The Controllable Preparation And Performance Study Of Low Density Silica Aerogel

SiO2 aerogels,as a kind of controllable nanoporous materials with low density,are used as target materials and supporting layer materials in ICF experiments.In this parper,we use ethylsilicate(TEOS)as silicon source,ethanol(EtOH)as solvent and combine with sol-gel technology to prepare centimetre-sized SiO2 aerogels sphere through controlling density and size of SiO2 aerogels.Besides,the microstructure,shrinkage rate,thermal stability,structure and mechanical properties of aerogels were characterized.The optimum preparation conditions were gained as follows n(TEOS):n(EtOH):n(H20):n(HCl):n(NH3·H20)=1:10:4:2×10-3:4.5×10-3.Under this condition,sphere silica aerogel with different diameter were prepared(A:35.2mm;B:49.5mm)and had low density.It was found that the more larger diameter of sample,the more serious shrinkage during drying.Every property of sample with 35.2 diameter is better than 49.5 diameter.Effect of gel temperature on density and shrinkage rate was studied.It was found that with the increase of gel temperature,the shrinkage rate of sphere silica aerogel gradually increased.Therefore,low temperature help to prepare sphere silica aerogel with low density and well sphericity.When the gel temperature at-5℃,the specific surface area was 1004.38 m2/g,the apparent density was 0.104 g/cm3,and the shrinkage rate was 16.2%,respectively.The result from SEM and TEM indicates that the sphere silica aerogel with typical nanometer porous network structure was prepared under this condition.We prepare low density silica aerogel through adopting expanding agent and then roasting with high temperature.Effect of different expanding agent on the structure and properties of silica aeroge was studied.The result indicate that six methyl tetramine is most appropriate expanding agent in this experiment,the best mole ratio of six methyl tetramine and ethylsilicate was 0.15.Compared the sample without expanding agent,the samples with expanding agent have lower density,while surface area and pore size were increased.When expanding agent is six methyl tetramine,the pore size mainly distributed from 15nm to 55nm,the average pore size was 35.4nm.However,expanding agent is not suitable for the preparation of large body aerogel samples limited by high temperature roasting.In this paper,we lay a solid foundation for making low density and large-sized silica aeroge,at the same time,it can provide experimental reference for studying new dry process and sol-gel technology.