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  • 1.
    Abelow, Alexis
    et al.
    University of Utah, Salt Lake City, USA.
    Persson, Kristin
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Jager, Edwin
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Berggren, Magnus
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Zharov, Ilya
    University of Utah, Salt Lake City, USA.
    Electroresponsive Nanoporous Membranes by Coating Anodized Alumina with Poly(3,4-ethylenedioxythiophone) and Polypyrrole2014In: Macromolecular materials and engineering, ISSN 1438-7492, E-ISSN 1439-2054, Vol. 299, no 2, p. 190-197Article in journal (Refereed)
    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.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Alling, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Steneteg, Peter
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Hultberg, Lasse
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Hellman, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Yu Mosyagin, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. 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 Thermodynamics2013In: TMS2013 Supplemental Proceedings, John Wiley & Sons, 2013, p. 617-626Chapter in book (Refereed)
    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.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Knutsson, Axel
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Alling, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Tasnádi, Ferenc
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Lind, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Odén, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Phase Stability and Elasticity of TiAlN2011In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 4, no 9, p. 1599-1618Article in journal (Refereed)
    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.

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  • 4.
    Adegoke, Olutayo
    et al.
    Univ West, Sweden.
    Polisetti, Satyanarayana Rao
    Univ West, Sweden.
    Xu, Jinghao
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Andersson, Joel
    Univ West, Sweden.
    Brodin, Hakan
    Siemens Ind Turbomachinery, Sweden.
    Pederson, Robert
    Univ West, Sweden.
    Harlin, Peter
    Univ West, Sweden; Sandvik Addit Mfg, Sweden.
    Influence of laser powder bed fusion process parameters on the microstructure of solution heat-treated nickel-based superalloy Alloy 247LC2022In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 183, article id 111612Article in journal (Refereed)
    Abstract [en]

    In this study, Alloy 247LC samples were built with different laser powder bed fusion (L-PBF) process parameters. The samples were then subjected to solution heat treatment at 1260 degrees C for 2 h. The grain size of all the samples increased significantly after the heat treatment. The relationship between the process parameters and grain size of the samples was investigated by performing a design of experiment analysis. The results indicated that the laser power was the most significant process parameter that influenced the grain height and aspect ratio. The laser power also significantly influenced the grain width. The as-built and as-built + heat-treated samples with high, medium, and low energy densities were characterized using a field emission gun scanning electron microscope equipped with an electron backscatter diffraction detector. The micrographs revealed that the cells present in the as-built samples disappeared after the heat treatment. Isolated cases of twinning were observed in the grains of the as-built + heat-treated samples. The disappearance of cells, increase in the grain size, and appearance of twins suggested that recrystallization occurred in the alloy after the heat treatment. The occurrence of recrystallization was confirmed by analyzing the grain orientation spread of the alloy, which was lower and more predominantly <1 degrees in the as-built + heat-treated conditions than in the as-built conditions. The microhardness of the as-built + heat-treated samples were high which was plausible because gamma precipitates were observed in the samples. However, the L-PBF process parameters had a very low correlation with the microhardness of the as-built + heat-treated samples.

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  • 5.
    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
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    An Approach in Prediction of Failure in Resistance Spot Welded Aluminum 6061-T6 under Quasi-static Tensile Test2012In: Proceedings of the Institution of mechanical engineers. Part B, journal of engineering manufacture, ISSN 0954-4054, E-ISSN 2041-2975, Vol. 226, no 6, p. 1026-1032Article in journal (Refereed)
    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.                   .

  • 6.
    Aghda, Soheil Karimi
    et al.
    Rhein Westfal TH Aachen, Germany.
    Bogdanovski, Dimitri
    Rhein Westfal TH Aachen, Germany.
    Lo, Lukas
    Sua, Heng Han
    Rhein Westfal TH Aachen, Germany.
    Patterer, Lena
    Rhein Westfal TH Aachen, Germany.
    Holzapfel, Damian M.
    Rhein Westfal TH Aachen, Germany.
    Le Febvrier, Arnaud
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hans, Marcus
    Rhein Westfal TH Aachen, Germany.
    Primetzhofer, Daniel
    Uppsala Univ, Sweden.
    Schneider, Jochen M.
    Rhein Westfal TH Aachen, Germany.
    Valence electron concentration- and N vacancy-induced elasticity in cubic early transition metal nitrides2023In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 255, article id 119078Article in journal (Refereed)
    Abstract [en]

    Motivated by frequently reported deviations from stoichiometry in cubic transition metal nitride (TMNx) thin films, the effect of N-vacancy concentration on the elastic properties of cubic TiNx, ZrNx, VNx, NbNx, and MoNx (0.72 & LE; x & LE; 1.00) is systematically studied by density functional theory (DFT) calculations. The predictions are validated experimentally for VNx (0.77 & LE; x & LE; 0.97). The DFT results indicate that the elastic behavior of the TMNx depends on both the N-vacancy concentration and the valence electron concentration (VEC) of the transition metal: While TiNx and ZrNx exhibit vacancy-induced reductions in elastic modulus, VNx and NbNx show an increase. These trends can be rationalized by considering vacancy-induced changes in elastic anisotropy and bonding. While introduction of N-vacancies in TiNx results in a significant reduction of elastic modulus along all directions and a lower average bond strength of Ti-N, the vacancy-induced reduction in [001] direction of VNx is overcompensated by the higher stiffness along [011] and [111] directions, resulting in a higher average bond strength of V-N. To validate the predicted vacancy-induced changes in elasticity experimentally, close-to-singlecrystal VNx (0.77 & LE; x & LE; 0.97) are grown on MgO(001) substrates. As the N-content is reduced, the relaxed lattice parameter a0, as probed by X-ray diffraction, decreases from 4.128 & ANGS; to 4.096 & ANGS;. This reduction in lattice parameter is accompanied by an anomalous 11% increase in elastic modulus, as determined by nanoindentation. As the experimental data agree with the predictions, the elasticity enhancement in VNx upon N-vacancy formation can be understood based on the concomitant changes in elastic anisotropy and bonding.

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  • 7.
    Ahmad, Maqsood
    et al.
    Base Engine & Materials Technology, Volvo Group, Gothenburg.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    König, Mathias
    Materials Technology for Basic Engine, Scania CV, Södertälje.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Bending Fatigue Behavior of Blast Cleaned Grey Cast Iron2017In: Residual Stresses 2016: ICRS-10, Materials Research Proceedings 2 (2016), 2017, Vol. 2, p. 193-198Conference paper (Refereed)
    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.

  • 8.
    Ahmadkhaniha, Donya
    et al.
    Jonkoping Univ, Sweden.
    Eriksson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Zanella, Caterina
    Jonkoping Univ, Sweden.
    Optimizing Heat Treatment for Electroplated NiP and NiP/SiC Coatings2020In: Coatings, ISSN 2079-6412, Vol. 10, no 12, article id 1179Article in journal (Refereed)
    Abstract [en]

    NiP (P > 10 wt.%) coatings are amorphous coatings whose structure can be transformed by heat treatment into a crystalline structure and hardened by precipitation of Ni3P. In this study, NiP coatings and composite ones with SiC nanoparticles were produced by electrodeposition, and their structural transformation by heat treatment was studied using differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The microhardness and the scratch and corrosion resistance of the coatings were evaluated and compared before and after different heat treatments. The results showed that in as-plated condition, the addition of SiC particles in the coatings did not modify the microstructure, microhardness, or electrochemical behavior. However, the SiC particles role was disclosed in combination with heat treatment. Composite coatings that were heat treated at 300 degrees C had higher microhardness and scratch resistance than the pure NiP one. In addition, composite coatings maintained their scratch resistance up to 400 degrees C, while in the case of the NiP ones, there was a reduction in scratch resistance by heating at 400 degrees C. It was also concluded that heating temperature has the main role in hardness and corrosion resistance of NiP and composite coatings, rather than heating time. The optimum heat-treatment protocol was found to be heating at 360 degrees C for 2 h, which resulted in a maximum microhardness of about 1500 HV0.02 for NiP and its composite coating without sacrificing the corrosion resistance.

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  • 9.
    Aid, Graham
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Environmental Technology and Management. Ragn-sells, Sweden.
    Kihl, Anders
    Ragn Sells AB.
    Driving forces and inhibitors of secondary stock extraction2014Conference paper (Other academic)
    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.

