Garcia-Martin E.Granados-Miralles C.del Campo A.Guzman-Minguez J.C....
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查看更多>>摘要：? 2022 The Author(s)The use of rare-earth-based permanent magnets is one of the critical points for the development of the current technology. On the one hand, industry of the rare-earths is highly polluting due to the negative environmental impact of their extraction and, on the other hand, the sector is potentially dependent on China. Therefore, investigation is required both in the development of rare-earth-free permanent magnets and in sintering processes that enable their greener fabrication with attractive magnetic properties at a more competitive price. This work presents the use of a cold sintering process (CSP) followed by a post-annealing at 1100 °C as a new way to sinter composite permanent magnets based on strontium ferrite (SFO). Composites that incorporate a percentage ≤ 10% of an additional magnetic phase have been prepared and the morphological, structural and magnetic properties have been evaluated after each stage of the process. CSP induces a phase transformation of SFO in the composites, which is partially recovered by the post-thermal treatment improving the relative density to 92% and the magnetic response of the final magnets with a coercivity of up to 3.0 kOe. Control of the magnetic properties is possible through the composition and the grain size in the sintered magnets. These attractive results show the potential of the sintering approach as an alternative to develop modern rare-earth-free composite permanent magnets.
查看更多>>摘要：? 2022Metallic Fe3Ga4 displays a complex magnetic phase diagram that supports an intermediate antiferromagnetic (AFM) helical spin structure (HSS) state at room temperature which lies between two ferromagnetic (FM) phases. Magnetic measurements along the three crystallographic axes were performed in order to develop a model for the temperature and field dependence of the HSS state. These results show that the AFM state is a helically ordered spiral propagating along the c-axis with the magnetic moments rotating in the ab-plane. Under applied magnetic field, the AFM state exhibits a metamagnetic transition to conical ordering before entering a fully field-polarized FM state at high fields. The conical ordering in the AFM state is anisotropic even within the ab-plane and may gives rise to Berry phase effects in transport measurements. Metallic conductivity from density of states computations was confirmed through resistivity measurements and no anomalous behavior was observed through the various magnetic transitions.
查看更多>>摘要：? 2022 Elsevier B.V.Yolk-shell structure is a promising material design for alloying type anode due to its void space accommodating the volume change during battery cycle life. However, the coordination between void space and core size is an issue for yolk-shell structured anode materials achieving excellent cycling stability and reasonable high volumetric energy density. Herein, we propose a strategy of in-situ shell-to-core evolution to accurately control the void space and core size in yolk-shelled spheres. Based on this approach, we have synthesized a yolk shelled composite with a Sn nanoparticle encapsulated in a N doped C shell (YS-Sn@void@NxC). The controlled core size and void space, and their relationship with anode electrochemical performance have been systematically studied. The optimal YS-Sn@void@NxC electrode demonstrates excellent cycling stability of 1110 mAh cm?3 for volumetric capacity and 820 mAh g?1 for gravimetric capacity after 1000 cycles at 1 C (1 C = 1000 mA g?1). We believe that the facile yolk-shelled structure designing strategy in this work could be extended to synthesize other low melting point metals, such as Bi, Pb, In, Ge, etc., for their functional applications.
查看更多>>摘要：? 2022 Elsevier B.V.We report on the preparation of spherical TbDyFe single-crystal particles as well as the giant magnetostriction of composite materials made from these particles. Spherical single-crystals with diameters ranging from 50 to 200 micrometers were fabricated through the low wettability effects between solid-liquid interfaces. Facilitated by those sphere-shaped crystals, a high particle-to-epoxy ratio and a high uniformity of particle orientation was realized in the composite. As the result, highly< 111 > -orientated TbDyFe/epoxy resin composites with a particulate volume fraction of 55% were designed. The magnetostriction of the composite is as high as 1820 ppm at a compressive preload of 10 MPa, which is comparable to 1400–1800 ppm of commercial monolithic Terfenol-D. The present work path a novel way to develop high-performance magnetostrictive composite materials.
查看更多>>摘要：? 2022 Elsevier B.V.We quantitatively investigated the magnetocrystalline anisotropy (MCA) of metamagnetic FeRh films epitaxially grown on MgO(001) substrates. The in-plane fourfold magnetic anisotropy of epitaxial FeRh films is reoriented from the<100>to<110>directions and meanwhile the strength is obvious enhanced when FeRh transfers from the ferromagnetic (FM) to antiferromagnetic (AF) states. In the nominal AF state, the observed fourfold magnetic anisotropy originates from the exchange coupling between the residual FM moments caused by antisite defects and the AF matrix, which therefore indicates the orientation and strength of the MCA of AF FeRh. The steep increase of the FM resonance linewidth when crossing the FM-AF phase transition temperature reveals the enhanced effective magnetic damping and an increased fourfold anisotropic two-magnon scattering. The first-principles calculations suggest that the in-plane lattice compressive strain imposed by the MgO substrate plays an important role in determining the magnetic structures FeRh films.
查看更多>>摘要：? 2022 Elsevier B.V.The microstructure and mechanical behaviors of as-built Inconel 625 prepared by selective laser melting (SLM) and laser engineered net shaping (LENS) technologies were investigated in this study. The results show that the microstructure of Inconel 625 alloy prepared by SLM process is composed of obvious columnar and cellular grains. Inconel 625 fabricated by LENS also has columnar and cellular structures, but the grain size is relatively large. Significant anisotropy of mechanical properties is observed in SLM and LENS printed Inconel 625. The mechanical properties in XY direction are higher than those in XZ direction, and the maximum tensile strength of SLM-XY sample is 1241.5 MPa. SLM printed Inconel 625 has a relatively higher dislocation density of 2.8 ± 1.2 × 1014 m?2. The difference in yield strength between SLM and LENS printed Inconel 625 is mainly caused by the different dislocation strengthening effects.
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