Explore the vast range of titles available.

The temperature resistance of a magnetic powder core is determined by the organic resin in it, while the conventionally used phenolic resin and epoxy resin are sensitive to temperature. Herein, iron-based amorphous powder cores with heat-resisting polytetrafluoroethylene (PTFE) insulating layers were fabricated by processes of ball-milling mixing, cold pressing, simultaneously sintering, and annealing, and the effect of different PTFE contents on magnetic properties was analyzed. The PTFE played the roles of lubricant, insulating layer, and binder in the fabrication of magnetic powder cores. The high lubricity and deformability of PTFE well protected the amorphous powder from ball-milling or cold-pressing damage, making it feasible for mixing amorphous powder with PTFE. In the sintering process, melting PTFE could fill the air gaps among powders and endow the powder cores with available strength. The analysis of microstructure showed that the amorphous powders could be well coated by PTFE, and the tests of magnetic properties showed that the PTFE content had a fluctuating influence on the total core losses of the powder cores. Owing to the better microstructure homogeneity and more proper compositions, the powder cores with 2.4% and 3.6% mass fractions of PTFE show relatively high effective permeabilities above 25 under 100 kHz, and relatively low total core losses of 1448 and 1402 kW/m3 respectively under 100 kHz, 100 mT. Moreover, all the prepared magnetic powder cores exhibit superior DC-bias properties, the percentages of incremental permeability are as high as 83–90% under a direct magnetic field of 100 Oe.

The corrosion behavior of TiZrHfBeCu(Ni) high-entropy bulk metallic glasses (HE-BMGs) has been investigated. The TiZrHfBeCu(Ni) HE-BMGs exhibited high corrosion resistance in 3.5 wt. % NaCl solution because of accumulation of ZrO 2 and TiO 2 in the passive film. Ni promoted increases of the ZrO 2 , TiO 2 , and HfO 2 contents and a decrease of the BeO content, which improved the HE-BMG corrosion behavior. Compared with Zr 41.2 Ti 13.8 Ni 10 Cu 12.5 Be 22.5 BMG, the high-entropy effect of HE-BMGs can significantly reduce the atomic mobility, which inhibits outward migration of Cu, reduces the kinetics of the dissolution reaction, and inhibits inward erosion by Cl − , thereby improving the corrosion performance.

Ubiquitous oxygen drives degradation, spoilage, and side reactions, making oxygen scavenging essential for materials preservation and reaction stabilization. However, conventional oxygen scavengers exhibit limited oxygen removal rates and capacities far below their theoretical maximums, wasting resources while lagging behind industry needs. Here, we report Fe-based metallic glasses as efficient oxygen scavengers, achieving oxygen removal rates 1–4 orders of magnitude higher than conventional systems. In FeSiB metallic glass, Fe oxidation synergistically activates Si, delivering a 24-hour oxygen removal capacity of 1.439 L g -1 —reaching the Fe-based theoretical limit—and a 48-hour capacity of 1.596 L g -1 , surpassing it. Density functional theory calculations reveal that the amorphous structure significantly lowers the oxygen adsorption energy barrier and facilitates O–O bond cleavage. Moreover, the generated self-reinforcing microdomains mediate O 2 /H 2 O transport via robust autocatalytic cycling. These results highlight a promising strategy for oxygen potential control and suggest a possible paradigm for catalytic applications. Fe-based metallic glasses are reported as efficient oxygen scavengers, achieving removal rates 1–4 orders of magnitude higher than conventional systems through rapid adsorption and autocatalytic effect, while approaching theoretical capacity limits.

As a medium to understand the nature of glass transition, ultrastable glasses have garnered increasing attention for their significance in fundamental science and technological applications. Most studies have produced ultrastable glasses through a surface-controlled process using physical vapor deposition. Here, we demonstrate an approach to accessing ultrastable glasses via the glass-to-glass transition, a bulk transformation that is inherently free from size constraints and anisotropy. The resulting ultrastable glass exhibits a significantly enhanced density (improved by 2.3%), along with high thermodynamic, kinetic, and mechanical stability. Furthermore, we propose that this method of accessing ultrastable glasses is general for metallic glasses, based on the examination of the competitive relationship between the glass-to-glass transition and crystallization. This strategy is expected to facilitate the proliferation of the ultrastable glass family, helping to resolve the instability issues of glass materials and devices and deepen our understanding of glasses and the glass transition. An alternative approach to physical vapor deposition is demonstrated here for accessing ultrastable metallic glasses via the glass-to-glass transition, a bulk transformation that is inherently free from size constraints and anisotropy.

Emerging for future spintronic/electronic applications, magnetic semiconductors have stimulated intense interest due to their promises for new functionalities and device concepts. So far, the so-called diluted magnetic semiconductors attract many attentions, yet it remains challenging to increase their Curie temperatures above room temperature, particularly those based on III–V semiconductors. In contrast to the concept of doping magnetic elements into conventional semiconductors to make diluted magnetic semiconductors, here we propose to oxidize originally ferromagnetic metals/alloys to form new species of magnetic semiconductors. We introduce oxygen into a ferromagnetic metallic glass to form a Co 28.6 Fe 12.4 Ta 4.3 B 8.7 O 46 magnetic semiconductor with a Curie temperature above 600 K. The demonstration of p – n heterojunctions and electric field control of the room-temperature ferromagnetism in this material reflects its p -type semiconducting character, with a mobility of 0.1 cm 2  V −1  s −1 . Our findings may pave a new way to realize high Curie temperature magnetic semiconductors with unusual multifunctionalities. Magnetic semiconductors provide control of spin states in addition to charge states realized in conventional semiconductors, yet currently limited to weak magnetism at low temperature. Liu et al . introduce oxygen into a ferromagnetic metallic glass, resulting in a Curie temperature above 600 K.

