Aramid Nanofibers Research Articles

Enhanced interfacial bonding of AF/PEEK composite based on CNT/aramid nanofiber multiscale flexible-rigid structure

The application of aramid fiber (AF)/polyetheretherketone (PEEK) composites is currently hindered by the inert surface and poor wettability of AF, resulting in weak interfacial adhesion and poor mechanical properties. Surface coating and the introduction of nanostructures have been proven to be effective approaches to address this problem. Herein, a simple hybrid sizing agent has been developed to modify the AF surface, consisting of soluble polyimide (PI) as a compatibilizer, carboxyl-functionalized carbon nanotubes (CNT-COOH) as a rigid unit, and aramid nanofibers (ANF) as a flexible component. The synergetic effects of PI and the multiscale flexible-rigid structure (CNT-COOH/ANF) contribute to the formation of chemical and physical bonds between AF and PEEK matrix, further improving the interfacial adhesion and stress transfer efficiency. Attributed to the enhanced wettability and roughness of AF, compared with unsized AF, the flexural strength (220.97 MPa), modulus (13.26 GPa), ILSS (13.36 MPa), and storage modulus (12.93 GPa) of the AF/PEEK composite increase by 132.60 %, 99.00 %, 18.97 %, and 82.70 % respectively. Additionally, the flexible-rigid nanonetwork facilitates the penetration of the PEEK resin into pore spaces. This simple and effective approach exhibits promising potential in enhancing the interfacial bonding of AF/PEEK composites.

Robust micro-nano hybrid aerogel derived from waste resources for thermal management and high-efficiency adsorption

Ultra-low density nanoaerogels as the lightest solid material have aroused extensive attention. However, lacking crack extension resistance limited their further development and application. Here, aramid and cellulose wastes were recycled to prepare high value-added nanofibers, which were further self-assembled to construct multilfunctional hybrid aerogels. In-situ growth of zeolitic imidazolate frameworks-8 (ZIF-8) on the cellulose nanofiber (CNF) created a robust skeleton. Flexible aramid nanofibers (ANF), as burgeoning building blocks were employed to inlay into the microscopic skeleton structure for establishing micro-nano double networks. Benefiting from the existence of multiscale networks, the maximum value in the compressive stress of S0, S1, S2 and S3 increased from 2.74 to 4.63, 5.19 and 6.61 MPa, respectively.Meanwhile, ANF-ZIF-8-CNF hybrid aerogels exhibited low thermal conductivity of 3.58–3.97 × 10-2 W/(m⋅K). The significant increase in the specific surface area (481.46 m2/g) endowed hybrid aerogels with high adsorption abilities for nitrogen (280.83 cm3/g), prussian blue (34.12 mg⋅g−1), rhodamine B (37.30 mg⋅g−1), DMF (25.13 g⋅g−1) and DMSO (15.48 g⋅g−1), respectively. This multiscale structural engineering strategy opens an avenue toward to upcycle waste resources into the next-generation high-performance nanoaerogels, showing huge application potential in thermal management, air purification and sewage treatment.

Highly Thermally Conductive Aramid Nanofiber Composite Films with Synchronous Visible/Infrared Camouflages and Information Encryption

AbstractThe development of highly thermally conductive composites that combine visible light/infrared camouflage and information encryption has been endowed with great significance in facilitating the application of 5G communication technology in military fields. This work uses aramid nanofibers (ANF) as the matrix, hetero‐structured silver nanowires@boron nitride nanosheets (AgNWs@BNNS) prepared by in situ growth as fillers, which are combined to fabricate sandwich structured thermally conductive and electrically insulating (BNNS/ANF)‐(AgNWs@BNNS)‐(BNNS/ANF) (denoted as BAB) composite films by “filtration self‐assembly, air spraying, and hot‐pressing” method. When the mass ratio of AgNWs@BNNS to BNNS is 1 : 1 and the total mass fraction is 50 wt %, BAB composite film has the maximum in‐plane thermal conductivity coefficient (λ∥ of 10.36 W/(m ⋅ K)), excellent electrical insulation (breakdown strength and volume resistivity of 41.5 kV/mm and 1.21×1015 Ω ⋅ cm, respectively) and mechanical properties (tensile strength of 170.9 MPa). 50 wt % BAB composite film could efficiently reduce the equilibrium temperature of the central processing unit (CPU) working at full power, resulting in 7.0 °C lower than that of the CPU solely integrated with ANF directly. In addition, BAB composite film boasts adaptive visible light/infrared dual camouflage properties on cement roads and jungle environments, as well as the function of fast encryption of QR code information within 24 seconds.

