Shielding Effectiveness Value Research Articles

BST@Copper Nanowire/Epoxy composites with excellent microwave absorption in the X-band

In this work, hybrid epoxy nanocomposites containing varying loading of copper nanowires (CuNW), Ba0.7Sr0.3TiO3 (BST), and BST@CuNW hybrid nanoparticles were prepared and analyzed for their microwave absorption characteristics. The nanoparticles used in this study were prepared using a facile co-precipitation and hydrothermal methodology. The synthesized nanoparticles were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD) for their morphology and phase determination. While the XRD results confirmed the presence of BST and CuNW, the SEM micrographs obtained on the hybrid BST@CuNW nanoparticles show BST anchored on the CuNW surfaces. A series of epoxy composites containing varying loading of synthesized nanoparticles were prepared and characterized for their microwave properties, such as complex permittivity, shielding effectiveness, and power coefficients. The results indicate that nanocomposites containing BST@CuNW hybrids exhibited enhanced dielectric loss and more significant microwave power absorption compared to samples with equivalent CuNW and/or BST loading. The best composite sample, i.e., a one-millimeter-thick epoxy containing 10:15 (wt/wt) CuNW: BST hybrid nanoparticles with an estimated density of 1.49 g/cc attenuated 99.1 % of incident microwave power and exhibited a shielding effectiveness value of 21.2 dB in the X-band (8–12 GHz) of the microwave frequency spectrum. These lightweight polymer composites with high microwave absorption in the X-band are useful for military and civilian applications.

In-situ microfibrilization of liquid metal droplets in polymer matrix for enhancing electromagnetic interference shielding and thermal conductivity

Herein, liquid metal microfibers (LMM) were constructed in poly (ε-caprolactone) (PCL) matrix and PCL/carbon nanotubes (CNT) composites via an in-situ microfibrilization of liquid metal (LM) droplets by a layer-by-layer stacking method. The aspect ratios of LMMs in the composites can be easily adjusted by controlling the number layers. The effect of LMM aspect ratios on electromagnetic interference (EMI) shielding effectiveness (SE) and thermal conductivity is discussed. The results show that the EMI SE value and the thermal conductivity increase with increasing aspect ratios of LMMs. In addition, the EMI shielding mechanism of PCL/LMM and PCL/LMM/CNT composites is evaluated comprehensively through the combination of electromagnetic simulation and experimental investigation. The efficiently conductive network can be formed in the composites with LMMs, which enhance EMI SE and thermal conductivity. Furthermore, the electric field distribution on the LMM surface is uneven, which enhances the polarization loss ability to electromagnetic waves.

Tailored eutectic alloy coating for enhanced EMI and X-ray protection by basalt fiber CNT/epoxy composite

In this study, eutectic-Bi–Sn-coated basalt fiber (BF)-reinforced carbon nanotube (CNT)/epoxy hybrid composites were fabricated for dual functionality, i.e., in managing and shielding clinical X-ray radiation and electromagnetic interference (EMI). BF mats were coated with Bi–Sn nanoparticles and subsequently layered with multi-walled CNTs mixed epoxy resin using the vacuum-assisted resin transfer method. High resolution field emission scanning electron microscopy revealed a good dispersion of Bi–Sn nanoparticles over BF and, CNTs within the epoxy matrix. X-ray diffraction analysis confirmed the presence of Bi–Sn, basalt, and CNT phases in the composites. High-resolution Raman spectroscopy revealed characteristic peaks corresponding to the CNTs, epoxy, and Bi–Sn phases. EMI total shielding effectiveness (SET) analysis in the X-band frequency range (8.2–12.4 GHz) demonstrated that the Bi–Sn/BF/CNT/epoxy (S3) exhibits the highest SET value of 30.4 dB, which is attributable to the synergistic effect of the Bi–Sn coating and CNT filler. Analysis of X-ray-radiation leakage revealed that all the composite samples effectively attenuated X-rays with minimal leakage, limited to 6.8 mR. These results indicate the potential of these composites for applications as eco-friendly, non-toxic, and lead-free various industries including healthcare, electronics, aerospace, and defense.

