Surface Of Carbon Nanofibers Research Articles

Electrospun Carbon Nanofiber Supported Zero Valent Iron Nanoparticles (nZVI@ECNFs) for Cr (VI) Remediation in Ground and Waste Water

ABSTRACTZero Valent Iron nanoparticles (nZVI) were synthesized and immobilized on electrospun carbon nanofibers (ECNFs) surface in a controllable manner through redox reaction. The novel nanomaterial, ECNFs-supported nZVI (nZVI@ECNFs), were evaluated for Cr(VI) ions removal from water for the first time. nZVI@ECNFs outperformed stand-alone nZVI as well as state-of-the-art nZVI research for Cr(VI) remediation in water. nZVI@ECNFs with 0.4 g/L nZVI loading could remove 100% Cr(VI) from 50 mg/L Cr(VI) aqueous solution in as little as 5 min at pH = 4. This is enabled by coupling nanofibrous form ECNFs with dispersed distribution of individual and/or cluster nZVI on surface of ECNFs. It is envisioned that nZVI@CNFs is going to serve as a novel supported nZVI nanomaterial for super-fast heavy metal remediation in ground water and waste water treatment with adjustable high capacity as well as straightforward and energy-saving heavy metal recovery.

Plasma-Induced Polyaniline Grafted on Carbon Nanotube-embedded Carbon Nanofibers for High-Performance Supercapacitors

Polyaniline is grafted onto the surface of high conductivity carbon nanotube-embedded carbon nanofibers (PANi-P-1.0) via plasma modification to fabricate an electrode for a high performance supercapacitor. The structure and morphology of polyaniline graft onto the carbon nanofiber (CNF) are confirmed by Raman, X-ray photoelectron spectroscopy, electron microscopy and transmission electron microscopy. The emeraldine base form of nanorod-polyaniline is well-distributed on the surface of the CNF. The PANi-P-1.0 has a high specific capacitance of 606 Fg−1. From the result of the electrochemical properties, the high capacitance is contributed by the electric double layer capacitance of the high conductivity CNF and the pseudocapacitance of the grafting polyaniline. In addition, compared to polyaniline coated on the surface of the CNF, the electrochemical properties of the PANi-P-1.0 are improved by reducing the charge transfer resistance (Rct) from 13.54 to 3.87Ω, the Warburg coefficient from 101.39 to 47.96Ωs−1/2 and the relaxation time constant from 0.794 to 0.194s due to the covalent bond between the polyaniline and CNF. The PANi-P-1.0 also show excellent cycling stability after 1,000 cycles of galvanostatic charge and discharge because the free space around the grafting polyaniline allows volumetric change.

Carbon Nanofibers (CNFs) Surface Modification to Fabricate Carbon Nanofibers_Nanopaper Integrated Polymer Composite Material.

Carbon Nanofibers (CNFs) have shown great potential to improve the physical and mechanical properties of conventional Fiber Reinforced Polymer Composites (FRPCs) surface. Excellent dispersion CNFs into water or polymer matrix was very crucial to get good quality CNFs enhanced FRPCs. Because of the hydrophobic properties of CNFs, we apply the reversible switching principles to transfer the hydrophobic surface into hydrophilic surface by growing polyaniline nanograss on the surface of CNFs which was carried out in hydrochloric acid condition. Incorporating CNFs into FRPCs as a surface layer named CNFs Nanopaper to increase the erosion resistance and electrical conductivity in this research which was very important in the wind energy field. In order to get high quality dispersed CNFs suspension, a sonication unit was used to detangle and uniform disperse the functionalized CNFs. A filter with vacuum pressure used to filter the suspension of CNFs onto Carbon veil to make CNFs Nanopaper. Vacuum Aided Resin Transfer Modeling (VARTM) process was used to fabricate Nano-enhanced FRPCs samples. In order to characterize the mechanical properties, three point bending experiment was measured. The flexural strength capacity and deformation resistance and behavior were compared and analyzed. In this paper, we discussed the methods used and provided experimental parameter and experimental results.

