers properties and the factors affecting them is very important for further development of epitaxial graphene.

    III-group nitrides have been extensively studied and already have proven their high efficiency as light sources for short wavelengths. High carrier mobilities and breakdown electric fields were demonstrated for III-group nitrides, making them attractive for high frequency and high power applications. Currently, In-rich InGaN alloys and AlGaN/GaN high electron mobility structures are of high interest for the research community due to open fundamental questions.

    Electrical characterization techniques, commonly used for the determination of free charge carrier properties, require good ohmic and Schottky contacts, which in certain cases can be difficult to achieve. Access to electrical properties of buried conductive channels in multilayered structures requires modification of samples and good knowledge of the electrical properties of all electrical contact within the structure. Moreover, the use of electrical contacts to electrically characterize two-dimensional electronic materials, such as graphene, can alter their intrinsic properties. Furthermore, the determination of effective mass parameters commonly employs cyclotron resonance and Shubnikov-de Haas oscillations measurements, which require long scattering times of free charge carriers, high magnetic fields and low temperatures.

    The optical Hall effect is an external magnetic field induced optical anisotropy in  conductive layers due to the motion of the free charge carriers under the influence of the Lorentz force, and is equivalent to the electrical Hall effect at optical frequencies. The optical Hall effect can be measured by generalized ellipsometry and provides a powerful method for the determination of free charge carrier properties in a non-destructive and contactless manner. In principle, a single optical Hall effect measurement can provide quantitative information about free charge carrier types, concentrations, mobilities and effective mass parameters at temperatures ranging from few kelvins to room temperature and above. Further, it was demonstrated that for transparent samples, a backside cavity can be employed to enhance the optical Hall effect.

    Measurement of the optical Hall effect by generalized ellipsometry is an indirect technique requiring subsequent data analysis. Parameterized optical models are fitted to match experimentally measured ellipsometric data by varying physically significant parameters. Analysis of the optical response of samples, containing free charge carriers, employing optical models based on the classical Drude model, which is augmented with an external magnetic field contribution, provide access to the free charge carrier properties.

    The main research results of the graduate studies presented in this licentiate thesis are summarized in the five scientific papers.

    Paper I. Description of the custom-built terahertz frequency-domain spectroscopic ellipsometer at Linköping University. The terahertz ellipsometer capabilities are demonstrated by an accurate determination of the isotropic and anisotropic refractive indices of silicon and m-plane sapphire, respectively. Further, terahertz optical Hall effect measurements of an AlGaN/GaN high electron mobility structures were employed to extract the two-dimensional electron gas sheet density, mobility and effective mass parameters. Last, in-situ optical Hall effect measurement on epitaxial graphene in a gas cell with controllable environment, were used to study the effects of environmental doping on the mobility and carrier concentration.

    Paper II. Presents terahertz cavity-enhanced optical Hall measurements of the monolayer and multilayer epitaxial graphene on semi-insulating 4H-SiC (0001) substrates. The data analysis revealed p-type doping for monolayer graphene with a carrier density in the low 1012 cm−2 range and a carrier mobility of 1550 cm2/V·s. For the multilayer epitaxial graphene, n-type doping with a carrier density in the low 1013 cm−2 range, a mobility of 470 cm2/V·s and an effective mass of (0.14 ± 0.03) m0 were extracted. The measurements demonstrate that cavity-enhanced optical Hall effect measurements can be applied to study electronic properties of two-dimensional materials.

    Paper III. Terahertz cavity-enhanced optical Hall effect measurements are employed to study anisotropic transport in as-grown monolayer, quasi free-standing monolayer and quasi free-standing bilayer epitaxial graphene on semi-insulating 4H-SiC (0001) substrates. The data analysis revealed a strong anisotropy in the carrier mobilities of the quasi freestanding bilayer graphene. The anisotropy is demonstrated to be induced by carriers scattering at the step edges of the SiC, by showing that the mobility is higher along the step than across them. The scattering mechanism is discussed based on the results of the optical Hall effect, low-energy electron microscopy, low-energy electron diffraction and Raman measurements.

    Paper IV. Mid-infrared spectroscopic ellipsometry and mid-infrared optical Hall effect measurements are employed to determine the electron effective mass in an In0.33Ga0.67N epitaxial layer. The data analysis reveals slightly anisotropic effective mass and carrier mobility parameters together with the optical phonon frequencies and broadenings.

    Paper V. Terahertz cavity-enhanced optical Hall measurements are employed to study the free charge carrier properties in a set of AlGaN/GaN high electron mobility structures with modified interfaces. The results show that the interface structure has a significant effect on the free charge carrier mobility and that the sample with a sharp interface between an AlGaN barrier and a GaN buffer layers exhibits a record mobility of 2332±73 cm2/V·s. The determined effective mass parameters showed an increase compared to the GaN value, that is attributed the the penetration of the electron wavefunction into the AlGaN barrier layer.

    Delarbeid
    1. Cavity-enhanced optical Hall effect in epitaxial graphene detected at terahertz frequencies
    Åpne denne publikasjonen i ny fane eller vindu >>Cavity-enhanced optical Hall effect in epitaxial graphene detected at terahertz frequencies
    Vise andre…
    2017 (engelsk)Inngår i: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 421, s. 357-360Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Cavity-enhanced optical Hall effect at terahertz (THz) frequencies is employed to determine the free charge carrier properties in epitaxial graphene (EG) with different number of layers grown by high-temperature sublimation on 4H-SiC(0001). We find that one monolayer (ML) EG possesses p-type conductivity with a free hole concentration in the low 1012 cmᅵᅵᅵ2 range and a free hole mobility parameter as high as 1550 cm2/Vs. We also find that 6 ML EG shows n-type doping behavior with a much lower free electron mobility parameter of 470 cm2/Vs and an order of magnitude higher free electron density in the low 1013 cmᅵᅵᅵ2 range. The observed differences are discussed. The cavity-enhanced THz optical Hall effect is demonstrated to be an excellent tool for contactless access to the type of free charge carriers and their properties in two-dimensional materials such as EG.

    sted, utgiver, år, opplag, sider
    Elsevier, 2017
    Emneord
    THz optical Hall effect, Epitaxial graphene, Free charge carrier properties
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-132407 (URN)10.1016/j.apsusc.2016.10.023 (DOI)000408756700015 ()
    Merknad

    Funding agencies: Swedish Research Council (VR) [2013-5580]; Swedish Governmental Agency for Innovation Systems (VINNOVA) under the VINNMER international qualification program [2011-03486, 2014-04712]; Swedish foundation for strategic research (SSF) [FFL12-0181, RIF14-055]

    Tilgjengelig fra: 2016-11-09 Laget: 2016-11-09 Sist oppdatert: 2019-03-05bibliografisk kontrollert
    2. Properties of two-dimensional electron gas in AlGaN/GaN HEMT structures determined by cavity-enhanced THz optical Hall effect
    Åpne denne publikasjonen i ny fane eller vindu >>Properties of two-dimensional electron gas in AlGaN/GaN HEMT structures determined by cavity-enhanced THz optical Hall effect
    Vise andre…
    2016 (engelsk)Inngår i: Physica Status Solidi C-Current Topics in Solid State Physics, Vol 13 No 5-6, Wiley-VCH Verlagsgesellschaft, 2016, Vol. 13, nr 5-6, s. 369-373Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    In this work we employ terahertz (THz) ellipsometry to determine two-dimensional electron gas (2DEG) density, mobility and effective mass in AlGaN/GaN high electron mobility transistor structures grown on 4H-SiC substrates. The effect of the GaN interface exposure to low-flow-rate trimethylaluminum (TMA) on the 2DEG properties is studied. The 2DEG effective mass and sheet density are determined tobe in the range of 0.30-0.32m0 and 4.3-5.5×1012 cm–2, respectively. The 2DEG effective mass parameters are found to be higher than the bulk effective mass of GaN, which is discussed in view of 2DEG confinement. It is shown that exposure to TMA flow improves the 2DEG mobility from 2000 cm2/Vs to values above 2200 cm2/Vs. A record mobility of 2332±61 cm2/Vs is determined for the sample with GaN interface exposed to TMA for 30 s. This improvement in mobility is suggested to be due to AlGaN/GaN interface sharpening causing the reduction of interface roughness scattering of electrons in the 2DEG.

