Lightweight Electromagnetic Interference Research Articles

Flexible conductive polymer composite film with sandwich-like structure for ultra-efficient and high-stability electromagnetic interference shielding

Flexible electromagnetic interference (EMI) shielding films with the merits of light-weight, flexibility, and high EMI shielding performance are the essential materials for the consumer electronics and communication products. Herein, we construct a hybrid conductive network based on the electrospinning thermoplastic polyurethane (TPU) film loaded with different dimensional conductive fillers, including 0D FeCl3, 1D carbon nanotube (CNT) and 2D graphene nanosheet (GN), which fabricate a flexible, light-weight, and ultra-efficient EMI shielding composite film. In specific, the electrospinning porous TPU film is firstly anchored by CNTs assisted by ultrasound to generate the porous TPU/CNT film. Thereafter, the as-prepared porous TPU/CNT film is filtered by GN/CNT/FeCl3 solution to generate a double-layer GN/CNT/FeCl3@TPU/CNT film. Finally, another porous TPU/CNT film is sealed onto the GN/CNT/FeCl3@TPU/CNT film by hot-pressing, which fabricates a sandwiched TPU/CNT@GN/CNT/FeCl3@TPU/CNT composite film. It is interesting to note that the composite film possesses the ultrahigh EMI shielding value (56.0 dB at 10.0 GHz) in the X-band (8.2-12.4 GHz) with high flexibility, excellent mechanical properties, long-term durability (acid-base environment resistance and stability after 1000 bends), as well as high thermal conductivity (6.53 W/(m K)). This work proposes a simple but efficiency strategy to design the flexible EMI shielding film with ultra-high performance and outstanding durability.

Structural, morphological, and EMI shielding evaluations of Sm-Mn co-doped Sr-based M-type hexaferrite for Ku band applications

High-performance, thin, and lightweight EMI (Electromagnetic interference) materials with outstanding shielding effectiveness were explored over the last years to solve the problems in electronic devices. Magnetic absorbing materials have extensive bandwidth, good impedance matching, and excellent absorption features. In the present study, Sm-Mn Sr-doped M hexaferrites with Sr1-xSmxFe12-yMnyO19 whereas (x= 0.00, 0.025, 0.05, 0.075, y = 0.00, 0.25, 0.5, 0.75) were prepared by the chemical route. XRD, FESEM, HRTEM, FTIR, VSM, and VNA are used to evaluate the properties of the Sm-Mn doped Sr-based M-type hexagonal ferrite. The XRD (X-ray diffraction) results revealed the presence of a hexagonal phase in the prepared samples. Rietveld refinement also confirmed the phase purity for the Sm-Mn doped Sr-based M-type hexagonal ferrites. The FESEM (Field emission scanning electron microscopy) and HRTEM (High-resolution transmission electron microscopy) images revealed the hexagon-type shapes of the particles in the Sm-Mn doped Sr-based M-type hexagonal ferrites. The FTIR (Fourier transform infrared spectroscopy) spectra showed the 446–620 cm-1 lines, confirming the presence of the tetrahedral and octahedral phases of hexagonal ferrites. Dielectric and electromagnetic shielding effectiveness (SE) parameters are evaluated for Sm-Mn doped Sr-based M-type hexagonal ferrite. The electromagnetic parameters, such as complex refractive index, absorption and impedance, are also investigated for the Sm-Mn doped Sr-based hexagonal ferrite powder with x=0.075, y=0.75 having epoxy resin with 20 wt%, 30 wt% and 50 wt% samples, respectively. SE parameters are higher at more extensive filler loading. The green shielding index was found higher for Sm-Mn doped Sr-based hexagonal ferrite powder with x=0.075, y=0.75 having 20 wt% epoxy resin and decreased with filler loading. It is found the epoxy/Sm-Mn doped Sr-based M-type hexagonal ferrites-based composites are excellent absorbers in the Ku band. The investigated absorbers could be the best candidates for next-generation EMI green shielding absorbing devices and applications.

