Surfactant Removal Study for Nano-Scale SmCo5 Powder Prepared by High Energy Ball Milling (Postprint)

Abstract : In the present study, nano-flake SmCo5 powders with typical flake thickness of 300 nm were prepared by high energy ball milling using valeric acid as a surfactant. In order to remove the surfactant the as-milled powders were heat treated in argon and the effect of the annealing temperature on structural and magnetic properties of the resulting powder was investigated. Partial (58%) and nearly complete (96%) surfactant removal was observed by DSC after treatments at 200 C and 400 C, respectively, without oxide formation detectable by powder X-ray diffraction. Demagnetization measurements revealed suppression of the energy product (BH)max and dramatic decrease in coercivity (Hci) after annealing. The results indicate that even a modest heat treatment of SmCo5 nano-powder severely degrades its magnetic properties. Either alternative methods of surfactant removal must be considered, or the surfactant must remain during further powder processing.