Aluminum-assisted dispersion of magnetic powders for particle size characterization

A new dispersion technique was developed to disperse magnetic powders for quantitative characterization of their particle sizes using scanning electron microscopy (SEM). In this technique, the magnetic particles/powders were dispersed effectively by non-magnetic aluminum powders, cold pressed, polished, and finally analyzed with SEM, combined with an image analysis software. It has been a challenge to disperse the magnetic powders for quantitative characterization of their particle size distribution due to the particle agglomeration resulting from their intrinsic magnetic attractions. By means of the aluminum assisted dispersion technique developed in this work and SEM, SmCo₅ magnetic powders were characterized quantitatively regarding their particle size distribution. The SmCo₅ magnet particles were distinguished in aluminum matrix in SEM backscattered images due to the z-contrast caused by the difference in atomic number between aluminum and SmCo₅ alloy. With the method, two SmCo powder preparation techniques, ball milling and jet milling, were also evaluated.