There is a high demand for electromagnetic interference (EMI) shielding materials with low reflection shielding effectiveness (SER) and high absorption SE (SEA) for 5 G mobile communication. This study prepared absorptiondominant EMI shielding films comprising polymer beads and a magnetic composite channel. The doublepercolation structure enhanced the SEA of the film by over 50%, compared to the homogeneous magnetic composite, without changing the SER. The mechanism of the enhanced SEA due to multiple reflections was discussed. The films exhibited low SER and high SEA, compared to those in previous studies on 5 G shielding materials. Therefore, they are applicable in 5 G-enabled mobile devices for effective EMI shielding.

LaAlO3-BaSnO3 ceramics as a new microwave dielectric material were investigated in terms of optimum synthesis conditions and thereby the relative density, microstructure, solid-solution state, and dielectric properties with the addition of various sintering aids at different sintering temperatures. The dielectric properties of 0.9LaAlO(3)-0.1BaSnO(3) (LA-0.1BS) were strongly influenced by relative density, microstructure, chemical ordering, and mixing rule of the dielectric constant. Densification of the LA-0.1BS ceramics was improved from 82.3 to 96.13% with an average grain size of around 1.9 mu m at reduced sintering temperature by 250 degrees C. The LA-0.1BS ceramics sintered with 3 mol% of Bi2O3-SiO2 (BS) showed dielectric constant (epsilon(r)) similar to 21.18 with associated dielectric loss (tan delta) similar to 0.00824 and Q x f similar to 1213.59 (10 GHz) which could be achieved at low sintering temperature of 1400-1450 degrees C.

It is of importance to explore a new carbon nanomaterial possessing vital functions to fulfill the high standards for practical achievement of the electromagnetic (EM) barrier for blocking EM waves and the electrochemical (EC) barrier as a functional separator for EC energy storage. Herein, facile synthesis of a new class of carbon nanostructures, which consist of interconnected N-doped graphitic carbon nanocubes partially embedded by nickel nanoparticles, is described. The hollow interior of graphitic nanocube induces internal reflection of EM waves and confines active materials of EC energy storage. Nitrogen functionalities implanted in graphitic structure enhance electrical conductivity as well as improve chemical interaction with active materials. Furthermore, nickel nanoparticles in graphitic nanocube function as an EM wave-absorbing material and an electrocatalyst for EC energy storage. Through comprehensive assessments, remarkable performances originating from distinctive nanostructures give new insights into structural design for the carbon nanostructure-based high-performance EM and EC barriers.

In this study, electroless nickel-plated carbon fiber (CF) was prepared with edge-selectively oxidized graphene (EOG) to reinforce the interface between nickel and CF for use in a composite for electromagnetic interference (EMI) shielding. The EOG layer was formed by generating ionic interaction through a modified layer-by-layer assembly between negatively charged EOG and positively charged polyethyleneimine (PEI). EOG-coated CFs with rough surfaces improved the specific surface area and adhesion strength with the nickel-plating layer. To evaluate the adhesion strength, the interfacial shear strength (IFSS) was investigated using microdroplet testing. After EOG coating, the interfacial bonding strength was enhanced by about 65%. The composite nickel-plated carbon fabric with EOG coating showed EMI shielding of around 58 dB, which is significant for future EMI shielding applications.

Herein, we introduce novel 1-dimensional nano-chained FeCo particles with unusually-high permeability prepared by a highly-productive thermal plasma synthesis and demonstrate an electromagnetic wave absorber with exceptionally low reflection loss in the high-frequency regime (1-26 GHz). During the thermal plasma synthesis, spherical FeCo nanoparticles are first formed through the nucleation and growth processes; then, the high temperature zone of the thermal plasma accelerates the diffusion of constituent elements, leading to surface-consolidation between the particles at the moment of collision, and 1-dimensional nano-chained particles are successfully fabricated without the need for templates or a complex directional growth process. Systematic control over the composition and magnetic properties of FexCo1-x nano-chained particles also has been accomplished by changing the mixing ratio of the Fe-to-Co precursors, i.e. from 7 : 3 to 3 : 7, leading to a remarkably high saturation magnetization of 151-227 emu g-1. In addition, a precisely-controlled and uniform surface SiO2 coating on the FeCo nano-chained particles was found to effectively modulate complex permittivity. Consequently, a composite electromagnetic wave absorber comprising Fe0.6Co0.4 nano-chained particles with 2.00 nm-thick SiO2 surface insulation exhibits dramatically intensified permeability, thereby improving electromagnetic absorption performance with the lowest reflection loss of -43.49 dB and -10 dB (90% absorbance) bandwidth of 9.28 GHz, with a minimum thickness of 0.85 mm.

