The Preparation And Property Characterization Of Novel Y₂SiO₅ Aerogel Composites

Hypersonic vehicles comprise a new type of aircraft that combine strong maneuverability and good penetration capability.To ensure the safety of aircraft under the harsh environment,it must have lightweight and efficient high-temperature thermal protection materials.Aerogels have the advantages of ultra-low density,ultra-high porosity,ultra-high specific surface area and low thermal conductivity,making them a potential insulating material for thermal protection system.However,the structure of traditional aerogel has poor high temperature resistance and is prone to damage,which greatly limits its application in practical engineering.In this work,a novel Y₂Si O₅aerogel with good high-temperature stability and thermal insulation property was developed,and the fiber reinforced Y₂Si O₅ aerogel composites and Y₂Si O₅ aerogel impregnated porous fiber ceramic composites were prepared.In this work,a novel Y₂SiO₅ aerogel was prepared by sol-gel method,supercritical drying followed by high-temperature calcination process.The effects of different calcination temperatures on the micromorphology,chemical composition,mechanical properties and thermal properties of Y₂Si O₅ aerogel and the forming mechanism of Y₂Si O₅ aerogel were investigated.The obtained nano-porous Y₂Si O₅ aerogel exhibits low thermal conductivity??0.029W/?m·K??,low density??0.330g/cm³?,good thermal stability,and the operating temperature of aerogel reaches 1300?.In order to enhance the mechanical properties of aerogel,the Zr O₂ fiber reinforced Y₂Si O₅ aerogel composite was prepared by adding the reinforced zirconia fiber into Y₂Si O₅ aerogel during the sol process.The effects of calcination temperature and content of zirconia fiber on the properties of aerogel were investigated.The results show that the addition of zirconia fiber effectively improved the compressive strength of aerogel,and significantly improve its mechanical properties while retaining the thermal properties of aerogel.When the calcination temperature is 1000?and the fiber content is 5wt%,the thermal insulation performance and high-temperature stability of aerogel are greatly improved.In this paper,Y₂Si O₅ aerogel and opacifier were combined with mullite porous fiber ceramics by vacuum impregnation method to prepare mullite porous fiber ceramics/Y₂Si O₅ aerogel/opacifier composite.The obtained composite exhibits good mechanical properties,high temperature stability and good heat insulation ability.The effects of the added content of opacifer on the properties of composite were investigared.It was found that there was an optimal value of the added content of opacifer.In the high-temperature environment,the addition of the opacifer can obviously shield the infrared radiation and improve the thermal insulation ability of the composite.Y₂Si O₅ aerogel and its composites exhibit excellent high temperature performance and have the potential to provide effective protection for hypersonic vehicles in high temperature environments.