PMDI cross-linked rare earth/liquid metal reinforced ANF/MXene membranes for multifunctional electromagnetic interference shielding

With the miniaturization of electronic devices, the creation of efficient and lightweight electromagnetic interference (EMI) shielding materials is of imminent significance. In this context, we reported an electromagnetic shielding membrane with hydrophobic, antioxidative, and high temperature stability. The chemically cross-linked Aramid nanofibers (ANF)/MXene@Ga/Gd2O3 (CAMG) nanocomposite membranes exhibit a considerable tensile strength and possess exceptional flexibility. The CAMG shielding membranes demonstrate multiple heterogeneous interfaces and a magnetic-dielectric synergistic system, thereby effectively enhancing the absorption shielding efficiency, with the specific shielding effectiveness per unit volume (SSE/t) reaching 6788 dB cm2 g−1. Furthermore, the composite membranes demonstrate remarkable electrothermal capabilities, acting as pliable heaters with notable, swiftly replicable, and consistent electrothermal effects at reduced voltages. Additionally, they possess superior heat dissipation efficiency and ensure a uniform heat dispersion. The exceptional electromagnetic shielding performance and multifunctionality of the C-ANF/MXene@Ga/Gd2O3 shielding membranes imply their instructive relevance in next-generation fields such as flexible electronics and aerospace.

Three-layered PBAT/CNTs composite foams prepared by supercritical CO2 foaming for electromagnetic interference shielding

Plastic pollution and electromagnetic radiation cause serious environmental problems. Herein, biodegradable poly(butylene adipate-co-terephthalate) (PBAT) and carbon nanotubes (CNTs) composite foams with three-layered structure for electromagnetic interference (EMI) shielding application were prepared by an environmentally friendly supercritical CO2 foaming method. For the CNTs content of 4.9 vol%, the EMI shielding efficiency (SE) of three-layered composite was 23.4 dB, which was improved by 125 % compared with that of single-layered composite with a CNTs content of 4.7 vol% owing to high conductivity in skin layer and multiple reflection between interfaces. The CNTs content in core has little effect on the EMI SE when the CNTs content in skin was 16 wt%. After foaming, SE values slightly decreased due to a decreased volume content of CNTs. However, considering the decreased density of foam, the specific EMI SE was improved by 26.2% after foaming when the CNTs content was 16 wt% in skin and 0 in core. This work provided a facile and green method for preparing lightweight EMI shielding materials.

High green index electromagnetic interference shields with semiconducting Bi2S3 fillers in a PEDOT:PSS matrix.

Conventional metallic electromagnetic interference (EMI) shields, as well as the emerging 2D material-based shields, meet the shielding effectiveness (SE) needs of most applications. However, their shielding performance is dominated by the reflection of incoming radiation due to their high electrical conductivity, which leads to secondary pollution. This problem is getting exacerbated with the proliferation of electronics and communication networks in modern society. Thus, EMI shields that function dominantly by the absorption of incoming radiation are highly desirable. Such shields would be characterized by a green index, which is the ratio of absorbance over reflectance, close to or greater than one. For nonmagnetic materials, the best way to reduce the undesirable large impedance mismatch is to reduce the effective permittivity of the shield material. Here, we present a new EMI shield with a semiconductor Bi2S3 filler in a conducting PEDOT:PSS polymer matrix, instead of the conventional conductive fillers, to reduce the effective permittivity and demonstrate that even a light loading of only 10% Bi2S3 provides high SE of over 40 dB with a green index value of 0.75. Increasing the filler content to 15 wt% increases the green index close to unity while dropping the SE to 30 dB. The shielding mechanism is explained through electromagnetic parameter measurements and supplemented by density functional theory calculations. This work lays the foundation for the advancement of lightweight and ultrathin green EMI shields with minimum secondary pollution.

Self-Assembly TiO2-Ti3C2Tx Ball-Plate Structure for Highly Efficient Electromagnetic Interference Shielding.