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  • 10.
    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
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. COMSATS Univ Islamabad, Pakistan.
    Effect of sintering temperature on properties of LiNiCuZn-Oxide: a potential anode for solid oxide fuel cell2019In: Materials Research Express, E-ISSN 2053-1591, Vol. 6, no 10, article id 105505Article in journal (Refereed)
    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.

  • 11.
    Albertini, Gianni
    et al.
    Dipartimento di Scienze dei Materiali e della Terra, Universita, Ancona, Italy.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials . Linköping University, The Institute of Technology.
    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 Steel2001In: Journal of Neutron Research, ISSN 1023-8166, E-ISSN 1477-2655, Vol. 9, p. 305-312Article in journal (Refereed)
  • 12.
    Ali, Amjad
    et al.
    COMSATS Univ Islamabad, Pakistan; Univ Okara, Pakistan.
    Raza, Rizwan
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. 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 fuel2019In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 434, article id 126679Article in journal (Refereed)
    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.

  • 13.
    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
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    Kaneto, Keiichi
    Kyushu Institute of Technology, Eamex Co. Ltd, Chuoku, Fukuoka, Japan.
    Conducting Polymers as EAPs: Device Configurations2016In: Electromechanically Active Polymers: A Concise Reference / [ed] Federico Carpi, Cham: Springer, 2016, p. 257-292Chapter in book (Other academic)
    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.

  • 14.
    Alimadadi, Majid
    et al.
    Department of Natural Sciences, Mid Sweden University, Sweden.
    Lindström, Stefan B
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    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 networks2018In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 14, p. 8945-8955Article in journal (Refereed)
    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.

  • 15. Alkaisee, Rasha
    et al.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Influence of Layer Removal Methods in Residual Stress Profiling of a Shot Peened Steel using X-ray Diffraction2014In: Residual Stresses IX, 2014, Vol. 996, p. 175-180Conference paper (Refereed)
  • 16.
    Almroth, Per
    Linköping University, Department of Mechanical Engineering. Linköping University, The Institute of Technology.
    Constitutive modeling of a nickel base superalloy: with a focus on gas turbine applications2003Licentiate thesis, comprehensive summary (Other academic)
    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.

  • 17.
    Almyras, Georgios
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Nanoscale engineering. Linköping University, Faculty of Science & Engineering.
    Sangiovanni, Davide Giuseppe
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Ruhr Univ Bochum, Germany.
    Sarakinos, Kostas
    Linköping University, Department of Physics, Chemistry and Biology, Nanoscale engineering. Linköping University, Faculty of Science & Engineering.
    Semi-Empirical Force-Field Model For The Ti1-XAlXN (0 ≤ x ≤ 1) System2019In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 2, article id 215Article in journal (Refereed)
    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.

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  • 18.
    Altgärde, Noomi
    Linköping University, Department of Physics, Chemistry and Biology.
    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 credits / 30 HE creditsStudent thesis
    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.

     

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  • 19.
    Alvi, Naveed Ul Hassan
    et al.
    RISE Res Inst Sweden, Norrkoping, Sweden.
    Sepat, Neha
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Sardar, Samim
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering. Ist Italiano Tecnol IIT, Italy.
    Berggren, Magnus
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Engquist, Isak
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Crispin, Xavier
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Toward Photoactive Wallpapers Based on ZnO-Cellulose Nanocomposites2023In: Global Challenges, E-ISSN 2056-6646, Vol. 7, article id 2300034Article in journal (Refereed)
    Abstract [en]

    The quest for eco-friendly materials with anticipated positive impact for sustainability is crucial to achieve the UN sustainable development goals. Classical strategies of composite materials can be applied on novel nanomaterials and green materials. Besides the actual technology and applications also processing and manufacturing methods should be further advanced to make entire technology concepts sustainable. Here, they show an efficient way to combine two low-cost materials, cellulose and zinc oxide (ZnO), to achieve novel functional and "green" materials via paper-making processes. While cellulose is the most abundant and cost-effective organic material extractable from nature. ZnO is cheap and known of its photocatalytic, antibacterial, and UV absorption properties. ZnO nanowires are grown directly onto cellulose fibers in water solutions and then dewatered in a process mimicking existing steps of large-scale papermaking technology. The ZnO NW paper exhibits excellent photo-conducting properties under simulated sunlight with good ON/OFF switching and long-term stability (90 minutes). It also acts as an efficient photocatalyst for hydrogen peroxide (H2O2) generation (5.7 x 10(-9) m s(-1)) with an envision the possibility of using it in buildings to enable large surfaces to spontaneously produce H2O2 at its outer surface. Such technology promise for fast degradation of microorganisms to suppress the spreading of diseases.

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  • 20.
    Amaia Beatriz, Ortega-Santos
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    Martinez, Jose Gabriel
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    Jager, Edwin
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    Enzymatic biofuel cells embedded polymer-based soft actuators2022Conference paper (Other academic)
    Abstract [en]

    Enzymatic biofuel cells are presented as an untethered alternative energy source that could power small implantable or wearable medical devices. However, most of these catalytic processes do not provide with enough energy to power common small electronic-mechanical devices. On the other hand, conducting polymer-based actuators are of great interest for their biocompatibility, flexibility, processability, possibility to be miniaturized and low power consumption. So far, these artificial muscles have been driven by external power sources that prevent them for being completely autonomous. There is a need for a novel power source to elaborate actuators that could use physiological processes as a driving force. These soft actuators’ low power consumption matches the electrical power generated by the biocatalysis of some enzymes, such as glucose oxidase and laccase in presence of glucose and oxygen in aqueous media. Here, we present the latest results in the development of polypyrrole-based soft actuators powered by enzymatic biofuel cells. The actuator consists of a tri-layer conductive substrate on which the polypyrrole is electrodeposited in both sides. The polypyrrole layers act as the active part, expanding and contracting upon a redox reaction, resulting in a bending movement. Tetrathiofulvlene-7,7,8,8-tetracyanoquinodimethane (TTF-TCNQ) and 2,2′-azino-di-(3-ethylbenzthiazoline sulfonic acid) (ABTS) electron transfer mediators are cast on the surface of the polypyrrole to help the electron transmission. The glucose oxidase and laccase enzymes are immobilized in the modified-conducting polymer surface, integrating the electrode to the actuator. The bio-catalysis of enzymes in presence of glucose and oxygen in aqueous solution provides the actuator with the electrons needed for the redox reaction, converting the chemical energy into mechanical energy, i.e., movement. The glucose-self-powered soft actuator may contribute to the development of more complex implantable, ingestible, or wearable biomedical devices such as cardio-stimulators, insulin pumps, or muscle implants.

  • 21.
    Amaia Beatriz, Ortega-Santos
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    Martinez, Jose Gabriel
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    Jager, Edwin
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    The effect of enzyme immobilization methods in polypyrrole-based soft actuators driven by glucose and O22023Conference paper (Other academic)
  • 22.
    Anderberg, Elin
    Linköping University, Department of Physics, Chemistry and Biology.
    LED Array Frequency Dependent Photocurrent Imaging of Organic Solar Cell Modules2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    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.

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  • 23.
    Andersen Söderbergh, Kim
    Linköping University, Department of Management and Engineering, Carl Malmsten - furniture studies. Linköping University, The Institute of Technology.
    Blästring av trä: Ett materialbibliotek av blästrade och ytbehandladeträytor2012Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    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.

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    Blästring av trä
  • 24.
    Andersson, Elise
    et al.
    Möbelkonservator på Nationalmuseum, styrelsemedlem i Malmstens Alumni.
    Brunne, UlfOrdförande i Malmstens Alumni, snickarmästare och möbelkonservator f.d. studierektor på Malmstens (LiU).Helgesson, RobinAnställd på Spågan möbelkonserevring AB, styrelsemedlem i Malmstens Alumni, möbelsnickare och möbelkonservator .Vaher, LauriLinköping University, Department of Management and Engineering, Malmstens Linköping University. Linköping University, Faculty of Science & Engineering.
    Proceedings of the symposium Woodworking Tools and Techniques – Past, Present and Future, Stockholm 16-19 September 20222023Conference proceedings (editor) (Other academic)
    Abstract [en]

    The 3rd Swedish Symposium on Furniture Technology& Design was held in Stockholm the 16th through the19th of September 2022, this time arranged by MalmstensAlumni in collaboration with the Swedish History Museum,Skokloster Castle and LiU Malmstens.