Multifunctional polyimide/boron nitride nanosheet/Ti3C2Tx MXene composite film with three-dimensional conductive network for integrated thermal conductive, electromagnetic interference shielding, and Joule heating performances

With the demand for further miniaturization and higher frequency operation of electronic devices, polymer films with high thermal conductivity and electromagnetic interference (EMI) shielding effectiveness (SE) are urgently required. Herein, polyimide (PI)/boron nitride nanosheets (BNNS) aerogels with oriented porous structure are fabricated by unidirectional-freezing and freeze-drying methods. Subsequently, hierarchical PI/BNNS/Ti3C2Tx composite films with consecutively electrically and thermally conductive networks are successfully prepared via a unidirectional PI/BNNS aerogels-assisted immersion and hot-pressing strategy. Owing to the three-dimensional conductive dual networks of BNNS and Ti3C2Tx, the composite film exhibits excellent thermal conductivity with the maximum in-plane value of 4.73 W/(m·K), increased by 456 % compared to pure PI film. Moreover, the conductive network of Ti3C2Tx is conducive to the excellent EMI shielding performance, endowing the PI/BNNS/Ti3C2Tx composite film with an outstanding EMI SE value of 49.2 dB at 8.2 GHz with a low MXene content of 6 wt% and thickness of 300 μm. Furthermore, the composite film shows the superior Joule heating performance with fast thermal response and sufficient reliability. Therefore, the resulting composite film exhibits excellent thermal conductive, EMI shielding and Joule heating performance, which enables the potential application of multifunctional composites for thermal management and EMI shielding.

Lightweight carbon foam composites embedded with RGO/SrFe12O19 hybrid: Fabrication, structural and electromagnetic shielding performance in 8.2 to 12.4 GHz

Today's growth of wireless technology has increased the demand for composite materials with absorption-based shielding capabilities and the composites of dielectric and magnetic materials are suitable for producing high shielding effectiveness (SE). The present study establishes a facile way to synthesize carbon foam embedded with strontium ferrite (SrFe12O19) nanoparticles decorated within/ on reduced graphene oxide (RGO) sheets. In this work, polyurathene templete slab is dipped in the homogenous slurry prepared from RGO/SrFe12O19 (RS) hybrid and phenolic resin followed by carbonization to produce the CF/RGO/SrFe12O19 (CRS) composite foam. The synthesized CRS3 nanocomposite foam exhibits maximum shielding effectiveness due to an absorption (SEA) value of 26.6 dB i.e., ∼99.7% attenuation, and absolute specific shielding effectiveness (SSEt) value of 250.70 dBcm2g–1. The high SEA value of synthesized composite carbon foam is obtained because of the synergistic effect of porous morphology, dielectric losses and magnetic losses.

Effects of surface modification on mechanical properties and electromagnetic interference shielding properties of carbon fiber/silk fiber hybrid composites

AbstractIn this paper, a hybrid approach was employed by integrating a high‐modulus, high‐tensile‐strength carbon fiber fabric (CFF) with a low‐density, high‐toughness silk nonwoven fabric (SNWF) to fabricate CFF‐SNWF reinforced epoxy (CFF‐SNWF/EP) hybrid composites. Through the surface freeze‐induced self‐assembly process, the multiscale hybrid modified layers were successfully constructed on the surfaces of both CFF and SNWF. This novel approach effectively enhanced the interfacial strength of the hybrid fibers (HFs). Comparing the performance of the modified composites with unmodified CFF reinforced epoxy (CFF/EP), significant improvements in both tensile strength and interlaminar shear strength were observed. Specifically, the tensile strength and interlaminar shear strength of the modified composites reached 626.7 and 39.16 MPa, a rise scope of 17.1% and 14.8%, respectively. In addition, the hybrid fibers reinforced polymers (HFRPs) exhibited a superior electromagnetic interference (EMI) shielding capabilities. For insistence, the modified CFF/EP with a thickness of 2.0 mm showed an impressive EMI shielding effectiveness value of 50 dB. These findings underscore the promising application potential of CFF‐SNWF/EP hybrid composites, particularly in the field of consumer electronics.Highlights The surface of hybrid fiber was modified by PDA‐GO‐OCNTs‐WPU. Multi‐scale structure contributes a lot in composite performance. Hybrid effect before and after interfacial modification is performed. The hybrid interface modification and hybrid structure were analyzed.

