Preparation And Performance Of High Temperature Anti-oxidation Thin-film Temperature Sensor

The performance of aero-engine is the main bottleneck restricting the development of aviation industry.Among them,the surface temperature measurement of engine high-temperature components provides key information for engine design and verification,and is crucial to the independent research and development in the field of aerospace.In view of the problem of high temperature oxidation of sensitive materials in the surface temperature measurement of high temperature components,this thesis carries out the sensitive material design,preparation,static and dynamic performance research of the new high temperature thin-film thermocouple temperature sensor.At the same time,the performance of the sensor is improved through the high temperature anti-oxidation protective layer technology.The main research contents are as follows:First,screening of sensitive thin film materials for high-temperature thin film thermocouples,Ir and Ir Rh₄₀ are selected as thin-film thermocouple sensitive materials,and the preparation and performance are studied systematically.The results show that the resistivity of Ir and Ir Rh₄₀ films decreases after annealing treatment,indicating that the crystal structure of the films are perfected during annealing.The static calibration test results show that the thermoelectric potential monotonically increases with the increasing temperature.Then,the Pt-ITO thin film thermocouple is designed for the higher temperature range.The static calibration test results from 200℃to 1300℃show that the maximum output thermal potential reaches 65.56 m V,and the output signal of the thin film thermocouple increases monotonically with the temperature increase.Various antioxidant protective layers of YAl O/Si₃N₄/Al₂O₃ multilayer membrane structure,Al₂O₃ and Si₃N₄ thin-film monolayer structure are selected.The YAl O/Si₃N₄/Al₂O₃ film is treated at high temperature,then the film microstructure is observed by XRD,and analyzed the high temperature reaction mechanism.The results show that the crystallinity of the film gradually increases with the annealing temperature and the crystalline phases are gradually increased.The composite protective layer with different Si₃N₄ thickness is prepared on the superalloy baseband for high temperature oxidation resistance test.The results show that the weight gain rate of the sample without the protective layer is 1.07%,and the maximum weight gain rate of composite protective layers with different thicknesses is 0.67%.It shows that the dense glass phase grid structure formed by the composite protective layer at high temperature can significantly reduce the oxidation rate of the alloy baseband and improve its oxidation resistance.A study was conducted on the impact of high-temperature antioxidant protective layer on the performance of thin-film thermocouples.First,monolayers of Al₂O₃ and Si₃N₄ films are prepared to protect the Ir-Ir Rh₄₀ thin-film thermocouple.The static calibration test results of the samples in the range of 100℃to 800℃show better stability and repeatability compared with the unprotected samples.Dynamic response testing of Ir-Ir Rh₄₀ thin-film thermocouples with/without Si₃N₄ protection yielded the average response time of 26.6μs and 28.6μs without protection.The static calibration test on Pt-ITO thin-film thermocouples with different protective layers in the range of 200℃to1300℃shows that the performance and high temperature stability of YAl O/Si₃N₄/Al₂O₃sample after atmospheric annealing is significantly improved,with a maximum error of0.97%.The high temperature signal drift rate is only 1.05（℃/h）,showing good high temperature stability.After the dynamic response test,the response time without/with a protective layer is 85.0μs and 96.3μs.The results show that the thin-film sensor has great application prospects in the surface temperature test of key components in aerospace and petrochemical industry.