Lidé na fakultě
Ing. Tomáš Vítů, Ph.D.

2024, Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 238 (1), p. 26-43), ISSN 1350-6501

Aerospace actuation gearboxes operate in low-temperature environments where increased lubricant viscosity leads to significant no-load power losses. Replacing fluid lubricants with coatings applied to the gear teeth is one potential approach to improving gearbox efficiency. Here we develop an approach to determining average wear rates of coated gears using a power-recirculating test stand, profile measurements and a model of the tooth contact. Worn gears are inspected using scanning electron imagery, and energy dispersive X-ray and Raman spectroscopy to understand the wear mechanisms and failure modes. Average coefficients of friction are determined at 20°C and −40°C using a power-absorbing test stand and isolation of tooth friction losses by calculation. These methods are then demonstrated on a promising C/Cr composite coating.

Článek v periodiku excerpovaném SCI Expanded

2023, Surface and Coatings Technology, 469, ISSN 0257-8972

Laser texturing is a well-established method used to customize the tribological performance of PVD coatings. To achieve this enhancement, two distinct strategies can be employed: laser texturing of the substrates prior to coating deposition, or laser texturing of the already deposited coating. Technological and economic problems of tuning laser parameters for different types of substrates can be significantly eliminated by laser texturing of already coated materials. Nerveless, the effect of structural changes caused by laser ablation on friction performance is not well studied. In this work, we investigated the differences in these two strategies on example of commercially available a-C:H/WC gradient coatings. The XPS, FIB, SEM and EDS results revealed that femtosecond laser texturing causes minor oxidation and graphitization of the a-C:H/WC coatings but only in a few top nanometers. Macroscale dry tribological tests reveal no statistically significant difference in tribological performance between samples manufactured using two different strategies irrespective of pattern type and tribotest parameters. This means femtosecond laser texturing of the coated substrates can be implemented in industry as a rapid, cost-, and environment-friendly strategy.

Článek v periodiku excerpovaném SCI Expanded

2022, Surface Engineering, 38 (10-12), p. 939-947), ISSN 0267-0844

For the first time, a dynamic beamshaping technology has been utilized for the efficient production of periodic nanostructures on top of AlTiN coating to enable dry machining without costly and environmentally hazardous cutting fluids. First, a variety of periodic nanostructures with periods in a range of 740–273 nm were produced utilizing different wavelengths. Additionally, beamshaping technology increased productivity by 4008% up to 105 cm2 min−1 by shaping the Gaussian beam into a rectangular beam of 500 × 30 μm. To simulate the application load and resulting heat production during manufacturing, friction analysis was performed at room and elevated temperature to 500°C. The analysis revealed a significant reduction in the friction coefficient – up to 27% and 19% at room temperature and 500°C, respectively. The combination of these results demonstrates that the proposed method can be scaled up for the mass production of functionalized machining tools for dry machining.

Článek v periodiku excerpovaném SCI Expanded

2022, Tribology International, 167, ISSN 0301-679X

Sliding of the WSC coated ceramics (ball-on-disc configuration) was investigated under vacuum condition at multiple loads (2–18 N), and each experiment was followed by detailed Raman and SEM analysis of both the wear track and the wear scar (on the ball). Main finding is that under low loads (up to 8 N), wear is polishing, carbon structure becomes more ordered and the number of WS2 monolayer increases. Above 8 N, wear transitions into an abrasive regime interrupting the aforementioned processes increasing both friction and wear. Furthermore, roles of the coating components were differentiated: WS component is responsible for the low friction, whereas the carbon part is responsible for excellent wear properties.

