Influence of spherical porous aggregate content on microstructures and properties of gas-permeable mullite-corundum refractories

In this study, six gas-permeable mullite-corundum refractories with 45-95 wt% spherical porous mullite aggregates were prepared. The influence of the spherical porous aggregate content (SPAC) on the microstructure, gas permeability, and mechanical properties was analysed by XRD, SEM, EDS and image analysis method, etc. It's found that the SPAC affected the pore characteristics and mechanical properties through changing the packing and sintering behaviours of the aggregate and matrix in the refractories. When the SPAC was 45-65 wt %, the refractories had higher strengths as well as two gas-permeable channels in the aggregate and matrix respectively. Whereas, when the SPAC increased to 75-95 wt%, the refractories had lower strength as well as one gas-permeable channel in the matrix. The optimized product contained 65 wt% spherical porous aggregate and combined a high gas permeability of 4.9 x 10(-12) m(2), a high compressive strength of 18.5 MPa, a good thermal shock resistance and well-distributed gas-permeable channels.