Acta Phys. -Chim. Sin. ›› 2002, Vol. 18 ›› Issue (10): 884-889.doi: 10.3866/PKU.WHXB20021004

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The Coating Process of Nano-scale Hydrous Silica Film on TiO2 Particles by Chemical Deposition in Aqueous Solution

Qin Cao;Wang Ting-Jie;Jin Yong   

  1. Department of Chemical Engineering, Tsinghua University, Beijing 100084
  • Received:2002-01-21 Revised:2002-03-27 Published:2002-10-15
  • Contact: Wang Ting-Jie

Abstract: 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 O 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 electrokinetic’s behavior of the particle surface remarkably.

Key words: Titanium dioxide, Coating, Silica, Chemical deposition, Modification