Frictional and Protective Characteristics of Hard Amorphous Carbon Film Deposited by High-velocity Impact of Carbon-black Particles

1986 Fiscal Year Final Research Report Summary

• Project/Area Number: 60550094
• Research Category: Grant-in-Aid for General Scientific Research (C)
• Allocation Type: Single-year Grants
• Research Field: 機械工作
• Research Institution: Ehime University
• Principal Investigator: IDE Takashi Ehime University , Associate Professor, 工学部, 助教授 (20029276)
• Co-Investigator(Kenkyū-buntansha): YAGI Hidetsugu Ehime University , Assistant, 工学部, 助手 (40036471) ; KONDA Isao Ehime University , Professor, 工学部, 教授 (40036223)
• Project Period (FY): 1985 – 1986
• Keywords: Hard Carbon Film / Amorphous Semiconductive Carbon Film / Ultra-Fine Particle / Carbon Black / Electrostatic Acceleration Of Powder Particle / High-Velocity Impact / Boundary Lubrication / 固体潤滑膜

Research Abstract

1. A hard amorphous carbon film can be unthermally prepared at deposition rate of several handred <ang> /min by electrostatically accelerating ultra-fine carbon-black particles to high velocity in a uniform electric field of the order of <10^6> V/m, by making the energetic particles mechanically collide with cold cathode (substrate) in vacuo.
2. It is considered that graphitic carbon-black is deposited with the structural change in an amorphous phase including excessive 4-fold and dangling bonds of carbon atoms due to high power density impact. This can be proved from the film characteristics such as the semi- conductive resistivity and its temperature dependence, their relaxation behaviour in annealing and the moderately high hardness.
3. For the purpose of tribological application, the frictional and the wear occurring mechanisms of the film are investigated under various atmospheric and frictional conditions with a ball-on-disk sliding friction test, by giving the ball sample a recipr ocating motion in the manner that the contact point describes a same locus repeatedly. And, the following results are obtained;
(1) It is found in normal humid atmosphere that the coefficient <mu> of friction decreases exponentially as the number of slides increases. This behaviour is considered to obey the boundary lubrication mechanism in which the <mu> depends on the coverage ratio of physisorbed water vapour as estimated the adsorption heat of about 36 kJ/mol.
(2) Excellent low values of <mu> of about 0.02 are presented at large number of slides as similar to diamond-like carbon films. This optimum lubrication means that the frictional desorption of the absorbate reaches in equilibrium with the adsorption at a low coverage state.
(3) In relatively severe condition such as low humidity, high speed and high load slidings, superior frictional desorption brings the break of the equilibrium state. Then, the <mu> increases gradually from the optimum value as a mild wear occurs.
(4) These results suggest that water vapour acts as an inhibitor not only to the essential lubrication efficiency of this film, but to the wear occurring as the adsorption will terminate active dungling bonds at film surface.