Multiphase interface regulation, impedance matching optimization and enhanced microwave absorption of Co₄₉Fe₄₉V₂-based composites

The Co₄₉Fe₄₉V₂ magnetic alloy material has the characteristics of high Curie temperature, large saturation magnetization and low coercivity, thus Co₄₉Fe₄₉V₂ (CFV) magnetic alloy material demonstrate promising application prospects in the field of microwave absorbing materials (MAMs). However, its high density, poor impedance matching and small skin depth limit its practical application. In this study, three Co₄₉Fe₄₉V₂–based composites, Co₄₉Fe₄₉V₂@M–OH (sample CFV–85), Co₄₉Fe₄₉V₂@m–SiO₂@C (sample CFV–S–C) and Co₄₉Fe₄₉V₂@β–SiC/α–SiO₂/C (sample CFV–S–S–C), were prepared, and their microstructure, static magnetic properties, microwave absorption properties and electromagnetic (EM) wave dissipation mechanisms were also investigated. Research indicates that the CFV–S–S–C sample shows excellent EM wave absorption properties, and the minimum reflection loss (RL_min) arrived –59.39 dB at the matching frequency of 5.14 GHz, while the maximum effective absorption bandwidth (EAB_max) widened up to 6.79 GHz at the corresponding coating thickness of 2.0 mm. This is attributed to the synergy of its magnetic loss phase Co₄₉Fe₄₉V₂ and dielectric loss phase (β–SiC+α–SiO₂+C), as well as the improvement of impedance matching, and its unique microstructure such as abundant point defects, line defects and phase interfaces. The dielectric and magnetic frequency spectrum of the CFV–S–S–C sample were analyzed in detail. The EM wave dissipation mechanism of the sample includes dipole polarization, interface polarization, conductance loss, magnetic resonance, and optimized impedance matching. Research has suggested that the sample Co₄₉Fe₄₉V₂@β–SiC/α–SiO₂/C (sample CFV–S–S–C) can be regarded as an ideal candidate MAMs for practical applications.