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Sample records for aligned carbon nanofiber

  1. Purification process for vertically aligned carbon nanofibers

    NASA Technical Reports Server (NTRS)

    Nguyen, Cattien V.; Delziet, Lance; Matthews, Kristopher; Chen, Bin; Meyyappan, M.

    2003-01-01

    Individual, free-standing, vertically aligned multiwall carbon nanotubes or nanofibers are ideal for sensor and electrode applications. Our plasma-enhanced chemical vapor deposition techniques for producing free-standing and vertically aligned carbon nanofibers use catalyst particles at the tip of the fiber. Here we present a simple purification process for the removal of iron catalyst particles at the tip of vertically aligned carbon nanofibers derived by plasma-enhanced chemical vapor deposition. The first step involves thermal oxidation in air, at temperatures of 200-400 degrees C, resulting in the physical swelling of the iron particles from the formation of iron oxide. Subsequently, the complete removal of the iron oxide particles is achieved with diluted acid (12% HCl). The purification process appears to be very efficient at removing all of the iron catalyst particles. Electron microscopy images and Raman spectroscopy data indicate that the purification process does not damage the graphitic structure of the nanotubes.

  2. Vertically Aligned Carbon Nanofiber based Biosensor Platform for Glucose Sensor

    SciTech Connect

    Al Mamun, Khandaker A.; Tulip, Fahmida S.; MacArthur, Kimberly; McFarlane, Nicole; Islam, Syed K.; Hensley, Dale

    2014-03-01

    Vertically aligned carbon nanofibers (VACNFs) have recently become an important tool for biosensor design. Carbon nanofibers (CNF) have excellent conductive and structural properties with many irregularities and defect sites in addition to exposed carboxyl groups throughout their surfaces. These properties allow a better immobilization matrix compared to carbon nanotubes and offer better resolution when compared with the FET-based biosensors. VACNFs can be deterministically grown on silicon substrates allowing optimization of the structures for various biosensor applications. Two VACNF electrode architectures have been employed in this study and a comparison of their performances has been made in terms of sensitivity, sensing limitations, dynamic range, and response time. The usage of VACNF platform as a glucose sensor has been verified in this study by selecting an optimum architecture based on the VACNF forest density. Read More: http://www.worldscientific.com/doi/abs/10.1142/S0129156414500062

  3. Vertically aligned carbon nanofiber electrode arrays for nucleic acid detection

    NASA Astrophysics Data System (ADS)

    Arumugam, Prabhu U.; Yu, Edmond; Riviere, Roger; Meyyappan, M.

    2010-10-01

    We present electrochemical detection of DNA targets that corresponds to Escherichia coli O157:H7 16S rRNA gene using a nanoelectrode array consisting of vertically aligned carbon nanofiber (VACNF) electrodes. Parylene C is used as gap filling 'matrix' material to avoid high temperature processing in electrode construction. This easy to deposit film of several micron heights provides a conformal coating between the high aspect ratio VACNFs with negligible pin-holes. The low background currents show the potential of this approach for ultra-sensitive detection. Consistent and reproducible electrochemical-signals are achieved using a simple electrode preparation. This simple, reliable and low-cost approach is a forward step in developing practical sensors for applications like pathogen detection, early cancer diagnosis and environmental monitoring.

  4. DC Plasma Synthesis of Vertically Aligned Carbon Nanofibers for Biointerfacing

    NASA Astrophysics Data System (ADS)

    Pearce, Ryan Christopher

    Vertically aligned carbon nanofibers (VACNFs) are a class of materials whose nanoscale dimensions and physical properties makes them uniquely suitable as functional elements in many applications for biodetection and biointerfacing on a cellular level. Control of VACNF synthesis by catalytic plasma enhanced chemical vapor deposition (PECVD) presents many challenges in integration into devices and structures designed for biointerfacing, such as transparent or flexible substrates. This dissertation addresses ways to overcome many of these issues in addition to deepening the fundamental understanding of nano-synthesis in catalytic PECVD. First, a survey of the field of VACNF synthesis and biointerfacing is presented, identifying the present challenges and greatest experimental applications. It is followed by experimental observations that elucidate the underlying mechanism to fiber alignment during synthesis, a critical step for deterministic control of fiber growth. Using a grid of electrodes patterned by photolithography on an insulating substrate, it was found that the alignment of the fibers is controlled by the anisotropic etching provided by ions during dc-PECVD synthesis. The VACNFs that have been utilized for many cellular interfacing experiments have unique mechanical and fluorescent properties due to a SiNx coating. The mechanism for SiNx deposition to VACNF sidewalls during synthesis is explored in addition to a detailed study of the optical properties of the coating. To explain the optical properties of this coating it is proposed that the source of photoluminescence for the SiNx coated VACNFs is quantum confinement effects due to the presence of silicon nanoclusters embedded in a Si3N4 matrix. These luminescent fibers have proven useful as registry markers in cell impalefection studies. To realize VACNF arrays used as an inflatable angioplasty balloon with embedded fibers to deliver drugs across the blood-brain barrier, a method for transferring fibers to

  5. Vertically aligned carbon nanofiber nanoelectrode arrays: electrochemical etching and electrode reusability

    PubMed Central

    Gupta, Rakesh K.; Meyyappan, M.; Koehne, Jessica E.

    2014-01-01

    Vertically aligned carbon nanofibers in the form of nanoelectrode arrays were grown on nine individual electrodes, arranged in a 3 × 3 array geometry, in a 2.5 cm2 chip. Electrochemical etching of the carbon nanofibers was employed for electrode activation and enhancing the electrode kinetics. Here, we report the effects of electrochemical etching on the fiber height and electrochemical properties. Electrode regeneration by amide hydrolysis and electrochemical etching is also investigated for electrode reusability. PMID:25089188

  6. Electrospun aligned poly(propylene carbonate) microfibers with chitosan nanofibers as tissue engineering scaffolds.

    PubMed

    Jing, Xin; Mi, Hao-Yang; Peng, Jun; Peng, Xiang-Fang; Turng, Lih-Sheng

    2015-03-01

    In this study, parallel-aligned poly(propylene carbonate) (PPC) microfibers with a fiber diameter of 1.48±0.42 μm were prepared by electrospinning and modified by oxygen plasma treatment. Next, chitosan nanofibers with a fiber diameter size of 278±98 nm were introduced into the PPC fiber mats by freeze drying. Morphological analyses showed that the PPC scaffolds treated with 0.05 mg/ml chitosan solution provided the best micro and nanofiber structure with abundant chitosan nanofibers but without the formation of films. Surface chemical properties were analyzed by X-ray photoelectron spectroscopy (XPS). The initial water contact angle of the scaffolds decreased from 122.3±0.4° for neat PPC scaffolds to 53.8±1.6° for scaffolds with plasma treatment and chitosan nanofibers. The mechanical properties of the scaffolds were affected by plasma treatment with Young's modulus experiencing a reduction of 63%. Meanwhile, Young's modulus experienced a 26% improvement after the introduction of chitosan nanofibers. Fibroblast cells were cultured on the scaffolds to study the effects of both the plasma treatment and the introduction of chitosan nanofibers on cell adhesion, proliferation, and morphology. The scaffolds with PPC microfibers and chitosan nanofibers showed a superior cell response in terms of cell attachment, cell proliferation, and cell-scaffold interactions over the other scaffolds.

  7. Vertically aligned carbon nanofiber as nano-neuron interface for monitoring neural function

    SciTech Connect

    Ericson, Milton Nance; McKnight, Timothy E; Melechko, Anatoli Vasilievich; Simpson, Michael L; Morrison, Barclay; Yu, Zhe

    2012-01-01

    Neural chips, which are capable of simultaneous, multi-site neural recording and stimulation, have been used to detect and modulate neural activity for almost 30 years. As a neural interface, neural chips provide dynamic functional information for neural decoding and neural control. By improving sensitivity and spatial resolution, nano-scale electrodes may revolutionize neural detection and modulation at cellular and molecular levels as nano-neuron interfaces. We developed a carbon-nanofiber neural chip with lithographically defined arrays of vertically aligned carbon nanofiber electrodes and demonstrated its capability of both stimulating and monitoring electrophysiological signals from brain tissues in vitro and monitoring dynamic information of neuroplasticity. This novel nano-neuron interface can potentially serve as a precise, informative, biocompatible, and dual-mode neural interface for monitoring of both neuroelectrical and neurochemical activity at the single cell level and even inside the cell.

  8. Aerosynthesis: Growths of Vertically Aligned Carbon Nanofibers with Air DC Plasma

    SciTech Connect

    Kodumagulla, A; Varanasi, V; Pearce, Ryan; Wu, W-C; Hensley, Dale K; Tracy, Joseph B; McKnight, Timothy E; Melechko, Anatoli

    2014-01-01

    Vertically aligned carbon nanofibers (VACNF) have been synthesized in a mixture of acetone and air using catalytic DC plasma enhanced chemical vapor deposition. Typically, ammonia or hydrogen is used as etchant gas in the mixture to remove carbon that otherwise passivates the catalyst surface and impedes growth. Our demonstration of using air as the etchant gas opens up a possibility that ion etching could be sufficient to maintain the catalytic activity state during synthesis. It also demonstrates the path toward growing VACNFs in open atmosphere.

  9. Imaging, Spectroscopy, Mechanical, Alignment and Biocompatibility Studies of Electrospun Medical Grade Polyurethane (Carbothane™ 3575A) Nanofibers and Composite Nanofibers Containing Multiwalled Carbon Nanotubes

    PubMed Central

    Sheikh, Faheem A.; Macossay, Javier; Cantu, Travis; Zhang, Xujun; Hassan, M. Shamshi; Salinas, M. Esther; Farhangi, Chakavak S.; Ahmad, Hassan; Kim, Hern; Bowlin, Gary L.

    2014-01-01

    In the present study, we discuss the electrospinning of medical grade polyurethane (Carbothane™ 3575A) nanofibers containing multi-walled-carbon-nanotubes (MWCNTs). A simple method that does not depend on additional foreign chemicals has been employed to disperse MWCNTs through high intensity sonication. Typically, a polymer solution consisting of polymer/MWCNTs has been electrospun to form nanofibers. Physiochemical aspects of prepared nanofibers were evaluated by SEM, TEM, FT-IR and Raman spectroscopy, confirming nanofibers containing MWCNTs. The biocompatibility and cell attachment of the produced nanofiber mats were investigated while culturing them in the presence of NIH 3T3 fibroblasts. The results from these tests indicated non-toxic behavior of the prepared nanofiber mats and had a significant attachment of cells towards nanofibers. The incorporation of MWCNTs into polymeric nanofibers led to an improvement in tensile stress from 11.40 ± 0.9 to 51.25 ± 5.5 MPa. Furthermore, complete alignment of the nanofibers resulted in an enhancement on tensile stress to 72.78 ± 5.5 MPa. Displaying these attributes of high mechanical properties and non-toxic nature of nanofibers are recommended for an ideal candidate for future tendon and ligament grafts. PMID:25460415

  10. Synthesis of vertically aligned carbon nanofibers-carbon nanowalls by plasma-enhanced chemical vapor deposition.

    PubMed

    Okamoto, Atsuto; Tanaka, Kei; Yoshimura, Masamichi; Ueda, Kazuyuki; Ghosh, Pradip; Tanemura, Masaki

    2013-03-01

    Vertically aligned carbon nanofibers (VA-CNFs)-carbon nanowalls (CNWs) have been prepared on a silicon (Si) substrate by plasma-enhanced chemical vapor deposition. The VA-CNFs-CNWs were formed at bias voltage of - 185 V, whereas conventional VA-CNFs were synthesized under conditions of high bias voltages. Degenerated CNWs with turbostratic graphite structure were created on amorphous carbon layer around CNFs like a flag attached to a pole, which is evidenced by scanning electron microscopy, transmission electron microscopy, electron diffraction, and micro-Raman spectroscopy. Electron field emission characteristics of VA-CNFs-CNWs with unique microstructure, fabricated on the Si substrate, were primarily investigated. As a result, the VA-CNFs-CNWs showed the turn-on and the threshold fields of 1.7 V x microm(-1) and 3.35 V x microm(-1) with current densities of 10 nA x cm(-2) and 1 microA x cm(-2), respectively. The field enhancement factor beta was estimated to be 1059 by using Fowler-Nordheim theory. PMID:23755628

  11. A Glucose Biosensor Using CMOS Potentiostat and Vertically Aligned Carbon Nanofibers.

    PubMed

    Al Mamun, Khandaker A; Islam, Syed K; Hensley, Dale K; McFarlane, Nicole

    2016-08-01

    This paper reports a linear, low power, and compact CMOS based potentiostat for vertically aligned carbon nanofibers (VACNF) based amperometric glucose sensors. The CMOS based potentiostat consists of a single-ended potential control unit, a low noise common gate difference-differential pair transimpedance amplifier and a low power VCO. The potentiostat current measuring unit can detect electrochemical current ranging from 500 nA to 7 [Formula: see text] from the VACNF working electrodes with high degree of linearity. This current corresponds to a range of glucose, which depends on the fiber forest density. The potentiostat consumes 71.7 [Formula: see text] of power from a 1.8 V supply and occupies 0.017 [Formula: see text] of chip area realized in a 0.18 [Formula: see text] standard CMOS process. PMID:27337723

  12. Actuatable membranes based on polypyrrole-coated vertically aligned carbon nanofibers.

    PubMed

    Fletcher, Benjamin L; Retterer, Scott T; McKnight, Timothy E; Melechko, Anatoli V; Fowlkes, Jason D; Simpson, Michael L; Doktycz, Mitchel J

    2008-02-01

    Nanoporous membranes are applicable to a variety of research fields due to their ability to selectively separate molecules with high efficiency. Of particular interest are methods for controlling membrane selectivity through externally applied stimuli and integrating such membrane structures within multiscale systems. Membranes comprised of deterministically grown, vertically aligned carbon nanofibers (VACNFs) are compatible with these needs. VACNF membranes can regulate molecular transport by physically selecting species as they pass between the fibers. Defined interfiber spacing allows for nanoscale control of membrane pore structure and resultant size selectivity. Subsequent physical or chemical modification of VACNF structures enables the tuning of physical pore size and chemical specificity allowing further control of membrane permeability. In this work, the dynamic physical modulation of membrane permeability that results when VACNFs are coated with an electrically actuatable polymer, polypyrrole, is demonstrated. Electrochemical reduction of polypyrrole on the VACNFs results in controlled swelling of the diameter of the nanofibers that in turn decreases the pore size. Dynamic control of membrane pore size enables selective transport and gating of nanoscale pores.

  13. Growth of High-Density Self-Aligned Carbon Nanotubes and Nanofibers Using Palladium Catalyst

    NASA Astrophysics Data System (ADS)

    Vollebregt, S.; Derakhshandeh, J.; Ishihara, R.; Wu, M. Y.; Beenakker, C. I. M.

    2010-04-01

    In this paper we demonstrate vertical self-aligned growth of carbon nanotubes (CNT) and carbon nanofibers (CNF) using 1 nm of Pd as the catalyst material. Results were compared with those obtained using traditional catalysts (Co, Fe, and Ni). Pd is of interest as it has been demonstrated to be an excellent material for electrical contact to nanotubes. CNT were grown using plasma-enhanced chemical vapor deposition (PECVD) at 450°C to 500°C and using atmospheric-pressure chemical vapor deposition (APCVD) between 450°C and 640°C. The results were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. High-density (1011 cm-2 to 1012 cm-2) self-aligned CNT growth was obtained using APCVD and Pd as the catalyst, while Co and Fe resulted in random growth. TEM revealed that the CNT grown by Pd with PECVD form large bundles of tubes, while Ni forms large-diameter CNF. It was found that the CNT grown using Pd or Ni are of low quality compared with those grown by Co and Fe.

  14. Understanding greater cardiomyocyte functions on aligned compared to random carbon nanofibers in PLGA

    PubMed Central

    Asiri, Abdullah M; Marwani, Hadi M; Khan, Sher Bahadar; Webster, Thomas J

    2015-01-01

    Previous studies have demonstrated greater cardiomyocyte density on carbon nanofibers (CNFs) aligned (compared to randomly oriented) in poly(lactic-co-glycolic acid) (PLGA) composites. Although such studies demonstrated a closer mimicking of anisotropic electrical and mechanical properties for such aligned (compared to randomly oriented) CNFs in PLGA composites, the objective of the present in vitro study was to elucidate a deeper mechanistic understanding of how cardiomyocyte densities recognize such materials to respond more favorably. Results showed lower wettability (greater hydrophobicity) of CNFs embedded in PLGA compared to pure PLGA, thus providing evidence of selectively lower wettability in aligned CNF regions. Furthermore, the results correlated these changes in hydrophobicity with increased adsorption of fibronectin, laminin, and vitronectin (all proteins known to increase cardiomyocyte adhesion and functions) on CNFs in PLGA compared to pure PLGA, thus providing evidence of selective initial protein adsorption cues on such CNF regions to promote cardiomyocyte adhesion and growth. Lastly, results of the present in vitro study further confirmed increased cardiomyocyte functions by demonstrating greater expression of important cardiomyocyte biomarkers (such as Troponin-T, Connexin-43, and α-sarcomeric actin) when CNFs were aligned compared to randomly oriented in PLGA. In summary, this study provided evidence that cardiomyocyte functions are improved on CNFs aligned in PLGA compared to randomly oriented in PLGA since CNFs are more hydrophobic than PLGA and attract the adsorption of key proteins (fibronectin, laminin, and vironectin) that are known to promote cardiomyocyte adhesion and expression of important cardiomyocyte functions. Thus, future studies should use this knowledge to further design improved CNF:PLGA composites for numerous cardiovascular applications. PMID:25565806

  15. A Precision Dose Control Circuit for Maskless E-Beam Lithography With Massively Parallel Vertically Aligned Carbon Nanofibers

    SciTech Connect

    Eliza, Sazia A.; Islam, Syed K; Rahman, Touhidur; Bull, Nora D; Blalock, Benjamin; Baylor, Larry R; Ericson, Milton Nance; Gardner, Walter L

    2011-01-01

    This paper describes a highly accurate dose control circuit (DCC) for the emission of a desired number of electrons from vertically aligned carbon nanofibers (VACNFs) in a massively parallel maskless e-beam lithography system. The parasitic components within the VACNF device cause a premature termination of the electron emission, resulting in underexposure of the photoresist. In this paper, we compensate for the effects of the parasitic components and noise while reducing the area of the chip and achieving a precise count of emitted electrons from the VACNFs to obtain the optimum dose for the e-beam lithography.

  16. A reagentless enzymatic amperometric biosensor using vertically aligned carbon nanofibers (VACNF)

    SciTech Connect

    Weeks, Martha L; Rahman, Touhidur; Frymier, Paul Dexter; Islam, Syed K; McKnight, Timothy E

    2008-01-01

    A reagentless amperometric enzymatic biosensor is constructed on a carbon substrate for detection of ethanol. Yeast alcohol dehydrogenase (YADH), an oxidoreductase, and its cofactor nicotinamide adenine dinucleotide (NAD+) are immobilized by adsorption and covalent attachment to the carbon substrate. Carbon nanofibers grown by plasma enhanced chemical vapor deposition (PECVD) are chosen as the electrode material due to their excellent structural and electrical properties. Electrochemical techniques are employed to test the functionality and performance of the biosensor using reduced form of nicotinamide adenine dinucleotide (NADH) which also determines the oxidation peak potential of NADH. Subsequently, amperometric measurements are conducted for detection of ethanol to determine the electrical current response due to the increase in analyte concentration. The detection range, storage stability, reusability, and response time of the biosensor are also examined.

  17. Enhanced catalytic activity of polyethylenedioxythiophene towards tri-iodide reduction in DSSCs via 1-dimensional alignment using hollow carbon nanofibers

    NASA Astrophysics Data System (ADS)

    Anothumakkool, Bihag; Game, Onkar; Bhange, Siddheshwar N.; Kumari, Tanya; Ogale, Satishchandra B.; Kurungot, Sreekumar

    2014-08-01

    Here, we report a highly conducting 1-dimensionally (1-D) aligned polyethylenedioxythiophene (PEDOT) along the inner and outer surfaces of a hollow carbon nanofiber (CNF) and its application as a counter electrode in a dye sensitized solar cell (DSSC). The hybrid material (CP-25) displays a conversion efficiency of 7.16% compared to 7.30% for the standard Pt counter electrode, 4.48% for bulk PEDOT and 5.56% for CNF. The enhanced conversion efficiency of CP-25 is attributed to the accomplishment of high conductivity and surface area of PEDOT through the 1-D alignment compared to its bulk counterpart. Reduced charge transfer resistance and high conductivity of CP-25 could be proven by cyclic voltammetry, impedance analysis and Tafel experiments. Further, through a long-term stability test involving efficiency profiling for 20 days, it is observed that CP-25 possesses excellent durability compared to the bulk PEDOT.Here, we report a highly conducting 1-dimensionally (1-D) aligned polyethylenedioxythiophene (PEDOT) along the inner and outer surfaces of a hollow carbon nanofiber (CNF) and its application as a counter electrode in a dye sensitized solar cell (DSSC). The hybrid material (CP-25) displays a conversion efficiency of 7.16% compared to 7.30% for the standard Pt counter electrode, 4.48% for bulk PEDOT and 5.56% for CNF. The enhanced conversion efficiency of CP-25 is attributed to the accomplishment of high conductivity and surface area of PEDOT through the 1-D alignment compared to its bulk counterpart. Reduced charge transfer resistance and high conductivity of CP-25 could be proven by cyclic voltammetry, impedance analysis and Tafel experiments. Further, through a long-term stability test involving efficiency profiling for 20 days, it is observed that CP-25 possesses excellent durability compared to the bulk PEDOT. Electronic supplementary information (ESI) available: Experimental methods and supporting figures. See DOI: 10.1039/c4nr00717d

  18. Electromechanically tunable carbon nanofiber photonic crystal.

    PubMed

    Rehammar, Robert; Ghavanini, Farzan Alavian; Magnusson, Roger; Kinaret, Jari M; Enoksson, Peter; Arwin, Hans; Campbell, Eleanor E B

    2013-02-13

    We demonstrate an electrically tunable 2D photonic crystal array constructed from vertically aligned carbon nanofibers. The nanofibers are actuated by applying a voltage between adjacent carbon nanofiber pairs grown directly on metal electrodes, thus dynamically changing the form factor of the photonic crystal lattice. The change in optical properties is characterized using optical diffraction and ellipsometry. The experimental results are shown to be in agreement with theoretical predictions and provide a proof-of-principle for rapidly switchable photonic crystals operating in the visible that can be fabricated using standard nanolithography techniques combined with plasma CVD growth of the nanofibers.

  19. Synthesis and properties of SiN coatings as stable fluorescent markers on vertically aligned carbon nanofibers

    SciTech Connect

    Pearce, Ryan; Klein, Kate L; Ivanov, Ilia N; Hensley, Dale K; Meyer III, Harry M; Melechko, Anatoli; McKnight, Timothy E

    2014-01-01

    The growth of vertically aligned carbon nanofibers (VACNFs) in a catalytic dc ammonia/acetylene plasma process on silicon substrates is often accompanied by sidewall deposition of material that contains mostly Si and N. In fluorescent microscopy experiments, imaging VACNF interfacing to live cell cultures it turned out that this material is broadly fluorescent, which made VACNFs useful as spatial markers, or created nuisance when DNA-labeling got masked. In this paper we provide insight into nature of this silicon/nitrogen in situ coatings. Here we have proposed a potential mechanism for deposition of SiNx coating on the sidewalls of VACNFs during PECVD synthesis in addition to exploring the origin of the coatings fluorescence. It seems most likely that the substrate reacts with the process gases through both processes similar to reactive sputtering and CVD to form silane and other silicon bearing compounds before being deposited isotropically as a SiNx coating onto the VACNFs. The case for the presence of Si-NCs is made strong through a combination of the strong fluorescence and elemental analysis of the samples. These broadly luminescent fibers can prove useful as registry markers in fluorescent cellular studies.

  20. Controlling dispersion and electric-field-assisted alignment of carbon nanotubes and nanofibers for multi-functional epoxy composites

    NASA Astrophysics Data System (ADS)

    Sharma, Ambuj

    The objective of this investigation is to enhance the elastic modulus and tailor the electrical conductivity of nanoreinforced epoxy composites. The resin employed in this investigation is a bisphenol F epoxide with an aromatic diamine curative, extensively used for high performance composites. The nanofillers are unfunctionalized and functionalized carbon nanofibers (CNFs) and multi-walled carbon nanotubes (MWCNTs). The objectives are achieved by controlling the dispersion and alignment of unfunctionalized and functionalized CNFs and CNTs. The process of ultrasonic agitation was used to disperse nanofillers in epoxy resin. The dispersed nanofillers were aligned using alternating current electric field (AC). Continuous use of ultrasonic agitation reduced the lengths, and increased the degree of dispersion of CNFs and CNTs. The parameters of the ultrasonic agitation process were optimized to minimize the reduction in CNF and CNT lengths while achieving good dispersion of CNFs and CNTs in the resin. The composites manufactured with well dispersed CNFs and CNTs increased the elastic modulus as expected based on the theory of short fiber reinforced composites. The alignment and chaining of CNFs and CNTs dispersed in resin were investigated by experiments and modeling. The assembly of chains was found to depend on the frequency of AC electric field used. The mechanism of CNF/CNT chain assembly and growth in a low viscosity epoxy was investigated by developing a finite element model of a chain attached to an electrode. The model includes the combined effects of electrostatic and electro-hydrodynamic forces on chain morphology. The electro-hydrodynamic forces are modeled using the theory of AC electroosmosis. Predictions of the model are compared to experimental results. The experiments were conducted on a CNF/epoxide/curative mixture by applying an AC field at frequencies ranging from 100 -- 100,000 Hz. Predictions of the model qualitatively capture the variations of

  1. Hybrid core-shell nanowire electrodes utilizing vertically aligned carbon nanofiber arrays for high-performance energy storage

    NASA Astrophysics Data System (ADS)

    Klankowski, Steven Arnold

    Nanostructured electrode materials for electrochemical energy storage systems have been shown to improve both rate performance and capacity retention, while allowing considerably longer cycling lifetime. The nano-architectures provide enhanced kinetics by means of larger surface area, higher porosity, better material interconnectivity, shorter diffusion lengths, and overall mechanical stability. Meanwhile, active materials that once were excluded from use due to bulk property issues are now being examined in new nanoarchitecture. Silicon was such a material, desired for its large lithium-ion storage capacity of 4,200 mAh g-1 and low redox potential of 0.4 V vs. Li/Li+; however, a ˜300% volume expansion and increased resistivity upon lithiation limited its broader applications. In the first study, the silicon-coated vertically aligned carbon nanofiber (VACNF) array presents a unique core-shell nanowire (NW) architecture that demonstrates both good capacity and high rate performance. In follow-up, the Si-VACNFs NW electrode demonstrates enhanced power rate capabilities as it shows excellent storage capacity at high rates, attributed to the unique nanoneedle structure that high vacuum sputtering produces on the three-dimensional array. Following silicon's success, titanium dioxide has been explored as an alternative high-rate electrode material by utilizing the dual storage mechanisms of Li+ insertion and pseudocapacitance. The TiO 2-coated VACNFs shows improved electrochemical activity that delivers near theoretical capacity at larger currents due to shorter Li+ diffusion lengths and highly effective electron transport. A unique cell is formed with the Si-coated and TiO2-coated electrodes place counter to one another, creating the hybrid of lithium ion battery-pseudocapacitor that demonstrated both high power and high energy densities. The hybrid cell operates like a battery at lower current rates, achieving larger discharge capacity, while retaining one-third of

  2. Novel continuous carbon and ceramic nanofibers and nanocomposites

    NASA Astrophysics Data System (ADS)

    Wen, Yongkui

    2004-12-01

    Manufacturing of carbon nanofibers from PAN precursor is described in Chapter 2 of the dissertation. The electrospun nanofibers were continuous, uniform in diameter, and the samples didn't contain impurities, unlike carbon nanotubes or vapor grown carbon fibers. Systematic studies on the electrospinning parameters showed that nanofiber diameter could be varied in a range of 80 to 1800 nm. XRD studies on the carbon nanofibers fired at different temperatures showed that higher temperature resulted in better nanostructure. Fracture-free random carbon nanofiber sheets were produced by stretch-stabilization and carbonization for the first time. Toughening effects of random as-spun PAN, stabilized PAN, and carbon nanofibers on Mode I and Mode II interlaminar fracture of advanced carbon-epoxy composites were examined by DCB and ENF tests respectively in Chapter 3. The results showed that the interlaminar fracture toughness increased the most with carbon nanofiber reinforcement. 200% improvement in Mode I fracture toughness and 60% in Mode II fracture toughness were achieved with a minimum increase of weight. SEM fractographic analysis showed nanofiber pullout and crack bridging as the main nanomechanisms of toughening. Chapter 4 describes manufacturing of aligned carbon nanofibers and nanocomposites by a modified electrospinning technique. Constant-load stretch-stabilization was applied on carbon nanofibers for the first time. Analysis showed that mechanical properties of nanofibers and nanocomposites improved with stretch-stabilization and alignment of carbon nanofibers. Nanofabrication of ceramic 3Al2O3-2SiO2, SiO2-TiO2 nanofibers by a novel combination of sol-gel and electrospinning techniques invented recently at UNL is described in Chapters 5. The 3Al2O3-2SiO2, SiO2-TiO 2 nanofibers were continuous, non circular in cross section and had crystalline structure after high temperature calcination. Effects of the process parameters on their geometry and structure were

  3. Effective Infiltration of Gel Polymer Electrolyte into Silicon-Coated Vertically Aligned Carbon Nanofibers as Anodes for Solid-State Lithium-Ion Batteries.

    PubMed

    Pandey, Gaind P; Klankowski, Steven A; Li, Yonghui; Sun, Xiuzhi Susan; Wu, Judy; Rojeski, Ronald A; Li, Jun

    2015-09-23

    This study demonstrates the full infiltration of gel polymer electrolyte into silicon-coated vertically aligned carbon nanofibers (Si-VACNFs), a high-capacity 3D nanostructured anode, and the electrochemical characterization of its properties as an effective electrolyte/separator for future all-solid-state lithium-ion batteries. Two fabrication methods have been employed to form a stable interface between the gel polymer electrolyte and the Si-VACNF anode. In the first method, the drop-casted gel polymer electrolyte is able to fully infiltrate into the open space between the vertically aligned core-shell nanofibers and encapsulate/stabilize each individual nanofiber in the polymer matrix. The 3D nanostructured Si-VACNF anode shows a very high capacity of 3450 mAh g(-1) at C/10.5 (or 0.36 A g(-1)) rate and 1732 mAh g(-1) at 1C (or 3.8 A g(-1)) rate. In the second method, a preformed gel electrolyte film is sandwiched between an Si-VACNF electrode and a Li foil to form a half-cell. Most of the vertical core-shell nanofibers of the Si-VACNF anode are able to penetrate into the gel polymer film while retaining their structural integrity. The slightly lower capacity of 2800 mAh g(-1) at C/11 rate and ∼1070 mAh g(-1) at C/1.5 (or 2.6 A g(-1)) rate have been obtained, with almost no capacity fade for up to 100 cycles. Electrochemical impedance spectroscopy does not show noticeable changes after 110 cycles, further revealing the stable interface between the gel polymer electrolyte and the Si-VACNFs anode. These results show that the infiltrated flexible gel polymer electrolyte can effectively accommodate the stress/strain of the Si shell due to the large volume expansion/contraction during the charge-discharge processes, which is particularly useful for developing future flexible solid-state lithium-ion batteries incorporating Si-anodes.

  4. Shear adhesion strength of aligned electrospun nanofibers.

    PubMed

    Najem, Johnny F; Wong, Shing-Chung; Ji, Guang

    2014-09-01

    Inspiration from nature such as insects' foot hairs motivates scientists to fabricate nanoscale cylindrical solids that allow tens of millions of contact points per unit area with material substrates. In this paper, we present a simple yet robust method for fabricating directionally sensitive shear adhesive laminates. By using aligned electrospun nylon-6, we create dry adhesives, as a succession of our previous work on measuring adhesion energies between two single free-standing electrospun polymer fibers in cross-cylinder geometry, randomly oriented membranes and substrate, and peel forces between aligned fibers and substrate. The synthetic aligned cylindrical solids in this study are electrically insulating and show a maximal Mode II shear adhesion strength of 27 N/cm(2) on a glass slide. This measured value, for the purpose of comparison, is 270% of that reported from gecko feet. The Mode II shear adhesion strength, based on a commonly known "dead-weight" test, is 97-fold greater than the Mode I (normal) adhesion strength of the same. The data indicate a strong shear binding on and easy normal lifting off. Anisotropic adhesion (Mode II/Mode I) is pronounced. The size and surface boundary effects, crystallinity, and bending stiffness of fibers are used to understand these electrospun nanofibers, which vastly differ from otherwise known adhesive technologies. The anisotropic strength distribution is attributed to a decreasing fiber diameter and an optimized laminate thickness, which, in turn, influences the bending stiffness and solid-state "wettability" of points of contact between nanofibers and surface asperities.

  5. Low temperature and cost-effective growth of vertically aligned carbon nanofibers using spin-coated polymer-stabilized palladium nanocatalysts

    NASA Astrophysics Data System (ADS)

    Saleem, Amin M.; Shafiee, Sareh; Krasia-Christoforou, Theodora; Savva, Ioanna; Göransson, Gert; Desmaris, Vincent; Enoksson, Peter

    2015-02-01

    We describe a fast and cost-effective process for the growth of carbon nanofibers (CNFs) at a temperature compatible with complementary metal oxide semiconductor technology, using highly stable polymer-Pd nanohybrid colloidal solutions of palladium catalyst nanoparticles (NPs). Two polymer-Pd nanohybrids, namely poly(lauryl methacrylate)-block-poly((2-acetoacetoxy)ethyl methacrylate)/Pd (LauMAx-b-AEMAy/Pd) and polyvinylpyrrolidone/Pd were prepared in organic solvents and spin-coated onto silicon substrates. Subsequently, vertically aligned CNFs were grown on these NPs by plasma enhanced chemical vapor deposition at different temperatures. The electrical properties of the grown CNFs were evaluated using an electrochemical method, commonly used for the characterization of supercapacitors. The results show that the polymer-Pd nanohybrid solutions offer the optimum size range of palladium catalyst NPs enabling the growth of CNFs at temperatures as low as 350 °C. Furthermore, the CNFs grown at such a low temperature are vertically aligned similar to the CNFs grown at 550 °C. Finally the capacitive behavior of these CNFs was similar to that of the CNFs grown at high temperature assuring the same electrical properties thus enabling their usage in different applications such as on-chip capacitors, interconnects, thermal heat sink and energy storage solutions.

  6. A novel approach for preparation of aligned electrospun polyacrylonitrile nanofibers

    NASA Astrophysics Data System (ADS)

    Heidari, Iman; Mosavi Mashhadi, Mahmoud; Faraji, Ghader

    2013-12-01

    In this Letter, a new type of collector named ‘rotating grid collector’ was introduced and its capability in aligning the nanofibers was examined. The results showed that electrospinning using rotating grid collector could produce well aligned fibers with fiber alignment percent of 76%. It was found that in a constant solution flow rate increasing collector rotation speed and eccentric distance improved the fiber alignments. Having prepared the fiber textiles, we found that increasing the rotation speed improved the tensile strength of the fiber textile. This new collector is promising for future application in aligning nanofibers.

  7. Silicon Whisker and Carbon Nanofiber Composite Anode

    NASA Technical Reports Server (NTRS)

    Ma, Junqing (Inventor); Newman, Aron (Inventor); Lennhoff, John (Inventor)

    2015-01-01

    A carbon nanofiber can have a surface and include at least one crystalline whisker extending from the surface of the carbon nanofiber. A battery anode composition can be formed from a plurality of carbon nanofibers each including a plurality of crystalline whiskers.

  8. Fabrication of aligned nanofibers by electric-field-controlled electrospinning: insulating-block method.

    PubMed

    Hwang, Wontae; Pang, Changhyun; Chae, Heeyeop

    2016-10-28

    Aligned nanofiber arrays and mats were fabricated with an electrospinning process by manipulating the electric field. The electric field was modified by insulating blocks (IBs) that were installed between the nozzle and the substrate as guiding elements to control the trajectory of the electrospinning jet flow. Simulation results showed that the electric field was deformed near the IBs, resulting in confinement of the electrospinning jet between the blocks. The balance of the electric field in the vertical direction and the repulsive force by space charges in the confined electrified jet stream was attributed to the aligned motion of the jet. Aligned arrays of 200 nm thick polyethylene oxide nanofibers were obtained, exhibiting wave-shaped and cross patterns as well as rectilinear patterns. In addition, 40 μm thick quasi-aligned carbon-nanofiber mats with anisotropic electrical property were also attained by this method. PMID:27651316

  9. Fabrication of aligned nanofibers by electric-field-controlled electrospinning: insulating-block method.

    PubMed

    Hwang, Wontae; Pang, Changhyun; Chae, Heeyeop

    2016-10-28

    Aligned nanofiber arrays and mats were fabricated with an electrospinning process by manipulating the electric field. The electric field was modified by insulating blocks (IBs) that were installed between the nozzle and the substrate as guiding elements to control the trajectory of the electrospinning jet flow. Simulation results showed that the electric field was deformed near the IBs, resulting in confinement of the electrospinning jet between the blocks. The balance of the electric field in the vertical direction and the repulsive force by space charges in the confined electrified jet stream was attributed to the aligned motion of the jet. Aligned arrays of 200 nm thick polyethylene oxide nanofibers were obtained, exhibiting wave-shaped and cross patterns as well as rectilinear patterns. In addition, 40 μm thick quasi-aligned carbon-nanofiber mats with anisotropic electrical property were also attained by this method.

  10. Fabrication of aligned nanofibers by electric-field-controlled electrospinning: insulating-block method

    NASA Astrophysics Data System (ADS)

    Hwang, Wontae; Pang, Changhyun; Chae, Heeyeop

    2016-10-01

    Aligned nanofiber arrays and mats were fabricated with an electrospinning process by manipulating the electric field. The electric field was modified by insulating blocks (IBs) that were installed between the nozzle and the substrate as guiding elements to control the trajectory of the electrospinning jet flow. Simulation results showed that the electric field was deformed near the IBs, resulting in confinement of the electrospinning jet between the blocks. The balance of the electric field in the vertical direction and the repulsive force by space charges in the confined electrified jet stream was attributed to the aligned motion of the jet. Aligned arrays of 200 nm thick polyethylene oxide nanofibers were obtained, exhibiting wave-shaped and cross patterns as well as rectilinear patterns. In addition, 40 μm thick quasi-aligned carbon-nanofiber mats with anisotropic electrical property were also attained by this method.

  11. Atomic layer deposition of Al-doped ZnO/Al2O3 double layers on vertically aligned carbon nanofiber arrays.

    PubMed

    Malek, Gary A; Brown, Emery; Klankowski, Steven A; Liu, Jianwei; Elliot, Alan J; Lu, Rongtao; Li, Jun; Wu, Judy

    2014-05-14

    High-aspect-ratio, vertically aligned carbon nanofibers (VACNFs) were conformally coated with aluminum oxide (Al2O3) and aluminum-doped zinc oxide (AZO) using atomic layer deposition (ALD) in order to produce a three-dimensional array of metal-insulator-metal core-shell nanostructures. Prefunctionalization before ALD, as required for initiating covalent bonding on a carbon nanotube surface, was eliminated on VACNFs due to the graphitic edges along the surface of each CNF. The graphitic edges provided ideal nucleation sites under sequential exposures of H2O and trimethylaluminum to form an Al2O3 coating up to 20 nm in thickness. High-resolution transmission electron microscopy (HRTEM) and scanning electron microscopy images confirmed the conformal core-shell AZO/Al2O3/CNF structures while energy-dispersive X-ray spectroscopy verified the elemental composition of the different layers. HRTEM selected area electron diffraction revealed that the as-made Al2O3 by ALD at 200 °C was amorphous, and then, after annealing in air at 450 °C for 30 min, was converted to polycrystalline form. Nevertheless, comparable dielectric constants of 9.3 were obtained in both cases by cyclic voltammetry at a scan rate of 1000 V/s. The conformal core-shell AZO/Al2O3/VACNF array structure demonstrated in this work provides a promising three-dimensional architecture toward applications of solid-state capacitors with large surface area having a thin, leak-free dielectric.

  12. Atomic layer deposition of Al-doped ZnO/Al2O3 double layers on vertically aligned carbon nanofiber arrays.

    PubMed

    Malek, Gary A; Brown, Emery; Klankowski, Steven A; Liu, Jianwei; Elliot, Alan J; Lu, Rongtao; Li, Jun; Wu, Judy

    2014-05-14

    High-aspect-ratio, vertically aligned carbon nanofibers (VACNFs) were conformally coated with aluminum oxide (Al2O3) and aluminum-doped zinc oxide (AZO) using atomic layer deposition (ALD) in order to produce a three-dimensional array of metal-insulator-metal core-shell nanostructures. Prefunctionalization before ALD, as required for initiating covalent bonding on a carbon nanotube surface, was eliminated on VACNFs due to the graphitic edges along the surface of each CNF. The graphitic edges provided ideal nucleation sites under sequential exposures of H2O and trimethylaluminum to form an Al2O3 coating up to 20 nm in thickness. High-resolution transmission electron microscopy (HRTEM) and scanning electron microscopy images confirmed the conformal core-shell AZO/Al2O3/CNF structures while energy-dispersive X-ray spectroscopy verified the elemental composition of the different layers. HRTEM selected area electron diffraction revealed that the as-made Al2O3 by ALD at 200 °C was amorphous, and then, after annealing in air at 450 °C for 30 min, was converted to polycrystalline form. Nevertheless, comparable dielectric constants of 9.3 were obtained in both cases by cyclic voltammetry at a scan rate of 1000 V/s. The conformal core-shell AZO/Al2O3/VACNF array structure demonstrated in this work provides a promising three-dimensional architecture toward applications of solid-state capacitors with large surface area having a thin, leak-free dielectric. PMID:24689702

  13. Aligned Nanofibers for Regenerating Arteries, Nerves, and Muscles

    NASA Astrophysics Data System (ADS)

    McClendon, Mark Trosper

    Cells are the fundamental unit of the human body, and therefore the ability to control cell behavior is the most important challenge in regenerative medicine. Peptides are the language of biology which is why synthetic peptide amphiphile (PA) molecules hold great potential as a biomaterial. The work presented in this dissertation explores a variety of liquid crystalline PA nanofibers as a means for directing cell growth. Shaping the alignment of these nanofiber networks requires a deep understanding of their rheological properties which presents a difficult challenge as they exist in complex solid and liquid environments. Using PA molecules that self-assemble into high aspect ratio nanofibers and liquid crystalline solutions, this work investigates the influence of shear flow on macroscopic and microscopic nanofiber alignment. To this end, a shear force applied to PA solutions was systematically varied while the alignment was probed using small angle x-ray scattering. Nanofibers were found to respond to shear flow by aligning parallel to the flow direction. By changing pH and PA chemical sequence it was observed that increasing the interfiber electrostatic repulsive interactions resulted in a greater dependence on shear rate. Nanofiber solutions having greater repulsion did not drastically increase in alignment when the applied strain was increased by two orders of magnitude (1 s -1 to 100 s-1), while solutions with nanofibers having less repulsion increased there alignment four fold with the same strain increase. say exactly what you mean by resulted in greater dependence: did it result in fibers aligning under lower shear rates or higher rates--give the results Anionic PA solutions typically used to encapsulate living cells at neutral pH were found to require minimal shear rates, <1s-1, to achieve significant nanofiber alignment. In an effort to produce tubular hydrogels composed of circumferentially aligned nanofibers, a procedure was designed that used an

  14. Plasma-enhanced chemical vapor deposition of multiwalled carbon nanofibers

    NASA Technical Reports Server (NTRS)

    Matthews, Kristopher; Cruden, Brett A.; Chen, Bin; Meyyappan, M.; Delzeit, Lance

    2002-01-01

    Plasma-enhanced chemical vapor deposition is used to grow vertically aligned multiwalled carbon nanofibers (MWNFs). The graphite basal planes in these nanofibers are not parallel as in nanotubes; instead they exhibit a small angle resembling a stacked cone arrangement. A parametric study with varying process parameters such as growth temperature, feedstock composition, and substrate power has been conducted, and these parameters are found to influence the growth rate, diameter, and morphology. The well-aligned MWNFs are suitable for fabricating electrode systems in sensor and device development.

  15. Electrospun nanofiber reinforcement of dental composites with electromagnetic alignment approach.

    PubMed

    Uyar, Tansel; Çökeliler, Dilek; Doğan, Mustafa; Koçum, Ismail Cengiz; Karatay, Okan; Denkbaş, Emir Baki

    2016-05-01

    Polymethylmethacrylate (PMMA) is commonly used as a base acrylic denture material with benefits of rapid and easy handling, however, when it is used in prosthetic dentistry, fracturing or cracking problems can be seen due to the relatively low strength issues. Besides, acrylic resin is the still prominent material for denture fabrication due to its handy and low cost features. Numerous proposed fillers that are used to produce PMMA composites, however electrospun polyvinylalcohol (PVA) nanofiber fillers for production of PMMA composite resins are not studied as much as the others. The other focus of the practice is to compare both mechanical properties and efficiency of aligned fibers versus non-aligned PVA nanofibers in PMMA based dental composites. Field-controlled electrospinning system is manufactured and provided good alignment in lab scale as one of contributions. Some novel auxiliary electrodes in controlled structure are augmented to obtain different patterns of alignment with a certain range of fiber diameters. Scanning electron microscopy is used for physical characterization to determine the range of fiber diameters. Non-woven fiber has no unique pattern due to chaotic nature of electrospinning process, but aligned fibers have round pattern or crossed lines. These produced fibers are structured as layer-by-layer form with different features, and these features are used in producing PMMA dental composites with different volume ratios. The maximum flexural strength figure shows that fiber load by weight of 0.25% w/w and above improves in the maximum level. As a result, mechanical properties of PMMA dental composites are improved by using PVA nanofibers as a filler, however the improvement was higher when aligned PVA nanofibers are used. The maximum values were 5.1 MPa (flexural strength), 0.8 GPa (elastic modulus), and 170 kJ/m(3) (toughness) in three-point bending test. In addition to the positive results of aligned and non-aligned nanofibers it was found

  16. Nanofiber alignment of a small diameter elastic electrospun scaffold

    NASA Astrophysics Data System (ADS)

    Patel, Jignesh

    Cardiovascular disease is the leading cause of death in western countries with coronary heart disease making up 50% of these deaths. As a treatment option, tissue engineered grafts have great potential. Elastic scaffolds that mimic arterial extracellular matrix (ECM) may hold the key to creating viable vascular grafts. Electrospinning is a widely used scaffold fabrication technique to engineer tubular scaffolds. In this study, we investigated how the collector rotation speed altered the nanofiber alignment which may improve mechanical characteristics making the scaffold more suitable for arterial grafts. The scaffold was fabricated from a blend of PCL/Elastin. 2D Fast Fourier Transform (FFT) image processing tool and MatLab were used to quantitatively analyze nanofiber orientation at different collector speeds (13500 to 15500 rpm). Both Image J and MatLab showed graphical peaks indicating predominant fiber orientation angles. A collector speed of 15000 rpm was found to produce the best nanofiber alignment with narrow peaks at 90 and 270 degrees, and a relative amplitude of 200. This indicates a narrow distribution of circumferentially aligned nanofibers. Collector speeds below and above 15000 rpm caused a decrease in fiber alignment with a broader orientation distribution. Uniformity of fiber diameter was also measured. Of 600 measures from the 15000 rpm scaffolds, the fiber diameter range from 500 nm to 899 nm was most prevalent. This diameter range was slightly larger than native ECM which ranges from 50 nm to 500 nm. The second most prevalent diameter range had an average of 404 nm which is within the diameter range of collagen. This study concluded that with proper electrospinning technique and collector speed, it is possible to fabricate highly aligned small diameter elastic scaffolds. Image J 2D FFT results confirmed MatLab findings for the analyses of circumferentially aligned nanofibers. In addition, MatLab analyses simplified the FFT orientation data

  17. Horizontal carbon nanotube alignment.

    PubMed

    Cole, Matthew T; Cientanni, Vito; Milne, William I

    2016-09-21

    The production of horizontally aligned carbon nanotubes offers a rapid means of realizing a myriad of self-assembled near-atom-scale technologies - from novel photonic crystals to nanoscale transistors. The ability to reproducibly align anisotropic nanostructures has huge technological value. Here we review the present state-of-the-art in horizontal carbon nanotube alignment. For both in and ex situ approaches, we quantitatively assess the reported linear packing densities alongside the degree of alignment possible for each of these core methodologies. PMID:27546174

  18. Horizontal carbon nanotube alignment.

    PubMed

    Cole, Matthew T; Cientanni, Vito; Milne, William I

    2016-09-21

    The production of horizontally aligned carbon nanotubes offers a rapid means of realizing a myriad of self-assembled near-atom-scale technologies - from novel photonic crystals to nanoscale transistors. The ability to reproducibly align anisotropic nanostructures has huge technological value. Here we review the present state-of-the-art in horizontal carbon nanotube alignment. For both in and ex situ approaches, we quantitatively assess the reported linear packing densities alongside the degree of alignment possible for each of these core methodologies.

  19. WAXS investigations on Polyethylene -- Carbon Nanofibers Composites

    NASA Astrophysics Data System (ADS)

    Jones, Brian; Li, Jianhua; Benitez, Rogelio; Lozano, Karen; Chipara, Mircea; Cristian Chipara, Alin; Dorina Chipara, Magdalena; Sellmyer, David J.

    2008-03-01

    Nanocomposites have been obtained by high-shear mixing of isotactic polyethylene with various amounts of purified nanofiller (vapor grown carbon nanofibers type PR-24AG from Pyrograf Products, Inc) by utilizing a HAAKE Rheomix at 65 rpm and 180 ^oC for 9 min followed by an additional mixing at 90 rpm for 5 min. Composites loaded with various amounts of vapor grown carbon nanofibers have been prepared. Various spectroscopic techniques have been used to assess the interactions between the polymeric matrix and carbon nanofibers. Wide angle X - Ray scattering investigations focused on the effect of carbon nanofibers on the crystalline phases of polypropylene and on the overall crystallinity degree of the polymeric matrix. This research aims at a better understanding of the nature and structure of the polymer -- carbon nanofibers interface.

  20. Aligned Nanofibers for Regenerating Arteries, Nerves, and Muscles

    NASA Astrophysics Data System (ADS)

    McClendon, Mark Trosper

    Cells are the fundamental unit of the human body, and therefore the ability to control cell behavior is the most important challenge in regenerative medicine. Peptides are the language of biology which is why synthetic peptide amphiphile (PA) molecules hold great potential as a biomaterial. The work presented in this dissertation explores a variety of liquid crystalline PA nanofibers as a means for directing cell growth. Shaping the alignment of these nanofiber networks requires a deep understanding of their rheological properties which presents a difficult challenge as they exist in complex solid and liquid environments. Using PA molecules that self-assemble into high aspect ratio nanofibers and liquid crystalline solutions, this work investigates the influence of shear flow on macroscopic and microscopic nanofiber alignment. To this end, a shear force applied to PA solutions was systematically varied while the alignment was probed using small angle x-ray scattering. Nanofibers were found to respond to shear flow by aligning parallel to the flow direction. By changing pH and PA chemical sequence it was observed that increasing the interfiber electrostatic repulsive interactions resulted in a greater dependence on shear rate. Nanofiber solutions having greater repulsion did not drastically increase in alignment when the applied strain was increased by two orders of magnitude (1 s -1 to 100 s-1), while solutions with nanofibers having less repulsion increased there alignment four fold with the same strain increase. say exactly what you mean by resulted in greater dependence: did it result in fibers aligning under lower shear rates or higher rates--give the results Anionic PA solutions typically used to encapsulate living cells at neutral pH were found to require minimal shear rates, <1s-1, to achieve significant nanofiber alignment. In an effort to produce tubular hydrogels composed of circumferentially aligned nanofibers, a procedure was designed that used an

  1. Magnetic alignment of nickel-coated carbon fibers

    SciTech Connect

    Hao, Chuncheng; Li, Xiaojiao; Wang, Guizhen

    2011-11-15

    Graphical abstract: Carbon nanofibers were subjected to a two-step pretreatment, sensitization and activation. Carbon nanofibers were encapsulated by a uniform layer of nickel nanoparticles. The prepared composites are ferromagnetic and with a small value of coercivity. Upon such functionalization, the carbon nanofibers can be aligned in a relatively small external magnetic field. Highlights: {center_dot} A simple microwave-assisted procedure for the magnetic composite. {center_dot} Dense layer of nickel on pretreated carbon nanofibers. {center_dot} Ferromagnetic properties and low coercivity. {center_dot} A long-chain aligned structure under magnetic field. -- Abstract: Magnetic composites of nickel-coated carbon nanofibers have been successfully fabricated by employing a simple microwave-assisted procedure. The scanning electron microscopy images show that a complete and uniform nickel coating with mean size of 25 nm could be deposited on carbon fibers. Magnetization curves demonstrate that the prepared composites are ferromagnetic and that the coercivity is 96 Oe. The magnetic carbon nanofibers can be aligned as a long-chain structure in an external magnetic field.

  2. Occupational Exposure to Carbon Nanotubes and Nanofibers

    MedlinePlus

    ... Current Intelligence Bulletin 65: Occupational Exposure to Carbon Nanotubes and Nanofibers Recommend on Facebook Tweet Share Compartir ... composed of engineered nanoparticles, such as metal oxides, nanotubes, nanowires, quantum dots, and carbon fullerenes (buckyballs), among ...

  3. Electrospun nanofiber reinforcement of dental composites with electromagnetic alignment approach.

    PubMed

    Uyar, Tansel; Çökeliler, Dilek; Doğan, Mustafa; Koçum, Ismail Cengiz; Karatay, Okan; Denkbaş, Emir Baki

    2016-05-01

    Polymethylmethacrylate (PMMA) is commonly used as a base acrylic denture material with benefits of rapid and easy handling, however, when it is used in prosthetic dentistry, fracturing or cracking problems can be seen due to the relatively low strength issues. Besides, acrylic resin is the still prominent material for denture fabrication due to its handy and low cost features. Numerous proposed fillers that are used to produce PMMA composites, however electrospun polyvinylalcohol (PVA) nanofiber fillers for production of PMMA composite resins are not studied as much as the others. The other focus of the practice is to compare both mechanical properties and efficiency of aligned fibers versus non-aligned PVA nanofibers in PMMA based dental composites. Field-controlled electrospinning system is manufactured and provided good alignment in lab scale as one of contributions. Some novel auxiliary electrodes in controlled structure are augmented to obtain different patterns of alignment with a certain range of fiber diameters. Scanning electron microscopy is used for physical characterization to determine the range of fiber diameters. Non-woven fiber has no unique pattern due to chaotic nature of electrospinning process, but aligned fibers have round pattern or crossed lines. These produced fibers are structured as layer-by-layer form with different features, and these features are used in producing PMMA dental composites with different volume ratios. The maximum flexural strength figure shows that fiber load by weight of 0.25% w/w and above improves in the maximum level. As a result, mechanical properties of PMMA dental composites are improved by using PVA nanofibers as a filler, however the improvement was higher when aligned PVA nanofibers are used. The maximum values were 5.1 MPa (flexural strength), 0.8 GPa (elastic modulus), and 170 kJ/m(3) (toughness) in three-point bending test. In addition to the positive results of aligned and non-aligned nanofibers it was found

  4. Carbon Nanofiber Electrode for Neurochemical Monitoring

    PubMed Central

    Zhang, David A.; Rand, Emily; Marsh, Michael; Andrews, Russell J.; Lee, Kendall H.; Meyyappan, M.

    2014-01-01

    The ability to rapidly detect neurotransmitter release has broad implications in the study of a variety of neurodegenerative diseases. Electrochemical detection methods using carbon nanofiber nanoelectrodes integrated into the Wireless Instantaneous Neurotransmitter Concentration Sensing System (WINCS) offer many important advantages including biocompatibility, selectivity, sensitivity, and rapid adsorption kinetics. Carbon nanofiber nanoelectrodes exhibit greater selectivity and sensitivity in the electrochemical detection of neurotransmitters compared to macroelectrodes and are able to resolve a ternary mixture of dopamine (DA), serotonin (5-HT), and ascorbic acid as well as to detect individual neurotransmitters in concentrations as low as 50 nM for DA and 100 nM for 5-HT using differential pulse voltammetry. Adsorption kinetics studies and isopropyl alcohol treatments modeled on previous studies on carbon fiber microelectrodes were conducted to investigate the analogous properties on carbon nanofiber electrodes using fast-scan cyclic voltammetry with WINCS and showed analogous results in carbon nanofiber electrodes compared with carbon fiber microelectrodes. PMID:23975638

  5. Highly Aligned Poly(vinylidene fluoride-co-hexafluoro propylene) Nanofibers via Electrospinning Technique.

    PubMed

    Han, Tae-Hwan; Nirmala, R; Kim, Tae Woo; Navamathavan, R; Kim, Hak Yong; Park, Soo Jin

    2016-01-01

    We report on the simple way of obtaining aligned poly(vinylidiene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanofibers by electrospinning process. The collector drum rotation speed was adjusted to prepare well aligned PVDF-HFP nanofibers. The degree of alignment and the orientation of PVDF-HFP nanofibers can be significantly altered by varying the speed of collector drum rotation. The resultant PVDF-HFP nanofibers were systematically characterized. From the scanning electron microscopy data, it was found that the electrospun PVDF-HFP nanofibers were formed with well-aligned nature. The X-ray diffraction results revealed that the electrospun PVDF-HFP nanofibers with β-phase can be formed by the increased collector drum rotation speed. Overall, the collector rotation speed during the electrospinning process plays an important role in obtaining well-aligned and improved characteristics of PVDF-HFP nanofibers. PMID:27398493

  6. Spectroscopic Investigations on Polypropylene -- Carbon Nanofibers Composites

    NASA Astrophysics Data System (ADS)

    Chipara, Mircea; Brian, Jones; Lozano, Karen; Villareal, John R.; Cristian Chipara, Alin; Hernandez, Anna; Dorina Chipara, Magdalena; Sellmyer, David J.

    2008-03-01

    Nanocomposites were obtained by high-shear mixing of isotactic polypropylene (Marlex HLN-120-01; Philips Sumika Polypropylene Company) with various amounts of vapor grown carbon nanofibers (PR-24AG; Pyrograf Products, Inc) by utilizing a HAAKE Rheomix at 65 rpm and 180 ^oC for 9 min followed by an additional mixing at 90 rpm for 5 min. Composites loaded with various amounts of vapor grown carbon nanofibers have been prepared. Wide angle X-Ray scattering investigations focus on the effect of carbon nanofibers on the crystalline phases of polypropylene and on the overall crystallinity degree of the polymeric matrix. Raman spectroscopy analysis concentrates on D and G bands. X-band electron spin resonance investigations aim at a better understanding of the purity of carbon nanofibers and of the ratio between conducting and paramagnetic.

  7. Electrospun Carbon Nanotube-Reinforced Nanofiber.

    PubMed

    Kim, Sung Mm; Hee Kim, Sung; Choi, Myong Soo; Lee, Jun Young

    2016-03-01

    We fabricated multi-walled carbon nanotube (MWNT) reinforced polyurethane (PU) nanofiber (MWNT-PU) web via electrospinning. In order to optimize the electrospinning conditions, we investigated the effects of various parameters including kind of solvent, viscosity of the spinning solution, and flow rate on the spinnability and properties of nanofiber. N,N-dimethylformamide (DMF), tetrahydrofuran (THF) and their mixture with various volume ratio were used as the spinning solvent. Morphology of the nanofiber was studied using scanning electron microscope (SEM) and transmission electron microscope (TEM), confirming successful fabrication of MWNT-PU nanofiber web with uniform dispersion of MWNT in longitudinal direction of the fiber. The MWNT-PU nanofiber web exhibited two times higher tensile strength than PU nanofiber web. We also fabricated electrically conducting MWNT-PU nanofiber web by coating poly(3,4-ehtylenedioxythiophene) (PEDOT) on the surface of MWNT-PU nanofiber web for electromagnetic interference (EMI) shielding application. The electromagnetic interference shielding effectiveness (EMI SE) was quite high as 25 dB in the frequency range from 50 MHz to 10 GHz. PMID:27455732

  8. Fluorescent carbon nanowires made by pyrolysis of DNA nanofibers and plasmon-assisted emission enhancement of their fluorescence.

