Study Of Rapid Preparation Of Silica Aerogels By Ambient Pressure Drying And Titania Aerogels Droped With Fe³⁺

The paper has investigated that excellent silica aerogels was prepared with TEOS, Ethanol, H2O, HC1and NH4OH as raw material by sol-gel method and ambient pressure drying according to the desired performance in a short period. The process of mixture surface mo-dification, solvent mixture exchange and their mechanism have been systematically researched. The surface group, thermal stability, morphology and microstructure of silica aerogels have been investigated by nitrogen adsorption/desorption tests (BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential-thermal gravimetric analysis (DSC-TG), infrared spectroscopy (FT-IR) and contact angle measurements.Granular and powdery silica aerogels were prepared by filling N-hexane into sol to improve silica sol’s double-layer electric struture and heighten the rate of aging. This paper redused the cycle time of aging from usual1day to8hours, lowered the usage mount of furface modifier (TMCS) from molar ratio of TEOS:N-hexane=1:0.6to1:0.3, redused the cycle time of the whole experimental period from3-7day to30hours. When filler content of N-hexane was0.2(molar ratio of TEOS:N-hexane=1:0.2), prepared silica aerogels have moderate gel time(40min), lower apparent density (0.108g/cm3), higher surface aera(972.5m2/g), higher pore volume(2.9cm3/g), uniformer pore size distribution, better hydrophobicity(contact angel0=150.5°), higher grope heat resistant temperature(400℃) and better light transmission property.silica aerogels with better light transmission and into-block property were prepared by using DMA as DCCA(molar ratio of TEOS:DMA=1:0.4) and aging under the condition of50℃to reduse the cycle time of aging(from18-24hours to6houes) and linear shrinkage. After surface modification of wet gels, gels were washed with EtOH three times to replace the H2O in gels and avoid additional pressure of H2O and low surface tension solvent(N-hexane and toluene).silica aerogels with better light transmission and into-block property were prepared within3days with lower apparent density (0.087g/cm3), higher surface aera (988.3m2/g), higher pore volume(3.0cm3/g), uniformer pore size distribution, better hydrophobicity(contact angel0=151.1°),higher grope heat resistant temperature(400℃).Titania aerogels droped with iron were prepared by sol-gel method and subsequent process with ambient pressure drying and in the sol process Fe(NO3)3was added to make sure that Fe3+was uniformly dispersed in titania aerogels. When filler content of Fe(NO3)3was0.05(molar ratio of Fe3+:TTIP=0.05), prepared titania aerogels droped with iron is in amorphous state with bulk densities of0.24g/cm3, the specific surface area of529.17m2·g-1and average pore size of20.10nm. After calcined at850℃in air anatase is the main crystalling phase and the surface area is136.22m2·g-1. A test of photo-catalytic degradation in methyl orange solution finds that TiO2aerogel doped with0.05%of Fe3+(molar ratio) possesses a better catalytic efficiency compared with pure TiO2aerogel.