Hollow Carbon Fibers Research Articles

Development of High–performance Carbon Hollow Fiber Membranes for Hydrogen Separation from Light Hydrocarbons

Development of High–performance Carbon Hollow Fiber Membranes for Hydrogen Separation from Light Hydrocarbons

Lattice composites with embedded short carbon fiber/Fe3O4/epoxy hollow spheres for structural performance and microwave absorption

Lightweight absorption materials with superior mechanical properties have received significant attention owing to their potential for use in military stealth and electromagnetic protection applications. Herein, a novel electromagnetic (EM) wave absorbing lattice structured composite material containing a hollow short carbon fiber (SCF)/Fe3O4/epoxy sphere filler, and an epoxy resin matrix, is described. The morphology, density, and isostatic compression strength of the hollow SCF/Fe3O4/epoxy spheres were measured, and the mechanical and electromagnetic wave absorption properties of the epoxy resin composite embedded with the hollow SCF/Fe3O4/epoxy spheres were studied. The results indicate that the composite possessed a high compression strength of ~57.3 MPa with a density of only ~0.92 g/cm3. Furthermore, the effective absorption bandwidth within the range of 2–18 GHz of the composite was 1.8 GHz, with an ultra-thin equivalent thickness of only ~0.48 mm. The macro-sized hollow structure spheres were effective EM wave absorption enhancements, and the lattice composite embedded with these hollow spheres presented a unique structure and excellent absorption performance.

Anisotropically enhanced heat transfer properties of phase change material reinforced by graphene-wrapped carbon fibers

Organic phase change materials (PCM, such as paraffin) are broadly used in thermal energy storage systems, especially for the efficient utilization of solar energy and industrial waste heat, whereas their low shape-stability and poor heat transfer performance have hindered the practical applications. In this work, we aim at producing high-performance phase change composites (PCCs) with high, anisotropic thermal conductivity and good shape-stability. The PCCs are supported by a biomass-derived porous carbon scaffolds, which are constructed with graphene-wrapped and vertically aligned hollow carbon fibers. The PCC with a filler content of 8.5 wt% exhibits a high lateral thermal conductivity of 1.36 W m−1 k−1 and an even higher thermal conductivity of 2.68 W m−1 K−1 along the axial fiber direction which is 10.7-fold higher than pure paraffin. The PCCs also show satisfactory shape stability, high latent heat, good thermal cycling and chemical stability. These results demonstrate the potential for fast thermal energy conversion and management using our novel carbon scaffold supported PCCs with tailored anisotropic thermal transfer properties.

Preparation and adsorption of CO2 and H2 by activated carbon hollow fibers from rubber wood (Hevea brasiliensis)

A series of activated carbon hollow fibers doped with charcoal powder (WC-ACHFs) were prepared from wood waste with great potential for application in the gas adsorption of CO2 and H2. The hydrogen storage of WC-ACHF-1.0% increased approximately 10.5% more than that of activated carbon hollow fibers (ACHF), and the highest hydrogen uptake reached 4.51 wt% at 77 K and 100 bar. Regarding the CO2 adsorption, the highest adsorption amount reached 7.13 mmol g-1 and the mass content was 31.35 at 273 K, which was 49.8% higher than the sample without doping. In addition, the multiple heteroatoms (N, P) from wood waste liquefaction had a synergistic effect on the gas adsorption properties of WC-ACHFs. These results showed that a facile method was promising for the preparation of wood-derived activated carbon hollow fibers from forestry and agricultural residues in the application of gas adsorption.

