Enhanced electromagnetic interference shielding performance of geopolymer nanocomposites by incorporating carbon nanotubes with controllable silica shell

The development of construction materials with exceptional electromagnetic interference (EMI) shielding performance is urgently needed to restrict the admittance of electromagnetic (EM) radiation. In this work, silica (SiO₂)-coated carbon nanotubes (S-CNT) with different shell thicknesses (～7, ～10, and ～15 nm) were prepared by a sol-gel method. The effect of SiO₂ shell thickness on the EMI shielding performance of the resulting geopolymer nanocomposites was studied. The coated SiO₂ shell effectively facilitated the dispersion of CNT in the geopolymer matrix due to the chemical reaction between SiO₂ and the geopolymer. The dispersability of modified CNT could be further improved by increasing the thickness of the SiO₂ shell. However, electron delocalization was hindered by the insulating SiO₂ shell. The conductive nature of CNT was restored during geopolymerization when the SiO₂ shell was thin. A high EMI shielding effectiveness (SE) of 24.2 dB was achieved for the geopolymer nanocomposite containing 5 vol% S-CNT with a thin SiO₂ shell. The value achieved was more competitive than reported composites for construction when the sample thickness and filler content were considered.     

Strong and Flexible Carbon Fiber Fabric Reinforced Thermoplastic Polyurethane Composites for High‐Performance EMI Shielding Applications

Electromagnetic shielding materials play a significant role in solving the increasing environmental problem of electromagnetic pollutions. The commonly used metal‐based electromagnetic materials suffer from high density, poor corrosion resistance, and high processing cost. Polymer composites exhibit unique combined properties of lightweight, good shock absorption, and corrosion resistance. In this study, a novel high angle sensitive composite is fabricated by combining carbon fiber (CF) fabric with thermoplastic polyurethane elastomer (TPU). The effect of stacking angle of CF fabric on EMI shielding performance of composite is studied. When the stacking angle of CF fabric changed, the electromagnetic interference (EMI) shielding effectiveness (SE) of CF fabric/TPU composite can reach a maximum of 73 dB, and the tensile strength can reach 168 MPa. In addition, the composite has anisotropic conductivity, which is conductive along the plane direction and nonconductive along the thickness direction. Moreover, the CF fabric/TPU composite manifests exceptional EMI‐SE/density/thickness value of 383 dB cm² g^?1, which is higher than most of current EMI shielding composites reported in literature. In summary, CF fabric/TPU composite is an excellent EMI shielding material that is lightweight, highly flexible, and mechanically robust, which can be applied to the field of aerospace and some intelligent electronic devices.     

Synergistic effect of polyindole decoration on bismuth neodymium ferrite powder for achieving wideband microwave absorber

Recently, composite materials with outstanding absorption properties, like extraordinary absorbing capability, light weight, and thin in size, are required to solve the challenges of electromagnetic pollution. In addition, most of the work is based on the optimization of absorber material structure, and microstructure. In the current work, we improved the reflection loss feature of Bi_0.5Nd_0.5FeO₃ nanopowders via decoration with polyindole polymer by tuning the filler loading of the nanocomposite in the matrix. XRD, UV–Vis, XPS, and FESEM were used to determine the physicochemical features of the as-prepared nanocomposite. The minimum RL was lowered further with the increasing filler loading at 25 wt%. The lower RL of ?22 dB was noticed for 2.2 mm thickness at 11.5 GHz. The maximum value of the SE_R for a 25 wt% sample was 5.5, whereas 19 dB and 24.5 dB values were recorded for SE_A and SET, respectively. The resonance peak above 11.5 GHz demonstrated the better outcome of the absorber at high frequency. Good impedance matching characteristics, conductive features, dielectrics, and magnetic losses were all credited with the excellent reflection loss and electromagnetic interference shielding efficiency. The as-prepared nanocomposite materials that have been proven are interesting prospects for electromagnetic reflection loss and interference shielding that is lightweight, flexible, and extremely effective.     

