dB Cm2 Research Articles

Highly Conductive PEDOT:PSS Aerogels

AbstractPoly(3,4‐ethylenedioxythiophene):poly(4‐styrenesulfonate) (PEDOT:PSS) aerogel has attracted much attention in bioelectronics, electromagnetic shielding, and energy‐related systems due to its biocompatibility, intrinsic electronic conductivity, and favorable processability. However, fabrication of highly conductive and low‐density PEDOT:PSS aerogels is still challenging. In this work, highly conductive PEDOT:PSS aerogels are produced via ice‐templated pre‐assembly followed by a specially designed thawing process in H2SO4 solution. Upon optimization of heat and mass transfer during the thawing process, along with the unique ice template effect, the microstructure and thin walls of PEDOT:PSS frozen samples are well preserved. Importantly, the porous structure and thin walls facilitate diffusion of H2SO4 into polymer matrix, inducing phase separation of PEDOT:PSS, thus increasing PEDOT crystallinity and partially removing of PSS component. As a result, the as‐prepared pristine PEDOT:PSS aerogels exhibit a high electrical conductivity of 1200 ± 231 S m−1 along the freezing direction at a low density of 15.3 ± 1.5 mg cm−3, enhanced mechanical properties, and a competitive electromagnetic interference shielding efficiency of 25 115 dB cm2 g−1. Moreover, the compressed aerogels show good performances as active materials in symmetrical supercapacitors with thickness‐independent capacitance (maximum 2.1 F cm−2 at 1.0 mA cm−2) and in current collector‐free micro‐supercapacitors processed by laser carving.

Guar gum assisted synthesis of high‐quality silver nanoplates and their polyimide matrix nanocomposites for electromagnetic interference shielding applications

AbstractTwo‐dimensional (2D) silver nanoplates are chemically synthesized in the presence of guar gum – a naturally occurring biopolymer. The polymer directs anisotropic growth of silver nuclei into high aspect ratio nanoplates spanning 4500 ± 500 nm lateral length with thickness as small as 40 ± 10 nm. After a thorough investigation of the reaction parameters (temperature, precursor to reductant ratio, and polymer quantity) on the morphology of the product, a scalable synthetic protocol to achieve good yields (95%–98%) of highly pure (~100%) 2D silver nanoplates (AgNPls) in a facile, inexpensive, room temperature, aqueous phase chemical reaction of only about 5 min is devised. The optimized AgNPls induce appreciable conductivity of 5.5 ± 0.38 S/cm in polyimide at only 12 wt% loading. Consequently, the resulting polymer nanocomposite (containing 12 wt% AgNPls), at only 130 ± 15 μm thickness and 0.45 g/cm3 density, effectively blocks electromagnetic radiation in X‐band with a total shield effectiveness of about 10 dB resulting in substantially high specific shielding effectiveness and absolute shielding effectiveness of 22.48 and 1729.23 dB cm3 g−1, respectively. Additionally, the nanocomposites remain thermally stable up to 500°C in oxidative environment and possess an appreciably high storage modulus of 3.113 GPa at 50°C. These low‐density conductive polyimide films, therefore, present great prospects in shielding against electromagnetic interference under extreme conditions.

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.

3D Graphene Straintronics for Broadband Terahertz Modulation

AbstractThe increasing utilization of terahertz (THz) bandwidth in both industrial and private sectors highlights the significance of efficient terahertz shielding and absorption devices. These devices play a crucial role in safeguarding electronic components from disruptive effects and rendering objects less detectable by radar systems. However, the limited availability of materials and devices hinders progress in this field. In this study, a strain engineering route is presented for the active control of terahertz shielding and absorption properties in 3D graphene through the application of mechanical strain. A straintronic modulator based on 3D graphene is demonstrated, capable of modulating absorption and reflection of THz radiation in real‐time over a wide range of 0.1–3 THz. The modulator can be tuned to exhibit either shielding capability with a specific shielding effectiveness of 0.3 × 105 dB cm2 g−1 or stealth characteristics with an average reflection loss of 25 dB and 99.4% absorption. These findings open new avenues for leveraging 2D materials in their 3D porous form, where strain‐induced changes in interlayer interactions enable control over the properties of these materials. This discovery unveils vast unexplored physical phenomena with immense potential for advanced THz imaging, radar, and electromagnetic applications.

