Synthesis of high surface area nanocrystalline anatase-TiO_2 powders derived from particulate sol-gel route by tailoring processing parameters

摘要

Stabilised titania sols were prepared using an additive free particulate sol-gel route,via electrostatic stabilisation mechanism,with various processing parameters.Peptisation temperature,50 deg C and 70 deg C,and TiO_2 concentration,0.1,0.2 and 0.4 molar,were chosen as processing parameters during sol preparation.Results from TiO_2 particle size and zeta potential of sols revealed that the smallest titania hydrodynamic diameter(13 nm)and the highest zeta potential(47.7 rnV)were obtained for the sol produced at the lower peptisation temperature of 50 deg C and lower TiO_2 concentration of 0.1 M.On the other hand,between the sols prepared at 70 deg C,smaller titania particles(20 nm)and higher zeta potential(46.3 mV)were achieved with increasing TiO_2 concentration up to 0.4 M.X-ray diffraction(XRD)and Brunauer-Emmett-Teller(BET)results of produced powders annealed at different temperatures showed that the 300 deg C annealed powder made from 0.1 M sol prepared at 50 deg C was a mixture of anatase and brookite,corresponding to a major phase of anatase(approx 95% estimated),with the smallest average crystallite size of 1.3 nm and the highest specific surface area(SSA)of 193 m~2/g.Furthermore,increasing TiO_2 concentration up to 0.4 molar for the sols prepared at 70 deg C resulted in decreasing the average crystallite size(1.9 nm at 300 deg C)and increasing SSA(116 m~2/g at 300 deg C)of the powders annealed at different temperatures.Anatase-to-rutile phase transformation temperature was increased with decreasing peptisation temperature down to 50 deg C,whereas TiO_2 concentration had no effect on this transition.Anatase percentage increased with decreasing both peptisation temperature and TiO_2 concentration.Such prepared powders can be used in many applications in areas from photo catalysts to gas sensors.