Studies On Thermal Stability Of ZrO₂-SiO₂ Aerogel By Aging And Ion Treatment

ZrO₂-SiO₂ aerogel is called super thermal insulation materials which has great potential in aviation and aerospace field.SiO₂ aerogel has been wildly used and its maximum service temperature is 800 ^oC.ZrO₂ aerogel is a promising material with high surface area and chemical stability,but its thermal stability is not ideal.Zr O₂-SiO₂ aerogel has good advantage in thermal stability and chemical resistance compared to other aerogel.However,the shrinkage at high temperature is still enormous and the specific surface area decrease great,which is far away from its practical application.We try to modify the specific surface area through aging process and Al³⁺treatment?The effect of pH value of aging solution on the microstructure of ZrO₂-SiO₂aerogel was studied.It was found that the microstructure changes with different pH value.When aged in acidic solution,the specific surface area increased and pore volume decreased.When aged in alkaline solution,the specific area decreasd and pore volume increased.The effect of aging temperature on microstructure and thermal stability of ZrO₂-SiO₂ aerogel is discussed in this project.When the aging temperature is increased from 60 ^oC to 210 ^oC,the specific surface area decreased and thermal stability is enhanced,which is independent to aging media.This is because high temperature would enhance the hydrolysis and condensation rate of gel particles and promote the rearrangement of skeleton,which will affect the microstructure of aerogel?.In this project,Al³⁺was introduced to ZrO₂-SiO₂ gel to improve the thermal stability of ZrO₂-SiO₂ aerogel.The effect of ion concentration and temperature was studied?The optimum ion concentration was 0.5mol/L and the optimum temperature was 170 ^oC?This is because Al³⁺replaces the surface hydrogel groups and prevent the migration of zirconia as“pin”,thus improved its thermal stability.