A Combined Method for Synthesis of Dense Nanoceramics Based on Aluminum Oxide

Resumo

Abstract—A new technological procedure for preparation of dense ceramics based on aluminum oxide is developed. It features use of a modifying additive and mechanochemical (MCA) activation of the starting material. Use of MCA has a beneficial effect on synthesis of dispersed precursor γ-Al₂O₃-based powders at 600°C, with the temperature of α-Al₂O₃ phase formation being reduced from 1200 to 1000°C. MCA is found to affect the relative density of aluminum oxide ceramics sintered at temperatures of 1000–1500°C, the sintering process occurring more intensely in the temperature range of 1000–1300°C. The presence of MgO in the aluminum oxide matrix at a level of 1 to 3 wt % is shown to slow down the growth of α-Al₂O₃ phase grains owing to the formation of a boundary layer consisting of MgAl₂O₄ nanocrystallites in the aluminum oxide matrix. A ceramic material prepared on the basis of α-Al₂O₃ has a mean grain size of ~70 nm, a relative density of 0.98, a microhardness of 25 GPa, and a bending strength of 650 MPa. The proposed combined method is facile and economical and enables us to produce high-density aluminum oxide ceramic with a grain size below 100 nm and high physicochemical characteristics. This ceramic can be used in fabrication of different construction and functional materials.