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The synthesis of wide bandwidth, thin thickness, and high performance microwave absorbing materials has become a hot topic of current research. Metal-organic frameworks with heterojunctions and porous structures are considered as suitable candidates to meet these characteristics. Herein, heterogeneous CoFe@N-doped porous carbon polyhedron composites were successfully synthesized via Fe 2+ to replace Co in zeolite imidazole frame-67. The dielectric properties of composites were enhanced by the replacement of Fe 2+ , and the synergistic effect of dielectric loss and magnetic loss was realized. The petal-like lamellar structure increases the travel of electromagnetic (EM) waves, and the formation of porous structures improves impedance matching. Specifically, a reflection loss of −67.30 dB was obtained at a thickness of 2.88 mm, and an ultrabroad wide effective absorption bandwidth of 8.40 GHz was obtained, covering most of the X-band (8–12 GHz) and the whole Ku-band (12–18 GHz). The radar cross section (RCS) reduction value can reach 29.4 dB·m 2 , which means that the radar detector has a smaller probability of detecting targets. This work describes the unique advantages of metal ion replacement metal-organic frameworks derived materials in structural design, impedance matching, and performance adjustment, and provides a new reference for the field of electromagnetic wave absorption.

Two-dimensional metal carbide or nitride materials (MXenes) are widely used in electromagnetic wave absorption because of their unique structure. Herein, a novel composite preparation strategy has been proposed to design dendritic nanofibers based on the electrostatic spinning methods. The multifunctional MXene nanosheets are used as the dendritic matrix, and magnetic nanoparticles are embedded in the nanosheets as magnetic loss units. Multidimensional nanocomposites have interlaced carbon fiber networks, large-scale magnetically coupled networks, and a lot of multi-heterojunction interface structures, which endow the composites with extraordinary conduction loss, magnetic loss, and polarization loss capabilities, respectively. The impedance matching and loss mechanisms of the composites are improved by optimizing the synergistic relationship between the components and building a suitable structure. The optimum reflection loss (RL) of −54.1 dB is achieved at 2.7 mm and a wide effective absorption bandwidth (EAB, RL below −10 dB) of 7.76 GHz is obtained at a small thickness of 2.1 mm for the nanocomposites. The distinctive microstructures of the nanofibrous membranes give rise to their flexibility, waterproof, and electromagnetic wave absorption performance and endow the nanofibrous membranes potential to be utilized as lightweight, efficient electromagnetic wave protective fabric in harsh environment.

HighlightsHeterogeneous interface engineering is designed by electrospinning.The introduction of Co3SnC0.7 nanoparticles increased the loss mechanism.Enhanced electromagnetic loss and improved impedance matching are achieved.The absorbers exhibit high-efficient electromagnetic wave absorption performance.Application of novel radio technologies and equipment inevitably leads to electromagnetic pollution. One-dimensional polymer-based composite membrane structures have been shown to be an effective strategy to obtain high-performance microwave absorbers. Herein, we reported a one-dimensional N-doped carbon nanofibers material which encapsulated the hollow Co3SnC0.7 nanocubes in the fiber lumen by electrospinning. Space charge stacking formed between nanoparticles can be channeled by longitudinal fibrous structures. The dielectric constant of the fibers is highly related to the carbonization temperature, and the great impedance matching can be achieved by synergetic effect between Co3SnC0.7 and carbon network. At 800 °C, the necklace-like Co3SnC0.7/CNF with 5% low load achieves an excellent RL value of − 51.2 dB at 2.3 mm and the effective absorption bandwidth of 7.44 GHz with matching thickness of 2.5 mm. The multiple electromagnetic wave (EMW) reflections and interfacial polarization between the fibers and the fibers internal contribute a major effect to attenuating the EMW. These strategies for regulating electromagnetic performance can be expanded to other electromagnetic functional materials which facilitate the development of emerging absorbers.

HighlightsA novel FeCoNi carbon fiber (FeCoNi/CF) is obtained through an improved electrospinning technology, which greatly endows the fiber with strong magnetic property.The FeCoNi/CF exhibits an enhanced electromagnetic loss capability due to the construction of one-dimensional magnetic FeCoNi alloy.The designed one-dimensional FeCoNi/CF exhibits excellent performance, with a broad effective absorption band of 1.3 GHz in the low-frequency electromagnetic field at an ultrathin thickness of 2 mm, which provides a great potential for practical application in the future.Rational designing of one-dimensional (1D) magnetic alloy to facilitate electromagnetic (EM) wave attenuation capability in low-frequency (2–6 GHz) microwave absorption field is highly desired but remains a significant challenge. In this study, a composite EM wave absorber made of a FeCoNi medium-entropy alloy embedded in a 1D carbon matrix framework is rationally designed through an improved electrospinning method. The 1D-shaped FeCoNi alloy embedded composite demonstrates the high-density and continuous magnetic network using off-axis electronic holography technique, indicating the excellent magnetic loss ability under an external EM field. Then, the in-depth analysis shows that many factors, including 1D anisotropy and intrinsic physical features of the magnetic medium-entropy alloy, primarily contribute to the enhanced EM wave absorption performance. Therefore, the fabricated EM wave absorber shows an increasing effective absorption band of 1.3 GHz in the low-frequency electromagnetic field at an ultrathin thickness of 2 mm. Thus, this study opens up a new method for the design and preparation of high-performance 1D magnetic EM absorbers.