Quantifying structural and electromagnetic interference (EMI) shielding properties of thermoplastic polyurethane–carbon nanofiber/magnetite nanocomposites

In this study, mixed-structure carbon–magnetite nanocomposites were prepared by decorating of carbon nanofiber (CNF) surfaces with magnetite (Fe3O4) nanoparticles synthesized via reflux method and characterized. The compositions of CNF–Fe3O4 nanocomposites were varied using different amounts of CNF into the Fe3O4 synthesis medium as 25/75, 50/50, and 75/25 (w/w). These nanocomposites were then used as functional fillers to prepare flexible, thermoplastic polyurethane (TPU)-based electromagnetic interference (EMI) shielding composites by solution mixing method. Structural features of fillers, morphological, and electromagnetic properties of flexible composites were studied. It was found that the magnetite nanoparticles with the average size of 8–10 nm were formed and successfully covered the oxidized CNF surfaces. It was also found that the resulting CNF–Fe3O4 nanocomposites exhibited sufficiently high saturation magnetization (Ms) values compared to Fe3O4. These CNF–Fe3O4 nanocomposites were embedded into TPU phase by employing the weight percent of 20 wt%. The flexible TPU–CNF–Fe3O4 nanocomposite having the composition of 80–5–15 wt% showed the reflection loss (RL) value of −32 dB which signified that the composite material could absorb the 97 % of an incident electromagnetic wave at around 12.14 GHz.

An effective and low cost Pd[sbnd]Ce bimetallic decorated carbon nanofibers as electro-catalyst for direct methanol fuel cells applications

In this paper, well decorated PdCe bimetallic on carbon nanofibers were synthesized by the cost effective electrospinning process and effectively applied as electro-catalyst for the detection of methanol fuel cells (MFCs). The synthesized PdCe bimetallic decorated carbon nanofibers were characterized in details using morphological, crystalline, structural, surface and electrochemical techniques. The crystalline and structural properties expressed the formation of PdCe alloys on the surface of carbon nanofibers during the electrospinning process. The PdCe bimetallic decorated carbon nanofibers were used to construct the effective anode for the high performance DMFCs and the cell performance evaluated by electrochemical measurements such as cyclovoltametry and electrochemical impedance. The PdCe bimetallic decorated carbon nanofibers based electrode presented the reasonable performance toward the methanol oxidation as increasing the current density with the increase of methanol concentration in alkaline medium. The addition of methanol in alkaline medium significantly increased the current density, which suggests that PdCe bimetallic decorated carbon nanofibers based electrode have excellent electrocatalytic activity towards the methanol.

Electrospinning, solvothermal, and self-assembly synthesis of recyclable and renewable AgBr[sbnd]TiO2/CNFs with excellent visible-light responsive photocatalysis

Novel carbon nanofibers (CNFs) modified by AgBrTiO2 composite nanoparticles (NPs) would be the most desirable nanostructure materials in preparing visible-driven catalysts because of its efficient charge separation and transport properties as well as superior light harvesting efficiency. In this study, TiO2 nanoparticles grown directly on Ag/CNFs were prepared by a simple solvothermal synthesis. The formation of AgBr, which derived from Ag NPs, was carried out by the gas/solid oxidization reaction. The characterization results indicate that AgBr-sensitized TiO2 NPs were uniformly covered on the surface of CNFs. Under visible light irradiation, the degradation efficiency of MO in the presence of AgBrTiO2/CNFs was much higher than that of TiO2/CNFs or AgTiO2/CNFs, and the as-prepared catalysts showed a universal degradation ability for different organics. Meanwhile, AgBrTiO2/CNFs had a certain photochemical stability and could be regenerated easily. The as-prepared composites could be easily separated from the solution phase due to the large length-diameter ratio of CNFs, suggesting that the AgBr-sensitized TiO2 nanoparticles loading on carbon nanofibers had a potential application in the field of dye degradation.

One-step solvothermal synthesis of Au-TiO2 loaded electrospun carbon fibers to enhance photocatalytic activity

Au-TiO2/CNFs composite materials were fabricated by electrospinning, high-temperature calcination, and solvothermal synthesis. After the one-step solvothermal synthesis, both gold and TiO2 nanoparticles were loaded on the surface of carbon nanofibers simultaneously. A series of characterizations including SEM, TEM, XRD and XPS were carried out to investigate the physicochemical properties of the as-prepared samples. The as-prepared Au-TiO2/CNFs exhibited a much higher photocatalytic activity than TiO2/CNFs in degrading MO, MB, and AR 18 under UV light irradiation, in which TiO2/CNFs sample was fabricated by the same procedures without the addition of Chloroauric acid. Moreover, the cycling tests demonstrated that Au-TiO2/CNFs had an excellent stability. This work offered a new idea on the modification and immobilization of titanium dioxide and the as-prepared Au-TiO2/CNFs has a potential application in sewage treatment and selective oxidation, etc.

