Superior Microwave Absorption Properties Derived from the Unique 3D Porous Heterogeneous Structure of a CoS@Fe3O4@rGO Aerogel.

A novel CoS@Fe3O4@rGO aerogel with a unique 3D porous heterostructure was prepared via the solvothermal method, in which cobalt sulfide (CoS) microspheres embedded with Fe3O4 nanoparticles were randomly scattered on reduced graphene oxide (rGO) flakes. The introduction of magnetic Fe3O4 nanoparticles and rGO regulated the impedance matching, and the excellent electromagnetic wave (EMW) absorption capability of the CoS@Fe3O4@rGO aerogel could be attributed to optimal dielectric loss and abundant conductive networks. The results demonstrated that the minimum reflection loss (RL) value of CoS@Fe3O4@rGO aerogel was -60.65 dB at a 2.5 mm coating thickness with an ultra-wide bandwidth of 6.36 GHz (10.24-16.6 GHz), as the filler loading was only 6 wt%. Such a lightweight CoS@Fe3O4@rGO aerogel with an outstanding absorbing intensity and an ultra-wide effective absorption bandwidth could become a potential EMW absorber.

Heterostructure Composites of CoS Nanoparticles Decorated on Ti3C2Tx Nanosheets and Their Enhanced Electromagnetic Wave Absorption Performance.

As a typical two-dimensional material, MXene possesses excellent conductivity and tunable interlayer space, which makes it have an impressive development potential in the field of electromagnetic (EM) waves absorbing materials. In this work, we fabricated a sandwich structure CoS@Ti3C2Tx composite using a simple solvothermal process. The CoS nanoparticles are anchored on the Ti3C2Tx MXene sheets, forming a heterolayered structure. The results demonstrate that the CoS@Ti3C2Tx composites with the sandwich-like architecture showed excellent EM absorbing performance due to the synergistic effects of the conductivity loss, interface polarization, and dipole polarization. When the doping ratio was 40 wt %, the maximum reflection loss value of CoS@Ti3C2Tx was up to -59.2 dB at 14.6 GHz, and the corresponding effective absorption bandwidth (below -10 dB) reached 5.0 GHz when the thickness was only 2.0 mm. This work endows a new candidate for the design of MXene-based absorption materials with optimal performance.

Polypyrrole Chains Decorated on CoS Spheres: A Core-Shell Like Heterostructure for High-Performance Microwave Absorption.

Cobalt sulfide composites have exhibited great potential in terms of microwave absorption, owing to their low price, relatively high capacitance, and excellent electrocatalytic activity. Thus, a novel core-shell like structure comprising cobalt sulfide@polypyrrole (CoS@PPy) composite was synthesized by a facile solvothermal synthesis method and in situ polymerization. When coated by the heterostructure polypyrrole aerogel, CoS@PPy composite exhibited excellent microwave absorption properties with an optimal reflection loss (RL) of -41.8 dB at 6.96 GHz. Furthermore, the absorption bandwidth (RL < -10 dB) of 5.4 GHz could be reached at a coating thickness of 2.05 mm, probably attributing to the synergistic effect of good impedance matching, interfacial polarization, dipole polarization, and conductivity loss. Moreover, this work proposed a loss mechanism mode which probably occurred in the CoS@PPy composites. It was demonstrated that the CoS@PPy composite is a promising material in the field of electromagnetic wave absorption.

NiS2@MoS2 Nanospheres Anchored on Reduced Graphene Oxide: A Novel Ternary Heterostructure with Enhanced Electromagnetic Absorption Property.

For the purposes of strength, military equipment camouflage, and protecting the health of organisms, electromagnetic wave absorbing materials have received a lot of attention and are widely studied. In addition to having a strong absorption intensity and a wide effective absorption bandwidth, materials that are lightweight, thermally stable, and antioxidative are also highly desirable. In this study, we fabricated core⁻shell structured NiS2@MoS2 nanospheres anchored on reduced graphene oxide (rGO) nanosheets (NiS2@MoS2/rGO) by a simple two-step hydrothermal method. The combination ratio was adjusted to achieve proper impedance matching. The electromagnetic parameters and the absorption performance were investigated in detail. A composite loaded with 30 wt.% of the sample achieved a minimum reflection loss (RL) value of -29.75 dB and the effective bandwidth (RL value of less than -10 dB) ranged from 4.95 GHz to 18.00 GHz (13.05 GHz), with a thickness ranging from 1.5 mm to 4.0 mm. This study proved that the generated significant interfacial polarization and synergetic interaction between components can result in NiS2@MoS2/rGO composites with enhanced electromagnetic absorption performance.

Excellent Microwave Absorption Properties Derived from the Synthesis of Hollow Fe3o4@Reduced Graphite Oxide (RGO) Nanocomposites.

Magnetic nanoparticles, such as Fe3O4 and Co3O4, play a vital role in the research on advanced microwave absorbing materials, even if problems such as high density and narrow band impedance matching are still unsolved. Herein, the study of lightweight hollow Fe3O4@reduced graphite oxide (RGO) nanocomposites synthesized via the solvothermal method is presented. The microstructure and crystal morphology of the materials were characterized by X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analyses. Single crystalline hollow Fe3O4 spheres were grown onto RGO flakes, leading to the formation of heterojunction, which further influenced the microwave absorption properties. The latter were evaluated by standard microwave characterization in the frequency range of 2⁻18 GHz. It was found that, for a specific Fe3O4@0.125 g RGO composite, the minimum reflection loss can reach -41.89 dB at 6.7 GHz, while the reflection loss was less than -10 dB from 3.4 GHz to 13.6 GHz for a nanocomposite sample thickness in the range of 1⁻4 mm. The combination of these two materials thus proved to give remarkable microwave absorption properties, owing to enhanced magnetic losses and favorable impedance matching conditions.