Článek v periodiku excerpovaném SCI Expanded

2021, Coatings, 11 (11), ISSN 2079-6412

The coating system MoN-Ag is an interesting candidate for industrial applications as a low friction coating at elevated temperatures, due to the formation of lubricous molybdenum oxides and silver molybdates. Film deposition was performed by high-power impulse magnetron sputtering and direct current magnetron sputtering. To facilitate a future transfer to industry Mo-Ag composite targets have been sputtered in Ar/N2 atmosphere. The chemical composition of the deposited MoN-Ag films has been investigated by wavelength dispersive X-ray spectroscopy. Morphology and crystallographic phases of the films were studied by scanning electron microscopy and X-ray diffraction. To obtain film hardness in relation to Ag content and bias voltage, the instrumented indentation test was applied. Pin-on-disc tribological tests have been performed at room temperature and at high temperature (HT, 450 °C). Samples from HT tests have been analyzed by Raman measurements to identify possible molybdenum oxide and/or silver molybdate phases. At low Ag contents (≤7 at.%), coatings with a hardness of 18–31 GPa could be deposited. Friction coefficients at HT decreased with increasing Ag content. After these tests, Raman measurements revealed the MoO3 phase on all samples and the Ag2Mo4O13 phase for the highest Ag contents (~23–26 at.%).

Článek v periodiku excerpovaném SCI Expanded

2021, Journal of Materials Engineering and Performance, 30 (6), p. 4117-4125), ISSN 1059-9495

The present work investigates chemical and structural modifications of molybdenum disulphide thin coatings induced by macroscale friction in both reactive (air) and inert conditions. Chemical and micro-structural modifications were analyzed in detail by Raman spectroscopy. We found no traces of oxide formation even when sliding was performed in the air. However, the formation of a well-adhered tribofilm, related to superior lubricating properties, was detected only in inert conditions. We can conclude that, in ambient condition, it is water physisorption and not oxidation, which impairs good lubrication. At the same time, Raman spectra indicated a re-crystallization effect induced by sliding.

Článek v periodiku excerpovaném SCI Expanded

2021, Wear, 480, p. 1-10), ISSN 0043-1648

Transition metal dichalcogenides such as MoS2 are widely used as solid lubricants for vacuum applications. On the other hand, diamond-like carbon coatings exhibit excellent sliding properties in the ambient environment. Our Mo-S-C coatings deposited by pulsed d.c. sputtering combine both structures to obtain stable properties regardless of the testing conditions. The coatings were studied using HR-TEM and Raman spectroscopy, revealing amorphous nature of the coating. The tribological properties were evaluated by pin-on-disc method. The results showed high lubrication ability in all the testing conditions. HR-TEM and Raman spectroscopy were employed to show the structural characteristics of the wear traces. Our results indicate that the low-friction effect should be attributed to carbon structure re-arrangement since expected wear-induced MoS2 formation was not observed.

Článek v periodiku excerpovaném SCI Expanded

2020, Journal of Cultural Heritage, 42, p. 1-7), ISSN 1296-2074

Salt degradation is a well-known but still poorly understood problem. Determination of crystallization pressure that growing crystals exert on the pore walls represents a challenge solved by authors from different points of view. Nevertheless, few papers are aimed at the experimental measurement of the crystallization pressure magnitude. A novel high precision device able to detect repulsive forces generated by a crystal at the crystal/glass interface has been designed. Although some problems with determining the correct contact area of the confined crystal surface, which is most probably not atomically smooth, still exist, the results are comparable to data from other experimental studies. Crystallization experiments were performed with sodium chloride under 30 + 2% and 60 + 2% relative humidity (RH) conditions and with sodium sulfate in 30 + 2% RH. The disjoining pressure values were variable but did not exceed 1 MPa. Special interest was aimed at determination of disjoining pressure of sodium sulfate during phase transition after wetting, since this phenomenon creates most damage during standard crystallization tests. The disjoining pressure values were between 0.957 and 3.159 MPa - sufficiently high to overcome the tensile strength of most of the porous building materials.