Highly Thermally Conductive Aramid Nanofiber Composite Films with Synchronous Visible/Infrared Camouflages and Information Encryption.

The development of highly thermally conductive composites that combine visible light/infrared camouflage and information encryption has been endowed with great significance in facilitating the application of 5G communication technology in military fields. This work uses aramid nanofibers (ANF) as the matrix, hetero-structured silver nanowires@boron nitride nanosheets (AgNWs@BNNS) prepared by in situ growth as fillers, which are combined to fabricate sandwich structured thermally conductive and electrically insulating (BNNS/ANF)-(AgNWs@BNNS)-(BNNS/ANF) (denoted as BAB) composite films by "filtration self-assembly, air spraying, and hot-pressing" method. When the mass ratio of AgNWs@BNNS to BNNS is 1 : 1 and the total mass fraction is 50 wt %, BAB composite film has the maximum in-plane thermal conductivity coefficient (λ∥ of 10.36 W/(m ⋅ K)), excellent electrical insulation (breakdown strength and volume resistivity of 41.5 kV/mm and 1.21×1015 Ω ⋅ cm, respectively) and mechanical properties (tensile strength of 170.9 MPa). 50 wt % BAB composite film could efficiently reduce the equilibrium temperature of the central processing unit (CPU) working at full power, resulting in 7.0 °C lower than that of the CPU solely integrated with ANF directly. In addition, BAB composite film boasts adaptive visible light/infrared dual camouflage properties on cement roads and jungle environments, as well as the function of fast encryption of QR code information within 24 seconds.

Multilayered silver nanowires and graphene fluoride-based aramid nanofibers for excellent thermoconductive electromagnetic interference shielding materials with low-reflection

Multilayered films composed of alternating layers of graphene fluoride (GF) and silver nanowires (AgNWs) in an aramid nanofiber (ANF) matrix were fabricated. The films were prepared by sequential vacuum filtration of GF@ANF and AgNWs@ANF suspensions to obtain multilayered composite architectures. The multilayered GF@ANF/AgNWs@ANF films exhibited exceptional mechanical flexibility and strength, with tensile strength up to 130 MPa and 5000 bending cycles with negligible performance deterioration. The films displayed remarkably high electromagnetic interference (EMI) shielding effectiveness up to 54 dB in X-band frequencies, attributed to the multiple internal reflections in the multilayered structure. EMI shielding was dominated by absorption rather than reflection, enabling attenuation of incident microwaves without secondary pollution. The multilayered films also exhibited ultrahigh in-plane thermal conductivity of up to 45 W/mK, owing to the thermally conductive GF and AgNWs networks. The EMI shielding effectiveness and thermal conductivity were retained after temperature and bending cycling. The composite films also demonstrated excellent flame retardancy. This study provides an effective route toward concurrent enhancement of multi-functional properties through architectural engineering at the nanoscale. The combination of robust EMI shielding, mechanical flexibility, thermal management, and fire safety highlights the potential of rationally designed multilayered composites for practical applications in 5 G wearable electronics devices, communications systems, and radar technologies.

