PDC-SiBCN High Temperature Resistant Wireless Passive Temperature Sensors

Aerospace and other fields usually involve harsh working environments such as high temperature,high pressure,high load,and acid-base corrosion.Therefore,how to accurately and instantaneously monitor the temperature of such extreme environments has been a problem that plagues the scientific community.Wired active temperature sensors are vulnerable to failure at high temperatures because of their wired and active drawbacks.Meanwhile,the special application background of aerospace has placed very high demands on sensor materials.Therefore,research and development of a new type of material wireless passive temperature sensor has great scientific significance and application value in the field of high temperature.As a new type of ceramic material,polymer derived ceramics(PDC)have excellent high temperature stability,oxidation/corrosion resistance,high creep resistance,high temperature semiconductor characteristics,and good piezoresistive properties.Moreover,the preparation process of PDC ceramics is simple and the price is low.The high temperature stability of the PDC-SiBCN quaternary system developed on the basis of the PDC-SiCN ternary system has been greatly improved,and dielectric constant of PDC-SiBCN ceramic is positively correlated with temperature at high temperatures.Therefore,PDC-SiBCN ceramic is the best choice for sensor materials used in high temperature extreme environments.In this paper,PDC-SiBCN ceramic is used as the internal temperature sensitive dielectric material of the sensor,and Pt is used as the outer metal cavity material.The resonator formed is based on the dielectric temperature characteristic of PDC-SiBCN ceramic.As the ambient temperature changes,a change in the dielectric constant causes a corresponding change in the resonant frequency.By establishing the relationship between the dielectric constant of the ceramic and the ambient temperature,the relationship between the resonant frequency of the sensor and the temperature can be obtained.Using polyborosilazane(PBSZ)as precursor material,PDC-SiBCN ceramic was obtained by several process steps such as cross-linking,ball milling,tableting,and pyrolysis.XRD,SEM,EPR,Raman and other methods were used to analyze and characterize morphological composition and structural properties of PDC-SiBCN ceramic.Electrical performance test analysis shows that the conductivity of PDC-SiBCN ceramic increases monotonically with the increase of test temperature,and PDC-SiBCN ceramic which is pyrolyzed at 1000 C and oxidized at 800℃ for 12 hours has an average dielectric constant of 2.9483 and an average loss tangent of 0.0062 in the frequency range of 12 to 14 GHz.Using high frequency structure simulation software(HFSS),the effects of structure parameters such as the radius and height of the resonator,the size and position of the slot antenna on the sensor performance(resonant frequency and quality factor)were studied,and the sensor structure parameters were optimized.According to the optimized parameters,the wireless passive temperature sensor with excellent performance was prepared by using PDC-SiBCN ceramic as a sensor temperature sensitive dielectric material.The effects of thermal oxidation treatment,pyrolysis temperature and radius on the performance of the sensor were studied,and the cycle stability and wireless transmission distance of the sensor during temperature rise were tested and analyzed.It is found that the resonant frequency of the sensor is negatively correlated with temperature,while the dielectric constant of PDC-SiBCN ceramic is positively correlated with temperature.Thermal oxidation treatment can significantly improve the high temperature test performance of the sensor and increase the effective test temperature.When PDC-SiBCN ceramics with pyrolysis temperatures of 1000 0C,1100℃,and 1200℃ are used as temperature sensitive dielectric materials,the highest test temperatures of the sensors are 1100 C,900℃,and 800℃ respectively.At the same test temperature,the resonant frequency of the sensor decreases with increasing pyrolysis temperature.At the same test temperature,the resonant frequency of the sensor decreases with increasing radius.The sensor has good cycle stability,and it has an actual wireless transmission distance of 42 mm at room temperature and a transmission distance of up to 8 mm when the test temperature is 1100 C.