Electromagnetic Interference Shielding Performance Research Articles

Fabrication of flexible polyimide/rGO composite foams and their derived carbon foams for thermal insulation and EMI shielding applications

In this work, a facile microwave-assisted foaming and thermal imidization treatment method was proposed to fabricate flexible polyimide (PI)/rGO composite foams with anisotropic pore structures. The PI/rGO composite foams (PIF/rGO) were used as the starting derivatives to prepare carbon foams that demonstrated excellent anisotropic thermal insulation and electromagnetic interference (EMI) shielding applications. The directional growth of pore structures during the foaming period resulted in the formation of aligned ellipsoidal strip-like pore structure in the horizontal direction (i.e., perpendicular to the pore growth direction), which was attributed to the escape of foaming gases such as tetrahydrofuran, methanol and H2O. The homogeneous dispersion of rGO in the PI-derived carbon skeleton endowed corresponding carbon foams with excellent mechanical and thermal stability, high thermal insulation and electrical conductivity (σ) as well as absorption dominated EMI shielding performance. The σ and EMI shielding effectiveness (SE) of carbon foams showed an increasing trend with increasing rGO content. The σ, EMI SE and specific EMI SE of the carbon foams reached up to 33.0 S/m, 49.0 dB and 8792.8 dB/(g/cm2) in the horizontal direction, respectively. Therefore, this work provided a facile strategy to fabricate lightweight and anisotropic pore structure rGO-containing PIFs and carbonized derivatives, which demonstrated promising applications in high-end industrial fields.

Thermally insulating carbon nanotubes and copper ferrite based porous polydimethylsiloxane foams for absorption-dominant electromagnetic interference shielding performance

The exponential growth of the electronic and communication industry in the last 50 years raised serious concerns about electromagnetic (EM) pollution. Consequently, suitable composite materials for electromagnetic interference (EMI) shielding have been developed to reduce EM pollution. In the present work, carbon nanotubes (CNT) and copper ferrite (CuFe2O4) nanoparticle-based porous polydimethylsiloxane (PDMS) composite foams were prepared using the baking soda template method. The PDMS foam acts as the 3-dimensional (3D) porous network, CNT gives the required conductive path and magnetic CuFe2O4 provides the necessary magnetic loss, so that the resultant foams achieved high EMI shielding through the absorption mechanism. Without the inclusion of CuFe2O4, the total EMI SE of the PDMS foam is lower than 20 dB, while various contents of the added CuFe2O4 improve the EMI SE up to 32 dB at a thickness of 3 mm. In addition, the thermal insulation properties are also reported and the resultant material shows a moderately low thermal conductivity of 0.046 W m−1 K−1. These characteristics of the composite foam highlight the strong absorption-dominated EMI shielding and thermal insulation performance, allowing it to successfully meet a wide range of applications.

Graphene Nanoplatelet Exoskeleton on Polyurethane Foam to Produce Flame‐Retardant, Piezoresistive, and Electromagnetic Interference Shielding Surfaces

AbstractPolyurethane foam (PUF)’s porous structure, light weight, flexibility, and low‐cost properties make it useful in various cutting‐edge technologies. However, time‐consuming, costly, and complicated surface modification methods severely hinder its commercial applications. Herein, an ultrafast, simple, and cost‐effective surface modification method based on the evaporation of a low boiling point solvent to prepare a multifunctional graphene nanoplatelet (GNP)‐decorated PUF (GNP@PUF) is proposed. Due to the passive heat barrier of GNP sheets, the resulting sponge exhibits excellent flame retardancy by reducing the critical fire retardancy metrics, that is, peak heat release rate, total heat release, and total smoke release by 72%, 50%, and 81%, respectively. In addition, GNP@PUF can function as a piezoresistive sensor and electromagnetic interference (EMI)‐shielding material. As a piezoresistive sensor, it exhibits a wide‐compressive pressure (2.4–112 kPa)/strain (5–70%) range and ultra‐fast response/relaxation time (48/35 ms), wide‐stretching strain (5–100%) range, and it can detect minute human motions by being attached to different parts of the human body. Meanwhile, the composite foam displays good absorption‐dominant EMI shielding performance (≈38 dB), possibly due to conductive dissipation and multiple reflections/scattering of EM waves inside the 3D conductive graphene network. This study provides a simple coating technique for developing multifunctional lightweight foam materials.

