Specific Electromagnetic Interference Shielding Effectiveness Research Articles

Lightweight polyimide/silica aerogel composite foams and their derived carbon foams for excellent flame retardancy, thermal insulation and EMI shielding performance

Multifunctional porous materials demonstrate ubiquitous applications in the fields of flame retardancy, thermal insulation and electromagnetic interference (EMI) shielding. In this work, a series of lightweight polyimide/silica aerogel (PIF/SiA) foams with exceptional thermal stability, flame retardancy and thermal insulation performance were prepared by employing microwave-assisted foaming and thermal imidization treatment, using polyester ammonium salt/silica aerogel (PEAS/SiA) powders as the derivative precursors. The limiting oxygen index and fire growth rate reached as high as 58.2 % and as low as 0.1 kW/(m2·s) for PIF/SiA composite foams, respectively, which was a result of the formation of micro/nano multi-scale pore structure of PIF skeleton and the “pearl-necklace-like” skeletal network of nano SiA. In addition, the PIF/SiA composite foams exhibited excellent thermal insulation and infrared stealth performance, which demonstrate a potential for long service life in fire protection use. Furthermore, the carbonized PIF/SiA (i.e., PICF/SiA) foams possessed enhanced mechanical (improvement of 117.6 %) and EMI shielding performance (specific EMI shielding effectiveness: 8541.9 dB/(g/cm2)) when compared with the original PIF/SiA composite foams. To sum up, a facile method was proposed to fabricate multifunctional PIF-based composite foams and their derived carbon foams for flame retardancy, thermal insulation and EMI shielding applications in high-end engineering sectors.

A Highly Deficient Medium-Entropy Perovskite Ceramic for Electromagnetic Interference Shielding under Harsh Environment.

Materials that can provide reliable electromagnetic interference (EMI) shielding in highly oxidative atmosphere at elevated temperature are indispensable in the fast-developing aerospace field. However, most of conductor-type EMI shielding materials such as metals can hardly withstand the high-temperature oxidation, while the conventional dielectric-type materials cannot offer sufficient shielding efficiency in gigahertz (GHz) frequencies. Here, a highly deficient medium-entropy (ME) perovskite ceramic as an efficient EMI shielding material in harsh environment, is demonstrated. The synergistic effect of entropy stabilization and aliovalent substitution on A-site generate abnormally high concentration of Ti and O vacancies that are stable under high-temperature oxidation. Due to the clustering of vacancies, the highly deficient perovskite ceramic exhibits giant complex permittivity and polarization loss in GHz, leading to the specific EMI shielding effectiveness above 30dB/mm in X-band even after 100 h of annealing at 1000°C in air. Along with the low thermal conductivity, the aliovalent ME perovskite can serve as a bifunctional shielding material for applications in aircraft engines and reusable rockets.

A Sandwich Structural Filter Paper-AgNWs/MXene Composite for Superior Electromagnetic Interference Shielding.

A thin, lightweight and flexible electromagnetic interference (EMI) shielding paper composite is an urgent need for modern military confrontations. Herein, a sandwich-structured EMI shielding paper composite with an easy pavement consisting of a filter paper layer, middle AgNWs/MXene layer, and polyvinyl butyral (PVB) layer was constructed by vacuum-assisted filtration, spraying and air-drying. The middle AgNWs/MXene compound endowed the filter paper with excellent electrical conductivity (166 S cm-1) and the fabricated filter paper-AgNWs/MXene-PVB composite exhibits superior EMI shielding (30 dB) with a 141 μm thickness. Remarkably, the specific EMI shielding effectiveness (SSE/t) of the filter paper-AgNWs/MXene-PVB composite reached 13,000 dB cm2 g-1 within the X-band frequency range. This value represents one of the highest reported for cellulose-based EMI shielding materials. Therefore, our sandwich-structured filter paper composite with superior EMI shielding performance can be used in the medical and military fields.

Flexible and Robust Core-Shell PANI/PVDF@PANI Nanofiber Membrane for High-Performance Electromagnetic Interference Shielding.

Developing high-performance electromagnetic interference (EMI) shielding materials that are lightweight and flexible and have excellent mechanical properties is an ideal choice for modern integrated electronic devices and microwave protection. Herein, we report the preparation of core-shell polyaniline (PANI)-based nanofiber membranes for EMI shielding through seed polymerization. Electrospinning a PANI solution leads to homogeneously dispersed PANI on the nanofiber surface, with abundant attachment sites for aniline through electrostatic adsorption and hydrogen bonding interaction, allowing PANI to grow on the nanofiber surfaces. This stable core-shell heterostructure provides more interfaces for reflecting and absorbing microwaves. The PANI/PVDF@PANI membranes achieved a shielding efficiency (SE) of 44.7 dB at a thickness of only 1.2 mm, exhibiting an exceptionally high specific EMI shielding effectiveness (SE/t) of 372.5 dB cm-1. Furthermore, the composite membrane exhibits outstanding mechanical stability, durability, air permeability, and moisture permeability, also making it suitable for applications such as EM shielding clothing.

