Carbon Nanofiber Composites Research Articles

Fe-added Fe3C carbon nanofibers as anode for Li ion batteries with excellent low-temperature performance

The poor conductivity of anodic carbon materials at low temperature hampers their high-level applications in Li ion batteries (LIBs). Introducing some reliable metals with good electrical conductivity into anodes could alleviate these problems. In this work, the novel composites of Fe-added Fe3C carbon nanofibers (Fe/Fe3CCNFs) were synthesized via facile electrospinning method and used as anode materials for LIBs. The resulting anodes with Fe/Fe3CCNF materials exhibited a high reversible capacity of 500mAhg−1 tested at 200mAg−1 even after 70 cycles and excellent performance at room temperature. Importantly, it delivered a high capacity of 250mAhg−1 at 400mAg−1 even after 55 cycles at a low temperature of −15°C. The superior low-temperature electrochemical performance of the Fe/Fe3CCNF anodes is associated with an improved effect of the highly conducting Fe at low temperature.

Growth mechanism of bioglass nanoparticles in polyacrylonitrile-based carbon nanofibers

Polyacrylonitrile (PAN) electrospinning in combination with sol–gel method has been a common technique to produce inorganic nanoparticles containing composite carbon nanofibers (CNFs) for diverse applications. To investigate the morphology evolution and crystal transformation of inorganic components along with CNF formation, bioactive glass (BG) containing CNFs (CNF/BG) were prepared by sintering as-spun PAN/precursor composite nanofibers in a nitrogen atmosphere at temperatures of 800, 1000 and 1200 °C. Comprehensive characterizations were performed with TEM, SEM-EDXA and XRD. For samples sintered at 800 °C, numerous BG nanoparticles were observed inside the CNFs and mainly in an amorphous state. With the sintering temperature raised to 1000 °C, a number of spherical BG nanoparticles were detected on the surface of the resulting CNFs, with a crystal structure of wollastonite (β-CaSiO3) polycrystals. When the samples were sintered at 1200 °C, the BG nanoparticles on the surface of CNFs merged into forms with cuboid-like geometry, mainly consisting of pseudowollastonite (Ca3(Si3O9)) single crystals. Based on the geometry evolution and dynamic size distribution function analyses (Ostwald ripening and Smoluchowski equations), it was concluded that the growth of BG nanoparticles conformed to the ripening mechanism at 800 °C and migration–coalescence mechanism at 1200 °C, while the process involved both ripening and migration–coalescence mechanisms at 1000 °C.

Greater cardiomyocyte density on aligned compared with random carbon nanofibers in polymer composites.

Carbon nanofibers (CNFs) randomly embedded in poly (lactic-co-glycolic-acid) (PLGA) composites have recently been shown to promote cardiomyocyte growth when compared with conventional PLGA without CNFs. It was shown then that PLGA:CNF composites were conductive and that conductivity increased as greater amounts of CNFs were added to pure PLGA. Moreover, tensile tests showed that addition of CNFs increased the tensile strength of the PLGA composite to mimic that of natural heart tissue. Most importantly, throughout all cytocompatibility experiments, cardiomyocytes were viable and expressed important biomarkers that were greatest on 50:50 wt% CNF:PLGA composites. The increased selective adsorption of fibronectin and vitronectin (critical proteins that mediate cardiomyocyte function) onto such composites proved to be the mechanism of action. However, the natural myocardium is anisotropic in terms of mechanical and electrical properties, which was not emulated in these prior PLGA:CNF composites. Thus, the aim of this in vitro study was to create and characterize CNFs aligned in PLGA composites (at 50:50 wt%, including their mechanical and electrical properties and cardiomyocyte density), comparing such results with randomly oriented CNFs in PLGA. Specifically, CNFs were added to soluble biodegradable PLGA (50:50 PGA:PLA weight ratio) and aligned by applying a voltage and then allowing the polymer to cure. CNF surface micron patterns (20 μm wide) on PLGA were then fabricated through a mold method to further mimic myocardium anisotropy. The results demonstrated anisotropic mechanical and electrical properties and significantly improved cardiomyocyte density for up to 5 days on CNFs aligned in PLGA compared with being randomly oriented in PLGA. These results indicate that CNFs aligned in PLGA should be further explored for improving cardiomyocyte density, which is necessary in numerous cardiovascular applications.