An energy-saving structural optimization strategy for high-performance multifunctional graphene films

Graphene has been widely studied for its excellent properties of outstanding conductivity, strength, and flexibility. However, interlayer defects formed during the macroscopic assembly of graphene nanosheets will severely degrade the performance of graphene films. Herein, a strategy combined with trace carboxyl graphene oxide (GO), mild reduction, and chemical crosslinking is employed to minimize the interlayer defects for enhancing both the conductivity and mechanical strength of graphene films. The trace carboxyl feature of GO allows nanosheets to assemble orderly into highly oriented GO films. Subsequently, the mild chemical reduction preserves the highly oriented and packed microstructure. Coupling with further crosslinking by introducing conjugated molecules with pyrene terminal groups (1-pyrene butyric acid-1,6-hexane diamine, PHD) to provide extra π-π bonds, both the mechanical strength and conductivity of graphene films are improved to 548.4 MPa and 1.7 × 105 S m−1, respectively. In addition, the graphene film with only ∼2 μm in thickness possesses an excellent electromagnetic interference shielding effectiveness (EMI SE) of ∼40 dB and a specific shielding effectiveness of up to 74 278 dB cm2 g−1 in a wide frequency range of 8.2–40.0 GHz. Thus, this study provides an energy-saving fabrication route for mechanically strong, effective thermal management and EMI shielding films.

Large flakes of Al–Ti3C2Tx MXene constructing highly ordered layered MXene/ANF films with integrated multifunctionalities

The simultaneous realization of high mechanical properties and excellent multifunctional performance for nanocomposite films is still a key challenge for practical applications. In this work, a dilute MXene (Al–Ti3C2Tx)/aramid nanofiber (ANF) dispersion (0.013 wt%) containing large-sized, long-term stable Al–Ti3C2Tx nanosheets (5.58 ± 1.68 μm) and branched ANFs was filtered under vacuum pressure to obtain highly ordered layered Al–Ti3C2Tx/ANF nanocomposite films with different Al–Ti3C2Tx contents (orientation factor: 0.91). Among them, the 40 wt% Al–Ti3C2Tx/ANF film offers the benefits of excellent mechanical properties (strength: 200.79 ± 1.32 MPa, strain-to-failure: 8.05 ± 0.65 %, toughness: 9.96 ± 0.84 MJ/m3), high electrical conductivity (201.6 ± 5.5 S/cm), superior EMI shielding effectiveness of up to 15 264 dB cm2 g−1 in accordance with the theoretical calculation and high electrothermal conversion temperature up to ≈120.7 °C with a rapid response time of 4 s. In addition, the nanocomposite film also boasts a superhydrophobic property with a water contact angle of 162.0 ± 1.6° along with flame retardancy. The inherent properties of 2D materials and their highly ordered arrangement in the polymer matrix are expected to provide a feasible design proposal for preparing all-in-one multifunctional films.

Scalable synthesis of high-quality, reduced graphene oxide with a large C/O ratio and its dispersion in a chemically modified polyimide matrix for electromagnetic interference shielding applications.

