Study On Gas Sensors Based On Iron Oxide Nnanostructure And Its Composite Oxide

Gas sensors for monitoring harmful gases have always been a hot research area,and the design of gas-sensitive materials is the key to improving gas-sensitive performance.In this paper,iron oxide is used as a gas-sensitive material,and different synthesis schemes are used,that is,Fe₂O₃ nanomaterials with different morphologies are successfully synthesized by changing the reaction temperature,reaction time,and adding different surfactants during the reaction process.And its composite oxide nanomaterials,and a hydrogen sulfide sensor with excellent performance was prepared.The main content of the thesis research includes:1)α-Fe₂O₃ nano-ellipsoid（long axis 275 nm,short axis 125 nm）is synthesized in one step by hydrothermal method without subsequent calcination.The nano-material is pureα-Fe₂O₃,and no other impurities are found.The surface ofα-Fe₂O₃ nano-ellipsoid is smooth,uniform in size and evenly distributed.The smooth surface is conducive to accelerating the adsorption and desorption of chemical gases,and can shorten the response and recovery time of the gas sensor.Theα-Fe₂O₃ nano-ellipsoid material was mixed with absolute ethanol to form a slurry and coated on the ceramic tube,and a gas sensor based on theα-Fe₂O₃ nano-ellipsoid was prepared.From the gas sensitivity test,theα-Fe₂O₃ nano-ellipsoid sensor has excellent gas selectivity for hydrogen sulfide gas.The optimal operating temperature is 260 ℃,with extremely fast response and recovery time to H₂S gas（0.8 s/2.2 s at 50 ppm）,lower detection limit（100 ppb）,excellent repeatability and long-term stability.2)Using solvothermal method,hexadecyl trimethyl ammonium bromide was used as the surfactant to prepare prismatic iron oxide nanoparticles of uniform size at a temperature of 140 ℃,and the nanomaterial was used as the sensitive medium to prepare gas sensor,the best working temperature measured by the gas sensor is 160 ℃,which high response to 50 ppm hydrogen sulfide is up to 34.0.In addition,the sensor has a lower detection limit（100 ppb）,good repeatability,repeated testing of 50 ppm,100 ppm hydrogen sulfide in 30 days,and found that its gas-sensing performance remained basically consistent,and showing better long-term stability.3)By solvothermal method,four stannic chloride and iron nitrate were used as raw materials,twelve alkyl sodium sulfate as surfactant,N,N-Dimethylformamide as additive,sodium hydroxide as precipitant,to prepare Fe-SnO₂ nanoparticles.It was found that the sensor has good gas sensing performance.The response and recovery time to 50 ppm H₂S at an operating temperature of 300 ℃ is 2.1 s/9.8 s,showing a faster response and recovery time.At the same time,the response reached 13.0.In addition,the detection limit of the sensor is as low as 200 ppb,at the same time,it showed good repeatability and long-term stability.