Opacifier embedded and fiber reinforced alumina-based aerogel composites for ultra-high temperature thermal insulation

Abstract A novel method was developed to uniformly disperse sub-micron TiO 2 opacifier into fiber reinforcements using agar and silica as binders via freeze drying. TiO 2 opacifier/ fiber/ alumina-based aerogel ternary (TFA) composites with high strength and excellent high-temperature thermal insulation were successfully prepared by sol-gel route, impregnation process and supercritical fluid drying. The microstructure, mechanical and thermal insulation properties of TFA composites were investigated comprehensively. The results show that the mechanical property of TFA composites can be significantly enhanced by mullite fiber felt and the incorporation of SiO 2 binder. The effect of TiO 2 opacifier on the high-temperature thermal conductivity was studied by adjusting the content of TiO 2 from 0 to 15 wt%. The obtained TFA composites exhibit high Young's modulus of up to 3.58 MPa and low high-temperature thermal conductivities of 0.129 W/m·K at 800 °C and 0.168 W/m·K at 1000 °C, respectively. The mechanism of heat transfer in TFA composites at high-temperature was also analyzed.