Preparation of Nano-sized Alpha-Alumina Crystallites Using Theta- Theta- Alumina Composite Powders

摘要

α-Al{sub}2O{sub}3 powders with mean particle sizes ～50 nm can be obtained using θ-Al{sub}2O{sub}3 as the precursor through θ- toα-phase transformation, if the θ-Al{sub}2O{sub}3 crystallites undergo transformation reach the critical size (d{sub}cθ) and then transform simultaneously. Two θ-Al{sub}2O{sub}3 powders of different sizes 20 and 11 nm in diameter were mixed at proper ratios to fulfill the requirement. α-Al{sub}2O{sub}3 powders and green compacts, both with particle sizes ～50 nm were obtained.