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Enhanced electromagnetic wave absorption through the unique hollow double shell structure and the synergistic effect of dielectric loss magnetic and loss. [Display omitted] • CoS 2 coated with metal-doped carbon was prepared by a soft template method and wet impregnation method. • The double-layer hollow shell structure is retained after the modification of metal nanoparticles. • Metal doping optimizes the electromagnetic wave loss mechanism of the material. • The RL min is −48.90 dB at 2.23 mm, and the maximum Effective Absorption Bandwidth is 5.04 GHz at 1.98 mm. Tunable designs of polymorphic structured transition metal dichalcogenide (TMDC) demonstrate promising applications in the field of electromagnetic wave absorption (EMW). However, it remains a technical challenge for achieving a balanced relationship between well-matched impedance characteristics and dielectric losses. Therefore, the co-modification strategies of polydopamine coating and wet impregnation are chosen to construct CoS 2 magnetic double-shell microspheres with phase component modulation to achieve the optimized performance. Dopamine hydrochloride forms a coating on the surface of CoS 2 microspheres by self-polymerization and forms a double-shell structure during the pyrolysis process. Then the different metal is doped to generate heterogeneous components in the process of heat treatment. The results show that the cobalt doped double-shell microspheres have an ultra-high electromagnetic wave absorption absorption capacity with an effective absorption bandwidth of 5.04 GHz (1.98 mm) and a minimum reflection loss value of −48.90 dB. The double-shell layer structure and metal ion hybridization can improve the interfacial polarization and magnetic loss behavior, which provides an explicit inspiration for the development of transition metal dichalcogenide and even transition metal compounds with tunable absorption properties. [ABSTRACT FROM AUTHOR]

Multiple reflection and scattering along with dielectric loss and magnetic loss are contributed to excellent electromagnetic wave absorption performance. [Display omitted] • CoFe alloys and ZnO are uniformly distributed on the two-dimensional porous carbon sheet. • The synergistic effect of multiple loss mechanism were contributed to excellent performance. • The absorption was up to −40.63 dB at 2.2 mm and widest EAB of 5.68 GHz at 2.4 mm. To obtain lightweight and efficient electromagnetic wave absorbing materials, Fe 2 O 3 @ZnCo-MOF composites were prepared in this paper by in-situ growth method, and CoFe alloys@ZnO@C composites were obtained by subsequent annealing process. By varying the loading of Fe 2 O 3 during the synthesis process, a series of composites were obtained. Among them, CoFe alloys@ZnO@C-0.1 has the best electromagnetic wave absorption performance, which can reach a reflection loss (RL) of −40.63 dB at a thickness of 2.2 mm, while the reflection loss is −44.13 dB at a thickness of 5.0 mm, and the maximum effective absorption bandwidth (EAB) is 5.84 GHz at a thickness of 2.4 mm. The excellent performance can be attributed to the synergistic effect of the dielectric and magnetic properties of the composites as well as the effective impedance matching properties. Thus, the CoFe alloys@ZnO@C composite is expected to be a lightweight and efficient material for electromagnetic wave absorption. [ABSTRACT FROM AUTHOR]

Multiple loss mechanisms involving multiple scattering and reflection, conductive loss, interface polarization, dipolar polarization as well as magnetic loss caused by exchange resonance, natural resonance and eddy current loss contribute to effective electromagnetic wave absorption behavior. • rGO/N-C/FeNi hybrids were synthesized via an environmentally friendly process. • Nitrogen was doped in the carbon matrix through exploiting pyrrole. • The hierarchical structure provides absorbers with favorable EM properties. A unique reduced graphene oxide (rGO)/nitrogen doped carbon (N-C)/FeNi hybrid was successfully synthesized via a green and environmentally friendly process by means of one pot method. The morphology, phase structure, composition and electromagnetic (EM) wave absorption behavior of all hybrids were studied in detail. All rGO/N-C/FeNi hybrids are composed of rGO sheets on which there are nitrogen doped carbon and FeNi nanoparticles, and the novel structure endows the absorber with multiple scattering and reflection, interfacial polarization, dipole polarization and so on, further bringing remarkable EM wave absorption behavior. Moreover, the complex permittivity of rGO/N-C/FeNi hybrids is able to be controlled through changing the amount of GO. All results show that the rGO/N-C/FeNi-3 hybrid displays a substantial improvement in EM wave absorption performance compared with other hybrids. The minimum reflection loss (RL min) value is −68.87 dB at 12.08 GHz with the thickness of 2.5 mm and the largest effective absorption bandwidth (EAB) achieves 6.88 GHz at 2.2 mm with RL min value of −14.73 dB at 12.16 GHz. Our research proves that the unique structure and composition have the potential to elevate EM wave absorption performance. [ABSTRACT FROM AUTHOR]

