INVESTIGATIONS ON THE CROSS-LINKING OF THE BINDER PITCH MATRIX OF CARBON BODIES WITH MOLECULAR-OXYGEN .2. KINETICS AND EFFECTS OF CROSS-LINKING OF THE BINDER PITCH MATRIX ON THE PROPERTIES OF THE CARBON BODIES

A green mix composed of 65% pitch coke powder and 35% petroleum pitch (Ashland A 240) was shaped into cylindrical bodies, 30 mm in diameter and 30 mm in height. The bodies were treated with flowing pure oxygen at 200 degrees C and pressures of 0.1 MPa and 1 MPa. The kinetics of o xidation were analyzed by measuring the oxygen uptake, radial temperat ure gradients in the body, formations of CO2 and CO and by determinati on of radial oxygen profiles. Properties of the bodies were determined after carbonization at 1000 degrees C and graphitization treatment at 2450 degrees C. Severe pore diffusion problems were found not to exis t This result is explained by a strong temperature selectivity of the oxidation reactions. At a given temperature, the reactions are limited to the oxidation of special groups, which allows the reaction front t o move from the surface into the core of the body without remarkable o ver-oxidation of the skin. By an optimum oxygen treatment the flexural strength after graphitization treatment of the bodies is increased fr om about 10 to about 40 MPa. (C) 1997 Elsevier Science Ltd.