Design of Ceramic Microstructure of Nanoscaled Transitional Alumina

Nanoscaled transitional alumina (γ-, δ-, θ- → α-phase) consolidated at P = 500 MPa and T = 1,500°C for 30 min gave compacts with a density of 75% of theoretical density (TD) and a vermicular microstructure. The temperature of the transition to α-Al2O3 was 1,304°C. After mechanical activation by attriting, the transformation temperature to α-Al2O3 was reduced to 1,080°C. The density of the compacts consolidated at P = 500 MPa and T = 1,500°C for 30 min was 95% TD. The grain size distribution reached from 100 to 600 nm.