Aramid nanofibers (ANFs) have emerged as versatile and readily accessible building blocks for multifunctional, complex nanostructures. A key motivation for studying and utilizing ANFs lies in their potential to directly recycle commercial macro-aramid plastics, such as poly(p-phenylene terephthalamide), for diverse applications. Retaining the advantageous properties of parent aramid fibers and fabrics, ANFs enable the creation of a variety of nanostructured solids, both independently and in combination with polymeric and nanoscale components. A wide spectrum of ANF-based aerogels is developed, many of which exhibit property sets previously unattainable in other materials-properties critical for advancing sustainable development. These biomimetic composites replicating complex organization of cartilage, combine high toughness, thermal resilience, nanoscale porosity, and low density with the capability for roll-to-roll manufacturing. The transformative advancements in materials for energy storage, electromagnetic interference shielding, thermal management, biomedical implants, water purification, and other applications are spurred by ANF-based aerogels and related composites. This review summarizes recent progress in the engineering, fabrication, characterization, modification, and implementation of ANF aerogels. It also highlights future research directions, potential applications, and key challenges including the development of structural descriptors for ANF solids, that must be addressed to fully realize the potential of ANF-based technologies.

Polysulfide shuttle and lithium dendrite formation limit practical applications of lithium-sulfur (Li-S) batteries. To address these issues, we propose a nacre-inspired design of MXene/aramid nanofiber (ANF) separator with "brick-and-mortar" microstructure. The combination of shortened ion transfer distance generated by holes on MXene and enlarged interlayer spacing provided by ANFs creates a hierarchical ion path "highway" that modulates the efficiency of ion transportation while synergistically suppressing the polysulfide shuttles. Furthermore, benefitting from the introduction of ANF, the composite membrane has good mechanical properties and impact tolerance. With simultaneous mitigation of dendrite growth and polysulfide poisoning of anodes, the cells with nacre-inspired separator exhibited excellent rate capability to 5 C and had a possible long cycle life of 3,500+ cycles with capacity decay of 0.013% per cycle to 3 C. This work offers a membrane design strategy inspired by the structure of pearl layers, aiming to resolve materials performance challenges of high-performance energy storage.

Lithium–sulfur (Li–S) batteries have a high specific capacity, but lithium polysulfide (LPS) diffusion and lithium dendrite growth drastically reduce their cycle life. High discharge rates also necessitate their resilience to high temperature. Here we show that biomimetic self-assembled membranes from aramid nanofibers (ANFs) address these challenges. Replicating the fibrous structure of cartilage, multifactorial engineering of ion-selective mechanical, and thermal properties becomes possible. LPS adsorption on ANF surface creates a layer of negative charge on nanoscale pores blocking LPS transport. The batteries using cartilage-like bioinspired ANF membranes exhibited a close-to-theoretical-maximum capacity of 1268 mAh g −1 , up to 3500+ cycle life, and up to 3C discharge rates. Essential for safety, the high thermal resilience of ANFs enables operation at temperatures up to 80 °C. The simplicity of synthesis and recyclability of ANFs open the door for engineering high-performance materials for numerous energy technologies.

Photocatalysts that can not only harvest broader solar irradiation (from UV to near infrared (NIR) light region) but also achieve higher solar-to-hydrogen conversion efficiency are critical for solar hydrogen economy. In this research, we report a ternary bridge chain W2N/C/TiO photocatalyst for the first time to realize an efficient and stable visible and NIR light driven water splitting. This photocatalyst can realize overall water splitting using bifunctional mechanism with hydrogen (H-2) generation part and oxygen (O-2) generation part. The optimal H-2 and O-2 generation rates based on the W2N/C/TiO photocatalyst are 2.01 and 1.11 mu mol g(-1)h(-1) under the irradiation of NIR light (lambda > 700 nm). In this new photocatalyst, W2N and TiO were integrated into nanosized carbon fibers that serve as H-2 and O-2 evolution active sites. And the hydrogen apparent quantum efficiency (AQE) for W2N/C/TiO composite photocatalyst for NIR light water splitting can reach as high as 2.14% at 700 +/- 15 nm. This research indicates that W2N/C/TiO photocatalyst can be effective under broaden (Ultraviolet, Visible and Near-Infrared) light. Combining interfacial and electrochemical characterizations, we have found that W2N/C/TiO photocatalyst can efficiently separate charges through the interfaces between C/W2N and C/TiO and harvest low energy photons in NIR region. Because of the bridge chain structure among W2N, C, and TiO electron transfer from W2N to TiO via C can promote charge separation and impede the recombination of photo-generated electron and hole pairs. It is therefore that this bridge chain structured W2N/C/TiO nanofiber photocatalyst can be a promising material for overall water splitting due to the capacity to utilize a broader solar spectrum.