Abstract An ultrawideband electromagnetic metamaterial absorber is proposed that consists of double-layer metapatterns optimally designed by the genetic algorithm and printed using carbon paste. By setting the sheet resistance of the intermediate carbon metapattern to a half of that of the top one, it is possible to find an optimal intermediate metapattern that reflects and absorbs the EM wave simultaneously. By adding an absorption resonance via a constructive interference at the top metapattern induced by the reflection from the intermediate one, an ultrawideband absorption can be achieved without increasing the number of layers. Moreover, it is found that the metapatterns support the surface plasmon polaritons which can supply an additional absorption resonance as well as boost the absorption in a broad bandwidth. Based on the simulation, the $$90\%$$ 90 % absorption bandwidth is confirmed from 6.3 to 30.1 GHz of which the fractional bandwidth is 130.77 $$\%$$ % for the normal incidence. The accuracy is verified via measurements well matched with the simulations. The proposed metamaterial absorber could not only break though the conventional concept that the number of layers should be increased to extend the bandwidth but also provide a powerful solution to realize a low-profile, lightweight, and low cost electromagnetic absorber.

The scalable and controllable preparation of carbon nanomaterial-based scaffolds with superior electromagnetic interference (EMI) shielding properties in addition to being ultrathin, robust, lightweight, flexible, and foldable is a challenging task. However, commonly used techniques such as integrating conducting moieties and hightemperature annealing cannot simultaneously meet the demands of high specific shielding effectiveness (SSE), robustness, and flexibility. Here, we adopted a novel PDA reduction technique to integrate various functionalities, including a nitrogen doping source, extended reduction of GO, and a large accessible area to accommodate multiwall carbon nanotubes (MWCNTs). The prepared ultrathin PDA-rGO/CNT composite sheet exhibited a low density (0.26 g/cm3), high flexibility, and superior shielding effectiveness (SE) under a wide range of microwave frequencies (i.e., the X band and Ku band). The total shielding effectiveness (SET) reached 47.6 dB and 48.7 dB in the X band and Ku band, respectively, at a thickness of 82 mu m and a high SSE; in particular, the SE/density reached a maximum value of 183.3 and 187.3 dB cm3/g, respectively, which are superior to those of previously reported studies. This comprehensive study revealed the synergistic effect of PDA doping and MWCNTs, resulting in excellent shielding properties. Hence, this superior SSE and flexibility makes ultrathin lightweight PDA-rGO/ CNT composite sheets a suitable candidate for replacing metallic counterparts for foldable and wearable electronic components.

The cost-effective spray coated composite was successfully synthesis and characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and X-ray diffraction techniques. The one step synthetic strategy was used for the synthesis of nanoplates that have a crystalline nature. The composites are amorphous and hydrophobic with micron thickness (<400 μm). The maximum contact angle showed by composite is 132.65° and have wetting energy of −49.32 mN m−1, spreading coefficient −122.12 mN m−1, and work of adhesion 23.48 mN m−1. The minimum thickness of synthesized nanoplate is 3 nm while the maximum sheet resistance, resistivity, and electrical conductivity of the composites are 11.890 ohm sq−1, 0.4399 Ω.cm−1, and 8.967 S.cm−1, respectively. The cobalt nanoplate coated non-woven carbon fabric (CoFC) possesses excellent sheet resistance, hydrophobic nature, and EMI shielding efficiency of 99.99964%. The composite can block above 99.9913% of incident radiation (X band). Hence, the composite can be utilized in application areas such as medical clothes, mobile phones, automobiles, aerospace, and military equipment.