Tuning the electromagnetic interference shielding performance of polypropylene cellular nanocomposites: Role of hybrid nanofillers of MXene and reduced graphene oxide

Electromagnetic interference (EMI) is deemed a disruptive influence on electronically-operated devices and human health, which can cause catastrophic and sometimes irreversible damage. To mitigate such a hindrance, cellular-based polymer nanocomposites, comprising conductive nanofillers, are considered a viable solution and have been shown to exhibit significant potential due to absorption dominancy of EM waves. Herein, we designed both solid and cellular nanocomposite based on polypropylene grafted maleic anhydride (PP-g-MA) comprising various contents of single MXene, as well as hybrid MXene/reduced graphene oxide (MXene/rGO) nanolayers and investigated their EMI shielding performance to systematically assess the influence of hybridization. The influence of including MXene and rGO on microstructure and morphology of PP nanocomposite foams was evaluated, and a correlation between microcellular structure and nanofiller loading was established. Electrical conductivity test showed an increase of conductivity in both types of nanocomposite samples comparing to the pristine PP. A considerable improvement resulted in the EMI shielding effectiveness (EMI SE) of solid hybrid samples at a constant weight percentage of 7 wt% using a 2:1 ratio of MXene to rGO compared to a sample comprising a 1:1 ratio of the nanofillers. When the MXene:rGO content was 10 wt.%, SEA contributed to SET by 83%, while for the cellular nanocomposites, SEA's contribution to SET raised to 92%. Finally, an appropriate improvement occurred in the case of compressive strength of both single- and hybrid-incorporated nanocomposites as a result of robust interactions between the fillers and PP chains. The present study demonstrates that the fabricated hybrid cellular system can act as a successful EMI shielding material, and can stand as a potential candidate for various EMI shielding applications.

Preparation of Porous Silver Nanowires‐Melamine Formaldehyde Hybrid Composite Materials and Their Electromagnetic Shielding and Flame‐Retardant Properties

Along with the booming development of communication technology and electronic equipment, higher requirements of flame‐retardant and EMI shielding performances for electromagnetic interference (EMI) shielding materials are put forward. Herein, the ultralight and porous silver nanowires (AgNWs)‐melamine formaldehyde (MF) hybrid composite with unique micro‐/nanostructure is developed by a facile dip‐coating method, which uses the AgNWs as 1D conductive coating and MF foam (MF foam) as 3D skeleton template. Benefiting from the unique porous micro‐/nanostructure, the resultant hybrid composite displays low density, excellent EMI shielding performances, and superior flame‐retardant property. The EMI shielding effectiveness (SE) and specific EMI SE (SSEt) of the hybrid composite in X‐band (8.2–12.4 GHz) can be up to 77 dB and 26971.4 dB cm−2 g−1, respectively. At the same time, the hybrid composite also passes the vertical burning test and shows an increased LOI value of 40.6%. The combination of flame‐retardant and EMI shielding performances for EMI shielding materials makes the AgNWs‐MF hybrid composite great application potential in civil and military fields. This work provides a new guide for the design of multifunctional high‐performance EMI shielding materials.

Durable cellulose paper by grafting thiol groups and controlling silver deposition for ultrahigh electromagnetic interference shielding

Electromagnetic interference (EMI) shielding paper with durability and high effectiveness is of significant importance to long-term service for preventing EMI pollution. Herein, we report a practical method for preparing cellulose paper/Ag composite with outstanding durable and ultrahigh EMI shielding performance by electroless silver plating. The silver deposition process, the surface morphology, the silver content and conductivity of the composite can be controlled by varying the amount of N-acetyl-L-cysteine (NAC) grafted onto the cellulose fibers and ammonia amount for silver-ammonia complex formation. Moreover, the grafted NAC with thiol groups on cellulose can enhance the adhesion between silver and cellulose paper, meanwhile, NAC as the reducing agent can result in a more complete flower-shaped silver structure and reducing the reflection of electromagnetic waves in silver layer. The composite exhibited excellent conductivity, EMI shielding effectiveness (SE) up to 106 dB and outstanding durability. After 10,000 bending times and 60 abrasion cycles respectively, the electrical resistance of the composite only increased from 0.030 Ω/sq. to 0.041 Ω/sq. and 0.050 Ω/sq., and the EMI SE decreased to 102 dB and 105 dB.

