Severe Electromagnetic Interference Research Articles

Investigation of Electromagnetic Wave Absorption Properties of Ni-Co and MWCNT Nanocomposites.

In recent years, severe electromagnetic interference among electronic devices has been caused by the unprecedented growth of communication systems. Therefore, microwave absorbing materials are required to relieve these problems by absorbing the unwanted microwave. In the design of microwave absorbers, magnetic nanomaterials have to be used as fine particles dispersed in an insulating matrix. Besides the intrinsic properties of these materials, the structure and morphology are also crucial to the microwave absorption performance of the composite. In this study, Ni-Co-MWCNT composites were synthesized, and the changes in electric permittivity, magnetic permeability, and reflectance loss of the samples were evaluated at frequencies of 2 to 18 GHz. Nickel-Cobalt-Multi Wall Carbon Nanotubes (MWCNT) composites were successfully synthesized by the co-precipitation chemical method. The structural, morphological, and magnetic properties of the samples were characterized and investigated by X-ray diffractometer (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Vibrating Sample Magnetometer (VSM), and Vector Network Analyzer (VNA). The results revealed that the Ni-Co-MWCNT composite has the highest electromagnetic wave absorption rate with a reflectance loss of -70.22 dB at a frequency of 10.12 GHz with a thickness of 1.8 mm. The adequate absorption bandwidth (RL <-10 dB) was 6.9 GHz at the high-frequency region, exhibiting excellent microwave absorbing properties as a good microwave absorber. Based on this study, it can be argued that the Ni-Co-MWCNT composite can be a good candidate for making light absorbers of radar waves at frequencies 2- 18 GHz.

A practicable geophysical resistivity imaging sensing approach for urban geological water disaster detection: A real-world case study

In the urban environment, the transient electromagnetic method often suffers from severe electromagnetic interference because it employs coils to perceive the electromagnetic field. To address this issue, the DC method employs electrodes to shield the electromagnetic noise in the urban environment. In this paper, a new geophysical resistivity imaging sensing approach based on a DC inversion model is proposed to explore and identify the path of underground water to solve the water disaster problem. A real-world case study is carried out in Xinjiang Region. In order to investigate the underground water conducted path, an electrode network is designed and installed for the buildings of interest to collect the DC electrical current and DC electrical potential data. Then, the proposed method establishes a DC resistivity inversion model based on the forward theory and finite-volume technique to extract the geological information from the collected data and visualize the underground water conducted path. Different from existing popular numerical techniques, such as the finite element and finite difference, the finite-volume technique has clear theoretical explanations to make the obtained geological images understandable. As a result, the underground water path can be directly observed from the geological images calculated by the proposed approach to successfully identify and locate the underground water disaster in real-world applications.

Constructing magnetic/dielectric dual loss and phonon/electron thermal carriers γ-Al2O3-based yolk-shell microspheres to collaboratively advance microwave absorption and heat conduction.

The severe electromagnetic (EM) interference and overheating issues in 5G/6G electric devices increasingly heighten the need for developing multifunctional materials with large heat conduction (HC) and high EM wave (EMW) absorption. Here, a series of γ-Al2O3-based yolk-shell microspheres (γ-AlOOH, γ-Al2O3, γ-Al2O3@C, γ-Al2O3@Fe3O4@C, and γ-Al2O3@FeAl2O4@Fe@C YSMSs) as multifunctional fillers are investigated for the simultaneous improvement in the HC and EMW absorption of γ-Al2O3-based composites. Using γ-AlOOH YSMSs as precursors produced from a hydrothermal method, the γ-Al2O3-based YSMSs were synthesized via an annealing route or soaking-annealing route; their phases, textures, and compositions were finely adjusted by changing the Al3+/Fe3+ molar ratio (β) and annealing temperature (Ta). Results show that the thermal transfers in the γ-Al2O3-based YSMSs are promoted by the synergic effect of phonons and electrons when they are utilized as thermally conductive fillers. Comparatively, the γ-Al2O3@FeAl2O4@Fe@C YSMSs formed at β = 8 : 2 and Ta = 700 °C exhibit a high HC of 1.84-3.29 W m-1 K-1 in a loading amount of 5-40%, exceeding those of not merely γ-Al2O3, γ-AlOOH, γ-Al2O3@C, and γ-Al2O3@Fe3O4@C YSMSs but also most previously reported fillers. Furthermore, the γ-Al2O3@Fe3O4@C YSMSs exhibit prominent EMW absorption properties with a large ABW/d of 4.49 GHz mm-1 (just 30% loading), superior to most other Al2O3-based absorbers. Such excellent EMW absorption could be explained by magnetic/dielectric dual loss and significant cavity and interfacial effects caused by yolk-shell structures. In conclusion, this work inspires the development of yolk-shell structures with magnetic/dielectric dual loss and phonon/electron thermal carriers as high-performance bifunctional materials with exceptional heat conduction and EMW absorption.

