Chemical conversion of Cu2O/PPy core-shell nanowires (CSNWs): A surface/interface adjustment method for high-quality Cu/Fe/C and Cu/Fe3O4/C CSNWs with superior microwave absorption capabilities

To improve the microwave absorption and antioxidation abilities of Cu nanowires (NWs) as microwave devices, we synthesized Cu/Fe/C and hollow Cu/Fe3O4/C core-shell nanowires (CSNWs) chemically converted from Cu2O/PPy CSNWs via an in-situ carbothermic reduction-CVD process. Changing temperature (Tc) and Fe(CO)5 vol (V) could handily adjust the surface component and structure of the products. Controlling N2 purity could selectively synthesize hollow Cu/Fe3O4/C CSNWs and solid Cu/Fe/C CSNWs with a strawberry-shaped surface based on the surface diffusion mechanism. The Cu/Fe/C CSNWs and hollow Cu/Fe3O4/C CSNWs possessed high soft magnetic and microwave absorbing properties. Considering the combination of high electromagnetic parameters, double dielectric relaxation and magnetic resonance, intense absorption, and excellent impedance matching, Cu/Fe/C CSNWs formed at Tc = 600 °C and V = 4 mL were superior absorbents that were characterized by high absorption, wide bandwidth, and light weight. The maximal reflection loss (RL) was −43.09 dB at 13.07 GHz with a 1.8 mm matching thickness, and RL values below −20 dB could be gained over 3.3–4.5 GHz and 5.11–15.9 GHz. This work has provided a general method for modulating the surface/interface and structure of carbon-based magnetic composites for lightweight and broad bandwidth microwave absorbing materials.