The Research Of Ni-SiC Gas Sensitive Gas Sensing Detection Device

Rarefied gas detected in harmful and dangerous environment has been gotten extensive attention in the research field of the micro/nano device.In recent years,gas sensitive method for detecting the concentration of the gas becomes the focus of research,for its excellent properties,especially good dielectric properties that gas sensitive materials slips displayed in the process of gas adsorption.Gas sensitive material is important for gas sensitive method to detect the gas concentration.SiC,as a new type of gas sensitive material,has the very high research value in the field of sensitive element because of the good adsorption properties for gases.In the article,three kinds of different proportion of doped Ni atom of SiC（001）planes are designed as gas sensitive adsorption substrate.Supercells of（3×3）that CO and CH₄ adsorb on the surfaces of the doped Material built with Material Studio,are simulated by the method of density functional theory based on first principles.After optimizing the model,4 different classical adsorption position（Top,Bridge,Hcp and Fcc）adsorption properties are analyzed through the bond structure change,adsorption energy,electron density difference,density of state and so on.For the chemical adsorption of CO molecule,the Fcc is the best adsorption position for 1/9 doping;The Bridge is the best adsorption position for 1/3 doping;The Hcp is the best adsorption position for 2/3 doping;By comparing different proportion of doping material,it is obtained that the 2/3 doping ratio have significant impact for SiC（001）.The system is not only more stable after the adsorption of CO molecule,but also electron transfer in the process of adsorption is more rapid.And,as a sensitive adsorption material,the resistivity can generate an obvious change.For the physical adsorption of CH₄ molecule on Top position,the change of the geometry and of the density of state of SiC show that 1/9 doped SiC（001）of physical adsorption of CH₄ is more stable.In the design of acquisition circuit,the weak voltage signal from the gas sensitive components is amplified by instrumentation amplifier and differential amplifier.The microcontroller STM32,embedded modulus conversion function collects the data of voltage.The data will been shown by four integrated digital tube,and the sound and light alarm signals will been triggered when the voltage value collected exceeds the designed value.Program for voltage acquisition and display are performed in Keil software,and verifed based a cyber-physical system which is made up of smallest system of STM32,potentiometer and four digital tube structures was used to detect the concentration of gas.The results show that the designed system will excellently detect the low concentration of gas.The research results can be used in the mining production and living,especially coal mine safety.It can make the mining environment safer,and reduce the probability of harmful gas accumulation and explosion.