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In order to effectively utilize the magnetic-dielectric synergy and interfacial engineering, in this paper, yolk—shell structured magnetic multicomponent nanocomposites (MCNCs) including CoNi@void@C and CoNi@void@C@MoS 2 were produced in large scale by in-situ pyrolysis of cubic CoNi Prussian blue analogs (PBAs) followed by the hydrothermal process, respectively. Because of their unique structures, excellent synergistic effect between dielectric and magnetic loss, the as-prepared CoNi@void@C and CoNi@void@C@MoS 2 MCNCs displayed very outstanding electromagnetic wave absorption performances (EMWAPs) including strong absorption capabilities, broad absorption bandwidth and thin matching thicknesses. Furthermore, the as-prepared CoNi@void@C and CoNi@void@C@MoS 2 MCNCs well maintained the cubic configuration of CoNi PBAs even after the thermal treatment and hydrothermal processes. The unique structure and formed carbon layers effectively prevented the corrosion of internal CoNi alloy during the formation of MoS 2 , and CoNi@void@C@MoS 2 MCNCs with different MoS 2 contents could be synthesized by controlling the hydrothermal temperature. The obtained results revealed that the EM parameters, dielectric and magnetic loss capabilities of CoNi@void@C@MoS 2 MCNCs could be tuned by controlling hydrothermal temperature and filler loading, which made their outstanding EMWAPs could be achieved in different frequency regions. Taking account of simple process, low density and high chemical stability, our findings provided a new and effective pathway to develop the strong wideband microwave absorbers.

To adapt the practical demand, designing and constructing the multifunctional microwave absorbers (MAs) is the key future direction of research and development. However, effective integrating the multiple functions into a single material remains a huge challenge. Herein, cellular carbon foams (CCFs) with different porous structures were elaborately designed and fabricated in high efficiency through a facile continuous freeze-drying and carbonization processes using a sustainable biomass chitosan as the precursor. The obtained results revealed that the thermal treated temperature and g-C 3 N 4 amount played a great impact on the carbonization degrees, pore sizes, and morphologies of CCFs, which led to their tunable electromagnetic (EM) parameters, improved conduction loss, and polarization loss abilities. Owing to the special cellular structure, the designed CCFs samples simultaneously displayed the strong absorption capabilities, broad absorption bandwidths, and thin matching thicknesses. Meanwhile, the as-prepared CCFs exhibited the strong hydrophobicity and good thermal insulation, endowing its attractive functions of self-cleaning and thermal insulation. Therefore, our findings not only presented a facile approach to produce different porous structures of CCFs, but also provided an effective strategy to develop multifunctional high-performance MAs on basis of three-dimensional CCFs.

Rational construction of hierarchical multi-component materials with abundant heterostructure is evolving as a promising strategy to achieve excellent metal-organic frameworks (MOFs) based electromagnetic wave (EMW) absorbers. Herein, hierarchical heterostructure WS 2 /CoS 2 @carbonized cotton fiber (CCF) was fabricated using the ZIF-67 MOFs nanosheets anchored cotton fiber (ZIF-67@CF) as a precursor through the tungsten etching, sulfurization, and carbonization process. Apart from the synergetic effect of dielectric-magnetic dual-loss mechanism, the hierarchical heterostructure and multicomponent of WS 2 /CoS 2 @CCF also display improved impedance matching. Furthermore, numerous W-S-Co bands and heterojunction interfaces of heterogeneous WS 2 /CoS 2 are beneficial to promoting additional interfacial/dipole polarization loss and conductive loss, thereby enhancing the EMW attenuation performance. Based on the percolation theory, a good balance between impedance matching and EMW absorption capacity was achieved for the WS 2 /CoS 2 @CCF/paraffin composite with 20 wt.% filler loading, exhibiting strong EMW absorption capability with a minimum reflection loss (RL min ) value of −51.26 dB at 17.36 GHz with 2 mm thickness and a maximum effective absorption bandwidth (EAB max ) as wide as 6.72 GHz. Our research will provide new guidance for designing high-efficient MOFs derived EMW absorbers.

With the aim to design broadband microwave absorbers with optically transparent, flexible and stable performances in 8–18 GHz, a sandwich structure is designed and fabricated by sandwiching the periodic arrayed ITO film into two transparent and flexible polyvinyl chloride layers. With the induced metamaterial structure to tailor the effective input impedance, the proposed sandwich absorber can realize more than 90% absorption in 8–18 GHz for both TE and TM polarization when the incident angle is less than 30°. Meanwhile, the optical transmittance of the designed absorber reaches more than 80% transmittance with the wavelength larger than 532 nm, and the average optical transmittance for the visible light (400–800 nm) is 80.2%. The proposed absorber shows broadband microwave absorption in both X and Ku band with simultaneously high transmittance in visible frequencies, indicating that the proposed sandwich metamaterial absorber has great potentials for developing optical transparent absorbing devices.

Electromagnetic interference (EMI) is one of the biggest challenges faced during the production of any electronic device. The effect on the performance of the instrument due to these inevitable interferences must be carefully measured to understand and quantify the electromagnetic compatibility (EMC) of the instrument under test. If the EMI profile of the system does not meet the accepted standards, then it becomes necessary to take measures to reduce the influence of these unwanted interferences so that the equipment can be used in the real world. Unfortunately, research and studies on EMI and EMC have not received their due attention from the scientific community. Moreover, the literature available for this area of research is scattered where different sources provide information on one or more (but not all) aspects of EMI/EMC while ignoring the others. With the objective of encompassing this extremely significant area of research in its entirety, this review presents both EMI measurement techniques and EMI reduction techniques in detail. EMI measurement techniques are presented under two sections that deal with emission testing and immunity testing, respectively. Herein, EMI reduction techniques are presented under four sections, where electromagnetic shielding has been given special attention under which various methods used by the scientific community to measure the shielding effectiveness of a material or microwave absorber and its application in EMI reduction are illustrated. This is followed by EMI filters, circuit topology modification and spread spectrum. This review can help students and young scientists in this area to get an idea of the ways to conduct EMI tests as well as the ways that can be employed to reduce the EMI of the system, depending on the application.