Zinc oxide/activated carbon nanofiber composites for high-performance supercapacitor electrodes

ZnO-containing porous activated carbon nanofibers (ZnO/ACNFs) are prepared through one-step electrospinning using zinc acetate and polyacrylonitrile (PAN), followed by thermal treatment. The electrochemical performance of the ZnO/ACNF composite electrodes is compared to that of pure ACNF electrodes in aqueous KOH as the electrolyte. Electrochemical measurements of ZnO/ACNFs reveal a maximum specific capacitance of 178.2 Fg−1, and high energy densities of 22.71–17.77 Whkg−1 in the power density range of 400 to 4000 W kg−1. Furthermore, this supercapacitor electrode exhibits excellent cycle life with a specific capacitance ∼75% of the initial value after 1000 cycles. The combination of ACNF's high surface area with ZnO's large specific capacity facilitates a synergistic effect between ZnO's faradaic capacitance and ACNF's double layer capacitance, which afforded good capacitive behavior.

N-Doped ZnO Nanoparticle-Carbon Nanofiber Composites for Use as Low-Cost Counter Electrode in Dye-Sensitized Solar Cells

【Nitrogen-doped ZnO nanoparticle-carbon nanofiber composites were prepared using electrospinning. As the relative amounts of N-doped ZnO nanoparticles in the composites were controlled to levels of 3.4, 9.6, and 13.8 wt%, the morphological, structural, and chemical properties of the composites were characterized by means of field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). In particular, the carbon nanofiber composites containing 13.8 wt% N-doped ZnO nanoparticles exhibited superior catalytic properties, making them suitable for use as counter electrodes in dye-sensitized solar cells (DSSCs). This result can be attributed to the enhanced surface roughness of the composites, which offers sites for $I_3{^-}$ ion reductions and the formation of Zn3N2 phases that facilitate electron transfer. Therefore, DSSCs fabricated with 13.8 wt% N-doped ZnO nanoparticle-carbon nanofiber composites showed high current density ( $16.3mA/cm^2$ ), high fill factor (57.8%), and excellent power-conversion efficiency (6.69%); at the same time, these DSSCs displayed power-conversion efficiency almost identical to that of DSSCs fabricated with a pure Pt counter electrode (6.57%).】

Improving the microstructure and electrochemical performance of carbon nanofibers containing graphene-wrapped silicon nanoparticles as a Li-ion battery anode

A novel anode material for lithium-ion batteries, graphene-wrapped Si nanoparticles (NPs) embedded in carbon composite nanofibers (CCNFs) with G/Si, is fabricated by electrospinning and subsequent thermal treatment. In CCNFs with G/Si, Si NPs are distributed and preserved inside the CNF surface because the graphene wrapping the Si NPs help prevent agglomeration and ensure a good dispersion of Si NPs inside the CNF matrix. 20-GSP prepared from a weight ratio of 20 wt% of G/Si to polyacrylonitrile exhibits stable capacity retention and a reversible capacity of above 600 mAh g−1 up to 100 cycles. The high cycling performance and superior reversible capacity of the 20-GSP anode can be attributed to the one-dimensional nanofibrous structure with non-agglomerated Si NPs in the CNF matrix, which promotes charge transfer, maintains a stable electrical contact, and buffers the Si volume expansion.

Effects of surface modification of carbon nanofibers on the mechanical properties of polyamide 1212 composites

ABSTRACTIn this study, the effects of carbon nanofiber (CNF) surface modification on mechanical properties of polyamide 1212 (PA1212)/CNFs composites were investigated. CNFs grafted with ethylenediamine (CNF‐g‐EDA), and CNFs grafted with polyethyleneimine (CNF‐g‐PEI) were prepared and characterized. The mechanical properties of the PA1212/CNFs composites were reinforced efficiently with addition of 0.3 wt % modified CNFs after drawing. The reinforcing effect of the drawn composites was investigated in terms of interfacial interaction, crystal orientation, crystallization properties and so on. After the surface modification of CNFs, the interfacial adhesion and dispersion of CNFs in PA1212 matrix were improved, especially for CNF‐g‐PEI. The improved interfacial adhesion and dispersion of CNFs in PA1212 matrix was beneficial to reinforcement of the composites. Compared with pure PA1212, improved degree of crystal orientation in the PA1212/CNF‐g‐PEI (CNF‐g‐EDA) composites was responsible for reinforcement of mechanical properties after drawing. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41424.

