Use of oxidized needle-coke in the preparation of carbon artifacts

Abstract

This study examines the microstrength, optical texture and bonding of baked carbons made from oxidized filler cokes and a pitch binder. Commercial needle-cokes and coke from a coal extract, after oxidation in the range of 0 to 20 wt% loss, were mixed with a coal-tar pitch and baked to produce a series of carbon artifacts. The microstrengths of these artifacts were measured and the interfaces between coke components were examined by optical microscopy. The microstrengths of carbon artifacts containing oxidized needle-coke filler decreases with increasing extent of oxidation of the filler. However, the strength of carbon artifacts containing oxidized coal extract coke filler increases with increasing extent of oxidation of the filler. Differences in wettability of the filler particles by the pitch appear to cause these changes in microstrength. The pitch appears to be unable to penetrate into the oxidation topography of the needle-coke surface at levels of oxidation below 20 wt% but can penetrate into the larger surface features of the oxidized coal extract filler coke. Penetration of the pitch into the oxidation topography of the filler cokes produces a wetted/keyed interface and improves the bonding between the filler and binder cokes in the resultant artifact.