The development of high-efficiency and cost-efficient oxygen evolution reaction (OER) catalysts is a core issue in the sector of water electrolysis. Cobalt-molybdenum bimetal oxide (Co2Mo3O8), as a kind of non-noble transition-metal oxides, is broadly employed as a good OER catalyst due to its abundant active sites. However, the relatively low conductivity of Co2Mo3O8 limits further improvement in its electrocatalytic performance. Herein, the cobalt nanoparticle-modified Co2Mo3O8 flakes are embedded into the flower-like N-doped carbon (NC) microspheres to effectively improve the electrocatalytic OER performance. The combination of Co2Mo3O8 and NC with a flower-like structure effectively improves the conductivity of the material while enhancing the electrolyte penetration. More importantly, the Co nanoparticles (NPs) on the surface of Co2Mo3O8 flakes have the capability to furnish more active electrocatalytic active sites. The obtained Co NP-modified Co2Mo3O8 embedded flower-like NC microspheres (Co/Co2Mo3O8@NC) exhibited an overpotential of 288 mV at 10 mA.cm(-2), which was relatively low in comparison to that of commercial RuO2. Besides, the Co/Co2Mo3O8@NC also shows long-term durability almost without attenuation after the 44 000 s I-T test.

A major challenge in the field of photocatalytic carbon dioxide (CO2) reduction is to design catalyst systems featuring high selectivity for CO production, long-term stability and a composition of Earth-abundant elements. Here, we present a metal-organic framework (MOF) based catalyst to mitigate the technical problems associated with the above-mentioned features. We report a carbon-coated CuNi alloy nanocatalyst obtained by high temperature vacuum treatment of a MOF material (CuNiBTC). The resulting carbon encapsulated CuNi (denoted as CuNi/C) nanoparticles possess a well-designed core-shell composite structure with graphene shells. Meanwhile, we investigated the reaction mechanism of CO2 on the surface of the CuNi/C photocatalyst in an aqueous solution containing triethanolamine. The experimental results show that the activity and catalytic yield of CuNi/C are much higher than those of Cu/C and Ni/C alone. At the same time, the catalytic activity of CuNi/C is also affected by changing the reaction temperature in the preparation process. As a result, the CuNi/C samples can achieve nearly 90% selectivity for NIR-light-driven CO2 reduction to CO. Our approach demonstrates the potential of non-semiconductor materials as catalysts for efficient and selective reduction of CO2 to CO.

Nowadays, rationally preparing heterostructure materials can not only make up for the shortage of individual components, but also exert unexpected performance through synergistic interactions between the components. Herein, a core-shell of WS2@NiCo2O4 screw-like heterostructure arrays grown on carbon cloth (CC) was prepared by a two-step solvothermal method for supercapacitors. As a binder-free flexible electrode, a high areal capacitance of 2449.9 mF cm-2 can be achieved for WS2@NiCo2O4/CC at a current density of 1 mA cm-2. Benefiting from the core-shell of the WS2@NiCo2O4 heterostructure, the capacitive property of the flexible WS2@NiCo2O4/CC electrode is better than those of WS2/CC and NiCo2O4/CC electrodes. Based on WS2@NiCo2O4/CC electrodes, the assembled flexible solid-state symmetric supercapacitor (FSS) device shows a high energy density of ∼45.67 W h kg-1 at a power density of 992.83 W kg-1. Meantime, the WS2@NiCo2O4/CC-assembled FSS device also exhibits high cycling stability with an excellent capacity retention of ∼85.59% after 5000 cycles.

Bioinspired ion transport membranes have been widely investigated for energy storage applications. High theoretical specific energy density (2600Wh/kg) and high specific capacity (1675mA/g) along with natural abundance and low toxicity of sulfur have been attracting significant attention for development of an alternative battery system to replace traditional lithium ion batteries which suffer from safety and capacity/energy density limitations in various applications. However, challenges such as polysulfide dissolution and shuttling prevent mass commercialization of metal sulfur batteries. Inspired from biological ion transport mechanisms, we show a practical yet comprehensive approach for development of high-performance metal sulfur batteries. Aramid nanofiber (ANF) based composite ion transport membranes not only prevent dendrite formation but also confine polysulfides on the cathode side. ANF composite battery separators provide diverse and opposing properties including high mechanical properties, high ionic conductivity and high thermal/chemical stability. Highly selective ion sieving properties of these biomimetic separators provide safe and high-performance batteries. Fabrication of such biocompatible, affordable, flexible and high energy density battery is quite crucial in powering next-generation electronics including but not limited to portable, wearable and implantable biomedical devices.

