Microwave Absorption Properties and Mechanism Analyses of Core-Shell Structured High-Entropy Oxides Coated with PPy

For HEO@PPy composites, there are mainly eddy current loss and hysteresis loss in the high-entropy oxides. For the effect on the magnetic loss performance, it is weakening for Fe, Ni, and Co successively. The composite of HEO(1)-FeNi@PPy has the largest reflection loss with a minimum RL value of -32.04 dB and an effective absorption bandwidth of 5.8 GHz, and the corresponding thicknesses are almost the same, which enables the optimization of both parameters simultaneously. The sample also has the optimal waveband-thickness absorption characteristics. A reciprocal relationship was found between magnetic loss and dielectric loss. By incorporating the HEO(1)-FeNi@PPy powder into paraffin, it was found that the greater the amount of powder material, the higher the electric conduction loss and polarization loss, and the magnetic loss would decrease. The microwave frequency f was found to be the main variable affecting the magnetic permeability and dielectric constant.