Coke Surface Research Articles

Observation of Microstructures of Brushes by Electron Microscope

As we found equi-centred multi-ringed bodies on each sliding surface of pitch coke brushes under an electron microscope, we tried to trace them to the origin in each manufacturing process and clear up their characteristics. As a consequence, we could confirm that they originated from vortex-like bodies which had been generated in flow layers of coal pitch coke through the coking process, but not in petroleum pitch coke; that these microstructures were formed with equi-centred multi-shells which were composed of fine carbon crystals and ordinary graphite grains in turn, whose orientations of crystalits on each shell were apparently perpendicular. Besides, dropping out traces of shells were observed easily on each polishing and sliding surface of brushes. Considering these structures and the others, then, we could estimate them to be hard or stiff and have high electric resistance.Trying to investigate how influential the multi-shelled body had been on electric sliding contacts, we could notice that it played a significant role in the brush ability; commutation, damages of a commutator and brush wear, and that variances in brush ability depended upon its distribution on the sliding surface.