Electromagnetic Interference Shielding Efficiency Research Articles

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

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

Single‐ and Double‐Layer Embedded Metal Meshes for Flexible, Highly Transparent Electromagnetic Interference Shielding

AbstractSimulation and experimental studies are carried out on single‐layer and double‐layer embedded metal meshes (SLEMM and DLEMM) to assess their performance as transparent electromagnetic interference (EMI) shielding. The structures consist of silver meshes embedded in polyethylene terephthalate (PET). As a transparent electrode, SLEMMs exhibit a transparency of 82.7% and a sheet resistance of 0.61 Ωsq−1 as well as 91.0% and 1.49 Ωsq−1. This performance corresponds to figures of merit of 3101 and 2620, respectively. The SLEMMs achieve 48.0 dB EMI shielding efficiency (SE) in the frequency range of 8–18 GHz (X‐ and Ku‐bands) with 91% visible transmission and 56.2 dB EMI SE with 82.7% visible transmission. Samples exhibit stable performance after 1000 bending cycles with a radius of curvature of 4 mm and 60 tape test cycles. DLEMMs consist of fabricating SLEMM on opposite sides of the substrate where the distance can be varied using a spacer. Simulations are performed to investigate how varying spacer distance between two layers of metal meshes influences the EMI SE. DLEMMs are fabricated and achieved an EMI SE of 77.7 dB with 81.7% visible transmission. SLEMMs and DLEMMs may have a wide variety of applications in aerospace, medical, and military applications.

Hybrid Foams based on Multi‐Walled Carbon Nanotubes and Cellulose Nanocrystals for Anisotropic Electromagnetic Shielding and Heat Transport

AbstractLightweight and mechanically robust hybrid foams based on cellulose nanocrystals (CNC) and multi‐walled carbon nanotubes (MWCNT) with an anisotropic structure are prepared by directional ice‐templating. The anisotropic hybrid CNC‐MWCNT foams displayed a combination of highly anisotropic thermal conductivity and an orientation‐dependent electromagnetic interference (EMI) shielding with a maximum EMI shielding efficiency (EMI‐SE) of 41–48 dB between 8 and 12 GHz for the hybrid foam with 22 wt% MWCNT. The EMI‐SE is dominated by absorption (SEA) which is important for microwave absorber applications. Modelling of the low radial thermal conductivity highlighted the importance of phonon scattering at the heterogeneous CNC‐MWCNT interfaces while the axial thermal conductivity is dominated by the solid conduction along the aligned rod‐like particles. The lightweight CNC‐MWCNT foams combination of an anisotropic thermal conductivity and EMI shielding efficiency is unusual and can be useful for directional heat transport and EMI shielding.

Flexible Embedded Metal Meshes by Sputter-Free Crack Lithography for Transparent Electrodes and Electromagnetic Interference Shielding.

A facile and novel fabrication method is demonstrated for creating flexible poly(ethylene terephthalate) (PET)-embedded silver meshes using crack lithography, reactive ion etching (RIE), and reactive silver ink. The crack width and spacing in a waterborne acrylic emulsion polymer are controlled by the thickness of the polymer and the applied stress due to heating and evaporation. Our innovative fabrication technique eliminates the need for sputtering and ensures stronger adhesion of the metal meshes to the PET substrate. Crack trench depths over 5 μm and line widths under 5 μm have been achieved. As a transparent electrode, our flexible embedded Ag meshes exhibit a visible transmission of 91.3% and sheet resistance of 0.54 Ω/sq as well as 93.7% and 1.4 Ω/sq. This performance corresponds to figures of merit (σDC/σOP) of 7500 and 4070, respectively. For transparent electromagnetic interference (EMI) shielding, the metal meshes achieve a shielding efficiency (SE) of 42 dB with 91.3% visible transmission and an EMI SE of 37.4 dB with 93.7% visible transmission. We demonstrate the highest transparent electrode performance of crack lithography approaches in the literature and the highest flexible transparent EMI shielding performance of all fabrication approaches in the literature. These metal meshes may have applications in transparent electrodes, EMI shielding, solar cells, and organic light-emitting diodes.

