Effects of carbon black addition on preparation of meso-carbon microbeads

The preparation of meso-carbon microbeads (MCMB) has been studied by heat-treating two synthetic isotropic naphthalene pitches at 380-430 degrees C for 1-12 hours in the presence of several types of carbon blacks. A larger number of beads with small diameter, ranging from 1 to 10 mu m, were obtained. The yields of the beads assessed volumetrically by microscope and gravimetrically by pyridine extraction reached to as high as 45 vol% and 30 wt%, respectively. A particular heat-treatment temperature (400 degrees C) appears optimum to give a narrower size distribution of the spheres than other temperatures (380 and 420 degrees C) with 1 wt% carbon black. The lower temperature and longer time with 3 wt% Ketjen Black favored the formation of uniform size of beads. The carbon black appears to enhance the nucleation and to inhibit the growth and coalescence of the mesophase sphere. In the presence of carbon blacks the synthetic isotropic pitches tended to produce extracted spheres consisting of basic domain units in coagulated forms. (C) 1997 Elsevier Science Ltd.