Preparation And Properties Of Flexible High Temperature Film Sensor

As the core component of the aircraft,the aero-engine works under extreme high temperature and harsh environment for long time.In-situ surface temperature measurement of the hot components such as turbine blades and combustion chamber are urgently needed for the design,verification and health monitoring of the aero-engine.Thin film thermocouples?TFTCs?could provide precise surface temperature measurement with fast response.However,due to the complex shape and big size of some hot components,it is not easy to achieve uniform deposition of thin films,which limits the application of TFTCs.Flexible temperature sensor brings many opportunities in surface temperature measurement of the hot components because of its light weight and the ability to bend and fit the surface of any components.In this thesis,based on the in-situ surface temperature measurement of the hot components,flexible Ni tapes was used as the substrate to prepare flexible high temperature thin film sensor.And a series of research on its fabrication and thermoelectric properties has been carried out.Firstly,nitrogen-doped ITO thin films were deposited on alumina ceramics by RF magnetron sputtering.The resistivity of the deposited film was 1.43×10^-3?·cm.While the resistivity of films annealed in air and nitrogen was 12.16×10^-3?·cm and 8.64×10^-3?·cm respectively.During air annealing,the oxygen in the air diffused into the film and filled oxygen vacancy,leading to the increase of the resistivity of film.During nitrogen annealing,the nitrogen in gas media diffuses into the film and fills the oxygen vacancy,leading to the increase of the resistivity of film.Moreover,the nitrogen and oxygen in the film form oxynitride and stabilize the oxygen vacancy,which made the resistivity of film tend to be more stable,so the resistivity of film is smaller than the film annealed in air.Secondly,the preparation and performance of the flexible Ni tapes surface composite insulating layer were studied.Multilayer Y₂O₃ and Al₂O₃ thin films were prepared on the flexible Ni tapes by solution method.The peeling occurs since the stress between Al₂O₃film and substrate was not fully released.Magnetron sputtering was also tried to prepare the AlON/Al₂O₃ composite insulating layer on the flexible Ni tapes.And the insulation performance of the composite insulating layer was tested.The results showed that when the temperature is up to 1000°C,the resistance of the insulating layer could reach 100k?.This demonstrated that the introduction of AlON amorphous barrier layer could greatly improve the high temperature insulation performance of the composite insulating layer.Finally,ITO/Pt and ITO/In₂O₃ TFTCs were separately prepared on the Al₂O₃ceramic substrate,and their thermoelectric properties in the temperature range of300°C¹000°C were studied by static calibration.The results show that the repeatability and stability of the thermocouple were greatly improved after the first calibration.The flexible high temperature thin film sensor was obtained by transferring the TFTCs preparation process to the flexible Ni tapes.ITO/In₂O₃ TFTCs and ITO/Pt TFTCs were prepared on the insulated Ni tapes respectively and and their thermoelectric properties in the temperature range of 25°C⁶00°C were studied.The results show that the following behavior and repeatability of ITO/In₂O₃ TFTCs became worse at the third calibration,and the output thermoelectric potential decreased from 1.2mV to 0.15mV.However,the ITO/Pt TFTCs kept good following behavior and stability in five cycle calibration.The device was intact after calibration and its maximum output thermoelectric potential was15 mV.