温和条件下不同形貌氧化钨的控制合成及其气敏性能研究

发布时间：2019-05-17 16:05

【摘要】：能够有效地对无机化合物的结构、尺寸和形貌进行控制,是制造各种纳米器件非常重要的前提条件。半导体传感器具有反应灵敏、寿命长等优点,为了进一步提高半导体传感器的性能,科研工作者进行了大量研究工作,如采用化学手段对半导体氧化物的结构、尺寸和形貌进行控制。三氧化钨具有特殊晶体结构和物理及化学性质,通过不同的方法制备具有特殊维度结构的三氧化钨粉体材料的研究比较广泛,但都存在可控性低、生产效率低、工艺复杂等缺点。因此通过一种操作简单、成本较低、具有产业化前景的方法,获得具有可控纳米尺寸、形貌均匀的WO3纳米材料仍然很有难度。如果能够通过分析生长机理和讨论形貌的特性,来进一步优化纳米材料的结构、提高制备工艺的稳定性、改善气敏性能的应用,会是一项很有意义的研究。本课题的主要工作为通过添加模板和辅助剂的水热法、水浴法等制备方法,控制合成不同维度、不同形貌的的氧化钨纳米材料,通过XRD、SEM、TEM、HRTEM和SAED等表征测试手段对材料的微观结构和微观形貌进行表征,结合晶体结构分析软件Diamond等来辅助探讨生长机理,测试不同微观结构的三氧化钨粉末对于乙醇等不同气体在不同浓度、不同温度等条件下的气敏响应,得到其最佳工作温度、灵敏度、选择性、检测极限和稳定性气敏性能参数,分析微观结构对于气敏性能的影响。课题旨在通过对合成工艺的研究和改进,找出较为简便的制备一维和二维等低维度的氧化钨基纳米材料可控生长的方法,探讨其生长机理并对气敏性能的解释和提高提供指导。另外,还优化制备工艺,控制合成了具有纳米分级结构的氧化钨纳米材料,探讨分析其生长机理并测试其气敏性能,讨论分级纳米结构对于气敏性能的影响和改善作用,为复杂结构的三氧化钨的控制合成和改性研究提供参考。本文的主要结论如下:①一维纳米线状氧化钨:在水热条件下通过添加适量的Na2SO4和K2SO4为封端剂来控制合成单分散的h-WO3纳米线,其能够一维定向生长的原因是由于Na+和K+离子的存在而造成的各向异性生长以及SO42-离子的吸附作用。这种粉末对于乙醇和甲醛这两种有毒有害气体表现出很好的气敏性能,在300 oC的条件下对于10 ppm两种气体的响应灵敏度可以达到10以上,并且具有很好的选择性,具有较高的应用潜力。②二维纳米片状氧化钨:通过水热法添加苹果酸(C4H6O5)控制合成规则的单分散WO3·H2O纳米片状结构,苹果酸在晶面上的选择性吸附是形成纳米片的重要原因,(010)为主要暴露面,其厚度可以通过调节反应时间来控制,苹果酸在(010)晶面上的选择性吸附和不同反应时间导致了不同厚度的WO3·H2O纳米片的生成。气敏性能测试证明两种厚度分别为20~30 nm和~100 nm的粉末制备的传感器具有很好的气敏性能,在300 oC对于100 ppm的乙醇气体的响应灵敏度分别为29.8和26.1,进一步对比分析得知薄的WO3·H2O纳米片粉末由于具有更多(010)晶面暴露,反应活性更高,因而表现出更好的气敏性能。③三维分级结构的氧化钨:在水热或水浴条件下可以控制合成多种三维分级结构的WO3粉体材料,讨论其生长机理并证明它们优越的气敏性能。以C微球为模板通过水热法制备C/WO3复合亚微球,并通过进一步烧结得到了具有介孔结构的WO3亚微球,这种亚微球具有较大的比表面积(22.2 m2/g),且对乙醇气体有显著的气敏响应,对50 ppm的乙醇气体的响应可以达到17.7。此外,通过采用添加K2SO4辅助的水热法成功地制备海胆状六方h-WO3微球结构,比较发现K2SO4对海胆状结构的形成起了很大的作用,气敏测试显示,300 oC时对400 ppm乙醇的响应灵敏度可以到达17。另外还成功通过草酸辅助的水浴法制备WO·H2O纳米花结构,发现在W/C比为1:1.6时制备的WO3·H2O具有最好的结晶性能和更好的组装的纳米花状结构。实验证明三维分级结构对于提高比表面积、避免纳米颗粒的聚集、提高气敏性能具有很好的促进作用。
[Abstract]:Can effectively control the structure, the size and the appearance of the inorganic compound, and is a prerequisite for manufacturing various nano-devices. The semiconductor sensor has the advantages of sensitivity, long service life and the like, and in order to further improve the performance of the semiconductor sensor, the scientific research worker has carried out a lot of research work, such as controlling the structure, the size and the appearance of the semiconductor oxide by adopting a chemical method. The tungsten trioxide has a special crystal structure and physical and chemical properties, and the preparation of the tungsten trioxide powder material with the special dimension structure is widely used through different methods, but the defects of low controllability, low production efficiency, complex process and the like exist. Therefore, the WO3 nano material with controllable nanometer size and uniform appearance is still difficult to obtain through a method of simple operation, low cost and industrialization prospect. If the structure of the nano-material can be further optimized by analyzing the growth mechanism and the characteristics of the morphology, the stability of the preparation process can be improved, and the application of the gas-sensitive performance can be improved. The main work of the project is to control the synthesis of tungsten oxide nano-materials with different dimensions and different shapes by means of a hydrothermal method, a water bath method and the like of a template and an auxiliary agent, The microstructure and micro-morphology of the materials were characterized by HRTEM and SAED, and the growth mechanism was studied by using the crystal structure analysis software Diamond and the like. The optimum operating temperature, sensitivity, selectivity, detection limit and stability gas-sensitive performance parameters were obtained under different temperature and other conditions, and the effect of microstructure on gas-sensitive performance was analyzed. The purpose of this paper is to find a simple and convenient method for the controllable growth of tungsten oxide-based nano-materials, such as