Physical Design Of 1D In₂O₃ Nanomaterials And Application Of Gas Sensor

In recent years,there is a qualitative change in life with the sharp and determined development of national economy.But at the same time,it has caused damage to the environment to some extent.People began to pay more and more attention to environment problems with the change of thoughts and the progress of society.Air pollution has become the focus of public opinion.So gas sensors has began to appear in life,used of drunk driving,monitoring of noxious gas in new house or flammable and explosive gas in factory.Gas sensor is based on gas sensitive materials.Gas sensitive material is one of the important cores of sensing devices.Gas sensors based on indium oxide materials are getting more and more attention for excellent chemical and thermal stability.The gas sensing performance of sensors based on In₂O₃has not been satisfied.In order to meet greater demands,it is necessary to design the structure of indium oxide to improve the gas sensing properties,such as low dimensional,porous structure,doped foreign elements and so on.This paper chooses In₂O₃ as gas sensitive material,which is prepared through electrospinning following different calcination process.Gas sensors are made based on these materials with different morphology.The effect of morphology on gas sensitive performance are systematically studied.Based on the former conclusion,In order to get the high performance of gas sensor,Eu-In₂O₃ nanotube with pore and Eu-In₂O₃ nanotube with bump are prepared and the gas sensing properties of these gas sensors based on these material are studied.The detailed work are as follows:（1）In₂O₃ materials with different morphology（nanofiber,nanotube,porous nanotube,nanotube with bumps）are prepared via electrospinning following different calcination process.The morphology and structure are characterized by scanning electron microscopy（SEM）and X ray diffraction（XRD）.Gas sensors are made based on these materials.Studies on the performance of gas sensors show that the morphology of material has certain effect on gas sensing properties.The gas sensor based on porous In₂O₃ nanotube exhibits best gas sensing properties,while the gas sensor based on In₂O₃ nanofiber has the lowest gas sensitivity.The response value of the gas sensor based on porous In₂O₃ nanotube to 100ppm ethanol are 16 at the optimum operating temperature of 260℃,which is 2.8 times lager than that of nanofiber.The gas sensor based on porous In₂O₃ nanotube could detect 5 ppm ethanol with response of 3.The response time and recovery time are the fastest（8s and24s,respectively）.Besides,the selectivity of this sensor to ethanol is muchu better than others.All these gas sensors possess better linearity（5-100ppm）.For the same gas sensitive material,its morphology has influence on the performance of gas sensing device in some way.（2）Based on the former conclusion,porous Eu-In₂O₃ nanotube with different doping concentration are prepared via electrospinning following calcination process.The structure and morphology are analyzed by scanning electron microscopy（SEM）,X ray diffraction（XRD）,energy dispersive spectroscopy（EDS）,X ray photoelectron spectroscopy（XPS）and transmission electron microscopy（TEM）.The results show that there are many irregular pores on the surface of Eu-In₂O₃ nanotube,which are favorable for the adsorption and diffusion of gase.Gas sensors are made based on these material.Studies on the gas sensing properties of gas sensors show that the doping element Eu can improve the gas sensing properties of sensors based on In₂O₃ nanotube to a large extent.The response of the gas sensor based on 3wt%porous Eu-In₂O₃ nanotube to 50ppm ethanol is 44 at the appropriate working temperature of 260℃,which is 6.2 times larger than that of the pure one.The gas sensor based on 3wt%porous Eu-In₂O₃ nanotube could detect 0.2ppm ethanol with corresponding response of 1.8.The gas sensor based on 3wt%porous Eu-In₂O₃ nanotube exhibits excellent selectivity to ethanol,good linearity,lower detection limit（0.2ppm）,repeatability and stability.The rapid response time and recovery time are 3s and 21s,respectively.These characteristics suggest that the gas sensor based on 3wt%porous Eu-In₂O₃nanotube will play a stronger role in gas monitoring field.（3）In₂O₃ and Eu-In₂O₃ nanotube with bump are prepared via electrospinning following calcination process.The structure and morphology are analyzed by scanning electron microscopy（SEM）,X ray diffraction（XRD）.The results show that there are many irregular bumps on the surface of Eu-In₂O₃ nanotube which provide greater contact area for gase reaction.Gas sensors are made based on these material.Studies on the gas sensing properties of gas sensors show that the gas sensor based on Eu-In₂O₃ nanotube with bump owns better performance than the pure one.At the optimum working temperature of 240℃,the sensitivity of the device to 50ppm acetone is 3.4 times lager than that of the original one,and the lowest detection concentration is 0.2ppm.The rapid response time is 3s.The ratio of sensitivity to acetone and ethanol for gas sensor based on Eu-In₂O₃ nanotube is 2.5,lager than the ratio（1.8）for gas sensor based on In₂O₃ nanotube,indicating that the selectivity of the device is better than before doping.