Synergistic magnetic/dielectric loss and layered structural design of Ni@carbon fiber/Ag@graphene fiber/polydimethylsiloxane composite for high-absorption EMI shielding

Simultaneously achieving excellent shielding effectiveness (SE) and high absorption rate of flexible electromagnetic interference (EMI) shielding materials has become a growing demand for the new generation of highly integrated electronic devices. This study constructed a double-layer polydimethylsiloxane (PDMS) EMI shielding composite film, with the upper layer using Ni-plated carbon fiber (Ni@CF) as the high absorption loss part and the lower layer using Ag-plated graphene fiber (Ag@GF) as the reflection attenuation part. Due to the synergistic magnetic/dielectric loss effect in the upper layer, high electrical conductivity in the lower layer, and the shielding mechanism of “absorption-reflection-reabsorption” induced by the double-layer structure, this composite film achieves efficient EMI shielding performance and high absorption characteristics in the X-band. The EMI SE values of the 2 mm thick film containing 0.03 wt% Ni@CF and 1.2 wt% Ag@GF reach 33.7 dB, while shielding effectiveness of reflection (SER) and absorption (SEA) is 0.8 dB and 32.9 dB, respectively. This result means that the composite film only reflects 17.2 % of the microwaves while shielding 99.9 % and absorbs nearly 82.7 %, exhibiting a significant absorption-dominated shielding mechanism. This flexible and efficient shielding film with a high absorption rate suits portable and wearable intelligent electronic products to reduce secondary electromagnetic pollution.

Investigation of electromagnetic shielding effectiveness of nano silver coated stainless steels

This paper presents the shielding effectiveness (SE) of various nanosilver-coated stainless steels (201, 304, 316 and 430), using a coaxial transmission line setup with waveguides and a vector network analyzer (VNA) in accordance with ASTM 4935 standards. The conducted experiments revealed excellent SE outcomes, indicating that the silver-coated stainless steel samples exhibited notably superior SE performance compared to their uncoated counterparts. The importance of SE in electromagnetic compatibility (EMC) applications, particularly in minimizing electromagnetic interference (EMI) and safeguarding sensitive electronic devices, is well acknowledged. This study further explored the shielding effectiveness of a novel hybrid material, nano silver (Ag) coated different stainless steels, with a focus on its potential for improved EMI shielding capabilities. Experimental measurements were conducted in the 5G frequency domain.It was found that nanosilver coating increased the SE of stainless steels by between 5 and 12 dB. This enhancement attributed to the incorporation of nanostructured silver particles on the stainless steel surface, which facilitates enhanced reflection of electromagnetic waves, resulting in superior shielding performance. Moreover, this study underlying the mechanisms of SE through various analyses, including X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). In summary, this research has demonstrated that nano silver coating increases the SE value of materials. This result suggests that all other materials can be used to increase the SE value. The results have implications for advancing electromagnetic shielding technologies and promoting the development of robust EMI shielding solutions in various industrial applications where effective shielding is of paramount importance.

Lightweight HfC nanowire-carbon fiber/graphene aerogel composites for high-efficiency electromagnetic interference shielding

Electromagnetic interference (EMI) and pollution triggered by electromagnetic waves are becoming a severe issue with the rapid development of various e-devices. Developing low-density and high-efficiency electromagnetic shielding materials is of great importance. Carbon aerogel materials have received worldwide attention due to their significant electromagnetic interference shielding properties and physicochemical stability. Herein, lightweight hafnium carbide nanowire (HfCnw)-carbon fiber (CF)/graphene aerogel (GA) composites with excellent electromagnetic shielding performance were fabricated by successively introducing CF via hydrothermal process, pyrolytic carbon (PyC) coating via chemical vapor infiltration (CVI), and HfCnw via catalytic chemical vapor deposition (CCVD) into GA. It was found that the electrical conductivity of the HfCnw-CF/GA composites with the HfCnw growth time of 4 h reached 94.0 S/cm, which was far higher than 1.1 S/cm of pristine GA and 2.7 S/cm of the CF/GA composites. The EMI shielding effectiveness (SE) of the HfCnw-CF/GA composites was as high as 66.4 dB in the X-band, which was 3 times that (25.4 dB) for GA and 1.5 times that (45.8 dB) for the CF/GA composites. The EMI shielding performance of the HfCnw-CF/GA composites was improved mainly due to the enhanced multiple reflection loss, conductance loss, and interfacial polarization loss. Moreover, the HfCnw-CF/GA composites had a specific SE (SSE) value of 364.1 dB cm3/g, which exhibits good application prospects in the EMI field to meet the needs for light weight and high SE.

