Carbonaceous Fibers Research Articles

Highly thermally conductive composites of graphene fibers

Carbon fiber-based polymer composites have rich electric and thermal functions, the merit of weight lightness to meet important applications in thermal management. Graphene fiber, a newly emerged carbonaceous fiber, features high thermal conductivity that surpasses conventional carbon fibers. For the realistic applications of graphene fiber, fiber composite is one necessary form but still remains unexplored. Here, we prepared graphene fiber based polymer composites and achieved high specific thermal conductivity up to 363 W∙cm3∙m−1∙K−1∙g−1, outperforming composites of mesophase pitch-based carbon fiber. Graphene fiber composites with a fiber content of 59 vol% have a low density of 1.53 g∙cm−3 and high axial thermal conductivity of 553 W∙m−1∙K−1. For the high breakage elongation of graphene fiber, graphene fiber composites can be fabricated to adapt sharp curvature structures. This work develops polymer composites of graphene fiber and their high thermal conductivity can have extensive applications in thermal management.

Large-scale preparation of thermally conductive graphene fiber filaments

Graphene fiber has emerged as a promising carbonaceous fiber with excellent integrated properties. Previous laboratory researches have focused on the prototype single fiber, but the scalable fabrication of graphene fiber filaments still remains nearly unexplored. Here, we report the large-scale industrial fabrication of graphene fiber filaments with high strength and superior thermal conductivity. During scalable wet-spinning process, we introduce step-wise solvent intercalation plastic stretching to improve the uniformity, density and structural order of precursor graphene oxide fiber filaments. The chemical reduction and high-temperature graphitization restore graphene atomic structure and achieve large graphitic crystallite sizes of filaments. The graphene fiber filaments demonstrate favorable overall performances, including tensile strength of 1.4 GPa, density of 1.93 g/cm3, electrical conductivity of 4.1 × 105 S/m, and thermal conductivity of 1204 W/mK. The fabrication of graphene fiber filaments lays a foundation of their wide applications as textiles and composites and the solvent intercalation plastic stretching could be a general method to fabricate high performance fiber filaments of two-dimensional materials.

Moisture resistance improvement of carbonaceous fibers for antistatic coating by modification with long carbon chain silane

Although the general carbon fibers are very stable, low-temperature carbonized carbonaceous fibers were sensitive to moisture, which would lead to unstable electrical conductivity, and seriously endanger the antistatic properties of antistatic coating when carbonaceous fibers were used as conductive filler. In this work, a simple dipping modification is proposed to improve the stability of fiber resistivity by using a long carbon chain silane coupling agent (hexadecyltrimethoxysilane) to perform surface moisture-proof treatment on carbonaceous fibers. The modification was demonstrated to significantly improve the stability of fiber resistivity by accelerated experiments in hygrothermal and salt spray environments. After 72 h treatment in hygrothermal environment, the increase percentage of untreated carbonaceous fiber resistivity reached 70%. Nevertheless, that of CF@KH1631-6 was 40%. Good hydrophobicity was achieved at a concentration of 6 wt%, water contact angle increasing from 135.6° to 152.2°. Furthermore, the whole preparation process had the potential of large-scale industrial production and application.

