Nanofibrous membrane constructed magnetic materials for high-efficiency electromagnetic wave absorption

Synthesis and electromagnetic wave absorption performances of a novel (Mo0.25Cr0.25Ti0.25V0.25)3AlC2 high-entropy MAX phase

Electromagnetic (EM) wave absorption materials have drawn a lot of attention because they can effectively reduce EM wave pollution from electronic equipment. In this work, we combined ZrO2 nanoparticles with multi-walled carbon nanotubes (MWCNTs) and explored applications of MWCNT/ZrO2 composites in EM wave absorbing field. ZrO2 nanoparticles with a high crystalline were synthesized by one-step hydrothermal method. Adding MWCNTs in this hydrothermal process, ZrO2 nanoparticles aggregated together to form uneven lumps and wraps on MWCNTs surfaces. MWCNTs improved the conductivity loss and electron polarization capability of composites. The minimum reflection loss (RL) of MWCNT/ZrO2 composites reached [Formula: see text]39.73 dB at a thickness of 2[Formula: see text]mm. Such excellent EM wave absorption properties are attributed to the dielectric loss, dipole polarizations and interfacial polarizations. This composite can be a promising candidate as high efficiency EM wave absorption material and used for commercial production because of the simple synthesis methods.

MoSe2 nanosheets decorated Co/C fibrous composite towards high efficiency electromagnetic wave absorption

A quantitative permittivity model for designing electromagnetic wave absorption materials with conduction loss: A case study with microwave-reduced graphene oxide

Ferromagnetic metal nanoparticle/graphene nanocomposites are promising as excellent electromagnetic (EM) wave absorption materials. In this work, we used a facile method to synthesize a cobalt nanoparticle–graphene (CoNP–G) nanocomposite. The obtained CoNPs–G exhibited a saturation magnetization (Ms) of 31.3 emu g−1 and a coercivity (HC) of 408.9 Oe at 298.15 K. In particular, the CoNPs–G nanocomposite provided high-performance EM wave absorption with multiband, wide effective absorption bandwidth, which was mainly attributed to the synergy effects generated by the magnetic loss of cobalt and the dielectric loss of graphene. In the range of 2–18 GHz, the sample (55 wt% CoNPs–G) held three effective reflection loss (RL) peaks (frequency ranges of 2.4–3.84, 7.84–11.87 and 13.25–18 GHz, respectively, RL ≤ −10 dB) with the coating thickness of 4.5 mm, and the effective bandwidth reached the maximum of 10.22 GHz, and the minimal RL reached −40.53 dB at 9.50 GHz. Therefore, the CoNPs–G nanocomposite presents a great promising application in the electromagnetic wave absorption field.

To meet the rigorous demands placed on electromagnetic (EM) wave absorbing (EWA) materials by harsh service conditions and to reduce EM wave power density, the development of ceramic‐based EWA materials with high reliability and stability has become a subject of significant focus. In this study, yttrium silicide carbide interphase was in situ synthesized on silicon carbide fibers to fabricate Y₃Si₂C₂–SiCf composite fibers by the molten salt method. These fibers were then incorporated into a mullite ceramic matrix, and Y₃Si₂C₂–SiCf/mullite composites were prepared by gel injection molding, aiming at enhancing the EWA properties. The Y₃Si₂C₂–SiCf/mullite composite exhibited a reflection loss of −28.97 dB at 2.44 mm thickness and an effective absorption bandwidth of 3.066 GHz, outperforming pure mullite and SiCf/mullite composites due to the addition of Y₃Si₂C₂–SiCf. A modified Drude–Lorentz model was developed to capture the multi‐peak permittivity behavior of Y₃Si₂C₂–SiCf/mullite composites. The results showed that dipole relaxation and hopping migration of localized electrons played key roles in the overall microwave energy attenuation, which closely matched the experimental data. Furthermore, simulations of the electric field distribution and radar cross‐section confirmed the superior energy loss capability and practical application potential of Y₃Si₂C₂–SiCf/mullite composites. This study offers valuable theoretical insights into the design and application of SiCf‐reinforced ceramic‐based EWA materials.