Mechanically robust and uniform aramid nanofiber films fabricated using repeated spin-coating and protonation processes

Aramid nanofiber (ANF) films show promise for various industrial applications, but their applicability has been constrained by the low mechanical properties, which are mainly due to their incomplete packing and non-uniform microstructure. This work introduces an efficient method for significantly improving the mechanical properties of ANF films using repeated spin coating and protonation. The method allows for the preparation of ANF films with highly uniform microstructures and adjustable thicknesses while achieving excellent mechanical properties. These ANF films have a Young's modulus of 6.8 GPa, tensile strength of 310 MPa and hardness of 248 MPa, surpassing those produced using previous methods. A comprehensive analysis of the surface and cross-sectional morphologies, chemical composition, thermal stability, and mechanical properties was also carried out to characterize the film properties.

Revealing Surface/Interface Chemistry of the Ordered Aramid Nanofiber/MXene Structure for Infrared Thermal Camouflage and Electromagnetic Interference Shielding.

The past decade has witnessed the advances of infrared (IR) thermal camouflage materials, but challenges remain in breaking the trade-off nature between emissivity and mechanical properties. In response, we identify the key role of a moderate reprotonation rate in the aramid nanofiber (ANF)/MXene film toward a surface-to-bulk alignment. Theoretical simulation demonstrates that the ordered ANF/MXene surface eliminates the local high electric field by field confinement and localization, responsible for the low IR emissivity. By scrutinizing the surface/interface chemistry, the processing optimization is achieved to develop an ordered and densely stacked ANF/MXene film, which features a low emissivity of 16%, accounting for sound IR thermal camouflage performances including a wide camouflage temperature range of 50-200 °C, a large reduction in radiation temperature from 200.5 to 63.6 °C, and long-term stability. This design also enables good mechanical performance such as a tensile strength of 190.8 MPa, a toughness of 12.1 MJ m-3, and a modulus of 7.9 GPa, responsible for better thermal camouflage applications. The tailor-made ANF/MXene film further attains an electromagnetic interference (EMI) shielding effectiveness (40.4 dB) in the X-band, manifesting its promise for IR stealth compatible EMI shielding applications. This work will shed light on the dynamic topology reconstruction of camouflage materials for boosting thermal management technology.

Thermal conductive aramid nanofiber/surface-decorated alumina microsphere composite separator

The development of lithium-sulfur (Li–S) batteries is hindered by inhomogeneous Li plating and irreversible loss of active materials. In this work, a thermal conductive and electrocatalytic aramid nanofiber (ANF) composite separator containing surface-decorated alumina (Al2O3) microspheres is prepared through a simple filtration approach using ZnO nanosheets decorated Al2O3 microspheres (Al2O3@ZnO) as the thermal conductive filler and electrocatalyst. Compared with the separators fabricated by surface modification of commercial polyolefin separators, the as-prepared ANF/Al2O3@ZnO composite separator features homogeneous compositions and ensures uniform thermal distribution in both the through-plane and in-plane directions of the membrane. By rationally designing the structure of Al2O3@ZnO and adjusting the mass ratio of Al2O3@ZnO to ANF, excellent thermal conduction networks are formed by overlapping the ZnO nanosheets. Hence, the prepared ANF/Al2O3@ZnO composite separator possesses higher thermal conductivity than ANF/Al2O3 composite separator, which benefits uniform thermal distribution and homogeneous Li plating within the battery. Moreover, the electrocatalytic ZnO nanosheets catalyze the conversion of lithium polysulfides, efficiently inhibiting the shuttle effect and improving sulfur utilization. When subjected to a temperature gradient, the ANF/Al2O3@ZnO composite separator assembled cells display high initial capacity, low decay rate, and superb cycle stability. This novel composite separator integrates both thermal conductive and electrocatalytic functional components with the heat-resistant ANF matrix, offering a new design strategy of separator towards high-performance Li–S batteries.

Self-Assembly of Ultrathin, Ultrastrong Layered Membranes by Protic Solvent Penetration.