Waffle-inspired thermal conductive silicone rubber composites with excellent electromagnetic shielding performance based on three-dimensional filler networks

Improving the thermal conductivity and electromagnetic shielding performance of silicone rubber composites is crucial for their application in electronic devices. In this work, inspired by the structure of waffle, a novel approach combining ice templating and mechanical vibration was employed to prepare reduced graphene oxide (rGO)/silicon carbide whisker (SiC) filler networks arranged in both horizontal and vertical directions. Silicone rubber composites were prepared by vacuum impregnation of silicone rubber into the three-dimensional filler networks. At the hybrid filler content of 3.88 vol%, the through-plane thermal conductivity reached 5.24 W/(m·K), exhibiting about 31 times higher than that of silicone rubber, and the anisotropy of thermal conductivity of the composite was only 1.35 due to the structural arrangement of the filler network in both vertical and horizontal directions. The total electromagnetic interference (EMI) shielding effectiveness of the composite with 3.88 vol% hybrid filler was 35.2 dB with low electromagnetic reflection, exhibiting good EMI shielding performance.

Modulus matching strategy of ultra-soft electrically conductive silicone composites for high performance electromagnetic interference shielding

Electrically conductive silicone composites have made significant advancements in the field of electromagnetic interference (EMI) shielding due to their excellent conductivity, elasticity, sealability and environmental reliability. Notably, chips and other miniature electronic components with limited pressure-bearing capacity often require composites with both low compressive stress and high EMI shielding performance. Unfortunately, conventional conductive silicone composites often exhibit high compressive stress as a result of the high modulus and high loading contents of fillers, which prevents them from fitting perfectly with the package cavity under low package stress conditions, resulting in inadequate EMI shielding. Herein, the elastic modulus of the silver@polydimethylsiloxane (Ag@PDMS) conductive filler can be adjusted by controlling the crosslinking ratio, which enables the creation-of-Ag@PDMS/Silicone-(APS)-conductive-composites-with-remarkable compressibility, EMI shielding and sealing capabilities. The-APS-composites exhibit a compressive stress of only 0.3 MPa under 50 % compressive strain, which is essential for the packaging-of-precision electronic components. The APS composites show a significant decrease in compressive stress (54 %) and elastic modulus (80 %) under 50 % compressive strain, in comparison to conventional polymer composites with hard fillers. Meanwhile, the APS composites exhibit a-satisfactory-EMI-shielding-effectiveness-(SE)-of-71-dB and demonstrate excellent electromagnetic sealing capabilities in practical electronics. This study provides an effective approach for developing and constructing high-performance ultra-soft composites for precision electronic components packaging.

Large scale fabrication of recyclable and multifunctional sandwich-structured electromagnetic interference shielding films based on waste Nylon-6 silk

Modern wearable electronics are being miniaturized with high integration and frequency, leading to excess electromagnetic radiation, heat storage, and fire risk. Besides overcoming these safety issues, realizing large-scale, low-cost and recyclable preparation of multifunctional films are urgently required for practical applications of electromagnetic interference (EMI) shielding. Herein, sandwich-structured films have been prepared using commercial nylon mesh (CNM) with a waste nylon-6 silk/ammonium polyphosphate (PA6/APP) porous flame-retardant outer layer and inner conductive ultra-long silver nanowires (AgNWs) network. Only 0.2 mg/cm2 of the conductive inner layer endows the films with excellent EMI shielding performance (53.7 dB), thermal diffusivity (5.206 ± 0.087 mm2/s) and antibacterial properties. In addition, the unique honeycomb structure of the PA6/APP outer layer produced during water bath treatment endows the films with superior printability. And such modified porous outer layer of the sandwich-structured films realizes a V0 rating during the UL-94 test. Even when these films are scrapped, they can still be recycled and reused. In summary, the methods described herein can be extended to realize the large-scale production of sandwich-structured films.

