Structural and rheological aspect of mesoporous nanocrystalline TiO2 synthesized

2019-07-27 04:15:20

ratio acid gel HCl H2O

责任者: Phonthammachai, N.;Chairassameewong, T.;Gulari, E.;Jamieson, A.M.;Wongkasemjit, S. 单位: Petroleum and Petrochemical College, Chulalongkorn University, Bangkok 10330, Thailand 来源出处: Microporous and Mesoporous Materials,2003,66(2-3):261-271 摘要: Mesoporous nanocrystalline titanium dioxide was prepared via the sol-gel technique using titanium glycolate as precursor in 1 M HCl solution at various HCl:H2O ratios. XRD analysis indicates the anatase phase forms at calcination temperatures in the range 600-800 °C. From the average grain sizes, we deduce that the nucleation rate dominates the kinetics at lower temperature, and growth rate becomes the controlling factor at higher temperature for materials prepared at HCl:H2O ratios of 0.28 and 0.33. At higher volume ratios, the growth rate appears to be the dominant factor at all temperatures. The highest specific surface area (BET) obtained was 125 m2/g at the HCl:H2O ratio of 0.28. A small decrease of specific surface area was observed from low to high acid ratio and a substantial decrease from lower to higher temperature. The material calcined at 800 °C was found to consist primarily of spherical particles with diameters smaller than 1 μm. Application of the Winter rheological criteria for the gel point indicates that the gelation time increases with increase of the HCl:H2O volume ratio. The fractal dimension of the critical gel cluster decreases with acid ratio, whereas the gel strength increases with acid ratio. Thus, increase of acidity leads to a less dense but stronger network structure. © 2003 Elsevier Inc. All rights reserved. 关键词: Mesoporous materials;Nanostructured materials;Titanium dioxide;Sol-gels;Rheology;Calcination;Hydrochloric acid;Acidity;Gelation;Nucleation;Grain size and shape;X ray diffraction;Gel clusters;Volume ratio