Carbon felt from acrylic dust bags as flexible EMI shielding layer and resistive heater

Carbon felt is widely used due to its lightweight and conductive nature. However, limited research has been conducted regarding the tension applied during its preparation. This study aims to explore the influence of different loading tensions during the carbonization process on the properties of acrylic-based carbon felts. Enhanced flexibility, lower shrinkage and improved mechanical and electrical properties were found for the samples obtained in the edge loading mode. Subsequently, the performance of carbon felts in electromagnetic interference (EMI) shielding and resistive heating was studied. The carbon felts achieved a notable EMI shielding effectiveness of 55 dB. The specific shielding effectiveness values are significantly higher than other reported materials due to their low density and high porosity. Moreover, the carbon felts displayed commendable electrical heating performance through high heating rates and superior heating efficiency. Lastly, the structural stability was assessed via self-designed bending experiments. Good stability of the resistance and heating behavior of the carbon felts across multiple bending cycles was observed. With low manufacturing costs, good stability and air permeability, the flexible carbon felt is expected to be widely used for barrier applications and wearable electronics.

Optimization of CoFe2O4 nanoparticles and graphite fillers to endow thermoplastic polyurethane nanocomposites with superior electromagnetic interference shielding performance.

The rapid growth, integration, and miniaturization of electronics have raised significant concerns about how to handle issues with electromagnetic interference (EMI), which has increased demand for the creation of EMI shielding materials. In order to effectively shield against electromagnetic interference (EMI), this study developed a variety of thermoplastic polyurethane (TPU)-based nanocomposites in conjunction with CoFe2O4 nanoparticles and graphite. The filler percentage and nanocomposite thickness were tuned and optimized. The designed GF15-TPU nanocomposite, which has a 5 mm thickness, 15 weight percent cobalt ferrite nanoparticles, and 35 weight percent graphite, showed the highest total EMI shielding effectiveness value of 41.5 dB in the 8.2-12.4 GHz frequency range, or 99.993% shielding efficiency, out of all the prepared polymer nanocomposites. According to experimental findings, the nanocomposite's dipole polarization, interfacial polarization, conduction loss, eddy current loss, natural resonance, exchange resonance, multiple scattering, and high attenuation significantly contribute to improving its electromagnetic interference shielding properties. The created TPU-based nanocomposites containing graphite and CoFe2O4 nanoparticles have the potential to be used in communication systems, defense, spacecraft, and aircraft as EMI shielding materials.

Thermoplastic polyurethane foams derived from cellulose nanofibril/carbon nanotube/(Fe/C) aerogels for efficient electromagnetic interference shielding

The electromagnetic interference (EMI) shielding performance of a material can be enhanced by combining carbon and magnetic components to make the material simultaneously conductive and magnetic. In this work, a series of cellulose nanofibril (CNF)/carbon nanotube (CNT)/(Fe/C)/thermoplastic polyurethane (TPU) foams are fabricated by preforming CNF/CNT/(Fe/C) aerogels followed by combing TPU to improve the mechanical property, where Fe/C is derived from Prussian blue (PB, Fe4[Fe(CN)6]3) after pyrolysis. Consequently, the obtained aerogels and foams display electrical conductivity and magnetism. The CNF/CNT/(Fe/C)/TPU foam reaches a high EMI shielding effectiveness value of 42.2 dB at a thickness of 2 mm when the mass ratio of PB and CNT is 5:1 and the pyrolysis temperature is 650 ℃. Furthermore, the CNF/CNT/(Fe/C)/TPU foam exhibits compression resilience and hydrophobicity. This study is expected to provide a feasible strategy to acquire absorption-dominated EMI shielding materials by imparting conductivity, magnetism and porous structures to the material.