Integrated super-engineering polymeric electromagnetic interference shielding films withstanding the extreme environments

The electromagnetic interference (EMI) poses a threat to electronic equipment and human health, which has spawned the development of polymer-based EMI shielding materials. However, it is challenging to combine their ease of fabrication with extreme environmental resistance. Herein, a simple and consecutive bottom-up assembly route is developed to prepare EMI shielding films based on a super-engineering polymer named polyarylene ether nitrile (PEN). Thanks to the morphological transformation of PEN films, the integration of polymeric matrix and commercial carbon nanotubes is throughout the vacuum-assisted deposition and hot-press molding, resulting in a series of sandwiched nanocomposite films. In the whole X-band, the EMI SE of the nanocomposite film is up to 30 dB with a low thickness of 0.268 mm. Besides, the absorption coefficient (A) can be significantly increased to 0.93, exhibiting an excellent adsorption-dominant shielding mechanism. Due to the super-engineering polymer as a matrix, the sandwiched nanocomposite films are endowed with excellent thermal stability (Td5 = 512 °C), superior tensile strength (69 MPa) as well as improved hydrophobicity (103°). Notably, the EMI shielding and mechanical performances manifest outstanding reliability under harsh environments, including strong acid, alkali, and high-temperature treatments. The integrated preparation towards super-engineered polymer-based nanocomposites is efficient and economical, affording EMI shielding films resisting multiple harsh environments.

Flexible Basalt Fiber/Aramid Nanofiber/Carbon Nanotube Electromagnetic Shielding Paper with Outstanding Environmental Stability and Joule Heating Performance.

In the field of electromagnetic shielding, it has become an important trend to manufacture thinner and better-performing electromagnetic interference (EMI) shielding materials. However, EMI shielding materials that are recyclable and resistant to extreme environments are of great significance for sustainable development and expanding their application areas. In this study, a composite paper with a "rebar-concrete" layered structure through the vacuum-assisted filtration approach by utilizing basalt fibers (BF) and aramid nanofibers (ANFs) with excellent temperature resistance and multiwalled carbon nanotubes with high electrical conductivity was prepared. The composite paper not only delivers a high electrical conductivity of 15.9 S cm-1 and a high electromagnetic interference shielding efficiency (EMI SE) of 24.6 dB but also exhibits a high specific shielding efficiency (SSE/t) of 12,504 dB cm2 g-1 at a thickness of 48 μm. Thanks to the excellent thermal stability of basalt fibers and aramid nanofibers, the composite paper exhibits long-term stable EMI shielding performance and structural integrity in various extreme environments, including fire, high/low temperature (-196 to 300 °C), and acid-base corrosion. Furthermore, the BF/ANF/CNT composite paper also shows excellent Joule heating performance, rapid electrothermal response, and good temperature controllability. Based on these excellent properties, the BF/ANF/CNT composite paper shows tremendous potential for practical applications to meet the requirements of various extreme environments.

Sandwich structure electromagnetic interference shielding composites based on Fe3O4 nanoparticles/PANI/laser-induced graphene with near-zero electromagnetic waves transmission

High-performance electromagnetic interference (EMI) shielding materials with flexible and lightweight characteristics are still a hot research direction, which will be highly promising in many application fields. In this work, laser-induced graphene (LIG) as the top and bottom layer, and binary composites of co-precipitated Fe3O4 NPs and in-situ chemical polymerized PANI (FePA) functioned as the intermediate layer is assembled to prepare a sandwich structure shielding material (FePA/LIG composite). 3D porous LIG with excellent conductivity is conducive to promote reflection and multiple reflections of incident electromagnetic waves (EMWs), while the transmitted EMWs will be further absorbed and attenuated via FePA composite due to its high impedance matching and microwave absorption (MA) properties. Near-zero EMWs transmission can be achieved and the average EMI shielding effectiveness (SE) of FePA/LIG composite (with thickness less than 2 mm) over the entire X-band and Ku-band is 50 dB and 63 dB, respectively. The admirable EMI shielding performance and flexibility of FePA/LIG composite endows enormous potential in portable electronic devices.