Morphology dependent EMI shielding performance of Ag-Ni core-shell nanowires

The proposed work reports a facile chemical reduction method for synthesizing the hierarchical silver-nickel core-shell nanowire structures with controllable morphologies by varying the Ag concentration. The growth of Ni shells around the Ag core to make thorny and smooth Ag-Ni core-shell nanowires is studied for addressing electromagnetic interference (EMI). The synthesized Ag-Ni nanowires show better EMI shielding effectiveness (SE) than Ni nanowires with much-improved absorption loss (SEA). Due to high electrical conductivity (8630 S cm−1), magnetic permeability (44.1 emu/g), and heterojunction core-shell interfaces, the bimetallic nanowires flakes exhibit exceptional average EMI SE of 90.5 dB in the X-band frequency range (8–12 GHz) with a thickness of 0.11 mm, taking specific EMI SE to 822.72 dB/mm. In addition, the EMI shielding performance of the smooth Ag-Ni nanowires showed a 45% enhancement in SEA with marginal change in reflection loss (SER) compared to the thorny ones, indicating high absorption of EM waves. The unique core-shell nanowires with high aspect ratio with tunable physical properties can be ideal candidates for futuristic applications in microwave absorption and electromagnetic interference shielding.

Mechanical, Crystallization, Rheological, and Supercritical CO2 Foaming Properties of Polybutylene Succinate Nanocomposites: Impact of Carbon Nanofiber Content.

As a substitute for conventional polymers for the preparation of biodegradable microcellular polymeric foams, polybutylene succinate (PBS) presents one of the most promising alternatives. However, the low melt strength of PBS makes it difficult to produce high-performance microcellular foams. This study aimed to improve the melt strength of PBS and explore the mechanical, thermal, crystalline, rheological, and supercritical CO2 foaming properties of PBS nanocomposites by using carbon nanofibers (CNFs). This study found that nanocomposites containing 7 wt% CNF exhibited the highest tensile strength, Young's modulus, and bending strength. Moreover, the CNF nanofillers were well dispersed in the PBS matrix without significant agglomeration, even at high filler concentrations. Furthermore, the nanocomposites demonstrated improved melting temperature and crystallinity compared with pure PBS. The rheological analysis showed that the addition of CNFs significantly increased PBS viscosity at low frequencies due to the interaction between the PBS molecular chains and CNFs and the entanglement of CNFs, resulting in a more complete physical network formation when the CNF content reached above 3 wt%. During the supercritical CO2 foaming process, the addition of CNFs resulted in increased cell density, smaller cells, and thicker cell walls, with good laps formed between the fibers on the cell walls of nanocomposite foams. Moreover, the electrical conductivity and electromagnetic interference (EMI) shielding properties of the foamed material were studied, and a nanocomposite foam containing 7 wt% CNF showed good electrical conductivity (4.5 × 10-3 S/m) and specific EMI shielding effectiveness (EMI SE) (34.7 dB/g·cm-1). Additionally, the nanocomposite foam with 7 wt% CNF also exhibited good compression properties (21.7 MPa). Overall, this work has successfully developed a high-performance, multifunctional PBS-based nanocomposite foam, making it suitable for applications in various fields.

Construction of strong and superhydrophobic MXene composite films by binary organosilane cross-linking for electromagnetic interference shielding and joule heating

Transition-metal carbide and/or nitride (MXene) with outstanding electrical conductivity and surface chemistry tunability shows great potential for constructing high-performance electromagnetic interference (EMI) shielding materials. Unfortunately, MXene has poor mechanical properties and ambient stability, limiting its practical applications. In this work, strong and superhydrophobic MXene/carboxymethylcellulose sodium (S-MC) composite films were prepared by blade coating followed by binary organosilane modification. Through the joint contributions of hydrogen-bonding interaction, alignment, and organosilane cross-linking of MXene nanosheets, the proposed S-MC films achieved outstanding mechanical properties and EMI shielding performance. For instance, the S-MC composite film containing 90 wt% MXene content demonstrated high specific EMI shielding effectiveness (152 069 dB/cm) and strong tensile strength (181.5 MPa), surpassing those of other reported MXene-based shields. The S-MC films also had excellent Joule heating performance with low applied voltage and quick thermal response. Furthermore, the binary organosilane cross-linking endowed the S-MC films with superhydrophobic properties by inducing rough surface and low surface energy, resulting in stable conductivity and EMI shielding performance in oxidizing and aqueous environments. The developed S-MC films showed enormous potential applications for EMI shielding and Joule heating. Our study offers a novel and scalable strategy to construct strong, stable, and multifunctional MXene-based composites.