Dynamic mechanical analysis and broadband electromagnetic interference shielding characteristics of poly (vinyl alcohol)-poly (4-styrenesulfonic acid)-titanium dioxide nanoparticles based tertiary nanocomposites

ABSTRACT

Novel tertiary nanocomposite films comprising of poly (vinyl alcohol) (PVA), poly (4-styrenesulfonic acid) (PSSA) and titanium dioxide (TiO₂) nanoparticles (NP_S) were prepared using simple solvent casting method. The structural, thermal, morphological, thermo-mechanical and electromagnetic interference (EMI) shielding properties of PVA/PSSA/TiO₂ nanocomposite films were investigated. The EMI shielding effectiveness (SE) of PVA/PSSA/TiO₂ nanocomposite films in the X and Ku band was found to be 12 dB and 13 dB respectively at 25 wt% TiO₂ NPs loading. These results demonstrate the possible applications of PVA/PSSA/TiO₂ nanocomposite films as low cost, lightweight and flexible material for EMI shielding.     

Roll-to-roll processable MXene-rGO-PVA composite films with enhanced mechanical properties and environmental stability for electromagnetic interference shielding

MXene films promise potential electromagnetic interference (EMI) shielding materials, but poor scalable processability, environmental instability, and weak mechanical properties severely restrict their applications. Herein, we engineer the large-area, high-performance, and compact nacre-like MXene-based composite films through cooperative co-assembly of Ti₃C₂T_X MXene and reduced graphene oxide (rGO) in the presence of polyvinyl alcohol (PVA). The resulting MXene-rGO-PVA composite films benefit from enhanced bonding strength and extra chain bridging effect of linear PVA molecules enriched with hydroxyl groups. Therefore, the composite film achieves high tensile strength (～238 MPa) and toughness (～1.72 MJ m^?3) while having high conductivity of ～32 S cm^?1. A significant EMI shielding effectiveness (41.35 dB) is also demonstrated, with an excellent absolute shielding effectiveness of ～20,200 dB cm² g^?1 at only 12-μm thickness. Moreover, due to the synergistic effect of multiple components, the composite films maintain a stable EMI shielding performance in harsh environments (sonication, hot/cold annealing, and acid solution) with mechanical properties that fluctuate only within 10% compared to the original film. More importantly, commercial polyethylene terephthalate release liner can be applied for the film coating, facilitating continuous roll-to-roll production of large-area films and future applications.     

Stretchable,mechanically resilient,and high electromagnetic shielding polymer/MXene nanocomposites

The increasingly disturbing electromagnetic wave pollution has intensified research for high-performance shielding materials to protect humans and the environment. It remains a great challenge to combine high electromagnetic interference (EMI) shielding performance with mechanical robustness and stretchability. These crucial features have been simultaneously achieved in this work by using a facile method to prepare elastomer/MXene nanocomposites. An EMI shielding effectiveness of 49 dB was obtained from a 1-mm thick nanocomposite film at 19.6 vol% of MXene; the film has a density of 1.25 g/cm³. The outstanding electrical conductivity of MXene – 4350 ± 125 S·cm⁻¹ – provided free charge carriers in the matrix to absorb electromagnetic signals, leading to the dominance of absorption mechanism over reflection mechanism. Owing to a nanofiller modification step, the nanocomposite films demonstrated not only outstanding EMI shielding but sufficient strength and stretchability. A nanocomposite at 14.0 vol% exhibited Young's modulus of 15.85 ± 0.75 MPa and tensile strength 25.94 ± 0.81 MPa with elongation at break of 170 ± 5.6%, which relates to high stretchability. These impressive properties make our nanocomposites suitable for use in harsh environments as well as applications in stretchable devices, protective clothing, aerospace, aircraft, and automotive industries.     

Ti3C2Tx-coated diatom frustules-derived porous SiO2 composites with high EMI shielding and mechanical properties

