High-throughput thermal plasma synthesis of FexCo1−x nano-chained particles with unusually high permeability and their electromagnetic wave absorption properties at high frequency (1–26 GHz)

Abstract

Herein, we introduce novel 1-dimensional nano-chained FeCo particles with unusually-high permeability prepared by a highly-productive thermal plasma synthesis and demonstrate an electromagnetic wave absorber with exceptionally low reflection loss in the high-frequency regime (1–26 GHz). During the thermal plasma synthesis, spherical FeCo nanoparticles are first formed through the nucleation and growth processes; then, the high temperature zone of the thermal plasma accelerates the diffusion of constituent elements, leading to surface-consolidation between the particles at the moment of collision, and 1-dimensional nano-chained particles are successfully fabricated without the need for templates or a complex directional growth process. Systematic control over the composition and magnetic properties of Fe_xCo_1−x nano-chained particles also has been accomplished by changing the mixing ratio of the Fe-to-Co precursors, i.e. from 7 : 3 to 3 : 7, leading to a remarkably high saturation magnetization of 151–227 emu g⁻¹. In addition, a precisely-controlled and uniform surface SiO₂ coating on the FeCo nano-chained particles was found to effectively modulate complex permittivity. Consequently, a composite electromagnetic wave absorber comprising Fe_0.6Co_0.4 nano-chained particles with 2.00 nm-thick SiO₂ surface insulation exhibits dramatically intensified permeability, thereby improving electromagnetic absorption performance with the lowest reflection loss of −43.49 dB and −10 dB (90% absorbance) bandwidth of 9.28 GHz, with a minimum thickness of 0.85 mm.