The Experts below are selected from a list of 261 Experts worldwide ranked by ideXlab platform
Jean-michel Martin - One of the best experts on this subject based on the ideXlab platform.
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Superlubricity of glycerol by self-sustained Chemical Polishing
Scientific Reports, 2019Co-Authors: Yun Long, Maria-isabel De Barros Bouchet, Ton Lubrecht, Tasuku Onodera, Jean-michel MartinAbstract:An impressive superlow coefficient of friction (CoF) as low as 0.004 (nearly equivalent to the rolling coefficient) was obtained by sliding a steel ball against a tetrahedral amorphous diamond-like carbon (ta-C) coating in glycerol under a boundary lubrication regime. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) revealed substantial changes in the surface chemistry and topography in the friction track. As shown by XPS analysis, a transfer of iron atoms from the steel ball to the ta-C layer occurred, forming iron oxy-hydroxide (FeOOH) termination on both surfaces. Between them, theoretical calculations show that a nanometre-thick fluid film consisting of glycerol and its degradation products prevents direct contact between the solid surfaces by nm-thick film EHL lubrication and results in the superlow friction, in agreement with the experiment. Furthermore, molecular dynamics (MD) simulations reveal that hydrogen atoms act as "low-friction brushes" between sliding layers of crystalline FeOOH, resulting also in low friction. A new model of sustainable green superlubricity is proposed. The tribo-formation of FeOOH with glycerol leads to a unique Polishing process, which in turn leads to a self-sustained Elasto-Hydrodynamic Lubrication (EHL) regime until the very thin fluid film is no more than a few nanometres thick. At lower thicknesses, the hydroxide layer takes over. Wear of the ta-C coating is negligible, while wear on the steel ball is very moderate and acceptable for many practical applications, such as bio-tribology and the food industry, in which green lubrication is especially needed.
Sonia R Biaggio - One of the best experts on this subject based on the ideXlab platform.
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electroPolishing of aisi 304 stainless steel using an oxidizing solution originally used for electroChemical coloration
Electrochimica Acta, 2005Co-Authors: Leonardo S Andrade, Sandro C Xavier, Romeu C Rochafilho, Nerilso Bocchi, Sonia R BiaggioAbstract:Abstract Chemical Polishing or electroPolishing, instead of mechanical Polishing, are recommended for the attainment of metallic surface polishes without the introduction of contaminants or tensions in the surface layers of the metal. The fundamental difference between the Chemical and electroChemical Polishing processes is that in the latter anodic currents/potentials are used to help in the dissolution and passivation of the metal. In this paper, the use of an oxidizing electrolytic solution (2.5 mol L−1 CrO3 + 5.0 mol L−1 H2SO4) originally employed in electroChemical coloration processes is reported for the electroPolishing of AISI-314 stainless steel. Parameters involved in this electroPolishing process, such as temperature, current density and time, were optimized so as to attain the best possible results evaluated by the obtained surface brightness measured by reflectance spectra. Surface analyses by scanning electron microscopy allowed a clear correlation between obtained brightness and surface smoothing. The best conditions obtained for the electroPolishing process are: temperature of 45 °C, electrolysis time of 10 min and current density of around 25 A dm−2. It should be pointed out that an electroPolishing process signature (periodic oscillations of the cell potential) was established; this may be an important tool for optimizing and monitoring electroPolishing processes.
Yun Long - One of the best experts on this subject based on the ideXlab platform.