Synthesis of centrifugally spun polyacrylonitrile-carbon fibers

This work demonstrates the carbonization of centrifugally spun polyacrylonitrile (PAN) fibers. Initially, the optimal centrifugal spinning conditions for producing homogeneous PAN fibers were identified. Second, the process continued by stabilization and carbonization of PAN to ensure a pure carbonaceous fiber material by eliminating all non-carbonaceous matter. The spun PAN fibers were stabilized at 240 °C in air at a heating rate of 1 °C/min, then carbonized between 600 and 1200 °C in argon at 5 °C/min. After carbonization, the fibers were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Raman spectroscopy (RS). The SEM results showed that by increasing the carbonization temperature, the prolonged elimination of other functional groups resulted in the formation of thinner carbon fibers. FTIR spectra of PAN fibers revealed that the peaks associated with C≡N bonds were substantially reduced and C–H bonds were eliminated in the fibers during the stabilization. These reductions are attributed to the cyclization of nitrile groups and the stabilizing process, and increasing carbonization temperatures resulted in flatter FTIR curves, supporting the findings. According to XRD, the structure of PAN was disturbed, as desired, and carbonization led to the formation of broad bumps resulting from amorphous carbon. Raman investigations found that increasing the carbonization temperature from 600 to 1200 °C resulted in no significant R values, suggesting that all fibers had no structural ordering. The study results could be used in many other areas, such as the fabrication of electrodes, supporting catalytic reactions, filter media, and energy.

Effect of moisture on the structure and electrical properties of carbonaceous fibers

Effect of moisture on the structure and electrical properties of carbonaceous fibers

Simultaneous improvement of interfacial bonding and thermal resistance of carbonaceous fiber/silicone composite coatings modified with aniline-methyl-triethoxysilane

Mechanical properties and thermal resistance reinforcement were achieved by a one-step dipping method, in which an aniline-methyl-triethoxysilane (AMT) coupling agent was grafted onto the carbonaceous fiber (CF) to fabricate CF/silicone resin (SR) composite coatings. Micromorphology and structure analysis of carbonaceous fibers showed that the AMT modification increase the roughness and the uniformity on the fiber surface, resulting in the link between AMT and fiber surface, and the polysiloxane formation by polymerization between the Si-OH groups. The AMT modification of the fiber surface introduced the AMT with a disordered structure on the fiber surface and improved the compatibility between CFs and SR. Mechanical testing showed that the tensile strength and elongation rate of the coating containing CF modified with 1wt%AMT coupling agent was increased by 45.32 % and 19.07 % compared with that of the unmodified one, respectively. The reinforcing mechanism revealed that the AMT modification improved interfacial bonding and mechanical riveting. Besides, the thermogravimetric analysis (TGA) analysis showed that the siloxane layer crosslinked at a high temperature, which was conducive to improving the thermal resistance for the long-term stability of the composite coatings. This special treatment provides an idea for simultaneously improving the mechanical properties and thermal resistance of silicone composites.

Engineering CSFe Bond Confinement Effect to Stabilize Metallic-Phase Sulfide for High Power Density Sodium-Ion Batteries.

Metallic-phase iron sulfide (e.g., Fe7 S8 ) is a promising candidate for high power density sodium storage anode due to the inherent metal electronic conductivity and unhindered sodium-ion diffusion kinetics. Nevertheless, long-cycle stability can not be achieved simultaneously while designing a fast-charging Fe7 S8 -based anode. Herein, Fe7 S8 encapsulated in carbon-sulfur bonds doped hollow carbon fibers (NHCFs-S-Fe7 S8 ) is designed and synthesized for sodium-ion storage. The NHCFs-S-Fe7 S8 including metallic-phase Fe7 S8 embrace higher electron specific conductivity, electrochemical reversibility, and fast sodium-ion diffusion. Moreover, the carbonaceous fibers with polar CSFe bonds of NHCFs-S-Fe7 S8 exhibit a fixed confinement effect for electrochemical conversion intermediates contributing to long cycle life. In conclusion, combined with theoretical study and experimental analysis, the multinomial optimized NHCFs-S-Fe7 S8 is demonstrated to integrate a suitable structure for higher capacity, fast charging, and longer cycle life. The full cell shows a power density of 1639.6Wkg-1 and an energy density of 204.5Whkg-1 , respectively, over 120 long cycles of stability at 1.1Ag-1 . The underlying mechanism of metal sulfide structure engineering is revealed by in-depth analysis, which provides constructive guidance for designing the next generation of durable high-power density sodium storage anodes.

