Composite materials for thermal applications

Abstract

The transfer of heat by conduction is involved in the use of a heat sink to dissipate heat from an electronic package, the heating of an object on a hot plate, the operation of a heat exchanger, the melting of ice on an airport runway by resistance heating, the heating of a cooking pan on an electric range, and in numerous industrial processes that involve heating or cooling. Effective transfer of heat by conduction requires materials (such as a heat sink material) of high thermal conductivity. In addition, it requires a good thermal contact between the two surfaces (such as the surface of a heat sink and the surface of a printed circuit board) across which heat transfer occurs. Without good thermal contacts, the use of expensive thermal conducting materials for the components is not cost effective. The attainment of a good thermal contact requires a thermal interface material, such as a thermal grease, which must be thin (small in thickness) between the mating surfaces, must conform to the topography of the mating surface and preferably should have a high thermal conductivity as well. This chapter addresses materials for thermal conduction, including materials of high thermal conductivity and thermal interface materials. In addition, this chapter addresses materials for thermal insulation and heat retention, which are important in buildings for the purpose of energy saving. Thermoelectric applications can be considered a subset of thermal applications, but they are addressed in Chapter 6 rather than this chapter.