The nonisothermal crystallization kinetics, fragility, and thermodynamics of Ti20Zr20Cu20Ni20Be20 high entropy bulk metallic glass (HE-BMG) have been investigated by differential scanning calorimetry. The activation energies for the glass transition and crystallization events were determined by Kissinger and Ozawa methods. The value of local Avrami exponent is less than 1.5 in most cases for all the three crystallization events, indicating that the major crystallization mechanism is diffusion-controlled growth of pre-existing nuclei. The local activation energy is stable during the whole crystallization process and this further confirms that the crystallization occurs through a single mechanism. Ti20Zr20Cu20Ni20Be20 alloy can be classified into “strong glass formers” according to the estimated fragility index and also shows a relatively low value of Gibbs free energy difference. However, compared with Zr41.2Ti13.8Cu12.5Ni10Be22.5 BMG, the glass-forming ability of Ti20Zr20Cu20Ni20Be20 HE-BMG is much lower and the related reasons have been discussed.

This paper presents a Markov chain random carrier frequency modulation (MRCFM) technique for suppressing sideband vibro-acoustic responses caused by discontinuous pulse-width modulation (DPWM) in permanent magnet synchronous motors (PMSMs) for new energy vehicles. Firstly, the spectral and order distributions of the sideband current harmonics and radial electromagnetic forces introduced by DPWM are characterized and identified. Then, the principle and implementation method of three-state Markov chain random number generation are proposed, and particle swarm optimization (PSO) algorithm is chosen to quickly find the key parameters of transition probability and random gain. A Simulink and JMAG multi-physics field co-simulation model is built to simulate and predict the suppression effect of the MRCFM method on the sideband vibro-acoustic response. Finally, a 12-slot-10-pole PMSM test platform is built for experimental testing. The results show that the sideband current harmonics and vibro-acoustic response are effectively suppressed after the optimization of Markov chain algorithm. The constructed multi-physics field co-simulation model can accurately predict the amplitude characteristics of the sideband current harmonics and vibro-acoustic response.

High-Cu-content (Cu-content > 1.3 at.%) nanocrystalline alloys exhibit wide heat-treatment windows and favorable soft magnetic properties due to the presence of pre-existing α-Fe nanocrystals. By fabricating ribbons with varying thicknesses to tailor cooling rates, distinct structural characteristics were achieved in Fe82B16.5Cu1.5 alloy ribbons. Notably, the face-centered cubic (fcc) γ-Fe phase was identified in Fe-based nanocrystalline alloys. The precipitation of the fcc γ-Fe phase originates from a phase-selection mechanism under specific cooling conditions, while its retention in the as-quenched ribbon with a thickness of 27 μm is attributed to kinetic suppression during rapid cooling and the nanoscale stabilization effect. The formation of the fcc γ-Fe phase significantly reduced the saturation flux density (Bs) and increased coercivity (Hc), concurrently destabilizing the residual amorphous matrix. By suppressing the precipitation of the γ-Fe and Fe3B phases through precise control of ribbon thickness and annealing parameters, the alloy ribbon with a thickness of 16 μm achieved an optimal combination of Bs (1.82 T) and Hc (8.3 A/m). These findings on anomalous fcc γ-Fe phase precipitation provide novel insights into metastable phase engineering and offer structural design guidelines for alloys containing pre-existing α-Fe nanocrystals.

We investigated the effects of the austenitizing temperature on the microstructure, hardness, and tensile properties of case-carburized steel after vacuum carburization at 930 °C and then re-austenitization at 820–900 °C followed by oil quenching and tempering. The results show that fractures occurred early with the increase in the austenitizing temperature, although all the carburized specimens showed a similar case hardness of 800 HV0.2 and case depth of 1.2 mm. The highest fracture stress of 1919 MPa was obtained for the experimental steel when the austenitizing temperature was 840 °C due to its fine microstructure and relatively high percentage of retained austenite transformed into martensite during the tensile tests. We also found that the stress–strain behavior of case-carburized specimens could be described by the area-weighted curves of the carburized case and the core in combination. The strain hardening exponent was about 0.4 and did not vary with the increase in the austenitizing temperature. We concluded that the optimum austenitizing temperature was around 840 °C for the experimental steel.

High entropy amorphous alloys (HEAAs) are materials that have received much attention in recent years. They exhibit many unique properties; however, research on their composition design method has not been deep enough. In this paper, we summarized some effective composition design strategies for HEAAs. By adjusting the atomic ratio from quinary bulk metallic glasses, Ti20Zr20Cu20Ni20Be20 HEAA with a high fracture strength of 2315 MPa was designed. By similar element addition/substitution, a series of Ti–(Zr, Hf, Nb)–Cu–Ni–Be HEAAs was developed. They possess good glass-forming ability with a maximum critical diameter of 30 mm. Combining elements from those ternary/quaternary bulk metallic glasses has also proved to be an effective method for designing new HEAAs. The effect of high entropy on the property of the alloy, possible composition design methods, and potential applications were also discussed. This paper may provide helpful inspiration for future development of HEAAs.