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Thermal stability of Ti/Ni multilayer thin films
Václavík, R. ; Zábranský, L. ; Souček, P. ; Sťahel, P. ; Buršík, Jiří ; Fořt, Tomáš ; Buršíková, V.
In this work, thermal stability and mechanical properties of Ti/Ni multilayer thin films were studied. The multilayer thin films were synthesised by alternately depositing Ti and Ni layers using magnetron sputtering. The thickness of constituent layers of Ti and Ni varied from 1.7 nm to 10 nm, and one coating was deposited by simultaneous sputtering of both targets. Single crystalline silicon was used as a substrate. The effects of thermal treatment on the mechanical properties were studied using nanoindentation and discussed in relation to microstructure evaluated by X-ray diffraction. Annealing was carried out under low-pressure conditions for 2 hours in the range of 100-800 degrees C.
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Influencing of the Pile-Up and the Sink-In by the Coefficient of Friction in the Nanoindentation Test
Kovář, J. ; Fuis, Vladimír ; Čtvrtlík, Radim
The influence of the coefficient of friction between an indenter and a specimen on the height of the pile-up or depth of the sink-in during the nanoindentation test is discussed in this paper. When the indenter is pressed into the hard material, the sink-in behavior causes the bending of the specimen’s surface under the indenter. When the indenter is pressed into the soft material, the deformed material accumulates under the sides of the indenter and makes a pile-up region. The pile-up or sink-in behavior influences the contact area. In this paper, the finite element method was used for calculation of the dependency between the depth of the sink-in or height of the pile-up and the coefficient of friction. The results showed that while there is not any dependency between the friction and the depth of the sink-in, there is a strong dependency between the friction and the height of the pile-up until a specific value of the coefficient of friction. When the pile-up behavior occurs, the friction influences the contact area and should be included into the calculation of the contact area.
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Povrchové a mechanické vlastnosti a-CSi:H a a-CSiO:H vrstev
Plichta, Tomáš ; Shukurov, Andrey (oponent) ; Klapetek, Petr (oponent) ; Čech, Vladimír (vedoucí práce)
Dizertační práce se zabývá přípravou a charakterizací tenkých a-CSi:H a a-CSiO:H vrstev připravených pomocí plazmochemické depozice z plynné fáze (PECVD). Tetravinylsilan (TVS) a jeho směsi s argonem a kyslíkem byly použity pro depozice vrstev jak na planární substráty, tak na svazky vláken. Hlavními charakterizačními technikami byla studována topografie vrstev, a to pomocí mikroskopie atomárních sil (AFM), jejich mechanické vlastnosti pomocí nanoindentace a míra adheze vrstev k substrátu vrypovou zkouškou. Mezi další analyzované vlastnosti patřilo vnitřní pnutí či frikční koeficient. Zvláštní pozornost byla věnována adhezní práci a jejímu stanovení. Tyto znalosti byly dále aplikovány při přípravě povrchových úprav skleněných vláken a následně polymerních kompozitů. Ty byly testovány pomocí vytlačovacího testu a smykového testu krátkých trámečků. Na základě výsledků byly stanoveny vlivy depozičních podmínek a vztahy mezi studovanými vlastnostmi a veličinami.
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Laser-induced surface acoustic waves for thin film characterization
Kudělka, R. ; Václavek, L. ; Tomáštík, Jan ; Malecová, S. ; Čtvrtlík, R.
Knowledge of mechanical properties of thin films is essential for most of their applications.However, their determination can be problematic for very thin films. LAW (Laser-induced acousticwaves) is a combined acousto-optic method capable of measuring films with thickness from fewnanometers. It utilizes ultrasound surface waves which are excited via short laser pulses and detectedby a PVDF foil. Properties such as Young’s modulus, Poisson’s ratio and density of both the film andthe substrate as well as film thickness can be explored.Results from the LAW method are successfullycompared with nanoindentation for Young’s modulus evaluation and with optical method for filmthickness evaluation and also with literature data. Application of LAW for anisotropy mapping ofmaterials with cubic crystallographic lattice is also demonstrated
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Influencing the Indentation Curves by the Bluntness of the Berkovich Indenter at the Fem Modelling
Kovář, J. ; Fuis, Vladimír ; Tomaštík, Jan
The influence of the Berkovich indenter bluntness on the indentation curves at nanoindentation test of fused silica is determined by the FEM (finite element method) in this paper. The Berkovich indenter, which is mostly used for the nanoindentation test, was assumed for calculations. The indenter is always blunted in real tests. The bluntness of the indenter has an influence on the results of the nanoindentation test. The combination of the nanoindentation test and the FE modelling can be used for the calculation of the parameters of fused silica plasticity and estimation of the bluntness of the indenter. In this paper, the FEM was used for calculating of the indentation curves. Two cases of bluntness were assumed. The curves for ideally sharp or blunted indenter were determined. The results of these calculations showed that the indentation curves are dependent on the bluntness of the Berkovich indenter. The greatest relative influence of the nanoindentation curves by the bluntness is in the area of small values of the indenter displacement. The impact of assuming blunted indenter to calculated parameters of plasticity was assessed. It is often difficult to measure the bluntness of the indenter but it has an influence on the results of the nanoindentation test and should be included into calculations to make it more precise.
