Study On The Structure, Properties And Formation Mechanism Of Several Kinds Of Low-dimensional Vanadium Oxide Nanomaterials

In this dissertation, hydrothermal method was developed to fabricate low-dimensional vanadium oxide nanomaterials. A series of controllable and novel routes were developed to synthesize various vanadium oxides with low dimension, such as vanadium oxide nanotubes (VOx-NTs), vanadium dioxide nanorods, nanowires and nanoplatelets. Different analysis and characterization technologier were utilized to study the relationship among components, structure and properties of low-dimensional vanadium oxide nanomaterials. Now sum up us fellows.(1) Multi-walls vanadium oxide nanotubes with length of 1-10 urn, inner diameter of 10~30nm, outer diameter of 50-100nm were synthesized via a sol-gel method with subsequent hydrothermal reaction. Electrochemical tests results show that the first charge and discharge capacities for VOx-NTs are 200mAh/g and 185mAh/g, respectively, which are obvious higher than other vanadium deprived cathode materials. This could be ascribed to the more intercalation space and better thermodynamic intercalation sites for Li+ in the nanotubes. Since of the existent of organic template molecules, the discharge capacity decrease to 120mAh/g after 10 cycles. The well-resolved photoluminescence band at 450-550 ran is discovered in VOx-NTs, which could lead to a calculated band gap of 2.7 eV. We note that the 3-2-ID mechanism is responsible for the self-assembly of VOx-NTs. We obtained VOx-NTs modification with MoO3. It was found that Mo doping changes the growth dynamics of the nanotubes, and results in bigger interlayer spacing and shorter diffusivity distance and better electrochemical performances.(2) VO2 (B) nanords with length of l~2um, diameter of 30~60nm, and the diameter of the nanorod were synthesized via reaction of V2O5 or V2O5 sols with CTAB in a one-step hydrothermal methods. The initial discharge capacity of VO2(B) nanorods is 306mAh/g, after 15 cycles, the nanorods even show a discharge capacity of 245 mAh/g. By started from V2O5 and ethylene glycol, or NH4I and oxalic acid, well defined B phase vanadium dioxide nanorods were also obtained. We give possible formationmechanisms of VO2(B) nanorods fabricated though different synthetic approaches.(3) By using the simple hydro thermal method, syntheses of vanadium dioxide nanowires, hydrated vanadium oxide nanowires, NH4V4O10 nanorods and vanadium dioxide nanoplatelets were carried out though reaction of V2O5 with 1, 2-Propanediol carbonate, Poly (ethylene glycol), NH4I and glycerol respectively, which enrich the low-dimensional vanadium oxide nanomaterials system.