Smart refractory bricks for high temperature applications
Processing of Metal Silicide/Refractory Oxide Composites for High-Temperature and Harsh-Environment Sensing Applications
High-temperature reactors and energy systems used in many industrial processes such as coal gasification, power generation, steel and glass manufacturing require better monitoring of the process conditions (temperature, pressure etc.) and also the refractory health. This is crucial for increasing the efficiency and safety of such industrial processes. Therefore, there is a great demand to the advanced sensing technologies, particularly for use at high-temperatures and harsh-environments. But current sensor technologies are primarily based on thermocouples inserted into the reactors via open access ports through the refractory, which typically leads to rapid corrosion by gaseous or molten reactants. Therefore, such thermocouples suffer from several structural and functional problems under high operating temperature (750°-1600°C), high pressure (1000 psi) and oxidizing/corrosive environment, limiting stability and long-term use.
Research is on-going to develop electrically conductive and thermally stable ceramic composites that are capable of operating under high-temperature and harsh-environments. The composites are mainly composed of transition metal silicides (MoSi 2,WSi2,TaSi2, etc.) and refractory oxide ceramics (Al 2O3,ZrO2,Cr2O3, etc.). Current work focuses on the densification, microstructural evolution and grain growth kinetics, high-temperature thermal/chemical stability and physical properties (electrical conductivity, CTE etc.) of the composites at high-temperatures up to 1400°-1600°C. The preliminary results presented that ceramic composites such as MoSi 2-Al 2O3 and WSi 2-ZrO2 were successfully produced with high thermal/chemical stability, very low grain growth rates and high electrical conductivities (83.3-107.4 S/cm) at high temperatures (900°-1400°C). In addition, an image analysis method for characterizing the degree of distribution (homogeneity) of the composites quantitatively was developed for better understanding of the microstructure-property relationship. With the development of these ceramic composites, advanced high-temperature and harsh-environment sensors (e.g. thermocouples, thermistors, strain sensors) can be fabricated for long-term and more efficient use in the high-temperature reactors and energy systems.