Research On The Temperature Drift Characteristic And Performance Of Wireless Passive PDC-SiCN Ceramic High-Temperature Pressure Sensors

With the rapid development of modern industry and aerospace technology,more and more researchers pay attention to how to detect the pressure parameter of the aeroengine internal environment in real-time and accurately.However,the working environment of the aero-engine(high temperature,high vibration and strong corrosion)is extremely harsh,which puts forward higher requirements for the pressure sensor applied in this environment.Polymer-derived ceramics(PDCs)as a kind of the ceramic,which has been widely concerned in recent years.PDCs have excellent high temperature resistance,corrosion resistance,oxidation resistance,good thermal mechanical properties and tunable electrical properties,and these properties make them have broad application prospect in the field of high-temperature sensors.However,during the preparation process of PDCs,a large number of cracks and pores will be generated inside PDCs,which will have negative influence to the properties of PDCs.On the other hand,compared with the traditional structure of pressure sensors,the structure of wireless and passive has no external power and lead wires,and has the characteristic of passive signal measurement,which shows superiority in extremely harsh environment.Among them,the resonant cavity wireless passive pressure sensor not only has the advantage of high measurement accuracy,strong anti-interference ability,but also has high Q factor,which makes it have great application potential in high-temperature harsh environment.However,the coupling effect between temperature and pressure of the resonant cavity wireless passive pressure sensor will cause the temperature drift characteristic of the sensor at high temperature,which is not beneficial to accurate measurement of pressure.Based on the above research background,PDC-SiCN ceramics was used to the material of the pressure sensor in this thesis,and according to the optimal structure parameters of the sensor determined after simulation,the corresponding wireless passive pressure sensors were prepared.The preparation process included two steps:the fabrication of SiCN ceramics and the assembly of pressure sensors.Subsequently,polymer infiltration and pyrolysis(PIP)technique was used to densify SiCN ceramics.After three PIP cycles,the porosity of SiCN ceramics decreased from 13.34%to 3.24%.Raman spectroscopy showed that the graphitization level of free-carbon in dense SiCN ceramics was higher than that in porous SiCN ceramics,which would lead to an increase in the conductivity of dense SiCN ceramics.After three PIP cycles,the conductivity increased by almost two orders of magnitude from 3.01E-10 S/cm to 1.28E-08 S/cm.In addition,the high-temperature performance of the wireless passive SiCN ceramic high-temperature pressure sensor was studied in this thesis.The results confirmed that the pressure sensor has excellent high temperature resistance and the temperature drift characteristic at high temperature.The main reason for the temperature drift of pressure sensors was that the permittivity of SiCN ceramics versus temperature.However,in the same temperature range,the permittivity of PIP-SiCN ceramics versus temperature was smaller than that of SiCN ceramics.By testing the high-temperature performance of the pressure sensor based on PIP-SiCN ceramics,it could be found that the average zero drift coefficient of the pressure sensor decreased from 187.9 kHz/℃ to 56.5 kHz/℃ through the PIP process,which significantly reduced the influence of temperature on the pressure sensor.Finally,the performance of wireless passive SiCN ceramic high-temperature pressure sensors was studied.The results presented that the relationship between the resonant frequency and the applied pressure was approximately linear at room temperature or high temperature.The sensitivity of two sensors is 6.42 MHz/N and 6.56 MHz/N at 800℃,respectively.In addition,the wireless transmission distance of the pressure sensor was large,and it had good stability and repeatability.In the future,it is expected to be applied in the high-temperature harsh environment to realize real-time and accurate monitoring of the pressure parameter.