Characterization of thermal properties of ball-milled copper-graphene powder as feedstock for additive manufacturing

Thermal properties of novel powder feedstocks, such as copper-graphene, remain largely unexplored despite their importance in heat dissipation and manufacturability in powder bed-based additive manufacturing (AM) processes. Therefore, this study characterizes the thermal properties of copper, graphene, and copper-graphene composite powder beds produced via ball milling (BM) using differential scanning calorimetry (DSC). Results reveal that BM reduces the effective thermal conductivity (ETC) up to ∼44 % for copper and ∼ 70 % for graphene powders. This is primarily due to the changes in particle morphology and the resulting modification in particle aspect ratio. Similar observations apply if copper and graphene are mixed, with up to ∼33 % reduction in ETC. This reduction is however attributed to the surface modification of the graphene-coated copper particle, providing a smaller contact radius compared to spherical copper and BM copper. This results in less effective heat conduction across the composite powder particle. Additionally, heat conduction through powder beds is analyzed by comparing the measured data with established thermal models, including Maxwell-Garnett approximation and thermal resistance network models. We demonstrate that microstructural modifications in powder beds, driven by particle morphology and surface modifications, substantially impact the ETC of copper-graphene composite powder beds.