Research On Preparation Process And Performance Of Alumina Humidity-sensitive Thin Film Sensor

Humidity sensors play an increasingly important role in industrial manufacturing,agricultural production and daily life.Many researchers use different measurement principles to prepare lots of humidity-sensitive components for different application environments.At present,because of the changing application environments and practical needs,the performance requirements of the moisture-sensitive sensors are continuously changing and improving.Based on different preparation methods,many different humidity-sensitive materials and processes are produced.In this thesis,porous Al₂O₃humidity-sensitive film is prepared by micro-arc oxidation process,and the influence law of the process factors on film is analyzed.First,the moisture sensing mechanism of porous materials is investigated and the equivalent circuit is obtained by combining the porous surfaces of materials.By exploring various preparation methods of Al₂O₃ materials,the film growth mechanism of micro-arc oxidation is mainly analyzed,and then the oxidation process platform is built by this method.The structures of various humidity sensors are compared,and the appropriate component structure is designed.Then,the porous Al₂O₃ humidity-sensitive films which are prepared by micro-arc oxidation and anodic oxidation are analyzed by XRD,SEM and EDS for crystal structure analysis and pore size analysis of thin films.The results show that enhancing the micro-arc oxidation current and extending the time will enhances the intensity ofα-Al₂O₃diffraction peak,while the temperature has such effects within a certain range.Overall,the increase of micro-arc oxidation current and time causes the film pore size to become larger.When the micro-arc oxidation time and temperature is increased to 120s and 185°C,the films start to show strongα-Al₂O₃ diffraction peaks.When the micro-arc current is reduced to 50 m A,the average pore size of the film can reach about 1.7μm.In addition,the influences of anodic oxidation on the film materials are also concerned.According to the principles of different humidity test platforms,a suitable moisture-sensitive measurement platform is built.The moisture-sensitive curves of resistance and capacitance are tested to explore the influence of humidity and frequency on different electrical parameters.The results show that increasing the ambient humidity increases the capacitance and decreases the resistance of the moisture-sensitive sensor,and that the Al₂O₃ film has a better moisture-sensing performance at 100Hz.The moisture-sensitive performance such as sensitivity,response and recovery speed,electrode area,repeatability and consistency of the sensor are mainly analyzed.Finally,the results show that the response and recovery time of the Al₂O₃ humidity-sensitive sensor prepared by the micro-arc oxidation process can reach 62s and 60s,and that the sensor has good stability,high repeatability and consistency.