    Contents:

    Foreword page 6Ulf Brunne, Chairman, Malmstens Alumni

    Woodworking Tools and Techniques – Technical and Aesthetical Aspects of Furniture Design and Cabinetmaking through the Ages page 7Johan Knutsson, Professor in Furniture Culture LiU Malmstens, Sweden

    From Tool Marks to Work Practises page 14Hans Piena, Curator of Domestic Culture, Dutch Open Air Museum, The Netherlands

    Characteristics of Japanese Woodworking Tools page 21Kenji Komatsu, Woodworker/Artist, Wood Workshop BYHAND, Japan

    A Reconstruction of an Early 16th Century Tondo Frame page 29Iskander Breebaart, Senior Furniture Conservator Rijksmuseum, The Netherlands

    Wave Mouldings and Ornamental Lathe page 37Josephine Erckrath, Cabinetmaker and Furniture Conservator Møbelarkitekt Tyge Axel Holm, Denmark

    Dutch Moulding Planes from Skokloster Castle, Sweden page 42Jaap Boonstra, Furniture Conservator, Amsterdam Museum, The Netherlands, Pol Bruijs, Furniture Conservator, Private Practise, The Netherlands

    Mahogany Spheres – Reconstruction of an Artistically Crafted Element of a Writing Cabinet by the Berlin Ebenist Joseph Schneevogl (1795–1864) page 54Prof. Dr. Angelika Rauch, University of Applied Sciences, Potsdam, GermanyDipl.-Rest. Jörg Weber, Head of Workshop, University of Applied Sciences Potsdam, Germany

    Construction Features that are Typical for Marquetry Cabinets by Jan van Mekeren page 60Paul van Duin, Head of Furniture Conservation, Rijksmuseum, The NetherlandsIskander Breebaart, Senior Furniture Conservator, Rijksmuseum, The Netherlands

    Australian Timbers and Contemporary Woodworking page 68Evan Dunstone, Dunstone Design, Australia

    Woodworking as Means for Understanding and Developing the Human-Technology Relationship – Discussed Through the Work of Cabinet Maker Thomas Tempte page 74Andreas Nobel, Professor in Furniture Design LiU Malmstens, Sweden

    The Future of Furniture Craft Education – a Churchill Fellowship page 80Joseph Bray, Head of Wood School Sylva Foundation, UK

    Applied Information Technology and Mathematics in Woodturning page 86Ulf Jansson, Engineer and Woodturner Private Practise, Sweden

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  • 25.
    Andersson, Mike
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, The Institute of Technology.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, The Institute of Technology.
    Technology and application opportunities for SiC-FET gas sensors2012In: Solid State Gas Sensors - Industrial Application / [ed] Maximilian Fleischer and Mirko Lehmann, Springer Berlin/Heidelberg, 2012, p. 189-214Chapter in book (Refereed)
    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.

  • 26.
    Andersson, Niklas
    Linköping University, Department of Management and Engineering.
    Gesällprovets tillverkningsprocess2008Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    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.

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  • 27.
    Andric, Jelena
    et al.
    Chalmers University of Technology.
    Fredriksson, Sam T.
    Chalmers University of Technology.
    Lindström, Stefan B
    Linköping University, Department of Management and Engineering, Mechanics. Linköping University, The Institute of Technology.
    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 flow2013In: Acta Mechanica, ISSN 0001-5970, E-ISSN 1619-6937, Vol. 224, no 10, p. 2359-2374Article in journal (Refereed)
    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.

  • 28.
    Andric, Jelena
    et al.
    Chalmers University of Technology, Göteborg, Sweden.
    Lindström, Stefan B
    Linköping University, Department of Management and Engineering, Mechanics. Linköping University, The Institute of Technology.
    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 fibers2014In: Journal of Non-Newtonian Fluid Mechanics, ISSN 0377-0257, E-ISSN 1873-2631, Vol. 212, p. 36-46Article in journal (Refereed)
    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.

  • 29.
    Angtoft, Carl
    Linköping University, Department of Management and Engineering, Malmstens Linköping University.
    Med omvärlden som inspirationskälla: En studie i träkonstruktioner med alternativa inspirationskällor2020Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    My thesis I study structures and joints. It is about lifting your eyes and looking at compositions on a larger scale to find new solutions to old problems.

    I have been inspired by materials and structures that are far away from the wood industry and the material wood. I have systematically collected structures and joints and analysed them. With further sketching and testing, they have been modified to work as wooden joints and structures. It’s about acquiring a ”wealth of perspective” that allows you to see solutions to your own field in your surroundings, which could lead to new innovative wooden structures. This is a method which not only works for the furniture industry but a lot of other fields that could evolve in studying solutions outside their own framework and tradition

    The result ended up in prototype with a joint inspired from a socket/wall socket. The joint is intuitive and demountable which could lead to increased understanding of structures and joints for the user and a greater appreciation of the craft.

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  • 30.
    Arbring Sjöström, Theresia
    et al.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Jonsson, Amanda
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering. Stanford University, CA 94305 USA.
    Gabrielsson, Erik
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Kergoat, Loig
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering. Aix Marseille University, France.
    Tybrandt, Klas
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Berggren, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Simon, Daniel
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Cross-Linked Polyelectrolyte for Improved Selectivity and Processability of lontronic Systems2017In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, no 36, p. 30247-30252Article in journal (Refereed)
    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.

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  • 31. Order onlineBuy this publication >>
    Armakavicius, Nerijus
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Study of novel electronic materials by mid-infrared and terahertz optical Hall effect2017Licentiate thesis, comprehensive summary (Other academic)
    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.

    List of papers
    1. Cavity-enhanced optical Hall effect in epitaxial graphene detected at terahertz frequencies
    Open this publication in new window or tab >>Cavity-enhanced optical Hall effect in epitaxial graphene detected at terahertz frequencies
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    2017 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 421, p. 357-360Article in journal (Refereed) 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.

    Place, publisher, year, edition, pages
    Elsevier, 2017
    Keywords
    THz optical Hall effect, Epitaxial graphene, Free charge carrier properties
    National Category
    Physical Sciences Condensed Matter Physics Atom and Molecular Physics and Optics Ceramics
    Identifiers
    urn:nbn:se:liu:diva-132407 (URN)10.1016/j.apsusc.2016.10.023 (DOI)000408756700015 ()
    Note

    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]

    Available from: 2016-11-09 Created: 2016-11-09 Last updated: 2023-12-28Bibliographically approved
    2. Properties of two-dimensional electron gas in AlGaN/GaN HEMT structures determined by cavity-enhanced THz optical Hall effect
    Open this publication in new window or tab >>Properties of two-dimensional electron gas in AlGaN/GaN HEMT structures determined by cavity-enhanced THz optical Hall effect
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    2016 (English)In: Physica Status Solidi C-Current Topics in Solid State Physics, Vol 13 No 5-6, Wiley-VCH Verlagsgesellschaft, 2016, Vol. 13, no 5-6, p. 369-373Conference paper, Published paper (Refereed)
    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.

    Place, publisher, year, edition, pages
    Wiley-VCH Verlagsgesellschaft, 2016
    Series
    Physica Status Solidi C-Current Topics in Solid State Physics, ISSN 1862-6351
    Keywords
    AlGaN/GaN HEMTs, THz ellipsometry, 2DEG properties, THz optical Hall effect
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-133135 (URN)10.1002/pssc.201510214 (DOI)000387957200045 ()
    Conference
    11th International Conference on Nitride Semiconductors (ICNS), Beijing, China, August 30-September 4. 2015
    Available from: 2016-12-12 Created: 2016-12-09 Last updated: 2023-12-28Bibliographically approved
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    Study of novel electronic materials by mid-infrared and terahertz optical Hall effect
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  • 32.
    Armakavicius, Nerijus
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Bouhafs, Chamseddine
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Stanishev, Vallery
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Kühne, Philipp
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Knight, Sean
    Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, USA.
    Hofmann, Tino
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. 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
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, USA.
    Darakchieva, Vanya
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Cavity-enhanced optical Hall effect in epitaxial graphene detected at terahertz frequencies2017In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 421, p. 357-360Article in journal (Refereed)
    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.

