The Studies Of Preparation And Doped Of Tetrapod-shape Zinc Oxide Whiskers

Tetrapod-like zinc oxide whisker (T-ZnOw) is one kind of multifunctional inorganic material with uniform three-dimensional structure. High pure zinc powders are unreasonably demanded in the present production techniques and fussy processing of zinc powder is a prerequisite in some cases. So the mass production is difficult to achieve and higher costs hinder its further application in many fields. From these considerations, this study explored the optimum process conditions of preparing T-ZnOw by direct oxidation of non high-grade Zn powders at ambient pressure on the basis of in-depth study of the theory of nucleation and growth. The effects of aluminum doping on the electrical resistivity of T-ZnOw were investigated. T-ZnOw doped with gallium was prepared and it had good electric conductivity preformance.In this thesis, many factors having the impact on whiskers size, shape and yield were studied systematically in synthesizing T-ZnOw and the optimum process conditions were explored. The structure and morphology of ZnO whiskers were characterized by Scanning Electron Microscopy (SEM) and X-ray diffraction(XRD). The results show that these whiskers are single crystal with hexagonal wurtzite structure, length of whiskers range from 30μm to 65μm, the average length is 50μm, diameter of whiskers range from 2μm to 5μm, and the average diameter is 3μm. The growth of ZnO whiskers is determined mainly by two factors: one is the supersaturation of ZnO above the substrates, and the other is the crystallization property of ZnO material itself. The supersaturation of ZnO is the most impotant and can be regulated by controlling the temperature and reaction rate. The experimental results showed that when pre-heating rate is 5°C/min, the morphology of T-ZnOw is the most perfect and the yield is as high as 95 percent. With the improvement of pre-heating rate, the product is uneven tetrapods zinc oxide whiskers, and whisker size increases. With the reaction temperature increasing, whisker size reduced, but the yields and integrity of whisker have decreased.In this paper, intrinsic defects doping of the Tetra-ZnO whiskers were used to make a breakthrough in conducting electricity function. The micro-morphology, crystal structure, conducting properties of doped T-ZnOw were measured and analyzed. T-ZnOw were doped with Al,Ga by solution absorption blending pretreatment following by high temperature diffusing process. The result showed that T-ZnOw lost parts of needle point and some grains covered the whiskers surface. The formation of ZnGa₂O₄ and ZnAl₂O₄ can be observed by carefully examining the XRD patterns of doped T-ZnOw especially when dealing with highly doped samples. The electric conducting properties of the doped samples were characterized by electric resistance tests. Both Al and Ga doped T-ZnOw have an increase in conductivity. The electrical resistivity of T-ZnOw doped with Al reduces by four orders of magnitude, and for T-ZnOw doped with Ga, it decresed by seven orders of magnitude.