Low-Carbon-Residue Multi-Principal-Element Magnetic Alloys for Excellent Microwave Absorption.
Magnetic alloy/carbon composites are promising microwave absorbers due to abundant interfaces and multiple loss mechanisms. However, reducing carbon content while maintaining uniform magnetic component distribution remains challenging. We report a spray-drying strategy to address this. By tuning nitrate precursor ratios and optimizing thermal treatment, we synthesize low-carbon alloy/oxide microspheres with uniformly distributed alloy phases. Limiting carbon content improves impedance matching, while selective nitrate precipitation creates a magnetic alloy architecture that suppresses nanoparticle agglomeration and enhances interfacial polarization. For this multiscale synergistic polarization is achieved: highly conductive Cu maximizes conduction loss, insulating Al2O3 buffers impedance, and Mn provides abundant polarization centers. The resulting microspheres exhibit tunable, exceptional performance. The attenuation-dominated FeCuMn system achieves -48.2 dB minimum reflection loss at 1.5 mm thickness. The impedance-matched FeCuAl system delivers an ultra-broad effective absorption bandwidth (EAB) of 5.12 GHz. Additionally, the FeAlMn system demonstrates superior polarization miniaturization for optimal absorption at extremely thin matching thicknesses. This work provides a practical strategy for designing electromagnetic composite structures with tunable component distribution.