  • 33.
    Arvidsson, Emma
    et al.
    Linköping University, Department of Mechanical Engineering.
    Ekblad, Emma
    Linköping University, Department of Mechanical Engineering.
    Framtagning av krypmodell för termomekanisk FE-analys av grenrör2006Independent thesis Advanced level (degree of Magister), 20 points / 30 hpStudent thesis
    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.

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  • 34.
    Arwin, Hans
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Schoeche, Stefan
    JA Woollam Co Inc, NE 68508 USA.
    Hilfiker, James
    JA Woollam Co Inc, NE 68508 USA.
    Hartveit, Mattias
    Univ Rochester, NY 14627 USA.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Juarez-Rivera, Olga Rubi
    Cinvestav Queretaro, Mexico.
    Mendoza-Galvan, Arturo
    Cinvestav Queretaro, Mexico.
    Magnusson, Roger
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Optical Chirality Determined from Mueller Matrices2021In: Applied Sciences, E-ISSN 2076-3417, Vol. 11, no 15, article id 6742Article in journal (Refereed)
    Abstract [en]

    Featured Application The analysis of the transmission of Mueller matrices facilitates studies of optical activity in samples that also exhibit linear anisotropy and depolarization and may have a multilayered structure. Such studies are important for the development of applications in chiroptics. Optical chirality, in terms of circular birefringence and circular dichroism, is described by its electromagnetic and magnetoelectric material tensors, and the corresponding optical activity contributes to the Mueller matrix. Here, spectroscopic ellipsometry in the spectral range 210-1690 nm is used to address chiral phenomena by measuring Mueller matrices in transmission. Three approaches to determine chirality parameters are discussed. In the first approach, applicable in the absence of linear polarization effects, circular birefringence and circular dichroism are evaluated directly from elements of a Mueller matrix. In the second method, differential decomposition is employed, which allows for the unique separation of chirality parameters from linear anisotropic parameters as well as from depolarization provided that the sample is homogeneous along the optical path. Finally, electromagnetic modeling using the Tellegen constitutive relations is presented. The last method also allows structural effects to be included. The three methods to quantify optical chirality are demonstrated for selected materials, including sugar solutions, alpha-quartz, liquid crystals, beetle cuticle, and films of cellulose nanocrystals.

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  • 35.
    Ashraf, Hina
    Linköping University, The Department of Physics, Chemistry and Biology.
    Investigation of the Symmetries of the Phonons in 4H and 6H-SiC by Infrared Absorption and Raman Spectroscopy2005Independent thesis Basic level (professional degree), 20 points / 30 hpStudent thesis
    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).

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  • 36.
    Aspenberg, David
    et al.
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Jergeus, Johan
    Volvo Cars Safety Centre, Göteborg.
    Nilsson, Larsgunnar
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Robust optimisation of front members in a full frontal car impactManuscript (preprint) (Other academic)
    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.

  • 37. Order onlineBuy this publication >>
    Atakan, Aylin
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Mesoporous material systems for catalysis and drug delivery2018Doctoral thesis, comprehensive summary (Other academic)
    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.

    List of papers
    1. Synthesis of a Cu-infiltrated Zr-doped SBA-15 catalyst for CO2 hydrogenation into methanol and dimethyl ethert
    Open this publication in new window or tab >>Synthesis of a Cu-infiltrated Zr-doped SBA-15 catalyst for CO2 hydrogenation into methanol and dimethyl ethert
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    2017 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 19, no 29, p. 19139-19149Article in journal (Refereed) 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.

    Place, publisher, year, edition, pages
    ROYAL SOC CHEMISTRY, 2017
    National Category
    Materials Chemistry
    Identifiers
    urn:nbn:se:liu:diva-139804 (URN)10.1039/c7cp03037a (DOI)000406334300033 ()28702581 (PubMedID)
    Note

    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]

    Available from: 2017-08-17 Created: 2017-08-17 Last updated: 2018-04-16
    2. Time evolution of the CO2 hydrogenation to fuels over Cu-Zr-SBA-15 catalysts
    Open this publication in new window or tab >>Time evolution of the CO2 hydrogenation to fuels over Cu-Zr-SBA-15 catalysts
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    2018 (English)In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 362, p. 55-64Article in journal (Refereed) 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.

    Keywords
    Cu-Zr-SBA-15, CO2 hydrogenation, Catalysis, Time evolution, Thermodynamics, Methanol, Dimethyl ether
    National Category
    Nano Technology Physical Chemistry
    Identifiers
    urn:nbn:se:liu:diva-147297 (URN)10.1016/j.jcat.2018.03.023 (DOI)000432770900007 ()
    Note

    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]

    Available from: 2018-04-16 Created: 2018-04-16 Last updated: 2018-06-14Bibliographically approved
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    Mesoporous material systems for catalysis and drug delivery
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  • 38. Order onlineBuy this publication >>
    Azam, Sher
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Wide Bandgap Semiconductor (SiC & GaN) Power Amplifiers in Different Classes2008Licentiate thesis, comprehensive summary (Other academic)
    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.

    List of papers
    1. Single-stage, High Efficiency, 26-Watt power Amplifier using SiC LE-MESFET
    Open this publication in new window or tab >>Single-stage, High Efficiency, 26-Watt power Amplifier using SiC LE-MESFET
    2006 (English)In: Microwave Conference, 2006. APMC 2006. Asia-Pacific December 12-15, 2006, p. 441-444Conference paper, Published paper (Refereed)
    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.

    Keywords
    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
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-13283 (URN)10.1109/APMC.2006.4429458 (DOI)
    Available from: 2008-05-13 Created: 2008-05-13 Last updated: 2009-09-24Bibliographically approved
    2. Designing, Fabrication and Characterization of Power Amplifiers Based on 10-Watt SiC MESFET & GaN HEMT at Microwave Frequencies
    Open this publication in new window or tab >>Designing, Fabrication and Characterization of Power Amplifiers Based on 10-Watt SiC MESFET & GaN HEMT at Microwave Frequencies
    2008 (English)In: IEEE European Microwave Week, October 10-15, Amsterdam, The Netherlands, 2008, p. 444-447Conference paper, Published paper (Refereed)
    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.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-13284 (URN)10.1109/EUMC.2008.4751484 (DOI)
    Available from: 2008-05-13 Created: 2008-05-13 Last updated: 2009-09-24Bibliographically approved
    3. Pulse Input Class-C Power Amplifier Response of SiC MESFET using Physical Transistor Structure in TCAD
    Open this publication in new window or tab >>Pulse Input Class-C Power Amplifier Response of SiC MESFET using Physical Transistor Structure in TCAD
    2008 (English)In: Solid-State Electronics, ISSN 0038-1101, E-ISSN 1879-2405, Vol. 52, no 5, p. 740-744Article in journal (Refereed) 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.

    Keywords
    Pulse, Class-C, Power amplifier, New technique, Silicon carbide, MESFET
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-13285 (URN)10.1016/j.sse.2007.09.022 (DOI)
    Available from: 2008-05-13 Created: 2008-05-13 Last updated: 2017-12-13Bibliographically approved
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  • 39.
    Azeez, Ahmed
    et al.
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Eriksson, Robert
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Calmunger, Mattias
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Lindström, Stefan B
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Low Cycle Fatigue Modelling of Steam Turbine Rotor Steel2019In: 9th International Conference Materials Structure & Micromechanics of Fracture (MSMF9) / [ed] Jaroslav Pokluda, Pavel Šandera, Elsevier, 2019, Vol. 23, p. 149-154Conference paper (Refereed)
    Abstract [en]

    Materials in steam turbine rotors are subjected to cyclic loads at high temperature, causing cracks to initiate and grow. To allow for more flexible operation, accurate fatigue models for life prediction must not be overly conservative. In this study, fully reversed low cycle fatigue tests were performed on a turbine rotor steel called FB2. The tests were done isothermally, within temperature range of room temperature to 600 °C, under strain control with 0.8-1.2 % total strain range. Some tests included hold time to calibrate the short-time creep behaviour of the material. Different fatigue life models were constructed. The life curve in terms of stress amplitude was found unusable at 600 °C, while the life curve in terms of total strain or inelastic strain amplitudes displayed inconsistent behaviour at 500 °C. To construct better life model, the inelastic strain amplitudes were separated into plastic and creep components by modelling the deformation behaviour of the material, including creep. Based on strain range partitioning approach, the fatigue life depends on different damage mechanisms at different strain ranges. This allowed the formulation of life curves based on plasticity or creep domination, which showed creep domination at 600 °C, while at 500 °C, creep only dominates for higher strain range.