Recently, polymer-based thermal management materials have been receiving more and more attention. Always, introducing the thermal conducive nanofillers to prepare polymer composites is one of the best ways to improve the thermal conductivity (TC) of the polymer. However, the simple and effective way to improve thermal conductivity by increasing fillers loading amount often brings the decrease of mechanical property resulted by agglomeration. Herein, we combined 2D transition metal carbides (Ti3C2Tx), and functionalized boron nitride nanosheets (f-BNNS) together for simultaneously enhancing the TC and mechanical property of poly-benzimidazole (PBI)-based composites. As the loading amounts of f-BNNS-Ti3C2Tx reached 25 wt% (f-BNNS: 12.5 wt%, Ti3C2Tx: 12.5 wt%), the in-plane and through-plane TCs of the f-BNNS-Ti3C2Tx/PBI composite film reach similar to 5.06 and similar to 3.44 W m(-1) K-1 which are similar to 12.05 and similar to 8.19 times higher than those of neat PBI film. More notably, the synergistic effect of interspace-filling and bridging between f-BNNS and Ti3C2Tx also prevents the agglomeration and facilitates the improvement of mechanical property, even at a high loading amount of 25 wt %, the yield and ultimate tensile strengths of f-BNNS-Ti3C2Tx/PBI composite film are similar to 175.5 and similar to 189.6 MPa with increases of similar to 61.1% and similar to 39.8% compared to those of neat PBI.

Batteries based on divalent metals, such as the Zn/Zn2+ pair, represent attractive alternatives to lithium-ion chemistry due to their high safety, reliability, earth-abundance, and energy density. However, archetypal Zn batteries are bulky, inflexible, non rechargeable, and contain a corrosive electrolyte. Suppression of the anodic growth of Zn dendrites is essential for resolution of these problems and requires materials with nanoscale mechanics sufficient to withstand mechanical deformation from stiff Zn dendrites. Such materials must also support rapid transport Zn2+ ions necessary for high Coulombic efficiency and energy density, which makes the structural design of such materials a difficult fundamental problem. Here, we show that it is possible to engineer a solid Zn2+ electrolyte as a composite of branched aramid nanofibers (BANFs) and poly(ethylene oxide) by using the nanoscale organization of articular cartilage as a blueprint for its design. The high stiffness of the BANF network combined with the high ionic conductivity of soft poly(ethylene oxide) enable effective suppression of dendrites and fast Zn2+ transport. The cartilage inspired composite displays the ionic conductance 10X higher than the original polymer. The batteries constructed using the nanocomposite electrolyte are rechargeable and have Coulombic efficiency of 96-100% after 50-100 charge discharge cycles. Furthermore, the biomimetic solid-state electrolyte enables the batteries to withstand not only elastic deformation during bending but also plastic deformation. This capability make them resilient to different type of damage and enables shape modification of the assembled battery to improve the ability of the battery stack to carry a structural load. The corrugated batteries can be integrated into body elements of unmanned aerial vehicles as auxiliary charge storage devices. This functionality was demonstrated by replacing the covers of several small drones with corrugated Zn/BANF/MnO2 cells, resulting in the extension of the total flight time. These findings open a pathway to the design and utilization of corrugated structural batteries in the future transportation industry and other fields of use.

Benefiting from unique planar structure, high flexibility, splendid thermal, and electric properties; graphene as a crucial component has been widely applied into smart materials and multi-stimulus responsive actuators. Moreover, graphene with easy processing and modification features can be decorated with various functional groups through covalent or non-covalent bonds, which is promising in the conversion of environmental energy from single and/or multi-stimuli, to mechanical energy. In this review, we present the actuating behaviors of graphene, regulated by chemical bonds or intermolecular forces under multi-stimuli and summarize the recent advances on account of the unique nanostructures in various actuation circumstances such as thermal, humidity, electrochemical, electro-/photo-thermal, and other stimuli.

