Hongliang Ge

During the sintering process of NdFeB bulks, temperature changes and significant temperature differences between the bulk interior and the surface region will produce high residual stress. Temperature field and stress field prediction during the sintering process is one of the key techniques for analyzing residual stress. Therefore, the sintering process simulation and residual stress prediction of NdFeB bulks under different sintering temperatures were conducted based on the modified Drucker–Prager cap (DPC) model in ABAQUS (ABAQUS 2024). The calculated field cloud charts were analyzed against the microstructure of the bulks observed by scanning electron microscope (SEM). The finite element analysis (FEA) results of the sintering process and the residual stress show good agreement with SEM morphologies, which validates the accuracy and predictability of the model. The results indicate that cracks predominantly formed in edge regions. As the sintering temperature increased, longitudinal compressive stress at the edge of the cross-section transitioned into tensile stress. These results indicate that the developed simulation framework effectively identifies crack-prone areas, enabling data-driven optimization to reduce experimental trial-and-error costs in engineering applications.

The structure and magnetic properties of Sm_6−xLa_xMn₂₃ (x = 0.5, 1, 2, 3 and 4) alloys have been studied systematically. We found that the Th₆Mn₂₃-type Sm_6−xLa_xMn₂₃ alloys become less stable with increasing La content, and α-Mn becomes the dominant phase at x = 4. More impurities were found to present in Sm₅LaMn₂₃ samples prepared by a rapid solidification process than those present in the as-cast ingots. The coercivity of Sm₄La₂Mn₂₃ induction-melted ingots and Sm₅LaMn₂₃ melt-spun ribbons reached up to 0.47 T and 0.53 T, respectively, indicating potential applications of this alloy in hard magnetic materials. The Curie temperature of Sm_6−xLa_xMn₂₃ falls in the range of 398 K for x = 1 to 438 K for x = 3. The La-substitution results in a reduced saturation magnetization of Sm_6−xLa_xMn₂₃, owing to a reduced total-magnetic-moment contribution of the Sm-sublattices. This work provides us a deeper understanding of the effect of La-substitution on the structure and magnetic properties of the ternary La-Sm-Mn alloys.

Materials for electromagnetic wave (EMW) absorption are rapidly advancing to meet the growing demand for stealth technology and to mitigate electromagnetic pollution. Herein, we innovatively synthesize a superlight Ni–Co Prussian blue analogue microcube/graphene aerogel (Ni–Co PBA/GA) monolith by hydrothermal reaction and freeze-drying. Compared to individual graphene aerogels, Ni–Co PBA/GA displays better impedance matching and multiple mechanisms for attenuating EMWs. Resultantly, Ni–Co PBA/GA presents outstanding EMW absorption performance, whose minimum refection loss is −62.3 dB at 13.3 GHz and the effective absorption bandwidth reaches 5.6 GHz. With the detection Phi of 0°, the simulated radar cross-section reduction of Ni–Co PBA/GA reaches −36.8 dB m², demonstrating the potential radar-evading ability in the actual far field. Ni–Co PBA/GA may be a promising candidate for a superlight, ecofriendly and high-performance EMW absorption material in the future.

Owing to the special planar structure and very high resistivity, [ ]-type hexaferrites possess the high initial permeability and cut-off frequency, indicating great application potential in high-frequency devices. Strontium Co₂Z hexaferrites (Sr₃Co₂Fe[ ]O[ ]) were successfully prepared by the sol–gel method and calcined at the different temperatures from [ ]C to [ ]C. The influence of the calcined temperatures on the microstructure, phase structures, magnetic properties and microwave absorption behavior of all samples was investigated in detail. All results indicated that strontium hexaferrites go through the [ ]-, [ ]-, [ ]-, and [ ]-phase transformation process from [ ]C to [ ]C, and S-1200 (calcined at [ ]C) is confirmed to be Co₂Z-type hexaferrites. S-1200 showed the highest imaginary permeability while the imaginary permittivity of all samples is close to zero, indicating the excellent microwave adsorption behavior of strontium Co₂Z hexaferrites. The reflection loss results indicate that S-1200 exhibits the best microwave absorption performance with the RL value of −32.4 dB for 4.0 mm thickness at 4.72 GHz, according to the impedance matching and quarter-wavelength theory.

Surfaces with translucent and wear-resistant effects have a wide range of applications, especially as protective layers. In this work, a simple and convenient method for the preparation of porous magnesium fluoride (MgF₂) coatings was proposed. Nano-porous MgF₂ powder was prepared with sol–gel and phase separation methods by optimizing the polymer amount and used for the preparation of thick layers onto PVC substrates. The automated surface area and porosity analyzer (BET) and scanning electron microscopy (SEM) confirmed that the layers containing 0.028‰ PEO presented a 3D structure with pore sizes in the range of 16 nm. The layer reached 93% transmittance in the visible region, a Vickers hardness value of 2889.1 kg/mm², and a friction coefficient of 0.2 in the wear test.