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  • 40.
    Aziz, Shazed
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    Martinez Gil, Jose Gabriel
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    Foroughi, Javad
    Univ Wollongong, Australia.
    Spinks, Geoffrey M.
    Univ Wollongong, Australia.
    Jager, Edwin
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering. Univ Wollongong, Australia.
    Artificial Muscles from Hybrid Carbon Nanotube-Polypyrrole-Coated Twisted and Coiled Yarns2020In: Macromolecular materials and engineering, ISSN 1438-7492, E-ISSN 1439-2054, Vol. 305, no 11, article id 2000421Article in journal (Refereed)
    Abstract [en]

    Electrochemically or electrothermally driven twisted/coiled carbon nanotube (CNT) yarn actuators are interesting artificial muscles for wearables as they can sustain high stress. However, due to high fabrication costs, these yarns have limited their application in smart textiles. An alternative approach is to use off-the-shelf yarns and coat them with conductive polymers that deliver high actuation properties. Here, novel hybrid textile yarns are demonstrated that combine CNT and an electroactive polypyrrole coating to provide both high strength and good actuation properties. CNT-coated polyester yarns are twisted and coiled and subjected to electrochemical coating of polypyrrole to obtain the hierarchical soft actuators. When twisted without coiling, the polypyrrole-coated yarns produce fully reversible 25 degrees mm(-1)rotation, 8.3x higher than the non-reversible rotation from twisted CNT-coated yarns in a three-electrode electrochemical system operated between +0.4 and -1.0 V (vs Ag/AgCl). The coiled yarns generate fully reversible 10 degrees mm(-1)rotation and 0.22% contraction strain, 2.75x higher than coiled CNT-coated yarns, when operated within the same potential window. The twisted and coiled yarns exhibit high tensile strength with excellent abrasion resistance in wet and dry shearing conditions that can match the requirements for using them as soft actuators in wearables and textile exoskeletons.

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  • 41.
    Aziz, Shazed
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    Martinez, Jose Gabriel
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    Salahuddin, Bidita
    Australian Institute For Innovative Materials University Of Wollongong Innovation Campus, Squires Way, North Wollongong, NSW 2522, Australia.
    Persson, Nils-Krister
    Smart Textiles Technology Lab Swedish School Of Textiles University Of Borås Borås SE-501 90, Sweden.
    Jager, Edwin
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    PEDOT:PSS coated twisted and coiled yarn actuators2021In: EuroEAP 2021: International conference on Electromechanically Active Polymer (EAP) transducers & artificial muscles, 2021Conference paper (Other academic)
    Abstract [en]

    Commercial yarns can be functionalized with conducting polymers (CPs) todevelop yarn and textile actuators. Here we show a method of functionalizationof commercial polyamide yarns by poly-3,4-ethylenedioxythiophene:polystyrenesulfonate (PEDOT:PSS) coating. Aftercoating, while PEDOT:PSS is drying, it is possible to twist and coil the yarns,resulting in a major improvement of their linear strain and speed of movement.By using a potential window between +0.6 V and -1.2 V vs Ag/AgCl it waspossible to obtain a fully reversible actuation of a coiled yarn providing up to1.62% strain. A strain higher than 1% was achieved in less than 1 second.Compared to the untwisted, regular yarns, the twisted and coiled yarns produce>9× and >20× higher strain, respectively. These results are a step forward towardsthe development of soft, silent and compliant smart textile exoskeletons.

  • 42.
    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 composite2014In: Materials & Design, ISSN 0261-3069, Vol. 54, p. 660-669Article in journal (Refereed)
    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.

  • 43.
    Backe, Carin
    et al.
    University of Borås.
    Guo, Li
    Jager, Edwin
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    Persson, Nils-Krister
    University of Borås.
    Towards responding fabrics – textile processing of thin threadlike pneumatic actuators2019Conference paper (Other academic)
    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).

  • 44.
    Backe, Carin
    et al.
    University of Borås, Borås, Sweden.
    Martinez, Jose Gabriel
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    Guo, Li
    University of Borås, Borås, Sweden.
    Jager, Edwin
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    Persson, Nils-Krister
    University of Borås, Borås, Sweden.
    Multi-Assembly of Soft Electroactive Polymeric Yarn Actuators by Using Textile Processes2021Conference paper (Other academic)
    Abstract [en]

    Textile assembly methods offer great possibilities to create complex, large-scale, multi-functional 2D materials (fabrics) by a continuous process of structuring yarns together, in an architected manner. By designing a specific pattern and using functionalized yarns the properties of such a fabric can enable a variety of roles for example actuation and mechanical stimuli. Moreover, actuation can be achieved in several directions as the textile assembly enables the construction of a network where yarns can be independently addressed in X and/or Y direction. These are advantages that can be utilized in the field of soft robotics in many ways. The requirements for human-robotic interactions call for soft and compliant materials that are safe for such collaborative interactions and involve several types of functionalities. Textiles are easily conformed to the body, whether that is a robotic or a human one. Here we report on the integration of novel functional actuating yarns in the purpose of creating pliable textile actuators that also exhibit versatile morphing  capabilities. The yarns consist of three layers; two of which are made of thin poly (3, 4-ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT: PSS) coatings that cover opposite sides of the third layer, an ionogel. This stretchable gel supplies the system with ions for the actuation mechanism and therefore enables in-air actuation. The yarns are transformed into fabrics by using woven assembly techniques. This is an additive method that structures one set of yarns in a parallel sequence that is perpendicular to another second set of yarns. By structuring a number of yarns together in parallel the performance in terms of force output including blocking force is shown to increase. The textile assembly process allows for two approaches, collective and individual addressing for the actuating yarns. For the former, arranging the yarns into different pre-determined segments enable collective actuation of each segment to change the overall shape of the textile structure. In regards to the latter, by individual addressing we show that a specific and targeted actuation can be achieved. Furthermore, the arrangement in which the yarns are interlaced in the fabric enables switching the modality of the actuation. This means that we can alter a motion specific to the yarns into another by their arrangement in the textile structure. With our developed textile assembly method, we are approaching low-cost, large-scale production of actuating systems for human-robotic applications

  • 45. Backe, Carin
    et al.
    Martinez, Jose Gabriel
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    Guo, Li
    Jager, Edwin
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    Persson, Nils-Krister
    Multi-Assembly of Soft Electroactive Polymeric Yarn Actuators by Using Textile Processes2021Conference paper (Other academic)
  • 46. Backe, Carin
    et al.
    Martinez, Jose Gabriel
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    Guo, Li
    Persson, Nils-Krister
    Jager, Edwin
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    Serially connected EAP based tape yarns for in-air actuation using textile structures2023Conference paper (Other academic)
  • 47.
    Bai, Sai
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. 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
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. Univ Oxford, England.
    Snaith, Henry J.
    Univ Oxford, England.
    Reproducible Planar Heterojunction Solar Cells Based on One-Step Solution-Processed Methylammonium Lead Halide Perovskites2017In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 29, no 1, p. 462-473Article in journal (Refereed)
    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.

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  • 48.
    Bakhit, Babak
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Multifunctional Transition-metal Diboride Coatings Synthesized by Magnetron sputtering with Synchronized Metal-ion Irradiation2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Refractory transition-metal diborides (TMB2), classified as ultra-high temperature ceramics, are promising materials for extreme thermal and chemical environments. There is a growing demand for employing TMB2 in high-temperature electrodes, advanced nuclear fission reactors, molten metal containment, refractory crucibles, thermocouple protection tubes in steel baths and aluminum reduction cells, reinforcement fibers, solar power, aerospace, and armor applications. Magnetron-sputter-deposited TMB2 have recently received increasing attention as the next class of hard ceramic protective thin films. These layers usually crystallize in a hexagonal AlB2 crystal structure (P6/mmm, SG-191) in which B atoms form graphite-like honeycomb sheets between hexagonal-close-packed TM layers. The strong covalent bonding between TM and B atoms as well as within the honeycomb B sheets provides high melting temperature, hardness, and stiffness, while metallic bonding within TM layers results in good electrical and thermal conductivities. However, sputter-deposited TMB2 films suffer from several critical issues such as boron overstoichiometry, high brittleness, and low oxidation resistance. All of these aspects are addressed in the thesis.