Systematic variation of copolymers (Poly (ethylene-covinylacetate)) composition provide an opportunity to change matrix polarities and thus explore their effects on the polymer/filler interactions and composite properties. The main objective of this work is to study the effect of vinyl acetate (VA) content on the extent of exfoliation and dispersion of thermally reduced graphite oxide (TrGO), as well as its impact on the thermal conductivity and mechanical properties of the resultant composites. The use of ethylene vinyl-acetate (EVA) copolymers of different (0-40 wt%) vinyl acetate content with similar melt viscosities allowed us to keep the processing conditions constant and quantitatively compare the thermal conductivity and mechanical properties of composites with different matrix polarities. Composites with conductive graphite (GT) and multiwalled carbon nanotubes (MWCNT) were also prepared and examined for comparison. Melt dispersion of TrGO in EVA copolymers was quantified using a range of characterization techniques: transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray scattering measurements. Electron microscopy and X-ray diffraction revealed highly exfoliated morphology of TrGO throughout the entire matrix, while GT remained multi-layer even after melt processing. Nanocomposites reinforced with TrGO showed significantly improved thermal conductivities and mechanical properties combined with low rheological percolation thresholds comparable to those achieved using MWCNT and GT. We propose a formalism to assess the thermal conductivity and mechanical properties of graphene nanocomposites based upon the interfacial excess energies of EVA copolymers. (C) 2017 Elsevier Ltd. All rights reserved.

CdSe0.25S0.25 nanoalloys were blended with asymmetric triblock copolymer of polystyrene-bpolyisoprene-b-polystyrene(PS-SIS) in tetrahydrofuran. The fraction of styrene block varies from 14 to 22% with respect to isoprene by mass. The morphology of the copolymer cast film experiences a phase change from cylinder to lamella. CdSe0.25S0.25 nanoalloys were prepared by two-phase method. The surface of the nanoalloys was capped by either oleic acid (OA) or n-tri-octylphosphonic acid (TOPO) in situ. The mean diameter of the alloyed particles is around 12 nm in both systems. The chemical nature of the nanoalloy surface was found to influence the dispersion of the particles over polymer volume. The size of the nanoalloy domains in PS is 50 nm, on average, consisting of approximately 0.7 wt% nanoalloys. However, the size of the nanoalloy domains is smaller when they are loaded into PS-SIS. The structure formation is predominantly determined by enthalpic compatibilization. Atomic force microscopy results suggest that the nanoalloys capped with TOPO sequester into PS-rich domains and enlarge the domain. On the other hand, the ones capped with OA prefer to locate in polyisoprene domains. The increase of particles over 1.0 wt% distorts the lamella structure. (C) 2016 Elsevier Ltd. All rights reserved.

This paper describes the production of graphene nanocomposites via melt mixing of thermally reduced graphite oxide with ethylene vinyl-acetate copolymers of different (0-70 wt%) vinyl acetate content, and their measured electrical and rheological properties. The aim of these studies was to investigate the influence of a continually changing polymer matrix polarity on the dispersion and percolating behavior of graphene fillers, an effect that can be expected to be most prominent with the high specific surfaces of the latter. Composites with graphite and multi-walled carbon nanotubes were produced and examined for comparison. The effectivity of the dispersion process was checked by measuring the melt rheology and electrical conductivity of the samples. The percolation thresholds derived from these measurements show a minimum for VA contents around 20 wt%. The thresholds for electrical conductivity are by a factor around 1.5 lower than the rheological values, and both are distinctively higher than those observed from composites produced via solution mixing. The percolation behavior is compared to predictions made from the surface energy of the compounds.

Electrically and thermally conductive composites made using high density polyethylene (HDPE) matrix blended with a special grade of branch-structured nickel particles were studied. Composites with high filler content were highly electrically and thermally conductive. The electrical conductivity of composites reached a value of 8.3 x 10(3) S m(-1) when filled with 30 vol.% of the filler, and the thermal conductivity obtained using this filler content was found to be 1.99 W m(-1) K-1. The percolation concentration of the filler within the HDPE matrix, which was determined from electrical conductivity measurements, was determined to be 8 vol.%.Young's modulus of composites significantly increased from 606 MPa to 1057 MPa when composites were filled with 20 vol.% of the filler. Further increasing the filler content caused no further increase in Young's modulus, probably due to high aggregation of the filler. The stress at break of the composites behaved nonlinearly; the low filler content suppressed necking, resulting in a decrease in stress at break, whereas higher filler content (higher than 10 vol.%) led to reinforcement of the composites and therefore increased the stress at break.The presence of nickel particles throughout the HDPE matrix increased the hydrophilicity of the composites. The contact angle of water on the neat HDPE decreased from 93 degrees to 80 degrees as the nickel content of the matrix was increased to 13 vol.% of nickel. Further increases in the filler content did not alter the contact angle. Similarly, the strength of the adhesive joint formed by the composite and aluminum foil increased from a value of 16 N m(-1) for the neat HDPE to 27 N m(-1) when the HDPE matrix was filled with 13 vol.% of the filler. (c) 2013 Elsevier Ltd. All rights reserved.