    sted, utgiver, år, opplag, sider
    Wiley-VCH Verlagsgesellschaft, 2016
    Serie
    Physica Status Solidi C-Current Topics in Solid State Physics, ISSN 1862-6351
    Emneord
    AlGaN/GaN HEMTs, THz ellipsometry, 2DEG properties, THz optical Hall effect
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-133135 (URN)10.1002/pssc.201510214 (DOI)000387957200045 ()
    Konferanse
    11th International Conference on Nitride Semiconductors (ICNS), Beijing, China, August 30-September 4. 2015
    Tilgjengelig fra: 2016-12-12 Laget: 2016-12-09 Sist oppdatert: 2019-03-05bibliografisk kontrollert
  • 25.
    Armakavicius, Nerijus
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Bouhafs, Chamseddine
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Stanishev, Vallery
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Kühne, Philipp
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Yakimova, Rositsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Knight, Sean
    Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, USA.
    Hofmann, Tino
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten. Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, USA / Department of Physics and Optical Science, University of North Carolina at Charlotte, USA.
    Schubert, Mathias
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten. Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, USA.
    Darakchieva, Vanya
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Cavity-enhanced optical Hall effect in epitaxial graphene detected at terahertz frequencies2017Inngår i: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 421, s. 357-360Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cavity-enhanced optical Hall effect at terahertz (THz) frequencies is employed to determine the free charge carrier properties in epitaxial graphene (EG) with different number of layers grown by high-temperature sublimation on 4H-SiC(0001). We find that one monolayer (ML) EG possesses p-type conductivity with a free hole concentration in the low 1012 cmᅵᅵᅵ2 range and a free hole mobility parameter as high as 1550 cm2/Vs. We also find that 6 ML EG shows n-type doping behavior with a much lower free electron mobility parameter of 470 cm2/Vs and an order of magnitude higher free electron density in the low 1013 cmᅵᅵᅵ2 range. The observed differences are discussed. The cavity-enhanced THz optical Hall effect is demonstrated to be an excellent tool for contactless access to the type of free charge carriers and their properties in two-dimensional materials such as EG.

  • 26.
    Arvidsson, Emma
    et al.
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik.
    Ekblad, Emma
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik.
    Framtagning av krypmodell för termomekanisk FE-analys av grenrör2006Independent thesis Advanced level (degree of Magister), 20 poäng / 30 hpOppgave
    Abstract [sv]

    Grenrören i en motor utsätts för stora termiska och mekaniska belastningar, vilka gör att grenrören ofta spricker. Idag kan inte sprickbildningen fullständigt uttydas ur beräkningarna, syftet med arbetet är därför att se om dessa kan förbättras genom att använda en mer avancerad krypmodell än den som används idag.

    Ett förslag till krypmodell har tagits genom att studera ett antal i litteraturen funna modeller. De som valts ut är modeller enligt Norton, Bailey-Norton, Marin-Pao, Picket och Findley. Parametrarna i de olika modellerna har bestämts genom kurvanpassning av enaxliga prov på de aktuella grenrörsmaterialen. Resultaten visar att modellerna enligt Marin-Pao, Picket och Findley alla kan beskriva mätkurvorna nästan exakt. Problem uppstår dock med att man får parametrar som beror av både spänning och temperatur. Av dessa tre modeller anses Marin-Pao vara den bästa, då det är den av de tre som har minst antal parametrar. Utvärderingen ger vidare att Norton är den modell som är enklast, och beaktat över alla prover, den vars resultat bäst ansluter sig till mätdata. Valet görs att gå vidare med både Marin-Paos och Nortons modell.

    De två aktuella modellerna har lagts in som subrutiner till FE-programmet ABAQUS. Tester av modellerna görs först på ett litet kubiskt element och sedan på hela grenröret. Jämförelser görs mellan Norton, Marin-Pao och den modell som används idag – ”Two-layer viscoplasticity model”. Såväl Marin-Paos modell som Nortons beskriver verkligheten bättre än den idag använda modellen och av de båda är Nortons modell den som mest tillfredställande speglar verkligheten. Det är dessutom den modell som är mest stabil och beräkningsmässigt effektivast. Som en rekommendation inför fortsatt arbete föreslås därför användning av Nortons modell, samt ett utökat antal krypprover.

  • 27.
    Ashraf, Hina
    Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Investigation of the Symmetries of the Phonons in 4H and 6H-SiC by Infrared Absorption and Raman Spectroscopy2005Independent thesis Basic level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    The goal of the project work has been to study the symmetry of the phonons in 4H and 6H-SiC for different measuring geometries by using two experimental techniques, Raman and infrared absorption (IR) spectroscopy, and a theoretical model. The Raman spectra were measured in different scattering configurations in order to obtain experimental data for detailed investigation of the phonon symmetries.

    The gross features of the spectra obtained in different geometries can be explained using general group-theoretical arguments. Using a lattice-dynamics model, we have also calculated the angular dependence of the phonon energies near the centre of the Brillouin zone, as well as the phonon displacements in some high-symmetry directions. The theoretical results are used to interpret the Raman lines in different configurations, and it was possible to estimate that if ionicity of the bonding of 12% is taken in the theoretical model for 4H-SiC, the splitting of the polar TO mode and the shift of the polar LO mode observed in our spectra are well reproduced theoretically. It was also observed that these polar modes have to be classified as longitudinal and transversal with respect to the direction of phonon wave vector, while the rest of the modes remain longitudinal or transversal with respect to the c-axis of the crystal. The Raman lines in the case of 4H SiC have been tentatively labelled with the irreducible representations of the point group of the crystal (C6v).

  • 28.
    Aspenberg, David
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Hållfasthetslära. Linköpings universitet, Tekniska högskolan.
    Jergeus, Johan
    Volvo Cars Safety Centre, Göteborg.
    Nilsson, Larsgunnar
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Hållfasthetslära. Linköpings universitet, Tekniska högskolan.
    Robust optimisation of front members in a full frontal car impactManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    In the search of a lightweight design of automobiles, it is necessary to assure that a robust crashworthiness performance is achieved. Structures that are optimised to handle a finite number of load cases may perform poorly when subjected to various dispersions. Thus, uncertainties must be accounted for in the optimisation process. This paper presents an approach to optimisation where all design evaluations include an evaluation of the robustness. Metamodel approximations are applied both to the design space and the robustness evaluations, using Artifical Neural Networks and polynomials, respectively. The features of the robust optimisation approach are displayed in an analytical example, and further demonstrated in a large scale design example of front side members of a car. Different optimisation formulations are applied and it is shown that the proposed approach works well. It is also concluded that a robust optimisation puts higher demands on the FE model performance than normally.

  • 29.
    Atakan, Aylin
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Nanostrukturerade material. Linköpings universitet, Tekniska fakulteten.
    Mesoporous material systems for catalysis and drug delivery2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Hybrid material systems possess multi-functional properties which make them intriguing for the materials science community since very early dates. However, it is not straightforward to produce such material systems. A smart and efficient approach is necessary to extract the desired properties of each component under the desired conditions. This study evolved to its last form primarily around this notion, where the development of a hybrid material is the core of the work. This hybrid material is then further explored for two different applications in the catalysis and drug delivery fields.

    A nanoassembly was established around a mesoporous silica support. SBA-15 was picked as this support among the other mesoporous silica due to its well-defined pore structure and accessible pore volume. The silica framework was doped with Zr atoms and the pores were partly infiltrated with Cu nanoparticles resulting in a hybrid material with tunable properties. SBA-15 was synthesized by a sol-gel method where a micellar solution was employed as a template for the silica framework. To achieve the doped version, a Zr precursor was added to the synthesis solution. The effects of different synthesis conditions, such as the synthesis catalyst (F-or a Cl-salt) and the Si source (tetraethyl orthosilicate (TEOS) or sodium metasilicate (SMS)) on the characteristics of the final material were investigated. It was observed that these changes in the synthesis conditions yielded different particle morphology, pore size (11-15 nm), and specific surface area (400-700 m2/g). Cu nanoparticles (NPs) were grown in the (Zr-)SBA-15 support using infiltration (Inf) or evaporation induced wetness impregnation (EIWI) methods. The infiltration method is based on functionalizing the (Zr-)SBA-15 support surfaces before the Cu ion attachment whereas EIWI is based on slow evaporation of the liquid from the (Zr-)SBA-15 - Cu aqueous suspension. Both methods are designed to yield preferential growth of Cu NPs in the pores with a diameter smaller than 10 nm and in oxidized form. However, depending on the loading method used, different chemical states of the final material were achieved, i.e. Zr content and porous network properties are different. 

    Cu-Zr-SBA-15 nanoassemblies produced under various synthesis conditions were used for the catalytic conversion of CO2into valuable fuels such as methanol and dimethyl ether (DME). The effect of different chemical states of the catalyst arising from variations in the synthesis parameters was investigated. It was found that the Si precursor (TEOS or SMS) had a considerable impact on the overall performance of the catalyst whereas the Cu loading method (Inf or EIWI) changed the catalytic selectivity between DME and methanol. The activity of the catalyst was further investigated in a time-evolution study where the accumulation of each product in the gas phase and the molecular groups attached to the catalyst surface were recorded over time. Accordingly, thermodynamic equilibrium was achieved on the 14th day of the reaction under 250°C and 33 bar. The resulting total CO2conversion was 24%, which is the thermodynamically highest possible conversion, according to theoretical calculations. It was also concluded from the experimental results that, DME is formed by a combination of two methoxy surface groups. Additionally, the formation of DME boosts the total CO2conversion to fuels, which otherwise is limited to 9.5%.

