Controllable preparation and broadband high-frequency absorption capabilities of Co fibers and Co/Cu bimetallic core-shell fibers

Abstract

To solve the increasingly serious electromagnetic (EM) pollution and EM interference, Co fibers were synthesized through a magnetic-field-assisted reduction method and subsequently converted into Co/Cu bimetallic core-shell fibers (BCSFs) by a simple galvanic replacement reaction in the presence of copper acetate monohydrate and Co fibers. The feeding ratio of Cu2+/Co2+ (β) was used to adjust the surface-interface morphology, ingredients, and capabilities of Co/Cu BCSFs. With increasing β, the saturation magnetization (Ms) of Co/Cu BCSFs shows a linear downward trend, and the coercivity (Hc) exhibits an inverted-U pattern and reaches the crest value (131.3 Oe) at β = 3:10 due to the increased content of antiferromagnetic Cu and oxides. Co fibers and Co/Cu BCSFs formed at β = 0.5:10 exhibit considerably stronger absorption (−41.82 ∼ −52.50 dB) and broader bandwidth (6.64–8.24 GHz, RL ≤ −10 dB) at a lower filling mass fraction (20–25 wt%) than other absorbers owing to the cooperation of enhanced EM parameters, dual dielectric relaxation, large attenuation moduli, excellent impedance match and eddy current loss. The bandwidth with RL less than −10 dB is 8.24 GHz in relation to a 2.2 mm thick sample; the frequency range with RL below −20 dB is 15.12 GHz. This work provides a general strategy for preparing bimetallic core-shell fibers and a basis for further studies on using bimetallic core-shell fibers as an EM wave attenuation material.