Multiple loss mechanisms of conductive loss, interface polarization loss, dipolar polarization and magnetic resonance loss endow excellent performance of Fe 3 N@C composites. • Fe 3 N@C hybrid composites were synthesized by using amino acids as nitrogen sources. • The relaxation times were calculated by Debye theory to investigate dielectric behavior of hybrid composites. • The optimal performance with RL min of −77.6 dB and EAB max of 7.76 GHz were achieved. Fe 3 N has been considered as a new generation of ideal ferromagnetic materials with the virtues of high saturated magnetization and high resistance to oxidation. However, a facile and eco-friendly fabrication of Fe 3 N still needs to be investigated. Herein, the gelatin derived from fish skin was chosen as the raw material of carbon and the amino acid inherent in fish skin can act as a nitrogen source for the generation of Fe 3 N. Besides, the influence of graphitization degree to dielectric behavior of composites was further investigated. In this work, the composites fabricated by 0.8 mmol Fe(NO 3) 3 exhibited optimal absorption performance with the minimum reflection loss of −77.6 dB at 2.2 mm. Besides, the absorption bandwidth was detected as 7.76 GHz (covering from 10.24 to 18 GHz) at the matching thickness of 2.7 mm. According to the analysis of dielectric constant, the degree of graphitization affects the dielectric behavior mainly in determining the orientation speed of the dipole and the conductive loss. This work provides a new thought for the investigation of the electromagnetic absorption mechanism of composite. [ABSTRACT FROM AUTHOR]

Multiple interface polarization along with conductive loss, dipolar polarization and magnetic loss are contributed to excellent electromagnetic wave absorption performance. • NiCo alloy nanospheres and CoNiO 2 nanoflowers were successfully embedded on the porous carbon skeleton. • The outstanding reflection loss was up to −74.3 dB in 3.8 mm and widest effective absorption was 6.32 GHz in 2.4 mm. • The synergistic effect of magnetic loss and dielectric loss are contributed to excellent absorbing performance. A series of NiCo/CoNiO 2 @C hybrid composites were successfully prepared by a hydrothermal method and subsequent heat-treatment process. Porous carbon was synthesized through a fabric carbonization process derived from fish skin. The micro-morphology and minor component of NiCo/CoNiO 2 @C hybrid composites could be tuned by controlling the adjunction amount of Co2+ and Ni2+. The NiCo/CoNiO 2 @C hybrid composite exhibited strong electromagnetic wave absorption performance when the adjunction amount of Co2+ and Ni2+ was 0.4 mmol and 0.2 mmol. The optimal reflection loss could up to −74.3 dB at the matching thickness of 3.8 mm, while the corresponding widest effective absorption bandwidth (reflection loss values lower than −10 dB) is up to 6.32 GHz covering from 11.78 GHz to 18.0 GHz at the matching thickness of 2.4 mm. Based on the Maxwell-Garnet theory, the pore size of porous carbon materials could influence the dielectric constant which has a great effect on impedance. Previous work has illustrated that porous carbon carbonized at 650 °C processes the proper pore size for excellent impedance matching. Besides, NiCo alloy nanosphere and CoNiO 2 nanoflower would provide magnetic loss and interface polarization for attenuating electromagnetic wave energy. Moreover, the conductive loss derived from porous carbon and dipolar loss which originated from the defects are also beneficial to decay electromagnetic energy. This work indicates that the as-prepared NiCo/CoNiO 2 @C hybrid composites accompanied with excellent electromagnetic wave absorption performance could act as a promising absorber to deal with the increasingly serious electromagnetic pollution. [ABSTRACT FROM AUTHOR]

[Display omitted] • 3D MXene-supported magnetic carbon nanotube composites are prepared. • Composite materials combine the advantages of dielectric and magnetic losses. • NiCo/TiC/TiO/CNTs exhibit the RL min of −51.98 dB (1.9 mm) and the EAB of 7.76 GHz (2.1 mm). • Detailed revelation of possible EMW absorption mechanisms. The widespread use of communication equipment has exacerbated the deterioration of the electromagnetic environment, urgently requiring the development of more efficient electromagnetic wave (EMW) absorption materials. Two-dimensional metal carbides are highly regarded for their characteristic structure and excellent electrical conductivity. Here, to break the single way of designing Ti 3 C 2 T x MXene composites and to compensate for their lack of magnetic loss capability, an attempt was made to prepare composites with magnetic NiCo/Carbon nanotubes (CNTs) modification to achieve EMW absorption. Such CNTs-encapsulated Ni and Co metal particles anchored in the matrix, coupled with a multilayer laminate structure, enable the composite to have enhanced EMW absorption. Remarkably, the NiCo/TiC/TiO/CNTs composites exhibit excellent EMW absorption performance at a filling level of only 14.2 wt%. The minimum reflection loss (RL) of −51.98 dB and the maximum effective absorption bandwidth of 7.76 GHz were obtained at thicknesses of 1.9 mm and 2.1 mm, respectively. In addition to this, the possible mechanisms involved in EMW absorption have been elucidated in detail. These results demonstrate an environmentally friendly and simple strategy for the preparation of EMW absorbers based on Ti 3 C 2 T x MXene substrate. [ABSTRACT FROM AUTHOR]