Článek v periodiku excerpovaném SCI Expanded

2014, Surface and Coatings Technology, 258, p. 734-745), ISSN 0257-8972

Amorphous carbon-based coatings (DLC) exhibit excellent mechanical and tribological properties such as high hardness, high elastic modulus, low friction and low wear. Reduced friction is often related to the formation of a low-friction tribolayer, which is formed during sliding and transferred to the counterpart. Here, we investigate the sliding of hydrogenated and non-hydrogenated DLC coatings alloyed with zirconium; pure DLC films are used as reference. The coatings were deposited by magnetron sputtering in Ar (non-hydrogenated) and Ar/methane atmosphere (hydrogenated) onto steel substrates and silicon wafers. The total thickness of the coatings was around 1.5 μm including a complex Ti/TiN/TiCN adhesion-improving interlayer with a thickness of 450 nm. All deposited coatings were amorphous, Zr/C ratio was approx. 0.05. The hardness was in the range of 9-13 GPa. Tribological tests were carried out in humid air at room temperature, at 100 °C and in nitrogen environment using pin-on-disk. Intermittent tribological test analysis has been performed to understand running-in behaviour. The worn surfaces and wear debris were analysed by Raman spectroscopy. Coatings alloyed with Zr showed lower friction and wear at room temperature compared to pure DLC. In general, Zr-doped hydrogenated coating outperformed the non-hydrogenated one when tested in an inert nitrogen atmosphere or at elevated temperature (100 °C), exhibiting almost super-low friction (μ = 0.03 in the steady-state regime) due to the formation of a homogenous, thick and stable tribolayer.

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2012, Proceedings of the conference NTF 2012, Brno, Department of Physics FEEC, Brno University of Technology), p. 235-237), ISBN 978-80-214-4594-9

In recent years, the world of modern technologies is changing very fast. Considering the students life, there is no need to study in the libraries. The easiest way for the study could be seen in the internet resources. In our physics education the students meet the practical laboratory tasks. The students should prepare some theoretical and practical description prior the task measurement and then, they should calculate the results and create a report. For this purpose, we usually prepare description and collection of photos in our website, the theory could be studied in the lecture notes or other resources. However, due to the wide-spread students' records system that could be found in the electronic resources, the students give up their own study gradually. In our opinion, this is a real danger supported by the whole society. We would like to spark off a debate about the society's further evolution because this could lead to the total high-school and one's own knowledge break up.

Stať ve sborníku z mezinár. konf. cizojazyčně

2012, Journal of QIRT, Napoli, University of Napoli), ISBN 9788890648441

Flow visualization techniques often enable the first insight into the investigated problem. Generally, the particle image velocimetry, smoke-wire, tuft filaments and oil-flow visualization techniques are used for wind-tunnel investigation. Considering the phenomenon of boundary layer separation bubble related to the low-Reynolds number's transition, these methods face several difficulties mainly with imposed influence to the sensitive flow mechanism. Infrared imaging allowing non-invasive visualization of the afore-mentioned investigations is one of the techniques currently undergoing further promising development in terms of resolution, device size, and price. In the presented paper, the focus was placed on validation of the infrared imaging as a standard visualization technique for wind-tunnel investigation of boundary layer development along an airfoil and its usage for roughness-due-to-insect investigation.

Stať ve sborníku z mezinár. konf.

2011, Proceedings: SEFI - PTEE 2011, Mannheim, HOCHSCHULE MANNHEIM - UNIVERSITY OF APPLIED SCIENCES), ISBN 978-3-931569-18-1

The working surfaces of the modern devices parts are most commonly coated by many types of thin films. These films significantly improve mechanical, chemical and optical properties of working surfaces. Nowadays, almost no working surface could sustain its loading without being coated by appropriate thin coating. Due to this industrial state-of-the-art, the students should meet some of these technologies during their study at the technical university. In the engineering practice, the most useful coating thickness evaluation method is the ball-cratering (calotest). The students' laboratory experiment consists of grinding out the ball-crater in selected sample of thin coating. According to the most practically applicable thin coatings, the thickness of TiN, TiC, CrN, CrCN, and several types of diamond-like structures (DLC's) is determined.

Stať ve sborníku z mezinár. konf.

2011, Chemické listy, 105 (S2), p. S102-S104), ISSN 0009-2770

W-C:H hard composite coatings were studied. The comparison of the wear rate of the coating/substrate system and the bare substrate obtained from dynamic impact test clearly demonstrated that the coating significantly extended the lifetime of the samples even for high loads and high number of loading cycles. The obtained results will support the research and development of new metal-doped a-C:H coatings, which exhibit promising properties for future engineering applications, especially in dynamically loaded contacts.