    In Paper 1, the common issue with sputter-deposited diboride thin films, i.e. the presence of excess B, is resolved by using high power impulse magnetron sputtering (HiPIMS). The B/Ti ratio in TiBx films, used as a model materials system, is controllably varied from 2.08 to 1.83 by adjusting the HiPIMS pulse length ton, while maintaining the average power and pulse frequency constant. As a result, the peak current density increases from 0.27 to 0.88 A/cm2, which leads to an increased gas rarefaction and, hence, higher metal-ion densities in the plasma. Film growth becomes then increasingly controlled by ionized target atoms, rather than neutral species. Since sputter-ejected Ti atoms have a higher probability of being ionized than B atoms, due to their lower first-ionization potential and larger ionization cross-section, the B/Ti ratio in the films decreases a function of target peak current.

    While TM diborides are inherently hard, that alone is not sufficient to prevent failure in applications involving high stresses, as hardness is typically accompanied by brittleness. In order to avoid brittle cracking, thin films must be both hard and relatively ductile, which is referred to as high toughness. In Paper 2, it is demonstrated that Zr1-xTaxBy thin films grown by hybrid high-power impulse and DC magnetron co-sputtering (Ta-HiPIMS/ZrB2-DCMS) with x ≥ 0.2 are not only hard, but also tough. The films with x ≥ 0.2 show a self-organized columnar core/shell nanostructure (see Paper 3), in which crystalline hexagonal Zr-rich stoichiometric Zr1-xTaxB2 cores are surrounded by narrow dense, disordered Ta-rich shells that are B-deficient.

    The disordered shells have the structural characteristics of metallic-glass thin films, which exhibit both high strength and toughness. Hence, such a nanostructure combines the benefits of crystalline diboride nanocolumns, providing the high hardness, with the dense metallic-glasslike shells, which give rise to enhanced toughness.

    The mechanical properties of Zr1-xTaxBy thin films annealed in Ar atmosphere are studied as a function of annealing temperature Ta up to 1200 °C in Paper 4. In-situ and ex-situ nanoindentation analyses reveal that all films undergo age hardening up to Ta = 800 °C, with the highest hardness achieved for Zr0.8Ta0.2B1.8 (45.5±1.0 GPa). The age hardening, which occurs without any phase separation or decomposition, can be explained by point-defect recovery that enhances chemical bond density. Although hardness decreases at Ta > 800 °C due mainly to recrystallization, column coarsening, and planar defect annihilation, all layers show hardness values above 34 GPa over the entire Ta range.

    The oxidation resistance of TiBx thin films is addressed in Paper 5. In general, TMB2 suffer from rapid high-temperature oxidation, which is a critical issue for many applications. In this study, it is demonstrated that alloying the films with Al significantly increases the oxidation resistance with only a slight decrease in hardness. Contrary to bulk TiB2 synthesized by powder metallurgy processes, the oxidation products of TiB2 thin films do not contain the B2O3 oxide scale, which is usually observed below 1000 °C in air, and merely consists of a TiO2 phase. The enhanced oxidation resistance is attributed to the formation of a dense, protective Al-containing oxide scale, which considerably decreases the oxygen diffusion rate by suppressing the oxidecrystallites coarsening.

    To realize the goal of fully multifunctional diborides, Zr1-xCrxBy thin films grown by hybrid Cr-HiPIMS/ZrB2-DCMS co-sputtering are studied in Paper 6. These layers exhibit a unique combination of high hardness, toughness, wear, oxidation, and corrosion resistance.

    The last paper (Paper 7) addresses the issue of efficient energy and resource consumption in industrial processes, which United Nations defines as one of the sustainable development goals. The idea here is to replace the conventionally used thermal-energy flux from resistive heaters with the irradiation by high mass metal ions (Hf+), which results in more efficient energy transfer to the deposited layer. We deposited Ti0.67Hf0.33B1.7 films using hybrid HfB2-HiPIMS/TiB2-DCMS co-sputtering at substrate temperature not exceeding 100 °C. Results reveal that dense layers can be achieved with high hardness values (> 40 GPa) even though no external substrate heating was used during the process.

    List of papers
    1. Controlling the B/Ti ratio of TiBx thin films grown by high-power impulse magnetron sputtering
    Open this publication in new window or tab >>Controlling the B/Ti ratio of TiBx thin films grown by high-power impulse magnetron sputtering
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    2018 (English)In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 36, no 3, article id 030604Article in journal (Refereed) Published
    Abstract [en]

    TiBx thin films grown from compound TiB2 targets by magnetron sputter deposition are typically highly over-stoichiometric, with x ranging from 3.5 to 2.4, due to differences in Ti and B preferential-ejection angles and gas-phase scattering during transport from the target to the substrate. Here, the authors demonstrate that stoichiometric TiB2 films can be obtained using highpower impulse magnetron sputtering (HiPIMS) operated in power-controlled mode. The B/Ti ratio x of films sputter-deposited in Ar is controllably varied from 2.08 to 1.83 by adjusting the length of HiPIMS pulses t(on) between 100 and 30 mu s, while maintaining average power and pulse frequency constant. This results in peak current densities J(T), peak ranging from 0.27 to 0.88 A/cm(2). Energy- and time-resolved mass spectrometry analyses of the ion fluxes incident at the substrate position show that the density of metal ions increases with decreasing t(on) due to a dramatic increase in J(T, peak) resulting in the strong gas rarefaction. With t(on)amp;lt;60 mu s (J(T),(peak)amp;gt; 0.4 A/cm(2)), film growth is increasingly controlled by ions incident at the substrate, rather than neutrals, as a result of the higher plasma dencity and, hence, electron-impact ionization probablity. Thus, since sputter- ejected Ti atoms have a higher probability of being ionized than B atoms, due to their lower first-ionization potential and larger ionization cross-section, the Ti concentration in as-deposited films increases with decreasing ton (increasing J(T,peak)) as ionized sputtered species are steered to the substrate by the plasma in order to maintain charge neutrality. Published by the AVS.

    Place, publisher, year, edition, pages
    A V S AMER INST PHYSICS, 2018
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-148101 (URN)10.1116/1.5026445 (DOI)000432372400013 ()
    Note

    Funding Agencies|Swedish Research Council VR [2014-5790, 642-2013-8020]; Knut and Alice Wallenberg foundation [KAW 2015.0043]; Aforsk foundation [16-359]; Carl Tryggers Stiftelse Contract [CTS 15:219, CTS 17:166, CTS 14:431]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO Mat LiU) [2009 00971]

    Available from: 2018-05-30 Created: 2018-05-30 Last updated: 2021-12-28
    2. Strategy for simultaneously increasing both hardness and toughness in ZrB2-rich Zr1-xTaxBy thin films
    Open this publication in new window or tab >>Strategy for simultaneously increasing both hardness and toughness in ZrB2-rich Zr1-xTaxBy thin films
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    2019 (English)In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 37, no 3, article id 031506Article in journal (Refereed) Published
    Abstract [en]

    Refractory transition-metal diborides exhibit inherent hardness. However, this is not always sufficient to prevent failure in applications involving high mechanical and thermal stress, since hardness is typically accompanied by brittleness leading to crack formation and propagation. Toughness, the combination of hardness and ductility, is required to avoid brittle fracture. Here, the authors demonstrate a strategy for simultaneously enhancing both hardness and ductility of ZrB2-rich thin films grown in pure Ar on Al2O3(0001) and Si(001) substrates at 475 degrees C. ZrB2.4 layers are deposited by dc magnetron sputtering (DCMS) from a ZrB2 target, while Zr1-xTaxBy alloy films are grown, thus varying the B/metal ratio as a function of x, by adding pulsed high-power impulse magnetron sputtering (HiPIMS) from a Ta target to deposit Zr1-xTaxBy alloy films using hybrid Ta-HiPIMS/ZrB2-DCMS sputtering with a substrate bias synchronized to the metal-rich portion of each HiPIMS pulse. The average power P-Ta (and pulse frequency) applied to the HiPIMS Ta target is varied from 0 to 1800W (0 to 300 Hz) in increments of 600W (100 Hz). The resulting boron-to-metal ratio, y = B/(Zr+Ta), in as-deposited Zr1-xTaxBy films decreases from 2.4 to 1.5 as P-Ta is increased from 0 to 1800W, while x increases from 0 to 0.3. A combination of x-ray diffraction (XRD), glancing-angle XRD, transmission electron microscopy (TEM), analytical Z-contrast scanning TEM, electron energy-loss spectroscopy, energy-dispersive x-ray spectroscopy, x-ray photoelectron spectroscopy, and atom-probe tomography reveals that all films have the hexagonal AlB2 crystal structure with a columnar nanostructure, in which the column boundaries of layers with 0 amp;lt;= x amp;lt; 0.2 are B-rich, whereas those with x amp;gt;= 0.2 are Ta-rich. The nanostructural transition, combined with changes in average column widths, results in an similar to 20% increase in hardness, from 35 to 42 GPa, with a simultaneous increase of similar to 30% in nanoindentation toughness, from 4.0 to 5.2MPa root m. Published by the AVS.