A Review of EMI Research of High Power Density Motor Drive Systems for Electric Actuator

With the global attention given to energy issues, the electrification of aviation and the development of more electric aircraft (MEA) have become important trends in the modern aviation industry. The electric actuator plays multiple roles in aircraft such as flight control, making it a crucial technology for MEA. Given the limited space available inside an aircraft, the power density of electric actuators has become a critical design factor. However, the pursuit of high power density results in the need for larger rated power and higher switching frequency, which can lead to severe electromagnetic interference (EMI) issues. This, in turn, poses significant challenges to the overall reliability of the electric actuator. This paper provides a comprehensive review of EMI in high power density motor drive systems for electric actuator systems. Firstly, the state of the art of electric actuator systems are surveyed, pointing out the contradictory relationship between high power density and EMI. Subsequently, various EMI modeling approaches of motor control systems are reviewed. Additionally, the main EMI suppression methods are summarized. Active EMI mitigation methods are emphasized in this paper due to their advantages of higher power density compared with passive EMI filters. Finally, the paper concludes by summarizing the EMI research in motor drive systems and offering the prospects of electric actuators.

Intelligent Mesh Cluster Algorithm for Device-Free Localization in Wireless Sensor Networks

Device-free localization (DFL) is a technology designed to determine the positions of targets without the need for them to carry electronic devices. It achieves this by analyzing the shadowing effects of radio links within wireless sensor networks (WSNs). However, obtaining high precision in DFL often results in increased energy consumption, severe electromagnetic interference, and other challenges that impact positioning accuracy. Most DFL schemes for accurate tracking require substantial memory and computing resources, which make them unsuitable for resource-constrained applications. To address these challenges, we propose an intelligent mesh cluster (IMC) algorithm that achieves accurate tracking by adaptively activating a subset of wireless links. This approach not only reduces electromagnetic interference but also saves energy. The IMC algorithm leverages geometric objects, such as meshes and mesh clusters formed by wireless links, to achieve low computational complexity. By scanning a subset of mesh cluster-related wireless links near the DFL target, the algorithm significantly reduces the computational requirements. The target’s location estimate is determined based on the connection information among the mesh clusters. We conducted numerous simulations to evaluate the performance of the IMC algorithm. The results demonstrate that the IMC algorithm outperforms grid-based and particle filter-based DFL methods, confirming its effectiveness in achieving accurate and efficient localization.

Electromagnetic disturbance characteristic of typical high voltage switchgear interruption process in offshore wind farm based on integrated conduction model

AbstractIn an offshore wind farm, a high‐voltage switchgear interruption in an offshore substation creates a high‐frequency, high‐amplitude overvoltage that can cause severe electromagnetic interference problems in the intelligent electronic device. To address this issue, mathematical models, vector fitting and finite element method were used to build an integrated electromagnetic disturbance conduction model, whose accuracy was verified by large current interruption tests. Through the simulation of a typical offshore wind farm's single‐phase grounding fault interruption process, the electromagnetic disturbance characteristics and the impact of the ground position are obtained. The results show that during the fault interruption process of phase B grounded, the dominant frequency of disturbance voltage can reach 4.34 MHz, and the amplitude can reach 1.12 kV. The ground grid has a large impact on the interference voltage, which can reach a maximum value of 2.28 kV under specific conditions. The disturbance voltage in the fault process mainly comes through the current transformer, while during the interruption process, it mainly comes through the ground grid. The authors provide a method to establish the integrated electromagnetic disturbance simulation model, which can improve the accuracy of the electromagnetic disturbance conduction process simulation of intelligent components.

