Controlled reduction synthesis of yolk-shell magnetic@void@C for electromagnetic wave absorption

The development of broadband and high-efficiency electromagnetic wave absorbing materials in the gigahertz is highly crucial and challenging. Here, typical magnetic-carbon composites were successfully obtained, which involves a controlled reduction process from a semiconductor to magnetic materials under reducing atmosphere. Due to the huge difference in lattice constants, yolk-shell Fe3O4@C and Fe@void@C powders were developed from core-shell a-Fe2O3@PDA precursor. The chemical composition, magnetic property, and morphology of the final magnetic@void@C powders were discussed comprehensively. Related electromagnetic parameters of all samples were tested to analyze the storage and loss ability toward electromagnetic wave energy. Inspiringly, both the Fe3O4@C and Fe@void@C composites exhibited high-performance energy absorption in the microwave band. The minimal reflection loss (RLmin) value of Fe3O4@C is -45.4 dB at the absorber thickness only at 1.5 mm and the efficient absorption (RL <= -10 dB) frequency up to 5.5 GHz at 2.0 mm thickness. Meanwhile, the RLmin value of Fe@void@C is -66.5 dB at the absorber thickness of only 1.6 mm and show broadband responding arrange, covering almost all the Ku-band. The synthesized magnetic-carbon composites display excellent electromagnetic properties and high-efficient energy conversion behaviors, meeting to the high requirements for modern microwave absorption materials.