A novel hollow alumina sphere-based ceramic bonded by in situ mullite whisker framework

In this study, a novel hollow alumina sphere-based ceramic enhanced by in situ mullite whisker framework was recommended. Hollow alumina spheres selected as the main pore-forming agent were bonded together by an active mullite powder at high temperature. To improve the mechanical properties of the hollow alumina sphere-based ceramic, AlF3 powder was added into the active mullite powder to fabricate the mullite whisker framework during the sintering process. The mechanical properties of as-received hollow alumina spheres ceramic can be tailored by the sintering procedure. The results indicated that the sample sintered at 1400 °C exhibited a low bulk density of 1.005 g/cm3 and a low thermal conductivity of 0.656 W/mK. The high aspect ratio of mullite whisker interacting with each other formed a unique framework structure, which enhanced the flexure strength (reaching 5.05 MPa) of the sample.