常压制备疏水型二氧化硅气凝胶及透光率分析

采用溶胶-凝胶法，通过常压干燥制备了疏水型二氧化硅气凝胶。研究了pH、水解时间等因素对二氧化硅气凝胶透光率的影响。以正硅酸乙酯为原料，通过酸（草酸）-碱（氨水）两步催化，采用溶胶-凝胶法常压干燥制备了疏水型介孔二氧化硅气凝胶。正硅酸四乙酯、乙醇、草酸、氨水物质的量比为1∶4∶5∶0.2，草酸和氨水的浓度分别为0.008、0.05 mol/L时，采用二甲基二氯硅烷为改性剂常压制备了二氧化硅气凝胶。透射电镜、扫描电镜测试表明：二氧化硅气凝胶具有纳米介孔结构。接触角测定表明：二氧化硅气凝胶与水的接触角为148°，表现出疏水性。

Analysis on transmittance of hydrophobic silica aerogels prepared at ambient pressure

Silica aerogels were prepared by sol-gel method with ambient pressure drying.The influences of pH and hydrolysis time on transmittance of silica aerogels were investigated.Through two-stage catalysis of acid（oxalic acid）-alkali（aqueous ammonia），hydrophobic mesoporous silica was firstly prepared by sol-gel method under ambient pressure drying with tetraethyl orthosilicate as raw material.Silica aerogels were finally prepared by keeping the amount-of-substance ratio of tetraethyl orthosilicate，ethanol，oxalic acid，and aqueous ammonia at 1∶4∶5∶0.2，concentrations of oxalic acid and aqueous ammonia fixed at 0.008 mol/L and 0.05 mol/L and with dichlorodimethylsilane（DMDCS） as the surface modification agent.The silica aerogels were analyzed by transmission electron microscopy and scanning electron microscopy.Results showed that silica aerogels had an amorphous nano-porous structure and the pore diameter was in the mesoporous range.Contact angle test showed that the contact angle was 148°.The results proved that the aerogels were hydrophobic.