Preparation Of ZrO₂ Aerogels And Composites

ZrO₂ aerogel has both characteristics of zirconia and aerogel, it is widely applied in catalyst area. At the same time, due to zirconia has a high melting point and low thermal conductivity, zirconia aerogel has attractive development prospects in high temperature insulation materials. In this paper, we prepared Zr O2 aerogel by dropping propylene oxide. We prepared ZrO₂-SiO₂ aerogel which had better heat stability by adding silicon in order to improve the heat stability of products. At the same time, we combined the fiber mat with ZrO₂ aerogel to prepare the fiber reinforced aerogel composite material, which had a low thermal conductivity at different temperatures. That indicated the products we prepared had good thermal insulation properties.In this paper, we used the yttrium nitrate as a stabilizer, formamide as the drying control additive and propylene oxide as a gelation promoter to prepare Zr O2 aerogels. The effects of the concentration of zirconyl nitrate, alcohol-water ratio, the addition of propylene oxide and formamide, heat treatment conditions were investigated on the structure and properties of ZrO₂ aerogels. The ZrO₂ aerogel was characterized by X-ray diffraction（XRD） analysis, SEM analysis and the specific surface area and pore size distribution test in order to get the best preparation technology parameters. The optimal processing paramters were the concentration of zirconyl nitrate of 0.3mol/L, alcohol to water ratio of 2:1, and mole ratio of Zr:PO:FA of1:6:1. The pure ZrO₂ aerogel we prepared had good pore structure and high specific surface area, but their thermal stability was poor. Therefore, we need to change the preparation process to improve the thermal stability of aerogels.Based on the optimal processing of pure ZrO₂ aerogel, we used TEOS as the silicon source to prepare ZrO₂-Si O2 aerogel by dropping propylene oxide. In order to get the best preparation technology parameters, Zr O2-SiO₂ aerogel was also characterized by SEM, XRD,BET, FTIR, TG-DTA. When the molar ratio of zirconium and silicon was 1:1, the composite aerogel possessed the highest specific surface area of 551.7m2/g. And the specific surface area of composite aerogel was 239.3m2/g at 1000℃. Compared to the pure ZrO₂ aerogels, the ZrO₂-SiO₂ aerogel possess better heat stability.To improve the disadvantage of brittleness of zirconium aerogel, we prepared fiberreinforced aerogel composite material. Compared with fiber reinforced aerogel composite material with pure ZrO₂ aerogel as the matrix, composite material with ZrO₂-SiO₂ aerogel as the matrix had lower thermal conductivity, which indicated that they possessed better thermal insulation properties.