Titania composition

Homogeneous, nanosized, copper-loaded anatase titania was synthesized by an improved sol-gel method [197], These titania composite photocatalysts were applied to the photoreduction of carbon dioxide to evaluate their photocatalytic performance. Methanol was found to be the primary hydrocarbon product [198], Under calcination conditions, small copper particles are well dispersed on the surface of anatase titania. According to XAS and XPS analysis, the oxidation state of Cu(I) was suggested to be the active species for C02 photoreduction [199], Higher copper dispersion and smaller copper particles on the titania surface are responsible for a great improvement in the performance of C02 photoreduction. 

In a similar approach, titania composites doped with CdSe and CdSe/ZnS NCs were prepared. Here the NCs were mixed with titanimn tetrabntoxide in a 2 1 THF/ethanol solvent system, and volnme fractions as high as 13% were reported in films that were spin-coated from the sol solutions. While QYs for the CdSe/ZnS-titania sols remained near 10%, smaller valnes were reported for CdSe NCs that were not initially overcoated with ZnS. In addition, the samples were not very stable, as the PL intensity was observed to decrease in the films almost immediately following processing. 

Several polymer/polyelectrolyte-nanocrystal hybrid devices have been fabricated seeking to exploit the electro and photoluminescent properties of such material [179-188]. Device fabrication in all these cases is by low-cost self-assembly based techniques. These devices utilize thin films of these hybrids obtained either by multilayer deposition or drop/spin casting methods. Thus, solar cells have been made from poly(2-hexylthiophene)-CdSe nanorod multilayers, lasers from drop cast films of CdSe-titania composites and an infrared emitter from multilayers... 

Extensive stress measurements has been reported in mesoporous alumina [13,26], titania and alumina-titania composite membranes [13,27] supported by... 

Li, H., Khor, K.A., and Cheang, P. (2003) Impact formation and microstructure characterization of thermal sprayed hydroxyapatite/titania composite coatings. Biomaterials, 24 (6), 949-957. 

Xiao, X.F., Liu, R.F., and Zheng, Y.Z. (2006) Characterization of hydroxyapatite/titania composite coatings codeposited by a hydrothermal-electrochemical method on titanium. Surf. Coat. Technol., 200 (14/15), 4406-4413. 

In 2002, the group of Rolinson [21] reported the use of gold-titania composite aerogels for room temperature oxidation of carbon monoxide. Alkanethiolate monolayer-protected gold clusters with a well controlled size distribution were added to the Ti(IV) precursor during the sol-gel chemistry. After calcination the Au particles aggregate to average diameters of 5-10 nm. 

Wang W, Serp P, Kalck P, Faria JL (2005) Photocatalytic degradation of phenol on MWNT and Titania composite catalysts prepared by a modified sol-gel method. AppI Catal B Environ 56 305-312... 

Yu-Peng Lu, Mu-Sen Li, Shi-Tong Li, Zhi-Gang Wang, and Rui-Fu Zhu. Plasma-sprayed hydroxyapatite + titania composite bond coat for hydroxyapatite coating on titanium substrate. Biomaterials 2004 25 4393M 403. 

In order to exploit the application of titania in electronic ceramics, Nair et al. (1999) studied sintering of nanostructured pure and doped titania samples. An aqueous sol containing titania particles of 10 nm or less size was used for the preparation ofpure and Cu, Ni, La-doped gel samples. The densification temperature and properties of some selected titania compositions are also shown in Table 6-2. Figures 6-2(a) and (b) show the field emission scanning electron micrographs (FE-SEM) ofpure titania sintered at 750°C and 800°C for 8 h. It may be noted that the 750°C calcined gel samples, though porous. 

TABLE 6-2. PROPERTIES OF SOME SELECTED TITANIA COMPOSITIONS (REPRODUCED WITH PERMISSION PARTIALLY FROM NAIR(1999) MATER. RES. BULL., 34 1275-1290 1999 ELSEVIER SCIENCE LTD.)... 

Page, K, Palgrave, R.G., Parkin, I.P., Wilson, M., Savin, S.L.P., and Chadwick, A.V. (2007) Titania and silver-titania composite films on glass potent antimicrobial coatings. Journal of Materials Chemistry, 17, 95—104,... 

J.K. Savaiano, T.J. Webster, Altered responses of chondrocytes to nanophase PLGA/nanophase titania composites. Biomaterials 25 (2004) 1205-1213. 

Antonucci et attributed the enhanced performance of the composite membrane to the hygroscopic properties of silica. Watanabe et investigated silica- and titania-impregnated Nation composite membranes in H2/O2 proton-exchange membrane fuel cells operating at 100 °C with minimal external humidification. They reported that the silica particles were superior to titania particles in terms of water retention qualities within the Nafion membrane, and attributed this to the higher water sorption properties of silica. Adjemian et reported that the performances of silica and titania composites at 130 °C and 75% RH are comparable (0.33 Qcm and 0.35 Qcm cell resistivities) while recast Nafion -based composites present high cell resistivity (0.9 Qcm ). 

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