Thin carbon hollow fiber membrane with Knudsen diffusion for hydrogen/alkane separation: Effects of hollow fiber module design and gas flow mode

Recovery of heavier hydrocarbons, C2~C4 olefins and paraffins, from gas streams is of great importance economically. In this study, asymmetric carbon hollow fiber membranes (CHFMs) were prepared by a one-step vacuum-assisted dip coating and pyrolysis, and investigated for H2/CO2, H2/C2H6, and H2/C3H8 separations. To increase the mechanical strength of the CHFMs, a porous alumina hollow fiber with ID/OD = 2 mm/4 mm was used as the supporting material. A solution of polyetherimide in N-methyl-2-pyrrolidone was used as the casting solution. The effects of (1) membrane preparation parameters, (2) fiber packing densities, (3) fiber packing arrangement, and (4) gas flow configuration (inside-out or outside-in) on the gas-separation performance were also investigated. The results showed that decreasing the concentration of the casting dope and the number of coating cycles was found to be the most effective approach to increase the H2 permeance, while maintaining the H2/CO2 selectivity. Further, as the fiber packing density was increased from 5.54% to 38.78% for the hexagonal packing configuration, the H2 permeance increased from 362.04 GPU to 711.61 GPU, without any decrease in the gas selectivity. The as-prepared CHFM exhibited the maximum gas permeance of 711.61 GPU for H2 and the following gas selectivity: 2.79, 4.65, and 5.34 towards H2/CO2, H2/C2H6, and H2/C3H8, respectively. The successful preparation and modularization of the CHFM is advantageous and industrially relevant for several gas-separation applications, such as H2 energy production from CO2, C2H6, and C3H8, and olefins/paraffins recovery.

Dispersed Nickel Cobalt Oxyphosphide Nanoparticles Confined in Multichannel Hollow Carbon Fibers for Photocatalytic CO2 Reduction

AbstractMaterials for high‐efficiency photocatalytic CO2 reduction are desirable for solar‐to‐carbon fuel conversion. Herein, highly dispersed nickel cobalt oxyphosphide nanoparticles (NiCoOP NPs) were confined in multichannel hollow carbon fibers (MHCFs) to construct the NiCoOP‐NPs@MHCFs catalysts for efficient CO2 photoreduction. The synthesis involves electrospinning, phosphidation, and carbonization steps and permits facile tuning of chemical composition. In the catalyst, the mixed metal oxyphosphide NPs with ultrasmall size and high dispersion offer abundant catalytically active sites for redox reactions. At the same time, the multichannel hollow carbon matrix with high conductivity and open ends will effectively promote mass/charge transfer, improve CO2 adsorption, and prevent the metal oxyphosphide NPs from aggregation. The optimized hetero‐metal oxyphosphide catalyst exhibits considerable activity for photosensitized CO2 reduction, affording a high CO evolution rate of 16.6 μmol h−1 (per 0.1 mg of catalyst).

Novel hollow fiber sandwich composite post system: mechanical characteristics.

There is currently no consensus on the optimal post system to provide effective long-term results. We used an engineering approach to investigate the mechanical properties of a sandwich hollow carbon fiber post in synergy with a new bonding technique. We studied two systems - a sandwich fiber hollow post (Techole®, Isasan, Como, Italy) composed of carbon fiber incorporated in a Dpp-MOR resin mix and a traditional non-hollow post (Tech 2000®, Isasan, Como, Italy). A bi-component composite (Clearfil Core®, Kuraray, New York, NY, USA) (2.2 gcm3, 12.3 GPa) and a dual cure composite with lower density and modulus of elasticity (Clearfil DC Core®, Kuraray, New York, NY, USA) (2.0 gcm3, 10.0 GPa) were also used into hollow posts. Results from three-point bending test (N.=81), compression test (N.=78) and cut test (N.=81) were achieved. In the three-point bending test there were significant differences in flexibility/bending when sandwich fiber hollow posts were filled with composite of different modulus of elasticity. Hollow sandwich posts showed also significant (P=0.000) better resistance to compression and cutting than solid posts, independently of the type of composite. Moreover, hollow posts filled plus composite with a modulus of elasticity of 12.3 GPa showed significant (P=0.000) improved resistance parameters rather than hollow posts filled with a composite of 10.0 GPa. The study confirms the favorable mechanical properties of the hollow sandwich fiber post system (Techole®) and the synergistic efficacy when used in combination with the composite Clearfil DC Core® (10.0 GPa) and, especially, Clearfil Core® (12.3 GPa).

