Crystallographically anisotropic SmCo 5 nanoflakes were fabricated directly by one-step surfactant-assisted high energy ball milling ͑HEBM͒ of Sm 17 Co 83 ingot powders for 5 h in heptane and oleic acid ͑OA͒ without preprocessing or further annealing. The SmCo 5 nanoflakes have a strong ͓001͔ out-of-plane texture. The thickness of nanoflakes is in the range of 8-80 nm while their length is 0.5-8 m. The surfactant OA plays an important role in the formation of SmCo 5 nanoflakes. HEBM of SmCo 5 ingots in heptane without OA resulted in the formation of magnetically isotropic more or less equiaxed SmCo 5 particles with a size of 2 -30 m. Closely packed "kebablike" SmCo 5 nanoflakes were formed by HEBM in heptane with 15 wt % OA. HEBM in 150 wt % OA led to well-separated nanoflakes instead of the closely packed kebablike nanostructure. This resulted in the enhanced ͓001͔ out-of-plane texture. In-plane transmission electron microscope examination showed that the SmCo 5 nanoflakes were composed of grains with sizes in the range of 4-8 nm. Coercivities of about 18.0 kOe were obtained for the anisotropic SmCo 5 nanoflakes.Using surfactants during ball milling influences not only the size of the particles but also their shape. 1-3 For malleable metals and alloys, the shape of ball-milled particles can be controlled by varying the milling environment. Dry milling in gas yields more or less equiaxed particles, 2 whereas wet milling in the presence of a solvent and/or surfactants, particularly with a high energy mill and/or at a high ball-topowder ratio, results in high-aspect-ratio flakes, usually with a submicron thickness. 2,3 Flakes of Ni, Cu, Fe-Co, Fe-CoZr, Fe-Si-Al, Sn-Ag-Cu, etc., have been fabricated by wet ball milling. 2,3 However, the rare earth-transition metal ͑RE-TM͒ hard magnetic materials are inherently brittle and, therefore, usually are not susceptible for the "flaking" during ball milling. Until now, there are few reports on textured and magnetically anisotropic RE-TM nanoflakes. SmCo 5 based alloys have the highest room-temperature magnetocrystalline anisotropy among the RE-TM magnetic materials. 1 In this work, magnetically anisotropic SmCo 5 nanoflakes with the ͓001͔ out-of-plane texture were fabricated directly by onestep surfactant-assisted high energy ball milling ͑HEBM͒ of SmCo 5 ingot powders in heptane and oleic acid ͑OA͒ without prior processing or further annealing. The nanostructure and magnetic properties of the anisotropic SmCo 5 nanoflakes were studied in detail.Sm 17 Co 83 ͑at. %͒ alloy was prepared by arc melting with the appropriate excess of Sm ͑1.5-4 wt % depending on the ingot weights͒ to compensate for the evaporation losses. The ingots were manually crushed and grinded down to less than 300 m. HEBM of 5 g crushed powder was carried out for 5 h in hardened stainless steel vial using a SPEX-8000 ball mill. Heptane ͑99.8 %͒ was used as the ball-milling medium and OA ͑90 %͒ as the surfactant. The amounts of surfactant used were 0, 15, 40, and 150 wt % of the starting powders. The harden-...
Dysprosium-added sintered magnets were prepared from blends of Nd15.5(Fe,Co,Ga)78.2B6.3 and Dy2S3 powders; their microstructure and magnetic properties were compared to those of the magnets made with Dy2O3 additions or from single (Nd,Dy)-(Fe,Co,Ga)-B alloys. The addition of Dy2S3 leads to replacement of the neodymium oxide phases in the sintered magnets by the Nd2O2S and NdS phases. The magnets prepared with both the Dy2S3 and Dy2O3 powders exhibited inhomogeneous distribution of Dy within the (Nd,Dy)2Fe14B grains with Dy-rich outer grain regions. However, in a marked difference from the Dy2O3-added and single-alloy magnets, where the grain-boundary oxide phases were Dy-rich, the magnets prepared with Dy2S3 had their sulfur-containing grain-boundary phases depleted of Dy. With the larger fraction of Dy atoms available for alloying the main (Nd,Dy)2Fe14B phase, the magnets prepared with Dy2S3 showed the largest coercivity gain per 1 at.% of the added Dy.
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