Multi-magnetic regulation of hollow CoNi microspheres via morphological evolution for ultrahigh electromagnetic wave absorption

Hollow cavity and multi-magnetic components are of great significance in adjusting impedance characteristics and realizing ultrahigh electromagnetic wave attenuation. Inspired by this thought, hollow CoNi microspheres are successfully fabricated by a sacrificial template strategy, in which the morphological evolution via the cation exchange reaction plays an indispensable role in regulating the multi-magnetic components. Results reveal that hollow cavity significantly balances the impedance matching and establishes more conductive networks for the enhancement of conduction loss, the cation exchange process promotes the morphological evolution from polyhedral structure to 2D nanosheets and the compositional regulation from single to multi-magnetic components, and the formation of multiple hetero-interfaces induces strong interfacial polarization. As expected, the as-synthesized hollow CoNi microspheres display ultrahigh electromagnetic wave absorption, the maximum reflection loss is up to -62.9 dB and the absorption bandwidth achieves 7.5 GHz with only 15 wt% filler loading. Moreover, the specific reflection loss and specific effective absorption bandwidth are higher than the vast majority of counterparts, demonstrating the potential practical applications in the field of electromagnetic stealth and protection.