Single-crystal and textured polycrystalline Nd2Fe14B flakes with a submicron or nanosize thickness

• Published in: Acta materialia Vol. 60; no. 4; pp. 1721 - 1730
• Main Authors: Cui, B.Z., Zheng, L.Y., Li, W.F., Liu, J.F., Hadjipanayis, G.C.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01-02-2012; Elsevier
• Subjects: Addition of Nd70Cu30 alloy; Applied sciences; Cleavage; Exact sciences and technology; Metals. Metallurgy; Nd2Fe14B single-crystal and textured poly-nanocrystalline flakes; Surfactant-assisted high-energy ball milling; Texture; Addition of Nd70Cu30 alloy; Cleavage; Texture; Nd2Fe14B single-crystal and textured poly-nanocrystalline flakes; Surfactant-assisted high-energy ball milling; alloy; Addition of Nd; Grinding(comminution); Surfactant; Rare earth metal alloy; Powder metallurgy; Single crystal; Thickness; Cu; B single-crystal and textured poly-nanocrystalline flakes; Nd; Microstructure; Nanocrystal; Fe
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2011.11.062

This paper reports on the fabrication, structure and magnetic property optimization of Nd2Fe14B single-crystal and [001] textured poly-nanocrystalline flakes prepared by surfactant-assisted high-energy ball milling (HEBM). Single-crystal Nd2Fe14B flakes first with micron and then with submicron thicknesses were formed via continuous basal cleavage along the (110) planes of the irregularly shaped single-crystal microparticles during the early stage of HEBM. With further milling, [001] textured polycrystalline submicron Nd2Fe14B flakes were formed. Finally, crystallographically anisotropic polycrystalline Nd2Fe14B nanoflakes were formed after milling for 5–6h. Anisotropic magnetic behavior was found in all of the flake samples. Nd2Fe14B flakes prepared with either oleic acid (OA) or oleylamine (OY) as the surfactant exhibited similar morphology, structure and magnetic properties. Both the addition of some low-melting-point eutectic Nd70Cu30 alloy and an appropriate post-annealing can increase the coercivity of the Nd2Fe14B flakes. The coercivity of Nd2Fe14B nanoflakes with an addition of 16.7wt.% Nd70Cu30 by milling for 5h in heptane with 20wt.% OY increased from 3.7 to 6.8kOe after annealing at 450°C for 0.5h. The mechanism for formation and coercivity enhancement of Nd2Fe14B single-crystal and textured poly-nanocrystalline flakes with a submicron or nanosize thickness was discussed.