Preparation of Powders by Carbothermal Reduction of Aluminum Oxide and Their Consolidation into Dense Polycrystalline Bodies.
Final rept. 1984-1986,
ISRAEL CERAMIC AND SILICATE INST HAIFA
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The conditions of carbothermal reduction of alumina and the formation of AIN andor ALON were investigated employing the parameters temperaturetime 1520-1780 C12-4hrs, initial carbonalumina ratio, X, Ca. 1.52-0.176 3CAl2O3, flow of nitrogen through bed mix, and source of carbon Ultracarbon and carbon black, with specific surface area of 6.4 Sg.mg and 1000 Sg.mg respectively. Conditions were delineated under which all the alumina was reduced and the product was either AlN or ALON. At 1780 C4hrs and X1.525, only AlN was produced, and at 1600 C1-2hrs and X0.176, ALON was practically the only product. Excess carbon was removed at 800 C15-20 in air. Hot pressing at 1700-1720 C12hr produced dense 3.69-3.70 and hard Vickers ca. 2000 KgSg.mm, somewhat dark coloured pellets. Bleaching of thin slices at 1200 C1hr gave very light grey, translucent product.
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