Crystallization Kinetics of α-Alumina and Mullite-Zirconia in Boehmite and Zircon Mixture

Abstract: The crystallization kinetics of α-alumina and mullite-zirconia formation in boehmite and zircon mixture was investigated by dilatometry, XRD and SEM. The powder of boehmite was obtained from partial dehydration of a gibbsite. As-received, raw materials were weighed to produce the 3:2 alumina: silica stoichiometric mixture. All raw powders have been ball milling, isostatically pressed and then sintered at different temperatures. The dilatometer conducted at heating rates of 5, 10, 15 and 20 °C/min showed two expansions at about 1,350 and 1,500 °C associated with α-alumina formation from θ-alumina and mullite crystallization, respectively. The non-isothermal activation energies for α-alumina formation and mullite crystallization were calculated by the Kissinger method. The results showed mullite crystals with a dominant bulk nucleation in the mullite crystallisation. This latter is followed by three-dimensional growth of mullite crystals with polyhedron-like morphology. Key words: