Co(x)Fe(y)@C Composites with Tunable Atomic Ratios for Excellent Electromagnetic Absorption Properties

The shell on the nano-magnetic absorber can prevent oxidation, which is very important for its practical utilization. Generally, the nonmagnetic shell will decrease the integral magnetic loss and thus weaken the electromagnetic absorption. However, maintaining the original absorption properties of the magnetic core is a major challenge. Here, we designed novel and facile Co(x)Fe(y)@C composites by reducing Co(x)Fe(3−x)O(4)@phenolic resin (x = 1, 0.5 and 0.25). High saturation magnetization value (Ms) of Co(x)Fe(y) particle, as a core, shows the interesting magnetic loss ability. Meanwhile, the carbon shell may increase the integral dielectric loss. The resulting composite shows excellent electromagnetic absorption properties. For example, at a coating thickness of 2 mm, the RL(min) value can reach to −23 dB with an effective frequency range of 7 GHz (11–18 GHz). The mechanisms of the improved microwave absorption properties are discussed.