Effective electromagnetic interference (EMI) shielding materials have garnered substantial interest for their efficacy in attenuating electromagnetic wave energy, ensuring data confidentiality, ensuring the operational stability of fragile electronic systems. To begin, artificially cultured diatom frustules (DF)-derived porous silica (DFPS) skeletons were constructed as templates in this study. Porous ceramics hot-pressed at 800 °C displayed a high compressive strength with a high specific surface area due to their three-dimensional (3D) multilayered and porous structures. Then, mechanically robust Ti₃C₂T_x/DFPS composites with exceptional EMI shielding performance were fabricated by immersing porous DF-based ceramics into Ti₃C₂T_x solutions and annealing in an argon environment to increase the materials’ shielding efficiency (SE). The EMI SE of composites hot-pressed at 800 °C achieved the maximum EMI SE of 43.2 dB in the X-band and a compressive strength of 67.5 MPa, establishing a hitherto unreported balance of mechanical characteristics and shielding performance. Prolonged transmission paths, multiple dissipation, scattering and reflection of electromagnetic energy were achieved using a well-maintained hierarchical porous silica framework decorated with MXene, with adsorption caused by surface MXene serving as the primary shielding mechanism for the composites. Due to their superior overall performance, MXene/DFPS EMI shielding composites have a bright future in the aircraft sector as delicate electronic device components.     

Modeling for the electromagnetic properties and EMI shielding of Cf/mullite composites in the gigahertz range

The electromagnetic properties and EMI shielding effectiveness of C_f/mullite composites via the spark plasma sintering were intensively investigated in the gigahertz range (8.2–12.4 GHz). Experimental results have revealed excellent electromagnetic properties and a high value of EMI shielding effectiveness (nearly 40 dB) for C_f/mullite composites with 1.65 vol% carbon fillers at thickness of 2 mm. We quantitatively characterize the contributions of microstructural features to overall EMI shielding effectiveness using a micromechanics-based homogenization model. The EMI shielding effectiveness enhances with respect to the C_f volume concentration before the threshold. The increasing trend of EMI shielding effectiveness with respect to AC (alternating current) frequency can be attributed to enhanced conductivity at high gigahertz range. It is demonstrated that filler and frequency dependent interface effects are essential to obtain excellent electromagnetic properties of C_f/mullite composite. The present research can provide guidances for the design of ceramic-based composites applied in high-temperature EMI shielding devices.     

Hydrothermal synthesis of micro-flower like morphology aluminum-doped MoS2/rGO nanohybrids for high efficient electromagnetic wave shielding materials

In this study, a three-dimensional (3D) micro-flower like morphology aluminum-doped molybdenum disulfide/reduced graphene oxide (Al@MoS₂/rGO) nanohybrids have been developed using a simple and sensitive hydrothermal approach. Their electromagnetic (EM) parameters (permittivity, permeability) and microwave shielding parameters (S₁₁, S₁₂) have been analyzed and reported for the first time in the microwave frequency range of 8.0–12.0 GHz. It is interesting to note that the electrical conductivity of the nanohybrids increases with the doping concentration of Al-ions, whereas skin-depth has a reverse trend. The 12% Al@MoS₂/rGO nanohybrid shows a higher total electromagnetic interference shielding effectiveness (EMI SE) value about SE_T ~33.38 dB, whereas undoped MoS₂/rGO nanohybrid exhibits a lower value around ~17.07 dB at the same thin thickness. The higher doping concentration of Al-ion creates lattice distortion and crystal defects with high charge carrier mobility between multiple interfaces and at defective sites. Hence, the Al-doping into MoS₂ lattice supported on the rGO surface can greatly enhance EM wave absorption and EMI SE value. The present work suggests that the 12% Al@MoS₂/rGO nanohybrid can be treated as a good microwave absorbing and shielding material and useful in various techno-commercial devices.     

Electromagnetic shielding Janus membrane for direct current-type pressure and sliding sensing

Facing increasing electromagnetic radiation pollution, soft sensors with electromagnetic interference (EMI) shielding is highly desirable. Here, flexible electromagnetic shielding [polyacrylonitrile/Fe₃O₄/polyaniline]//[multiwalled carbon nanotube/polyvinyl pyrrolidone] (denoted [PAN/Fe₃O₄/PANI]//[MWCNT/PVP]) Janus membrane is reported for pressure and sliding sensing. The [PAN/Fe₃O₄/PANI] layer of Janus membrane as the force and sliding sensing unit can generate direct current-type (DC-type) voltage signals by conducting polymer/metal Schottky junction, whereas [MWCNT/PVP] layer serves as main electromagnetic shielding unit. Under the vertical force and horizontal sliding of aluminum (Al) foil, it can output DC-type voltage signals based on the Schottky contact. The performance of [PAN/Fe₃O₄/PANI]//[MWCNT/PVP] Janus membrane for pressure and sliding sensing is appropriately explored and assessed. Moreover, the Janus membrane exhibits excellent shielding effects with average EMI shielding effectiveness (SE) of 37.54 dB in 8.2–12.4 GHz (X-Band) frequency ranges. Thus, based on the asymmetrical double-layer structure, soft DC-type sensor with EMI shielding is achieved, showing utilization potential in wearable electronics and intelligent robots.     

