Development, characterization and comparison of spark plasma-sintered Gr-Cu and Gr-Al composites reinforced with SiC and ZrB2 particles for thermal management

Graphite-copper (Gr-Cu) and graphite-aluminum (Gr-Al) composites are potential candidates for enhanced thermal management for different engineering applications. However, their applications are limited by inadequate thermal conductivity, high coefficient of thermal expansion (CTE) and low microhardness. In this study, SiC and ZrB2 were incorporated into Gr-Cu and Gr-Al powders, and then sintered in a spark plasma sintering (SPS) system to produce Gr-Cu + 8wt%SiC, Gr-Cu + 4wt%SiC + 4wt%ZrB2, Gr-Al + 8wt%SiC and Gr-Al + 4wt%SiC + 4wt%ZrB2 composites. After sintering, the physical, morphological, thermal, electrical and mechanical properties of the composites were evaluated. Results indicated 8.5% increase in relative density for reinforced Gr-Cu composites over the unreinforced Gr-Cu. The porosity of the reinforced Gr-Cu composites is 40.5% lower than that of the unreinforced and similar to 8% for reinforced Gr-Al. For all the sintered samples, Gr-Cu + 4wt%SiC + 4wt%ZrB2 sample has the highest hardness value of 44.5 HV0.1, highest peak intensity ratio of 80.19% and minimum CTE of 2.02 x 10(-5)/K. The huge increase in the microhardness and peak intensity ratio of Gr-Cu + 4wt%SiC + 4wt%ZrB2 is partially attributed to the formation of hard ZrC phase and three-bond system in ZrB2. This composite is recommended for thermal management of heat sinks and heat spreaders in electronics and pistons in automobiles.