Abstract. Effect of magnetic fields on growth morphology of aluminum crystals was studied in a fluidized bed thermal plasma reactor assisted by magnetic mirrors. Aluminum crystals were precipitated in the reactor using aluminum powder or aluminum-graphite mixture as precursors. The absent of magnetic field was also studied for comparison. Products were characterized by scanning electron microscopy (SEM) and X-ray Diffraction (XRD). Results indicated that, regardless the precursor used, it was observed the presence of aluminum nanowires when the external magnetic mirror was applied, suggesting that magnetic fields are able to modify growth morphology at nanoscale.