    The design of Cu-Zr-SBA-15 was also investigated for drug delivery applications, due to its potential as a biomaterial, e.g., a filler in dental composites, and the antibacterial properties of Cu. Also, the bioactivity of SiO2and ZrO2was considered to be an advantage. With this aim, Cu infiltrated Zr doped SBA-15 material was prepared by using TEOS as the silica precursor and the Inf-method to grow Cu NPs. The performance of the final material as a drug delivery vehicle was tested by an in-vitro delivery study with chlorhexidine digluconate.The nanoassemblies show a drug loading capacity of 25-40% [mg drug / mg (drug+carrier)]. The drug release was determined to be composed of two steps. First, a burst release of the drug molecules that are loosely held in the voids of the mesoporous carrier followed by the diffusion of the drug molecules that are attached to the carrier surface. The presence of Zr and Cu limits the burst release and beneficially slows down the drug release process. 

    The effect of pore properties of SBA-15 was explored in a study where the antibiotic doxycycline hyclate was loaded in SBA-15 materials with different pore sizes. It was observed that the pore size is directly proportional to the drug loading capacity [mg drug / mg (drug+carrier)] and the released drug percentage (the released drug amount/total amount of loaded drug). The drug release was fast due to its weak interactions with the SBA-15 materials. 

    In summary, this work demonstrates the multifunctional character of a smart-tailored nanoassembly which gives valuable insights for two distinct applications in catalysis and drug delivery.

    Delarbeid
    1. Synthesis of a Cu-infiltrated Zr-doped SBA-15 catalyst for CO2 hydrogenation into methanol and dimethyl ethert
    Åpne denne publikasjonen i ny fane eller vindu >>Synthesis of a Cu-infiltrated Zr-doped SBA-15 catalyst for CO2 hydrogenation into methanol and dimethyl ethert
    Vise andre…
    2017 (engelsk)Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 19, nr 29, s. 19139-19149Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    A catalytically active nanoassembly comprising Cu-nanoparticles grown on integrated and active supports (large pore Zr-doped mesoporous SBA-15 silica) has been synthesized and used to promote CO2 hydrogenation. The doped mesoporous material was synthesized using a sal-gel method, in which the pore size was tuned between 11 and 15 nm while maintaining a specific surface area of about 700 m(2) g (1). The subsequent Cu nanoparticle growth was achieved by an infiltration process involving attachment of different functional groups on the external and internal surfaces of the mesoporous structure such that 7-10 nm sized Cu nanoparticles grew preferentially inside the pores. Chemisorption showed improved absorption of both CO2 and H-2 for the assembly compared to pure SBA-15 and 15% of the total CO2 was converted to methanol and dimethyl ether at 250 degrees C and 33 bar.

    sted, utgiver, år, opplag, sider
    ROYAL SOC CHEMISTRY, 2017
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-139804 (URN)10.1039/c7cp03037a (DOI)000406334300033 ()28702581 (PubMedID)
    Merknad

    Funding Agencies|EUs Erasmus-Mundus program; Swedish Research Council; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [SFO-Mat-LiU 11 2009-00971]; Knut och Alice Wallenbergs Foundation [KAW 2012.0083]

    Tilgjengelig fra: 2017-08-17 Laget: 2017-08-17 Sist oppdatert: 2018-04-16
    2. Time evolution of the CO2 hydrogenation to fuels over Cu-Zr-SBA-15 catalysts
    Åpne denne publikasjonen i ny fane eller vindu >>Time evolution of the CO2 hydrogenation to fuels over Cu-Zr-SBA-15 catalysts
    Vise andre…
    2018 (engelsk)Inngår i: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 362, s. 55-64Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Time evolution of catalytic CO2 hydrogenation to methanol and dimethyl ether (DME) has been investigated in a high-temperature high-pressure reaction chamber where products accumulate over time. The employed catalysts are based on a nano-assembly composed of Cu nanoparticles infiltrated into a Zr doped SiOx mesoporous framework (SBA-15): Cu-Zr-SBA-15. The CO2 conversion was recorded as a function of time by gas chromatography-mass spectrometry (GC-MS) and the molecular activity on the catalyst’s surface was examined by diffuse reflectance in-situ Fourier transform infrared spectroscopy (DRIFTS). The experimental results showed that after 14 days a CO2 conversion of 25% to methanol and DME was reached when a DME selective catalyst was used which was also illustrated by thermodynamic equilibrium calculations. With higher Zr content in the catalyst, greater selectivity for methanol and a total 9.5% conversion to methanol and DME was observed, yielding also CO as an additional product. The time evolution profiles indicated that DME is formed directly from methoxy groups in this reaction system. Both DME and methanol selective systems show the thermodynamically highest possible conversion.

    Emneord
    Cu-Zr-SBA-15, CO2 hydrogenation, Catalysis, Time evolution, Thermodynamics, Methanol, Dimethyl ether
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-147297 (URN)10.1016/j.jcat.2018.03.023 (DOI)000432770900007 ()
    Merknad

    Funding agencies: EUs Erasmus-Mundus program (The European School of Materials Doctoral Programme - DocMASE); Knut och Alice Wallenbergs Foundation [KAW 2012.0083]; Swedish Government Strategic Research Area (SFO Mat LiU) [2009 00971]; Swedish Energy Agency [42022-1]

    Tilgjengelig fra: 2018-04-16 Laget: 2018-04-16 Sist oppdatert: 2018-06-14bibliografisk kontrollert
  • 30.
    Azam, Sher
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik. Linköpings universitet, Tekniska högskolan.
    Wide Bandgap Semiconductor (SiC & GaN) Power Amplifiers in Different Classes2008Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    SiC MESFETs and GaN HEMTs have an enormous potential in high-power amplifiers at microwave frequencies due to their wide bandgap features of high electric breakdown field strength, high electron saturation velocity and high operating temperature. The high power density combined with the comparably high impedance attainable by these devices also offers new possibilities for wideband power microwave systems. In this thesis, Class C switching response of SiC MESFET in TCAD and two different generations of broadband power amplifiers have been designed, fabricated and characterized. Input and output matching networks and shunt feedback topology based on microstrip and lumped components have been designed, to increase the bandwidth and to improve the stability. The first amplifier is a single stage 26-watt using a SiC MESFET covering the frequency from 200-500 MHz is designed and fabricated. Typical results at 50 V drain bias for the whole band are, 22 dB power gain, 43 dBm output power, minimum power added efficiency at P 1dB is 47 % at 200 MHz and maximum 60 % at 500 MHz and the IMD3 level at 10 dB back-off from P 1dB is below ‑45 dBc. The results at 60 V drain bias at 500 MHz are, 24.9 dB power gain, 44.15 dBm output power (26 W) and 66 % PAE.

    In the second phase, two power amplifiers at 0.7-1.8 GHz without feed back for SiC MESFET and with feedback for GaN HEMT are designed and fabricated (both these transistors were of 10 W). The measured maximum output power for the SiC amplifier at Vd = 48 V was 41.3 dBm (~13.7 W), with a PAE of 32 % and a power gain above 10 dB. At a drain bias of Vd= 66 V at 700 MHz the Pmax was 42.2 dBm (~16.6 W) with a PAE of 34.4 %. The measured results for GaN amplifier are; maximum output power at Vd = 48 V is 40 dBm (~10 W), with a PAE of 34 % and a power gain above 10 dB. The SiC amplifier gives better results than for GaN amplifier for the same 10 W transistor.

    A comparison between the physical simulations and measured device characteristics has also been carried out. A novel and efficient way to extend the physical simulations to large signal high frequency domain was developed in our group, is further extended to study the class-C switching response of the devices. By the extended technique the switching losses, power density and PAE in the dynamics of the SiC MESFET transistor at four different frequencies of 500 MHz, 1, 2 and 3 GHz during large signal operation and the source of switching losses in the device structure was investigated. The results obtained at 500 MHz are, PAE of 78.3%, a power density of 2.5 W/mm with a switching loss of 0.69 W/mm. Typical results at 3 GHz are, PAE of 53.4 %, a power density of 1.7 W/mm with a switching loss of 1.52 W/mm.

