氧化钼微结构控制合成及气敏性能

发布时间：2018-02-14 11:16

本文关键词： 三氧化钼微纳结构三甲胺气敏性能　出处：《天津理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：Mo O3是禁带宽度为3.3 e V的n型半导体氧化物,近年来因其对易燃易爆有毒气体优良的气敏性能而得到了人们的广泛关注。Mo O3常见物相有正交相(α-Mo O3)、六方相(h-Mo O3)和单斜相(β-Mo O3)三种,其中正交相是热力学稳定相,六方相与单斜相是热力学介稳相。本文利用条件温和的水浴法和水热法,在不添加表面活性剂的条件下,合成了h-Mo O3和α-Mo O3微结构,并研究了其气敏性能。利用条件温和的溶液法,以浓硝酸酸化的钼酸铵饱和溶液为初始反应物,通过改变反应介质的水醇比和反应时间,65oC水浴下制备出不同形貌的h-Mo O米棒。利用所制备的h-Mo O3微米棒作为基体制备烧结型气敏传感器件,340oC的工作温度下对不同浓度的三甲胺气体进行气敏性能测试。结果表明,水醇比为15:15、反应时间为30 min时制备的样品气敏性能最好,器件对500 ppm的三甲胺气体测量灵敏度可达95.2,响应时间和恢复时间分别为10 s和7 s。尤其是,在这种反应条件下制备的h-Mo O3对低浓度的三甲胺有着良好的气敏性,当三甲胺气体浓度为1 ppm时,其灵敏度仍可达2.61。这种良好的气敏性能可能是由于反应介质中无水乙醇的加入,使得到的h-Mo O3六棱柱表面出现层片状结构;且反应时间适中,所得到的h-Mo O3尺寸适中,因而使得其具有较大的比表面积,从而有利于还原性气体的表面反应过程。利用低温水浴法,对酸化若干天的钼酸铵饱和溶液进行处理,通过研究改变酸化天数和反应时间,在95oC下制备了不同形貌的h-Mo O米花球。利用所得到的h-Mo O3微米花球制备烧结型气敏传感器件,340oC工作温度下对不同浓度的三甲胺气体做了气敏性能测试。结果表明,酸化时间为40天、反应时间30 min时制备的样品气敏性能最佳,对500 ppm三甲胺灵敏度可达到272,较前述h-Mo O3微米棒提高了2.85倍,响应和恢复时间分别为8 s和7 s,在低浓度1 ppm下,其灵敏度能够达到4.44。h-Mo O3微米花球较h-Mo O3微米棒气敏性有了较大的提升,可能是由于酸化一段时间后的钼酸铵饱和溶液在水浴反应的过程中生成的微米棒自组装成微米花球,从而大大提高其比表面积,且增加了(001)面的比例,改善了其气敏性能。将市售Mo O3溶于33%的双氧水中,并在硝酸的作用下170oC水热反应,得到了α-Mo O3纳米带。为进一步提升其气敏性能,采用简单的液相法在其表面进行修饰,制备了p-Cu O/n-Mo O3异质结纳米带。对制备出的样品进行气敏性能测试结果表明,当Cu O与α-Mo O3理论摩尔比为0.5:1时气敏性最佳,300oC工作温度下对500 ppm三甲胺灵敏度可达到84.2,是单纯a-Mo O3纳米带的3.89倍,其响应恢复时间分别为12 s和15 s。低浓度1 ppm下,其灵敏度可达到4.32。这主要是因为在p-Cu O纳米颗粒与n-Mo O3纳米带之间形成的p-n结,在界面形成较厚的耗尽层,因此气敏性能得到了明显提升。
[Abstract]:MoO3 is an n-type semiconductor oxide with a band gap of 3.3 EV. In recent years, due to its excellent gas sensitivity to flammable and explosive toxic gases, people have paid more and more attention to the common phase of MoO _ 3, which consists of the normal phase (伪 -MoO _ 3, hexagonal phase) and the monoclinic phase (尾 -MoO _ 3), in which the orthotropic phase is a thermodynamically stable phase. The hexagonal phase and monoclinic phase are thermodynamically metastable phases. In this paper, h-MoO3 and 伪 -MoO3 microstructures were synthesized without adding surfactants by water bath and hydrothermal method with mild conditions. The gas sensing properties were studied. The saturated solution of ammonium molybdate, which was acidified by concentrated nitric acid, was used as the initial reactant by the solution method with mild conditions. H Mo O O rods with different morphologies were prepared by changing the water / alcohol ratio of reaction medium and reaction time of 65oC in water bath. The sintered gas sensing devices were prepared by using the prepared h-MoO 3 micron rods as the substrate for different operating temperatures. The concentration of trimethylamine gas was tested by gas sensitivity test. When the ratio of water to alcohol is 15: 15, and the reaction time is 30 min, the gas sensitivity of the device is up to 95.2, the response time and recovery time are 10 s and 7 s, respectively. The h-MoO3 prepared under this reaction condition has good gas sensitivity to trimethylamine at low concentration. When the concentration of trimethylamine is 1 ppm, The sensitivity is still up to 2.61.This good gas sensing property may be due to the presence of lamellar structure on the surface of h-MoO _ 3 hexagonal prism due to the addition of anhydrous ethanol in the reaction medium, and the appropriate reaction time and the appropriate size of h-MoO _ 3. Therefore, it has a large specific surface area, which is beneficial to the surface reaction process of reductive gas. The saturated solution of ammonium molybdate for several days was treated by low temperature water bath method. The h-MoO _ 2 flower balls with different morphologies were prepared at 95oC. The gas sensing properties of different concentrations of trimethylamine were measured by using the h-MoO _ 3 micron spheres to prepare sintered gas sensing devices (340oC) at different temperatures. When the acidizing time was 40 days and the reaction time was 30 min, the gas sensitivity of the sample was 272for 500 ppm trimethylamine, which was 2.85 times higher than that for h-MoO _ 3 micron rod mentioned above. The response and recovery time were 8 s and 7 s, respectively, and at low concentration of 1 ppm. Its sensitivity can reach 4.44.h-MoO3 micron flower ball, which is more sensitive than h-MoO3 micron rod gas sensitivity. It may be due to the formation of micron bouquet by self-assembly of micron rod formed by saturated ammonium molybdate solution during water bath reaction after acidizing for a period of time. Therefore, the specific surface area is greatly increased, the ratio of the surface is increased, and the gas sensing property is improved. The available MoO3 is dissolved in 33% hydrogen peroxide and hydrothermal reaction is carried out in 170oC under the action of nitric acid. 伪 -MoO _ 3 nanobelts were obtained. In order to further improve their gas-sensing properties, p-Cu O _ (-) / n-MoO _ 3 heterojunction nanobelts were prepared by a simple liquid-phase method. The gas sensing properties of the prepared nanobelts were measured. When the theoretical molar ratio of Cu O to 伪 -MoO 3 is 0.5: 1, the optimum gas sensitivity of 300oC is 84.2% for 500 ppm trimethylamine, which is 3.89 times higher than that of pure a-MoO 3 nanobelts. The response recovery time is 12 s and 15 s 路1 ppm, respectively. The sensitivity is 4.32. This is mainly due to the formation of p-n junctions between p-CuO nanoparticles and n-MoO3 nanobelts and the formation of a thicker depletion layer at the interface.
【学位授予单位】：天津理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ136.12

【参考文献】