Preparation Of Anisotropic Nanocrystalline （Sm,Pr）₁Co₅Permanent Flakes Using Surfactant-assisted High Energy Ball Milling

Using surfactant-assisted high energy ball milling, anisotropic nanocrystalline(Sm,Pr)1Co5permanent naoflakes were successfully fabracted in the present study. Twokinds of wet milling methods were used, with one of which oleic acid was used assurfactant with heprane being the solvent and with the other，polyvinylpyrrolidone(PVP)was used as surfactant with ethaonal being the solvent. The effect of milling time anddifferent surfactants on the microstructure, morphology and magnetic properties werestudied using the XRD, FESEM and VSM mesurements, respectively.As a result, anisotropic nanocrystalline (Sm,Pr)1Co5permanent naoflakes with [00l]out-plane texture were successfully fabracted following both methods, while onlyistropic powders with low coercivity were obtained using dry milling mechod. Usingoleic acid as the surfacatant, an in-plane size from0.5to6micrometers of nanoflakeswas yielded after milling for4h. As the milling time icreases, the coercivity of alignedpowders first increases, peaks at12.2kOe with the milling time of8h, and then dereaseswith prolonged milling time. By PVP-assisted ball milling, however, the thickness of thenanoflakes deacreases with prolonged milling time, while the coercitity of the flakes firstincreases, then stabilize at about12.0kOe even milling up to40h. As a result, a flakethickness of30nm and a high coercivity of12.0kOe were obtained after milling for30h.Besides, it proved that using PVP as surfactant, it is easy to obtain smaller patticle sizewith narrower size distribution. An in-plane size of about1micrometer was obtainedafter milling for40h. Further studies show that, more content of PVP is more effective toimprove the (00l) texture and protect the powders from oxidation and amorphizatin.In our study, it shows that, the surfactant plays an important role in the millingprocess. The change and contentof surfactant has an important role in controlling themorphology and magnetic properties of the powders, providing a possibility to fabricatepowders with both ideal morphology and magnetic property.