[Display omitted] • Self-assembly of flower-like MoS 2 encapsulated with CuFe 2 O 4 nanoparticles was achieved. • The synergy between components can receive outstanding impedance matching. • The reflection loss (RL) of − 40.33 dB at 2.3 mm and an effective absorption bandwidth (EAB) of 8.16 GHz can be achieved. Transition metal sulfides (TMDs) are considered to be high-performance electromagnetic absorbing materials on account of their small band gap and excellent dielectric properties. As a typical TMDs, two-dimensional MoS 2 nanosheet, has attracted extensive research. However, single absorption mechanism has no longer satisfy the pursuit for novel absorbers. Herein, we introduce magnetic ferrite CuFe 2 O 4 to construct novel absorber of CuFe 2 O 4 /MoS 2 composite. The CuFe 2 O 4 particles are encased in the 2D MoS 2 nanosheets, forming a unique flower-like structure. Under the cooperative interaction of dielectric and magnetic loss, the CuFe 2 O 4 /MoS 2 composite absorber realizes a wide effective absorption bandwidth (EAB) of 8.16 GHz (9.84 GHz −18 GHz) at 2.3 mm, when the optimum reflection loss is −40.33 dB, it means that electromagnetic waves in the entire Ku-band and part of the X-band can be effectively absorbed by the absorber. Moreover, an optimum reflection loss of −49.43 at 2.7 mm can be achieved. In brief, this work presents a strategy for obtaining novel high-performance absorbers. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesized flower-like NiCo-LDH and Ti 3 C 2 T x MXene flakes. • Synthesized NiCo-LDH/MXene hybrids with heterojunction surface. • The optimal absorption was up to −64.24 dB at 2.18 mm and EAB to 4.48 GHz at 2.00 mm. In this research, a flower-like nickel/cobalt layered double hydroxide (NiCo-LDH) was synthesized and mixed with flaky MXene to obtain a series of NiCo-LDH/MXene hybrids. The NiCo-LDH/MXene hybrids with excellent electromagnetic wave (EMW) absorption performance were obtained by adjusting the load of MXene in the mixture. For a NiCo-LDH/MXene hybrid, its excellent EMW performance comes from the synergistic effect of dielectric loss and magnetic loss as well as the excellent attenuation ability and impedance matching characteristics of the material. The results showed that only with a thickness of 2.18 mm at 12.0 GHz, a minimum reflection loss (RL min) of −64.24 dB was obtained when the MXene content is 75 wt%. For the same sample, a maximum effective absorption bandwidth (EAB, RL <−10 dB) of 4.48 GHz (11.04 ~15.52 GHz) was obtained only with a thickness of 2.00 mm. This research proved the effect of the structure and composition of EMW absorber on its performance, and developed ideas for the design and development of high-performance EMW absorption materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • The 2D MXene-based accordion-like hybrid structure was obtained. • Controlling the addition of Ti 3 C 2 T x can effectively control the dielectric parameters. • The effective bandwidth is up to 4.24 GHz with a matched thickness of 1.5 mm. Owing to their unique structure and high dielectric loss, two-dimensional transition metal carbides and nitrides (MXenes) are widely used in electromagnetic wave absorption. The novel Co 9 S 8 /C/Ti 3 C 2 T x hybrid material with a multilayer structure was successfully fabricated by hydrothermal and annealing processes. The unique multilayered hybrid material is assembled from Ti 3 C 2 T x film layers, Co 9 S 8 particles, and carbon flakes. The Co 9 S 8 particles were uniformly anchored on Ti 3 C 2 T x and carbon flakes. The Co 9 S 8 /C/Ti 3 C 2 T x -100 hybrid material has demonstrated impressive electromagnetic absorption performance after the multi-component introduction and interface design were optimized. Besides, the hybrid material exhibits the maximum reflection loss of −50.07 dB at 7.6 GHz under a matched thickness of 2.51 mm, and the effective absorption bandwidth (RL ≤ -10 dB) is covered 4.24 GHz. The synergistic effect of dielectric and magnetic loss, interfacial polarization, and multilayer structure was beneficial to the improvement of electromagnetic wave absorption performance. This research provides a simple demonstration of the design and synthesis of high-performance MXenes-based absorbing materials. [ABSTRACT FROM AUTHOR]

