SiO_2气凝胶的常温法合成研究及表征

以正硅酸乙酯（TEOS）为硅源,采用酸、碱两步催化的溶胶-凝胶法,通过L9（34）四因素三水平正交试验,研究了无水乙醇（ETOH）、草酸（H2C2O4）和氨水（NH3 H2O）之间的摩尔比以及酸碱间隔时间对气凝胶性能的影响,并对所得产品结构和性能进行了比表面（BET）、傅立叶转换、红外线光谱（FTIR）和扫描电镜（SEM）表征,从而首次实现了SiO2气凝胶的常温合成。实验结果表明：原料最佳摩尔比为TEOS∶ETOH∶H2C2O4∶NH3.H2O=1∶7∶3.5∶2.5,酸碱最佳间隔时间为18 h,SiO2气凝胶的平均粒径为6.58 nm,密度为100 kg/m3,孔径分布为2～30 nm,比表面达到938.17 m2/g,室温条件下合成的SiO2气凝胶,不亚于高温合成法的产品性能。

Study on Synthesis and Characterization of Silica Aerogels at Room Temperature

At room temperature,SiO2 alcogels were prepared by tetraethoxysilane（TEOS） via two-step acid-base sol-gel process.The orthogonal experiment was designed by using four factors and three levels to study the influence of molar ratio（ethanol,oxalic acid,ammonia）and the interval time of acid and base on SiO2 alcogels properies.The structure and properties of the silica aerogels were investigated by SEM,FTIR,and BET.The results showed that the optimal mixture ratio of tetraethoxysilane,alcohol,oxalic acid and ammonia was 1：7：3.5：2.5,and the interval time of acid and base was 18 h.It observed that the average diameter of the aerogels was about 6.58 nm.The diameter of the pore sizes was in the range of 2~30 nm,and the density of the aerogels was 100 kg/m3.The specific surface area of the aerogels can be as high as 938.17 m2/g.The properties was not bad than that prepared at the condition of higeh temperature.