Ultrathin and flexible MXene-contained electromagnetic interference shielding composite paper designed with a protective hydrogel film

MXene-contained paper is a good choice to design ultrathin and flexible electromagnetic interference (EMI) shielding materials. However, the deficiencies in strength and stability of MXene-contained paper impede its practical applications. Herein, a composite paper was proposed to address the problems, in which a filter paper was modified with a three-layer structured surface via a facile layer-by-layer coating procedure. Specifically, the TEMPO-oxidized cellulose nanofibers (TOCN)/cationic starch (CS)/MXene gel layer and TOCN/MXene nacre structure layer ensured the good EMI shielding and mechanical performances of the composite paper, while the uppermost TOCN/CS hydrogel film layer mainly protected MXene. The composite paper achieved an EMI SE of 40.3 dB at a thickness of merely 0.1894 mm (SE/t value of ca. 212.8 dB mm−1, SSE/t values of ca.13216 dB cm2 g−1) and the total MXene dosage was 20 g m−2. Its tensile strength could be up to 11.7 MPa while the original filter paper was 6.4 MPa. Four pieces of this composite papers could be easily packed together to attain an EMI SE of nearly 70 dB. Importantly, the hydrogel film layer efficiently protected the MXene and maintained the EMI shielding performance of the composite paper when immersed in different liquids including water, HCl (1 M) and ethanol, due to the dense and compact structure of hydrogel film layer. This work provides a practical way to develop ultrathin, flexible and durable EMI shielding materials.

Slippery Graphene-Bridging Liquid Metal Layered Heterostructure Nanocomposite for Stable High-Performance Electromagnetic Interference Shielding.

Gallium-based liquid metal (LM) with intriguing high electrical conductivity and room-temperature fluidity has attracted substantial attention for its potential application in flexible electromagnetic interference (EMI) shielding. However, the EMI shielding performance of the existing LM-based composites is unsatisfying due to the irreconcilable contradiction between high EMI shielding efficiency (SE) and low thickness. In addition, the research on environmentally stable EMI shielding material has become an urgent need due to the increasingly sophisticated application scenarios. Herein, we prepared a reduced graphene oxide (rGO) bridging LM layered heterostructure nanocomposite with the liquid-infused slippery surface (S-rGO/LM), which exhibits an ultrahigh X-band EMI SE of 80 dB at a mere internal thickness of 33 μm, and an extremely high value of 100 dB at an internal thickness of 67 μm. More significantly, protected by the ultrathin (2 μm) yet effective slippery surface, the S-rGO/LM film exhibits exceptional EMI shielding stability (EMI SE stays above 70 dB) after enduring various harsh conditions (harsh chemical environments, extreme operating temperatures, and severe mechanical wearing). Moreover, the S-rGO/LM film also demonstrates satisfying photothermal behavior and excellent Joule heating performance (surface temperature of 179 °C at 1.75 V, thermal response <10 s), which endows it with the capability of anti-icing/de-icing. This work proposes a way to construct an LM-based nanocomposite with reliable high-performance EMI shielding capability, which shows great potential for applications in wearable devices, defense, and aeronautics and astronautics.

Parasitic reaction driven facile preparation of segregated-MXene/polycarbonate nanocomposites for efficient electromagnetic interference shielding

Conductive polymer composites with segregated structures (s-CPCs) would have great potential in electromagnetic interference (EMI) shielding applications owing to their superior electrical conductivity along with a low percolation threshold. This study investigated a facile manufacturing approach for synthesizing s-CPCs by introducing parasitic reaction of MXene flakes into positively charged polycarbonate microspheres simply prepared by a cationic surfactant. As a result, an electrostatic assembly of MXene flakes and PC microspheres was successfully formed, resulting in unprecedented efficient and effective manufacturing process. Given with the fabrication approach investigated in this study, it was experimentally found that the resultant s-CPCs exhibited the considerably low percolation threshold of 0.15 vol% as well as outstanding EMI shielding performance of 38.7 ± 1.2 dB with only 2.75 vol% of MXene. This study can show, if properly optimized, the great potential of the use of s-CPCs in a wide range of EMI shielding applications.

