CoFe2O4/N-doped reduced graphene oxide aerogels for high-performance microwave absorption

Electromagnetic pollution has been causing a series of problems in people’s life, and electromagnetic absorbers with lightweight and broad absorbing bandwidth properties are widely desired. In this work, novel sandwich-like 2D laminated Fe&TiO2 nanoparticles@C nanocomposites were rationally designed and successfully developed from the MXene–MOFs hybrids. The formation of Fe and rutile-TiO2 nanoparticles sandwiched by the two-dimensional carbon nanosheets provided strong electromagnetic energy attenuation and good impedance matching for electromagnetic wave (EMW) absorption. As expected, the nanocomposites achieved a broad effective absorption bandwidth of 6.5 GHz at a thickness of only 1.6 mm and the minimum reflection loss (RL) value of − 51.8 dB at 6.6 GHz with a thickness of 3 mm. This work not only provides a good design and fabricating concept for the laminated metal and functional nanoparticles@C nanocomposites with good EMW absorption, but also offers an important guideline to fabricate various two-dimensional nanocomposites derived from the MXene precursors.

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Sandwich-Like Fe&TiO 2 @C Nanocomposites Derived from MXene/Fe-MOFs Hybrids for Electromagnetic Absorption

. Intrinsic electric-magnetic property and special nano-micro architecture of functional materials have a significant effect on its electromagnetic wave energy conversion, especially in the microwave absorption (MA) field. Herein, porous Ni1−xCox@Carbon composites derived from metal-organic framework (MOF) were successfully synthesized via solvothermal reaction and subsequent annealing treatments. Benefiting from the coordination, carbonized bimetallic Ni-Co-MOF maintained its initial skeleton and transformed into magnetic-carbon composites with tunable nano-micro structure. During the thermal decomposition, generated magnetic particles/clusters acted as a catalyst to promote the carbon sp2 arrangement, forming special core-shell architecture. Therefore, pure Ni@C microspheres displayed strong MA behaviors than other Ni1−xCox@Carbon composites. Surprisingly, magnetic-dielectric Ni@C composites possessed the strongest reflection loss value − 59.5 dB and the effective absorption frequency covered as wide as 4.7 GHz. Meanwhile, the MA capacity also can be boosted by adjusting the absorber content from 25% to 40%. Magnetic–dielectric synergy effect of MOF-derived Ni1−xCox@Carbon microspheres was confirmed by the off-axis electron holography technology making a thorough inquiry in the MA mechanism.

/pdf/mof-derived-ni1-xcox-carbon-with-tunable-nano-microstructure-32xakl29az.pdf

MOF-Derived Ni1-xCox@Carbon with Tunable Nano-Microstructure as Lightweight and Highly Efficient Electromagnetic Wave Absorber.

Electromagnetic (EM) wave absorption materials possess exceptionally high EM energy loss efficiency. With vigorous developments in nanotechnology, such materials have exhibited numerous advanced EM functions, including radiation prevention and antiradar stealth. To achieve improved EM performance and multifunctionality, the elaborate control of microstructures has become an attractive research direction. By designing them as core-shell structures with different dimensions, the combined effects, such as interfacial polarization, conduction networks, magnetic coupling, and magnetic-dielectric synergy, can significantly enhance the EM wave absorption performance. Herein, the advances in low-dimensional core-shell EM wave absorption materials are outlined and a selection of the most remarkable examples is discussed. The derived key information regarding dimensional design, structural engineering, performance, and structure-function relationship are comprehensively summarized. Moreover, the investigation of the cutting-edge mechanisms is given particular attention. Additional applications, such as oxidation resistance and self-cleaning functions, are also introduced. Finally, insight into what may be expected from this rapidly expanding field and future challenges are presented. 

Dimensional Design and Core–Shell Engineering of Nanomaterials for Electromagnetic Wave Absorption

Developing electromagnetic absorption materials with a strong absorption ability and wide absorption bandwidth has attracted widespread attention in the field of electromagnetic shielding, but it still remains a great challenge. Herein, we successfully developed 2D hierarchically laminated Fe3O4@nanoporous carbon (NPC)@rGO magnetic/dielectric nanocomposites as high-performance microwave absorbers through a facile microwave-assisted approach. The rational design of the composition (Fe3O4, NPC and rGO) and the hierarchical microstructure provided the nanocomposite with a micro-scale 3D magnetic coupling network, a hierarchical dielectric carbon network and good impedance matching, which were identified by the off-axis electronic holography and electromagnetic characterization. As expected, the Fe3O4@NPC@rGO composites achieved a strong reflection loss of −72.6 dB, a matching thickness of 2.0 mm and a broad bandwidth of 5.5 GHz. Such excellent achievements encourage the development of hierarchical magnetic EMA absorbers and provide remarkable inspiration for designing high-performance microwave absorbers.