High-purity reduced graphene oxide (RGO or rGO) with appreciable conductivity is a desired conductive filler for lightweight polymer composites used in coatings, electronics, catalysts, electromagnetic interference (EMI) shielding, and energy storage devices. However, the intrinsic conductivity and the uniform dispersion of RGO in relatively polar matrices are challenging, leading to poor overall conductivity and performance of the composite material. The reported study improved the RGO intrinsic conductivity by increasing its C/O ratio while also simultaneously enhancing its compatibility with the polyimide (PI) matrix through ester linkages for better dispersion. A two-step reduction method drastically increased the number of structural defects and carbon content in the resulting RGO, corresponding to a maximum ID/IG and C/O of 1.54 and ∼87, respectively. Moreover, the 2D nanosheets with limited hydroxyl (-OH) groups effectively interacted with anhydride-terminated polyamic acid (AT-PAA) through chemical linkages to make high-performance RGO/PI nanocomposites. Consequently, the polymer matrix composites possessed the highest direct current conductivity of 15.27 ± 0.61 S cm-1 for 20 wt% of the prepared RGO. Additionally, the composite material was highly stiff (3.945 GPa) yet flexible (easily bent through 180°), lightweight (∼0.34 g cm-3), and capable of forming thin films (162 ± 15 μm). Unlike most polymer matrix composites, it showcased one of its class's highest thermal stabilities (a weight loss of only 5% at 638 °C). Ultimately, the composite performed as an effective electromagnetic interference (EMI) shielding material in the X-Band (8 to 12 GHz), demonstrating outstanding shielding effectiveness (SE), shielding effectiveness per unit thickness (SEt), specific shielding effectiveness (SSE), and absolute shielding effectiveness (SSEt) of 46 dB, 2778 dB cm-2, 138 dB cm3 g-1, and 8358 dB cm2 g-1, respectively. As a consequence of this research, the high-purity RGO and its high-performance PI matrix nanocomposites are anticipated to find practical applications in conductive coatings and flexible substrates demanding high-temperature stability.

A novel strategy to prepare high performance multifunctional composite films by combining electrostatic assembly, crosslinking, topology enhancement and sintering.

Currently, polymer-fiber composite films face the challenge of striking a balance between good mechanical properties and multi-functionalities. Here, aramid fibers (ANFs), chitosan (CS) dendritic particles, and silver nanowires (AgNWs) were used to create high-performance multifunctional composite films. AgNWs and polymer dendritic particles form an interpenetrating segregated network that ensures both a continuous conductive filler and a polymer network. Electrostatic assembly eliminates repulsion between negatively charged ANFs, cross-linked CS particles generate a stable three-dimensional network, and a "brick-mortar" structure composed of multiple materials contributes to topological enhancement. Sintering encourages local overlap and fusing of the AgNWs while reducing their internal flaws. Based on the above strategy, these films achieve a strength of 306.5 MPa, a toughness of 26.5 MJ m-3, and a conductivity of 392 S cm-1. Density functional theory (DFT) and Comsol simulations demonstrate that the introduction of CS thin layers leads to strong hydrogen bonds and three-dimensional continuous conductive networks. With its outstanding mechanical and electrical properties, the AgNW@ANF/CS-CH film demonstrates excellent electromagnetic shielding (22 879.1 dB cm2 g-1) and Joule heating (70 °C within 10 s) capabilities. This work presents a novel approach to fabricate high-performance conductive films and expand their potential applications in lightweight wearable electronics and electrothermal therapy.

'Donor-acceptor', 'interpenetrating polymer network' and 'electrostatic self-assembly' work in tandem to achieve extraordinary specific shielding effectiveness.

The exploration of 'electrostatic self-assembly' on solid surfaces has garnered significant interest across various fields. With the sophistication of gadgets, managing electromagnetic interference (EMI) from stray signals, especially in stealth applications, necessitates materials that can absorb microwaves. A promising approach involves integrating lightweight self-healing polymeric materials. This study employs electrostatic self-assembly to design a carbon nanotube structure on an interpenetrating polymer network (IPN) made of PVDF and bismaleimide (BMI)-grafted dopamine hydrochloride, enhancing mechanical integrity through well-formed IPNs. Graphene oxide (GO) is introduced before IPN formation to facilitate an 'acceptor-donor' interaction via the Diels-Alder adduct between BMI and GO, which binds with multi-walled carbon nanotubes (MWCNTs). MWCNTs, modified with PQ7 or PDDA for a positive charge, self-assemble onto the IPN-GO construct, creating a lightweight and chemically stable structure capable of absorbing electromagnetic radiation. The 21 μm thick construct exhibits enhanced microwave absorption within the X-band (8.2-12.4 GHz), with a specific shielding effectiveness of 8637 dB cm2 g-1 and a green index (gs ≈ 1.41). The construct is coated with self-healable polyetherimide (PEI) containing exchangeable disulfide bonds to address maintenance challenges, providing heat-triggered self-healing properties. These innovative structures offer solutions for 5G and IoT applications where lightweight, durable, and multifunctional properties are essential for effectively shielding electronic devices from stray signals.

