Structural and magnetic properties of rare-earth-free MnAl(MCNT)/Fe nanocomposite magnets processed by resin-bonding technique

Abstract

In this study, the potential of multi-walled carbon nanotubes (MCNT) in processing rare-earth-free MnAl(MCNT)/Fe nanocomposite magnets was exploited through adopting a combination of surfactant-assisted milling and resin-bonding techniques. The required hard and soft magnetic phases such as MnAl(MCNT) and α-Fe, respectively, were individually subjected to surfactant-assisted high-energy ball milling. The surfactant-coated MnAl(MCNT) and Fe nanopowders, thus, obtained were characterized with respect to their structural and magnetic properties. Relatively, a very high coercivity, Hc (4.48 kOe), was obtained for the surfactant-coated MnAl(MCNT) powders after 6 h of milling, while in the case of Fe powders with high saturation magnetization, Ms (218.6 emu/g) was achieved at 3 h of surfactant-assisted milling. The MnAl(MCNT) powders with high Hc were mixed with the Fe powders of high Ms with different weight percentages: 0, 5 and 10. The nanocomposite powder mixtures were further milled for 1 h and then processed in the form of resin bonded magnets under aligning magnetic field of 20 kOe. The obtained bonded nanocomposite magnet, i.e. MnAl(MCNT) with 5 wt% of Fe addition demonstrated a good combination of high Ms (63.7 emu/g) and high Hc (4.46 kOe).