Eight Phenomena to Explain the Frictional Properties of Carbon-Based Thin Films

抄録

Carbon-based films such as diamond, diamond-like carbon, and carbon nitride exhibit a low coefficient of friction in the order of 0.1 or an ultra-low coefficient of friction in the order of 0.01. In addition, depending on the friction conditions, they may exhibit a high friction coefficient of 0.3 or higher. However, there are no reports explaining why carbon-based films exhibit these properties. To address this issue, the factors involved in the development of low friction coefficients in carbon-based films in dry environments are considered in this study, and eight phenomena are proposed. The basic concept is that a carbon-based film is graphitized by frictional heat in the presence of trace amounts of oxygen and/or water; which results in the generation of gases such as CO, CO₂, H₂, and N₂, further reducing its friction coefficient. Consequently, it was possible to reasonably interpret the various frictional properties of carbon-based films, and to clarify the relationship between conditions such as the atmosphere of friction and friction properties, in relation to these eight phenomena.