J111026 First-Principles Molecular Dynamics and Tight-Binding Quantum Chemical Molecular Dynamics Studies of Super-Low Friction Mechanism on Carbon Nitride Films Interface

Sato, Seiichiro; Hayashi, Kentaro; Bai, Shandan; Higuchi, Yuji; Ozawa, Nobuki; Shimazaki, Tomomi; Adachi, K.; Kubo, Momoji

doi:10.1299/jsmemecj.2012._j111026-1

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“…When the water content of the nitrogen gas was high (> 1.0%RH, Mode II), friction increased because the structure of transferred carbon is not maintained and oxidation products formed on the surface of the Si 3 N 4 ball [14]. Kubo et al used a tight-binding quantum chemical molecular dynamics simulation and found that hydrogen termination of DLC or CN X coatings and hydroxyl termination of DLC contributed to low friction [20][21][22][23]. They also reported that non-hydrogen-terminated DLC coatings display very high friction because of the formation of C-C bonds [22].…”

Section: The Roles Of Water and Oxygen Molecules Inmentioning

confidence: 99%

Role of Water and Oxygen Molecules in the Lubricity of Carbon Nitride Coatings under a Nitrogen Atmosphere

et al. 2016

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In this study, an experimental apparatus was developed where the relative humidity (RH) and oxygen concentration could be controlled between 0.01-10%RH and 1-100000 ppm, respectively. This apparatus was used to study the roles of water and oxygen molecules on the friction of carbon nitride (CN X) coatings. The friction properties of Si 3 N 4 balls sliding against CN X (Si 3 N 4 /CN X) under a nitrogen atmosphere were classified into the following three modes according to their average friction coefficients (µ a) and the stability of the friction: Mode I, µ a < 0.05 (stable); Mode II, 0.05 < µ a < 0.3 (stable); and Mode III, 0.3 < µ a (unstable). To achieve a low friction coefficient (e. g. < 0.05), the optimum RH and oxygen concentration were 0.1-1.0%RH and 100-10000 ppm, respectively. Time-of-flight secondary ion mass spectroscopy (TOF-SIMS) showed that hydrogen and hydroxyl radicals derived from water molecules chemisorbed onto the worn surfaces of the CN X coatings. Raman spectroscopy suggested that the structure of carbon on the worn surfaces was different from that of the deposited CN X coating. We concluded that low friction (Mode I) arose from the water and oxygen molecules terminating carbon dangling bonds and structural changes in CN X .

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