Structures and High Temperature Frictional Behaviors of Coal Pitch-Derived Carbonaceous Mesophases (CMs) Ball Milled for Different Durations

A coal tar pitch-derived carbonaceous mesophase (CM) was treated in a high energy ball mill apparatus. The structures for 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 calorimetry (DSC) measurement system, and the frictional behaviors for the CMs were investigated by using an SRV high temperature friction- and wear- tester. The results have shown that high energy ball milling leads 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 facilitates the structural amorphous transition for the CMs. In addition, high energy ball milling results in a lower structural stability for the CMs, and the stability further decreases as the ball milling time increases. The CMs display a high temperature lubrication effect. High energy ball milling is supposed to have a beneficial effect to the graphitization of the CMs induced by frictional mechanical action and, therefore, facilitate the high temperature lubrication effect to some extent. This effect can be enhanced through prolonged ball milling.