Nanostructure composites of ferromagnetic materials embedded in nanoporous carbon (NC) derived from metal-organic frameworks (MOFs) have attracted enormous attention due to their potential application in many fields, such as microwave absorption, energy storage, and conversion. The rational design of nanocomposites holds a determinant factor for overcoming the challenges involving the microwave absorption performance. Herein, CoS/NC, CoP/NC, and CoSP/NC with a rhombic dodecahedral structure have been successfully fabricated by using the template cobalt-based MOFs (ZIF-67). A morphology analysis indicates that ferromagnetic nanoparticles are embedded in NC matrix. It is obvious that the rhombic dodecahedron can be maintained after the phosphorization and sulfurization of Co/NC derived from the thermal decomposition of ZIF-67. The microwave absorption performance can obviously be improved by the phosphorization and sulfurization of Co/NC. CoSP/NC exhibits an excellent microwave absorption property and the minimum reflection loss (RL) of CoSP/NC can reach -68 dB at 14.6 GHz with a thickness of 1.5 mm. An RL value less than -10 dB can be achieved in the microwave frequency range of 12.7-17.3 GHz (4.6 GHz) with a thickness of 1.5 mm for CoSP/NC. This article offers a novel way to fabricate cobalt-based materials/carbon composites for an excellent microwave absorber.
Recently, intrinsic ferromagnetism of layered van der Waals compounds (such as CrCl3, CrI3, and Cr2Ge2Te6) has received widespread attention. Herein, layered van der Waals heterostructure composites of two dimensional layered magnetic material CrCl3 and graphene nanosheets (GNSs) are facilely obtained and investigated as microwave absorption materials. The complex permittivity and complex permeability of heterostructure composites can be adjusted by modulating the mass ratio of GNS and CrCl3. The real part and imaginary part of permittivity increase with the increase in the mass fraction of GNS in composites, due to the high conductivity of GNS. Thus, dielectric loss is enhanced and originates from the Debye relaxation process and the interfacial polarization process. The minimum reflection loss (RL) of the CrCl3-GNS heterostructure composite with a GNS mass fraction of 40 wt. % can reach −46.2 dB at a microwave frequency of 10 GHz with a thickness of 1.9 mm. In addition, the RL less than −10 dB can be achieved at different frequencies with all thicknesses (1–5 mm). This work might provide the practical application of two dimensional layered magnetic materials as ultrahigh-performance microwave absorption materials.
The Ni@C nanohybrids were prepared by a unique and efficient method of annealing the organic carbon compound and metal nitrate. Morphology detection demonstrated the Ni nanoparticles were uniformly encapsulated into the carbon network. The microwave absorption of 10 wt % Ni@C nanohybrids with paraffin matrix was measured over the range of 1−18 GHz. The complex permittivity was adjusted by changing the carbon proportions because of the superior conductivity of graphite. The minimum reflection loss (RL) value of −56 dB was obtained at 15.8 GHz with a thickness of 1.8 mm and the effective absorption bandwidth (RL ≤ −10 dB) was 5.4 GHz. Therefore, the Ni@C nanohybrids have great potential to be utilized as a high-efficiency and lightweight microwave absorber.
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