Dispersed Nickel Cobalt Oxyphosphide Nanoparticles Confined in Multichannel Hollow Carbon Fibers for Photocatalytic CO2 Reduction.

Materials for high-efficiency photocatalytic CO2 reduction are desirable for solar-to-carbon fuel conversion. Herein, highly dispersed nickel cobalt oxyphosphide nanoparticles (NiCoOP NPs) were confined in multichannel hollow carbon fibers (MHCFs) to construct the NiCoOP-NPs@MHCFs catalysts for efficient CO2 photoreduction. The synthesis involves electrospinning, phosphidation, and carbonization steps and permits facile tuning of chemical composition. In the catalyst, the mixed metal oxyphosphide NPs with ultrasmall size and high dispersion offer abundant catalytically active sites for redox reactions. At the same time, the multichannel hollow carbon matrix with high conductivity and open ends will effectively promote mass/charge transfer, improve CO2 adsorption, and prevent the metal oxyphosphide NPs from aggregation. The optimized hetero-metal oxyphosphide catalyst exhibits considerable activity for photosensitized CO2 reduction, affording a high CO evolution rate of 16.6 μmol h-1 (per 0.1 mg of catalyst).

PPy‐Derived Sandwich‐Structured Hollow Carbon Fiber Anchoring Sn4P3 as Anode Materials with Improved Na+ Storage

AbstractSn4P3 has been considered as one of the promising anode materials for sodium ion batteries (SIBs) due to its high reversible capacity and low redox potential. However, the large volume expansion and Sn aggregation during the sodiation‐desodiation process result in the poor cycle stability, limiting its commercial use. Herein, a sandwich‐structured hollow carbon fiber anchoring Sn4P3 quantum dots (C@Sn4P3@HCF) is synthesized by carbon coating, carbonization/reduction and phosphorization with PPy hollow fiber as a template. Benefitting from the unique sandwiched architecture as well as the synergistic effect between Sn4P3 and N‐doped hollow carbon fiber, C@Sn4P3@HCF hybrids deliver a high initial discharge capacity of 631 mAh g−1 at 100 mA g−1, excellent rate capability (205 mAh g−1 at 50 mA g−1, 108 mAh g−1 at 1500 mA g−1) and ultrastable capacity retention of >103 mAh g−1 with a coulombic efficiency of 99.4% over 1000 cycles at 300 mA g−1. Hence, C@Sn4P3@HCF hybrids show great potential as an alternative anode material for next‐generation SIBs.

Controlled Design of a Robust Hierarchically Porous and Hollow Carbon Fiber Textile for High-Performance Freestanding Electrodes.

For most carbon‐based materials, hierarchical porous structure including well‐defined macropores, mesopores, and micropores is commonly seen in 3D aerogels, monoliths, or some carbothermic natural biomass. However, because of the filiform character and long draw ratio, it is difficult to achieve such pore network as well as attain excellent mechanical performance in a 1D single carbon fiber system. To address this issue, an innovative hierarchical porous and hollow carbon textile (HPHCT) is developed via the “dynamic template (KOH, SiO2, and Al2O3) calcination” strategy. Unlike conventional one‐step activated carbonized fiber simply with meso or micropores, the fabricated textile generates honeycomb‐like macropores uniformly spreading on fiber surface. More importantly, the ultra‐lightweight yet flexible HPHCT is mechanically robust, superior to ordinary carbonized one. In addition, it delivers high capacitance of maximum 220 F g−1 as well as keeping long term stability with 100% retention after 10 000 cycles as freestanding electrodes in supercapacitor. Meanwhile, the all‐solid integrated symmetric HPHCT supercapacitors demonstrates its high potential in powering electronics for wearable energy storage application.

