Preparation Of Nano TiO₂ Materials By Sol-Gel Method And Acetone Gas Sensing Property Study

Compared with other gas-sensing materials,nano-TiO₂ has the advantages of simple preparation procedure,excellent gas-sensing performance,low price,safety and environmental protection.However,the TiO₂ based gas sensor still has some shortcomings,such as poor selectivity,poor stability,long response-recovery time and so on.In addition,the gas sensor usually has a higher response at a higher working temperature,which makes the power consumption of gas sensor become larger,resulting in a waste of resources.At the same time,high working temperature is not conducive to the development and application of portable sensors,and it is risky when detecting flammable and explosive gases.In this paper,CuO-TiO₂ nano-gas sensing materials were prepared by sol-gel method.The structure and composition of CuO-TiO₂ materials were characterized by XRD,SEM,EDS and XPS.The gas sensing performance of the gas sensor prepared by the material was tested by Gas Sensing Test System.The effects of doping type,doping amount,annealing temperature,operating temperature and UV/visible light excitation on the gas sensing properties of the elements were studied.The selectivity and stability of gas sensor were studied.Finally,the gas sensing mechanism was discussed.The results show that:The TiO₂ materials prepared is anatase,the doped materials have more obvious porous structure than that undoped,the doping of CuO effectively inhibits the increase of TiO₂ grain size.The porous structure of the material is beneficial to the adsorption of the gas to be measured.In this thesis,the operating temperature of CuO-TiO₂ gas sensor is as low as 75?,and the gas sensor has the single selectivity to acetone.The CuO-TiO₂ gas sensor that is prepared by 6.64wt%CuO doping(mass fraction)material annealed at 500?has optimal response to acetone of 1000×10^-6(volume fraction).The sensitivity is 106.7,the response time and recovery time are 2s.After being aged at the operating temperature of 75?with relative humidity of 60%RH for 30 days,the sensitivity of the gas sensor to acetone is 92.1,the element still has single selectivity to acetone.Both UV and visible light excitation can significantly improve the gas sensing performance of the sensor.The sensitivity to acetone under UV irradiation is 95%more than that in dark.What's more,compared with the condition of no light,the sensitivity of the sample to acetone under visible light irradiation can still increase by 50%.The band gap of 6.64wt%CuO-TiO₂ material is reduced to 2.32 e V from the UV-Vis spectrum,which makes the optical absorption range of the material extend to visible light.It is advantageous to reduce the working temperature.Finally,the mechanism is studied by using the surface conductance control model of semiconductor and the theoretical model of grain boundary barrier.