    Delarbeid
    1. Single-stage, High Efficiency, 26-Watt power Amplifier using SiC LE-MESFET
    Åpne denne publikasjonen i ny fane eller vindu >>Single-stage, High Efficiency, 26-Watt power Amplifier using SiC LE-MESFET
    2006 (engelsk)Inngår i: Microwave Conference, 2006. APMC 2006. Asia-Pacific December 12-15, 2006, s. 441-444Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    This paper describes a single-stage 26 W negative feedback power amplifier, covering the frequency range 200-500 MHz using a 6 mm gate width SiC lateral epitaxy MESFET. Typical results at 50 V drain bias for the whole band are, around 22 dB power gain, around 43 dBm output power, minimum power added efficiency at P1 dB is 47% at 200 MHz and maximum 60% at 500 MHz and the IMD3 level at 10 dB back-off from P1 dB is below -45 dBc. The results at 60 V drain bias at 500 MHz are, 24.9 dB power gain, 44.15 dBm output power (26 W) and 66% PAE.

    Emneord
    Schottky gate field effect transistors, feedback, microwave power amplifiers, silicon compounds, SiC, frequency 200 MHz to 500 MHz, lateral epitaxy MESFET, negative feedback, power 26 W, power amplifier, size 6 mm, voltage 50 V
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-13283 (URN)10.1109/APMC.2006.4429458 (DOI)
    Tilgjengelig fra: 2008-05-13 Laget: 2008-05-13 Sist oppdatert: 2009-09-24bibliografisk kontrollert
    2. Designing, Fabrication and Characterization of Power Amplifiers Based on 10-Watt SiC MESFET & GaN HEMT at Microwave Frequencies
    Åpne denne publikasjonen i ny fane eller vindu >>Designing, Fabrication and Characterization of Power Amplifiers Based on 10-Watt SiC MESFET & GaN HEMT at Microwave Frequencies
    2008 (engelsk)Inngår i: IEEE European Microwave Week, October 10-15, Amsterdam, The Netherlands, 2008, s. 444-447Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    This paper describes the design, fabrication and measurement of two single-stage class-AB power amplifiers covering the frequency band from 0.7-1.8 GHz using a SiC MESFET and a GaN HEMT. The measured maximum output power for the SiC amplifier at Vd = 48 V was 41.3 dBm (~13.7 W), with a PAE of 32% and a power gain above 10 dB. At a drain bias of Vd= 66 V at 700 MHz the Pmax was 42.2 dBm (~16.6 W) with a PAE of 34.4%. The measured results for GaN amplifier are; maximum output power at Vd = 48 V is 40 dBm (~10 W), with a PAE of 34% and a power gain above 10 dB. The results for SiC amplifier are better than for GaN amplifier for the same 10-W transistor.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-13284 (URN)10.1109/EUMC.2008.4751484 (DOI)
    Tilgjengelig fra: 2008-05-13 Laget: 2008-05-13 Sist oppdatert: 2009-09-24bibliografisk kontrollert
    3. Pulse Input Class-C Power Amplifier Response of SiC MESFET using Physical Transistor Structure in TCAD
    Åpne denne publikasjonen i ny fane eller vindu >>Pulse Input Class-C Power Amplifier Response of SiC MESFET using Physical Transistor Structure in TCAD
    2008 (engelsk)Inngår i: Solid-State Electronics, ISSN 0038-1101, E-ISSN 1879-2405, Vol. 52, nr 5, s. 740-744Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    The switching behavior of a previously fabricated and tested SiC transistor is studied in Class-C amplifier in TCAD simulation. The transistor is simulated for pulse input signals in Class-C power amplifier. The simulated gain (dB), power density (W/mm) and power added efficiency (PAE%) at 500 MHz, 1, 2 and 3 GHz was studied using computational TCAD load pull simulation technique. A Maximum PAE of 77.8% at 500 MHz with 45.4 dB power gain and power density of 2.43 W/mm is achieved. This technique allows the prediction of switching response of the device for switching amplifier Classes (Class-C–F) before undertaking an expensive and time consuming device fabrication. The beauty of this technique is that, we need no matching and other lumped element networks for studying the large signal behavior of RF and microwave transistors.

    Emneord
    Pulse, Class-C, Power amplifier, New technique, Silicon carbide, MESFET
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-13285 (URN)10.1016/j.sse.2007.09.022 (DOI)
    Tilgjengelig fra: 2008-05-13 Laget: 2008-05-13 Sist oppdatert: 2017-12-13bibliografisk kontrollert
  • 31.
    Azeez, Ahmed
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Eriksson, Robert
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Filosofiska fakulteten. Linköpings universitet, Tekniska fakulteten.
    Calmunger, Mattias
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Lindström, Stefan B
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Hållfasthetslära. Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Low Cycle Fatigue Modelling of Steam Turbine Rotor Steel2019Inngår i: Structural Integrity Procedia / [ed] Elsevier, Elsevier, 2019Konferansepaper (Fagfellevurdert)
  • 32.
    Aziz, Shazed
    et al.
    Department of Chemical and Environmental Engineering, Faculty of Engineering, University Putra Malaysia, Selangor, Malaysia.
    Suraya, A. R.
    Department of Chemical and Environmental Engineering, Faculty of Engineering, University Putra Malaysia, Selangor, Malaysia; Nanotechnology and Nanomaterials Group, Materials Processing and Technology Laboratory, Institute of Advanced Technology, University Putra Malaysia, Selangor, Malaysia.
    Rahmanian, S.
    Nanotechnology and Nanomaterials Group, Materials Processing and Technology Laboratory, Institute of Advanced Technology, University Putra Malaysia, Selangor, Malaysia.
    Salleh, M.A. Mohd
    Department of Chemical and Environmental Engineering, Faculty of Engineering, University Putra Malaysia, Selangor, Malaysia; Nanotechnology and Nanomaterials Group, Materials Processing and Technology Laboratory, Institute of Advanced Technology, University Putra Malaysia, Selangor, Malaysia.
    Effect of fibre coating and geometry on the tensile properties of hybrid carbon nanotube coated carbon fibre reinforced composite2014Inngår i: Materials & Design, ISSN 0261-3069, Vol. 54, s. 660-669Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Hierarchically structured hybrid composites are ideal engineered materials to carry loads and stresses due to their high in-plane specific mechanical properties. Growing carbon nanotubes (CNTs) on the surface of high performance carbon fibres (CFs) provides a means to tailor the mechanical properties of the fibre–resin interface of a composite. The growth of CNT on CF was conducted via floating catalyst chemical vapor deposition (CVD). The mechanical properties of the resultant fibres, carbon nanotube (CNT) density and alignment morphology were shown to depend on the CNT growth temperature, growth time, carrier gas flow rate, catalyst amount, and atmospheric conditions within the CVD chamber. Carbon nanotube coated carbon fibre reinforced polypropylene (CNT-CF/PP) composites were fabricated and characterized. A combination of Halpin–Tsai equations, Voigt–Reuss model, rule of mixture and Krenchel approach were used in hierarchy to predict the mechanical properties of randomly oriented short fibre reinforced composite. A fractographic analysis was carried out in which the fibre orientation distribution has been analyzed on the composite fracture surfaces with Scanning Electron Microscope (SEM) and image processing software. Finally, the discrepancies between the predicted and experimental values are explained.

  • 33.
    Backe, Carin
    et al.
    University of Borås.
    Guo, Li
    Jager, Edwin
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Sensor- och aktuatorsystem. Linköpings universitet, Tekniska fakulteten.
    Persson, Nils-Krister
    University of Borås.
    Towards responding fabrics – textile processing of thin threadlike pneumatic actuators2019Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    With few exceptions (such as 1) textiles have not been considered as means for obtaining actuation. This is surprising as textiles have many advantageous characteristics such as the D=M property, which stands for Doing Devices while Making the Material. This means that functions are introduced simultaneously as the material, such as in a weave, is built up tread by tread. Traditionally a tread could have a certain colour so in total an aesthetical pattern is formed. Now we take a step beyond this working with threads having more advanced functions. Included are fiber formed structures showing actuation behavior. 

    This we employ here. We make fiber formed actuating structures (FAS) following the McKibben principle (2) with braided mesh sleeves surrounding a prolonged inflatable tube. Here we worked with relatively large diameters in the relaxed state but show that there is prospect for obtaining relaxed diameters of less than 1 mm approaching the range of large scale weaving manufacturing.

    We study the behavior of these fibre formed actuating structures individually. Length changes obtained are -20%. We then make textile constructions by integrating several of these FASes with textile processing. By this, we build simple models of fabrics showing actuating behavior.  

     

    This study shows how textile constructions can support or hinder overall movement. It is a first logical step in order to get an understanding of actuating fabrics based also on other actuating mechanisms (3).

