| According to the requirements of volatile organic gas detection,combined with the existing problems in the application of semiconductor gas sensor,based on the modification of the core gas sensitive materials of semiconductor gas sensor,the research on the modification of transition metal oxide and gas sensitive characteristics was carried out.The performance of semiconductor metal oxide gas sensitive materials and semiconductor gas sensor was improved through morphology improvement,modification and multi-component composite.In this paper,the surface morphology and crystal structure of the gas sensitive materials were improved by controlling the preparation conditions.The gas sensitive materials were modified by graphene modification,metal oxide composite and noble metal doping.And WO3,WO3/r GO,Zn O/Zn Co2O4 nanorod,Zn O-Zn Co2O4 nanotube and Cu O/Pt O2 polyhedron were prepared.The surface morphology,structure and crystal form of the prepared materials were detected and characterized by various analysis and characterization methods.The gas sensor was made based on the prepared gas sensitive materials,and its performance was tested.According to the test and analysis results,the influence of doping modification on the gas sensitive properties was studied.A quadrilateral two-dimensional WO3 nano sheet gas sensitive material was prepared by hydrothermal method.Its rough surface morphology and porous structure will be conducive to the improvement of its gas sensitive characteristics.The results of gas sensitivity test show that the sensitivity of WO3 nano sheet to 10 ppm ethanol at 200 oC is about twice as high as that of WO3 irregular nano granular material.The response recovery time performance is also significantly improved,and has good selectivity,repeatability and long-term stability.Using the good conductivity of graphene material to improve the gas sensitivity of WO3nano sheet,and by changing the amount of GO solution,the composite materials with the amount of r GO added of 4.1,6.1,7.9 and 9.7 wt%were prepared.The results of gas sensitivity test showed that the gas sensitivity of graphene modified WO3 nano sheet was significantly improved,and the sensitivity of modified WO3 nano sheet to 10 ppm NO2 was 3times higher than that of unmodified WO3 nano sheet when the content of r GO was 7.9 wt%.The sensitivity of modified WO3 nano sheet to 10 ppm NO2 was significantly improved when the optimal temperature was reduced by 50 oC.Zn O/Zn Co2O4 composite nanorods were prepared by two-step method.The results of physical and chemical tests showed that Zn O and Zn Co2O4 were successfully compounded.The composite materials could form p-n junction and effectively improve the gas sensitivity of the materials.The test results of 10 ppm acetone gas showed that when the molar ratio of Zn O and Zn Co2O4 was 1:1,the gas sensitivity was the best.Compared with pure Zn O nanorods,not only the optimum working temperature is reduced by 40 oC,but also the sensitivity is 4 times of that of Zn O nanorods,which fully proves that the gas sensitivity of composite materials is greatly improved.Zn O nanotubes and Zn O-Zn Co2O4 composite nanotubes with tubular structure were prepared by electrospinning.The sensitivity of the composite Zn O-Zn Co2O4 nanotubes to 10ppm acetone was greatly improved compared with that of the pure Zn O nanotubes.The sensitivity was 3 times of that of the composite Zn O nanotubes,and the optimal operating temperature was reduced by 25 oC,which indicates that the nanotube structure can significantly enhance the sensitive activity of the materials.In view of the significant effect of noble metal doping on the gas sensitivity of metal oxide materials,a simple two-step method was used to prepare the Cu O/Pt O2 polyhedron composite.In order to study the effect of Pt O2 content on gas sensitivity,polyhedral materials with different Pt O2 content were prepared:2,3.5 and 10 wt%.The results showed that when the content of Pt O2 was 3.5 wt%,the gas sensitivity was the best,the sensitivity to 100 ppm n-butanol was twice as high as that of pure Cu O polyhedral materials,and the best working temperature was reduced by 20 oC.Due to the excellent catalytic effect of precious metals,the material can effectively improve the gas sensitivity. |
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