【作者】 杨丰；

【导师】 贺德衍；

【作者基本信息】 兰州大学 ， 凝聚态物理， 2010， 博士

【摘要】 一维纳米材料由于有独特的结构和性能以及巨大的应用前景,成为当前材料科学的研究重点之一。本论文采用水热法合成了W03和M003一维纳米结构。利用XRD、SEM、RAMAN、FTIR等研究了合成产物的形貌和微观结构,阐明了生长参数对WO3和MoO3一维纳米结构的影响,探讨了它们的生长机制并对它们的应用展开研究。1.用水热法合成了h-WO3纳米线,研究了实验条件对产物的影响,并分析了纳米线的生长机制。以WO3纳米线为正极材料组装了锂离子电池,对其充放电性能进行了系统的研究。当放电电流为0.05 mA／cm2时,放电平台在2.25V左右,第二次放电比容量可达到264 mAh／g,循环15次之后,放电容量达到平稳,但容量仅为75 mAh／g,整个循环过程库仑效率均保持在90%以上。分别测试了不同电压工作窗口的循环性能,结果表明在1.0-4.0 V区间内,该电池充放电性能最好。2.制备了单根W03纳米紫外探测器,发现合成的h-W03纳米线为n型半导体材料。我们分别测试了探测器对不同波长光的响应谱,观察到探测器对波长为312 nm的紫外光灵敏度最大。探测器在功率为2 mW／cm2,激发波长为312 nm的紫外光辐照下,表现出高的灵敏度和良好的可重复性。分别测试了欧姆接触型探测器和肖特基接触型探测器的光电导性能,发现肖特基势垒可以极大提高紫外探测器的灵敏度和响应速度。3.用简单的水热法合成了宽度约为200 nm,厚度20 nnm,长度达到5μm的a-MoO3纳米带。分析了反应温度、反应时间、反应溶液PH值对产物形貌和结构的影响。结果表明,在反应温度为80℃时,反应过程中存在过渡相产物h-MoO3微米六棱柱。以a-MoO3纳米带为正极材料组装了锂离子电池,研究了其充放电性能。放电电流为0.02 mA／cm2时,在2.0 V左右存在一个平稳的放电平台,且第二次放电比电容量可以达到315 mAh／g。a-MoO3纳米带电极表现出优异的循环性能,经过30次循环后容量仍然能够保持在180 mAh／g。测试了不同电压工作窗口的循环性能,结果表明,在1.2-3.8 V区间内,锂离子电池充放电性能最好。更多还原

【Abstract】 One-dinmensional (ID) nanomaterials have been significantly attracted attentions due to their unique structure and properties. In this paper, 1D WO3 and MoO3 were synthesized by hydrothermal method. Morphologies and microstructures of as-synthesized products were characterized by XRD, SEM, RAMAN, FTIR. Effect of growth parameters on nanostructures was clarified, growth mechanisms of the nanostructures were discussed.h-WO3 nanowires have been synthesized by hydrothermal method. Any one different experimental parameters can lead to the different structures and morphologies of the final products in this experiment. The electrochemeical performances of the as-synthesized h-WO3 nanowires as anode materials of Li-ion batteries have been investigated. For h-WO3 nanowires electrode, the second diacharge capacity at current density of 0.05 mA/cm2 arrived at 264 mAh/g. After 15th cycles, the discharge capacity can reach a steady state. The mean coulombic efficiency of h-WO3 nanowires electrode during the the charge/discharge test at current density of 0.05 mA/cm2 is more than 90%. The electrochemecial performance of h-WO3 nanowires electrode is the best between 1.0-4.0 V.Ultraviolet (UV) photodetectors were fabricated based on individual WO3 nanowires. Electrical transport measurements show that the as-synthesized h-WO3 nanowires are of n-type semiconductors. The divice characteristics, including spectral response and time response, were studied systematically. It is found that the WO3 nanowires showed the higest light sensitivity at 312 nm. And the photodetectors show high stability and reversibility to 312 nm UV light with an intensity of 2 mW/cm2. The Shottky type (ST) photodetectors and Ohmic type (OT) photodetectors have been investigated. The result shows that the sensitivity and response rate have been improved by shottky contact.α-MoO3 nanoribbons have been synthesized by a simple hydrothermal method. The as-synthesized products were up to 5μm in length,200 nm in width,20 nm in thickness. The influence of hydrothermal temperature, reaction time and PH value on the structure and morphology of the products have been investigated, when the hydrothermal temperature was 80℃, the metastable h-MoO3 microrods were formed firstly. Electrochemical properties ofα-MoO3 nanoribbons electrode were studied. The second diacharge capacity at current density of 0.02 mA/cm2 arrived at 315 mAh/g and there is a plateaus at around 2.0 V, respectively, maintaining 180 mAh/g after 30 cycles. The electrochemecial performance ofα-MoO3 nanoribbons electrode is the best between 1.2-3.8 V.更多还原