The Preparation And Property Characterization Of Novel Oxide Aerogel Composites

The new hypersonic vehicle thermal protection system urgently needs new thermal insulation materials,which exhibit high-temperature resistance,lightweight,high efficiency heat insulation,good mechanical property and usablity.Aerogel,an outstanding thermal insulation material,exhibits ultralow thermal conductivity,low bulk density,high porosity and high specific surface area.However,the existing SiO2 aerogel has low temperature resistance,which is hardly satisfied the needs in high-temperature insulation.Besides,aerogel matrix possesses poor the mechanical properties due to the fragile nanoporous structure,which is difficult to be applied in practical engineering.In this work,we developed oxide aerogels with higher temperature resistance and high performance fiber porous network with heat resistance above 1400?.And we prepared aerogel/porous fibrous network composites and ultra lightweight aerogel composites.We systematically studied the preparation process,structure and properties of the mullite/zirconia porous fibrous network.The effect of sintering aids,absorbent,molding height on the properties of mullite/zirconia porous fibrous network was analyzed.And the porous fibrous network with low density(?0.29g/cm3),excellent thermal property(?0.060W/(m K))and high mechanical strength(?2.1MPa)was prepared by vacuum squeeze moulding technique.Besides,we prepared mullite/zirconia porous fibrous network impregnated Al2O3-SiO2 and ZrO2-SiO2 aerogels by sol-gel impregnation.nanoporous Al2O3-SiO2 and ZrO2-SiO2 aerogels were prepared by sol-gel method.The sol-gel method was optimized.The density of the as-prepared A12O3-SiO2 aerogel was 0.15g/cm3,and the thermal conductivity is 0.027W/(m·K);The density of the as-prepared ZrO2-SiO2 aerogel was 0.16g/cm3,and the thermal conductivity is 0.0235W/(m·K).We studied the difference of structure and properties of aerogel/porous mullite-zirconia composites before and after impregnation.The results showed that the as-prepared composites synthesized the advantages of aerogels and fibrous porous networks.The thermal conductivity obviously decreased and the mechanical property observably increased after impregnation aerogels.This paper also explored two kinds of new ultra-lightweight aerogel composites.The ABOw/Al2O3-SiO2 aerogel composites and ZrO2f/ZrO2-SiO2 aerogel composites were prepared by using ABO whiskers and ZrO2 fibers as reinforcement.The results indicated that whisker-bridge(fiber-bridge),whisker(fiber)pulling-out,and crack deflection exhibited in the compressed composites after adding ABO whiskers or ZrO2 fibers,which improved the mechanical strength of the composites.The self-reinforcing ZrO2-SiO2 aerogel composites were prepared by multiple impregnation.In this work,we researched the effect of the different impregnation times on the structure and properties of the composites.The results showed that the mechanical properties of the ZrO2-SiO2 aerogel composites obviously increased.