MXene is a promising candidate for the next generation of lightweight electromagnetic interference (EMI) materials owing to its low density, excellent conductivity, hydrophilic properties, and adjustable component structure. However, MXene lacks interlayer support and tends to agglomerate, leading to a shorter service life and limiting its development in thin-layer electromagnetic shielding material. In this study, we designed self-assembled TiO2-Ti3C2Tx materials with a ball-plate structure to mitigate agglomeration and obtain a thin-layer and multiple absorption porous materials for high-efficiency EMI shielding. The TiO2-Ti3C2Tx composite with a thickness of 50 μm achieved a shielding efficiency of 72 dB. It was demonstrated that the ball-plate structure generates additional interlayer cavities and internal interface, increasing the propagation path for an electromagnetic wave, which, in turn, raises the capacity of materials to absorb and dissipate the wave. These effects improve the overall EMI shielding performance of MXene and pave the way for the development of the next-generation EMI shielding system.

Stretchable and lightweight 2D MXene-based elastomeric composite foam for suppressing electromagnetic interference

The utilization of lightweight materials that provide electromagnetic interference (EMI) shielding and impact attenuation is crucial for safeguarding fragile components in portable electronic devices. Although conductive foams have shown promise in providing lightweight electromagnetic interference (EMI) shielding, their potential for impact attenuation has yet to be thoroughly investigated. In this study, we fabricated a composite foam consisting of MXene and carboxylated nitrile rubber (MXene/XNBR) to achieve multifunctional properties such as electromagnetic interference (EMI) shielding and thermal management. The fabrication method involved the utilization of MXene nanoflakes and XNBR elastomer through a dual mixing approach, which encompassed both melt and solution mixing techniques. Utilizing a chemical blowing agent in integrating cellular structure inside a composite material has resulted in several advantageous properties, including reduced weight, enhanced processability, and improved thermal management capabilities. The MXene/XNBR foam composite exhibits a higher EMI shielding efficiency (SE) of − 30.9 dB. With a remarkably low density of 0.7 g.cm−3, this material exhibits a specific shielding effectiveness of 441.4 dB.cm2.g−1 with desirable stretchability and mechanical strength, positioning it as one of the most promising options for lightweight applications. Our multifunctional elastomeric foam composites collectively offer a significant pathway for developing high-performance foam material that exhibits exceptional shielding efficiency, thermal management, stretchability, and superior mechanical properties.

Conductivity-Controlled Polyvinylidene Fluoride Nanofiber Stack for Absorption-Dominant Electromagnetic Interference Shielding Materials.

This work presents a novel method for achieving lightweight electromagnetic interference (EMI) shielding materials with high EMI shielding effectiveness (SE) through absorption-dominant mechanisms, utilizing only organic polymer nanofibers (NFs). Instead of incorporating high-density fillers, the approach involves adjusting the concentrations of iron chloride in the NFs and subsequent vapor phase polymerization (VPP) to control the polymerization density of poly(3,4-ethylenedioxythiophene) (PEDOT) on the surface of polyvinylidene fluoride (PVDF) NFs. This process results in NF layers with varying conductivity, creating a conductivity gradient structure. The conductivity gradient structure of the NF layers significantly enhances absorptivity by reducing impedance mismatches between the shielding material and the surrounding air, as well as between different interlayers. This reduction in impedance mismatches allows for efficient dissipation of absorbed electromagnetic (EM) waves within the highly conductive NF layer. This improved absorptivity is also attributed to the attenuation of EM wave energy through multiple reflections and scattering within the NF pores. Moreover, the gradient structure of the NF layers promotes interfacial polarization, further contributing to the effective absorption of electromagnetic waves. As a result, a high absolute EMI SE (SSEt) of 12,390 dB·cm2 g-1 with low reflectivity (0.32) was achieved without compromising the lightweight and flexible properties.