Controllable Fabrication of Fe3O4/ZnO Core⁻Shell Nanocomposites and Their Electromagnetic Wave Absorption Performance in the 2⁻18 GHz Frequency Range.

In this study, Fe3O4/ZnO core⁻shell nanocomposites were synthesized through a chemical method of coating the magnetic core (Fe3O4) with ZnO by co-precipitation of Fe3O4 with zinc acetate in a basic medium of ammonium hydroxide. The phase structure, morphology and electromagnetic parameters of the Fe3O4/ZnO core⁻shell nanocomposites were investigated. The results indicated that the concentration of the solvent was responsible for controlling the morphology of the composites, which further influenced their impedance matching and microwave absorption properties. Moreover, Fe3O4/ZnO nanocomposites exhibited an enhanced absorption capacity in comparison with the naked Fe3O4 nanospheres. Specifically, the minimum reflection loss value reached −50.79 dB at 4.38 GHz when the thickness was 4.5 mm. It is expected that the Fe3O4/ZnO core⁻shell structured nanocomposites could be a promising candidate as high-performance microwave absorbers.

Decorating MOF-Derived Nanoporous Co/C in Chain-Like Polypyrrole (PPy) Aerogel: A Lightweight Material with Excellent Electromagnetic Absorption.

To clear away the harmful effects of the increment of electromagnetic pollution, high performance absorbers with appropriate impedance matching and strong attenuation capacity are strongly desired. In this study, a chain-like PPy aerogel decorated with MOF-derived nanoporous Co/C (Co/C@PPy) has been successfully prepared by a self-assembled polymerization method. With a filler loading ratio of 10 wt %, the composite of Co/C@PPy could achieve a promising electromagnetic absorption performance both in intensity and bandwidth. An optimal reflection loss value of −44.76 dB is achieved, and the effective bandwidth (reflection loss lower than −10 dB) is as large as 6.56 GHz. Furthermore, a composite only loaded with 5 wt % Co/C@PPy also achieves an effective bandwidth of 5.20 GHz, which is even better than numerous reported electromagnetic absorption (EA) materials. The result reveals that the as-fabricated Co/C@PPy—with high absorption intensity, broad bandwidth, and light weight properties—can be utilized as a competitive absorber.

Direct Growth of a Polypyrrole Aerogel on Hollow CuS Hierarchical Microspheres Yields Particles with Excellent Electromagnetic Wave Properties.

A current hot topic in polymer science is the development of electromagnetic wave-absorbing materials with desired properties (i.e., proper impedance matching and strong attenuation capability), but it presents a considerable challenge. In this work, solvothermal, and self-assembled polymerization were employed for the controlled fabrication of a uniform polypyrrole (PPy) aerogel coated on hollow CuS hierarchical microspheres (CuS@PPy). The PPy coating thickness of the heterostructure could be tuned by varying the feeding weight ratios of CuS/pyrrole monomer. The electromagnetic wave absorption properties of the CuS@PPy composites were estimated to be in the frequency range 2⁻18 GHz. The as-prepared Sample B (fabricated by the addition of 35 mg CuS) showed a maximum reflection loss (RL) of -52.85 dB at a thickness of 2.5 mm. Moreover, an ultra-wide effective bandwidth (RL ≤ -10 dB) from 9.78 to 17.80 GHz (8.02 GHz) was achieved. Analysis of the electromagnetic properties demonstrated that the CuS@PPy had a remarkable enhancement compared to pure CuS platelet-based spheres and pure PPy, which can be attributed to the increased relatively complex permittivity and the promoted dielectric loss by the intense interfacial dielectric polarizations. We believe that the as-fabricated CuS@PPy can be a good reference for the fabrication of lightweight and optimal broadband absorbers.

Fe3O4 nanoparticles decorated on a CuS platelet-based sphere: a popcorn chicken-like heterostructure as an ideal material against electromagnetic pollution.

Electromagnetic irradiation has caused environmental pollution and harmful effects on human health. The use of effective materials to attenuate electromagnetic energy is urgently required. In this study, Fe3O4 nanoparticles (NPs) decorated on a CuS platelet-based sphere (CuS/Fe3O4) with popcorn chicken-like micromorphology were synthesized through a solvothermal deposition method. The effects of reaction temperature and quantity of Fe3O4 NPs on the heterostructures, morphologies and electromagnetic absorption (EA) properties of the heterostructures were investigated. CuS/Fe3O4 heterostructures exhibited remarkable enhancement in comparison with pure Fe3O4 NPs and the CuS platelet-based sphere. With the contribution from dielectric and magnetic losses, a CuS/Fe3O4 heterostructure-loaded composite could achieve a minimum reflection loss (RL) of -61.32 dB at 14.00 GHz and an effective EA bandwidth (≤-10 dB) of 4.15 GHz at a thickness of only 1.5 mm simultaneously. The current study indicates that the CuS/Fe3O4 heterostructures can potentially be applied as advanced electromagnetic absorbers.