Magnetite/graphene oxide/Prussian blue composite with robust effectiveness for electromagnetic interference shielding

Considering the promising efficiency of composites, in the current study, a graphene oxide (GO)-magnetite-Prussian blue (PB) composite material was prepared. The composite exhibited electrical conductivity, magnetic permeability, and permittivity nature, and was evaluated using electromagnetic interference (EMI) shielding studies. GO was developed by the Hummer's method, ferrite (Fe₃O₄) was incorporated by the sol-gel method, and PB was introduced in the mixture by an in-situ process. The fabricated samples were studied by X-ray diffraction, Raman Spectroscopy, Fourier-transform infrared spectroscopy along with EMI shielding efficiency (SE) evaluation. The SE of ?71.66 dB of reflection losses was measured at a frequency of 1.5 MHz. The GO/Fe₃O₄/PB composite provided the best results for the detection in the 1–18 MHz frequency range because of its excellent electric and magnetic properties. The obtained results demonstrated that the GO/Fe₃O₄/PB composite has promising potential applications in EMI shielding.     

Electromagnetic interference shielding properties of graphene quantum-dots reinforced poly(vinyl alcohol)/polypyrrole blend nanocomposites

Graphene quantum dots (GQDs) reinforced poly(vinyl alcohol) (PVA)/polypyrrole (WPPy) nanocomposite films with various GQDs loadings were synthesized using the versatile solvent casting method. The structural and morphological properties of PVA/WPPy/GQDs nanocomposite films were investigated by employing Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. The thermogravimetric analysis revealed enhanced thermal stability of synthesized nanocomposites while enhanced dielectric properties were also observed. The maximum dielectric constant value for PVA/WPPy/GQDs nanocomposite films was observed to be ε = 6,311.85 (50 Hz, 150°C). The electromagnetic interference (EMI) shielding effectiveness (SE) of nanocomposite films was determined in the X-band (8–12 GHz) and Ku-band (12–18 GHz) frequency region. The EMI SE was found to be increased from 0.8 dB for the pure PVA film to 9.8 dB for the PVA/WPPy/GQDs nanocomposite film containing 10 wt% GQDs loading. The enhanced EMI shielding efficiency of nanocomposite films has resulted from the homogenous dispersion of GQDs in PVA/WPPy blend nanocomposites. Thus, the prepared nanocomposites are envisioned to utilize as a lightweight, flexible, and low-cost material for EMI shielding applications.     

Electromagnetic interference shielding effectiveness of hybrid multifunctional Fe3O4/carbon nanofiber composite

Electromagnetic interference shielding effectiveness (EMI SE) of multifunctional Fe₃O₄/carbon nanofiber composites in the X-band region (8.2–12.4 GHz) is studied. Here, we examine the contributing effects of various parameters such as Fe₃O₄ content, carbonization temperature and thickness on total shielding efficiency (SE_total) of different samples. The maximum EMI SE of 67.9 dB is obtained for composite of 5 wt.% Fe₃O₄ (0.7 mm thick) with the dominant shielding by absorption (SE_A) of electromagnetic radiation. The enhanced electromagnetic shielding performance of Fe₃O₄/carbon nanofiber composites is attributed to the increment of both magnetic and dielectric losses due to the incorporation of magnetite nanofiller (Fe₃O₄) in electrically conducting carbon nanofiber matrix as well as the specific nanofibrous structure of carbon nanofiber mats, which forms a higher aspect ratio structure with randomly aligned nanofibers. Furthermore, we prove that the addition of elastomeric polydimethylsiloxane (PDMS) as a coating for carbon nanofiber composite strengthens the composite structure without interfering with its electromagnetic shielding efficiency.     