  • 34.
    Bai, Sai
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten. Univ Oxford, England.
    Sakai, Nobuya
    Univ Oxford, England.
    Zhang, Wei
    Univ Oxford, England; Univ Lincoln, England.
    Wang, Zhiping
    Univ Oxford, England.
    Wang, Jacob T.-W.
    Univ Oxford, England.
    Gao, Feng
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten. Univ Oxford, England.
    Snaith, Henry J.
    Univ Oxford, England.
    Reproducible Planar Heterojunction Solar Cells Based on One-Step Solution-Processed Methylammonium Lead Halide Perovskites2017Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 29, nr 1, s. 462-473Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Metal halide perovskites have been demonstrated as one of the most promising materials for low-cost and high-performance photovoltaic applications. However, due to the susceptible crystallization process of perovskite films on planar substrates and the high sensitivity of the physical and optoelectronic nature of the internal interfaces within the devices, researchers in different laboratories still experience poor reproducibility in fabricating efficient perovskite solar cells with planar heterojunction device structures. In this method paper, we present detailed information on the reagents, equipment, and procedures for the fabrication of planar perovskite solar cells in both "regular" n-i-p and "inverted" p-i-n architectures based on one-step solution-processed methylammonium lead triiodide (MAPbI(3)) perovskite films. We discuss key parameters affecting the crystallization of perovskite and the device interfaces. This method paper will provide a guideline for the reproducible fabrication of planar heterojunction solar cells based on MAPbI3 perovskite films. We believe that the shared experience on MA-based perovskite films and planar solar cells will be also useful for the optimization process of perovskites with varied compositions, and other emerging perovskite-based optoelectronic devices.

  • 35.
    Bakoglidis, Konstantinos
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten. Univ Manchester, England.
    Palisaitis, Justinas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    dos Santos, Renato B.
    Univ Fed Bahia, Brazil.
    Rivelino, Roberto
    Univ Fed Bahia, Brazil.
    Persson, Per O A
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Gueorguiev, Gueorgui Kostov
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Hultman, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Self-Healing in Carbon Nitride Evidenced As Material Inflation and Superlubric Behavior2018Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, nr 19, s. 16238-16243Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    All known materials wear under extended mechanical contacting. Superlubricity may present solutions, but is an expressed mystery in C-based materials. We report negative wear of carbon nitride films; a wear-less condition with mechanically induced material inflation at the nanoscale and friction coefficient approaching ultralow values (0.06). Superlubricity in carbon nitride is expressed as C-N bond breaking for reduced coupling between graphitic-like sheets and eventual N-2 desorption. The transforming surface layer acts as a solid lubricant, whereas the film bulk retains its high elasticity. The present findings offer new means for materials design at the atomic level, and for property optimization in wear-critical applications like magnetic reading devices or nanomachines.

  • 36.
    Bakoglidis, Konstantinos
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Schmidt, Susann
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Greczynski, Grzegorz
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Hultman, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Improved adhesion of carbon nitride coatings on steel substrates using metal HiPIMS pretreatments2016Inngår i: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 302, s. 454-462Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We investigate the effect of low-temperature metal pretreatments in order to improve the adhesion of CNx coatings on steel substrates, which is crucial for tribological applications. The substrate pretreatments were conducted using five different metal targets: Ti, Zr, Al, Cr, and W, operated in high power impulse magnetron sputtering mode, known to produce significant ionization of the sputtered material flux. The CNx adhesion, as assessed by Rockwell C tests, did not improve upon Ti and Zr pretreatments. This is primarily ascribed to the fact that no interlayer was formed owing to severe re-sputtering due to high fluxes of doubly-ionized metal species in the plasma. A slight improvement in adhesion was observed in the case an Al pretreatment was carried out, while the best results were obtained using Cr and W. Here, 30-s-long pretreatments were sufficient to clean the steel surface and form a metallic interlayer between substrate and coating. Transmission electron microscopy in combination with energy dispersive X-ray spectroscopy revealed that Al, Cr, and W created intermixing zones at the interlayer/substrate and the interlayer/CNx interfaces. The steel surfaces, pretreated using Cr or W, showed the highest work of adhesion with W-adh(Cr) = 1.77 J/m(2) and W-adh(W) = 1.66 J/m(2), respectively. (C) 2016 Elsevier B.V. All rights reserved.

  • 37.
    Balachandramurthi, Arun Ramanathan
    et al.
    Univ West, Sweden.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Univ West, Sweden.
    Dixit, Nikhil
    Univ West, Sweden.
    Deng, Dunyong
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Pederson, Robert
    Univ West, Sweden.
    Microstructural influence on fatigue crack propagation during high cycle fatigue testing of additively manufactured Alloy 7182019Inngår i: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 149, s. 82-94Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A study of the microstructure of additively manufactured Alloy 718 was performed in order to better understand the parameters that have an influence on the fatigue properties of the material. The specimens were manufactured using two powder bed fusion techniques - Electron Beam Melting (EBM) and Selective Laser Melting (SLM). Four point bending fatigue tests were performed at room temperature with a stress ratio of R = 0.1 and 20 Hz frequency, on material that was either in hot isostatically pressed (HIP) and solution treated and aged (STA) condition or in STA condition without a prior HIP treatment. The grains in the SLM material in the HIP + STA condition have grown considerably both in the hatch and the contour regions; EBM material, in contrast, shows grain growth only in the contour region. Fractographic analysis of the specimens in HIP + STA condition showed a faceted appearance while the specimens in STA condition showed a more planar crack appearance. The crack propagation occurred in a transgranular mode and it was found that precipitates such as NbC, TiN or 8-phase, when present, did not affect the crack path. The areas with larger grains corresponded to the faceted appearance of the fracture surface. This could be attributed to the plastic zone ahead of the crack tip being confined within one grain, in case of the larger grains, which promotes single shear crack growth mode.

  • 38.
    Balachandramurthi, Arun Ramanathan
    et al.
    Univ West, Sweden.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Univ West, Sweden.
    Dixit, Nikhil
    Univ West, Sweden.
    Pederson, Robert
    Univ West, Sweden.
    Influence of defects and as-built surface roughness on fatigue properties of additively manufactured Alloy 7182018Inngår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 735, s. 463-474Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Electron beam melting (EBM) and Selective Laser Melting (SLM) are powder bed based additive manufacturing (AM) processes. These, relatively new, processes offer advantages such as near net shaping, manufacturing complex geometries with a design space that was previously not accessible with conventional manufacturing processes, part consolidation to reduce number of assemblies, shorter time to market etc. The aerospace and gas turbine industries have shown interest in the EBM and the SLM processes to enable topology-optimized designs, parts with lattice structures and part consolidation. However, to realize such advantages, factors affecting the mechanical properties must be well understood - especially the fatigue properties. In the context of fatigue performance, apart from the effect of different phases in the material, the effect of defects in terms of both the amount and distribution and the effect of "rough" as-built surface must be studied in detail. Fatigue properties of Alloy 718, a Ni-Fe based superalloy widely used in the aerospace engines is investigated in this study. Four point bending fatigue tests have been performed at 20 Hz in room temperature at different stress ranges to compare the performance of the EBM and the SLM material to the wrought material. The experiment aims to assess the differences in fatigue properties between the two powder bed AM processes as well as assess the effect of two post-treatment methods namely - machining and hot isostatic pressing (HIP). Fractography and metallography have been performed to explain the observed properties. Both HIPing and machining improve the fatigue performance; however, a large scatter is observed for machined specimens. Fatigue properties of SLM material approach that of wrought material while in EBM material defects severely affect the fatigue life.

  • 39.
    Balachandramurthi, Arun Ramanathan
    et al.
    Univ West, Sweden.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Univ West, Sweden.
    Mahade, Satyapal
    Univ West, Sweden.
    Pederson, Robert
    Univ West, Sweden.
    Additive Manufacturing of Alloy 718 via Electron Beam Melting: Effect of Post-Treatment on the Microstructure and the Mechanical Properties2019Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, nr 1, artikkel-id 68Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Alloy 718 finds application in gas turbine engine components, such as turbine disks, compressor blades and so forth, due to its excellent mechanical and corrosion properties at elevated temperatures. Electron beam melting (EBM) is a recent addition to the list of additive manufacturing processes and has shown the capability to produce components with unique microstructural features. In this work, Alloy 718 specimens were manufactured using the EBM process with a single batch of virgin plasma atomized powder. One set of as-built specimens was subjected to solution treatment and ageing (STA); another set of as-built specimens was subjected to hot isostatic pressing (HIP), followed by STA (and referred to as HIP+STA). Microstructural analysis of as-built specimens, STA specimens and HIP+STA specimens was carried out using optical microscopy and scanning electron microscopy. Typical columnar microstructure, which is a characteristic of the EBM manufactured alloy, was observed. Hardness evaluation of the as-built, STA and HIP+STA specimens showed that the post-treatments led to an increase in hardness in the range of similar to 50 HV1. Tensile properties of the three material conditions (as-built, STA and HIP+STA) were evaluated. Post-treatments lead to an increase in the yield strength (YS) and the ultimate tensile strength (UTS). HIP+STA led to improved elongation compared to STA due to the closure of defects but YS and UTS were comparable for the two post-treatment conditions. Fractographic analysis of the tensile tested specimens showed that the closure of shrinkage porosity and the partial healing of lack of fusion (LoF) defects were responsible for improved properties. Fatigue properties were evaluated in both STA and HIP+STA conditions. In addition, three surface conditions were also investigated, namely the raw as-built surface, the machined surface with the contour region and the machined surface without the contour region. Machining off the contour region completely together with HIP+STA led to significant improvement in fatigue performance.

