Research On The Preparation And Properties Of Nano Vanadium Oxide Materials

Vanadium oxides have attracted tremendous interest due to their excellent properties and applications in a wide range of fields. For example, vanadium pentoxide (V2O5) exhibits properties such as chemical sensing, photochromism and catalysis, and is a candidate material for applications in electronic information displays, electrochromic devices, optical-electrical switch and color memory devices, etc., Since materials having reduced dimensions may possess interesting properties that are very different from their bulk states, efforts have been directed recently to the synthesis of nanostructures of vanadium oxides and to the study of their structure-property relationships.In this dissertation, the low-dimensioned Vanadium Oxide nanomaterials were chosen as the objects. Some modern methods were used to study the preparation, structure and properties of low-dimensioned Vanadium Oxide nanomaterials. The main results are as follows:(1) VO₂ of a BCC structure: a new phase in the vanadium oxides systemFilms of aligned rods of vanadium oxides were deposited by heating a sheet of vanadium in a rough vacuum. Careful identification indicates that the rods are VO₂ with a body-centered-cubic structure. Due to the cone shape, they exhibited good field emission property. Upon heating in air at 400oC, the VO₂ rods were oxidized into V₂O₅, which induced intense visible light emission.(2) Synthesis and optical properties of V2O5 nanorodsTwo-step method was proposed to synthesize V2O5 nanorods on planar substrates. The V₂O₅ nanorods are single crystalline and could emit intense visible light at room temperature. This study provides a simple and low-substrate temperature route to fabricate V2O5 nanorods on planar substrates, which might be also applicable to other metal oxides.(3) Optical properties adjustment of V2O5 films by"Defect Engineering"The effect of optical properties with different heat-treatment of V₂O₅ films has been investigated. The relationship of the heat-treatment process on the red PL has been studied in detail. We find the photoluminescence property can be modified by different heat-treatment process. Meantime, the photosensitivity property is also changed. By calculation of the ab initio simulation and positron annihilation method, the PL property can be concluded caused by the Oxygen vacancies.(4) The influence of the strong magnetic fieldThe heat-treatment in strong magnetic field has been investigated. The result shows that the crystallization and PL property will both be modified by magnetic field. Stronger the magnetic field, harder could the nanorods grow, and weaker could the PL intensity be.