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.

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.

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.

Electrostatic induced self-assembled MXene/EPOSS for high-performance electromagnetic interference shielding materials

It is still a challenge to prepare flexible electromagnetic interference (EMI) shielding materials based on Ti3C2Tx MXene through a facial and scalable method. In this study, epoxied octamethyl-cyclotetrasiloxane (EPOSS) was self-assembled with Ti3C2Tx to construct EMI shielding composites via facial spraying coating. Because the EPOSS decreased the surface free energy of Ti3C2Tx in the acid-base component, the Ti3C2Tx/EPOSS suspension was able to be sprayed on carboxylated polybutadiene (CPB) uniformly. Molecular dynamics (MD) simulations were explored to demonstrate the interaction energy between EPOSS and CPB with different –COOH contents. The prepared EMI shielding composite has high abrasion resistance and good bending durability because EPOSS reinforced the interface interaction between Ti3C2Tx and CPB through covalent bonds. Based on a pre-stretching spray method, the prepared composite has high surface roughness, leading to a high specific EMI shielding effectiveness of 1800 dB cm2 g−1 at a low Ti3C2Tx loading of 8.5 wt%. Additionally, the physically protective effect of Si–O–Si cages in EPOSS provided good flame retardancy. Therefore, the proposed EPOSS-assisted Ti3C2Tx spraying strategy could prepare EMI shielding materials with high effectiveness, excellent abrasion resistance, and good flame retardancy, which has a broad prospect for the application of high-power, portable, and wearable flexible electronic devices.

Scalable Production of Catecholamine-Densified MXene Coatings for Electromagnetic Shielding and Infrared Stealth.

Processing transition metal carbides/nitrides (MXenes) inks into large-area functional coatings expects promising potential for electromagnetic interference (EMI) shielding and infrared stealth. However, the coating performances, especially for scalable fabrication techniques, are greatly constrained by the flake size and stacking manner of MXene. Herein, the large-area production of highly densified and oriented MXene coatings is demonstrated by engineering interfacial interactions of small MXene flakes with catecholamine molecules. The catecholamine molecules can micro-crosslink MXene nanosheets, significantly improving the ink's rheological properties. It favors the shear-induced sheet arrangement and inhibition of structural defects in the blade coating process, making it possible to achieve high orientation and densification of MXene assembly by either large-area coating or patterned printing. Interestingly, the MXene/catecholamine coating exhibits high conductivity of up to 12 247 S cm-1 and ultrahigh specific EMI shielding effectiveness of 2.0 ×10 5 dB cm2 g-1 , obviouslysuperior to most of the reported MXene materials. Furthermore, the regularly assembled structure also endows the MXene coatings with low infrared emissivities for infrared stealth applications. Therefore, MXene/catecholamine coatings with ultraefficient EMI shielding and low infrared emissivity prove the feasibility of applications in aerospace, military, and wearable devices.

Flexible and ultrathin GO@MXene sandwich-type multilayered film toward superior electromagnetic interference shielding in a wide gigahertz range of 3.95–18.0 GHz

Conductive MXene-based films are potential in electromagnetic interference (EMI) shielding. However, multilayered MXene-based films are rarely reported, and the EMI shielding investigations are confined in only X band (8–12 GHz). Herein, sandwich-type multilayered [email protected] films were constructed by an alternating vacuum-assisted filtration technique. Benefiting from interlayer scattering and high conductivity, the flexible multilayered [email protected] films show excellent EMI shielding performance in 3.95–18.0 GHz at an ultrathin film thickness. The mechanical properties and EMI shielding performance are related to the layered structure, film thickness and content of MXene. Especially, the trilaminar [email protected] film (only ∼8 µm) shows superior EMI shielding and mechanical properties. The average EMI shielding effectiveness (SE) values are 44.5, 46.6 and 45.0 dB at C, X and Ku bands, respectively, with the corresponding specific EMI SE values of 22,429.4, 23,487.9 and 22,681.5 dB cm2 g−1. The [email protected] film exhibits remarkable stability in acid, alkaline and organic solvent. This work not only provides a flexible film with high EMI shielding performance at a wide gigahertz range, but also suggests that the mechanical properties and EMI shielding can be tuned by simply changing the layered structure. This is helpful to give guidance to the design of novel MXene-based EMI shielding films and expand their applications.