A Flexible Silver‐Hollow‐Fiber Film by Blow‐Spinning and UV‐Induced Microstructural Engineering for High‐Efficiency Electromagnetic Interference Shielding

AbstractAs the prevalence of electromagnetic interference (EMI) continues to rise, there is a growing demand for shielding materials, which play a crucial role in electronic devices, communication systems, health protection, etc. However, conventional EMI shielding materials encounter difficulties in effectively addressing the escalating intricacies of electromagnetic environments and diverse shielding scenarios, wherein foldability, flexibility, and lightweight are desired. In this work, a novel EMI shielding material, silver‐hollow‐fiber (AgHF), is developed by combining blow‐spinning, UV radiation, and temperature‐controlled annealing technologies. During the fabrication process, UV radiation is used to selectively reduce silver ions on the outer surface of precursor fiber, and temperature‐controlled annealing is further employed to remove the inside polymer, forming a hollow fiber structure. The AgHF exhibits superior flexibility, lightweight, remarkable mechanical stability, and excellent EMI shielding efficiency (SE). Particular, the AgHF with a thickness of 163 µm demonstrates an EMI SE of 101.65 dB, and with minimal degradation of less than 10% even after undergoing 2000 bending cycles. The remarkable EMI shielding performance, combined with the lightweight, flexibility, and mechanical stability of AgHF, positions it as a highly promising material for a wide range of EMI shielding applications in the future.

MOF@wood Derived Ultrathin Carbon Composite Film for Electromagnetic Interference Shielding with Effective Absorption and Electrothermal Management

AbstractRecently, there has been a growing demand for ultra‐thin carbonized wood films (CWF) with high shielding efficiency (SE) to replace non‐renewable alternatives. Researchers aim to enhance electromagnetic (EM) wave absorption and improve electromagnetic interference (EMI) SE in CWF materials to reduce secondary pollution from reflected EM waves. In this work, the carbonized wood composite film (CWF/EP/Co) with a thickness of 120 µm through the process of hot‐pressing and carbonizing wood soaked in a mixed solution of water‐borne epoxy (EP) and Co/Zn‐MOF (ZIF‐67/8) is obtained. The CWF/EP/Co film exhibits excellent conductivity (105 S cm−1) and demonstrates an excellent EMI SE (73 dB) at a 200 µm thickness. Remarkably, the specific EMI shielding effectiveness (SSE/t) of CWF/EP/Co films reached 15833.3 dB·cm2·g−1 in the X‐band, making it the highest reported value among all wood‐derived EMI shielding materials. CWF/EP/Co films have a high absorption coefficient (A) of 0.4, indicating their effectiveness in absorbing EM waves. Furthermore, the EMI shielding effect of the large‐scale wallpaper (170 mm×170 mm) is confirmed by finite element analysis. Additionally, the CWF/EP/Co film exhibits good mechanical properties and effective Joule heating performance. This shielding film shows promise in applications such as buildings and smart homes, providing EMI shielding and warming effects.

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.

Silver Meshes for Record-Performance Transparent Electromagnetic Interference Shielding.

We present a simulation and experimental study of silver meshes to determine their performance for transparent electromagnetic interference (EMI) shielding. Simulations were employed to study the effects of the silver mesh's width, pitch, and thickness on EMI shielding efficiency (SE) in the 8-18 GHz frequency range and transparency in the visible spectrum. We demonstrate a scalable, facile fabrication method that involves embedding meshes in glass by etching trenches in glass and filling and curing reactive particle-free silver ink in these trenches. Our silver meshes achieve 58.4 dB EMI SE with 83% visible light transmission and 48.3 dB EMI SE with 90.3% visible transmission. The combination of high-conductivity silver, small widths (1.3 to 5 μm), and large thicknesses (0.5 to 2.0 μm) enables the best performance of metal meshes as well as single-sided shielding materials for transparent EMI shielding, as reported in the literature.

