Preparation And Properties Of Silica Aerogel Particles

SiO2silica aerogel is a kind of nano lightweigh porous materials with highporosity, high specific surface area, low conductivity. It can be wildly used in thermaladsorption, catalysis, insulation and other application field. Appropriate particle sizeof silica aerogel powder keeps the pore structure and make it easy to disperse, fills,composite, etc. Based on W/O emulsion method, silica sol micro-droplet dispersed inoil phase translates into wet gel particles and then through atmospheric drypreparation translates into silica particles.First with sodium silicate as silicon source, SPAN-80and TWEEN-80assurfactants, sodium silicate, SPAN-80and TWEEN-80will be dispersed in then-heptane. Through atmospheric dry aerogel particles are modified bytrimethylchlorosilane to improve its hydrophobicity. The influence of mechanicalstirring speed, ratio of surface active agent, water-oil ratio has been studied. When themechanical agitation rate exceed600rpm, SiO2aerogel particles cannot formcompletely. With high speed gel process, amorphous aerogel particles were formedfinally; High ratio of surfactant and water-oil ratio will not lead to form morphologyaerogel particles. Using acetone can effectively separate wet gel at the same timewash to remove residual surfactant. Water contact angle reach126.9°. Direct dryingwithout aging and exchange, inverse emulsion can form spherical particles, butnanopores collapsed. When the mechanical stirring speed is600rpm, proportion ofSPAN-80and TWEEN-80is1:4, water-oil ratio is1:10, after separation of acetone,the white silica aerogel particles size is approximately20microns and nearlyspherical.FT-IR, EDS, SEM and BET surface area have been studied to characterize phase,surface area, particle size, morphology and hydrophobic of SiO2. The result showsthat: SiO2aerogel was a kind of amorphous material with density0.2983g/cm3,specific surface area905.1780m2/g, pore size6.9nm. It appears white. SiO2aerogelwas composited by nanometer-grade grain with a loose structure which was homogeneous diameter. FI-IR shows that there was–CH3in surface and wellhydrophobicity. TG-DSC show that it is stable below300℃in air atmosphere, in400~600℃about14%lost.After1000℃it keeps stable.