Multi-Amplification-Channel Active EMI Filter Based on Period Spread-Spectrum PWM for Common-Mode EMI Suppression

Due to the existing coupling loop between the motor drive system and the ground, when switching devices in the drive system operate at a high speed, common-mode (CM)-conducted electromagnetic interference (EMI) is generated in the loop. The electromagnetic environment quality of the motor and peripheral equipment is reduced. As a small and lightweight EMI suppression device, the active EMI filter (AEF) can be used in the motor drive system to suppress the CM-conducted EMI. As the unity gain bandwidth of the operational amplifier (OPAMP) in the AEF is fixed, the CM-conducted EMI suppression effect of the AEF is poor. To solve this problem, the multiple-amplification-channel method is used to spread the frequency range of the CM voltage that the AEF can sense; therefore, the frequency of the compensation current output using the AEF is more complete, and a better CM-conducted EMI attenuation effect is obtained. At the same time, a combination of the period frequency carrier modulation (PCFM) and the multi-amplification-channel AEF is adopted so that the CM-conducted EMI in the whole EMI frequency range of the motor drive system is effectively suppressed.

Lightweight and anti-corrosive carbon nanotubes (CNTs)/bamboo fiber/HDPE composite for efficient electromagnetic interference shielding

Electromagnetic pollution causes significant harm to human health and information security. The development of materials for shielding against electromagnetic interference (EMI) is important in reducing electromagnetic pollution. In this study, an eco-friendly, lightweight EMI shielding material was prepared by mechanically mixing carbon nanotubes (CNTs), hydrophobic bamboo fibers, and recycled high-density polyethylene (HDPE), followed by hot-pressing (150 °C, 10 MPa, 30 min) the mixture to obtain CNTs/bamboo fiber/HDPE composites (CNTs-BPC). The CNTs-BPC exhibited satisfactory conductivity (1.1 ×104 S/cm) and EMI shielding effectiveness (49.6 dB, 8.2–12.4 GHz). The uniform dispersion of an appropriate amount of CNTs created a conductive pathway in CNT-BPC, prompting the absorption of incident EM waves. In addition, the CNTs-BPC possessed a high tensile strength (30.5 MPa), thermal stability, and corrosion resistance. The CNTs-BPC composite developed in this study shows excellent overall performance and holds broad application prospects as a high-temperature and corrosion-resistant EMI shielding material.

Graphene and Fe2O3 filled composites for mitigation of electromagnetic pollution and protection of electronic appliances

With extensive advancement and abundant availability of telecommunication and electronic devices, electromagnetic pollution has become a serious concern not only for human health but also for much sensitive electronic equipment which may fail or malfunction due to electromagnetic interference. Therefore, effective and lightweight electromagnetic interference (EMI) shielding structures are of vital importance for human protection as well as for safeguarding sensitive electronic equipment from interference. In this regard, carbon fiber reinforced composite structures (CFRCS) have proven as one of the best options due to their light weight, extraordinary mechanical properties, and excellent durability. This study explored the synergistic incorporation of graphene and ferric oxide nanoparticles in the CFRCS at various loading concentrations to enhance their electromagnetic shielding effectiveness (EMI SE). According to the results, maximum EMI shielding effectiveness of 95.57 dB was attained at a 4% loading concentration of graphene and a 6% loading concentration of ferric oxide, over a broader frequency range of 0.1 GHz–13.6 GHz. In light of these results, different EMI shielding structures can be developed, including EMI shielding rooms for better protection of humans as well as any sensitive electronic equipment from the harmful effect of electromagnetic radiation. The obtained results are outstanding and may be employed commercially for the protection of electronic equipment and human individuals.