Flexible membranes with ultrathin thickness and excellent mechanical properties have shown great potential for broad uses in solid polymer electrolytes (SPEs), on-skin electronics, etc. However, an ultrathin membrane (<5 μm) is rarely reported in the above applications due to the inherent trade-off between thickness and antifailure ability. We discover a protic solvent penetration strategy to prepare ultrathin, ultrastrong layered films through a continuous interweaving of aramid nanofibers (ANFs) with the assistance of simultaneous protonation and penetration of a protic solvent. The thickness of a pure ANF film can be controlled below 5 μm, with a tensile strength of 556.6 MPa, allowing us to produce the thinnest SPE (3.4 μm). The resultant SPEs enable Li-S batteries to cycle over a thousand times at a high rate of 1C due to the small ionic impedance conferred by the ultrathin characteristic and regulated ionic transportation. Besides, a high loading of the sulfur cathode (4 mg cm-2) with good sulfur utilization was achieved at a mild temperature (35 °C), which is difficult to realize in previously reported solid-state Li-S batteries. Through a simple laminating process at the wet state, the thicker film (tens of micrometers) obtained exhibits mechanical properties comparable to those of thin films and possesses the capability to withstand high-velocity projectile impacts, indicating that our technique features a high degree of thickness controllability. We believe that it can serve as a valuable tool to assemble nanomaterials into ultrathin, ultrastrong membranes for various applications.

Nacre-Inspired Aramid Nanofibers/Basalt Fibers Composite Paper with Excellent Flame Retardance and Thermal Stability by Constructing an Organic-Inorganic Fiber Alternating Layered Structure.

The flame-retardant paper has gradually evolved into a necessary material in various industries as a result of the rising importance of fire safety, energy efficiency, and environmental preservation. Traditional cellulose paper requires the addition of a large amount of flame retardants to achieve flame retardancy, which poses a serious threat to mechanical quality and the environment. Therefore, there is an urgent need to develop inorganic fiber flame-retardant paper with good flexibility, high thermal stability, and inherent flame retardancy. Herein, inspired by the "brick-and-mortar" layered structure of nature nacre, we developed a layered composite paper with a unique alternating arrangement of organic-inorganic fibers by synergistically integrating environmentally sustainable basalt fiber (BF) and high-performance aramid nanofibers (ANFs) through a vacuum-assisted filtration process. The as-prepared ANFs/BF composite paper exhibited low thermal conductivity (0.024 W m-1 K-1), high tensile strength (54.22 MPa), and excellent flexibility. Thanks to its excellent thermal stability, the mechanical strength remains at a high level (92%) after heat treatment at 300 °C for 60 min. Furthermore, the peak heat release rate and smoke generation of ANFs/BF composite paper decreased by 44.6 and 95.3%, respectively. Therefore, the composite paper is promising for applications as a protective layer in flexible electronic devices, cables, and fire-retardant and high-temperature fields.

CO2‐Assisted Induced Self‐Assembled Aramid Nanofiber Aerogel Composite Solid Polymer Electrolyte for All‐Solid‐State Lithium‐Metal Batteries

AbstractAll‐solid‐state lithium metal batteries (ASSLMBs) hold great promise for the development of next‐generation high‐safety, high‐energy‐density lithium batteries, but still face the challenges of lithium dendrite growth and thickness. Herein, the ultrathin PEO‐based composite solid polymer electrolyte (denoted as PAL) supported by a low‐density self‐supporting aramid nanofiber (ANF) aerogel framework is developed. The ANF aerogel obtained by a novel CO2‐assisted induced self‐assembly method has a well‐designed bilayer structure with double cross‐linking degree. Benefiting from the intermolecular interaction between ANFs and PEO, the PAL achieves an ultrathin thickness (20 µm) with excellent thermal stability and mechanical strength. Meanwhile, due to the modulation of ionic pathways by the functionalized ANF, the PAL achieves uniform lithium deposition without dendrites, resulting in stable long cycling (1400 h) for symmetric cells. Consequently, the Li|PAL|LiFePO4 (LFP) cell has excellent long‐term cycling stability (1 C, &gt;700 cycles, Coulombic efficiency &gt; 99.8%) and fast charge/discharge performance (rate, 10 C). More practically, the Li|PAL|LFP cell achieves an energy density of 180 Wh kg−1 due to the ability to match a high‐loading (8 mg cm−2) cathode. Furthermore, the double‐layer Li|PAL|LFP pouch cell demonstrates excellent flexibility and safety in cycling and abuse tests.