Preparation of Three-Dimensional Nitrogen-Doped Hollow Fiber Carbon and Its Application to Electrochemical Energy Device

Three-dimensional nitrogen-doped carbon materials are prepared using thermally decomposable polystyrene(PS) and mussel-inspired polydopamine(PDA), as a sacrificial template and a nitrogen-doped carbon precursor, respectively. By virtue of the versatile coating ability associated with the high nitrogen content, dopamine was demonstrated to be an effective precursor for the preparation of nitrogen-doped carbon. In previous studies, PDA has been used as a nitrogen source by coating its layer onto a main carbon source. Herein, however, the PDA is utilized not only for the nitrogen precursor but also for the carbon source, without any additional carbon source, in order to achieve the higher nitrogen content and simple synthetic procedure. As a result, nitrogen content on carbon increased to over 4 at. %, which was limited to under 1 at. % when PDA was just coated onto the other carbon source. Moreover, due to highly moldable characteristics of polymer ingredients, three-dimensional carbon structures with various configurations could be prepared such as micron-sized hollow carbon fiber. First, nitrogen-doped hollow carbon fiber with μm-sized diameter was synthesized by coating PDA around the electrospun PS fiber and following pyrolysis for PS removal and PDA carbonization. The length of hollow carbon fiber was also able to be controlled from several μm to hundreds of μm, using ultra-sonication. Completely hollow carbon fiber with about 3-μm diameter was successfully obtained and analyzed its physical characteristics from XPS, Raman and Mercury porosimeter. Nearly 4 at. % of nitrogen was detected on the hollow carbon fiber and the over 68 % of nitrogen-doping structure is revealed to be graphitic-N, which is known as the most effective nitrogen-doping structure for oxygen reduction reaction. Since both PDA-derived carbon materials have relatively high nitrogen content and can form a self-supporting network, endowing high applicability as a binder-free electrode, they can be effectively applied to electrochemical energy device, specifically polymer electrolyte membrane fuel cell (PEMFC) and Li-O2 battery system where the oxygen reduction reaction is the dominant reaction.

Boosting the Reversibility of Sodium Metal Anode via Heteroatom-Doped Hollow Carbon Fibers.

Sodium (Na) metal anodes stand out with their remarkable capacity and natural abundance. However, the dendritic Na growth, infinite dimensional changes, and low Coulombic efficiency (CE) present key bottlenecks plaguing practical applications. Here, heteroatom-doped (nitrogen, sulfur) hollow carbon fibers (D-HCF) are rationally synthesized as a nucleation-assisting host to enable a highly reversible Na metal. The "sodiophilic" functional groups introduced by the heteroatom-doping and large surface area (≈1052 m2 g-1 ) synchronously contribute to a homogenous plating morphology with dissipated local current density. High "sodiophilicity" of the D-HCF is confirmed by first-principle calculations and experimental results, where strong adsorption energy of -3.52 eV with low Na+ nucleation overpotential of 3.2 mV at 0.2 mA cm-2 is realized. As such, highly reversible plating/stripping is achieved at 1.0 mA cm-2 with average CE approximating 99.52% over 600 cycles. The as-assembled Na@D-HCF symmetric cells exhibit a prolonged lifetime for 1000 h. A full-cell paired with Na3 V2 (PO4 )3 cathode further demonstrates stable electrochemical behavior for 200 cycles at 1 C along with excellent rate performance (102 mAh g-1 at 5 C). The results clearly show the effectiveness of the D-HCF in manipulating Na+ deposition and thus the significance of nucleation control in realizing dendrite-free metal anodes.

Improvement of electrochemical properties of activated carbon hollow fibers from liquefied wood by charcoal power

Abstract A series of activated carbon hollow fibers doped with charcoal powder (WC-ACHFs) were prepared from wood waste by liquefaction, melt spinning and steam activation methods. When evaluated as electrodes, activated carbon hollow fibers doped with charcoal powder exhibited an outstanding gravimetric specific capacitance of 481 F g−1 at 0.5 A g−1 and cyclic stability with 98.8% capacitance retention over 2000 cycles. In addition, the multiple heteroatoms-doping of N and P from wood waste liquefaction have synergistic effect on electrochemical properties of WC-ACHFs, which is due to its combined merits of pseudocapacitance for sufficient charge storage and the good wettability for efficient ion diffusion. These results display that a facile method is promising for the preparation of wood-derived activated carbon hollow fibers from forestry and agricultural residues in the application of electrochemical energy storage.