Eco-friendly and multifunctional aluminum flake/carbon fiber/cellulose composite papers with electromagnetic interference shielding

Recycling every viable material to produce new value-added products not only reduces waste, but also provides an opportunity to create sustainable and innovative solutions while preserving our natural resources. With this motivation, electrically conductive one-dimensional carbon fibers and two-dimensional aluminum flakes reinforced cellulose matrix composite papers were manufactured using recycled materials with a scalable, eco-friendly, and low-cost papermaking process. The designed composite paper showed 36.1 dB electromagnetic interference shielding efficiency (EMSE) with an absorbance-dominated performance by absorbing 98.85% of electromagnetic waves. An efficient impedance matching was obtained on the composite paper surface using reinforcements with different morphologies. Cellulose paper samples were converted to electrically conductive composites (0.415 S/cm), and the electrical conductivity was altered by tailoring the reinforcement ratios. Thermo-mechanical test results revealed that the cellulose matrix’s storage modulus was increased from 1.44 to 2.1 GPa with a 46.5% improvement. The composite cellulose paper represented increased hydrophilicity with higher porosity. The environmentally friendly composite paper responses to the escalating environmental worries and possesses a tremendous possibility of being utilized as an electromagnetic shielding material.

Dopant Engineering of Flexible MNPs/TPU/PPy Core-Shell Films for Controllable Electromagnetic Interference Shielding.

Intrinsically conductive polymers have attracted much attention in the electromagnetic interference (EMI) shielding field because of their high conductivity and favorable flexibility. Delocalized π-electrons migrating along the conjugated long-chain structures can form a current. Based on this special conductive mechanism, the doping process significantly influences the conductivity and EMI shielding efficiency (SE). However, it is challenging to investigate the influence of the doping process on EMI shielding performance, which would enable the optimization of dopant selection. In this study, dopant engineering was explored for controllable conductivity, EMI SE, and mechanical properties. Polypyrrole (PPy) doped with various dopants serves as a conductive coating owing to its adjustable conductivity and abundant functional groups. Elastic thermoplastic polyurethane was chosen as the porous framework because of its high tensile strength, and magnetic nanoparticles supplied the magnetic loss in the 3D network. Eventually, the composite film showed the best properties when PPy was doped with sodium p-toluenesulfonate. The film exhibited an average SE of 26.3 dB in the X band and a specific SE of 1563.17 dB cm2 g-1 with a thickness of merely 0.2 mm. This film withstood a tensile stress of 16.0 MPa, while the breaking elongation ratio reached 538.0%. After 10,000 cyclic bending, 92.3% of the EMI shielding property was retained. In summary, this study highlights the most suitable dopant for EMI shielding applications and provides a prospective alternative for advanced, flexible, and smart devices.

Nanostructured Films of Ordered Fe Nanowires for High-Performance Transparent Electromagnetic Interference Shielding

Although metal nanowires (NWs), such as silver NWs, are ideal materials for flexible transparent electromagnetic shielding films, the challenge of obtaining absorptive shielding films with high transmittance and shielding efficiency (SE) still exists. To address this issue, this study used iron nanowires (Fe NWs) with excellent microwave absorbing properties to construct structures with ordered NW distributions. A series of polyethylene terephthalate (PET)/Fe NWs/poly (3,4-ethylenedioxythiophene) (PEDOT) electromagnetic interference (EMI) shielding films were prepared using the magnetic-field-induced orientation. The results demonstrate that the ordered Fe NW network structure can effectively overcome the problem of the trade-off between light transmittance and EMI SE. Specifically, at a Fe NW surface density of 201.78 mg/m2, the ordered PET/Fe NWs/PEDOT films demonstrated a 49.06% increase in light transmittance and a 32.94% increase in EMI SE (19.37 dB), compared to the films with randomly distributed Fe NWs. Furthermore, constructing a double-layer Fe NW network with a stagger angle of 45° at the same surface density increased the EMI SE by 73.2% relative to the monolayer-ordered Fe NW structure, reaching an SE value of 33.54 dB, while maintaining almost unchanged light transmittance. Additionally, the PET/Fe NWs/PEDOT films maintain 97.4% of EMI performance after 3000 bending cycles. Overall, this study provides a new approach for creating high-performance flexible transparent EMI shielding films.

