Carbon disc of high density and strength prepared from heat-treated mesophase pitch grains Original Research Article

Carbonaceous grains for binderless moulding were prepared by control of the preheat-treatment of the naphthalene-derived mesophase pitch. The carbonized and graphitized discs were evaluated in terms of physical properties and textures. Carbon disc of strikingly high bulk density, 2.04 g/cm3, high compressive strength, 1.94 tf/cm2, and large shrinkage ratio, 15.9%, was obtained through the grinding of the pitch preheat-treated at 753 K, their cold moulding, carbonization at a heating rate of 12 K/h, and successive graphitization at 2173 K. A homogeneous fine-mosaic texture of optical anisotropy was observed over the whole region in the artifact, indicative of sufficient adhesion among grains during the carbonization. X-ray analyses suggested a graphitizing nature of the grains in their moulds. Grains preheat-treated under 753 K exhibited excess fusibility for adhesion, leading to partial flow texture, where many cracks were easily induced during the calcination, decreasing the strength of the disc. In contrast, preheat-treatment over 753 K caused insufficient adhesion among grains, decreasing markedly both density and strength of the disc. A slight but significant presence of the pyridine-insoluble/quinoline-soluble fraction in the preheattreated pitch system is indicated to play a major role in adhesive ability of the grains preheat-treated at 753 K.