Článek v periodiku excerpovaném SCI Expanded

2011, Applied Surface Science, 257 (23), p. 9982-9985), ISSN 0169-4332

Influence of heat treatment regime on adhesion and wear resistance of Ni-P electroless coating on AZ91 magnesium alloy is investigated in this work. The pretreated substrate was plated using a bath containing nickel sulphate, sodium hypophosphite and sodium acetate as main constituents. The coated samples were heat treated at 400-450 °C for 1-8 h. Adhesion of coating was estimated from the scratch test with an initial load of 8.80 N. Wear resistance was studied using the pin-on-disc method. It was found that there is no significant dependence of the coating wear resistance on heat treatment regime, as the formation of Al-Ni intermetallic sub-layers that reduce coating adhesion is limited to regions where Al17Mg12 phase is present in the substrate. Moreover, the coating shows good sliding properties due to the formation of oxide glazes in the wear track.

Článek v periodiku excerpovaném SCI Expanded

2011, International Conference Experimental Fluid Mechanics 2011 Conference Proceedings, Liberec, Technical University of Liberec), p. 405-416), ISBN 978-80-7372-784-0

Infrared camera, Particle Image Velocimetry, smoke-wire, tuft filaments and oil-flow visualization techniques were used for wind-tunnel and in-flight investigation of boundary layer separation, both stall and separation bubbles, related to the low-Reynolds numbers transition mechanism. Airfoils of Wortmann FX66 series and FX66 series wing-fuselage interaction, as well as modern airfoils and their wing-fuselage geometry were subject to study. The presence of previously identified structures in the CFD modelling, such as horse-shoe vortices, was confirmed in the flow.

Stať ve sborníku z mezinár. konf. cizojazyčně

2010, Chemické listy, 104, p. S375-S377), ISSN 0009-2770

We evaluated the influence of humidity on tribological behaviour, impact resistance and tribological behaviour at elevated temperatures of carbon-based hard composite coatings deposited by PACVD with an interface metallic layer prepared by unbalanced magnetron sputtering.

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2010, Tribology International, 43 (7), p. 1228-1233), ISSN 0301-679X

CrCN coatings were prepared by cathode arc evaporation technology using constant N2 flow and variable C2H2 flow. The coatings with a thickness of 3-4 μm were deposited on hardened steel substrates and high-temperature resistant alloy. The carbon content varied from 0 at.% (i.e. CrN) up to 31 at.%. The standard coating characterization included the nano-hardness, adhesion, chemical composition and structure (including hot X-ray diffraction). Wear testing was done using a high temperature tribometer (pin-on-disc); the maximum testing temperature was 700 oC. The coatings with carbon content 12-31 at.% showed almost identical tribological behaviour up to 700 oC.

Článek v periodiku excerpovaném SCI Expanded

2010, Materials Characterization, 61 (6), p. 668-673), ISSN 1044-5803

Influence of heat treatment regime on microstructure, phase composition and adhesion of Al2O3 fiber-reinforced Ni-P electroless coating on an Al-10Si-0.3 Mg casting alloy is investigated in this work.

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2010, Applied Surface Science, 256 (9), p. 2956-2960), ISSN 0169-4332

Evolution of tribological properties of electroless Ni-P and Ni-P-Al2O3 coating on an Al-10Si-0.3Mg casting alloy during heat treatment is investigated in this work. The pre-treated substrate was plated using a bath containing nickel hypophosphite, nickel lactate and lactic acid. For preparation of fiber-reinforced coating Al2O3 Saffil fibers pre-treated in demineralised water were used. The coated samples were heat treated at 400-550 °C/1-8 h. Tribological properties were studied using the pin-on-disc method. It is found that the best coating performance is obtained using optimal heat treatment regime (400 °C/1 h). Annealing at higher temperatures (450 °C and above) leads to the formation of intermetallic compounds that reduce the coating wear resistance. It was found that fiber reinforcement reduces this scaling and increases wear resistance of coatings as compared to the non-reinforced Ni-P coatings.

