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The effects of hydrophilic and hydrophobic SiO2 composite organic resin on the properties of FeSiCr magnetic powder cores and the effects of annealing treatment on magnetic properties were studied. After phosphating, the FeSiCr alloy powders were coated by two types of SiO2 composite resin, which are hydrophobic and hydrophilic, respectively. The FeSiCr magnetic powder cores were prepared by compaction and curing. The results show that the coating effect of coupling modified hydrophilic SiO2 composite organic resin is better than that of hydrophobic SiO2 composite organic resin. With the increase of SiO2 addition, the specific resistance and coercivity of the magnetic powder cores are increased, while the density, saturation magnetization and effective permeability are decreased. The FeSiCr magnetic powder cores coated with 0.5% hydrophobic SiO2 composite organic resin have excellent comprehensive performance after annealing. Under the condition of 20 mT, 100 kHz, the magnetic core loss is 49.84 kW/m3, which is 16.9% lower than that of the magnetic powder cores coated with pure resin. Annealing can effectively promote magnetic properties of FeSiCr magnetic powder cores.

Flaky structures can effectively enhance the microwave absorbing properties of metallic magnetic particles, but the interaction between the electromagnetic waves and particles in different directions is not well understood. Here, the oriented FeSiAl/paraffin composites were prepared under a rotational magnetic field and made into co-axial rings for electromagnetic measurements. The FeSiAl flakes in the rings are oriented along different angles with respect to the electric and magnetic fields of the microwave. The effects of the angles on the electric and magnetic properties as well as the microwave absorbing properties of the composite are investigated. It is found that the electric and magnetic properties can be modified independently by adjusting the angles between the flakes and the electric field and between the flakes and the magnetic field, respectively. The underlying mechanisms can be understood using electromagnetic and micromagnetic simulations. The anisotropic permittivity originates from the induced electric field of the flaky particles, while the anisotropic permeability results from the effect of the demagnetization field. An optimal orientation structure can reduce the permittivity by suppressing the induced electric field while maintaining high permeability by reducing the demagnetization energy in the magnetization process, which is beneficial to the impedance matching of the composite. Thus, the orientation structure is extremely efficient in regulating the microwave absorption performance of the flaky particles. This work proposed a general strategy for microwave absorbers to modulate microwave absorption performances between high-frequency and low-frequency by simply operating the orientation structures of the flaky particles. [ABSTRACT FROM AUTHOR]

Domestic induction heating shows advantages over traditional open fire heating, but the uneven temperature distribution in the pan is still one of the problems to be solved. In this work, to improve the heating uniformity of the induction cooker, the finite element analysis (FEA) is employed to investigate the relationship between the structure of induction coil and the temperature distribution in the heating pan. The results indicate that the structure of single-coil can be optimized by varying the winding turns in different positions. More uniform temperature distribution in the pan has been obtained by increasing the number of turns at the center and edge of the coil. The advance of this design is to achieve uniform induction heating without redesigning the power source or adding an additional coil. Based on the simulation results, the refined induction coil has been fabricated and assembled into a commercial domestic induction cooker with little modification of the power supply system. A specific parameter named relative standard deviation (RSD) is proposed to define the temperature uniformity. By real-time temperature measurement, the improved heating uniformity has been demonstrated for the refined system. The present work provides a cost-effective and efficient solution to improve heating performance of domestic induction cooker. [ABSTRACT FROM AUTHOR]

The preparation of nanocrystalline anisotropic NdFeB permanent magnets generally includes two steps, hot pressing (HP) and hot deformation (HD). Herein, one‐step HD process is proposed to fabricate NdFeB magnets using amorphous powders. The effects of deformation ratio on the microstructure, magnetic properties, and corrosion resistance are investigated. Compared to traditional HP and HD process, one‐step HD can significantly reduce the volume fraction of coarse‐grain zone in the magnet. The increase of deformation ratio can promote the formation of the textured platelet‐shaped grains and uniform grain boundary phase. The magnetic properties, temperature stability, and corrosion resistance of the magnets increase with increasing deformation ratio until 80%. The best magnetic properties with intrinsic coercivity Hcj = 930 kA m−1, remanence Jr = 1.17 T, and maximum energy product (BH)max = 263 kJ m−3 have been achieved for the magnet prepared by one‐step HD, which are comparable to those obtained by conventional HP/HD. In addition, different Co element segregations are observed in the magnets with different deformation ratios, which have important effects on the Curie temperature and thermal stability of the magnets. The results suggest that, by replacing HP/HD process and using amorphous powder, one‐step HD can simplify the process while maintaining good properties. [ABSTRACT FROM AUTHOR]