Interfacial design of Mg/graphite flakes-MP (MP=Fe, Co or Ni) ferromagnetic composites with low density and high thermal conductivity

Abstract

In the present work a new material based on the recently developed graphite flakes-SiC particles/metal composite, is described. The latter was processed by gas-pressure infiltration of the liquid metal into a preform obtained by packing a mixture of graphite flakes and SiC particles. Its microstructure consists of alternating layers of oriented graphite flakes and metal-particles composite, and, thus, it is highly anisotropic. Its highest thermal conductivity (>300 Wm−1K−1), attained in the plane parallel to the flakes plane, makes it suitable for heat sinking applications. Replacing SiC by particles of similar size and of ferromagnetic nature (Fe, Co and Ni), a material with moderate-to-high magnetic permeability and reasonably high thermal conductivity, has been produced. Mixtures of packed magnetic particles and graphite flakes were infiltrated with pure magnesium. In order to avoid chemical reaction, Co and Ni particles were carbon coated. Optimizing the combination of thermal conductivity and magnetic properties requires proper control of liquid metal infiltration variables, such as, temperature, pressure and contact time before metal solidification.