Preparation of Powders by Carbothermal Reduction of Aluminum Oxide and Their Consolidation into Dense Polycrystalline Bodies

摘要

The conditions of carbothermal reduction of alumina and the formation of AIN and/or ALON were investigated employing the parameters: temperature/time (1520-1780 C)/1/2-4hrs, initial carbon/alumina ratio, X, (Ca. 1.52-0.176 3C/Al2O3), flow of nitrogen through bed mix, and source of carbon (Ultracarbon and carbon black, with specific surface area of 6.4 Sg.m/g and 1000 Sg.m/g respectively). Conditions were delineated under which all the alumina was reduced and the product was either AlN or ALON. At 1780 C/4hrs and X=1.525, only AlN was produced, and at 1600 C/1-2hrs and X=0.176, ALON was practically the only product. Excess carbon was removed at 800 C/15-20' in air. Hot pressing at 1700-1720 C/(1/2)hr produced dense (3.69-3.70) and hard (Vickers ca. 2000 Kg/Sg.mm), somewhat dark coloured pellets. Bleaching of thin slices at 1200 C/1hr gave very light grey, translucent product.