Achieving superior electromagnetic wave absorbers through the novel metal-organic frameworks derived magnetic porous carbon nanorods

Renewable porous biochar and 2D MXene have attracted significant attention in high-end electromagnetic interference (EMI) shielding fields, due to unique orderly structures and excellent electrical conductivity (σ) value. In this work, the wood-derived porous carbon (WPC) skeleton from natural wood was performed as a template. And excellent conductive and ultra-light 3D MXene aerogel was then constructed to prepare the MXene aerogel/WPC composites, based on highly ordered honeycomb cells inner WPC as a microreactor. Higher carbonization temperature is more conducive to the graphitization degree of natural wood. MXene aerogel/WPC composites achieve the optimal EMI SE value of up to 71.3 dB at density as low as 0.197 g/cm3. Such wall-like “mortar-brick” structures (WPC skeleton as “mortar” and MXene aerogel as “brick”) not only effectively solve the unstable structure problem of MXene aerogel networks, but also greatly prolong the transmission paths of the electromagnetic waves and dissipate the incident electromagnetic waves in the form of heat and electric energy, thereby exhibiting the superior EMI shielding performance. In addition, MXene aerogel/WPC composites also exhibit good anisotropic compressive strength, excellent thermal insulation and flame retardant properties. Such ultra-light, green and efficient multi-functional bio-carbon-based composites have great application potential in the high-end EMI shielding fields of aerospace and national defence industry, etc.

Ultra-light MXene aerogel/wood-derived porous carbon composites with wall-like “mortar/brick” structures for electromagnetic interference shielding

Carbon-based composites have gained extensive attention as microwave absorbing materials due to the lighter weight compared with other materials. In this work, Co/C nanocomposites with Co nanoparticles uniformly distributed in amorphous carbon sheets are prepared by a freezing dry and carbothermic reduction process. Hierarchical porous microstructures (micropores, mesopores, macropores) are achieved by ice template and huge amounts of gas during carbothermal reduction. Excellent absorption performance is achieved at a very low Co/C content (10% and 15%), which is a great success to design ultralight absorbers. At 10% content level, the effective absorption bandwidth is 5.0 GHz with a thin thickness of 1.8 mm, while the absorption bandwidth is 4.7 GHz with a thin thickness of 1.5 mm at 15% Co/C content level. The excellent absorption performance is attributed to excellent impedance matching resulting from synergy of cobalt and carbon and strong interfacial polarization induced by the hierarchical porous microstructures. This work provides a new pathway of designing ultralight absorbers with the advantage of thin thickness and wide bandwidth. Excellent absorption performance is achieved at only 10% Co/C content level, a success to design ultralight absorbers.

Hierarchically porous Co/C nanocomposites for ultralight high-performance microwave absorption

With the booming development of electronic information technology, the problems caused by electromagnetic (EMs) waves have gradually become serious, and EM wave absorption materials are playing an essential role in daily life. Carbon nanostructures stand out for their unique structures and properties compared with the other absorption materials. Graphene, carbon nanotubes, and other special carbon nanostructures have become especially significant as EM wave absorption materials in the high-frequency range. Moreover, various nanocomposites based on carbon nanostructures and other lossy materials can be modified as high-performance absorption materials. Here, the EM wave absorption theories of carbon nanostructures are introduced and recent advances of carbon nanostructures for high-frequency EM wave absorption are summarized. Meanwhile, the shortcomings, challenges, and prospects of carbon nanostructures for high-frequency EM wave absorption are presented. Carbon nanostructures are typical EM wave absorption materials being lightweight and having broadband properties. Carbon nanostructures and related nanocomposites represent the developing orientation of high-performance EM wave absorption materials.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/advs.201801057

Toward the Application of High Frequency Electromagnetic Wave Absorption by Carbon Nanostructures

Magnetite (Fe3O4)/carbon (C) composite flowers with an average size of 4–6 μm were prepared through a facile route including a solvothermal approach and a carbon reduction process. The resultant Fe3O4/C composites are porous and exhibit a three-dimensional (3D) flower-like morphology with the core–shell Fe3O4@C nanoparticles hybridized by amorphous carbon sheets. The epoxy resin composites containing 50 wt % 3D porous Fe3O4/C composite flowers display an optimal reflection loss (RL) value of −54.6 dB at 5.7 GHz at a thin thickness of 4.27 mm and the effective bandwidth with RL < −10 dB reaches 6.0 GHz at a thickness of 2.1 mm. These enhanced EM wave absorption performances are attributed to the synergistic effects of Fe3O4 and carbon as well as the structural advantages, e.g., three-dimensional structure with large surface area, porous and core–shell structures of Fe3O4/C flowers. These results suggest the 3D porous Fe3O4/C composite flowers designed here can serve as ideal candidates for high-performance...

