Study On The Sintering Behaviors, Gas-sensing Properties And Optical Properties Of Nano-tetrapod ZnO

Tetrapod ZnO(T-ZnO) nanopowders have been produced by a thermophysical method. The sintering behaviors, gas-sensing behaviors and optical properties have been studied. The results showed that the oxygen pressure influenced the morphology of nano-ZnO. The nano-ZnO has a longer needle length at low oxygen pressure of 650Pa. The nano-ZnO changes from tetrapod to particle, when the oxygen pressure changes from 2500Pa to 8500Pa. Most of the T-ZnO tip radius were about 8nm and 100-200nm of needle length at oxygen pressure of 2500Pa.The morphology of T-ZnO has a very small change at a low sintered temperature. The needle of T-ZnO sublimated vanished with the increase of sintering temperature because of Joule-Thomson effect, and ZnO particles and massive ZnO appeared. Sintering above 750℃, the ZnO tetrahedron generated when the ZnO gas, sublimated at T-ZnO tip, was transport to the joint of the needles of T-ZnO.The concentration of interstitial zinc of T-ZnO decreased with the increase of sintering temperature. The reduced free electrons caused the increased air resistance of nano-ZnO. The results of gas-sensing properties of T-ZnO nanopowders showed that the optimal sintering temperatures of T-ZnO gas sensors were 550℃,both to ethanol and benzene.The blue band emission of T-ZnO intensity decreased when enhance the sintering temperature because of the decreased density of interstitial zinc. At the same time, the green band appeared because of the emergence of oxygen vacancies.The paper has four parts. In the first part, the preparation and applications of T-ZnO nanopowders at home and abroad have been summarized, and then the purpose and importance of our research have been presented. In the second part, T-ZnO nanopowders were prepared by thermophysical method, and its growth mechanism were investigated. In the third part, sintering behaviors of T-ZnO were discussed. In the fourth , fifth part, the influences of sintering temperature on gas sensitivity and optical characteristic, relation between the sintering temperature and the density of defects in T-ZnO nanopowders were studied.