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Preparation of the Stripe ZnO Films with Micro/nano Needles by Elctrodeposition-Thermal Oxidation and Their Photocatalytic Performance

Author: ZhangNan
Tutor: NiuZhenJiang
School: Zhejiang Normal University
Course: Physical and chemical
Keywords: ZnO thin film stripe morphology micro/nano needle elctrodeposition-thermal oxidation photocatalysis
CLC: O614.241
Type: Master's thesis
Year: 2013
Downloads: 23
Quote: 0
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Abstract


In presence of polyvinyl pyrrolidone (PVP), the stripe morphology of Zn films were galvanostatically deposited on304stainless steel sheets at0.03A·cm-2in zinc sulfate-ammonium chloride solution in this paper. Effects of preparing conditions including the concentrations of PVP and Zn+, different depositional times and current densities on the morphologies, structures and compositions of zinc films were studied by XRD and SEM. The zinc films were calcined at air by various heating temperatures, times and one/two steps. The stripe ZnO thin films with micro/nano needles were obtained. And photocatalytic performances of ZnO thin films were investigated. Minute research work was as follows:1. The electrodeposition of the zinc filmsa) The Zn films were galvanostatically deposited on a304stainless steel substrate under the conditions of J=0.03A·cm-2for600s in solution of0.05mol·dm-3ZnSO4and2mol·dm-3NH4Cl with0.001-1%various mass concentrations of PVP. the effects of the concentrations of PVP on the morphologies and structures of zinc films were investigated. Results showed that the topographies of deposited zinc films depended on the concentrations of PVP. The continuous and complete fringe Zn appearence could be obtained under the conditions of0.005%PVP for600s.b) The effects of depositional times on Zn stripe morphologies were researched by keeping the additive concentration of0.005%and other things being equal, only changing the deposition times, Results showed that there was not fringe morphology in compact zinc film which was deposited for60s, the stripe morphology had been formed around electrodepositional time of300s, the stripe morphology continuous vertically growed on basement when Zn film was deposited for600s. In conclution, the stripe zinc film did not form on the stainless steel substrate surface, but grew on the dense zinc film.c) Changing the concentration of Zn2+and current densitis in condition of0.005%PVP for600s found that unsuitable Zn2+concentration couldnot form the stripe morphology, the dense zinc film was preparated in low current density, but the dendritic and three-dimensional porous morphologies were obtained in high current density, which diffusion control is the dominant control step.2. Preparation of ZnO films with micro/nano needles by thermal oxidationa) The stripe Zn films by preparation in conditions of0.005%PVP, galvanostatic deposition300s were calcined at temperature ranging from150℃to600℃under air in the muffle furnace. The effects of calcination temperatures, calcination times and calcination methods on the formation of ZnO micro/nano needles by thermal oxidation were studied. Experimental results by one-step thermal oxidation showed that the stripe zinc film began with the growth of micro/nano needles by thermal oxidation at250℃for1h; With the increasing of oxidation temperature, the density of micro/nano needles firstly increased then decreased, high temperature went against the growth of nanometer needles; Prolonged oxidation time was beneficial to promote the growth of micro/nano needles below zinc melting, however when calcination temperature was above zinc melting point, ZnO micro/nano needles gradually reduced in thermal oxidation process; Comparing one step thermal oxidation, a two-step thermal oxidation was favorable to enhance adhesive force between ZnO films and basement and promote the growth of ZnO micro/nano needles.b) The structures of Zn thin film materials present various characteristics in different calcination temperatures. Zn/ZnO, Alloys or spinel type mixed oxide (AB2O4) such as ZnFe2O4, ZnCr2O4maybe gernerated by reaction of Zn or ZnO with the compounds of stainless steel in heating process. 3. The photocatalytic properties of ZnO filmsc) The photocatalytic properties of the ZnO films were test by photocatalytic degradation of3mg-L"1rhodamine B(RhB) under the conditions of the illumination intensity of the fluorescent and high pressure mercury lamp for20mW·cm-2and air flow for60ml·L-1Results showed that the stripe ZnO thin films with micro/nano needles displayed higher photocatalytic activities and recycling performance.

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CLC: > Mathematical sciences and chemical > Chemistry > Inorganic Chemistry > Metal elements and their compounds > Section II group metal element and its compounds > The zinc Vice family (Ⅱ B group metal elements ) > Zinc Zn
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