ZHANG Can,　LU Gui-min,　YU Jian-guo

Controlling the volumetric dilation during baking is a key factor in the preparation of excellent graphite and carbon materials. The mechanism of expansion of shaped carbonaceous products at different forming temperatures during baking was investigated. Results showed that the green body hot-pressed at 170℃ can easily form a convex surface, cracks and other deformations during baking, which is in accordance with the gas dilation mechanism because of the poor gas permeability of the green body. The expansion and deformation can be inhibited by lowering the heating rate during baking. The expansion of the green body hot-pressed at 135℃ was caused by both the relaxation of residual stress and the gas dilation mechanism. The gas permeability of green body hot-pressed at 135℃ is superior to that hot-pressed at 170℃ and the dilation of the former mainly occurred at the pitch softening stage, and was also affected by heating rate during baking. The performance of the baked products can be improved by optimizing pitch/carbon ratio, molding temperature and pressure and by lowering the heating rate during baking.

The Fundamental Research Funds for the Central Universities, National Natural Science Foundation of China (50874048).