Electrospun Fe2O3-carbon Composite Nanofibers as Anode Materials for Sodium-Ion Batteries

Background: With the increasing demand for large scale energy storage, people pay more and more attention on the development of sodium-ion batteries (SIBs) because of its low cost and abundance resource. This paper provides a new kind of anode material with satisfied electrical performance for SIBs. Methods: Fe2O3-carbon composite nanofibers (FeCNFs) were synthesized through an uncomplicated and meliorable electrospinning process followed by calcination. The obtained FeCNFs were applied as anode materials for sodium-ion batteries. Results: The FeCNFs SIBs show excellent performance. At a current density of 50 mA g-1, a high reversible capacity of 606 mA h g-1 is achieved. Moreover, an ideal reversible capacity of 167 mAh g-1 is achieved even at a current density of 500 mA g-1, demonstrating good rate capability of FeCNFs. Conclusion: As compared with pure carbon nanofibers (CNFs), the capacity and rate capability of FeCNFs are drastically improved due to the homogeneous dispersed Fe2O3 nanoparticles on the surface of carbon nanofibers. Such a structure prevents the aggregation of Fe2O3 nanoparticles, maintains the structure integrity and thus enhances the electrochemical performance. Keywords: Anode materials, electrospun, Fe2O3-carbon composite nanofibers, sodium-ion battery.

Enhancement of catalytic durability through nitrogen-doping treatment on the CNF-derivatized ACF support for high temperature PEMFC

As a new carbon support for high temperature – proton exchange membrane fuel cell (HT-PEMFC), the nitrogen doped CNF/ACF (N/CNF/ACF) was synthesized by coating and annealing the polypyrrole to the surface of carbon nanofiber (CNF) grown on activated carbon fiber (ACF). The durability and electrochemical performance of Pt/N/CNF/ACF and commercial Pt/C was examined and compared with various analytical tools as well as accelerated life-time test (ALT) at high temperature of 120 °C. The catalytic durability on Pt/N/CNF/ACF was improved due to the enhanced π-bonding and the basic electron donor property of nitrogen contents. Such stability of Pt/N/CNF/ACF was originated from the strong interaction between Pt particles and carbon matrix with nitrogen contents. The evidences on the nitrogen effect of Pt/N/CNF/ACF were elucidated with the gentle loss of electrochemical active surface area (ECSA) and the shift of XPS peak (Pt 4f) to the direction of higher binding energy, comparing with those of commercial Pt/C, before and after ALT. The physical and chemical properties on the Pt/N/CNF/ACF was characterized with HR-TEM, FE-SEM, FT-IR, XRD and XPS, in detail. And, their electrochemical properties for HT-PEMFC were examined with single cell and half cell test, before and after ALT.

Effect of carbon nanofiber surface morphology on convective heat transfer from cylindrical surface: Synthesis, characterization and heat transfer measurement

In this work, heat transfer surface modification is made by layers of carbon nanofiber (CNF) on a 50 μm nickel wire using Thermal chemical vapor deposition process (TCVD). Three different CNF layer morphologies are made, at 500 °C, 600 °C and 700 °C, to investigate the influence of morphology on heat transfer performance characteristics. Experimental results show that a CNF layer made at 500 °C behaves like an additional heat resistance, which is attributed to the dense structure of the layer of fibers. This results in 25% lower heat transfer compared to the heat transfer performance of the bare wire. However, samples made at 600 °C, exhibit a relatively porous layer of CNFs with relatively lower thermal conductivity compared to samples made 500 °C, resulting in an enhancement of 24%. This is because the relative porous structure leads to relatively better flow permeability which reduces the thermal resistance of the layer. Samples made at 700 °C are partly covered with a dense CNFs layer and partly with an amorphous layer of carbon. Heat transfer enhancement of 34% is achieved which is attributed to the combined effect of the highly conductive layer, high effective heat transfer surface area and rough surface morphology.

Carbon nanofibers–SiO2 composites: Preparation and characterization

A method has been developed for preparing carbon fibers–SiO2 composites using oligomethylhydridesiloxane (OMHS) as the precursor for SiO2. The presence of active hydrogen in OMHS made it possible to attain chemical interaction between the surface of carbon nanofibers (CNFs) and the applied silicon oxide layer. The oxidation rate of CNF–SiO2 composite is found to be lower by about one order of magnitude compared to that of the as-synthesized CNF. The thermal stability of CNF–SiO2 composites has been studied. Under an inert atmosphere, CNF–SiO2 composite has thermal stability up to 1300°C. At temperatures above 1350°C, silicon carbide (SiC) fibers are formed as a result of the carbothermal reduction of silicon oxide.