Highly flexible, PEDOT:PSS-polyvinylpyrrolidone coated carbon nanofiber-polydimethylsiloxane composite for electromagnetic interference shielding

Lightweight, flexible and portable electronics, and wearable devices are recognized as the next-generation electronic devices. Rapid growth in the usage of such devices will add to electromagnetic interference (EMI) or EM pollution in an alarming magnitude. Hence, lightweight, hydrophobic, and flexible EMI shielding materials capable of effectively reducing EMI are urgently required. The present work reports fabrication of poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) and polyvinylpyrrolidone (PVP) coated, carbonized electrospun polyacrylonitrile (PAN) nanofiber (CNF) and their flexible polydimethylsiloxane (PDMS) composites. The material showed excellent EMI shielding effectiveness of 44 dB in the frequency range of 8–26.5 GHz with a thickness of 0.06 mm due to the synergetic effect of CNF matrix, PEDOT: PSS, and PVP. It also exhibited a high absolute EMI SE of 5678 dB cm2 g−1 with low loading of PEDOT:PSS-PVP. Here, PEDOT:PSS-PVP/CNF shows EMI shielding through an absorption dominated mechanism rather than reflection. These findings indicate the potential of these composites as thin, flexible, hydrophobic, and lightweight EMI shielding materials for practical applications.

Ti3C2Tx MXene/polyimide composites film with excellent mechanical properties and electromagnetic interference shielding properties

With the development of electronic products to miniaturization and high frequency, high-performance flexible electromagnetic interference (EMI) shielding materials are urgently needed to deal with electromagnetic pollution. Two-dimensional transition metal carbide/polyimide (Ti3C2Tx MXene/PI) films were synthesized by in situ polymerization and a simple scratch method in this paper. The Ti3C2Tx MXene nanosheets give the films good EMI shielding effectiveness (SE) and electrical conductivity. Specifically, the film with a thickness of 0.11 mm (Ti3C2Tx content of 30 wt%) exhibits an EMI SE of 34.73 dB and a specific EMI SE (SE/thickness) of 315.73 dB/mm in the frequency range of 8.2–12.4 GHz (X-band). In addition, the films have a tensile strength of 67.58 MPa, and a high decomposition temperature of 510 ℃ in N2 atmosphere. Therefore, we believe that the prepared Ti3C2Tx/PI films with good comprehensive performance have enormous potential in the field of lightweight and flexible EMI shielding materials.

Carbon nanotube films embedded with Cu@C nanocubes for electromagnetic interference shielding

AbstractFlexible carbon tube films for electromagnetic interference (EMI) shielding are assembled by mixing the well‐aligned Cu@C core‐shell nanocubes with multi‐walled carbon nanotubes (MWCNTs). The Cu@C core‐shell nanocubes are achieved by the thermal pyrolysis of polyvinylpyrrolidone (PVP) coating on Cu2O nanocubes. With the optimal PVP concentration of 1.5 mg/mL, the Cu@C/MWCNTs composite film with ultra‐thin thickness (52.2 μm) displays good conductivity of 12.5 S cm−1 and excellent specific EMI shielding value of 510.73 dB mm−1, which is higher than the pure MWCNTs film (439.50 dB mm−1) under the same weight condition. Moreover, the 1.5 mg/mL‐Cu@C/MWCNTs composite film exhibits highly mechanical repeatability after being bended for 10,000 cycles. The carbon layers protecting metal nanoparticles can partly replace precious carbon nanotubes to construction highly flexible composite film with anticipated electrical conductivity, which have a good application prospect for thin, lightweight and flexible EMI shielding fields.

Fabrication of Ni-Encapsulated Carbon Tube/Poly(dimethylsiloxane) Composite Materials for Lightweight and Flexible Electromagnetic Interference Shielding Material.

The exploration of flexible and lightweight electromagnetic interference (EMI) shielding materials with excellent shielding effectiveness, as a means to effectively alleviate electromagnetic pollution, is still a tremendous challenge. This paper proposes a conducting material named the textured Ni-encapsulated carbon tube, which can be applied in EMI shielding material by being inserted in the center of a poly(dimethysiloxane) (PDMS) polymer. We demonstrated that Pd2+ could be absorbed by the active groups on the plant fiber surface to catalyze the reduction of Ni2+ as a catalytic center by means of a textured Ni-encapsulated plant fiber. Owing to the outstanding heat-conducting capability of the Ni coating, the inner plant fiber was carbonized and attached to the Ni-tube inside the surface during annealing. To be precise, the textured Ni-encapsulated C tube was fabricated successfully after annealing at 300 °C. On further increasing the annealing temperature, the C tube disappeared gradually with the Ni coating being oxidized to NiO. Of note, the C tube acted as a support layer for the external Ni coating, providing sufficient mechanical strength. When combined with the coating PDMS layer, a flexible and lightweight EMI shielding material is fabricated successfully. It displays an outstanding EMI shielding effectiveness of 31.34 dB and a higher specific shielding efficiency of 27.5 dB·cm3/g, especially showing excellent mechanical property and flexibility with only 2 mm thickness. This study provides a new method to fabricate outstanding EMI shielding materials.