EMI shielding, thermal and antibacterial performances of ecofriendly castor oil–based waterborne polyurethane favored by combining carbon nanotube and cetyltrimethylammonium bromide

Many ecofriendly and antibacterial polymer-based shielding nanocomposites have been designed to address the increasingly serious issues of electromagnetic interference (EMI) pollution and antibiotic resistance. These composites contain high amounts of conductive and antibacterial material and exhibit an unsurpassed EMI shielding performance and strong antibacterial properties. However, it is extremely challenging to prepare these materials because of the formation of large aggregates coupled with the high viscosity. Herein, carbon nanotubes (CNTs) and an antibacterial surfactant (cetyltrimethylammonium bromide (CTAB)) are mixed with castor oil–based waterborne polyurethane (WPU) via ultrasonic-assisted solution mixing followed by a freeze-drying approach. Owing to the presence of CTAB, CNTs (at a concentration of 24.3 wt%) are evenly dispersed and connected to each other in the WPU matrix. This morphology and intrinsic characteristics of CNTs enable the resultant CNT/WPU composites to exhibit an excellent electrical conductivity (635.8 S/m) and thermal conductivity (0.308 W/(m·K)) as well as an incomparable shielding effectiveness (SE, 88.81 dB). Notably, the specific SE reaches 997.4 dB/cm, which exceeds those of the reported composites. Moreover, the combination of CNTs and CTAB improves the antibacterial activities of the WPU composites. Due to these merits, the resultant composites have great potential for applications in portable and wearable smart electronics. Overall, this study opens a new way toward the manufacture of ecofriendly and multifunctional polymer composites.

Robust multifunctional composite films with alternating multilayered architecture for highly efficient electromagnetic interference shielding, Joule heating and infrared stealth

Developing ultrathin electromagnetic interference (EMI) shielding materials with high-efficiency EMI shielding effectiveness (SE), anisotropic thermal conductivity and robust mechanical performance is urgently required but challenging to satisfy the integration and miniaturization of modern flexible electronics. Herein, an alternating multilayered film containing alternating CoFe2O4@MXene/cellulose nanofibers (CNF) layers and silver nanowires (AgNWs)/CNF layers was successfully fabricated via a facile alternating vacuum-assisted filtration strategy. Profiting from the rational arrangement of CoFe2O4@MXene/CNF layers and AgNWs/CNF layers, electric/magnetic coupling effect and unique “absorption-reflection-reabsorption” shielding behavior among the alternating multilayered films, the resultant composite film with alternating six-layered architecture realizes an ultra-high EMI SE of 87.8 dB with low electromagnetic waves reflection effectiveness of 5.6 dB at a thickness of only 0.1 mm. The film remains reliable EMI shielding performance (over 97% EMI SE retention) after undergoing persistently physical damage and prolonged chemical attack. Meanwhile, owing to the construction of overlapping AgNWs network, the obtained film acquires outstanding in-plane thermal conductivity (6.875 W/(m·K)) and controllable Joule heating performance (steady temperature over 90 °C at applied voltage of 3.0 V within 20 s). The inferior through-plane thermal conductivity (0.689 W/(m·K)) caused by the design of multilayered structure guarantees the remarkable infrared stealth performance. Additionally, the good interfacial interaction endows the prepared film with robust mechanical properties (tensile strength of 183.2 MPa and fracture strain of 5.4%). This work not only offers a creative avenue for designing and preparing multifunctional EMI shielding composite films with excellent mechanical properties, but also broadens the applications of EMI shielding composite films in military fields, artificial intelligence and wearable electronics.