Hyperaging Tuning of a Carbon Molecular‐Sieve Hollow Fiber Membrane with Extraordinary Gas‐Separation Performance and Stability

AbstractThis study reports 6FDA:BPDA‐DAM polyimide‐derived hollow fiber carbon molecular‐sieve (CMS) membranes for hydrogen and ethylene separation. Since H2/C2H4 selectivity is the lowest among H2/(C1‐C3) hydrocarbons, an optimized CMS fiber for this gas pair is useful for removing hydrogen from all‐cracked gas mixtures. A process we term hyperaging provides highly selective CMS fiber membranes by tuning CMS ultramicropores to favor H2 over larger molecules to give a H2/C2H4 selectivity of over 250. Hyperaging conditions and a hyperaging mechanism are discussed in terms of an expedited physical aging process, which is largely controlled by the hyperaging temperature. For the specific CMS material considered here, a hyperaging temperature beyond 90 °C but less than 250 °C works best. Hyperaging also stabilizes CMS materials against physical aging and stabilizes the performance of H2 separation over extended periods. This work opens a door in the development of CMS materials for the separation of small molecules from large molecules.

Hyperaging Tuning of a Carbon Molecular‐Sieve Hollow Fiber Membrane with Extraordinary Gas‐Separation Performance and Stability

This study reports 6FDA:BPDA-DAM polyimide-derived hollow fiber carbon molecular-sieve (CMS) membranes for hydrogen and ethylene separation. Since H2 /C2 H4 selectivity is the lowest among H2 /(C1 -C3 ) hydrocarbons, an optimized CMS fiber for this gas pair is useful for removing hydrogen from all-cracked gas mixtures. A process we term hyperaging provides highly selective CMS fiber membranes by tuning CMS ultramicropores to favor H2 over larger molecules to give a H2 /C2 H4 selectivity of over 250. Hyperaging conditions and a hyperaging mechanism are discussed in terms of an expedited physical aging process, which is largely controlled by the hyperaging temperature. For the specific CMS material considered here, a hyperaging temperature beyond 90 °C but less than 250 °C works best. Hyperaging also stabilizes CMS materials against physical aging and stabilizes the performance of H2 separation over extended periods. This work opens a door in the development of CMS materials for the separation of small molecules from large molecules.

Screening Cellulose Spinning Parameters for Fabrication of Novel Carbon Hollow Fiber Membranes for Gas Separation

Novel carbon hollow fiber membranes (CHFMs) have been, for the first time, prepared from cellulose precursors directly spun with a cellulose/(1-ethyl-3-methylimidazolium acetate (EmimAc) + dimethyl...

Self-healing liquid metal nanoparticles encapsulated in hollow carbon fibers as a free-standing anode for lithium-ion batteries

As a novel self-healing material, room-temperature liquid metal (LM) composed of Ga and Sn is a promising anode in lithium-ion batteries (LIBs). Although there is no structural pulverization of the anode material with self-healing ability, the volume change during cycling may cause cracks in the supporting structure, such as binders or conductive additives, and thus significantly limits the cycling stability and high capacity for lithium-alloy electrodes. Here, novel self-healing core-shell fibers, with liquid metal nanoparticles as the core coated with a carbon shell (denoted as LMNPs@CS fibers), were synthesized by facile coaxial electrospinning and a carbonization process. The as-prepared fibers, which encapsulated nanosized self-healing LM particles with a well-designed inner void space of the shell, served as free-standing anodes for LIBs. Such anodes offered a reversible capacity of 603.9 mAh g−1 at 1000 mA g−1, excellent rate capability, and a highly stable cycling performance with a discharge capacity of 552 mAh g−1 after 1500 cycles at 1000 mA g−1. The superior electrochemical performance can be attributed to (1) the self-healing ability of the LMNPs, which ensured the superior cycling performance of the electrode, (2) the unique core-shell structure with a well-designed void space, which alleviated the volume changes of LMNPs during the lithiation/delithiation processes, and (3) the self-healing LMNPs, composed of Ga and Sn, possessed high theoretical capacities. These promising strategies and associated opportunities demonstrate great potential for fabricating advanced self-healing anode materials for LIBs.

