Crystallite orientation in polycrystalline graphites made from glass-like carbons under high pressure

Abstract

The preferred orientation of crystallites was investigated on polycrystalline graphites made from the glass-like carbons with spherical particles under a pressure of 5 kbar at 1300 to 2000‡ C. The glassy carbon spheres 40 to 70 Μm diameter which were pre-heated at 1000‡ C under normal pressure, gave sintered discs with a bulk density of 1.5 g cm−3 and a relatively high degree of orientation. However, spheres of the same type pre-heated at 2000‡ C gave the high bulk density of 1.9 g cm−3 and a very low degree of orientation. The carbon beads 40 to 70 Μm diameter gave a relatively low degree of orientation and pre-heating at 2000‡ C reduced the degree very remarkably. Carbon beads with a smaller particle size, <20 Μm, gave a lower degree of orientation. Pre-heating of the initial carbon of small particle size at temperatures as high as 2000‡ C resulted in a low degree of preferred orientation of the crystallites in the sintered discs, the temperature dependence being the strongest.