Carbothermal reduction of metal-oxide powders by synthetic pitch to carbide and nitride ceramics

Abstract

The carbothermal reduction potential of mesophase synthetic pitch was investigated. Powders of cobalt oxide, iron oxide, zirconium oxide, manganese oxide, silicon oxide, vanadium oxide, tantalum oxide, tungsten oxide, chromium oxide, and titanium oxide were mixed with pitch and pyrolyzed at a variety of temperatures up to 1500 °C in nitrogen, 5% hydrogen balance argon, and anhydrous ammonia. Pitch was found superior to graphite (and both were superior to charcoal) in carbothermal reactivity by forming carbides and nitrides more completely and at lower temperatures and, in some instances, where no conversion was observed for graphite. It is hypothesized that wetting of the liquid pitch at high temperatures before graphitization leads to better surface contact, and thus, increased kinetics of the carbothermal reduction.