Jiawei Li

We constructed a multi-layer composite magnetic shield composed of Fe-based nanocrystalline (FN) and Co-based amorphous (CA) ribbons, and focused on the influence of the number of layers and their arrangement on the shielding effectiveness (SE). Finite element analysis (FEA) and layer-by-layer inversion calculations were performed to analyze the attenuation process of the magnetic field between shield layers. Increasing the number of shield layers improves the maximum value of SE (SE_max) and significantly broadens the working range (WWR). In a weak magnetic field, CA exhibits higher shielding performance, whereas FN is better in a strong magnetic field. The FN/FN/CA combination (FN is closer to the field source) exhibits an SE_max of up to 51.7 dB within a WWR of 674.3 A/m, and demonstrates a 14.4% improvement in SE compared to FN/FN/FN combination across the entire tested magnetic field range. Finally, a gradient layering design is proposed that enables each layer to operate within its optimal permeability range, thereby improving the overall SE and broadening the effective working magnetic field range.

External stray magnetic fields from permanent magnet synchronous motors (PMSMs) may cause electromagnetic interference to nearby equipment and limit their application in space-constrained systems. To address this issue, this paper investigates the use of laminated Co-based amorphous ribbon shields for stray-field suppression. An efficient equivalent modeling method is proposed for the simulation of such multilayer thin shielding structures, in which the laminated shield is replaced by an equivalent single-layer model while preserving its macroscopic shielding behavior. The method is first assessed in 2-D through comparisons between refined laminated and simplified equivalent models under both linear permeability and nonlinear magnetization-curve descriptions, and is then extended to 3-D PMSM shielding analysis under static and rotating no-load conditions with experimental validation. Results show that the 10-layer amorphous ribbon shield, with a total thickness of 420 μm, achieves a maximum shielding effectiveness of 7.9 dB at a measurement distance of two motor radii. The maximum deviation between simulation and experiment is 7.4%, and the equivalent model reduces computation time by 28% relative to the refined model. This method provides an accurate and efficient approach for the analysis and design of compact low-frequency magnetic shields for PMSMs.

The interplay between melting viscosity, amorphous forming ability (AFA), nanocrystalline structure, and soft magnetic properties (SMPs) in Fe-based multicomponent alloys remains unclear. This study systematically explores the effects of Sn doping on the viscosity, precursor structure, and nanocrystallization behavior of Fe-Si-B-Nb-Cu-Al-P alloys. Sn doping reduces melting viscosity and induces an abnormal viscosity rise during cooling, lowering the fragility parameter ratio (F) between high- and low-temperature zones, thereby enhancing the AFA of the precursor ribbons. High-temperature heat preservation treatment (HTP) of the melt further reduces the F, improves precursor disorder, and refines nanocrystals, leading to reduced average magnetocrystalline anisotropy and optimized SMPs. The HTP-treated Sn-dopped alloy shows superior SMPs, including low coercivity of 0.4 A/m and high permeability of 32,400 at 5 kHz, making it highly promising for advanced electromagnetic device applications. This work reveals the relationship between viscosity, precursor structure, nanocrystalline structure, and SMPs of Fe-based alloys, which provides an approach for the optimization of SMPs.

Soft-magnetic fibers (SMFs) play a crucial role in energy conversion, transmission, and storage within electronic devices. However, conventional SMFs have poor plasticity and are therefore difficult to withstand long-term tensile, torsional, and shear deformation. A high fraction of grain boundaries could improve plastic deformability of conventional SMFs, but deteriorates the coercivity. This severely limits their applications in flexible electronics and multifunctional components. Herein, we propose a strategy to overcome this dilemma, which is realized by coarsening the grains of a Fe₃₄Co₂₉Ni₂₉Al₃Ta₃Si₂ high entropy alloy (HEA) fiber containing ordered coherent nanoprecipitates with small lattice misfit via a simple one-step in-rotating-water spinning method. This allows to reduce domain wall pinning and improve dislocation mobility. The resultant micron-diameter soft-magnetic HEA fiber has a tensile strength of 674 MPa at 23% elongation, a low coercivity of 8.1 Oe, a moderate magnetization of 116 emu/g at 10 kOe and a high Curie temperature of 770 K.

Nowadays, in view of the increasingly serious problems of electromagnetic interference (EMI) and radiation pollution, smart EMI shielding materials with tunable shielding effectiveness (SE), especially “On/Off” switchable capability, are highly desirable. Herein, Co‐based amorphous wires (AWs) with excellent soft magnetic and mechanical properties are regularly arranged on a 3D‐printed mold as tunable EMI shielding composites. The EMI SE can be easily tuned in the range of ≈0.6–24.7 dB by way of rotation, which has been confirmed to be an effective way to achieve free tuning of EMI SE by simulation. In addition, by compositing AWs with reduced graphene oxide and constructing a double‐layer structure with a gap of 1/4 wavelength in the X‐band, a much wider SE tuning range of ≈1.0–57.7 dB is further realized. The representative “On/Off” switchable shielding capability that can switch between EM transmission and effective shielding, together with the wide SE tuning range larger than 50 dB, shows the great potential of Co‐based AW composites in smart EMI shielding applications.