Influence of calcium oxide on alumina phase transition and morphology development in NaCl–KCl flux

Abstract

Plate-like α-Al2O3 particles are used as reinforcements of metals, resins or ceramics to improve their mechanical properties, such as elastic modulus, toughness and strength. Ceramic platelets are easier to disperse into matrix phase compared with whiskers, short fibres or nanoparticles. The well developed plate-like α-Al2O3 particles were obtained in NaCl–KCl flux by sintering at 1000°C for 4 h using Al(OH)3 powders as starting materials. The influences of calcium oxide on alumina phase transition and morphology development were focused. When calcium oxide was added, the phase of the sample was κ-Al2O3, and plate-like particles were not observed by firing at 1000°C for 4 h. The α-Al2O3 and H–Al2O3 phases were obtained, but plate-like particles were hardly observed, when the sample was sintered at 1200°C for 4 h.