Comparative Effects of Hydrazine and Thermal Reduction Methods on Electromagnetic Interference Shielding Characteristics in Foamed Titanium Carbonitride MXene Films.

The urgent need for the development of micro-thin shields against electromagnetic interference (EMI) has sparked interest in MXene materials owing to their metallic electrical conductivity and ease of film processing. Meanwhile, postprocessing treatments can potentially exert profound impacts on their shielding effectiveness (SE). This work comprehensively compares two reduction methods, hydrazine versus thermal, to fabricate foamed titanium carbonitride (Ti3CNTx) MXene films for efficient EMI shielding. Upon treatment of ≈ 100µm-thick MXene films, gaseous transformations of oxygen-containing surface groups induce highly porous structures (up to ≈ 74.0% porosity). The controlled application of hydrazine and heat allows precise regulation of the reduction processes, enabling tailored control over the morphology, thickness, chemistry, and electrical properties of the MXene films. Accordingly, the EMI SE values are theoretically and experimentally determined. The treated MXene films exhibit significantly enhanced SE values compared to the pristine MXene film (≈ 52.2dB), with ≈ 38% and ≈ 83% maximum improvements for the hydrazine and heat-treated samples, respectively. Particularly, heat treatment is more effective in terms of this enhancement such that an SE of 118.4dB is achieved at 14.3GHz, unprecedented for synthetic materials. Overall, the findings of this work hold significant practical implications for advancing high-performance, non-metallic EMI shielding materials.

Insitu assembly of Fe3O4@FeNi3 spherical mesoporous nanoparticles embedded on 2D reduced graphene oxide (RGO) layers as protective barrier for EMI pollution

Electromagnetic interference (EMI) is a major issue due to the increased use of electronic devices operating in the gigahertz frequency range. Consequently, to reduce electromagnetic pollution, materials with considerable magnetic and dielectric loss can be used for the attenuation of electromagnetic waves. In this paper, Fe3O4 FeNi3 spherical mesoporous nanoparticles embedded on reduced graphene oxide (RGO) layers have been synthesized using the hydrothermal reduction method. The specific surface area of Fe3O4@FeNi3/RGO nanocomposite was 67.4 m2/g with a pore size diameter of 3.4 nm (i.e., mesoporous range). Fe3O4@FeNi3/RGO nanocomposites show an enhanced absorption dominant shielding effectiveness (SE) value of 46.49 dB as compared to its binary counterpart Fe3O4@FeNi3, having SE value of 25.21 dB. The synthesized Fe3O4@FeNi3/RGO nanocomposite of thickness 1.42 mm has SER of ∼10.32 dB and SEA of ∼36.15 dB at 15 GHz. Furthermore, it is observed that shielding efficiency increases with increasing reduced graphene oxide (RGO) content in Fe3O4@FeNi3, which is owing to an excellent interconnected network between RGO and Fe3O4@FeNi3. The RGO sheets can create a comprehensive conductive network for the distribution of charges and can enhance dielectric loss because of the layered structure, greater specific surface area and large aspect ratio. Additionally, the mesoporous Fe3O4@FeNi3 hybrid embellished on the surface of RGO may be employed as a multi-pole polarisation centre, enhancing the electronic and space charge polarization of the composites, which is helpful for strong EM wave absorption. It was believed that these nanocomposites would pave the way for the development of RGO-based mesoporous nanocomposites as broadband, lightweight and effective shielding material for practical applications.

Electromagnetic Shielding Effectiveness and Impact Test Performance of Carbon Fiber Reinforced Polymer Composites with Hematite and Goethite

AbstractCarbon fibers (CFs) are versatile materials widely employed in carbon fiber‐reinforced polymer (CFRP) composites, known for their superior mechanical properties and electromagnetic interference (EMI) shielding capabilities. This study focuses on the successful production of 2‐layer CFRP composites reinforced with hematite (Fe2O3) particles, in two different sizes (≈44 µm (325 mesh) and 50 nm), and goethite (FeO(OH)), utilizing the hand lay‐up method. The investigation encompasses EMI shielding effectiveness (SE) within a frequency range of 700 to 6000 MHz, and the drop‐impact strength resistance properties (under a 6 J load). Results indicate that the highest EMI SE value, 60.19 dB at 5900 MHz, is achieved with 5 wt.% goethite reinforcements, while with a reduction in drop‐impact strength. For hematite‐reinforced composites, the highest EMI SE, measuring 57.85 dB at 5800 MHz, is observed for samples containing 15 wt.% hematite particles with a size of 50 nm, which exhibited an overall improvement in impact strength compared to non‐reinforced samples. This research highlights the potential of these CFRP composites for EMI shielding applications, with considerations for their impact on mechanical properties, providing valuable insights for applications demanding both EMI protection and structural integrity.

