In situ synthesis and microstructure of porous CaAl4O7 monolith and CaAl4O7/CaZrO3 composite

In situ processing and microstructure of calcium dialuminate (CaAl4O7)-based porous material have been investigated. Powder mixtures of CaCO3 and alpha -Al2O3 (1 : 2 in molar ratio, doped with 0.5 mass% LIF), and CaCO3, alpha -Al2O3, and ZrO2 (2 :2 : 1 with 0.5 mass% LiF) were prepared by a high-energy ball-mill process. Reactions of the powder mixtures during heating processes were revealed by high-temperature X-ray diffraction ((HT-XRD), and by thermogravimetry and differential thermal analysis (TG-DTA). Porous CaAl4O7 monolith and its CaAl4O7/50 mol% CaZrO3 composite have been successfully synthesized using reactive pressureless sintering (at 1100-1200 degreesC, for 2 h in air) of powder mixtures. Both porous monolith and composite had homogeneous microstructure and very narrow pore-size distribution with mean pore size of similar to1 mum. These porous materials, which are expected to have good thermal shock resistance, can be applied to high-temperature gas filters and lightweight structural components.