Excellent microwave-absorbing performance in nanofiber nanocomposites by biomass conversion of sodium alginate

Sodium alginate, as one of natural polymer existing in marine plants, can function as precursor of carbon-based microwave-absorbing materials with the advantages of low cost, easy degradation, and non-toxicity. However, its resultant carbon-based materials suffer from the poor impedance matching and low lossy capacity due to no magnetism and small amount of interface. In this work, CoNi alloy nanoparticles were uniformly located on the surface of carbon nanofibers (CNFs) derived from the sodium alginate fabricated by the electrospinning and solvothermal method to construct the CNFs/CoNi nanocomposites. The results show that CNFs/CoNi nanocomposites have the good absorbing performance, where the minimum RL of − 56.96 dB at a very thin thickness of 1.63 mm and an effective absorption bandwidth of 5.3 GHz (12.7–18 GHz) at a very thin thickness of 1.7 mm are obtained, respectively. The excellent wave-absorbing performance is mainly attributed to the appropriate impedance matching and high attenuation factor. The multilevel interfacial polarization from the interfaces between CoNi nanoparticles and carbon nanofiber makes the main contribution to the wave-absorbing performance at the whole test frequency range, while the natural ferromagnetic resonance of CoNi composition dominates the low frequency range and eddy current loss plays a major role at higher frequency range. This work develops a simple method for designing high-performance microwave-absorbing nanocomposites by using the marine raw materials of sodium alginate.