Nanostructured Al/Al₄C₃ composites reinforced with graphite or fullerene and manufactured by mechanical milling and spark plasma sintering

Nanostructured Al matrix composites with reinforcements of graphite or fullerene (C₆₀ + C₇₀ + soot) have been produced by mechanical milling and spark plasma sintering (SPS). X-ray diffraction and transmission electron microscopy show that C₆₀ + C₇₀ withstand longer mechanical milling/alloying times than graphite. Fullerene is a good control agent during mechanical alloying resulting in a denser Al/fullerene composite when compared to the Al/graphite one. A refinement mechanism that takes place during mechanical alloying of fullerene and graphite is experimentally found and correspondingly discussed. Such a mechanism plays a major role in the amorphization of graphite. The larger surface area of the fullerene mix after milling promotes a better interaction with Al and hence allows its complete transformation into Al₄C₃ during the SPS process. The sintered products show an increase in hardness for the Al/fullerene composite of 6 times and only 4 times for the Al/graphite composite. The SPS technique shows to be an excellent method to transform the fullerene into Al₄C₃ while preserving its nanostructured nature.