High‐Voltage Asymmetric Supercapacitors based on Carbon and Manganese Oxide/Oxidized Carbon Nanofiber Composite Electrodes

AbstractAsymmetric supercapacitors with high operating voltages have been successfully developed, using manganese oxide/oxidized carbon nanofibers (MnO2/CNFox) composites as the positive electrode and activated carbon (AC) as the negative electrode, in a neutral aqueous 0.5 mol L−1 K2SO4 solution. The assembled MnO2/CNFox//AC supercapacitor can operate reversibly in a wide voltage range up to 2.3 V, showing an excellent stability with only a 7.6 % loss of its initial capacitance after 5000 cycles at 1 A g−1. A high energy density of 24.8 Wh kg−1 at a power density of 100 W kg−1 is achieved. This unique electrochemical performance is attributed to the presence of CNFox with hydrophilic surface properties in the MnO2‐based electrode, which ensures a perfect dispersion of nanofibers in the bulk MnO2 and a very good adhesion between the components of the MnO2/CNFox composite. The obtained results show great potential in developing asymmetric supercapacitors with high energy and power densities working in neutral aqueous media.

Effects of carbon nanofiber on the dissolution and diffusion of CO2 in polypropylene nanocomposites

The effects of nanofiller with elongated structure on the dissolution and diffusion behaviors of CO2 in polypropylene (PP)/carbon nanofiber (CNF) composites were investigated in this work. The solubility of CO2 in PP and PP composites containing 5wt% and 10wt% CNF was measured by using magnetic suspension balance (MSB) combined with the experimental swelling correction by using a self-designed high-temperature and -pressure view cell at the temperatures of 200 and 220°C and pressures up to 20MPa. The diffusion coefficient of CO2 in PP and PP composites was also determined from the sorption line at CO2 pressures ranging from 5 to 10MPa. It was found that the solubility and diffusivity of CO2 in PP/CNF composites increased with increasing the filler content, which should be mainly attributed to the change of the distribution of free volume in the polymer matrix besides the small amount of adsorption capacity of CO2 in CNF. A modified Henry model incorporated with Langmuir adsorption factor was proposed to correlate the solubility of CO2 in the PP/CNF composites with an average relative deviation less than 3%. A new model based on free volume theory incorporated with the diffusion driving force factor was established to correlate the experimental diffusion coefficient of CO2 in the PP/CNF composites within an average relative deviation of 2%.

Ultrafast Nano-Crystalline and Highly-Dispersed-TiO2 (B) /CNF Composites for Negative Electrode of ‘Nanohybrid Capacitor’

We have been applying our original in-situ material processing technology called ‘Ultra-Centrifuging (UC) Treatment’ to prepare a novel ultrafast nano-crystalline Li4Ti5O12 (nc-LTO) /carbon nano fiber (CNF) composite electrode for the generation-II capacitive energy storage device of ‘Nanohybrid Capacitor’ producing more than triple energy density of a conventional electrochemical capacitor.[1] For the further improvement in the energy density of ‘Nanohybrid Capacitor’, LTO alternatives are needed. Among different candidates, TiO2 (B) possesses several advantages such as its 2-folds theoretical capacity (335 mAh g-1) of LTO (175 mAh g-1) and the comparable redox potential (1.6 V vs. Li/Li+). In addition, TiO2 (B) is an industrially attractive material because of its inexpensive raw materials and its environmentally benign synthesis using only aqueous solution (e.g., water-soluble complexes [2]) without any Li-sources.[2-4] However, TiO2 (B) has intrinsic problems; its low electronic conductivity and Li+ diffusivity due to the b-axis oriented growth of TiO2 (B) [3]. In this report, we successfully synthesized b-axis shortened and hyper-dispersed nc-TiO2 (B)/CNF composites, which has a potential to substitute nc-LTO/CNF as a negative electrode of ‘Nanohybrid capacitor’. Inhibition of b-axis growth and hyper dispersion of TiO2 (B) into the carbon matrix were simultaneously achieved by the UC treatment and the subsequent hydrothermal method [4]. The prepared nc-TiO2/CNF exhibited 236 mAh g-1 (active material) at high rate of 300 C, which even exceeds that of nc-LTO/CNF composites. A significant decrease of peak intensity corresponding to the C-site intercalation around 2 V vs. Li/Li+ indicates that the Li+ was directly accommodated into A1 and A2 site of TiO2 (B) owing to the limitation of b-axis growth. Furthermore, the combined analysis of the N2 adsorption experiment and electochemical characterization suggests that the "dispersibility" of nc-TiO2 (B) on CNF matrix correlates closely with its electrochemical performance.