    PubMed

    Nakao, Hidenobu; Tokonami, Shiho; Yamamoto, Yojiro; Shiigi, Hiroshi; Takeda, Yoshihiko

    2014-10-14

    We report on a facile method for preparing fluorescent carbon nanowires (CNWs) with pyrolysis of highly aligned DNA nanofibers as carbon sources. Silver nanoparticle (AgNP)-doped CNWs were also produced using pyrolysis of DNA nanofibers with well-attached AgNPs, indicating emission enhancement assisted by localized plasmon resonances.

  9. Production of aligned microfibers and nanofibers and derived functional monoliths

    DOEpatents

    Hu, Michael Z.; DePaoli, David W.; Kuritz, Tanya; Omatete, Ogbemi

    2007-08-14

    The present invention comprises a method for producing microfibers and nanofibers and further fabricating derived solid monolithic materials having aligned uniform micro- or nanofibrils. A method for producing fibers ranging in diameter from micrometer-sized to nanometer-sized comprises the steps of producing an electric field and preparing a solid precipitative reaction media wherein the media comprises at least one chemical reactive precursor and a solvent having low electrical conductivity and wherein a solid precipitation reaction process for nucleation and growth of a solid phase occurs within the media. Then, subjecting the media to the electric field to induce in-situ growth of microfibers or nanofibers during the reaction process within the media causing precipitative growth of solid phase particles wherein the reaction conditions and reaction kinetics control the size, morphology and composition of the fibers. The fibers can then be wet pressed while under electric field into a solid monolith slab, dried and consolidated.

  10. Carbon Nanofiber Nanoelectrodes for Biosensing Applications

    NASA Technical Reports Server (NTRS)

    Koehne, Jessica Erin

    2014-01-01

    A sensor platform based on vertically aligned carbon nanofibers (CNFs) has been developed. Their inherent nanometer scale, high conductivity, wide potential window, good biocompatibility and well-defined surface chemistry make them ideal candidates as biosensor electrodes. Here, we report two studies using vertically aligned CNF nanoelectrodes for biomedical applications. CNF arrays are investigated as neural stimulation and neurotransmitter recording electrodes for application in deep brain stimulation (DBS). Polypyrrole coated CNF nanoelectrodes have shown great promise as stimulating electrodes due to their large surface area, low impedance, biocompatibility and capacity for highly localized stimulation. CNFs embedded in SiO2 have been used as sensing electrodes for neurotransmitter detection. Our approach combines a multiplexed CNF electrode chip, developed at NASA Ames Research Center, with the Wireless Instantaneous Neurotransmitter Concentration Sensor (WINCS) system, developed at the Mayo Clinic. Preliminary results indicate that the CNF nanoelectrode arrays are easily integrated with WINCS for neurotransmitter detection in a multiplexed array format. In the future, combining CNF based stimulating and recording electrodes with WINCS may lay the foundation for an implantable smart therapeutic system that utilizes neurochemical feedback control while likely resulting in increased DBS application in various neuropsychiatric disorders. In total, our goal is to take advantage of the nanostructure of CNF arrays for biosensing studies requiring ultrahigh sensitivity, high-degree of miniaturization, and selective biofunctionalization.

  11. Morphology and internal structure of polymeric and carbon nanofibers

    NASA Astrophysics Data System (ADS)

    Zhong, Zhenxin

    Evaporation and the associated solidification are important factors that affect the diameter of electrospun nanofibers. The evaporation and solidification of a charged jet were controlled by varying the partial pressure of water vapor during electrospinning of poly(ethylene oxide) from aqueous solution. As the partial pressure of water vapor increases, the solidification process of the charged jet becomes slower, allowing elongation of the charged jet to continue longer and thereby to form thinner fibers. The morphology and internal structure of electrospun poly(vinylidene fluorides) nanofibers were investigated. Low voltage high resolution scanning electron microscopy was used to study the surface of electrospun nanofibers. Control of electrospinning process produced fibers with various morphological forms. Fibers that were beaded, branched, or split were obtained when different instabilities dominated in the electrospinning process. The high ratio of stretching during electrospinning aligns the polymer molecules along the fiber axis. A rapid evaporation of solvent during electrospinning gives fibers with small and imperfect crystallites. These can be perfected by thermal annealing. Fibers annealed at elevated temperature form plate-like lamellar crystals tightly linked by tie molecules. Electrospinning can provide ultrafine nanofibers with cross-sections that contain only a few polymer molecules. Ultrafine polymer nanofibers are extremely stable in transmission electron microscope. Electrospun nanofibers suspended on a holey carbon film showed features of individual polymer molecules. Carbon fibers with diameters ranging from 100 nm to several microns were produced from mesophase pitch by a low cost gas jet process. The structure of mesophase pitch-based carbon fibers was investigated as a function of heat treatment temperatures. Submicron-sized graphene oxide flakes were prepared by a combination of oxidative treatment and ultrasonic radiation. Because pitch is

  12. Flexible and Conducting Carbon Nanofibers Obtained from Electrospun Polyacrylonitrile/Phosphoric Acid Nanofibers.

    PubMed

    Lim, Baek Ho; Nirmala, R; Navamathavan, R; Kim, Hak Yong

    2016-01-01

    We report on the feasible synthesis of flexible and conductive carbon nanofibers by electrospinning process using polyacrylonitrile (PAN) and phosphoric acid (PA) as precursors. The carbon nanofibers were subsequently obtained by stabilization and carbonization of the electrospun PAN nanofibers. From SEM data, it was found that the electrospun PAN nanofibers showed a smooth surface and had an average diameter of approximately 200 nm. Afterwards, the electrospun PAN nanofibers were stabilized at 250 °C and heated at 900 °C for the carbonization process to obtain the carbon nanofibers. The carbonized PAN nanofibers exhibited a drastic improvement of electrical conduction. From Raman spectroscopy data, it was found that the carbonization at 900 °C gave a decrease of the intensity ratio of D and G peaks, indicating higher graphitic structure. PMID:27398565

  13. Control of carbon nanostructure: From nanofiber toward nanotube and back

    SciTech Connect

    Melechko, A. V.; Klein, K. L.; Fowlkes, J. D.; Hensley, D. K.; Merkulov, I. A.; McKnight, T. E.; Rack, P. D.; Horton, J. A.; Simpson, M. L.

    2007-10-01

    The unique properties of carbon nanofibers (CNFs) make them attractive for numerous applications ranging from field emitters to biological probes. In particular, it is the deterministic synthesis of CNFs, which requires precise control over geometrical characteristics such as location, length, diameter, and alignment, that enables the diverse applications. Catalytic plasma enhanced chemical vapor deposition of vertically aligned CNFs is a growth method that offers substantial control over the nanofiber geometry. However, deterministic synthesis also implies control over the nanofiber's physical and chemical properties that are defined by internal structure. Until now, true deterministic synthesis has remained elusive due to the lack of control over internal graphitic structure. Here we demonstrate that the internal structure of CNFs can be influenced by catalyst preparation and ultimately defined by growth conditions. We have found that when the growth rate is increased by 100-fold, obtained through maximized pressure, plasma power, and temperature, the resulting nanofibers have an internal structure approaching that of multiwalled nanotubes. We further show that the deliberate modulation of growth parameters results in modulation of CNF internal structure, and this property has been used to control the CNF surface along its length for site specific chemistry and electrochemistry.

  14. Polarized fluorescent emission from aligned electrospun nanofiber sheets containing semiconductor nanorods

    NASA Astrophysics Data System (ADS)

    Hasegawa, Masaki; Hirayama, Yuki; Dertinger, Stephan

    2015-02-01

    We fabricated sheets consisting of aligned electrospun polymer nanofibers embedded with semiconductor nanorods (NRs) and confirmed the production of polarized fluorescence emission. Electrospun nanofibers with embedded semiconductor NRs were rolled around a drum to form a sheet in which each nanofiber was aligned parallel to the rotation direction. The thickness and polarization ratio of the sheet were 1.5 μm and 0.6, respectively. We also examined how electrospinning parameters affected the polarization ratio of the sheet.

  15. Large-Scale and Selective Synthesis of Carbon Nanofiber Bundles, Curved Carbon Nanofibers and Helical Carbon Nanofibers.

    PubMed

    Qi, X S; Ding, Q; Zhong, W; Deng, C Y; Du, Y W

    2015-03-01

    Through the pyrolysis of acetylene at 250 °C, large quantities of carbon nanofiber bundles (CNFBs), curved carbon nanofibers (CCNFs) and helical carbon nanofibers (HCNFs) can be synthesized selectively by controlling the Fe:Cu molar ratio of Fe-Cu nanoparticles. In this study, the systematic experimental results indicated that the Cu content in the Fe-Cu nanoparticles and pyrolysis temperature had great impact on the yield and structure of the final samples. Moreover, the transmission electron microscopic observation indicated that the catalyst nanoparticles were enwrapped tightly by graphite layers, and the obtained HCNFs show good magnetic property. Compared to the methods reported in the literature, the approach described herein has the advantages of being simple, low-cost, and environment-friendly. It is suitable for the controllable and mass production of CNFBs, CCNFs and HCNFs. PMID:26413672

  16. Oriented growth of rat Schwann cells on aligned electrospun poly(methyl methacrylate) nanofibers.

    PubMed

    Xia, Haijian; Sun, Xiaochuan; Liu, Dan; Zhou, Yudong; Zhong, Dong

    2016-10-15

    Transplanted Schwann cells have the potential to serve as a support for regenerating neurites after spinal cord injury. However, implanted Schwann cells die off rapidly once transplanted partly owing to the absence of a proper matrix support, with a glia scar and a cavity being present instead at the injury site. For this report, we evaluated aligned electrospun poly(methyl methacrylate) nanofibers as a Schwann cell-loading scaffold in vitro. By monitoring the fluorescence of green fluorescence protein-containing Schwann cells cultured on nanofibers, we found that aligned nanofibers provided better support for the cells than did non-aligned nanofibers. The cells elongated along the long axes of the aligned nanofibers and formed longer cell processes than when the substrate was non-aligned nanofibers. By coculturing Schwann cells with dorsal root ganglion neurons, it was also found that Schwann cells and neurites of dorsal root ganglion neurons could share and both elongate along the orientation of aligned nanofibers and thus they had a higher chance of colocalization than cocultured on film and non-aligned fibers, which might be beneficial to the ensuring process of myelination. The results of the study indicate that aligned electrospun nanofibers may serve as a Schwann cell-loading scaffold for future implantation research. PMID:27653871

  17. A bioengineered peripheral nerve construct using aligned peptide amphiphile nanofibers

    PubMed Central

    Yalom, Anisa; Berns, Eric J.; Stephanopoulos, Nicholas; McClendon, Mark T.; Segovia, Luis A.; Spigelman, Igor; Stupp, Samuel I.; Jarrahy, Reza

    2014-01-01

    Peripheral nerve injuries can result in lifelong disability. Primary coaptation is the treatment of choice when the gap between transected nerve ends is short. Long nerve gaps seen in more complex injuries often require autologous nerve grafts or nerve conduits implemented into the repair. Nerve grafts, however, cause morbidity and functional loss at donor sites, which are limited in number. Nerve conduits, in turn, lack an internal scaffold to support and guide axonal regeneration, resulting in decreased efficacy over longer nerve gap lengths. By comparison, peptide amphiphiles (PAs) are molecules that can self-assemble into nanofibers, which can be aligned to mimic the native architecture of peripheral nerve. As such, they represent a potential substrate for use in a bioengineered nerve graft substitute. To examine this, we cultured Schwann cells with bioactive PAs (RGDS-PA, IKVAV-PA) to determine their ability to attach to and proliferate within the biomaterial. Next, we devised a PA construct for use in a peripheral nerve critical sized defect model. Rat sciatic nerve defects were created and reconstructed with autologous nerve, PLGA conduits filled with various forms of aligned PAs, or left unrepaired. Motor and sensory recovery were determined and compared among groups. Our results demonstrate that Schwann cells are able to adhere to and proliferate in aligned PA gels, with greater efficacy in bioactive PAs compared to the backbone-PA alone. In vivo testing revealed recovery of motor and sensory function in animals treated with conduit/PA constructs comparable to animals treated with autologous nerve grafts. Functional recovery in conduit/PA and autologous graft groups was significantly faster than in animals treated with empty PLGA conduits. Histological examinations also demonstrated increased axonal and Schwann cell regeneration within the reconstructed nerve gap in animals treated with conduit/PA constructs. These results indicate that PA nanofibers may

  18. Magnetic Properies of Ni Nanoparticles Used for Carbon Nanofiber Synthesis

    NASA Astrophysics Data System (ADS)

    Sorge, K. D.; Malkina, O.; Finkel, C.; Fowlkes, J. D.; Rack, P. D.; Klein, K. L.; Melechko, A. V.; Simpson, M. L.

    2007-03-01

    Magnetic properties of Ni catalyst particles used for vertically-aligned carbon nanofiber (VACNF) synthesis are investigated. Ni thin films are deposited on Si wafers by sputter-depositing to thicknesses of 2--10 nm. The VACNFs are then grown in a Plasma-Enhanced Chemical Vapor Deposition (PECVD) chamber with NH3 and C2H2 at relative flow rates of 80/40 sccm, respectively, a pressure of 3 Torr, and a temperature of 700^oC. The catalyst particles, after nanofiber growth, are 10--150 nm in diameter. Magnetic properties are investigated by SQUID magnetometry in applied magnetic fields of |H| < 10 kOe and temperatures T = 5--300 K. The catalyst particles are ferromagnetic with low coercivity and remanence. The ferromagnetic properties are thermally stable up to room temperature in all but the smallest particle sizes. Saturation magnetization is much less than would be expected from the deposited quantity of Ni metal.

  19. Dielectric transition of polyacrylonitrile derived carbon nanofibers

    NASA Astrophysics Data System (ADS)

    Li, Jiangling; Su, Shi; Zhou, Lei; Abbot, Andrew M.; Ye, Haitao

    2014-09-01

    The dielectric behavior of polyacrylonitrile derived carbon nanofibers formed at different carbonization temperatures was investigated using impedance spectroscopy. The impedance data are presented in the form of Cole-Cole plots and four equivalent electrical circuits are derived. It is found that by increasing carbonization temperature from 500 to 800 °C, a strong capacitive element in the parallel equivalent circuit is transformed into an inductive element, while the contact resistance and parallel resistance are significantly decreased. Along with the morphological and chemical structural evolution, respectively witnessed by scanning electron microscopy and Raman spectroscopy, the dielectric transition deduced from the transformation of electrical circuits can be correlated to the proposed microstructural changes of polyacrylonitrile derived carbon nanofibers and the interaction/interference among them.

  20. Alignment and composition of laminin–polycaprolactone nanofiber blends enhance peripheral nerve regeneration

    PubMed Central

    Neal, Rebekah A.; Tholpady, Sunil S.; Foley, Patricia L.; Swami, Nathan; Ogle, Roy C.; Botchwey, Edward A.

    2012-01-01

    Peripheral nerve transection occurs commonly in traumatic injury, causing deficits distal to the injury site. Conduits for repair currently on the market are hollow tubes; however, they often fail due to slow regeneration over long gaps. To facilitate increased regeneration speed and functional recovery, the ideal conduit should provide biochemically relevant signals and physical guidance cues, thus playing an active role in regeneration. To that end, laminin and laminin–polycaprolactone (PCL) blend nanofibers were fabricated to mimic peripheral nerve basement membrane. In vitro assays established 10% (wt) laminin content is sufficient to retain neurite-promoting effects of laminin. In addition, modified collector plate design to introduce an insulating gap enabled the fabrication of aligned nanofibers. The effects of laminin content and fiber orientation were evaluated in rat tibial nerve defect model. The lumens of conduits were filled with nanofiber meshes of varying laminin content and alignment to assess changes in motor and sensory recovery. Retrograde nerve conduction speed at 6 weeks was significantly faster in animals receiving aligned nanofiber conduits than in those receiving random nanofiber conduits. Animals receiving nanofiber-filled conduits showed some conduction in both anterograde and retrograde directions, whereas in animals receiving hollow conduits, no impulse conduction was detected. Aligned PCL nanofibers significantly improved motor function; aligned laminin blend nanofibers yielded the best sensory function recovery. In both cases, nanofiber-filled conduits resulted in better functional recovery than hollow conduits. These studies provide a firm foundation for the use of natural–synthetic blend electrospun nanofibers to enhance existing hollow nerve guidance conduits. PMID:22106069

  1. Aligned Electrospun Polyvinyl Pyrrolidone/Poly ɛ-Caprolactone Blend Nanofiber Mats for Tissue Engineering

    NASA Astrophysics Data System (ADS)

    Charernsriwilaiwat, Natthan; Rojanarata, Theerasak; Ngawhirunpat, Tanasait; Opanasopit, Praneet

    2016-02-01

    Electrospun nanofibrous materials are widely used in medical applications such as tissue engineering scaffolds, wound dressing material and drug delivery carriers. For tissue engineering scaffolds, the structure of the nanofiber is similar to extracellular matrix (ECM) which promotes the cell growth and proliferation. In the present study, the aligned nanofiber mats of polyvinyl pyrrolidone (PVP) blended poly ɛ-caprolactone (PCL) was successfully generated using electrospinning technique. The morphology of PVP/PCL nanofiber mats were characterized by scanning electron microspore (SEM). The chemical and crystalline structure of PVP/PCL nanofiber mats were analyzed using Fourier transform infrared spectroscopy (FTIR) and powder X-ray diffactometer (PXRD). The water contact angle of mats was investigated. Cell culture studies using normal human fibroblasts (NHF) were performed to assess cell morphology, cell alignment and cell proliferation. The results indicated that the fiber were in nanometer range. The PVP/PCL was well dispersed in nanofiber mats and was in amorphous form. The water contact angle of PVP/PCL nanofiber mats was lower than PCL nanofiber mats. The PVP/PCL nanofiber mats exhibited good biocompatibility with NHF cells. In summary, the PVP/PCL nanofiber mats had potential to be used in tissue engineering and regenerative medicine.

  2. A new method for the alignment of electrospun nanofibers by oxygen plasma treatment

    NASA Astrophysics Data System (ADS)

    Kobayashi, Natsumi; Miki, Norihisa; Hishida, Koichi; Hotta, Atsushi

    2014-03-01

    An effective way of controlling the alignment of electrospun nanofibers using oxygen plasma treatment was introduced. Poly (dimethylsiloxane) (PDMS) was selected as a base material for electrospinning and polyvinyl alcohol (PVA) was chosen as an electrospun-nanofiber material. It was found that most of PVA nanofibers were selectively deposited on the O2 plasma-treated area of PDMS, while only a few PVA nanofibers were randomly deposited on the untreated area of the PDMS film. Interestingly, a number of PVA nanofibers were neatly aligned along the border of the untreated area and the O2 plasma-treated area of PDMS. The surface structures and the morphology of the PDMS films with PVA nanofibers were analyzed by scanning electron microscopy, water contact angle measurements, and X-ray photon spectroscopy. By selecting the optimized ratio of treated and untreated area of PDMS film, it was found that more than 80% of PVA nanofibers could be deposited parallel to the border of the treated and untreated area of PDMS. We used PVA as a reference material for the nanofiber alignment in this study, but similar deposition behavior was also observed for polyurethane (PU) fibers.

  3. Electrospinning of unidirectionally and orthogonally aligned thermoplastic polyurethane nanofibers: Fiber orientation and cell migration

    PubMed Central

    Mi, Hao-Yang; Salick, Max R.; Jing, Xin; Crone, Wendy C.; Peng, Xiang-Fang; Turng, Lih-Sheng

    2015-01-01

    Unidirectionally and orthogonally aligned thermoplastic polyurethane (TPU) nanofibers were electrospun using a custom-built electrospinning device. The unidirectionally aligned fibers were collected using two parallel copper plates, and the orthogonally aligned fibers were collected using two orthogonal sets of parallel copper plates with alternate negative connections. Carbon nanotubes (CNT) and polyacrylic acid (PAA) were added to modify the polymer solution. It was found that both CNT and PAA were capable of increasing solution conductivity. The TPU/PAA fiber showed the highest degree of fiber orientation with more than 90% of the fibers having an orientation angle between −10° and 10° for unidirectionally aligned fibers, and for orthogonally aligned fibers, the orientation angle of 50% fibers located between −10° and 10° and 48% fibers located between 80° and 100°. Viability assessment of 3T3 fibroblasts cultured on TPU/PAA fibers suggested that the material was cytocompatible. The cells’ orientation and migration direction closely matched the fibers’ orientation. The cell migration velocity and distance were both enhanced with the guidance of fibers compared with cells cultured on random fibers and common tissue culture plastic. Controlling cell migration velocity and directionality may provide ways to influence differentiation and gene expression and systems that would allow further exploration of wound repair and metastatic cell behavior. PMID:24771704

  4. Electrospinning of unidirectionally and orthogonally aligned thermoplastic polyurethane nanofibers: fiber orientation and cell migration.

    PubMed

    Mi, Hao-Yang; Salick, Max R; Jing, Xin; Crone, Wendy C; Peng, Xiang-Fang; Turng, Lih-Sheng

    2015-02-01

    Unidirectionally and orthogonally aligned thermoplastic polyurethane (TPU) nanofibers were electrospun using a custom-built electrospinning device. The unidirectionally aligned fibers were collected using two parallel copper plates, and the orthogonally aligned fibers were collected using two orthogonal sets of parallel copper plates with alternate negative connections. Carbon nanotubes (CNT) and polyacrylic acid (PAA) were added to modify the polymer solution. It was found that both CNT and PAA were capable of increasing solution conductivity. The TPU/PAA fiber showed the highest degree of fiber orientation with more than 90% of the fibers having an orientation angle between -10° and 10° for unidirectionally aligned fibers, and for orthogonally aligned fibers, the orientation angle of 50% fibers located between -10° and 10° and 48% fibers located between 80° and 100°. Viability assessment of 3T3 fibroblasts cultured on TPU/PAA fibers suggested that the material was cytocompatible. The cells' orientation and migration direction closely matched the fibers' orientation. The cell migration velocity and distance were both enhanced with the guidance of fibers compared with cells cultured on random fibers and common tissue culture plastic. Controlling cell migration velocity and directionality may provide ways to influence differentiation and gene expression and systems that would allow further exploration of wound repair and metastatic cell behavior. PMID:24771704

  5. Zinc oxide nanorod assisted rapid single-step process for the conversion of electrospun poly(acrylonitrile) nanofibers to carbon nanofibers with a high graphitic content

    NASA Astrophysics Data System (ADS)

    Nain, Ratyakshi; Singh, Dhirendra; Jassal, Manjeet; Agrawal, Ashwini K.

    2016-02-01

    The effect of incorporation of rigid zinc oxide (ZnO) nanostructures on carbonization behavior of electrospun special acrylic fiber grade poly(acrylonitrile) (PAN-SAF) nanofibers was investigated. ZnO nanorods with high aspect ratios were incorporated into a PAN-N,N-dimethylformamide system and the composite nanofibers reinforced with aligned ZnO rods up to 50 wt% were successfully electrospun, and subsequently, carbonized. The morphology and the structural analysis of the resultant carbon nanofibers revealed that the rigid ZnO nanorods, present inside the nanofibers, possibly acted as scaffolds (temporary support structures) for immobilization of polymer chains and assisted in uniform heat distribution. This facilitated rapid and efficient conversion of the polymer structure to the ladder, and subsequently, the graphitized structure. At the end of the process, the ZnO nanorods were found to completely separate from the carbonized fibers yielding pure carbon nanofibers with a high graphitic content and surface area. The approach could be used to eliminate the slow, energy intensive stabilization step and achieve fast conversion of randomly laid carbon nanofiber webs in a single step to carbon nanofibers without the application of external tension or internal templates usually employed to achieve a high graphitic content in such systems.The effect of incorporation of rigid zinc oxide (ZnO) nanostructures on carbonization behavior of electrospun special acrylic fiber grade poly(acrylonitrile) (PAN-SAF) nanofibers was investigated. ZnO nanorods with high aspect ratios were incorporated into a PAN-N,N-dimethylformamide system and the composite nanofibers reinforced with aligned ZnO rods up to 50 wt% were successfully electrospun, and subsequently, carbonized. The morphology and the structural analysis of the resultant carbon nanofibers revealed that the rigid ZnO nanorods, present inside the nanofibers, possibly acted as scaffolds (temporary support structures) for

  6. Influence of Poly(L-Lactic Acid) Aligned Nanofibers on PC12 Differentiation.

    PubMed

    Yu, Yadong; Lü, Xiaoying; Ding, Fei

    2015-05-01

    The aim of this study was to unveil the mechanism by which aligned nanofibers influence neuronal differentiation. PC12 cells were seeded on three different poly(L-lactic acid) (PLLA) substrates (PLLA films (control), electrospun PLLA random nanofibers (RF) and electrospun PLLA aligned nanofibers (AF)). Subsequently, cellular experiments, cDNA microarrays and molecular biological approaches were employed to investigate the impacts of the different PLLA substrates on PC12 cell differentiation. Scanning electron microscope observation revealed that neurite outgrowth in the AF group was parallel to the direction of nanofiber alignment and that the filopodias at the neurite tips spread along the aligned nanofiber axis. Meanwhile, both neurite length and the expression of GAP43 (a neuronal differentiation marker gene) were higher in the AF group than those in the control and RF groups. These results suggested that the PLLA aligned nanofibers enhanced PC12 cell differentiation. cDNA microarray experiment revealed that 876 and 1937 genes had significantly changed expression in the RF and AF groups, respectively. Based on gene ontology analysis, 493 and 1193 differentially expressed genes involved in neuronal differentiation were found in the RF and AF groups, respectively. Pathway analysis showed that the PLLA aligned nanofibers mainly mediated their effects via integrin-mediated pathways. qRT-PCR and western blotting assays further confirmed that gene and protein expression levels in the integrin-mediated FAK-MEK-ERK pathway (e.g., Tln1, Mapk6, phosphorylated-ERK1/2) were enhanced by the PLLA aligned nanofibers. Both PC12 cell differentiation and the expressions of genes and proteins in the integrin-mediated FAK-MEK-ERK pathway were inhibited when integrins were blocked by the pentapeptide GRGDS. In addition, the Pafah1b-1 gene was found to be involved in PLLA aligned nanofibers' promotion of PC12 cell differentiation. Taken together, the results suggested that PLLA

  7. The Interactions Between Aligned Poly(L-Lactic Acid) Nanofibers and SH-SY5Y Cells In Vitro.

    PubMed

    Yu, Yadong; Meng, Dianhuai; Man, Lili; Wang, Xin

    2016-06-01

    Aligned nanofibers have been regarded as promising nanomaterials in facilitating nerve regeneration. Investigating the interactions between aligned nanofibers and neuronal cells will be critically important for the design and application of aligned nanofibers in nerve tissue engineering. In this study, we explored the effects of electrospun Poly(L-Lactic Acid) (PLLA) aligned nanofibers on SH-SY5Y cells (a type of human neuroblastoma cell line) and specifically focused on the role of integrin in the PLLA aligned nanofiber-SH-SY5Y cell interaction. We found that PLLA aligned nanofibers could significantly guide the neurite outgrowth of SH-SY5Y cell, and promote the viability, proliferation, glucose and lactic acid metabolism of SH-SY5Y cell. This promotion effect could be alleviated when the functions of integrins on the SH-SY5Y cell membrane were hampered by pentapeptide GRGDS. Moreover, we found that PLLA aligned nanofibers could enhance the expression of phosphorylated-ERK1/2 (p-ERK1/2) in the SH-SY5Y cells and blocking the integrins would decrease p-ERK1/2 expression. These results suggested that PLLA aligned nanofibers might affect many cellular behaviors of SH-SY5Y cells via integrin mediated ERK pathway. Our findings provided more insights for understanding the interaction between aligned nanofibers and neuronal cells. PMID:27427727

  8. The Interactions Between Aligned Poly(L-Lactic Acid) Nanofibers and SH-SY5Y Cells In Vitro.

    PubMed

    Yu, Yadong; Meng, Dianhuai; Man, Lili; Wang, Xin

    2016-06-01

    Aligned nanofibers have been regarded as promising nanomaterials in facilitating nerve regeneration. Investigating the interactions between aligned nanofibers and neuronal cells will be critically important for the design and application of aligned nanofibers in nerve tissue engineering. In this study, we explored the effects of electrospun Poly(L-Lactic Acid) (PLLA) aligned nanofibers on SH-SY5Y cells (a type of human neuroblastoma cell line) and specifically focused on the role of integrin in the PLLA aligned nanofiber-SH-SY5Y cell interaction. We found that PLLA aligned nanofibers could significantly guide the neurite outgrowth of SH-SY5Y cell, and promote the viability, proliferation, glucose and lactic acid metabolism of SH-SY5Y cell. This promotion effect could be alleviated when the functions of integrins on the SH-SY5Y cell membrane were hampered by pentapeptide GRGDS. Moreover, we found that PLLA aligned nanofibers could enhance the expression of phosphorylated-ERK1/2 (p-ERK1/2) in the SH-SY5Y cells and blocking the integrins would decrease p-ERK1/2 expression. These results suggested that PLLA aligned nanofibers might affect many cellular behaviors of SH-SY5Y cells via integrin mediated ERK pathway. Our findings provided more insights for understanding the interaction between aligned nanofibers and neuronal cells.

  9. Synthesis of carbon nanofibers on copper particles

    NASA Astrophysics Data System (ADS)

    Kol'tsova, T. S.; Larionova, T. V.; Shusharina, N. N.; Tolochko, O. V.

    2015-08-01

    We analyze the synthesis of carbon nanostructures from the gas phase (mixture of acetylene or ethylene with hydrogen) on the surface of copper particles without using other catalysts. The synthesized structures (multilayer graphene and carbon nanofibers) are analyzed by transmission electron microscopy and Raman scattering. It is shown that the fiber structure is determined by the C: H ratio in the gas phase. The kinetics of synthesis is analyzed in terms of the formal kinetics of conversion in accordance with the Johnson—Mehl—Avrami equation.

  10. High performance carbon nanotube - polymer nanofiber hybrid fabrics

    NASA Astrophysics Data System (ADS)

    Yildiz, Ozkan; Stano, Kelly; Faraji, Shaghayegh; Stone, Corinne; Willis, Colin; Zhang, Xiangwu; Jur, Jesse S.; Bradford, Philip D.

    2015-10-01

    Stable nanoscale hybrid fabrics containing both polymer nanofibers and separate and distinct carbon nanotubes (CNTs) are highly desirable but very challenging to produce. Here, we report the first instance of such a hybrid fabric, which can be easily tailored to contain 0-100% millimeter long CNTs. The novel CNT - polymer hybrid nonwoven fabrics were created by simultaneously electrospinning nanofibers onto aligned CNT sheets which were drawn and collected on a grounded, rotating mandrel. Due to the unique properties of the CNTs, the hybrids show very high tensile strength, very small pore size, high specific surface area and electrical conductivity. In order to further examine the hybrid fabric properties, they were consolidated under pressure, and also calendered at 70 °C. After calendering, the fabric's strength increased by an order of magnitude due to increased interactions and intermingling with the CNTs. The hybrids are highly efficient as aerosol filters; consolidated hybrid fabrics with a thickness of 20 microns and areal density of only 8 g m-2 exhibited ultra low particulate (ULPA) filter performance. The flexibility of this nanofabrication method allows for the use of many different polymer systems which provides the opportunity for engineering a wide range of nanoscale hybrid materials with desired functionalities.Stable nanoscale hybrid fabrics containing both polymer nanofibers and separate and distinct carbon nanotubes (CNTs) are highly desirable but very challenging to produce. Here, we report the first instance of such a hybrid fabric, which can be easily tailored to contain 0-100% millimeter long CNTs. The novel CNT - polymer hybrid nonwoven fabrics were created by simultaneously electrospinning nanofibers onto aligned CNT sheets which were drawn and collected on a grounded, rotating mandrel. Due to the unique properties of the CNTs, the hybrids show very high tensile strength, very small pore size, high specific surface area and electrical

  11. Effect of twist and porosity on the electrical conductivity of carbon nanofiber yarns

    NASA Astrophysics Data System (ADS)

    Chawla, S.; Naraghi, M.; Davoudi, A.

    2013-06-01

    This study focuses on the effect of twist and porosity on the electrical conductivity of carbon nanofiber (CNF) yarns. The process of fabrication of CNF yarns included the synthesis of aligned ribbons of polyacrylonitrile (PAN) nanofibers via electrospinning. The PAN ribbons were twisted into yarns with twist levels ranging from zero twist to high twists of 1300 turn per meter (tpm). The twist imposed on the ribbons substantially improved the interactions between nanofibers and reduced the porosity. The PAN yarns were subsequently stabilized in air, and then carbonized in nitrogen at 1100 ° C for 1 h. Compressive stresses developed between the PAN nanofibers as a result of twist promoted interfusion between neighboring nanofibers, which was accelerated by heating the yarns during stabilization to temperatures above the glass transition of PAN. The electrical conductivity of the yarns was measured with a four point probe measurement technique. Although increasing the twist promotes electrical conductivity between nanofibers by forming junctions between them, our results indicate that the electrical conductivity does not continuously increase with increasing twist, but reaches a threshold value after which it starts to decrease. The causes for this behavior were studied through experimental techniques and further explored using a yarn-equivalent electrical circuit model.

  12. Tubular Hydrogels of Circumferentially Aligned Nanofibers to Encapsulate and Orient Vascular Cells

    PubMed Central

    McClendon, Mark T.; Stupp, Samuel I.

    2012-01-01

    There is a great clinical need for tissue engineered blood vessels that could be used to replace or bypass damaged arteries. The success of such grafts will depend strongly on their ability to mimic the cellular and matrix organization found in native arteries, but currently available cell scaffolds such as electrospun fibers or hydrogels lack the ability to simultaneously encapsulate and align cells. Our laboratory has recently developed liquid crystalline solutions of peptide amphiphile nanofibers that form aligned domains at exceedingly low concentrations (<1wt%), and can be trapped as gels with macroscopic alignment using low shear rates and ionic crosslinking. We describe here the use of these systems to fabricate tubes with macroscopic circumferential alignment and demonstrate their potential as arterial cell scaffolds. The nanofibers in these tubes were circumferentially aligned by applying small amounts of shear in a custom built flow chamber prior to gelation. Small angle X-ray scattering confirmed that the direction of nanofiber alignment was the same as the direction of shear flow. We also show the encapsulation of smooth muscle cells during the fabrication process without compromising cell viability. After two days in culture the encapsulated cells oriented their long axis in the direction of nanofiber alignment thus mimicking the circumferential alignment seen in native arteries. Cell density roughly doubled after 12 days demonstrating the scaffold’s ability to facilitate necessary graft maturation. Since these nanofiber gels are composed of >99% water by weight, the cells have abundant room for proliferation and remodeling. In contrast to previously reported arterial cell scaffolds, this new material can encapsulate cells and direct cellular organization without the requirement of external stimuli or gel compaction. PMID:22591610

  13. Bis-GMA/TEGDMA Dental Composites Reinforced with Electrospun Nylon 6 Nanocomposite Nanofibers Containing Highly Aligned Fibrillar Silicate Single Crystals.

    PubMed

    Tian, Ming; Gao, Yi; Liu, Yi; Liao, Yiliang; Xu, Riwei; Hedin, Nyle E; Fong, Hao

    2007-04-24

    The objective of this research was to study the reinforcement of electrospun nylon 6/fibrillar silicate nanocomposite nanofibers on Bis-GMA/TEGDMA dental composites. The hypothesis was that the uniform distribution of nano-scaled and highly aligned fibrillar silicate single crystals into electrospun nylon 6 nanofibers would improve the mechanical properties of the resulting nanocomposite nanofibers, and would lead to the effective reinforcement of dental composites. The nylon 6/fibrillar silicate nanocomposite nanofibers were crystalline, structurally oriented and had an average diameter of approximately 250 nm. To relatively well distribute nanofibers in dental composites, the nanofiber containing composite powders with a particle structure similar to that in interpenetration networks were prepared first, and then used to make the dental composites. The results indicated that small mass fractions (1 % and 2 %) of nanofiber impregnation improved the mechanical properties substantially, while larger mass factions (4 % and 8 %) of nanofiber impregnation resulted in less desired mechanical properties.

  14. Fabrication of Thermoresponsive Nanofibers for Cell Sorting and Aligned Cell Sheet Engineering.

    PubMed

    Zhao, Xiaomei; Wang, Lin; Wang, Peilan; Yang, Yan; Wang, Feng

    2016-06-01

    Poly(N-isopropylacrylamide-co-N-hydroxysuccinimide ester) was synthesized by free radical polymerization followed by gelatin grafting to obtain biocompatible thermosensitive poly(N-isopropylacrylamide-co-N-hydroxysuccinimide ester)-g-gelatin. Electrospinning was then applied to fabricate aligned thermoresponsive poly(N-isopropylacrylamide-co-N-hydroxysuccinimide ester)-g-gelatin nanofiber mats. Cell coculture study showed that this kind of nanofiber mats performed different surface adhesion to rat fibroblast cells and phoenix cells at 37 degrees C, phoenix cells can then be sorted out firstly by gradient cooling treatment. The fibroblast cells that had attached on the nanofiber mats were allowed to proliferate to reach confluence. These fibroblast cells tended to elongate along with the oriented direction of the nanofibers during culture and finally formed oriented cell sheets. This kind of aligned cell sheet could easily detach from nanofiber mats by low temperature treatment. This technique is simple and can easily harvest target cells and aligned cell sheets with minimum invasion, which has the potential to be applied in tissue engineering and regenerative medicine. PMID:27427592

  15. Fabrication of Thermoresponsive Nanofibers for Cell Sorting and Aligned Cell Sheet Engineering.

    PubMed

    Zhao, Xiaomei; Wang, Lin; Wang, Peilan; Yang, Yan; Wang, Feng

    2016-06-01

    Poly(N-isopropylacrylamide-co-N-hydroxysuccinimide ester) was synthesized by free radical polymerization followed by gelatin grafting to obtain biocompatible thermosensitive poly(N-isopropylacrylamide-co-N-hydroxysuccinimide ester)-g-gelatin. Electrospinning was then applied to fabricate aligned thermoresponsive poly(N-isopropylacrylamide-co-N-hydroxysuccinimide ester)-g-gelatin nanofiber mats. Cell coculture study showed that this kind of nanofiber mats performed different surface adhesion to rat fibroblast cells and phoenix cells at 37 degrees C, phoenix cells can then be sorted out firstly by gradient cooling treatment. The fibroblast cells that had attached on the nanofiber mats were allowed to proliferate to reach confluence. These fibroblast cells tended to elongate along with the oriented direction of the nanofibers during culture and finally formed oriented cell sheets. This kind of aligned cell sheet could easily detach from nanofiber mats by low temperature treatment. This technique is simple and can easily harvest target cells and aligned cell sheets with minimum invasion, which has the potential to be applied in tissue engineering and regenerative medicine.

  16. Improving conducting polymer electrochromic speeds and depositing aligned polymeric nanofibers by electrospinning process

    NASA Astrophysics Data System (ADS)

    Asemota, Chris I.

    . Lastly, the alignment of electrospun nanofibers during electrospinning was investigated to prepare composites of aligned nanofiber mats on macro-mesh fabric, and control alignment by non-conventional methods. Nanofibers produced during electrospinning are usually collected as non-woven randomly oriented fibers, but by manipulating the electric field at the collector, aligned nanofibers were obtained. Further modifications using a mesh fabric as collector, or using non-conventional conductive surfaces, deposition of continuous and aligned nanofibers of poly lactic acid was achieved.

  17. Ultrasensitive, Label Free, Chemiresistive Nanobiosensor Using Multiwalled Carbon Nanotubes Embedded Electrospun SU-8 Nanofibers

    PubMed Central

    Durga Prakash, Matta; Vanjari, Siva Rama Krishna; Sharma, Chandra Shekhar; Singh, Shiv Govind

    2016-01-01

    This paper reports the synthesis and fabrication of aligned electrospun nanofibers derived out of multiwalled carbon nanotubes (MWCNTs) embedded SU-8 photoresist, which are targeted towards ultrasensitive biosensor applications. The ultrasensitivity (detection in the range of fg/mL) and the specificity of these biosensors were achieved by complementing the inherent advantages of MWCNTs such as high surface to volume ratio and excellent electrical and transduction properties with the ease of surface functionalization of SU-8. The electrospinning process was optimized to precisely align nanofibers in between two electrodes of a copper microelectrode array. MWCNTs not only enhance the conductivity of SU-8 nanofibers but also act as transduction elements. In this paper, MWCNTs were embedded way beyond the percolation threshold and the optimum percentage loading of MWCNTs for maximizing the conductivity of nanofibers was figured out experimentally. As a proof of concept, the detection of myoglobin, an important biomarker for on-set of Acute Myocardial Infection (AMI) has been demonstrated by functionalizing the nanofibers with anti-myoglobin antibodies and carrying out detection using a chemiresistive method. This simple and robust device yielded a detection limit of 6 fg/mL. PMID:27563905

  18. Ultrasensitive, Label Free, Chemiresistive Nanobiosensor Using Multiwalled Carbon Nanotubes Embedded Electrospun SU-8 Nanofibers.

    PubMed

    Durga Prakash, Matta; Vanjari, Siva Rama Krishna; Sharma, Chandra Shekhar; Singh, Shiv Govind

    2016-01-01

    This paper reports the synthesis and fabrication of aligned electrospun nanofibers derived out of multiwalled carbon nanotubes (MWCNTs) embedded SU-8 photoresist, which are targeted towards ultrasensitive biosensor applications. The ultrasensitivity (detection in the range of fg/mL) and the specificity of these biosensors were achieved by complementing the inherent advantages of MWCNTs such as high surface to volume ratio and excellent electrical and transduction properties with the ease of surface functionalization of SU-8. The electrospinning process was optimized to precisely align nanofibers in between two electrodes of a copper microelectrode array. MWCNTs not only enhance the conductivity of SU-8 nanofibers but also act as transduction elements. In this paper, MWCNTs were embedded way beyond the percolation threshold and the optimum percentage loading of MWCNTs for maximizing the conductivity of nanofibers was figured out experimentally. As a proof of concept, the detection of myoglobin, an important biomarker for on-set of Acute Myocardial Infection (AMI) has been demonstrated by functionalizing the nanofibers with anti-myoglobin antibodies and carrying out detection using a chemiresistive method. This simple and robust device yielded a detection limit of 6 fg/mL. PMID:27563905

  19. Guiding the orientation of smooth muscle cells on random and aligned polyurethane/collagen nanofibers.

    PubMed

    Jia, Lin; Prabhakaran, Molamma P; Qin, Xiaohong; Ramakrishna, Seeram

    2014-09-01

    Fabricating scaffolds that can simulate the architecture and functionality of native extracellular matrix is a huge challenge in vascular tissue engineering. Various kinds of materials are engineered via nano-technological approaches to meet the current challenges in vascular tissue regeneration. During this study, nanofibers from pure polyurethane and hybrid polyurethane/collagen in two different morphologies (random and aligned) and in three different ratios of polyurethane:collagen (75:25; 50:50; 25:75) are fabricated by electrospinning. The fiber diameters of the nanofibrous scaffolds are in the range of 174-453 nm and 145-419 for random and aligned fibers, respectively, where they closely mimic the nanoscale dimensions of native extracellular matrix. The aligned polyurethane/collagen nanofibers expressed anisotropic wettability with mechanical properties which is suitable for regeneration of the artery. After 12 days of human aortic smooth muscle cells culture on different scaffolds, the proliferation of smooth muscle cells on hybrid polyurethane/collagen (3:1) nanofibers was 173% and 212% higher than on pure polyurethane scaffolds for random and aligned scaffolds, respectively. The results of cell morphology and protein staining showed that the aligned polyurethane/collagen (3:1) scaffold promote smooth muscle cells alignment through contact guidance, while the random polyurethane/collagen (3:1) also guided cell orientation most probably due to the inherent biochemical composition. Our studies demonstrate the potential of aligned and random polyurethane/collagen (3:1) as promising substrates for vascular tissue regeneration.

  20. Enhancement of conductivity by diameter control of polyimide-based electrospun carbon nanofibers.

    PubMed

    Xuyen, Nguyen Thi; Ra, Eun Ju; Geng, Hong-Zhang; Kim, Ki Kang; An, Kay Hyeok; Lee, Young Hee

    2007-10-01

    Oxydianiline-pyromellitic dianhydride poly(amic acid) (ODA-PMDA PAA) was polymerized with a catalyst support of triethyl amine for controlling molecular weight. This polymer was used for electrospinning in the preparation of PAA nanofibers, a precursor of carbon nanofibers. Here the amount of catalyst and concentration of PAA solution were optimized to produce polyimide-based carbon nanofibers approximately 80 nm in diameter. The effects of molecular weight of PAA, bias voltage, and spinning rate on the morphology of electrospun PAA and polyimide nanofibers have been evaluated. We showed that the conductivity of the carbon nanofiber mat decreased with increasing nanofiber diameter, where the conductivity of polyimide-based carbon nanofiber mat was much higher than those of other types of carbon nanofiber mat. The key ingredient to increase conductivity in a carbon nanofiber mat was found to be the number of cross junctions between nanofibers. PMID:17850139

  1. Nanofiber Alignment Regulates NIH3T3 Cell Orientation and Cytoskeletal Gene Expression on Electrospun PCL+Gelatin Nanofibers

    PubMed Central

    Fee, Timothy; Surianarayanan, Swetha; Downs, Crawford; Zhou, Yong; Berry, Joel

    2016-01-01

    To examine the influence of substrate topology on the behavior of fibroblasts, tissue engineering scaffolds were electrospun from polycaprolactone (PCL) and a blend of PCL and gelatin (PCL+Gel) to produce matrices with both random and aligned nanofibrous orientations. The addition of gelatin to the scaffold was shown to increase the hydrophilicity of the PCL matrix and to increase the proliferation of NIH3T3 cells compared to scaffolds of PCL alone. The orientation of nanofibers within the matrix did not have an effect on the proliferation of adherent cells, but cells on aligned substrates were shown to elongate and align parallel to the direction of substrate fiber alignment. A microarray of cyotoskeleton regulators was probed to examine differences in gene expression between cells grown on an aligned and randomly oriented substrates. It was found that transcriptional expression of eight genes was statistically different between the two conditions, with all of them being upregulated in the aligned condition. The proteins encoded by these genes are linked to production and polymerization of actin microfilaments, as well as focal adhesion assembly. Taken together, the data indicates NIH3T3 fibroblasts on aligned substrates align themselves parallel with their substrate and increase production of actin and focal adhesion related genes. PMID:27196306

  2. Uniaxially aligned electrospun all-cellulose nanocomposite nanofibers reinforced with cellulose nanocrystals: scaffold for tissue engineering.

    PubMed

    He, Xu; Xiao, Qiang; Lu, Canhui; Wang, Yaru; Zhang, Xiaofang; Zhao, Jiangqi; Zhang, Wei; Zhang, Ximu; Deng, Yulin

    2014-02-10

    Uniaxially aligned cellulose nanofibers with well oriented cellulose nanocrystals (CNCs) embedded were fabricated via electrospinning using a rotating drum as the collector. Scanning electron microscope (SEM) images indicated that most cellulose nanofibers were uniaxially aligned. The incorporation of CNCs into the spinning dope resulted in more uniform morphology of the electrospun cellulose/CNCs nanocomposite nanofibers (ECCNN). Polarized light microscope (PLM) and transmission electron microscope (TEM) showed that CNCs dispersed well in ECCNN nonwovens and achieved considerable orientation along the long axis direction. This unique hierarchical microstructure of ECCNN nonwovens gave rise to remarkable enhancement of their physical properties. By incorporating 20% loading (in weight) of CNCs, the tensile strength and elastic modulus of ECCNN along the fiber alignment direction were increased by 101.7 and 171.6%, respectively. Their thermal stability was significantly improved as well. In addition, the ECCNN nonwovens were assessed as potential scaffold materials for tissue engineering. It was elucidated from MTT tests that the ECCNN were essentially nontoxic to human cells. Cell culture experiments demonstrated that cells could proliferate rapidly not only on the surface but also deep inside the ECCNN. More importantly, the aligned nanofibers of ECCNN exhibited a strong effect on directing cellular organization. This feature made the scaffold particularly useful for various artificial tissues or organs, such as blood vessel, tendon, nerve, and so on, in which cell orientation was crucial for their performance.

  3. Continuous High-Aligned Polyacrylonitrile Electrospun Nanofibers Yarns via Circular Deposition on Water Bath.

    PubMed

    Bin, Yu; Hao, Yu; Zhu, Meifang; Wang, Hongzhi

    2016-06-01

    A novel strategy for preparing high-aligned continuous Polyacrylonitrile (PAN) electrospun nanofibers yarns is introduced. The yarn is rolled up from circular deposition, which can be changed by controlling the humidity of spinning environment. High-aligned yarn is obtained with the rolling speed of 57 m/min. Very few defects are found in the received yarn. Also the as-spun yarn is drawn in hot water bath to improve its mechanical properties further. The mechanical properties and X-Ray Diffraction (XRD) tests are systematically investigated. The tensile strength of the as-spun yarn rolled with 57 m/min can reach 240 MPa, close to that of as-spun fibers from wet spinning. Furthermore, after drawn of 5 ratios, tensile strength of yarn comes to 580 MPa, which broaden the applied fields of electrospun nanofibers. In addition, the forming mechanism of yarn in the water bath is analyzed and compared with the previous work. Actually, it can be testified experimentally that PAN nanofibers yarn has the same mechanical properties as that prepared with the other approaches with the same testing conditions in this work. The continuous high-aligned electrospun nanofibers PAN yarn via circular deposition in this paper is capable of meeting the requirement of the more applications needing of high mechanical properties and alignment degree. PMID:27427608

  4. Catalytic Growth of Macroscopic Carbon Nanofibers Bodies with Activated Carbon

    SciTech Connect

    Abdullah, N.; Muhammad, I. S.; Hamid, S. B. Abd.; Rinaldi, A.; Su, D. S.; Schlogl, R.

    2009-06-01

    Carbon-carbon composite of activated carbon and carbon nanofibers have been synthesized by growing Carbon nanofiber (CNF) on Palm shell-based Activated carbon (AC) with Ni catalyst. The composites are in an agglomerated shape due to the entanglement of the defective CNF between the AC particles forming a macroscopic body. The macroscopic size will allow the composite to be used as a stabile catalyst support and liquid adsorbent. The preparation of CNT/AC nanocarbon was initiated by pre-treating the activated carbon with nitric acid, followed by impregnation of 1 wt% loading of nickel (II) nitrate solutions in acetone. The catalyst precursor was calcined and reduced at 300 deg. C for an hour in each step. The catalytic growth of nanocarbon in C{sub 2}H{sub 4}/H{sub 2} was carried out at temperature of 550 deg. C for 2 hrs with different rotating angle in the fluidization system. SEM and N{sub 2} isotherms show the level of agglomeration which is a function of growth density and fluidization of the system. The effect of fluidization by rotating the reactor during growth with different speed give a significant impact on the agglomeration of the final CNF/AC composite and thus the amount of CNFs produced. The macrostructure body produced in this work of CNF/AC composite will have advantages in the adsorbent and catalyst support application, due to the mechanical and chemical properties of the material.

  5. Improved fire retardancy of thermoset composites modified with carbon nanofibers

    NASA Astrophysics Data System (ADS)

    Zhao, Zhongfu; Gou, Jan

    2009-01-01

    Multifunctional thermoset composites were made from polyester resin, glass fiber mats and carbon nanofiber sheets (CNS). Their flaming behavior was investigated with cone calorimeter under well-controlled combustion conditions. The heat release rate was lowered by pre-planting carbon nanofiber sheets on the sample surface with the total fiber content of only 0.38 wt.%. Electron microscopy showed that carbon nanofiber sheet was partly burned and charred materials were formed on the combusting surface. Both the nanofibers and charred materials acted as an excellent insulator and/or mass transport barrier, improving the fire retardancy of the composite. This behavior agrees well with the general mechanism of fire retardancy in various nanoparticle-thermoplastic composites.

  6. Spherical and rodlike inorganic nanoparticle regulated the orientation of carbon nanotubes in polymer nanofibers

    NASA Astrophysics Data System (ADS)

    Jiang, Linbin; Tu, Hu; Lu, Yuan; Wu, Yang; Tian, Jing; Shi, Xiaowen; Wang, Qun; Zhan, Yingfei; Huang, Zuqiang; Deng, Hongbing

    2016-04-01

    PVA nanofibers containing carboxylic-modified MWCNTs were fabricated via electrospinning of PVA/MWCNTs mixed solution. The alignment of MWCNTs in PVA nanofibers was studied using transmission electron microscope and scanning electron microscope. In addition, the orientation of MWCNTs in PVA nanofibers was further investigated in the presence of rod-like nanoparticle rectorite (REC) and of spherical nanoparticle titanium dioxide (TiO2). The images demonstrated the embedment of MWCNTs in the nanofibers and the alignment of MWCNTs along the fiber axis. Moreover, the addition of REC and TiO2 improved the alignment of MWCNTs in PVA nanofibers.

  7. Uniaxially aligned electrospun cellulose acetate nanofibers for thin layer chromatographic screening of hydroquinone and retinoic acid adulterated in cosmetics.

    PubMed

    Tidjarat, Siripran; Winotapun, Weerapath; Opanasopit, Praneet; Ngawhirunpat, Tanasait; Rojanarata, Theerasak

    2014-11-01

    Uniaxially aligned cellulose acetate (CA) nanofibers were successfully fabricated by electrospinning and applied to use as stationary phase for thin layer chromatography. The control of alignment was achieved by using a drum collector rotating at a high speed of 6000 rpm. Spin time of 6h was used to produce the fiber thickness of about 10 μm which was adequate for good separation. Without any chemical modification after the electrospinning process, CA nanofibers could be readily devised for screening hydroquinone (HQ) and retinoic acid (RA) adulterated in cosmetics using the mobile phase consisting of 65:35:2.5 methanol/water/acetic acid. It was found that the separation run on the aligned nanofibers over a distance of 5 cm took less than 15 min which was two to three times faster than that on the non-aligned ones. On the aligned nanofibers, the masses of HQ and RA which could be visualized were 10 and 25 ng, respectively, which were two times lower than those on the non-aligned CA fibers and five times lower than those on conventional silica plates due to the appearance of darker and sharper of spots on the aligned nanofibers. Furthermore, the proposed method efficiently resolved HQ from RA and ingredients commonly found in cosmetic creams. Due to the satisfactory analytical performance, facile and inexpensive production process, uniaxially aligned electrospun CA nanofibers are promising alternative media for planar chromatography.

  8. Engineering hybrid polymer-protein super-aligned nanofibers via rotary jet spinning.

    PubMed

    Badrossamay, Mohammad R; Balachandran, Kartik; Capulli, Andrew K; Golecki, Holly M; Agarwal, Ashutosh; Goss, Josue A; Kim, Hansu; Shin, Kwanwoo; Parker, Kevin Kit

    2014-03-01

    Cellular microenvironments are important in coaxing cells to behave collectively as functional, structured tissues. Important cues in this microenvironment are the chemical, mechanical and spatial arrangement of the supporting matrix in the extracellular space. In engineered tissues, synthetic scaffolding provides many of these microenvironmental cues. Key requirements are that synthetic scaffolds should recapitulate the native three-dimensional (3D) hierarchical fibrillar structure, possess biomimetic surface properties and demonstrate mechanical integrity, and in some tissues, anisotropy. Electrospinning is a popular technique used to fabricate anisotropic nanofiber scaffolds. However, it suffers from relatively low production rates and poor control of fiber alignment without substantial modifications to the fiber collector mechanism. Additionally, many biomaterials are not amenable for fabrication via high-voltage electrospinning methods. Hence, we reasoned that we could utilize rotary jet spinning (RJS) to fabricate highly aligned hybrid protein-polymer with tunable chemical and physical properties. In this study, we engineered highly aligned nanofiber constructs with robust fiber alignment from blends of the proteins collagen and gelatin, and the polymer poly-ε-caprolactone via RJS and electrospinning. RJS-spun fibers retain greater protein content on the surface and are also fabricated at a higher production rate compared to those fabricated via electrospinning. We measured increased fiber diameter and viscosity, and decreasing fiber alignment as protein content increased in RJS hybrid fibers. RJS nanofiber constructs also demonstrate highly anisotropic mechanical properties mimicking several biological tissue types. We demonstrate the bio-functionality of RJS scaffold fibers by testing their ability to support cell growth and maturation with a variety of cell types. Our highly anisotropic RJS fibers are therefore able to support cellular alignment

  9. Improvement of thermal contact resistance by carbon nanotubes and nanofibers

    NASA Technical Reports Server (NTRS)

    Chuang, Helen F.; Cooper, Sarah M.; Meyyappan, M.; Cruden, Brett A.

    2004-01-01

    Interfacial thermal resistance results of various nanotube and nanofiber coatings, prepared by chemical vapor deposition (CVD) methods, are reported at relatively low clamping pressures. The five types of samples examined include multi-walled and single-walled nanotubes growth by CVD, multi-walled nanotubes grown by plasma enhanced CVD (PECVD) and carbon nanofibers of differing aspect ratio grown by PECVD. Of the samples examined, only high aspect ratio nanofibers and thermally grown multi-walled nanotubes show an improvement in thermal contact resistance. The improvement is approximately a 60% lower thermal resistance than a bare Si-Cu interface and is comparable to that attained by commercially available thermal interface materials.

  10. Patterned Growth of Carbon Nanotubes or Nanofibers

    NASA Technical Reports Server (NTRS)

    Delzeit, Lance D.

    2004-01-01

    A method and apparatus for the growth of carbon nanotubes or nanofibers in a desired pattern has been invented. The essence of the method is to grow the nanotubes or nanofibers by chemical vapor deposition (CVD) onto a patterned catalyst supported by a substrate. The figure schematically depicts salient aspects of the method and apparatus in a typical application. A substrate is placed in a chamber that contains both ion-beam sputtering and CVD equipment. The substrate can be made of any of a variety of materials that include several forms of silicon or carbon, and selected polymers, metals, ceramics, and even some natural minerals and similar materials. Optionally, the substrate is first coated with a noncatalytic metal layer (which could be a single layer or could comprise multiple different sublayers) by ion-beam sputtering. The choice of metal(s) and thickness(es) of the first layer (if any) and its sublayers (if any) depends on the chemical and electrical properties required for subsequent deposition of the catalyst and the subsequent CVD of the carbon nanotubes. A typical first-sublayer metal is Pt, Pd, Cr, Mo, Ti, W, or an alloy of two or more of these elements. A typical metal for the second sublayer or for an undivided first layer is Al at a thickness .1 nm or Ir at a thickness .5 nm. Proper choice of the metal for a second sublayer of a first layer makes it possible to use a catalyst that is chemically incompatible with the substrate. In the next step, a mask having holes in the desired pattern is placed over the coated substrate. The catalyst is then deposited on the coated substrate by ion-beam sputtering through the mask. Optionally, the catalyst could be deposited by a technique other than sputtering and/or patterned by use of photolithography, electron- beam lithography, or another suitable technique. The catalytic metal can be Fe, Co, Ni, or an alloy of two or more of these elements, deposited to a typical thickness in the range from 0.1 to 20 nm.

  11. Carbon Nanotubes/Nanofibers by Plasma Enhanced Chemical Vapour Deposition

    NASA Technical Reports Server (NTRS)

    Teo, K. B. K.; Hash, D. B.; Bell, M. S.; Chhowalla, M.; Cruden, B. A.; Amaratunga, G. A. J.; Meyyappan, M.; Milne, W. I.

