Synthesis, evaluation and characterization of alumina ceramics with elongated grains

Alumina ceramics with high fracture toughness were synthesised by introducing seeds and controlling processing using the in situ self-toughening technique. The preparation of the high tough alumina materials started with cheap commercial aluminum hydroxide as raw materials. alpha-Alumina powder was gained by low temperature calcination of the aluminum hydroxide with seeds, which were introduced by high purity alumina ball medium during grinding. The alumina powders were hot-pressed, then, the high tough alumina ceramics with elongated grains were obtained. The elongated grain structure is originally considered to play a significant role in the increment of fracture toughness. Meanwhile, in order to investigate in situ toughening mechanism of elongated alumina grains, which can produce crack bridging, crack deflection and pull-out as dominant toughening mechanisms to greatly increase toughness, fractal characteristics and model were studied in detail. (c) 2005 Elsevier Ltd and Techna Group S.r.l. All rights reserved.