Carbon induced multiple interfaces and in-situ formed defects in oxidation of Co toward enhancing microwave absorption performances

In order to obtain multiple interfaces of Co/CoO by tuning the oxidation process and simultaneously clarify the interface migration, Co particles loaded on mangosteen shell-derived carbon (MSC) were prepared, and then oxidized under a mixed atmosphere of Ar/O₂ and 300 °C with different oxidation time. Due to the existence of MSC, the Co can completely oxidized in short time of 60 min and low O₂ concentration of 5 %. The oxidation process is: Co→CoO→Co₃O₄. A lot of defects in-situ formed in the oxidation process can be clearly detectable. Co/MSC composites oxidized at 300 °C for 10 min exhibits considerable minimum reflection loss of −37.86 dB and an effective absorption bandwidth of 5.28 GHz among the composites with different oxidation times. The Co/CoO, CoO/C, Co/C heterogeneous interfaces are conducive to the depletion of electromagnetic waves through interfacial polarization. The in-situ formed defects are positive for enhancing the dipole prolarization, and the natural resonance is also enhanced due to the presence of Co and its oxides. The positive effects of carbon additive in the oxidation of Co on the in-situ defects formation and multiple interface construction provide a new perspective for designing high performance microwave absorption materials.