Improving the liquid phase exfoliation efficiency of graphene based on the enhanced intermolecular and interfacial interactions

The liquid phase exfoliation (LPE) technique presents significant advantages and potential for the large-scale production of high-quality graphene nanosheets (GNs) with minimal defects. Nevertheless, the Hansen solubility parameters and surface tension matched principle were limited the range of suitable solvents for LPE process. As a result, commonly employed solvents such as N-methyl-2-pyrrolidone (NMP) and N, N-Dimethylformamide (DMF) exhibit low viscosity, leading to a low transmission efficiency of shear force from solvent to graphite, resulting in inadequate shear force and low exfoliation efficiency. In this work, to break through limitations of existing solvent systems, we investigate the influence of solvent viscosity on the LPE efficiency in various pyrrolidone solvents, which share similar structures with NMP but have longer molecular chains and higher viscosity. When compared to the NMP system, the concentration of GNs in the N-octyl-2-pyrrolidone (NOP) suspension system exhibits a significant increase of approximately 70 %, which primarily attributed to the higher intermolecular and interfacial interactions in NOP suspension. Moreinterestingly, the interactions could be further intensified by reducing the operating temperature in the NOP suspension system, which leading to an about 150 % improvement in LPE efficiency when compared to the NMP system at standard temperature. Given the remarkable conductivity of GNs, the prepared Cellulose nanofibers/graphene nanosheets (CNF/GNs) composite film exhibits lightweight and efficient electromagnetic shielding performance of 2.4 × 104 dB cm2 g−1.This work is expected to establish a universal and efficient pathway for the economical and high-yield production of GNs, elucidating the microscopic mechanism by which molecular conformation at the solid–liquid interface influences the transfer of shear forces from solvent to graphite, thereby promoting the development of widespread applications of GNs ang other two-dimensional (2D) nanomaterials.

Heterogeneous interface engineering of N–doped carbon onion nanotube chains toward prominent microwave absorption

Synthesizing lightweight, thin–profile, and high–performance microwave absorbers has emerged as an urgent research topic. A promising strategy for carbon–based materials to achieve these attributes is to rationally construct heterostructures. Herein, 0.89–1.54 at.% nitrogen(N)–doped carbon onion nanotube chains (NCONCs) were produced by blending CONCs harvested from candle combustion with HH4Cl and subjecting them to heating at 300–400 °C for 3 h. The hinge–like NCONCs revealed numerous electron transport paths, facilitating the formation of multi–tiered conduction networks. The N–doping introduced C–N groups and interfaces into the CONCs, which yielded extensive dipole and interfacial polarization. Simultaneously, the 1.14 at.% N–doping endowed NCONC–400 with suitable conductivity, thereby ensuring excellent impedance matching. The resulting synergistic effect of impedance matching and electromagnetic wave attenuation was clearly observed. Specifically, NCONC–400 exhibited exceptional performance with a maximum effective absorption bandwidth of 4.71 GHz and a peak reflection loss of –35.47 dB at 1.4 mm. The radar cross–section reduction demonstrated by NCONC–400 composites reached 21.43 dB cm2. These impressive results prove the distinctive advantages of CONCs in tailoring performance and optimizing impedance matching, which are appealing for lightweight and efficient microwave absorbers.

Alternating current assisted preparation of three-dimensional graphene aerogels and the application in electromagnetic interference shielding

Three-dimensional (3D) graphene aerogels (GA) have obtained significant attention across various fields due to their lightweight and porous properties. Nevertheless, the development of a scalable and environmentally friendly method for synthesizing self-supported 3D GA remains a challenge. In this study, we introduced an innovative method for the preparation of 3D GA using alternating current (AC) strategy, which fully used the characteristic of AC's constantly changing current direction to attract graphene oxide (GO) particles to the electrode surface and subsequently reduced them to reduced GO (rGO). Ultimately, GA is self-assembled on the electrode surface under repeated cycles. An applied AC signal with optimal parameters produced a porous GA with an oxygen content of 10.76 at%, which is 66.67% less than that of the original GO. When applying GA to electromagnetic interference (EMI) shielding, it provides a maximum specific shielding effectiveness of 9100 dB cm2 g−1 at X-band due to the repeated reflection and absorption of electromagnetic waves (EMWs) by the abundant pore wall. Furthermore, the shielding effectiveness can be significantly improved to 68.60 dB at the X-band for a multilayer GA. Notably, it is worth emphasizing that this AC-assisted synthesis method has proven its adaptability to various metal electrodes, such as cost-effective iron and copper. Importantly, this method avoids the high-temperature treatments and the use of environmentally hazardous chemicals. It is envisaged that this environmentally friendly and low-cost approach will greatly facilitate the cost-effective production of 3D GA with diverse applications.

