The Japanese Society of Tribologists is pleased to announce that the 2008 Paper Award of Tribology Online was awarded to:

“Effect of Step Length and Walking Speed on Traction Coefficient and Slip between Shoe Sole and Walkway,” by Takeshi Yamaguchi, Shintaro Hatanaka and Kazuo Hokkirigawa, Vol. 3, No. 2 (2008) 59-64.

and

“Direct Observation of Thermo-Reversible Gel-Lubricants in EHL by FT-IR Micro-Spectroscopy,” by Kazutoshi Takahashi, Yuji Shitara and Shigeyuki Mori, Vol. 3, No. 2 (2008) 131-136.

The Award Medals were presented to the authors by Professor Takashi Yamamoto, the former President of the Japanese Society of Tribologists, at the Annual Meeting on 19th May, 2009.

The Paper Award of Tribology Online, is a new award established this year by the Japanese Society of Tribologists. It is given annually to the author(s), either the JAST members or non-members, of the papers judged as the best paper(s) published in Tribology Online (TROL) for the previous three years. All papers that appeared in TROL for the three years are reviewed by the JAST Awards Committee.

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The authors have developed the new hard porous carbon material “Rice Husk ceramics” (RH ceramics) by carbonizing the mixture of rice husk and phenol resin at 900 °C in inert gas environment. The RH ceramics are composed of amorphous carbon and amorphous silica, about 90 and 10 wt.%, respectively. The friction and wear properties of RH ceramics sliding against austenitic stainless steel (JIS SUS304) were evaluated under dry and water lubricated conditions using a ball-on-disk apparatus. The test results showed that RH ceramics have lower friction coefficients and specific wear rates under dry than under water lubricated condition. The friction coefficient took very low values of 0.06 to 0.11 under dry condition, whereas, it was 0.09 to 0.15 under water lubricated condition. The specific wear rate was less than 10^-8 mm²/N under both conditions, though it was much lower under dry than under water lubricated condition. Transmission electron microscopy with energy dispersive X-ray spectroscopy and electron diffraction analyses were employed to characterize the properties of the worn surfaces of SUS304 ball samples. It was found that the tribological behavior of RH ceramics is strongly governed by the characteristics of the transferred film formed on counterpart surfaces.

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A new tribo experiment system is developed for sliding tests under high purity gas environments including hydrogen. It uses a transfer vessel such that surface oxidation does not substantially occur during transfer of specimens to surface analyzers. The system’s seal ability is confirmed with surface analysis with XPS and sliding tests with stainless steel. It is found that oxidation as well as adsorption of hydrocarbons as contaminants on steel surfaces during transfer is prevented. In the sliding test, differences in oxide formation on steel surfaces in hydrogen, in vacuum and in air are detected clearly.

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To elucidate the bonding mechanism of a non-polar perfluoropolyether lubricant (PFPE lube) under ultraviolet (UV) irradiation, the UV wavelength ranges in which photoelectrons emanate were identified using photoelectron spectroscopy in air (PESA), and the bonding behavior of the lube at various UV wavelengths was studied. The results showed that photoelectrons emanated from magnetic disk substrates at wavelengths of 240 nm or less and the lube was bonded to the substrate in the wavelength range where photoelectrons were emanated. For comparison, Si, SiO₂/Si, and Si₃N₄/Si were also used as substrate; the Si substrate which emanated the highest photoelectron intensity showed the highest bonded ratio of the lube. The lube, however, also bonded to the SiO₂/Si and Si₃N₄/Si substrates under UV irradiation at 222 nm, where photoelectrons do not emanate from the substrates. These observations suggest that the bonding mechanism between the PFPE chains and the carbon overcoat (COC) surfaces under UV irradiation was affected by factors other than photoelectrons.

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Molecular dynamics simulations were conducted in order to investigate the behaviors of dissolved gas molecules in lubricating film under shear. The lubricants were n-hexane and perfluorohexane, and the dissolved components were hydrogen. When the lubricant film was sheared, the dissolved gas molecules moved, and the number of molecules that adsorb on the solid surfaces increased. Shear induced the diffusion of gas molecules in lubricants. The behaviors of the dissolved molecules were affected by a sliding velocity.

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