Structural modification of mesoporous lanthanum oxide into 3D coral-like and nano needle-like structure for effective broadband microwave absorbing materials☆

With the fast advancement of up-to-date communication technologies, electromagnetic wave (EMW) absorption materials are widely required for various applications. However, it is still a big challenge to produce lightweight, flexible, and high-efficiency EMW absorption materials in a broad-ranging frequency. Herein, we designed to fabricate the magnetic and dielectric nanofibrous membranes which can be effectively used as EMW absorption materials by facile electrospinning process. The as-fabricated composite carbon nanofibers (CNFs), which combined the components of nickel, cobalt antioxidant nanoparticles, and carbon nanotubes, exhibited outstanding magnetic and dielectric properties and strong absorption ability in a wide frequency range. These nanoparticles encapsulated in CNFs are extremely beneficial to the electrical conductivity of the composites through decreasing the contact loss within the CNFs by formation of the metal-metal interfaces. Correspondingly, the RL value of -46.60 dB was reached at 4.88 GHz frequency range with a layer thickness of 5.5 mm for these mechanically light and flexible membranes. The enhanced absorption performance (<-10 dB) in the wide frequency band (4.16-18 GHz) can be achieved by selecting a suitable thickness of the material. Results demonstrate that the permittivity and permeability of developed samples have been largely improved because of the integrated interaction of all introduced components in the structure. The composite membranes are a promising candidate for scalable, lightweight, and high-performance EMW absorption materials in the frequency range from C band to Ku band (4-18 GHz).

Synthesis of dendritic cobalt with flower-like structure by a facile wet chemistry method as an excellent electromagnetic wave absorber

Electromagnetic wave (EMW) absorption materials with high efficiency and simple preparation process are highly desirable for practical applications. However, there are still many obstacles to simultaneously satisfy the practical requirements. Herein, fly ash cenospheres (FACs), solid waste from power plants, were selected as a framework to prepare OH-functionalized multi-walled carbon nanotube (MWCNT)/FAC hybrids with multilayer, connected and porous architectures via a facile physical mixing process for the first time. Accordingly, a novel tubular/spherical model for EMW absorption materials was established. The effect of the unique heterostructure, which possessed multiple interfaces, on the EMW absorption property was studied. The results indicated that this structure is conducive to extending the transmission route, adjusting the conductivity and improving the dielectric loss. Thus, the composite showed an excellent EMW absorption performance. The minimum reflection loss of −44.67 dB occurs at 4.9 GHz and the effective bandwidth below −10 dB (90% attenuation of EMW) could shift from 4.1 to 19.2 GHz with a thickness in the range of 1.5–5.5 mm. The superior absorption property is mostly attributed to the synergistic effect of good impedance matching, multiple loss mechanisms, and multiple reflections and scatterings. Thus, this product meets the requirement of high absorption performance and simple preparation, which greatly enhance its applicability.

Outstanding electromagnetic wave absorption performance of polyacrylonitrile-based ultrahigh modulus carbon fibers decorated with CoZn-bimetallic ZIFs

Excellent electromagnetic wave loss and impedance matching are typical characteristics of superior‐performance electromagnetic wave (EMW) absorption materials. Changing the component ratios and multidimensional combinations of various absorbing materials is one of the best methods to improve absorption performance. This work used a convenient physical mixing approach to combine three wave‐absorbing materials with various dimensions to successfully prepare Graphene/carbon nanotubes/Fe3O4 (G/C/Fe3O4)/paraffin composites. One‐dimensional (1D) tube carbon nanotubes (CNTs) pierced two‐dimensional (2D) sheet graphene to form a strong three‐dimensional (3D) conductive network, enhancing interfacial polarization without introducing zero‐dimensional (0D) magnetic Nano‐Fe3O4. Nevertheless, because of their significant dielectric characteristics, the graphene/carbon nanotube (G/C) paraffin composites displayed low impedance matching and electromagnetic wave absorption properties. At a mass ratio of 1:1, the G/C/paraffin composites achieved an ideal reflection loss (RL) of −11.99 db and an impedance matching value of 0.59. Adding Fe3O4 improved the impedance matching and electromagnetic wave loss performance and promoted the formation of a non‐homogeneous interface, improving interfacial polarization and reflection. The G/C/Fe3O4/paraffin composite, with a mass ratio of 1:1:6 and a filler ratio of 20%, achieved an optimum reflection loss of −37.2 dB and an effective absorption bandwidth of 4.16 GHz. This work optimized and improved the performance of EMW materials practically and rapidly, providing a research method for the widespread application of superior‐performance electromagnetic wave absorption materials.Highlights The EMW absorption materials with various architectures. 1D CNTs pierced 2D sheet graphene to form a strong 3D conductive network. Adding Fe3O4 promoted the formation of a non‐homogeneous interface. Electromagnetic synergies and different structural combinations It achieved excellent impedance matching and electromagnetic loss performance.

Smart shape memory composite foam enabled rapid and conformal manipulation of electromagnetic wave absorption performance

Plentiful heterogeneous interfaces coupling in hydrangea-like NiMn-LDH decorated MXene hybrids for enhancing electromagnetic wave absorption

Broadband high-performance electromagnetic wave absorption of Co-doped NiZn ferrite/polyaniline on MXenes