The influence of B4C content on the pore structure of reaction-synthesized porous Ti3AlC2-TiB2 composite ceramics

Abstract

Using a mixture of TiH2, Al, B4C, and graphite powders with a molar ratio of 3+2 m/1.2/m/2-m (where m ranges from 0 to 0.25, with increments of 0.05), porous Ti3AlC2-TiB2 composite ceramics were successfully synthesized through activated reaction sintering. The effect of B4C content on the phase composition, volumetric expansion, microstructure, and pore structure parameters (including pore size, porosity, and permeability) was systematically studied. When the molar ratio of B4C was less than 0.1, the volumetric expansion rate, average pore size, and permeability increased with the addition of B4C, reaching maximum values of −5.46 %, 2.23 μm, and 92.4 m3 m−2·10 kPa−1 h−1, respectively. Conversely, when the B4C molar ratio exceeded 0.1, the parameters related to the pore structure of the porous Ti3AlC2-TiB2 composite ceramics decreased, with minimum values of −10.40 %, 1.46 μm, and 68 m3 m−2·10 kPa−1 h−1, respectively. In addition, the pore formation mechanism of the porous Ti3AlC2-TiB2 composite ceramics was systematically explored. The revolution tendency of pores is related to the decomposition of TiH2, Kirkendall partial diffusion, diffusion between B and C, and the transition process of the final phase Ti3AlC2-TiB2. This research work could provide a reference for the preparation of the MAX phase composite porous materials.