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2010, METAL 2010, Ostrava, Technická universita Ostrava - Vysoká škola báňská), p. 606-610), ISBN 978-80-87294-17-8

The aim of this work is to describe the evolution of tribological properties of electroless Ni-P based coatings reinforced with Al(2)O(3) fibres. Coatings were prepared using nickel lactate-hypophosphite bath, conventional AlSi10Mg0.3 cast alloy was used as a substrate. Coated samples were heat treated in a resistance furnace at 400-550 degrees C for 1 - 8 hours. The adherence of coatings was estimated from the scratch-test. Chosen samples were subjected to the \"pin-on-disc\" test to determine coating wear resistance. Having superior hardness, alumina fibres significantly increase coating wear resistance compared to that of the non-reinforced Ni-P coatings. As it was already described in case of Ni-P coatings, the intermetallic phases formed during heat treatment decrease wear resistance of coatings. However, the presence of Al(2)O(3) fibres partially suppresses this negative effect and, thus, increases the coating\'s performance.

Stať ve sborníku z mezinár. konf. cizojazyčně

2009, Proceedings of the SEFI Conference on Physics Teaching in Engineering Education PTEE 2009, Wroclaw, Institute of Physics, University of Technology), p. 37-40), ISBN 978-83-929400-0-5

In the new concept of the bachelor study the practical applications are emphasized. Considering this fact we tried to strengthen the education in measurement methodology. We let a certain segment of the exercises in the classic setting, i.e. with simple service undemanding expensive devices and without computer support. The remaining part of exercises we tried to match to the modern trends in measurement technology, often with a direct computer controlling the measurement process. The goal of our new project is to establish a Laboratory of computerized physical experiments and to execute the practical laboratory tasks for our new subject called "Computer controlled experiments".

Stať ve sborníku z mezinár. konf.

2009, Proceedings of the SEFI Conference on Physics Teaching in Engineering Education PTEE 2009, Wroclaw, Institute of Physics, University of Technology), p. 93-96), ISBN 978-83-929400-0-5

The second course of physics lectured at FTS CTU is mainly based on physical problems related to basic and derivative properties of electron. Although many of these topics are supported by practical laboratory tasks, the exam results show that the students comprehend problems of electric and magnetic field with difficulties. Our new laboratory task should demonstrate the effect of Lorenz force in a simple way. The physical task dealing with electron specific charge is very simple and could contribute to comprehend many principles of electric and magnetic field. We suppose that this experiment will positively fill up the blind spots in education and due to simple demonstration also attract the students' interest to applied physics.

Stať ve sborníku z mezinár. konf.

2009, ISBN 978-80-01-04220-5

Mechanika hmotného bodu a soustav. Tuhé těleso. Úvod do mechaniky kontinua. Vlnění. Hydrodynamika. Termodynamika. Elektrostatické pole. Ustálený elektrický proud.

Vysokoškolské skriptum v češtině

2009, Surface and Coatings Technology, 203 (20-21), p. 3254-3259), ISSN 0257-8972

Chromium nitride (CrN) and multilayers Cr/CrN coatings were deposited by low cathodic arc technology. The thickness of Cr and CrN layers was identical; two different multilayer coatings were deposited with layer thicknesses of 85 and 160 nm. The structural analysis showed that CrN coatings exhibited the cubic CrN phase, while a mixture of CrN, Cr2N and Cr phases was observed in the case of multilayers. The annealing of the samples at 800 and 900 °C in air led to: (1) the decomposition of the chromium nitride phases into chromium; (2) a moderate oxidation by forming a thin Cr2O3 layer on the coating surface and, (3) carbon diffusion from the steel substrate.

