Research On Preparation And Applications Of Vanadium Based Nanomaterials By Low Temperature Combustion Synthesis

Vanadium based nanomaterials present some unusual light, electricity, heat or magnetism properties. Up to now, they have benn applied in the area of energy, catalysis, alloy, and so forth. In recent years, low temperature combustion synthesis (LCS) is emerging as a new wet-chemical method for the preparation of nanopowders. This process is time-and energy-efficiency, simple and low-cost. In this paper, LCS methord was used to prepare vanadium based nanomaterials. The main research work of the paper focused on several aspects as follows:(1) The influence of various combustion parameters, i.e., fuel and oxidant styles, atmospheres, and lighting conditions. on the synthesis of vanadium oxides have been studied in detail. Various nanoscale vanadium oxides powders with pure phases (V2O5, VO2, and V2O3) have been synthesized by one-pot LCS method. When the citric acid/glycine is 4. VO2 nanoparticles with special surface area of 18.5 m2·g-1 and an average size of 15?20 nm can be synthesized. The DSC curve substantiates the typical phase transition of VO2 between the monoclinic phase and the rutile phase. Combustion synthesis in an inert atmosphere can result in low-valent vanadium oxides. The combustion product, prepared in N2 atmosphere, comprises of well-distributed nanoparticles of V2O3 with the average size ranging from 40 to 80nm. The single crystalline V2O5 sheet with lateral dimensions of 4-6?m is synthesized with urea as fuel. As a cathode materials for lithium-ion batteries, the V2O5 sheets delivers capacity of 234 mAh·g-1 and the coulombic efficiency remains close to 100% after 50 cycles.(2) The VOx/C composites were first successfully prepared by one-pot LCS methord with introducing glucose into solution as a carbon sources. The influences of contents of glucose on the composition and morphology of the VOx/C composites were investigated. When the glucose/ammonium metavanadate is 0.2, the amorphous mixed-valence VOx/C composites can be synthesized by the easy one-step LCS method. The as-prepared VOx/C composites exhibit 2D porous sheet structures, in which small VOx particles encapsulated in carbon sheets. Upon evaluating the material as an anode material for lithium-ion batteries, it exhibits excellent reversible capacity (1088 mAh·g-1 at 0.1 A·g-1 after 100cycles,776 mAh·g-1 at 1 A·g-1 after 400 cycles).(3) The VN material has been synthesized by ammonia reduction of the precursor prepared by LCS. The influences of precursors with different valences on the ammonia reduction process and the synthesis of VN products were investigated in detail. The results showed that precursors with different valence have great influences on the phase change process. the composition and morphology and electrochemical property of the VN products. For the VO2 precursor, it is reduced to V5O9(400?), V2O3(500 ?) and VO0.9 (600 ?) step by step, and the single-phase VN powders comprised of nanoparticles ranging from 30 to 40 nm can be synthesized at 700? for 2 h. In the mode of V2O5 precursor, it is reduced to VO2(400?), the mixture of VO2 and VO (500?) and VO0.9 (600 ?) step by step, and then nitrided to VN at 700? for 2 h. The VN sample prepared by V2O5 precursor is comprised of nanoparticles ranging from 30 to 40 nm. Upon evaluating the VN as an electrode material for supercapacitors, the VN powers prepared with VO2 precursors exhibites specific capacitance of 83 F·g-1 at 0.1 A·g-1.(4) The VN/C composites have been synthesized by ammonia reduction of the precursors prepared by LCS, and the influences of contents of glucose and ammonia reduction parameters on the VN/C products were investigated. The ammonia reduction parameters have been optimized and the as-prepared VN/C powers exhibit excellent electrochemical properties. When the glucose/ammonium metavanadate is 1, the VN/1C-600 composites with special surface area of 21.1 m2·g-1 and an average size of 7-10 nm can be synthesized. The VN/1C-600 as an anode material for lithium-ion batteries shows well reversible capacity (712 mAh·g-1 at 0.1 A·g-1 after 100 cycles,650 mAh·g-1 at 1 A·g-1 after 500 cycles). Increasing the ammonolysis temperature to 700 ?, the VN/1C-700 sample with special surface area of 29.2 m2·g-1 and an average size of 9-13 nm can be synthesized. Upon evaluating the VN/1C-700 as an electrode material for supercapacitors. it exhibits specific capacitance of 196,139,123,110. 102 and 78 F·g-1 respectively at 0.1.0.25.0.5,1,2 and 5 A·g-1.