Facile preparation of light-weight biodegradable and electrically conductive polymer based nanocomposites for superior electromagnetic interference shielding effectiveness

Harmful electromagnetic radiations that are generated from different electronic devices could be absorbed by a light weight and mechanically flexible good electromagnetic interference (EMI) shielding polymer nanocomposite. On the other hand, different electronic wastes (“e-wastes”) which are generally polymer building materials generated from wastes of dysfunctional electronic devices are not naturally biodegradable. Our recent effort has been employed to produce bio-degradable EMI shielding polymer nanocomposite. For that purpose, we had prepared a 50:50 ratio polylactic acid/thermoplastic polyurethane polymer nanocomposite by mixing the conducting carbon black with the blend following the facile and industrially feasible solution mixing method. Morphological characterizations by scanning electron microscopy and transmission electron microscopy analysis revealed the co-continuous morphology of the neat blend as well as polymer nanocomposites with the preferential distribution of conductive filler on a particular polymer phase. The polymer nanocomposites gave good mechanically with improved thermal properties. We got EMI shielding effectiveness around −27 dB with a low percolation threshold at around 30 wt% filler loading in the polymer nanocomposite at the X-band frequency domain (8.2–12.4 GHz). Later we had studied the biodegradability of the PLA/TPU along with their composites (T_XP_XC_X) by employing the respirometry method and got a satisfactory result to ensure their biodegradability.     

High-strength,flexible and superhydrophobic graphene/aramid nanofiber nanocomposite films for electromagnetic interference shielding application

Electromagnetic interference (EMI) shielding composite materials exhibit many amazing characteristics, including low density, excellent flexibility and corrosion resistance, compared with metals. However, it is a long-standing challenge for EMI shielding materials to overcome inferior mechanical properties and limited hydrophobic characteristics. In this work, the high-strength, flexible and superhydrophobic graphene nanosheet/aramid nanofiber (GNS/ANF) nanocomposite films with layered microstructure were prepared by the sol-gel transformation and spray coating process. The resultant film exhibits excellent mechanical properties with a high tensile strength (131.17 ± 2.77 MPa), large fracture strain (9.58 ± 0.58%), and favorable toughness (8.84 ± 0.74 MJ m^?3), which are 26.2 times, 7.5 times and 221.0 times higher than those of pure GNS films. These results are attributed to synergistic effect between intensive stretching of three dimensional (3D) nanofiber network and extensive sliding of GNS produced effective energy dissipation. Moreover, the film with content of 70 wt% GNS has EMI shielding effectiveness of 31.3 dB, and its reflection coefficient is more than 0.89, revealing a reflection-dominant shielding mechanism. Meanwhile, the film possesses superhydrophobic property (158.7° ± 1.1°) and flame retardancy. The multilayered nanocomposite films have excellent potential for high-performance EMI shielding applications under some outdoor conditions.     

Multifunctional Shape-Stabilized Phase Change Materials with Enhanced Thermal Conductivity and Electromagnetic Interference Shielding Effectiveness for Electronic Devices

A paraffin-based shape-stabilized composite phase change material (CPCM) is fabricated with dramatically enhanced thermal conductivity and excellent electromagnetic interference (EMI) shielding capacity. The as-prepared CPCMs are supported by graphene-based frameworks with many bubble-like micropores that are prepared by the addition of polystyrene microspheres into graphene oxide hydrogel as hard templates. These bubble-like micropores can encapsulate paraffin wax (PW) due to the strong capillary force between the graphene-based framework and PW and leading to enhanced shape stability of the as-prepared CPCMs. Moreover, the continuous thermally and electrically conductive network formed by graphene nanoplatelets endows the as-prepared CPCMs with a high thermal conductivity and an excellent EMI shielding effectiveness. When the ratio of graphene-based framework is 23.0 wt%, the thermal conductivity and latent heat of CPCM reaches 28.7 W m⁻¹ k⁻¹ and 175.8 J g⁻¹, respectively, and the EMI shielding effectiveness is higher than 45 dB in the frequency of 8.2–12.4 GHz. Their outstanding thermal and EMI shielding performance makes the as-prepared CPCMs promising candidates for use in thermal management and EMI shielding of electronic devices.     

