Xinjiang Zhang

Fe-based amorphous and nanocrystalline alloys are essential core materials for high-efficiency distribution transformers, high-frequency transformers, and power electronic transformers, owing to their high saturation magnetic flux density (B_s), low coercivity (H_c), low core loss, and excellent high-frequency response. This review summarizes recent progress in the modulation of soft magnetic properties, covering composition design, heat treatments, structural engineering, and transformer applications. For compositional design, a central issue is how to achieve high B_s while retaining sufficient Glass-forming ability (GFA), and appropriate additions of metalloid and transition-metal elements provide an effective route to this balance. Conventional isothermal, stress, magnetic-field, and rapid annealing processes enable structural relaxation, nanocrystallization, and anisotropy modulation. Ultrafine nanocrystals, amorphous/nanocrystalline transitional structures, and gradient and multilayer structures further improve overall performance through grain refinement, interface engineering, and domain optimization. Key engineering challenges include continuous ribbon casting, heat-treatment uniformity, winding-induced residual stress, and practical operating conditions. Future advances require the integration of in situ characterization, multiscale modeling, and machine learning, alongside advances in continuous heat treatment and low-stress manufacturing, to facilitate wider application in transformers.

The rapid advancement of flexible electronics has propelled the development of lightweight, wearable piezoresistive sensors that integrate high sensitivity, excellent mechanical properties, and multifunctionality, making them a research hotspot. This work presents a flexible and lightweight multifunctional polyvinyl alcohol (PVA) composite hydrogel film, which is constructed based on a synergistic conductive network of cuttlefish ink-derived carbon nanospheres (CNPs) and polypyrrole (PPy). Within this composite, the CNPs and PPy form an interpenetrating conductive network throughout the PVA matrix, where PPy effectively suppresses the agglomeration of CNPs, thereby significantly enhancing the electron transport efficiency. This unique structure endows the material with improved flame retardancy and hydrophobicity while maintaining its lightweight characteristic. Consequently, the sensor demonstrates fast response (64 ms) and recovery times (66 ms) and a high sensitivity factor of 4.34 kPa⁻¹ within a pressure range of 11.2–16.8 kPa. Excellent stability is retained after nearly 6000 loading–unloading cycles, primarily attributed to the efficient response of the contact points and conductive pathways within the synergistic network under stress. Furthermore, this flexible sensor can not only reliably monitor human physiological activities (such as finger joint bending and facial expression changes) but also generate distinct current responses to subtle mouse-clicking actions, enabling tactile handwriting input. This study provides a novel strategy for constructing high-performance sensing materials by utilizing natural biomass-derived carbon materials and conductive polymers, highlighting the significant application potential of such lightweight, multifunctional hydrogel films in next-generation flexible electronic devices.