Effect of surfactant molecular weight on particle morphology of SmCo5 prepared by high energy ball milling

Abstract

Surfactant-assisted high energy ball milling (HEBM) is a widely used technique for producing nanostructured magnetic materials with oleic acid (OA) being the most commonly utilized surfactant reported in literature to date. No conclusive explanation has been presented for the wide use of OA and only a few studies have deviated from its use. OA has a boiling point of 360 °C which presents issues for complete removal of the surfactant after the HEBM process. Exposing the nanostructured materials to the high temperatures required for surfactant removal is known to result in grain growth and oxidation. In other studies, select surfactant systems, such as octanoic acid or oleylamine, have been used, however, a systematic study examining the dependence of surfactant selection on overall particle (flake) morphology has yet to be performed. In this study, we have qualitatively and quantitatively examined the effects of surfactant selection on the morphology and magnetic properties of SmCo5 utilizing surfactants with lower boiling points that are structurally similar to OA. Our results demonstrate that there was little change in the morphological and magnetic properties for the different surfactants. The implication is that lower boiling point surfactants may be used for HEBM, which require less severe conditions for surfactant removal after milling thereby preserving the integrity of the powders.