| In the process of cooling effect test and whole machine test of aeroengine research, the accurate measurement of surface temperature and its distribution of turbine blade is of great importance. Thin film thermocouples deposited on the surface of turbine blade is one of the advanced methods of precise measurement of turbine blade surface temperature. Compared with the wire counterparts, thin film thermocouples can integrate with blade as a non-intrusive method, minimal interference with flow field environment, small thermal capacity, rapid response et al. It is very suitable for the surface temperature measurement of turbine blade. In2O3 and ITO are both semiconductor materials which also have wide bandgap, the thin film thermocouples that composed of In2O3 and ITO possess good high temperature stability and thermal sensitivity. The highest working temperature can be up to 1200 ℃. The high temperature thermoelectric performances of that are better than K(Ni Cr/Ni Si) type and S(Pt/Pt Rh) type thin film thermocouples.As a result, it has a very important application prospect for surface temperature measurement of engine blade, especially in the ultra high temperature(higher than 1100℃) work environment. In this thesis, based on the previous research results of K type, S type and Pt/ITO thin film thermocouples, the preparation processes of In2O3 films, the preparation and calibration of In2O3/ITO thin film thermocouples deposited on Al2O3 ceramic substrates and on nickel base alloy plate substrates were explored systematically.First of all, the In2O3 thin films were deposited on the Al2O3 ceramic substrates by radio frequency magnetron sputtering method. The influences of depositing parameters, such as argon/oxygen gas flow ratio, sputtering pressure, doping nitrogen on the electrical performance and deposition rate of In2O3 thin-films were studied in detail. The results indicate that the deposition rate of samples increases monotonously with increase of sputtering power and the resistivity decreases initially then increases slightly with the further increase of sputtering power. With the increase of sputtering pressure in pure argon atmosphere, the deposition rate decreases and the resistivity of the samples increases gradually. With the increase of oxygen argon flow percentage, the resistivity of the samples increases and the deposition rate decreases significantly.With the increase of N2/Ar flow ratio, the resisitivity of the sample increases and the deposition rate decreases.Secondly, the In2O3/ITO thin film thermocouples deposited on the alumina substrates were analyzed by static calibration. Results indicate that the more the resistivity of indium oxide electrode increases, the greater the Seebeck coefficient and thermal electromotive force output of thin film thermocouples are. Temperature sensitivity and potential output of samples prepared in nitrogen/argon atmosphere reduces dramatically. With the increase of annealing temperature, the Seebeck coefficient and thermal potential output of samples increase. The Seebeck coefficients and thermal potential output stabilities of samples annealed in air are better than that of samples in oxygen or nitrogen atmosphere. Annealing time has not much impact on Seebeck coefficients of samples, but annealing time is too long, the stabilities of thermal power outputs decrease in a way. The Seebeck coefficients of the samples with alumina protection layer is 177.7 μV/℃, its temperature measurement error is less than ±0.95 % and the service lifetime is greater than 20 h.Finally, 10 μm Ni Cr Al Y as buffer layer by magnetron sputtering method, thermal growth alumina layer in high temperature enviroment, 10 μm alumina insulation layer prepared by electron beam evaporatiom, In2O3/ITO thin film thermocouple function layer which thickness is 1.5 μm deposited by radio frequency magnetron sputtering method and alumina protective layer which thickness is about 2 μm prepared by electron beam evaporatiom were fabricated on nickel base alloy substrates successfully. The size of In2O3/ITO thin film thermocouples on metal matrix is 63 mm×1 mm×1.5 μm(length, line width and thickness). The static calibration results showed that the average Seebeck coefficient of the samples was about 175.3 μV/℃ and the deviation of temperature measurement is less than ±2.78 % and The service lifetime of thin film thermocouple is more than 20 hours and still functional after. The sample can work stably for 20 hours in 350~1050 ℃ and 7 hours at 1050 ℃. |
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