摘要
采用溶胶 凝胶方法在碱性条件下制备了SiO2 和ZrO2 溶胶 ,应用同步辐射小角X射线散射 (SAXS)法研究了溶胶的结构 .结果表明 ,溶胶粒子是多分散的 ,其生长、聚集受RLCA和Eden模型的共同控制 ,是一种非线性的动力学过程 ,所形成的聚集体呈随机、分岔、稠密不同的结构 ,具有质量分形的特征 .同时还发现所研究溶胶的散射曲线均不遵守Porod定理 ,形成负偏离或正偏离 ,这说明在溶胶粒子与分散介质间有过渡相存在 .对上述偏离进行了定性和定量的分析 ,提出了正偏离时的定量解析方法 ,从而得到了胶体系统中有关过渡层 (界面层 )结构的重要信息 .
SiO\-2 and ZrO\-2 sols were prepared by base\|catalyzed hydrolysis and condensation of alkoxides in alcohol. PEG and diglycol were used as organic modifiers of SiO\-2 and ZrO\-2 sols respectively. The structure evolution during the sol\|gel process was investigated by small angle X\|ray scattering (SAXS) with synchrotron radiation as X\|ray source. SAXS results show that the silica and zirconic sols are polydispersed, i.e., with proper size distribution. SAXS results also show that silica and zirconic aggregates are mass fractals, fractal dimensions span the regime 0\^23—2\^56 corresponding to very sparse and more branched and compact structures. The formation of a mass fractal is a kind of nonlinear process. Both RLCA and Eden models dominate the kinetic growth under base\|catalyzed condition. It is also shown that the SAXS profiles do not agree with Porod's law and have negative or positive slopes, suggesting that the dispersive interfacial layer exists between sol particle and dispersing agent. The thickness of the interfacial layer falls between approximately 1\^00 and 22\^00?nm for samples prepared under various conditions. Both agreement with and deviation from Porod's law in SAXS are summarized, especially proposing the analysis method upon positive deviation with slit\|smeared SAXS data.
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2000年第4期775-780,共6页
Acta Physica Sinica