The practical application of 2D MXenes in electronic and energy fields has been hindered by the severe variation in the quality of MXene products depending on the parent MAX phases, manufacturing techniques, and preparation parameters. In particular, their synthesis has been impeded by the lack of studies reporting the synthesis of high-quality parent MAX phases. In addition, controllable and uniform deposition of 2D MXenes on various large-scale substrates is urgently required to use them practically. Herein, a method of pelletizing raw materials could synthesize a stoichiometric Ti3AlC2 MAX phase with high yield and processability, and fewer impurities. The Ti3AlC2 could be exfoliated into 1-2-atom-thick 2D Ti3C2Tx flakes, and their applicability was confirmed by the deposition and additional alignment of the 2D flakes with tunable thickness and electrical properties. Moreover, a practical MXene ink was fabricated with rheological characterization. MXene ink exhibited much better thickness uniformity while retaining excellent electrical performances (e.g., sheet resistance, electromagnetic interference shielding ability) as those of a film produced by vacuum filtration. The direct functional integration of MXenes on various substrates is expected to initiate new and unexpected MXene-based applications.

In this paper, the durability of an electromagnetic metamaterial absorber is verified in a temperature varying condition mimicking a maritime environment for the purpose of applying it to reduce the radar cross section of an integrated mast of the next-generation destroyer. To validate the durability, the reflectance of the electromagnetic metamaterial absorber was measured after storing it in a chamber that can control the temperature according to Procedure I of Method 501.7 included in MIL-STD-810H. Before and after the environmental test, both of the measured reflectances were retained less than -10 dB over the X band, that can guarantee the stealth functionality.

Nanoparticle/graphene hybrid composites have been of great interest in various disciplines due to their unique synergistic physicochemical properties. In this study, we report a facile and generalized synthesis method for preparing nanoparticle/exfoliated graphene (EG) composites by tailored electrostatic interactions. EG was synthesized by an electrochemical method, which produced selectively oxidized graphene sheets at the edges and grain boundaries. These EG sheets were further conjugated with polyethyleneimine to provide positive charges at the edges. The primary organic ligands of the colloidal nanoparticles were exchanged with Cl- or MoS42- anions, generating negatively charged colloidal nanoparticles in polar solvents. By simple electrostatic interactions between the EG and nanoparticles in a solution, nanoparticles were controllably assembled at the edges of the EG. Furthermore, the generality of this process was verified for a wide range of nanoparticles, such as semiconductors, metals, and magnets, on the EG. As a model application, designed composites with size-controlled FeCo nanoparticle/EG were utilized as electromagnetic interference countermeasure materials that showed a size-dependent shift of the frequency ranges on the electromagnetic absorption properties. The current generalized process will offer great potential for the large-scale production of well-designed graphene nanocomposites for electronic and energy applications.

Magnetic metal and graphene hybrids possess the high dielectric properties of graphene and the high magnetic properties of the metal, which render them suitable as electromagnetic (EM) wave-absorbing materials. In this research, we fabricated an EM wave-absorbing film with excellent performance (reflection loss of -68 dB) based on a FeCoNi@graphene hybrid. We developed a new electroless plating method for fabricating magnetic metal@graphene hybrids without any heat treatment, and the new hybrid material showed a higher saturation magnetization (120.4 emu/g) than that of a hybrid material prepared by conventional electroless plating (56.8 emu/g). The sizes, structures, and oxidation ratios of the FeCoNi nanoparticles on graphene were different depending on the synthesis method, and Ni played an important role in the growth of the FeCoNi nanoparticles. The FeCoNi@graphene hybrid was well dispersed in tetrahydrofuran, and thus, could be fabricated into free-standing and flexible composite films by mixing with thermoplastic polyurethane. The high permeability of the FeCoNi@graphene film resulted in a high EM wave-absorbing performance due to impedance matching. These results provide an important advancement toward not only the commercialization of EM wave-absorbing films for healthcare, electronic reliability, and tactical security applications but also the development of magnetic metal and graphene hybrid materials using a scalable process.

