溶液燃烧合成纳米钨基材料及性能研究

发布时间：2018-01-26 02:43

  本文关键词： 溶液燃烧合成 纳米材料 钨基材料 光催化性能 氧化物弥散强化　出处：《北京科技大学》2017年博士论文　论文类型：学位论文

【摘要】：纳米钨基材料由于其独特的理化特性被广泛应用于催化、电子、航空航天、国防军工等众多领域。溶液燃烧合成是近年来发展迅速的一种制备纳米材料的新的湿化学方法,具有简便、快捷、能耗小、成本低、产物活性高等诸多优点。本论文研究将低温燃烧合成应用于纳米钨基材料的制备。主要研究了以下几个方面的内容：(1)研究了燃料种类、配比等参数对燃烧反应的过程、机理以及产物的结构、形貌、物相的影响,成功通过一步燃烧法合成了单相的WO_ 3、W_(18)O_(49)。在甘氨酸、尿素/柠檬酸混合为燃料的两种燃烧体系中,反应过程中可形成了泡沫状网络结构,制备出直径小于100nm,长度为5μm左右的纳米针状纯相W_(18)O_(49)。单独采用尿素作为燃料时,制备出了粒径小于100nm颗粒状纯相WO_ 3。所制备纳米氧化钨具有优异光催化性能,能够在50min内将40ppm的MB溶液降解完全。(2)通过引入掺杂元素,利用溶液燃烧法制备出掺杂氧化钨粉体材料,可进一步提高其光催化性能。通过在燃烧体系中引入硝酸铁作为铁源,首次利用溶液燃烧合成一步制备Fe~(3+)掺杂W_(18)O_(49),Fe与W_(18)O_(49)的光反应协同作用以及掺杂造成的缺陷使其催化性能提高。在Fe~(3+)掺杂量为0.5wt%时,得到的复合粉末的光催化性能最好,能够在30min内将40ppm的MB溶液降解完全。通过在燃烧体系中引入葡萄糖作为碳源,利用溶液燃烧法制备出无定型C复合WO_ x粉体,在碳复合与缺陷结构的协同作用下,C复合WO_ x粉体材料可以在40min内将80ppm的MB溶液降解完全,并呈现出优异的循环稳定性。(3)通过在燃烧体系中引入硝酸镧作为稀土源,首次利用溶液燃烧法制备出粒度细小、掺杂均匀的氧化钨与稀土氧化物的复合前驱体。以该前驱体为原料,在700℃的氢气气氛中还原2小时,制备出粒径为20-30nm、分散性好、氧化镧掺杂均匀的钨基粉末。(4)所制备氧化镧掺杂钨基(La_2O_3—W)粉末具有很高的烧结活性,在1500℃下烧结可达到95%以上的致密度。随着氧化镧含量的增加(氧化镧含量在0～1%范围内),晶粒尺寸减小。随着温度的升高,材料的显微硬度先上升后下降,在1500℃呈现出最大值。对于La_2O_3含量为1.0%样品,在1500℃烧结,材料晶粒尺寸为300～500nm,第二相粒子尺寸小于50nm,分布均匀,显微硬度达到703HV_(0.2),力学性能优异。
[Abstract]:Nanocrystalline tungsten based materials have been widely used in catalysis, electronics and aerospace due to their unique physical and chemical properties. Solution combustion synthesis is a new wet chemical method for the preparation of nanomaterials in recent years. It is simple, fast, low energy consumption and low cost. In this paper, low temperature combustion synthesis was applied to the preparation of nanocrystalline tungsten-based materials. The single phase WO _ 3 was successfully synthesized by one-step combustion method with the influence of the ratio and other parameters on the process, mechanism, structure, morphology and phase of the product. In the combustion systems of glycine and urea / citric acid, the foam network structure can be formed during the reaction, and the diameter is less than 100 nm. When using urea alone as fuel, the nanoscale needle-like pure phase WA18 / O _ (9) is about 5 渭 m in length. The pure phase WO _ 3 with particle size less than 100 nm was prepared. The prepared nanocrystalline tungsten oxide has excellent photocatalytic performance. The 40 ppm MB solution can be completely degraded within 50 min.) doped tungsten oxide powder materials were prepared by solution combustion method by introducing doping elements. By introducing ferric nitrate as Tie Yuan in combustion system, Fe~(3 was synthesized by solution combustion for the first time. The synergistic effect of Fe and W _ S _ (18) O _ (9) and the defects caused by doping can improve its catalytic performance. When the doping amount of Fe~(3 is 0.5 wt%. The composite powder has the best photocatalytic performance and can completely degrade 40 ppm MB solution in 30 min. Glucose is introduced as carbon source in combustion system. Amorphous C composite WO _ x powder was prepared by solution combustion method. C composite WO _ x powder can completely degrade 80 ppm MB solution in 40 min. And showed excellent cycle stability. 3) by introducing lanthanum nitrate as rare earth source in combustion system, the particle size was prepared by solution combustion method for the first time. The composite precursor doped with tungsten oxide and rare earth oxide was prepared by reducing the precursor in hydrogen atmosphere at 700 鈩，

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