PROPERTIES OF HIGH THERMAL CONDUCTIVITY CARBON-CARBON COMPOSITES FOR THERMAL MANAGEMENT APPLICATIONS

摘要

Carbon-Carbon (C-C) fiber-matrix composite materials (C-C's) possess unique characteristics which make them attractive for a wide spectrum of current and potential applications, e.g., brake pads for commercial and military airplanes and for race cars, heat exchangers, re-entry cones for missiles, aerospace structural components, heat sinks and spreaders for power electronics, and bipolar plates for proton-exchange-membrane fuel cells. C-C's have very low densities in the range 1.6-2.2 g/cm~3, lower than that of aluminum (2.7 g/cm~3) and four times lower than that of stainless steel. C-C's have higher thermal conductivities than those of copper and silver and the highest thermal conductivity per unit density among materials suitable for thermal management applications, see Fig. 1. They have high mechanical strength, which increases with temperature, by contrast to metals and ceramics, the strength of which decreases with temperature. C-C's also evidence graceful failure under load, as do ceramic fiber-matrix composites, while graphite and monolithic ceramics fail abruptly when their ultimate strength is exceeded. C-C's also possess high toughness and can be used in a wide range of temperatures and in severe and chemically aggressive environments; they require protection from oxidation for continuous use above ～350°C in an oxidizing environment [see companion paper, I. Golecki et al., this conference]. Many properties of C-C composites, such as the coefficient of thermal expansion (CTE), can be tailored by choosing the type of fiber, fabric, matrix and processing conditions. Here we describe several properties of C-C materials which we have developed for heat management applications at elevated temperatures.