【作者】 李巍；

【导师】 陈文哲；

【作者基本信息】 福州大学 ， 材料物理与化学， 2006， 硕士

【摘要】 近年来,煤矿事故频发给矿工的生产生活带来了极大的灾难。瓦斯（主要成分为甲烷（CH₄））是煤矿安全生产的最大危害。要解决瓦斯突出及爆炸问题,必须加强对瓦斯的监测监控。目前,我国装备的煤矿安全监控系统大多采用热催化原理检测CH₄,但利用该原理制备的器件有结构复杂、功耗大、寿命短和稳定性差等缺点。而当前另一种相对比较成熟的检测方式――氧化物半导体气敏传感器也存在一致性和稳定性较差。本论文从气敏研究的三个主要方面（即材料、制备、器件）出发,朝着一致性、高灵敏、低功耗、小型化的方向对氧化物半导体气敏传感器和载体催化元件进行了研究。采用了X射线衍射、差热-热重、傅立叶红外光谱、扫描电镜、透射电镜等测试手段对气敏材料进行表征。考察了不同材料制备方法、煅烧温度、掺杂物及器件结构对性能的影响。探索了双氧水和半透膜结合的新的无机盐溶胶-凝胶工艺方法制备纳米SnO₂气敏材料,该工艺方法可以控制胶凝过程,得到化学成分分布均匀,分散性好的SnO₂基气敏粉体材料,具有重复性强,一致性好、成本低廉的特点。确定600℃热处理1小时为SnO₂气敏材料理想的热处理温度。分别对SnO2进行了1.5%（wt%）PdCl2和5%（wt%）α-Fe₂O₃的掺杂。气敏性能测试表明,两种掺杂后制备的元件在2.5V加热电压下对5000 ppm的CH₄,灵敏度均接近5。分析后认为PdCl₂掺杂烧结后形成的PdO微晶表面的氧缺陷能够吸附更多的氧,产生溢流效应增加元件灵敏度; α-Fe₂O₃的掺杂能够抑制SnO₂的晶粒的长大,并利用本身的体电导气敏效应提高元件的性能。在WO₃气敏材料方面,热分解法制备的晶形呈八角状γ-WO3材料对CH₄几乎没有气敏性能; 气相反应法制备晶形呈菱形八面体状的β-WO3和非晶态的混合物材料在加热电压为2.5V的条件下对5000ppm的CH4最高灵敏度可达2.6,对WO₃基半导体氧化物气敏材料检测CH4领域有指导意义。基于赛贝克效应的启发,利用温差电动势的原理及催化剂对性能的影响,对载体催化元件进行简化和改进。设计出了一种全新结构的载体催化元件,它的特点是将两元件间的温差电动势的变化量作为衡量CH4气体浓度变化的标准,直接进行测试,有别于传统的利用电阻变化引起惠斯登电桥输出电动势变化的测试模式。新型的结构元件有高灵敏度、小型、简单、低耗等优点。更多还原

【Abstract】 In recent years, the frequently happened coal mine accidents have invoked the disaster for miner’s lives. Gas （ consists mainly of methane） is fatal to harm the safety in production of coal mines. It should be strengthen the control of gas to prevent the danger of high-density gas and gas explosion. At present, most of the safety control systems in our country’s coal mines use the thermocatalytic principle to detect methane, but there are many disadventages of this device, such as complicated, high power consumption, short-lived and instability. The another comparatively mature method ----oxide semiconductor gas sensor also lacks consistence and stability. In this paper, we made a critical review of the advantages of the carrier catalysis component and the semiconductoring gas sensor for methane detection like consistency, sensitivity, low power consumption, integration, basing on three main headings of the gas-sensing research （ i.e.material,process,apparatus）. The gas sensitive has been tested by XRD, TG-DTA, FT-IR, SEM, TEM and so on, in order to detect the effect of preparation method, calcination temperature and dopant . A new inorganic salt sol-gel which combined the hydrogen peroxide with semi-permeable membrane was first to make the nanometer SnO2 gas sensitive . This method can control the process of jelling and obtain the SnO2 powder gas sensitive with uniform distribution and pretty dispersibility. These materials are featured by excellent repeatability and consistency, low-cost. I t ensure that heating one hour at 600℃is the most suitable heat treatment for the SnO₂ gas sensitive. Through dopping 1.5%（wt%）PdCl₂ and 5%（wt%）α-Fe₂O₃ separately. The testing of the performance shows that the two dopants’ sensibility to the 5000 ppm methane will reach to 5 when heated at 2.5 voltage. It consider on analysis that the oxide defect of the PdO which derive from the fired PdCl₂ dopant by absorb more oxygen and develop an overflow effect to improve the component’s sensitibility. α-Fe₂O₃ dopant by restrain the growth of the SnO₂ crystalline and improve the effect by its bulk conductor characteristic. In the terms of WO₃ gas sensitive, the crystal octagonal γ-WO₃ gas sensitive which made by the thermal decomposition has hardly sensibility to the methane. However, the sensibility of the lozenge – shapedly octagonal β-WO3 and amorphous mixture to the 5000 ppm methane can reach to 2.6 when heated at 2.5 voltage. It has guiding significance in the field of WO3 semiconducting oxide gas sensitive methane detecting. A new structure carrier catalysis component has been designed via an edification based on the Seebeck effect that taken use of the impacts of the thermoelectromotive force regulation and catalyzer to the capability to simplify and improve the carrier catalysis component. The device takes the varying quantity of the thermoelectromotive force regulation between that two components as the standard for the change of methane’s density. The device can test the density directly, differs from the traditional test pattern which use the resistance change to cause the variation of the Wheatstone bridge output electromotive force. The new component is featured by high-sensibility, compact sized, simple and low-cost consumption and so on.更多还原