9 - Metal-Matrix Composites

Abstract

Metal-matrix composites with discontinuous or continuous carbon fibers or carbon nanotubes (CNTs) are attractive for the thermal conductivity of the metal matrix, the low coefficient of thermal expansion (CTE), high thermal conductivity, and high elastic modulus of the fibrous carbon. The combination of high thermal conductivity and low CTE is valuable for heat sinks and other components in microelectronic packaging. In addition, the fibrous carbon enhances the lubricity and wear resistance. Methods of composite fabrication include liquid metal infiltration, powder metallurgy, and stir casting. Due to the reactivity of liquid metals with carbon to form carbides and the inadequate wetting of the fibrous carbon by liquid metals, the coating of the fibrous carbon is commonly conducted prior to composite fabrication. The coatings include metals and ceramics. Common metal matrices for structural applications include aluminum, magnesium, copper, and titanium. For soldering and brazing, tin-matrix and silver-matrix composites are relevant. The processing, structure, and properties of metal-matrix composites are covered.