Highly conductive polystyrene/carbon nanotube/PEDOT:PSS nanocomposite with segregated structure for electromagnetic interference shielding

Highly conductive polymer nanocomposites (CPNs) are promising alternatives to metals for electromagnetic interference (EMI) shielding applications. However, constructing a well-established conductive network within a polymer matrix using conventional processes is still challenging. This research aimed to improve the EMI shielding performance of CPNs by developing highly conductive segregated structures through a facile innovative dispersion mixing process. The nanocomposites were fabricated by dispersing polystyrene beads (PS), CNT, and PEDOT:PSS in deionized water, followed by vacuum filtration, solvent treatment, and hot press molding. The employed technique effectively constructed a highly conductive network in the PS/CNT nanocomposite, resulting in the lowest ever reported percolation threshold of 0.009 vol% among CNT-based segregated structures. Moreover, adding PEDOT:PSS to the nanocomposite as an additional constituent significantly promoted the conductive network by improving the dispersion of CNTs and the interparticle contact. The PS/CNT/PEDOT:PSS (100:2:4 w/w/w) exhibited a high electrical conductivity of 2.352 S/cm with notable specific EMI shielding effectiveness (SE) of 55.7 dB/mm (with dominant absorption mechanism), which is among the best performance reported for CNT-based conductive segregated structures, to the best of our knowledge. In brief, this work proposed a novel approach of using a facile, cost-effective, and eco-friendly method to fabricate highly CPNs for EMI shielding applications.

Ti3C2Tx MXene/polyimide composites film with excellent mechanical properties and electromagnetic interference shielding properties

With the development of electronic products to miniaturization and high frequency, high-performance flexible electromagnetic interference (EMI) shielding materials are urgently needed to deal with electromagnetic pollution. Two-dimensional transition metal carbide/polyimide (Ti3C2Tx MXene/PI) films were synthesized by in situ polymerization and a simple scratch method in this paper. The Ti3C2Tx MXene nanosheets give the films good EMI shielding effectiveness (SE) and electrical conductivity. Specifically, the film with a thickness of 0.11 mm (Ti3C2Tx content of 30 wt%) exhibits an EMI SE of 34.73 dB and a specific EMI SE (SE/thickness) of 315.73 dB/mm in the frequency range of 8.2–12.4 GHz (X-band). In addition, the films have a tensile strength of 67.58 MPa, and a high decomposition temperature of 510 ℃ in N2 atmosphere. Therefore, we believe that the prepared Ti3C2Tx/PI films with good comprehensive performance have enormous potential in the field of lightweight and flexible EMI shielding materials.

Highly aligned reduced graphene oxide in alumina composites for strengthening, toughening, and electromagnetic interference shielding

Engineering ceramics with high strength, toughness and electromagnetic interference (EMI) shielding effectiveness (SE) are highly desirable as electromagnetic protecting material in harsh environment. Herein, we show that both excellent mechanical and EMI shielding performance can be realized in alumina composites embedded with highly aligned reduced graphene oxide (RGO), which are readily prepared via sintering of core-shell structured RGO@Al2O3 nanoplates with pressure. Compared to monolithic Al2O3, the highly aligned RGO/Al2O3 composites show simultaneously improved strength and toughness up to ∼26.1% and ∼60.2%, respectively. The steeply rising R-curve behavior proves the better crack tolerance in the highly aligned structure with respect to randomly oriented one. Moreover, the RGO/Al2O3 composites also exhibit a high specific EMI SE reaching ∼34 dB/mm in K band, due to the reflection and highly enhanced absorption after percolation in the out-of-plane direction. These findings provide a novel strategy of designing mechanically reliable engineering ceramic for EMI shielding.

Ti3C2Tx MXene-Ferroferric Oxide/Carbon Nanotubes/Waterborne Polyurethane-Based Asymmetric Composite Aerogels for Absorption-Dominated Electromagnetic Interference Shielding

