(searched for: doi:10.1016/j.jcis.2021.01.013)
Chinese Chemical Letters; doi:10.1016/j.cclet.2021.07.027
Various advanced microwave absorbing materials have been developed for reducing/avoiding the harm of microwave radiation. Among them, core-shell structural nanomaterials have been widely fabricated for microwave absorption. However, the “structure-performance” relationship between shell thickness and microwave absorption performance is rarely reported. In this paper, we first explored the “structure-performance” relationship between shell thickness and microwave absorption performance, based on the core-shell α[email protected] nanoparticles with a constant α-Fe2O3-core size and changeable SiO2-shell thickness. With increasing the SiO2-shell thickness, the microwave absorption ability first increased, then decreased. Under a proper SiO2-shell thickness of 35 nm, α[email protected] sample achieved the strongest microwave absorbing ability with a reflection loss minimum value of –4.3 dB, better than that of pure α-Fe2O3 (–3.8 dB). This enhanced microwave absorption performance was mainly derived from the dielectric loss. Although the absolute value of the reflection loss was relatively low (-4.3 dB), this study shed an important reference on designing next-generation advanced iron oxide-based materials for microwave absorption.
Carbon, Volume 179, pp 566-578; doi:10.1016/j.carbon.2021.04.050
The development of advanced electromagnetic wave (EMW) materials with high reflection loss (RL), wide effective absorption bandwidth (EAB), low filler loading and thin matching thickness is considered as an effective strategy to solve the EMW pollution in emerging areas. Nevertheless, it is still a tremendous challenge to design a reasonable structure and a proper composition to meet the requirements of advanced absorbing materials. Herein, a nanocomposite composed of nitrogen-doped (N-doped) biomass-derived carbon (BDC) and Ni/C nanosphere derived from Ni-MOF ([email protected]/C) has been designed and synthesized. The results show that the continuous conductive network can not only improve the conductive loss, but also provide the prospect for the reflection and scattering of EMW. Also, the petal-like [email protected]/C nanocomposite with a great quantity defects and heterogeneous interfaces delivers multi-polarization. At the same time, the ultra-small Ni nanoparticles and Ni/C nanospheres with good dispersion on carbon materials are beneficial toward dielectric-magnetic combination, resulting in impedance matching. Accordingly, the optimized [email protected]/C nanocomposite exhibits extraordinary microwave absorption performance. Precisely, when the filler loading is 20 wt%, the maximum RL of [email protected]/C reaches −73.8 dB and a corresponding EAB is up to 5.8 GHz with 2.2 mm thickness. This work fills the vacuum in the study of the nanocomposites composed of MOF derivatives and BDC. It provides a reference value for the synthetic strategies in designing high-performance absorbing materials.
Composites Part B: Engineering; doi:10.1016/j.compositesb.2021.109178
Recently, thin, lightweight, wide and strong microwave absorption performance are the main targets for researchers to design high-performance absorbers. A new two-dimension MXene material has attracted significant attention because of its unique hierarchical structure, large specific surface area and special metallic features. However, its improperly high electrical conductivity of MXene causes the bad microwave absorption performance. To meet the needs of practical application, the sandwich-like [email protected]@MXene nanocomposites were fabricated via multilayered MXene and core-shell [email protected] nanoparticles. By the synergistic effects from the SiO2 (transparent medium) improving impedance matching and the two-dimensional laminated MXene increasing conductive loss, the microwave absorption performance of [email protected]@MXene can be effectively regulated and optimized. As a result, the minimum reflection loss of [email protected]@MXene reaches −52.8 dB at 11.6 GHz with a thickness of 2 mm, and the maximum effective absorption bandwidth is 7.2 GHz (10.8–18 GHz) covering the whole Ku-band with only a 1.5 mm thickness. It has proved that microcosmic sandwich-like structure design is an efficient approach to achieving excellent microwave absorption performance. The multiple components and unique structure generate heterogeneous interfaces, multiple reflections, polarization features and well-matched impedance. This work provides an insight for rationally constructing hybrid materials with a complex structure in the application of microwave absorption field.
Composites Science and Technology, Volume 210; doi:10.1016/j.compscitech.2021.108801
The ternary composite material [email protected] with a core-shell structure and excellent electromagnetic absorption properties has been prepared by covalently modifying reducing graphene oxide with the binary magnetic material [email protected] The ternary composite material [email protected]/rGO forms a " CO–NH ″ covalent bond between [email protected] and rGO through hydrothermal routes and mechanical stirring. By comparing the two types of the connection method covalent and non-covalent bonds, it was surprised to find that formed by covalently connecting the binary [email protected] material and rGO (C-ZPr) to obtain extremely excellent electromagnetic absorption performance. By adjusting the thickness from 1 mm to 4 mm, when the filler ratio is 20%, the minimum reflection loss (RLmin) at 2.1 mm was as low as −49.99 dB at 17.28 GHz and the effective absorption bandwidth (RL < 10 dB) was almost 4.32 GHz. The introduction of covalent bonds becomes a bridge connecting magnetic materials and dielectric materials, adjusting electromagnetic parameters, enhancing reflection loss, and achieving impedance matching and improved electromagnetic absorbing performance. This preparation method is expected to provide new ideas for the preparation of high-performance absorbing materials in the future.
