Combustion of Uniformly Sized Glassy Carbon Particles

Abstract

A method for production of spherical particles of glassy carbon has been developed. The panicles exhibit some differences in surface structure, but are otherwise uniform in size and shape. In drop-tube combustion experiments at wall temperatures ranging from 1200 K to 1600 K, some panicles ignited and burned rapidly, reaching temperatures several hundred degrees higher than the wall temperature, while others burned as much as two orders of magnitude more slowly at temperatures only slightly higher than that of the reactor wall. In spite of these differences in ignition behavior, the particles burned with an intrinsic reaction rate that was in close agreement with the Nagle and Strickland-Constable rate for pyrolytic graphite as well as rates previously measured for carbon black and coal char oxidation. X-ray diffraction measurements show that graphitization occurs rapidly in a hot oxidizing atmosphere. Rapid anneal ing of the carbon structure might account for the similarity of the high temperature oxidation rates of carbons from different sources.