    2005-01-01

    Plasma enhanced chemical vapour deposition (PECVD) has been recently used for the production of vertically aligned carbon nanotubedfibers (CN) directly on substrates. These structures are potentially important technologically as electron field emitters (e.g. microguns, microwave amplifiers, displays), nanoelectrodes for sensors, filter media, superhydrophobic surfaces and thermal interface materials for microelectronics. A parametric study on the growth of CN grown by glow discharge dc-PECVD is presented. In this technique, a substrate containing thin film Ni catalyst is exposed to C2H2 and NH3 gases at 700 C. Without plasma, this process is essentially thermal CVD which produces curly spaghetti-like CN as seen in Fig. 1 (a). With the plasma generated by biasing the substrate at -6OOV, we observed that the CN align vertically during growth as shown in Fig. l(b), and that the magnitude of the applied substrate bias affects the degree of alignment. The thickness of the thin film Ni catalyst was found to determine the average diameter and inversely the length of the CN. The yield and density of the CN were controlled by the use of different diffusion barrier materials under the Ni catalyst. Patterned CN growth [Fig. l(c)], with la variation in CN diameter of 4.1% and 6.3% respectively, is achieved by lithographically defining the Ni thin film prior to growth. The shape of the structures could be varied from very straight nanotube-like to conical tip-like nanofibers by increasing the ratio of C2H2 in the gas flow. Due to the plasma decomposition of C2H2, amorphous carbon (a-C) is an undesirable byproduct which could coat the substrate during CN growth. Using a combination of depth profiled Auger electron spectroscopy to study the substrate and in-situ mass spectroscopy to examine gas phase neutrals and ions, the optimal conditions for a-C free growth of CN is determined.

  12. Functionalized carbon nanotubes and nanofibers for biosensing applications

    SciTech Connect

    Wang, Jun; Lin, Yuehe

    2008-07-30

    This review summarizes the recent advances of carbon nanotube (CNT) and carbon nanofiber (CNF)-based electrochemical biosensors with an emphasis on the applications of CNTs. Carbon nanotubes and carbon nanofibers have unique electric, electrocatalytic, and mechanical properties which make them efficient materials for the use in electrochemical biosensor development. In this article, the functionalization of CNTs for biosensors is simply discussed. The electrochemical biosensors based on CNT and their various applications, e.g., measurement of small biological molecules and environmental pollutants, detection of DNA, and immunosensing of disease biomarkers, are reviewed. Moreover, the development of carbon nanofiber-based electrochemical biosensors and their applications are outlined. Finally, some challenges are discussed in the conclusion.

  13. Aligned SF/P(LLA-CL)-blended nanofibers encapsulating nerve growth factor for peripheral nerve regeneration.

    PubMed

    Kuihua, Zhang; Chunyang, Wang; Cunyi, Fan; Xiumei, Mo

    2014-08-01

    Artificial nerve guidance conduits (NGCs) containing bioactive neurotrophic factors and topographical structure to biomimic native tissues are essential for efficient regeneration of nerve gaps. In this study, aligned SF/P(LLA-CL) nanofibers encapsulating nerve growth factor (NGF), which was stabilized by SF in core, were fabricated via a coaxial electrospinning technique. The controlled release of NGF from the nanofibers was evaluated using enzyme-linked immune sorbent assay (ELISA) and PC12 cell-based bioassay over a 60-day time period. The results demonstrated that NGF presented a sustained release and remained biological activity over 60 days. Nerve guidance conduits (NGCs) were fabricated by reeling the aligned SF/P(LLA-CL) nanofibrous scaffolds encapsulating NGF and then used as a bridge implanted across a 15-mm defect in the sciatic nerve of rats to promote nerve regeneration. The outcome in terms of regenerated nerve at 12 weeks was evaluated by a combination of electrophysiological assessment, histochemistry, and electron microscopy. All results clarified that the NGF-encapsulated-aligned SF/P(LLA-CL) NGCs promoted peripheral nerve regeneration significantly better than the aligned SF/P(LLA-CL) NGCs, suggesting that the released NGF from nanofibers could effectively promote the regeneration of peripheral nerve.

  14. Aligned Nanofibers from Polypyrrole/Graphene as Electrodes for Regeneration of Optic Nerve via Electrical Stimulation.

    PubMed

    Yan, Lu; Zhao, Bingxin; Liu, Xiaohong; Li, Xuan; Zeng, Chao; Shi, Haiyan; Xu, Xiaoxue; Lin, Tong; Dai, Liming; Liu, Yong

    2016-03-23

    The damage of optic nerve will cause permanent visual field loss and irreversible ocular diseases, such as glaucoma. The damage of optic nerve is mainly derived from the atrophy, apoptosis or death of retinal ganglion cells (RGCs). Though some progress has been achieved on electronic retinal implants that can electrically stimulate undamaged parts of RGCs or retina to transfer signals, stimulated self-repair/regeneration of RGCs has not been realized yet. The key challenge for development of electrically stimulated regeneration of RGCs is the selection of stimulation electrodes with a sufficient safe charge injection limit (Q(inj), i.e., electrochemical capacitance). Most traditional electrodes tend to have low Q(inj) values. Herein, we synthesized polypyrrole functionalized graphene (PPy-G) via a facile but efficient polymerization-enhanced ball milling method for the first time. This technique could not only efficiently introduce electron-acceptor nitrogen to enhance capacitance, but also remain a conductive platform-the π-π conjugated carbon plane for charge transportation. PPy-G based aligned nanofibers were subsequently fabricated for guided growth and electrical stimulation (ES) of RGCs. Significantly enhanced viability, neurite outgrowth and antiaging ability of RGCs were observed after ES, suggesting possibilities for regeneration of optic nerve via ES on the suitable nanoelectrodes. PMID:26926578

  15. Guiding the orientation of smooth muscle cells on random and aligned polyurethane/collagen nanofibers.

    PubMed

    Jia, Lin; Prabhakaran, Molamma P; Qin, Xiaohong; Ramakrishna, Seeram

    2014-09-01

    Fabricating scaffolds that can simulate the architecture and functionality of native extracellular matrix is a huge challenge in vascular tissue engineering. Various kinds of materials are engineered via nano-technological approaches to meet the current challenges in vascular tissue regeneration. During this study, nanofibers from pure polyurethane and hybrid polyurethane/collagen in two different morphologies (random and aligned) and in three different ratios of polyurethane:collagen (75:25; 50:50; 25:75) are fabricated by electrospinning. The fiber diameters of the nanofibrous scaffolds are in the range of 174-453 nm and 145-419 for random and aligned fibers, respectively, where they closely mimic the nanoscale dimensions of native extracellular matrix. The aligned polyurethane/collagen nanofibers expressed anisotropic wettability with mechanical properties which is suitable for regeneration of the artery. After 12 days of human aortic smooth muscle cells culture on different scaffolds, the proliferation of smooth muscle cells on hybrid polyurethane/collagen (3:1) nanofibers was 173% and 212% higher than on pure polyurethane scaffolds for random and aligned scaffolds, respectively. The results of cell morphology and protein staining showed that the aligned polyurethane/collagen (3:1) scaffold promote smooth muscle cells alignment through contact guidance, while the random polyurethane/collagen (3:1) also guided cell orientation most probably due to the inherent biochemical composition. Our studies demonstrate the potential of aligned and random polyurethane/collagen (3:1) as promising substrates for vascular tissue regeneration. PMID:24682037

  16. Mechanical Properties of Individual Composite Poly(methyl-methacrylate) -Multiwalled Carbon Nanotubes Nanofibers

    NASA Astrophysics Data System (ADS)

    Grabbert, Niels; Wang, Bei; Avnon, Asaf; Zhuo, Shuyao; Datsyuk, Vitaliy; Trotsenko, Svitlana; Mackowiak, Piotr; Kaletta, Katrin; Lang, Klaus-Dieter; Ngo, Ha-Duong

    2014-08-01

    Multiwalled carbon nanotubes with their superb mechanical properties are an unique filler material for polymer composites. Here, we present an investigation of mechanical properties of electrospun Poly-(methyl-methacrylate) multiwalled carbon nanotubes composite nanofibers. The method of electrospinning was used to fabricate suspended individual Poly-(methyl-methacrylate) multiwalled carbon nanotubes nanofibers. In order to reinforce the nanofibers, different high concentration of multiwalled carbon nanotubes were used. Transmission electron microscopy measurements reveal a successful filling of the nanofibers. The different types of nanofibers were deposited at SiO2 substrates. Which were previously etched, to create trenches for bend tests. Followed by fixing the nanofiber with a focus ion beam platinum deposition at the trench edges. An atomic force microscopy was used to perform the mechanical nanofiber bending tests over trenches. The results were compared with pristine Poly-(methyl- methacrylate) nanofibers to nanofibers with 15 weight% and 20 weight% multiwalled carbon nanotubes composite fibers. We observed that pristine nanofibers have Young's modulus of 136 MPa, while for composite nanofibers with 15 weight% have 2.65 GPa and with 20 weight% have 6.06 GPa (at room temperature and air ambiance). This corresponds to an increase of Young's modulus of 19 fold between the pristine nanofibers and the 15 weight% of mutliwalled carbon nanotubes filled nanofibers. Therefore the increase of the Young's modulus compared between the pristine and the 20 weight% MWCNT filled nanofibers corresponds to 45 fold.

  17. Silane coupling agent structures on carbon nanofibers.

    PubMed

    Palencia, Cristina; Rubio, Juan; Rubio, Fausto; Fierro, José Luis G; Oteo, José Luis

    2011-05-01

    Carbon nanofibers (CNFs) are considered ideal materials for reinforcing polymers due to their excellent mechanical properties, among others. In order to obtain composites of optimal properties the clue is to enhance the interaction between reinforcement (CNFs) and polymer matrix. Surface modification of CNFs with silane coupling agents (SCAs) has revealed as one of the most interesting methods. The silanization process has been carried out mixing at room temperature and for one minute the hydrolysed silane with CNFs. We have use four different SCAs: 3-aminopropyltriethoxyxilane (APS), 3-aminopropyltrimethoxysilane (AMMO), N-(2-aminoethyl)-3-(aminopropyltrimethoxysilane) (DAMO), and 3-glycidoxypropyltrimethoxysilane (GLYMO), in order to elucidate the SCA-CNFs interaction and the silane structures formed on CNFs surface. XPS and FTIR-ATR techniques have pointed out that each silane adsorbs on CNFs surface through chemical bonding, forming multilayers. Silane nature determines the structure taken on CNFs surface. APS and AMO silanes adsorb taking vertical structures on CNFs surface, while DMO and GMO adsorb on CNFs taking horizontal structures, stabilized by zwitterions formed through H-bonds with hydroxyl groups from CNFs surface.

  18. Label-Free Detection of Cardiac Troponin-I Using Carbon Nanofiber Based Nanoelectrode Arrays

    NASA Technical Reports Server (NTRS)

    Periyakaruppan, Adaikkappan; Koehne, Jessica Erin; Gandhiraman, Ram P.; Meyyappan, M.

    2013-01-01

    A sensor platform based on vertically aligned carbon nanofibers (CNFs) has been developed. Their inherent nanometer scale, high conductivity, wide potential window, good biocompatibility and well-defined surface chemistry make them ideal candidates as biosensor electrodes. A carbon nanofiber (CNF) multiplexed array has been fabricated with 9 sensing pads, each containing 40,000 carbon nanofibers as nanoelectrodes. Here, we report the use of vertically aligned CNF nanoelectrodes for the detection of cardiac Troponin-I for the early diagnosis of myocardial infarction. Antibody, antitroponin, probe immobilization and subsequent binding to human cardiac troponin-I were characterized using electrochemical impedance spectroscopy and cyclic voltammetry techniques. Each step of the modification process resulted in changes in electrical capacitance or resistance to charge transfer due to the changes at the electrode surface upon antibody immobilization and binding to the specific antigen. This sensor demonstrates high sensitivity, down to 0.2 ng/mL, and good selectivity making this platform a good candidate for early stage diagnosis of myocardial infarction.

  19. Treated Carbon Nanofibers for Storing Energy in Aqueous KOH

    NASA Technical Reports Server (NTRS)

    Firsich, David W.

    2004-01-01

    A surface treatment has been found to enhance the performances of carbon nanofibers as electrode materials for electrochemical capacitors in which aqueous solutions of potassium hydroxide are used as the electrolytes. In the treatment, sulfonic acid groups are attached to edge plane sites on carbon atoms. The treatment is applicable to a variety of carbon nanofibers, including fibrils and both single- and multiple-wall nanotubes. The reason for choosing nanofibers over powders and other forms of carbon is that nanofibers offer greater power features. In previous research, it was found that the surface treatment of carbon nanofibers increased energy-storage densities in the presence of acid electrolytes. Now, it has been found that the same treatment increases energy-storage densities of carbon nanofibers in the presence of alkaline electrolytes when the carbon is paired with a NiOOH electrode. This beneficial effect varies depending on the variety of carbon substrate to which it is applied. It has been conjectured that the sulfonic acid groups, which exist in a deprotonated state in aqueous KOH solutions, undergo reversible electro-chemical reactions that are responsible for the observed increases in energystorage capacities. The increases can be considerable: For example, in one case, nanofibers exhibited a specific capacitance of 34 Farads per gram before treatment and 172 Farads per gram (an increase of about 400 percent) after treatment. The most promising application of this development appears to lie in hybrid capacitors, which are devices designed primarily for storing energy. These devices are designed to be capable of (1) discharge at rates greater than those of batteries and (2) storing energy at densities approaching those of batteries. A hybrid capacitor includes one electrode like that of a battery and one electrode like that of an electrochemical capacitor. For example, a hybrid capacitor could contain a potassium hydroxide solution as the electrolyte

  20. Preparation of Electrically Conductive Polystyrene/Carbon Nanofiber Nanocomposite Films

    ERIC Educational Resources Information Center

    Sun, Luyi; O'Reilly, Jonathan Y.; Tien, Chi-Wei; Sue, Hung-Jue

    2008-01-01

    A simple and effective approach to prepare conductive polystyrene/carbon nanofiber (PS/CNF) nanocomposite films via a solution dispersion method is presented. Inexpensive CNF, which has a structure similar to multi-walled carbon nanotubes, is chosen as a nanofiller in this experiment to achieve conductivity in PS films. A good dispersion is…

  1. Aligned natural-synthetic polyblend nanofibers for peripheral nerve regeneration.

    PubMed

    Wang, Chun-Yang; Zhang, Kui-Hua; Fan, Cun-Yi; Mo, Xiu-Mei; Ruan, Hong-Jiang; Li, Feng-Feng

    2011-02-01

    Peripheral nerve regeneration remains a significant clinical challenge to researchers. Progress in the design of tissue engineering scaffolds provides an alternative approach for neural regeneration. In this study aligned silk fibroin (SF) blended poly(L-lactic acid-co-ε-caprolactone) (P(LLA-CL)) nanofibrous scaffolds were fabricated by electrospinning methods and then reeled into aligned nerve guidance conduits (NGC) to promote nerve regeneration. The aligned SF/P(LLA-CL) NGC was used as a bridge implanted across a 10mm defect in the sciatic nerve of rats and the outcome in terms of of regenerated nerve at 4 and 8 weeks was evaluated by a combination of electrophysiological assessment and histological and immunohistological analysis, as well as electron microscopy. The electrophysiological examination showed that functional recovery of the regenerated nerve in the SF/P(LLA-CL) NGC group was superior to that in the P(LLA-CL) NGC group. The morphological analysis also indicated that the regenerated nerve in the SF/P(LLA-CL) NGC was more mature. All the results demonstrated that the aligned SF/P(LLA-CL) NGC promoted peripheral nerve regeneration significantly better in comparison with the aligned P(LLA-CL) NGC, thus suggesting a potential application in nerve regeneration.

  2. High-throughput and high-yield fabrication of uniaxially-aligned chitosan-based nanofibers by centrifugal electrospinning.

    PubMed

    Erickson, Ariane E; Edmondson, Dennis; Chang, Fei-Chien; Wood, Dave; Gong, Alex; Levengood, Sheeny Lan; Zhang, Miqin

    2015-12-10

    The inability to produce large quantities of nanofibers has been a primary obstacle in advancement and commercialization of electrospinning technologies, especially when aligned nanofibers are desired. Here, we present a high-throughput centrifugal electrospinning (HTP-CES) system capable of producing a large number of highly-aligned nanofiber samples with high-yield and tunable diameters. The versatility of the design was revealed when bead-less nanofibers were produced from copolymer chitosan/polycaprolactone (C-PCL) solutions despite variations in polymer blend composition or spinneret needle gauge. Compared to conventional electrospinning techniques, fibers spun with the HTP-CES not only exhibited superior alignment, but also better diameter uniformity. Nanofiber alignment was quantified using Fast Fourier Transform (FFT) analysis. In addition, a concave correlation between the needle diameter and resultant fiber diameter was identified. This system can be easily scaled up for industrial production of highly-aligned nanofibers with tunable diameters that can potentially meet the requirements for various engineering and biomedical applications.

  3. Morphology of PEG-Stabilized Carbon Nanofibers in Water

    SciTech Connect

    Zhao, Jian; Schaefer, Dale W.

    2009-09-02

    Small-angle light scattering is used to assess the dispersion of poly(ethylene glycol) (PEG)-functionalized carbon nanofibers suspended in water. Analysis of these data elucidates the mechanism by which the functionalized nanofibers are solubilized in water. Linear, tube-like morphology is observed for the PEG-functionalized nanofibers dispersed in water. However, dispersion is not down to the individual tube level as determined by analysis of the light scattering data in conjunction with transmission electron micrographs. Rather, scattering entities are polydisperse side-by-side fiber aggregates (bundles). Because of the presence of water-soluble PEG oligomers on the surfaces of the nanofibers these small-scale aggregates do not agglomerate to form the large-scale clusters that are observed for untreated and acid-treated nanofibers. Acid-treated nanofibers, by contrast, do agglomerate, but in an unusual fashion, showing a 10-h induction period of followed by linear growth of large-scale agglomerates. PEG-functionalization of the acid-treated fibers leads to stabilization by inhibiting formation of the large-scale agglomerates, not by disrupting the side-by-side bundles.

  4. Electrospinning fabrication of high strength and toughness polyimide nanofiber membranes containing multiwalled carbon nanotubes.

    PubMed

    Chen, Dan; Liu, Tianxi; Zhou, Xiaoping; Tjiu, Wuiwui Chauhari; Hou, Haoqing

    2009-07-23

    Polyimide (PI) and PI nanocomposite fibers containing different amounts of multiwalled carbon nanotubes (MWNTs) were produced for the first time by electrospinning. The membranes prepared were composed of highly aligned nanofibers and showed significant enhancement in mechanical properties, compared with the membranes prepared by conventional solution-casting method. Surface-functionalized MWNTs were homogeneously dispersed and highly aligned along the fiber axis, whereas most of the pristine MWNTs formed aggregates or bundles and even protruded out of the electrospun nanofibers. The thermal and mechanical properties of polyimide matrix were significantly improved with the incorporation of MWNTs. And the elongation at break of the nanofiber membranes can reach 100% for the nanotube loading level of 3.5 wt %. It was found that electrospinning the in situ prepared MWNT/poly(amic acid) solution can achieve better polymer chain orientation and thus better mechanical properties of the as-prepared membranes. Our study demonstrates a good example for the preparation of high-performance polymer/carbon nanotube nanocomposites by using electrospinning.

  5. Non-continuum, anisotropic nanomechanics of random and aligned electrospun nanofiber matrices

    NASA Astrophysics Data System (ADS)

    Chery, Daphney; Han, Biao; Mauck, Robert; Shenoy, Vivek; Han, Lin

    Polymer nanofiber assemblies are widely used in cell culture and tissue engineering, while their nanomechanical characteristics have received little attention. In this study, to understand their nanoscale structure-mechanics relations, nanofibers of polycaprolactone (PCL) and poly(vinyl alcohol) (PVA) were fabricated via electrospinning, and tested via AFM-nanoindentation with a microspherical tip (R ~10 μm) in PBS. For the hydrophobic, less-swollen PCL, a novel, non-continuum linear F-D dependence was observed, instead of the typical Hertzian F-D3/2 behavior, which is usually expected for continuum materials. This linear trend is likely resulted from the tensile stretch of a few individual nanofibers as they were indented in the normal plane. In contrast, for the hydrophilic, highly swollen PVA, the observed typical Hertzian response indicates the dominance of localized deformation within each nanofiber, which had swollen to become hydrogels. Furthermore, for both matrices, aligned fibers showed significantly higher stiffness than random fibers. These results provide a fundamental basis on the nanomechanics of biomaterials for specialized applications in cell phenotype and tissue repair.

  6. Aligned PVDF-TrFE nanofibers with high-density PVDF nanofibers and PVDF core–shell structures for endovascular pressure sensing.

    PubMed

    Sharma, Tushar; Naik, Sahil; Langevine, Jewel; Gill, Brijesh; Zhang, John X J

    2015-01-01

    Nanostructures of polyvinyledenedifluoride-tetrafluoroethylene (PVDF-TrFE), a semicrystalline polymer with high piezoelectricity, results in significant enhancement of crystallinity and better device performance as sensors, actuators, and energy harvesters. Using electrospinning of PVDF to manufacture nanofibers, we demonstrate a new method to pattern high-density, highly aligned nanofibers. To further boost the charge transfer from such a bundle of nanofibers, we fabricated novel core-shell structures. Finally, we developed pressure sensors utilizing these fiber structures for endovascular applications. The sensors were tested in vitro under simulated physiological conditions. We observed significant improvements using core-shell electrospun fibers (4.5 times gain in signal intensity, 4000 μV/mmHg sensitivity) over PVDF nanofibers (280 μV/mmHg). The preliminary results showed that core-shell fiber-based devices exhibit nearly 40-fold higher sensitivity, compared to the thin-film structures demonstrated earlier. PMID:25095247

  7. Hydrogen storage capacity of catalytically grown carbon nanofibers.

    PubMed

    Rzepka, Matthias; Bauer, Erich; Reichenauer, Gudrun; Schliermann, Thomas; Bernhardt, Babette; Bohmhammel, Klaus; Henneberg, Eva; Knoll, Uta; Maneck, Heinz-Eberhard; Braue, Wolfgang

    2005-08-11

    In 1996, R. T. K. Baker, and N. M. Rodriguez claimed to have synthesized a new type of carbon nanofiber material capable of storing large amounts of hydrogen at room temperature and pressures above 100 bar, thus making it a powerful candidate for a very efficient energy storage system in mobile applications. Consequently, many scientists all over the world tried to test and verify these findings, however, with partly inconsistent results. We present here for the first time independent hydrogen storage measurements for several types of nanofibers, both synthesized by our group following precisely the specifications given in the literature as well as original samples supplied by Rodriguez and Baker for this study. The hydrogen storage capacities at room temperature and pressures up to 140 bar were quantified independently by gravimetric and volumetric methods, respectively. No significant hydrogen storage capacity has been detected for all carbon nanofibers investigated.

  8. Enhanced Schwann cell attachment and alignment using one-pot "dual click" GRGDS and YIGSR derivatized nanofibers.

    PubMed

    Zheng, Jukuan; Kontoveros, Dimitria; Lin, Fei; Hua, Geng; Reneker, Darrell H; Becker, Matthew L; Willits, Rebecca K

    2015-01-12

    Using metal-free click chemistry and oxime condensation methodologies, GRGDS and YIGSR peptides were coupled to random and aligned degradable nanofiber networks postelectrospinning in a one-pot reaction. The bound peptides are bioactive, as demonstrated by Schwann cell attachment and proliferation, and the inclusion of YIGSR with GRGDS alters the expression of the receptor for YIGSR. Additionally, aligned nanofibers act as a potential guidance cue by increasing the aspect ratio and aligning the actin filaments, which suggest that peptide-functionalized scaffolds would be useful to direct SCs for peripheral nerve regeneration.

  9. Aligned-to-random” nanofiber scaffolds for mimicking the structure of the tendon-to-bone insertion site

    PubMed Central

    Xie, Jingwei; Li, Xiaoran; Lipner, Justin; Manning, Cionne N.; Schwartz, Annie G.; Thomopoulos, Stavros; Xia, Younan

    2013-01-01

    We have demonstrated the fabrication of “aligned-to-random” electrospun nanofiber scaffolds that mimic the structural organization of collagen fibers at the tendon-to-bone insertion site. Tendon fibroblasts cultured on such a scaffold exhibited highly organized and haphazardly oriented morphologies, respectively, on the aligned and random portions. PMID:20648290

  10. Positional control of catalyst nanoparticles for the synthesis of high density carbon nanofiber arrays.

    PubMed

    Retterer, Scott T; Melechko, Anatoli; Hensley, Dale K; Simpson, Michael L; Doktycz, Mitchel J

    2008-01-01

    Precise arrangement of nanoscale elements within larger systems, is essential to controlling higher order functionality and tailoring nanophase material properties. Here, we present findings on growth conditions for vertically aligned carbon nanofibers that enable synthesis of high density arrays and individual rows of nanofibers, which could be used to form barriers for restricting molecular transport, that have regular spacings and few defects. Growth through plasma-enhanced chemical vapor deposition was initiated from precisely formed nickel catalyst dots of varying diameter and spacing that were patterned through electron beam lithography. Nanofiber growth conditions, including power, precursor gas ratio, growth temperature and pressure were varied to optimize fiber uniformity and minimize defects that result from formation and migration of catalyst particles prior to growth. It was determined that both catalyst dot diameter and initial plasma power have a considerable influence on the number and severity of defects, while growth temperature, gas ratio (C(2)H(2):NH(3)) and pressure can be varied within a considerable range to fine-tune nanofiber morphology.

  11. A Controlled Design of Aligned and Random Nanofibers for 3D Bi-functionalized Nerve Conduits Fabricated via a Novel Electrospinning Set-up

    PubMed Central

    Kim, Jeong In; Hwang, Tae In; Aguilar, Ludwig Erik; Park, Chan Hee; Kim, Cheol Sang

    2016-01-01

    Scaffolds made of aligned nanofibers are favorable for nerve regeneration due to their superior nerve cell attachment and proliferation. However, it is challenging not only to produce a neat mat or a conduit form with aligned nanofibers but also to use these for surgical applications as a nerve guide conduit due to their insufficient mechanical strength. Furthermore, no studies have been reported on the fabrication of aligned nanofibers and randomly-oriented nanofibers on the same mat. In this study, we have successfully produced a mat with both aligned and randomly-oriented nanofibers by using a novel electrospinning set up. A new conduit with a highly-aligned electrospun mat is produced with this modified electrospinning method, and this proposed conduit with favorable features, such as selective permeability, hydrophilicity and nerve growth directional steering, were fabricated as nerve guide conduits (NGCs). The inner surface of the nerve conduit is covered with highly aligned electrospun nanofibers and is able to enhance the proliferation of neural cells. The central part of the tube is double-coated with randomly-oriented nanofibers over the aligned nanofibers, strengthening the weak mechanical strength of the aligned nanofibers. PMID:27021221

  12. Modeling of Carbon Nanotubes (Nanofibers) as Macromolecular Coils

    NASA Astrophysics Data System (ADS)

    Mikitaev, A. K.; Kozlov, G. V.

    2015-12-01

    Modeling of carbon nanotubes (nanofibers) in polymer nanocomposites as macromolecular coils is performed. This approach offers an estimation of the real degree of anisotropy of these nanofillers and allows predicting the properties of the resulting nanocomposites. An important role of the nanofiller - polymer matrix interface is demonstrated.

  13. Improvement of thermal contact resistance by carbon nanotubes and nanofibers.

    PubMed

    Chuang, Helen F; Cooper, Sarah M; Meyyappan, M; Cruden, Brett A

    2004-11-01

    Interfacial thermal resistance results of various nanotube and nanofiber coatings, prepared by chemical vapor deposition (CVD) methods, are reported at relatively low clamping pressures. The five types of samples examined include multi-walled and single-walled nanotubes growth by CVD, multi-walled nanotubes grown by plasma enhanced CVD (PECVD) and carbon nanofibers of differing aspect ratio grown by PECVD. Of the samples examined, only high aspect ratio nanofibers and thermally grown multi-walled nanotubes show an improvement in thermal contact resistance. The improvement is approximately a 60% lower thermal resistance than a bare Si-Cu interface and is comparable to that attained by commercially available thermal interface materials. PMID:15656186

  14. Silver-functionalized carbon nanofiber composite electrodes for ibuprofen detection

    NASA Astrophysics Data System (ADS)

    Manea, Florica; Motoc, Sorina; Pop, Aniela; Remes, Adriana; Schoonman, Joop

    2012-06-01

    The aim of this study is to prepare and characterize two types of silver-functionalized carbon nanofiber (CNF) composite electrodes, i.e., silver-decorated CNF-epoxy and silver-modified natural zeolite-CNF-epoxy composite electrodes suitable for ibuprofen detection in aqueous solution. Ag carbon nanotube composite electrode exhibited the best electroanalytical parameters through applying preconcentration/differential-pulsed voltammetry scheme.

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

    PubMed

    Nam, Ki-Mok; Park, Heai-Ku; Lee, Chang-Seop

    2015-11-01

    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.

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

    PubMed

    Jiang, Jianjun; Zhao, Ziwei; Deng, Chao; Liu, Fa; Li, Dejia; Fang, Liangchao; Zhang, Dan; Castro Jose M; Chen, Feng; Lee, L James

    2016-06-01

    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. PMID:27427606

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

    PubMed

    Jiang, Jianjun; Zhao, Ziwei; Deng, Chao; Liu, Fa; Li, Dejia; Fang, Liangchao; Zhang, Dan; Castro Jose M; Chen, Feng; Lee, L James

    2016-06-01

    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.

  18. Synthesis of amorphous carbon nanofibers using iron nanoparticles as catalysts

    NASA Astrophysics Data System (ADS)

    Ali, Mokhtar; Ramana, G. Venkata; Padya, Balaji; Srikanth, V. V. S. S.; Jain, P. K.

    2013-06-01

    Amongst various carbon nanomaterials, carbon nanofibers (CNFs) have lately attracted considerable interest as a promising reinforcement in polymer matrix composites. CNFs are often synthesized using copper nanoparticles as catalysts and by using chemical vapor deposition (CVD). In this work iron (Fe) nanoparticles are used as catalysts to synthesize amorphous carbon nanofibers. This owes significance since Fe nanoparticles often lead to tubes rather than fibers. Fe nanoparticles (size ˜30-60nm) are prepared by first mixing an appropriate quantity of potassium sodium tartrate tetrahydrate salt with iron (II) chloride dehydrate to obtain iron tartrate and then dried and heated in vacuum oven at about 250°C to remove tartrate. In a subsequent step, CNFs are obtained by using CVD. Acetylene was used as the carbon source in the CVD process. Scanning and transmission electron microscopy show the formation of nanofibers whose diameter is dependent on the size of Fe catalysts. Raman scattering from the fibers show that they are made up of carbon and are amorphous.

  19. Electrochemical enzymatic biosensors using carbon nanofiber nanoelectrode arrays

    NASA Astrophysics Data System (ADS)

    Li, Jun; Li, Yi-fen; Swisher, Luxi Z.; Syed, Lateef U.; Prior, Allan M.; Nguyen, Thu A.; Hua, Duy H.

    2012-10-01

    The reduction of electrode size down to nanometers could dramatically enhance detection sensitivity and temporal resolution. Nanoelectrode arrays (NEAs) are of particular interest for ultrasensitive biosensors. Here we report the study of two types of biosensors for measuring enzyme activities using NEAs fabricated with vertically aligned carbon nanofibers (VACNFs). VACNFs of ~100 nm in average diameter and 3-5 μm in length were grown on conductive substrates as uniform vertical arrays which were then encapsulated in SiO2 matrix leaving only the tips exposed. We demonstrate that such VACNF NEAs can be used in profiling enzyme activities through monitoring the change in electrochemical signals induced by enzymatic reactions to the peptides attached to the VACNF tip. The cleavage of the tetrapeptide with a ferrocene tag by a cancerrelated protease (legumain) was monitored with AC voltammetry. Real-time electrochemical impedance spectroscopy (REIS) was used for fast label-free detection of two reversible processes, i.e. phosphorylation by c-Src tyrosine kinase and dephosphorylation by protein tyrosine phosphatase 1B (PTP1B). The REIS data of phosphorylation were slow and unreliable, but those of dephosphorylation showed large and fast exponential decay due to much higher activity of phosphatase PTP1B. The kinetic data were analyzed with a heterogeneous Michaelis-Menten model to derive the "specificity constant" kcat/Km, which is 8.2x103 M-1s-1 for legumain and (2.1 ± 0.1) x 107 M-1s-1 for phosphatase (PTP1B), well consistent with literature. It is promising to develop VACNF NEA based electrochemical enzymatic biosensors as portable multiplex electronic techniques for rapid cancer diagnosis and treatment monitoring.

  20. Layered chitosan-collagen hydrogel/aligned PLLA nanofiber construct for flexor tendon regeneration.

    PubMed

    Deepthi, S; Nivedhitha Sundaram, M; Deepti Kadavan, J; Jayakumar, R

    2016-11-20

    The aim of our study was to develop a tendon construct of electrospun aligned poly (l-lactic acid) (PLLA) nanofibers, to mimic the aligned collagen fiber bundles and layering PLLA fibers with chitosan-collagen hydrogel, to mimic the glycosaminoglycans of sheath ECM for tendon regeneration. The hydrogel coated electrospun membrane was rolled and an outer coating of alginate gel was given to prevent peritendinous adhesion. The developed constructs were characterized by SEM, FT-IR and tensile testing. Protein adsorption studies showed lower protein adsorption on coated scaffolds compared to uncoated scaffolds. The samples were proven to be non-toxic to tenocytes. The chitosan-collagen/PLLA uncoated scaffolds and alginate gel coated chitosan-collagen/PLLA scaffolds showed good cell proliferation. The tenocytes showed good attachment and spreading on the scaffolds. This study indicated that the developed chitosan-collagen/PLLA/alginate scaffold would be suitable for flexor tendon regeneration. PMID:27561521

  1. Hierarchical carbon nanostructure design: ultra-long carbon nanofibers decorated with carbon nanotubes

    NASA Astrophysics Data System (ADS)

    El Mel, A. A.; Achour, A.; Xu, W.; Choi, C. H.; Gautron, E.; Angleraud, B.; Granier, A.; Le Brizoual, L.; Djouadi, M. A.; Tessier, P. Y.

    2011-10-01

    Hierarchical carbon nanostructures based on ultra-long carbon nanofibers (CNF) decorated with carbon nanotubes (CNT) have been prepared using plasma processes. The nickel/carbon composite nanofibers, used as a support for the growth of CNT, were deposited on nanopatterned silicon substrate by a hybrid plasma process, combining magnetron sputtering and plasma-enhanced chemical vapor deposition (PECVD). Transmission electron microscopy revealed the presence of spherical nanoparticles randomly dispersed within the carbon nanofibers. The nickel nanoparticles have been used as a catalyst to initiate the growth of CNT by PECVD at 600 °C. After the growth of CNT onto the ultra-long CNF, SEM imaging revealed the formation of hierarchical carbon nanostructures which consist of CNF sheathed with CNTs. Furthermore, we demonstrate that reducing the growth temperature of CNT to less than 500 °C leads to the formation of carbon nanowalls on the CNF instead of CNT. This simple fabrication method allows an easy preparation of hierarchical carbon nanostructures over a large surface area, as well as a simple manipulation of such material in order to integrate it into nanodevices.

  2. Hierarchical carbon nanostructure design: ultra-long carbon nanofibers decorated with carbon nanotubes.

    PubMed

    El Mel, A A; Achour, A; Xu, W; Choi, C H; Gautron, E; Angleraud, B; Granier, A; Le Brizoual, L; Djouadi, M A; Tessier, P Y

    2011-10-28

    Hierarchical carbon nanostructures based on ultra-long carbon nanofibers (CNF) decorated with carbon nanotubes (CNT) have been prepared using plasma processes. The nickel/carbon composite nanofibers, used as a support for the growth of CNT, were deposited on nanopatterned silicon substrate by a hybrid plasma process, combining magnetron sputtering and plasma-enhanced chemical vapor deposition (PECVD). Transmission electron microscopy revealed the presence of spherical nanoparticles randomly dispersed within the carbon nanofibers. The nickel nanoparticles have been used as a catalyst to initiate the growth of CNT by PECVD at 600°C. After the growth of CNT onto the ultra-long CNF, SEM imaging revealed the formation of hierarchical carbon nanostructures which consist of CNF sheathed with CNTs. Furthermore, we demonstrate that reducing the growth temperature of CNT to less than 500°C leads to the formation of carbon nanowalls on the CNF instead of CNT. This simple fabrication method allows an easy preparation of hierarchical carbon nanostructures over a large surface area, as well as a simple manipulation of such material in order to integrate it into nanodevices. PMID:21971265

  3. Synthesis and characterization of multiwalled CNT-PAN based composite carbon nanofibers via electrospinning.

    PubMed

    Kaur, Narinder; Kumar, Vipin; Dhakate, Sanjay R

    2016-01-01

    Electrospun fibrous membranes find place in diverse applications like sensors, filters, fuel cell membranes, scaffolds for tissue engineering, organic electronics etc. The objectives of present work are to electrospun polyacrylonitrile (PAN) nanofibers and PAN-CNT nanocomposite nanofibers and convert into carbon nanofiber and carbon-CNT composite nanofiber. The work was divided into two parts, development of nanofibers and composite nanofiber. The PAN nanofibers were produced from 9 wt% PAN solution by electrospinning technique. In another case PAN-CNT composite nanofibers were developed from different concentrations of MWCNTs (1-3 wt%) in 9 wt% PAN solution by electrospinning. Both types of nanofibers were undergone through oxidation, stabilization, carbonization and graphitization. At each stage of processing of carbon and carbon-CNT composite nanofibers were characterized by SEM, AFM, TGA and XRD. It was observed that diameter of nanofiber varies with processing parameters such as applied voltage tip to collector distance, flow rate of solution and polymer concentrations etc. while in case of PAN-CNT composite nanofiber diameter decreases with increasing concentration of CNT in PAN solution. Also with stabilization, carbonization and graphitization diameter of nanofiber decreases. SEM images shows that the minimum fiber diameter in case of 3 wt% of CNT solution because as viscosity increases it reduces the phase separation of PAN and solvent and as a consequence increases in the fiber diameter. AFM images shows that surface of film is irregular which give idea about mat type orientation of fibers. XRD results show that degree of graphitization increases on increasing CNT concentration because of additional stresses exerting on the nanofiber surface in the immediate vicinity of CNTs. TGA results shows wt loss decreases as CNT concentration increases in fibers. PMID:27217998

  4. Synthesis and characterization of multiwalled CNT-PAN based composite carbon nanofibers via electrospinning.

    PubMed

    Kaur, Narinder; Kumar, Vipin; Dhakate, Sanjay R

    2016-01-01

    Electrospun fibrous membranes find place in diverse applications like sensors, filters, fuel cell membranes, scaffolds for tissue engineering, organic electronics etc. The objectives of present work are to electrospun polyacrylonitrile (PAN) nanofibers and PAN-CNT nanocomposite nanofibers and convert into carbon nanofiber and carbon-CNT composite nanofiber. The work was divided into two parts, development of nanofibers and composite nanofiber. The PAN nanofibers were produced from 9 wt% PAN solution by electrospinning technique. In another case PAN-CNT composite nanofibers were developed from different concentrations of MWCNTs (1-3 wt%) in 9 wt% PAN solution by electrospinning. Both types of nanofibers were undergone through oxidation, stabilization, carbonization and graphitization. At each stage of processing of carbon and carbon-CNT composite nanofibers were characterized by SEM, AFM, TGA and XRD. It was observed that diameter of nanofiber varies with processing parameters such as applied voltage tip to collector distance, flow rate of solution and polymer concentrations etc. while in case of PAN-CNT composite nanofiber diameter decreases with increasing concentration of CNT in PAN solution. Also with stabilization, carbonization and graphitization diameter of nanofiber decreases. SEM images shows that the minimum fiber diameter in case of 3 wt% of CNT solution because as viscosity increases it reduces the phase separation of PAN and solvent and as a consequence increases in the fiber diameter. AFM images shows that surface of film is irregular which give idea about mat type orientation of fibers. XRD results show that degree of graphitization increases on increasing CNT concentration because of additional stresses exerting on the nanofiber surface in the immediate vicinity of CNTs. TGA results shows wt loss decreases as CNT concentration increases in fibers.

  5. Direct imaging of copper catalyst migration inside helical carbon nanofibers.

    PubMed

    Dong, Lifeng; Yu, Liyan; Cui, Zuolin; Dong, Hongzhou; Ercius, Peter; Song, Chengyu; Duden, Thomas

    2012-01-27

    By using a double-aberration-corrected (scanning) transmission electron microscope (STEM/TEM) at an acceleration voltage of only 80 kV, we demonstrate that, due to the low solubility of copper (Cu) in carbon and its affinity with oxygen (O), single-crystal Cu catalysts dissociate into small cuprous oxide (Cu2O) nanoparticles after the growth of carbon nanofibers, and Cu2O nanoparticles ultimately localize on the fiber surfaces. This new finding is a step toward a better understanding of the interactions between Cu catalysts and carbon nanomaterials and could suggest a simple and effective method for eliminating Cu impurities from the fibers. PMID:22172975

  6. Fabrication and Characterization of High Temperature Resin/Carbon Nanofiber Composites

    NASA Technical Reports Server (NTRS)

    Ghose, Sayata; Watson, Kent A.; Working, Dennis C.; Criss, Jim M.; Siochi, Emilie J.; Connell, John W.

    2005-01-01

    Multifunctional composites present a route to structural weight reduction. Nanoparticles such as carbon nanofibers (CNF) provide a compromise as a lower cost nanosize reinforcement that yields a desirable combination of properties. Blends of PETI-330 and CNFs were prepared and characterized to investigate the potential of CNF composites as a high performance structural medium. Dry mixing techniques were employed and the effect of CNF loading level on melt viscosity was determined. The resulting powders were characterized for degree of mixing, thermal and rheological properties. Based on the characterization results, samples containing 30 and 40 wt% CNF were scaled up to approx.300 g and used to fabricate moldings 10.2 cm x 15.2 cm x 0.32 cm thick. The moldings were fabricated by injecting the mixtures at 260-280 C into a stainless steel tool followed by curing for 1 h at 371 C. The tool was designed to impart high shear during the process in an attempt to achieve some alignment of CNFs in the flow direction. Moldings were obtained that were subsequently characterized for thermal, mechanical and electrical properties. The degree of dispersion and alignment of CNFs were investigated using high-resolution scanning electron microscopy. The preparation and preliminary characterization of PETI-330/CNF composites are discussed. Keywords: resins, carbon nanofibers, scanning electron microscopy, electrical properties, thermal conductivity,injection

  7. In vitro cardiomyocyte-driven biogenerator based on aligned piezoelectric nanofibers

    NASA Astrophysics Data System (ADS)

    Liu, Xia; Zhao, Hui; Lu, Yingxian; Li, Song; Lin, Liwei; Du, Yanan; Wang, Xiaohong

    2016-03-01

    Capturing the body's mechanical energy from the heart, lungs, and diaphragm can probably meet the requirements for in vivo applications of implantable biomedical devices. In this work, we present a novel contractile cardiomyocyte (CM)-driven biogenerator based on piezoelectric nanofibers (NFs) uniaxially aligned on a PDMS thin film. Flexible nanostructures interact with the CMs, as a physical cue to guide the CMs to align in a specific way, and create mechanical interfaces of contractile CMs and piezoelectric NFs. As such, the cellular construct features specific alignment and synchronous contraction, which realizes the maximal resultant force to drive the NFs to bend periodically. Studies on contraction mapping show that neonatal rat CMs self-assemble into a functional bio-bot film with well-defined axes of force generation. Consequently, the biogenerator produces an average voltage of 200 mV and current of 45 nA at the cell concentration of 1.0 million per ml, offering a biocompatible and scalable platform for biological energy conversion.Capturing the body's mechanical energy from the heart, lungs, and diaphragm can probably meet the requirements for in vivo applications of implantable biomedical devices. In this work, we present a novel contractile cardiomyocyte (CM)-driven biogenerator based on piezoelectric nanofibers (NFs) uniaxially aligned on a PDMS thin film. Flexible nanostructures interact with the CMs, as a physical cue to guide the CMs to align in a specific way, and create mechanical interfaces of contractile CMs and piezoelectric NFs. As such, the cellular construct features specific alignment and synchronous contraction, which realizes the maximal resultant force to drive the NFs to bend periodically. Studies on contraction mapping show that neonatal rat CMs self-assemble into a functional bio-bot film with well-defined axes of force generation. Consequently, the biogenerator produces an average voltage of 200 mV and current of 45 nA at the cell

  8. Decreased functions of astrocytes on carbon nanofiber materials.

    PubMed

    McKenzie, Janice L; Waid, Michael C; Shi, Riyi; Webster, Thomas J

    2004-01-01

    Carbon nanofibers possess excellent conductivity properties, which may be beneficial in the design of more effective neural prostheses; however, limited evidence on their cytocompatibility properties currently exists. The objective of the present in vitro study was to determine cytocompatibility properties of formulations containing carbon nanofibers pertinent to neural implant applications. Substrates were prepared from four different types of carbon fibers, two with nanoscale diameters (nanophase, or less than or equal to 100 nm) and two with conventional diameters (or greater than 100 nm). Within these two categories, both a high and a low surface energy fiber were investigated and tested. Carbon fibers were compacted in a manual hydraulic press via a uniaxial loading cycle. Astrocytes (glial scar tissue-forming cells) were seeded onto the substrates for adhesion, proliferation, and long-term function studies (such as total intracellular protein and alkaline phosphatase activity). Results provided the first evidence that astrocytes preferentially adhered and proliferated on carbon fibers that had the largest diameter and the lowest surface energy. Based on these results, composite substrates were also formed using different weight percentages (0-25 wt%) of the nanophase, high surface energy fibers in a polycarbonate urethane matrix. Results provided the first evidence of decreased adhesion of astrocytes with increasing weight percents of the high surface energy carbon nanofibers in the polymer composite; this further demonstrates that formulations containing carbon fibers in the nanometer regime may limit astrocyte functions leading to decreased glial scar tissue formation. Positive interactions with neurons, and, at the same time, limited astrocyte functions leading to decreased gliotic scar tissue formation are essential for increased neuronal implant efficacy.

  9. Physicochemical investigations of carbon nanofiber supported Cu / ZrO2 catalyst

    NASA Astrophysics Data System (ADS)

    Din, Israf Ud; Shaharun, Maizatul S.; Subbarao, Duvvuri; Naeem, A.

    2014-10-01

    Zirconia-promoted copper/carbon nanofiber catalysts (Cu - ZrO2/ CNF ) were prepared by the sequential deposition precipitation method. The Herringbone type of carbon nanofiber GNF-100 (Graphite nanofiber) was used as a catalyst support. Carbon nanofiber was oxidized to (CNF-O) with 5% and 65 % concentration of nitric acid (HNO3). The CNF activated with 5% HNO3 produced higher surface area which is 155 m2/g. The catalyst was characterized by X-ray Diffraction (XRD), Fourier Transform Infra-Red (FTIR) and N2 adsorption-desorption. The results showed that increase of HNO3 concentration reduced the surface area and porosity of the catalyst.

  10. Preparation of porous carbon nanofibers derived from PBI/PLLA for supercapacitor electrodes

    NASA Astrophysics Data System (ADS)

    Jung, Kyung-Hye; Ferraris, John P.

    2016-10-01

    Porous carbon nanofibers were prepared by electrospinning blend solutions of polybenzimidazole/poly-L-lactic acid (PBI/PLLA) and carbonization. During thermal treatment, PLLA was decomposed, resulting in the creation of pores in the carbon nanofibers. From SEM images, it is shown that carbon nanofibers had diameters in the range of 100-200 nm. The conversion of PBI to carbon was confirmed by Raman spectroscopy, and the surface area and pore volume of carbon nanofibers were determined using nitrogen adsorption/desorption analyses. To investigate electrochemical performances, coin-type cells were assembled using free-standing carbon nanofiber electrodes and ionic liquid electrolyte. cyclic voltammetry studies show that the PBI/PLLA-derived porous carbon nanofiber electrodes have higher capacitance due to lower electrochemical impedance compared to carbon nanofiber electrode from PBI only. These porous carbon nanofibers were activated using ammonia for further porosity improvement and annealed to remove the surface functional groups to better match the polarity of electrode and electrolyte. Ragone plots, correlating energy density with power density calculated from galvanostatic charge-discharge curves, reveal that activation/annealing further improves energy and power densities.

  11. Preparation of porous carbon nanofibers derived from PBI/PLLA for supercapacitor electrodes.

    PubMed

    Jung, Kyung-Hye; Ferraris, John P

    2016-10-21

    Porous carbon nanofibers were prepared by electrospinning blend solutions of polybenzimidazole/poly-L-lactic acid (PBI/PLLA) and carbonization. During thermal treatment, PLLA was decomposed, resulting in the creation of pores in the carbon nanofibers. From SEM images, it is shown that carbon nanofibers had diameters in the range of 100-200 nm. The conversion of PBI to carbon was confirmed by Raman spectroscopy, and the surface area and pore volume of carbon nanofibers were determined using nitrogen adsorption/desorption analyses. To investigate electrochemical performances, coin-type cells were assembled using free-standing carbon nanofiber electrodes and ionic liquid electrolyte. cyclic voltammetry studies show that the PBI/PLLA-derived porous carbon nanofiber electrodes have higher capacitance due to lower electrochemical impedance compared to carbon nanofiber electrode from PBI only. These porous carbon nanofibers were activated using ammonia for further porosity improvement and annealed to remove the surface functional groups to better match the polarity of electrode and electrolyte. Ragone plots, correlating energy density with power density calculated from galvanostatic charge-discharge curves, reveal that activation/annealing further improves energy and power densities. PMID:27632072

  12. Preparation of porous carbon nanofibers derived from PBI/PLLA for supercapacitor electrodes.

    PubMed

    Jung, Kyung-Hye; Ferraris, John P

    2016-10-21

    Porous carbon nanofibers were prepared by electrospinning blend solutions of polybenzimidazole/poly-L-lactic acid (PBI/PLLA) and carbonization. During thermal treatment, PLLA was decomposed, resulting in the creation of pores in the carbon nanofibers. From SEM images, it is shown that carbon nanofibers had diameters in the range of 100-200 nm. The conversion of PBI to carbon was confirmed by Raman spectroscopy, and the surface area and pore volume of carbon nanofibers were determined using nitrogen adsorption/desorption analyses. To investigate electrochemical performances, coin-type cells were assembled using free-standing carbon nanofiber electrodes and ionic liquid electrolyte. cyclic voltammetry studies show that the PBI/PLLA-derived porous carbon nanofiber electrodes have higher capacitance due to lower electrochemical impedance compared to carbon nanofiber electrode from PBI only. These porous carbon nanofibers were activated using ammonia for further porosity improvement and annealed to remove the surface functional groups to better match the polarity of electrode and electrolyte. Ragone plots, correlating energy density with power density calculated from galvanostatic charge-discharge curves, reveal that activation/annealing further improves energy and power densities.

  13. Order in vertically aligned carbon nanotube arrays

    SciTech Connect

    Wang, Hsin; Xu, Z; Eres, Gyula

    2006-01-01

    We report the direct measurements on the bulk morphology of vertically aligned multiwalled carbon nanotube (CNT) arrays using small angle neutron scattering (SANS). SANS measurements at different heights of CNT arrays corresponding to different stages of the growth reveal increasing alignment order along the thickness and two distinctly different CNT morphologies. The observations suggest that the evolution of the macroscopic CNT morphologies be driven by competing collective growth and spatial constraints.

  14. Nanowire-directed templating synthesis of metal-organic framework nanofibers and their derived porous doped carbon nanofibers for enhanced electrocatalysis.

    PubMed

    Zhang, Wang; Wu, Zhen-Yu; Jiang, Hai-Long; Yu, Shu-Hong

    2014-10-15

    A nanowire-directed templating synthesis of metal-organic framework (MOF) nanofibers has been demonstrated, where ultrathin tellurium nanowires (TeNWs) with excellent dispersivity can act as templates for directed growth and assembly of ZIF-8 nanocrystals (one typical MOF), resulting in the formation of uniform ZIF-8 nanofibers. The as-obtained ZIF-8 nanofibers can be conveniently converted into highly porous doped carbon nanofibers by calcination. Compared with bulk porous carbon by direct carbonization of MOF crystals, these doped carbon nanofibers exhibit complex network structure, hierarchical pores, and high surface area. Further doped by phosphorus species, the co-doped carbon nanofibers exhibit excellent electrocatalytic performance for oxygen reduction reaction, even better than the benchmark Pt/C catalyst.

  15. An efficient template synthesis of aligned boron carbide nanofibers using a single-source molecular precursor

    SciTech Connect

    Pender, M.J.; Sneddon, L.G.

    2000-02-01

    Boron carbide is a highly refractory material that is of great interest for both its structural and electronic properties. Of particular importance are its high-temperature stability, high hardness, high cross section for neutron capture, and excellent high-temperature thermoelectric properties. This combination of properties gives rise to numerous applications, including uses as an abrasive wear-resistant material, ceramic armor, a neutron moderator in nuclear reactors, and, potentially, for power generation in deep-space flight applications. In this communication , the authors report a simple, straightforward method for the generation of aligned, monodispersed boron carbide nanofibers based on the use of the porous alumina templating technique in combination with a new single-source molecular precursor.

  16. In vitro cardiomyocyte-driven biogenerator based on aligned piezoelectric nanofibers.

    PubMed

    Liu, Xia; Zhao, Hui; Lu, Yingxian; Li, Song; Lin, Liwei; Du, Yanan; Wang, Xiaohong

    2016-04-01

    Capturing the body's mechanical energy from the heart, lungs, and diaphragm can probably meet the requirements for in vivo applications of implantable biomedical devices. In this work, we present a novel contractile cardiomyocyte (CM)-driven biogenerator based on piezoelectric nanofibers (NFs) uniaxially aligned on a PDMS thin film. Flexible nanostructures interact with the CMs, as a physical cue to guide the CMs to align in a specific way, and create mechanical interfaces of contractile CMs and piezoelectric NFs. As such, the cellular construct features specific alignment and synchronous contraction, which realizes the maximal resultant force to drive the NFs to bend periodically. Studies on contraction mapping show that neonatal rat CMs self-assemble into a functional bio-bot film with well-defined axes of force generation. Consequently, the biogenerator produces an average voltage of 200 mV and current of 45 nA at the cell concentration of 1.0 million per ml, offering a biocompatible and scalable platform for biological energy conversion. PMID:26976074

  17. Hemoglobin regulates the migration of glioma cells along poly(ε-caprolactone)-aligned nanofibers.

    PubMed

    Roth, Alexander D; Elmer, Jacob; Harris, David R; Huntley, Joseph; Palmer, Andre F; Nelson, Tyler; Johnson, Jed K; Xue, Ruipeng; Lannutti, John J; Viapiano, Mariano S

    2014-01-01

    Aligned fibers have been shown to facilitate cell migration in the direction of fiber alignment while oxygen (O2 )-carrying solutions improve the metabolism of cells in hypoxic culture. Therefore, U251 aggregate migration on poly(ε-caprolactone) (PCL)-aligned fibers was studied in cell culture media supplemented with the O2 storage and transport protein hemoglobin (Hb) obtained from bovine, earthworm and human sources at concentrations ranging from 0 to 5 g/L within a cell culture incubator exposed to O2 tensions ranging from 1 to 19% O2 . Individual cell migration was quantified using a wound healing assay. In addition, U251 cell aggregates were developed and aggregate dispersion/cell migration quantified on PCL-aligned fibers. The results of this work show that the presence of bovine or earthworm Hb improved individual cell viability at 1% O2 , while human Hb adversely affected cell viability at increasing Hb concentrations and decreasing O2 levels. The control data suggests that decreasing the O2 tension in the incubator from 5 to 1% O2 decreased aggregate dispersion on the PCL-aligned fibers. However, the addition of bovine Hb at 5% O2 significantly improved aggregate dispersion. At 19% O2 , Hb did not impact aggregate dispersion. Also at 1% O2 , aggregate dispersion appeared to increase in the presence of earthworm Hb, but only at the latter time points. Taken together, these results show that Hb-based O2 carriers can be utilized to improve O2 availability and the migration of glioma spheroids on nanofibers. PMID:25044995

  18. High Performance Flexible Piezoelectric Nanogenerators based on BaTiO3 Nanofibers in Different Alignment Modes.

    PubMed

    Yan, Jing; Jeong, Young Gyu

    2016-06-22

    Piezoelectric nanogenerators, harvesting energy from mechanical stimuli in our living environments, hold great promise to power sustainable self-sufficient micro/nanosystems and mobile/portable electronics. BaTiO3 as a lead-free material with high piezoelectric coefficient and dielectric constant has been widely examined to realize nanogenerators, capacitors, sensors, etc. In this study, polydimethylsiloxane (PDMS)-based flexible composites including BaTiO3 nanofibers with different alignment modes were manufactured and their piezoelectric performance was examined. For the study, BaTiO3 nanofibers were prepared by an electrospinning technique utilizing a sol-gel precursor and following calcination process, and they were then aligned vertically or horizontally or randomly in PDMS matrix-based nanogenerators. The morphological structures of BaTiO3 nanofibers and their nanogenerators were analyzed by using SEM images. The crystal structures of the nanogenerators before and after poling were characterized by X-ray diffraction. The dielectric and piezoelectric properties of the nanogenerators were investigated as a function of the nanofiber alignment mode. The nanogenerator with BaTiO3 nanofibers aligned vertically in the PDMS matrix sheet achieved high piezoelectric performance of an output power of 0.1841 μW with maximum voltage of 2.67 V and current of 261.40 nA under a low mechanical stress of 0.002 MPa, in addition to a high dielectric constant of 40.23 at 100 Hz. The harvested energy could thus power a commercial LED directly or be stored into capacitors after rectification.

  19. High Performance Flexible Piezoelectric Nanogenerators based on BaTiO3 Nanofibers in Different Alignment Modes.

    PubMed

    Yan, Jing; Jeong, Young Gyu

    2016-06-22

    Piezoelectric nanogenerators, harvesting energy from mechanical stimuli in our living environments, hold great promise to power sustainable self-sufficient micro/nanosystems and mobile/portable electronics. BaTiO3 as a lead-free material with high piezoelectric coefficient and dielectric constant has been widely examined to realize nanogenerators, capacitors, sensors, etc. In this study, polydimethylsiloxane (PDMS)-based flexible composites including BaTiO3 nanofibers with different alignment modes were manufactured and their piezoelectric performance was examined. For the study, BaTiO3 nanofibers were prepared by an electrospinning technique utilizing a sol-gel precursor and following calcination process, and they were then aligned vertically or horizontally or randomly in PDMS matrix-based nanogenerators. The morphological structures of BaTiO3 nanofibers and their nanogenerators were analyzed by using SEM images. The crystal structures of the nanogenerators before and after poling were characterized by X-ray diffraction. The dielectric and piezoelectric properties of the nanogenerators were investigated as a function of the nanofiber alignment mode. The nanogenerator with BaTiO3 nanofibers aligned vertically in the PDMS matrix sheet achieved high piezoelectric performance of an output power of 0.1841 μW with maximum voltage of 2.67 V and current of 261.40 nA under a low mechanical stress of 0.002 MPa, in addition to a high dielectric constant of 40.23 at 100 Hz. The harvested energy could thus power a commercial LED directly or be stored into capacitors after rectification. PMID:27237223

  20. Electricity Generation from Microbial Fuel Cell with Polypyrrole-Coated Carbon Nanofiber Composite.

    PubMed

    Roh, Sung-Hee

    2015-02-01

    Polyacrylonitrile (PAN) nanofibers, with and without embedded carbon nanotubes (CNTs) were fabricated by the electrospinning process. Polypyrrole (PPy) was coated on the activated PAN/CNT nanofiber by in-situ chemical polymerization in order to improve the electrochemical performance. The electrocatalytic behaviors of the PPy-PAN/CNT composite anode were investigated by means of cyclic voltammetry to evaluate as the anode for microbial fuel cells (MFCs) application. In comparison with unmodified carbon cloth (CC) anodes, PPy-PAN/CNT nanofiber composite showed the improvement of the maximum power density by 40%. The PPy-PAN/CNT nanofiber composite electrode therefore offers good prospects for application in MFCs. PMID:26353717

  1. Synthesis, characterization and formation process of transition metal oxide nanotubes using carbon nanofibers as templates

    SciTech Connect

    Ogihara, Hitoshi; Masahiro, Sadakane; Nodasaka, Yoshinobu; Ueda, Wataru

    2009-06-15

    Mono and binary transition metal oxide nanotubes could be synthesized by the immersion of carbon nanofiber templates into metal nitrate solutions and removal of the templates by heat treatment in air. The transition metal oxide nanotubes were composed of nano-crystallites of metal oxides. The functional groups on the carbon nanofiber templates were essential for the coating of these templates: they acted as adsorption sites for the metal nitrates, ensuring a uniform metal oxide coating. During the removal of the carbon nanofiber templates by calcination in air, the metal oxide coatings promoted the combustion reaction between the carbon nanofibers and oxygen. - Graphical abstract: Mono and binary transition metal-oxide nanotubes could be synthesized by the immersion of carbon nanofiber templates into metal nitrate solutions and removal of the templates by heat treatment in air.