Porous polypyrrole Nanotube-Based Organohydrogels: Versatile materials for robust electromagnetic interference shielding in harsh environments

Wearable and multi-functional electromagnetic interference (EMI) shielding materials are an inevitable trend in order to cope with increasingly complex practical applications. In the present work, polypyrrole nanotube (PNT)-based organohydrogels (POGs) with excellent electromagnetic shielding effectiveness (SE) were synthesized through a facile sol–gel strategy. The obtained POGs offer distinct shielding performance, anti-drying, anti-freezing, plasticity and recyclable ability. The POG with a 20 wt% PNTs filling exhibits a SET of 63.6 dB in the X-band at a thickness of 2.0 mm. After being placed at ambient temperature for 30 days and − 40 ℃ for 4 h, its SE values still retained at 50.3 dB and 59.3 dB, respectively. Moreover, after being immersed in the solvents, the POG (left in the air for 30 days) can recover flexibility and 92 % of its original EMI shielding performance. Importantly, crushing the fully dried organohydrogels into the powder and placing it again in the solvents fully restores its flexibility and EMI shielding properties. The glorious shielding and mechanical characteristics can be ascribed to the superior conductivity of PNTs and the highly crosslinked stable network of PVA, as well as the further enhancement of the crosslinked network by cellulose nanofibers. In addition, ​sensors based on POGs can effectively detect human movement and strain deformations. This work thus provides fresh insight into exploring the sustainability of flexible and wearable EMI shielding materials for handling extreme environments.

The Impact of Structural Variations and Coating Techniques on the Microwave Properties of Woven Fabrics Coated with PEDOT:PSS Composition

Minimizing the impact of electromagnetic radiation (EMR) holds paramount importance in safeguarding individuals who frequently utilize electrical and electronic devices. Electrically conductive textiles, which possess specialized EMR shielding features, present a promising solution to mitigate the risks related to EMR. Furthermore, these textile-based shielding materials could find application as radar-absorbing materials in stealth technology, emphasizing the need for substantial absorption capabilities in shielding mechanisms. In this study, various textile-based materials with an electrically conductive coating that contain the conjugated polymer system poly(3,4-ethylene-dioxythiophene)-polystyrene sulfonate (PEDOT:PSS) were prepared and investigated. The influence of the textile substrate structural parameters, coating deposit, and coating method on their microwave properties—transmission, reflection, and absorption—was investigated. Reflection and transmission measurements were conducted within a frequency range of 2 to 18 GHz. These measurements revealed that, for the tested samples, the shielding properties are determined by the combined effect of reflection and absorption. However, the role of these two parameters varies across the tested frequency range. It was defined that for fabrics coated on one side, better reflection reduction is obtained when the shielding effectiveness (SE) is below |20| dB. It was found that by controlling the coating deposition on the fabric, it is possible to fine-tune the electrical properties to a certain extent, thereby influencing the microwave properties of the coated fabrics. The studies of prepared samples have shown that reflection and transmission parameters depend not only on the type and quantity of conductive paste applied to the fabric but also on the fabric’s construction parameters and the coating technique used. It was found that the denser the substrate used for coating, the more conductive paste solidifies on the surface, forming a thicker coat on the top. For conductive fabrics with the same substrate to achieve a particular SE value using the knife-over-roll coating technology, the required coating deposit amount is considerably lower as compared with the deposit necessary in the case of screen printing: for the knife-over-roll-coated sample to reach SE 15 dB, the required deposit is approximately 14 g/m2; meanwhile, for a sample coated via screen printing, this amount rises to 23 g/m2.

