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Titania Nanowire and Hollow Polyhedron Via Direct Oxidation of Metallic Titanium

Author: XueHongXing
Tutor: WuJinMing
School: Zhejiang University
Course: Materials Science and Engineering
Keywords: Titanium dioxide TiO2 Nanowires Polyhedron Low-temperature growth Photocatalytic
CLC: TB383.1
Type: Master's thesis
Year: 2011
Downloads: 130
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Abstract


The use of hydrogen peroxide solution directly dioxide metal preparation of titanium dioxide (TiO2) nanowires and hollow polyhedron, to study the growth mechanism and photocatalytic properties. Reactant H2O2 and cold-rolled titanium sheet, by adding melamine to H2O2 and concentrated nitric acid, and adjusting the process parameters, control of the low-temperature growth of TiO2 films successful TiO2 nanowires array film; NaF and concentrated nitric acid by adding to H2O2 supplemented with appropriate follow-up of heat treatment and washing treatment success polyhedral TiO2; while adding hydrogen peroxide solution of NaF, melamine and HNO3, after subsequent heat treatment directly TiO2 hollow polyhedron. By field emission scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, UV - visible diffuse reflectance testing methods, laser Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis, N2 adsorption analysis of the morphology of nanostructured TiO2 structure and its optical response behavior to investigate the growth mechanism, and the ability to dye auxiliary Degradation of Rhodamine B (RhB). The papers achieved major results are as follows: 1.TiO2 nanowires: R \u0026 D TiO2 nanowire arrays prepared on a titanium metal matrix technology, the process is simple and easy to industrialized, repeatable, no template and catalyst. 80 ° C reaction temperature, the titanium metal by H2O2 corrosion and oxidation on the metal surface TiO2 porous film of amorphous structure is formed at the same time, is released to the solution of hydrated Ti (Ⅳ) ion. Solution hydrated Ti (Ⅳ) ion concentration reaches a critical value, the heterogeneous nucleation of TiO2 porous film at the metal surface precipitation TiO2. On the other hand, the strong acidic environment, the solution melamine decomposition of cyanuric acid, and role as a bridge-OH adsorbed on the surface of TiO2 nanocrystals. Differences due to the different crystal surface-OH density, cyanuric acid can achieve selective adsorption to the surface of TiO2 nanocrystals, eventually leading to the self-assembly of TiO2 nanocrystals precipitated from the solution (though poor crystallinity) directed fusion mechanism formation of an average diameter of 25nm, and an aspect ratio of about 40 nanowire arrays. The follow-up to 450 ° C in air heat treatment significantly increased the degree of crystallinity of TiO2 nanowire arrays. The photocatalytic performance test results show that the nanowire arrays of anatase TiO2 photocatalytic degradation of water, the ability of Rhodamine B was significantly better than the commercial P25 TiO2 nano powder. Add NaF and HNO3 the 2.TiO2 (hollow) polyhedron: Ti and H2O2 reaction system, a temperature of 80 ° C for 10 min for 96 h, in titanium surface generate Na3TiF6 polyhedron. The reaction to 30 min, mainly generated cube; With the reaction to proceed, the cube eight vertices are truncated, gradually evolved into the octahedral structure. Subsequent heat treatment process, the majority of Na3TiF6 polyhedron in 209 ℃ oxidation reaction decomposition of TiO2 and NaF, the TiO2 sheet thickness of about 20 nm, a vertical cross polyhedron. After further washing with water to remove the NaF and residual Na3TiF6 obtained TiO2 polyhedron to 196.3m2 / g and its specific surface area the indirect bandgap degree of 3.11 eV, a clear catalytic effect of light. While adding hydrogen peroxide solution of NaF, melamine and HNO3, 80 ° C for 72 h, after subsequent heat treatment can be obtained directly TiO2 hollow polyhedron.

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