Electrochemical behavior of zinc oxide-based porous carbon composite nanofibers as an electrode for electrochemical capacitors

Zinc oxide (ZnO)-based porous carbon composite nanofibers (ZnO–CCNFs) are prepared by one-step electrospinning and subsequent thermal treatment using zinc acetate, as the pore generator and ZnO precursor. In particular, the PAN-based nanofiber paper contains in-frame incorporated nitrogen surface functionalities, due to its large residual nitrogen content in the char. The N functionalities doped at the graphite edges enhances their capacitance by the pseudocapacitive effect.Therefore, the ZnO–CCNFs showed higher capacitance (163Fg−1 at 1mAcm−2) and energy density (20.80–14.80Whkg−1 in the power density range of 400–20,000Wkg−1) than the control sample of carbon nanofibers (CNFs) in aqueous electrolyte. The combination of the high surface area of CNFs with the large capacity of surface functional groups such as N, O, and ZnO as the faradic electrode material affords the advantages of both the double layer capacitance and the pseudocapacitance, thereby offering potential applications for supercapacitors.

Silver-incorporated composites of Fe2O3 carbon nanofibers as anodes for high-performance lithium batteries

Composites of Ag-incorporated carbon nanofibers (CNFs) confined with Fe2O3 nanoparticles (Ag–Fe2O3/CNFs) have been synthesized through an electrospinning method and evaluated as anodes for lithium batteries (LIBs). The obtained Ag–Fe2O3/CNF anodes show good LIB performance with a capacity of 630 mAh g−1 tested at 800 mA g−1 after 150 cycles with almost no capacity loss and superb rate performance. The obtained properties for Ag–Fe2O3/CNF anodes are much better than Fe2O3/CNF anodes without Ag-incorporating. In addition, the low-temperature LIB performances for Ag–Fe2O3/CNF anodes have been investigated for revealing the enhanced mechanism of Ag-incorporating. The superior electrochemical performances of the Ag–Fe2O3/CNFs are associated with a synergistic effect of the CNF matrix and the highly conducting Ag incorporating. This unique configuration not only facilitates electron conduction especially at a relative temperature, but also maintains the structural integrity of active materials. Meanwhile, the related analysis of the AC impedance spectroscopy and the corresponding hypothesis for DC impedance confirm that such configuration can effectively enhance the charge-transfer efficiency and the lithium diffusion coefficient. Therefore, CNF-supported coupled with Ag incorporating synthesis supplied a promising route to obtain Fe2O3 based anodes with high-performance LIBs especially at low temperature.

Enhanced electrical capacitance of heteroatom-decorated nanoporous carbon nanofiber composites containing graphene

Heteroatom-decorated nanoporous carbon nanofiber composites (Si-CNFCs) containing grapheneare prepared through one-step electrospinning with the help of tetraethylorthosilicate (TEOS) and a subsequent thermal treatment, and their electrochemical properties as supercapacitor electrodes are investigated. The introduction of TEOS and graphene into the polyacrylonitrile (PAN) solution induced superior material properties, such as a high surface area, stabilized Si-related structures, and increased electrical conductivity, resulting in the enhancement of the electrochemical performances of electrodes. The supercapacitor electrode prepared with 3wt% graphene and 10 wt% TEOS shows high specific capacitance, 144.79 Fg−1, and high energy density, 16.82-8.33 Whkg−1, at power densities ranging from 400-20,000 Wkg−1 in a 6 M KOH aqueous solution. Therefore, the Si-CNFC electrodes promote desirable interactions and improve the accessibility of the ions solvated with a polar solvent, yielding a high charge capacity and improving the energy/power capabilities through the electrical double-layer and pseudo-capacitive effects.

