摘要
通过加入稳定剂、催化剂 ,由锡酸四丁酯Sn(OBun) 4制备出稳定的SnO2 溶胶液 ,并有效地控制其Sol-Gel过程 ,同时测量Sol-Gel过程中SnO2 溶胶液pH ,粘度 η随时间动态变化关系及凝胶时间Tg,对凝胶液稳定性、acacH稳定作用机理、催化机理、SnO2 胶粒分形结构进行了研究分析 .结果表明 :acacH与Sn(OBun) 4形成双螯合中间体 ,降低锡酯单体水解活性而使胶粒稳定生长 ,导致胶粒的准线性无机聚合物特性 ;催化剂阴离子通过对acac -螯环的部分取代反应 ,旋即水解、缩合 ,生产催化作用 .阴离子尺寸大小支配催化作用强弱 ,溶胶液pH平稳值及Sol-Gel过程速度 .流变学实验数据分析发现 :溶胶液特性粘度 [η]很好地符合近似线性模型 ,改性单体官能度 f≈ 2 .0 ,SnO2 胶粒为准线性分子链 ,分型维度D≈ 1.80 ,分形结构介于自回避无规链 (SAW )和无规高斯链之间 .
By incorporating stability agent, catalysts into sol solutions, stable SnO2 sol derived by precurosor tetrabutylorthostannate Sn(OBun)4 were prepared. At the same time, experimental measurements including pH, variations of shear viscosity with time in sol-gel process and gelling time Tg for each sol solution were conducted. Based on the experimental observations sol solution stability, stability mechanism, catalysis mechanisms, fractal structures of sol particles are suggested. It is shown that acacH reacts with Sn(OBun)4 by substituting two-OBun groups leading to the formation of bi-chelated intermediate Sn(OBun)2(acac)2, which reduces hydrolysis activity of Sn(OBun)4 monomer, makes sol grains growth stable, and regulates quasi chain-like structures of SnO2 sol grains. Whereas, catalysis action takes place as catalyst anions make nucleophile attack-acac chelate ring, causing immediately hydrolysis and condensation. Catalyst anion sizes significantly influence catalysis action, stationary pH and sol-gel process pace. It is found from rheological measurements of SnO2 sol systems that the relationship between the intrinsic viscosity η and the sol solution concentration of SnO2 sol particles is in good agreement with Quasi-linear model of macromolecules. The functionality of modified monomer f is approximately equal to 2.0, and SnO2 sol particles showed themselves as quasi-linear chains. On the other hand, its fractal dimension D=1.80, and fractal structure stands between self-avoiding walk (SAW) chain and random Gussian chain.
出处
《硅酸盐学报》
EI
CAS
CSCD
北大核心
2001年第2期157-162,共6页
Journal of The Chinese Ceramic Society
基金
国家科委九五重点科技攻关项目! (96 -119-0 4-0 1-0 5 )
