Development of a Wireless Temperature Sensor Using Polymer-Derived Ceramics
A temperature sensor has been developed using an embedded system and a sensor head made of polymer-derived SiAlCN ceramics (PDCs). PDC is a promising material for measuring high temperature and the embedded system features low-power consumption, compact size, and wireless temperature monitor. The developed temperature sensor has been experimentally tested to demonstrate the possibility of using such sensors for real world applications.
Accurate temperature measurements are crucial for many applications, such as chemical processing, power generation, and engine monitoring. As a result, development of temperature sensors has always been a focus of microsensor field. A variety of materials have been studied for temperature sensor applications, for example, semiconducting silicon and silicon carbide. Silicon based sensors are typically used at temperatures lower than 350°C due to accelerated material degradation at higher temperature [1, 2]. Silicon carbide based sensors are better than silicon based sensors in high temperature measurement and can be applied in temperatures up to 500°C [3–5].
Polymer-derived SiAlCN ceramics (PDCs) are another widely studied material that demonstrate properties such as excellent high temperature stability  as well as good oxidation/corrosion resistance . PDCs have been considered as a promising material for measuring high temperature . Our early works have showed that PDC sensor head can accurately measure high temperature up to 830°C  using data acquisition system from National Instruments. The cost and size of the sensor system must be significantly reduced before it can be deployed for real world applications. In this paper, we develop a temperature sensor using PDC and an embedded system. Comparing to the National Instruments data acquisition equipment used in the previous paper, the newly developed embedded sensor is much smaller (9.7 dm3 versus 0.3 dm3), lighter (5.97 kg versus 0.19 kg), and cheaper (approximately $8000 versus $170). A WiFi module is also added so the temperature measurement can be transmitted wirelessly. The embedded board and WiFi module used in this paper are commercially available. The experiments in this paper demonstrate the possibility of deploying PDC based sensors for real world applications.
2. Fabrication of the PDC Sensor Head
In this study, the PDC sensor head is fabricated by following the procedure reported previously . In brief, 8.8 g of commercially available liquid-phased polysilazane (HTT1800, Kion) and 1.0 g of aluminum-tri-sec-butoxide (ASB, Sigma-Aldrich) are first reacted together at 120°C for 24 hours under constant magnetic stirring to form the liquid precursor for SiAlCN. The precursor is then cooled down to room temperature, followed by adding 0.2 g of dicumyl peroxide (DP) into the liquid under sonication for 30 minutes. DP is the thermal initiator which can lower the solidification temperature and tailor the electrical properties . The resultant liquid mixture is solidified by heat-treatment at 150°C for 24 hours. The disk-shaped green bodies are then prepared by ball-milling the solid into fine powder of ~1 μm and subsequently uniaxially pressing. A rectangular-shaped sample is cut from the discs and pyrolyzed at 1000°C for 4 hours. The entire fabrication is carried out in high-purity nitrogen to avoid any possible contamination.