Carbon, Volume 178, pp 273-284; doi:10.1016/j.carbon.2021.03.042
Core-shell [email protected](3,4-ethylenedioxythiophene) (PEDOT) microspheres are compounded with reduced graphene oxide (rGO) to prepare [email protected]/rGO composite as an efficient electromagnetic (EM) wave absorber. The microstructure, element composition, morphology and saturation magnetization are characterized, and EM wave absorption properties are analyzed in the frequency range of 2.0–18.0 GHz. The results show that PEDOT is polymerized on the surface of Fe3O4 microspheres, and prepared core-shell microspheres are supported on rGO nanosheets. The reflection loss (RL) of [email protected]/rGO composite is −48.8 dB at 9.12 GHz, and effective absorption bandwidth (EAB) (RL < −10 dB) is 4.32 GHz, when the matching thickness is 2.9 mm. Additionally, when the matching thickness is 2.1 mm, the EAB covers 7.20 GHz. The excellent absorption performance benefits from good impedance matching, attenuation characteristic, synergistic effect of dielectric and magnetic loss, and the absorption mechanism is explained in detail in the article. Furthermore, radar cross section (RCS) analysis is adopted to simulate and calculate EM scattering performance of Al metal plate with absorption coating. The results demonstrate that [email protected]/rGO composite exhibits enhanced absorption performance and can be used as an excellent EM wave absorber.
Published: 26 June 2021
Journal of Materials Science: Materials in Electronics pp 1-18; doi:10.1007/s10854-021-06397-1
Recently, microwave absorbers with strong absorption along with wide absorption band have gained abundant attention due to their low cost, simple fabrication, and sustainability. However, it remains a challenge for pure biomass to achieve this goal without adding other components. Herein, a wheat flour-derived magnetic carbon nanocomposite was prepared and hydrochloric acid was used to fabricate doped PANI on the magnetic porous carbon (MPC), in which PANI was grown on the MPC network. The introduction of NiFe2O4 particles is helpful in balancing permittivity, permeability, and impedance matching. This distinctive PANI structure heightens conductive loss, interfacial polarization, and multiple reflections of the incident EM waves. Overall, the optimal reflection of NiFe2O4/PC/PANI can reach up to -59.3 dB at 2 mm with 20 wt% filler loading and the efficient bandwidth (RL exceeding -10 dB) is as wide as 5.6 GHz (12.4–18 GHz) with a thickness of 1.5 mm. To sum up, this strategy provides a novel scope for the controllable construction of a hierarchical carbon composite and the as-prepared composite possesses a promising potential for exploration of biomass carbon on high-performance microwave absorbers.
Advanced Functional Materials; doi:10.1002/adfm.202103436
Skin effect and high density are the main reasons that restrict the search of lightweight and high-performance metal-based electromagnetic (EM) wave absorbing materials. Although nanostructured metal materials have been fabricated to solve above problems, poor dispersibility and chemical stability issues brought about by high surface energy due to existing nano-size effect. In this work, lightweight Ni foam with NiO/NiFe2O4 in situ growth composites are fabricated by a facile and universal route as an effective alternative to high-performance metal-based EM wave absorber. Impressively, it is found that the foam structure and NiO/NiFe2O4/Ni components can synergistically boost EM wave absorption capacity. In detail, impedance matching from foam structure and energy dissipation from interfacial polarization and defect induced polarization provided by NiO/NiFe2O4 mainly contributes to its ultra-broadband EM wave absorption performance. As a result, the as-prepared sample (0.06 g·cm−3) delivers a wide absorption bandwidth of 14.24 GHz and thin thickness of 0.6 mm, as well as, high specific effective absorption bandwidth of 19444.4 GHz·g−1·cm−2. This work sheds light on the novel view on the synergistic effect of structure and components on EM wave absorption behaviors and demonstrates a new pathway for preparation of lightweight and high-performance metal-based EM wave absorbers.
Nano-Micro Letters, Volume 13, pp 1-15; doi:10.1007/s40820-021-00646-y
Phase engineering is an important strategy to modulate the electronic structure of molybdenum disulfide (MoS2). MoS2-based composites are usually used for the electromagnetic wave (EMW) absorber, but the effect of different phases on the EMW absorbing performance, such as 1T and 2H phase, is still not studied. In this work, micro-1T/2H MoS2 is achieved via a facile one-step hydrothermal route, in which the 1T phase is induced by the intercalation of guest molecules and ions. The EMW absorption mechanism of single MoS2 is revealed by presenting a comparative study between 1T/2H MoS2 and 2H MoS2. As a result, 1T/2H MoS2 with the matrix loading of 15% exhibits excellent microwave absorption property than 2H MoS2. Furthermore, taking the advantage of 1T/2H MoS2, a flexible EMW absorbers that ultrathin 1T/2H MoS2 grown on the carbon fiber also performs outstanding performance only with the matrix loading of 5%. This work offers necessary reference to improve microwave absorption performance by phase engineering and design a new type of flexible electromagnetic wave absorption material to apply for the portable microwave absorption electronic devices.