https://pubs.rsc.org/en/content/articlepdf/2020/tc/c9tc06526a

Rational design of 2D hierarchically laminated Fe3O4@nanoporous carbon@rGO nanocomposites with strong magnetic coupling for excellent electromagnetic absorption applications

Developing lightweight and broadband microwave absorbers for dealing with serious electromagnetic radiation pollution is a great challenge. Here, a novel Fe–Co/N-doped carbon/reduced graphene oxide (Fe–Co/NC/rGO) composite with hierarchically porous structure was designed and synthetized by in situ growth of Fe-doped Co-based metal organic frameworks (Co-MOF) on the sheets of porous cocoon-like rGO followed by calcination. The Fe–Co/NC composites are homogeneously distributed on the sheets of porous rGO. The Fe–Co/NC/rGO composite with multiple components (Fe/Co/NC/rGO) causes magnetic loss, dielectric loss, resistance loss, interfacial polarization, and good impedance matching. The hierarchically porous structure of the Fe–Co/NC/rGO enhances the multiple reflections and scattering of microwaves. Compared with the Co/NC and Fe–Co/NC, the hierarchically porous Fe–Co/NC/rGO composite exhibits much better microwave absorption performances due to the rational composition and porous structural design. Its minimum reflection loss (RLmin) reaches − 43.26 dB at 11.28 GHz with a thickness of 2.5 mm, and the effective absorption frequency (RL ≤ − 10 dB) is up to 9.12 GHz (8.88–18 GHz) with the same thickness of 2.5 mm. Moreover, the widest effective bandwidth of 9.29 GHz occurs at a thickness of 2.63 mm. This work provides a lightweight and broadband microwave absorbing material while offering a new idea to design excellent microwave absorbers with multicomponent and hierarchically porous structures.

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Rational Construction of Hierarchically Porous Fe–Co/N-Doped Carbon/rGO Composites for Broadband Microwave Absorption

Metal - organic frameworks derived Ni5P4/NC@CoFeP/NC composites for highly efficient oxygen evolution reaction.

MOF-derived core-shell structured Cu9S5/NC@Co3S4/NC composite as a high-efficiency electromagnetic wave absorber

In this paper, micro-mesoporous HZSM-5/MCM-41 zeolites were prepared by a two-step hydrothermal method using commercial HZSM-5 with two different silica/alumina ratios (38 and 50) as starting materials. The structures, morphologies and acidity of as-prepared zeolites were analyzed using XRD, FT-IR, SEM, N2-adsorption/desorption and NH3-TPD. The HZSM-5/MCM-41 zeolites combined the acidity of microporous HZSM-5 with the pore advantages of mesoporous MCM-41. Mesopores and microspores of 3.34 and 0.95 nm in diameter were found to be present in HZSM-5/MCM-41 zeolites. When they were used to catalyze the pyrolysis of waste tires, the selectivity of light olefins for HZSM-5/MCM-41 prepared using HZSM-5 with the silica/alumina ratio of 50 as starting materials was 21.42%, higher than 18.43% of HZSM-5/MCM-41 synthesized using HZSM-5 with the silica/alumina ratio of 38. In order to further overcome the pore size constraints and mass transfer limitations of HZSM- -5/MCM-41 zeolites for catalyzing pyrolysis of waste tires, macroporous γ-Al2O3 were mixed with HZSM-5/MCM-41 and used as catalysts. The selectivity to light olefins for the mixture of γ-Al2O3 and HZSM-5/MCM-41 prepared using HZSM-5 with the silica/alumina ratio of 50 as starting materials was 33.65%, which was obviously enhanced by the introduction of γ-Al2O3.

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Light olefin production using the mixture of HZSM-5/MCM-41 and γ-Al2O3 as catalysts for catalytic pyrolysis of waste tires

Reasonable design and construction of low-cost overall water splitting catalyst with high efficiency is of great significance to green chemistry industry. Herein, a CoFeP/NC@CoP/Ni2P heterostructure is constructed via phosphiding CoFe-Prussian...

Ruru Fu

Papers

Rational Construction of Hierarchically Porous Fe–Co/N-Doped Carbon/rGO Composites for Broadband Microwave Absorption

Metal - organic frameworks derived Ni5P4/NC@CoFeP/NC composites for highly efficient oxygen evolution reaction.

MOF-derived core-shell structured Cu9S5/NC@Co3S4/NC composite as a high-efficiency electromagnetic wave absorber

Light olefin production using the mixture of HZSM-5/MCM-41 and γ-Al2O3 as catalysts for catalytic pyrolysis of waste tires

CoFeP/NC@CoP/Ni2P Heterostructure for Efficient Overall Water Splitting