Článek v periodiku excerpovaném SCI Expanded

2009, METAL 2009, Ostrava, Tanger), p. 279-284), ISBN 978-80-87294-03-1

The aim of this work was to describe evolution of tribological properties of electroless Ni-P based coatings during heat treatment. Coatings were prepared using nickel lactate- hypophosphite bath, conventional AlSi10Mg0.3 cast alloy was used as a substrate. Coated samples were heat treated at 400 - 550 degrees C for 1-8 hours. Adherence of coatings to the substrate was estimated from the scratch test. To determine wear resistance, chosen samples were subjected to "pin-on-disc" test. It was found that intermetallic phases formed during heat treatment due to the diffusion of nickel into the substrate severely decrease wear resistance of coatings.

Stať ve sborníku z mezinár. konf. cizojazyčně

2009, ISBN 978-80-01-04311-0

Model měření. Základní metody měření. Metody měření a přesnost měření základních fyzikálních veličin. Zpracování naměřených dat. Chyby.Nejistoty. Návody k 15-20 laboratorním úlohám z mechaniky, tepla, elektrostatiky, akustiky hydrodynamiky.

Vysokoškolské skriptum v češtině

2009, Vrstvy a povlaky 2009, Trenčín, Digital Graphic), p. 101-102), ISBN 978-80-969310-9-5

Carbon hard composite coatings were exposed to dynamical load and high temperature pin-on-disc tests, to evaluate the impact resistance of thin hard composite coating in dynamic loading wear applications an impact test was used.

Stať ve sborníku z mezinár. konf.

2009, ISBN 978-80-01-04359-2

Příklady z fyziky.

Vysokoškolské skriptum v češtině

2009, Solid State Sciences, 11 (11), p. 1757-1761), ISSN 1293-2558

The development of a mechanically stable, functionally graded Ti-doped a-C:H interface layer in combination with a functional a-C:H coating requires a reduction of the brittle phases which induce generally problems in the transitions from Ti to TiC/a-C:H. The core objective of this study was to develop an optimum interlayer between the substrate and the functional top layer for biomedical applications, namely for tooth implants. Since the interlayer may be exposed to the sliding process, in the case of local failure of the top layer it has to fulfil the same criteria: biocompatibility, high wear resistance and low friction.

Článek v periodiku excerpovaném SCI Expanded

2009, Plasma Processes and Polymers, 6 (S), p. 935-940), ISSN 1612-8850

Chromium aluminium nitride (Cr-Al-N) coatings produced by PVD are routinely deposited on tools and tested as components for machining and forming applications. However, the addition of a doping element, such as Si, can further improve the properties of such coatings. In this study, Cr-Al-N and Cr-Al-Si-N coatings with different Cr/Al ratio were prepared on WC substrates by low cathodic arc deposition and their structure and tribological properties analyzed in situ at high temperatures. In spite of excellent thermal stability and oxidation resistance, the hot-sliding tests showed unsatisfactory coating behavior.

Článek v periodiku excerpovaném SCI Expanded

2009, Vrstvy a povlaky 2009, Trenčín, Digital Graphic), p. 117-122), ISBN 978-80-969310-9-5

A new tribological systems based on functionally graded metal doped hydrocarbon nanocomposite coatings (Me-C:H) have been developed. Tribological properties of Me-C:H coatings were investigated using pin-on-disc tribometer both in dry environment and in NaCl solutions.

Stať ve sborníku z mezinár. konf.

2008, Proceedings of Eleventh International Conference on Plasma Surface Engineering (PSE 2008), Garmisch-Partenkirchen, European Joint Committee on Plasma and Ion Surface Engineering), p. 307-307)

Comparative FEM analysis for ball-coating contact in the tribological pin-on-disc test

Abstrakt ve sborníku z mezinár. konf.

2008, Surface and Coatings Technology, 202 (22-23), p. 5790-5793), ISSN 0257-8972

Ti-C:H coatings with different carbon content for biomedical applications were deposited by PECVD. Ti was varied by magnetron sputtering a Ti-target with different power in a dc discharge regime having Ar in the atmosphere. Ti-C:H coating was tribologically tested reflecting its expected use as an interlayer for improving the adhesion of functional a-C:H coatings. The tribological properties were studied using a pin-on-disc CSM Tribometer in order to ensure stable tribological properties of the whole Ti-C:H/DLC system for any case of top layer failure.