Online long-distance monitoring of subway vibration reduction effect using ultra-weak fiber Bragg grating arrays

Monitoring the subway vibration reduction effect is vital since subway train-induced vibration brings great damage and distress to the buildings and residents along the metro line. To deal with the problems encountered in traditional electrical monitoring methods, such as severe electromagnetic interference and short monitoring distance, we propose an online long-distance vibration monitoring method based on ultra-weak fiber Bragg grating vibration sensing arrays. First, two parallel fiber optic cables are laid separately on the metro line's track bed and tunnel wall for the real-time acquisition of the dynamic response signals of passing trains. Next, the time–frequency and correlation signal characteristics of specific measurement points are extracted and analyzed to show the single-point performance of the sensing arrays. Finally, the subway vibration reduction effect of the entire monitoring area in the metro line is calculated to verify the feasibility of the proposed method.

Hierarchical structures of carbon nanotubes anchored on core-sheath microrads toward electromagnetic wave absorption and shielding with Joule heating and superhydrophobic capacities

Hierarchical structures with synergistic dielectric-magnetic compositions are highly desired for electromagnetic wave absorption and interference shielding applications. Fabricating lightweight and high-performance electromagnetic protection composites with additional functions are demanded to suppress severe electromagnetic radiation and interference pollution. Herein, a unique three-dimensional hierarchical structure consisting of 1D multi-walled carbon nanotubes anchored on 1D MXene@CF core-sheath microrods are rationally proposed via electrostatic self-assembly and hydrothermal strategy as well as subsequent thermal-catalysis treatment. The multi-walled carbon nanotubes encapsulated with magnetic CoNi nanoparticles are immobilized onto core-sheath microrods matrix, constructing effective 1D/1D electron migration bridges and the uniformly dispersed magnetic component to facilitate magnetic coupling effect. Consequently, profiting from the optimized impedance matching, enhanced conduction loss, dielectric polarization, and magnetic loss, the as-prepared sample shows an outstanding absorption capacity with reflection loss value of −56.8 dB and X-band full absorption. When used as electromagnetic shielding materials, the composites exhibit exceptional electromagnetic interference shielding properties. In addition, the upgraded mechanical strength, remarkable voltage-driven Joule heating and superhydrophobic properties endow the absorbers with multi-scenario adaptability and long life-time applications. This work provides well-designed hierarchical structures for high-performance electromagnetic absorbing and shielding with the great prospect of multifunctional applications.

EMSim: A Fast Layout Level Electromagnetic Emanation Simulation Framework for High Accuracy Pre-Silicon Verification

Electromagnetic (EM) emanation measurement and evaluation is one important testing for modern integrated circuits (ICs). Severe electromagnetic interference may degrade the performance of electronic devices or even cause system crashes. As a result, modern ICs need to follow strict electromagnetic compatibility (EMC) requirements. Moreover, EM emanations offer a covert channel for adversaries to steal secret information from fabricated ICs, causing side channel attacks. Due to the lack of fast and high-accuracy EM simulation tools, existing EM measurements often happen at the post-silicon stage. Any identification of side channel vulnerability or EM incompatibility may lead to high cost and delay the time-to-market. As a result, design-time EM simulation tools with fast simulation speed and high accuracy for pre-silicon designs are urgently needed. To this end, we propose EMSIM, a layout-level EM simulation framework that significantly speeds up the EM simulation process while maintaining high accuracy of the simulated EM emanations. To achieve this goal, we provide the theoretical explanation for the root cause of EM emanations from ICs. Guiding by this, EMSIM leverages techniques of parasitic network reduction and device model approximation to reduce the computation complexities while still ensuring high simulation accuracy. EMSIM further leverages Graphics Processing Unit (GPU) resources to solve equations for EM simulation. The efficiency and effectiveness of EMSIM are validated by showing the consistency between simulation results and physical measurements obtained from fabricated circuit designs.

