Facile Preparation of Snowflake‐Like MnO₂@NiCo₂O₄ Composites for Highly Efficient Electromagnetic Wave Absorption

Abstract

Snowflake-like MnO 2 @NiCo 2 O 4 composites were successfully fabricated by employingc rossed snowflake-like MnO 2 nanorodsa sc ores and one-dimensional (1D) NiCo 2 O 4 nanoneedles as shells.I mpressively, the MnO 2 @NiCo 2 O 4 compositese xhibited ah ighly efficient electromagnetic wave (EMW) absorbing capability,a nd the minimum reflection loss (RL) value reached À58.4 dB at 6.8 GHz forathickness of 4.0 mm. The reasons for the improvedE MW absorption capabilityo fs nowflake-like MnO 2 @NiCo 2 O 4 compositesw ere analyzed. The unique core-shell structure, good impedance matching, and high dielectricl oss were all found to be important contributors. Moreover,t he interfacial polarization mainly stemmedf rom the heterostructure, am icrocurrent generated from the 1D MnO 2 nanorods and NiCo 2 O 4 nanoneedles under alternating electromagnetic fields, and the synergistic effect from the differentc omponents werea ll beneficial to improve the EMW absorption performance. These results demonstrated that snowflake-like MnO 2 @NiCo 2 O 4 composites could be utilizeda sp romising materials for practical EMW absorbinga pplications.[a] S.

Synthesis and Characterization of a NiCo2O4@NiCo2O4 Hierarchical Mesoporous Nanoflake Electrode for Supercapacitor Applications

“…Figure 6 b shows EIS test graphs identifying the ion diffusion and electron transfer in the three samples. As can be seen, the two impedance spectra are identical; each contains linear and semicircle shapes at low and high frequencies, respectively [ 31 ]. The summary of the contact resistance at the active current–material collector interface, intrinsic resistances of the active materials, and electrolyte ionic resistance is called the internal resistance (Rs), which is attained from the intercept of the plot on the real axis.…”

Facile synthesis of a 2D multilayer core–shell MnO2@LDH@MMT composite with a nanoflower shape for electromagnetic wave absorption

“…43 Its eddy current loss is described as follows: 45 Fig. 7c shows that the C o values and μ″ remain in the same range, and at 9-18 GHz, the C o values of the composite remain essentially constant, with small fluctuations present, which are mainly caused by eddy current losses and exchange resonances (10)(11)(12)(13)(14)(15)(16)(17)(18). At 2-9 GHz, C o undergoes a large increase, which is attributable to natural resonance (2-10 GHz).…”

“…7,8 Therefore, various types of composite materials are currently designed to promote EW absorption performance by exploiting the synergistic effects between different components and structures. 9,10 Examples are snowflake MnO 2 @NiCo 2 O 4 , 11 CF/SiO, 12 flower-like NiFe 2 O 4 / graphene, 13 NiM-MF/PEG, 14 cellulose/m-SiC NW/m-BN aerogel, 15 PVDF-Ni/PE-CNTs, 16 Fe/SiC, 17 Co/C crabapples, 18 MXene and conducting polymer matrix composites, 19 etc. Two-dimensional materials 20 provide conditions for structural design and performance optimization of electromagnetic materials owing to their distinctive two-dimensional structure, high specific surface area, and surface modification space.…”

MnO2‐Based Materials for Environmental Applications

“…Many heterojunctions formed by AB 2 O 4 spinel and MnO 2 have also been reported in recent years, including ZnCo 2 O 4 /MnO 2 , [ 232–236 ] ZnFe 2 O 4 /MnO 2 , [ 237 ] CoFe 2 O 4 /MnO 2 , [ 238 ] MnFe 2 O 4 /MnO 2 , [ 239 ] MnCo 2 O 4 /MnO 2 , [ 240 ] NiCo 2 O 4 /MnO 2 , [ 241,242 ] and CuBi 2 O 4 /MnO 2 . [ 243,244 ] Zhang et al.…”