Článek v periodiku excerpovaném SCI Expanded

2008, E-MRS 2008 Spring Meeting - Abstracts, Strasbourg, European Materials Research Society), p. 18-18)

Tribological system based on functionally graded metal doped hydrocarbon nanocomposite coatings (me+nc-C :H) has been developed. The functional me+nc-C :H coatings were deposited by PECVD using magnetron sputtering of Ti or WC target in C2H2 + Ar atmosphere in dc discharge regime. Varying content of C:H components was controlled by C2H2 flow during the deposition process. The physical and mechanical properties of Ti and W doped coatings were thoroughly studied.

Abstrakt ve sborníku z mezinár. konf.

2008, Proceedings of the SAIT International Tribology Conference Tribology 2008, Pretoria, SAIT), p. 114-119), ISBN 978-0-620-38082-9

The dependence of tribological properties of Ti-C:H coatings on C:H component content was studied using pin-on-disc CSM Tribometer. Ti-C:H layers were deposited by PECVD using magnetron sputtering of Ti-target . The tribological performance was examined with respect to the friction coefficient, the wear rates of coatings and counter-parts and analysis of wear debris. To determine the dominant wear mechanism, the wear tracks were studied using optical microscopy, confocal microscopy and scanning electron microscopy.

Stať ve sborníku z mezinár. konf.

2008, Proceedings of Eleventh International Conference on Plasma Surface Engineering (PSE 2008), Garmisch-Partenkirchen, European Joint Committee on Plasma and Ion Surface Engineering), p. 287-287)

Tribological Performance of CrAlSiN Coatings at High Temperatures

Abstrakt ve sborníku z mezinár. konf.

2007, Proceedings of the 5th International Confernce on Physics Teaching in Engineering Education PTEE 2007, Delft, Delft University of Technology), ISBN 978-90-8649-108-7

Properly chosen laboratory exercises could significantly support understanding of the difficult physical themes. Because in the new concept of the bachelor study the practical applications are emphasized, we decided to include in the laboratory tasks which employ the advanced measurements technology. As an example we describe a measurement of temperature fields with an infra red camera. Despite of the complexity of infra red camera measurements our students reach satisfactory results and this new task undoubtedly contributed to the atractiveness of the laboratory exercises.

Stať ve sborníku z mezinár. konf.

2007, ISBN 978-80-01-03889-5

Skriptum obsahuje návody k laboratorním úlohám z Fyziky 2.

Vysokoškolské skriptum v češtině

2007, Proceedings of Sixth Asian-European International Conference on Plasma Surface Engineering (AEPSE 2007), Nagasaki, Asian Joint Committee on Plasma Surface Engineering (AJC/PSE)), p. 361-361)

Ti-C:H coatings with different carbon content for biomedical applications were deposited by PECVD. Ti was varied by magnetron sputtering a Ti-target with different power in a dc discharge regime having Ar in the atmosphere. The tribological properties were studied using a pin-on-disc CSM Tribometer in order to ensure stable tribological properties of the whole Ti-C:H/DLC system for any case of top layer failure. The sliding tests were carried out at room temperature in room environment with relative air humidity 40+-5%, in 0.9% NaCl water solution (physiological solution, PS) and in 10% fetal bovine serum (FBS) dissolved in Ringer's saline solution using 440C steel balls with a diameter of 8 mm. The Ti-rich coatings exhibited poor wear resistance, while the best tribological properties were achieved for TiC/a-C:H coatings deposited with the highest C2H2 flows.

Stať ve sborníku z mezinár. konf.

2007, New Trends in Physics 2007 Proceedings of the Conference, Brno, Ing. Zdeněk Novotný, CSc.), p. 11-11), ISBN 978-80-7355-078-3

The tribological properties of thin coatings were usually studied using pin-on-disc measurements. The coating wear rates were determined on the basis of multiple wear track profile measurements but the results couldn't respect possible variations in the cross-section area values caused by holes or large pores in the coating and bonded wear debris eventually. The evaluation of coating wear rate was improved by 3D surface analysis using confocal microscope Olympus LEXT OLS 3000.