  • 40.
    Barazande, Saina
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Carl Malmsten - furniture studies. Linköpings universitet, Tekniska högskolan.
    Om att berätta något: en undersökning av skapandeprocessen med berättelsen och jaget som utgångspunkt2014Independent thesis Basic level (degree of Bachelor), 10,5 poäng / 16 hpOppgave
    Abstract [sv]

    Mitt arbete är ett sökande efter en skapandeprocess som passar mig. Jag riktar blicken utåt för att hitta nya sätt att göra på och att ge fler möjligheter i mitt eget skapande och i förlängningen komma närmare mitt eget sätt att skapa. Genom intervjuer med verksamma kulturutövare inom olika media, såsom designers, en serietecknare, en musiker och en poet söker jag efter nya möjliga metoder och processer. Liksom de personer jag intervjuar vill jagmed mitt skapande dela med mig av berättelser sprungna ur mitt jag och ursprung. Jag vill berätta för att väcka tankar, minnen och reflektion.

    Min utgångspunkt är metodiken som förespråkas på Carl Malmsten Furniture Studies samt litteratur om skapande och jaget som utgångspunkt. Genom intervjuerna jag har gjort har jag utvecklats i min process och metodik och utforskat nya vägar för mitt skapande. Detta har även resulterat i två fysiska objekt, en diktbok och en förvaring. Dessa två berättar tillsammans om mina tankar om det innersta rummet, som vi alla bär inom oss.

  • 41.
    Baric, Marina
    Linköpings universitet, Institutionen för fysik, kemi och biologi.
    The effects of accelerated aging on optical components: Application to vehicle camera systems2019Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Companies providing products have many requirements, both from standards and customers, that they need to comply with in order to be able to sell their product. Veoneer AB is a leading automotive machine vision supplier, providing mono, stereo, night vision and driver monitoring systems consisting of both electronic, mechanical and optical components. These systems have to withstand certain environmental tests in order to assure the lifetime of the totalsystems. Since the life time is usually several years accelerated tests are used that correspond to a few weeks ormonths. The tests used at Veoneer are specified for electronic equipment and what Veoneer does not know today is ifthe accelerated environmental tests stated for electronic equipment are relevant for the optical component of the visionsystem.

    In this master thesis project two different accelerated environmental tests, dry and damp heat, have been chosen inorder to investigate the effect of temperature and relative humidity on the adhesive in the optical component connecting the sensor and lens. The optical components where characterized by measurement of focus position and mechanicalstrength. Different combinations of temperature and relative humidity where chosen in order to compare the effect of different stress levels but also for the purpose of deriving parameters needed for accelerated testing models such as theArrhenius, Eyring, Lawson and Peck model.

    Amongst the results from this thesis work is the focus shift measurement which follows the same trend as seen in previous research regarding the effect of temperature and relative humidity on adhesives. With an exponentialdistribution being seen in different directions for the respective stresses. Pull tests show a greater degradation withhigher stress levels, where one test case shows the greatest degradation. Calculations regarding activation energy and constants for models match previous research where one model, combining temperature and relative humidity, showssimilar values as found in literature. Calculations also show that standard accelerated life time tests overexpose adhesives due to calculations of test times with lower activation energies.

  • 42.
    Barrirero, Jenifer
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Nanostrukturerade material. Linköpings universitet, Tekniska fakulteten. Department of Material Science, Saarland University, Saarbrücken, Germany.
    Eutectic Modification of Al-Si casting alloys2019Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Aluminum alloys with silicon as the major alloying element are the most widely used aluminum casting alloys. The eutectic phase in these alloys is formed by hard and brittle silicon plates in an aluminum matrix. Such silicon plates can act as crack propagation paths deteriorating the toughness of the material. To enhance ductility, silicon can be modified to a coral-like microstructure by addition of a modifying agent. Amongst the elements proposed as modifiers, only strontium, sodium and europium induce a plate-tocoral transition, while others such as ytterbium, only refine the silicon plates. The exact mechanism for the remarkable plate-to-coral change, and the reason why certain elements only refine the structure, is still not completely understood.

    In this investigation, atom probe tomography and transmission electron microscopy were used to analyze and compare the crystal structure and the distribution of solute atoms in silicon at the atomic level. An unmodified alloy and alloys modified by strontium, sodium, europium and ytterbium were studied. Elements inducing silicon plate-to-coral transition were found to contain nanometer sized clusters at the defects in silicon with stoichiometries corresponding to compounds formed at the ternary eutectic reaction of each system. In contrast, the addition of ytterbium, that only refines the silicon plates, is unable to form clusters in silicon. We propose that the formation of ternary compound clusters AlSiNa, Al2Si2Sr and Al2Si2Eu at the silicon / liquid interface during solidification restrict silicon growth. The formation of clusters on silicon facets create growth steps and increase growth direction diversity. The incorporation of clusters in silicon explains the high density of crystallographic defects and the structural modification from plates to corals.

    The parallel lattice plane-normals 011Si // 0001Al2Si2Eu, 011Si // 610Al2Si2Eu and 111Si // 610Al2Si2Eu were found between Al2Si2Eu and silicon, and absent between Al2Si2Yb and silicon. We propose a favorable heterogeneous formation of Al2Si2Eu on silicon. The misfit between 011Si and 0002Al2Si2X interplanar spacings shows a consistent trend with the potency of modification for several elements such as strontium, sodium, europium, calcium, barium, ytterbium and yttrium.

    Delarbeid
    1. Comparison of segregations formed in unmodified and Sr-modified Al-Si alloys studied by atom probe tomography and transmission electron microscopy
    Åpne denne publikasjonen i ny fane eller vindu >>Comparison of segregations formed in unmodified and Sr-modified Al-Si alloys studied by atom probe tomography and transmission electron microscopy
    Vise andre…
    2014 (engelsk)Inngår i: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 611, s. 410-421Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    The mechanical properties of Al-7 wt.% Si can be enhanced by structural modifications of its eutectic phase. Addition of low concentrations of certain elements, in this case 150 wt-ppm Sr, is enough to cause a transition from a coarse plate-like Si structure to a finer coralline one. To fully understand the operating mechanism of this modification, the composition of the eutectic Si phase in unmodified and Sr-modified alloys was analysed and compared by atom probe tomography and (scanning) transmission electron microscopy. The unmodified alloy showed nanometre sized Al-segregations decorating defects, while the Sr-modified sample presented three types of Al-Sr segregations: (1) rod-like segregations that promote smoothening of the Al-Si boundaries in the eutectic phase, (2) particle-like segregations comparable to the ones seen in the unmodified alloy, and (3) planar segregations favouring the formation of twin boundaries. Al and Sr solubilities in Si after solidification were determined to be 430 +/- 160 at-ppm and 40 +/- 10 at-ppm, respectively. Sr predominantly segregates to the Si phase confirming its importance in the modification of the eutectic growth.

    sted, utgiver, år, opplag, sider
    Elsevier, 2014
    Emneord
    Aluminium-silicon alloys; Strontium modification; Atom probe tomography; Transmission electron microscopy; Microstructure
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-109356 (URN)10.1016/j.jallcom.2014.05.121 (DOI)000338932400064 ()
    Tilgjengelig fra: 2014-08-15 Laget: 2014-08-15 Sist oppdatert: 2019-09-13bibliografisk kontrollert
    2. Cluster formation at the Si/liquid interface in Sr and Na modified Al-Si alloys
    Åpne denne publikasjonen i ny fane eller vindu >>Cluster formation at the Si/liquid interface in Sr and Na modified Al-Si alloys
    Vise andre…
    2016 (engelsk)Inngår i: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 117, s. 16-19Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Atom probe tomography was used to compare Na and Sr modified Al-Si hypoeutectic alloys. Both Na and Sr promote the formation of nanometre-sized clusters in the Si eutectic phase. Compositional analyses of the clusters show an Al:Sr ratio of 2.92 +/- 0.46 and an Al:Na ratio of 1.07 +/- 0.23. It is proposed that SrAl2Si2 and NaAlSi clusters are formed at the Si/liquid interface and take part in the modification process by altering the eutectic Si growth.

