Thermally Conductive Ceramic Matrix Composites

Abstract

As a result of increased performance in a wide range of engineered products ranging from computer processors to advanced aerospace vehicles, there is a critical need for improved thermal management systems for transferring heat. The required enhancements include increased thermal conductivity, increased surface area, reduced weight/volume, as well as operability in harsh environments, such as durability under high flow rates, vibrations, stress, elevated temperatures, and oxidative environments. For example, improved thermal management is needed to increase the power density of electronics and more effectively cool electronic enclosures that are envisioned for future aircraft, spacecraft, and surface ships. Typically, heat exchangers must increase in size in order to more effectively dissipate any increased heat loads. This is impossible in many cases, thus new materials and concepts for heat exchanger cores/systems are required. Another high-profile application involves thermal protection systems (TPS) for aerospace vehicles (e.g., the reinforced carbon composite leading edge of the Space Shuttle). Future TPS systems will include a systematic approach where a temperature-resistant, durable exterior composite skin is coupled with a combination of conductive and insulating core materials both of which will need to be capable of withstanding extreme environments. Thermally conductive ceramic composites have been actively developed for meeting these requirements in thermal management of electronic packaging. Fiber, whisker, particulate, or nanotube reinforced composites can be made tougher, stronger, and more effective for thermal management with tailored coefficient of thermal expansion (CTE). The desirable characteristics of ceramic matrix composites (CMCs) include high-temperature stability, high thermal shock resistance, high hardness, high corrosion resistance, light weight, nonmagnetic and nonconductive properties, and versatility in providing unique engineering solutions. The combination of these characteristics makes CMCs attractive alternatives to thermal management of electronic packaging, particularly for high-temperature electronic packaging systems. The aim of this chapter is to discuss and highlight newly developed CMC materials and the associated technologies related to thermal management. Examples of these new materials include diamond or carbon reinforced silicon carbide (SiC) composites, reaction-bonded SiC composites, aluminum-toughened SiC composites, and ceramic-based nanocomposites.