Low dielectric loss and infrared emissivity coating with enhanced mechanical property by grafting modification of EPDM

Composite coating materials or structures with low infrared emissivity and high radar transmittance are in urgent need in practical applications, among which binder is one of the important factors affecting the mechanical properties, infrared and dielectric properties of coatings. Acrylic acid (AA) and maleic anhydride (MAH) were used as graft monomers to modify ethylene propylene diene monomer (EPDM) binder. Composite coating with low infrared emissivity and low dielectric properties was prepared by using modified EPDM as binder, floating aluminum (Al) powder and antistatic carbonaceous fiber (CF) as filler. The effects of the type and amount of modified monomer on the mechanical properties, infrared emissivity and dielectric properties of the binder and the composite coating were systematically studied. The results show that the tensile strength (σb) and elongation at break (e) of the composite coating can be increased by 32% and 18%, respectively, by appropriate grafting modification of the binder. The infrared emissivity and the dielectric properties of the composite coating has a slight change with the increase of graft monomer content. Grafting modification of the binder improves the compatibility, wettability and interfacial bonding between filler and binder, which remarkably enhanced the mechanical and comprehensive properties of the composite coating. The effect mechanism of grafting modification of AA and MAH is disclosed from the aspects of polarity, branching and crosslinking. This work increases the selection range of binders needed to prepare low infrared emissivity materials.

Embedding Metal–Organic Frameworks for the Design of Flexible Hybrid Supercapacitors by Electrospinning: Synthesis of Highly Graphitized Carbon Nanofibers Containing Metal Oxide Nanoparticles

Electrospun carbonaceous fibers have emerged as promising electrode materials for application in energy storage devices. However, their relatively poor electrical conductivity (due to their amorphous carbon structures) and low capacitive performance lead to poor prospects for their further application. Herein, a universal synthesis of highly graphitized carbon nanofibers, containing various metal oxide nanoparticles (e.g., Fe2O3, NiO), by the pyrolysis of metal–organic framework (MOF)‐embedded electrospun nanofibers, is reported. The resulting carbon nanofibers exhibit large mesopore volumes, contain large quantities of Faradic metal oxide nanoparticles, and are highly graphitized. The fibers also have excellent mechanical flexibility, provide fast ion transfer characteristics, and a large pseudocapacitance combined with excellent electrical conductivity, leading to large specific capacitances. Consequently, asymmetric flexible hybrid supercapacitors assembled from Fe2O3‐embedded highly graphitized carbon nanofibers (FOCNF) and NiO‐embedded highly graphitized carbon nanofibers (NOCNF) exhibit a high energy density of 43.1 Wh kg−1 at a power density of 412.5 W kg−1 and possess excellent flexibility (capacitance retention of 94.4% at 180° bending and 96.2% at 30° twisting) with superior cycling stability. This strategy provides a new MOF‐based approach for the design and synthesis of multifunctional flexible carbonaceous materials and might lead to their further application in flexible energy storage devices.

Low-infrared-emissivity Al@SiO2/EPDM composite coating compatible with low dielectric loss and antistatic property

Low infrared emissivity coatings have been widely used in many fields. At present, there are few researches on coatings that are compatible with low infrared emissivity and high radar wave transmittance. In this paper, floating aluminum (Al) powdercoated with SiO2 was prepared using tetraethyl orthosilicate (TEOS) as raw material by sol-gel method. The composite coating was prepared using modified Al powder and antistatic carbonaceous fiber (CF) as filler, EPDM as binder. The surface morphology, infrared absorption properties of the modified Al powder and the infrared emissivity, surface resistivity, electromagnetic properties and mechanical properties of the composite coating were analyzed. The results show that with the increase of TEOS addition amount, more SiO2 was covered to the surface of floating Al powder. By adjusting the thickness of the surface modification layer of floating Al powder,the dielectric constant (ε) and dielectric loss tangent values (tanδ) of the composite coating were significantly reduced. When the addition amount of TEOS is 1 g for Al@SiO2, the ε and tanδ can be significantly reduced, and the infrared emissivity was less than 0.6, the tensile strength (σb) and elongation rate at break (e) decreased slightly. This suggests that the composite coating has low infrared emissivity compatible with high radar wave transmittance was obtained, which is expected to be applied to the surface of aircraft radome.

