溶胶凝胶制备TiO2

1、Sol-gel Method in Preparation of Titania Nano-powder2 photocatalyticelectrochromichigh-dielectric constant sensing propertiesphotocatalyticcapacitorssmart window photovoltaic2applicationsgas sensor smart window gas sensing devicesair cleaner Photocatalytic Applicationsthe most efficient and environm

2、entally benign photocatalystTiO2 nanocrystalline electrodesthe dye-sensitized nanocrystalline solar cellPhotocatalytic Water Splittingthe photocatalytic reaction cell for splitting waterLattice structure of TiO2O2-ions are in CCPCrystal system: tetragonalUnit cell dimensions a = 3.7845 c = 9.5143 O2

3、-ions are in HCPCrystal system: tetragonalUnit cell dimensions: a=4.5937 ; c=2.9587 Lattice structure of TiO2Anatase Rutile Certain concentration TiCl4 solutionPutting into reactorprecipitateAging at 65-120TiO2 powdercentrifugation , washing, drying small size big specific surface finely dispersed h

4、igh pressure and temperature complex technology equipment high costThis method is easy to operate, the preparation of TiO2 powder has the following advantages:1.Uniform size2.Large surface area3.Good dispersion4.High-purity5.High catalytic activity 3. Experimental Sol-gel synthesis of nano-TiO2 powd

5、er used in raw materials, generally as Ti (OR) 4 (R =- C2H5,-C3H7,-C4H9). The prepared process: First of all, the homogeneous solution was obtained by dissolving titanium salt in solvent to ensure that the titanium alkoxide hydrolysis is at the molecular level; Then, the hydrolysis and condensation

6、reactions started and the products aggregate to particles( around 1nm ), the sol was formed; After aging, the three-dimensional network of sol-gel was formed ; Drying the wet gel to remove residual moisture ,organic groups and organic solvents, to be dry gel; Calcining, to remove the chemical adsorp

7、tion and-alkyl groups, as well as the physical absorption of water and organic solvents, then, nano-TiO2 powder was obtained.4. Results and discussion 4.1. Calcination temperatureThe phase structure of the powder calcined at temperatures below 600is mainly of anatase type.The phase transformation fr

8、om anatase to rutile occurred at about600 and completed at about 800 The grain size increaseswith the increasing calcination temperature.It grows slowly at low calcination temperatures and then becomes very fast at high calcination temperatures.(A) 350 (B) 500 (C) 600 TEM of the nano-TiO2 powders4.2

9、. Calcination time(a) 350 (b)500 (c) 1000 At low calcination Temperatures the calcination time has little influence upon the particle size.At relatively high temperatures the calcination time seems to have greater effect upon the grain size.4.3. pH valueIt is found that when the pH value is below 7

10、the valueof grain size is almost constant, which means acid solutioncould restrain grain growth. When the pH value is beyond 7, the line goes up very quickly which indicates that a total alkali environment would enhance grain growth.5. Conclusion Nano-TiO2 powders have been prepared by solgel method

11、 successfully. By controlling the conditions properly,nano-TiO2 powders with the grain size less than 6 nm could be obtained. Among the elements which may have effect upon the grain size and microstructure of nano-TiO2 powders, the calcination temperature and pH value were found to be more effective

12、 compared with the calcination time.The grain size tends to increase with increasing temperature and the increase in pH value.References1. Y. Li, T.J. White, S.H. Lim.Low-temperature synthesis and microstructural control of titania nano-particles J. Journal of Solid State Chemistry 177 (2004) 137213

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14、gineering B 47 (1997) 33-40.4. Xiaoheng Liu, Juan Yang, Ling Wang et al. An improvement on sol-gel method for preparing ultrafine and crystallized titania powder J. Materials Science and Engineering A289 (2000) 241245.5. Prashant V. Kamat. Meeting the Clean Energy Demand: Nanostructure Architectures

15、 for Solar Energy Conversion J. J. Phys. Chem. C 111 (2007) 2834-2860.6. Hui Wang, Pingan Liu, Xiaosu Cheng et al. Effect of surfactant s on synthesis of TiO2 nano-particles by homogeneous precipitation method J. Powder Technology 188(2008) 52-54References7. Gianluca Li Puma, Awang Bono, Duduku Kris

16、hnaiah et al. Prearation of titanium dioxide photocatalyst loaded onto activated carbon support using chemical vapor deposition: A review paper J. Journal of Hazardous Materials 157(2008)209-2198. Chung-Hsin Lu, Wei-hong Wu,Rohidas B.Kale Microemulsion-mediated hydrothermal synthesis of photocatalytic TiO2 powders J. Journal of Hazardous Materials 154(2008)649-6549. Junjun Li, Sang Il Seok, Baojin Chu et al. Nanocomposites of ferroelectric polymers with TiO