    Place, publisher, year, edition, pages
    A V S AMER INST PHYSICS, 2019
    National Category
    Inorganic Chemistry
    Identifiers
    urn:nbn:se:liu:diva-159001 (URN)10.1116/1.5093170 (DOI)000472182400035 ()
    Note

    Funding Agencies|Swedish Research Council VR [2014-5790, 2018-03957, 642-2013-8020]; Knut and Alice Wallenbergs foundation [KAW 2015.0043]; VINNOVA [2018-04290]; Aforsk Foundation [16-359]; Carl Tryggers Stiftelse [CTS 15: 219, CTS 17: 166, CTS 14: 431]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO Mat LiU) [2009 00971]

    Available from: 2019-07-19 Created: 2019-07-19 Last updated: 2021-12-28
    3. Self-organized columnar Zr0.7Ta0.3B1.5 core/shell-nanostructure thin films
    Open this publication in new window or tab >>Self-organized columnar Zr0.7Ta0.3B1.5 core/shell-nanostructure thin films
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    2020 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 401, article id 126237Article in journal (Refereed) Published
    Abstract [en]

    We recently showed that Zr1−xTaxBy thin films have columnar nanostructure in which column boundaries are B-rich for x < 0.2, while Ta-rich for x ≥ 0.2. Layers with x ≥ 0.2 exhibit higher hardness and, simultaneously, enhanced toughness. Here, we determine the atomic-scale nanostructure of sputter-deposited columnar Zr0.7Ta0.3B1.5 thin films. The columns, 95 ± 17 Å, are core/shell nanostructures in which 80 ± 15-Å cores are crystalline hexagonal-AlB2-structure Zr-rich stoichiometric Zr1−xTaxB2. The shell structure is a narrow dense, disordered region that is Ta-rich and highly B-deficient. The cores are formed under intense ion mixing via preferential Ta segregation, due to the lower formation enthalpy of TaB2 than ZrB2, in response to the chemical driving force to form a stoichiometric compound. The films with unique combination of nanosized crystalline cores and dense metallic-glass-like shells provide excellent mechanical properties.

    Place, publisher, year, edition, pages
    Elsevier, 2020
    Keywords
    Thin films, Transition-metal (TM) diborides, Self-organized, Core/shell nanostructure, Hardness and toughness
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-169201 (URN)10.1016/j.surfcoat.2020.126237 (DOI)000583161500008 ()2-s2.0-85089079938 (Scopus ID)
    Note

    Funding agencies:  Knut and Alice Wallenberg (KAW) FoundationKnut & Alice Wallenberg Foundation [KAW 2015.0043]; electron microscopy laboratory in Linkoping; Swedish Research Council VRSwedish Research Council [2014-5790, 2018-03957, 2019-05403, 642-2013-8020]; VINNOVA Gran

    Available from: 2020-09-11 Created: 2020-09-11 Last updated: 2021-12-28Bibliographically approved
    4. Age hardening in superhard ZrB2-rich Zr1-xTaxBy thin films
    Open this publication in new window or tab >>Age hardening in superhard ZrB2-rich Zr1-xTaxBy thin films
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    2021 (English)In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 191, p. 120-125Article in journal (Refereed) Published
    Abstract [en]

    We recently showed that sputter-deposited Zr1-xTaxBy thin films have hexagonal AlB2-type columnar nanostructure in which column boundaries are B-rich for x < 0.2, while Ta-rich for x ≥ 0.2. As-deposited layers with x ≥ 0.2 exhibit higher hardness and, simultaneously, enhanced toughness. Here, we study the mechanical properties of ZrB2.4, Zr0.8Ta0.2B1.8, and Zr0.7Ta0.3B1.5 films annealed in Ar atmosphere as a function of annealing temperature Ta up to 1200 °C. In-situ and ex-situ nanoindentation analyses reveal that all films undergo age hardening up to Ta = 800 °C, with the highest hardness achieved for Zr0.8Ta0.2B1.8 (45.5±1.0 GPa). The age hardening, which occurs without any phase separation or decomposition, can be explained by point-defect recovery that enhances chemical bond density. Although hardness decreases at Ta > 800 °C due mainly to recrystallization, column coarsening, and planar defect annihilation, all layers show hardness values above 34 GPa over the entire Ta range.

    Place, publisher, year, edition, pages
    Elsevier, 2021
    Keywords
    Thin films; Transition-metal (TM) diboridesAge hardening; Thermal stability; Hardness and elastic modulus
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-170224 (URN)10.1016/j.scriptamat.2020.09.026 (DOI)urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-170224 ()2-s2.0-85091672167 (Scopus ID)
    Available from: 2020-10-02 Created: 2020-10-02 Last updated: 2024-02-01Bibliographically approved
    5. Improving the high-temperature oxidation resistance of TiB2 thin films by alloying with Al
    Open this publication in new window or tab >>Improving the high-temperature oxidation resistance of TiB2 thin films by alloying with Al
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    2020 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 196, p. 677-689Article in journal (Refereed) Published
    Abstract [en]

    Refractory transition-metal diborides (TMB2) are candidates for extreme environments due to melting points above 3000 degrees C, excellent hardness, good chemical stability, and thermal and electrical conductivity. However, they typically suffer from rapid high-temperature oxidation. Here, we study the effect of Al addition on the oxidation properties of sputter-deposited TiB2-rich Ti1-xAlxBy thin films and demonstrate that alloying the films with Al significantly increases the oxidation resistance with a slight decrease in hardness. TiB2.4 layers are deposited by dc magnetron sputtering (DCMS) from a TiB2 target, while Ti1-xAlxBy alloy films are grown by hybrid high-power impulse and dc magnetron co-sputtering (Al-HiPIMS/TiB2-DCMS). All as-deposited films exhibit columnar structure. The column boundaries of TiB2.4 are B-rich, while Ti0.68Al0.32B1.35 alloys have Ti-rich columns surrounded by a Ti(1-x)Al(x)By tissue phase which is predominantly Al rich. Air-annealing TiB2.4 at temperatures above 500 degrees C leads to the formation of oxide scales that do not contain B and mostly consist of a rutile-TiO2 (s) phase. The resulting oxidation products are highly porous due to the evaporation of B2O3 (g) phase as well as the coarsening of TiO2 crystallites. This poor oxidation resistance is significantly improved by alloying with Al. While air-annealing at 800 degrees C for 0.5 h results in the formation of an similar to 1900-nm oxide scale on TiB2.4, the thickness of the scale formed on the Ti0.68Al0.32B1.35 alloys is similar to 470 nm. The enhanced oxidation resistance is attributed to the formation of a dense, protective Al-containing oxide scale that considerably decreases the oxygen diffusion rate by suppressing the oxide-crystallites coarsening. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

    Place, publisher, year, edition, pages
    PERGAMON-ELSEVIER SCIENCE LTD, 2020
    Keywords
    Thin films; Titanium diboride (TiB2); Nanostructure; XPS; High temperature oxidation
    National Category
    Materials Chemistry
    Identifiers
    urn:nbn:se:liu:diva-168859 (URN)10.1016/j.actamat.2020.07.025 (DOI)000557651000060 ()
    Note