Fabrication of Cellulose Nanofiber/Reduced Graphene Oxide/Nitrile Rubber Flexible Films Using Pickering Emulsion Technology for Electromagnetic Interference Shielding and Piezoresistive Sensor

With the rapid development of flexible electronics, the demand for flexible electromagnetic interference (EMI) shielding materials is increasing. This study develops a new green and effective strategy, consisting of graphene oxide (GO) and cellulose nanofibrils (CNF) co-stabilized Pickering emulsion combined with hot-pressing technology, to prepare flexible and conductive nitrile rubber (NBR) composite films. The composite films consist of a 3D network conductive skeleton structure of reduced GO (RGO) and an isolated NBR structure. This specific design results in a maximum high conductivity of 99 S m⁻¹, which is higher by an order of magnitude compared with that of the composites obtained using the traditional solution blending method, and a stable EMI shielding effectiveness of 25.81 dB in the X band. The introduction of the flexible NBR results in the excellent flexibility and structural strength of the composite film, and exhibits a decrease of 2.51% in the EMI shielding efficacy after 5000 cycles. As a piezoresistive sensor for wearable devices, the CNF-RGO/NBR flexible film can hold precise current signals and respond to finger motion. The findings of this study can provide new insights for the design of conductive and flexible composites as wearable and portable medical equipment and electronic devices.     

Electrical and Electromagnetic Interference (EMI) shielding properties of hexagonal boron nitride nanoparticles reinforced polyvinylidene fluoride nanocomposite films

The hexagonal boron nitride nanoparticles (h-BNNPs) reinforced flexible polyvinylidene fluoride (PVDF) nanocomposite films were prepared via a simple and versatile solution casting method. The morphological, thermal and electrical properties of h-BNNPs/PVDF nanocomposite films were elucidated. The electromagnetic interference (EMI) shielding properties of prepared nanocomposite films were investigated in the X-band frequency regime (8–12 GHz). The EMI shielding effectiveness (SE) was increased from 1 dB for the PVDF film to 11.21 dB for the h-BNNPs/PVDF nanocomposite film containing 25 wt% h-BNNPs loading. The results suggest that h-BNNPs/PVDF nanocomposite films can be used as lightweight and low-cost EMI shielding materials.     

Electromagnetic shielding properties of carbon‐rich chemical vapor infiltration‐prone silicon carbide matrix composites

This study focuses on the electromagnetic interference shielding effectiveness (EMI SE) of SiC nanowire/SiC ceramic composites (SiC_nw/SiC) manufactured by chemical vapor infiltration of SiC_nw aerogels with carbon‐rich SiC. The total EMI SE of a 1.0 mm thick ceramic composite specimen with density of only 2.68 g/cm³, was found to be 43‐44 dB, which indicates an excellent EM shielding capability of the ceramic composite corresponding to blocking of 99.99% of the incident EM signal. It was found that the carbon‐rich CVI‐SiC matrix possess excellent EM shielding properties, therefore, the CVI‐SiC CMCs themselves possess an excellent EM shielding property as a result of the carbon‐rich SiC matrix.     

Design of artificial nacre-like hybrid films as shielding to mitigate electromagnetic pollution

Multifunctional designs of biomimetic layered materials are in great demand for broadening their applications. Artificial hybrid films are fabricated using a simple evaporation-induced assembly method, using nacre as the structural model, two-dimensional reduced graphene oxide (RGO) and magnetic graphene (MG) as inorganic building blocks and poly(vinyl alcohol) (PVA) as glue. The nacre-like films exhibit good mechanical performance, such as high stiffness, strength and toughness. The biomimetic materials possess the shielding properties of electromagnetic pollution. MG based nacre-like films present more significant electromagnetic interference (EMI) shielding performance than RGO film, because of a synergism between dielectric loss of graphene and magnetic loss of magnetic nanoparticles. Average EMI shielding effectiveness (SE) reaches ∼20.3 dB over the frequency range of 8.2–12.4 GHz (X band) for MG hybrid film only 0.36 mm thick. The lightweight, flexible and thin MG artificial hybrid films possess good potential for EMI shielding applications.