Dedicating to the exploration of efficient electromagnetic (EM) absorption and electromagnetic interference (EMI) shielding materials is the main strategy to solve the EM radiation issues. The development of multifunction EM attenuation materials that are compatible together EM absorption and EMI shielding properties is deserved our exploration and study. Here, the graphene-wrapped multiloculated NiFe 2 O 4 composites are reported as multifunction EM absorbing and EMI shielding materials. The conductive networks configurated by the overlapping flexible graphene promote the riched polarization genes, as well as electron transmission paths, and thus optimize the dielectric constant of the composites. Meanwhile, the introduction of magnetic NiFe 2 O 4 further establishes the magnetic-dielectric synergy effect. The abundant non-homogeneous interfaces not only generate effective interfacial polarization, also the deliberate multiloculated structure of NiFe 2 O 4 strengthens multi-scattering and multi-reflection sites to expand the transmission path of EM waves. As it turns out, the best impedance matching is matched at a lower filled concentration to achieve the strongest reflection loss value of −48.1 dB. Simultaneously, green EMI shielding based on a predominantly EM absorption and dissipation is achieved by an enlargement of the filled concentration, which is helpful to reduce the secondary EM wave reflection pollution to the environment. In addition, the electrocatalytic properties are further examined. The graphene-wrapped multiloculated NiFe 2 O 4 shows the well electrocatalytic activity as electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), which is mainly attributed to the interconnected structures formed by graphene and NiFe 2 O 4 connection. The structural advantages of multiloculated NiFe 2 O 4 expose more active sites, which plays an important role in optimizing catalytic reactions. This work provides an excellent jumping-off point for the development of multifunction EM absorbing materials, eco-friendliness EMI shielding materials and electrocatalysts.

HighlightsNiCo/C aerogel was prepared by pyrolysis carbonization self-assembly of NiCo- metal–organic frameworks (MOFs).The assembly mechanism of MOF aerogel was studied by adjusting the ratio of metal ion /BTC. Aerogel combines hydrophobic, lightweight, self-cleaning, and electromagnetic wave absorption properties.Although multifunctional aerogels are expected to be used in applications such as portable electronic devices, it is still a great challenge to confer multifunctionality to aerogels while maintaining their inherent microstructure. Herein, a simple method is proposed to prepare multifunctional NiCo/C aerogels with excellent electromagnetic wave absorption properties, superhydrophobicity, and self-cleaning by water-induced NiCo-MOF self-assembly. Specifically, the impedance matching of the three-dimensional (3D) structure and the interfacial polarization provided by CoNi/C as well as the defect-induced dipole polarization are the primary contributors to the broadband absorption. As a result, the prepared NiCo/C aerogels have a broadband width of 6.22 GHz at 1.9 mm. Due to the presence of hydrophobic functional groups, CoNi/C aerogels improve the stability in humid environments and obtain hydrophobicity with large contact angles > 140°. This multifunctional aerogel has promising applications in electromagnetic wave absorption, resistance to water or humid environments.

HighlightsA multifunctional SiC@SiO2 nanofber aerogel (NFA) was successfully prepared, which exhibits ultra-elastic, fatigue-resistant, high-temperature thermalstability, thermal insulation properties, and signifcant strain-dependent piezoresistive sensing behavior.The SiC@SiO2 NFA shows excellent electromagnetic wave absorption performance with a minimum refection loss value of −50.36 dB and a maximum effective absorption bandwidth of 8.6 GHz.Traditional ceramic materials are generally brittle and not flexible with high production costs, which seriously hinders their practical applications. Multifunctional nanofiber ceramic aerogels are highly desirable for applications in extreme environments, however, the integration of multiple functions in their preparation is extremely challenging. To tackle these challenges, we fabricated a multifunctional SiC@SiO2 nanofiber aerogel (SiC@SiO2 NFA) with a three-dimensional (3D) porous cross-linked structure through a simple chemical vapor deposition method and subsequent heat-treatment process. The as-prepared SiC@SiO2 NFA exhibits an ultralow density (~ 11 mg cm− 3), ultra-elastic, fatigue-resistant and refractory performance, high temperature thermal stability, thermal insulation properties, and significant strain-dependent piezoresistive sensing behavior. Furthermore, the SiC@SiO2 NFA shows a superior electromagnetic wave absorption performance with a minimum refection loss (RLmin) value of − 50.36 dB and a maximum effective absorption bandwidth (EABmax) of 8.6 GHz. The successful preparation of this multifunctional aerogel material provides a promising prospect for the design and fabrication of the cutting-edge ceramic materials.

