Titania microspheres

Reverse microemulsion, a rather soft method, has been used to prepare hollow titania microspheres [51] TiCLi was dissolved in HCl-acidified water and added to a solution of TX-lOO in cycloheptane after addition of ammonia and stirring... 

Li, H., Ha, C-S., and Kim, I. (2008) Facile fribrication of hollow silica and titania microspheres using plasma-treated polystyrene spheres as sacrificial templates. Langmuir, 24,10552-10556. 

Subramania, G., Constanf K., Biswas, R. et al.. Visible frequency thin film photonic crystals from colloidal systems of nanocrystalline titania and polystyrene microspheres, J.Am. Ceram. Soc., 85, 1383, 2002. 

Song X, Zhao Y, Wang H, Du Q (2009) Fabrication of polymer microspheres using titania as a photocatalyst and Picketing stabilizer. Langmuir 25(8) 4443-4449... 

As one example, the force-versus-distance between a sUica particle and a titania flat is shovra in Fig. 7. Like in many publications, the force is scaled by division through the radius of the silica microsphere. According to Eq. (7), the scaled force, F/R, is equal to 2tiVa. Force curves were recorded at different pH values ranging from pH 8.8 for the top curve to pH 3.0 for the bottom curve. The surface charges of both materials are mainly determined by the pH. Sihca has... 

Fig. 7 Force between a silica (Si02) microsphere of 2.5-pm radius and a titania (Ti02) crystal versus distance. The force is scaled by the radius of the sphere. The curves were recorded at pH values of 8.8, 7.2, 5.3, 5.3, and 3.0 from top to bottom with 1 mM KNO3 background electrolyte. (The figure is reproduced with kind permission from C. ]. Drummond [73].)...

In polymerization-induced colloidal aggregation (PICA) processes, a reactive monomer, generally urea formaldehyde, is mixed with a stable, submicrometer diameter metal oxide sol and undergoes an acid-catalyzed polymerization that results in porous, uniformly sized polymer-oxide composite microspheres [24,25], PICA has been applied to a variety of metal oxide systems, primarily silica, but also alumina, titania, zirconia, ferric oxide, and antimony pentoxide [24,25]. The process is affected strongly by solution acidity [26]. At lower pH, polymerization is more rapid and a more porous but mechanically weaker particle is formed. 

The electrolyte induced rapid coagulation of polydisperse mixtures of polystyrene microspheres, titania and kaolinite was studied by Photon Correlation Spectroscopy (PCS). A method has been developed that enables the rate constant to be calculated without precise knowledge of the particle size distribution (7). For Brownian Diffusion-controlled Aggregation ... 

Work in this area involves applying polysiloxane coatings on inorganic substrates as has been done on silica, Al Og/GaAs, and the channels in microfluidic devices. Variations include sol-gel blends of PDMS and titania and titania coatings on PDMS. ° PDMS cores have also been coated with poly(N-isopropylacrylamide) shells to give thermoresponsive microspheres. ... 

Padovan et al. [38, 39] developed a method based on the impregnation of dried microspherical porous silica up to incipient wetness with an aqueous solution obtained by hydrolyzing the titania source (tetraisopropylorthotitanate) with TPAOH, followed by calcination at 448 K in a sealed glass tube. Pure and well crystallized TS-1 is obtained after 10 hours, while extra-framework titanium species start to appear after longer crystallization times. 

Ti02-loaded 25-pm carbon microspheres were prepared from Ti02-loaded cellulose microspheres, formed by one-step phase separation using cellulose xantate and sodium polyacrylate aqueous solutions with dispersed TiOj powder (P25) [264]. The titania particles were located preferentially on the external microsphere surface, whose content was either 41.5 or 15.6 mass%. Decomposition of acetaldehyde under UV irradiation was found to be enhanced in comparison with as-received P25 powder. 

Yu, J., Liu, W., and Yu, H. (2008) A one-pot approach to hierarchically nanoporous titania hollow microspheres with high photocatalytic activity. Cryst. Growth Des., 8, 930-934. 

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