Simple control of the pore structures and gas separation performances of carbon hollow fiber membranes by chemical vapor deposition of propylene

In this study, we investigated the effects of one-step chemical vapor deposition (CVD) of propylene on the pore structures and gas separation performances of carbon hollow fiber membranes derived from sulfonated poly(phenylene oxide) (SPPO). The CVD is performed by feeding a 5–100% of propylene gas at the carbonization peak temperature. The obtained CVD carbon membranes had higher carbon concentrations and were hydrophobic. Their water permeances were considerably lower than those of uncoated membranes in pervaporation experiments. The gas permeances of the CVD membranes also decreased but the ideal selectivities greatly improved, especially for H2/CH4 from 130 to 1625 with the membrane prepared by pyrolysis at 650 °C for 60 min in combination with CVD of 100% propylene for 5 min. We found that the gas separation performance could be easily controlled by changing the propylene volume fraction and CVD time. The highest H2/CH4 selectivity of 29,940 was obtained for a membrane pyrolyzed at 700 °C for 20 min with CVD using 10% propylene for 20 min.

Analysis of Bulletproof Vest Made from Fiber Carbon Composite and Hollow Glass Microsphere (HGM) in Absorbing Energy due to Projectile Impact

Bulletproof vest serves as a barrier and simultaneously absorbing the impact energy of a projectile shot from a firearm so it could not injure the users. Manufacture of lighter bulletproof vests with good absorbent of impact energy, is expected, because it supports the mobility and safety of its users. In this study, a composite composed of an epoxy matrix with a 16% Hollow Glass Microsphere (HGM) and carbon fiber reinforce to be implemented in a bulletproof vest. The objective of this research is to analyze the bullet-proof vests made of epoxy matrix composites with reinforcement in the form of HGM and carbon fiber through simulation with finite element method. Simulations with Ansys conducted in accordance with NIJ Standard 0101.06 from the U.S. Department of Justice, where the projectile initial velocity of 426 m/s for the category IIIA class weapon with a kinetic energy of projectile amounted to 528.37 Joules. The simulation with Ansys was performed by varying the thickness of bulletproof vests to obtain optimum thickness. The outcome of this research is a bulletproof vest that absorbs the impact energy of the projectile, so that the energy transmitted to the body is smaller than 170 Joules. Having obtaining the optimum thickness of bulletproof vest, an experimental verification will be performed to validate the simulation results. In the simulation results showed that a bullet proof vest with a thickness of 20 mm has been able to meet the standards of Major General Julian S. Hatcher, a U.S. Army ordnance expert with great energy generated at 138.77 Joules.

Nitrogen‐Doped Hollow Carbonized Cotton Fully Covered with Trumpet‐Like Nanocarbons for High‐Performance Supercapacitors

AbstractCarbon materials obtained by carbonizing low‐cost natural materials tend to achieve a nearly solid original structure with a smaller specific surface area (SSA), which limits their application in electrochemical energy storage. In this work, by precisely controlling the heating rate and gas flow in the carbonization process, we successfully fabricated hollow carbonized cotton fibers fully covered with trumpet‐like nanocarbons (HCC@TNC) and the nitrogen‐doped product (N−HCC@TNC). N−HCC@TNC achieves a high SSA of 1477 m2 g−1 and specific capacitance of 381 F g−1 at a current density of 2 A g−1. Even at 400 A g−1, N−HCC@TNC still retains 77 % of the capacitance at 2 A g−1. Our approach to the hollow carbon fibers with surface trumpet‐like nanocarbons might provide a new way for carbonizing natural materials and low‐cost, high‐performance energy storage devices.