Synthesis of monolithic alumina-silica hollow microspheres and their heat-shielding performance for adiabatic materials

Al2O3 ceramic foams-based composites were firstly synthesized to be used as the thermal insulation material which has excellent mechanical properties of the substrate material and better thermal properties of hollow microspheres. In this research, by doping TEOS, the monolithic hollow microspheres were prepared via a novel and effective synthesis route using propylene oxide as the gelation initiator to induce the gelation of aluminum chloride hexahydrate solution. The influence of TEOS on the morphology and high-temperature stability of the monolithic hollow microspheres was clarified in detail. Based on the optimized additive amount of TEOS, Al2O3 ceramic foams were introduced as the substrate material of alumina-silica hollow microspheres to fabricate the final Al2O3 ceramic foams-based composites. Benefited from this special structure, the Al2O3 ceramic foams-based composites displayed excellent mechanical properties and thermal properties. The samples changed less in appearance and did not show significant shrinkage after heat-treatment at 1200 °C. The density, bending strength and thermal conductivity of the Al2O3 ceramic foams-based composite were 0.32 g/cm3, 1.8 MPa and 0.12 W/m K, respectively.