Hierarchical nanostructures of BiOBr/AgBr on electrospun carbon nanof ibers with enhanced photocatalytic activity

Abstract

Strong shear-driven large scale formation of hybrid shish-kebab in carbon nanofiber reinforced polyethylene composites during the melt second flow.

The formation of a hybrid shish-kebab (HSK) structure with different degrees of lamellar orientations was first observed in the solution crystallization of polyethylene (PE) in the presence of carbon nanofibers (CNFs). In this study, PE crystal lamellae were periodically decorated on the surface of CNFs and were aligned approximately perpendicular to the long axes of the CNFs, forming aligned hybrid shish-kebab nanostructures. More importantly, the fascinating structure was directly formed in all regions of the injection molded bars of HDPE/CNF composites, via a gas-assisted injection molding (GAIM), instead of the shell-core structure. In the GAIM process, an intense shear was imposed onto the melt during the melt second flow and drove PE chains to orient along the axes of the CNFs. Then the entropy penalty for PE chains deposited on the CNF surface was drastically decreased. Although the attractive van der Waals interactions were weak, the oriented PE chains could successfully adsorb on the CNF surface due to the decrease of the entropy penalty, therewith the underlayer coating was formed along the axis based on a two-dimensional mode for early nucleation on the CNF surface. Subsequently, subglobules appeared on the ordered structure, which could be regarded as the crystal nucleus. Finally, the oriented PE chains began to epitaxially grow from the subglobules with a folded-chain shape to decrease the polymer surface energy and grew perpendicular to the CNFs long axis, abiding by the "soft epitaxy" crystallization mechanism regardless of strict lattice matching.

PH controlled adsorption of water-soluble ruthenium clusters onto carbon nanotubes and nanofiber surfaces.

Supported catalysts were prepared from water-soluble molecular clusters by pH controlled impregnations in order to probe the interactions occurring between the supports and the clusters and to maximize them. The PZC of different nano-carbon solids (nanotubes and nanofibers) was determined. The EpHL method of measuring the PZC could be successfully extended for the first time to these nano-carbon supports. When impregnating these nano-carbons with water-soluble Ru clusters by varying the pH, we found that two adsorption mechanisms were taking place. We postulate that interactions in the form of π-bond coordination or reactions with higher reactivity zones of the carbon surface occur at all pH values. Electrostatic interactions coexist with the latter and play a determining role, allowing or hindering maximal adsorption. Our water-impregnated samples exhibit smaller and better distributed nanoparticles in comparison to an organic-solvent-impregnated sample. Sintering of the particles at higher activation temperature led to nanoparticles with a bimodal size distribution on the nanofibers. The bimodal size distribution is a strong indication of two different adsorption mechanisms. The obtained Ru/nano-C catalysts present a valuable activity and selectivity in the hydrogenation of lactose into lactitol.

Comparative Studies of Pristine and Functionalized CNFs Surface Properties and their Performance in Iron Distribution

Carbon nanofibers (CNFs) is one of carbon material type and has received fascinating attention to be used a metal support. In this study, two portions of samples were prepared separately into pristine CNFs (CNF-P) and functionalized CNFs (CNF-2RX) sample. CNF-2RX sample was refluxed in HNO3 solution for 2h. Subsequently, surface properties for both samples were evaluated by BET, FESEM-EDX, TEM, XPS, and FTIR. Results have shown significant differences of surface properties between CNF-P and CNF-2RX. It revealed that CNF-2RX which has been introduced to HNO3 treatment was increased 12.43% of surface area, pore volume and formed oxygen surface group (carboxylic group) compared to pristine CNFs. Then performance of iron distribution and loaded onto two different types of supports which are Fe/CNF-P and Fe/CNF-2RX by DP method were characterized by TEM, BET and XRF. These results revealed high loaded of iron were obtained for both samples (Fe/CNF-P with 8.43wt. % and 9.15wt. % for Fe/CNF-2RX) but only Fe/CNF-2RX shown uniform and close distribution between iron particles. Deposition of iron particles at Fe/CNF-2RX were found to be at internal surface which cause decrease of support surface area and pore volume with confirmed that strong interaction by adsorption between iron and oxygen surface group at CNF-2RX surface have obtained.

Direct interfacial growth of MnO2 nanoparticles on carbon nanofiber surfaces for high-performance asymmetric supercapacitors

Facile interfacial growth of MnO2 nanoparticles on carbon nanofibers (MnO2/CNF) and the application of this material as a high-performance positive electrode material in asymmetric supercapacitors are presented.

