Study On Formaldehyde Gas Sensor Based On The Nano-materials Of Fe₂O₃/Ag

The concentration of formaldehyde gas sent out by the indoor decoration materials is generally high,which seriously endangers human health,so the concentration of indoor formaldehyde gas monitoring has become a top priority.In order to solve this problem,the nano-materials of Ag-doped Fe₂O₃ were prepared by hydrothermal method and a side heated type formaldehyde gas sensor was further prepared.The sensitivity and response recovery characteristics of the sensor were improved by changing the doping carbon nano-tubes.The main work of this paper is as follows:Firstly,we prepared the Ag-doped Fe₂O₃ nano-materials and their characterization studies.The crystal morphology,grain size and surface performances of the Ag-doped nano-materials were investigated by X-ray diffraction（XRD）,scanning electron microscopy（SEM）,energy dispersive spectrometer（EDS）,F-Sorb2400（BET）and other method.Under the same condition,the results show that Fe₂O₃ doped with Ag has more specific surface area than the pure nano-materials of Fe₂O₃.and with the improvement of Ag doping quantity,specific surface area of the material is increasing.Secondly,we have fabricated Ag-doped Fe₂O₃ nano-materials to produce sintered side-by-side formaldehyde gas sensors for gas-sensing properties.The results show that the Ag-doped Fe₂O₃ sensor has higher sensitivity and better selectivity to formaldehyde.The sensitivity of Fe₂O₃ to formaldehyde gas is the best,when the calcination temperature is600℃,the molar ratio of Ag is 6%.At the optimum working temperature of 180℃,the sensitivity of the sensor to the volume concentration of 100 ppm formaldehyde is 3.9,the response time is 5min,the recovery time is 3min.The sensor was placed on the AS-20 sensor aging station for 30 days,ageing with continuously.The component’s resistance has not changed almost.This suggests that it has an excellent stability.Thirdly,we conducted a gas-sensing performance of formaldehyde gas sensors doped with carbon nano-tubes.The results shown that Fe₂O₃/Ag doped with 5% carbonnano-tubes has the better sensitivity to formaldehyde gas,and at the same time,the response recovery characteristics of gas sensor are improved obviously.The sensor has the best gas-sensitivity to formaldehyde,when the calcination temperature is 600℃,and the carbon nano-tube doping amount is 5%.At the optimum working temperature of 180℃,the sensitivity of the sensor to the volume concentration of 100 ppm formaldehyde is 6.1,the response time is 3min,the recovery time is 4min.