Lightweight MXene/carbon composite foam with hollow skeleton for air-stable, high-temperature-resistant and compressible electromagnetic interference shielding

Lightweight electromagnetic interference (EMI) shielding materials with temperature resistant and compressible performance are highly desirable for applications in harsh and complex environment. Herein, we report MXene/carbon composite foam with three-dimensional hollow skeleton structure and low MXene loading by self-assembly and low heating rate (1 °C/min) pyrolysis methods. The composite foam exhibits a density of as low as 5 mg cm−3 with only 3 wt% MXene loading. An average EMI shielding effectiveness (SE) of more than 25 dB over the whole X-band (8.2–12.4 GHz) and more than 30 dB covering the Ku-band (12.4–18 GHz) and the K-band (18–26.5 GHz) with 2 mm thickness are achieved. Benefiting from the low density, the corresponding specific EMI SE (SSE/t) is up to 27300 dB cm2 g−1, which is comparable to or even better than the values of many shielding materials. The foams still display excellent EMI shielding performance after exposure to air in ambient atmosphere (temperature: 25 °C, humidity: ∼30%) for a year or being heated to 210 °C, demonstrating an excellent air stability and temperature resistance. Furthermore, the MXene/carbon composite foam maintains the high EMI shielding performance after 1000 compressing-releasing cycles, demonstrating excellent compressibility.

Synthesis and microwave absorption studies on 2D graphitic carbon nitride loaded polyaniline/polyvinyl alcohol nanocomposites

A light weight electromagnetic interference (EMI) shielding and microwave absorbing composite films has been developed by loading varying weight content of graphitic carbon nitride (g-C3N4) nanosheets and polyaniline (PANI) into polyvinyl alcohol (PVA) matrix. The prepared PVA/PANI/g-C3N4 (1%, 3%, 5%) composites has been subjected to FTIR, X-Ray powder diffraction, SEM, Thermal studies, Dielectric studies and electromagnetic shielding effectiveness (EMI SE) analysis. The PVA/PANI/g-C3N4 (1%, 3%, 5%) composites was discovered to have improved electrical conductivity, dielectric loss, and dielectric constant. It is observed from the SEM images that the sheet layers of g-C3N4 are wrapped by the polymer matrix and the morphology to PVA/PANI composite in the g-C3N4 indicates homogeneous blending of PVA/PANI without any phase separation and has porous in it. The PANI/g-C3N4 fractured surfaces present are smooth but irregular in appearance indicating good compatibility between the PVA and PANI matrices. The dielectric properties was found to increase on increasing the concentration of the g-C3N4 nanofiller and reached a maximum of 9.8 × 106 at 1 MHz for 3% g-C3N4 in PVA/PANI. The incorporation of g-C3N4 into PVA/PANI enhanced the conductivity and the 5% g-C3N4 loaded composite film exhibited a conductivity value of 0.043 S/cm at 1 MHz. The PVA/PANI/g-C3N4 (1%, 3%, 5%) composites exhibited potential EMI SE values ranging from 24 to 35 dB at 8.6 GHz and from 42 to 63 dB at 12.4 GHz, for instance the PVA/PANI/g-C3N4 5% composite showed highest value of 63 dB at 12.4 GHz. The PVA/PANI/g-C3N4 5% exhibits the maximum highest reflection loss 8 GHz–12 GHz in which the higher absorption of −36 dB is observed at 10.3 GHz of the X-band region.

