液相沉积法制备TiO_2颗粒表面包覆SiO_2纳米膜

The Coating Process of Nano-scale Hydrous Silica Film on TiO_2 Particles by Chemical Deposition in Aqueous Solution

研究了用液相沉积法在TiO2颗粒表面包覆SiO2纳米膜的过程.通过透射电镜（TEM）和酸溶实验分析,证实本实验在TiO2颗粒表面包覆了一层连续、致密的SiO2纳米膜.(?)-电位分析表明,颗粒表面只需少量包覆就可以显著改变颗粒表面的电动力学行为.采用X射线荧光光谱分析仪（XRF）测定SiO2包覆量随包覆过程的变化.通过X射线光电子能谱（XPS）分析,获得Ti2p、Si2p及Ols电子结合能及其相对强度随包覆过程的变化规律,揭示硅酸分子在TiO2颗粒表面的包覆过程.分析表明,初期形成的活性硅酸分子与TiO2颗粒表面的羟基反应形成Ti-O-Si键,后期形成的硅酸分子与已键合在表面的硅酸发生缩合反应,形成连续致密的硅膜,膜层在陈化过程中继续缓慢生长.

The coating process of nano-scale hydrous silica film on TiO2 pigmentary particles by chemical deposition in aqueous solution has been investigated. Through the analysis of TEM images and dissolving the samples with hot sulfuric acid, it is proved that a uniform dense film of hydrous silica on TiO2 pigmentary particles is produced. Samples were taken in the coating process and analyzed by X-ray photoelectron spectroscopy (XPS), X-ray fluorescence (XRF), zeta-potential analyzer and transmission electron microscope (TEM). The silica composition and structure of the film on the coated particles in the coating process were measured and analyzed. It is inferred that polymeric silicate ions first hydrolyze into Si (OH)(4), the later then reacts with OH- groups on the surface of TiO2 particles. The silica acids subsequently produced condense on the surface of the core particles, forming a nano-scale film of polymerized silica. According to the chemical shift of binding energy of Ti 2p, Si 2p and 0 1s on the coated particles, the Ti - O - Si bond formation is inferred at the interface of the film and the surface of TiO2 particles. The thickness of the film increases with coating time and aging time. Zeta potential measurement shows that a very thin film coating of 0.5% mass fraction can change the electrokinectic behavior of the particle surface remarkably.