Uv–vis spectral characteristics of para-aramid fiber deprotonation products in KOH/DMSO system and their applications

This paper reported a spectroscopic method for quantifying the charge content (CT) during para-aramid fiber (PPTA) deprotonation in KOH/DMSO system. The results showed that there were two deprotonation products, i.e., PPTA- and PPTA2- that had spectral absorption at UV/visible wavelength range. It was found that 360 nm was an isosbestic absorption point of PPTA- and PPTA2-, while the absorption at 400 nm was only contributed by PPTA2-. Based on the spectral information, the charge absorption coefficients of PPTA- and PPTA2- at the characteristic wavelengths of interest (i.e., k336PPTA-, k360PPTA- and k400PPTA2-) were calculated, and an equation for quantifying the total charge content was also generated. The present method could provide an efficient quantification tool for monitoring the degree of deprotonation reaction of PPTA in the DMSO/KOH system in the aramid nanofibers related research and application.

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.

Robust anti-impact, energy absorption and thermal properties of polyurethane nanocomposites modified by phenol-amine chemistry

It is still a considerable challenge for polyurethane elastomers (PUE) to possess outstanding mechanical and thermal performance simultaneously against harsh dynamic impact environment due to their heat accumulation, thermal stress softening and mechanical failure. Thus, this article innovatively prepared binary nanofibers composed of carbon nanofiber (CNFs) and aramid nanofibers (ANFs) to reinforce PUE, where catechol (CC) and polyethyleneimine (PEI) were served as interfacial modifier between nanofibers and polymer matrix. PUE with 1.5 wt% binary nanofibers achieve 31.62 % increase in crosslinking density, 146.8 °C improvement in thermal decomposition temperature compared to Neat PUE. Besides, the absorption energy and dynamic compression strength of composites were increased by 40.36 % and 38.26 %, respectively. Because reinforced nanofibers with crosslinking network structures improve the interface interaction between fillers and matrix, facilitate stress transfer and increase the energy threshold of thermal decomposition. The paper supplements the impact resistance analysis of PUE-based protective materials under impact loads, providing a systematic and scientific reference for the design and manufacture of impact resistant materials.

Electromagnetic interference shielding performance of lightweight aramid nanofiber/graphene composite aerogels

Aramid nanofiber (ANF)/graphene (GN) composite aerogels were fabricated be the ice template following by freeze-drying, and the composite aerogels obtained excellent EMI shielding performance as well as good compression strength and heat resistance.

Water vapor assisted aramid nanofiber reinforcement for strong, tough and ionically conductive organohydrogels as high-performance strain sensors.

Conductive organohydrogels have gained increasing attention in wearable sensors, flexible batteries, and soft robots due to their exceptional environment adaptability and controllable conductivity. However, it is still difficult for conductive organohydrogels to achieve simultaneous improvement in mechanical and electrical properties. Here, we propose a novel "water vapor assisted aramid nanofiber (ANF) reinforcement" strategy to prepare robust and ionically conductive organohydrogels. Water vapor diffusion can induce the pre-gelation of the polymer solution and ensure the uniform dispersion of ANFs in organohydrogels. ANF reinforced organohydrogels have remarkable mechanical properties with a tensile strength, stretchability and toughness of up to 1.88 ± 0.04 MPa, 633 ± 30%, and 6.75 ± 0.38 MJ m-3, respectively. Furthermore, the organohydrogels exhibit great crack propagation resistance with the fracture energy and fatigue threshold as high as 3793 ± 167 J m-2 and ∼328 J m-2, respectively. As strain sensors, the conductive organohydrogel demonstrates a short response time of 112 ms, a large working strain and superior cycling stability (1200 cycles at 40% strain), enabling effective monitoring of a wide range of complex human motions. This study provides a new yet effective design strategy for high performance and multi-functional nanofiller reinforced organohydrogels.