  2. Occupational nanosafety considerations for carbon nanotubes and carbon nanofibers.

    PubMed

    Castranova, Vincent; Schulte, Paul A; Zumwalde, Ralph D

    2013-03-19

    Carbon nanotubes (CNTs) are carbon atoms arranged in a crystalline graphene lattice with a tubular morphology. CNTs exhibit high tensile strength, possess unique electrical properties, are durable, and can be functionalized. These properties allow applications as structural materials, in electronics, as heating elements, in batteries, in the production of stain-resistant fabric, for bone grafting and dental implants, and for targeted drug delivery. Carbon nanofibers (CNFs) are strong, flexible fibers that are currently used to produce composite materials. Agitation can lead to aerosolized CNTs and CNFs, and peak airborne particulate concentrations are associated with workplace activities such as weighing, transferring, mixing, blending, or sonication. Most airborne CNTs or CNFs found in workplaces are loose agglomerates of micrometer diameter. However, due to their low density, they linger in workplace air for a considerable time, and a large fraction of these structures are respirable. In rat and mouse models, pulmonary exposure to single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), or CNFs causes the following pulmonary reactions: acute pulmonary inflammation and injury, rapid and persistent formation of granulomatous lesions at deposition sites of large CNT agglomerates, and rapid and progressive alveolar interstitial fibrosis at deposition sites of more dispersed CNT or CNF structures. Pulmonary exposure to SWCNTs can induce oxidant stress in aortic tissue and increases plaque formation in an atherosclerotic mouse model. Pulmonary exposure to MWCNTs depresses the ability of coronary arterioles to respond to dilators. These cardiovascular effects may result from neurogenic signals from sensory irritant receptors in the lung. Pulmonary exposure to MWCNTs also upregulates mRNA for inflammatory mediators in selected brain regions, and pulmonary exposure to SWCNTs upregulates the baroreceptor reflex. In addition, pulmonary exposure to

  3. Occupational nanosafety considerations for carbon nanotubes and carbon nanofibers.

    PubMed

    Castranova, Vincent; Schulte, Paul A; Zumwalde, Ralph D

    2013-03-19

    Carbon nanotubes (CNTs) are carbon atoms arranged in a crystalline graphene lattice with a tubular morphology. CNTs exhibit high tensile strength, possess unique electrical properties, are durable, and can be functionalized. These properties allow applications as structural materials, in electronics, as heating elements, in batteries, in the production of stain-resistant fabric, for bone grafting and dental implants, and for targeted drug delivery. Carbon nanofibers (CNFs) are strong, flexible fibers that are currently used to produce composite materials. Agitation can lead to aerosolized CNTs and CNFs, and peak airborne particulate concentrations are associated with workplace activities such as weighing, transferring, mixing, blending, or sonication. Most airborne CNTs or CNFs found in workplaces are loose agglomerates of micrometer diameter. However, due to their low density, they linger in workplace air for a considerable time, and a large fraction of these structures are respirable. In rat and mouse models, pulmonary exposure to single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), or CNFs causes the following pulmonary reactions: acute pulmonary inflammation and injury, rapid and persistent formation of granulomatous lesions at deposition sites of large CNT agglomerates, and rapid and progressive alveolar interstitial fibrosis at deposition sites of more dispersed CNT or CNF structures. Pulmonary exposure to SWCNTs can induce oxidant stress in aortic tissue and increases plaque formation in an atherosclerotic mouse model. Pulmonary exposure to MWCNTs depresses the ability of coronary arterioles to respond to dilators. These cardiovascular effects may result from neurogenic signals from sensory irritant receptors in the lung. Pulmonary exposure to MWCNTs also upregulates mRNA for inflammatory mediators in selected brain regions, and pulmonary exposure to SWCNTs upregulates the baroreceptor reflex. In addition, pulmonary exposure to

  4. Controlled Deposition and Alignment of Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Smits, Jan M. (Inventor); Wincheski, Russell A. (Inventor); Patry, JoAnne L. (Inventor); Watkins, Anthony Neal (Inventor); Jordan, Jeffrey D. (Inventor)

    2012-01-01

    A carbon nanotube (CNT) attraction material is deposited on a substrate in the gap region between two electrodes on the substrate. An electric potential is applied to the two electrodes. The CNT attraction material is wetted with a solution defined by a carrier liquid having carbon nanotubes (CNTs) suspended therein. A portion of the CNTs align with the electric field and adhere to the CNT attraction material. The carrier liquid and any CNTs not adhered to the CNT attraction material are then removed.

  5. Controlled Deposition and Alignment of Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Smits, Jan M. (Inventor); Wincheski, Russell A. (Inventor); Ingram, JoAnne L. (Inventor); Watkins, Anthony Neal (Inventor); Jordan, Jeffrey D. (Inventor)

    2009-01-01

    A carbon nanotube (CNT) attraction material is deposited on a substrate in the gap region between two electrodes on the . substrate. An electric potential is applied to the two electrodes. The CNT attraction material is wetted with a solution defined by a carver liquid having carbon nanotubes (CNTs) suspended therein. A portion of the CNTs align with the electric field and adhere to The CNT attraction material. The carrier liquid and any CNTs not adhered to the CNT attraction material are then removed.

  6. Carbon-coated Li3 N nanofibers for advanced hydrogen storage.

    PubMed

    Xia, Guanglin; Li, Dan; Chen, Xiaowei; Tan, Yingbin; Tang, Ziwei; Guo, Zaiping; Liu, Huakun; Liu, Zongwen; Yu, Xuebin

    2013-11-20

    3D porous carbon-coated Li3 N nanofibers are successfully fabricated via the electrospinning technique. The as-prepared nanofibers exhibit a highly improved hydrogen-sorption performance in terms of both thermodynamics and kinetics. More interestingly, a stable regeneration can be achieved due to the unique structure of the nanofibers, over 10 cycles of H2 sorption at a temperature as low as 250 °C.

  7. Preparation of Size-Controlled Hat-Stacked Carbon Nanofibers

    NASA Astrophysics Data System (ADS)

    Sato, Y.; Yokoyama, A.; Motomiya, K.; Jeyadevan, B.; Tohji, K.

    2007-03-01

    Hat-stacked carbon nanofibers (H-CNFs) were size-separated using a multi-step microfiltration process employing polycarbonate membrane filters with respective cylindrical pore diameters of 2.0, 1.2 and 0.4 μm after being cut and dispersed in distilled water using sonication in a mixture of concentrated H2SO4 and HNO3. The average length of separated H-CNFs was 2.4 μm, 1.2 μm and 0.6 μm, respectively.

  8. Electrospun aligned PLGA and PLGA/gelatin nanofibers embedded with silica nanoparticles for tissue engineering.

    PubMed

    Mehrasa, Mohammad; Asadollahi, Mohammad Ali; Ghaedi, Kamran; Salehi, Hossein; Arpanaei, Ayyoob

    2015-08-01

    Aligned poly lactic-co-glycolic acid (PLGA) and PLGA/gelatin nanofibrous scaffolds embedded with mesoporous silica nanoparticles (MSNPs) were fabricated using electrospinning method. The mean diameters of nanofibers were 641±24 nm for the pure PLGA scaffolds vs 418±85 nm and 267±58 nm for the PLGA/10 wt% MSNPs and the PLGA/gelatin/10 wt% MSNPs scaffolds, respectively. The contact angle measurement results (102°±6.7 for the pure PLGA scaffold vs 81°±6.8 and 18°±8.7 for the PLGA/10 wt% MSNPs and the PLGA/gelatin/10 wt% MSNPs scaffolds, respectively) revealed enhanced hydrophilicity of scaffolds upon incorporation of gelatin and MSNPs. Besides, embedding the scaffolds with MSNPs resulted in improved tensile mechanical properties. Cultivation of PC12 cells on the scaffolds demonstrated that introduction of MSNPs into PLGA and PLGA/gelatin matrices leads to the improved cell attachment and proliferation as well as long cellular processes. DAPI staining results indicated that cell proliferations on the PLGA/10 wt% MSNPs and the PLGA/gelatin/10 wt% MSNPs scaffolds were strikingly (nearly 2.5 and 3 folds, respectively) higher than that on the aligned pure PLGA scaffolds. These results suggest superior properties of silica nanoparticles-incorporated PLGA/gelatin eletrospun nanofibrous scaffolds for the stem cell culture and tissue engineering applications.

  9. Fabrication of Aligned Nanofiber Polymer Yarn Networks for Anisotropic Soft Tissue Scaffolds.

    PubMed

    Wu, Shaohua; Duan, Bin; Liu, Penghong; Zhang, Caidan; Qin, Xiaohong; Butcher, Jonathan T

    2016-07-01

    Nanofibrous scaffolds with defined architectures and anisotropic mechanical properties are attractive for many tissue engineering and regenerative medicine applications. Here, a novel electrospinning system is developed and implemented to fabricate continuous processable uniaxially aligned nanofiber yarns (UANY). UANY were processed into fibrous tissue scaffolds with defined anisotropic material properties using various textile-forming technologies, i.e., braiding, weaving, and knitting techniques. UANY braiding dramatically increased overall stiffness and strength compared to the same number of UANY unbraided. Human adipose derived stem cells (HADSC) cultured on UANY or woven and knitted 3D scaffolds aligned along local fiber direction and were >90% viable throughout 21 days. Importantly, UANY supported biochemical induction of HADSC differentiation toward smooth muscle and osteogenic lineages. Moreover, we integrated an anisotropic woven fiber mesh within a bioactive hydrogel to mimic the complex microstructure and mechanical behavior of valve tissues. Human aortic valve interstitial cells (HAVIC) and human aortic root smooth muscle cells (HASMC) were separately encapsulated within hydrogel/woven fabric composite scaffolds for generating scaffolds with anisotropic biomechanics and valve ECM like microenvironment for heart valve tissue engineering. UANY have great potential as building blocks for generating fiber-shaped tissues or tissue microstructures with complex architectures.

  10. Label-free detection of C-reactive protein using a carbon nanofiber based biosensor

    PubMed Central

    Gupta, Rakesh K.; Periyakaruppan, Adaikkappan; Meyyappan, M.; Koehne, Jessica E.

    2014-01-01

    We report the sensitive detection of C-reactive protein (CRP), a biomarker for cardiac disease, using a carbon nanofiber based biosensor platform. Vertically aligned carbon nanofibers were grown using plasma enhanced chemical vapor deposition to fabricate nanoelectrode arrays in a 3 X 3 configuration. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used for the CRP detection. The CV responses show a 25 % reduction in redox current upon the immobilization of anti-CRP on the electrode where as a 30% increase in charge transfer resistance is seen from EIS. Further reduction in redox current and increase in charge transfer resistance result from binding of CRP on anti-CRP immobilized surface, proportional to the concentration of the CRP target. The detection limit of the sensor is found to be ~90 pM or ~11 ng/ml, which is in the clinically relevant range. Control tests using non-specific myoglobin antigen confirmed the specificity of the present approach. PMID:24709327

  11. Making Macroscopic Assemblies of Aligned Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Smalley, Richard E.; Colbert, Daniel T.; Smith, Ken A.; Walters, Deron A.; Casavant, Michael J.; Qin, Xiaochuan; Yakobson, Boris; Hauge, Robert H.; Saini, Rajesh Kumar; Chiung, Wan-Ting; Huffman, Charles B.

    2005-01-01

    A method of aligning and assembling single-wall carbon nanotubes (SWNTs) to fabricate macroscopic structures has been invented. The method entails suspending SWNTs in a fluid, orienting the SWNTs by use of a magnetic and/or electric field, and then removing the aligned SWNTs from suspension in such a way as to assemble them while maintaining the alignment. SWNTs are essentially tubular extensions of fullerene molecules. It is desirable to assemble aligned SWNTs into macroscopic structures because the common alignment of the SWNTs in such a structure makes it possible to exploit, on a macroscopic scale, the unique mechanical, chemical, and electrical properties that individual oriented SWNTs exhibit at the molecular level. Because of their small size and high electrical conductivity, carbon nanotubes, and especially SWNTs, are useful for making electrical connectors in integrated circuits. Carbon nanotubes can be used as antennas at optical frequencies, and as probes in scanning tunneling microscopes, atomic-force microscopes, and the like. Carbon nanotubes can be used with or instead of carbon black in tires. Carbon nanotubes are useful as supports for catalysts. Ropes of SWNTs are metallic and, as such, are potentially useful in some applications in which electrical conductors are needed - for example, they could be used as additives in formulating electrically conductive paints. Finally, macroscopic assemblies of aligned SWNTs can serve as templates for the growth of more and larger structures of the same type. The great variety of tubular fullerene molecules and of the structures that could be formed by assembling them in various ways precludes a complete description of the present method within the limits of this article. It must suffice to present a typical example of the use of one of many possible variants of the method to form a membrane comprising SWNTs aligned substantially parallel to each other in the membrane plane. The apparatus used in this variant

  12. Thermal conductivity of tubrostratic carbon nanofiber networks

    DOE PAGES

    Bauer, Matthew L.; Saltonstall, Chris B.; Leseman, Zayd C.; Beechem, Thomas E.; Hopkins, Patrick E.; Norris, Pamela M.

    2016-01-01

    Composite material systems composed of a matrix of nano materials can achieve combinations of mechanical and thermophysical properties outside the range of traditional systems. While many reports have studied the intrinsic thermal properties of individual carbon fibers, to be useful in applications in which thermal stability is critical, an understanding of heat transport in composite materials is required. In this work, air/ carbon nano fiber networks are studied to elucidate the system parameters influencing thermal transport. Sample thermal properties are measured with varying initial carbon fiber fill fraction, environment pressure, loading pressure, and heat treatment temperature through a bidirectional modificationmore » of the 3ω technique. The nanostructures of the individual fibers are characterized with small angle x-ray scattering and Raman spectroscopy providing insight to individual fiber thermal conductivity. Measured thermal conductivity varied from 0.010 W/(m K) to 0.070 W/(m K). An understanding of the intrinsic properties of the individual fibers and the interactions of the two phase composite is used to reconcile low measured thermal conductivities with predictive modeling. This methodology can be more generally applied to a wide range of fiber composite materials and their applications.« less

  13. Thermal conductivity of tubrostratic carbon nanofiber networks

    SciTech Connect

    Bauer, Matthew L.; Saltonstall, Chris B.; Leseman, Zayd C.; Beechem, Thomas E.; Hopkins, Patrick E.; Norris, Pamela M.

    2016-01-01

    Composite material systems composed of a matrix of nano materials can achieve combinations of mechanical and thermophysical properties outside the range of traditional systems. While many reports have studied the intrinsic thermal properties of individual carbon fibers, to be useful in applications in which thermal stability is critical, an understanding of heat transport in composite materials is required. In this work, air/ carbon nano fiber networks are studied to elucidate the system parameters influencing thermal transport. Sample thermal properties are measured with varying initial carbon fiber fill fraction, environment pressure, loading pressure, and heat treatment temperature through a bidirectional modification of the 3ω technique. The nanostructures of the individual fibers are characterized with small angle x-ray scattering and Raman spectroscopy providing insight to individual fiber thermal conductivity. Measured thermal conductivity varied from 0.010 W/(m K) to 0.070 W/(m K). An understanding of the intrinsic properties of the individual fibers and the interactions of the two phase composite is used to reconcile low measured thermal conductivities with predictive modeling. This methodology can be more generally applied to a wide range of fiber composite materials and their applications.

  14. Carbon nanofiber polymer composites: evaluation of life cycle energy use.

    PubMed

    Khanna, Vikas; Bakshi, Bhavik R

    2009-03-15

    Holistic evaluation of emerging nanotechnologies using systems analysis is pivotal for guiding their safe and sustainable development. While toxicity studies of engineered nanomaterials are essential, understanding of the potential large scale impacts of nanotechnology is also critical for developing sustainable nanoproducts. This work evaluates the life cycle energetic impact associated with the production and use of carbon nanofiber (CNF) reinforced polymer nanocomposites (PNC). Specifically, both simple CNF and carbon nanofiber-glass fiber (CNF-GF) hybrid PNCs are evaluated and compared with steel for equal stiffness design. Life cycle inventory is developed based on published literature and best available engineering information. A cradle-to-gate comparison suggests that for equal stiffness design, CNF reinforced PNCs are 1.6-12 times more energy intensive than steel. It is anticipated that the product use phase may strongly influence whether any net savings in life cycle energy consumption can be realized. A case study involving the use of CNF and CNF-GF reinforced PNCs in the body panels of automobiles highlights that the use of PNCs with lower CNF loading ratios has the potential for net life cycle energy savings relative to steel owing to improved fuel economy benefits. Other factors such as cost, toxicity impact of CNF, and end-of-life issues specific to CNFs need to be considered to evaluate the final economic and environmental performance of CNF reinforced PNC materials.

  15. Chlorine effect on the formation of carbon nanofibers.

    PubMed

    Lin, Wang-Hua; Takahashi, Yusuke; Li, Yuan-Yao; Sakoda, Akiyoshi

    2012-12-01

    Platelet graphite nanofibers (GNFs) and turbostratic carbon nanofibers (CNFs) are synthesized by the thermal evaporation and decomposition of a polymer-based mixture at 700 degrees C using Ni as a catalyst. The mixture consists of poly(ethylene glycol) (PEG), serving as the carbon source, and hydrochloric acid solution (HCl(aq)), serving as the promoter/additive for the growth of CNFs. High-purity zigzag-shaped platelet GNFs form with 10 wt% HCl(aq) as an additive in the PEG. The diameters of the platelet GNFs are in the range of 40-60 nm, with lengths of a few micrometers. High-resolution transmission electron microscopy images indicate a high degree of graphitization and well ordered graphene layers along the fiber axis. In contrast, high-purity turbostratic CNFs form with 20 wt% HCl(aq) in the PEG. The diameter and length of the turbostratic CNFs are 20-40 nm and a few micrometers, respectively. The participation of HCl in the thermal process leads to the formation of Ni-Cl compounds. The amount of chlorine affects the shape of the Ni catalyst, which determines the type of CNF formed. PMID:23447943

  16. Carbon nanofibers derived from cellulose nanofibers as a long-life anode material for rechargeable sodium-ion batteries

    SciTech Connect

    Luo, W; Schardt, J; Bommier, C; Wang, B; Razink, J; Simonsen, J; Ji, XL

    2013-01-01

    A highly reversible anode is indispensable to the future success of sodium-ion batteries (SIBs). Herein, carbon nanofibers (CNFs) derived from cellulose nanofibers are investigated as an anode material for SIBs. The CNFs exhibit very promising electrochemical properties, including a high reversible capacity (255 mA h g(-1) at 40 mA g(-1)), good rate capability (85 mA h g(-1) at 2000 mA g(-1)), and excellent cycling stability (176 mA h g(-1) at 200 mA g(-1) over 600 cycles).

  17. Method for production of polymer and carbon nanofibers from water-soluble polymers.

    PubMed

    Spender, Jonathan; Demers, Alexander L; Xie, Xinfeng; Cline, Amos E; Earle, M Alden; Ellis, Lucas D; Neivandt, David J

    2012-07-11

    Nanometer scale carbon fibers (carbon nanofibers) are of great interest to scientists and engineers in fields such as materials science, composite production, and energy storage due to their unique chemical, physical, and mechanical properties. Precursors currently used for production of carbon nanofibers are primarily from nonrenewable resources. Lignin is a renewable natural polymer existing in all high-level plants that is a byproduct of the papermaking process and a potential feedstock for carbon nanofiber production. The work presented here demonstrates a process involving the rapid freezing of an aqueous lignin solution, followed by sublimation of the resultant ice, to form a uniform network comprised of individual interconnected lignin nanofibers. Carbonization of the lignin nanofibers yields a similarly structured carbon nanofiber network. The methodology is not specific to lignin; nanofibers of other water-soluble polymers have been successfully produced. This nanoscale fibrous morphology has not been observed in traditional cryogel processes, due to the relatively slower freezing rates employed compared to those achieved in this study.

  18. Method for production of polymer and carbon nanofibers from water-soluble polymers.

    PubMed

    Spender, Jonathan; Demers, Alexander L; Xie, Xinfeng; Cline, Amos E; Earle, M Alden; Ellis, Lucas D; Neivandt, David J

    2012-07-11

    Nanometer scale carbon fibers (carbon nanofibers) are of great interest to scientists and engineers in fields such as materials science, composite production, and energy storage due to their unique chemical, physical, and mechanical properties. Precursors currently used for production of carbon nanofibers are primarily from nonrenewable resources. Lignin is a renewable natural polymer existing in all high-level plants that is a byproduct of the papermaking process and a potential feedstock for carbon nanofiber production. The work presented here demonstrates a process involving the rapid freezing of an aqueous lignin solution, followed by sublimation of the resultant ice, to form a uniform network comprised of individual interconnected lignin nanofibers. Carbonization of the lignin nanofibers yields a similarly structured carbon nanofiber network. The methodology is not specific to lignin; nanofibers of other water-soluble polymers have been successfully produced. This nanoscale fibrous morphology has not been observed in traditional cryogel processes, due to the relatively slower freezing rates employed compared to those achieved in this study. PMID:22716198

  19. The Formation of Carbon Nanofibers on Powdered Activated Carbon Impregnated with Nickel

    NASA Astrophysics Data System (ADS)

    Ahmed, Y. M.; Al-Mamun, A. A.; Muyibi, S. A.; Al-Khatib, M. F. R.; Jameel, A. T.; AlSaadi, M. A.

    2009-06-01

    In the present work, the production and characterization of carbon nanofibers (CNFs) composite is reported. Carbon nanofibers (CNF) were produced on powdered activated carbon PAC—impregnated with nickel—by Chemical Vapor Deposition (CVD) of a hydrocarbon in the presence of hydrogen at ˜780° C. The flow rates of carbon source and hydrogen were fixed. The CNFs were formed directly over the impregnated AC. Variable weight percentage ratios of the catalyst salt (Ni+2) were used for the impregnation (1, 3, 5, 7 and 9%, respectively). The product displays a relatively high surface area, essentially constituted by the external surface, and the absence of the bottled pores encountered with activated carbon. FSEM, TEM and TGA were used for the characterization of the product.

  20. Functionalization of vertically aligned carbon nanotubes

    PubMed Central

    Snyders, Rony; Colomer, Jean-François

    2013-01-01

    Summary This review focuses and summarizes recent studies on the functionalization of carbon nanotubes oriented perpendicularly to their substrate, so-called vertically aligned carbon nanotubes (VA-CNTs). The intrinsic properties of individual nanotubes make the VA-CNTs ideal candidates for integration in a wide range of devices, and many potential applications have been envisaged. These applications can benefit from the unidirectional alignment of the nanotubes, the large surface area, the high carbon purity, the outstanding electrical conductivity, and the uniformly long length. However, practical uses of VA-CNTs are limited by their surface characteristics, which must be often modified in order to meet the specificity of each particular application. The proposed approaches are based on the chemical modifications of the surface by functionalization (grafting of functional chemical groups, decoration with metal particles or wrapping of polymers) to bring new properties or to improve the interactions between the VA-CNTs and their environment while maintaining the alignment of CNTs. PMID:23504581

  1. Effects of Microstructure of Carbon Nanofibers for Amperometric Detection of Hydrogen Peroxide

    SciTech Connect

    Li, Zhizhou; Cui, Xiaoli; Zheng, Junsheng; Wang, Qingfei; Lin, Yuehe

    2007-08-10

    Carbon nanofibers (CNFs) with different microstructures, including platelet-carbon nanofibers (PCNFs), fish-bone-carbon nanofibers (FCNFs), and tube-carbon nanofibers (TCNFs), were synthesized, characterized, and evaluated for electrochemical sensing of hydrogen peroxide. The CNFs studied here can show several microstructures in which various stacked morphologies and their sizes and graphite-layer ordering can be well controlled. Glassy carbon (GC) electrodes modified by CNFs were fabricated and compared for amperometric detection of hydrogen peroxide. Sensors of PCNFs/GC, FCNFs/GC, and TCNFs/GC were used in the amperometric detection of H2O2 in a solution of 0.05 M phosphate buffered saline solution (pH 7.4).

  2. Tunable Graphitic Carbon Nano-Onions Development in Carbon Nanofibers for Multivalent Energy Storage

    SciTech Connect

    Schwarz, Haiqing L.

    2016-01-01

    We developed a novel porous graphitic carbon nanofiber material using a synthesis strategy combining electrospinning and catalytic graphitization. RF hydrogel was used as carbon precursors, transition metal ions were successfully introduced into the carbon matrix by binding to the carboxylate groups of a resorcinol derivative. Transition metal particles were homogeneously distributed throughout the carbon matrix, which are used as in-situ catalysts to produce graphitic fullerene-like nanostructures surrounding the metals. The success design of graphitic carbons with enlarged interlayer spacing will enable the multivalent ion intercalation for the development of multivalent rechargeable batteries.

  3. Characterization of polyacrylonitrile based carbon nanofiber mats via electron beam processing.

    PubMed

    Kim, Du-Yeong; Shin, Hye-Kyoung; Jeun, Joon-Pyo; Kim, Hyun-Bin; Oh, Seung-Hwan; Kang, Phil-Hyun

    2012-07-01

    The aim of this study was to evaluate the ability of electron beam irradiation to drive stabilization reactions within PAN nanofiber mats to obtain carbon nanofiber mats. PAN nanofiber mats with fiber diameters of 300-400 nm were prepared via an electrospinning method. Electrospun PAN nanofiber mats were stabilized by electron beam irradiation with various doses up to 5,000 kGy. Using the irradiation-stabilized PAN nanofiber mats, carbon nanofibers were obtained by pyrolysis in a tube furnace for 1 h at 1,000 degrees C under an N2 atmosphere. FT-IR analysis indicated that the transformation of C[triple bond]N groups to C==N groups was accelerated by electron beam stabilization. The thermal behavior of the PAN nanofiber mats was studied using DSC and TGA. DSC thermograms showed that the peak temperatures of the exothermic reactions were found to decrease with increasing electron beam irradiation doses. Irradiation-stabilized PAN nanofiber mats were not observed to dramatically decrease in weight between 290 degrees C and 320 degrees C, an observation presumed to be related to cyclization. The char yields of PAN were found to increase with increasing irradiation doses. PMID:22966719

  4. Synthesis and Characterization of Carbon Nanofibers on Transition Metal Catalysts by Chemical Vapor Deposition.

    PubMed

    Hyun, Yura; Park, Eun-Sil; Mees, Karina; Park, Ho-Seon; Willert-Porada, Monika; Lee, Chang-Seop

    2015-09-01

    Carbon nanofibers were synthesized on transition metal (Fe, Co, Cu) catalysts by Chemical Vapor Deposition (CVD). The variations of thickness and surface of the fibers were investigated according to the concentration of the transition metal. In order to prepare the metal catalysts for synthesis, transition metal nitrate and copper nitrate at a weight ratio were dissolved in distilled water. The obtained catalyst precipitates were filtered and then dried for more than 24 hours at 110 degrees C. Carbon nanofibers were synthesized by using ethylene gas of carbon source by CVD after pulverization of the fully-dried catalyst precipitates. They were characterized by SEM, EDS, Raman, XRD, XPS and TG/DTA, and their specific surface area was measured by BET. The characteristics of the synthesized carbon nanofibers were greatly influenced by the concentration ratio of the metal catalysts. Especially, uniform carbon nanofibers grew when the concentration ratio of Fe and Cu was 7:3, and that of Co and Cu was 6:4. Carbon nanofibers synthesized under such concentration conditions had the best crystallizability, compared to carbon nanofibers synthesized with metal catalysts of different concentration ratios, and revealed high amorphicity as well as high specific surface area. PMID:26716326

  5. Electron gun using carbon-nanofiber field emitter.

    PubMed

    Sakai, Y; Haga, A; Sugita, S; Kita, S; Tanaka, S-I; Okuyama, F; Kobayashi, N

    2007-01-01

    An electron gun constructed using carbon-nanofiber (CNF) emitters and an electrostatic Einzel lens system has been characterized for the development of a high-resolution x-ray source. The CNFs used were grown on tungsten and palladium tips by plasma-enhanced chemical-vapor deposition. Electron beams with the energies of 10

  6. Characterization of Plasma Synthesized Vertical Carbon Nanofibers for Nanoelectronics Applications

    NASA Technical Reports Server (NTRS)

    Lee, Jaesung; Feng, Philip X.-L.; Kaul, Anupama B.

    2013-01-01

    We report on the material characterization of carbon nanofibers (CNFs) which are assembled into a three-dimensional (3D) configuration for making new nanoelectromechanical systems (NEMS). High-resolution scanning electron microscopy (SEM) and x-ray electron dispersive spectroscopy (XEDS) are employed to decipher the morphology and chemical compositions of the CNFs at various locations along individual CNFs grown on silicon (Si) and refractory nitride (NbTiN) substrates, respectively. The measured characteristics suggest interesting properties of the CNF bodies and their capping catalyst nanoparticles, and growth mechanisms on the two substrates. Laser irradiation on the CNFs seems to cause thermal oxidation and melting of catalyst nanoparticles. The structural morphology and chemical compositions of the CNFs revealed in this study should aid in the applications of the CNFs to nanoelectronics and NEMS.

  7. Fabrication and Characterization of Carbon Nanofiber Reinforced Shape Memory Epoxy (CNFR-SME) Composites

    NASA Astrophysics Data System (ADS)

    Wang, Jiuyang

    Shape memory polymers have a wide range of applications due to their ability to mechanically change shapes upon external stimulus, while their achievable composite counterparts prove even more versatile. An overview of literature on shape memory materials, fillers and composites was provided to pave a foundation for the materials used in the current study and their inherent benefits. This study details carbon nanofiber and composite fabrication and contrasts their material properties. In the first section, the morphology and surface chemistry of electrospun-poly(acrylonitrile)-based carbon nanofiber webs were tailored through various fabrication methods and impregnated with a shape memory epoxy. The morphologies, chemical compositions, thermal stabilities and electrical resistivities of the carbon nanofibers and composites were then characterized. In the second section, an overview of thermal, mechanical and shape memory characterization techniques for shape memory polymers and their composites was provided. Thermal and mechanical properties in addition to the kinetic and dynamic shape memory performances of neat epoxy and carbon nanofiber/epoxy composites were characterized. The various carbon nanofiber web modifications proved to have notable influence on their respective composite performances. The results from these two sections lead to an enhanced understanding of these carbon nanofiber reinforced shape memory epoxy composites and provided insight for future studies to tune these composites at will.

  8. Strong magnetic field-assisted growth of carbon nanofibers and its microstructural transformation mechanism

    PubMed Central

    Luo, Chengzhi; Fu, Qiang; Pan, Chunxu

    2015-01-01

    It is well-known that electric and magnetic fields can control the growth direction, morphology and microstructure of one-dimensional carbon nanomaterials (1-DCNMs), which plays a key role for its potential applications in micro-nano-electrics and devices. In this paper, we introduce a novel process for controlling growth of carbon nanofibers (CNFs) with assistance of a strong magnetic field (up to 0.5 T in the center) in a chemical vapor deposition (CVD) system. The results reveal that: 1) The CNFs get bundled when grown in the presence of a strong magnetic field and slightly get aligned parallel to the direction of the magnetic field; 2) The CNFs diameter become narrowed and homogenized with increase of the magnetic field; 3) With the increase of the magnetic field, the microstructure of CNFs is gradually changed, i.e., the strong magnetic field makes the disordered “solid-cored” CNFs transform into a kind of bamboo-liked carbon nanotubes; 4) We propose a mechanism that the reason for these variations and transformation is due to diamagnetic property of carbon atoms, so that it has direction selectivity in the precipitation process. PMID:25761381

  9. Strong magnetic field-assisted growth of carbon nanofibers and its microstructural transformation mechanism.

    PubMed

    Luo, Chengzhi; Fu, Qiang; Pan, Chunxu

    2015-01-01

    It is well-known that electric and magnetic fields can control the growth direction, morphology and microstructure of one-dimensional carbon nanomaterials (1-DCNMs), which plays a key role for its potential applications in micro-nano-electrics and devices. In this paper, we introduce a novel process for controlling growth of carbon nanofibers (CNFs) with assistance of a strong magnetic field (up to 0.5 T in the center) in a chemical vapor deposition (CVD) system. The results reveal that: 1) The CNFs get bundled when grown in the presence of a strong magnetic field and slightly get aligned parallel to the direction of the magnetic field; 2) The CNFs diameter become narrowed and homogenized with increase of the magnetic field; 3) With the increase of the magnetic field, the microstructure of CNFs is gradually changed, i.e., the strong magnetic field makes the disordered "solid-cored" CNFs transform into a kind of bamboo-liked carbon nanotubes; 4) We propose a mechanism that the reason for these variations and transformation is due to diamagnetic property of carbon atoms, so that it has direction selectivity in the precipitation process. PMID:25761381

  10. Strong magnetic field-assisted growth of carbon nanofibers and its microstructural transformation mechanism

    NASA Astrophysics Data System (ADS)

    Luo, Chengzhi; Fu, Qiang; Pan, Chunxu

    2015-03-01

    It is well-known that electric and magnetic fields can control the growth direction, morphology and microstructure of one-dimensional carbon nanomaterials (1-DCNMs), which plays a key role for its potential applications in micro-nano-electrics and devices. In this paper, we introduce a novel process for controlling growth of carbon nanofibers (CNFs) with assistance of a strong magnetic field (up to 0.5 T in the center) in a chemical vapor deposition (CVD) system. The results reveal that: 1) The CNFs get bundled when grown in the presence of a strong magnetic field and slightly get aligned parallel to the direction of the magnetic field; 2) The CNFs diameter become narrowed and homogenized with increase of the magnetic field; 3) With the increase of the magnetic field, the microstructure of CNFs is gradually changed, i.e., the strong magnetic field makes the disordered ``solid-cored'' CNFs transform into a kind of bamboo-liked carbon nanotubes; 4) We propose a mechanism that the reason for these variations and transformation is due to diamagnetic property of carbon atoms, so that it has direction selectivity in the precipitation process.

  11. Neural adhesion, growth, and activity on carbon nanotubes and carbonized nanofibers

    NASA Astrophysics Data System (ADS)

    Franca, Eric William

    This dissertation focuses on how the physical and electrical properties of carbon nanotubes (CNTs) and carbonized nanofibers (CNFs) affect the physiological and electrophysiological properties of neurons and neural networks and how this may affect the efficacy of these nanomaterials as microelectrode materials. In general, the pursuit of increasing electrode sensitivity while maintaining low noise levels is addressed by investigating and utilizing novel electrode materials. Carbon nanomaterials have a native conductivity and nano-scale roughness that should decrease microelectrode noise levels and impedance by virtue of a substantially increased surface area. In addition to the beneficial microelectrode properties, these carbon nanomaterials could increase the integration of the electrode to the neural tissue. The work here is an investigation of how selected CNT and CNF materials affect the viability, outgrowth, and adhesion of cortical neurons in vitro and how the physical and chemical properties of each substrate correlates to these measurements. The intent is that properties detailed in vitro can be assumed to extrapolate to performance in vivo assuming the same materials are utilized for invasive, implanted microelectrodes. Carbon nanotubes were deposited by a layer-by-layer (LBL) method with poly(ethylenimine) (PEI). Carbon nanofiber substrates were prepared in conjunction with collaborators via electrospinning a photosensitive polymer (SU-8), photopatterning, and pyrolyzing the depositions. In addition to these substrates, control samples were prepared in the form of PEI-treated glass coverslips, carbonized thin films, SU-8 thin films, and SU-8 nanofibers. The primary variable between all of these substrates is the roughness or topography of each deposition (ranging from 0.26 nm to 160 nm average roughness). Physical and chemical characteristics of the depositions are presented in addition to the electrical characteristics which make them attractive as

  12. Physicochemical investigations of carbon nanofiber supported Cu/ZrO{sub 2} catalyst

    SciTech Connect

    Din, Israf Ud E-mail: maizats@petronas.com.my; Shaharun, Maizatul S. E-mail: maizats@petronas.com.my; Subbarao, Duvvuri; Naeem, A.

    2014-10-24

    Zirconia-promoted copper/carbon nanofiber catalysts (Cu‐ZrO{sub 2}/CNF) were prepared by the sequential deposition precipitation method. The Herringbone type of carbon nanofiber GNF-100 (Graphite nanofiber) was used as a catalyst support. Carbon nanofiber was oxidized to (CNF-O) with 5% and 65 % concentration of nitric acid (HNO{sub 3}). The CNF activated with 5% HNO{sub 3} produced higher surface area which is 155 m{sup 2}/g. The catalyst was characterized by X-ray Diffraction (XRD), Fourier Transform Infra-Red (FTIR) and N{sub 2} adsorption-desorption. The results showed that increase of HNO{sub 3} concentration reduced the surface area and porosity of the catalyst.

  13. Synthesis of nitrogen-doped porous carbon nanofibers as an efficient electrode material for supercapacitors.

    PubMed

    Chen, Li-Feng; Zhang, Xu-Dong; Liang, Hai-Wei; Kong, Mingguang; Guan, Qing-Fang; Chen, Ping; Wu, Zhen-Yu; Yu, Shu-Hong

    2012-08-28

    Supercapacitors (also known as ultracapacitors) are considered to be the most promising approach to meet the pressing requirements of energy storage. Supercapacitive electrode materials, which are closely related to the high-efficiency storage of energy, have provoked more interest. Herein, we present a high-capacity supercapacitor material based on the nitrogen-doped porous carbon nanofibers synthesized by carbonization of macroscopic-scale carbonaceous nanofibers (CNFs) coated with polypyrrole (CNFs@polypyrrole) at an appropriate temperature. The composite nanofibers exhibit a reversible specific capacitance of 202.0 F g(-1) at the current density of 1.0 A g(-1) in 6.0 mol L(-1) aqueous KOH electrolyte, meanwhile maintaining a high-class capacitance retention capability and a maximum power density of 89.57 kW kg(-1). This kind of nitrogen-doped carbon nanofiber represents an alternative promising candidate for an efficient electrode material for supercapacitors.

  14. Finite element analysis of in-situ alignment of nanoparticles in polymeric nanofibers using magnetic field assisted electrospinning

    NASA Astrophysics Data System (ADS)

    Jayaseelan, D.; Biji, P.

    2015-09-01

    In this study, a three-dimensional magnetic field assisted electrospinning (MFAES) system has been modeled to understand the correlation between the applied magnetic field and electric field distributions during nanoparticle alignment. The results reveal that the electric field distribution has been altered by positioning the magnets at the needle end. The analysis explored the possibility to create a stable liquid jet under a magnetic field, which allows the formation of organized nanostructures in nanofibers. The polarity of the magnet has been used to manipulate the electric field distribution in the electrospinning system. Based on the configuration of magnetic flux lines, the distribution of the electric field has been found to be altered. An axial magnetic field has been provided by the repulsive mode configuration, which could be the reason for alignment of nanoparticles during electrospinning. Simulation proved that the bending instability of the charged liquid jet can be efficiently controlled by placing the magnets on both sides of the fiber formation path in the electrospinning system. The impact of an axial magnetic field on nanofiber formation and nanoparticle alignment during the MFAES process was further experimentally validated.

  15. Method for production of carbon nanofiber mat or carbon paper

    SciTech Connect

    Naskar, Amit K.

    2015-08-04

    Method for the preparation of a non-woven mat or paper made of carbon fibers, the method comprising carbonizing a non-woven mat or paper preform (precursor) comprised of a plurality of bonded sulfonated polyolefin fibers to produce said non-woven mat or paper made of carbon fibers. The preforms and resulting non-woven mat or paper made of carbon fiber, as well as articles and devices containing them, and methods for their use, are also described.

  16. A method to evaluate the tensile strength and stress-strain relationship of carbon nanofibers, carbon nanotubes, and C-chains.

    PubMed

    Márquez-Lucero, Alfredo; Gomez, Jorge A; Caudillo, Román; Miki-Yoshida, Mario; José-Yacaman, Miguel

    2005-06-01

    A method is introduced to assess the tensile strength of carbon nanofibers, carbon nanotubes (CNTs), and linear chains of carbon atoms (C-chains) obtained from thin amorphous carbon films by electron irradiation. Transmission electron microscopy images show that the nanofibers undergo a radiation-induced necking process, characterized by CNT formation and often followed by the formation of a C-chain. Simulations of the necking process are carried out to determine the tensile stress supported by the nanofiber and CNT neck.

  17. Cobalt/copper-decorated carbon nanofibers as novel non-precious electrocatalyst for methanol electrooxidation

    PubMed Central

    2014-01-01

    In this study, Co/Cu-decorated carbon nanofibers are introduced as novel electrocatalyst for methanol oxidation. The introduced nanofibers have been prepared based on graphitization of poly(vinyl alcohol) which has high carbon content compared to many polymer precursors for carbon nanofiber synthesis. Typically, calcination in argon atmosphere of electrospun nanofibers composed of cobalt acetate tetrahydrate, copper acetate monohydrate, and poly(vinyl alcohol) leads to form carbon nanofibers decorated by CoCu nanoparticles. The graphitization of the poly(vinyl alcohol) has been enhanced due to presence of cobalt which acts as effective catalyst. The physicochemical characterization affirmed that the metallic nanoparticles are sheathed by thin crystalline graphite layer. Investigation of the electrocatalytic activity of the introduced nanofibers toward methanol oxidation indicates good performance, as the corresponding onset potential was small compared to many reported materials; 310 mV (vs. Ag/AgCl electrode) and a current density of 12 mA/cm2 was obtained. Moreover, due to the graphite shield, good stability was observed. Overall, the introduced study opens new avenue for cheap and stable transition metals-based nanostructures as non-precious catalysts for fuel cell applications. PMID:24387682

  18. Cobalt/copper-decorated carbon nanofibers as novel non-precious electrocatalyst for methanol electrooxidation

    NASA Astrophysics Data System (ADS)

    Barakat, Nasser A. M.; El-Newehy, Mohamed; Al-Deyab, Salem S.; Kim, Hak Yong

    2014-01-01

    In this study, Co/Cu-decorated carbon nanofibers are introduced as novel electrocatalyst for methanol oxidation. The introduced nanofibers have been prepared based on graphitization of poly(vinyl alcohol) which has high carbon content compared to many polymer precursors for carbon nanofiber synthesis. Typically, calcination in argon atmosphere of electrospun nanofibers composed of cobalt acetate tetrahydrate, copper acetate monohydrate, and poly(vinyl alcohol) leads to form carbon nanofibers decorated by CoCu nanoparticles. The graphitization of the poly(vinyl alcohol) has been enhanced due to presence of cobalt which acts as effective catalyst. The physicochemical characterization affirmed that the metallic nanoparticles are sheathed by thin crystalline graphite layer. Investigation of the electrocatalytic activity of the introduced nanofibers toward methanol oxidation indicates good performance, as the corresponding onset potential was small compared to many reported materials; 310 mV (vs. Ag/AgCl electrode) and a current density of 12 mA/cm2 was obtained. Moreover, due to the graphite shield, good stability was observed. Overall, the introduced study opens new avenue for cheap and stable transition metals-based nanostructures as non-precious catalysts for fuel cell applications.

  19. Carbon Nanofiber Nanoelectrodes for Neural Stimulation and Chemical Detection: The Era of Smart Deep Brain Stimulation

    NASA Technical Reports Server (NTRS)

    Koehne, Jessica E.

    2016-01-01

    A sensor platform based on vertically aligned carbon nanofibers (CNFs) has been developed. Their inherent nanometer scale, high conductivity, wide potential window, good biocompatibility and well-defined surface chemistry make them ideal candidates as biosensor electrodes. Here, we report two studies using vertically aligned CNF nanoelectrodes for biomedical applications. CNF arrays are investigated as neural stimulation and neurotransmitter recording electrodes for application in deep brain stimulation (DBS). Polypyrrole coated CNF nanoelectrodes have shown great promise as stimulating electrodes due to their large surface area, low impedance, biocompatibility and capacity for highly localized stimulation. CNFs embedded in SiO2 have been used as sensing electrodes for neurotransmitter detection. Our approach combines a multiplexed CNF electrode chip, developed at NASA Ames Research Center, with the Wireless Instantaneous Neurotransmitter Concentration Sensor (WINCS) system, developed at the Mayo Clinic. Preliminary results indicate that the CNF nanoelectrode arrays are easily integrated with WINCS for neurotransmitter detection in a multiplexed array format. In the future, combining CNF based stimulating and recording electrodes with WINCS may lay the foundation for an implantable "smart" therapeutic system that utilizes neurochemical feedback control while likely resulting in increased DBS application in various neuropsychiatric disorders. In total, our goal is to take advantage of the nanostructure of CNF arrays for biosensing studies requiring ultrahigh sensitivity, high-degree of miniaturization, and selective biofunctionalization.

  20. Fabrication and Characterization of High Temperature Resin/Carbon Nanofiber Composites

    NASA Technical Reports Server (NTRS)

    Ghose, Sayata; Watson, Kent A.; Working, Dennis C.; Criss, Jim M.; Siochi, Emilie J.; Conell, John W.

    2005-01-01

    As part of ongoing efforts to develop multifunctional advanced composites, blends of PETI-330 and carbon nanofibers (CNF) were prepared and characterized. Dry mixing techniques were employed and the effect of CNF loading level on melt viscosity was determined. The resulting powders were characterized for degree of mixing, thermal and rheological properties. Based on the characterization results, samples containing 30 and 40 wt% CNF were scaled up to approx.300 g and used to fabricate moldings 10.2 cm x 15.2 cm x 0.32 cm thick. The moldings were fabricated by injecting the mixtures at 260-280 C into a stainless steel tool followed by curing for 1 h at 371 C. The tool was designed to impart high shear during the injection process in an attempt to achieve some alignment of CNFs in the flow direction. Moldings were obtained that were subsequently characterized for thermal, mechanical and electrical properties. The degree of dispersion and alignment of CNFs were investigated using high-resolution scanning electron microscopy. The preparation and preliminary characterization of PETI-330/CNF composites will be discussed.

  1. microRNA regulatory mechanism by which PLLA aligned nanofibers influence PC12 cell differentiation

    NASA Astrophysics Data System (ADS)

    Yu, Yadong; Lü, Xiaoying; Ding, Fei

    2015-08-01

    Objective. Aligned nanofibers (AFs) are regarded as promising biomaterials in nerve tissue engineering. However, a full understanding of the biocompatibility of AFs at the molecular level is still challenging. Therefore, the present study focused on identifying the microRNA (miRNA)-mediated regulatory mechanism by which poly-L-lactic acid (PLLA) AFs influence PC12 cell differentiation. Approach. Firstly, the effects of PLLA random nanofibers (RFs)/AFs and PLLA films (control) on the biological responses of PC12 cells that are associated with neuronal differentiation were examined. Then, SOLiD sequencing and cDNA microarray were employed to profile the expressions of miRNAs and mRNAs. The target genes of the misregulated miRNAs were predicted and compared with the mRNA profile data. Functions of the matched target genes (the intersection between the predicted target genes and the experimentally-determined, misregulated genes) were analyzed. Main results. The results revealed that neurites spread in various directions in control and RF groups. In the AF group, most neurites extended in parallel with each other. The glucose consumption and lactic acid production in the RF and AF groups were higher than those in the control group. Compared with the control group, 42 and 94 miRNAs were significantly dysregulated in the RF and AF groups, respectively. By comparing the predicted target genes with the mRNA profile data, five and 87 matched target genes were found in the RF and AF groups, respectively. Three of the matched target genes in the AF group were found to be associated with neuronal differentiation, whereas none had this association in the RF group. The PLLA AFs induced the dysregulation of miRNAs that regulate many biological functions, including axonal guidance, lipid metabolism and long-term potentiation. In particular, two miRNA-matched target gene-biological function modules associated with neuronal differentiation were identified as follows: (1) miR-23b, mi

  2. Preparation and characterization of carbon nanofiber-polymide composites

    NASA Astrophysics Data System (ADS)

    Li, Xiaobing

    Carbon nanofibers (CNFs) are potentially excellent reinforcements in polymer-based composites due to very good mechanical properties, thermal and electrical conductivity, and low cost to manufacture. The dispersion of fibers and the interfacial interaction with the polymer matrix need to be improved for CNF composites to achieve this potential. Treatment of the nanofiber surface with groups that are compatible with the polymer is key to addressing these issues. Attached functional groups may enhance the adhesion between reinforcement phase and matrix phase and reduce the slip of polymer chains on the surfaces of fibers. As a result, load can be transferred to fibers efficiently. In this investigation, CNFs were used as reinforcements in a polyimide (PI) matrix to produce a composite. To improve dispersion of fibers as well as interfacial adhesion, oxidized carbon nanofibers (OCNFs) were functionalized by covalently attaching 1,4-phenylenediamine (1,4-PDA) or polyimide oligomer to the surfaces. The functionalization with diamine was carried out either through direct reaction with OCNFs in dimethylacetimide (DMAc) solvent or through a two-step approach in which oxidized fibers were reacted with thionyl chloride (SOCl2) to improve surface reactivity followed by reaction with PDA in DMAc. The PDA was successfully bonded to the surfaces of fibers using both strategies. The further attachment of oligomer proceeded as expected in DMAc. The functionalized CNFs were characterized using Raman spectroscopy, thermal gravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) to confirm the functionalization reaction. Raman spectra and XPS spectra qualitatively indicated target chemical bonds were formed in each reaction step. Quantifications of TGA and XPS consistently supported that desired chemical moieties were present on the surfaces of fibers. In short, the interfaces of fibers were tailored with groups that would mimic the structure of polyimide and can

  3. Nanometer surface roughness increases select osteoblast adhesion on carbon nanofiber compacts.

    PubMed

    Price, Rachel L; Ellison, Karen; Haberstroh, Karen M; Webster, Thomas J

    2004-07-01

    Carbon nanofibers have exceptional theoretical mechanical properties (such as low weight-to-strength ratios) that, along with possessing nanoscale fiber dimensions similar to crystalline hydroxyapatite found in bone, suggest strong possibilities for use as an orthopedic/dental implant material. To determine, for the first time, cytocompatibility properties pertinent for bone prosthetic applications, osteoblast (bone-forming cells), fibroblast (cells contributing to callus formation and fibrous encapsulation events that result in implant loosening), chondrocyte (cartilage-forming cells), and smooth muscle cell (for comparison purposes) adhesion were determined on carbon nanofibers in the present in vitro study. Results provided evidence that, compared to conventional carbon fibers, nanometer dimension carbon fibers promoted select osteoblast adhesion. Moreover, adhesion of other cells was not influenced by carbon fiber dimensions. In fact, smooth muscle cell, fibroblast, and chondrocyte adhesion decreased with an increase in either carbon nanofiber surface energy or simultaneous change in carbon nanofiber chemistry. To determine properties that selectively enhanced osteoblast adhesion, similar cell adhesion assays were performed on polymer (specifically, poly-lactic-co-glycolic; PLGA) casts of carbon fiber compacts previously tested. Compared to PLGA casts of conventional carbon fibers, results provided the first evidence of enhanced select osteoblast adhesion on PLGA casts of nanophase carbon fibers. The summation of these results demonstrate that due to a high degree of nanometer surface roughness, carbon fibers with nanometer dimensions may be optimal materials to selectively increase osteoblast adhesion necessary for successful orthopedic/dental implant applications.

  4. Vertically aligned nanostructure scanning probe microscope tips

    DOEpatents

    Guillorn, Michael A.; Ilic, Bojan; Melechko, Anatoli V.; Merkulov, Vladimir I.; Lowndes, Douglas H.; Simpson, Michael L.

    2006-12-19

    Methods and apparatus are described for cantilever structures that include a vertically aligned nanostructure, especially vertically aligned carbon nanofiber scanning probe microscope tips. An apparatus includes a cantilever structure including a substrate including a cantilever body, that optionally includes a doped layer, and a vertically aligned nanostructure coupled to the cantilever body.

  5. Experimental study and modeling of swelling and bubble growth in carbon nanofiber filled mesophase pitch during carbonization

    NASA Astrophysics Data System (ADS)

    Calebrese, Christopher

    Graphite and all carbon bipolar plates show corrosion resistance in fuel cells and provide good electrical conductivity. These materials typically need to be individually machined, a time consuming and costly process. Mesophase pitch is used to manufacture carbon fibers and carbon-carbon composites. This material provides a good starting point for the production of a moldable, all carbon bipolar plate. However, processing of mesophase pitch to produce all carbon materials requires a time intensive oxidation step to prevent swelling during carbonization. In this work, carbon nanofibers were used to reduce swelling in mesophase pitch. It was found that the increase in viscosity with the addition of carbon nanofibers was responsible for the reduction in swelling. The influence of the filler became apparent above the percolation threshold. At loadings below the percolation threshold, the swelling of the mesophase pitch was not reduced after carbonization. The swelling of the mesophase pitch at a given carbon nanofiber loading was also dependent on the length of the carbon nanofibers. Longer carbon nanofibers led to greater increases in the viscosity of the melt and thus led to greater reduction in swelling. The final carbon product was evaluated for use as a low temperature fuel cell bipolar plate material. Constraining the mesophase pitch during carbonization led to a final product with strength and electrical conductivity comparable to current composite bipolar plate materials. The addition of micron size chopped glass fibers with a softening point near 850°C and carbon nanofibers led to a final product with air permeability less than that of graphite. A spherically symmetric, single bubble growth model was also developed. The model included temperature dependence, liquid to bubble mass transfer and reactions in the system. Results from simulations showed that that the increase in viscosity due to the addition of carbon nanofibers slows the growth of bubbles, but

  6. Pt/Carbon Nanofiber Nanocomposites as Electrocatalysts for Direct Methanol Fuel Cells: Prominent Effects of Carbon Nanofiber Nanostructures

    SciTech Connect

    Li, Zhizhou; Cui, Xiaoli; Zhang, Xinsheng; Wang, Qingfei; Shao, Yuyan; Lin, Yuehe

    2009-04-01

    Carbon nanofibers (CNFs) with different microstructures, including platelet-CNFs (PCNFs), fish-bone-CNFs, and tube-CNFs, were synthesized, characterized and evaluated toward methanol oxidation reaction (MOR). The CNFs studied here showed several structures in which various stacked morphologies as well as the ordering of their size and graphite layers can be well controlled. Platinum nanoparticles have been electrodeposited on CNFs surfaces, and their electrocatalytic activities toward MOR have been studied by using cyclic voltammetry, chronoamperometry, and linear sweep voltammograms. Morphologies, textural properties, and the crystalline structure of the CNFs supports and catalysts have been characterized with transmission electron microscopy and scanning electron microscopy. The comparative tests conclude that Pt/PCNFs have the best electrocatalytic performance and good stability at room temperature. The high electrocatalytic activity and stability can be attributed to the specific microstructure of PCNFs, which have large numbers of edge-active carbon atoms on the surface of the CNFs as well as synergistic effects between CNFs and the platinum nanoparticles. The results suggest that PCNFs are excellent potential candidates as catalyst supports in direct methanol fuel cells.

  7. Peripheral Nerve Repair in Rats Using Composite Hydrogel-Filled Aligned Nanofiber Conduits with Incorporated Nerve Growth Factor

    PubMed Central

    Jin, Jenny; Limburg, Sonja; Joshi, Sunil K.; Landman, Rebeccah; Park, Michelle; Zhang, Qia; Kim, Hubert T.

    2013-01-01

    Repair of peripheral nerve defects with current synthetic, tubular nerve conduits generally shows inferior recovery when compared with using nerve autografts, the current gold standard. We tested the ability of composite collagen and hyaluronan hydrogels, with and without the nerve growth factor (NGF), to stimulate neurite extension on a promising aligned, nanofiber poly-L-lactide-co-caprolactone (PLCL) scaffold. In vitro, the hydrogels significantly increased neurite extension from dorsal root ganglia explants. Consistent with these results, the addition of hydrogels as luminal fillers within aligned, nanofiber tubular PLCL conduits led to improved sensory function compared to autograft repair in a critical-size defect in the sciatic nerve in a rat model. Sensory recovery was assessed 3 and 12 weeks after repair using a withdrawal assay from thermal stimulation. The addition of hydrogel did not enhance recovery of motor function in the rat model. The NGF led to dose-dependent improvements in neurite out-growth in vitro, but did not have a significant effect in vivo. In summary, composite collagen/hyaluronan hydrogels enhanced sensory neurite outgrowth in vitro and sensory recovery in vivo. The use of such hydrogels as luminal fillers for tubular nerve conduits may therefore be useful in assisting restoration of protective sensation following peripheral nerve injury. PMID:23659607

  8. Spun-wrapped aligned nanofiber (SWAN) lithography for fabrication of micro/nano-structures on 3D objects.

    PubMed

    Ye, Zhou; Nain, Amrinder S; Behkam, Bahareh

    2016-07-01

    Fabrication of micro/nano-structures on irregularly shaped substrates and three-dimensional (3D) objects is of significant interest in diverse technological fields. However, it remains a formidable challenge thwarted by limited adaptability of the state-of-the-art nanolithography techniques for nanofabrication on non-planar surfaces. In this work, we introduce Spun-Wrapped Aligned Nanofiber (SWAN) lithography, a versatile, scalable, and cost-effective technique for fabrication of multiscale (nano to microscale) structures on 3D objects without restriction on substrate material and geometry. SWAN lithography combines precise deposition of polymeric nanofiber masks, in aligned single or multilayer configurations, with well-controlled solvent vapor treatment and etching processes to enable high throughput (>10(-7) m(2) s(-1)) and large-area fabrication of sub-50 nm to several micron features with high pattern fidelity. Using this technique, we demonstrate whole-surface nanopatterning of bulk and thin film surfaces of cubes, cylinders, and hyperbola-shaped objects that would be difficult, if not impossible to achieve with existing methods. We demonstrate that the fabricated feature size (b) scales with the fiber mask diameter (D) as b(1.5)∝D. This scaling law is in excellent agreement with theoretical predictions using the Johnson, Kendall, and Roberts (JKR) contact theory, thus providing a rational design framework for fabrication of systems and devices that require precisely designed multiscale features.

  9. Spun-wrapped aligned nanofiber (SWAN) lithography for fabrication of micro/nano-structures on 3D objects.

    PubMed

    Ye, Zhou; Nain, Amrinder S; Behkam, Bahareh

    2016-07-01

    Fabrication of micro/nano-structures on irregularly shaped substrates and three-dimensional (3D) objects is of significant interest in diverse technological fields. However, it remains a formidable challenge thwarted by limited adaptability of the state-of-the-art nanolithography techniques for nanofabrication on non-planar surfaces. In this work, we introduce Spun-Wrapped Aligned Nanofiber (SWAN) lithography, a versatile, scalable, and cost-effective technique for fabrication of multiscale (nano to microscale) structures on 3D objects without restriction on substrate material and geometry. SWAN lithography combines precise deposition of polymeric nanofiber masks, in aligned single or multilayer configurations, with well-controlled solvent vapor treatment and etching processes to enable high throughput (>10(-7) m(2) s(-1)) and large-area fabrication of sub-50 nm to several micron features with high pattern fidelity. Using this technique, we demonstrate whole-surface nanopatterning of bulk and thin film surfaces of cubes, cylinders, and hyperbola-shaped objects that would be difficult, if not impossible to achieve with existing methods. We demonstrate that the fabricated feature size (b) scales with the fiber mask diameter (D) as b(1.5)∝D. This scaling law is in excellent agreement with theoretical predictions using the Johnson, Kendall, and Roberts (JKR) contact theory, thus providing a rational design framework for fabrication of systems and devices that require precisely designed multiscale features. PMID:27283144

  10. Graphitic Carbon Nitride/Nitrogen-Rich Carbon Nanofibers: Highly Efficient Photocatalytic Hydrogen Evolution without Cocatalysts.

