Preparation Of In₂O₃ Based Nanocomposites And Their Gas Sensing Properties

During our daily life and work,gas sensors play a vital role.Typical applications of gas sensors include detecting toxic and harmful substances and flammable and explosive gases.They are widely used in public and household safety,industrial process safety,environmental pollution and air quality monitoring.Among the numerous kinds of gas sensors,resistive gas sensors are the most attractive because of their simple operation,easy manufacture,low production cost and miniaturization.As a new gas sensing material,In₂O₃ is widely applied in the realm of gas sensors owing to its unique electrical properties and functional material properties.However,single component In₂O₃ nano materials still can not get rid of the shortcomings of traditional metal oxide gas sensing materials,such as low response and poor selectivity to gas.Therefore,after studying the effects of three reaction conditions of hydrothermal synthesis of In₂O₃ nano materials with different particle sizes on the experiment,this paper further carried out noble metal loading experiments,the improvement of ethanol gas sensing performance of pure In₂O₃ supported by gold nanoparticles was studied;Secondly,the composite experiment of pure In₂O₃ and other metal oxides was carried out to study the effect of the formation of heterojunction on the gas sensitivity of nanocomposites;Finally,based on the prepared gas sensor,the alarm system of gas sensor is studied and designed to realize the practical application of gas sensor.The concrete research work is as follows:（1）The effect of In₂O₃ nanoparticles with different particle sizes on the ethanol gas sensing performance of the sensor was deeply discussed.During the synthesis experiment,the influence of hydrothermal conditions such as PH value of solutions,hydrothermal temperature and hydrothermal time on the dimensions of the synthesized In₂O₃ nanoparticles were contrasted,and the synthesis method of the final pure In₂O₃ nanoparticles was optimized.（2）An experimental scheme of hydrothermal synthesis of In₂O₃ nanospheres and in-situ reduction reaction supported gold nanoparticles was proposed.Compared with a single pure In₂O₃ material,the raw material ratio,hydrothermal time,calcination temperature and gold doping amount are optimized,the surface topography and specific surface area of In₂O₃modified by nano gold are increased,the catalytic activity of gold particles significantly improves the oxygen vacancy content,and realizes its ultra-high sensitivity detection of ethanol gas.（3）In the experimental process,we considered the synergistic effects of unique hexagonal heterostructure,large specific surface area and surface mesoporous structure,and successfully synthesized the three-dimensional heterostructure of Zn O hexagonal mesoporous nanosheets with In₂O₃ nanospheres on the surface by hydrothermal method and subsequent calcination treatment.The response value of the gas sensor made of Zn O@In₂O₃ heterojunction nano materials to ethanol gas reached 28.6,and its working temperature was reduced to 160°C,which reduced the power consumption of the sensor.Furthermore,the stability test and detection repeatability of the sensor within 30 days are also excellent.（4）The internal synergy of ternary composites was deeply discussed.Pt-Zn O-In₂O₃ternary composite gas sensing materials were successfully synthesized by hydrothermal method,combining the catalysis of noble metals,the enhanced gas sensitivity of heterojunctions and the structural characteristics of In₂O₃ materials.The response of the gas sensor based on Pt-Zn O-In₂O₃ to 100 ppm ethanol gas at 120°C is 78.2,and the response time and recovery time are 4s and 6 s respectively,which is much higher than that of In₂O₃（S=27.9）,Zn O（S=14.2）and Zn O-In₂O₃（S=30）.（5）For the sake of the real-time monitoring and actual use function of the gas sensor for the gas,an alarm system is specially designed for the research and design of the gas sensor.The alarm system can realize the detection function of the gas sensor for the target gas,the alarm function when the target gas concentration in the application environment exceeds the standard,as well as the real-time storage and liquid crystal date display of the gas concentration.An ethanol gas concentration test comparison experiment was designed to compare the accuracy between the prepared gas sensor alarm system and the commercially available gas detector.