Influence of structural and textural parameters of carbon nanofibers on their capacitive behavior

Herringbone, platelet, and tubular carbon nanofibers (CNFs) were synthesized by catalytic chemical vapor deposition using methane, propane, and ethylene as carbon precursors. Alumina-supported nickel and iron catalysts were used for the syntheses. The resultant CNFs were characterized by scanning electron microscopy, transmission electron microscopy, and nitrogen sorption at 77 K. The performance of a CNF-based supercapacitor working in 6 mol L−1 KOH was analyzed using cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy techniques. The Brunauer–Emmett–Teller (BET) surface area of the CNFs ranged between 150 and 296 m2 g−1. An increase in the CNF diameter was accompanied by a decrease in the BET surface area. A comparison of the porous textures and the structure types of the CNFs demonstrated that the performance of the CNF-based supercapacitor is enhanced primarily by the exposed edges of the graphitic layers on the CNF surface, followed by the specific surface area. Among the studied CNFs, the highest capacitance value, 26 F g−1 at 0.2 A g−1, was obtained for the platelet-type CNFs. Tubular CNFs exhibited the lowest capacitance value, which increased from 4 to 33 F g−1 at 0.2 A g−1 upon air treatment at 450 °C. The presence of exposed graphitic edges on the air-treated CNT surface and an increase in the specific surface area are considered to be responsible for the enhancement of the capacitor performance.

Strongly Bonded Selenium/Microporous Carbon Nanofibers Composite as a High-Performance Cathode for Lithium–Selenium Batteries

Although lithium–selenium batteries have attracted significant attention for high-energy-density energy storage systems due to their high volumetric capacity, their implementation has been hampered by the dissolution of polyselenide intermediates into electrolyte. Herein, we report a novel selenium/microporous carbon nanofiber composite as a high-performance cathode for lithium–selenium batteries through binding selenium in microporous carbon nanofibers. Under vacuum and heat treatment, selenium particles are easily transformed into chainlike Sen molecules that chemically bond with the inner surfaces of microporous carbon nanofibers. This chemical bonding can not only promote robust and intimate contact between selenium and carbonaceous nanofiber matrix but also alleviate the active material dissolution during cycling. Moreover, selenium is homogeneously distributed in the micropores of the highly conductive carbonaceous nanofiber matrix, which is favorable for the fast diffusions of both lithium ions and...

Synthesis and Electrochemical Properties of Carbon Nanofibers and SiO2/Carbon Nanofiber Composite on Ni-Cu/C-Fiber Textiles.

In this study, carbon nanofibers (CNFs) were grown by chemical vapor deposition on C-fiber textiles that had Ni and Cu catalyst deposited via electrophoretic deposition. Before the CNFs were coated with silica layer via hydrolysis of TEOS (Tetraethyl orthosilicate), the carbon nanofibers were oxidized by nitric acid. Due to oxidation, the hydroxyl group was created on the carbon nanofibers and this was used as an activation site for the SiO2. The physicochemical properties of the grown carbon nanofibers were investigated with Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS), X-ray Diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The structures of SiO2-coated carbon nanofibers were characterized by XPS and TEM. The electrochemical properties and the capacitance of the materials were investigated by galvanostatic charge-discharge and cyclic voltammetry. Different types of carbon nanofibers were grown upon the deposition utilizing catalysts, with the SiO2 uniformly coated on the surface of carbon nanofibers. When used as an anode material for the Li secondary battery, the SiO2/CNFs composite had a lower capacity maintenance and a greater discharge capacity as compared to the carbon nanofibers.

Effect of the carbon nanomaterials structure on silica carbothermal reduction

“Carbon nanomaterial-SiO2” composites were synthesized using carbon nanofibers (CNF) and carbon nanotubes (CNT). Oligomethylhydridesiloxane (OMHS) was used as the SiO2 precursor. The CNT–SiO2 composite was shown to be thermally stable up to 1100–1200°C. The calcination temperature increase to 1300°C resulted in segregation of the CNT–SiO2 composite into individual components: CNT and SiO2 particles. In distinction to CNT+SiO2, the CNF–SiO2 system showed stronger interaction of the amorphous silica film with the end faces of graphite terminating at the external surface of CNF. Calcination of the CNF–SiO2 composite in an inert atmosphere at 1300°C for 1h did not lead to segregation of the components. Calcination of the CNF–SiO2 composite in an argon flow at 1400°C for 1h changed the phase composition of the sample. Silicon diffused to the interplane layers of graphite. In addition, the formation of silicon carbide was observed.