    PubMed

    Han, Qing; Wang, Bing; Gao, Jian; Qu, Liangti

    2016-08-26

    An interconnected framework of mesoporous graphitic-C3 N4 nanofibers merged with in situ incorporated nitrogen-rich carbon has been prepared. The unique composition and structure of the nanofibers as well as strong coupling between the components endow them with efficient light-harvesting properties, improved charged separation, and a multidimensional electron transport path that enhance the performance of hydrogen production. The as-obtained catalyst exhibits an extremely high hydrogen-evolution rate of 16885 μmol h(-1)  g(-1) , and a remarkable apparent quantum efficiency of 14.3 % at 420 nm without any cocatalysts, which is much higher than most reported g-C3 N4 -based photocatalysts even in the presence of Pt-based cocatalysts.

  11. Effects of feed gas composition and catalyst thickness on carbon nanotube and nanofiber synthesis by plasma enhanced chemical vapor deposition.

    PubMed

    Garg, R K; Kim, S S; Hash, D B; Gore, J P; Fisher, T S

    2008-06-01

    Many engineering applications require carbon nanotubes with specific characteristics such as wall structure, chirality and alignment. However, precise control of nanotube properties grown to application specifications remains a significant challenge. Plasma-enhanced chemical vapor deposition (PECVD) offers a variety of advantages in the synthesis of carbon nanotubes in that several important synthesis parameters can be controlled independently. This paper reports an experimental study of the effects of reacting gas composition (percentage methane in hydrogen) and catalyst film thickness on carbon nanotube (CNT) growth and a computational study of gas-phase composition for the inlet conditions of experimentally observed carbon nanotube growth using different chemical reaction mechanisms. The simulations seek to explain the observed effects of reacting gas composition and to identify the precursors for CNT formation. The experimental results indicate that gas-phase composition significantly affects the synthesized material, which is shown to be randomly aligned nanotube and nanofiber mats for relatively methane-rich inlet gas mixtures and non-tubular carbon for methane-lean incoming mixtures. The simulation results suggest that inlet methane-hydrogen mixture coverts to an acetylene-methane-hydrogen mixture with minor amounts of ethylene, hydrogen atom, and methyl radical. Acetylene appears to be the indicator species for solid carbon formation. The simulations also show that inlet methane-hydrogen mixture does not produce enough gas-phase precursors needed to form quality CNTs below 5% CH4 concentrations in the inlet stream. PMID:18681048

  12. Effects of carbon nanofiber on physiology of Drosophila

    PubMed Central

    Lee, Shin-Hae; Lee, Hye-Yeon; Lee, Eun-Ji; Khang, Dongwoo; Min, Kyung-Jin

    2015-01-01

    As nanomaterials are now widely utilized in a wide range of fields for both medical and industrial applications, concerns over their potential toxicity to human health and the environment have increased. To evaluate the toxicity of long-term exposure to carbon nanofibers (CNFs) in an in vivo system, we selected Drosophila melanogaster as a model organism. Oral administration of CNFs at a concentration of 1,000 μg/mL had adverse effects on fly physiology. Long-term administration of a high dose of CNFs (1,000 μg/mL) reduced larval viability based on the pupa:egg ratio, adult fly lifespan, reproductive activity, climbing activity, and survival rate in response to starvation stress. However, CNFs at a low concentration (100 μg/mL) did not show any significant deleterious effect on developmental rate or fecundity. Furthermore, long-term administration of a low dose of CNFs (100 μg/mL) increased lifespan and climbing ability, coincident with mild reactive oxygen species generation and stimulation of the antioxidant system. Taken together, our data suggest that a high dose of CNFs has obvious physiological toxicity, whereas low-dose chronic exposure to CNFs can actually have beneficial effects via stimulation of the antioxidant defense system. PMID:26056448

  13. A novel nano-nonwoven fabric with three-dimensionally dispersed nanofibers: entrapment of carbon nanofibers within nonwovens using the wet-lay process

    NASA Astrophysics Data System (ADS)

    Karwa, Amogh N.; Barron, Troy J.; Davis, Virginia A.; Tatarchuk, Bruce J.

    2012-05-01

    This study demonstrates, for the first time, the manufacturing of novel nano-nonwovens that are comprised of three-dimensionally distributed carbon nanofibers within the matrices of traditional wet-laid nonwovens. The preparation of these nano-nonwovens involves dispersing and flocking carbon nanofibers, and optimizing colloidal chemistry during wet-lay formation. The distribution of nanofibers within the nano-nonwoven was verified using polydispersed aerosol filtration testing, air permeability, low surface tension liquid capillary porometry, SEM and cyclic voltammetry. All these characterization techniques indicated that nanofiber flocks did not behave as large solid clumps, but retained the ‘nanoporous’ structure expected from nanofibers. These nano-nonwovens showed significant enhancements in aerosol filtration performance. The reduction-oxidation reactions of the functional groups on nanofibers and the linear variation of electric double-layer capacitance with nanofiber loading were measured using cyclic voltammetry. More than 65 m2 (700 ft2) of the composite were made during the demonstration of process scalability using a Fourdrinier-type continuous pilot papermaking machine. The scalability of the process with the control over pore size distribution makes these composites very promising for filtration and other nonwoven applications.

  14. Fabrication and characterization of vitamin B5 loaded poly (l-lactide-co-caprolactone)/silk fiber aligned electrospun nanofibers for schwann cell proliferation.

    PubMed

    Bhutto, M Aqeel; Wu, Tong; Sun, Binbin; Ei-Hamshary, Hany; Al-Deyab, Salem S; Mo, Xiumei

    2016-08-01

    Bioengineering strategies for peripheral nerve regeneration have been focusing on the development of alternative treatments for nerve repair. In present study we have blended the Vitamin B5 (50mg) with 8% P(LLA-CL) and P(LLA-CL)/SF solutions and produced aligned electrospun nanofiber mashes and characterized the material for its physiochemical and mechanical characteristics. The vitamin loaded composites nanofibers showed tensile strength of 8.73±1.38 and 8.4±1.37 in P(LLA-CL)/Vt and P(LLA-CL)/SF/Vt nanofibers mashes, respectively. By the addition of vitamin B5 the P(LLA-CL) nanofibers become hydrophilic and the contact angle decreased from 96° to 0° in 6min of duration. The effect of vitamin B5 on Schwann cells proliferation and viability were analyzed by using MTT assay and the number of cells cultured on vitamin loaded nanofiber mashes was significantly higher than the without vitamin loaded nanofiber samples after 5th day (p<0.05) whereas, P (LLA-CL)/SF/Vt exhibit the consistently highest cell numbers after 7th days culture as compare to P (LLA-CL)/Vt. The in vitro vitamin release behavior was observed in PBS solution and released vitamin was calculated by revers phase HPLC method. The sustain release behavior of vitamin B5 were noted higher in P(LLA-CL)/Vt (80%) nanofibers as compared to P (LLA-CL)/SF/Vt (62%) nanofibers after 24h. The present work provided a basis for further studies of this novel aligned nanofibrous material in nerve tissue repair or regeneration.

  15. Fabrication and characterization of vitamin B5 loaded poly (l-lactide-co-caprolactone)/silk fiber aligned electrospun nanofibers for schwann cell proliferation.

    PubMed

    Bhutto, M Aqeel; Wu, Tong; Sun, Binbin; Ei-Hamshary, Hany; Al-Deyab, Salem S; Mo, Xiumei

    2016-08-01

    Bioengineering strategies for peripheral nerve regeneration have been focusing on the development of alternative treatments for nerve repair. In present study we have blended the Vitamin B5 (50mg) with 8% P(LLA-CL) and P(LLA-CL)/SF solutions and produced aligned electrospun nanofiber mashes and characterized the material for its physiochemical and mechanical characteristics. The vitamin loaded composites nanofibers showed tensile strength of 8.73±1.38 and 8.4±1.37 in P(LLA-CL)/Vt and P(LLA-CL)/SF/Vt nanofibers mashes, respectively. By the addition of vitamin B5 the P(LLA-CL) nanofibers become hydrophilic and the contact angle decreased from 96° to 0° in 6min of duration. The effect of vitamin B5 on Schwann cells proliferation and viability were analyzed by using MTT assay and the number of cells cultured on vitamin loaded nanofiber mashes was significantly higher than the without vitamin loaded nanofiber samples after 5th day (p<0.05) whereas, P (LLA-CL)/SF/Vt exhibit the consistently highest cell numbers after 7th days culture as compare to P (LLA-CL)/Vt. The in vitro vitamin release behavior was observed in PBS solution and released vitamin was calculated by revers phase HPLC method. The sustain release behavior of vitamin B5 were noted higher in P(LLA-CL)/Vt (80%) nanofibers as compared to P (LLA-CL)/SF/Vt (62%) nanofibers after 24h. The present work provided a basis for further studies of this novel aligned nanofibrous material in nerve tissue repair or regeneration. PMID:27085042

  16. Towards Scalable Binderless Electrodes: Carbon Coated Silicon Nanofiber Paper via Mg Reduction of Electrospun SiO2 Nanofibers

    PubMed Central

    Favors, Zachary; Bay, Hamed Hosseini; Mutlu, Zafer; Ahmed, Kazi; Ionescu, Robert; Ye, Rachel; Ozkan, Mihrimah; Ozkan, Cengiz S.

    2015-01-01

    The need for more energy dense and scalable Li-ion battery electrodes has become increasingly pressing with the ushering in of more powerful portable electronics and electric vehicles (EVs) requiring substantially longer range capabilities. Herein, we report on the first synthesis of nano-silicon paper electrodes synthesized via magnesiothermic reduction of electrospun SiO2 nanofiber paper produced by an in situ acid catalyzed polymerization of tetraethyl orthosilicate (TEOS) in-flight. Free-standing carbon-coated Si nanofiber binderless electrodes produce a capacity of 802 mAh g−1 after 659 cycles with a Coulombic efficiency of 99.9%, which outperforms conventionally used slurry-prepared graphite anodes by over two times on an active material basis. Silicon nanofiber paper anodes offer a completely binder-free and Cu current collector-free approach to electrode fabrication with a silicon weight percent in excess of 80%. The absence of conductive powder additives, metallic current collectors, and polymer binders in addition to the high weight percent silicon all contribute to significantly increasing capacity at the cell level. PMID:25655007

  17. Towards scalable binderless electrodes: carbon coated silicon nanofiber paper via Mg reduction of electrospun SiO2 nanofibers.

    PubMed

    Favors, Zachary; Bay, Hamed Hosseini; Mutlu, Zafer; Ahmed, Kazi; Ionescu, Robert; Ye, Rachel; Ozkan, Mihrimah; Ozkan, Cengiz S

    2015-02-06

    The need for more energy dense and scalable Li-ion battery electrodes has become increasingly pressing with the ushering in of more powerful portable electronics and electric vehicles (EVs) requiring substantially longer range capabilities. Herein, we report on the first synthesis of nano-silicon paper electrodes synthesized via magnesiothermic reduction of electrospun SiO2 nanofiber paper produced by an in situ acid catalyzed polymerization of tetraethyl orthosilicate (TEOS) in-flight. Free-standing carbon-coated Si nanofiber binderless electrodes produce a capacity of 802 mAh g(-1) after 659 cycles with a Coulombic efficiency of 99.9%, which outperforms conventionally used slurry-prepared graphite anodes by over two times on an active material basis. Silicon nanofiber paper anodes offer a completely binder-free and Cu current collector-free approach to electrode fabrication with a silicon weight percent in excess of 80%. The absence of conductive powder additives, metallic current collectors, and polymer binders in addition to the high weight percent silicon all contribute to significantly increasing capacity at the cell level.

  18. Towards Scalable Binderless Electrodes: Carbon Coated Silicon Nanofiber Paper via Mg Reduction of Electrospun SiO2 Nanofibers

    NASA Astrophysics Data System (ADS)

    Favors, Zachary; Bay, Hamed Hosseini; Mutlu, Zafer; Ahmed, Kazi; Ionescu, Robert; Ye, Rachel; Ozkan, Mihrimah; Ozkan, Cengiz S.

    2015-02-01

    The need for more energy dense and scalable Li-ion battery electrodes has become increasingly pressing with the ushering in of more powerful portable electronics and electric vehicles (EVs) requiring substantially longer range capabilities. Herein, we report on the first synthesis of nano-silicon paper electrodes synthesized via magnesiothermic reduction of electrospun SiO2 nanofiber paper produced by an in situ acid catalyzed polymerization of tetraethyl orthosilicate (TEOS) in-flight. Free-standing carbon-coated Si nanofiber binderless electrodes produce a capacity of 802 mAh g-1 after 659 cycles with a Coulombic efficiency of 99.9%, which outperforms conventionally used slurry-prepared graphite anodes by over two times on an active material basis. Silicon nanofiber paper anodes offer a completely binder-free and Cu current collector-free approach to electrode fabrication with a silicon weight percent in excess of 80%. The absence of conductive powder additives, metallic current collectors, and polymer binders in addition to the high weight percent silicon all contribute to significantly increasing capacity at the cell level.

  19. High sensitivity Schottky junction diode based on monolithically grown aligned polypyrrole nanofibers: Broad range detection of m-dihydroxybenzene.

    PubMed

    Ameen, Sadia; Akhtar, M Shaheer; Seo, Hyung-Kee; Shin, Hyung Shik

    2015-07-30

    Aligned p-type polypyrrole (PPy) nanofibers (NFs) thin film was grown on n-type silicon (100) substrate by an electrochemical technique to fabricate Schottky junction diode for the efficient detection of m-dihydroxybenzene chemical. The highly dense and well aligned PPy NFs with the average diameter (∼150-200 nm) were grown on n-type Si substrate. The formation of aligned PPy NFs was confirmed by elucidating the structural, compositional and the optical properties. The electrochemical behavior of the fabricated Pt/p-aligned PPy NFs/n-silicon Schottky junction diode was evaluated by cyclovoltametry (CV) and current (I)-voltage (V) measurements with the variation of m-dihydroxybenzene concentration in the phosphate buffer solution (PBS). The fabricated Pt/p-aligned PPy NFs/n-silicon Schottky junction diode exhibited the rectifying behavior of I-V curve with the addition of m-dihydroxybenzene chemical, while a weak rectifying I-V behavior was observed without m-dihydroxybenzene chemical. This non-linear I-V behavior suggested the formation of Schottky barrier at the interface of Pt layer and p-aligned PPy NFs/n-silicon thin film layer. By analyzing the I-V characteristics, the fabricated Pt/p-aligned PPy NFs/n-silicon Schottky junction diode displayed reasonably high sensitivity ∼23.67 μAmM(-1)cm(-2), good detection limit of ∼1.51 mM with correlation coefficient (R) of ∼0.9966 and short response time (10 s).

  20. Carbon nanofiber mesoporous films: efficient platforms for bio-hydrogen oxidation in biofuel cells.

    PubMed

    de Poulpiquet, Anne; Marques-Knopf, Helena; Wernert, Véronique; Giudici-Orticoni, Marie Thérèse; Gadiou, Roger; Lojou, Elisabeth

    2014-01-28

    The discovery of oxygen and carbon monoxide tolerant [NiFe] hydrogenases was the first necessary step toward the definition of a novel generation of hydrogen fed biofuel cells. The next important milestone is now to identify and overcome bottlenecks limiting the current densities, hence the power densities. In the present work we report for the first time a comprehensive study of herringbone carbon nanofiber mesoporous films as platforms for enhanced biooxidation of hydrogen. The 3D network allows mediatorless hydrogen oxidation by the membrane-bound hydrogenase from the hyperthermophilic bacterium Aquifex aeolicus. We investigate the key physico-chemical parameters that enhance the catalytic efficiency, including surface chemistry and hierarchical porosity of the biohybrid film. We also emphasize that the catalytic current is limited by mass transport inside the mesoporous carbon nanofiber film. Provided hydrogen is supplied inside the carbon film, the combination of the hierarchical porosity of the carbon nanofiber film with the hydrophobicity of the treated carbon material results in very high efficiency of the bioelectrode. By optimization of the whole procedure, current densities as high as 4.5 mA cm(-2) are reached with a turnover frequency of 48 s(-1). This current density is almost 100 times higher than when hydrogenase is simply adsorbed at a bare graphite electrode, and more than 5 times higher than the average of the previous reported current densities at carbon nanotube modified electrodes, suggesting that carbon nanofibers can be efficiently used in future sustainable H2/O2 biofuel cells.

  1. A carbon nanofiber based biosensor for simultaneous detection of dopamine and serotonin in the presence of ascorbic acid

    PubMed Central

    Rand, Emily; Periyakaruppan, Adaikkappan; Tanaka, Zuki; Zhang, David; Marsh, Michael P.; Andrews, Russell J.; Lee, Kendall H.; Chen, Bin; Meyyappan, M.; Koehne, Jessica E.

    2013-01-01

    A biosensor based on an array of vertically aligned carbon nanofibers (CNFs) grown by plasma enhanced chemical vapor deposition is found to be effective for the simultaneous detection of dopamine (DA) and serotonin (5-HT) in the presence of excess ascorbic acid (AA). The CNF electrode outperforms the conventional glassy carbon electrode (GCE) for both selectivity and sensitivity. Using differential pulse voltammetry (DPV), three distinct peaks are seen for the CNF electrode at 0.13 V, 0.45 V, and 0.70 V for the ternary mixture of AA, DA, and 5-HT. In contrast, the analytes are indistinguishable in a mixture using a GCE. For the CNF electrode, the detection limits are 50 nM for DA and 250 nM for 5-HT. PMID:23228495

  2. High-performance supercapacitor electrode from cellulose-derived, inter-bonded carbon nanofibers

    NASA Astrophysics Data System (ADS)

    Cai, Jie; Niu, Haitao; Wang, Hongxia; Shao, Hao; Fang, Jian; He, Jingren; Xiong, Hanguo; Ma, Chengjie; Lin, Tong

    2016-08-01

    Carbon nanofibers with inter-bonded fibrous structure show high supercapacitor performance when being used as electrode materials. Their preparation is highly desirable from cellulose through a pyrolysis technique, because cellulose is an abundant, low cost natural material and its carbonization does not emit toxic substance. However, interconnected carbon nanofibers prepared from electrospun cellulose nanofibers and their capacitive behaviors have not been reported in the research literature. Here we report a facile one-step strategy to prepare inter-bonded carbon nanofibers from partially hydrolyzed cellulose acetate nanofibers, for making high-performance supercapacitors as electrode materials. The inter-fiber connection shows considerable improvement in electrode electrochemical performances. The supercapacitor electrode has a specific capacitance of ∼241.4 F g-1 at 1 A g-1 current density. It maintains high cycling stability (negligible 0.1% capacitance reduction after 10,000 cycles) with a maximum power density of ∼84.1 kW kg-1. They may find applications in the development of efficient supercapacitor electrodes for energy storage applications.

  3. Effect of carbon nanofibers on the infiltration and thermal conductivity of carbon/carbon composites

    SciTech Connect

    Li, Jinsong; Luo, Ruiying; Yan, Ying

    2011-09-15

    Highlights: {yields} The CNFs improve the infiltration rate and thermal properties of carbon/carbon composites. {yields} The densification rate increases with the CNF content increasing at the beginning of infiltration. {yields} The values of the thermal conductivity of the composite obtain their maximum values at 5 wt.%. -- Abstract: Preforms containing 0, 5, 10, 15 and 20 wt.% carbon nanofibers (CNFs) were fabricated by spreading layers of carbon cloth, and infiltrated using the electrified preform heating chemical vapor infiltration method (ECVI) under atmospheric pressure. Initial thermal gradients were determined. Resistivity and density evolutions with infiltration time have been recorded. Scanning electron microscopy, polarized light micrograph and X-ray diffraction technique were used to analyze the experiment results. The results showed that the infiltration rate increased with the rising of CNF content, and after 120 h of infiltration, the density was the highest when the CNF content was 5 wt.%, but the composite could not be densified efficiently as the CNF content ranged from 10 wt.% to 20 wt.%. CNF-reinforced C/C composites have enhanced thermal conductivity, the values at 5 wt.% were increased by nearly 5.5-24.1% in the X-Y direction and 153.8-251.3% in the Z direction compared to those with no CNFs. When the additive content was increased to 20 wt.%, due to the holes and cavities in the CNF web and between carbon cloth and matrix, the thermal conductivities in the X-Y and Z directions decreased from their maximum values at 5 wt.%.

  4. Synthesis and mechanical properties of interconnected carbon nanofiber network reinforced polydimethylsiloxane composites.

    PubMed

    Zhao, Z Y; Khatri, N D; Nguyen, K; Song, S Q; Sun, L

    2011-02-01

    Carbon nanofiber (CNF) reinforced elastomer composites with light weight, sustainability of large deformation, chemical stability, corrosion and fatigue resistance, and vibration and noise reduction capability can have positive impact on a wide range of applications. However, this type of composite is still a under studied research area due to the difficulties in material handling and processing. To improve processing control and reproducibility for large scale engineering applications, cost effective carbon nanofibers (CNFs) in form of interconnected porous network structure were used as nanofillers. Processing, microstructure and mechanical properties of carbon nanofibers reinforced polydimethylsiloxane (PDMS) have been studied. Mechanical measurements on the composites show that the CNF-PDMS interfacial bonding can be until failure, interfacial debonding happens in the CNF-PDMS composites and the resulted permanent deformation stabilizes with increasing load-unload cycles with significant energy dissipation. PMID:21456144

  5. Genotoxicity of carbon nanofibers: are they potentially more or less dangerous than carbon nanotubes or asbestos?

    PubMed Central

    Kisin, E. R.; Murray, A.R.; Sargent, L.; Lowry, D.; Chirila, M.; Siegrist, K.J.; Schwegler-Berry, D.; Leonard, S.; Castranova, V.; Fadeel, B.; Kagan, V.E.; Shvedova, A.A.

    2011-01-01

    The production of carbon nanofibers and nanotubes (CNF/CNT) and their composite products is increasing globally. CNF are generating great interest in industrial sectors such as energy production and electronics, where alternative materials may have limited performance or are produced at a much higher cost. However, despite the increasing industrial use of carbon nanofibers, information on their potential adverse health effects is limited. In the current study, we examine the cytotoxic and genotoxic potential of carbon-based nanofibers (Pyrograf®-III) and compare this material with the effects of asbestos fibers (crocidolite) or single-walled carbon nanotubes (SWCNT). The genotoxic effects in the lung fibroblast (V79) cell line were examined using two complementary assays: the comet assay and micronucleus (MN) test. In addition, we utilized fluorescence in situ hybridization to detect the chromatin pan-centromeric signals within the MN indicating their origin by aneugenic (chromosomal malsegregation) or clastogenic (chromosome breakage) mechanisms. Cytotoxicity tests revealed a concentration- and time-dependent loss of V79 cell viability after exposure to all tested materials in the following sequence: asbestos>CNF>SWCNT. Additionally, cellular uptake and generation of oxygen radicals was seen in the murine RAW264.7 macrophages following exposure to CNF or asbestos but not after administration of SWCNT. DNA damage and MN induction were found after exposure to all tested materials with the strongest effect seen for CNF. Finally, we demonstrated that CNF induced predominately centromere-positive MN in primary human small airway epithelial cells (SAEC) indicating aneugenic events. Further investigations are warranted to elucidate the possible mechanisms involved in CNF-induced genotoxicity. PMID:21310169

  6. Genotoxicity of carbon nanofibers: Are they potentially more or less dangerous than carbon nanotubes or asbestos?

    SciTech Connect

    Kisin, E.R.; Murray, A.R.; Sargent, L.; Lowry, D.; Chirila, M.; Siegrist, K.J.; Schwegler-Berry, D.; Leonard, S.; Castranova, V.; Fadeel, B.; Kagan, V.E.; Shvedova, A.A.

    2011-04-01

    The production of carbon nanofibers and nanotubes (CNF/CNT) and their composite products is increasing globally. CNF are generating great interest in industrial sectors such as energy production and electronics, where alternative materials may have limited performance or are produced at a much higher cost. However, despite the increasing industrial use of carbon nanofibers, information on their potential adverse health effects is limited. In the current study, we examine the cytotoxic and genotoxic potential of carbon-based nanofibers (Pyrograf (registered) -III) and compare this material with the effects of asbestos fibers (crocidolite) or single-walled carbon nanotubes (SWCNT). The genotoxic effects in the lung fibroblast (V79) cell line were examined using two complementary assays: the comet assay and micronucleus (MN) test. In addition, we utilized fluorescence in situ hybridization to detect the chromatin pan-centromeric signals within the MN indicating their origin by aneugenic (chromosomal malsegregation) or clastogenic (chromosome breakage) mechanisms. Cytotoxicity tests revealed a concentration- and time-dependent loss of V79 cell viability after exposure to all tested materials in the following sequence: asbestos > CNF > SWCNT. Additionally, cellular uptake and generation of oxygen radicals was seen in the murine RAW264.7 macrophages following exposure to CNF or asbestos but not after administration of SWCNT. DNA damage and MN induction were found after exposure to all tested materials with the strongest effect seen for CNF. Finally, we demonstrated that CNF induced predominately centromere-positive MN in primary human small airway epithelial cells (SAEC) indicating aneugenic events. Further investigations are warranted to elucidate the possible mechanisms involved in CNF-induced genotoxicity.

  7. Neurogenic differentiation of human umbilical cord mesenchymal stem cells on aligned electrospun polypyrrole/polylactide composite nanofibers with electrical stimulation

    NASA Astrophysics Data System (ADS)

    Zhou, Junfeng; Cheng, Liang; Sun, Xiaodan; Wang, Xiumei; Jin, Shouhong; Li, Junxiang; Wu, Qiong

    2016-09-01

    Adult central nervous system (CNS) tissue has a limited capacity to recover after trauma or disease. Recent medical cell therapy using polymeric biomaterialloaded stem cells with the capability of differentiation to specific neural population has directed focuses toward the recovery of CNS. Fibers that can provide topographical, biochemical and electrical cues would be attractive for directing the differentiation of stem cells into electro-responsive cells such as neuronal cells. Here we report on the fabrication of an electrospun polypyrrole/polylactide composite nanofiber film that direct or determine the fate of mesenchymal stem cells (MSCs), via combination of aligned surface topography, and electrical stimulation (ES). The surface morphology, mechanical properties and electric properties of the film were characterized. Comparing with that on random surface film, expression of neurofilament-lowest and nestin of human umbilical cord mesenchymal stemcells (huMSCs) cultured on film with aligned surface topography and ES were obviously enhanced. These results suggest that aligned topography combining with ES facilitates the neurogenic differentiation of huMSCs and the aligned conductive film can act as a potential nerve scaffold.

  8. Facile synthesis of carbon nanofibers-bridged porous carbon nanosheets for high-performance supercapacitors

    NASA Astrophysics Data System (ADS)

    Jiang, Yuting; Yan, Jun; Wu, Xiaoliang; Shan, Dandan; Zhou, Qihang; Jiang, Lili; Yang, Deren; Fan, Zhuangjun

    2016-03-01

    A facile and one-step method is demonstrated to prepare carbon nanofibers (CNFs)-bridged porous carbon nanosheets (PCNs) through carbonization of the mixture of bacterial cellulose and potassium citrate. The CNFs bridge PCNs to form integrated porous carbon architecture with high specific surface area of 1037 m2 g-1, much higher than those of pure PCNs (381 m2 g-1) and CNFs (510 m2 g-1). As a consequence, the PCN/CNF composite displays high specific capacitance of 261 F g-1, excellent rate capability and outstanding cycling stability (97.6% of capacitance retention after 10000 cycles). Moreover, the assembled symmetric supercapacitor with PCN/CNF electrodes delivers an ultrahigh energy density of 20.4 Wh kg-1 and outstanding cycling life (94.8% capacitance retention after 10000 cycles) in an aqueous electrolyte.

  9. Mesoporous Carbon Nanofibers Embedded with MoS2 Nanocrystals for Extraordinary Li-Ion Storage.

    PubMed

    Hu, Shan; Chen, Wen; Uchaker, Evan; Zhou, Jing; Cao, Guozhong

    2015-12-01

    MoS2 nanocrystals embedded in mesoporous carbon nanofibers are synthesized through an electrospinning process followed by calcination. The resultant nanofibers are 100-150 nm in diameter and constructed from MoS2 nanocrystals with a lateral diameter of around 7 nm with specific surface areas of 135.9 m(2)  g(-1) . The MoS2 @C nanofibers are treated at 450 °C in H2 and comparison samples annealed at 800 °C in N2 . The heat treatments are designed to achieve good crystallinity and desired mesoporous microstructure, resulting in enhanced electrochemical performance. The small amount of oxygen in the nanofibers annealed in H2 contributes to obtaining a lower internal resistance, and thus, improving the conductivity. The results show that the nanofibers obtained at 450 °C in H2 deliver an extraordinary capacity of 1022 mA h g(-1) and improved cyclic stability, with only 2.3 % capacity loss after 165 cycles at a current density of 100 mA g(-1) , as well as an outstanding rate capability. The greatly improved kinetics and cycling stability of the mesoporous MoS2 @C nanofibers can be attributed to the crosslinked conductive carbon nanofibers, the large specific surface area, the good crystallinity of MoS2 , and the robust mesoporous microstructure. The resulting nanofiber electrodes, with short mass- and charge-transport pathways, improved electrical conductivity, and large contact area exposed to electrolyte, permitting fast diffusional flux of Li ions, explains the improved kinetics of the interfacial charge-transfer reaction and the diffusivity of the MoS2 @C mesoporous nanofibers. It is believed that the integration of MoS2 nanocrystals and mesoporous carbon nanofibers may have a synergistic effect, giving a promising anode, and widening the applicability range into high performance and mass production in the Li-ion battery market. PMID:26515375

  10. Mesoporous Carbon Nanofibers Embedded with MoS2 Nanocrystals for Extraordinary Li-Ion Storage.

    PubMed

    Hu, Shan; Chen, Wen; Uchaker, Evan; Zhou, Jing; Cao, Guozhong

    2015-12-01

    MoS2 nanocrystals embedded in mesoporous carbon nanofibers are synthesized through an electrospinning process followed by calcination. The resultant nanofibers are 100-150 nm in diameter and constructed from MoS2 nanocrystals with a lateral diameter of around 7 nm with specific surface areas of 135.9 m(2)  g(-1) . The MoS2 @C nanofibers are treated at 450 °C in H2 and comparison samples annealed at 800 °C in N2 . The heat treatments are designed to achieve good crystallinity and desired mesoporous microstructure, resulting in enhanced electrochemical performance. The small amount of oxygen in the nanofibers annealed in H2 contributes to obtaining a lower internal resistance, and thus, improving the conductivity. The results show that the nanofibers obtained at 450 °C in H2 deliver an extraordinary capacity of 1022 mA h g(-1) and improved cyclic stability, with only 2.3 % capacity loss after 165 cycles at a current density of 100 mA g(-1) , as well as an outstanding rate capability. The greatly improved kinetics and cycling stability of the mesoporous MoS2 @C nanofibers can be attributed to the crosslinked conductive carbon nanofibers, the large specific surface area, the good crystallinity of MoS2 , and the robust mesoporous microstructure. The resulting nanofiber electrodes, with short mass- and charge-transport pathways, improved electrical conductivity, and large contact area exposed to electrolyte, permitting fast diffusional flux of Li ions, explains the improved kinetics of the interfacial charge-transfer reaction and the diffusivity of the MoS2 @C mesoporous nanofibers. It is believed that the integration of MoS2 nanocrystals and mesoporous carbon nanofibers may have a synergistic effect, giving a promising anode, and widening the applicability range into high performance and mass production in the Li-ion battery market.

  11. Evaluation of Changes in Morphology and Function of Human Induced Pluripotent Stem Cell Derived Cardiomyocytes (HiPSC-CMs) Cultured on an Aligned-Nanofiber Cardiac Patch

    PubMed Central

    Khan, Mahmood; Xu, Yanyi; Hua, Serena; Johnson, Jed; Belevych, Andriy; Janssen, Paul M. L.; Gyorke, Sandor; Guan, Jianjun; Angelos, Mark G.

    2015-01-01

    Introduction Dilated cardiomyopathy is a major cause of progressive heart failure. Utilization of stem cell therapy offers a potential means of regenerating viable cardiac tissue. However, a major obstacle to stem cell therapy is the delivery and survival of implanted stem cells in the ischemic heart. To address this issue, we have developed a biomimetic aligned nanofibrous cardiac patch and characterized the alignment and function of human inducible pluripotent stem cell derived cardiomyocytes (hiPSC-CMs) cultured on this cardiac patch. This hiPSC-CMs seeded patch was compared with hiPSC-CMs cultured on standard flat cell culture plates. Methods hiPSC-CMs were cultured on; 1) a highly aligned polylactide-co-glycolide (PLGA) nanofiber scaffold (~50 microns thick) and 2) on a standard flat culture plate. Scanning electron microscopy (SEM) was used to determine alignment of PLGA nanofibers and orientation of the cells on the respective surfaces. Analysis of gap junctions (Connexin-43) was performed by confocal imaging in both the groups. Calcium cycling and patch-clamp technique were performed to measure calcium transients and electrical coupling properties of cardiomyocytes. Results SEM demonstrated >90% alignment of the nanofibers in the patch which is similar to the extracellular matrix of decellularized rat myocardium. Confocal imaging of the cardiomyocytes demonstrated symmetrical alignment in the same direction on the aligned nanofiber patch in sharp contrast to the random appearance of cardiomyocytes cultured on a tissue culture plate. The hiPSC-CMs cultured on aligned nanofiber cardiac patches showed more efficient calcium cycling compared with cells cultured on standard flat surface culture plates. Quantification of mRNA with qRT-PCR confirmed that these cardiomyocytes expressed α-actinin, troponin-T and connexin-43 in-vitro. Conclusions Overall, our results demonstrated changes in morphology and function of human induced pluripotent derived cardiomyocytes

  12. Porous Carbon Nanofibers from Electrospun Biomass Tar/Polyacrylonitrile/Silver Hybrids as Antimicrobial Materials.

    PubMed

    Song, Kunlin; Wu, Qinglin; Zhang, Zhen; Ren, Suxia; Lei, Tingzhou; Negulescu, Ioan I; Zhang, Quanguo

    2015-07-15

    A novel route to fabricate low-cost porous carbon nanofibers (CNFs) using biomass tar, polyacrylonitrile (PAN), and silver nanoparticles has been demonstrated through electrospinning and subsequent stabilization and carbonization processes. The continuous electrospun nanofibers had average diameters ranging from 392 to 903 nm. The addition of biomass tar resulted in increased fiber diameters, reduced thermal stabilities, and slowed cyclization reactions of PAN in the as-spun nanofibers. After stabilization and carbonization, the resultant CNFs showed more uniformly sized and reduced average diameters (226-507 nm) compared to as-spun nanofibers. The CNFs exhibited high specific surface area (>400 m(2)/g) and microporosity, attributed to the combined effects of phase separations of the tar and PAN and thermal decompositions of tar components. These pore characteristics increased the exposures and contacts of silver nanoparticles to the bacteria including Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli, leading to excellent antimicrobial performances of as-spun nanofibers and CNFs. A new strategy is thus provided for utilizing biomass tar as a low-cost precursor to prepare functional CNFs and reduce environmental pollutions associated with direct disposal of tar as an industrial waste. PMID:26110209

  13. Aligned carbon nanotube sheet piezoresistive strain sensors

    NASA Astrophysics Data System (ADS)

    Li, Ang; Bogdanovich, Alexander E.; Bradford, Philip D.

    2015-09-01

    Carbon nanotubes (CNTs) have a unique set of properties that may be useful in the production of next generation structural health monitoring composites. This research introduces a novel CNT based material system for strain and damage sensing applications. An aligned sheet of interconnected CNTs was drawn from a chemical vapor deposition grown CNT array and then bonded to the surface of glass fiber/epoxy composite coupons. Various types of mechanical tests were conducted, accompanied by real-time electrical data acquisition, in order to evaluate the electro-mechanical behavior of the developed sensing material. Specimens were loaded in the longitudinal and transverse CNT sheet orientations to investigate the anisotropy of the piezoresistive effect. The CNT sheets exhibited good sensing stability, linearity, sensitivity and repeatability within a practical strain range; which are crucial sensor features for health monitoring. It was also demonstrated that the CNT orientation in the sheet had a dramatic effect on the sensitivity, thus validating the usefulness of this sensing material for directional strain/damage monitoring. Finally, pre-straining of the CNT sheet sensors was conducted to further enhance the linearity of electro-mechanical response and long-term stability of the sensors during cyclic loading.

  14. Plasma oxidation and stabilization of electrospun polyacrylonitrile nanofiber for carbon nanofiber formation

    NASA Astrophysics Data System (ADS)

    Hamideh Mortazavi, S.; Pilehvar, Soheil; Ghoranneviss, Mahmood; Hosseinnejad, M. T.; Zargham, Shamim; Mirarefi, Ali A.; Mirarefi, Amir Y.

    2013-11-01

    The effect of plasma treatment on the stabilization of copolymer P(AN-MA) containing 6.1 mol% methyl acrylate (MA) prepared by an electrospinning technique has been investigated at various oxygen contents (10 %, 20 % and 30 %) and different exposure times. The morphology and chemical structural evolution of electrospun and oxidized nanofibers were studied using field-emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy and differential scanning calorimetry (DSC). FT-IR analysis indicated that the treated nanofibers were effectively oxidized under different contents of oxygen and prolonged plasma exposure times by increasing the peak intensities of polar groups at 1730 and 3400 cm-1 corresponding to C=O stretching band and OH stretching vibration mode, respectively. Additionally, a reduction in the extent of the cyclization reaction is observed with further increase in exposure times and contents of oxygen, which implies lower conversion of C≡N bands into C=N ones in the copolymer chain. According to the FE-SEM studies, the surfaces of the treated nanofibers were completely etched after 15 min of treatment due to the existence of strong ion bombardment and a reduction in the average fiber diameters was observed.

  15. Strong and stiff aramid nanofiber/carbon nanotube nanocomposites.

    PubMed

    Zhu, Jiaqi; Cao, Wenxin; Yue, Mingli; Hou, Ying; Han, Jiecai; Yang, Ming

    2015-03-24

    Small but strong carbon nanotubes (CNTs) are fillers of choice for composite reinforcement owing to their extraordinary modulus and strength. However, the mechanical properties of the nanocomposites are still much below those for mechanical parameters of individual nanotubes. The gap between the expectation and experimental results arises not only from imperfect dispersion and poor load transfer but also from the unavailability of strong polymers that can be effectively utilized within the composites of nanotubes. Aramid nanofibers (ANFs) with analogous morphological features to nanotubes represent a potential choice to complement nanotubes given their intrinsic high mechanical performance and the dispersible nature, which enables solvent-based processing methods. In this work, we showed that composite films made from ANFs and multiwalled CNTs (MWCNTs) by vacuum-assisted flocculation and vacuum-assisted layer-by-layer assembly exhibited high ultimate strength of up to 383 MPa and Young's modulus (stiffness) of up to 35 GPa, which represent the highest values among all the reported random CNT nanocomposites. Detailed studies using different imaging and spectroscopic characterizations suggested that the multiple interfacial interactions between nanotubes and ANFs including hydrogen bonding and π-π stacking are likely the key parameters responsible for the observed mechanical improvement. Importantly, our studies further revealed the attractive thermomechanical characteristics of these nanocomposites with high thermal stability (up to 520 °C) and ultralow coefficients of thermal expansion (2-6 ppm·K(-1)). Our results indicated that ANFs are promising nanoscale building blocks for functional ultrastrong and stiff materials potentially extendable to nanocomposites based on other nanoscale fillers. PMID:25712334

  16. Label-free electrochemical impedance detection of kinase and phosphatase activities using carbon nanofiber nanoelectrode arrays

    PubMed Central

    Li, Yifen; Syed, Lateef; Liu, Jianwei; Hua, Duy H.; Li, Jun

    2012-01-01

    We demonstrate the feasibility of a label-free electrochemical method to detect the kinetics of phosphorylation and dephosphorylation of surface-attached peptides catalyzed by kinase and phosphatase, respectively. The peptides with a sequence specific to c-Src tyrosine kinase and protein tyrosine phosphatase 1B (PTP1B) were first validated with ELISA-based protein tyrosine kinase assay and then functionalized on vertically aligned carbon nanofiber (VACNF) nanoelectrode arrays (NEAs). Real-time electrochemical impedance spectroscopy (REIS) measurements showed reversible impedance changes upon the addition of c-Src kinase and PTP1B phosphatase. Only a small and unreliable impedance variation was observed during the peptide phosphorylation, but a large and fast impedance decrease was observed during the peptide dephosphorylation at different PTP1B concentrations. The REIS data of dephosphorylation displayed a well-defined exponential decay following the Michaelis-Menten heterogeneous enzymatic model with a specific constant, kcat/Km, of (2.1 ± 0.1) × 107 M−1 s−1. Consistent values of the specific constant was measured at PTP1B concentration varying from 1.2 to 2.4 nM with the corresponding electrochemical signal decay constant varying from 38.5 to 19.1 s. This electrochemical method can be potentially used as a label-free method for profiling enzyme activities in fast reactions. PMID:22935373

  17. Magnetic Properties of Fe-alloy Catalyst Nanoparticles for Carbon Nanofiber Synthesis

    NASA Astrophysics Data System (ADS)

    Sorge, K. D.; Leventouri, Th.; Finkel, C.; Malkina, O.; Rack, P. D.; Melechko, A. V.; Fowlkes, J. D.; Klein, K. L.; Simpson, M. L.

    2006-03-01

    The magnetic properties of Fe-alloy nanoparticles, used as catalysts in vertically-aligned carbon nanofiber (VACNF) growth, has been investigated. First, Fe and Co or Ni were co-sputtered onto Si substrates in order to make a catalyst alloy film. These substrates were then placed in a plasma-enhanced CVD chamber with a substrate temperature of 700^oC and a flowing mixture of acetylene (C2H2) and ammonia (NH3) gas. During the PECVD, the catalyst film breaks into nanoparticles of 50--200 nm and VACNFs are grown. EDX shows that the catalyst nanoparticles nominally have the deposited alloy ratio. In addition, the nanoparticles are still magnetic and have a non-negligible remanence and hysteresis. Their magnetic properties are investigated by SQUID magnetometry in applied field of |H| <=50 kOe and temperatures of 5--400 K. In addition, AC susceptibility studies give energy loss characteristics of the co-synthesized VACNF system.

  18. Carbon nanofibers arrays: A novel tool for microdelivery of biomolecules to plants

    DOE PAGES

    Davern, Sandra M.; McKnight, Timothy E.; Kalluri, Udaya C.; Standaert, Robert F.; Mirzadeh, Saed; Greenberg, Jean T.; Jelenska, Joanna; Shpak, Elena D.; Morrell-Falvey, Jennifer L.

    2016-04-27

    Effective methods for delivering bioprobes into the cells of intact plants are essential for investigating diverse biological processes. Increasing research on trees, such as Populus spp., for bioenergy applications is driving the need for techniques that work well with tree species. This report introduces vertically aligned carbon nanofiber (VACNF) arrays as a new tool for microdelivery of labeled molecules to Populus leaf tissue and whole plants. We demonstrated that VACNFs penetrate the leaf surface to deliver sub-microliter quantities of solution containing fluorescent or radiolabeled molecules into Populus leaf cells. Importantly, VACNFs proved to be gentler than abrasion with carborundum, amore » common way to introduce material into leaves. Unlike carborundum, VACNFs did not disrupt cell or tissue integrity, nor did they induce production of hydrogen peroxide, a typical wound response. We show that femtomole to picomole quantities of labeled molecules (fluorescent dyes, small proteins and dextran), ranging from 0.5–500 kDa, can be introduced by VACNFs, and we demonstrate the use of the approach to track delivered probes from their site of introduction on the leaf to distal plant regions. VACNF arrays thus offer an attractive microdelivery method for the introduction of biomolecules and other probes into trees and potentially other types of plants.« less

  19. Carbon Nanofiber Arrays: A Novel Tool for Microdelivery of Biomolecules to Plants

    PubMed Central

    Davern, Sandra M.; McKnight, Timothy E.; Morrell-Falvey, Jennifer L.; Shpak, Elena D.; Kalluri, Udaya C.; Jelenska, Joanna; Greenberg, Jean T.; Mirzadeh, Saed

    2016-01-01

    Effective methods for delivering bioprobes into the cells of intact plants are essential for investigating diverse biological processes. Increasing research on trees, such as Populus spp., for bioenergy applications is driving the need for techniques that work well with tree species. This report introduces vertically aligned carbon nanofiber (VACNF) arrays as a new tool for microdelivery of labeled molecules to Populus leaf tissue and whole plants. We demonstrated that VACNFs penetrate the leaf surface to deliver sub-microliter quantities of solution containing fluorescent or radiolabeled molecules into Populus leaf cells. Importantly, VACNFs proved to be gentler than abrasion with carborundum, a common way to introduce material into leaves. Unlike carborundum, VACNFs did not disrupt cell or tissue integrity, nor did they induce production of hydrogen peroxide, a typical wound response. We show that femtomole to picomole quantities of labeled molecules (fluorescent dyes, small proteins and dextran), ranging from 0.5–500 kDa, can be introduced by VACNFs, and we demonstrate the use of the approach to track delivered probes from their site of introduction on the leaf to distal plant regions. VACNF arrays thus offer an attractive microdelivery method for the introduction of biomolecules and other probes into trees and potentially other types of plants. PMID:27119338

  20. Reactor design considerations in the hot filament/direct current plasma synthesis of carbon nanofibers

    NASA Astrophysics Data System (ADS)

    Cruden, Brett A.; Cassell, Alan M.; Ye, Qi; Meyyappan, M.

    2003-09-01

    A combined hot filament/direct current (dc) plasma approach to chemical vapor deposition of carbon nanofibers (CNFs) using an acetylene/ammonia feedstock has been explored. As a part of the study, the impact of filament usage and substrate holder design has been examined by scanning electron microscopy imaging of deposition products and monitoring of downstream products by residual gas analysis (RGA). It is demonstrated that the filament wire is important primarily in the pretreatment of the substrate, improving CNF growth quality. However, the filament has a more minor impact when combined with the dc plasma, increasing growth rate but reducing growth quality. The substrate holder is modified by introducing a graphite spacer into the electrode. By varying the size of the spacer, the effective surface area of the cathode is modified, allowing control over the power input to the reactor while holding the voltage constant. This allows for some independent control of physicochemical processes that are typically inseparable in plasma processing, including gas phase chemistry, substrate heating and etching by ion bombardment, and growth alignment effects due to the electric field. This work demonstrates how separating these processes allows for better control over the desired growth product.

  1. Spun-wrapped aligned nanofiber (SWAN) lithography for fabrication of micro/nano-structures on 3D objects

    NASA Astrophysics Data System (ADS)

    Ye, Zhou; Nain, Amrinder S.; Behkam, Bahareh

    2016-06-01

    Fabrication of micro/nano-structures on irregularly shaped substrates and three-dimensional (3D) objects is of significant interest in diverse technological fields. However, it remains a formidable challenge thwarted by limited adaptability of the state-of-the-art nanolithography techniques for nanofabrication on non-planar surfaces. In this work, we introduce Spun-Wrapped Aligned Nanofiber (SWAN) lithography, a versatile, scalable, and cost-effective technique for fabrication of multiscale (nano to microscale) structures on 3D objects without restriction on substrate material and geometry. SWAN lithography combines precise deposition of polymeric nanofiber masks, in aligned single or multilayer configurations, with well-controlled solvent vapor treatment and etching processes to enable high throughput (>10-7 m2 s-1) and large-area fabrication of sub-50 nm to several micron features with high pattern fidelity. Using this technique, we demonstrate whole-surface nanopatterning of bulk and thin film surfaces of cubes, cylinders, and hyperbola-shaped objects that would be difficult, if not impossible to achieve with existing methods. We demonstrate that the fabricated feature size (b) scales with the fiber mask diameter (D) as b1.5 ~ D. This scaling law is in excellent agreement with theoretical predictions using the Johnson, Kendall, and Roberts (JKR) contact theory, thus providing a rational design framework for fabrication of systems and devices that require precisely designed multiscale features.Fabrication of micro/nano-structures on irregularly shaped substrates and three-dimensional (3D) objects is of significant interest in diverse technological fields. However, it remains a formidable challenge thwarted by limited adaptability of the state-of-the-art nanolithography techniques for nanofabrication on non-planar surfaces. In this work, we introduce Spun-Wrapped Aligned Nanofiber (SWAN) lithography, a versatile, scalable, and cost-effective technique for

  2. Fischer-Tropsch synthesis on hierarchically structured cobalt nanoparticle/carbon nanofiber/carbon felt composites.

    PubMed

    Zarubova, Sarka; Rane, Shreyas; Yang, Jia; Yu, Yingda; Zhu, Ye; Chen, De; Holmen, Anders

    2011-07-18

    The hierarchically structured carbon nanofibers (CNFs)/carbon felt composites, in which CNFs were directly grown on the surface of microfibers in carbon felt, forming a CNF layer on a micrometer range that completely covers the microfiber surfaces, were tested as a novel support material for cobalt nanoparticles in the highly exothermic Fischer-Tropsch (F-T) synthesis. A compact, fixed-bed reactor, made of disks of such composite materials, offered the advantages of improved heat and mass transfer, relatively low pressure drop, and safe handling of immobilized CNFs. An efficient 3-D thermal conductive network in the composite provided a relatively uniform temperature profile, whereas the open structure of the CNF layer afforded an almost 100 % effectiveness of Co nanoparticles in the F-T synthesis in the fixed bed. The greatly improved mass and heat transport makes the compact reactor attractive for applications in the conversion of biomass, coal, and natural gas to liquids. PMID:21563315

  3. Fischer-Tropsch synthesis on hierarchically structured cobalt nanoparticle/carbon nanofiber/carbon felt composites.

    PubMed

    Zarubova, Sarka; Rane, Shreyas; Yang, Jia; Yu, Yingda; Zhu, Ye; Chen, De; Holmen, Anders

    2011-07-18

    The hierarchically structured carbon nanofibers (CNFs)/carbon felt composites, in which CNFs were directly grown on the surface of microfibers in carbon felt, forming a CNF layer on a micrometer range that completely covers the microfiber surfaces, were tested as a novel support material for cobalt nanoparticles in the highly exothermic Fischer-Tropsch (F-T) synthesis. A compact, fixed-bed reactor, made of disks of such composite materials, offered the advantages of improved heat and mass transfer, relatively low pressure drop, and safe handling of immobilized CNFs. An efficient 3-D thermal conductive network in the composite provided a relatively uniform temperature profile, whereas the open structure of the CNF layer afforded an almost 100 % effectiveness of Co nanoparticles in the F-T synthesis in the fixed bed. The greatly improved mass and heat transport makes the compact reactor attractive for applications in the conversion of biomass, coal, and natural gas to liquids.

  4. Electrospun carbon nanofibers for improved electrical conductivity of fiber reinforced composites

    NASA Astrophysics Data System (ADS)

    Alarifi, Ibrahim M.; Alharbi, Abdulaziz; Khan, Waseem S.; Asmatulu, Ramazan

    2015-04-01

    Polyacrylonitrile (PAN) was dissolved in dimethylformamide (DMF), and then electrospun to generate nanofibers using various electrospinning conditions, such as pump speeds, DC voltages and tip-to-collector distances. The produced nanofibers were oxidized at 270 °C for 1 hr, and then carbonized at 850 °C in an argon gas for additional 1 hr. The resultant carbonized PAN nanofibers were placed on top of the pre-preg carbon fiber composites as top layers prior to the vacuum oven curing following the pre-preg composite curing procedures. The major purpose of this study is to determine if the carbonized nanofibers on the fiber reinforced composites can detect the structural defects on the composite, which may be useful for the structural health monitoring (SHM) of the composites. Scanning electron microscopy images showed that the electrospun PAN fibers were well integrated on the pre-preg composites. Electrical conductivity studies under various tensile loads revealed that nanoscale carbon fibers on the fiber reinforced composites detected small changes of loads by changing the resistance values. Electrically conductive composite manufacturing can have huge benefits over the conventional composites primarily used for the military and civilian aircraft and wind turbine blades.

  5. Fabrication and characterization of hybrid nanofibers from poly(vinyl alcohol), milk protein and metal carbonates.

    PubMed

    Mahanta, Narahari; Teow, Yiwei; Valiyaveettil, Suresh

    2012-08-01

    Porous three dimensional nanofibrous membranes were fabricated from poly(vinyl alcohol) (PVA), milk protein and inorganic salts such as calcium carbonate (CaCO3) or magnesium carbonate (MgCO3). Microscopic investigations showed that the fibers have smooth morphology with an average diameter of 300-500 nm and a surface area of 5.29 m2g(-1). Thermal analysis of the composite nanofibers showed a decrease in glass transition temperature as compared to PVA nanofiber. Incorporation of CaCO3 and MgCO3 into the nanofiber matrix was confirmed by energy dispersive spectroscopy and X-ray diffraction analysis. The cytocompatibility of electrospun composite nanofiber sheets was evaluated using human lung fibroblasts (IMR-90). There was an increase in cell attachment and cell density on milk protein incorporated to PVA-CaCO3 and PVA-MgCO3 fibers within a week of cell seeding. The cytocompatibility and increase in cell adhesion property of the hybrid nanofiber may provide significant advantages for such materials in biomedical applications. PMID:22962721

  6. Flame Synthesis Of Single-Walled Carbon Nanotubes And Nanofibers

    NASA Technical Reports Server (NTRS)

    Wal, Randy L. Vander; Berger, Gordon M.; Ticich, Thomas M.

    2003-01-01

    Carbon nanotubes are widely sought for a variety of applications including gas storage, intercalation media, catalyst support and composite reinforcing material [1]. Each of these applications will require large scale quantities of CNTs. A second consideration is that some of these applications may require redispersal of the collected CNTs and attachment to a support structure. If the CNTs could be synthesized directly upon the support to be used in the end application, a tremendous savings in post-synthesis processing could be realized. Therein we have pursued both aerosol and supported catalyst synthesis of CNTs. Given space limitations, only the aerosol portion of the work is outlined here though results from both thrusts will be presented during the talk. Aerosol methods of SWNT, MWNT or nanofiber synthesis hold promise of large-scale production to supply the tonnage quantities these applications will require. Aerosol methods may potentially permit control of the catalyst particle size, offer continuous processing, provide highest product purity and most importantly, are scaleable. Only via economy of scale will the cost of CNTs be sufficient to realize the large-scale structural and power applications on both earth and in space. Present aerosol methods for SWNT synthesis include laser ablation of composite metalgraphite targets or thermal decomposition/pyrolysis of a sublimed or vaporized organometallic [2]. Both approaches, conducted within a high temperature furnace, have produced single-walled nanotubes (SWNTs). The former method requires sophisticated hardware and is inherently limited by the energy deposition that can be realized using pulsed laser light. The latter method, using expensive organometallics is difficult to control for SWNT synthesis given a range of gasparticle mixing conditions along variable temperature gradients; multi-walled nanotubes (MWNTs) are a far more likely end products. Both approaches require large energy expenditures and

  7. Remarkable improvement in microwave absorption by cloaking a micro-scaled tetrapod hollow with helical carbon nanofibers.

    PubMed

    Jian, Xian; Chen, Xiangnan; Zhou, Zuowan; Li, Gang; Jiang, Man; Xu, Xiaoling; Lu, Jun; Li, Qiming; Wang, Yong; Gou, Jihua; Hui, David

    2015-02-01

    Helical nanofibers are prepared through in situ growth on the surface of a tetrapod-shaped ZnO whisker (T-ZnO), by employing a precursor decomposition method then adding substrate. After heat treatment at 900 °C under argon, this new composite material, named helical nanofiber-T-ZnO, undergoes a significant change in morphology and structure. The T-ZnO transforms from a solid tetrapod ZnO to a micro-scaled tetrapod hollow carbon film by reduction of the organic fiber at 900 °C. Besides, helical carbon nanofibers, generated from the carbonization of helical nanofibers, maintain the helical morphology. Interestingly, HCNFs with the T-hollow exhibit remarkable improvement in electromagnetic wave loss compared with the pure helical nanofibers. The enhanced loss ability may arise from the efficient dielectric friction, interface effect in the complex nanostructures and the micro-scaled tetrapod-hollow structure.

  8. Polyaniline-coated freestanding porous carbon nanofibers as efficient hybrid electrodes for supercapacitors

    NASA Astrophysics Data System (ADS)

    Tran, Chau; Singhal, Richa; Lawrence, Daniel; Kalra, Vibha

    2015-10-01

    Three-dimensional, free-standing, hybrid supercapacitor electrodes combining polyaniline (PANI) and porous carbon nanofibers (P-CNFs) were fabricated with the aim to integrate the benefits of both electric double layer capacitors (high power, cyclability) and pseudocapacitors (high energy density). A systematic investigation of three different electropolymerization techniques, namely, potentiodynamic, potentiostatic, and galvanostatic, for electrodeposition of PANI on freestanding carbon nanofiber mats was conducted. It was found that the galvanostatic method, where the current density is kept constant and can be easily controlled facilitates conformal and uniform coating of PANI on three-dimensional carbon nanofiber substrates. The electrochemical tests indicated that the PANI-coated P-CNFs exhibit excellent specific capacitance of 366 F g-1 (vs. 140 F g-1 for uncoated porous carbon nanofibers), 140 F cm-3 volumetric capacitance, and up to 2.3 F cm-2 areal capacitance at 100 mV s-1 scan rate. Such excellent performance is attributed to a thin and conformal coating of PANI achieved using the galvanostatic electrodeposition technique, which not only provides pseudocapacitance with high rate capability, but also retains the double-layer capacitance of the underlying P-CNFs.

  9. Nanoelectrode Arrays Based on Low Site Density Aligned Carbon Nanotubes

    SciTech Connect

    Yi, Tu; Lin, Yuehe ); Ren, Zhifeng N.

    2003-01-29

    Nanoelectrode arrays (NEAs) were fabricated from the low site density aligned carbon nanotubes (CNTs). The CNTs were grown by plasma enhanced chemical vapor deposition (PECVD) on Ni nanoparticles made by the electrochemical deposition.

  10. Supercapacitor Electrodes Based on High-Purity Electrospun Polyaniline and Polyaniline-Carbon Nanotube Nanofibers.

    PubMed

    Simotwo, Silas K; DelRe, Christopher; Kalra, Vibha

    2016-08-24

    Freestanding, binder-free supercapacitor electrodes based on high-purity polyaniline (PANI) nanofibers were fabricated via a single step electrospinning process. The successful electrospinning of nanofibers with an unprecedentedly high composition of PANI (93 wt %) was made possible due to blending ultrahigh molecular weight poly(ethylene oxide) (PEO) with PANI in solution to impart adequate chain entanglements, a critical requirement for electrospinning. To further enhance the conductivity and stability of the electrodes, a small concentration of carbon nanotubes (CNTs) was added to the PANI/PEO solution prior to electrospinning to generate PANI/CNT/PEO nanofibers (12 wt % CNTs). Scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) porosimetry were conducted to characterize the external morphology of the nanofibers. The electrospun nanofibers were further probed by transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). The electroactivity of the freestanding PANI and PANI/CNT nanofiber electrodes was examined using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. Competitive specific capacitances of 308 and 385 F g(-1) were achieved for PANI and PANI-CNT based electrodes, respectively, at a current density of 0.5 A g(-1). Moreover, specific capacitance retentions of 70 and 81.4% were observed for PANI and PANI-CNT based electrodes, respectively, after 1000 cycles. The promising electrochemical performance of the fabricated electrodes, we believe, stems from the porous 3-D electrode structure characteristic of the nonwoven interconnected nanostructures. The interconnected nanofiber network facilitates efficient electron conduction while the inter- and intrafiber porosity enable excellent electrolyte penetration within the polymer matrix, allowing fast ion transport to the active sites. PMID:27467445

  11. Enhancing capacitive deionization performance of electrospun activated carbon nanofibers by coupling with carbon nanotubes.

    PubMed

    Dong, Qiang; Wang, Gang; Wu, Tingting; Peng, Senpei; Qiu, Jieshan

    2015-05-15

    Capacitive deionization (CDI) is an alternative, effective and environmentally friendly technology for desalination of brackish water. The performance of the CDI device is highly determined by the electrode materials. In this paper, a composite of carbon nanotubes (CNTs) embedded in activated carbon nanofiber (ACF) was prepared by a direct co-electrospinning way and subsequent CO2 activation. The introduction of CNTs can greatly improve the conductivity while the CO2-mediated activation can render the final product with high porosity. As such, the hybrid structure can provide an excellent storage space and pathways for ion adsorption and conduction. When evaluated as electrode materials for CDI, the as-prepared CNT/ACF composites with higher electrical conductivity and mesopore ratios exhibited higher electrosorption capacity and good regeneration performance in comparison with the pure ACF.

