Effect of Alumina\Titanium Diboride Nano-Composite Synthesis Method on Sintering Behaviour and Properties of Sintered Sample

The consolidation of the Al2O3/TiB2 into a dense and high-strength body is difficult because of the high degree of covalent bonding and low self-diffusion coefficient of the constituent elements. Synthesis of fine and homogenous structure in which one phase homogenously dispersed in the other can resolve this problem. Consolidation of Al2O3/TiB2 nano-composite powder derived from two different synthesis methods was investigated. Also the effect of processing condition on the sintering behavior, microstructure, and hardness of the densified samples were evaluated. In the first synthesis method a composite structure containing of an Al2O3 matrix with dispersed TiB2 particles was obtained via mechanical alloying of Al, TiO2 and B2O3 powder mixture. In the second method Al2O3/TiB2 nano-composite powder was prepared from TTIP(titanium tetra iso propoxide) and B2O3 using a sol-gel method followed by mechano-chemical reduction in the presence of Al. For sample which prepared by milling assisted sol-gel method, vickers hardness value of hot pressed sample at 1500°C was measured as 15.3 GPa and indentation fracture toughness was calculated as 10.1 MPa.m1/2; while for mechano-chemically synthesized sample this parameters are 20 GPa and 11.4 MPa.m1/2, respectively. Analysis of the diffraction pattern of samples revealed the presence of Al2O3, TiB2, and Al18B4O33 in the samples. Several factors favors the sintering process of the Al2O3-TiB2 nano-composite particles at low temperature and short time which include; (1) the nanostructured Al2O3-TiB2 particles, (2) the disordered crystal structure of the powder and (3) liquid phase formation of Al18B4O33.