High-Speed Blow Spinning of Neat Graphene Fibrous Materials.

Achieving high spinning speed is critical to the production efficiency and viable application of fiber species. Graphene fiber (GF) has recently emerged as a carbonaceous fiber with excellent functionality. However, the extremely low wet spinning speed of GF has limited its applications. We realized high-speed blow spinning of neat GF and fabric by modulating the rheological properties of the graphene oxide (GO) dispersion. We achieved a speed of 556 m min-1, 2 orders of magnitude faster than that for wet spinning. We chose ultrahigh molecular weight polymers as transient additives to circumvent the intrinsic barrier effect of GO and achieve high spinning dope stretchability at low polymer percentages-down to 25 wt %. Minimizing the polymer additive content ensures the high electrical/thermal conductivity of the blow-spun fiber and fabric. This work provides insight into the unique flow properties of 2D sheets and will promote the efficient production of graphene-based fibrous materials.

Stress relaxation behaviors of graphene fibers

Stress relaxation, the decreasing trend of stress at a given strain along with time, is an essential mechanical behavior for any structural material. Graphene fiber (GF), a new kind of carbonaceous fiber, has emerged prominent mechanical performance and multifunctionality since first invented in 2011. However, most of efforts were focused on the improvement of mechanical strength and electrical/thermal conductivity and dynamic mechanical behavior has been ignored. Here, we studied the stress relaxation behavior of GF and revealed a severe stress drop for nascent GF. We found that the drop in stress during relaxation decreased with the promotion of the orientation degree and crystallinity. Plasticization stretching strategy and graphitization process were presented to relieve the relaxation of GF, accompanying with excellent mechanical strength. The optimized GF exhibits best stress relaxation property with 99% stress remained after relaxation. This work reveals an essential relaxation behavior of GFs and develops effective processes to conquer stress relaxation, making GFs for practical applications as structural materials.

Electro-induced shape memory effect of 4D printed auxetic composite using PLA/TPU/CNT filament embedded synergistically with continuous carbon fiber: A theoretical & experimental analysis

A novel strategy is proposed to fabricate continuous fiber-reinforced electro-induced shape memory auxetic composites (CFRSMCs) by combining conductive filaments and continuous carbon fiber through 3D printing technology. In the first step, the conductive filaments were manufactured based on Poly-lactic-acid/Thermoplastic-urethane/Carbon-nanotube (PLA/TPU/CNT) blend nanocomposite, and the CFRSMCs were then prepared, composing different carbonaceous fiber content with a variety of extrusion width. The main aim of the present work is to evaluate the mechanical, electrical, and thermal properties as well as the shape memory effect (SME). With regard to this, the negative Poisson's ratio effect of the printed CFRSMCs was precisely assessed through tensile measurement, and a well-adjusted theoretical model was employed for further predictions. Accordingly, as compared to free-fiber printed samples, the CFRSMCs exhibited superb mechanical properties and rapid electro-induced SME (a recovery ratio of 94% under 10 V within 25 s). Moreover, due to tailoring co-conductive networks by the CNTs and carbon fibers in the printed composites, a great deal of activation capability in the auxetic CFRSMCs could be revealed by various stimuli and for smart applications. This advanced strategy indicates a great potential to fabricate various auxetic electro-induced CFRSMCs used in small scale of deployable trusses or other lightweight smart components like adaptive energy absorption devices and human-scale orthopedic materials.

Enveloping a Si/N-doped carbon composite in a CNT-reinforced fibrous network as flexible anodes for high performance lithium-ion batteries

A CNT-reinforced carbonaceous fibers network anchored with N-doped carbon-coated Si (C/Si/CNTs) has been fabricated. Utilized as flexible anodes for lithium-ion batteries, the C/Si/CNT delivers excellent cycling performance and rate capabilities.