Design of an Effective Antenna for Partial Discharge Detection in Insulation Systems of Inverter-fed Motors

Partial discharge (PD) measurements under repetitive impulse voltages are critical for the qualification of inverter-fed motor insulation systems. Severe electromagnetic interference due to high frequency switching from power electronic devices can cause the traditional PD detection techniques of sinusoidal voltage unfeasible. This article presents the design of an Archimedes spiral antenna that can work effectively for PD detection under fast rise time repetitive impulse voltages. The antenna structure is optimized by a media superstrate with a high dielectric constant over the radiant surface. Through the optimized design, both the gains of the antenna in the 0.5–1.5 GHz frequency range and the signal-to-noise ratio for PD detection are increased substantially. Modeling and experimental results prove that the gain of the antenna can reach 2.5 dB in the frequency range of 500–900 MHz and become higher than 7.0 dB in the frequency range of 900–2.0 GHz, with a voltage standing–wave ratio smaller than 1.4. This seems to be a significant achievement for PD detection under fast rise time impulse voltages.

Polypyrrole hollow tube/polyethylene geotextile composite for multifunctional protection prepared based on the soft template method of methyl orange

Herein, the application of a low-cost, multifunctional polypyrrole hollow tube composite was investigated in the building field. Firstly, polydopamine was made on the surface of a polyethylene geotextile that was the base material. Secondly, the complexes of FeCl3 and methyl orange as soft templates were used in the in situ polymerization method to prepare a multifunctional polypyrrole hollow tube/polyethylene geotextile composite. Polydopamine played a role in improving the adhesion between the polyethylene fibers and polypyrrole hollow tubes. Finally, the electromagnetic shielding, sound absorption, piezoresistive sensing, and electrochemical properties of the composite were tested. The results showed that the shielding effectiveness value of the composite was higher than 32.7 dB in the X-band, which can shield at least 99% of electromagnetic waves. The average sound absorption coefficient value of the composite was 0.36, which was doubled compared with the polyethylene geotextile, and the peak sound absorption coefficient value reached 0.85 at the frequency of 5437 Hz. The composite could respond to deformation in the range of 4.9–99.9 kPa, and the highest sensitivity was 2.01 kPa−1 at a pressure of 14.2 kPa. The composite had an electrochemical response to KOH solutions, and the specific capacitance was 78.78 F/g at a sweep speed of 0.01 V/s. The composite had the advantages of simple preparation, low cost, and a wide range of use, and had broad application prospects in solving the increasingly severe electromagnetic interference, noise pollution, building structure nondestructive monitoring, and energy storage.

Common-mode Electromagnetic Interference Mitigation for Solid-state Transformers

Solid-state transformers (SSTs) have been widely used in many areas owing to their advantages of high-frequency isolation and high power density. However, high-frequency switching causes severe electromagnetic interference (EMI) problems. Particularly, the common-mode (CM) EMI caused by the switching of the dual active bridge (DAB) converter is conducted through the parasitic capacitances in the high-frequency transformer and impacts the system reliability. With the understanding of the CM EMI model in SSTs, CM EMI mitigation methods have been studied. For passive mitigation, the coupled inductor can be integrated with the phase-shift inductor function to reduce CM EMI. For active mitigation, variations in the DAB switching frequency can help reduce the CM EMI peak. An active EMI filter can also be designed to sample and compensate for CM EMI. Using these methods, CM EMI can be reduced in SSTs.