Reasonable nanostructure design and composition are conducive to the electromagnetic wave (EM) absorption behavior of absorbers. Herein, Fe 3 O 4 @C/reduced graphene oxide (rGO) nanocomposites with layered structure were fabricated by a feasible solvothermal method. By adjusting the amount of graphene oxide (GO), different dielectric characteristics and impedance matching conditions of Fe 3 O 4 @C/rGO nanocomposites could be obtained. Moreover, with amorphous carbon as the matching layer, Fe 3 O 4 and rGO provide strong magnetic loss and dielectric loss, respectively. The results exhibit that Fe 3 O 4 @C/rGO nanocomposites own salient EM absorption properties under the combined action of various components and three-level layered structure. In addition, the Fe 3 O 4 @C/rGO-20 nanocomposites (the addition of GO is 20 mg) are endowed with the best EM absorption performance, which demonstrates a minimum reflection loss (RL min) value of −59.23 dB at 6.24 GHz with a sample thickness of 3.57 mm and effective absorption bandwidth (EAB) is 6.72 GHz. Moreover, the widest EAB is 8.24 GHz at a thinner thickness of 2.6 mm with the RL value of −25.80 dB at 14 GHz. This work could be a reference for lightweight, broadband, strong absorption composite absorber. Image 1 • The Fe 3 O 4 @C/rGO composites were synthesized via a simple solvothermal method. • By introducing carbon as a matching layer and rGO as a carrier to preparing efficient electromagnetic wave absorbers. • The minimum RL value is -59.23 dB with the thickness of 3.57mm and the effective absorption bandwidth is 6.72 GHz. [ABSTRACT FROM AUTHOR]

Conversional electromagnetic shielding material with strong reflection coefficient are becoming insufficient for today's application, since the serious 2nd electromagnetic pollution. Herein, we demonstrate a magnetic carbon based shielding material constructed by magnetic Fe nanoparticles (NPs) and N dotted amorphous carbon nanosphere (~200 nm). The structure, morphology, chemical composition of the samples have been studied in depth. It is observed that the average sizes of Fe NPs is ~8.0 nm and can be loaded well on the surface of N dotted amorphous spheres. The electromagnetic shielding performance has been investigated. Significantly, the as-prepared samples show excellent electromagnetic shielding performance. The maximum shielding effectiveness can up to 30 dB under a thickness of 1.2 mm. More importantly, the reflection coefficient can be reduced to 2.3 dB, presenting excellent absorptiondominate shielding performance. The desirable shielding mechanism with less reflection are attributed to the boosted loss ability and matched impedance matching behavior, which originate from N doping and magnetic component. This work which integrates magnetic component with N dotted amorphous carbon has been demonstrated as a useful strategy for the development of absorption dominate EM shielding material. The magnetic N dotted carbon/Fe sample with tunable component was developed and showed excellent absorption dominate electromagnetic shielding performance. Image 1 • Magnetic component (Fe) nanoparticles can be easily loaded on N dotted carbon. • The as-prepared shows dual magnetic and dielectric loss ability. • The impedance matching ability can be greatly improved. • The optimal sample has an excellent absorption dominate ability with a reduced SE R value of 2.1 dB. • The total shielding effectiveness was ~21 dB under a thickness of 1.2 mm. [ABSTRACT FROM AUTHOR]

The shielding mechanism for conversional electromagnetic shielding material is mainly dependent on the reflection, thus the electromagnetic interference (EMI) or pollution can't be really solved, owing to the 2nd interference or pollution. To overcome this barrier, we developed an absorption dominate EMI shielding material, using low permittivity component (TiO 2 , amorphous carbon and SiO 2) to decorate magnetic carbonyl iron (CIF). Consequently, the impedance matching ability can be greatly improved, simultaneously showing desirable dual magnetic and dielectric loss ability. The varied morphology, crystal phases and EMI shielding performance of resultants have been well studied. It has been confirmed that the reflection coefficient of SiO 2 decorated CIF sample could be reduced from 90 to 56.6%, suggesting the improved EM absorption ability. Meanwhile, it corresponding absorption coefficient could up to 43.3%, which is also much better than TiO 2 or amorphous decorated CIF. The method for the successfully use low-dielectric component to decorate magnetic metal has been demonstrated as a useful strategy for the preparation of achieving absorption dominate EM shielding material. Carbonyl iron decorated by the component with low dielectric exhibits excellent absorption dominate electromagnetic shielding performance. Image 1 • Low-dielectric component (SiO 2 , C and TiO 2) can be easily coated on carbonyl iron. • The as-prepared shows dual magnetic and dielectric loss ability. • The impedance matching ability can be greatly improved. • The optimal sample has an excellent absorption dominate ability with a absorption coefficient of 43.3%. • The total shielding effectiveness was ~29 dB under a thickness of 1.5 mm. [ABSTRACT FROM AUTHOR]