  12. Vapor-phase polymerization of poly(3, 4-ethylenedioxythiophene) nanofibers on carbon cloth as electrodes for flexible supercapacitors

    NASA Astrophysics Data System (ADS)

    Zhao, Xin; Dong, Mengyang; Zhang, Junxian; Li, Yingzhi; Zhang, Qinghua

    2016-09-01

    In this study, an evaporative vapor-phase polymerization approach was employed to fabricate vertically aligned poly(3, 4-ethylenedioxythiophene) (PEDOT) nanofibers on the surface of carbon cloth (CC). Optimized reaction conditions can obtain well distributed and uniform layers of high-aspect-ratio PEDOT nanofibers on CC. The hierarchical PEDOT/CC structure as a freestanding electrode exhibits good electrochemical properties. As a flexible symmetric supercapacitor, the PEDOT/CC hybrid electrode displays a specific areal capacitance of 201.4 mF cm-2 at 1 mA cm-2, good flexibility with a higher value (204.6 mF cm-2) in the bending state, and a good cycling stability of 92.4% after 1000 cycles. Moreover, the device shows a maximum energy density of 4.0 Wh kg-1 (with a power density of 3.2 kW kg-1) and a maximum power density of 4.2 kW kg-1 (with an energy density of 3.1 Wh kg-1). The results demonstrate that PEDOT may be a promising material for storage devices through a simple and efficient vapor-phase polymerization process with precisely controlled reaction conditions.

  13. Vapor-phase polymerization of poly(3, 4-ethylenedioxythiophene) nanofibers on carbon cloth as electrodes for flexible supercapacitors

    NASA Astrophysics Data System (ADS)

    Zhao, Xin; Dong, Mengyang; Zhang, Junxian; Li, Yingzhi; Zhang, Qinghua

    2016-09-01

    In this study, an evaporative vapor-phase polymerization approach was employed to fabricate vertically aligned poly(3, 4-ethylenedioxythiophene) (PEDOT) nanofibers on the surface of carbon cloth (CC). Optimized reaction conditions can obtain well distributed and uniform layers of high-aspect-ratio PEDOT nanofibers on CC. The hierarchical PEDOT/CC structure as a freestanding electrode exhibits good electrochemical properties. As a flexible symmetric supercapacitor, the PEDOT/CC hybrid electrode displays a specific areal capacitance of 201.4 mF cm‑2 at 1 mA cm‑2, good flexibility with a higher value (204.6 mF cm‑2) in the bending state, and a good cycling stability of 92.4% after 1000 cycles. Moreover, the device shows a maximum energy density of 4.0 Wh kg‑1 (with a power density of 3.2 kW kg‑1) and a maximum power density of 4.2 kW kg‑1 (with an energy density of 3.1 Wh kg‑1). The results demonstrate that PEDOT may be a promising material for storage devices through a simple and efficient vapor-phase polymerization process with precisely controlled reaction conditions.

  14. Vapor-phase polymerization of poly(3, 4-ethylenedioxythiophene) nanofibers on carbon cloth as electrodes for flexible supercapacitors.

    PubMed

    Zhao, Xin; Dong, Mengyang; Zhang, Junxian; Li, Yingzhi; Zhang, Qinghua

    2016-09-23

    In this study, an evaporative vapor-phase polymerization approach was employed to fabricate vertically aligned poly(3, 4-ethylenedioxythiophene) (PEDOT) nanofibers on the surface of carbon cloth (CC). Optimized reaction conditions can obtain well distributed and uniform layers of high-aspect-ratio PEDOT nanofibers on CC. The hierarchical PEDOT/CC structure as a freestanding electrode exhibits good electrochemical properties. As a flexible symmetric supercapacitor, the PEDOT/CC hybrid electrode displays a specific areal capacitance of 201.4 mF cm(-2) at 1 mA cm(-2), good flexibility with a higher value (204.6 mF cm(-2)) in the bending state, and a good cycling stability of 92.4% after 1000 cycles. Moreover, the device shows a maximum energy density of 4.0 Wh kg(-1) (with a power density of 3.2 kW kg(-1)) and a maximum power density of 4.2 kW kg(-1) (with an energy density of 3.1 Wh kg(-1)). The results demonstrate that PEDOT may be a promising material for storage devices through a simple and efficient vapor-phase polymerization process with precisely controlled reaction conditions. PMID:27533130

  15. Surface analysis and electrochemistry of a robust carbon-nanofiber-based electrode platform H2O2 sensor

    NASA Astrophysics Data System (ADS)

    Suazo-Dávila, D.; Rivera-Meléndez, J.; Koehne, J.; Meyyappan, M.; Cabrera, C. R.

    2016-10-01

    A vertically aligned carbon nanofiber-based (VACNF) electrode platform was developed for an enzymeless hydrogen peroxide sensor. Vertical nanofibers have heights on the order of 2-3 μm, and diameters that vary from 50 to 100 nm as seen by atomic force microscopy. The VACNF was grown as individual, vertically, and freestanding structures using plasma-enhanced chemical vapor deposition. The electrochemical sensor, for the hydrogen peroxide measurement in solution, showed stability and reproducibility in five consecutive calibration curves with different hydrogen peroxide concentrations over a period of 3 days. The detection limit was 66 μM. The sensitivity for hydrogen peroxide electrochemical detection was 0.0906 mA cm-2 mM-1, respectively. The sensor was also used for the measurement of hydrogen peroxide as the by-product of the reaction of cholesterol with cholesterol oxidase as a biosensor application. The sensor exhibits linear behavior in the range of 50 μM-1 mM in cholesterol concentrations. The surface analysis and electrochemistry characterization is presented.

  16. Polyaniline nanofiber/large mesoporous carbon composites as electrode materials for supercapacitors

    NASA Astrophysics Data System (ADS)

    Liu, Huan; Xu, Bin; Jia, Mengqiu; Zhang, Mei; Cao, Bin; Zhao, Xiaonan; Wang, Yu

    2015-03-01

    A composite of polyaniline nanofiber/large mesoporous carbon (PANI-F/LMC) hybrid was prepared by an in situ chemical oxidative polymerization of aniline monomer with nano-CaCO3 templated LMC as host matrix for supercapacitors. The morphology, composition and electronic structure of the composites (PANI-F/LMC) together with pure PANI nanofibers and the LMC were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), FT-IR, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). It is found that the PANI nanofibers were incorporated into the large mesochannels of LMC with interpenetrating framework formed. Such unique structure endows the PANI-F/LMC composite with a high capacitance of 473 F g-1 at a current load of 0.1 A g-1 with good rate performance and cycling stability, suggesting its potential application in the electrode material for supercapacitors.

  17. Carbon Nanotubes-Adsorbed Electrospun PA66 Nanofiber Bundles with Improved Conductivity and Robust Flexibility.

    PubMed

    Guan, Xiaoyang; Zheng, Guoqiang; Dai, Kun; Liu, Chuntai; Yan, Xingru; Shen, Changyu; Guo, Zhanhu

    2016-06-01

    Electrospun polyamide (PA) 66 nanofiber bundles with high conductivity, improved strength, and robust flexibility were successfully manufactured through simply adsorbing multiwall carbon nanotubes (MWNTs) on the surface of electrospun PA66 nanofibers. The highest electrical conductivity (0.2 S/cm) and tensile strength (103.3 MPa) were achieved for the bundles immersed in the suspension with 0.05 wt % MWNTs, indicating the formation of conductive network from adsorbed MWNTs on the surface of PA66 nanofibers. The decrease of porosity for the bundles immersed in the MWNT dispersion and the formation of hydrogen bond between PA66 nanofibers and MWNTs suggest a superb interfacial interaction, which is responsible for the excellent mechanical properties of the nanocomposite bundles. Furthermore, the resistance fluctuation under bending is less than 3.6%, indicating a high flexibility of the nanocomposite bundles. The resistance of the nanocomposite bundle had a better linear dependence on the temperature applied between 30 and 150 °C. More importantly, such highest working temperature of 150 °C far exceeded that of other polymer-based temperature sensors previously reported. This suggests that such prepared MWNTs-adsorbed electrospun PA66 nanofiber bundles have great potentials in high temperature detectors.

  18. Carbon Nanotubes-Adsorbed Electrospun PA66 Nanofiber Bundles with Improved Conductivity and Robust Flexibility.

    PubMed

    Guan, Xiaoyang; Zheng, Guoqiang; Dai, Kun; Liu, Chuntai; Yan, Xingru; Shen, Changyu; Guo, Zhanhu

    2016-06-01

    Electrospun polyamide (PA) 66 nanofiber bundles with high conductivity, improved strength, and robust flexibility were successfully manufactured through simply adsorbing multiwall carbon nanotubes (MWNTs) on the surface of electrospun PA66 nanofibers. The highest electrical conductivity (0.2 S/cm) and tensile strength (103.3 MPa) were achieved for the bundles immersed in the suspension with 0.05 wt % MWNTs, indicating the formation of conductive network from adsorbed MWNTs on the surface of PA66 nanofibers. The decrease of porosity for the bundles immersed in the MWNT dispersion and the formation of hydrogen bond between PA66 nanofibers and MWNTs suggest a superb interfacial interaction, which is responsible for the excellent mechanical properties of the nanocomposite bundles. Furthermore, the resistance fluctuation under bending is less than 3.6%, indicating a high flexibility of the nanocomposite bundles. The resistance of the nanocomposite bundle had a better linear dependence on the temperature applied between 30 and 150 °C. More importantly, such highest working temperature of 150 °C far exceeded that of other polymer-based temperature sensors previously reported. This suggests that such prepared MWNTs-adsorbed electrospun PA66 nanofiber bundles have great potentials in high temperature detectors. PMID:27172292

  19. Influence of oxygen on nitrogen-doped carbon nanofiber growth directly on nichrome foil

    NASA Astrophysics Data System (ADS)

    Vishwakarma, Riteshkumar; Shinde, Sachin M.; Saufi Rosmi, Mohamad; Takahashi, Chisato; Papon, Remi; Mahyavanshi, Rakesh D.; Ishii, Yosuke; Kawasaki, Shinji; Kalita, Golap; Tanemura, Masaki

    2016-09-01

    The synthesis of various nitrogen-doped (N-doped) carbon nanostructures has been significantly explored as an alternative material for energy storage and metal-free catalytic applications. Here, we reveal a direct growth technique of N-doped carbon nanofibers (CNFs) on flexible nichrome (NiCr) foil using melamine as a solid precursor. Highly reactive Cr plays a critical role in the nanofiber growth process on the metal alloy foil in an atmospheric pressure chemical vapor deposition (APCVD) process. Oxidation of Cr occurs in the presence of oxygen impurities, where Ni nanoparticles are formed on the surface and assist the growth of nanofibers. Energy-dispersive x-ray spectroscopy (EDXS) and x-ray photoelectron spectroscopy (XPS) clearly show the transformation process of the NiCr foil surface with annealing in the presence of oxygen impurities. The structural change of NiCr foil assists one-dimensional (1D) CNF growth, rather than the lateral two-dimensional (2D) growth. The incorporation of distinctive graphitic and pyridinic nitrogen in the graphene lattice are observed in the synthesized nanofiber, owing to better nitrogen solubility. Our finding shows an effective approach for the synthesis of highly N-doped carbon nanostructures directly on Cr-based metal alloys for various applications.

  20. Influence of oxygen on nitrogen-doped carbon nanofiber growth directly on nichrome foil.

    PubMed

    Vishwakarma, Riteshkumar; Shinde, Sachin M; Rosmi, Mohamad Saufi; Takahashi, Chisato; Papon, Remi; Mahyavanshi, Rakesh D; Ishii, Yosuke; Kawasaki, Shinji; Kalita, Golap; Tanemura, Masaki

    2016-09-01

    The synthesis of various nitrogen-doped (N-doped) carbon nanostructures has been significantly explored as an alternative material for energy storage and metal-free catalytic applications. Here, we reveal a direct growth technique of N-doped carbon nanofibers (CNFs) on flexible nichrome (NiCr) foil using melamine as a solid precursor. Highly reactive Cr plays a critical role in the nanofiber growth process on the metal alloy foil in an atmospheric pressure chemical vapor deposition (APCVD) process. Oxidation of Cr occurs in the presence of oxygen impurities, where Ni nanoparticles are formed on the surface and assist the growth of nanofibers. Energy-dispersive x-ray spectroscopy (EDXS) and x-ray photoelectron spectroscopy (XPS) clearly show the transformation process of the NiCr foil surface with annealing in the presence of oxygen impurities. The structural change of NiCr foil assists one-dimensional (1D) CNF growth, rather than the lateral two-dimensional (2D) growth. The incorporation of distinctive graphitic and pyridinic nitrogen in the graphene lattice are observed in the synthesized nanofiber, owing to better nitrogen solubility. Our finding shows an effective approach for the synthesis of highly N-doped carbon nanostructures directly on Cr-based metal alloys for various applications. PMID:27479000

  1. Carbon nanofibers grafted on activated carbon as an electrode in high-power supercapacitors.

    PubMed

    Gryglewicz, Grażyna; Śliwak, Agata; Béguin, François

    2013-08-01

    A hybrid electrode material for high-power supercapacitors was fabricated by grafting carbon nanofibers (CNFs) onto the surface of powdered activated carbon (AC) through catalytic chemical vapor deposition (CCVD). A uniform thin layer of disentangled CNFs with a herringbone structure was deposited on the carbon surface through the decomposition of propane at 450 °C over an AC-supported nickel catalyst. CNF coating was controlled by the reaction time and the nickel content. The superior CNF/AC composite displays excellent electrochemical performance in a 0.5 mol L(-1) solution of K2 SO4 due to its unique structure. At a high scan rate (100 mV s(-1) ) and current loading (20 A g(-1) ), the capacitance values were three- and fourfold higher than those for classical AC/carbon black composites. Owing to this feature, a high energy of 10 Wh kg(-1) was obtained over a wide power range in neutral medium at a voltage of 0.8 V. The significant enhancement of charge propagation is attributed to the presence of herringbone CNFs, which facilitate the diffusion of ions in the electrode and play the role of electronic bridges between AC particles. An in situ coating of AC with short CNFs (below 200 nm) is a very attractive method for producing the next generation of carbon composite materials with a high power performance in supercapacitors working in neutral medium. PMID:23794416

  2. Photocatalytic Oxidation of Volatile Organic Compounds Over Electrospun Activated TIO2/CARBON Nanofiber Composite

    NASA Astrophysics Data System (ADS)

    Gholamvand, Zahra; Aboutalebi, Seyed Hamed; Keyanpour-Rad, Mansoor

    In this study, TiO2/PAN-based fibers were prepared by electrospinning a composite solution containing both the desirable contents of TiO2 and a 10 wt. % PAN polymer solution dissolved in N, N-dimethylformamide. The TiO2 loaded electrospun PAN nanofibers were then carbonized at 1000 °C in N2 atmosphere furnace after stabilization at 230 °C in air. Then CNF/TiO2 nanofibers were oxidized at 450 °C in air. The morphology and structure of the TiO2-embeded carbon nanofibers were investigated by SEM and Raman spectroscopy. Specific surface area was determined using BET equation from N2 adsorption analysis. Photocatalytic tests were conducted in a UV illuminated set-up specialized for the filters using ethanol vapor. The results have shown that ethanol vapor was efficiently degraded on TiO2/CNF composite nanofiber mat under UV illumination. The aim of this study was to further investigate the feasibility of TiO2/ACF for practical indoor air purification.

  3. Carbon-Encapsulated Hollow Porous Vanadium-Oxide Nanofibers for Improved Lithium Storage Properties.

    PubMed

    An, Geon-Hyoung; Lee, Do-Young; Ahn, Hyo-Jin

    2016-08-01

    Carbon-encapsulated hollow porous vanadium-oxide (C/HPV2O5) nanofibers have been fabricated using electrospinning and postcalcination. By optimized postcalcination of vanadium-nitride and carbon-nanofiber composites at 400 °C for 30 min, we synthesized a unique architecture electrode with interior void spaces and well-defined pores as well as a uniform carbon layer on the V2O5 nanofiber surface. The optimized C/HPV2O5 electrode postcalcined at 400 °C for 30 min showed improved lithium storage properties with high specific discharge capacities, excellent cycling durability (241 mA h g(-1) at 100 cycles), and improved high-rate performance (155 mA h g(-1) at 1000 mA g(-1)), which is the highest performance in comparison with previously reported V2O5-based cathode materials. The improved electrochemical feature is due to the attractive properties of the carbon-encapsulated hollow porous structure: (I) excellent cycling durability with high specific capacity relative to the adoption of carbon encapsulation as a physical buffer layer and the effective accommodation of volume changes due to the hollow porous structure, (II) improved high-rate performance because of a shorter Li-ion diffusion pathway resulting from interior void spaces and well-defined pores at the surface. This unique electrode structure can potentially provide new cathode materials for high-performance lithium-ion batteries.

  4. Carbon-Encapsulated Hollow Porous Vanadium-Oxide Nanofibers for Improved Lithium Storage Properties.

    PubMed

    An, Geon-Hyoung; Lee, Do-Young; Ahn, Hyo-Jin

    2016-08-01

    Carbon-encapsulated hollow porous vanadium-oxide (C/HPV2O5) nanofibers have been fabricated using electrospinning and postcalcination. By optimized postcalcination of vanadium-nitride and carbon-nanofiber composites at 400 °C for 30 min, we synthesized a unique architecture electrode with interior void spaces and well-defined pores as well as a uniform carbon layer on the V2O5 nanofiber surface. The optimized C/HPV2O5 electrode postcalcined at 400 °C for 30 min showed improved lithium storage properties with high specific discharge capacities, excellent cycling durability (241 mA h g(-1) at 100 cycles), and improved high-rate performance (155 mA h g(-1) at 1000 mA g(-1)), which is the highest performance in comparison with previously reported V2O5-based cathode materials. The improved electrochemical feature is due to the attractive properties of the carbon-encapsulated hollow porous structure: (I) excellent cycling durability with high specific capacity relative to the adoption of carbon encapsulation as a physical buffer layer and the effective accommodation of volume changes due to the hollow porous structure, (II) improved high-rate performance because of a shorter Li-ion diffusion pathway resulting from interior void spaces and well-defined pores at the surface. This unique electrode structure can potentially provide new cathode materials for high-performance lithium-ion batteries. PMID:27404906

  5. Electrospun carbon nanofibers reinforced 3D porous carbon polyhedra network derived from metal-organic frameworks for capacitive deionization.

    PubMed

    Liu, Yong; Ma, Jiaqi; Lu, Ting; Pan, Likun

    2016-01-01

    Carbon nanofibers reinforced 3D porous carbon polyhedra network (e-CNF-PCP) was prepared through electrospinning and subsequent thermal treatment. The morphology, structure and electrochemical performance of the e-CNF-PCP were characterized using scanning electron microscopy, Raman spectra, nitrogen adsorption-desorption, cyclic voltammetry and electrochemical impedance spectroscopy, and their electrosorption performance in NaCl solution was studied. The results show that the e-CNF-PCP exhibits a high electrosorption capacity of 16.98 mg g(-1) at 1.2 V in 500 mg l(-1) NaCl solution, which shows great improvement compared with those of electrospun carbon nanofibers and porous carbon polyhedra. The e-CNF-PCP should be a very promising candidate as electrode material for CDI applications. PMID:27608826

  6. Electrospun carbon nanofibers reinforced 3D porous carbon polyhedra network derived from metal-organic frameworks for capacitive deionization

    PubMed Central

    Liu, Yong; Ma, Jiaqi; Lu, Ting; Pan, Likun

    2016-01-01

    Carbon nanofibers reinforced 3D porous carbon polyhedra network (e-CNF-PCP) was prepared through electrospinning and subsequent thermal treatment. The morphology, structure and electrochemical performance of the e-CNF-PCP were characterized using scanning electron microscopy, Raman spectra, nitrogen adsorption-desorption, cyclic voltammetry and electrochemical impedance spectroscopy, and their electrosorption performance in NaCl solution was studied. The results show that the e-CNF-PCP exhibits a high electrosorption capacity of 16.98 mg g−1 at 1.2 V in 500 mg l−1 NaCl solution, which shows great improvement compared with those of electrospun carbon nanofibers and porous carbon polyhedra. The e-CNF-PCP should be a very promising candidate as electrode material for CDI applications. PMID:27608826

  7. Electrospun carbon nanofibers reinforced 3D porous carbon polyhedra network derived from metal-organic frameworks for capacitive deionization

    NASA Astrophysics Data System (ADS)

    Liu, Yong; Ma, Jiaqi; Lu, Ting; Pan, Likun

    2016-09-01

    Carbon nanofibers reinforced 3D porous carbon polyhedra network (e-CNF-PCP) was prepared through electrospinning and subsequent thermal treatment. The morphology, structure and electrochemical performance of the e-CNF-PCP were characterized using scanning electron microscopy, Raman spectra, nitrogen adsorption-desorption, cyclic voltammetry and electrochemical impedance spectroscopy, and their electrosorption performance in NaCl solution was studied. The results show that the e-CNF-PCP exhibits a high electrosorption capacity of 16.98 mg g‑1 at 1.2 V in 500 mg l‑1 NaCl solution, which shows great improvement compared with those of electrospun carbon nanofibers and porous carbon polyhedra. The e-CNF-PCP should be a very promising candidate as electrode material for CDI applications.

  8. Aligning carbon fibers in micro-extruded composite ink

    NASA Astrophysics Data System (ADS)

    Mahajan, Chaitanya G.

    Direct write processes include a wide range of additive manufacturing techniques with the ability to fabricate structures directly onto planar and non-planar surfaces. Most additive manufacturing techniques use unreinforced polymers to produce parts. By adding carbon fiber as a reinforcing material, properties such as mechanical strength, electrical conductivity, and thermal conductivity can be enhanced. Carbon fibers can be long and continuous, or short and discontinuous. The strength of carbon fiber composite parts is greatly increased when the fibers are preferentially aligned. This research focuses on increasing the strength of additively manufactured parts reinforced using discontinuous carbon fibers that have been aligned during the micro extrusion process. A design of experiments (DOE) approach was used to identify significant process parameters affecting fiber alignment. Factors such as the length of carbon fibers, nozzle diameter, fiber loading fraction, air pressure, translational speed and standoff distance were considered. A two dimensional Fast Fourier Transform (2D FFT) was used to quantify the degree of fiber alignment in the extruded composite inks. ImageJ software supported by an oval profile plugin was used with micrographs of printed samples to obtain the carbon fiber alignment values. The optimal value for the factors was derived by identifying the significant main and interaction effects. Based on the results of the DOE, tensile test samples were printed with fibers aligned parallel and perpendicular to the tensile axis. A standard test method for tensile properties of plastic revealed that the extruded parts with fibers aligned along the tensile axis were better in tensile strength and modulus.

  9. Performance of electrodes synthesized with polyacrylonitrile-based carbon nanofibers for application in electrochemical sensors and biosensors.

    PubMed

    Adabi, Mahdi; Saber, Reza; Faridi-Majidi, Reza; Faridbod, Farnoush

    2015-03-01

    The purpose of this work was to investigate the performance of electrodes synthesized with Polyacrylonitrile-based carbon nanofibers (PAN-based CNFs). The homogenous PAN solutions with different concentrations were prepared and electrospun to acquire PAN nanofibers and then CNFs were fabricated by heat treatment. The effective parameters for the production of electrospun CNF electrode were investigated. Scanning electron microscopy (SEM) was used to characterize electrospun nanofibers. Cyclic voltammetry was applied to investigate the changes of behavior of electrospun CNF electrodes with different diameters. The structure of CNFs was also evaluated via X-ray diffraction (XRD) and Raman spectroscopy. The results exhibited that diameter of nanofibers reduced with decreasing polymer concentration and applied voltage and increasing tip-to-collector distance, while feeding rate did not have significant effect on nanofiber diameter. The investigations of electrochemical behavior also demonstrated that cyclic voltammetric response improved as diameter of CNFs electrode decreased. PMID:25579970

  10. Carbon nanofibers and carbon nanotubes sensitize prostate and bladder cancer cells to platinum-based chemotherapeutics.

    PubMed

    Ringel, Jessica; Erdmann, Kati; Hampel, Silke; Kraemer, Kai; Maier, Diana; Arlt, Marcus; Kunze, Doreen; Wirth, Manfred P; Fuessel, Susanne

    2014-03-01

    Recent data suggest that carbon nanomaterials can act as antitumor agents themselves by increasing the efficiency of cytotoxic agents when applied in combination. Here, carbon nanofibers (CNFs) and multi-walled carbon nanotubes (CNTs) were investigated regarding their impact on cellular function, cellular uptake and ability to sensitize cancer cells of urological origin to the conventional chemotherapeutics cisplatin and carboplatin. CNFs and CNTs (1-200 microg/ml) showed a low to moderate impairment of cellular function with CNFs being more deleterious than CNTs. Inhibition of cellular viability by the nanomaterials was about 20% at most. In combinatory treatments, CNFs and CNTs markedly enhanced the effects of cisplatin and carboplatin on cellular viability by 1.2- to 2.8-fold in prostate, bladder and cisplatin-resistant prostate cancer cells in comparison to the individual effects of the chemotherapeutics. Particularly the cell viability-diminishing effect of CNFs alone and in combination with the chemotherapeutics was more pronounced with dispersions prepared with human serum albumin than with phospholipid-polyethylene glycol. Albumin might mediate the cellular uptake of carbon nanomaterials which was underlined by the co-localization of albumin and carbon nanomaterials along the cellular surface as evidenced by fluorescence microscopy. Transmission electron microscopy revealed that both carbon nanomaterials were internalized by cancer cells, thereby possibly leading to an enhanced accumulation of the chemotherapeutic drugs. In fact, CNFs enhanced the cellular accumulation of carboplatin by 28% as compared to the single treatment with carboplatin. In conclusion, carbon nanomaterial-based applications could present a new strategy to overcome chemoresistance by sensitizing cancer cells to conventional chemotherapeutics.

  11. Improved Synthesis of Aligned Carbon Nanotube Arrays for Optical Applications

    NASA Astrophysics Data System (ADS)

    Paudel, Trilochan; Gao, Yantao; Lan, Yucheng; Macmohan, Gregs; Kempa, Krzysztof; Naughton, Michael; Ren, Zhifeng

    2009-03-01

    Vertically aligned carbon nanotubes were grown on the high temperature glass (Aluminosilicate, Corning 1737) substrates with improved characteristics compared to previous attempts. The glass substrates were first coated with a buffer layer of either Chromium or Titanium, thick enough to facilitate CNT growth, but thin enough as to be largely transparent. On the top of the buffer layer, a monolayer of polystyrene spheres was deposited with close compaction, and then a Nickel catalyst film was evaporated. The polystyrene spheres were then removed to obtain honeycomb Ni patterns. On top of the Ni patterns, vertically aligned carbon nanotubes were grown by the direct current plasma enhanced chemical vapor deposition (dc PECVD). These aligned carbon nanotubes, which can range in height from 0.5 to 10 microns, and in diameter from 50 to 350 nm, can then be coated with various dielectrics to function as components in optical waveguides, including solar cells.

  12. The Effect of Nanofiber Alignment on the Maturation of Engineered Meniscus Constructs

    PubMed Central

    Baker, Brendon M.; Mauck, Robert L.

    2007-01-01

    The fibrocartilaginous menisci are load-bearing tissues vital to the normal functioning of the knee. Removal of damaged regions of the meniscus subsequent to injury impairs knee function and predisposes patients to osteoarthritis. In this study, we employed biodegradable nanofibrous scaffolds for the tissue engineering of the meniscus. Non-aligned (NA) or fiber-aligned (AL) nanofibrous scaffolds were seeded with meniscal fibrochondrocytes (MFCs) or mesenchymal stem cells (MSCs) to test the hypothesis that fiber-alignment would augment matrix content and organization, resulting in improved mechanical properties. Additionally, we proposed that MSCs could serve as an alternative to MFCs. With time in culture, MSC- and MFC-seeded NA and AL constructs increased in cellularity and extracellular matrix (ECM) content. Counter our initial hypothesis, NA and AL constructs contained comparable amounts of ECM, although a significantly larger increase in mechanical properties was observed for AL compared to NA constructs seeded with either cell type. Cell-seeded NA constructs increased in modulus by ~1 MPa over 10 weeks while cell-seeded AL construct increased by >7 MPa. Additionally, MSC-constructs yielded greater amounts of ECM and demonstrated comparable increases in mechanical properties, thereby confirming the utility of MSCs for meniscus tissue engineering. These results demonstrate that cell-seeded fiber aligned nanofibrous scaffolds may serve as an instructive micro-pattern for directed tissue growth, reconstituting both the form and function of the native tissue. PMID:17250888

  13. Regeneration of the Cavernous Nerve by Sonic Hedgehog Using Aligned Peptide Amphiphile Nanofibers

    PubMed Central

    Angeloni, Nicholas L.; Bond, Christopher W.; Tang, Yi; Harrington, Daniel A.; Zhang, Shuming; Stupp, Samuel I.; McKenna, Kevin E.; Podlasek, Carol A.

    2010-01-01

    Efforts to regenerate the cavernous nerve (CN), which provides innervation to the penis, have been minimally successful, with little translation into improved clinical outcomes. We propose that, Sonic hedgehog (SHH), is critical to maintain CN integrity, and that SHH delivered to the CN by novel peptide amphiphile (PA) nanofibers, will promote CN regeneration, restore physiological function, and prevent penile morphology changes that result in erectile dysfunction (ED). We performed localization studies, inhibition of SHH signaling in the CN, and treatment of crushed CNs with SHH protein via linear PA gels, which are an innovative extended release method of delivery. Morphological, functional and molecular analysis revealed that SHH protein is essential to maintain CN architecture, and that SHH treatment promoted CN regeneration, suppressed penile apoptosis and caused a 58% improvement in erectile function in less than half the time reported in the literature. These studies show that SHH has substantial clinical application to regenerate the CN in prostatectomy and diabetic patients, that this methodology has broad application to regenerate any peripheral nerve that SHH is necessary for maintenance of its structure, and that this nanotechnology method of protein delivery may have wide spread application as an in vivo delivery tool in many organs. PMID:20971506

  14. Electrospun polyvinyl alcohol/carbon dioxide modified polyethyleneimine composite nanofiber scaffolds.

    PubMed

    Wu, Han-Bing; Bremner, David H; Nie, Hua-Li; Quan, Jing; Zhu, Li-Min

    2015-05-01

    A novel biocompatible polyvinyl alcohol/carbon dioxide modified polyethyleneimine (PVA/PEI-CO2) composite nanofiber was fabricated by a green and facile protocol, which reduces the cytotoxicity of PEI through the surface modification of the PEI with CO2. The (13)C NMR spectrum, elemental analysis, and TGA show that CO2 has been incorporated in the PEI surface resulting in a relatively stable structure. The resulting PVA/PEI-CO2 composite nanofibers have been characterized by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), contact angle, and scanning electron microscopy (SEM). The results show that the average diameters of the nanofibers range from 265 ± 53 nm to 423 ± 80 nm. The cytotoxicity of PVA/PEI-CO2 composite nanofibers was assessed by cytotoxicity evaluation using the growth and cell proliferation of normal mice Schwann cells. SEM and the MTT assay demonstrated the promotion of cell growth and proliferation on the PVA/PEI-CO2 composite scaffold. It suggests that PEI-CO2 can have tremendous potential applications in biological material research. PMID:25540321

  15. Self-floating graphitic carbon nitride/zinc phthalocyanine nanofibers for photocatalytic degradation of contaminants.

    PubMed

    Xu, Tiefeng; Ni, Dongjing; Chen, Xia; Wu, Fei; Ge, Pengfei; Lu, Wangyang; Hu, Hongguang; Zhu, ZheXin; Chen, Wenxing

    2016-11-01

    The effective elimination of micropollutants by an environmentally friendly method has received extensive attention recently. In this study, a photocatalyst based on polyacrylonitrile (PAN)-supported graphitic carbon nitride coupled with zinc phthalocyanine nanofibers (g-C3N4/ZnTcPc/PAN nanofibers) was successfully prepared, where g-C3N4/ZnTcPc was introduced as the catalytic entity and the PAN nanofibers were employed as support to overcome the defects of easy aggregation and difficult recycling. Herein, rhodamine B (RhB), 4-chlorophenol and carbamazepine (CBZ) were selected as the model pollutants. Compared with the typical hydroxyl radical-dominated catalytic system, g-C3N4/ZnTcPc/PAN nanofibers displayed the targeted adsorption and degradation of contaminants under visible light or solar irradiation in the presence of high additive concentrations. According to the results of the radical scavenging techniques and the electron paramagnetic resonance technology, the degradation of target substrates was achieved by the attack of active species, including photogenerated hole, singlet oxygen, superoxide radicals and hydroxyl radicals. Based on the results of ultra-performance liquid chromatography and mass spectrometry, the role of free radicals on the photocatalytic degradation intermediates was identified and the final photocatalytic degradation products of both RhB and CBZ were some biodegradable small molecules.

  16. Self-floating graphitic carbon nitride/zinc phthalocyanine nanofibers for photocatalytic degradation of contaminants.

    PubMed

    Xu, Tiefeng; Ni, Dongjing; Chen, Xia; Wu, Fei; Ge, Pengfei; Lu, Wangyang; Hu, Hongguang; Zhu, ZheXin; Chen, Wenxing

    2016-11-01

    The effective elimination of micropollutants by an environmentally friendly method has received extensive attention recently. In this study, a photocatalyst based on polyacrylonitrile (PAN)-supported graphitic carbon nitride coupled with zinc phthalocyanine nanofibers (g-C3N4/ZnTcPc/PAN nanofibers) was successfully prepared, where g-C3N4/ZnTcPc was introduced as the catalytic entity and the PAN nanofibers were employed as support to overcome the defects of easy aggregation and difficult recycling. Herein, rhodamine B (RhB), 4-chlorophenol and carbamazepine (CBZ) were selected as the model pollutants. Compared with the typical hydroxyl radical-dominated catalytic system, g-C3N4/ZnTcPc/PAN nanofibers displayed the targeted adsorption and degradation of contaminants under visible light or solar irradiation in the presence of high additive concentrations. According to the results of the radical scavenging techniques and the electron paramagnetic resonance technology, the degradation of target substrates was achieved by the attack of active species, including photogenerated hole, singlet oxygen, superoxide radicals and hydroxyl radicals. Based on the results of ultra-performance liquid chromatography and mass spectrometry, the role of free radicals on the photocatalytic degradation intermediates was identified and the final photocatalytic degradation products of both RhB and CBZ were some biodegradable small molecules. PMID:27239724

  17. Urea-treated carbon nanofibers as efficient catalytic materials for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Liu, Dong; Zhang, Xueping; You, Tianyan

    2015-01-01

    Nitrogen-doped carbon nanofibers (NCNFs) are prepared by the thermal treatment of carbon nanofibers (CNFs) using urea as nitrogen source. Scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy have been employed to characterize the morphology and composition of CNFs and NCNFs. Compared with CNFs, NCNFs display thinner diameter, rougher surface and higher content of pyrrolic-N. As a metal-free catalyst for ORR, NCNFs exhibit comparable catalytic activity, significantly enhanced long-time stability and selectivity in comparison with commercial available Pt/C catalyst. Importantly, the self-supported NCNFs films could be conveniently utilized for electrode modification which is attractive in fuel cells. This work offers a promising metal-free catalyst as an alternative for Pt/C catalyst.

  18. Preparation and Study on Nickel Oxide Reduction of Polyacrylonitrile-Based Carbon Nanofibers by Thermal Treatment.

    PubMed

    Lee, Yeong Ju; Kim, Hyun Bin; Jeun, Joon Pyo; Lee, Dae Soo; Koo, Dong Hyun; Kang, Phil Hyun

    2015-08-01

    Carbon materials containing magnetic nanopowder have been attractive in technological applications such as electrochemical capacitors and electromagnetic wave shielding. In this study, polyacrylonitrile (PAN) fibers containing nickel nanoparticles were prepared using an electrospinning method and thermal stabilization. The reduction of nickel oxide was investigated under a nitrogen atmosphere within a temperature range of 600 to 1,000 °C. Carbon nanofibers containing nickel nanoparticles were characterized by FE-SEM, EDS, XRD, TGA, and VSM. It was found that nickel nanoparticles were formed by a NiO reduction in PAN as a function of the thermal treatment. These results led to an increase in the coercivity of nanofibers and a decrease in the remanence magnetization.

  19. Controllable synthesis of helical, straight, hollow and nitrogen-doped carbon nanofibers and their magnetic properties

    SciTech Connect

    Li, Xun; Xu, Zheng

    2012-12-15

    Graphical abstract: The helical, straight and hollow carbon nanofibers can be selectively synthesized by adjusting either the reaction temperature or feed gas composition. Display Omitted Highlights: ► CNFs were synthesized via pyrolysis of acetylene on copper NPs. ► The helical, straight, hollow and N-doped CNFs can be selectively synthesized. ► The growth mechanism of different types of CNFs was proposed. -- Abstract: Carbon nanofibers (CNFs) with various morphologies were synthesized by catalytic pyrolysis of acetylene on copper nanoparticles which were generated from the in situ decomposition of copper acetylacetonate. The morphology of the pristine and acid-washed CNFs was investigated by field emission scanning electron microscope and high-resolution transmission electron microscope. Helical, straight and hollow CNFs can be selectively synthesized by adjusting either the reaction temperature or feed gas composition. The growth mechanism for these three types of CNFs was proposed.

  20. Effects of vapor grown carbon nanofibers on electrical and mechanical properties of a thermoplastic elastomer

    NASA Astrophysics Data System (ADS)

    Basaldua, Daniel Thomas

    Carbon nanofiber (CNF) reinforced composites are exceptional materials that exhibit superior properties compared to conventional composites. This paper presents the development of a vapor grown carbon nanofiber (VGCNF) thermoplastic polyurethane (TPU) composite by a melt mixing process. Dispersion and distribution of CNFs inside the TPU matrix were examined through scanning electron microscopy to determine homogeneity. The composite material underwent durometer, thermal gravimetric analysis, differential scanning calorimetry, heat transfer, hysteresis, dynamic modulus, creep, tensile, abrasion, and electrical conductivity testing to characterize its properties and predict behavior. The motivation for this research is to develop an elastomer pad that is an electrically conductive alternative to the elastomer pads currently used in railroad service. The material had to be a completely homogenous electrically conductive CNF composite that could withstand a harsh dynamically loaded environment. The new material meets mechanical and conductive requirements for use as an elastomer pad in a rail suspension.

  1. Preparation and Study on Nickel Oxide Reduction of Polyacrylonitrile-Based Carbon Nanofibers by Thermal Treatment.

    PubMed

    Lee, Yeong Ju; Kim, Hyun Bin; Jeun, Joon Pyo; Lee, Dae Soo; Koo, Dong Hyun; Kang, Phil Hyun

    2015-08-01

    Carbon materials containing magnetic nanopowder have been attractive in technological applications such as electrochemical capacitors and electromagnetic wave shielding. In this study, polyacrylonitrile (PAN) fibers containing nickel nanoparticles were prepared using an electrospinning method and thermal stabilization. The reduction of nickel oxide was investigated under a nitrogen atmosphere within a temperature range of 600 to 1,000 °C. Carbon nanofibers containing nickel nanoparticles were characterized by FE-SEM, EDS, XRD, TGA, and VSM. It was found that nickel nanoparticles were formed by a NiO reduction in PAN as a function of the thermal treatment. These results led to an increase in the coercivity of nanofibers and a decrease in the remanence magnetization. PMID:26369192

  2. Electrospun composite nanofibers of poly vinyl pyrrolidone and zinc oxide nanoparticles modified carbon paste electrode for electrochemical detection of curcumin.

    PubMed

    Afzali, Moslem; Mostafavi, Ali; Shamspur, Tayebeh

    2016-11-01

    A simple and novel ferrocene-nanofiber carbon paste electrode was developed to determine curcumin in a phosphate buffer solution at pH=8. ZnO nanoparticles were produced via a sonochemical process and composite nanofibers of PVP/ZnO were prepared by electrospinning. The characterization was performed by SEM, XRD and IR. The results suggest that the electrospun composite nanofibers having a large surface area promote electron transfer for the oxidation of curcumin and hence the FCNFCPE exhibits high electrocatalytic activity and performs well in regard to the oxidation of curcumin. The proposed method was successfully applied for measurement of curcumin in urine and turmeric as real samples.

  3. Curvature aided efficient axial field emission from carbon nanofiber-reduced graphene oxide superstructures on tungsten wire substrate

    NASA Astrophysics Data System (ADS)

    Jha, Arunava; Roy, Rajarshi; Sen, Dipayan; Chattopadhyay, Kalyan K.

    2016-03-01

    Field emission characteristics found in reduced graphene oxide (RGO) and RGO based composite systems have always been an area of research interest mainly due to presence of prolific quasi aligned edges working as emitter sites. However, the specific role and extent of edge curvature geometry in RGO systems in regards to the enhancement of field emission has not discussed thoroughly prior to this work. In this work we demonstrate enhanced axial field emission due to top assembly of thin RGO layer over a quasi-vertically aligned carbon nanofiber thin film supported on a tungsten wire substrate. Furthermore, simulation analysis for our RGO based hybrid system using finite element modeling showed that two-stage local field amplification in RGO is responsible for the overall improvement of field emission characteristics. In support of our findings, a tentative explanation has been proposed based on the additional emission from RGO edges in between the CNF network resulting to the enhancement of axial field emission in the nanocomposite superstructure.

  4. Analysis of alignment effect on carbon nanotube layer in nanocomposites

    NASA Astrophysics Data System (ADS)

    Joshi, Preeti; Upadhyay, S. H.

    2015-02-01

    In this work, effect of various alignments of double walled carbon nanotubes (DWCNTs) in composite is evaluated for axial, lateral and through plane properties. Layers of DWCNTs are incorporated in the matrix. Four models with different layer combinations are analysed using 3D representative volume element. The highest value of axial modulus is observed for composite in which DWCNTs are aligned in direction of loading. Enhancement in lateral stiffness is observed for the models in which layers are aligned in plane perpendicular direction. Through plane stiffness is improved in vertically aligned DWCNT composite. It is observed that both axial and lateral moduli of composite behave non-linearly with respect to DWCNT volume fraction. This is because of the effect of agglomeration, due to the higher content of DWCNT in the composite. The proposed simulation is based on the experimentally adopted alignment of carbon nanotubes. DWCNT based composites with specific properties along various directions can be designed by controlling the volume fractions and alignment of the DWCNT sheets.

  5. Polymer-carbon nanotube composites: electrospinning, alignment and interactions

    NASA Astrophysics Data System (ADS)

    Winter, A. Douglas; Larios, Eduardo; Alamgir, Faisal M.; Jaye, Cherno; Fischer, Daniel A.; Campo, Eva M.

    2014-09-01

    The possibility of novel nanocomposite materials with dramatically improved properties requires fundamental studies of interactions. Full elucidation of these concepts will allow the tailoring of such systems for particular applications. Using near-edge X-ray absorption fine structure spectroscopy, we investigated interactions in electrospun poly(dimethylsiloxane)-poly(methyl methacrylate)-multiwall carbon nanotube composites. This paper describes these interactions through a building-block model, addresses their dependence upon filler size, and discusses electrospinning as an alignment solution. Though alignment of filler and polymeric chains was not observed spectrally, SEM imaging confirmed uniaxial carbon nanotube alignment in composite fibres. Spectra acquired at different incidence angles revealed differences in energy and intensity of resonances, suggesting conformational configurations. These differences were more significant in composites with larger nanofiller. This supported proposed models of CH-π interactions and hydrogen bonding as adhesion mechanisms.

  6. Chemical vapor-deposited carbon nanofibers on carbon fabric for supercapacitor electrode applications

    PubMed Central

    2012-01-01

    Entangled carbon nanofibers (CNFs) were synthesized on a flexible carbon fabric (CF) via water-assisted chemical vapor deposition at 800°C at atmospheric pressure utilizing iron (Fe) nanoparticles as catalysts, ethylene (C2H4) as the precursor gas, and argon (Ar) and hydrogen (H2) as the carrier gases. Scanning electron microscopy, transmission electron microscopy, and electron dispersive spectroscopy were employed to characterize the morphology and structure of the CNFs. It has been found that the catalyst (Fe) thickness affected the morphology of the CNFs on the CF, resulting in different capacitive behaviors of the CNF/CF electrodes. Two different Fe thicknesses (5 and 10 nm) were studied. The capacitance behaviors of the CNF/CF electrodes were evaluated by cyclic voltammetry measurements. The highest specific capacitance, approximately 140 F g−1, has been obtained in the electrode grown with the 5-nm thickness of Fe. Samples with both Fe thicknesses showed good cycling performance over 2,000 cycles. PMID:23181897

  7. Recent advancements in carbon nanofiber and carbon nanotube applications in drug delivery and tissue engineering.

    PubMed

    Stout, David A

    2015-01-01

    Since the discovery and synthesis of carbon nanotubes (CNTs) and carbon nanofibers (CNFs) over a decade ago, researchers have envisioned and discovered new potential applications for these materials. CNTs and CNFs have rapidly become a platform technology for a variety of uses, including biomedical applications due to their mechanical, electrical, thermal, optical and structural properties. CNTs and CNFs are also advantageous due to their ability to be produced in many different shapes and sizes. Since their discovery, of the many imaginable applications, CNTs and CNFs have gained a significant amount of attention and therapeutic potential in tissue engineering and drug delivery applications. In recent years, CNTs and CNFs have made significant contributions in designing new strategies for, delivery of pharmaceuticals, genes and molecular probes into cells, stem cell therapies and assisting in tissue regeneration. Furthermore, it is widely expressed that these materials will significantly contribute to the next generation of health care technologies in treating diseases and contributing to tissue growth. Hence, this review seeks to explore the recent advancements, current status and limitations of CNTs and CNFs for drug delivery and tissue engineering applications.

  8. Increased Alignment in Carbon Nanotube Growth

    NASA Technical Reports Server (NTRS)

    Delzeit, Lance D. (Inventor)

    2007-01-01

    Method and system for fabricating an array of two or more carbon nanotube (CNT) structures on a coated substrate surface, the structures having substantially the same orientation with respect to a substrate surface. A single electrode, having an associated voltage source with a selected voltage, is connected to a substrate surface after the substrate is coated and before growth of the CNT structures, for a selected voltage application time interval. The CNT structures are then grown on a coated substrate surface with the desired orientation. Optionally, the electrode can be disconnected before the CNT structures are grown.

  9. Preparation and electrochemical properties of carbon-coated LiFePO4 hollow nanofibers

    NASA Astrophysics Data System (ADS)

    Wei, Bin-bin; Wu, Yan-bo; Yu, Fang-yuan; Zhou, Ya-nan

    2016-04-01

    Carbon-coated LiFePO4 hollow nanofibers as cathode materials for Li-ion batteries were obtained by coaxial electrospinning. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Brunauer-Emmett-Teller specific surface area analysis, galvanostatic charge-discharge, and electrochemical impedance spectroscopy (EIS) were employed to investigate the crystalline structure, morphology, and electrochemical performance of the as-prepared hollow nanofibers. The results indicate that the carbon-coated LiFePO4 hollow nanofibers have good long-term cycling performance and good rate capability: at a current density of 0.2C (1.0C = 170 mA·g-1) in the voltage range of 2.5-4.2 V, the cathode materials achieve an initial discharge specific capacity of 153.16 mAh·g-1 with a first charge-discharge coulombic efficiency of more than 97%, as well as a high capacity retention of 99% after 10 cycles; moreover, the materials can retain a specific capacity of 135.68 mAh·g-1, even at 2C.

  10. Antitumor Activity of Doxorubicin-Loaded Carbon Nanotubes Incorporated Poly(Lactic-Co-Glycolic Acid) Electrospun Composite Nanofibers

    NASA Astrophysics Data System (ADS)

    Yu, Yuan; Kong, Lijun; Li, Lan; Li, Naie; Yan, Peng

    2015-08-01

    The drug-loaded composite electrospun nanofiber has attracted more attention in biomedical field, especially in cancer therapy. In this study, a composite nanofiber was fabricated by electrospinning for cancer treatment. Firstly, the carbon nanotubes (CNTs) were selected as carriers to load the anticancer drug—doxorubicin (DOX) hydrochloride. Secondly, the DOX-loaded CNTs (DOX@CNTs) were incorporated into the poly(lactic-co-glycolic acid) (PLGA) nanofibers via electrospinning. Finally, a new drug-loaded nanofibrous scaffold (PLGA/DOX@CNTs) was formed. The properties of the prepared composite nanofibrous mats were characterized by various techniques. The release profiles of the different DOX-loaded nanofibers were measured, and the in vitro antitumor efficacy against HeLa cells was also evaluated. The results showed that DOX-loaded CNTs can be readily incorporated into the nanofibers with relatively uniform distribution within the nanofibers. More importantly, the drug from the composite nanofibers can be released in a sustained and prolonged manner, and thereby, a significant antitumor efficacy in vitro is obtained. Thus, the prepared composite nanofibrous mats are a promising alternative for cancer treatment.

  11. Characterization of carbon nanofiber mats produced from electrospun lignin-g-polyacrylonitrile copolymer.

    PubMed

    Youe, Won-Jae; Lee, Soo-Min; Lee, Sung-Suk; Lee, Seung-Hwan; Kim, Yong Sik

    2016-01-01

    The graft copolymerization of acrylonitrile (AN) onto methanol-soluble kraft lignin (ML) was achieved through a two-step process in which AN was first polymerized with an α,α'-azobisisobutyronitrile initiator, followed by radical coupling with activated ML. A carbon nanofiber material was obtained by electrospinning a solution of this copolymer in N,N-dimethylformamide, then subjecting it to a heat treatment including thermostabilization at 250°C and subsequent carbonization at 600-1400°C. Increasing the carbonization temperature was found to increase the carbon content of the resulting carbon nanofibers from 70.5 to 97.1%, which had the effect of increasing their tensile strength from 35.2 to 89.4 MPa, their crystallite size from 13.2 to 19.1 nm, and their electrical conductivity from ∼0 to 21.3 Scm(-1). The morphology of the mats, in terms of whether they experienced beading or not, was found to be dependent on the concentration of the initial electrospinning solution. From these results, it is proposed that these mats could provide the basis for a new class of carbon fiber material.

  12. Characterization of carbon nanofiber mats produced from electrospun lignin-g-polyacrylonitrile copolymer.

    PubMed

    Youe, Won-Jae; Lee, Soo-Min; Lee, Sung-Suk; Lee, Seung-Hwan; Kim, Yong Sik

    2016-01-01

    The graft copolymerization of acrylonitrile (AN) onto methanol-soluble kraft lignin (ML) was achieved through a two-step process in which AN was first polymerized with an α,α'-azobisisobutyronitrile initiator, followed by radical coupling with activated ML. A carbon nanofiber material was obtained by electrospinning a solution of this copolymer in N,N-dimethylformamide, then subjecting it to a heat treatment including thermostabilization at 250°C and subsequent carbonization at 600-1400°C. Increasing the carbonization temperature was found to increase the carbon content of the resulting carbon nanofibers from 70.5 to 97.1%, which had the effect of increasing their tensile strength from 35.2 to 89.4 MPa, their crystallite size from 13.2 to 19.1 nm, and their electrical conductivity from ∼0 to 21.3 Scm(-1). The morphology of the mats, in terms of whether they experienced beading or not, was found to be dependent on the concentration of the initial electrospinning solution. From these results, it is proposed that these mats could provide the basis for a new class of carbon fiber material. PMID:26459170

  13. Preparation and characterization of Polyacrylonitrile/ Manganese Dioxides- based Carbon Nanofibers via electrospinning process

    NASA Astrophysics Data System (ADS)

    Che Othman, F. E.; Yusof, N.; Jaafar, J.; Ismail, A. F.; Hasbullah, H.; Abdullah, N.; Ismail, M. S.

    2016-06-01

    This research reports the production of precursor polyacrylonitrile (PAN)/ manganese dioxide (MnO2) nanofibers (NFs) via electrospinning method followed by stabilization and carbonization processes. Nowadays, electrospinning has become a suitable method in manufacturing continuous NFs, thus it is employed to fabricate NFs in this study. The microstructural properties and adsorption competencies of the produced NFs were also studied. The NFs were prepared by electrospinning the polymer solution of Polyacrylonitrile (PAN) and Manganese Dioxide (MnO2) in, N, N-Dimethylformamide (DMF) solvent. The factors considered in this study were various polymer PAN/MnO2 concentrations which will significantly affect the specific surface area, fiber morphology and the diameter of the NFs prepared. Subsequently, heat treatment is applied by setting up the stabilization temperature at 275 °C and carbonization temperature at 800 °C with constant dwelling time (30 min). Nitrogen gas at constant rate 0.2 L/min was used for stabilization and carbonization with the stabilization rate (2 °C/min) and carbonization rate (5 °C/min). The carbon nanofibers (CNFs) produced were characterized using Scanning Electron Microscopy (SEM), Brunauer Emmett and Teller (BET) surface area and Fourier Transmission Infrared Spectroscopy (FTIR). It was found that the PAN/MnO2 CNFs were successfully produced with the carbonization temperature of 800 °C. The prepared PAN/MnO2 CNFs prepared showed an enhanced in specific surface area about two times compared to it precursor NFs.

  14. Iron Carbide Nanoparticles Encapsulated in Mesoporous Fe-N-Doped Carbon Nanofibers for Efficient Electrocatalysis.

    PubMed

    Wu, Zhen-Yu; Xu, Xing-Xing; Hu, Bi-Cheng; Liang, Hai-Wei; Lin, Yue; Chen, Li-Feng; Yu, Shu-Hong

    2015-07-01

    Exploring low-cost and high-performance nonprecious metal catalysts (NPMCs) for oxygen reduction reaction (ORR) in fuel cells and metal-air batteries is crucial for the commercialization of these energy conversion and storage devices. Here we report a novel NPMC consisting of Fe3 C nanoparticles encapsulated in mesoporous Fe-N-doped carbon nanofibers, which is synthesized by a cost-effective method using carbonaceous nanofibers, pyrrole, and FeCl3 as precursors. The electrocatalyst exhibits outstanding ORR activity (onset potential of -0.02 V and half-wave potential of -0.140 V) closely comparable to the state-of-the-art Pt/C catalyst in alkaline media, and good ORR activity in acidic media, which is among the highest reported activities of NPMCs. PMID:26014581

  15. Controlling the Dimensions of Carbon Nanofiber Structures through the Electropolymerization of Pyrrole.

    PubMed

    Fletcher, Benjamin L; McKnight, Timothy E; Fowlkes, Jason D; Allison, David P; Simpson, Michael L; Doktycz, Mitchel J

    2007-04-01

    Electrically conductive polymers, such as polypyrrole (PPy), show promise for modifying the dimensions and properties of micro- and nanoscale structures. Mechanisms for controlling the formation of PPy films of nanoscale thickness were evaluated by electrochemically synthesizing and examining PPy films on planar gold electrodes under a variety of growth conditions. Tunable PPy coatings were then deposited by electropolymerization on the sidewalls of individual, electrically addressable carbon nanofibers (CNFs). The ability to modify the physical size of specific nanofibers in controllable fashion is demonstrated. The biocompatibility, potential for chemical functionalization, and ability to effect volume changes of this nanocomposite can lead to advanced functionality, such as specific, nanoscale valving of materials and morphological control at the nanoscale.

  16. Controlling SEI Formation on SnSb-Porous Carbon Nanofibers for Improved Na Ion Storage

    SciTech Connect

    Ji, Liwen; Gu, Meng; Shao, Yuyan; Li, Xiaolin; Engelhard, Mark H.; Arey, Bruce W.; Wang, Wei; Nie, Zimin; Xiao, Jie; Wang, Chong M.; Zhang, Jiguang; Liu, Jun

    2014-05-14

    Porous carbon nanofiber (CNF)-supported tin-antimony (SnSb) alloys is synthesized and applied as sodium ion battery anode. The chemistry and morphology of the solid electrolyte interphase (SEI) film and its correlation with the electrode performance are studied. The addition of fluoroethylene carbonate (FEC) in electrolyte significantly reduces electrolyte decomposition and creates a very thin and uniform SEI layer on the cycled electrode surface which could promote the kinetics of Na-ion migration/transportation, leading to excellent electrochemical performance.

  17. Mesoporous carbon nanofibers with a high surface area electrospun from thermoplastic polyvinylpyrrolidone

    NASA Astrophysics Data System (ADS)

    Wang, Peiqi; Zhang, Dan; Ma, Feiyue; Ou, Yun; Chen, Qian Nataly; Xie, Shuhong; Li, Jiangyu

    2012-10-01

    Carbon nanofibers (CNFs) have been synthesized from thermoplastic polyvinylpyrrolidone (PVP) using electrospinning in combination with a novel three-step heat treatment process, which successfully stabilizes the fibrous morphology before carbonization that was proven to be difficult for thermoplastic polymers other than polyacrylonitrile (PAN). These CNFs are both mesoporous and microporous with high surface areas without subsequent activation, and thus overcome the limitations of PAN based CNFs, and are processed in an environmentally friendly and more cost effective manner. The effects of heat treatment parameters and precursor concentration on the morphologies and porous properties of CNFs have been investigated, and their application as anodes for lithium ion batteries has also been demonstrated.

  18. Mesoporous carbon nanofibers with a high surface area electrospun from thermoplastic polyvinylpyrrolidone.

    PubMed

    Wang, Peiqi; Zhang, Dan; Ma, Feiyue; Ou, Yun; Chen, Qian Nataly; Xie, Shuhong; Li, Jiangyu

    2012-11-21

    Carbon nanofibers (CNFs) have been synthesized from thermoplastic polyvinylpyrrolidone (PVP) using electrospinning in combination with a novel three-step heat treatment process, which successfully stabilizes the fibrous morphology before carbonization that was proven to be difficult for thermoplastic polymers other than polyacrylonitrile (PAN). These CNFs are both mesoporous and microporous with high surface areas without subsequent activation, and thus overcome the limitations of PAN based CNFs, and are processed in an environmentally friendly and more cost effective manner. The effects of heat treatment parameters and precursor concentration on the morphologies and porous properties of CNFs have been investigated, and their application as anodes for lithium ion batteries has also been demonstrated.

  19. Nanofiber Yarn/Hydrogel Core-Shell Scaffolds Mimicking Native Skeletal Muscle Tissue for Guiding 3D Myoblast Alignment, Elongation, and Differentiation.

    PubMed

    Wang, Ling; Wu, Yaobin; Guo, Baolin; Ma, Peter X

    2015-09-22

    Designing scaffolds that can mimic native skeletal muscle tissue and induce 3D cellular alignment and elongated myotube formation remains an ongoing challenge for skeletal muscle tissue engineering. Herein, we present a simple technique to generate core-shell composite scaffolds for mimicking native skeletal muscle structure, which comprise the aligned nanofiber yarn (NFY) core and the photocurable hydrogel shell. The aligned NFYs are prepared by the hybrid composition including poly(caprolactone), silk fibroin, and polyaniline via a developed dry-wet electrospinning method. A series of core-shell column and sheet composite scaffolds are ultimately obtained by encapsulating a piece and layers of aligned NFY cores within the hydrogel shell after photo-cross-linking. C2C12 myoblasts are seeded within the core-shell scaffolds, and the good biocompatibility of these scaffolds and their ability to induce 3D cellular alignment and elongation are successfully demonstrated. Furthermore, the 3D elongated myotube formation within core-shell scaffolds is also performed after long-term cultivation. These data suggest that these core-shell scaffolds combine the aligned NFY core that guides the myoblast alignment and differentiation and the hydrogel shell that provides a suitable 3D environment for nutrition exchange and mechanical protection to perform a great practical application for skeletal muscle regeneration.

