Studies On Preparation Of Ultra-fine WO₃ Via Hydrothermal

WO₃ is a kind of multi-functional material with perfect performances in fields of electrochromism, catalysis and gas-sensitivity, etc. It is a great potential research that ultra-fine WO₃ is developed in new materials.In this paper, APT, H₂WO₄ and W as precursors, the ultra-fine WO₃ powder has been yielded in orthogonal experiments via hydrothermal crystallization method, respectively. The effects of precursors, hydrothermal synthetic conditions and heat treatment on properties of products have been investigated. The products have been characterized using laser scattered particle analyzer, specific surface areas measuring and testing instruments, XRD, TEM and TG-DTA.APT as precursor, ultra-fine WO₃ was yielded by calcination, hydrochloric acid acidification-deposition and hydrothermal, respectively. Hydrothermal crystallization is in favor of forming hexagonal WO₃ and integrity crystal, but the granularity of product is from 0.25 to 1.2 μm due to soft-aggregation.H₂WO₄ as start material, ultra-fine WO₃ was prepared by calcination and hydrothermal. The granularity of product was between 0.03 and 0.15 u m. Hydrothermal temperature effects granularity of produa. The temperature higher, the granularity bigger.Tungsten trioxide and its hydrates were synthesized by hydrothermal method, peroxotungstic acid as precursor, which using a route based on the dissolution of tungsten metal powder in an excess of hydrogen peroxide solution (30%)to give. Theresults indicated that granularity, the distribution of granularity and the B.E.T. were influenced by some factors in preparation of precursor. Hydrothermal treatment temperature and time had great effects on the phase, morphology and particle size. In case of inadequate treatment temperature or time, orthogonal WO3-0.33H2O and monoclinic WO3 were yielded. And orthogonal WO3-0.33H2O disappeared in condition of higher temperature or adequate time. It seems that hydrothermal crystallization treatment is benefit to form hexagonal phase of WO3, and high temperature and long time help to a high degree of crystallization. In addition, hexagonal WO3 is apt to transform to monoclinic WO3 according to higher temperature or longer time. The characterization showed that WO3 powder between 35 and 120nm was yielded by this method and the particle was regular. However, the upper heat treatment increases the granularity and forms monoclinic WO3 to a greater extent.WO3 prepared by hydrothermal is smaller than that by calcination. Hydrothermal is benefit to form semi-steady hexagonal WO3, which provides a good base for its application in Li-batteries.