Microstructure and mechanical properties of porous alumina ceramics fabricated by the decomposition of aluminum hydroxide

The mechanical properties of Al2O3-based porous ceramics fabricated from pu re Al2O3 powder and the mixtures with Al(OH)(3) were investigated. The frac ture strength of the porous Al2O3 specimens sintered from the mixture was s ubstantially higher than that of the pure Al2O3 sintered specimens because of strong grain bonding that resulted from the fine Al2O3 grains produced b y the decomposition of Al(OH)(3). However, the elastic modulus of the porou s Al2O3 specimens did not increase with the incorporation of Al(OH)(3), so that the strain to failure of the porous Al2O3 ceramics increased considera bly, especially in the specimens with high porosity, because of the unique pore structures related to the large original Al(OH)(3) particles. Fracture toughness also increased with the addition of Al(OH)(3) in the specimens w ith higher porosity. However, fracture toughness did not improve in the spe cimens with lower porosity because of the fracture-mode transition from int ergranular, at higher porosity, to transgranular, at lower porosity.