    sted, utgiver, år, opplag, sider
    PERGAMON-ELSEVIER SCIENCE LTD, 2016
    Emneord
    Eutectic solidification; Atom probe tomography; Aluminium alloys; Eutectic modification; Transmission electron microscopy
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-127548 (URN)10.1016/j.scriptamat.2016.02.018 (DOI)000373547500004 ()
    Merknad

    Funding Agencies|German Federal Ministry of Economics and Technology [AiF 17204 N]; European Regional Development Fund (AME-Lab) [C/4-EFRE-13/2009/Br]; German Research Foundation (DFG); Federal State Government of Saarland [INST 256/298-1 FUGG]; Erasmus Mundus Doctoral Programme DocMASE of the European Commission [FPA 2011-0020]; VINNOVA Strategic Faculty Grant VINNMER Marie Curie Chair [2011-03464]; Major International (Regional) Joint Research Project from China [51420105005]

    Tilgjengelig fra: 2016-05-04 Laget: 2016-05-03 Sist oppdatert: 2019-09-13
    3. Eutectic modification by ternary compound cluster formation in Al-Si alloys
    Åpne denne publikasjonen i ny fane eller vindu >>Eutectic modification by ternary compound cluster formation in Al-Si alloys
    Vise andre…
    2019 (engelsk)Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, artikkel-id 5506Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Al-alloys with Si as the main alloying element constitute the vast majority of Al castings used commercially today. The eutectic Si microstructure in these alloys can be modified from plate-like to coral-like by the addition of a small amount of a third element to improve ductility and toughness. In this investigation the effects of Eu and Yb are studied and their influence on the microstructure is compared to further understand this modification. The two elements impact the alloy differently, where Eu modifies Si into a coral-like structure while Yb does not. Atom probe tomography shows that Eu is present within the Si phase in the form of ternary compound Al2Si2Eu clusters, while Yb is absent in the Si phase. This indicates that the presence of ternary compound clusters within Si is a necessary condition for the formation of a coral-like structure. A crystallographic orientation relationship between Si and the Al2Si2Eu phase was found, where the following plane normals are parallel: 011(Si) //0001(Al2Si2Eu), 111(Si)//6 (7) over bar 10(Al2Si2Eu) and 011(Si)//6 (7) over bar 10(Al2Si2Eu). No crystallographic relationship was found between Si and Al2Si2Yb. The heterogeneous formation of coherent Al2Si2Eu clusters inside the Si-phase is suggested to trigger the modification of the microstructure.

    sted, utgiver, år, opplag, sider
    NATURE PUBLISHING GROUP, 2019
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-156563 (URN)10.1038/s41598-019-41919-2 (DOI)000462990000048 ()30940873 (PubMedID)
    Merknad

    Funding Agencies|European Regional Development Fund (ERDF); DFG; Federal State Government of Saarland [INST 256/298-1 FUGG]; Erasmus Mundus Programme of the European Commission within the Doctoral Programme DocMASE; Major International (Regional) Joint Research Project from China [51420105005]; Overseas, Hong Kong, Macao Scholars Cooperative Research Fund from China [51728101]

    Tilgjengelig fra: 2019-05-15 Laget: 2019-05-15 Sist oppdatert: 2019-10-22
    4. Nucleation and Growth of Eutectic Si in Al-Si Alloys with Na Addition
    Åpne denne publikasjonen i ny fane eller vindu >>Nucleation and Growth of Eutectic Si in Al-Si Alloys with Na Addition
    Vise andre…
    2015 (engelsk)Inngår i: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 46, nr 3, s. 1300-1311Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Al-5 wt pct Si-based alloys with Na additions (19 and 160 ppm) have been produced by controlled sand casting and melt spinning. Entrained droplet technique and differential scanning calorimetry were employed to investigate the nucleation behavior of eutectic Si. High-resolution transmission electron microscopy and atom probe tomography were used to investigate the distribution of Na atoms within eutectic Si and at the interfaces between eutectic Si and eutectic Al. It was found that (i) only 19 ppm Na addition results into a high undercooling (49 K (49 °C)) of the entrained eutectic droplet. However, further increasing Na addition up to 160 ppm exerts no positive effect on the nucleation of eutectic Si, instead a decreased undercooling (29 K (29 °C)) was observed. (ii) Na addition suppresses the growth of eutectic Si due to the Na segregation at the interface between eutectic Si and eutectic Al, and (iii) Na addition promotes significant multiple Si twins, which can be attributed to the proposed adsorption of Na atoms at the intersection of Si twins and along the 〈112〉Si growth direction of Si. The present investigation demonstrates, for the first time, a direct observation on the distribution of Na atoms within eutectic Si and thereby provides strong experimental supports to the well-accepted impurity-induced twinning growth mechanism and poisoning of the twin plane re-entrant edge growth mechanism.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-160234 (URN)10.1007/s11661-014-2702-6 (DOI)
    Tilgjengelig fra: 2019-09-12 Laget: 2019-09-12 Sist oppdatert: 2019-09-13
    5. Phase Selective Sample Preparation of Al-Si alloys for Atom Probe Tomography
    Åpne denne publikasjonen i ny fane eller vindu >>Phase Selective Sample Preparation of Al-Si alloys for Atom Probe Tomography
    2019 (engelsk)Inngår i: Praktische metallographie, ISSN 0032-678X, E-ISSN 2195-8599, Vol. 56, nr 2, s. 76-90Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    We present how the conventional focused ion beam (FIB) lift-out method can be modified to obtain phase selective specimens for atom probe tomography (APT). The modified method combines selective deep etching with site-specific lift-out using a micromanipulator in a FIB/SEM workstation. This method is used for phase-selective sample preparation in alloys with complex microstructures such as the coral- and plate-like silicon structures in the eutectic phase of Al-Si castings. The method proves to be both, practical and robust, with a high success rate of high-quality phase-specific APT specimens.

    sted, utgiver, år, opplag, sider
    CARL HANSER VERLAG, 2019
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-154847 (URN)10.3139/147.110557 (DOI)000458507500002 ()
    Merknad

    Funding Agencies|EU; DFG; Federal State Government of Saarland [INST 256/298-1 FUGG]; Erasmus Mundus Programme of the European Commission within the Doctoral Programme DocMASE

    Tilgjengelig fra: 2019-03-05 Laget: 2019-03-05 Sist oppdatert: 2019-09-13
  • 43.
    Barrirero, Jenifer
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Nanostrukturerade material. Linköpings universitet, Tekniska fakulteten. Saarland Univ, Germany.
    Pauly, C.
    Saarland Univ, Germany.
    Engstler, M.
    Saarland Univ, Germany.
    Ghanbaja, J.
    Univ Lorraine, France.
    Ghafoor, Naureen
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Li, J.
    Univ Leoben, Austria.
    Schumacher, P.
    Univ Leoben, Austria.
    Odén, Magnus
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Nanostrukturerade material. Linköpings universitet, Tekniska fakulteten.
    Muecklich, F.
    Saarland Univ, Germany.
    Eutectic modification by ternary compound cluster formation in Al-Si alloys2019Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, artikkel-id 5506Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Al-alloys with Si as the main alloying element constitute the vast majority of Al castings used commercially today. The eutectic Si microstructure in these alloys can be modified from plate-like to coral-like by the addition of a small amount of a third element to improve ductility and toughness. In this investigation the effects of Eu and Yb are studied and their influence on the microstructure is compared to further understand this modification. The two elements impact the alloy differently, where Eu modifies Si into a coral-like structure while Yb does not. Atom probe tomography shows that Eu is present within the Si phase in the form of ternary compound Al2Si2Eu clusters, while Yb is absent in the Si phase. This indicates that the presence of ternary compound clusters within Si is a necessary condition for the formation of a coral-like structure. A crystallographic orientation relationship between Si and the Al2Si2Eu phase was found, where the following plane normals are parallel: 011(Si) //0001(Al2Si2Eu), 111(Si)//6 (7) over bar 10(Al2Si2Eu) and 011(Si)//6 (7) over bar 10(Al2Si2Eu). No crystallographic relationship was found between Si and Al2Si2Yb. The heterogeneous formation of coherent Al2Si2Eu clusters inside the Si-phase is suggested to trigger the modification of the microstructure.

