Nacre‐Inspired, Efficient, and Multifunctional Soft Magnetic Composites by Cold Sintering Design

Abstract

Nacre‐mimetics hold great promise as integration of structure and function. Various techniques have been proposed to prepare nacre‐inspired materials, but in most cases, organic materials are usually used that decrease high‐temperature stability. Factually, efficient synthesis of nacre‐like high‐performance soft magnetic composites (SMCs) with good thermal stability is still challenging. Herein, a novel and simple strategy is reported on designing nacre‐like SMCs by cold sintering of ferrite‐coated alloy flakes with the absence of polymers. By selecting NH4HCO3 aqueous solution as transport solvent, a highly ordered nacre‐like structure and enhanced densification with large electrical resistivities and strong interfacial bonding are successfully achieved, which are superior to the cold‐sintered composites using water as transport solvent as well as the hot‐pressed composites based on alloy flakes and epoxy resin. The resultant composites illustrate large density (≈6.286 g cm−3) and electrical resistivity (≈3.9 × 105 Ω cm), allowing remarkable flexural strength (≈46.5 MPa), high permeability (μ′ = ≈107.3 at f = 10 MHz), together with low tanδ μ (≈0.09 at f = 10 MHz) and P cv (≈183.6 kW m−3 at 50 mT/100 kHz), which show great potential in high‐frequency power electronic and electrical systems. The synthesis strategy sheds light on designing other nacre‐like materials or developing new metal−ceramic composites.