Hydrothermal And Microwave Hydrothermal Synthesis Of Tungsten Oxide Nanopowders With Controllable Morphology

As a member of the novel semiconductor materials, tungsten oxide has been under an extensive research in recent years for its unique physicochemical properties. It has been widely used in many different applications, such as electrochemical windows, optical devices, fuel cells, gas sensors, and photocatalyst materials, etc. As is known, the morphologies and structures of the materials have great influence on their properties. So it is important to study in detail the preparation and physicochemical properties of tungsten oxide nano-materials.In this paper, nanoscale tungsten oxide powders were prepared by hydrothermal and microwave hydrothermal(MH) methods, respectively. The analysis reagent Na2WO4·2H₂O was used as starting material. The obtained powders were characterized by XRD,SEM, TEM, EDS, respectively. The effects of the preparation conditions on the structure, morphology and particle size of products were explored in details and the conditions of preparation special morphologies (rod-like, sphere-like, square-like and hexagonal-like) nanoscale tungsten oxide powders were obtained. The impact of the mass of assisted agent, pH value, reaction temperature, reaction time et al on the nanoscale tungsten oxide powders were also studied. The contents of this work contain six parts:1. Prospect and applications for tungsten oxide were discussed. Hydrothermal and microwave hydrothermal methods were introduced in detail. Recent development of MH in synthesizing oxides and sulphides were also reviewed.2. The agents and equipments used in experiments were introduced, the synthesis method and characterization results of the powders were displayed.3. Nanoscale tungsten oxide powders were obtained by hydrothermal and microwave hydrothermal method via assembly of tartaric acid and citric acid. The effects of the preparation conditions on the structure, morphology and particle size of products were explored in details. The obtained powders were characterized by XRD,SEM, TEM respectively. Rod-like WO₃·H₂O was obtained by MH at low power for 20 min without tartaric acid assisted, sphere-like WO₃·2H₂O was obtained with tartaric acid assisted, WO₃·H₂O nanoparticle was obtained when citric acid was added. Conventional hydrothermal could get WO₃ nanoparticle without assisted, rectangle-like WO₃ was obtained with tartaric acid assisted; square-like WO₃ was obtained with citric acid assisted.4. Nanoscale tungsten oxide powders were obtained by hydrothermal and microwave hydrothermal method via assembly of p-nitrobenzoic acid and p-aminobenzoic acid. The effects of the preparation conditions on the structure, morphology and particle size of products were explored in details. The obtained powders were characterized by XRD,SEM, respectively. Rod-like WO₃ was obtained by MH at middle power for 15 min with citric acid assisted. Hexagonal-like WO₃ was obtained with p-nitrobenzoic acid and p-aminobenzoic acid assisted, all of the powders belong to hexagonal crystal series WO₃.5. Nanoscale tungsten oxide powders were obtained by hydrothermal and microwave hydrothermal method via assembly of urea and thiourea. The effects of the preparation conditions on the structure, morphology and particle size of products were explored in details. The obtained powders were characterized by XRD,SEM, EDS, respectively. Square-like monocline crystal series WO₃ was obtained by Hydrothermal with urea assisted; sphere-like hexagonal crystal series WO₃ was obtained by hydrothermal with thiourea assisted.6. Summary for the contents of this paper was discussed, also addressed was the prospect of the development of our work based on the current experiments.