In order to realize reducing wear of both overhead wires and pantograph sliders, the authors have developed new composite materials for pantograph sliders by using hard porous carbon materials “RB ceramics”. The new composite materials were developed by sintering compounds of copper, carbon and the RB ceramics particles. Friction and wear properties of these copper/carbon/RB ceramics composite materials (Cu/C/RBC composites) sliding against a copper alloy pin under dry condition were investigated. The friction coefficient for the Cu/C/RBC composites was lower and more stable than that for the conventional pantograph slider material, Cu/C composite. The friction coefficient for the Cu/C/RBC composites was about 1/2 ∼ 3/5 of that for the Cu/C composite. The specific wear rate of the Cu/C/RBC composites was extremely lower than that of the Cu/C composite. The specific wear rate of the Cu/C/RBC composites was decreased with a decrease of the weight fraction and the mean particle size of the RB ceramics particles. The specific wear rate of the Cu/C/RBC composites was about 1/220 ∼ 1/70 of that of the conventional Cu/C composite. Furthermore, the specific wear rate of a copper alloy pin sliding against the Cu/C/RBC composites is about 1/1700 ∼ 1/150 of that sliding against the conventional Cu/C composite.

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Measurements of both thermal and lubrication properties of urea-based grease composites were conducted with and without additives of vapor grown carbon nanofiber (VGCNF) and solid lubricant molybdenum disulfide (MoS₂). As a result, a synergetic effect was found to greatly improve both the wear resistance and thermal properties of the urea grease composite with VGCNF and MoS₂.

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The influences of interactions between C₆₀ thin films and Si substrates were investigated using atomic force microscopy (AFM). It was found that higher friction coefficient was obtained at the C₆₀ domains formed on the H-terminated Si(001) substrate and lower ones on the Si(001)-2×1 substrate. Moreover, lowest friction coefficient was found for the C₆₀ film on the Si(001)-2×1 remained after scratching. Therefore, it is thought that higher interactions between C₆₀ and Si substrate caused lower friction coefficient of C₆₀ thin film. The prepared substrate was examined by reflection high energy electron diffraction (RHEED), X-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy (AES).

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Polyvinyl alcohol (PVA) hydrogel is one of the candidate materials for artificial cartilage. In previous research, it was found that the structure of protein boundary film is important essence for wear reduction of PVA hydrogel, and the stability of protein boundary film changes with relative ratio and total concentration of proteins. In this study, the behavior of protein adsorption on the glass surface rubbed with PVA hydrogel was observed by using total internal reflection fluorescence microscopy (TIRFM). Amount of adsorbed proteins under rubbed condition increased compared to those under statically immersed condition. In lubricant in which a stable protein boundary film was formed, the amount of adsorbed proteins in bottom layer of protein boundary film increased significantly with an increase of sliding distance. In addition, the ratio of adsorbed immuno globulin G (IgG) to albumin was higher than that in lubricant in which an exfoliative protein boundary film was formed. These results indicate that the formation of bottom layer mainly composed of γ-globulin is a critical element to form a stable boundary film, and the friction-induced enhancement of forming protein boundary film may occur in lubricant with appropriate protein constituents.

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The corrected paper is published because a part of text was lacked in the paper published in Tribology Online, 3, 4, 2008, pp. 228-231.

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Measurements of both thermal and lubrication properties of urea-based grease composites were conducted with and without additives of vapor grown carbon nanofiber (VGCNF) and solid lubricant molybdenum disulfide (MoS₂). As a result, a synergetic effect was found to greatly improve both the wear resistance and thermal properties of the urea grease composite with VGCNF and MoS₂.

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