Titania powders

In this study, nanoparticles of titanium dioxide (TiCh) have been successfully synthesized by. reduction method. These nanoparticles were characterized by using X-ray diffraction (XRD) and TEM (transmission electron microscopy). XRD revealed the presence of pure TiCL NPs. XRD studies suggested that the titanium dioxide, TiCL exists in anatase form. The nanostructured character of the produced titania powders was characterised by Scherer method and TEM examinations. The TEM images indicate that the crystalline size of titanium dioxide precipitates varies from 1.81 nm to 13.15 nm This shows that nanoparticles obtained from reduction method are in more nanorange as compared to those obtained for precipitation method. 

Navvio, J.A., Testa, J.J., Djedjeian, P., Padron, J.R., Rodriguez, D., Litter, M.I. 1999. Iron-doped titania powders prepared by a sol-gel method. Appl Catal A General 178 191-203. 

Structural data for pure and iron-doped titania powders have been reported... 

Upon stirring a suspension of titania powders in an aqueous solution of H2[PtCl6] in the dark, different maximum amounts were adsorbed. Whereas 4.0 and 1.1% were taken up by the anatase and... 

Goellner, J. P, and Gates, B. G, Synthesis and characterization of site-isolated hexarhodium clusters on titania powder. J. Phys. Chem. B. 105, 3269 (2001). 

When air equilibrated samples of the dye Acid Orange 7 adsorbed on Ti02 were irradiated with visible light, ( > 380 nm) they readily underwent degradation and the colored titania powders were completely bleached. Figure 8A shows the... 

Figure 1. XRD pattern of titania powders synthesized under various conditions (1, 2), as well as commercial Ti02 Degussa P25 (5). The sample (1) was not exposed to the hydrothermal treatment (HTT) and was only calcinated at 500 °C, the sample (2) was exposed to HTT at 175 °C and then calcinated at 500 °C.

Kolen ko Y.V., Churagulov B.R., Kunst M. et al. (2004) Photocatalytic properties of titania powders prepared by hydrothermal method, Appl. Catal. B, 54(1), 51-58. 

Upon stirring a suspension of titania powders in an aqueous solution of H2[PtCl6] in the dark, different maximum amounts were adsorbed. For the anatase hydrate and anatase/rutile samples TH (Kronos) and P25 (Degussa), there were taken up 4.0% and 1.1%, respectively, whereas only traces were adsorbed onto the rutile material Aid. The almost four times larger amount adsorbed by TH corresponds with the about four times larger surface area as compared to P25 (vide infra). Subsequent heat treatment at 200 °C afforded the desired photocatalyst (21). Surface modification may be performed also by simple grinding with PtCU, but the resulting powders are of lower photocatalytic activity and less stability (18,20). 

In many cases, anhydrous metal oxides have been prepared by solvothermal treatments of sol-gel or micro-emulsion-based precursors. Wu and coworkers prepared anatase and rutile Ti02 by a micro-emulsion-mediated method, in which the micro-emulsion medium was further treated by hydrothermal reaction [171]. This micro-emulsion-mediated hydrothermal (MMH) method could lead to the formation of crystalline titania powders under much milder reaction conditions. 

Ding X.Z. and He Y.Z., Study of the room temperature ageing effect on structural evolution of gel-drived nanociystalline titania powders. J. Mater. Sci. Lett. 15 (1996) pp 320-322. 

Early studies on titania powders showed that methanol generated methyl formate as the principle photooxidation product. Molybdena- and vanadia-modified Ti02 catalysts demonstrated at least an eighty percent drop in activity relative to pure titania, although selectivity to dimethoxymethane (and thus suppression of further oxidation products) was almost total [87]. 

Kammler, H.K., Jossen, R., Morrison, P.W., Jr., Pratsinis, S.E., and Beaucage, G., The effect of external electric fields during flame synthesis of titania, Powder TechnoL, 310, 135-136, 2003. 

Yamanaka T, Fukumori Y (1995) Molecular aspects of the electron transfer system which participates in the oxidation of iron by Thiobacillus ferrooxidans. FEMS Microbiol Rev 17 401-413 Yanagisawa K, Ovenstone J (1999) Crystallization of anatase from amorphous titania using the hydrothermal technique Effects of starting material and temperature. J Phys Chem B 103 7781-87 Yang J, Mei S, Ferreira IMF (2000) Hydrothermal synthesis of nanosized titania powders lirfluence of peptization and peptizing agents on the crystalline phases and phase transition. J Am Ceram Soc 83 1361-1368... 

Rao, A.S., Rheology of aqueous dispersions of alumina, titania and mixture of alumina and titania powders, J. Dispersion Sci. Technol., 8, 457, 1987. 

Chibowski, S., Effect of molecular weight of a polymer on the structure of a layer adsorbed on the surface of titania, Powder Technol.. 63, 75, 1990. 

Yang, J., Mei, S., and Ferreira, J.M.R, Hydrothermal synthesis of nanosized titania powders Influence of tetraalkyl ammonium hydroxides on particle characteristics, J. Am. Ceram. Soc., 84, 1696, 2001. 

Figure 12. Isoelectric points of DS-coated titanias O, titania dispersed in aqueous silica , dried, coated titania powders. The hose titania was 20 m2/g.

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