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FEM simulation of the nanoindentation test with rigid non-rigid indenter
Kovář, J. ; Fuis, Vladimír
This paper focuses on the comparing of the results of the FEM simulations of fused silica nanoindentation tests. Fused silica is modelled like bilinear elasto-plastic material with the parameters estimated from the experiment. FEM simulations are made with the 2D axisymmetric conical indenter which is equivalent to the Berkovich indenter and the indentation curves are evaluated. The FEM simulations were made with the rigid and the non-rigid indenter and the difference between the indentation curves obtained with these models is assessed. The evaluated indentation curves are compared with the indentation curves obtained from the experiment.
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Using homogenization and nanoindentation for microfibril angle determination of spruce
Kucíková, L. ; Hrbek, Vladimír ; Vorel, J. ; Šejnoha, M.
This paper is concerned with the evaluation of microfibril angle of spruce. The microfibril angle is defined as an inclination of microfibrils from the longitudinal axis, the direction of lumens. It is well known and further supported by the present study that the microfibril angle has a great influence on the final mechanical properties of wood. This angle could be measured either directly using, e.g. polarisation microscopy, X-ray diffraction, infrared spectroscopy, or indirectly, as used in this study, by employing the nanoindentation measurements. Therein, the measured indentation modulus is compared with that obtained numerically using the anisotropic theory of indentation. The latter one depends on the entire stiffness matrix derived through homogenization and the searched microfibril angle. In view of the cell wall microstructure, the effective cell properties were found using the two-step micromechanical homogenization adopting both the Self-consistent and Mori-Tanaka methods.
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Comparison of properties and behaviour of selected systems of thin film - Substrate with TiSiN, AlCrN and AlTiN on samples and selected cutting tools
Mertová, Andrea ; Štěpánek, Ivo ; Šimečková, Lucie ; Dudáčková, Simona ; Ulrychová, Monika
The paper is devoted by evaluation of comparison of selected systems of thin film - basic material, which are optimized in the range of solution of the project with goal application of thin films on selected real cutting tools. There are evaluated thin films prepared by low voltage reactive arc evaporation in vacuum with different composition of ternary nitride. The evaluation of properties and behaviour is oriented on systems with thin films TiSiN, AlCrN and AlTiN. The surfaces of these systems of thin film - basic material are evaluated from point of view of verification homogeneity of thin films through of area of samples and through of geometry of selected real tools too. The distribution of thickness is evaluated by x-ray fluorescence analysis on samples and real selected places of geometry of tools too. The other comparison is realised from point of view of differences of mechanical properties and behaviour by using of indentation methods namely of nanoindentation and scratch indentation for evaluation of differences in hardness and adhesive cohesive behaviour of systems thin films - basic material.
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Verification of possibilities of evaluation of changing of polymeric surface properties and behaviour evoked by sun radiation and temperature loading
Šimečková, Lucie ; Dudáčková, Simona ; Štěpánek, Ivo ; Mertová, Andrea
The paper is devoted by simulation of conditions of sun radiation in correlation with real loading in operational conditions of selected polymeric materials. In the second the paper is devoted by simulation of temperature conditions of loading again in correlation with temperature loading in real operational conditions of selected polymeric materials. There are tested sensitivity of selected analytic methods in connection on running processes of ageing of polymeric materials for evaluation of initial of radiation ageing and temperature ageing with possibilities of prediction of evolution of running changing of properties and behaviour of evaluated materials. There are tested method x-ray fluorescence analysis and parameters of this method are optimized for increasing sensitivity for evaluation initial changing of properties and behaviour of tested materials on the base the first results. Indentation methods are used for analysis of changing of mechanical properties and behaviour namely static nanoindentation and scratch nanoindentation. These methods are optimized on the base the first results too. There are used more possibilities for control of indentation tests by the use different modes of measurements namely simple and cyclic measurement, setting different rate of loading and using different type of indentors for realization of measurements.
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Nanoindentation methods of evaluation of mechanical properties and behaviour and complex application for evaluation of technology and degradation
Štěpánek, Ivo ; Mertová, Andrea ; Šimečková, Lucie ; Štěpánová, Lucie ; Ulrychová, Monika
Nanoindentation methods used for evaluation surface layers are static indentation and scratch indentation too. Static indentation methods are used namely for evaluation hardness characteristics and for evaluation elastic deformation and plastic deformation of surface layers too based on measurement indentation curves - dependence depth indentation and normal force during all indentation process during loading and unloading. Cyclic and step by step indentation modes give possibilities to evaluate much more information about resistivity of surface layers to the indentation stress. Scratch indentation methods are used for evaluation namely adhesive cohesive properties and behaviour of surface layers with very small thickness or/and thin films with very low resistivity of thin films and low hardness. The surface layering is created by technology process of creation of thin films and surface treatment process or by initiation and evolution of degradation process and\nageing process. The initiation of degradation and ageing are evaluated in the starting stadium and in the next with step by step sensitive analysis of changing properties and behaviour. From this point of view static nanoindentation and scratch nanoindentation are very useful for analysis step by step changing of mechanical properties and behaviour with high sensitivity and depth resolution too. The paper presented utilization of nanoindentation static and scratch nanoindentation too for very different application in surface treatment but for evaluation of degradation and ageing process too.
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