Multifunctional graphene/carbon fiber aerogels toward compatible electromagnetic wave absorption and shielding in gigahertz and terahertz bands with optimized radar cross section

Lightweight absorption-dominated electromagnetic interference (EMI) shielding materials with multifunctional integration of multiband absorption, mechanical durability and thermal insulation are urgently required in the practical application of next-generation communication technology combined with flexible electronics. In this work, ultralight and mechanically durable graphene/carbon fiber composite aerogels (CGAs) are synthesized via solvothermal reaction and freeze-drying. The as-prepared CGAs demonstrate excellent compatible electromagnetic wave absorption and shielding performance in both gigahertz (GHz) and terahertz (THz) bands without addition of magnetic component. Specifically, a broad efficient absorption bandwidth of 8.72 GHz at 2–18 GHz and a high mean absorptivity of 97.4% at 0.3–1.5 THz are achieved, respectively. Furthermore, absorbing coatings with CGAs have been proved to contribute to remarkable radar cross section reduction of 39.06 dBm2 by computer-assisted simulation. Additionally, the compressible CGA demonstrates superior and stable EMI shielding performance under in-situ compression. The EMI shielding effectiveness exceeds 35 dB in X-band when a compression ratio of 78.9% is applied. Moreover, CGAs are thermally insulating and self-extinct, making them reliable in practical application. This work provides a series of promising multifunctional lightweight EMI shielding materials for future high-frequency wireless communication.

Effect of Multilayered Structure on the Static and Dynamic Properties of Magnetic Nanospheres.

The development of flexible and lightweight electromagnetic interference (EMI)-shielding materials and microwave absorbers requires precise control and optimization of core–shell constituents within composite materials. Here, a theoretical model is proposed to predict the static and dynamic properties of multilayered core–shell particles comprised of exchange-coupled layers, as in the case of a spherical iron core coupled to an oxide shell across a spacer layer. The theory of exchange resonance in homogeneous spheres is shown to be a limiting special case of this more general theory. Nucleation of magnetization reversal occurs through either quasi-uniform or curling magnetization processes in core–shell particles, where a purely homogeneous magnetization configuration is forbidden by the multilayered morphology. The energy is minimized through mixing of modes for specific interface conditions, leading to many inhomogeneous solutions, which grow as 2n with increasing layers, where n represents the number of magnetic layers. The analytical predictions are confirmed using numerical simulations.

Lightweight and textured Ni@Cu-encapsulated carbon tube with outstanding electromagnetic interference shielding performance

The low-reflection electromagnetic interference (EMI) shielding material is highly desirable, which would facilitate the reduction of the EM-wave secondary pollution, but classic conflict between performance and density makes it very challenging in practical application. Herein, a textured Ni@Cu-encapsulated carbon tube was designed and fabricated as a conducting material inserted into the middle of polydimethylsiloxane (PDMS) polymer and its application in flexible, light-weight and low-reflection EMI shielding material. Results showed that the active groups on the plant fiber surface could absorb Pd2+, acting as catalytic center, which can catalyze electroless nickel plating (EP Ni) on its surface by means of textured Ni-encapsulated plant fiber. The inside plant fiber was carbonized and attached to Ni-tube inside surface after annealing, owning to the outstanding heat-conducting capability of Ni coating. To be precise, textured Ni encapsulated C tube was fabricated successfully after annealing at 300 °C. Interestingly, the surface Ni tube could catalyze the EP Cu on its surface by means of textured Ni@Cu-encapsulated carbon tube structure, endowing the composites with efficient dielectric loss and magnetic loss capacity. Combined with PDMS coating, a flexible, light-weight and low-reflection EMI shielding material is fabricated successfully. More importantly, it displays outstanding EMI shielding effectiveness of 35.4 dB, lower reflection one of 0.9 dB, higher specific one of 28.7 dB cm3/g, superior flexibility and mechanical properties with a thickness of only 2 mm. This work open a new window for fabricating EMI shielding materials with outstanding EMI shielding performance.