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Detecting plasticity in al thin films by means of bulge test
Holzer, Jakub ; Pikálek, Tomáš ; Buchta, Zdeněk ; Lazar, Josef ; Tinoco, H.A. ; Chlupová, Alice ; Náhlík, Luboš ; Sobota, Jaroslav ; Fořt, Tomáš ; Kruml, Tomáš
The Bulge test proved to be a useful tool for measuring elastic properties of thin films and\nfree standing membranes, particularly Young’s modulus and residual stress. The basic principle\nof bulge test is application of differential pressure on one side of the a membrane, measurement of\nthe shape of bulged surface as a function of pressure, in this case via laser interferometer, and\nevaluation of a pressure-deflection relationship. In this study, bilayer membrane consisting of a\nsilicon nitride supporting layer and an aluminium layer deposited by means of magnetron\nsputtering is subjected to the bulge test. The results clearly show signs of a non-linear behavior\nthat is caused by plastic deformation in the aluminium layer. Finite element analysis is being\ndeveloped to describe this behavior because analytical model using deflection of central point and\npressure relation falls apart in case of non-linearity.
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Reflectivity of a mirror in XUV spectral region (46.9 nm).
Schmidt, Jiří ; Koláček, Karel ; Štraus, Jaroslav ; Frolov, Oleksandr ; Prukner, Václav ; Melich, Radek ; Psota, Pavel ; Sobota, Jaroslav ; Fořt, Tomáš
A focusing mirror as an optical element is used in our applications that require light collection (e.g. for laser ablation studies). A knowledge of the mirror reflectivity is important for determination of focused laser pulse energy, or for determination of local fluencies near the laser focus. The reflectivity of our spherical focusing mirror with(/without) multi-layer coating was measured. Reflection coefficients of this mirror in a long period of time are also reported. Further, the incidence-angle dependence of the XUV reflectivity of flat mirrors is presented as well.
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Interferometrical system for bulge test thin film characterization
Pikálek, Tomáš ; Holzer, Jakub ; Tinoco, H.A. ; Buchta, Zdeněk ; Lazar, Josef ; Chlupová, Alice ; Náhlík, Luboš ; Sobota, Jaroslav ; Fořt, Tomáš ; Kruml, Tomáš
Behavior of thin film materials undergoing stress and deformation differs from bulk materials. A common method for the mechanical characterization of thin films is nanoindentation based on indenting a small tip into the material. A different approach is a bulge test technique. In this method, a differential pressure is applied on a free-standing membrane and the mechanical properties (Young’s modulus and residual stress) are calculated from the shape of the bulged membrane. In our experiments, we developed an interferometrical system for the membrane shape measurement during the bulge test.
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Impact resistence on nanocomposite Mo-B-C- and W-B-C coatings deposited using magnetron sputtering technique
Fořt, Tomáš ; Grossman, Jan ; Daniel, Josef ; Sobota, Jaroslav ; Dupák, Libor ; Buršíková, V. ; Zábranský, L. ; Souček, L. ; Mirzaei, S. ; Alishahi, M. ; Vašina, P. ; Buršík, Jiří
Recently, based on attractive mechanical properties of boride and carbide based X2BC ternary compounds (X = Mo, W and Ta) they became subjects of both theoretical calculations and experimental work. In the case of stoichiometric composition, X2BC with X = Mo, W and Ta are very promising candidates for protection of cutting and forming tools due to their unusually stiffness and moderate ductility.\nIn this work we focus on nanostructured Mo-B-C and W-B-C layers grown by magnetron sputtering on high speed steel (HSS) substrates. Mechanical properties of the layers were characterized by nanoindentation experiments in both static and dynamic loading regimes. Elastic modulus, indentation hardness and fracture resistance were evaluated and discussed. The fracture resistance of both Mo-B-C and W-B-C coatings was compared using both indentation and dynamic impact tests.\n
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Role of the superconductivity in radiative heat transfer
Králík, Tomáš ; Musilová, Věra ; Srnka, Aleš ; Fořt, Tomáš ; Frolec, Jiří
The absorption and emission of thermal radiation by metals is related to their electrical properties that are influenced by impurities, defects and temperature. We show by some examples of measurements on common metals how different can be the thermal radiative properties. When the heat is transferred across a microscopic vacuum gap in the near field regime, it is possible to achieve a step-like change of the heat\ntransfer based on a superconducting transition. An interesting feature of this effect is the nonlinear thermal conductivity effecting a change of the sign of the differential thermal conductivity across the vacuum gap.
