Ni-SiC气敏型瓦斯传感检测器件的研究

发布时间：2018-03-12 07:37

本文选题：SiC　切入点：吸附　出处：《西安科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：有害、危险环境下稀薄气体的探测一直以来都是微纳米器件研究领域的热门课题。近年来气体敏感材料切片在气体吸附脱附过程中表现出来的优异特性,特别是良好的介电特性,使得采用气敏法来检测瓦斯气体的浓度成为研究的焦点。气敏法检测瓦斯气体浓度中气敏材料的选取对气体浓度探测精度至关重要,而作为新型气敏材料的SiC对气体有良好的吸附特性,在敏感元件领域具有非常高的研究价值。本文中以3种不同比例掺杂Ni原子的SiC(001)切面为气体敏感吸附基底,使用Material Studio软件构建(3×3)的超晶胞,利用基于第一性原理的密度泛函理论方法模拟计算了CO和CH_4分子在掺杂材料表面的吸附性能。优化模型后分别从吸附系统结构变化、吸附能、电荷密度差以及态密度等几个方面,对比分析气体分子在掺杂材料表面4个不同经典吸附位置(Top、Bridge、Hcp、Fcc)的吸附特性。在对CO分子进行化学吸附时得出,在1/9掺杂时Fcc位为最佳吸附位置;1/3掺杂时Bridge位为最佳吸附位置;2/3掺杂时Hcp位为最佳吸附位置;通过不同比例掺杂的对比,得出2/3掺杂比例时对SiC(001)切面的影响最大,不仅在吸附CO分子后系统更加稳定,而且吸附过程中电子转移速度加快,作为敏感吸附材料时,电阻率将发生明显的变化。在对CH_4分子进行Top位物理吸附时得出,无论是从结构的变化还是从作用过程中态密度的变化都表明1/9掺杂时的SiC(001)对CH_4的物理吸附更稳定。在采集电路的设计上,耦合仪表放大器与差动放大器采集气体敏感器件输出的微弱电压信号并进行逻辑放大,采用内含模数转换功能的微控制器STM32进行电压采集,将采集到的电压信号输出显示在4位一体数码管上,当采集到的电压值超过报警阈值时进行声光报警。在Keil软件中编写相应的电压采集和显示输出程序,利用基于STM32的最小系统、电位器以及4位一体数码管搭建实物系统对软件程序进行测试,结果表明该系统可实现对稀薄瓦斯气体的探测和报警。本研究成果可应用于矿业生产生活中,特别是煤矿开发方面可以减少有害气体的积累和爆炸的可能性,使得开采环境更加安全。
[Abstract]:The detection of rarefied gases in hazardous and harmful environments has always been a hot topic in the field of micro and nano devices. In recent years, the slice of gas sensitive materials has shown excellent characteristics in the process of gas adsorption and desorption. Especially because of its good dielectric properties, it is very important to select gas sensitive materials for detecting gas concentration by using gas sensing method to detect the concentration of gas gas. As a new gas sensing material, SiC has good adsorption properties for gas and has a high value in the field of sensitive elements. In this paper, the gas sensitive adsorption substrate is three different proportions doped with Ni atoms. The supercell of 3 脳 3) was constructed by using Material Studio software. The adsorption properties of CO and CH_4 molecules on the surface of doped materials were simulated by density functional theory (DFT) method based on the first principle. After optimizing the model, the adsorption energy and the structure of the adsorption system were changed, respectively. The adsorption characteristics of gas molecules on four different classical adsorption sites on the surface of doped materials such as charge density difference and density of state are compared and analyzed. When the Fcc site is the best adsorption site at 1/9 doping, the Bridge site is the best adsorption site when the Bridge site is the best adsorption site, and the Hcp site is the best adsorption position when the Bridge site is doped with 2 / 3. By the comparison of different doping ratios, it is concluded that the influence of 2/3 doping ratio on the cutting plane of sic _ (1 / 1) is the greatest. Not only is the system more stable after the adsorption of CO molecules, but also the electron transfer rate is accelerated during the adsorption process. As a sensitive adsorption material, the resistivity will change obviously. When the CH_4 molecule is physically adsorbed at Top site, Both the change of structure and the change of density of states in the process of action indicate that the physical adsorption of CH_4 is more stable by 1/9 doped sic _ (001). In the design of the acquisition circuit, The coupling instrument amplifier and differential amplifier collect the weak voltage signal from the gas sensing device and amplify it logically. The voltage is collected by the microcontroller STM32, which contains the function of analog-to-digital conversion. The output of the collected voltage signal is displayed on the 4-bit integrated digital tube. The acousto-optic alarm is carried out when the collected voltage value exceeds the alarm threshold. The corresponding program of voltage acquisition and display output is written in Keil software. The software program is tested by using the minimum system based on STM32, potentiometer and 4-bit digital tube. The results show that the system can detect and alarm rarefied gas. The research results can be used in mining production and life, especially in coal mine development can reduce the accumulation of harmful gas and the possibility of explosion. Make the mining environment safer.
【学位授予单位】：西安科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD712.55

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