Effect of Ball Milling Time on Structure and High Temperature Friction and Wear Behavior of Carbonaceous Mesophases

A coal tar pitch-derived carbonaceous mesophase (CM) was treated in a high-energy ball mill apparatus.The structures of the raw and the as-milled CMs were characterized by X ray diffraction and Laser-Raman spectroscopic techniques,the structural stability for the as-milled CMs was measured with a differential scanning calorimeter(DSC),and the friction and wear behavior for the CMs as lubricating additives were investigated in a step heating scheme by using a SRV high temperature friction and wear tester.The results showed that high-energy ball milling led to a drop in the crystallinity of the CMs and a decrease in the size of graphite planar micro-crystals,implying a higher structural amorphism caused by the high energy ball milling.Furthermore, the extended ball milling facilitated the structural amorphous transition for the CMs.In addition,high-energy ball milling resulted in a lower structural stability for the CMs,and the stability further decreased as the ball milling time increased.The as-milled CMs exhibited friction-reducing and wear resistant effect at high temperature,which was strengthened by longer ball milling.High-energy ball millingis supposed to have a beneficial effect for the graphitization of the CMs induced by friction and mechanical interaction,and,therefore,facilitate the high temperature anti-friction and wear resistant effect to some extent.This effect can be enhanced through prolonged ball milling.