Research Of Hot-Press Sintered Al₂O₃/Si₃N Nanocomposites Ceramics

Al₂O₃/Si₃N₄ nanocomposites ceramics is studied in this paper. We used commerce-produced Al₂O₃ and Si₃N₄ powders, hot-pressing sintered method to fabricate the Al₂O₃/Si₃N₄ nanocomposites. By analysis the relationship of the sintering process and the grain grow process, we should master the principle of how to fabricate good properties Al₂O₃/Si₃N₄ nanocomposites ceramics with tight structure and small -size grains.Test show that the samples sintered under 1600℃ is the best. Sample B4, the content of Si₃N₄ is 3wt%, is the best of best .its hardness is 15.59 GPa, fracture toughness is 4.21 Mpa.m¹/2 compared with pure Al₂O₃ ceramics, the hardness and the fracture toughness is improved much.It was observed by SEM that the Al₂O₃ grains were in the shape of elongated columns with aspect ratios in the range 2.5-4. The presence of liquid phase during sintering was found to responsible for the appearance of columnar grains. β-SIALON grains formed during sintering were mainly situated at grain boundaries of the matrix material while irregular smaller particles trapped within the Al₂O₃ grains. The improvement in the mechanical properties is attributed to the change in fracture mode from intergranular fracture to transgranular fracture. The "self-reinforcement effect" arising from the elongated columnar grains of the matrix as well as the "pinning effect" due to the existence of intergranular P-SIALON particles, thedifference of the two phases' mechanical properties lead to the Al₂O₃ grains have the trend of "nano-size" is also good to the improvement of the material.