Study On Performance Of Zinc - Based Gas Sensor

Quartz crystal microbalance (QCM) is one of the most promising sensors at present, deriving on merits of structurally simple, high sensitivity, high accuracy (Nano-gram class is possible) and low costs. In addition to insufficient understanding on its gas-sensitive property&mechanism, extending studies focusing on its application range is not yet clear, which may be attributed to relatively late starts&slow development of correlation research. Therefore, in this paper, ZnO with different structure and morphology has been prepared and used for decorating QCM, then correlation researches between microstructure, morphology and properties of ZnO modified QCM are performed by XRD, SEM&QCM. The application range of sensor has been presumed and obtained at the same time. The results as follows:(1)ZnO prepared by sol gel method show:The size of ZnO colloid spheres first enhanced and then abated with increasing liquid amount, The grain size is ennhanced with increasing liquid amount, ZnO prepared by hydrothermal method show:The effect of molar ratio on the ZnO morphology and structure have a big effect:ZnO morphology mainly showed granular for the molar ratio is1:1, when the molar ratio is1:2, ZnO morphology mainly showed patchy. When molar ratio of1:3,the ZnO like a flower. Then ZnO was used to decorate QCM as a sensor to research gas sensitivity.The results show that:The humidity sensitivity enhanced with increasing size of ZnO colloid spheres, flower ZnO sensor have a good humidity sensitivity better than sheets ZnO sensor than pachy ZnO sensor. ZnO sensor have a best sensitivty that there was a suitable grain size(11.85、27.07nm).we found a technical characteristics at the same time:It is that recovery time is equal or more than response time in low-humidity condition (RH=33%,55%),while their relative relationship is diametrically opposed in high-humidity condition(RH=75%,85%&95%).(2) ZnO sensors with flowers morphology in different gases (hexane, ethanol, ethyl acetate) have a lowest frequency response, particles ZnO sensor have maximum response to hexane, ZnO with sheets morphology have maximum response to ethanol, ethyl acetate, ZnO gas sensor with different morphologies have a selective response to gas, ZnO sensor with one morphology has certain selectivity to different gases at the same time. From the adsorption/desorption dynamics,There was some relationship between adsorption/desorption characteristics and gas sensitive materials, Firstly, The adsorption behavior is a adsorption model rely on surface area.surface area is the main factors affecting the adsorption, The second, The adsorption behavior is a multilayer adsorption model rely on the pore.(3) ZnO sensor in alkanes, alcohol, ester gas frequency shift results is:△fheptane>△fhexane>△fpentane;△fbutanul>△fpropanol>△fethanol>△fmathanol；△fethyl propionate>△fethyl acetate>△ fethyl formate,The frequency shift is enhanced with increaseing gas molecular chain becsuse of induction effect. ZnO sensor adsorption of gas molecules mainly rely on atomic hydrogen of volatile organic compounds (VOC). Lead to gas sensors in hexane gas have a high frequency response and linearity w than cyclohexane, And gas sensors in ethyl propionate frequency responese and the curve of stability is better than in ethyl acrylate, gas sensors with same molecular and different structure have a different sensitive properties at the same time.