  20. Advanced Multifunctional Properties of Aligned Carbon Nanotube-Epoxy Composites from Carbon Nanotube Aerogel Method

    NASA Astrophysics Data System (ADS)

    Tran, Thang; Liu, Peng; Fan, Zeng; Ngern, Nigel; Duong, Hai

    2015-03-01

    Unlike previous methods of making carbon nanotube (CNT) thin films, aligned CNT thin films in this work are synthesized directly from CNT aerogels in a CVD process. CH4/H2/He gases and ferrocene/thiophene catalysts are mixed and reacted in the reactor at 1200 °C to form CNT aerogel socks. By pulling out the socks with a metal rod, CNT thin films with 15-nm diameter MWNTs are aligned and produced continuously at a speed of a few meters per minute. The number of the aligned CNT thin film layers/ thickness can also be controlled well. The as-synthesized aligned CNT films are further condensed by acetone spray and post-treated by UV light. The aligned CNT films without any above post-treatment have a high electrical conductivity of 400S/cm. We also develop aligned CNT-epoxy composites by infiltrating epoxy into the above aligned CNT thin films using Vacuum Assisted Resin Transfer Molding (VARTM) method. Our cost-effective fabrication method of the aligned CNT films is more advanced for developing the composites having CNT orientation control. The mechanical, electrical and optical properties of the aligned CNT epoxy composites are measured. About 2% of the aligned CNTs can enhance significantly the electrical conductivity and hardness of aligned CNT-epoxy composite films. Effects of morphologies, volume fraction, and alignment of the CNTs on the advanced multifunctional properties of the aligned CNT-epoxy composites are also quantified.

  1. Nanodrawing of Aligned Single Carbon Nanotubes with a Nanopen.

    PubMed

    Yeshua, Talia; Lehmann, Christian; Hübner, Uwe; Azoubel, Suzanna; Magdassi, Shlomo; Campbell, Eleanor E B; Reich, Stephanie; Lewis, Aaron

    2016-03-01

    Single-walled carbon nanotubes (SWCNTs) are considered pivotal components for molecular electronics. Techniques for SWCNT lithography today lack simplicity, flexibility, and speed of direct, oriented deposition at specific target locations. In this paper SWCNTs are directly drawn and placed with chemical identification and demonstrated orientation using fountain pen nanolithography (FPN) under ambient conditions. Placement across specific electrical contacts with such alignment is demonstrated and characterized. The fundamental basis of the drawing process with alignment has potential applications for other related systems such as inorganic nanotubes, polymers, and biological molecules.

  2. Synthesis of Vertically-Aligned Single-Walled Carbon Nanotubes in Micro Structure of Atmospheric Pressure Non-Equilibrium Plasma

    NASA Astrophysics Data System (ADS)

    Ohnishi, Kuma; Nozaki, Tomohiro; Okazaki, Ken; Heberlein, Joachim; Kortshagen, Uwe

    Plasma enhanced chemical vapor deposition (PECVD) is recognized as one of the viable fabrication techniques of carbon nanotubes. The outstanding advantage of PECVD is that free-standing, vertically-aligned carbon nanotubes (VA-CNTs) are synthesized due to the electric field normal to the substrate. This feature draws intense attention for the fabrication of nanoelectronic devices such as high-resolution scanning nanoprobes, interconnects, and field emission devices. However, carbon nanotubes synthesized in PECVD are overwhelmingly carbon nanofibers (CNFs) or multi-walled carbon nanotubes (MWNTs) with measurable structural defects. Tremendous interest in the preparation and characterization of vertically-aligned single-walled carbon nanotubes (VA-SWNTs) and related applications had not been realized in the scope of PECVD until recently. Here we present a fabrication technique of high-purity vertically-aligned single-walled carbon nanotubes using atmospheric pressure plasma enhanced chemical vapor deposition. By now, we have developed the atmospheric pressure radio-frequency discharge (APRFD) for this purpose. Although densely mono-dispersed Fe-Co catalysts of a few nanometers is primarily responsible for VA-SWNT growth, carbon precipitation was virtually absent in the thermal CVD regime at 700°C. On the other hand, high-yield VA-SWNTs were grown at 4 μm min-1 by applying the atmospheric pressure radio-frequency discharge. The results proved that cathodic ion sheath adjacent to the substrates, where a large potential drop exists, also plays an essential role for the controlled growth of SWNTs, while ion damage to the VA-SWNTs is inherently avoided due to high collision frequency among molecules in atmospheric pressure. In this paper, operation regime of APRFD and tentative reaction mechanisms for VA-SWNT growth are discussed along with optical imaging of near substrate region of APRFD.

  3. Growth of aligned carbon nanotubes on carbon microfibers by dc plasma-enhanced chemical vapor deposition

    SciTech Connect

    Chen, L H.; AuBuchon, J F.; Chen, I C.; Daraio, C; Ye, X R.; Gapin, A; Jin, Sungho; Wang, Chong M.

    2006-01-16

    It is shown that unidirectionally aligned carbon nanotubes can be grown on electrically conductive network of carbon microfibers via control of buffer layer material and applied electric field during dc plasma chemical vapor deposition growth. Ni catalyst deposition on carbon microfiber produces relatively poorly aligned nanotubes with significantly varying diameters and lengths obtained. The insertion of Ti 5 nm thick underlayer between Ni catalyst layer and C microfiber substrate significantly alters the morphology of nanotubes, resulting in much better aligned, finer diameter, and longer array of nanotubes. This beneficial effect is attributed to the reduced reaction between Ni and carbon paper, as well as prevention of plasma etching of carbon paper by inserting a Ti buffer layer. Such a unidirectionally aligned nanotube structure on an open-pore conductive substrate structure may conveniently be utilized as a high-surface-area base electrodes for fuel cells, batteries, and other electrochemical and catalytic reactions.

  4. High performance piezoelectric devices based on aligned arrays of nanofibers of poly(vinylidenefluoride-co-trifluoroethylene).

    PubMed

    Persano, Luana; Dagdeviren, Canan; Su, Yewang; Zhang, Yihui; Girardo, Salvatore; Pisignano, Dario; Huang, Yonggang; Rogers, John A

    2013-01-01

    Multifunctional capability, flexible design, rugged lightweight construction and self-powered operation are desired attributes for electronics that directly interface with the human body or with advanced robotic systems. For these applications, piezoelectric materials, in forms that offer the ability to bend and stretch, are attractive for pressure/force sensors and mechanical energy harvesters. Here, we introduce a large area, flexible piezoelectric material that consists of sheets of electrospun fibres of the polymer poly[(vinylidenefluoride-co-trifluoroethylene]. The flow and mechanical conditions associated with the spinning process yield free-standing, three-dimensional architectures of aligned arrangements of such fibres, in which the polymer chains adopt strongly preferential orientations. The resulting material offers exceptional piezoelectric characteristics, to enable ultra-high sensitivity for measuring pressure, even at exceptionally small values (0.1 Pa). Quantitative analysis provides detailed insights into the pressure sensing mechanisms, and establishes engineering design rules. Potential applications range from self-powered micro-mechanical elements, to self-balancing robots and sensitive impact detectors.

  5. High performance piezoelectric devices based on aligned arrays of nanofibers of poly(vinylidenefluoride-co-trifluoroethylene)

    NASA Astrophysics Data System (ADS)

    Persano, Luana; Dagdeviren, Canan; Su, Yewang; Zhang, Yihui; Girardo, Salvatore; Pisignano, Dario; Huang, Yonggang; Rogers, John A.

    2013-03-01

    Multifunctional capability, flexible design, rugged lightweight construction and self-powered operation are desired attributes for electronics that directly interface with the human body or with advanced robotic systems. For these applications, piezoelectric materials, in forms that offer the ability to bend and stretch, are attractive for pressure/force sensors and mechanical energy harvesters. Here, we introduce a large area, flexible piezoelectric material that consists of sheets of electrospun fibres of the polymer poly[(vinylidenefluoride-co-trifluoroethylene]. The flow and mechanical conditions associated with the spinning process yield free-standing, three-dimensional architectures of aligned arrangements of such fibres, in which the polymer chains adopt strongly preferential orientations. The resulting material offers exceptional piezoelectric characteristics, to enable ultra-high sensitivity for measuring pressure, even at exceptionally small values (0.1 Pa). Quantitative analysis provides detailed insights into the pressure sensing mechanisms, and establishes engineering design rules. Potential applications range from self-powered micro-mechanical elements, to self-balancing robots and sensitive impact detectors.

  6. Ultralight anisotropic foams from layered aligned carbon nanotube sheets.

    PubMed

    Faraji, Shaghayegh; Stano, Kelly L; Yildiz, Ozkan; Li, Ang; Zhu, Yuntian; Bradford, Philip D

    2015-10-28

    In this work, we present large scale, ultralight aligned carbon nanotube (CNT) structures which have densities an order of magnitude lower than CNT arrays, have tunable properties and exhibit resiliency after compression. By stacking aligned sheets of carbon nanotubes and then infiltrating with a pyrolytic carbon (PyC), resilient foam-like materials were produced that exhibited complete recovery from 90% compressive strain. With density as low as 3.8 mg cm(-3), the foam structure is over 500 times less dense than bulk graphite. Microscopy revealed that PyC coated the junctions among CNTs, and also increased CNT surface roughness. These changes in the morphology explain the transition from inelastic behavior to foam-like recovery of the layered CNT sheet structure. Mechanical and thermal properties of the foams were tuned for different applications through variation of PyC deposition duration while dynamic mechanical analysis showed no change in mechanical properties over a large temperature range. Observation of a large and linear electrical resistance change during compression of the aligned CNT/carbon (ACNT/C) foams makes strain/pressure sensors a relevant application. The foams have high oil absorption capacities, up to 275 times their own weight, which suggests they may be useful in water treatment and oil spill cleanup. Finally, the ACNT/C foam's high porosity, surface area and stability allow for demonstration of the foams as catalyst support structures.

  7. LDRD final report : chromophore-functionalized aligned carbon nanotube arrays.

    SciTech Connect

    Vance, Andrew L.; Yang, Chu-Yeu Peter; Krafcik, Karen Lee

    2011-09-01

    The goal of this project was to expand upon previously demonstrated single carbon nanotube devices by preparing a more practical, multi-single-walled carbon nanotube (SWNT) device. As a late-start, proof-of-concept project, the work focused on the fabrication and testing of chromophore-functionalized aligned SWNT field effect transistors (SWNT-FET). Such devices have not yet been demonstrated. The advantages of fabricating aligned SWNT devices include increased device cross-section to improve sensitivity to light, elimination of increased electrical resistance at nanotube junctions in random mat devices, and the ability to model device responses. The project did not achieve the goal of fabricating and testing chromophore-modified SWNT arrays, but a new SWNT growth capability was established that will benefit future projects. Although the ultimate goal of fabricating and testing chromophore-modified SWNT arrays was not achieved, the work did lead to a new carbon nanotube growth capability at Sandia/CA. The synthesis of dense arrays of horizontally aligned SWNTs is a developing area of research with significant potential for new discoveries. In particular, the ability to prepare arrays of carbon nanotubes of specific electronic types (metallic or semiconducting) could yield new classes of nanoscale devices.

  8. Ultralight anisotropic foams from layered aligned carbon nanotube sheets.

    PubMed

    Faraji, Shaghayegh; Stano, Kelly L; Yildiz, Ozkan; Li, Ang; Zhu, Yuntian; Bradford, Philip D

    2015-10-28

    In this work, we present large scale, ultralight aligned carbon nanotube (CNT) structures which have densities an order of magnitude lower than CNT arrays, have tunable properties and exhibit resiliency after compression. By stacking aligned sheets of carbon nanotubes and then infiltrating with a pyrolytic carbon (PyC), resilient foam-like materials were produced that exhibited complete recovery from 90% compressive strain. With density as low as 3.8 mg cm(-3), the foam structure is over 500 times less dense than bulk graphite. Microscopy revealed that PyC coated the junctions among CNTs, and also increased CNT surface roughness. These changes in the morphology explain the transition from inelastic behavior to foam-like recovery of the layered CNT sheet structure. Mechanical and thermal properties of the foams were tuned for different applications through variation of PyC deposition duration while dynamic mechanical analysis showed no change in mechanical properties over a large temperature range. Observation of a large and linear electrical resistance change during compression of the aligned CNT/carbon (ACNT/C) foams makes strain/pressure sensors a relevant application. The foams have high oil absorption capacities, up to 275 times their own weight, which suggests they may be useful in water treatment and oil spill cleanup. Finally, the ACNT/C foam's high porosity, surface area and stability allow for demonstration of the foams as catalyst support structures. PMID:26419855

  9. Control of physical properties of carbon nanofibers obtained from coaxial electrospinning of PMMA and PAN with adjustable inner/outer nozzle-ends.

    PubMed

    Kaerkitcha, Navaporn; Chuangchote, Surawut; Sagawa, Takashi

    2016-12-01

    Hollow carbon nanofibers (HCNFs) were prepared by electrospinning method with several coaxial nozzles, in which the level of the inner nozzle-end is adjustable. Core/shell nanofibers were prepared from poly(methyl methacrylate) (PMMA) as a pyrolytic core and polyacrylonitrile (PAN) as a carbon shell with three types of normal (viz. inner and outer nozzle-ends are balanced in the same level), inward, and outward coaxial nozzles. The influence of the applied voltage on these three types of coaxial nozzles was studied. Specific surface area, pore size diameter, crystallinity, and degree of graphitization of the hollow and mesoporous structures of carbon nanofibers obtained after carbonization of the as spun PMMA/PAN nanofibers were characterized by BET analyses, X-ray diffraction, and Raman spectroscopy in addition to the conductivity measurements. It was found that specific surface area, crystallinity, and graphitization degree of the HCNFs affect the electrical conductivity of the carbon nanofibers. PMID:27067734

  10. Exposure and Emissions Monitoring during Carbon Nanofiber Production—Part I: Elemental Carbon and Iron–Soot Aerosols

    PubMed Central

    Birch, M. Eileen; Ku, Bon-Ki; Evans, Douglas E.; Ruda-Eberenz, Toni A.

    2015-01-01

    Production of carbon nanofibers and nanotubes (CNFs/CNTs) and their composite products is increasing globally. High volume production may increase the exposure risks for workers who handle these materials. Though health effects data for CNFs/CNTs are limited, some studies raise serious health concerns. Given the uncertainty about their potential hazards, there is an immediate need for toxicity data and field studies to assess exposure to CNFs/CNTs. An extensive study was conducted at a facility that manufactures and processes CNFs. Filter, sorbent, cascade impactor, bulk, and microscopy samples, combined with direct-reading instruments, provided complementary information on air contaminants. Samples were analyzed for organic carbon (OC) and elemental carbon (EC), metals, and polycyclic aromatic hydrocarbons (PAHs), with EC as a measure of CNFs. Transmission electron microscopy with energy-dispersive X-ray spectroscopy also was applied. Fine/ultrafine iron-rich soot, PAHs, and carbon monoxide were production byproducts. Direct-reading instrument results were reported previously [Evans DE et al. (Aerosol monitoring during carbon nanofiber production: mobile direct-reading sampling. Ann Occup Hyg 2010;54:514–31.)] Results for time-integrated samples are reported as companion papers in this Issue. OC and EC, metals, and microscopy results are reported here, in Part I, while results for PAHs are reported in Part II [Birch ME. (Exposure and Emissions Monitoring during Carbon Nanofiber Production—Part II: Polycyclic Aromatic Hydrocarbons. Ann. Occup. Hyg 2011; 55: 1037–47.)]. Respirable EC area concentrations inside the facility were about 6–68 times higher than outdoors, while personal breathing zone samples were up to 170 times higher. PMID:21965464

  11. Superior Electrochemical Properties of Nanofibers Composed of Hollow CoFe2 O4 Nanospheres Covered with Onion-Like Graphitic Carbon.

    PubMed

    Hong, Young Jun; Cho, Jung Sang; Kang, Yun Chan

    2015-12-01

    Nanofibers composed of hollow CoFe2 O4 nanospheres covered with onion-like carbon are prepared by applying nanoscale Kirkendall diffusion to the electrospinning process. Amorphous carbon nanofibers embedded with CoFe2 @onion-like carbon nanospheres are prepared by reduction of the electrospun nanofibers. Oxidation of the CoFe2 -C nanofibers at 300 °C under a normal atmosphere produces porous nanofibers composed of hollow CoFe2 O4 nanospheres covered with onion-like carbon. CoFe2 nanocrystals are transformed into the hollow CoFe2 O4 nanospheres during oxidation through a well-known nanoscale Kirkendall diffusion process. The discharge capacities of the carbon-free CoFe2 O4 nanofibers composed of hollow nanospheres and the nanofibers composed of hollow CoFe2 O4 nanospheres covered with onion-like carbon are 340 and 930 mA h g(-1) , respectively, for the 1000th cycle at a current density of 1 A g(-1) . The nanofibers composed of hollow CoFe2 O4 nanospheres covered with onion-like carbon exhibit an excellent rate performance even in the absence of conductive materials.

  12. Alignment and Load Transfer in Carbon Nanotube and Dicyclopentadiene Composites

    NASA Astrophysics Data System (ADS)

    Severino, Joseph Vincent

    Individual carbon nanotubes (CNTs) are the strongest materials available but their macroscopic assemblies are weak. This work establishes a new thermosetting dicyclopentadiene (DCPD) and CNT composite that increases the strength of CNT assemblies. These high volume fraction and void free structures constitute advanced materials that could one day replace traditional composite systems. To further the understanding of physical interactions between polymer and CNTs, a novel "capstan" load transfer mechanism is also introduced. Self-supporting assemblies of interconnected carbon nanotubes were stretched, twisted and compressed to fashion composites by the infusion and polymerization of low viscosity DCPD based monomeric resins. The properties of the CNTs, polymer and composite were characterized with thermal gravimetric analysis (TGA), dynamic mechanical analysis (DMA) and Raman spectroscopy. The microstructure was analyzed by wide angle X-ray scattering (WAXS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Sheets were drawn at 15 m/min from a growth furnace to impart alignment then stretched to further modify alignment. The mechanical properties were determined in five orientations with respect to the growth direction. The strength was nearly three times higher along this growth direction than it was perpendicular, and modulus was nearly six times higher. Transverse stretching achieved 1.5 times the elongation but alignment was inferior due to CNT kinking that prevented alignment and consolidation. Composites yarns and sheets were investigated for the mechanical properties, microstructure and load transfer. The DCPD resin was found to wet the CNTs and lubricated deformation. This reduced loads during processing, and curing solidified the aligned and consolidated structure. The stretched and twisted composite yarns increased the failure stress 51%. In aligned composite sheet, the failure stress increased 200%. The increased stresses

  13. Diamond synthesis from carbon nanofibers at low temperature and low pressure.

    PubMed

    Luo, Chengzhi; Qi, Xiang; Pan, Chunxu; Yang, Wenge

    2015-01-01

    In this article, we report a new route to synthesize diamond by converting "solid" carbon nanofibers with a Spark Plasma Sintering system under low temperature and pressure (even at atmospheric pressure). Well-crystallized diamond crystals are obtained at the tips of the carbon nanofibers after sintering at 1500 °C and atmospheric pressure. Combining with scanning electron microscopy, transmission electron microscopy, electron-energy loss spectroscopy and Raman spectroscopy observations, we propose the conversion mechanism as follows: the disorder "solid" carbon nanofibers→well crystallined carbon nanofibers→bent graphitic sheets→onion-liked rings→diamond single crystal→the bigger congregated diamond crystal. It is believed that the plasma generated by low-voltage, vacuum spark, via a pulsed DC in Spark Plasma Sintering process, plays a critical role in the low temperature and low pressure diamond formation. This Spark Plasma Sintering process may provide a new route for diamond synthesis in an economical way to a large scale. PMID:26351089

  14. Characterization of carbon nanofibers grown over Ni and Ni-cu catalysts.

    PubMed

    Echegoyen, Y; Suelves, I; Lázaro, M J; Moliner, R; Palacios, J M; Müller, J O; Su, D; Schlögl, R

    2009-07-01

    Carbon nanofibers were obtained by thermo-catalytic decomposition of methane at 700 degrees C over Ni and Ni-Cu catalysts prepared by different methods (co-precipitation, impregnation and fusion) and using either Al or Mg as textural promoter. Characterization of the carbon thus obtained was performed by N2 adsorption isotherms (BET surface area), temperature programmed desorption (TPD), temperature programmed oxidation (TPO), X-ray diffraction, Raman spectrometry, and electron microscopy SEM and TEM. The carbon obtained possesses high crystallinity and poor surface chemistry. The crystallinity is enhanced when using Mg as textural promoter and in the presence of copper. SEM and TEM examinations show that the fibers have fishbone structure and they grow generally from one nickel particle (tip growing) although there are some bidirectional growing. Copper-doping lead to the formation of thicker filaments and promotes the formation of bamboo-like structures. Catalyst particles higher than 100 nm do not promote the formation of nanofibers and the carbon deposits as uniform coatings.

  15. Diamond synthesis from carbon nanofibers at low temperature and low pressure

    NASA Astrophysics Data System (ADS)

    Luo, Chengzhi; Qi, Xiang; Pan, Chunxu; Yang, Wenge

    2015-09-01

    In this article, we report a new route to synthesize diamond by converting “solid” carbon nanofibers with a Spark Plasma Sintering system under low temperature and pressure (even at atmospheric pressure). Well-crystallized diamond crystals are obtained at the tips of the carbon nanofibers after sintering at 1500 °C and atmospheric pressure. Combining with scanning electron microscopy, transmission electron microscopy, electron-energy loss spectroscopy and Raman spectroscopy observations, we propose the conversion mechanism as follows: the disorder “solid” carbon nanofibers → well crystallined carbon nanofibers → bent graphitic sheets → onion-liked rings → diamond single crystal → the bigger congregated diamond crystal. It is believed that the plasma generated by low-voltage, vacuum spark, via a pulsed DC in Spark Plasma Sintering process, plays a critical role in the low temperature and low pressure diamond formation. This Spark Plasma Sintering process may provide a new route for diamond synthesis in an economical way to a large scale.

  16. Diamond synthesis from carbon nanofibers at low temperature and low pressure.

    PubMed

    Luo, Chengzhi; Qi, Xiang; Pan, Chunxu; Yang, Wenge

    2015-09-09

    In this article, we report a new route to synthesize diamond by converting "solid" carbon nanofibers with a Spark Plasma Sintering system under low temperature and pressure (even at atmospheric pressure). Well-crystallized diamond crystals are obtained at the tips of the carbon nanofibers after sintering at 1500 °C and atmospheric pressure. Combining with scanning electron microscopy, transmission electron microscopy, electron-energy loss spectroscopy and Raman spectroscopy observations, we propose the conversion mechanism as follows: the disorder "solid" carbon nanofibers→well crystallined carbon nanofibers→bent graphitic sheets→onion-liked rings→diamond single crystal→the bigger congregated diamond crystal. It is believed that the plasma generated by low-voltage, vacuum spark, via a pulsed DC in Spark Plasma Sintering process, plays a critical role in the low temperature and low pressure diamond formation. This Spark Plasma Sintering process may provide a new route for diamond synthesis in an economical way to a large scale.

  17. Diamond synthesis from carbon nanofibers at low temperature and low pressure

    PubMed Central

    Luo, Chengzhi; Qi, Xiang; Pan, Chunxu; Yang, Wenge

    2015-01-01

    In this article, we report a new route to synthesize diamond by converting “solid” carbon nanofibers with a Spark Plasma Sintering system under low temperature and pressure (even at atmospheric pressure). Well-crystallized diamond crystals are obtained at the tips of the carbon nanofibers after sintering at 1500 °C and atmospheric pressure. Combining with scanning electron microscopy, transmission electron microscopy, electron-energy loss spectroscopy and Raman spectroscopy observations, we propose the conversion mechanism as follows: the disorder “solid” carbon nanofibers → well crystallined carbon nanofibers → bent graphitic sheets → onion-liked rings → diamond single crystal → the bigger congregated diamond crystal. It is believed that the plasma generated by low-voltage, vacuum spark, via a pulsed DC in Spark Plasma Sintering process, plays a critical role in the low temperature and low pressure diamond formation. This Spark Plasma Sintering process may provide a new route for diamond synthesis in an economical way to a large scale. PMID:26351089

  18. Large-scale synthesis of flexible free-standing SERS substrates with high sensitivity: electrospun PVA nanofibers embedded with controlled alignment of silver nanoparticles.

    PubMed

    He, Dian; Hu, Bo; Yao, Qiao-Feng; Wang, Kan; Yu, Shu-Hong

    2009-12-22

    A new and facile way to synthesize a free-standing and flexible surface-enhanced Raman scattering (SERS) substrate has been successfully developed, where high SERS-active Ag dimers or aligned aggregates are assembled within poly(vinyl alcohol) (PVA) nanofibers with chain-like arrays via electrospinning technique. The aggregation state of the obtained Ag nanoparticle dimers or larger, which are formed in a concentrated PVA solution, makes a significant contribution to the high sensitivity of SERS to 4-mercaptobenzoic acid (4-MBA) molecules with an enhancement factor (EF) of 10(9). The superiority of enhancement ability of this Ag/PVA nanofiber mat is also shown in the comparison to other substrates. Furthermore, the Ag/PVA nanofiber mat would keep a good reproducibility under a low concentration of 4-MBA molecule (10(-6) M) detection with the average RSD values of the major Raman peak less than 0.07. The temporal stability of the substrate has also been demonstrated. This disposable, easy handled, flexible free-standing substrate integrated the advantages including the superiority of high sensitivity, reproducibility, stability, large-scale, and low-cost production compared with other conventional SERS substrates, implying that it is a perfect choice for practical SERS detection application.

  19. Growth of horizontally aligned dense carbon nanotubes from trench sidewalls.

    PubMed

    Lu, Jingyu; Miao, Jianmin; Xu, Ting; Yan, Bin; Yu, Ting; Shen, Zexiang

    2011-07-01

    Horizontally aligned, dense carbon nanotubes (HADCNTs) in the form of CNT cantilevers/bridges were grown from selected trench sidewalls in silicon substrate by chemical vapor deposition (CVD). The as-grown CNT cantilevers/bridges are packed with multiwalled carbon nanotubes (MWCNTs) with a linear density of about 10 CNTs µm(-1). The excellent horizontal alignment of these CNTs is mainly ascribed to the van der Waals interactions within the dense CNT bundles. What is more, the Raman intensity ratio I(G)/I(D) shows a gradual increase from the CNT roots to tips, indicating a defect gradient along CNTs generated during their growth. These results will inspire further efforts to explore the fundamentals and applications of HADCNTs. PMID:21586807

  20. Growth and characterization of vertically aligned carbon nanotubes using PECVD

    NASA Astrophysics Data System (ADS)

    Neupane, Suman; Li, Wenzhi

    2010-03-01

    Vertically aligned carbon nanotubes (CNTs) have been grown by using plasma enhanced chemical vapor deposition technique (PECVD). The density of the CNTs is controlled by the density of the nickel catalyst nanoparticles on silicon (Si) surface. Photolithography and nanosphere lithography have been employed to form a catalyst nanoparticle pattern on Si to grow periodic array of CNTS with controllable size and distribution. The electron emission properties of the CNT array have also been investigated.

  1. The effect of filler aspect ratio on the electromagnetic properties of carbon-nanofibers reinforced composites

    SciTech Connect

    De Vivo, B.; Lamberti, P.; Spinelli, G. Tucci, V.; Guadagno, L.; Raimondo, M.

    2015-08-14

    The effect of filler aspect ratio on the electromagnetic properties of epoxy-amine resin reinforced with carbon nanofibers is here investigated. A heat treatment at 2500 °C of carbon nanofibers seems to increase their aspect ratio with respect to as-received ones most likely due to a lowering of structural defects and the improvement of the graphene layers within the dixie cup conformation. These morphological differences revealed by Raman's spectroscopy and scanning electron microscopy analyses may be responsible for the different electrical properties of the resulting composites. The DC characterization of the nanofilled material highlights an higher electrical conductivity and a lower electrical percolation threshold for the heat-treated carbon nanofibers based composites. In fact, the electrical conductivity is about 0.107 S/m and 1.36 × 10{sup −3} S/m for the nanocomposites reinforced with heat-treated and as received fibers, respectively, at 1 wt. % of nanofiller loading, while the electrical percolation threshold falls in the range [0.05–0.32]wt. % for the first nanocomposites and above 0.64 wt. % for the latter. Moreover, also a different frequency response is observed since the critical frequency, which is indicative of the transition from a resistive to a capacitive-type behaviour, shifts forward of about one decade at the same filler loading. The experimental results are supported by theoretical and simulation studies focused on the role of the filler aspect ratio on the electrical properties of the nanocomposites.

  2. Copper-encapsulated vertically aligned carbon nanotube arrays.

    PubMed

    Stano, Kelly L; Chapla, Rachel; Carroll, Murphy; Nowak, Joshua; McCord, Marian; Bradford, Philip D

    2013-11-13

    A new procedure is described for the fabrication of vertically aligned carbon nanotubes (VACNTs) that are decorated, and even completely encapsulated, by a dense network of copper nanoparticles. The process involves the conformal deposition of pyrolytic carbon (Py-C) to stabilize the aligned carbon-nanotube structure during processing. The stabilized arrays are mildly functionalized using oxygen plasma treatment to improve wettability, and they are then infiltrated with an aqueous, supersaturated Cu salt solution. Once dried, the salt forms a stabilizing crystal network throughout the array. After calcination and H2 reduction, Cu nanoparticles are left decorating the CNT surfaces. Studies were carried out to determine the optimal processing parameters to maximize Cu content in the composite. These included the duration of Py-C deposition and system process pressure as well as the implementation of subsequent and multiple Cu salt solution infiltrations. The optimized procedure yielded a nanoscale hybrid material where the anisotropic alignment from the VACNT array was preserved, and the mass of the stabilized arrays was increased by over 24-fold because of the addition of Cu. The procedure has been adapted for other Cu salts and can also be used for other metal salts altogether, including Ni, Co, Fe, and Ag. The resulting composite is ideally suited for application in thermal management devices because of its low density, mechanical integrity, and potentially high thermal conductivity. Additionally, further processing of the material via pressing and sintering can yield consolidated, dense bulk composites. PMID:24143862

  3. Microwave characterization of vertically aligned multiwalled carbon nanotube arrays

    NASA Astrophysics Data System (ADS)

    Katsounaros, Anestis; Rajab, Khalid Z.; Hao, Yang; Mann, Mark; Milne, William I.

    2011-05-01

    Vertically aligned multiwalled carbon nanotube (VACNT) films have been characterized by rectangular waveguide measurements. The complex scattering parameters (S-parameters) are measured by a vector network analyzer at X-band frequencies. The effective complex permittivity and permeability of the VACNT films have been extracted. The extracted parameters are verified by full wave simulations and very good agreement has been obtained. The results of the systematic error analysis are presented and the errors are within the acceptable range. The performance of VACNT films as an absorber is examined, and comparison with the conventional carbon loaded materials shows that a 90% size reduction is possible while maintaining the same absorption level.

  4. Plum-branch-like carbon nanofibers decorated with SnO2 nanocrystals

    NASA Astrophysics Data System (ADS)

    Yang, Zunxian; Du, Guodong; Guo, Zaiping; Yu, Xuebin; Li, Sean; Chen, Zhixin; Zhang, Peng; Liu, Huakun

    2010-06-01

    Novel plum-branch-like carbon nanofibers (CNFs) decorated with SnO2 nanocrystals have been synthesized by electrospinning and subsequent thermal treatment in an Ar/H2O atmosphere. The morphologies of the as-synthesized SnO2/CNF composites and the contents of carbon and SnO2 can be controlled by adjusting the heat treatment temperature. It is proposed that the growth of SnO2/CNF composites follows the outward diffusion of tin composites from the as-spun tin composite/polyacrylonitrile (PAN) nanofibers, pyrolysis of PAN and oxidation of tin composites, and then formation of SnO2 nanocrystals around the CNFs. This novel 1D SnO2/CNF composite may have potential application in nanobatteries, nano fuel cells, and nanosensors. A preliminary result has revealed that the SnO2/CNF composite presents favourable electrochemical performance in lithium-ion batteries.Novel plum-branch-like carbon nanofibers (CNFs) decorated with SnO2 nanocrystals have been synthesized by electrospinning and subsequent thermal treatment in an Ar/H2O atmosphere. The morphologies of the as-synthesized SnO2/CNF composites and the contents of carbon and SnO2 can be controlled by adjusting the heat treatment temperature. It is proposed that the growth of SnO2/CNF composites follows the outward diffusion of tin composites from the as-spun tin composite/polyacrylonitrile (PAN) nanofibers, pyrolysis of PAN and oxidation of tin composites, and then formation of SnO2 nanocrystals around the CNFs. This novel 1D SnO2/CNF composite may have potential application in nanobatteries, nano fuel cells, and nanosensors. A preliminary result has revealed that the SnO2/CNF composite presents favourable electrochemical performance in lithium-ion batteries. Electronic supplementary information (ESI) available: Figures S1-S6. See DOI: 10.1039/c0nr00009d

  5. Cu grown carbon nanofibers - Variation of their chemical and physical properties

    NASA Astrophysics Data System (ADS)

    Bhoware, Shrikant; Maubane, Manoko S.; Phaahlamohlaka, Tumelo; Shaikjee, Ahmed; Coville, Neil J.

    2013-07-01

    Carbon nanofibers (CNFs) were prepared by passing a mixture of acetylene/H2 or acetylene/N2 over different Cu catalysts. The Soxhlet extracted CNFs were characterized by TEM, TGA and IR spectroscopy and revealed that the morphology, diameter distribution and crystallinity of the CNFs varied with gas atmosphere and Cu particle size. TEM images revealed that coiled CNFs were only produced from Cu/SiO2 grown in the presence of H2. It is thus revealed that the CNFs produced by different Cu catalysts have different chemical and physical properties and that these properties correlate with catalyst particle size and the gas mixtures used.

  6. CdS loaded on coal based activated carbon nanofibers with enhanced photocatalytic property

    NASA Astrophysics Data System (ADS)

    Guo, Jixi; Guo, Mingxi; Jia, Dianzeng; Song, Xianli; Tong, Fenglian

    2016-08-01

    The coal based activated carbon nanofibers (CBACFs) were prepared by electrospinning a mixture of polyacrylonitrile (PAN) and acid treated coal. Cadmium sulfide (CdS) nanoparticles loaded on CBACFs were fabricated by solvothermal method. The obtained samples were characterized by FESEM, TEM, and XRD. The results reveal that the CdS nanoparticles are homogeneously dispersed on the surfaces of CBACFs. The CdS/CBACFs nanocomposites exhibited higher photoactivity for photodegradation of methyl blue (MB) under visible light irradiation than pure CdS nanoparticles. CBACFs can be used as low cost support materials for the preparation of nanocomposites with high photocatalytic activity.

  7. Aligned carbon nanotube array stiffness from stochastic three-dimensional morphology

    NASA Astrophysics Data System (ADS)

    Stein, Itai Y.; Lewis, Diana J.; Wardle, Brian L.

    2015-11-01

    The landmark theoretical properties of low dimensional materials have driven more than a decade of research on carbon nanotubes (CNTs) and related nanostructures. While studies on isolated CNTs report behavior that aligns closely with theoretical predictions, studies on cm-scale aligned CNT arrays (>1010 CNTs) oftentimes report properties that are orders of magnitude below those predicted by theory. Using simulated arrays comprised of up to 105 CNTs with realistic stochastic morphologies, we show that the CNT waviness, quantified via the waviness ratio (w), is responsible for more than three orders of magnitude reduction in the effective CNT stiffness. Also, by including information on the volume fraction scaling of the CNT waviness, the simulation shows that the observed non-linear enhancement of the array stiffness as a function of the CNT close packing originates from the shear and torsion deformation mechanisms that are governed by the low shear modulus (~1 GPa) of the CNTs.The landmark theoretical properties of low dimensional materials have driven more than a decade of research on carbon nanotubes (CNTs) and related nanostructures. While studies on isolated CNTs report behavior that aligns closely with theoretical predictions, studies on cm-scale aligned CNT arrays (>1010 CNTs) oftentimes report properties that are orders of magnitude below those predicted by theory. Using simulated arrays comprised of up to 105 CNTs with realistic stochastic morphologies, we show that the CNT waviness, quantified via the waviness ratio (w), is responsible for more than three orders of magnitude reduction in the effective CNT stiffness. Also, by including information on the volume fraction scaling of the CNT waviness, the simulation shows that the observed non-linear enhancement of the array stiffness as a function of the CNT close packing originates from the shear and torsion deformation mechanisms that are governed by the low shear modulus (~1 GPa) of the CNTs. Electronic

  8. WO3-x Nanoplates Grown on Carbon Nanofibers for an Efficient Electrocatalytic Hydrogen Evolution Reaction.

    PubMed

    Chen, JiaDong; Yu, DanNi; Liao, WeiSha; Zheng, MengDan; Xiao, LongFei; Zhu, Han; Zhang, Ming; Du, MingLiang; Yao, JuMing

    2016-07-20

    The search for non-noble metal catalysts with high activity for the hydrogen evolution reaction (HER) is crucial for efficient hydrogen production at low cost and on a large scale. Herein, we report a novel WO3-x catalyst synthesized on carbon nanofiber mats (CFMs) by electrospinning and followed by a carbonization process in a tubal furnace. The morphology and composition of the catalysts were tailored via a simple method, and the hybrid catalyst mats were used directly as cathodes to investigate their HER performance. Notably, the as-prepared catalysts exhibit substantially enhanced activity for the HER, demonstrating a small overpotential, a high exchange current density, and a large cathodic current density. The remarkable electrocatalytic performances result from the poor crystallinity of WO3-x, the high electrical conductivity of WO3-x, and the use of electrospun CNFs. The present work outlines a straightforward approach for the synthesis of transition metal oxide (TMO)-based carbon nanofiber mats with promising applications for the HER. PMID:27356101

  9. Construction of solid-state Z-scheme carbon-modified TiO2/WO3 nanofibers with enhanced photocatalytic hydrogen production

    NASA Astrophysics Data System (ADS)

    Hu, Junhua; Wang, Lijie; Zhang, Peng; Liang, Changhao; Shao, Guosheng

    2016-10-01

    Carbon-layer-coated TiO2/WO3 nanofibers (WTC) were fabricated by combining the electrospinning technique (for TiO2/WO3 nanofibers) and hydrothermal method (for carbon shell). The structure characterization results showed that TiO2/WO3 nanofibers (WT) were encased within an uniform carbon shell about 10 nm in thickness. By adjusting the content of WO3, the graphitization degree of carbon layer could be controlled, and the WTC nanofibers had remarkable light absorption in the visible region. Furthermore, the photoelectrochemical performance and photocatalytic activity were investigated systematically. As expected, the H2-generation rate of the as-prepared composite materials was greatly enhanced compared with pure TiO2 nanofibers (TNFs), TiO2/WO3 nanofibers (WT) and TiO2@carbon core/shell nanofibers (TC). The enhanced activities were mainly attributed to the multichannel-improved charge-carrier photosynthetic heterojunction system with the carbon layer on the surface of TiO2 as an electron collector and WO3 as a hole collector, leading to effective charge separation on these components, which were evidenced by photoluminescence spectroscopy (PL), electrochemical impedance spectroscopy (EIS) and photocurrent analysis. Besides, the addition of WO3 promoted the graphitization of carbon layer, which in turn improved transport of electrons in the carbon layer and also contributed to the performance improvement.

  10. Magnetic properties of NiFe2O4/carbon nanofibers from Venezuelan petcoke

    NASA Astrophysics Data System (ADS)

    Briceño, Sarah; Silva, Pedro; Molina, Wilmer; Brämer-Escamilla, Werner; Alcalá, Olgi; Cañizales, Edgard

    2015-05-01

    NiFe2O4/carbon nanofibers (NiFe2O4/CNFs) have been successfully synthesized by hydrotermal method using Venezuelan petroleum coke (petcoke) as carbon source and NiFe2O4 as catalyst. The morphology, structural and magnetic properties of nanocomposite products were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), vibrating sample magnetometry (VSM) and electron paramagnetic resonance (EPR). XRD analysis revealed a cubic spinel structure and ferrite phase with high crystallinity. HR-TEM reveals the presence of CNFs with diameters of 4±2 nm. At room temperature, NiFe2O4/CNFs show superparamagnetic behavior with a maximum magnetization of 15.35 emu/g. Our findings indicate that Venezuelan petroleum coke is suitable industrial carbon source for the growth of magnetic CNFs.

  11. Properties that Influence the Specific Surface Areas of Carbon Nanotubes and Nanofibers

    PubMed Central

    BIRCH, M. EILEEN; RUDA-EBERENZ, TONI A.; CHAI, MING; ANDREWS, RONNEE; HATFIELD, RANDAL L.

    2015-01-01

    Commercially available carbon nanotubes and nanofibers were analyzed to examine possible relationships between their Brunauer–Emmett–Teller specific surface areas (SSAs) and their physical and chemical properties. Properties found to influence surface area were number of walls/diameter, impurities, and surface functionalization with hydroxyl and carboxyl groups. Characterization by electron microscopy, energy-dispersive X-ray spectrometry, thermogravimetric analysis, and elemental analysis indicates that SSA can provide insight on carbon nanomaterials properties, which can differ vastly depending on synthesis parameters and post-production treatments. In this study, how different properties may influence surface area is discussed. The materials examined have a wide range of surface areas. The measured surface areas differed from product specifications, to varying degrees, and between similar products. Findings emphasize the multiple factors that influence surface area and mark its utility in carbon nanomaterial characterization, a prerequisite to understanding their potential applications and toxicities. Implications for occupational monitoring are discussed. PMID:24029925

  12. Design and evaluation of carbon nanofiber and silicon materials for neural implant applications

    NASA Astrophysics Data System (ADS)

    McKenzie, Janice L.

    Reduction of glial scar tissue around central nervous system implants is necessary for improved efficacy in chronic applications. Design of materials that possess tunable properties inspired by native biological tissue and elucidation of pertinent cellular interactions with these materials was the motivation for this study. Since nanoscale carbon fibers possess the fundamental dimensional similarities to biological tissue and have attractive material properties needed for neural biomaterial implants, this present study explored cytocompatibility of these materials as well as modifications to traditionally used silicon. On silicon materials, results indicated that nanoscale surface features reduced astrocyte functions, and could be used to guide neurite extension from PC12 cells. Similarly, it was determined that astrocyte functions (key cells in glial scar tissue formation) were reduced on smaller diameter carbon fibers (125 nm or less) while PC12 neurite extension was enhanced on smaller diameter carbon fibers (100 nm or less). Further studies implicated laminin adsorption as a key mechanism in enhancing astrocyte adhesion to larger diameter fibers and at the same time encouraging neurite extension on smaller diameter fibers. Polycarbonate urethane (PCU) was then used as a matrix material for the smaller diameter carbon fibers (100 and 60 nm). These composites proved very versatile since electrical and mechanical properties as well as cell functions and directionality could be influenced by changing bulk and surface composition and features of these matrices. When these composites were modified to be smooth at the micronscale and only rough at the nanoscale, P19 cells actually submerged philopodia, extensions, or whole cells bodies beneath the PCU in order to interact with the carbon nanofibers. These carbon nanofiber composites that have been formulated are a promising material to coat neural probes and thereby enhance functionality at the tissue interface. This

  13. Ultralight anisotropic foams from layered aligned carbon nanotube sheets

    NASA Astrophysics Data System (ADS)

    Faraji, Shaghayegh; L. Stano, Kelly; Yildiz, Ozkan; Li, Ang; Zhu, Yuntian; Bradford, Philip D.

    2015-10-01

    In this work, we present large scale, ultralight aligned carbon nanotube (CNT) structures which have densities an order of magnitude lower than CNT arrays, have tunable properties and exhibit resiliency after compression. By stacking aligned sheets of carbon nanotubes and then infiltrating with a pyrolytic carbon (PyC), resilient foam-like materials were produced that exhibited complete recovery from 90% compressive strain. With density as low as 3.8 mg cm-3, the foam structure is over 500 times less dense than bulk graphite. Microscopy revealed that PyC coated the junctions among CNTs, and also increased CNT surface roughness. These changes in the morphology explain the transition from inelastic behavior to foam-like recovery of the layered CNT sheet structure. Mechanical and thermal properties of the foams were tuned for different applications through variation of PyC deposition duration while dynamic mechanical analysis showed no change in mechanical properties over a large temperature range. Observation of a large and linear electrical resistance change during compression of the aligned CNT/carbon (ACNT/C) foams makes strain/pressure sensors a relevant application. The foams have high oil absorption capacities, up to 275 times their own weight, which suggests they may be useful in water treatment and oil spill cleanup. Finally, the ACNT/C foam's high porosity, surface area and stability allow for demonstration of the foams as catalyst support structures.In this work, we present large scale, ultralight aligned carbon nanotube (CNT) structures which have densities an order of magnitude lower than CNT arrays, have tunable properties and exhibit resiliency after compression. By stacking aligned sheets of carbon nanotubes and then infiltrating with a pyrolytic carbon (PyC), resilient foam-like materials were produced that exhibited complete recovery from 90% compressive strain. With density as low as 3.8 mg cm-3, the foam structure is over 500 times less dense than

  14. Broadband laser polarization control with aligned carbon nanotubes.

    PubMed

    Yang, He; Fu, Bo; Li, Diao; Tian, Ying; Chen, Ya; Mattila, Marco; Yong, Zhenzhong; Li, Ru; Hassanien, Abdou; Yang, Changxi; Tittonen, Ilkka; Ren, Zhaoyu; Bai, Jintao; Li, Qingwen; Kauppinen, Esko I; Lipsanen, Harri; Sun, Zhipei

    2015-07-01

    We introduce a simple approach to fabricate an aligned carbon nanotube (ACNT) device for broadband polarization control in fiber laser systems. The ACNT device was fabricated by pulling from as-fabricated vertically-aligned carbon nanotube arrays. Their anisotropic properties are confirmed with various microscopy techniques. The device was then integrated into fiber laser systems (at two technologically important wavelengths of 1 and 1.5 μm) for polarization control. We obtained a linearly-polarized light output with the maximum extinction ratio of ∼12 dB. The output polarization direction could be fully controlled by the ACNT alignment direction in both lasers. To the best of our knowledge, this is the first time that the ACNT device is applied to polarization control in laser systems. Our results exhibit that the ACNT device is a simple, low-cost, and broadband polarizer to control laser polarization dynamics, for various photonic applications (such as material processing, polarization diversity detection in communications etc.), where linear polarization control is necessary. PMID:26060940

  15. Tin nanoparticle-loaded porous carbon nanofiber composite anodes for high current lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Shen, Zhen; Hu, Yi; Chen, Yanli; Zhang, Xiangwu; Wang, Kehao; Chen, Renzhong

    2015-03-01

    Metallic Sn is a promising high-capacity anode material for use in lithium-ion batteries (LIBs), but its huge volume variation during lithium ion insertion/extraction typically results in poor cycling stability. To address this, we demonstrate the fabrication of Sn nanoparticle-loaded porous carbon nanofiber (Sn-PCNF) composites via the electrospinning of Sn(II) acetate/mineral oil/polyacrylonitrile precursors in N,N-dimethylformamide solvent and their subsequent carbonization at 700 °C under an argon atmosphere. This is shown to result in an even distribution of pores on the surface of the nanofibers, allowing the Sn-PCNF composite to be used directly as an anode in lithium-ion batteries without the need to add non-active materials such as polymer binders or electrical conductors. With a discharge capacity of around 774 mA h g-1 achieved at a high current of 0.8 A g-1 over 200 cycles, this material clearly has a high rate capability and excellent cyclic stability, and thanks to its unique structure and properties, is an excellent candidate for use as an anode material in high-current rechargeable lithium-ion batteries.

  16. Improving Microstructure of Silicon/Carbon Nanofiber Composites as A Li Battery Anode

    SciTech Connect

    Howe, Jane Y; Burton, David J.; Meyer III, Harry M; Nazri, Maryam; Nazri, G. Abbas; Palmer, Andrew C.; Lake, Patrick D.

    2013-01-01

    We report the interfacial study of a silicon/carbon nanofiber (Si/CNF) nanocomposite material as a potentially high performance anode for rechargeable lithium ion batteries. The carbon nanofiber is hollow, with a graphitic interior and turbostratic exterior. Amorphous silicon layers were uniformly coated via chemical vapor deposition on both the exterior and interior surfaces of the CNF. The resulting Si/CNF composites were tested as anodes for Li ion batteries and exhibited capacities near 800 mAh g{sup -1} for 100 cycles. After cycling, we found that more Si had fallen off from the outer wall than from the inner wall of CNF. Theoretical calculations confirmed that this is due to a higher interfacial strength at the Si/C-edge interface at the inner wall than that of the Si/C-basal interface at the outer wall. Based upon the experimental analysis and theoretical calculation, we have proposed several interfacial engineering approaches to improve the performance of the electrodes by optimizing the microstructure of this nanocomposite.

  17. A nanobursa mesh: a graded electrospun nanofiber mesh with metal nanoparticles on carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Senturk-Ozer, Semra; Chen, Tao; Degirmenbasi, Nebahat; Gevgilili, Halil; Podkolzin, Simon G.; Kalyon, Dilhan M.

    2014-07-01

    A new type of material, a ``nanobursa'' mesh (from ``bursa'' meaning ``sac or pouch''), is introduced. This material consists of sequential layers of porous polymeric nanofibers encapsulating carbon nanotubes, which are functionalized with different metal nanoparticles in each layer. The nanobursa mesh is fabricated via a novel combination of twin-screw extrusion and electrospinning. Use of this hybrid process at industrially-relevant rates is demonstrated by producing a nanobursa mesh with graded layers of Pd, Co, Ag, and Pt nanoparticles. The potential use of the fabricated nanobursa mesh is illustrated by modeling of catalytic hydrocarbon oxidation.A new type of material, a ``nanobursa'' mesh (from ``bursa'' meaning ``sac or pouch''), is introduced. This material consists of sequential layers of porous polymeric nanofibers encapsulating carbon nanotubes, which are functionalized with different metal nanoparticles in each layer. The nanobursa mesh is fabricated via a novel combination of twin-screw extrusion and electrospinning. Use of this hybrid process at industrially-relevant rates is demonstrated by producing a nanobursa mesh with graded layers of Pd, Co, Ag, and Pt nanoparticles. The potential use of the fabricated nanobursa mesh is illustrated by modeling of catalytic hydrocarbon oxidation. Electronic supplementary information (ESI) available: Experimental methods and computational details. See DOI: 10.1039/c4nr01145g

  18. Morphological characterization of carbon-nanofiber-reinforced epoxy nanocomposites using ultra-small angle scattering

    SciTech Connect

    Justice, R.S.; Anderson, D.P.; Brown, J.M.; Arlen, M.J.; Colleary, A.J.; Lafdi, K.; Schaefer, D.W.

    2010-07-01

    Studies of the properties of nanocomposites reinforced with vapor-grown carbon nanofibers (VGCFs) can be found throughout the literature. Electrical, mechanical, viscoelastic, and rheological properties are just a few of the characteristics that have been well discussed. Although these properties depend on morphology, morphological characterization is rare. Due to its 2-dimensional nature, microscopy is of limited value when analyzing network morphologies. This work will show how the characterization of the three-dimensional geometry and network formation of VGCFs can be determined using ultra-small angle scattering techniques. Ultra-small angle x-ray and neutron scattering (USAXS and USANS) were used to characterize the morphology of carbon nanofibers suspended in epoxy. Using a simplified tube model, we estimate the dimensions of suspended fibers. The assumption of tubular fibers accounts for the increased surface area observed with USAXS that is not accounted for using a solid rod model. Furthermore, USANS was used to search for a structural signature associated with the electrical percolation threshold. USANS extends to longer dimensional scales than USAXS, which measures a smaller range of momentum transfer. To determine the electrical percolation threshold, AC impedance spectroscopy was employed to verify that an electrically conductive, percolated network forms at VGCNF loadings of 0.8% < CNF wt% < 1.2%. These values correlate with the USANS data, where a morphological transition is seen at {approx}1.2% loading.

  19. Touch- and Brush-Spinning of Nanofibers.

    PubMed

    Tokarev, Alexander; Asheghali, Darya; Griffiths, Ian M; Trotsenko, Oleksandr; Gruzd, Alexey; Lin, Xin; Stone, Howard A; Minko, Sergiy

    2015-11-01

    Robust, simple, and scalable touch- and brush-spinning methods for the drawing of nanofibers, core-shell nanofibers, and their aligned 2D and 3D meshes using polymer solutions and melts are discussed.

  20. Graphitized-Carbon-Nanofiber Paper-Enzyme Electrode Fabrication Through Non-Covalent Modification for Enzyme Biofuel Cell Application.

    PubMed

    Fapyane, Deby; Lee, Soo-Jin; Kang, Seung-Hwan; Ahn, Jou-Hyeon; Chang, In Seop

    2015-01-01

    Carbon nanofibers are an emerging smart material that are promising for use as a biosensor and a biofuel cell transducer material due to their morphological and electrochemical characteristics. In particular, graphitized carbon nanofibers possess unique structures of graphite-like edges within their high surface area that provide a large active site for enzyme attachment. For a specific application such as a biofuel cell, which requires highly stable electrical communication and electricity generation, non-covalent enzyme immobilization using bifunctional molecule is suggested as an appropriate approach because it does not change the carbon hybridization from sp2 to sp3 as covalent immobilization by acid treatment does. Graphitized carbon-nanofiber paper (GCNFp) electrode were fabricated through dispersion-filtration method in which glucose oxidase as model enzyme were immobilized by a bifunctional molecule that forms π-π stacking of the pyrene moiety with the nanofiber wall coupled by a reactive end-amine reaction. This system provides a practical enzyme-electrode hybrid that facilitates comparatively faster enzyme-electrode electrical communication than other system using similar material, as calculated from the heterogeneous electron-transfer rate constant (K(s)) which was 5.45 s(-1). PMID:26301307

  1. LiFePO4 - 3D carbon nanofiber composites as cathode materials for Li-ions batteries

    NASA Astrophysics Data System (ADS)

    Dimesso, L.; Spanheimer, C.; Jaegermann, W.; Zhang, Y.; Yarin, A. L.

    2012-03-01

    The characterization of carbon nanofiber 3D nonwovens, prepared by electrospinning process, coated with olivine structured lithium iron phosphate is reported. The LiFePO4 as cathode material for lithium ion batteries was prepared by a Pechini-assisted reversed polyol process. The coating has been successfully performed on carbon nanofiber 3D nonwovens by soaking in aqueous solution containing lithium, iron salts and phosphates at 70 °C for 2-4 h. After drying-out, the composites were annealed at 600 °C for 5 h under nitrogen. The surface investigation of the prepared composites showed a uniform coating of the carbon nonwoven nanofibers as well as the formation of cauliflower-like crystalline structures which are uniformly distributed all over the surface area of the carbon nanofibers. The electrochemical measurements on the composites showed good performances delivering a discharge specific capacity of 156 mAhg- 1 at a discharging rate of C/25 and 152 mAhg- 1 at a discharging rate of C/10 at room temperature.

  2. Graphene oxides and carbon nanotubes embedded in polyacrylonitrile-based carbon nanofibers used as electrodes for supercapacitor

    NASA Astrophysics Data System (ADS)

    Hsu, Hsin-Cheng; Wang, Chen-Hao; Chang, Yu-Chung; Hu, Jin-Hao; Yao, Bing-Yuan; Lin, Chun-Yao

    2015-10-01

    This study investigates the use of graphene oxides (GOs) and carbon nanotubes (CNTs) embedded in polyacrylonitrile-based carbon nanofibers (GO-CNT/CNF) as electrodes for the supercapacitor. GO-CNT/CNF was prepared by electrospinning, and was subsequently stabilized and activated. The specific capacitance of GO-CNT/CNF is 120.5 F g-1 in 0.5 M Na2SO4 electrolyte, which is higher than or comparable to the specific capacitances of carbon-based materials in neutral aqueous electrolyte, as prepared in this study. GO-CNT/CNF also exhibits a superior cycling stability, and 109% of the initial specific capacitance after 5000 cycles. The high capacitance of GO-CNT/CNF could be attributed to the edge planes and the functional groups of GO, the highly electrical conductivity of CNT, and the network structure of the electrode.

  3. Free-standing porous carbon nanofibers-sulfur composite for flexible Li-S battery cathode

    NASA Astrophysics Data System (ADS)

    Zeng, Linchao; Pan, Fusen; Li, Weihan; Jiang, Yu; Zhong, Xiongwu; Yu, Yan

    2014-07-01

    Flexible and free-standing sulphur/(PCNFs-CNT) composite (S@PCNFs-CNT) electrode was successfully prepared by infiltrating sulfur into microporous carbon nanofibers-carbon nanotube (PCNFs-CNT) composite. When used as a cathode material for Li-S batteries, the S@PCNFs-CNT exhibits much better cycle performance and rate performance compared to CNT-free S@PCNFs. It delivers a reversible capacity of 637 mA h g-1 after 100 cycles at 50 mA g-1 and a rate capability of 437 mA h g-1 at 1 A g-1. The improved electrochemical performance is attributed to synergistic effect of the 3D interconnected structure, the additive of CNT, and the uniform distribution of micropores (<2 nm) in the PCNFs-CNT matrix. Our results indicate the potential suitability of PCNFs-CNT for efficient, free-standing, and high-performance batteries.

  4. Compression behaviour of thick vertically aligned carbon nanotube blocks.

    PubMed

    Pavese, Matteo; Musso, Simone; Pugno, Nicola M

    2010-07-01

    Blocks of vertically aligned multiwall carbon nanotubes were prepared by thermal chemical vapor deposition starting from camphor and ferrocene precursors. The blocks, having a thickness of approximately 2 mm and composed of nanotubes with diameter ranging between 30 and 80 nm, were submitted to compression tests. The results were analyzed accordingly with a simple model consisting in a parallel array of nanotubes under compression and bending suffering microscopic instability and compaction. The model mostly fits the experimental stress-strain curves, with a small deviation attributed to dissipative phenomena, such as frictional forces and nanotube wall breakage. PMID:21128406

  5. Mass Production of Carbon Nanofibers Using Microwave Technology.

    PubMed

    Mubarak, N M; Abdullah, E C; Sahu, J N; Jayakumar, N S; Ganesan, P

    2015-12-01

    Carbon nanotubes (CNFs) were produced by gas phase single stage microwave assisted chemical vapour deposition (MA-CVD) using ferrocene as a catalyst and acetylene (C2H2) and hydrogen (H2) as precursor gases. The effect of the process parameters such as microwave power, radiation time, and gas ratio of C2H2/H2 was investigated. The CNFs were characterized using scanning and transmission electron microscopy (TEM), and by thermogravimetric analysis (TGA). Results reveal that the optimized conditions for CNF production were 1000 W reaction power, 35 min radiation time, and 0.8 gas ratio of C2H2/H2. TEM analyses revealed that the uniformly dispersed CNFs diameters ranging from 115-131 nm. The TGA analysis showed that the purity of CNF produced was 93%. PMID:26682380

  6. INHALATION EXPOSURE TO CARBON NANOTUBES (CNT) AND CARBON NANOFIBERS (CNF): METHODOLOGY AND DOSIMETRY

    PubMed Central

    Oberdörster, Günter; Castranova, Vincent; Asgharian, Bahman; Sayre, Phil

    2015-01-01

    Carbon nanotubes (CNT) and nanofibers (CNF) are used increasingly in a broad array of commercial products. Given current understandings, the most significant life-cycle exposures to CNT/CNF occur from inhalation when they become airborne at different stages of their life cycle, including workplace, use, and disposal. Increasing awareness of the importance of physicochemical properties as determinants of toxicity of CNT/CNF and existing difficulties in interpreting results of mostly acute rodent inhalation studies to date necessitate a reexamination of standardized inhalation testing guidelines. The current literature on pulmonary exposure to CNT/CNF and associated effects is summarized; recommendations and conclusions are provided that address test guideline modifications for rodent inhalation studies that will improve dosimetric extrapolation modeling for hazard and risk characterization based on the analysis of exposure-dose-response relationships. Several physicochemical parameters for CNT/CNF, including shape, state of agglomeration/aggregation, surface properties, impurities, and density, influence toxicity. This requires an evaluation of the correlation between structure and pulmonary responses. Inhalation, using whole-body exposures of rodents, is recommended for acute to chronic pulmonary exposure studies. Dry powder generator methods for producing CNT/CNF aerosols are preferred, and specific instrumentation to measure mass, particle size and number distribution, and morphology in the exposure chambers are identified. Methods are discussed for establishing experimental exposure concentrations that correlate with realistic human exposures, such that unrealistically high experimental concentrations need to be identified that induce effects under mechanisms that are not relevant for workplace exposures. Recommendations for anchoring data to results seen for positive and negative benchmark materials are included, as well as periods for postexposure observation

  7. Electrospun composite nanofibers of poly vinyl pyrrolidone and zinc oxide nanoparticles modified carbon paste electrode for electrochemical detection of curcumin.