  • 44.
    Beni, Valerio
    et al.
    Tyndall National Institute, University College Cork, Ireland.
    Valsesia, Andrea
    Joint Research Centre, Ispra, Italy.
    Colpo, Pascal
    Joint Research Centre, Ispra, Italy.
    Bretagnol, Frederic
    Joint Research Centre, Ispra, Italy.
    Rossi, Francois
    Joint Research Centre, Ispra, Italy.
    Arrigan, Damien
    Tyndall National Institute, University College Cork, Ireland.
    Electrochemical properties of polymeric nanopatterned electrodes2007Inngår i: Electrochemistry communications, ISSN 1388-2481, E-ISSN 1873-1902, Vol. 9, nr 7, s. 1833-1839Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An investigation of the electrochemical behaviour of gold electrodes coated with poly(ethylene glycol) (PEG), poly(acrylic acid)(PAA) and nanopatterned PAA/PEG layers is presented. Plasma-enhanced chemical vapour deposition and colloidal lithography wereused to produce nanodomes of PAA in a matrix of PEG. The electrochemical response at these nanostructured electrodes was studied asa function of the probe ion charge. Results show that the film structures allow the electrodes to retain their electrochemical activity whileminimising surface fouling and will thus be useful in the development of electrochemical nanobiosensors for various applications.

  • 45.
    Benselfelt, Tobias
    et al.
    Department of Fiber Technology, KTH, Stockholm, Sweden.
    Nordenström, Malin
    Department of Fiber Technology, KTH, Stockholm, Sweden.
    Lindström, Stefan B
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Wågberg, Lars
    Department of Fiber Technology, KTH, Stockholm, Sweden.
    Explaining the Exceptional Wet Integrity of Transparent Cellulose Nanofibril Films in the Presence of Multivalent Ions: Suitable Substrates for Biointerfaces2019Inngår i: Advanced Materials Interfaces, ISSN 2196-7350, Vol. 13, nr 6, artikkel-id 1900333Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cellulose nanofibrils (CNFs) assemble into water‐resilient materials in the presence of multivalent counter‐ions. The essential mechanisms behind these assemblies are ion–ion correlation and specific ion effects. A network model shows that the interfibril attraction indirectly influences the wet modulus by a fourth power relationship to the solidity of the network (Ew ∝ φ4). Ions that induce both ion–ion correlation and specific ion effects significantly reduce the swelling of the films, and due to the nonlinear relationship dramatically increase the wet modulus. Herein, this network model is used to explain the elastoplastic behavior of wet films of 2,2,6,6‐tetramethylpiperidine‐1‐oxyl radical (TEMPO)‐oxidized, carboxymethylated, and phosphorylated CNFs in the presence of different counter‐ions. The main findings are that the aspect ratio of the CNFs influences the ductility of the assemblies, that the bivalency of phosphorylate ligands probably limits the formation of interfibril complexes with divalent ions, and that a higher charge density increases the friction between fibrils by increasing the short‐range attraction from ion–ion correlation and specific ion effects. These findings can be used to rationally design CNF materials for a variety of applications where wet strength, ductility, and transparency are important, such as biomaterials or substrates for bioelectronics.

  • 46.
    Bentzer, Justinius Erik
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Carl Malmsten - furniture studies. Linköpings universitet, Tekniska högskolan.
    Textil, faner och jag: en möbelkollektion sprungen ur en undersökning av materialkombinationer faner och textil2014Independent thesis Basic level (degree of Bachelor), 10,5 poäng / 16 hpOppgave
    Abstract [sv]

    Jag har ett intresse för att utforska och undersöka olika material och hur vi upplever dessa material. I detta examensarbete skapar jag två möbler genom en gestaltningsprocess som grundar sig i ett undersökande av materialkombinationen faner och textil. Arbetet är uppdelat i två delar, en undersökande del där jag testar att kombinera olika faner, textilier och limmer, för att se hur jag upplever dessa och för att få en grund till min gestaltningsprocess. I den andra delen formger jag två möbler som har till syfte att väcka intresse för materialet hos betraktaren. Det blir ett klädskåp och en sittmöbel, som visar på olika sido !och mervärden med materialkombinationerna. Förhoppningsvis kan detta  arbete väcka intresset för nya materialkombinationer även hos er läsare.

  • 47.
    Berglund, Jonas
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Malmstens Linköpings universitet.
    Stark, starkare, starkast: en jämförelse av fasta tappar och centrumtappar med utgångspunkt i tappens dimensioner, inpassning, komprimering, antal och limning2018Independent thesis Basic level (degree of Bachelor), 10,5 poäng / 16 hpOppgave
    Abstract [sv]

    I mitt examensarbete jämför jag styrkan för sammanfogningar i trämöbler med fasta tappar och centrumtappar utifrån fem parametrar: tappens dimensioner, tappens inpassning, tappens komprimering, tappens antal och tappens limning. Den övergripande frågan har varit, ”är fasta tappar eller centrumtappar starkast?” Målet har varit att sålla i olika teorier rörande dessa två typer av sammanfogningar och skapa ett underlag i syfte att hjälpa möbelsnickare och formgivare att kunna ta medvetna beslut vad gäller sina val av dessa typer av sammanfogningar. Genom litteraturstudier och verkstads besök har jag samlat kunskap som ligger till grund för det hållfasthets test jag sedan gjort i materiallabbet på Linköpings universitet. Testet har utgått från ett scenario där en stols bakben ska fogas samman med en sarg. Testet visar, utifrån ett antal angivna avgränsningar, att fasta tappar utan undantag är starkare än centrumtappar.Det visar också att en dubbel fast tapp fördelar belastningen bättre än en enkel fast tapp och bidrar till en betydligt starkare fog. För c-tappar gäller generellt att ökat antal tappar ökar fogens seghet men inte nödvändigtvis maxbelastningen. Inpassning och komprimering har betydelse för hur seg en fog är.

  • 48.
    Bergström, Alexander
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Carl Malmsten - furniture studies. Linköpings universitet, Tekniska högskolan.
    Träkärnor i alpina skidor: ett examensarbete kring olika träslag och dess egenskaper som träkärna i alpina skidor.2014Independent thesis Basic level (degree of Bachelor), 10,5 poäng / 16 hpOppgave
    Abstract [sv]

    Syftet med detta arbete är att ta fram den ultimata träkärnan utefter uppspaltade önskemål på egenskaper i ett par allmountainskidor med nordiska träslag.

    Studien är deskriptiv och kvantitativ då den syftar till att mäta förändringsgraden under påverkan på träslagen. För att få in data till mina frågeställningar har tester genomförts som genererar datainsamling. En förundersökning gjordes med intervjuer för att få fram ett mer specificerat underlag för att konstruera vilken metod jag skulle ha i det slutgiltiga arbetet.

    Resultatet av studien visade att träslaget bok hade de bästa egenskaperna vad gäller böjhållfasthet. Ask hade de bästa egenskaperna när det kom till testerna på vridstyvhet. Det negativa med dessa träslag är att de är för tunga. Det lättaste träslaget av de som var med i testerna var poppel. Därför har jag valt att i den slutgiltiga träkärnan kombinera träslag. Två olika förslag har tagits fram. Den ena med en kombination av bok och poppel, den andra med ask och poppel. Den första ger en förhållandevis lätt skida med bra böjhållfasthet. Den andra en lätt skida med bra vridstyvhet. Dessa två träkärnor kommer användas i byggandet av mina skidor och testas på berget.

  • 49. Bergwall, Mats
    et al.
    Hederberg, Hampus
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial.
    Calmunger, Mattias
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Murtagh, Timothy
    Rinn, Florence
    Loukil, Mohamed Sahbi
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. mohamed.loukil@ri.se.
    Innovative Out-of-Autoclave Composite Manufacturing Method for Saving Cost2019Konferansepaper (Fagfellevurdert)
  • 50.
    Bernard, Antoine
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling.
    Offshore Oil and Gas Platform: Construction methods applied to Jackets erection2007Independent thesis Advanced level (degree of Magister), 20 poäng / 30 hpOppgave
    Abstract [en]

    My Master thesis was carried out from mid June 2006 until March 2007 within a major oil & gas subcontractor. My firm had been awarded a contract for the development of a new promising offshore oil field. Our role was limited to the fabrication of six Jackets designed to support the newly developed Topsides, each weighing more than fifteen thousands tonnes. Throughout the project, jacket after jacket, it has been felt that some room for improvement existed in the construction methods used for their erection. Safety always being the first motto of any oil & gas project, it is always of high interest to improve the erection methods used to carry out the most potentially dangerous operations. This is to be reached through a more detailed and careful approach of the heavy lifting operations design. More specifically, as part of the methods engineering department, my master thesis aimed at supporting the designing and setting up of all heavy lifting operations used for the erection and assembly of the external frames of the last Jacket to be fabricated. As an outcome of the work carried out by our department and all company’s teams, the Jacket was assembled and erected in due time with no remarkable incident.

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