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Superlubricity of glycerol by self-sustained Chemical Polishing
Scientific Reports, 2019Co-Authors: Yun Long, Maria-isabel De Barros Bouchet, Ton Lubrecht, Tasuku Onodera, Jean-michel MartinAbstract:An impressive superlow coefficient of friction (CoF) as low as 0.004 (nearly equivalent to the rolling coefficient) was obtained by sliding a steel ball against a tetrahedral amorphous diamond-like carbon (ta-C) coating in glycerol under a boundary lubrication regime. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) revealed substantial changes in the surface chemistry and topography in the friction track. As shown by XPS analysis, a transfer of iron atoms from the steel ball to the ta-C layer occurred, forming iron oxy-hydroxide (FeOOH) termination on both surfaces. Between them, theoretical calculations show that a nanometre-thick fluid film consisting of glycerol and its degradation products prevents direct contact between the solid surfaces by nm-thick film EHL lubrication and results in the superlow friction, in agreement with the experiment. Furthermore, molecular dynamics (MD) simulations reveal that hydrogen atoms act as "low-friction brushes" between sliding layers of crystalline FeOOH, resulting also in low friction. A new model of sustainable green superlubricity is proposed. The tribo-formation of FeOOH with glycerol leads to a unique Polishing process, which in turn leads to a self-sustained Elasto-Hydrodynamic Lubrication (EHL) regime until the very thin fluid film is no more than a few nanometres thick. At lower thicknesses, the hydroxide layer takes over. Wear of the ta-C coating is negligible, while wear on the steel ball is very moderate and acceptable for many practical applications, such as bio-tribology and the food industry, in which green lubrication is especially needed.
Leonardo S Andrade - One of the best experts on this subject based on the ideXlab platform.
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electroPolishing of aisi 304 stainless steel using an oxidizing solution originally used for electroChemical coloration
Electrochimica Acta, 2005Co-Authors: Leonardo S Andrade, Sandro C Xavier, Romeu C Rochafilho, Nerilso Bocchi, Sonia R BiaggioAbstract:Abstract Chemical Polishing or electroPolishing, instead of mechanical Polishing, are recommended for the attainment of metallic surface polishes without the introduction of contaminants or tensions in the surface layers of the metal. The fundamental difference between the Chemical and electroChemical Polishing processes is that in the latter anodic currents/potentials are used to help in the dissolution and passivation of the metal. In this paper, the use of an oxidizing electrolytic solution (2.5 mol L−1 CrO3 + 5.0 mol L−1 H2SO4) originally employed in electroChemical coloration processes is reported for the electroPolishing of AISI-314 stainless steel. Parameters involved in this electroPolishing process, such as temperature, current density and time, were optimized so as to attain the best possible results evaluated by the obtained surface brightness measured by reflectance spectra. Surface analyses by scanning electron microscopy allowed a clear correlation between obtained brightness and surface smoothing. The best conditions obtained for the electroPolishing process are: temperature of 45 °C, electrolysis time of 10 min and current density of around 25 A dm−2. It should be pointed out that an electroPolishing process signature (periodic oscillations of the cell potential) was established; this may be an important tool for optimizing and monitoring electroPolishing processes.
Natsuo Tatsumi - One of the best experts on this subject based on the ideXlab platform.
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Polishing mechanism and surface damage analysis of type iia single crystal diamond processed by mechanical and Chemical Polishing methods
Diamond and Related Materials, 2016Co-Authors: Natsuo Tatsumi, Katsuko Harano, Hitoshi SumiyaAbstract:Abstract The Polishing mechanisms and surface damages of mechanically and Chemically polished diamond crystals were investigated. A metal bonded diamond wheel was used for mechanical Polishing, while an SiO 2 wheel was used for Chemical Polishing. After Polishing, samples underwent surface treatment with hydrogen plasma to exhibit negative electron affinity. SEM observation revealed that the scratches consisted of dark cracks with cleavage facets. Dark contrast was observed around the cracks on the hydrogen terminated diamond surface, indicating that carriers excited by primary electrons were eliminated by crystal defects around the cracks. The Polishing rate increased nonlinearly with the rotating speed of the SiO 2 wheel. The difference of Polishing rate of the (100) surface between the direction and the direction became smaller when using the SiO 2 wheel than when using the metal bonded diamond grinding wheel. The Polishing rates became more isotropic, suggesting that the wear reactions of the diamond and the SiO 2 wheel were mainly Chemical. Although abrasion traces were also observed by optical microscopy on the sample polished by an SiO 2 wheel, dark contrast due to lattice distortion or crystal defects was not observed by SEM. This result shows that the sample surface and subsurface Chemically polished by the SiO 2 wheel had very little damages.