Poly(L-lactic acid)/graphene composite films with asymmetric sandwich structure for thermal management and electromagnetic interference shielding

The blowout growth of the power density and transmission efficiency of microelectronic devices makes the problems of “overheating” and electromagnetic pollution of electronic devices increasingly prominent, and it is raising an urgent demand to improve the thermal conductivity and electromagnetic interference (EMI) shielding performance of packaging materials. Additionally, the environmental damage caused by fossil-based electronic waste should not be ignored. Hence, a scalable production strategy was proposed to prepare sandwich structure poly(L-lactic acid) (PLLA) composite films with high thermal conductivity and excellent EMI shielding efficiency (SE), which was achieved via solution pouring method and stacking hot-pressing process, in which PLLA/graphene nanoplatelets (PLLA/GNPs) with different GNPs contents was the top and substrate layers, and PLLA/poly(D-lactic acid)/Fe3O4 (PLLA/PDLA/Fe3O4) with a small amount of PDLA and Fe3O4 was the middle layer. Owing to the asymmetric distribution of filler and the successful introduction of magnetic particles, when the GNPs and Fe3O4 contents of the whole film are respectively only 5.61 wt% and 4.39 wt%, and the asymmetric ratio is 1:9, the in-plane thermal conductivity (K‖) and EMI SE of the composite film reaches 7.49 W m−1 K−1 and 41.7 dB, respectively, higher than those of PLLA film with symmetric structure (3.31 W m−1 K−1 and 33.0 dB) at the same contents of fillers. Furthermore, a small amount of PDLA (4.39 wt%) promotes the formation of stereocomplex (SC) crystallites in the middle layer and further induces the interlayer SC microcrystals during the stacking hot-pressing process, enhancing the interlayer interaction to maintain the mechanical robustness of the PLLA film. This work provides a new direction for the manufacture of polymer based composite films with high thermal conductivity and directional EMI shielding, and has broad application potential in the field of large-scale production of green electronic products.

Conformal Passivation of Self-Cleanable, Flexible, and Transparent Polytetrafluoroethylene Thin Films on Two-Dimensional MXene and Three-Dimensional Ag Nanowire Composite Electrodes

Despite the excellent performance of MXene–Ag nanowire (MA) composite transparent conductive electrodes (TCEs), they rapidly and severely degrade in ambient and humid environments. To address this critical issue, we developed conformal polytetrafluoroethylene (PTFE) passivation thin films prepared using magnetron sputtering at room temperature. Compared to the PTFE passivated electrode, the nonpassivated bare MA-composite electrode exhibited a considerably increased sheet resistance, and the electrode flexibility and electromagnetic interference (EMI) shielding efficiency (SE) degraded rapidly over time because the moisture and impurities severely oxidized the MXene layer in the harsh testing environment. However, the MA-composite electrode with PTFE passivation shows constant sheet resistance, transmittance, flexibility, and EMI SE, even after the 85 °C–85% relative humidity (RH) test. Compared to the nonpassivated MA-electrode-based thin film heaters (TFHs), the PTFE-passivated MA-composite electrode-based TFHs exhibited improved stability and reliability, indicating that the sputtered PTFE film effectively prevented the moisture and impurity penetration of the MA-composite electrodes.

High-performance transparent electromagnetic interference shielding film based on metal meshes

Transparent electromagnetic interference (EMI) shielding films have gained considerable attention for the commercialization of the 5G wireless technology based on electromagnetic waves in the GHz range. In this study, transparent EMI shielding films with embedded metal meshes on a 100 μm thick polyethylene terephthalate film for EMI shielding were fabricated using ultraviolet imprinting and Ag paste filling techniques. The various EMI shielding film types were fabricated by varying the width, aperture size, and height of the mesh electrode to evaluate the efficiency of the EMI shielding according to the incident electromagnetic wave frequency and morphology of the mesh metallic electrodes. The results indicate that the EMI shielding efficiency (SE) increased with a decrease in the aperture size of the metal mesh electrodes and an increase in their height. The average EMI SE values of the fabricated film in the 0.5–18 GHz range reached 48.3 dB and 59.6 dB at a light transmittance of approximately 90% and 77%, respectively. The fabricated EMI shielding films can be used for various applications, such as communications, aerospace, medical equipment, and military.

Development of Electromagnetic-Wave-Shielding Polyvinylidene Fluoride-Ti3C2Tx MXene-Carbon Nanotube Composites by Improving Impedance Matching and Conductivity.