Difunctional composite coatings with low infrared emissivity and electrostatic dissipation property

The functional coatings play a critical role in many fields. To obtain difunctional composite coatings with low infrared emissivity and electrostatic dissipation (ESD) property, the composite coatings reinforced by aluminum-doped zinc oxide (AZO) and ESD carbonaceous fiber (CF) hybrid pigments were prepared, which were characterized by X-ray diffraction, scanning electron microscopy, infrared emissometer and insulation resistance tester. The effects of Al doping ratio of AZO, pigment adding amount and pigment type on the infrared emissivity and surface resistivity of the composite coating have been studied. The results confirmed that AZO of 7at.% doping concentration has lower infrared emissivity, and the infrared emissivity of AZO and CF coatings decreases with the increase of filler content. When AZO and CF are mixed at 1:1, the surface resistivity of the coating is 6380 Ω, which is much lower than that of any single pigment coating. Their synergy effect was contributed to form a continuous conductive path in the coating, enhance the tunnel current and obtain low surface resistivity for electrostatic dissipation. This work provides a new strategy for developing difunctional composite coatings with low infrared emissivity and electrostatic dissipation property.

Did a Complex Carbon Cycle Operate in the Inner Solar System?

Solids in the interstellar medium consist of an intimate mixture of silicate and carbonaceous grains. Because 99% of silicates in meteorites were reprocessed at high temperatures in the inner regions of the Solar Nebula, we propose that similar levels of heating of carbonaceous materials in the oxygen-rich Solar Nebula would have converted nearly all carbon in dust and grain coatings to CO. We discuss catalytic experiments on a variety of grain surfaces that not only produce gas phase species such as CH4, C2H6, C6H6, C6H5OH, or CH3CN, but also produce carbonaceous solids and fibers that would be much more readily incorporated into growing planetesimals. CH4 and other more volatile products of these surface-mediated reactions were likely transported outwards along with chondrule fragments and small Calcium Aluminum-rich Inclusions (CAIs) to enhance the organic content in the outer regions of the nebula where comets formed. Carbonaceous fibers formed on the surfaces of refractory oxides may have significantly improved the aggregation efficiency of chondrules and CAIs. Carbonaceous fibers incorporated into chondritic parent bodies might have served as the carbon source for the generation of more complex organic species during thermal or hydrous metamorphic processes on the evolving asteroid.

Tunable agglomeration of Co3O4 nanowires as the growing core for in-situ formation of Co2NiO4 assembled with polyaniline-derived carbonaceous fibers as the high-performance asymmetric supercapacitors

Cobalt-based multicomponent oxides nanocomposites deliver extraordinary rate capabilities and electrochemical capacitance owing to the fast reaction kinetics, regarded as advanced electrodes for novel renewable energy harvest and conversion with great attention recently. Herein, by manipulating the concentration of fluoride ions (F−), the in-situ agglomeration states of cobalt oxides nanowires on 3D Ni Foam are investigated systemically, which benefiting the further growth of novel spinel Co2NiO4 through electrochemical routine. Acting as the positive electrode for supercapacitor, Co2NiO4@Co3O4 composite exhibits the specific capacitance as high as 1241.8 F g−1, together with the excellent rate capabilities of 92.83% retention with a 20-fold specific current increase. Based on the kinetics analysis, the capacitive contribution achieves 83.3% at the scan rates of 50 mV s−1. Matching core-shell like Co2NiO4@Co3O4 composites with self N,O-doped conducting polymers derived carbon, as-fabricated asymmetric supercapacitor (ASC) devices could deliver an energy density of 85.97 Wh kg−1 at the power density of 0.8 W kg−1. Taking advantage of Faradic redox electrodes couple with pseudocapacitive ones can be proved as a promising way to obtain high performance energy storage devices.

