Improving thermal fracture resistance in ceramic microcomponents for spacecraft propulsion
Abstract: Because of thermal transients and gradients occurring upon rapid heating or cooling, microcomponents made from High-Temperature Co-fired Ceramics (HTCC) often fail at temperatures far below what the materials can withstand per se. This work investigates how resistance to thermal fracture in HTCC microcomponents can be increased by improving the component design, aiming at increasing the thermal performance of a microthruster with integrated heaters. The effect of four design parameters: component and cavity geometries (circular or square), heater placement (central or peripheral), and addition of embedded platinum layers, on thermal fracture resistance was investigated experimentally through a study employing design of experiments. Components of different designs were manufactured, and their thermal fracture resistance tested by rapid heating until the occurrence of failure. Peripheral heater placement and presence of embedded platinum layers were seen to improve resistance to thermal fracture, whereas the shape of the component and the cavity did not significantly affect thermal performance. The most favourable design was then applied for a microthruster that was fabricated and evaluated with respect to thermal fracture resistance. The microthruster survived rapid heating up to 1461°C, and was operated as a cold gas microthruster at temperatures up to 772°C. None of these temperatures were limited by component failure, but by the component interface.
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