Abstrakt ve sborníku z mezinár. konf. cizojazyčně

2007, New Trends in Physics 2007 Proceedings of the Conference, Brno, Ing. Zdeněk Novotný, CSc.), p. 340-343), ISBN 978-80-7355-078-3

Interferometric measurements are widely used for very low distances observation. Tens of nanometers are the obvious order of values determined by Michelson interferometer. Our Michelson interferometer was equipped with digital camera to pan the interference fringes in the imaging plane. The counting of fringes was performed by computer imaging. A small optical chamber was designed for changing the optical path in one of the light beams by changing the air pressure. The chamber was evacuated by hand vacuum pump and the shifted interference fringes were counted. The described simple technique showed the relative measurement uncertainty of about 5 % in the deviation of air refractive index from the vacuum refractive index. Moreover, using of interference fringes counting taken from the digital camera produced benefits in the lowering of possible human error. Recently the principle was used for creating a new illustrative laboratory measurement as a part of applied wave optics.

Stať ve sborníku z mezinár. konf. cizojazyčně

2007, ABSTRACTS BOOK of 2nd International Conference on Surfaces, Coatings and Nanostructured Materials, Algarve, Society of Nanoscience and Nanotechnology), p. 159-159)

The tribological properties of Ti-C:H coatings were studied using pin-on-disc CSM Tribometer. The functional Ti-C:H layers were deposited by PECVD using magnetron sputtering of Ti-target in C2H2 + Ar atmosphere. The sets of coatings samples were prepared with varying content of C:H components controlled by C2H2 flow. The typical thickness of Ti-C:H coatings varied from 2.5 to 3.5 um. The sliding tests were carried out at room temperature (RT) and at 100 °C using HS steel and ceramic Al2O3 balls with a diameter of 6 mm. The results showed relative clear correlation between tribological properties and coatings composition. There is assumed the commercial production for biomedical applications using Ti-C:H coatings deposited on Ti-alloy. The results acquired in this study will support the research and development of deposited surgical tools and prostheses with improved sliding properties.

Stať ve sborníku z mezinár. konf.

2007, Abstract Booklet of the Int. Conf. NANO´07, Ostrava, Česká společnost pro nové materiály a technologie), p. 20-20), ISBN 978-80-214-3460-8

Development of stable system using functionally graded Ti-doped C:H layers deposited as adhesion interlayer in combination with functional DLC coating requires to reduce brittle phases inducing general problems in transitions from pure Ti to Ti-C:H coating. In this study, tribological characteristics of Ti-C:H coatings were studied in order to ensure stable tribological properties of the whole Ti-C:H/DLC system in case of eventual top layer failure. The coatings were prepared using PECVD method with reactive atmosphere of C2H2. The proportion of C:H components in coatings sets was controlled by C2H2 flow rate in the range [10-60 sccm]. The tribological performance was examined with respect to the friction coefficient and the wear rates of coating and counter-parts. Additionally, the measurements of Vickers hardness and Raman spectroscopy were taken into account. The study supported selecting the optimal C2H2 flows to deposit Ti-C:H adhesion interlayer for industrial production.

Abstrakt ve sborníku z mezinár. konf. cizojazyčně

2007, Plasma Processes and Polymers, 4 (S1), p. S237-S240), ISSN 1612-8850

Tribological properties of nanostructural DLC/WC coatings were measured with a high temperature pin-on-disc CSM Tribometer in the range from room temperature (RT) up to 500 °C. The tribological performance was evaluated with respect to the wear rates of balls and coatings, friction coefficient and wear debris analysis. The running-in phenomenon of steel ball sliding against DLC coating was studied by sequential in situ measurements of ball wear rate. The wear volume was almost constant from number of cycles of 1500 to 5000. This phenomenon was caused by lowering of contact pressure and couldn't be caused by changing of wear mode; the measured friction coefficient showed no fluctuation at 1500 cycles. Friction and wear characteristics described in this study showed their limitations of DLC applicability.

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