Synthesis Of Vanadium Oxides Based Micro-nanostructures And Their Properties

The goal of this dissertation is to develop novel chemical reaction routes for controlling synthesis of vanadium oxides based micro-nanostructures with novel morphologies via deep analysing the crystal structural characteristics of the objective products and study the corresponding performance of the synthetic vanadium oxides based micro-nanostructures, such as electrical transport, magnetism, and electrochemical property as active anode electrode material. Also, the related structure-property relationships have been also reasearched in this dissertation. The further details are summarized briefly as follows:1. We synthesized barnesite Na2V6O16·3H2O nanobelts and nanorings coiled by nanobelts by a simple and novel cost-effective low-temperature solution route successfully, and also find out room temperature ferromagnetism in the product for the first time. The XPS spectra, and the hysteresis loops of the sample before and after annealing both demonstrate that the origin of ferromagnetism in Na2VeO16·3H2O product are attributed to the introduction of oxygen vacancies. The polarization-induced self-coiling of in-situ formed Na2V6O16·3H2O nanobelts is responsible for the formation of the perfectly circular nanoring geometry and may useful to investigate polar surface-induced growth processes, fundamental physics phenomena, and the design for nanoscale devices. In the meantime, the similar way to successfully synthesis K2V6O16·5H2O nanobelts and (NH4)2V6O16·5H2O nanorings both further demonstrate the formation mechanism, pave the way for the design of nanorings.2. Inspired by the fonner work, the new vanadium oxide compound K2V6O16·5H2O nanobelts with room temperature ferromagnetism have been synthesized by a simple low-temperature hydrothermal way, and also confirmed as a novel semiconductor with the band gap of1.95eV theoretically and experimentally for the first time. Experimently, the XPS spectra, and the hysteresis loops of the sample before and after annealing both demonstrate that the origin of ferromagnetism in synthetic K2V6O16·5H2O nanobelts are attributed to the introduction of oxygen vacancies into crystal structure during solution fabrication process. In the mean time, our results are consistent with density-functional calculations theoretically showing that oxygen vacancies lead to ferromagnetism.3. Herein, the aligned superlong barnesite Na2VeO16·3H2O nanobelts film electrode is realized as dense and thick film for the first time by a convenient solution route, providing a new strategy to synthesize aligned nanobelts film electrodes. Thereinto, the Na2V6O16·3H2O nanobelts with length of100-200μm growing along [010] is fabricated successfully, and the superlong single nanobelt enables the first investigation of electrical transport property. Encouragingly, the individual nanobelt with aspect ratios exceeding1000has a high conductivity of～100S·m-1. Furthermore, the synthetic aligned superlong barnesite Na2V6O16·3H2O nanobelts film electrode displays enhanced anisotropic electrical transport property and good electrical conductivity, presenting an ideal candidate as nanoelectrode.4. Haggite V4O6(OH)4hierarchical micro-nanostructures have been first successfully synthesized via one-step facile hydrothermal route using polymer poly vinyl pyrrolidone (PVP, K30) as capping reagent after sixty years later. Due to the synergetic effect of the microscopic layered crystal structure and macroscopic morphological features, which provide the easy infiltration of electrolyte, short diffusion lengths for lithium ions and electron transport, the walnut like V4O6(OH)4micro-nanostructures have been applied as the novel electrode material in aqueous lithium ion batteries for the first time.