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AWO4 （A=Mn, Cd, Ca, Zn） Nanoparticles: Size and Doping Effect on Lattice Structure and Properties

Author: ZuoWenMing
Tutor: LiGuangShe
School: Inner Mongolia University
Course: Chemistry
Keywords: MnWO4 CdWO4 CA1 - xZnxWO4 Lattice structure Surface distortion layer Photocatalytic
CLC: TB383.1
Type: Master's thesis
Year: 2010
Downloads: 91
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Abstract


Structure and physical and chemical properties of nanomaterials is closely related to its grain size and grain surface state. The grain size change will bring about a corresponding change in the lattice structure and physical and chemical properties, so that the nano-materials exhibit specific properties of the conventional bulk powder. In addition, the doping effects can change the internal structure of the lattice, thus changing the nature of the material, research material size effect and doping effect has important scientific significance. The ABO4 type oxide is an important class of compounds has a wide application field in the scintillator material, a multi-iron material, the the laser matrix material and the display apparatus. This article the binary oxide universally representative tungstate select ABO4 categories (AWO4) as the research object, \\The main results are as follows: (the nanocrystals) MnWO4 growth dynamics control and nanostructures regulation. Using hydrothermal method successfully synthesized size to 8-29 nm MnWO4 nanocrystalline and to determine the growth of the particle size under the conditions of reaction time t and the reaction temperature T D kinetic equation. Characterization and analysis of the structure of the system show that the decrease of grain size cause nano-MnWO4 lattice expansion of the lattice symmetry lower band broadening. Block MnWO4, nano-sized MnWO4 Infrared and Raman Spectroscopy new vibration mode, respectively, at 913 and 930 cm-1 and the peak intensity increases with decreasing grain size, this site nanocrystals surface distortion layer. Through the core-shell model fitting calculation out MnWO4 nanoparticle surface distortion layer thickness of approximately 1.8 nm, equivalent to three MnWO4 cell thickness. (2) of CdWO4 nanocrystalline particle size control and photocatalytic performance optimization. Citric acid as the complexing agent by adjusting the reaction temperature CdWO4 nanocrystals synthesized a series of different grain size and the degree of crystallinity. X-ray powder diffraction (XRD), transmission electron microscopy, IR, UV diffuse scattering spectroscopy, fluorescence emission spectra, and BET surface area test system characterization and analysis show that the grain size increased as the reaction temperature from 160 ° C to 220 ° C nano CdWO4 from 11 nm increased to 21 nm. With the decrease of grain size CdWO4 lattice volume expansion, the lattice symmetry lower band broadening, redshift Infrared Au vibration mode. 254 nm UV light degradation of methyl orange test results show that the the 21 nm of CdWO4 photocatalytic activity of more than three times the 11 nm CdWO4 nanocrystalline. These results indicate that regulation CdWO4 nanocrystalline crystallinity and grain size to optimize the purpose of its photocatalytic properties, this synthesis method can also be extended to other semiconductor photocatalyst system. (3) the CA1-xZnxWO4 nanocrystals synthesized and Zn-doped effect on the the CaWO4 band, light-emitting and conductive properties of impact. Small organic molecules citric acid as complexing agent series CA1-xZnxWO4 nanocrystals were prepared by co-precipitation method at room temperature. ICP element test results show that the Zn content is between 0-0.104. The system structural characterization and data analysis showed that with increasing the content of nano of Zn-doped the Ca1-xZnxWO4 lattice volume contraction, the UV absorption edge red-shifted fluorescence emission intensity decreased conductivity enhancement. The initial the estimated Zn solid solution in CaWO4 line is about 10%.

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