UCB-Based Route and Power Selection Optimization for SDN-Enabled Industrial IoT in Smart Grid

As an essential building block for smart grid, the industrial internet of things (IIoT) plays a significant role in providing powerful sensing capability and ubiquitous connectivity for differentiated power services. The rapid development of smart grid imposes higher data monitoring and transmission requirements in terms of delay and energy efficiency. However, due to the severe electromagnetic interference (EMI) caused by massive electrical equipment, the transmission performance of IIoT becomes inferior. The traditional single-hop transmission mode evolves towards a multihop cooperation mode to satisfy differentiated quality of service (QoS) requirements. In this paper, we propose an upper confidence bound- (UCB-) based joint route and power selection optimization algorithm to support multihop cooperation mode evolution, which adopts a software-defined networking- (SDN-) enabled IIoT network framework to simplify network configuration and management. Compared with existing local-side-information-based route selection (LSI-RS) and random route selection (RRS) algorithms, simulation results demonstrate that the proposed algorithm has superior performances in total delay, energy efficiency, and utility.

HeartMate 3: new challenges in ventricular tachycardia ablation.

To describe clinical characteristics, procedural details, specific challenges, and outcomes in patients with HeartMate3™ (HM3), a left ventricular assist device system with a magnetically levitated pump, undergoing ventricular tachycardia ablation (VTA). Data were collected from patients with an HM3 system who underwent VTA in seven tertiary centres. Data included baseline patient characteristics, procedural data, mortality, and arrhythmia-free survival. The study cohort included 19 patients with cardiomyopathy presenting with ventricular tachycardia (VT) (53% with VT storm). Ventricular tachycardias were induced in 89% of patients and a total of 41 VTs were observed. Severe electromagnetic interference was present on the surface electrocardiogram. Hence, VT localization required analysis of intra-cardiac signals or the use of filter in the 40-20 Hz range. The large house pump HM3 design obscured the cannula inflow and therefore multi imaging modalities were necessary to avoid catheter entrapment in the cannula. A total of 32 VTs were mapped and were successfully ablated (31% to the anterior wall, 38% to the septum and only 9% to the inflow cannula region). Non-inducibility of any VT was reached in 11 patients (58%). Over a follow-up of 429 (interquartile range 101-692) days, 5 (26%) patients underwent a redo VT ablation due to recurrent VTA and 2 (11%) patients died. Ventricular tachycardia ablation in patients with HM3 is feasible and safe when done in the appropriate setup. Long-term arrhythmia-free survival is acceptable but not well predicted by non-inducibility at the end of the procedure.

A review on efficient electromagnetic interference shielding materials by recycling waste-a trio of land to lab to land concept.

The materials used in electrical and electronic applications have great importance and broader applications, but they have severe electromagnetic interference (EMI). These materials have extensive applications in broadcasting, medical industries, research, defence sectors, communication and similar fields. The EMI can be addressed by using effective EMI shielding materials. This review presents a detailed, comprehensive description for making electromagnetic interference shielding material by recycling various wastes. It starts with highlighting the overview of electromagnetic interference shielding (EMI) and its theoretical aspects. It provides a comprehensive and detailed understanding of recent trends in the novel approaches towards fabricating EMI shielding from industrial waste, agricultural waste and other miscellaneous wastes. This paper critically reviews the works related to the recycling of wastes like red mud (waste from the aluminium refining industry), ground tyre rubber, tea waste (biowaste) from tea industries, bagasse (waste from sugar cane industry), peanut and hazelnut shells (agricultural waste), waste tissue paper and polyethylene and other miscellaneous wastes like hydrocarbon carbon black and ash for the fabrication of highly effective electromagnetic (EM) interference shielding materials. Highly effective results have been reported using red mud showing maximum efficiency of 51.4 dB in X-band range, various agricultural waste displaying reflection loss of up to - 87.117 dB (in the range 0.01 to 20 GHz) and miscellaneous waste giving EMI SE of 80 dB in X-band frequency. A separate section is dedicated to emphasizing future work and recommendations.