Enhanced Electromagnetic Wave Absorption of Three-Dimensional Porous Fe3O4/C Composite Flowers

The invention relates to a ZnO/Co composite nano hollow fiber electromagnetic wave absorption material and a preparation method thereof and relates to the technical field of electromagnetic wave absorption materials. The method comprises the following steps: (1) dissolving a cobalt source and a zinc source in DMF, continuously adding PVP, stirring and then reacting to obtain a uniform viscous solution; (2) spinning the viscous solution in the step (1) by using a high-voltage electrostatic spinning method to obtain organic nanofibers, drying and pre-oxidizing the organic fibers, and then calcining the organic fibers; and (3) placing the organic fibers calcined in the step (2) in reducing atmosphere and carrying out reduction treatment to obtain the ZnO/Co composite nano hollow fiber material. The ZnO/Co composite nano hollow fiber material prepared through combination of the high-voltage electrostatic spinning method, calcining and reducing is high in saturation magnetic susceptibility,strong in coercive force, light in weight, high in oxidation resistance and excellent in electromagnetic wave absorption property; meanwhile, the preparation method is simple and feasible, and is lowin cost.

ZnO/Co composite nano hollow fiber electromagnetic wave absorption material and preparation method thereof

Enhanced electromagnetic wave absorption of nitrogen-doped reduced graphene oxide aerogels with LaFeO3 cluster modifications

Developing carbon encapsulated magnetic composites with rational design of microstructure for achieving high-performance electromagnetic wave (EMW) absorption in a facile, sustainable, and energy-efficiency approach is highly demanded yet remains challenging. Here, a type of N-doped carbon nanotube (CNT) encapsulated CoNi alloy nanocomposites with diverse heterostructures are synthesized via the facile, sustainable autocatalytic pyrolysis of porous CoNi-layered double hydroxide/melamine. Specifically, the formation mechanism of the encapsulated structure and the effects of heterogenous microstructure and composition on the EMW absorption performance are ascertained. With the presence of melamine, CoNi alloy emerges its autocatalysis effect to generate N-doped CNTs, leading to unique heterostructure and high oxidation stability. The abundant heterogeneous interfaces induce strong interfacial polarization to EMWs and optimize impedance matching characteristic. Combined with the inherent high conductive and magnetic loss capabilities, the nanocomposites accomplish a high-efficiency EMW absorption performance even at a low filling ratio. The minimum reflection loss of -84.0 dB at the thickness of 3.2 mm and a maximum effective bandwidth of 4.3 GHz are obtained, comparable to the best EMW absorbers. Integrated with the facile, controllable, and sustainable preparation approach of the heterogenous nanocomposites, the work shows a great promise of the nanocarbon encapsulation protocol for achieving lightweight, high-performance EMW absorption materials.

In-Situ Fabrication of Sustainable-N-Doped-Carbon-Nanotube-Encapsulated CoNi Heterogenous Nanocomposites for High-Efficiency Electromagnetic Wave Absorption.

Hollow Core–Shell Zno/Fe3o4@C Nanocomposite Fibers for Efficient Electromagnetic Wave Absorption

The invention belongs to the field of electromagnetic wave absorbing materials, and particularly relates to a TiO2/Co-supported carbonaceous fiber electromagnetic wave absorbing material and a preparation method and application thereof. The electromagnetic wave absorbing material is of a three-dimensional network structure formed by interweaving one-dimensional fibers, the fibers are composed of acarbonaceous substrate and TiO2 and Co nanoparticles, wherein the TiO2 and Co nanoparticles are distributed in the carbonaceous substrate and the surface of the carbonaceous substrate. The method comprises the steps that (1) a cobalt source, an oxygen-containing organic titanium source and anhydrous acetic acid are prepared into an electrospinning viscous solution, wherein the electrospinning viscous solution comprises a carbon source, then spinning is performed on the viscous solution by adopting a high-pressure electrostatic spinning method to obtain nanofibers, and then the nanofibers aredried and pre-oxidized; (2) the pre-oxidized calcined nanofibers are placed in a protective atmosphere to convert cobalt ions in the cobalt source into elemental cobalt and convert the oxygen-containing organic titanium source into TiO2, and the TiO2/Co-supported carbonaceous fiber electromagnetic wave absorbing material is obtained. The TiO2/Co-supported carbonaceous fiber electromagnetic wave absorbing material and the preparation method and application thereof have the advantages that nanoscale composition is effectively performed on the TiO2, Co and carbon fibers, and the prepared materialhas excellent properties.

Jing Qiao

Papers

ZnO/Co composite nano hollow fiber electromagnetic wave absorption material and preparation method thereof

Enhanced electromagnetic wave absorption of nitrogen-doped reduced graphene oxide aerogels with LaFeO3 cluster modifications

In-Situ Fabrication of Sustainable-N-Doped-Carbon-Nanotube-Encapsulated CoNi Heterogenous Nanocomposites for High-Efficiency Electromagnetic Wave Absorption.

Hollow Core–Shell Zno/Fe3o4@C Nanocomposite Fibers for Efficient Electromagnetic Wave Absorption

TiO2/Co-supported carbonaceous fiber electromagnetic wave absorbing material and preparation method and application thereof