The incorporation of expanded 1T-enriched MoS2 boosts hybrid fiber improved charge storage capability

In order to enhance the charge storage capability of carbonaceous fibers for wearable supercapacitors, efforts have been devoted to the incorporation of transition metal dichalcogenides (e.g., MoS2), nevertheless the improvement is moderate since the electrochemical properties of MoS2 severely depend on their crystal phase and interlayer spacing. Herein, a facile space-confined hydrothermal method is developed to synthesize graphene fibers embedded with expanded 1T-enriched MoS2 in a single-step. In such a fiber configuration, 1T phase enables MoS2 hydrophilicity and high electrical conductivity while expanded interlayer spacing facilitates fast ion intercalation/de-intercalation. The hybrid fibers exhibit significantly enhanced volumetric specific capacitance (CV) of 491.1 F cm−3 for single electrode and 44.6 F cm−3 for solid-state device, respectively, with good rate performance and excellent cycling stability.

Nitrogen/sulphur dual-doped hierarchical carbonaceous fibers boosting potassium-ion storage

Boosting potassium-ion storage by nitrogen/sulphur dual-doped hierarchical carbonaceous fibers derived from Aspergillus niger with large interlayer spacing, abundant defects and storage sites. The carbon materials as anode electrodes have been widely studied for potassium ion batteries (PIBs). However, the large size of potassium ions prevents their intercalation/deintercalation, resulting in poor storage behaviors. Herein, a novel design of N/S codoped hierarchical carbonaceous fibers (NSHCF) formed from nanosheets self-assembled by catalyzing Aspergillus niger with Sn is reported. The as-prepared NSHCF at 600 °C (NSHCF-600) exhibits a high reversible capacity of 345.4 mAh g −1 at 0.1 A g −1 after 100 cycles and an excellent rate performance of 124.5 mAh g −1 at 2 A g −1 . The excellent potassium storage performance can be ascribed to the N/S dual-doping, which enlarges interlayer spacing (0.404 nm) and introduces more defects. The larger interlayer spacing and higher pyridinic N active sites can promote K ions diffusion and storage. In addition, the ex situ transmission electron microscopy reveals the high reversibility of potassiation/depotassiation process and structural stability.

Tungsten incorporation in nickel doped carbon nanofibers as efficient electrocatalyst for ethanol oxidation

To find proper non-expensive electrocatalyst materials for ethanol oxidation is a big challenge. Transition metals catalysts are considered as the ideal solution for the electro-oxidation of ethanol. Nickel demonstrates high electrocatalytic activity that makes it the predominant candidate for ethanol electro-oxidation. In this study, the electrocatalytic activity of nickel was improved by the synergetic effect of a co-catalyst (Tungsten based nanomaterial) and a proper support (carbon nanofibers). Due to its high adsorption capacity, a nanomaterial of carbonaceous fibers has been used as support for Ni -based electrocatalysts. Different contents of tungsten incorporated in Ni-doped carbon nanofibers (Ni/C) were prepared and the effect of different parameters such as morphology, W content, calcination temperature, ethanol concentration and reaction temperature on the electro-oxidation performance of ethanol have been studied. At 2.0 M ethanol concentration and 25 wt% tungsten content, the electro-oxidation current density of nanoparticles and nanofibers morphologies were 28.23 and 99 mA.cm−2, respectively. The nanofibers calcinated at 1000 °C shows the highest electrocatalytic activity compared to the samples calcinated at 700 and 850 °C. The sample containing 10 wt% tungsten and calcinated at 1000 °C gives a current density of 2.5 times higher than of the sample prepared at 850 °C. The sample of 25 wt% tungsten incorporated in Ni-doped carbon nanofibers shows the best performance towards electro-oxidation of ethanol in basic medium where a current density of 99.3 ± 0.02 mA.cm−2 was obtained. This work will open the window towards a new non-expensive electrocatalyst in the ethanol electro-oxidation process.