[en] Anisotropic SmCo₅/Co magnetic nanocomposites have been fabricated by chemical deposition of Co nanowires based on SmCo₅ nanoflakes. The SmCo₅ nanoflakes with an average thickness of 200 nm and diameter of 4 μm were first prepared by surfactant-assisted high-energy ball-milling. The Co nanowires with mean diameter of 20 nm and length of 200 nm were then deposited via a solvothermal chemical process. This strategy can effectively control the content of SmCo₅ nanoflakes and Co nanowires, and the hard magnetic nanoflakes can be coated with a uniform distribution of Co nanowires. Both of the SmCo₅ nanoflakes and Co nanowires are anisotropic, and could be magnetically aligned simultaneously in the nanocomposites, which is confirmed by XRD patterns. Magnetic measurements of the “bi-anisotropic” SmCo₅/Co composites show an enhanced remanent magnetization with increasing the content of Co nanowires. The exchange-coupled SmCo₅/Co nanocomposites with up to 40 wt % Co content exhibits the highest (BH)_max value of 23.8 MGOe, larger than the single phase SmCo₅ nanoflakes.

[en] In present study, surfactant assisted ball-milling method was applied to prepare SmCo₅ nanoflakes, which were then magnetically aligned and warm compacted with a liquid binder to make bulk anisotropic SmCo₅ bonded magnets. Warm compaction with magnetic-field-assisted liquid phase processing can decrease the viscosity of the binder to enhance the alignment of the magnetic nanoflakes, and thus can produce high density magnets, providing a novel method to fabricate anisotropic bonded magnets. The magnetic properties, microstructure, and crystal alignment of both nanoflakes and bonded magnets are systematically investigated. The X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM) characterizations suggest that the obtained liquid phase bonded magnets exhibit enhanced magnetic anisotropy compared with those without magnetic field alignment and the solid phase bonded anisotropic magnets. The remanence of anisotropic phenol formaldehyde (PF) bonded magnets (4.43 kG) is higher than isotropic bonded magnets (3.76 kG), and the energy product of bonded magnets increases from 3.4 MGOe to 4.8 MGOe under the effect of the magnetic field.

[en] Highlights: • Using α-Fe nanoflakes can optimize microstructure and performance of nanocomposites. • α-Fe nanoflakes are easier to realize nanocrystallization during HEBM process. • A giant M_r of 9.75 kG was achieved in the nanocomposite with 25 wt% α-Fe content. Keeping a high proportion of soft magnetic phase with small grain size and uniform distribution of soft and hard magnetic phase is the key factor to fabricate bulk nanocomposites. We report a novel design to fabricate high performance SmCo₅/α-Fe nanocomposites by choosing nanoscale α-Fe flakes as raw material of soft magnetic phase instead of micron scale α-Fe particles. Microstructure optimization, i.e., fine and dispersive distribution of α-Fe grains in SmCo₅ matrix, and high soft magnetic phase proportion up to 25 wt% were achieved simultaneously. As a consequence, the remanence, intrinsic coercivity, and maximum energy product rise by 13.55%, 46.99%, and 80.03% in the SmCo₅/α-Fe nanocomposites with 20 wt% α-Fe, respectively. Moreover, a giant remanence of 9.75 kG is achieved in the SmCo₅/α-Fe nanocomposite with 25 wt% α-Fe nanoflakes content.