HeartMate 3- Challenges in Ventricular Tachycardia Ablation

Abstract Funding Acknowledgements Type of funding sources: None. Background HeartMate3TM (HM3) is a relatively new left ventricular assist device (LVAD) system. Its design and magnetically levitated pump may impact VTA. Objectives To describe clinical characteristics, procedural details, specific challenges and outcomes in patients with HM3 referred for ventricular tachycardia ablation (VTA). Methods Data was collected from patients implanted with an HM3 system who underwent VTA in 7 tertiary centers. Data included baseline patient characteristics, procedural data, mortality, and arrhythmia-free survival. Results The study cohort included 19 patients (18 male, aged 65 ± 7.8 years) with low left ventricular ejection fraction (LVEF, 17 ± 5%), presenting with VT (53% with storm VT). VTs were induced in 89% of patients and a total of 41 VTs were observed. Severe electromagnetic interference was present in the surface ECG (Figure A) but not on endocardial electrograms (Figure B). Hence, VT localization required analysis of intra-cardiac signals or the use of filter in the 40-20 Hz range. A total of 32 VTs were mapped and were successfully ablated (31% to the anterior wall, 38% to the septum, and only 9% to the inflow cannula region). Notably, the large pump housing tends to obscure clear visualization of the apical region in fluoroscopy particularly in the LAO view (Figure C,D). Therefore, three-dimensional electro-anatomical mapping was aided by ICE or CARTOSound in 71% cases (Figure E). Non-inducibility of any VT was reached in 11 patients (58%). Over a follow up of 429 (IQR 101-692) days, 5 (26%) patients underwent a redo VT ablation due to recurrent VTA and 2 (11%) patients died. Conclusions VT ablation in patients with HM3 is feasible and safe when done in the appropriate setup. Long-term arrhythmia free survival is acceptable but not well predicted by non-inducibility at the end of the procedure. Abstract Figure. HeartMate3 ablation Challenges

A Fast-Response RBAOT-Controlled Buck Converter With Pseudofixed Switching Frequency and Enhanced Output Accuracy

A ripple-based constant on-time (RBCOT) control scheme is excellent in achieving fast transient response during the load current step. However, it suffers from severe electromagnetic interference (EMI) noise and inherent output voltage offset problem. A monolithic ripple-based adaptive on-time (RBAOT)-controlled buck converter is presented to overcome both drawbacks while retaining the advantage of RBCOT. The on-time is adjusted adaptively by detecting the switching node voltage, and thereby ensuring a pseudofixed switching frequency in a steady state, regardless of the input, output voltage, and load current conditions. A correction voltage generated by a coefficient in a virtual inductor current (VIC) circuit is introduced to counteract the offset voltage and enhance the output accuracy. The proposed scheme is simple to implement and suitable for high-conversion ratio applications. Experimental results show that the switching frequency is centered at 1 MHz with less than 6% variation for an output of 5 V and inputs ranging from 8 to 18 V. The output offset voltage is reduced from 16 to 1 mV for an 18 to 1.05-V conversion. For a load current step of 1 A, the output can be settled within <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$6~\mu \text{s}$ </tex-math></inline-formula> and the undershoot and overshoot voltages are controlled to be within 20 mV.

Physical modeling and design optimization of 4H-SiC insulated gate bipolar transistors for dv/dt reduction

The extremely high dv/dt of 4H-SiC insulated gate bipolar transistor (IGBT) becomes the major concern in its next-generation large-volume power conversion applications because severe electromagnetic interference (EMI) is induced. However, the root reason for its high dv/dt and the method of suppressing EMI have not been extensively investigated yet. In this paper, we proposed a novel physical model for SiC IGBT to identify the major limiting device design parameters of dv/dt during switching transients. The influences of SiC IGBT’s design parameters on its dv/dt and power dissipation are quantitatively analyzed by means of the physical model. Comparisons between the theoretical predictions and technology computer-aided design simulation results validate the physical model. The results on design optimization of a 18 kV n-channel SiC IGBT shows that 80% reduction of dv/dt and 60% reduction in turn-off power dissipation are achieved simultaneously without sacrificing its forward voltage drop.

