Mullite ceramic foams with controlled pore structures and low thermal conductivity prepared by SLS using core-shell structured polyamide12/FAHSs composites

Mullite ceramic foams with high structural complexity, controlled pore structures and low thermal conductivity were manufactured by selective laser sintering (SLS) using core-shell structured polyamide12 (PA12)/fly ash hollow spheres (FAHSs) composites, which were prepared by thermally induced phase separation that exhibit a good flowability and formability for SLS. Crack-free honeycomb green body with intersecting pore channels were fabricated under the optimized processing parameters. Total porosity and closed/open pore size distribution of mullite ceramic foams can be well adjusted by the sintering temperature and PA12 content. The thermal conductivity increased gradually due to increased porosity as decreasing sintering temperature, while decreased probably due to phase change with an increasing PA12 content. The relatively low thermal conductivity of 0.08 W/(m▪K) was obtained when added 30 wt% PA12 content, with a high porosity of 85.0 ± 0.2% and compressive strength of 2.61 ± 0.2 MPa. The understanding pore structure characteristics will help design the high-porosity mullite ceramic foams with controlled pore structures and low thermal conductivity.