Robust Ti3C2Tx MXene foam modified with natural antioxidants for long-term effective electromagnetic interference shielding

MXenes have been proven to be outstanding lossy phase of advanced electromagnetic interference (EMI) shielding materials. However, their poor tolerance to oxygen and water results in fast degradation of the pristine two-dimensional (2D) nanostructure and fading of the functional performance. Herein, in this research, natural antioxidants (e.g., melatonin, tea polyphenols, and phytic acid) were employed to protect the Ti3C2Tx MXene from its degradation in order to achieve a long-term stability of the EMI shielding performance. The results showed that the synthesized composites comprised of antioxidants and Ti3C2Tx exhibited a decelerating degradation rate resulting in an improved EMI shielding effective (SE) stability. The antioxidation mechanism of the applied antioxidants is discussed with respect to the nanostructure evolution of the Ti3C2Tx MXene. This work contributes to the basic foundations for the further development of advanced MXenes for stable applications in the EM field.

Fabrication of Flexible FCI/PDMS Electromagnetic Shielding Composites Based on Pulsed Magnetic Field-Induced Alignment

Conductive polymer composites have been utilized in the field of electromagnetic interference (EMI) shielding, albeit requiring a high concentration of conductive fillers to achieve desirable EMI performance. To address this issue and enable the creation of superior EMI shielding composites with reduced filler loadings, this study employed a pulsed magnetic field featuring an amplitude of 0.7 T, a pulse width of 10 μs, and a frequency of 100 Hz to align flaky carbonyl iron (FCI) in poly(dimethylsiloxane) (PDMS). This method resulted in an improved EMI shielding performance of the composites. The outcomes revealed that the pulsed magnetic field effectively controlled the orientation of the FCI, forming a conductive network structure, with the average orientation angle of the FCI reaching 69.3°. The aligned composites exhibited a significant improvement in EMI shielding effectiveness, with the enhancement effect reaching 37.53% and the EMI shielding effectiveness reaching 24.87 dB. Moreover, the flexible tensile properties of the aligned composites were superior to those of the unaligned composites, particularly the elongation at break, which reached 197.46%. The concordance between the theoretical analysis and experimental results affirms the efficacy of the microsecond pulsed magnetic field in enhancing the EMI shielding performance of composite materials. Ultimately, the high-performance, flexible electromagnetic shielding composite materials prepared in this study demonstrate potential for use in advanced electronic equipment.

High-performance flexible nanocomposites with superior fire safety and ultra-efficient electromagnetic interference shielding

High-performance multifunctional polymeric materials integrated with high fire safety, excellent mechanical performances and electromagnetic interference (EMI) shielding properties have great prospects in practical applications. However, designing highly fire-safe and mechanically robust EMI shielding nanocomposites remains a great challenge. Herein, hierarchical thermoplastic polyurethane/cyclophosphazene functionalized titanium carbide/carbon fiber fabric (TPU/CP-Ti3C2Tx/CF) nanocomposites with high fire safety and mechanical strength and toughness were prepared through the methods of melt blending, layer-by-layer stacking and thermocompression. The TPU/CP-Ti3C2Tx showed improved thermal stability. Moreover, the peak of heat release rate and total heat release of the hierarchical TPU sample containing 4.0 wt.% CP-Ti3C2Tx were respectively reduced by 64.4% and 31.8% relative to those of pure TPU, which were far higher than those of other TPU-based nanocomposites. The averaged EMI shielding effectiveness value of the hierarchical TPU/CP-Ti3C2Tx-2.0/CF nanocomposite reached 30.0 dB, which could satisfy the requirement for commercial applications. Furthermore, the tensile strength of TPU/CP-Ti3C2Tx-2.0/CF achieved 43.2 MPa, and the ductility and toughness increased by 28.4% and 84.3% respectively compared to those of TPU/CF. Interfacial hydrogen bonding in combination with catalytic carbonization of CP-Ti3C2Tx nanosheets and continuous conductive network of CF were responsible for the superior fire safety, excellent EMI shielding and outstanding mechanical performances. This work offers a promising strategy to prepare multifunctional TPU-based nanocomposites, which have the potential for large-scale application in the fields of electronics, electrical equipment and 5 G facilities.