Multi-layer carbon fiber paper @reduced graphene oxide/Co/C composite with adjustable electromagnetic interference shielding properties

Paper-based composite materials exhibit a marked tendency towards thinner and lighter profiles in the context of electromagnetic interference (EMI) shielding. Carbon fiber paper (CFP) has excellent electrical conductivity and Lightweight base characteristics. However, its single electrical loss characteristic and uncontrollable EMI shielding performance are limited in application. Therefore, we prepared CFP@ graphene oxide (GO)/ZIF-67 composites by chemical bonding and in-situ polymerization, and then prepared CFP@rGO/Co/C composites with integrated structure and function by heat treatment. Layer-by-layer assembly technology was employed to develop composite materials with tunable EMI shielding performance. The composite material has excellent high conductivity (2475.86 S/m) and excellent EMI shielding performance (average X-band EMI efficiency (SE)38.46 dB, absolute shielding effectiveness (SSE/t) = 14388.56 dB cm2 g−1). Through the layer-by-layer assembly technology, the EMI SE performance of the 7-layer assembled material reached 85.83 dB, and the EMI SSE/t reached 32110.51 dB cm2 g−1. Through simulation verification, the EMI shielding performance of the materials is compared, and ideas for EMI material design are provided. In addition, the material also has excellent Joule heating performance, fast electrothermal response and good temperature controllability. The material exhibits remarkable resilience against harsh environmental conditions, including strong acids, bases, organic reagents, ultrasonic waves, combustive processes, and extremely low temperatures. Despite these severe treatments, its performance remains above 90 % intact. This study proposes a magnetic-dielectric synergistic, performance-adjustable CFP-based shielding material, which has great application potential in the future wearable, defense, and aerospace fields.

Asymmetric c-MWCNT/AgNWs/PANFs hybrid film constructed by tailoring conductive-blocks strategy for efficient EMI shielding

Currently, extensive utilization of wireless devices require human being tantamount to tackle electromagnetic wave pollution to avoid serious harm to health body and precision equipment. Herein, asymmetric structure hybrid film were developed from para-aramid nanofiber (PANFs), carboxylated multiwalled carbon nanotubes (c-MWCNT) and silver nanowire (AgNWs) through vacuum-assistant filtration and freeze drying route. The robust and high aspect ratio PANFs established matrix foundation for forming large scale hybrid film, which rendered feasible support for conductive building blocks c-MWCNT and AgNW. Thanks to the unique asymmetric porous structure, the as-prepared c-MWCNT/AgNWs/PANFs hybrid film with 8 wt% of c-MWCNT and 4 wt% of AgNW remained efficient EMI shielding performance, whose shielding effectiveness (SE) and specific effectiveness (SEE/t) reached 40.59 dB and 10678.17 dB cm2 g−1 at thickness of 0.061 mm in X band, respectively. Furthermore, the shielding effectiveness and absorption coefficient could be regulated by c-MWCNT content, AgNW content, and ratio of c-MWCNT and AgNW. With improving the conductive ratio, the c-MWCNT/AgNWs/PANFs hybrid film possessed tunable shielding effectiveness between 9.40～40.59 dB and absorption coefficient between 0.028～0.303. This work provided feasible avenue for controlling electromagnetic feature through tailoring conductive blocks strategy.

