Optimization of the preparation conditions of polygranular carbons from mesophase

Polygranular carbons were prepared from a coal-tar pitch based mesophase by sintering, using different experimental conditions. The temperature and time of mesophase stabilization, the pressure applied during moulding, and the sintering heating rate were investigated in order to obtain materials with optimum properties. Oxidative stabilization with air between 225 and 250°C causes a significant reduction in the plasticity of the coal-tar pitch based mesophase, allowing moulding and sintering to be performed. An increase in the moulding pressure results in an increase in the bulk density of the green materials. However, sintering must be carried out at low heating rates in order to control the release of gases and thus avoid damage to the sintered material. Higher sintering heating rates are compatible with low moulding pressures and a high degree of stabilization. Whenever the materials do not distort during sintering, a common feature observed is that mechanical and electrical properties improve with increasing moulding pressure, while an increase in sintering heating rate only serves to improve the strength of the materials.