The Preparation Of Vanadium Dioxide Powder By Hydrothermal Method

Vanadium dioxide (VO2),as a new type of functional material, is a kind of metaloxide with low temperature phase change properties.It change reversiblely fromsemiconductor phase to the metallic phase in68℃. And physical properties such aselectrical resistivity, magnetic susceptibility and spectral transmittance and physicalproperties make mutation. Among the transition temperature of metalcompounds,VO2is the most close to room temperature at the same time.As a solidfoundation for VO2to be energy-saving materials can be reduced the ransitiontemperature by doping under to r room temperature..At present, the relevantresearches focuse on by sputtering method, sedimentary method or the sol gel methodand direct preparation of VO2thin film, V2O5reductes into VO2, or using vanadiumsputtering target directly.But the process is hard to be controlled,and the finishedproduct can not be guaranteed and impurity. Using VO2powder as raw materialsmake the film products. Fine-grained VO2powder significantly reduce the stress ofphase change material, and with the decrease of the granularity, and the lighttransmittance. To increase the product practicality. This experiment adopts thehydrothermal method preparation of VO2powder, through different reductant toreduce reaction of V2O5, The best reductant is found out by changing the additives,temperature, time, annealing treatment, PH and other process parameters, study theeffect of these parameters reduction reaction, the final reduction product are analyzedby X-ray diffraction (XRD), transmission electron microscopy (TEM).The results show that among the oxalic acid, phenethylamine and NaHSO3asreductant, oxalic acid is best reductive. In the same process,Al2O3is the best obviousamong the Urea, tungsten acid and Al2O3as additive. Change the solution pH, whenthe solution is weakly acidic reduction effect of V2O5is best.The grain growth of neat,good crystallization, uniform grain. After the vacuum nitrogen protection in thetemperature of450℃or550℃, VO2(M) is reduced in550℃, with hot qualitativechange effect. In the preparation of producting VO2(M),The best reductant is oxalicacid, The best additive is Al2O3,The best temperature is200℃, the best heatpreservation time is10h,The best annealing temperature is550℃.