Absorption-dominated electromagnetic interference (EMI) shielding materials are more attractive to manage the increasing electromagnetic radiation pollution than conventional reflection-dominated counterparts due to their advantages of balancing the efficient EMI shielding performance while minimizing the secondary pollution of the reflected electromagnetic (EM) wave. Herein, we first fabricate ferroferric oxide/carbon nanotubes/waterborne polyurethane (Fe3O4/CNTs/WPU) aerogels and then coat Ti3C2Tx MXene at the bottom to construct an asymmetric structure. Moreover, the medium or transition layer is formed during the coating process of MXene-ferroferric oxide by the gravity and aerogel’s capillary action. This delicate design makes them with obvious absorption, transition, and reflection layers according to the progressive modular design principle. The composite aerogels show an average EMI shielding effectiveness (SE) of 20.06 dB, low reflectivity of 0.396, and specific EMI SE of SSE/t of 332.60 dB cm2 g–1 in the X-band when the MXene content is only 2.35 vol %. Additionally, the resultant aerogels exhibit remarkable flexible and mechanical properties, which could even bear weights of about 4500 times their own weight. In sum, this work provides a promising absorption-dominated EMI shielding candidate with flexible and high strength features.

High Value Utilization of Waste Wood toward Porous and Lightweight Carbon Monolith with EMI Shielding, Heat Insulation and Mechanical Properties.

With the increasing pollution of electromagnetic (EM) radiation, it is necessary to develop low-cost, renewable electromagnetic interference (EMI) shielding materials. Herein, wood-derived carbon (WC) materials for EMI shielding are prepared by one-step carbonization of renewable wood. With the increase in carbonization temperature, the conductivity and EMI performance of WC increase gradually. At the same carbonization temperature, the denser WC has better conductivity and higher EMI performance. In addition, due to the layered superimposed conductive channel structure, the WC in the vertical-section shows better EMI shielding performance than that in the cross-section. After excluding the influence of thickness and density, the specific EMI shielding effectiveness (SSE/t) value can be calculated to further optimize tree species. We further discuss the mechanism of the influence of the microstructure of WC on its EMI shielding properties. In addition, the lightweight WC EMI material also has good hydrophobicity and heat insulation properties, as well as good mechanical properties.

Lightweight MXene/carbon composite foam with hollow skeleton for air-stable, high-temperature-resistant and compressible electromagnetic interference shielding

Lightweight electromagnetic interference (EMI) shielding materials with temperature resistant and compressible performance are highly desirable for applications in harsh and complex environment. Herein, we report MXene/carbon composite foam with three-dimensional hollow skeleton structure and low MXene loading by self-assembly and low heating rate (1 °C/min) pyrolysis methods. The composite foam exhibits a density of as low as 5 mg cm−3 with only 3 wt% MXene loading. An average EMI shielding effectiveness (SE) of more than 25 dB over the whole X-band (8.2–12.4 GHz) and more than 30 dB covering the Ku-band (12.4–18 GHz) and the K-band (18–26.5 GHz) with 2 mm thickness are achieved. Benefiting from the low density, the corresponding specific EMI SE (SSE/t) is up to 27300 dB cm2 g−1, which is comparable to or even better than the values of many shielding materials. The foams still display excellent EMI shielding performance after exposure to air in ambient atmosphere (temperature: 25 °C, humidity: ∼30%) for a year or being heated to 210 °C, demonstrating an excellent air stability and temperature resistance. Furthermore, the MXene/carbon composite foam maintains the high EMI shielding performance after 1000 compressing-releasing cycles, demonstrating excellent compressibility.

Ultrathin Wood‐Derived Conductive Carbon Composite Film for Electromagnetic Shielding and Electric Heating Management

AbstractRecently, wood‐based composites have absorbed widespread concern in the field of electromagnetic interference (EMI) shielding due to their sustainability and inherent layered porous structure. The channel structure of wood is often used to load highly conductive materials to improve the EMI shielding performance of wood‐based composites. However, there is little research on how to use pure wood to prepare ultrathin EMI shielding materials. Herein, ultrathin veneer is obtained by cutting wood in parallel to the annual rings. Then, carbonized wood film (CWF) is prepared by a simple two‐step compressing and carbonization. The specific EMI shielding effectiveness (SSE/t) of CWF‐1200 with an ultrathin thickness (140 µm) and high electrical conductivity (58 S cm−1) can reach 9861.41 dB cm2 g−1, which is much higher than other reported wood‐based materials. In addition, the zeolitie imidazolate framework‐8 (ZIF‐8) nanocrystals are grown in situ on the surface of the CWF to obtain CWF/ZIF‐8. CWF/ZIF‐8 exhibits an EMI shielding effectiveness (SE) of up to 46 dB and an ultrahigh SSE/t value of 11 330.04 dB cm2 g−1 in X band. In addition, the ultrathin CWF also shows an excellent Joule heating effect. Therefore, the development of ultrathin wood‐based film provides a research basis for wood biomass to replace traditional non‐renewable and expensive electromagnetic (EM) shielding materials.