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Efficient and cost-effective soft magnetic materials (SMMs) are essential for accelerating the adoption of electric vehicles and the sustainable growth of renewable electricity. While amorphous and nanocrystalline SMMs offer remarkably low magnetic losses, their poor mechanical properties, limited availability in size and shape (particularly ribbon widths), and high cost prevent them from widespread industrial application. Here, we show that ductile Fe-6.5%Si 2-D flakes could be used as building blocks for making high performance bulk SMMs. This approach bypasses the brittleness problem and creates a new morphology and a new fabrication method for the SMMs with improved energy efficiency and lower processing cost. Ductile Fe-6.5%Si flakes are mass-produced by melt spinning and are then consolidated to bulk SMMs with a brick-wall type of structure. The novel process introduces anisotropic electrical and magnetic properties and enables near net shape processing. Resulting Fe-6.5%Si thin sheets display low iron loss (W10/400 = 6.1 W/kg) and high permeability (µ r = 28,000), which are comparable to the current state of the art high silicon steel. CaF 2 coating reduces the iron losses for thick Fe-6.5%Si parts. Polymer coated Fe-6.5%Si flake cores show potential for high power inductors with greater permeability and lower losses than traditional powder cores. Image, graphical abstract [ABSTRACT FROM AUTHOR]

MnBi is an attractive rare-earth-free permanent magnetic material due to its low materials cost, high magnetocrystalline anisotropy (1.6 × 106 J m−3), and good magnetization (81 emu g−1) at room temperature. Although the theoretical maximum energy product (BH) max of 20 MGOe is lower than that of NdFeB-based magnets, the low temperature phase (LTP) of MnBi has a positive temperature coefficient of coercivity, up to 200 °C, which makes it a potential candidate for high temperature applications such as permanent magnet motors. However, the oxygen sensitivity of the MnBi compound and the peritectic reaction between Mn and Bi make it difficult to synthesize into a material with high purity. This challenge is partly offset by adding excess Mn to the alloy, with composition close to Mn 55 Bi 45 resulting in the highest saturation magnetization after common processing techniques such as arc melting, casting, melt spinning, and ball milling. Here we report a systematic process which reduces the amount of excessive Mn, while simultaneously providing a large saturation magnetization (M S) of 79 emu g−1 at 300 K in the annealed Mn 52 Bi 48 ribbons. We also report excellent magnetic properties in the ball powders, resulting in 0.5–5 µm particles with M S of 75.5 emu g−1, coercivity H ci of 10.8 kOe, and (BH) max of 13 MGOe using 9 T applied field at 300 K. A secondary annealing treatment on various ball milled powders increased H ci by up to 21%, and also resulted in an increase in M S up to 78.8 emu g−1. Image, graphical abstract [ABSTRACT FROM AUTHOR]

We briefly summarize the results from a set of experiments designed to demonstrate the effects of high magnetic fields applied during thermal annealing of amorphous Nd2Fe14B produced through melt-spinning. A custom-built differential scanning calorimeter was used to determine the crystallization temperatures in zero-field and in applied fields of 20 kOe and 90 kOe, which guided subsequent heat treatments to evaluate phase evolution. X-ray diffraction was used for phase identification and transmission electron microscopy was employed for observation of the crystallite size and morphology. Magnetization measurements were also used to evaluate the resulting magnetic phases after thermomagnetic processing. While the applied magnetic fields do not appear to affect the crystallization temperature, significant effects on the kinetics of phase evolution are observed and correlated strongly to the magnetic behavior. [ABSTRACT FROM AUTHOR]