In order to extend the performance of radar absorbing materials, it is necessary to design new structures with wideband properties and large angles of incidence which are also as thin as possible. The objective of this work, realized within the framework of the SAFAS project (self-complementary surface with low signature) is, then, the development of an ultra-wideband microwave absorber of low thickness. The design of such material requires a multilayered structure composed with dielectric layers, metasurfaces, and wide-angle impedance matching layers. This solution has been realized with on-the-shelf materials, and measured to validate the concept. At normal incidence, the bandwidth ratio, defined for a magnitude of the reflection coefficient below −10 dB, is 4.7:1 for an absorber with a total thickness of 11.5 mm, which corresponds to λ/7 at the lowest operating frequency. For an incidence of 60°, this bandwidth ratio is reduced to 3.8:1, but the device remains ultra-wideband.

We have proposed an ultra-broadband dielectric-resonator-based microwave absorber with a water substrate. A dielectric resonator, which comprises two stacking cubic cavities and one cross-shaped cavity, was filled with water to provide ultra-broadband microwave absorption. The simulation results show that the absorptivity of the proposed absorber is greater than 90% in the frequency range from 16.52 GHz to the upper microwave frequency band of 100.00 GHz, with the relative absorption bandwidth of 143.3%. Moreover, the absorber is insensitive to wave polarization and has high absorptivity over a wide frequency range under oblique incidences. Thanks to the 3D-printing technology, the proposed microwave absorber can be fabricated precisely and cost-effectively. The experimental results demonstrated that the structure is capable of broadband absorption and wide-incident-angle stability. The proposed design of ultra-broadband absorbers has much potential in the fields of electromagnetic shielding and stealth technology.

Silver (Ag) nanoparticles fabricated by chemical reduction process were grafted onto the surface of carbon nanotubes (CNTs) to prepare hybrid nanocomposites. The Ag/CNT hybrid nanomaterials were characterized using transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. The Ag/CNT hybrid nanomaterials were then loaded in paraffin wax, and pressed into toroidal shape with thickness of 1 mm to evaluate their complex permittivity and complex permeability by scattering parameters measurement method in reflection mode using vector network analyzer. The reflection loss of the samples was calculated according to the transmission line theory using their measured complex permittivity and permeability. The minimum reflection loss of the Ag/CNT hybrid nanocomposite sample with a thickness of 1 mm reached 21.9 dB (over 99 % absorption) at 12.9 GHz, and also exhibited a wide response bandwidth where the frequency bandwidth of the reflection loss of less than −10 dB (over 90 % absorption) was from 11.7 to 14.0 GHz. The Ag/CNT hybrid nanocomposite with thickness of 6 mm showed a minimum reflection loss of ~−32.1 dB (over 99.9 % absorption) at 3.0 GHz and was the best absorber when compared with the other samples of different thickness. The reflection loss shifted to lower frequency as the thickness of the samples increased. The capability to modulate the absorption band of these samples to suit various applications in different frequency bands simply by manipulating their thickness indicates that these hybrid nanocomposites could be a promising microwave absorber.

Chemical stripping adversely affects the quality of cotton fabric due to prolonged exposure to harsh chemicals. High temperatures also affect the surface and tearing characteristics of recycled cotton. Microwave-assisted stripping is a viable approach to addressing these problems, requiring less time, energy, and chemical consumption. Furthermore, utilizing a microwave-absorbing molecule that assisted the heat generation, multiple treatment methods were applied to remove the dye reactive turquoise CLB from cotton fabric. In the reductive process, pretreatment with sodium citrate as a microwave absorber showed 94.8% stripping efficiency, while in the meta-treatment, stripping efficiency was 96.2%. In the conventional stripping procedure, 75.7% stripping efficiency was observed, much lower than microwave absorber stripping with an absorber. Moreover, FTIR analysis of treated and untreated fabrics confirmed the removal of Reactive Turquoise CLB from the cellulosic structure. The quality assurance parameters, weight loss, and tearing strength assure the performance of developed methods by showing higher tearing strength and negligible weight loss compared to conventional methods.

In this paper, an ultra-broadband three-dimensional metamaterial microwave absorber (MMA) is proposed based on a composite structure of a split-ring loaded with resistors and magnetic material. The proposed composite MMA (CMMA) exhibits significantly enhanced bandwidth and absorption performance compared to single magnetic absorbing materials. The physics mechanism of the absorption is analyzed by the distributions of electric field, magnetic field, and power flow and loss density. The features of ultra-broadband and wide-angle absorption were systematically characterized by the angular absorption spectrum for both transverse electric and transverse magnetic waves. A parametric study was also performed to achieve ultra-broadband properties of the proposed CMMA. A tested prototype of the proposed CMMA with 18 × 18 unit cells was fabricated and measured. The final experimental results show that the designed CMMA with total thickness of 7.4 mm exhibits absorptance of over 90% from 3.7 GHz to 18 GHz with a relative bandwidth of about 131.8%, which is in good agreement with simulation results. The proposed CMMA has potential applications in stealth, shielding, and energy harvesting.