Preparation And Characterization Of High Temperature Thermal Insulation Aerogel Composites

Advanced thermal insulation composite materials are the key materials for thermal protection of hot end components consisted of aerospace and aviation.Aerogel has become one of the best choices for thermal insulation materials due to its excellent characteristics including of low density,low thermal conductivity,and high porosity.Pure aerogels have poor mechanical properties and can not be directly used in practical engineering.Fiber reinforced aerogels are generally used to form composite materials.In addition,the large-scale preparation and mass production technology of aerogel composites based on supercritical technology have become the main factors limiting their wide application.In this paper,fiber reinforced Al₂O₃-SiO₂ aerogel composites were prepared by atmospheric drying technology,and silica aerogel insulation composites were prepared by room temperature casting process.In order to enable materials to be used in ultra-high temperature environment,Y₂SiO₅ aerogel insulation composites with better temperature resistance were prepared.The main contents of this paper are as follows:(1)Fiber reinforced Al₂O₃-SiO₂aerogel composites were prepared by sol-gel,vacuum infiltration and atmospheric drying technology.The effect of TEOS concentration and time on the microstructure,mechanical properties,thermal insulation and hydrophobicity of aerogel composites was investigated.Finally,a fiber reinforced Al₂O₃-SiO₂ aerogel composite with low density(0.25g/cm³),low thermal conductivity(0.037W/(m·K))and high hydrophobic angle(143.6?)was prepared.The strength of aerogel composites at 60%strain is 2.02MPa.At the same time,it has good heat insulation performance at high temperature.(2)Silica aerogel composites were prepared by casting silica gel aerogel powder,chopped silica fiber and Si C shading agent.Different fiber/silica aerogel powder and different deionized water were prepared.The effects of SiO₂ gas coagulant powder and different sunscreens on the density,strength,thermal conductivity and drying shrinkage of SiO₂ aerogel composites at room temperature were studied.The effect of light screening agent on the thermal insulation properties of aerogel composites was analyzed.The final SiO₂ aerogel composite has a density of 0.501g/cm³ and a thermal conductivity of 0.044W/(m·K))at room temperature and a compressive strength of0.76MPa.The results show that the aerogel composites still have good thermal insulation at 1200?.(3)Y₂SiO₅ aerogel composite materials with Y₂SiO₅ aerogel powder,mullite fiber as reinforcing phase and Ti O₂ as shielding agent were prepared by casting process,which is expected to be applied in the field of ultra high temperature insulation.The influence of different fiber content on the comprehensive properties of materials at room temperature was explored.The Y₂SiO₅ aerogel composite material is rich in nanoporous structure,which greatly improves its thermal insulation performance.By comparing the effects of different Ti O₂ content on the thermal insulation performance of the composite,it is found that the composite with 10wt%Ti O₂ content has the best thermal insulation effect.The addition of shading agent reduces the radiation heat transfer of the material in high temperature environment and improves the high temperature heat insulation performance.The Y₂SiO₅ aerogel composite material is still intact after testing 20min at1400?,providing data support for its reliable use in ultra-high temperature environment.