Optimization And Performance Study Of High Temperature Stabilization Technology For Aluminum Based Aerogel

Aluminum-based aerogels have extremely broad application prospects due to their excellent thermal conductivity,high temperature resistance,adsorption performance and high catalytic performance.In this paper,aluminum-based aerogel will be discussed as the research object,and the approach of technical optimization treatment and performance were investigated.Technical optimization can include:doping,improved mechanical properties,improved temperature resistance,low-cost technical improvements,and corresponding improvements can be considered as a means of technical optimization.In order to further improve the high temperature stability of alumina aerogel and reduce the thermal conductivity,we introduced an opacifier into the aerogel.In order to obtain a uniformly doped aerogel material,we first confirmed the choice of aluminum source.By comparing aluminum arsenate with aluminum chloride,aluminum chloride and butyl titanate were selected as raw materials to synthesize aluminum.The mechanical properties and high temperature properties were stuided;secondly,in order to reduce the cost,we directly use alumina powder as raw material to prepare aerogel,but the low purity is not conducive to the preparation of aluminum sol.Therefore,we first pretreated the alumina powder,and pretreated the alumina powder by hydrothermal method and CO₂ pressure,and obtained high purity.The boehmite powder with a small particle size and the comparison under different pressures obtained the optimal solution.Finally,using the prepared boehmite powder as raw material,an alumina aerogel material with regular shape and complete shrinkage at high temperature was prepared.The addition of TiO₂ can delay the crystal transformation of alumina aerogel to a certain extent and improve the high temperature stability of alumina aerogel.At the same time,the addition of TiO₂ will also transform the fibrous particles in alumina aerogel into spherical particles increase the specific surface area but reduce the mechanical properties of the material.However,the Young's modulus of aerogel doped with 10%TiO₂ after calcination at 1000°C is higher than that of pure alumina aerogel.We found that the pure Al₂O₃ aerogel,which had fiber-like particles,was stronger than those with minor TiO₂ dopants that presented the mixture of the sphere-like particles and the fiber-like particles.The sphere-likeparticle sturned into the fiber-like particles after being heat-treatedat 1000°C for 2h.Then,the mechanical strengths of the Al₂O₃aerogel with TiO₂ dopants were enhanced.The fiber-like particles enhance strength but reduce SSA.The ceramic fibers reinforced Al₂O₃ aerogel composites were fabricated.The thermal conductivity of the Al₂O₃ aerogel composite with 10 mol%TiO₂ dopants possessed a thermal conductivity of 0.136 W/m?K,better than those of the pure Al₂O₃aerogel composite?0.158W/m·K?and ceramic fiber blankets?0.30 W/m?K?,indicating the potential application as high temperature thermal insulator.At the same time,the effects of different hydrothermal and CO₂ pressures on the particle size and purity of?-Al₂O₃ powder were also studied.Commercial?-Al₂O₃ is fully converted to boehmite at a hydrothermal pressure of 3.5 MPa.The particle sizes decrease as the increase of hydrothermal pressures when the pressure below 3.5MPa.The particle sizes deduce to as small as 50-100 nm for the powders treated at 3.5 MPa.However,the particle sizes increase in the pressure range of 3.5 MPa-4 MPa.Therefore,the optimum hydrothermal pressure for treated powders is 3.5MPa.CO₂ pretreatment has been found to be very efficient in the purification of the powders.Finally,we used the prepared boehmite powder as a raw material for the preparation of alumina aerogel.The results show that the addition of a small amount of aluminum sol prepared by using aluminum chloride as a raw material and the addition of a small amount of propylene oxide can well solve the problem of easy powder formation in the powder dispersion method,and the use of boehmite powder as a raw material can be well The shrinkage of the aerogel material at 1200?was reduced from 60%to 39%.