Low Friction of Diamond-Like Carbon Film Due to Liquid Hydrocarbon Generated by Laser Heating in a Nitrogen Gas Environm
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ORIGINAL PAPER
Low Friction of Diamond‑Like Carbon Film Due to Liquid Hydrocarbon Generated by Laser Heating in a Nitrogen Gas Environment H. Tani1 · R. Naito2 · R. Lu1 · S. Koganezawa1 · N. Tagawa1 Received: 1 May 2020 / Accepted: 8 August 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract In this study, we investigated the low friction mechanism of a diamond-like carbon (DLC) film heated by laser irradiation in a nitrogen gas environment. The friction coefficient decreased from 0.5 to 0.06 when the contact area was heated to 250 °C. Subsequently, we heated the DLC film under non-contact conditions (2 μm distance between DLC film and pin surface) and collected the liquid materials adhered on the pin surface. The adhered materials were revealed to be hydrocarbons with – CH2– main-chains, as observed using Raman spectroscopy. On the other hand, thermal desorption gas chromatography with mass spectrometry using helium as a carrier gas demonstrated that hydrocarbons such as alkenes and alkanes with relatively high molecular weight were generated from heated DLC. This agreement between the results of the two analysis techniques suggested that the hydrocarbons in the liquid phase at room temperature were generated from the DLC film heated to a high temperature over 250 °C in an inert gas atmosphere. In addition, we confirmed the reduction in the friction coefficient after pre-heating a different location, as well as the dependence of the friction coefficient on the sliding velocity. The results suggest that hydrocarbons (e.g., alkenes or alkanes) generated upon DLC heating could possibly act as a lubricant to reduce the friction coefficient. Graphical Abstract
Keywords DLC · Superlubricity · Tribochemistry · Thermal desorption spectroscopy · Laser heating · Heat-assisted magnetic recording · Flash temperature * H. Tani hrstani@kansai‑u.ac.jp 1
Mechanical Engineering Department, Kansai University, 3‑3‑35, Yamate‑cho, Suita‑shi, Osaka 564‑8680, Japan
Graduate School of Kansai University, 3‑3‑35, Yamate‑cho, Suita‑shi, Osaka 564‑8680, Japan
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1 Introduction Among the various types of friction control technologies, diamond-like carbon (DLC) coatings have garnered considerable attention in recent years due to their unique friction
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and wear properties [1]. They are applied on rolling, rotating, and sliding components of several machines to control the friction and wear. One of the earliest applications of these coatings was to hard disk drives (HDDs), where such coatings with an extremely small thickness of approximately 2 nm increased the areal data storage densities of modern disk drives to nearly 1 TB/in2 [2]. DLC films are generally prepared using physical vapor deposition (PVD) and chemical vapor deposition (CVD). Plasma enhanced CVD (PECVD) is quite a common deposition method for hydrogenated DLC coatings. Typically, hydrocarbon gases (such as acetylene and methane) are used as the carbon source in this method, and the DLC films
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