HighlightsCellulose aerogel with vertically oriented structure was obtained by constructing a vertically aligned SiC nanowires/BN network via the ice template assisted strategy.The thermal conductivity of the composite in the vertical direction reaches 2.21 W m−1 K−1 at a low hybrid filler loading of 16.69 wt%, which was increased 890% compared to pure epoxy.The composite exhibits good electrically insulating with a volume electrical resistivity about 2.35×1011 Ω cm, and displays excellent electromagnetic wave absorption performance.With the innovation of microelectronics technology, the heat dissipation problem inside the device will face a severe test. In this work, cellulose aerogel (CA) with highly enhanced thermal conductivity (TC) in vertical planes was successfully obtained by constructing a vertically aligned silicon carbide nanowires (SiC NWs)/boron nitride (BN) network via the ice template-assisted strategy. The unique network structure of SiC NWs connected to BN ensures that the TC of the composite in the vertical direction reaches 2.21 W m−1 K−1 at a low hybrid filler loading of 16.69 wt%, which was increased by 890% compared to pure epoxy (EP). In addition, relying on unique porous network structure of CA, EP-based composite also showed higher TC than other comparative samples in the horizontal direction. Meanwhile, the composite exhibits good electrically insulating with a volume electrical resistivity about 2.35 × 1011 Ω cm and displays excellent electromagnetic wave absorption performance with a minimum reflection loss of − 21.5 dB and a wide effective absorption bandwidth (< − 10 dB) from 8.8 to 11.6 GHz. Therefore, this work provides a new strategy for manufacturing polymer-based composites with excellent multifunctional performances in microelectronic packaging applications.

Highly thermal conductivity materials with excellent electromagnetic interference shielding and Joule heating performances are ideal for thermal management in the next generation of communication industry, artificial intelligence and wearable electronics. In this work, silver nanowires (AgNWs) are prepared using silver nitrate as the silver source and ethylene glycol as the solvent and reducing agent, and boron nitride (BN) is performed to prepare BN nanosheets (BNNS) with the help of isopropyl alcohol and ultrasonication-assisted peeling method, which are compounded with aramid nanofibers (ANF) prepared by chemical dissociation, respectively, and the (BNNS/ANF)-(AgNWs/ANF) thermal conductivity and electromagnetic interference shielding composite films with Janus structures are prepared by the “vacuum-assisted filtration and hot-pressing” method. Janus (BNNS/ANF)-(AgNWs/ANF) composite films exhibit “one side insulating, one side conducting” performance, the surface resistivity of the BNNS/ANF surface is 4.7 × 10 13 Ω, while the conductivity of the AgNWs/ANF surface is 5,275 S/cm. And Janus (BNNS/ANF)-(AgNWs/ANF) composite film with thickness of 95 µm has a high in-plane thermal conductivity coefficient of 8.12 W/(m·K) and superior electromagnetic interference shielding effectiveness of 70 dB. The obtained composite film also has excellent tensile strength of 122.9 MPa and tensile modulus and 2.7 GPa. It also has good temperature-voltage response characteristics (high Joule heating temperature at low supply voltage (5 V, 215.0 °C), fast response time (10 s)), excellent electrical stability and reliability (stable and constant real-time relative resistance under up to 300 cycles and 1,500 s of tensile-bending fatigue work tests).

HighlightsConstructing a porous carbon fiber/polymethacrylimide (CP) structure for acquiring promising electromagnetic absorption performance and withstanding both elevated temperature and high strength in a low density.The absorption bandwidth of CP composite can reach ultra-wideband absorption of 14 GHz at room temperature and even cover the whole X-band at 473 K.The lightweight of the CP composite with a density of only 110 mg cm−3 coupled with high compressive strength of 1.05 MPa even at 453 K.Realizing ultra-wideband absorption, desirable attenuation capability at high temperature and mechanical requirements for real-life applications remains a great challenge for microwave absorbing materials. Herein, we have constructed a porous carbon fiber/polymethacrylimide (CP) structure for acquiring promising microwave absorption performance and withstanding both elevated temperature and high strength in a low density. Given the ability of porous structure to induce desirable impedance matching and multiple reflection, the absorption bandwidth of CP composite can reach ultra-wideband absorption of 14 GHz at room temperature and even cover the whole X-band at 473 K. Additionally, the presence of imide ring group in polymethacrylimide and hard bubble wall endows the composite with excellent heat and compressive behaviors. Besides, the lightweight of the CP composite with a density of only 110 mg cm−3 coupled with high compressive strength of 1.05 MPa even at 453 K also satisfies the requirements in engineering applications. Compared with soft and compressible aerogel materials, we envision that the rigid porous foam absorbing material is particularly suitable for environmental extremes.