Study On The Direct Construction And Performance Of ?-Fe₂O₃ Gas Sensors With Nanostructure

Nanoscale iron oxide??-Fe₂O₃?is one of the hot research topics in gas sensitive materials.It is a kind of wide band gap semiconductor material,which is cheap,non-toxic and easy to synthesize.In the field of gas sensing applications,the conductivity of?-Fe₂O₃ is very sensitive to the gas in its environment,so it can be used as an efficient gas sensing material.In addition,the?-Fe₂O₃ has certain chemical stability and thermal stability,which ensures its reproducibility as gas sensitive material.The traditional preparation method of the?-Fe₂O₃gas sensing device is made by coating the obtained?-Fe₂O₃ powder material.The disadvantage of this method is that the material will easily fall off and distribute unevenly,and the intrinsic physical structure will be destroyed,which will affect the gas sensing property of the material.In this experiment,the above shortcomings will be improved by the preparation of in situ one dimensional?-Fe₂O₃ nanoneedles?NNs?,and the gas sensing properties of the two P-N heterostructures are constructed by the construction of Zinc Ferrites?ZnFe₂O₄?/?-Fe₂O₃ and polyaniline?PANI?/a-Fe₂O₃ P-N heterostructures.1.Using a facile hydrothermal method,no seed layer-assisted growth techniques are required,and?-Fe₂O₃ NN arrays with excellent morphology and regular arrangement are grown directly on the Al₂O₃ tube.According to the experimental results,the optimal condition is that FeCl₃ is used as raw material was heated at 140? for 12 h.At this point,the growth of the?-Fe₂O₃ nanoneedle is vertical,and the contact between NNs,the NNs and Al₂O₃ tube is more conducive to electron transfer.Test results show that the optimum operating temperature of?-Fe₂O₃ NNs sensors is 280?.Toward 100 ppm trimethylamine,the sensing response of pristine?-Fe₂O₃ NNs sensors could reach about 27 at 280?.Moreover,the sensor exist good selectivity to triethylamine.There are also some disadvantages,such as,low response at low temperature,high working temperature and high detection limit.We prepared P-N heterojunction to improve the gas sensing performance.2.The strategy of improving gas sensing is proposed and proved,which is constructing P-N heterojunction depletion layer with gas sensing materials.The combination sensor of ZnFe₂O₄ and?-Fe₂O₃ can not only improve the sensitivity of gas sensitive materials and the response to low concentration gas,but also improve the shortcoming of the baseline drift in the test process.The PLD method was used to control the number of ZnFe₂O₄ deposited on the surface of?-Fe₂O₃ NNs,and the content of compound ZnFe₂O₄ was changed.After that,the gas sensing property of the composite was tested.The test results show that the sensitivity of the ZnFe₂O₄/?-Fe₂O₃ NNs device is higher than that of the pure?-Fe₂O₃ NNs device.And the sensitivity is maximum value when the content of ZnFe₂O₄ sputtering is 2000 times,which proves that the structure of the heterojunction can effectively improve the gas sensitivity of the gas sensor.In a continuous gas sensitivity test in a certain concentration range,it was found that the working temperature of the device was still higher but the sensitivity of the low concentration of increased triethylamine,and the gas sensitive response is 4 toward to 1 ppm triethylamine.3.The sensing property was also enhanced by room temperature conductivity of PANI and constructing the P-N heterojunction on the surface of?-Fe₂O₃ NNs.It has the characteristics of low power consumption and high selectivity for ammonia?NH₃?gas.Therefore,different acid doped PNAI and?-Fe₂O₃ NNs were compounded and made into devices.The gas sensitivity test results show that the sensitivity of PANI/?-Fe₂O₃ device is improved and the working temperature is reduced.The sensitivity of HCl-PANI/?-Fe₂O₃ is the highest,and can reach 20 to 2 ppm NH₃ at 120?,indicating that the?-Fe₂O₃ based gas sensors can operate at lower temperatures and at lower NH₃ concentrations.It is confirmed that the P type PANI composite can improve the gas sensitivity of pure?-Fe₂O₃ NNs,and achieve the detection of low temperature and low concentration NH₃.