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SMV-2016-03: Precise relief structures
Matějka, Milan ; Horáček, Miroslav ; Meluzín, Petr ; Chlumská, Jana ; Král, Stanislav ; Kolařík, Vladimír ; Krátký, Stanislav ; Fořt, Tomáš ; Oulehla, Jindřich ; Šerý, Mojmír
Research and development in the field of precise relief structures using electron beam lithography and other ultra-precise micro manufacturing techniques.
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Reactive sputtering Al2O3
Dušek, Jan ; Boušek, Jaroslav (referee) ; Fořt, Tomáš (advisor)
Diploma thesis describes technology of pulse reactive magnetron sputtering of Al2O3 coating. Furthermore it deals with design of deposition process and testing new aluminium target. The technological window was determined by tests. As a result, it was possible to create Al2O3 coatings in the widest possible working range. The coatings created by apparatus PLS 160 were tested for optical properties in order to obtain transmittance. Besides the optical tests, the evaluation of mechanical properties and adhesion were performed. The obtained results from measurement were evaluated. Based on the results, some possible applications of the coating were suggested.
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Characterisation of Nanostructure Deposited by PVD and CVD Technology
Fořt, Tomáš ; Boušek, Jaroslav (referee) ; RNDr.Vilma Buršíková, Ph.D. (referee) ; Sobota, Jaroslav (advisor)
The thesis deals with mechanical properties of thin hard wear-resistant coatings. The work presents a method of dynamic testing of thin hard coatings on a newly constructed prototype of impact wear tester. It provides a comparison with standard methods of layer testing and presents new experimental results of dynamic impact wear test of the coatings. Finally, the thesis covers preparation techniques of thin film systems deposited on various substrates and their characterization using optical and electron microscopy.
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Workplace for testing of solar cells using LBIC method
Harašta, Tomáš ; Jandová, Kristýna (referee) ; Fořt, Tomáš (advisor)
Subject this diploma thesis is introduction to solar problems, with folow-up focus on solar elements and reflection about their defects. The next part is dedicated diagnostic method LBIC (Light Beam Induced Current) that help to detect defects of solar elements. The work is concerned with aplication this method in general view, from construction of workplace, throuhg hardware to software. The last part is focused on results processing and analysis.
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Study of fracture toughness and wear resistance of thin MoBC coating under dynamic conditions
Buršíková, V. ; Grossman, Jan ; Fořt, Tomáš ; Souček, P. ; Zábranský, L. ; Buršík, Jiří ; Vašina, P. ; Dupák, Libor ; Sobota, Jaroslav
The aim of the present work was to study the mechanical properties of thin amorphous MoBC coatings and MoBC coatings consisting of nanocrystalline Mo2BC embedded in amorphous MoBC matrix. The hardness of the amorphous MoBC coatings (20 GPa) is comparable with the common amorphous diamond-like carbon coatings, however their elastic modulus as well as fracture toughness and ductility are significantly higher. Magnetron sputtering of three targets, B4C, C and Mo, for MoBC was used for coatings preparation. The aim of this work was to study the mechanical and tribological properties of MoBC coatings deposited on high speed steel substrate. The classification of MoBC coatings was performed using an impact tester in a dynamic mode and enabled us to predict the limit load causing the coating destruction.
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