| Summary: | 博士 === 國立臺北科技大學 === 電機工程系 === 106 === In this study, with 99.97% of zinc (Zn), tungsten (W) metals and pure water as the dielectric liquid, spark discharge method is adopted to prepare nano zinc oxide (ZnO) and nano tungsten oxide (WO3) colloids. This is a green preparation method and has never been presented in the past literature. Generally, zinc oxide and tungsten oxide are mostly prepared by chemical synthesis. This is the first time that the laboratory made zinc oxide and tungsten oxide by spark discharge. In order to understand the characteristics and microstructure of the prepared nano zinc oxide (ZnO) and nano tungsten oxide (WO3) colloids, the analysis applied instruments such as Zetasizer Nano System, UV-Visible Spectrophotometer (abbreviated as UV-Vis Spectrophotometer), Raman spectroscopy, Photoluminescence (abbreviated as PL), X-ray diffraction (abbreviated as XRD), Selected area diffraction (abbreviated as SAED), Scanning Electron Microscope, Through-type Scanning Electron Microscope and so on. The initial experiment of preparing zinc oxide and tungsten oxide by spark discharge method is rarely presented in the past literature, and so are the compared similarities and differences between the characteristics of zinc oxide and tungsten oxide in this method and that in other synthetic methods.
The zinc oxide and tungsten oxide colloid prepared by the spark discharge method were tested by various instruments, and the measured characteristics and microstructure are roughly described as follows: (1) Analysis results from the Zetasizer Nano System: The particle size distribution of zinc oxide (ZnO) is concentrated at 1.117 nm, and the zeta potential measurement is -36.2 mV, indicating good levitation. Tungsten oxide (WO3) colloidal nanoparticles have an average distribution of 62.75 nm and a zeta potential of -59.7 mV, which also shows good suspension of tungsten oxide (WO3) colloid. (2) Analysis of spectral absorbance intensity measured by UV-Visible Spectrophotometer (UV-Vis instrument)：The maximum absorbance intensity of zinc oxide (ZnO) is near zero when the wavelength is below 190 nm and greater than 388 nm. There are two maximum absorbance peaks measured in Tungsten oxide (WO3) and its maximum absorbance intensity red-shifst as the colloid concentration increases. (3) XRD and SAED were used to detect the composition and crystal structure of tungsten oxide (WO3) and zinc oxide (ZnO). And it is found that the prepared zinc oxide (ZnO) colloid contains the two elements, including zinc (Zn) and zinc oxide (ZnO). The Miller index of Zinc oxide (ZnO) with a indice spacing of 0.281nm is (100), while the Miller index of Zinc oxide (ZnO) with a indice spacing of 0.259nm is (002). The Miller index of Zinc oxide (ZnO) with a indice spacing of 0.247nm is (101), which is the maximum peak of zinc oxide (ZnO) X-ray diffraction. The Miller index of zinc (Zn) with a indice spacing of 0.230 nm is (100) and the Miller index of zinc (Zn) with a indice spacing of 0.209 nm is (101), which is the maximum peak of zinc (Zn) X light diffraction. The prepared tungsten oxide (WO3) colloid contains two elements, including tungsten (W) and tungsten oxide hydrate (WO3•H2O). The Miller index of tungsten (W) with a indice spacing of 0.223 nm is (110), which is the maximum peak of tungsten (W) X-ray diffraction. The tungsten oxide hydrate (WO3•H2O) has a 0.375 nm indice spacing when the Miller index is (120) and a 0.347 nm indice spacing when the Miller index is (111), which is the maximum peak of tungsten oxide hydrate (WO3•H2O) X-ray diffraction.
The results of the composition analysis of the zinc oxide colloid and tungsten oxide colloid prepared with electric spark discharge method are as the followings: Zinc oxide (ZnO) colloid contains zinc (Zn) and zinc oxide (ZnO). Tungsten oxide WO3) colloid contains tungsten (W) and tungsten oxide hydrate (WO3•H2O). In the Raman spectroscopy of zinc oxide (ZnO), E1(LO) characteristic peak and E2(H) characteristic peak are produced on the positions of 412 cm-1 and 570cm-1 respectively. In the analysis of Photoluminescence (PL), the nano zinc oxide (ZnO) illuminates as the wavelength reaches 366nm and 498m. This indicates that both the structural quality and crystallinity of the zinc oxide (ZnO) prepared in this experiment are high and there is no condition of unfavorable Miller index. In the analysis of the Raman spectroscopy of tungsten (W) and tungsten oxide hydrate (WO3•H2O), obvious characteristic peaks can be found on four positons including 247.5 cm-1、313.1 cm-1、706.8 cm-1 and 807.5 cm-1. In the study of Photoluminescence (PL), there are five obvious characteristic peaks found on the PL spectroscopy, which are 446nm, 470nm, 489nm, 520nm and 570nm respectively. This shows that the structural quality of tungsten oxide hydrate is high.
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