Fabrication and characterization of anorthite foam ceramics having low thermal conductivity

Porous anorthite ceramics with low thermal conductivity were successfully prepared using fly ash and gypsum by direct foaming and slip casting method. Effects of dispersant and foaming process on the performance of the porous materials were investigated. The results show adiabatic anorthite ceramics with the highest open porosity (94%) and the lowest thermal conductivity (0.042 W/m K) can be fabricated by adding 10% content of gypsum, 0.8% content of SHMP and using two-step foaming process. High porosity and small pore size are the main factors resulting in the low thermal conductivity. Meanwhile, the thermal conductivity can be predicted with the proportionality coefficient χ obtained by fitting the experimental data based on previous Gong's model. The a and b values in the expression of the proportionality coefficient χ were further discussed. The results show that they are affected by the pore size and distribution, and then the thermal conductivity will change accordingly.