Ultra-low Friction Behavior during Gas Adsorption to a Hard Amorphous Carbon Film

在炭黑颗粒静电冲击沉积制备的硬质非晶碳膜上，通过评价膜的结构和边界润滑性能，研究了气体分子表面吸附下的超低摩擦行为，得到了以下结果；碳膜是由起始材料的石墨相和受冲击的非晶结构组成的，包含了许多缺陷，如碳的悬垂键。当薄膜加热超过100℃时，非晶结构逐渐转变为石墨相，这意味着悬垂键的密度增加。通过不同大气条件下的滑动摩擦实验，揭示了涂覆球与圆盘试样之间以接触点重复描述同一轨迹的往复运动方式进行的超低摩擦表面吸附条件。得到了以下结果：(1)气体吸附氢、水和氮的密度状态下，摩擦系数很低，特别是在氢气气氛下，摩擦系数在0.01以下。然而，在摩擦作用下，氧气促进了碳膜的界面粘附。(2)澄清了空气中的边界润滑受水吸附的影响较大。在当前往复摩擦实验条件下，低摩擦下的低水吸附可以在适当的解吸速率和吸附速率平衡下实现；前者可由摩擦条件决定，后者可由大气条件和石墨含量、表面自由基含量等薄膜质量决定。

On a hard amorphous carbon film prepared by electrostatic impact-deposition of carbon black particle, the ultra-low friction behavior under the surface adsorption of gas molecules was investigated by evaluating the structure and the boundary lubrication properties of the film, and the following results are obtained;1.The carbon film is composed with graphitic phase of starting material and its impact-subjected one of amorphous structure, including numerous defects such as dangling bond of carbon. For the film heating beyond 100 C, the amorphous structure gradually transforms to graphitic phase, which reads to the increase in the density of dangling bond.2.Surface adsorption condition for ultra-low friction was revealed with a sliding friction experiment in several atmospheric gases, using the reciprocating motion between coated ball and disc specimens in the manner that the contact point describes a same locus repeatedly. And the following results are obtained; (1)Very low friction was attained for the density state of gas adsorption of hydrogen, water and nitrogen, especially in hydrogen atmosphere the frictional coefficient became of below 0.01. However, it is proved that oxygen gas promotes the interfacial adhesion of carbon film under frictional action. (2)It was clarified that the boundary lubrication in air is considerably affected by water adsorption. In the present experimental condition of reciprocating friction, the low water adsorption for low friction can be attained in an appropriate equilibrium of the desorption and adsorption rates; the former can be dominated by the friction condition, and the latter can be by the atmospheric condition and film quality such as the content of graphite and surface radical.