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Investigation of the tribological performance of ionic liquids in non-conformal EHL contacts under electric field activation

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Friction 2020年第5期8卷 982-994页

作者： Michal MICHALEC petr svoboda Ivan KRUPKA Martin HARTL Aleksandar VENCL Faculty of Mechanical Engineering Brno University of TechnologyBrno 61669Czech Republic Central European Institute of Technology Brno University of TechnologyBrno 61200Czech Republic Faculty of Mechanical Engineering University of BelgradeBelgrade 11120Serbia South Ural State University Chelyabinsk 454080Russia

Real-time external alteration of the internal properties of lubricants is highly desirable in all mechanical systems. However, fabricating a suitable and effective smart lubricant is a long-lasting experimental process. In this study, the film thickness and frictional response of ionic liquid-lubricated non-conformal contacts to an electric field excitation under elastohydrodynamic conditions were examined. Film thickness was evaluated using a "ball-on-disc" optical tribometer with an electric circuit. Friction tests were carried on a mini traction machine (MTM) tribometer with a "ball-on-disc" rotation module and an electric circuit for contact area excitation. The results demonstrate that there is a difference in the behaviour of the ionic liquid during electric field excitation at the evaluated film thicknesses. The results of evaluated film thicknesses demonstrate that there is a difference in the behaviour of the ionic liquid during electric field excitation. Therefore, the ionic liquids could be a new basis for the smart lubrication of mechanical components. Moreover, the proposed experimental approach can be used to identify electrosensitive fluids.

关键词： friction thin film lubrication electro-rheological fluid smart fluid lubrication

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Erosive wear properties of ZA-27 alloy-based nanocomposites: Influence of type, amount, and size of nanoparticle reinforcements

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Friction 2019年第4期7卷 340-350页

作者： Aleksandar VENCL Ilija BOBIC Biljana BOBIC Kristina JAKIMOVSKA petr svoboda Mara KANDEVA Faculty of Mechanical Engineering University of BelgradeKraljice Marije 16Belgrade 11120Serbia Institute of Nuclear Sciences'Vinca' University of BelgradeMike Petrovica Alasa 12-14Belgrade 11001Serbia Institute of Chemistry Technology and MetallurgyUniversity of BelgradeNjegoseva 12Belgrade 11000Serbia Faculty of Mechanical Engineering in Skopje Ss.Cyril and Methodius UniversityKarposh II bbSkopje 1000Macedonia Faculty of Mechanical Engineering Brno University of TechnologyTechnicka2896/2Brno 61669Czech Republic Faculty of Industrial Technology Technical University of Sofia8 Kliment Ohridski BlvdSofia 1000Bulgaria

Metal matrix nanocomposites(MMnCs)comprise a metal matrix filled with nanosized reinforcements with physical and mechanical properties that are very different from those of the *** ZA-27 alloy-based nanocomposites,the metal matrix provides ductility and toughness,while usually used ceramic reinforcements give high strength and *** ZA-27 alloy-based nanocomposites,reinforced with different types(Si C and Al2O3),amounts(0.2 wt.%,0.3 wt.%,and 0.5 wt.%)and sizes(25 nm,50 nm,and 100 nm)of nanoparticles were produced through the compocasting process with mechanical alloying pre-processing(ball milling).It was previously shown that the presence of nanoparticles in ZA-27 alloy-based nanocomposites led to the formation of a finer structure in the nanocomposites matrix and an improvement in the basic mechanical properties(hardness and compressive yield strength)through the enhanced dislocation density strengthening *** particle erosive wear testing demonstrated that these improvements were followed with an increase in the erosive wear resistance of tested nanocomposites,as ***,by analyzing the influences of type,amount,and size of nanoparticles on the erosive wear resistance of nanocomposites,it was demonstrated that there is an optimal amount of nanoparticles,which in our case is 0.3 wt.%,and that the presence of SiC nanoparticles and smaller nanoparticles in nanocomposites had more beneficial influence on erosive wear resistance.

关键词： ZA-27 alloy nanocomposites nanoparticles compocasting fractography erosive wear

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Synthesis of PMMA-co-PMAA Copolymer Brush on Multi-Wall Carbon Nanotubes

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Journal of Surface Engineered Materials and Advanced Technology 2012年第3期2卷 221-226页

作者： petr Slobodian petr svoboda Pavel Riha Roman Boruta petr Saha Centre of Polymer Systems University Institute Tomas Bata University Zlin Czech Republic Department of Polymer Engineering Faculty of Technology Tomas Bata University Zlin Czech Republic 4Institute of Hydrodynamics Academy of Sciences Prague Czech Republic Institute of Hydrodynamics Academy of Sciences Prague Czech Republic. Polymer Centre Faculty of Technology Tomas Bata University Zlin Czech Republic

Poly(methyl methacrylate)/poly(methacrylamide) copolymer (PMMA-co-PMAA) was synthesized by a free radical copolymerization of MMA and MAA monomers in methylethyl ketone using AIBN as radical initiator. Multi-wall carbon nanotubes (MWCNT) were oxidized in KMnO4 acidic suspension. Carboxyl groups on the surface oxidized MWCNT were reacted with primary amide group of PMMA-co-PMAA copolymer in MEK solution under ultrasound to form polymer brush on the surface of MWCNT. With the help of TG analyses the amount of covalently grafted PMMA-co-PMAA copolymer onto MWCNT surface was determined as ?47 wt%. TEM analyses identified thin co-polymer layer adhered onto MWCNT surface with average thickness ?5 nm.

关键词： Carbon Nanotubes Functionalization PMMA PMAA Polymer brush

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Zn_(x)Cd_(1-x)S量子点组成与其光催化活性的关系

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催化学报 2015年第3期36卷 328-335页

作者： Alice Hospodková Ladislav svoboda petr Praus Institute of Physics of the Academy of Sciences of the Czech Republic v.v.i.CZ-16200 Prague 6Czech Republic Department of Chemistry VSB-Technical University of Ostrava17.listopadu 15708 33 Ostrava-PorubaCzech Republic Institute of Environmental Technology VSB-Technical University of Ostrava17.listopadu 15/2172Ostrava 708 33Czech Republic

Aqueous colloidal dispersions containing Znx Cd1‐x S quantum dots (QDs) of different x compositions were prepared by precipitating zinc and cadmium acetates with sodium sulphide,in the presence of a cetyltrimethylammonium bromide ***‐visible absorption spectroscopy was used to determine the transition energies of the QDs,which in turn were used to calculate their sizes,which depended on their *** QD size decreased with increasing Zn *** photocatalytic activity of the Znx Cd1‐x S QDs was studied by the decomposition of methylene blue under ultraviolet irradiation,at a maximum intensity at 365 nm (3.4 e V).Three different photo‐catalytic activity regions were observed,which depended on the Zn *** quantum levels of the QDs could be excited by incident irradiation,and influenced the resulting photocatalytic *** photocatalytic activity was achieved at x = 0.6,where the QD transition energy was equal to the irradiation photon *** photocatalytic efficiency of the QDs depended on their surface area and arrangement of quantum levels,because of the quantum size effect.

关键词： Quantum dot Znx Cd1-xS Photocatalysis Quantum level

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