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Song C.-L.,Zhejiang University | Wang J.,Zhejiang University | Zeng M.-L.,Zhejiang University | Zhu J.-Q.,WeiHai Blue Star Glass Holding Co. | And 3 more authors.
Journal of Sol-Gel Science and Technology

Fluorine-doped TiO2 thin films featuring columnar structure were prepared on fluorine-doped tin oxide (SnO2:F) substrate using a sol-gel method. The F doping ratios were varied in the range of 0-8 %. The effect of [F]/[Ti + F] ratio on the structural, morphological, optical, photocatalytic and low-emissivity properties has been investigated in detail. X-ray diffraction studies revealed that all the composited films are mainly composed of anatase TiO2 and rutile SnO2 without other phases. The prepared TiO2:F films possessed the columnar morphology with the single layer thickness ranging from 28 to 31 nm. The best photocatalytic activity was obtained for the films with 4 % F doping ratio which is mainly attributed to the highest crystallization and crystallite size. The transmission and hemispherical emissivity of the composite films could still reach approximately 70 % and 0.20, which match the requirements of the Chinese National Standard (GB/T18915.2-2002), promoting the films for the practical applications. © 2013 Springer Science+Business Media New York. Source

Ni L.,Zhejiang University | Liu Y.,Zhejiang University | Song C.,Zhejiang University | Wang W.,Weihai China Glass Solar Co. | And 2 more authors.
Physica B: Condensed Matter

First-principle calculations were carried out to investigate the epitaxial strain dependence of the structural stability and related properties of SrTiO 3. The P4mm-to-P4/mmm-to-Amm2 phase transitions in SrTiO 3 with the epitaxial strain changing from compressive to expansive have been identified by analysis of the soft-mode eigendisplacement. The zero-temperature critical strains for the P4mm-to-P4/mmm and P4/mmm-to-Amm2 phase transitions are -0.72% and 0.83%, respectively, which is consistent with the previous predictions based on the phenomenological thermodynamic model and the parameterized total-energy model. The influences of the epitaxial strain on the dielectric tensor and spontaneous polarization along the phase transition path are discussed in terms of charge transfer. Further investigations on the vibration modes show unusual softening behaviors of the A 1 and B 2 modes in the Amm2 phase, which may be associated with the soft phonon modes away from Γ point and possibly result in other phase transitions unreported by any previous studies. © 2011 Elsevier B.V. All Rights Reserved. Source

Wang K.,Zhejiang University | Hua Y.,Zhejiang University of Technology | Wang J.,Zhejiang University | Song C.,Zhejiang University | And 3 more authors.
Thin Solid Films

A five-layer model for low-emissivity (Low-E) coated glass with SnO 2:F/SiCxOy tandem thin films has been developed for spectroscopic ellipsometry (SE) measurement. A comprehensive interpretation of this structure model is also presented. The theoretical, optical, and structural parameters obtained by fitting the SE experimental data have been proven credible using other auxiliary measurements, including spectrophotometry, atomic force microscopy, scanning electronic microscopy and transmission electronic microscopy. The effect of the diffusing sodium ions on the optical and electronic properties of the film is also discussed. These results demonstrate that SE, accompanied with this five-layer model, is helpful for an on-line characterization of the Low-E coating process used as a non-destructive and low time-consuming method. © 2013 Elsevier B.V. All rights reserved. Source

Cheng B.,Zhejiang University | Wang K.K.,Zhejiang University | Wang K.P.,Zhejiang University | Jiang W.,Zhejiang University | And 5 more authors.
Solar Energy Materials and Solar Cells

Selective solar absorbers based on composition of porous titania and carbon with a well-defined interconnected macropores structure have been fabricated by a photopolymerization-induced phase-separation method in the framework of a sol-gel technique. Scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, thermogravimetric and differential thermal analysis, Fourier transform infrared spectroscopy, and spectroscopic ellipsometry were used to characterize the C-TiO2 films. The results showed that the macroporous structures of the films could be tuned by changing the reaction parameters. The reduction of the HNO3 concentration in the solution effectively decreases the mean size of pores, carbon content, and the thickness of the nanocomposite films, leading to an optimization of the spectral selective absorption performance. The solar absorptance (α) and thermal emittance (ε) of the optimized single layer film with a thickness of about 300 nm were about 0.95 and 0.12, respectively. The films also show good stability under the high temperature (~500 °C). Based on these results, porous carbon-titania composite films proved to be a good candidate as solar selective absorbers. © 2014 Elsevier B.V. Source

Cheng B.,Zhejiang University | Wang K.K.,Zhejiang University | Wang K.P.,Zhejiang University | Li M.,Zhejiang University | And 6 more authors.
Journal of Alloys and Compounds

Newly proposed selective solar absorbers of porous carbon-titania nanocomposite films with a well-defined interconnected macropores structure were prepared via a polymer-assisted photopolymerization-induced phase-separation method. The microstructure and optical properties of as-deposited nanocomposite films were characterized and discussed in detail. The results show that non-ionic water-soluble polymer polyvinylpyrrolidone works as a sol modifier advantaging the mean size of the interconnected macropores, residual carbon content, and films thickness, but suppresses the order degree of the carbon remained in the films. The high-resolution transmission electron microscopy demonstrated that a small amount of graphite particles with size of around 1.1 nm embedded in the cavity of the porous while the wall of the porous consists of amorphous carbon and titania composites. The single layer of as-prepared porous C/TiO2 nanocomposite films exhibits high solar absorptance (α = 0.928-0.959) with low thermal emittance (ε = 0.074-0.105), yielding an optimized photothermal conversion efficiency η = α - ε of 0.864 corresponding to a film thickness of around 338 nm, indication of such film is fair enough to serve as an excellent solar absorber. © 2015 Elsevier B.V. Source

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