All-in-one integrated flexible PE@PET/MXene films for high-performance electromagnetic shields with self-reinforced conductivity and mechanical properties

MXene-based composites are deemed as promising electromagnetic interference (EMI) shielding candidates to address the rapidly increasing electromagnetic interference and radiation concerns. However, developing high-performance flexible polymer-MXene composites with excellent EMI shielding efficiency (EMI SE), good mechanical properties and superior serving stability is a significant challenge. Herein, a type of all-in-one designed lightweight, thin, ultra-flexible PE@PET/MXene films are developed using a novel PE@PET nonwoven fabric (NWF) as the supporter. A mussel-inspired polydopamine modification facilitates the uniform loading of MXene, achieving high electrical conductivity of the resultant PE@PET/MXene films. A simple hot-pressing process is then employed to melt the sheath PE component of PE@PET to serve as a “self-glue” in adhering and wrapping the loaded MXene nanosheets, while maintaining the core PET fibers as the internal “steel” skeleton. As such, the resultant PE@PET/MXene films exhibit multiple self-enhancement metrics involving high mechanical strength, good electrical conductivity, robust serving stability, and superior EMI shielding performance. An optimized PE@PET/MXene film can preserve an excellent EMI SE of 50.44 dB and an ultra-high absolute shielding effectiveness (SSE/t) of 10606 dB cm2 g−1. The versatility of PE@PET/MXene EMI shielding films is further indicated by integrating the flame-retardant additives to endow its flame-retardant function, demonstrating excellent versability and expandability.

Heterogeneous Ti3C2Tx MXene-MWCNT@MoS2 Film for Enhanced Long-Term Electromagnetic Interference Shielding in the Moisture Environment.

MXene, as a novel two-dimensional (2D) material, has unique inherent features such as lightweight, flexibility, high electrical conductivity, customizable surface chemistry, and facile solution processability. However, utilizing MXene (Ti3C2Tx) films for long-term electromagnetic interference (EMI) shielding poses challenges, as they are susceptible to chemical deterioration through oxidation into TiO2. In this work, an ultrathin heterogeneous film of Ti3C2Tx MXene integrated with multiwalled carbon nanotubes supporting MoS2 clusters (MXene/MWCNT@MoS2) was developed. The heterogeneous film with 15 wt % of MWCNT@MoS2 clusters exhibited improved EMI shielding performance such as the highest EMI shielding effectiveness of 50 dB and the specific shielding effectiveness of 20,355 dB cm2 g -1, mainly attributed to the excellent electrical conductivity, distinctive porous structure, and multiple interfacial interactions. The heterogeneous films underwent extended exposure to a moisture environment (35 days), and their structural stability and EMI shielding performance were enhanced by the integration of MWCNT@MoS2 clusters. As a result, the engineered heterostructure of multilayered hybrid films holds promise as a viable option for improving the EMI shielding effectiveness and stability of Ti3C2Tx MXene.

Surfactant-Mediated Highly Conductive Cellulosic Inks for High-Resolution 3D Printing of Robust and Structured Electromagnetic Interference Shielding Aerogels.

Technological fusion of emerging three-dimensional (3D) printing of aerogels with gel processing enables the fabrication of lightweight and functional materials for diverse applications. However, 3D-printed constructs via direct ink writing for fabricating electrically conductive structured biobased aerogels suffer several limitations, including poor electrical conductivity, inferior mechanical strength, and low printing resolution. This work addresses these limitations via molecular engineering of conductive hydrogels. The hydrogel inks, namely, CNC/PEDOT-DBSA, featured a unique formulation containing well-dispersed cellulose nanocrystal decorated by a poly(3,4-ethylene dioxythiophene) (PEDOT) domain combined with dodecylbenzene sulfonic acid (DBSA). The rheological properties were precisely engineered by manipulating the solid content and the intermolecular interactions among the constituents, resulting in 3D-printed structures with excellent resolution. More importantly, the resultant aerogels following freeze-drying exhibited a high electrical conductivity (110 ± 12 S m-1), outstanding mechanical properties (Young's modulus of 6.98 MPa), and fire-resistance properties. These robust aerogels were employed to address pressing global concerns about electromagnetic pollution with a specific shielding effectiveness of 4983.4 dB cm2 g-1. Importantly, it was shown that the shielding mechanism of the 3D printed aerogels could be manipulated by their geometrical features, unraveling the undeniable role of additive manufacturing in materials design.

