Facile Preparation of Snowflake-Like MnO2 @NiCo2 O4 Composites for Highly Efficient Electromagnetic Wave Absorption.

Snowflake-like MnO2 @NiCo2 O4 composites were successfully fabricated by employing crossed snowflake-like MnO2 nanorods as cores and one-dimensional (1D) NiCo2 O4 nanoneedles as shells. Impressively, the MnO2 @NiCo2 O4 composites exhibited a highly efficient electromagnetic wave (EMW) absorbing capability, and the minimum reflection loss (RL) value reached -58.4 dB at 6.8 GHz for a thickness of 4.0 mm. The reasons for the improved EMW absorption capability of snowflake-like MnO2 @NiCo2 O4 composites were analyzed. The unique core-shell structure, good impedance matching, and high dielectric loss were all found to be important contributors. Moreover, the interfacial polarization mainly stemmed from the heterostructure, a microcurrent generated from the 1D MnO2 nanorods and NiCo2 O4 nanoneedles under alternating electromagnetic fields, and the synergistic effect from the different components were all beneficial to improve the EMW absorption performance. These results demonstrated that snowflake-like MnO2 @NiCo2 O4 composites could be utilized as promising materials for practical EMW absorbing applications.