ZHANG Chao, ZHANG Ling, ZHENG Peiyu, LI Fengyou, ZHANG Huan
(School of High Temperature Materials and Magnesium Resource Engineering, University of Science and Technology Liaoning, Anshan 114051, Liaoning, China)
Abstract: High-purity alumina ceramics were fabricated by hot-pressed sintering using MgO as additive. Nano-η-Al2O3 powder was used as the raw material. The densification, microstructure evolution and mechanical properties of the alumina ceramics were studied by the Archimedes method, SEM and the three-point bending test. The results show that the nano-η-Al2O3 is small in size and high in activity, and it is transformed to α-Al2O3 at 1084 °C; the addition of MgO can produce liquid phase during sintering, promote ion diffusion and accelerate reaction sintering, and the optimum content of MgO of 1.0wt.% is found. The relative density of the sample sintered at 1400 °C is 99.2%, and there is a more uniform distribution of matrix grains with an average size of 2 μm. The bending strength and the fracture toughness of the sample are 475 MPa and 5.1 MPa·m1/2, respectively.
Key words: nano-η-Al2O3; hot-pressed sintering; MgO; microstructure; mechanical properties