Improvement of Copper–Graphene Composites Properties due to the Lubricating Effect of Graphene in the Powder Metallurgy Fabrication Process

Abstract

Bulk copper–graphene composites are regarded as novel materials for the application for electronics. However, the properties of the composites and their microstructure are highly dependent on synthesis technique parameters as well as the graphene additive contents and its type: graphene flakes, graphene nanoparticles, reduced graphene oxide particles, etc. In the present work, powder metallurgy technique was modified to produce copper–graphene composites; the milling procedure was optimized basing on particle size distribution data. The optimal amount of graphene additive to copper powder was calculated via the simple mathematical model, where metal–graphene composite is regarded as a core–shell particle. That approach was used to produce copper–graphene composites with the graphene contents of 0.1, 0.5, and 1.0 wt%. In case of 3 wt% of carbon additive (thermally exfoliated graphite) copper-graphite–graphene composites were obtained. The microstructure of samples was studied by scanning electron microscopy and electron back-scattering diffraction. The identification of carbon allotropes was performed by Raman spectroscopy. It was shown that the graphene additive acts as a lubricant during powder metallurgy process: carbon allotrope flakes are not introduced into the material matrix but extruded to pores. As a result, a new synthesis approach for copper–graphene composites manufacturing with improved microstructure and mechanical properties was suggested.