Silicon carbide (SiC) is often proposed as a sensor material for use in harsh environment applications such as monitoring gas turbines and internal combustion engines. However, little SiC survivability research has been reported for these environments. In the first half of this work, exposure testing results are reported for silicon and amorphous silicon carbide (a-SiC) coated Si die tested within a combustion engine with an exhaust temperature of 800 degrees C. It was found that an oil residue was deposited on the test samples, the surfaces of both sample types were roughened, and no measurable oxide was grown on any samples. Preliminary data indicates that the oil deposition rate increases with time for both samples, but there is greater oil adhesion on the silicon. There is an apparent correlation between material type and the severity of the surface roughening, however there were not enough samples tested for this to be statistically significant. These results lay the groundwork for robust in-cylinder SiC sensor design and operation.
For the second half of this research, simple, two lead, platinum thermoresistors were fabricated using a lift-off process. These sensors were mechanically and electrically connected to modified low-resistance sparkplugs, used as high-temperature, high-pressure feedthroughs. Both ceramic and nickel adhesives and aluminum wire bonds were used for these connections. They were tested in a modified 1000-watt generator engine to both collect real-time temperature data within the combustion environment and to observe residue deposition on the sensor surface. The thermoresistors were able to measure a change in temperature of approximately 6 degrees C between each spark ignition. Once the engine was warmed up, the dies had little to no oil deposition on their surfaces. This change from the first half of this research is attributed to the decrease in the distance between the samples and the firing sparkplug within the 1000-watt generator engine.