Design And Synthesis Of Metal Oxide Composites And Their Gas Sensing Properities

Gas sensors have been used for the detection of toxic gases and have been widely used in various fields related to people's lives.Gas-sensing materials are the key factors affecting the performance of gas sensors.Among them,semiconductor types have attracted great attention from researchers due to their advantages of high sensitivity,adjustable selectivity,high reliability,and low cost.However,they also have the disadvantages of high operating temperature and low selectivity.Therefore,this paper mainly aims at building a high-performance gas sensor.For the defects of high working temperature and low selectivity,we systematically carried out this work on the compounding and structural optimization of semiconductor oxides.The specific work is as follows:1.Preparation of Ni0/Zn0/Sn02 mixed metal oxide composites and its application in ethanol gas sensing.NiO has been introduced into ZnSn-mixed metal oxide composites(ZnSn-MMOCs)via a simple co-precipitation route,and a new type of gas sensing material NiO/ZnO/SnO2 mixed metal oxide composites(NiZnSn-MMOCs)has been prepared.It is found that the introduction of NiO broadens the visible light absorption range of ZnSn-MMOCs,reduces the band gap value and enhances the photoelectric response of the material.In addition,the introduction of NiO increases the specific surface area and oxygen defects of ZnSn-MMOCs,and the oxygen defects and specific surface area increase the coverage of chemically adsorbed oxygen on the surface of the materials,which in turn enhances its sensing performance.Also the p-n heterostructures between NiO and ZnSn-MMOCs promotes the increase of the resistance of the sensor material.It turns out that the sample(Ni0.5Zn3Sn0.9500)with NiO molar number x=0.5 has the best gas sensitivity,which obatiend under 500? calcination conditions,and it has a fast response speed,better stability and selectivity.Ni0.5Zn3Sn0.9500 sensor reveals the highest response of 180 to 200 ppm ethanol at 225? and quick response-recovery time of 21 s and 11 s to 1 ppm ethanol.2.Novel hierarchical Zn/In metal oxides nanostructures(ZnInxO,x represents the measured molar ratios of Indium element)with small secondary nanosheets grown on primary spindle-shaped were prepared by hydrothermal synthesis and followed by calcination.The results show that In-doped ZnO metal oxide has a spindle-shaped hierarchical structure,which has a regular and uniform morphology and a high atomic utilization rates.It has a high response to triethylamine at room temperature.The existence of indium significantly improves the optical performance and the gas-sensing properties of ZnO-based gas sensor under light excitation conditions.Among them,the ZnIn0.13O hierarchical oxides have a size about 15-20 ?m,and have better gas sensitivity up to 390 under light excitation conditions.In conclusion,the in-situ growth of hierarchical structures on ceramic tubes provides a new direction for the preparation of room temperature gas-sensitive materials.