Graphenization of graphene oxide films for strongly anisotropic thermal conduction and high electromagnetic interference shielding

A macroscopic carbon film that has a “graphenic” structure (defect-free in-plane graphene lattice yet absence of Bernal type graphitic stacking order), may inherit the exotic properties of rotated/slipped few-layer graphene (e.g., high flexibility and anisotropic transport properties). However, the fabrication of such a film remains challenging and unreported. Here we show that the annealing of reduced electrochemical graphene oxide (REGO), which has fewer in-plane defects than the conventional graphene oxide from Hummers’ method, leads to a nearly intact graphene lattice (Raman ID/IG down to 0.03) without restoring the graphitic stacking order (I2D/IG > 1 and a single Lorentzian 2D peak). Atomic resolution transmission electron microscopy verifies the unique graphenic structure with random interlayer rotations. Density functional theory calculations imply the low defect density of REGO can suppress the interplanar interaction between undercoordinated carbon atoms, therefore inhibiting cross-plane migration of vacancies and the consequent establishment of stacking order. The annealed, graphenic REGO film is highly flexible and has an in-plane to cross-plane thermal conductivity ratio of 835 (among the highest reported for anisotropic thermal conductors). This high anisotropic ratio is attributed to the inhibited through-plane heat transport (0.26 W m−1 K−1) by the interlayer rotations and the high in-plane thermal conductivity (218 W m−1 K−1) enabled by intact graphene lattice. The graphenic films show high electromagnetic interference shielding effectiveness of 80.3 dB at a thickness of 53 μm and 42.4 dB at 5.7 μm, with an absolute effectiveness (>70000 dB cm2 g−1) superior to two-dimensional metal carbides (MXenes) and Al foil.

Lightweight and flexible Ag-wrapped polyimide aerogel fabrics for electromagnetic interference shielding

Lightweight, flexible and highly effective electromagnetic interference (EMI) shielding fabrics are urgent demanded to protect the human body from harmful electromagnetic radiation. However, the design of fiber microstructures for achieving high-performance EMI shielding still remains significant challenges. Herein, novel EMI shielding fabrics have been designed based on polydopamine-assisted Ag deposition on polyimide (Ag@PI) aerogel fabrics. The Ag@PI aerogel fabric integrates highly conductive Ag and leverages the three-dimensional porous structure of aerogel to facilitate multiple reflections and interface polarization of electromagnetic waves. The Ag@PI aerogel fabrics exhibit ultra-high electromagnetic interference shielding performance of 89.4 dB owing to their unique porous structure, while the Ag@PI fabric without porous structure is only 65.1 dB. The normalized specific shielding effectiveness (SSE) of the Ag@PI aerogel fabrics is up to 812.7 dB cm3 g−1, significantly exceeding that of other EMI shielding textiles reported so far.

Asymmetric and Flexible Ag-MXene/ANFs Composite Papers for Electromagnetic Shielding and Thermal Management.

Lightweight, flexible, and electrically conductive thin films with high electromagnetic interference (EMI) shielding effectiveness and excellent thermal management capability are ideal for portable and flexible electronic devices. Herein, the asymmetric and multilayered structure Ag-MXene/ANFs composite papers (AMAGM) were fabricated based on Ag-MXene hybrids and aramid nanofibers (ANFs) via a self-reduction and alternating vacuum-assisted filtration process. The resultant AMAGM composite papers exhibit high electrical conductivity of 248,120 S m-1, excellent mechanical properties with tensile strength of 124.21 MPa and fracture strain of 4.98%, superior EMI shielding effectiveness (62 dB), ultra-high EMI SE/t (11,923 dB cm2 g-1) and outstanding EMI SE reliability as high as 96.1% even after 5000 cycles of bending deformation benefiting from the unique structure and the 3D network at a thickness of 34 μm. Asymmetric structures play an important role in regulating reflection and absorption of electromagnetic waves. In addition, the multifunctional nanocomposite papers reveal outstanding thermal management performances such as ultrafast thermal response, high heating temperatures at low operation voltage, and high heating stability. The results indicate that the AMAGM composite papers have excellent potential for high-integration electromagnetic shielding, wearable electronics, artificial intelligence, and high-performance heating devices.