Absorption-dominated electromagnetic interference (EMI) shielding is attained by improving impedance matching and conductivity through structural design. Polyvinylidene fluoride (PVDF)-Ti3C2Tx MXene-single-walled carbon nanotubes (SWCNTs) composites with layered heterogeneous conductive fillers and segregated structures were prepared through electrostatic flocculation and hot pressing of the PVDF composite microsphere-coated MXene and SWCNTs in a layer-by-layer fashion. Results suggest that the heterogeneous fillers improve impedance matching and layered coating, and hot compression allows the MXene and SWCNTs to form a continuous conducting network at the PVDF interface, thereby conferring excellent conductivity to the composite. The PVDF-MXene-SWCNTs composite showed a conductivity of 2.75 S cm-1 at 2.5% MXene and 1% SWCNTs. The EMI shielding efficiency (SE) and contribution from absorption loss to the total EMI SE of PVDF-MXene-SWCNTs were 46.1 dB and 85.7%, respectively. Furthermore, the PVDF-MXene-SWCNTs composite exhibited excellent dielectric losses and impedance matching. Therefore, the layered heteroconductive fillers in a segregated structure optimize impedance matching, provide excellent conductivity, and improve absorption-dominated electromagnetic shielding.

Superior mechanical, electrical, dielectric, and EMI shielding properties of ethylene propylene diene monomer (EPDM) based carbon black composites.

In this study, the mechanical, electrical, dielectric, and electromagnetic interference (EMI) shielding properties of ethylene propylene diene monomer (EPDM) based carbon black composites, namely high abrasion furnace (HAF) and conductive Printex blacks, were investigated and their effectiveness compared. The results show that Printex black filled composites exhibited superior properties in all aspects compared to HAF filled composites. The electrical percolation threshold value of Printex black filled composites was approximately 1/2 to 1/3 lower compared to HAF black filled composites based on classical theory and the Sigmoidal model. Moreover, the tensile modulus, dielectric permittivity, and EMI shielding efficiency (SE) of the Printex black filled composites were 4.6 times, in the order of 106 at 1 kHz, and 6.65 times improved compared to HAF black filled composites at their 40 phr loadings, respectively. The Printex black filled 40 phr loaded composite showed an EMI SE of 49.94 dB that is 99.999% the attenuation of EM radiation. These properties can be attributed to the high structure of Printex black, which facilitates the ease of formation of the conductive channel through the polymer matrix, higher reinforcement, higher interfacial polarization, and high absorption of radiation. These properties were compared with some published literature on carbon black filled composites and it was found that the results of the Printex black filled composites are highly competitive with the published work. The results show that these composites are highly effective for load bearing materials, supercapacitors, and EM radiation protection.

Silver-Sandwiched Natural Rubber/St-LDH/MWCNT Hybrid Bio-Nano-Composite System as a High-Performing Multimedia Laminated Electromagnetic Interference Shield Through a Tripling Mechanism

High-performance electromagnetic interference (EMI) shields are extremely important to protect human beings and sophisticated electronic devices from harmful EM radiation emissions in this digital age. Herein, a novel multimedia laminated system based on silver nanosheet-sandwiched natural rubber/stearic acid-modified layered double hydroxide/multiwalled carbon nanotube hybrid bio-nano-composites [NR/St-LDH/MWCNT]-Ag-[NR/St-LDH/MWCNT] has been fabricated successfully. The fabricated nanocomposite presents a remarkably high electromagnetic interference shielding efficiency (EMI-SE) of −28 dB in the absence of a silver sheet and an enhanced EMI-SE of −84 dB in the presence of a silver nanosheet. The very low percolation threshold of MWCNT (0.009) and the maximum dielectric strength of the NR/St-LDH/MWCNT hybrid biocomposite (15,556) satisfied the criteria for the composite to act as an EMI shield. The mechanism behind this significant enhancement that is tripling in the EMI-SE value of this novel hybrid material is analyzed in detail. An EM absorption process through an innovative tripling mechanism is proposed for the first time by interpreting experimental results. In the tripling mechanism, the first hybrid nanocomposite sheet absorbs radiation and the light thence transmitted from the first sheet is reflected back to the same sheet by the sandwiched silver sheet for further absorption and the residual light transmitted from the silver sheet is absorbed by the second hybrid nanocomposite sheet. The absorbing efficiency of the silver-sandwiched system was found to be 99.999%, which is a shred of solid evidence for the tripling mechanism. Further, detailed physico-chemical and EMI shielding efficiency measurements indicate that the proposed hybrid material can be used as a very smart, lightweight shielding material for future EMI shielding applications.

