Y.Y. Wang

Hydrothermal synthesis of vanadium oxide nanotubes by a facile route

Vanadium oxide nanotubes were synthesized by hydrothermal treatment from V2O5·nH2O sols as precursor and dodecylamine as structure-directing template. The morphology and structure of the nanotubes were characterized by SEM, TEM, XRD, TG-DTA and FTIR. The experimental results reveal that the duration of the hydrothermal treatment is of importance for obtaining VOx-NTs which have a layered structure. TG-DTA study indicates that V5+ cations in nanotubes are partially reduced to V4+ cations. The results from FTIR spectra indicate the difference in V-O vibrations between before and after hydrothermal treatment. From the results, it suggests that during hydrothermal treatment, the rearrangement of the vanadium oxide structure leads to the formation of VOx nanotubes from lamellar structure because of the presence of V4+ species.

Modulation of Three Dimensional Photonic Band Gap in Visible Region

Three dimensional (3D) SiO2 photonic crystals films were fabricated on quartz substrate by vertical deposition method. The effects of various preparation parameters on optical properties were studied by optical transmission measurements. Bragg reflection on parallel sets of (111) planes were observed in all the samples. The center wavelength of [111] photonic band gap (PBG) varied from 450 nm to 680 nm with the increasing sphere size. For a given sphere size, the (111) Bragg reflection of as-deposited sample shifted towards lower wavelengths as the sintering temperature T increased. The role of evaporation temperature on the optical properties of the film was also investigated. The PBG can be correspondingly modulated in visible region by changing various preparation parameters.

Influence of temperature on the microstructure of V2O5 film prepared by DC magnetron sputtering

Abstract V 2 O 5 films were prepared on silicon wafers by DC magnetron sputtering and post-annealing under various conditions. The influence of depositing and post-annealing temperatures on microstructure of V 2 O 5 films was studied by XRD and Raman scattering measurements. The results reveal that sputtered V 2 O 5 films show preferred growth orientation along (001) planes and the c -axis is perpendicular to the silicon substrate surface. It is interesting to find that both the V 2 O 5 film deposited at temperature of 511 °C and the one annealed at 500 °C exhibit desirable layer-type structure of orthorhombic symmetry. Such layer-typed V 2 O 5 films are promising candidates for cathodes of rechargeable lithium or magnesium thin-film batteries.