    Funding Agencies|Knut and Alice Wallenberg (KAW) foundationKnut & Alice Wallenberg Foundation [KAW 2015.0043]; Swedish Research Council VR Grant [2014-5790, 2018-03957, 642-2013-8020]; VINNOVAVinnova [2018-04290]; Aforsk foundation [16-359]; Carl Tryggers Stiftelse [CTS 15:219, CTS 17:166, CTS 14:431]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO Mat LiU) [2009 00971]; Swedish research council VR-RFISwedish Research Council [2017-00646_9]; Swedish Foundation for Strategic ResearchSwedish Foundation for Strategic Research [RIF14-0053, RIF14-0074]

    Available from: 2020-09-11 Created: 2020-09-11 Last updated: 2021-12-29
    6. Multifunctional ZrB2-rich Zr1-xCrxBy thin films with enhanced mechanical, oxidation, and corrosion properties
    Open this publication in new window or tab >>Multifunctional ZrB2-rich Zr1-xCrxBy thin films with enhanced mechanical, oxidation, and corrosion properties
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    2021 (English)In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 185, article id 109990Article in journal (Refereed) Published
    Abstract [en]

    Refractory transition-metal (TM) diborides have high melting points, excellent hardness, and good  chemical  stability.  However, these properties are not sufficient for applications involving extreme  environments that require high mechanical strength as well as oxidation and corrosion resistance. Here, we study the effect of Cr addition on the properties of ZrB2-rich Zr1-xCrxBy thin films grown by hybrid high-power impulse and dc magnetron co-sputtering (Cr-HiPIMS/ZrB2-DCMS) with a 100-V Cr-metal-ion synchronized potential. Cr metal fraction, x = Cr/(Zr+Cr), is increased from 0.23 to 0.44 by decreasing the power Pzrb2 applied to the DCMS ZrB2 target from 4000 to 2000 W, while the average power, pulse width, and frequency applied to the HiPIMS Cr target are maintained constant. In addition, y decreases from 2.18 to 1.11 as a function of Pzrb2, as a result of supplying Cr to the growing film and preferential B resputtering caused by the pulsed Cr-ion flux. ZrB2.18, Zr0.77Cr0.23B1.52, Zr0.71Cr0.29B1.42, and Zr0.68Cr0.32B1.38 2 films have hexagonal AlB2 crystal structure with a columnar nanostructure, while Zr0.64Cr0.36B1.30 and Zr0.56Cr0.44B1.11 are  amorphous. All films show hardness above 30 GPa. Zr0.56Cr0.44B1.11 alloys exhibit much better toughness, wear, oxidation, and corrosion resistance than ZrB2.18. This combination of properties   makes Zr0.56Cr0.44B1.11 ideal candidates for numerous strategic applications.

    Keywords
    Thin films, Transition-metal (TM) diborides, Mechanical properties, Wear, Oxidation, Corrosion
    National Category
    Inorganic Chemistry
    Identifiers
    urn:nbn:se:liu:diva-171888 (URN)10.1016/j.vacuum.2020.109990 (DOI)000618239100003 ()
    Note

    Funding agencies: We acknowledge support from the Knut and Alice Wallenberg (KAW) foundation for Project funding (KAW 2015.0043). Financial support from the Swedish Research Council VR Grant 2018–03957 and 642-2013-8020, the VINNOVA Grant 2019–04882, and Carl Tryggers Stiftelse contracts CTS 15:219, CTS 17:166, and CTS 14:431 are also gratefully acknowledged. Furthermore, the authors acknowledge financial support from the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linköping University (Faculty Grant SFO Mat LiU No. 2009 00971). Supports from the Swedish research council VR-RFI (#2017–00646_9) for the Accelerator based ion-technological center and from the Swedish Foundation for Strategic Research (contract RIF14-0053; for the tandem accelerator laboratory in Uppsala University, and contract RIF14-0074; for the electron microscopy laboratory) are acknowledged.

    Available from: 2020-12-11 Created: 2020-12-11 Last updated: 2021-12-28
    7. Dense Ti0.67Hf0.33B1.7 thin films grown by hybrid HfB2-HiPIMS/TiB2-DCMS co-sputtering without external heating
    Open this publication in new window or tab >>Dense Ti0.67Hf0.33B1.7 thin films grown by hybrid HfB2-HiPIMS/TiB2-DCMS co-sputtering without external heating
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    2021 (English)In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 186, article id 110057Article in journal (Refereed) Published
    Abstract [en]

    There is a need for developing synthesis techniques that allow the growth of high-quality functional films at low substrate temperatures to minimize energy consumption and enable coating temperature-sensitive substrates. A typical shortcoming of conventional low-temperature growth strategies is insufficient atomic mobility, which leads to porous microstructures with impurity incorporation due to atmosphere exposure, and, in turn, poor mechanical properties. Here, we report the synthesis of dense Ti0.67Hf0.33B1.7 thin films with a hardness of ∼41.0 GPa grown without external heating (substrate temperature below ∼100 °C) by hybrid high-power impulse and dc magnetron co-sputtering (HfB2-HiPIMS/TiB2-DCMS) in pure Ar on Al2O3(0001) substrates. A substrate bias potential of −300 V is synchronized to the target-ion-rich portion of each HiPIMS pulse. The limited atomic mobility inherent to such desired low-temperature deposition is compensated for by heavy-mass ion (Hf+) irradiation promoting the growth of dense Ti0.67Hf0.33B1.7.

    Place, publisher, year, edition, pages
    Elsevier, 2021
    Keywords
    Thin films, Borides, Low-temperature sputter deposition, Hybrid HiPIMS/DCMS, Hardness
    National Category
    Ceramics
    Identifiers
    urn:nbn:se:liu:diva-172653 (URN)10.1016/j.vacuum.2021.110057 (DOI)000620647100008 ()
    Funder
    Knut and Alice Wallenberg Foundation, KAW 2015.0043Swedish Research Council, 2018-03957, 642-2013-8020Vinnova, 2019-04882Swedish Energy Agency, 51201-1Carl Tryggers foundation , CTS 15:219, CTS 17:166, CTS 14:431Linköpings universitet, 2009 00971Swedish Research Council, #2017-00646_9Swedish Foundation for Strategic Research , RIF14-0053, RIF14-0074
    Note

    Additional funding agencies: German Science Foundation (DFG) : SCHN735/42-1.

    Available from: 2021-01-15 Created: 2021-01-15 Last updated: 2021-12-28Bibliographically approved
  • 49.
    Bakhit, Babak
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Mráz, Stanislav
    Materials Chemistry, RWTH Aachen University, Aachen, Germany.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Schneider, Jochen M.
    Materials Chemistry, RWTH Aachen University, Aachen, Germany.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Materials Research Laboratory and Department of Materials Science, University of Illinois, Urbana, IL, USA; Department of Materials Science and Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Dense Ti0.67Hf0.33B1.7 thin films grown by hybrid HfB2-HiPIMS/TiB2-DCMS co-sputtering without external heating2021In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 186, article id 110057Article in journal (Refereed)
    Abstract [en]

    There is a need for developing synthesis techniques that allow the growth of high-quality functional films at low substrate temperatures to minimize energy consumption and enable coating temperature-sensitive substrates. A typical shortcoming of conventional low-temperature growth strategies is insufficient atomic mobility, which leads to porous microstructures with impurity incorporation due to atmosphere exposure, and, in turn, poor mechanical properties. Here, we report the synthesis of dense Ti0.67Hf0.33B1.7 thin films with a hardness of ∼41.0 GPa grown without external heating (substrate temperature below ∼100 °C) by hybrid high-power impulse and dc magnetron co-sputtering (HfB2-HiPIMS/TiB2-DCMS) in pure Ar on Al2O3(0001) substrates. A substrate bias potential of −300 V is synchronized to the target-ion-rich portion of each HiPIMS pulse. The limited atomic mobility inherent to such desired low-temperature deposition is compensated for by heavy-mass ion (Hf+) irradiation promoting the growth of dense Ti0.67Hf0.33B1.7.

    Download full text (pdf)
    fulltext
  • 50.
    Bakoglidis, Konstantinos
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Univ Manchester, England.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    dos Santos, Renato B.
    Univ Fed Bahia, Brazil.
    Rivelino, Roberto
    Univ Fed Bahia, Brazil.
    Persson, Per O A
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Gueorguiev, Gueorgui Kostov
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Self-Healing in Carbon Nitride Evidenced As Material Inflation and Superlubric Behavior2018In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, no 19, p. 16238-16243Article in journal (Refereed)
    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.

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