Study On Gas Sensitivity Of Titanium-based Nanomaterial

Gas detection play important roles in many fields,such as industrial control,fuel emission control,automobile exhaust emission control,household safety and environmental pollution monitoring.Polluted gases in life,such as fuel combustion,automobile exhaust emissions,volatile harmful gases from decoration,odorous fish corrosion gases,these volatile organic compounds（VOCs）are the main indoor pollution gases and endangering people’s health.In gas detection technology,solid-state gas sensor based on semiconductor metal oxide is the most promising.Gas sensors can be seen in anywhere,wards,laboratories,hospitals and almost all technical facilities.Sensitive material is the core of gas sensor.It is an important way to improve the performance of gas sensor by changing synthesis method,controlling material morphology and compounding with other materials.In this paper,different morphologies of titanium-based nanomaterials were prepared with volatile organic compounds as target gases.The electron transfer and energy barrier changes on the surface of the materials were analyzed.The mechanism of heterojunction and nuclear structure improving the performance of semiconductor gas sensors was studied in depth.The main work is divided into three parts:（1）A novel heterostructure of titanium ferrite nanoparticles was prepared by hydrothermal and wet chemical deposition using octahedral iron oxide as precursor.Titanium ferrite nanoparticles with a large number of pores have a high surface area,which is conducive to improving the performance of gas sensors.Compared with pure Fe₂O₃ and TiO₂,Fe-O-Ti composites have much faster response recovery time（Tres=6s,Trec=48 s）,faster response speed（Response=35.6）,and better selectivity.The results show that the special morphology and large specific surface area of mulberry-like Fe-O-Ti heterostructure provide a larger contact area for gas reaction.（2）Anatase/rutile TiO₂@SnO₂ hollow spheres for TEA gas sensor detection were prepared.Compared with pure TiO₂,the hollow grading structure of TiO₂@SnO₂ exhibits higher response value and faster response speed in low TEA concentration.At 240°C,the concentration of TiO₂ is 5 ppm TEA,and the response value of TiO₂@SnO₂ is 4.04,which is three times higher than pure TiO₂.Because SnO₂ nanoparticles are uniformly distributed on TiO₂ hollow spheres,N-N heterojunction is formed,which enhances the gas sensitivity of TEA.The interface between TiO₂ and SnO₂ provides more active sites for the reaction of TEA target gas with negative oxygen ions.Anatase/rutile TiO₂ and SnO₂ are well interconnected,which is conducive to effective electron transfer.（3）The preparation and characterization of AgO/TiO₂/In₂O₃ nanobelts were introduced.AgO/TiO₂/In₂O₃ heterostructures were successfully prepared by hydrothermal method and wet chemical deposition method.The morphology of the material was observed by scanning electron microscopy（SEM）.Compared with pure TiO₂,the introduction of In₂O₃ into TiO₂ could significantly shorten the response time and working temperature.The effect of Ag loading on the sensing performance shortened the response recovery time.The optimum working temperature of AgO/In₂O₃/TiO₂ was280°C,and the response value of 100 ppm ethanol was 68.5.The response time is 33s and the recovery time is 52s.