Smart membrane absorbing electromagnetic waves based on polyvinyl chloride/graphene composites

The rapid proliferation and intensive use of electronic devices have led to an increase in electronic pollution, such as electronic noise, electromagnetic interference (EMI), and radiofrequency interference (RFI), which cause malfunctions of electronic devices. The emergence of flexible polymer composites has a remarkable potential for electromagnetic shielding depending on their unique characteristics, such as their electrical, thermal, mechanical, and magnetic properties, which are very useful for suppressing electromagnetic noise. Graphene (G) and its composites can serve as better shielding materials against these interferences due to their lightweight and high corrosion resistance. Researchers are still grappling with the need for flexible and scalable smart composite materials to prevent radioactive pollution from electronic devices. The inclusion of next-generation graphene (G) conductive fillers loaded with polyvinyl chloride (PVC) /graphene is the subject of our current research (G). Due to the absorption-dominated shielding process, the composite has an extraordinarily low percolation threshold and a high shielding efficiency (SE) against electromagnetic interference (EMI).The distribution and dispersion patterns of graphene particles in the matrix phase were validated by SEM electron micrographs. The composite, which contains just 40% graphene by weight, has an EMI SE value of 26 dB in the frequency range of 10 to 15 GHz and is only 2 mm thick.In this case, we believe that promoting a scalable and industrially viable G/PVC composite, which is a novel and strong candidate in the burgeoning field of high-stress electromagnetic shielding applications in the future, is the best option.

The evaluation of microstructure of carbon/carbon composites generated by ultra-high temperature treatment towards excellent electromagnetic interference shielding property

Due to the need of electromagnetic shielding materials for satellites, carbon/carbon (C/C) composites have become a research focus due to their excellent properties. In this study, the ultrahigh treatment temperature was raised from 2500 °C to 2700 °C and 3000 °C, and the influence of micromorphology on the mechanical and electromagnetic shielding properties of materials was explored with an innovative image recognition method. The porosity of the C/C composites increased with increasing heat treatment temperature, from 6.95% to 8.65% after 3000 °C. The density decreased, and the graphitization degree increased gradually, indicating an improvement in the texture order degree. For the compression properties of the material, the Z direction after treatment at 3000 °C maintained a high compressive strength of 171 MPa. The electromagnetic interference (EMI) shielding efficiency (SE) of the C/C composites, which is completely consistent with the trend of electrical conductivity, increased with increasing heat treatment temperature, and the EMI SE of the C/C composites reached ∼80 dB after 3000 °C. It was found that reflection was the dominant EMI shielding mechanism of C/C composite materials. By comparing the comprehensive data indexes of C/C composites with other materials, the composites are expected to be a new generation of satellites with electromagnetic shielding material.

A New Strategy of 3D Printing Lightweight Lamellar Graphene Aerogels for Electromagnetic Interference Shielding and Piezoresistive Sensor Applications

AbstractLamellar 3D structures are beneficial to raise the electrical properties of graphene aerogels like electrical conductivity, electromagnetic interference (EMI) shielding efficiency (SE) and pressure sensitivity. In this paper, a strategy of 3D printing lamellar graphene aerogel (LGA) based on shear‐thinning and ice‐growth‐inhibition mechanisms is demonstrated. A well‐designed slit extrusion printhead is used to produce shear thinning graphene oxide (GO) water‐based dispersions. Tert‐butyl alcohol is added into GO water‐based dispersions to inhibit ice growth which will destroy the GO flakes arrangement. After freeze‐drying and chemical reduction of the printed GO samples, the lightweight LGAs are prepared. Comparing to the traditional way, the strategy in this paper shows much better size and shape scalable freedom. The LGA exhibits electrical conductivity up to 705.6 S m−1, which is rather high for graphene‐based aerogels. Benefiting from the lamellar structure and high electrical conductivity, the aerogel achieves up to 68.75 dB EMI SE at X‐band with the thickness of 3 mm, while the absolute EMI SE can reach up to 15351.9 dB cm3 g−1. The LGA can also be used as a piezoelectric pressure sensor, which exhibits high compressible stress and rapid response time.