Nonlinear optical limiters of pulsed laser radiation based on carbon‐containing nanostructures in viscous and solid matrices

Results of the study of optical limiters of pulsed laser radiation based on nonlinear effects in carbon nanostructures placed into viscous and solid matrices are presented. A nonlinear optical limiting was studied by nanomaterials based on multi‐wall polyhedral carbon nanostructures (astralens) placed in a sol–gel matrix. Similar studies for single‐wall and multi‐wall carbon‐containing nanotubes placed in polymer matrices with various viscosities were performed. No additional mechanism of optical limiting due to electron structure of single‐wall carbon‐containing nanotubes at their introduction into viscous and solid composite media was found. An influence of polymer matrix composition containing carbon nanotubes (CNTs) on a threshold and ratio of attenuation of laser radiation was demonstrated. The best limiting characteristics were observed at placing CNT into polymethylsiloxane matrix. An effect of “self‐healing” of a medium after laser radiation passage through high viscous liquids was obtained. The high parameters of nonlinear optical limiting (the threshold of limiting 10−5 J, ratio of attenuation 103) achieved for the composite material CNT (HiPCO High‐Pressure Carbon Monoxide) and carbon nanofibers in high viscous and solid polymethylsiloxane media allow the design of protective filters for laser radiation operating in wide spectral range. Copyright © 2014 John Wiley & Sons, Ltd.

Preparation and characterization of porous carbon based nanocomposite for supercapacitor

Porous nanocomposites are prepared by electrospinning blended polyacrylonitrile, copper acetate and mutiwalled carbon nanotube in N, N-dimethylformamide. The electrospun nanofiber webs are oxidatively stabilized and then carbonized resulting in composite carbon nanofibers. The study reveals that composite nanofibers with relatively smooth surface morphology are successfully prepared. X-ray diffraction is used to confirm the presence of Cu in carbon nanofibers. The carbon nanofibers with CNTs have better thermal stability and higher electrical conductivity. The Brunauer-Emmett-Teller analysis reveals that C/Cu/CNTs nanocomposites with mesopores possess larger specific surface area and narrower pore size distribution than that of C/Cu nanofibers. The electrochemical properties are investigated by cyclic voltammetry and galvanostatic charge-discharge tests. The nanocomposite with 0.5 wt.% CNT loading exhibits an energy density of 2 Whkg−1, power density of 1916 Wkg−1, a specific capacitance of about 225 Fg−1 at a current density of 2 Ag−1 and its capacitance decreased to 78 % of its initial value after 3,000 cycles.

Comparison and analysis of physical properties of carbon nanomaterial-doped polymer composites

Low-temperature curing approach has been adopted to fabricate the composites along with room temperature method involving four types of nanofillers. With the purpose to investigate the multifunctionality caused by carbon nanotubes (CNTs)/carbon nanofibers (CNFs), mechanical properties such as flexural modulus, flexural strength, and hardness and electrical property such as conductivity of various epoxy nanocomposites were determined. These results were supplemented and complemented by scanning electron microscopy and transmission electron microscopy. Both mechanical and microscopic observations indicated that among all the nanocomposites, refrigerated, aligned CNTs and functionalized CNT composites show a significant reinforcement in the epoxy matrix along with bridging mechanism. Lower mechanical results were obtained in CNF composites that attributes to breaking of nanofibers after mechanical tests. All nanocomposites showed electrical percolation that occurs due to network formation of nanoparticles inside the matrix.

Carbon Nanofibers and Their Composites: A Review of Synthesizing, Properties and Applications.