One-step synthesis and electromagnetic absorption properties of high entropy rare earth hexaborides (HE REB6) and high entropy rare earth hexaborides/borates (HE REB6/HE REBO3) composite powders

Considering the emergence of severe electromagnetic interference problems, it is vital to develop electromagnetic (EM) wave absorbing materials with high dielectric, magnetic loss and optimized impedance matching. However, realizing the synergistic dielectric and magnetic losses in a single phase material is still a challenge. Herein, high entropy (HE) rare earth hexaborides (REB6) powders with coupling of dielectric and magnetic losses were designed and successfully synthesized through a facial one-step boron carbide reduction method, and the effects of high entropy borates intermedia phases on the EM wave absorption properties were investigated. Five HE REB6 ceramics including (Ce0.2Y0.2Sm0.2Er0.2Yb0.2)B6, (Ce0.2Eu0.2Sm0.2Er0.2Yb0.2)B6, (Ce0.2Y0.2Eu0.2Er0.2Yb0.2)B6, (Ce0.2Y0.2Sm0.2 Eu0.2Yb0.2)B6, and (Nd0.2Y0.2Sm0.2Eu0.2 Yb0.2)B6 possess CsCl-type cubic crystal structure, and their theoretical densities range from 4.84 to 5.25 g/cm3. (Ce0.2Y0.2Sm0.2Er0.2 Yb0.2)B6 powders with the average particle size of 1.86 µm were found to possess the best EM wave absorption properties among these hexaborides. The RLmin value of (Ce0.2Y0.2Sm0.2Er0.2Yb0.2)B6 reaches −33.4 dB at 11.5 GHz at thickness of 2 mm; meanwhile, the optimized effective absorption bandwidth (EAB) is 3.9 GHz from 13.6 to 17.5 GHz with a thickness of 1.5 mm. The introduction of HE REBO3 (RE = Ce, Y, Sm, Eu, Er, Yb) as intermediate phase will give rise to the mismatching impedance, which will further lead to the reduction of reflection loss. Intriguingly, the HEREB6/HEREBO3 still possess wide effective absorption bandwidth of 4.1 GHz with the relative low thickness of 1.7 mm. Considering the better stability, low density, and good EM wave absorption properties, HE REB6 ceramics are promising as a new type of EM wave absorbing materials.

Ferrocene decorative phenolic epoxy resin as lightweight thermal-stable dielectric relaxor for electromagnetic wave absorption

Given the severe electromagnetic (EM) energy wasting and radiation interference, it is critically regarded to develop EM absorbing materials. In this work, a new type of lightweight heat-resistant polymer-based dielectric relaxor was manufactured as an efficient electromagnetic absorber by ferrocene (Fc) decorative phenolic epoxy resin (EPN) ferroelectric. A series of resin samples have been obtained as different amount of hydroxyethyl ferrocene (Fc-OH) was taken part in the EPN curing systems with 4,4′-diaminodiphenylmethane (DDM) as curing agent. Finally, the obtained results indicated that the EPN was gradually transformed into a typical relaxor ferroelectric from normal ferroelectric with the increasing amount of Fc decoration. The thermal stability was greatly optimized as the onset temperature of thermal decomposition was increased to 245 °C. It was confirmed that the optimized dielectric properties have strengthened the impedance matching and polarization relaxation behavior, which resulted in excellent EM dissipation. In details, the minimum reflection loss (RLmin) of EPN with 15 wt% Fc decoration reached -30.79 dB with an effective absorption band (fE) of 3.92 GHz at 1.9 mm and the maximum fE was 4.08 GHz at 2.00 mm. It is worth emphasized that the matching thickness was effectively decreased by modification of Fc moieties. Therefore, this research provides an effective path for EM absorption, opening up novel ideas for exploration of lightweight high-performance polymer-based EM absorbers.