Research For Methane Sensor Based On SnO₂Nanoparticles

Nature gas has been widely used because of the constantly improving standard ofliving, since reform and open policy was implemented thirty years ago. Although thenature gas is very convenient, it is dangerous when it leaks. According to theincomplete statistics, the number of fire and explosion caused by the leak of naturegas increases every year which has been a serious threat to people’s life safety andproperty security. Science researcher had been studying methane sensor all the timewhich has high reliability and good sensitivity since methane is the major componentof nature gas. Oxide semiconductor gas sensor has been widely used in themeasurement of environment gas and the alarm of inflammable and explosive gas andtoxic gas through years of research and improvement. Although methane gas sensorhas realized the commercial production, it has a lot of shortages such as lowsensitivity, short working life and low selectivity and cannot be integrated. Aiming atthe existing problem of methane sensor, we want to find a way to fabricate methanegas sensor which has high reliability, good sensitivity and long working life throughsimple and reliable preparation technology using cheap raw materials. We alsodesigned a structure of micro hotplate to realize the integration and miniaturization ofmethane gas sensor.The main work of this paper is as follows:1. We choose the SnO₂as sensitive material for gas sensor, and prepare SnO₂nanomaterials with the simplest chemical precipitation method using SnCl4solutionand low concentration of ammonia. Scanning electron microscope （SEM） and X-raypowder diffraction （XRD） have been measured. We analyse the relationship betweenthe concentration of precursor solution and the particle size of SnO₂. We find that theconcentration of precursor solution does not affect the particle size of SnO₂, and theparticle size of SnO₂is30-50nm. We doped SnO₂nanomaterials with different massfraction of Pd, and investigate the gas sensing properties. According to the test result, 3wt%Pd is the best proportion. The gas sensor based on the sample doped with3wt%Pd has the highest sensitivity and excellent response-recovery feature, but itsselectivity and stability is poor.2. Ultrasonic is a kind of special form of energy, its wavelength range is10cm-10-3cm, which is much long than the size of molecule. The chemical action ofultrasonic is done through liquid medium to spread around, so ultrasonic is a kind ofradiation. The material prepared by ultrasonic assisted precipitation method has bigspecific surface area and good dispersion. Here, we prepared SnO₂with ultrasonicassisted precipitation method, and measured its gas sensing properties. The sensitivityof gas sensor based on SnO₂prepared with ultrasonic assisted precipitation method to3000ppm methane is57, which is three times higher than the sample prepared bychemical precipitation method. And the gas sensor based on SnO₂prepared withultrasonic assisted precipitation method has better response-recovery feature,selectivity and stability.