one-dimensional and two-dimensional, through the research and improvement of the synthesis process, to study the mechanism of growth and to provide guidance for the interpretation and improvement of gas-sensing performance. in addition, the preparation process is optimized, the tungsten oxide nano material with the nano-grade structure is synthesized, the growth mechanism of the tungsten oxide nano material is analyzed, the gas-sensitive performance of the tungsten oxide nano-material is tested, the influence and the effect of the graded nano-structure on the gas-sensitive performance are discussed, And provides a reference for controlling synthesis and modification of tungsten trioxide with complex structure. The main conclusions of this paper are as follows:1-D nano-wire-like tungsten oxide: the h-WO3 nanowires are controlled by adding appropriate amount of Na2SO4 and K2SO4 as a blocking agent under the hydrothermal condition, The reason for its one-dimensional directional growth is the anisotropic growth due to the presence of Na + and K + ions and the adsorption of SO42-ions. The powder has good gas-sensing performance for the two toxic and harmful gases of ethanol and formaldehyde, and the response sensitivity of the two gases can be more than 10 for 10 ppm under the condition of 300 DEG C, and has good selectivity and high application potential. A two-dimensional nano-sheet tungsten oxide is prepared by adding malic acid (C4H6O5) by a hydrothermal method to control the monodispersed WO3 路 H2O nano-sheet structure of the synthesis rule, the selective adsorption of the malic acid on the crystal face is an important reason for forming the nano sheet, (010) is the main exposed surface, The thickness can be controlled by adjusting the reaction time, and the selective adsorption and the different reaction time of the malic acid on the (010) crystal plane result in the generation of WO3 路 H2O nanosheets with different thicknesses. The gas-sensitive performance test shows that the two kinds of sensors with the thickness of 20-30 nm and ~ 100 nm have good gas-sensing performance. The response sensitivity of the 300 oC for 100 ppm ethanol gas is 29.8 and 26.1, respectively. Further comparison and analysis revealed that the thin WO3 路 H2O nanosheet powder exhibited better gas-sensing performance due to the higher exposure of the (010) crystal face and higher reactivity. The tungsten oxide of a three-dimensional hierarchical structure can be controlled under hydrothermal or water-bath conditions, and the growth mechanism of the WO3 powder material can be controlled and the excellent gas-sensing properties of the WO3 powder material can be proved. the C/ WO3 composite submicroballoon is prepared by a hydrothermal method by using the C microsphere as a template, and the WO3 submicroballoon with the mesoporous structure is obtained by further sintering, The response to 50 ppm of ethanol gas can reach 17.7. In addition, the formation of the sea urchin-like hexagonal h-WO3 microballoon was successfully prepared by the addition of K2SO4-assisted hydrothermal method, and it was found that K2SO4 had a great effect on the formation of the sea urchin-like structure. The sensitivity of the response to 400 ppm of ethanol at the time of 300 oC can reach 17. In addition, the WO 路 H2O nano-flower structure was successfully prepared by the oxalic acid-assisted water bath method, and it was found that WO3 路 H2O prepared at the W/ C ratio of 1: 1.6 has the best crystallization property and better assembled nano-flower structure. The experimental results show that the three-dimensional hierarchical structure can improve the specific surface area, avoid the aggregation of the nano-particles, and improve the gas-sensing performance.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1;O614.613

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