We investigated the electroless plating of magnetic metal nanoparticles on graphene to achieve nanoparticles with a tunable size and structure, a degree of exposure of the graphene surface, and magnetic properties of the hybrid material. FeCoNi ternary alloy nanoparticles were grown on the surface of graphene with various ratios of FeCoNi to graphene using two different electroless plating methods. The small size of the FeCoNi nanoparticles synthesized by conventional electroless plating resulted in a large amount of oxide and a low saturation magnetization of the hybrids. In contrast, the FeCoNi nanoparticles synthesized by dropwise electroless plating exhibited a large particle size and a high saturation magnetization. When the ratio of FeCoNi to graphene was increased, the saturation magnetization of both hybrids increased, but the size and structure of the nanoparticles were still different. These results imply that it is possible to synthesize tailored magnetic metal@graphene hybrid materials using an electroless plating method. This work provides guidelines for the preparation of metal nanoparticle@nanocarbon hybrid materials based on an electroless plating method.

We prepared a series of composites consisting of FeCoNi/graphene and paraffin wax with a different weight ratio to tune the electromagnetic (EM) properties. The permittivity, permeability and microwave absorption of the fabricated composites were evaluated, and the effective synergistic effect of the dielectric and magnetic loss mechanism were investigated. The minimum reflective loss (RL) can be tuned to-33.0 dB and 1.74 GHz bandwidth (RL-10 dB) for a thickness of 7mm and to-18.4 dB RL and 2.44 GHz bandwidth for a thickness of 2mm, depending on the amount of FeCoNi/graphene. Moreover, the quantity of FeCoNi/graphene gives selectivity to the absorbers for efficient absorption. Our results demonstrate that the selective tuning of FeCoNi/graphene ratios is a promising candidate for various applications, such as communication devices, high speed processors, information security, electronic countermeasures, electromagnetic absorption and electromagnetic interference shielding.

MXenes, carbon nanotubes, and nanoparticles are attractive candidates for electromagnetic interference (EMI) shielding. The composites were prepared through a filtration technique and spray coating process. The functionalization of non-woven carbon fabric is an attractive strategy. The prepared composite was characterized using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), and Raman spectroscopy. The MXene-oxidized carbon nanotube-sodium dodecyl sulfate composite (MXCS) exhibited 50.5 dB (99.999%), and the whole nanoparticle-based composite blocked 99.99% of the electromagnetic radiation. The functionalization increased the shielding by 15.4%. The composite possessed good thermal stability, and the maximum electric conductivity achieved was 12.5 Scm-1. Thus, the composite shows excellent potential applications towards the areas such as aeronautics, mobile phones, radars, and military.

In order to evaluate the electromagnetic (EM) absorption and shielding effects in near-field and far-field regions, the FeCoNi-coated glass fabric/polycarbonate composite sheets were fabricated. The composite sheets were composed of the laminated structure, which has one or two ply-FeCoNi-coated glass fabrics with or without Ni grid in polymer matrix. The evaluation of EM absorption and shielding behaviors was measured by using a microstrip line and a shielded loop antenna, which is based on IEC62333 in near field and rectangular waveguide at the X-band region in the far-field region. The power absorptions were up to about 86% at 10 GHz. The inter-decoupling effect for FeCoNi-coated glass fabric with Ni grid in composite exhibited about 45 dB at around 1.3 GHz, which is comparable to that of a conductive Cu foil. The shielding effectiveness was obtained over 70 dB at the X-band region for FeCoNi-coated glass fabric with Ni grid composite sheets.

To evaluate the electromagnetic (EM) absorption and shield of magnetic composite sheet, we prepared the FeCoNi coated glass fibers filled in composite sheet. The FeCoNi was coated by electroless plating on glass fiber as a filler. The coated FeCoNi found that consist of mixtures of bcc and fcc phase. The magnetization and coercivity of coated FeCoNi are about 110 emu/g and 57 Oe, respectively. The permittivity and permeability of the FeCoNi composite sheet were about 21 and 1, respectively. Power absorption increased 95% with the increment of frequency up to 10 GHz. Inter-decoupling of this composite sheet showed maximum 30 dB at around 5.3 GHz, which is comparable to that of a conductive Cu foil. Shielding effectiveness (SE) was measured by using rectangular waveguide method. SE of composite obtained about 37 dB at X-band frequency region. (C) 2016 Elsevier B.V. All rights reserved.