Microstructural, Fractal, and Phase Analysis of MnO₂–Carbon Powder Treated Aluminium Can Scrap

Abstract

Recycling aluminium can scrap is often accompanied by dross formation and non-metallic inclusions that may reduce the quality of recovered metal. This study investigated the effect of MnO₂–carbon particle treatment on the microstructure, fractal characteristics, and phase composition of recycled aluminium cans. A charge containing 90 wt% waste aluminium cans and 10 wt% MnO₂–carbon powder was processed at 700 ± 5 °C, with stirring at 250 rpm for 3 min. The resulting materials were characterised by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), fractal analysis, and X-ray diffraction (XRD) with Rietveld refinement. SEM observations indicated that the treated aluminium exhibited a denser α-Al matrix, fewer micro-voids, and a more homogeneous distribution of dispersed particles than the untreated material. Fractal analysis showed no distinct linear relationship between particle sphericity and fractal dimension, consistent with a predominantly random geometric distribution. XRD-Rietveld analysis identified α-Al, α-Al₂O₃, AlN, Al₄C₃, and MgAl₂O₄ as major crystalline phases in the treated system. A conceptual reaction mechanism was proposed to describe possible chemical processes during MnO₂–carbon-assisted melt treatment. Overall, the findings indicate that MnO₂–carbon treatment is associated with microstructural refinement and altered phase development in recycled aluminium can material, while the fractal results provide a quantitative description of pore and particle morphology.