Production of Anorthite from Kaolinite and CaCO<sub>3</sub> via Colemanite

Boron oxide has been found to be useful flux for the preparation of dense anorthite ceramics (CaO.Al 2O3.2SiO 2). Inexpensive starting materials of kaolinite, calcium carbonate and silica were used for anorthite ceramic production. Colemanite (2CaO.3B 2O3.5H 2O) was added into the mixtures and the effects of colemanite upon the transformation towards anorthite and on the densification were investigated between 900-1400 °C. Single phase anorthite ceramic formed at lower temperatures in boron containing mixtures. Boron containing powder compacts were sintered above 90% theoretical density at 1350 °C.