小角x射线散射法研究氧化硅溶胶的制备环境依赖性

根据氧化硅溶胶的不同制备环境(如老化时间、酸碱性和溶剂种类等)，利用小角x射线散射( SAXS)技术，辅以动态光散射等方法，对氧化硅溶胶的界面性质和微结构进行比较性分析.发 现在碱或酸催化下氧化硅溶胶的SAXS结果表现出极大差异，用低分子有机酸作催化剂不仅可 以得到聚硅氧烷大分子，而且有机酸和正硅酸乙酯的酸解反应使溶胶形成内部结构很复杂的 颗粒悬浮体系.溶剂极性越大，则颗粒形貌越不规则.甲酸酸解得到的溶胶颗粒的硅氧四面体 形成程度是所有体系中最差的.发现了在水为溶剂时溶胶SAXS结果中不同寻常的正、负偏离 共存情况，并给出了相应的解释. 关键词： 小角x射线散射 氧化硅 溶胶_凝胶

Dependence of silica sol properties on synthesis situation studied by SAXS

The properties of silica sol, such as the interface characteristics and microstr ucture, were comparatively studied by small angle x-ray scattering (SAXS) assis ted by dynamic light scattering. Four synthesis routes were adopted to relate th e properties of silica sol with the synthesis situation. Very big difference of SAXS results was found between the base-catalyzed and the acid-catalyzed silic a sols with ethanol used as solvent. Under the acid-catalysis of low molecule-w eight organic acid, not only were polysiloxane macromolecules obtained, particle suspension of silica was also produced with complicated inner structures of pa rticles. With ethanol or water as solvent, it was found that the silica particl e would become more irregular in morphology with more polarity of solvent. The formation of Si-O tetrahedron was more difficult in the acidolysis of tetraetho xysilane by formic acid than in the other hydrolysis routes. An interesting co- existing of positive deviation and negative deviation from Porod’s law was foun d in the silica sol with water solvent, and a detailed explanation has been giv en.Many nano-scaled structural difference among these different synthesis situa tions were revealed, which was difficult to be recognized by the experimental m ethods other than SAXS.