Investigation of electric current-assisted fabrication parameters for nanocarbon-Al composites with improved electrical conductivity and tensile strength

Electric current-assisted processing of a class of materials, called “covetics,” presents a scalable method of production for nanocarbon-Al composites by applying a direct current to a molten mixure of Al-1350 and activated carbon precursor. Increased tensile strength and electrical conductivity have been measured in Al covetics; however, there is limited understanding of the current-assisted process parameters and variation in structure and properties among trials. Within the metal matrix the activated carbon is converted to sp² graphitic carbon with increased crystallite size of the graphitic carbon, as measured by the Tuinstra-Koenig relation for Raman spectra. Electrical conductivity is enhanced in areas that show increased crystallite size of the graphitic carbon. Applied current during fabrication has been varied to understand the effect of current density on carbon crystallization rate. Local electromechanical behavior is measured by nanoindentation and AFM to gain insight into the structure-property relationship at the nanoscale, which can be used to further inform optimization of the current-assisted process.