Effects of additives on combustion synthesis of Al2O3-TiB2 ceramic composite

Al2O3, SiC and kaolin were employed as additives in combustion synthesizing Al2O3-TiB2 ceramic composite. Effects of the additives on adiabatic temperature, combustion wave velocity, volume change and composite density were studied, and bending strength of the synthesized ceramics was evaluated. By theoretical calculation, the adiabatic temperature of Al-TiO2-H3BO3 system is 2314.85 degrees C and decreases with increasing the additive addition. With Al2O3 addition, the phases presented in the ceramic composite are unchanged, and the phases of SiC and 3Al(2)O(3)center dot 2SiO(2) emerges when SiC and kaolin are added. The addition of the additives results in a refined TiB2 particulate size and reduces combustion wave velocity. The highest density is achieved with the addition of kaolin from 10 to 30 wt.% making the volume change from -4.6 to - 1.2%. The bending strength of the TiB2-Al2O3 composite is improved eight times with the addition of 30 wt.% kaolin. (C) 2008 Elsevier Ltd. All rights reserved.