Carbon nanofiber (CNF), as one of the most important members of carbon fibers, has been investigated in both fundamental scientific research and practical applications. CNF composites are able to be applied as promising materials in many fields, such as electrical devices, electrode materials for batteries and supercapacitors and as sensors. In these applications, the electrical conductivity is always the first priority need to be considered. In fact, the electrical property of CNF composites largely counts on the dispersion and percolation status of CNFs in matrix materials. In this review, the electrical transport phenomenon of CNF composites is systematically summarized based on percolation theory. The effects of the aspect ratio, percolation backbone structure and fractal characteristics of CNFs and the non-universality of the percolation critical exponents on the electrical properties are systematically reviewed. Apart from the electrical property, the thermal conductivity and mechanical properties of CNF composites are briefly reviewed, as well. In addition, the preparation methods of CNFs, including catalytic chemical vapor deposition growth and electrospinning, and the preparation methods of CNF composites, including the melt mixing and solution process, are briefly introduced. Finally, their applications as sensors and electrode materials are described in this review article.

PdxCoy Nanoparticle/Carbon Nanofiber Composites with Enhanced Electrocatalytic Properties

Novel bimetallic PdxCoy alloy nanoparticle (NP)/carbon nanofiber (CNF) composites with superior electrocatalytic performances were successfully prepared by electrospinning Pd and Co precursors, i.e., Pd(acac)2 and Co(acac)2, in polyacrylonitrile followed by a thermal treatment. Uniform dispersion of PdxCoy nanoparticles in carbon nanofibers was achieved. Chemical composition and size of the resulting PdxCoy NPs, which showed a substantial effect on the electrocatalytic properties of PdxCoy/CNF nanocomposites, can be readily controlled by adjusting the feed ratio of metal precursors. In comparison with commercial Pd/C and other state-of-the-art Pd- or Pt-based catalysts, PdxCoy/CNF nanocomposites prepared in this study exhibited much higher electrocatalytic activity and stability in formic acid and methanol oxidation reactions. This improved electrocatalytic performance is very attractive for fuel cell applications and can be attributed to the unique bimetallic Pd–Co alloy formation, a modified electronic structure of Pd in PdxCoy, as well as uniform dispersion and firm embedment of PdxCoy NPs in CNF.

Carbon-enhanced electrodeposited SnO2/carbon nanofiber composites as anode for lithium-ion batteries

Tin oxides (SnO2) are promising anode material candidate for next-generation lithium-ion batteries due to their high capacity, low cost, high abundance, and low toxicity. However, the practical use of SnO2 anodes is currently limited by their large volume changes during cycling. Severe volume changes of SnO2 anodes lead to intense pulverization and loss of electrical contact between the active material and carbon conductor. Herein, we introduce binder-free SnO2-electrodeposited carbon nanofibers (CNF@SnO2) and SnO2-electrodeposited porous carbon nanofibers (PCNF@SnO2) composites that can maintain their structural stability during repeated charge–discharge cycling. Results indicated that the amount of the electrodeposited SnO2 nanoparticles and the capacity of the resultant composites were successfully enhanced by using a porous nanofiber structure. Both CNF@SnO2 and PCNF@SnO2 composites were also coated with amorphous carbon layers by chemical vapor deposition to further improve the structural stability. Electrochemical performance results demonstrated that the combination of porous nanofiber structure and CVD amorphous coating led to a novel carbon-coated PCNF@SnO2 composite anode with high capacity retention of 78% and large coulombic efficiency of 99.8% at the 100th cycle.

Self-heating function of carbon nanofiber cement pastes

The viability of carbon nanofiber (CNF) composites incement matrices as a self-heating material is reported in this paper. This functional application would allow the use of CNF cement composites as a heating element in buildings, or for deicing pavements of civil engineering transport infrastructures, such as highways or airport runways. Cement pastes with the addition of different CNF dosages (from 0 to 5% by cement mass) have been prepared. Afterwards, tests were run at different fixed voltages (50, 100 and 150V), and the temperature of the specimens was registered. Also the possibility of using a casting method like shotcrete, instead of just pouring the fresh mix into the mild (with no system’s efficiency loss expected) was studied. Temperatures up to 138 °C were registered during shotcrete-5% CNF cement paste tests (showing initial 10 °C/min heating rates). However a minimum voltage was required in order to achieve a proper system functioning.