Growth mechanism of Ni on the graphite particles regulated by the OH− ionic concentration

In this work, nickel–coated graphite (C@Ni) particles with varying morphologies of Ni were prepared by electroless plating under different OH− ionic concentrations. The microstructure of resultant particles was characterized by XRD, SEM, EDS and TEM. At the OH− ionic concentration of 0.75 M, tiny thorn–like Ni particles with a length of approximately 150 nm grew on the graphite after the electroless plating. Flocculent Ni whiskers decorated with thorn–like crystals of about 50 nm in diameter were fabricated as the OH− ionic concentration was increased to 1 M. When the OH− ionic concentration was further raised to 1.5 M, the synthesized Ni whiskers consisted of the stacking quasi–spherical Ni nanoparticles in the diameter around 25 nm. Combined with the first–principles calculation, it is found that OH− ions tend to absorb on the Ni (111) plane and form the ions barrier layer against the deposition of Ni atoms. With the increasing of OH− ionic concentration, the barrier layer became denser and exhibited higher resistance toward the deposition of Ni atoms on to the Ni (111) plane. And this promoted more Ni atoms to deposit on the Ni (220) and (200) planes with lower deposition resistance, leading to the reduction of gap in the growth rate among the low–index crystal planes. The change in stacking behavior of Ni crystal also induced the variation in the electromagnetic shielding and microwave absorbing properties of C@Ni particles. The C@Ni particles with flocculent Ni whiskers exhibited desirable electromagnetic shielding and microwave absorbing properties, and the corresponding average values of electromagnetic shielding effectiveness and absorption loss were about 37 dB and 25.9 dB in the frequency range of 1 to 18 GHz, respectively.

Shielding Effectiveness of Unmanned Aerial Vehicle Electronics with Graphene-Based Absorber

Within this study, we explored the augmented security measures for the electronics of unmanned aerial vehicles (UAVs) within an RF environment. UAVs are commonly utilised across various sectors, and their use as auxiliary platforms for cellular networks, as parallel networks working in tandem with ground-based base stations, holds considerable promise. In this context, ensuring the uninterrupted operation of UAVs is a paramount objective. However, the considerable external electromagnetic interference emitted by existing base stations may jeopardise the functionality of UAV electronics. This could potentially lead to an unintended flight path and a sudden cessation of communication with the operator. To mitigate the detrimental impact of the RF field, we advocate covering the UAV casing with reduced graphene oxide (RGO). The efficacy of RGO’s shielding effectiveness (SE) was investigated over a frequency spectrum from 100 MHz to 10 GHz. Our scrutiny of this property was centred around the measurement of scattering matrix coefficients of the unadulterated material—without additives of any kind. Our findings show that this material is a favourable candidate for UAV absorbers due to its low reflection coefficient coupled with its high absorption capacity. The studied absorber ensures an SE value of 25 dB and 30 dB for a 3 mm layer at frequencies of 3.6 GHz (pertaining to the 5G system) and 5.8 GHz (pertaining to LTE), respectively.

Realizing balanced flame retardancy and electromagnetic interference shielding in hierarchical elastomer nanocomposites

The combination of electromagnetic interference (EMI) shielding performance and flame-retardant property is essential for applications in the field of electronics and electrics. To date, there have been few successful cases in achieving such portfolios, due to the different mechanisms and even mutual exclusivity of these two attributes. Herein, an ammonium polyphosphate@chitosan@carbon nanotube (APP@CS@MWCNT) core-multishell hybrid was synthesized by microencapsulation technology. Then, the hybrid was introduced into TPU matrix to fabricate TPU composites, acting as surface layer. Meanwhile, MXene film was used as intermediate layer to construct hierarchical TPU composites. The obtained results showed that after introduction of 1 wt% APP@CS@MWCNT hybrid, the peak of heat release rate (PHRR) and the peak of smoke produce rate (PSPR) of TPU composites decreased by 67.4% and 35.6%, respectively, compared with those of pure TPU. Owing to multiple reflection losses, interface polarization losses, and charge carrier movement-induced thermal dissipation, TPU/15AC@4M−SW exhibited the highest EMI shielding performance, and obtained shielding effectiveness values of 35.7 dB and 38.9 dB in X band and K band, respectively.