二甲基硅油/硅溶胶共前驱体法制备二氧化硅气凝胶微球

由于二氧化硅气凝胶具有低密度、高孔隙率、高比表面积、低导热系数等特点，引起了人们的广泛关注。但是，其较差的机械性能和较高的制备成本一直限制二氧化硅气凝胶的应用和推广。采用带有活性端基的二甲基硅油和硅溶胶制备共前驱体溶液，以微乳液法和滴定法分别制备了不同尺寸的二氧化硅气凝胶微球，并探究了甲基含量对其性能的影响。实验结果表明，相对于滴定法，微乳液法制备的气凝胶粒径分布范围较宽，在硅溶胶与硅油体积比相同时，两种方法所制备的气凝胶微球具有相近的比表面积、堆积密度及导热系数；滴定法制备的气凝胶随着甲基含量减少，气凝胶微球的比表面积减小，堆积密度增大，接触角减小，导热系数增大，机械强度增大。

Preparation of SiO2 aerogel microspheres by a dimethyl silicone oil/silica sol co-precursor method

Silica aerogels have attracted wide attention due to their low density, high porosity, high specific surface area and low thermal conductivity arising from their special structure, but their poor mechanical properties and the high cost of preparation have limited their practical application. Based on the previous work, a co-precursor solution was prepared using dimethyl silicone oil with reactive end groups and silica sol. Silica aerogel microspheres with different sizes were prepared by microemulsion and trickle titration methods. The effect of varying the content of methyl substituents on the properties of the silica aerogel microspheres was explored. Compared with the aerogel prepared by trickle titration method, the aerogel prepared by microemulsion method possessed broader particle size distribution range. With the same volume ratio of silica sol to silicone oil, the aerogel microspheres prepared by the two methods showed similar specific surface area, bulk density and thermal conductivity. The decreasing the content of methyl substituents resulted in a decrease in the specific surface area of the aerogel microspheres, whilst the bulk density increased, the contact angle decreased, the thermal conductivity increased, and the mechanical strength increased.