Microstructure and mechanical performance of acicular mullite-reinforced porous self-bonded ceramics

Abstract

Acicular mullite-reinforced porous self-bonded ceramics were fabricated using mullite powders as principal raw materials, alumina and silicon dioxide powders as starting synthetic source of self-bonded mullite phase, and 2 wt% AlF3·3H2O as an accelerant. The influences of self-bonded mullite weight percent on the phase composition, microstructures, mechanical performance and thermal conductivities of acicular mullite-reinforced porous self-bonded samples were investigated. As self-bonded mullite weight percent varied between 0 and 50 wt%, linear shrinkage, bulk density and thermal conductivities of fired porous self-bonded mullite samples reduced, whereas their porosity increased. Addition of appropriate amounts of self-bonded mullite decreased the mean pore size and window size in porous sample, and enhanced the mechanical strength. When self-bonded mullite weight percent reached 50 wt%, the compressive and flexural strength of acicular mullite-reinforced porous self-bonded ceramics was, respectively, kept as 19.9 MPa and 8.8 MPa, with a porosity of 74.7%, a diminutive mean pore size of 159 μm and a window size of 44 μm. Moreover, the linear shrinkage and thermal conductivity of the materials at 50 °C were only 7.4% and 0.23 W m K−1, respectively.