Design And Fabrication Technology Of Fast Response Probe Type Thin Film Thermocouples

In aviation,aerospace and weapon equipment,there are a large number of parts that need to accurately measure the transient temperature,such as the temperature of the tail flame of the engine tail nozzle,the gas temperature of the combustion chamber,the explosion temperature of the explosive,and the surface temperature of the nose cone of the high-speed aircraft.Temperature measurement technologies such as thermocoupless and armored thermocoupless are difficult to achieve rapid and accurate temperature measurement of these parts.It is urgent to develop temperature measurement sensors with simple structure,high temperature measurement accuracy and short response time.To this end,this thesis designed and fabricated a fast-response ceramic probe-type thin-film thermocouples,and mainly carried out research on the design,preparation,performance characterization and application technology of the thermocouples.The main work of the thesis is as follows:First,the structure of the fast-response probe-type thin-film thermocouples is designed and fabricated.The thermocouples probe consists of a 99% alumina ceramic rod with a diameter of 5 mm × 2.5 mm and two K-type thermocouples wires of NiCr/NiSi with a diameter of 0.8 mm.It is composed of a metal conduction film,wherein the ceramic column has two through holes with a diameter of 0.8 mm,the center distance between the two holes is 2.3 mm,the length of the Ni Cr wire is 50 mm,and the length of the Ni Si wire is 40 mm.The function is to realize the electrical connection of the thermocouples wire.The thermocouples wire and alumina ceramic rod are fixed and formed by high temperature sintering process.The thermocouples samples were prepared by depositing platinum,nickel-chromium and nickel-silicon films on the top surface of the ceramic probe base as the metal conduction layers by DC magnetron sputtering technology.Secondly,the thermoelectric properties of the thin film thermocouples samples were calibrated by the static calibration method.The results showed that when the thickness of the Pt metal conduction layer was increased from 0.5 μm to 2 μm,the output of the sample in the temperature range of 200 ～ 850 ℃ decreased.There is a good linear relationship between thermoelectric potential and temperature gradient,and the average Seebeck coefficient is around 40 μV/℃,which is comparable to standard k-type thermocoupless.The average Seebeck coefficients of the three metal conduction layer thermocouples samples of platinum,nickel chromium and nickel silicon with thickness of 1 μm are all about 41.59 μV/℃,which is comparable to the standard k-type thermocouples,indicating that the metal conduction layer has The material has no effect on the thermoelectric performance of the thermocouples.However,due to the excellent high-temperature oxidation resistance of the metal platinum conduction layer,the life,temperature upper limit and stability of the thermocouples samples with Pt as the conduction layer are higher than those of the samples with nickel-chromium and nickel-silicon as the metal conduction layer,in the temperature range of 200 ～ 850 ℃,its life is more than 40 h,the upper limit of temperature measurement is 1100 ℃,and the temperature measurement error is 0.54%.The three metal conduction layer probe-type thin film thermocouples samples all have linear thermoelectric output in the low temperature environment of-80 ℃ ～ 80 ℃,but the temperature measurement error increases slightly,and the test results under different heating rates show that platinum metal conduction The thermoelectric performance of the through-layer probe-type thin-film thermocouples is still good at different heating rates.Third,the short-pulse laser method was used to calibrate the response time of probe-type thin-film thermocouples.They are 6.60 μs,8.01 μs,and 8.20 μs,respectively.The reason is that the specific heat capacity of the three metal films is different.The smaller the specific heat capacity,the faster the temperature rise and the shorter the response time;The response times of the thermocouples samples with μm and 2 μm are2.95 μs,6.86 μs,11.64 μs,and 17.33 μs,respectively,indicating that with the gradual increase of the thickness of the conduction layer,the heat capacity of the conduction layer gradually increases,and the response time of the sample increases.The time gradually increases accordingly.Finally,the prepared fast-response ceramic-based probe-type thin-film thermocouples was installed on the surface of a certain type of warhead,and the temperature measurement was carried out.The transient temperature of the warhead surface was successfully obtained.The peak temperature is 469.72 ℃ after temperature compensation,which indicates that this fast-response ceramic-based probe-type thin-film thermocouples can be used to measure the transient temperature of the warhead surface.