Polymeric composites were prepared using ethylene-vinylacetate (EVA) matrix and expanded graphite (EG). Mechanical properties were investigated and it was found that Young's modulus and the yield stress of EVA-EG composites significantly increased with graphite content. However, for higher EG content the composites became brittle. The dependence of stress at the break of composites reached maximum at 30 vol.% of the filler. The morphology of both EG filler and composites were investigated using transmission electron microscopy and Raman spectroscopy. All these structural characterizations indicated partial exfoliation of EG within EVA matrix, which leads to the increase of the reinforcement effect.

The primary purpose of the study is to investigate the temperature dependence of heat capacity and thermal conductivity of composites having different fiber/matrix combinations by means of heat-flux differential scanning calorimetry (DSC). The materials used as samples in this study were epoxy- and polyester-based composites. Noncrimp stitched glass, carbon, and aramid fabric were used as reinforcements for making unidirectional composites. For the heat capacity measurements the composite sample and a standard material are separately subjected to same linear temperature program. By recording the heat flow rate into the composite sample as a function of temperature, and comparing it with the heat flow rate into a standard material under the same conditions, the temperature dependence of heat capacity of the composite sample is determined. Measurements were carried out over a wide range of temperatures from about 20 to 250 degrees C. The differential scanning calorimeter was adapted to perform the thermal conductivity measurements in the direction perpendicular to the fiber axis over the temperature range of 45-235 degrees C. The method used in this study utilizes the measurement of rate of heat flow into a sensor material during its first-order phase transition to obtain the thermal resistance of a composite material placed between the sensor material and the heater in the DSC. POLYM. COMPOS., 30:1299-1311, 2009. (C) 2008 Society of Plastics Engineers

The purpose of this article is to determine the structure of gamma-glycidoxypropyltrimethoxysilane (gamma-GPS) on glass fiber surfaces. The interfacial adhesion of glass fiber-polymer can be improved by the silane treatment of the glass fiber. To change the composition of the glass and regenerate to the hydroxyl groups, activation pretreatment of heat cleaned woven glass fabric was performed using a 10% (v/v) hydrochloric acid aqueous solution for different durations before silane treatment. The treatment of silanization of heat cleaned and acid activated glass fibers with (gamma-GPS) were conducted at various time intervals. These fibers would be used to quantify the relationship between contact angle of glass fiber surface and the interfacial shear strength of the fiber-polymer interface. The effect of acid activation on glass surface and the interaction between glass fibers and silane coupling agent were examined using Fourier transform infrared spectroscopy. The experiments, in conjunction with electron photomicrographs of glass surfaces treated with coupling agent, are interpreted in an attempt to explain the stability of coupling agent-glass interfaces. From SEM analysis, it was clearly observed that agglomerations of silane agent in the cavities among the heat cleaned fibers are available. However, this case was not observed for the silanization of acid activated glass fibers. In addition, contact angle measurements on glass fibers were performed to evaluate surface structure. POLYM. COMPOS., 30:550-558, 2009. (C) 2008 Society of Plastics Engineers

In this study, effects of fiber surface treatments on mechanical behavior and fracture mechanism of glass fiber/epoxy composites were investigated experimentally. To change the composition of the glass and regenerate to the hydroxyl groups, activation pretreatment of heat cleaned woven glass fabric was performed using (v/v) HCl aqueous solution at different concentrations before silane treatment. The treatment of silanization of heat cleaned and acid activated glass fibers with γ-glycidoxypropyltrimethoxysilane were performed. In this work, short beam shear test has been conducted to determine the performance of the acid treatment and the silane treatment in terms of the interlaminar shear strength. The silane coating on the heat cleaned glass fibers increased the interlaminar shear strength of the composite. However, the silane coating on the acid activated glass fibers did not improve the interlaminar shear strength of the composite. In addition, the strengths of the glass fabric specimens in tension and flexure were investigated. When the glass fibers are first treated with HCl solution and then with silane coupling agent, the tensile strengths of the composites decreased significantly. Scanning electron photomicrographs of fractured surfaces of composites were performed to explain the failure mechanisms in the composite laminates broken in tension.