Fabrication of fluorinated graphene based aramid nanofibers films with excellent thermal conductivity and mechanical properties

The rapid advancement of technology has spurred the development of a wide range of sophisticated electronic devices leading to an increasing demand for the utilization of thermoconductive materials to address thermal management. However, most of the available thermoconductive materials possess inadequate mechanical properties and low resistance to temperatures. To address this limitation, this study focuses on fabricating the thermoconductive films using aramid nanofiber (ANF) as strengthening components and fluorinated graphene (FG) as a thermoconductive filler. The films are prepared through the simple vacuum filtration method. The obtained FG/ANF film with 40 wt% of FG reached the in-plane thermal conductivity of 9 W/mK. Additionally, the FG40/ANF film exhibits excellent mechanical properties, including a tensile strength exceeding 110 MPa and toughness greater than 7.2 MJ/m³. Given these remarkable characteristics, the FG/ANF film holds significant promise as a material for dissipating heat in electronic devices, particularly in applications that demand high mechanical performance and temperature stability.

Intercross-linked aramid nanofibers/graphene hybrid films toward high mechanical strength and electrical conductivity

Although macro graphene films exhibit excellent electrical conductivity, the low tensile strength severely hampers the application of graphene films. Combined with polymers can improve the mechanical properties to a degree, but it usually dramatically decreases the electrical conductivities of graphene films. It is thus a great challenge to make a trade-off between high electrical conductivity and excellent mechanical properties of graphene films. Herein, we designed a homogeneous layer-by-layer microstructure combining reduced graphene oxide (rGO) nanosheets with aramid nanofiber (ANF) to obtain composite films referred to as rGO/ANF. By tuning the concentration of ANF, a balanced electrical and mechanical performance can be achieved. It is revealed that the tensile strength of the optimized composite film with 10 wt% ANF was dramatically improved by 194% comparing to the pure rGO film, and the electrical conductivity still maintained at a relatively high level (8495 S m−1). The remarkable overall properties can be attributed to the unique structure with abundant hydrogen bonds and π-π interactions formed between rGO and ANF. The results demonstrate that this is indeed an efficient strategy to balance the electrical conductivity and tensile strength of the graphene-polymer composites, making it promising in the application of multi-functional electronic devices.

Solvent‐Induced Deformation of Aramid Nanofibers for Ultrahigh‐Flux Nanofiltration Membranes

AbstractAramid nanofibers (ANFs), as promising organic nano building blocks for their high mechanical strength and thermal stability, are widely applied to fabricate energy‐efficient membranes for ionic and molecular sieving in aqueous solutions. However, the existing ANFs often have small diameters, limiting the permeability of the resulting membranes. Here, the ANFs with a diameter in the hundred‐nanometer scale are fabricated through a progressive protonation process, in which dimethylformamide as a secondary deprotonation solvent is added into dimethyl sulfoxide to provide a mild deformation environment. Then, the deformed ANFs are applied to prepare membranes with a larger pore size distribution and higher surface charge. Notably, the water flux of the resulting membranes can reach up to 410 L m−2 h−1 bar−1, which is 40 times higher than commercially available nanofiltration membranes and much higher than currently reported ANF‐based membranes. Impressively, these membranes with super‐stable nanochannels maintain a high water flux of over 194 L m−2 h−1 bar−1 in a wide range of pH values from 4 to 10 and show excellent long‐term durability over 120 h. The application of deformed ANFs provides a new and promising approach for designing the next generation nanofiltration membranes which balance the trade‐off between permeability and selectivity.

Thermoconductive Graphene Fluoride Cross-Linked Aramid Nanofiber Composite Films with Enhanced Mechanical Flexibility and Flammable Retardancy for Thermal Management in Wearable Electronics

Thermoconductive Graphene Fluoride Cross-Linked Aramid Nanofiber Composite Films with Enhanced Mechanical Flexibility and Flammable Retardancy for Thermal Management in Wearable Electronics