    PubMed

    Afzali, Moslem; Mostafavi, Ali; Shamspur, Tayebeh

    2016-11-01

    A simple and novel ferrocene-nanofiber carbon paste electrode was developed to determine curcumin in a phosphate buffer solution at pH=8. ZnO nanoparticles were produced via a sonochemical process and composite nanofibers of PVP/ZnO were prepared by electrospinning. The characterization was performed by SEM, XRD and IR. The results suggest that the electrospun composite nanofibers having a large surface area promote electron transfer for the oxidation of curcumin and hence the FCNFCPE exhibits high electrocatalytic activity and performs well in regard to the oxidation of curcumin. The proposed method was successfully applied for measurement of curcumin in urine and turmeric as real samples. PMID:27524081

  8. Preparation of poly(L-lactic acid) nanofiber scaffolds with a rough surface by phase inversion using supercritical carbon dioxide.

    PubMed

    Yang, Ding-Zhu; Chen, Ai-Zheng; Wang, Shi-Bin; Li, Yi; Tang, Xiao-Lin; Wu, Yong-Jing

    2015-06-01

    Phase inversion using supercritical carbon dioxide (SC-CO2) has been widely used in the development of tissue engineering scaffolds, and particular attention has been given to obtaining desired morphology without additional post-treatments. However, the main challenge of this technique is the difficulty in generating a three-dimensional (3D) nanofiber structure with a rough surface in one step. Here, a poly(L-lactic acid) (PLLA) 3D nanofiber scaffold with a rough surface is obtained via phase inversion using SC-CO2 by carefully choosing fabrication conditions and porogens. It is found that this method can effectively modulate the structure morphology, promote the crystallization process of semicrystalline polymer, and induce the formation of rough structures on the surface of nanofibers. Meanwhile, the porogen of ammonium bicarbonate (AB) can produce a 3D structure with large pores, and porogen of menthol can improve the interconnectivity between the micropores of nanofibers. A significant increase in the fiber diameter is observed as the menthol content increases. Furthermore, the menthol may affect the mutual transition between the α' and α crystals of PLLA during the phase separation process. In addition, the results of protein adsorption, cell adhesion, and proliferation assays indicate that cells tend to have higher viability on the nanofiber scaffold. This process combines the characteristic properties of SC-CO2 and the solubility of menthol to tailor the morphology of polymeric scaffolds, which may have potential applications in tissue engineering. PMID:26107415

  9. Preparation of poly(L-lactic acid) nanofiber scaffolds with a rough surface by phase inversion using supercritical carbon dioxide.

    PubMed

    Yang, Ding-Zhu; Chen, Ai-Zheng; Wang, Shi-Bin; Li, Yi; Tang, Xiao-Lin; Wu, Yong-Jing

    2015-06-24

    Phase inversion using supercritical carbon dioxide (SC-CO2) has been widely used in the development of tissue engineering scaffolds, and particular attention has been given to obtaining desired morphology without additional post-treatments. However, the main challenge of this technique is the difficulty in generating a three-dimensional (3D) nanofiber structure with a rough surface in one step. Here, a poly(L-lactic acid) (PLLA) 3D nanofiber scaffold with a rough surface is obtained via phase inversion using SC-CO2 by carefully choosing fabrication conditions and porogens. It is found that this method can effectively modulate the structure morphology, promote the crystallization process of semicrystalline polymer, and induce the formation of rough structures on the surface of nanofibers. Meanwhile, the porogen of ammonium bicarbonate (AB) can produce a 3D structure with large pores, and porogen of menthol can improve the interconnectivity between the micropores of nanofibers. A significant increase in the fiber diameter is observed as the menthol content increases. Furthermore, the menthol may affect the mutual transition between the α' and α crystals of PLLA during the phase separation process. In addition, the results of protein adsorption, cell adhesion, and proliferation assays indicate that cells tend to have higher viability on the nanofiber scaffold. This process combines the characteristic properties of SC-CO2 and the solubility of menthol to tailor the morphology of polymeric scaffolds, which may have potential applications in tissue engineering.

  10. In situ Polymerization of Multi-Walled Carbon Nanotube/Nylon-6 Nanocomposites and Their Electrospun Nanofibers.

    PubMed

    Saeed, Khalid; Park, Soo-Young; Haider, Sajjad; Baek, Jong-Beom

    2009-01-01

    Multiwalled carbon nanotube/nylon-6 nanocomposites (MWNT/nylon-6) were prepared by in situ polymerization, whereby functionalized MWNTs (F-MWNTs) and pristine MWNTs (P-MWNTs) were used as reinforcing materials. The F-MWNTs were functionalized by Friedel-Crafts acylation, which introduced aromatic amine (COC(6)H(4)-NH(2)) groups onto the side wall. Scanning electron microscopy (SEM) images obtained from the fractured surfaces of the nanocomposites showed that the F-MWNTs in the nylon-6 matrix were well dispersed as compared to those of the P-MWNTs. Both nanocomposites could be electrospun into nanofibers in which the MWNTs were embedded and oriented along the nanofiber axis, as confirmed by transmission electron microscopy. The specific strength and modulus of the MWNTs-reinforced nanofibers increased as compared to those of the neat nylon-6 nanofibers. The crystal structure of the nylon-6 in the MWNT/nylon-6 nanofibers was mostly gamma-phase, although that of the MWNT/nylon-6 films, which were prepared by hot-pressing the pellets between two aluminum plates and then quenching them in icy water, was mostly alpha-phase, indicating that the shear force during electrospinning might favor the gamma-phase, similarly to the conventional fiber spinning. PMID:20596470

  11. Facile Synthesis of Coaxial CNTs/MnOx-Carbon Hybrid Nanofibers and Their Greatly Enhanced Lithium Storage Performance

    PubMed Central

    Yang, Zunxian; Lv, Jun; Pang, Haidong; Yan, Wenhuan; Qian, Kun; Guo, Tailiang; Guo, Zaiping

    2015-01-01

    Carbon nanotubes (CNTs)/MnOx-Carbon hybrid nanofibers have been successfully synthesized by the combination of a liquid chemical redox reaction (LCRR) and a subsequent carbonization heat treatment. The nanostructures exhibit a unique one-dimensional core/shell architecture, with one-dimensional CNTs encapsulated inside and a MnOx-carbon composite nanoparticle layer on the outside. The particular porous characteristics with many meso/micro holes/pores, the highly conductive one-dimensional CNT core, as well as the encapsulating carbon matrix on the outside of the MnOx nanoparticles, lead to excellent electrochemical performance of the electrode. The CNTs/MnOx-Carbon hybrid nanofibers exhibit a high initial reversible capacity of 762.9 mAhg−1, a high reversible specific capacity of 560.5 mAhg−1 after 100 cycles, and excellent cycling stability and rate capability, with specific capacity of 396.2 mAhg−1 when cycled at the current density of 1000 mAg−1, indicating that the CNTs/MnOx-Carbon hybrid nanofibers are a promising anode candidate for Li-ion batteries. PMID:26621615

  12. Gas sensing with gold-decorated vertically aligned carbon nanotubes

    PubMed Central

    Mudimela, Prasantha R; Scardamaglia, Mattia; González-León, Oriol; Reckinger, Nicolas; Snyders, Rony; Llobet, Eduard; Colomer, Jean-François

    2014-01-01

    Summary Vertically aligned carbon nanotubes of different lengths (150, 300, 500 µm) synthesized by thermal chemical vapor deposition and decorated with gold nanoparticles were investigated as gas sensitive materials for detecting nitrogen dioxide (NO2) at room temperature. Gold nanoparticles of about 6 nm in diameter were sputtered on the top surface of the carbon nanotube forests to enhance the sensitivity to the pollutant gas. We showed that the sensing response to nitrogen dioxide depends on the nanotube length. The optimum was found to be 300 µm for getting the higher response. When the background humidity level was changed from dry to 50% relative humidity, an increase in the response to NO2 was observed for all the sensors, regardless of the nanotube length. PMID:24991529

  13. Gas sensing with gold-decorated vertically aligned carbon nanotubes.

    PubMed

    Mudimela, Prasantha R; Scardamaglia, Mattia; González-León, Oriol; Reckinger, Nicolas; Snyders, Rony; Llobet, Eduard; Bittencourt, Carla; Colomer, Jean-François

    2014-01-01

    Vertically aligned carbon nanotubes of different lengths (150, 300, 500 µm) synthesized by thermal chemical vapor deposition and decorated with gold nanoparticles were investigated as gas sensitive materials for detecting nitrogen dioxide (NO2) at room temperature. Gold nanoparticles of about 6 nm in diameter were sputtered on the top surface of the carbon nanotube forests to enhance the sensitivity to the pollutant gas. We showed that the sensing response to nitrogen dioxide depends on the nanotube length. The optimum was found to be 300 µm for getting the higher response. When the background humidity level was changed from dry to 50% relative humidity, an increase in the response to NO2 was observed for all the sensors, regardless of the nanotube length. PMID:24991529

  14. Growing Aligned Carbon Nanotubes for Interconnections in ICs

    NASA Technical Reports Server (NTRS)

    Li, Jun; Ye, Qi; Cassell, Alan; Ng, Hou Tee; Stevens, Ramsey; Han, Jie; Meyyappan, M.

    2005-01-01

    A process for growing multiwalled carbon nanotubes anchored at specified locations and aligned along specified directions has been invented. Typically, one would grow a number of the nanotubes oriented perpendicularly to a silicon integrated-circuit (IC) substrate, starting from (and anchored on) patterned catalytic spots on the substrate. Such arrays of perpendicular carbon nanotubes could be used as electrical interconnections between levels of multilevel ICs. The process (see Figure 1) begins with the formation of a layer, a few hundred nanometers thick, of a compatible electrically insulating material (e.g., SiO(x) or Si(y)N(z) on the silicon substrate. A patterned film of a suitable electrical conductor (Al, Mo, Cr, Ti, Ta, Pt, Ir, or doped Si), having a thickness between 1 nm and 2 m, is deposited on the insulating layer to form the IC conductor pattern. Next, a catalytic material (usually, Ni, Fe, or Co) is deposited to a thickness between 1 and 30 nm on the spots from which it is desired to grow carbon nanotubes. The carbon nanotubes are grown by plasma-enhanced chemical vapor deposition (PECVD). Unlike the matted and tangled carbon nanotubes grown by thermal CVD, the carbon nanotubes grown by PECVD are perpendicular and freestanding because an electric field perpendicular to the substrate is used in PECVD. Next, the free space between the carbon nanotubes is filled with SiO2 by means of CVD from tetraethylorthosilicate (TEOS), thereby forming an array of carbon nanotubes embedded in SiO2. Chemical mechanical polishing (CMP) is then performed to remove excess SiO2 and form a flat-top surface in which the outer ends of the carbon nanotubes are exposed. Optionally, depending on the application, metal lines to connect selected ends of carbon nanotubes may be deposited on the top surface. The top part of Figure 2 is a scanning electron micrograph (SEM) of carbon nanotubes grown, as described above, on catalytic spots of about 100 nm diameter patterned by

  15. Direct Electrochemistry of Glucose Oxidase on Novel Free-Standing Nitrogen-Doped Carbon Nanospheres@Carbon Nanofibers Composite Film

    NASA Astrophysics Data System (ADS)

    Zhang, Xueping; Liu, Dong; Li, Libo; You, Tianyan

    2015-05-01

    We have proposed a novel free-standing nitrogen-doped carbon nanospheres@carbon nanofibers (NCNSs@CNFs) composite film with high processability for the investigation of the direct electron transfer (DET) of glucose oxidase (GOx) and the DET-based glucose biosensing. The composites were simply prepared by controlled thermal treatment of electrospun polypyrrole nanospheres doped polyacrylonitrile nanofibers (PPyNSs@PAN NFs). Without any pretreatment, the as-prepared material can directly serve as a platform for GOx immobilization. The cyclic voltammetry of immobilized GOx showed a pair of well-defined redox peaks in O2-free solution, indicating the DET of GOx. With the addition of glucose, the anodic peak current increased, while the cathodic peak current decreased, which demonstrated the DET-based bioelectrocatalysis. The detection of glucose based on the DET of GOx was achieved, which displayed high sensitivity, stability and selectivity, with a low detection limit of 2 μM and wide linear range of 12-1000 μM. These results demonstrate that the as-obtained NCNSs@CNFs can serve as an ideal platform for the construction of the third-generation glucose biosensor.

  16. Direct electrochemistry of glucose oxidase on novel free-standing nitrogen-doped carbon nanospheres@carbon nanofibers composite film.

    PubMed

    Zhang, Xueping; Liu, Dong; Li, Libo; You, Tianyan

    2015-01-01

    We have proposed a novel free-standing nitrogen-doped carbon nanospheres@carbon nanofibers (NCNSs@CNFs) composite film with high processability for the investigation of the direct electron transfer (DET) of glucose oxidase (GOx) and the DET-based glucose biosensing. The composites were simply prepared by controlled thermal treatment of electrospun polypyrrole nanospheres doped polyacrylonitrile nanofibers (PPyNSs@PAN NFs). Without any pretreatment, the as-prepared material can directly serve as a platform for GOx immobilization. The cyclic voltammetry of immobilized GOx showed a pair of well-defined redox peaks in O2-free solution, indicating the DET of GOx. With the addition of glucose, the anodic peak current increased, while the cathodic peak current decreased, which demonstrated the DET-based bioelectrocatalysis. The detection of glucose based on the DET of GOx was achieved, which displayed high sensitivity, stability and selectivity, with a low detection limit of 2 μM and wide linear range of 12-1000 μM. These results demonstrate that the as-obtained NCNSs@CNFs can serve as an ideal platform for the construction of the third-generation glucose biosensor. PMID:25943704

  17. Direct Electrochemistry of Glucose Oxidase on Novel Free-Standing Nitrogen-Doped Carbon Nanospheres@Carbon Nanofibers Composite Film

    PubMed Central

    Zhang, Xueping; Liu, Dong; Li, Libo; You, Tianyan

    2015-01-01

    We have proposed a novel free-standing nitrogen-doped carbon nanospheres@carbon nanofibers (NCNSs@CNFs) composite film with high processability for the investigation of the direct electron transfer (DET) of glucose oxidase (GOx) and the DET-based glucose biosensing. The composites were simply prepared by controlled thermal treatment of electrospun polypyrrole nanospheres doped polyacrylonitrile nanofibers (PPyNSs@PAN NFs). Without any pretreatment, the as-prepared material can directly serve as a platform for GOx immobilization. The cyclic voltammetry of immobilized GOx showed a pair of well-defined redox peaks in O2-free solution, indicating the DET of GOx. With the addition of glucose, the anodic peak current increased, while the cathodic peak current decreased, which demonstrated the DET-based bioelectrocatalysis. The detection of glucose based on the DET of GOx was achieved, which displayed high sensitivity, stability and selectivity, with a low detection limit of 2 μM and wide linear range of 12–1000 μM. These results demonstrate that the as-obtained NCNSs@CNFs can serve as an ideal platform for the construction of the third-generation glucose biosensor. PMID:25943704

  18. Effect of thermal interface on heat flow in carbon nanofiber composites.

    PubMed

    Gardea, F; Naraghi, M; Lagoudas, D

    2014-01-22

    The thermal transport process in carbon nanofiber (CNF)/epoxy composites is addressed through combined micromechanics and finite element modeling, guided by experiments. The heat exchange between CNF constituents and matrix is studied by explicitly accounting for interface thermal resistance between the CNFs and the epoxy matrix. The effects of nanofiber orientation and discontinuity on heat flow and thermal conductivity of nanocomposites are investigated through simulation of the laser flash experiment technique and Fourier's model of heat conduction. Our results indicate that when continuous CNFs are misoriented with respect to the average temperature gradient, the presence of interfacial resistance does not affect the thermal conductivity of the nanocomposites, as most of the heat flow will be through CNFs; however, interface thermal resistance can significantly alter the patterns of heat flow within the nanocomposite. It was found that very high interface resistance leads to heat entrapment at the interface near to the heat source, which can promote interface thermal degradation. The magnitude of heat entrapment, quantified via the peak transient temperature rise at the interface, in the case of high thermal resistance interfaces becomes an order of magnitude more intense as compared to the case of low thermal resistance interfaces. Moreover, high interface thermal resistance in the case of discontinuous fibers leads to a nearly complete thermal isolation of the fibers from the matrix, which will marginalize the contribution of the CNF thermal conductivity to the heat transfer in the composite.

  19. Preparation and electrochemical performance of heteroatom-enriched electrospun carbon nanofibers from melamine formaldehyde resin.

    PubMed

    Ma, Chang; Song, Yan; Shi, Jingli; Zhang, Dongqing; Guo, Quangui; Liu, Lang

    2013-04-01

    Melamine formaldehyde resin was used to prepare heteroatom-enriched carbon nanofibers by electrospinning for the first time. The melamine formaldehyde resin-based carbon fibers without any activation treatment showed a moderate specific surface area ranging from 130 to 479 m2/g and rich surface functionalities (2.56-5.34 wt.% nitrogen and 10.39-11.2 9 wt.% oxygen). Both the specific surface area and surface functionality greatly depended on the carbonization temperature. The capacitive performance was evaluated in 6M KOH aqueous solution. The electrochemically active surface functionalities played an important role in improving the surface capacitance of the electrodes. The sample carbonized at 600°C showed the highest specific surface capacitance of 1.4 F/m2, which was attributed to the most active functionalities (10.69 wt.% of N and O). In addition, the sample carbonized at 750°C exhibited the highest specific capacitance of 206 F/g.

  20. Graphitic Carbon-Coated FeSe2 Hollow Nanosphere-Decorated Reduced Graphene Oxide Hybrid Nanofibers as an Efficient Anode Material for Sodium Ion Batteries.

    PubMed

    Cho, Jung Sang; Lee, Jung-Kul; Kang, Yun Chan

    2016-04-01

    A novel one-dimensional nanohybrid comprised of conductive graphitic carbon (GC)-coated hollow FeSe2 nanospheres decorating reduced graphene oxide (rGO) nanofiber (hollow nanosphere FeSe2@GC-rGO) was designed as an efficient anode material for sodium ion batteries and synthesized by introducing the nanoscale Kirkendall effect into the electrospinning method. The electrospun nanofibers transformed into hollow nanosphere FeSe2@GC-rGO hybrid nanofibers through a Fe@GC-rGO intermediate. The discharge capacities of the bare FeSe2 nanofibers, nanorod FeSe2-rGO-amorphous carbon (AC) hybrid nanofibers, and hollow nanosphere FeSe2@GC-rGO hyrbid nanofibers at a current density of 1 A g(-1) for the 150th cycle were 63, 302, and 412 mA h g(-1), respectively, and their corresponding capacity retentions measured from the 2nd cycle were 11, 73, and 82%, respectively. The hollow nanosphere FeSe2@GC-rGO hybrid nanofibers delivered a high discharge capacity of 352 mA h g(-1) even at an extremely high current density of 10 A g(-1). The enhanced electrochemical properties of the hollow nanosphere FeSe2@GC-rGO composite nanofibers arose from the synergetic effects of the FeSe2 hollow morphology and highly conductive rGO matrix.

  1. Graphitic Carbon-Coated FeSe2 Hollow Nanosphere-Decorated Reduced Graphene Oxide Hybrid Nanofibers as an Efficient Anode Material for Sodium Ion Batteries

    PubMed Central

    Cho, Jung Sang; Lee, Jung-Kul; Kang, Yun Chan

    2016-01-01

    A novel one-dimensional nanohybrid comprised of conductive graphitic carbon (GC)-coated hollow FeSe2 nanospheres decorating reduced graphene oxide (rGO) nanofiber (hollow nanosphere FeSe2@GC–rGO) was designed as an efficient anode material for sodium ion batteries and synthesized by introducing the nanoscale Kirkendall effect into the electrospinning method. The electrospun nanofibers transformed into hollow nanosphere FeSe2@GC–rGO hybrid nanofibers through a Fe@GC–rGO intermediate. The discharge capacities of the bare FeSe2 nanofibers, nanorod FeSe2–rGO–amorphous carbon (AC) hybrid nanofibers, and hollow nanosphere FeSe2@GC–rGO hyrbid nanofibers at a current density of 1 A g−1 for the 150th cycle were 63, 302, and 412 mA h g−1, respectively, and their corresponding capacity retentions measured from the 2nd cycle were 11, 73, and 82%, respectively. The hollow nanosphere FeSe2@GC–rGO hybrid nanofibers delivered a high discharge capacity of 352 mA h g−1 even at an extremely high current density of 10 A g−1. The enhanced electrochemical properties of the hollow nanosphere FeSe2@GC–rGO composite nanofibers arose from the synergetic effects of the FeSe2 hollow morphology and highly conductive rGO matrix. PMID:27033096

  2. Graphitic Carbon-Coated FeSe2 Hollow Nanosphere-Decorated Reduced Graphene Oxide Hybrid Nanofibers as an Efficient Anode Material for Sodium Ion Batteries

    NASA Astrophysics Data System (ADS)

    Cho, Jung Sang; Lee, Jung-Kul; Kang, Yun Chan

    2016-04-01

    A novel one-dimensional nanohybrid comprised of conductive graphitic carbon (GC)-coated hollow FeSe2 nanospheres decorating reduced graphene oxide (rGO) nanofiber (hollow nanosphere FeSe2@GC-rGO) was designed as an efficient anode material for sodium ion batteries and synthesized by introducing the nanoscale Kirkendall effect into the electrospinning method. The electrospun nanofibers transformed into hollow nanosphere FeSe2@GC-rGO hybrid nanofibers through a Fe@GC-rGO intermediate. The discharge capacities of the bare FeSe2 nanofibers, nanorod FeSe2-rGO-amorphous carbon (AC) hybrid nanofibers, and hollow nanosphere FeSe2@GC-rGO hyrbid nanofibers at a current density of 1 A g-1 for the 150th cycle were 63, 302, and 412 mA h g-1, respectively, and their corresponding capacity retentions measured from the 2nd cycle were 11, 73, and 82%, respectively. The hollow nanosphere FeSe2@GC-rGO hybrid nanofibers delivered a high discharge capacity of 352 mA h g-1 even at an extremely high current density of 10 A g-1. The enhanced electrochemical properties of the hollow nanosphere FeSe2@GC-rGO composite nanofibers arose from the synergetic effects of the FeSe2 hollow morphology and highly conductive rGO matrix.

  3. Hollow porous carbon nitride immobilized on carbonized nanofibers for highly efficient visible light photocatalytic removal of NO.

    PubMed

    Wu, Hongxin; Chen, Dongyun; Li, Najun; Xu, Qingfeng; Li, Hua; He, Jinghui; Lu, Jianmei

    2016-06-01

    With the deterioration of air quality, great efforts were devoted to designing various photocatalysts for effective removal of NOx in air. However, the present photocatalysts have a fatal problem of low photocatalytic efficiency. In this work, a hollow porous carbon nitride nanosphere coupled with reduced graphene oxide (HCNS/rGO) was exploited as a visible-light photocatalyst to remove nitrogen monoxide in air at a low concentration (600 ppb level) under irradiation of an energy saving lamp. HCNS/rGO showed a NO removal ratio of 64%, which was superior to that of most other visible-light photocatalysts. The excellent photocatalytic ability of HCNS/rGO originates from the hollow porous morphology of HCNS and the grafted rGO on the surface. HCNS/rGO was immobilized on porous carbonized polymer nanofibers to obtain a photocatalytic membrane without affecting photocatalytic efficiency. Furthermore, the membrane showed excellent photochemical stability and recyclability. PMID:27245319

  4. Hollow porous carbon nitride immobilized on carbonized nanofibers for highly efficient visible light photocatalytic removal of NO

    NASA Astrophysics Data System (ADS)

    Wu, Hongxin; Chen, Dongyun; Li, Najun; Xu, Qingfeng; Li, Hua; He, Jinghui; Lu, Jianmei

    2016-06-01

    With the deterioration of air quality, great efforts were devoted to designing various photocatalysts for effective removal of NOx in air. However, the present photocatalysts have a fatal problem of low photocatalytic efficiency. In this work, a hollow porous carbon nitride nanosphere coupled with reduced graphene oxide (HCNS/rGO) was exploited as a visible-light photocatalyst to remove nitrogen monoxide in air at a low concentration (600 ppb level) under irradiation of an energy saving lamp. HCNS/rGO showed a NO removal ratio of 64%, which was superior to that of most other visible-light photocatalysts. The excellent photocatalytic ability of HCNS/rGO originates from the hollow porous morphology of HCNS and the grafted rGO on the surface. HCNS/rGO was immobilized on porous carbonized polymer nanofibers to obtain a photocatalytic membrane without affecting photocatalytic efficiency. Furthermore, the membrane showed excellent photochemical stability and recyclability.With the deterioration of air quality, great efforts were devoted to designing various photocatalysts for effective removal of NOx in air. However, the present photocatalysts have a fatal problem of low photocatalytic efficiency. In this work, a hollow porous carbon nitride nanosphere coupled with reduced graphene oxide (HCNS/rGO) was exploited as a visible-light photocatalyst to remove nitrogen monoxide in air at a low concentration (600 ppb level) under irradiation of an energy saving lamp. HCNS/rGO showed a NO removal ratio of 64%, which was superior to that of most other visible-light photocatalysts. The excellent photocatalytic ability of HCNS/rGO originates from the hollow porous morphology of HCNS and the grafted rGO on the surface. HCNS/rGO was immobilized on porous carbonized polymer nanofibers to obtain a photocatalytic membrane without affecting photocatalytic efficiency. Furthermore, the membrane showed excellent photochemical stability and recyclability. Electronic supplementary information

  5. Fabrication of field emission display prototype utilizing printed carbon nanotubes/nanofibers emitters

    NASA Astrophysics Data System (ADS)

    Guo, P. S.; Chen, T.; Chen, Y. W.; Zhang, Z. J.; Feng, T.; Wang, L. L.; Lin, L. F.; Sun, Z.; Zheng, Z. H.

    2008-06-01

    Carbon nanotubes/nanofibers (CNTs) used as emitters, diode-type field emission display (FED) prototypes of dot matrix and character images were fabricated by low-cost techniques and equipments, respectively. The technical development in the design and fabrication of the cathode, the anode, and the panel, is described. CNTs were produced by a simple, low-cost and easily-controllable thermal chemical vapor deposition. The cathode was prepared by the screen-printing method. The field emission characteristics were enhanced by a heat post-treatment in H2 gas atmosphere. The panel structure was packaged by a vacuum fluorescent display-like process and vacuum-sealed through an exhaust glass tube. The fully-sealed CNTs FED (c-FED) showed good emission properties. The brightness of 600 cd/m2 was achieved from the yellow phosphor at a relatively low applied electric field. The developed technology has a potential practical application in c-FED.

  6. Carbon nanofiber aerogels for emergent cleanup of oil spillage and chemical leakage under harsh conditions

    PubMed Central

    Wu, Zhen-Yu; Li, Chao; Liang, Hai-Wei; Zhang, Yu-Ning; Wang, Xin; Chen, Jia-Fu; Yu, Shu-Hong

    2014-01-01

    To address oil spillage and chemical leakage accidents, the development of efficient sorbent materials is of global importance for environment and water source protection. Here we report on a new type of carbon nanofiber (CNF) aerogels as efficient sorbents for oil uptake with high sorption capacity and excellent recyclability. Importantly, the oil uptake ability of the CNF aerogels can be maintained over a wide temperature range, from liquid nitrogen temperature up to ca. 400°C, making them suitable for oil cleanup under harsh conditions. The outstanding sorption performance of CNF aerogels is associated with their unique physical properties, such as low density, high porosity, excellent mechanical stability, high hydrophobicity and superoleophilicity. PMID:24518262

  7. Characterization of field emission from carbon nanofibers on a metal tip

    NASA Astrophysics Data System (ADS)

    Sakai, Y.; Tone, D.; Nagatsu, S.; Endo, T.; Kita, S.; Okuyama, F.

    2009-08-01

    Field electron emission from carbon nanofibers (CNFs) grown on a tungsten tip has been characterized by measuring emission current-voltage (I-V) curves and observing emission patterns on a phosphor screen. CNFs were vertically grown on the tip by plasma-enhanced chemical vapor deposition. Field emission from the CNFs over 100 μA was strongly dependent on emitter-anode distance, and the dominant field electrons were emitted within an angular spread of Δθ ˜25°, indicating the electron emission took place mainly from the emitter's apex area. By analyzing the I-V curves with the aid of the Fowler-Nordheim theory, the maximum current density was estimated to be about J =2×109 A/m2.

  8. A fine-focusing x-ray source using carbon-nanofiber field emitter

    NASA Astrophysics Data System (ADS)

    Sugimoto, W.; Sugita, S.; Sakai, Y.; Goto, H.; Watanabe, Y.; Ohga, Y.; Kita, S.; Ohara, T.

    2010-08-01

    A fine-focusing x-ray source has been constructed employing a field electron emitter prepared by growing carbon-nanofibers (CNFs) on a metal tip. The x-ray source is composed of a CNF field electron emitter, an electrostatic lens, two magnetic lenses, and a W-target for generating x-rays by electron impact. The CNFs provided field electrons with a current density of J ˜5×109 A/m2, which was evaluated with the aid of Fowler-Nordheim theory. The electron beam extracted from the CNF emitter was accelerated to the energies of E =10-25 keV, and then focused by the lenses. By recording the x-ray images of test charts, the optimum resolution of the x-ray source was estimated to be approximately Dx=0.5 μm.

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

    NASA Astrophysics Data System (ADS)

    Kim, Chang Hyo; Kim, Bo-Hye

    2015-01-01

    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.

  10. Silica decorated on porous activated carbon nanofiber composites for high-performance supercapacitors

    NASA Astrophysics Data System (ADS)

    Kim, So Yeun; Kim, Bo-Hye

    2016-10-01

    A hybrid of silica decorated on porous activated carbon nanofibers (ACNFs) is fabricated in the form of a web via electrospinning and an activation process as an electrode material for electrochemical capacitors in an organic electrolyte. The introduction of PhSiH3 (PS) into the polyacrylonitrile (PAN) solution induces a porous ACNF structure containing silica nanoparticles (NPs) via the spontaneous sol-gel process of PS by steam in the subsequent physical activation process. These inorganic-organic hybrid composites of porous ACNF containing silica NPs show superior specific capacitance and energy density in electrochemical tests, along with good rate capability and excellent cycle life in an organic electrolyte, which is attributed to the combination of ACNF's high surface area and silica's hydrophilicity. The electrochemical performance decreases with increasing PS concentration, and this trend is consistent with the specific surface area results, which reveal the rapid formation of a double layer.

  11. Fabrication and properties of ethylene vinyl acetate-carbon nanofiber nanocomposites.

    PubMed

    George, Jinujacob; Bhowmick, Anil K

    2008-01-01

    Carbon nanofiber (CNF) is one of the stiffest materials produced commercially, having excellent mechanical, electrical, and thermal properties. The reinforcement of rubbery matrices by CNFs was studied in the case of ethylene vinyl acetate (EVA). The tensile strength was greatly (61%) increased, even for very low fiber content (i.e., 1.0 wt.%). The surface modification of the fiber by high energy electron beam and gamma irradiation led to better dispersion in the rubber matrix. This in turn gave rise to further improvements in mechanical and dynamic mechanical properties of EVA. The thermal conductivity also exhibited improvements from that of the neat elastomer, although thermal stability of the nanocomposites was not significantly altered by the functionalization of CNFs. Various results were well supported by the morphological analysis of the nanocomposites. PMID:20596388

  12. Carbon Nanofibers Modified Graphite Felt for High Performance Anode in High Substrate Concentration Microbial Fuel Cells

    PubMed Central

    Shen, Youliang; Zhou, Yan; Chen, Shuiliang; Yang, Fangfang; Zheng, Suqi; Hou, Haoqing

    2014-01-01

    Carbon nanofibers modified graphite fibers (CNFs/GF) composite electrode was prepared for anode in high substrate concentration microbial fuel cells. Electrochemical tests showed that the CNFs/GF anode generated a peak current density of 2.42 mA cm−2 at a low acetate concentration of 20 mM, which was 54% higher than that from bare GF. Increase of the acetate concentration to 80 mM, in which the peak current density of the CNFs/GF anode greatly increased and was up to 3.57 mA cm−2, was seven times as that of GF anode. Morphology characterization revealed that the biofilms in the CNFs/GF anode were much denser than those in the bare GF. This result revealed that the nanostructure in the anode not only enhanced current generation but also could tolerate high substrate concentration. PMID:24883348

  13. Mechanical Properties of Carbon Nanofiber Reinforced Polymer Composites-Molecular Dynamics Approach

    NASA Astrophysics Data System (ADS)

    Sharma, Sumit; Chandra, Rakesh; Kumar, Pramod; Kumar, Navin

    2016-06-01

    Molecular dynamics simulation has been used to study the effect of carbon nanofiber (CNF) volume fraction ( V f) and aspect ratio ( l/d) on mechanical properties of CNF-reinforced polypropylene (PP) composites. Materials Studio 5.5 has been used as a tool for finding the modulus and damping in composites. CNF composition in PP was varied by volume from 0% to 16%. The aspect ratio of CNF was varied from l/d = 5 to l/d = 100. Results show that, with only 2% addition by volume of CNF in PP, E 11 increases 748%. Increase in E 22 is much less in comparison to the increase in E 11. With the increase in the CNF aspect ratio ( l/d) up to l/d = 60, the longitudinal loss factor ( η 11) decreases rapidly. The results of this study have been compared with those available in the literature.

  14. Electrosorption of ions from aqueous solutions with carbon nanotubes and nanofibers composite film electrodes

    NASA Astrophysics Data System (ADS)

    Wang, X. Z.; Li, M. G.; Chen, Y. W.; Cheng, R. M.; Huang, S. M.; Pan, L. K.; Sun, Z.

    2006-07-01

    Electrosorption of ions from aqueous solutions with carbon nanotubes and nanofibers (CNTs-CNFs) composite film electrodes has been demonstrated. The large area CNTs-CNFs film was directly grown on Ni plate by low pressure and low temperature thermal chemical vapor deposition. The CNTs-CNFs electrodes have great advantages such as low cost, easy operation, long-term reproducibility, and integrity of monolithic CNTs-CNFs film and current collector. Batch-mode experiments at low voltage (0.4-2V) were conducted in a continuously recycling system to investigate the electrosorption process. Purification of water with good reproducibility was achieved because of optimal pore size distribution of CNTs-CNFs composite films.

  15. Flexible Sensing Arrays Fabricated with Carbon Nanofiber Composite Thin Films for Posture Monitoring

    NASA Astrophysics Data System (ADS)

    Chang, Fuh-Yu; Wang, Ruoh-Huey; Lin, Yu-Hsien; Chen, Tse-Min; Lee, Yueh-Feng; Huang, Shu-Jiuan; Liu, Chia-Ming

    2011-06-01

    Faulty posture increases joint stress and causes postural pain syndrome. In this paper, we present a portable strain sensing system with flexible sensor arrays to warn patients to correct inappropriate posture. A 3×3 flexible strain sensing array system was fabricated using patterned surface treatment and the tilted-drop process with carbon nanofiber composite solutions on polyimide substrates. Atmospheric plasma was used to enhance or reduce the surface energy in specific areas for patterned surface treatment. A scanning circuit was also developed to capture the signal from the flexible sensing array. The developed system has been used to measure the bent angle of the human neck from 15 to 60°. The results indicate that human posture can be successfully captured by analyzing the measured strains from a flexible strain sensing array.

  16. Carbon nanofibers modified graphite felt for high performance anode in high substrate concentration microbial fuel cells.

    PubMed

    Shen, Youliang; Zhou, Yan; Chen, Shuiliang; Yang, Fangfang; Zheng, Suqi; Hou, Haoqing

    2014-01-01

    Carbon nanofibers modified graphite fibers (CNFs/GF) composite electrode was prepared for anode in high substrate concentration microbial fuel cells. Electrochemical tests showed that the CNFs/GF anode generated a peak current density of 2.42 mA cm(-2) at a low acetate concentration of 20 mM, which was 54% higher than that from bare GF. Increase of the acetate concentration to 80 mM, in which the peak current density of the CNFs/GF anode greatly increased and was up to 3.57 mA cm(-2), was seven times as that of GF anode. Morphology characterization revealed that the biofilms in the CNFs/GF anode were much denser than those in the bare GF. This result revealed that the nanostructure in the anode not only enhanced current generation but also could tolerate high substrate concentration.

  17. Direct measurement of the percolation probability in carbon nanofiber-polyimide nanocomposites.

    SciTech Connect

    Wang, David H.; Trionfi, Aaron; Vaia, Richard A.; Hsu, Julia W. P.; Jacobs, J. David; Tan, L.-Seng

    2008-11-01

    We present the first experimental measurement of the geometric critical exponent {beta} associated with the percolation probability, the probability a metallic filler belongs to the conducting network, of an electrical composite. The technique employs conducting-tip atomic force microscopy to obtain a conducting areal density, and is demonstrated on polyimide nanocomposites containing different concentrations of carbon nanofibers. We find {beta} {approx} 1 and t (the exponent for bulk conductivity) {approx} 3. These values are consistent with the predictions for the Bethe lattice and larger than the values predicted in the 3D lattice percolation model. Hence, this electrical composite likely belongs to the same universality class as the Bethe lattice. The ability to measure geometric and transport critical exponents on the same material is critical to drawing this conclusion.

  18. Carbon nanofibers suppress fungal inhibition of seed germination of maize (Zea mays) and barley (Hordeum vulgare L.) crop

    NASA Astrophysics Data System (ADS)

    Joshi, Anjali; Sharma, Arti; Nayyar, Harsh; Verma, Gaurav; Dharamvir, Keya

    2015-08-01

    Carbon nanofibers (CNFs) are one of allotropes of carbon, consists of graphene layers arrangement in the form of stacked cones or like a cup diameter in nanometer and several millimeters in length. Their extraordinary mechanical, chemical and electronic properties are due to their small size. CNFs have been successfully applied in field of medicine in variety of diagnostic methods. They proven to be an excellent system for drug delivery, tissue regeneration, biosensor etc. This research focuses the applications of CNFs in all fields of Agriculture. In the we treated some fungal disease seed of maize and barley using functionalised CNFs. We find that the tested seeds grow just as well as the healthy seeds whereas the untreated fungal disease seeds, by themselves show very poor germination and seedling growth. This simple experiment shows the extraordinary ability of Carbon nanofibers in carrying effectively inside the germinated seeds.

  19. Carbon nanofibers suppress fungal inhibition of seed germination of maize (Zea mays) and barley (Hordeum vulgare L.) crop

    SciTech Connect

    Joshi, Anjali Sharma, Arti; Nayyar, Harsh; Verma, Gaurav; Dharamvir, Keya

    2015-08-28

    Carbon nanofibers (CNFs) are one of allotropes of carbon, consists of graphene layers arrangement in the form of stacked cones or like a cup diameter in nanometer and several millimeters in length. Their extraordinary mechanical, chemical and electronic properties are due to their small size. CNFs have been successfully applied in field of medicine in variety of diagnostic methods. They proven to be an excellent system for drug delivery, tissue regeneration, biosensor etc. This research focuses the applications of CNFs in all fields of Agriculture. In the we treated some fungal disease seed of maize and barley using functionalised CNFs. We find that the tested seeds grow just as well as the healthy seeds whereas the untreated fungal disease seeds, by themselves show very poor germination and seedling growth. This simple experiment shows the extraordinary ability of Carbon nanofibers in carrying effectively inside the germinated seeds.

  20. Face-centered-cubic lithium crystals formed in mesopores of carbon nanofiber electrodes.

    PubMed

    Lee, Byoung-Sun; Seo, Jong-Hyun; Son, Seoung-Bum; Kim, Seul Cham; Choi, In-Suk; Ahn, Jae-Pyoung; Oh, Kyu Hwan; Lee, Se-Hee; Yu, Woong-Ryeol

    2013-07-23

    In the foreseeable future, there will be a sharp increase in the demand for flexible Li-ion batteries. One of the most important components of such batteries will be a freestanding electrode, because the traditional electrodes are easily damaged by repeated deformations. The mechanical sustainability of carbon-based freestanding electrodes subjected to repeated electrochemical reactions with Li ions is investigated via nanotensile tests of individual hollow carbon nanofibers (HCNFs). Surprisingly, the mechanical properties of such electrodes are improved by repeated electrochemical reactions with Li ions, which is contrary to the conventional wisdom that the mechanical sustainability of carbon-based electrodes should be degraded by repeated electrochemical reactions. Microscopic studies reveal a reinforcing mechanism behind this improvement, namely, that inserted Li ions form irreversible face-centered-cubic (FCC) crystals within HCNF cavities, which can reinforce the carbonaceous matrix as strong second-phase particles. These FCC Li crystals formed within the carbon matrix create tremendous potential for HCNFs as freestanding electrodes for flexible batteries, but they also contribute to the irreversible (and thus low) capacity of HCNFs.

  1. Alignment control of carbon nanotube forest from random to nearly perfectly aligned by utilizing the crowding effect.

    PubMed

    Xu, Ming; Futaba, Don N; Yumura, Motoo; Hata, Kenji

    2012-07-24

    Alignment represents an important structural parameter of carbon nanotubes (CNTs) owing to their exceptionally high aspect ratio, one-dimensional property. In this paper, we demonstrate a general approach to control the alignment of few-walled CNT forests from nearly random to nearly ideally aligned by tailoring the density of active catalysts at the catalyst formation stage, which can be experimentally achieved by controlling the CNT forest mass density. Experimentally, we found that the catalyst density and the degree of alignment were inseparably linked because of a crowding effect from neighboring CNTs, that is, the increasing confinement of CNTs with increased density. Therefore, the CNT density governed the degree of alignment, which increased monotonically with the density. This relationship, in turn, allowed the precise control of the alignment through control of the mass density. To understand this behavior further, we developed a simple, first-order model based on the flexural modulus of the CNTs that could quantitatively describe the relationship between the degree of alignment (HOF) and carbon nanotube spacing (crowding effect) of any type of CNTs.

  2. Growth of vertically aligned multiwall carbon nanotubes columns

    NASA Astrophysics Data System (ADS)

    Shahzad, M. I.; Giorcelli, M.; Perrone, D.; Virga, A.; Shahzad, N.; Jagdale, P.; Cocuzza, M.; Tagliaferro, A.

    2013-06-01

    Capability of patterning carbon nanotubes (CNTs) growth is of tantamount importance for a number of applications ranging from thermal to electronic. This article reports on the columnar growth of vertically aligned multiwall carbon nanotubes (VA-MWCNTs) on patterned Silicon (Si) surface. We have developed procedures based on negative as well as positive masking approaches which allows the growth of predetermined MWCNTs patterns. We describe in detail the process steps leading to Si surface patterning. As quoted above, patterns are exploited to grow VA-MWCNTs. We have focused in particular on the growth of CNT pillars by chemical vapor despoition (CVD) technique at 850°C with camphor and ferrocene as carbon precursors and catalyst respectively. Field emission scanning electron microscopy (FESEM) is employed at low magnification to verify the correct patterning, and at high magnification to examine the surface morphology of CNTs pillars. The pillars are up to 2 mm high, their height being tailored through the deposition time. The diameter of each MWCNT is in the range 30-70 nm and the length is up to few hundred micrometers. The small CNT pillars produced, have several electrical and thermal applications. For instance they can be very useful for heat transfer systems as the lower thermal conductivity of fluids can be improved by the inclusion of nanotubes thanks to their peculiar 1-dimensional heat transfer characteristics.

  3. Growth of well-aligned carbon nanotubes with different shapes

    NASA Astrophysics Data System (ADS)

    Zhao, Tingkai; Ji, Xianglin; Liu, Hongzhen; Yao, Pengyang; Liu, Wujian; Xiong, Chuanyin; Li, Tianxin; Wang, Chen

    2015-12-01

    Well-aligned carbon nanotubes (CNTs) with different shapes, namely coiled CNTs (CCNTs), V-shape CNTs (VCNTs) and ribbon-like CNTs (RCNTs), were prepared by floating catalyst chemical vapor deposition (FC-CVD) using triethylsilane and ferrocene as catalyst precursors and xylene as carbon source. The products were characterized by transmission electron microscopy, scanning electron microscopy, X-ray diffraction and energy dispersive spectrometer. The experimental results indicated that triethylsilane limited the catalyst effectivity in the formation of the novel shapes. When the mole ratio of ferrocene and triethylsilane reached 10:1, the array morphology was maintained and several shapes appeared. It inferred that the catalyst particles were formed by two phases, namely Fe-C-Si solid solution and cementite Fe3C. The different absorption and desorption rates of carbon atoms between this two phases as well as the catalyst morphology change during the growth consequently lead to the formation of CCNTs and RCNTs. As for the VCNTs, it concluded that the partial inactivation of catalysts lead to two separated growth areas of CNTs which formed this CNTs. A mechanism is proposed to explain the relationships between the adding of triethylsilane and the formation of the novel structure.

  4. High Thermal and Electrical Conductivity of Template Fabricated P3HT/MWCNT Composite Nanofibers.

    PubMed

    Smith, Matthew K; Singh, Virendra; Kalaitzidou, Kyriaki; Cola, Baratunde A

    2016-06-15

    Nanoporous alumina membranes are filled with multiwalled carbon nanotubes (MWCNTs) and then poly(3-hexylthiophene-2,5-diyl) (P3HT) melt, resulting in nanofibers with nanoconfinement induced coalignment of both MWCNT and polymer chains. The simple sonication process proposed here can achieve vertically aligned arrays of P3HT/MWCNT composite nanofibers with 3 wt % to 55 wt % MWCNT content, measured using thermogravimetric methods. Electrical and thermal transport in the composite nanofibers improves drastically with increasing carbon nanotube content where nanofiber thermal conductivity peaks at 4.7 ± 1.1 Wm(-1)K(-1) for 24 wt % MWCNT and electrical percolation occurs once 20 wt % MWCNT content is surpassed. This is the first report of the thermal conductivity of template fabricated composite nanofibers and the first proposed processing technique to enable template fabrication of composite nanofibers with high filler content and long aspect ratio fillers, where enhanced properties can also be realized on the macroscale due to vertical alignment of the nanofibers. These materials are interesting for thermal management applications due to their high thermal conductivity and temperature stability. PMID:27200459

  5. High Thermal and Electrical Conductivity of Template Fabricated P3HT/MWCNT Composite Nanofibers.

    PubMed

    Smith, Matthew K; Singh, Virendra; Kalaitzidou, Kyriaki; Cola, Baratunde A

    2016-06-15

    Nanoporous alumina membranes are filled with multiwalled carbon nanotubes (MWCNTs) and then poly(3-hexylthiophene-2,5-diyl) (P3HT) melt, resulting in nanofibers with nanoconfinement induced coalignment of both MWCNT and polymer chains. The simple sonication process proposed here can achieve vertically aligned arrays of P3HT/MWCNT composite nanofibers with 3 wt % to 55 wt % MWCNT content, measured using thermogravimetric methods. Electrical and thermal transport in the composite nanofibers improves drastically with increasing carbon nanotube content where nanofiber thermal conductivity peaks at 4.7 ± 1.1 Wm(-1)K(-1) for 24 wt % MWCNT and electrical percolation occurs once 20 wt % MWCNT content is surpassed. This is the first report of the thermal conductivity of template fabricated composite nanofibers and the first proposed processing technique to enable template fabrication of composite nanofibers with high filler content and long aspect ratio fillers, where enhanced properties can also be realized on the macroscale due to vertical alignment of the nanofibers. These materials are interesting for thermal management applications due to their high thermal conductivity and temperature stability.

  6. Self aligned hysteresis free carbon nanotube field-effect transistors

    NASA Astrophysics Data System (ADS)

    Shlafman, M.; Tabachnik, T.; Shtempluk, O.; Razin, A.; Kochetkov, V.; Yaish, Y. E.

    2016-04-01

    Hysteresis phenomenon in the transfer characteristics of carbon nanotube field effect transistor (CNT FET) is being considered as the main obstacle for successful realization of electronic devices based on CNTs. In this study, we prepare four kinds of CNTFETs and explore their hysteretic behavior. Two kinds of devices comprise on-surface CNTs (type I) and suspended CNTs (type II) with thin insulating layer underneath and a single global gate which modulates the CNT conductance. The third and fourth types (types III and IV) consist of suspended CNT over a metallic local gate underneath, where for type IV the local gate was patterned self aligned with the source and drain electrodes. The first two types of devices, i.e., type I and II, exhibit substantial hysteresis which increases with scanning range and sweeping time. Under high vacuum conditions and moderate electric fields ( |E |>4 ×106 V /cm ), the hysteresis for on-surface devices cannot be eliminated, as opposed to suspended devices. Interestingly, type IV devices exhibit no hysteresis at all at ambient conditions, and from the different roles which the global and local gates play for the four types of devices, we could learn about the hysteresis mechanism of this system. We believe that these self aligned hysteresis free FETs will enable the realization of different electronic devices and sensors based on CNTs.

  7. Fabrication and characterization of vertically aligned carbon-nanotube membranes

    NASA Astrophysics Data System (ADS)

    Castellano, Richard; Akin, Cevat; Purri, Matt; Shan, Jerry; Kim, Sangil; Fornasiero, Francesco

    2015-11-01

    Membranes having vertically-aligned carbon-nanotube (VACNT) pores offer promise as highly efficient and permeable membranes for use as breathable thin films, or in filtration and separation applications, among others. However, current membrane-fabrication techniques utilizing chemical-vapor-deposition-grown VACNT arrays are costly and difficult to scale up. We have developed a solution-based, electric-field-assisted approach as a cost-effective and scalable method to produce large-area VACNT membranes. Nanotubes are dispersed in a liquid polymer, and aligned and electrodeposited with the aid of an electric field prior to crosslinking the polymer to create VACNT membranes. We experimentally examine the electrodeposition process, focusing on parameters including the electric field, composition of the solution, and CNT functionalization that can affect the nanotube number density in the resulting membrane. We characterize the CNT pore size and number density and investigate the transport properties of the membrane. Size-exclusion tests are used to check for defects and infer the pore size of the VACNT membranes. Dry-gas membrane permeability is measured with a pressurized nitrogen-flow system, while moisture-vapor-transfer rate is measured with the ASTM-E96 upright-cup test. We discuss the measured transport properties of the solution-based, electric-field-fabricated VACNT membranes in reference to their application as breathable thin films. We would like to acknowledge DTRA for their funding and support of our research.

  8. Freestanding Aligned Multi-walled Carbon Nanotubes for Supercapacitor Devices

    NASA Astrophysics Data System (ADS)

    Moreira, João Vitor Silva; Corat, Evaldo José; May, Paul William; Cardoso, Lays Dias Ribeiro; Lelis, Pedro Almeida; Zanin, Hudson

    2016-08-01

    We report on the synthesis and electrochemical properties of multi-walled carbon nanotubes (MWCNTs) for supercapacitor devices. Freestanding vertically-aligned MWCNTs and MWCNT powder were grown concomitantly in a one-step chemical vapour deposition process. Samples were characterized by scanning and transmission electron microscopies and Fourier transform infrared and Raman spectroscopies. At similar film thicknesses and surface areas, the freestanding MWCNT electrodes showed higher electrochemical capacitance and gravimetric specific energy and power than the randomly-packed nanoparticle-based electrodes. This suggests that more ordered electrode film architectures facilitate faster electron and ion transport during the charge-discharge processes. Energy storage and supply or supercapacitor devices made from these materials could bridge the gap between rechargeable batteries and conventional high-power electrostatic capacitors.

  9. Freestanding Aligned Multi-walled Carbon Nanotubes for Supercapacitor Devices

    NASA Astrophysics Data System (ADS)

    Moreira, João Vitor Silva; Corat, Evaldo José; May, Paul William; Cardoso, Lays Dias Ribeiro; Lelis, Pedro Almeida; Zanin, Hudson

    2016-11-01

    We report on the synthesis and electrochemical properties of multi-walled carbon nanotubes (MWCNTs) for supercapacitor devices. Freestanding vertically-aligned MWCNTs and MWCNT powder were grown concomitantly in a one-step chemical vapour deposition process. Samples were characterized by scanning and transmission electron microscopies and Fourier transform infrared and Raman spectroscopies. At similar film thicknesses and surface areas, the freestanding MWCNT electrodes showed higher electrochemical capacitance and gravimetric specific energy and power than the randomly-packed nanoparticle-based electrodes. This suggests that more ordered electrode film architectures facilitate faster electron and ion transport during the charge-discharge processes. Energy storage and supply or supercapacitor devices made from these materials could bridge the gap between rechargeable batteries and conventional high-power electrostatic capacitors.

  10. Aligned/micropatterned carbon nanotube arrays: surface functionalization and electrochemical sensing

    NASA Astrophysics Data System (ADS)

    Qu, Liangti; He, Pingang; Li, Lingchuan; Gao, Mei; Wallace, Gordon; Dai, Liming

    2005-03-01

    We have previously developed a simple pyrolytic method for large-scale production of aligned multi-wall carbon nanotube arrays perpendicular to the substrate. These aligned carbon nanotube arrays can be transferred onto various substrates of particular interest (e.g. polymer films for organic optoelectronic devices) in either a patterned or non-patterned fashion. The well-aligned structure provides additional advantages for not only an efficient device construction but also for surface functionalization. The surface functionalization of aligned carbon nanotubes is particularly attractive, as it allows surface characteristics of the aligned carbon nanotubes to be tuned to meet specific requirements for particular applications while their alignment structure can be largely retained. These aligned carbon nanotubes with tunable surface characteristics are of great significance to various practical applications ranging from sensors to electronics. Single-strand DNA chains could be covalently immobilized onto plasma-activated aligned carbon nanotubes for sensing complementary DNA and/or target DNA chains of specific sequences with a high sensitivity and selectivity. Furthermore, glucose oxidase (GOX) could also be immobilized onto the aligned carbon nanoutbe arrays by electropolymerization of pyrrole in the presence of GOX. The resultant GOX-containing polypyrrole-carbon nanotube coaxial nanowires were shown to be promising new sensing active materials for making advanced glucose sensors with a high sensitivity.

  11. A nucleation and growth model of vertically-oriented carbon nanofibers or nanotubes by plasma-enhanced catalytic chemical vapor deposition.

    PubMed

    Cojocaru, C S; Senger, A; Le Normand, F

    2006-05-01

    Carbon nanofibers are grown by direct current and hot filaments-activated catalytic chemical vapor deposition while varying the power of the hot filaments. Observations of these carbon nanofibers vertically oriented on a SiO2 (8 nm thick)/Si(100) substrate covered with Co nanoparticles (10-15 nm particle size) by Scanning Electron and Transmission Electron Microscopies show the presence of a graphitic "nest" either on the surface of the substrate or at the end of the specific nanofiber that does not encapsulate the catalytic particle. Strictly in our conditions, the activation by hot filaments is required to grow nanofibers with a C2H2 - H2 gas mixture, as large amounts of amorphous carbon cover the surface of the substrate without using hot filaments. From these observations as well as data of the literature, it is proposed that the nucleation of carbon nanofibers occurs through a complex process involving several steps: carbon concentration gradient starting from the catalytic carbon decomposition and diffusion from the surface of the catalytic nanoparticles exposed to the activated gas and promoted by energetic ionic species of the gas phase; subsequent graphitic condensation of a "nest" at the interface of the Co particle and substrate. The large concentration of highly reactive hydrogen radicals mainly provided by activation with hot filaments precludes further spreading out of this interfacial carbon nest over the entire surface of the substrate and thus selectively orientates the growth towards the condensation of graphene over facets that are perpendicular to the surface. Carbon nanofibers can then be grown within the well-known Vapor-Liquid-Solid process. Thus the effect of energetic ions and highly reactive neutrals like atomic hydrogen in the preferential etching of carbon on the edge of graphene shells and on the broadening of the carbon nanofiber is underlined.

  12. Synthesis and electron emission properties of aligned carbon nanotube arrays

    NASA Astrophysics Data System (ADS)

    Neupane, Suman

    Carbon nanotubes (CNTs) have become one of the most interesting allotropes of carbon due to their intriguing mechanical, electrical, thermal and optical properties. The synthesis and electron emission properties of CNT arrays have been investigated in this work. Vertically aligned CNTs of different densities were synthesized on copper substrate with catalyst dots patterned by nanosphere lithography. The CNTs synthesized with catalyst dots patterned by spheres of 500 nm diameter exhibited the best electron emission properties with the lowest turn-on/threshold electric fields and the highest field enhancement factor. Furthermore, CNTs were treated with NH3 plasma for various durations and the optimum enhancement was obtained for a plasma treatment of 1.0 min. CNT point emitters were also synthesized on a flat-tip or a sharp-tip to understand the effect of emitter geometry on the electron emission. The experimental results show that electron emission can be enhanced by decreasing the screening effect of the electric field by neighboring CNTs. In another part of the dissertation, vertically aligned CNTs were synthesized on stainless steel (SS) substrates with and without chemical etching or catalyst deposition. The density and length of CNTs were determined by synthesis time. For a prolonged growth time, the catalyst activity terminated and the plasma started etching CNTs destructively. CNTs with uniform diameter and length were synthesized on SS substrates subjected to chemical etching for a period of 40 minutes before the growth. The direct contact of CNTs with stainless steel allowed for the better field emission performance of CNTs synthesized on pristine SS as compared to the CNTs synthesized on Ni/Cr coated SS. Finally, fabrication of large arrays of free-standing vertically aligned CNT/SnO2 core-shell structures was explored by using a simple wet-chemical route. The structure of the SnO2 nanoparticles was studied by X-ray diffraction and electron microscopy

  13. Chamber-confined silicon-carbon nanofiber composites for prolonged cycling life of Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Fu, Kun; Lu, Yao; Dirican, Mahmut; Chen, Chen; Yanilmaz, Meltem; Shi, Quan; Bradford, Philip D.; Zhang, Xiangwu

    2014-06-01

    Silicon is a promising high capacity (4200 mA h g-1) anode material for lithium ion batteries but the significant volume change (over 300%) of silicon during lithiation/delithiation remains a challenge in terms of silicon pulverization and solid-electrolyte-interphase (SEI) accumulation in the silicon composite electrode. To alleviate the volumetric change of silicon, we built a flexible and self-supporting carbon-enhanced carbon nanofiber (CNF) structure with vacant chamber to encapsulate Si nanoparticles (vacant Si@CNF@C). This composite was tested directly without any polymer and current collector. The confined vacant chamber allowed the increasing volume of silicon and SEI accumulates to be well retained for a long cycle life. This chamber-confined silicon-carbon nanofiber composite exhibited an improved performance in terms of good cycling performance (620 mA h g-1), high coulombic efficiency (99%), and good capacity retention (80%) after 200 cycles. This self-supported silicon-carbon nanofiber structure showed high flexibility and good electrochemical performance for the potential as flexible electrode for lithium-ion batteries.

  14. Chamber-confined silicon-carbon nanofiber composites for prolonged cycling life of Li-ion batteries.

    PubMed

    Fu, Kun; Lu, Yao; Dirican, Mahmut; Chen, Chen; Yanilmaz, Meltem; Shi, Quan; Bradford, Philip D; Zhang, Xiangwu

    2014-07-01

    Silicon is a promising high capacity (4200 mA h g(-1)) anode material for lithium ion batteries but the significant volume change (over 300%) of silicon during lithiation/delithiation remains a challenge in terms of silicon pulverization and solid-electrolyte-interphase (SEI) accumulation in the silicon composite electrode. To alleviate the volumetric change of silicon, we built a flexible and self-supporting carbon-enhanced carbon nanofiber (CNF) structure with vacant chamber to encapsulate Si nanoparticles (vacant Si@CNF@C). This composite was tested directly without any polymer and current collector. The confined vacant chamber allowed the increasing volume of silicon and SEI accumulates to be well retained for a long cycle life. This chamber-confined silicon-carbon nanofiber composite exhibited an improved performance in terms of good cycling performance (620 mA h g(-1)), high coulombic efficiency (99%), and good capacity retention (80%) after 200 cycles. This self-supported silicon-carbon nanofiber structure showed high flexibility and good electrochemical performance for the potential as flexible electrode for lithium-ion batteries.

  15. Copper/zinc bimetal nanoparticles-dispersed carbon nanofibers: A novel potential antibiotic material.

    PubMed

    Ashfaq, Mohammad; Verma, Nishith; Khan, Suphiya

    2016-02-01

    Copper (Cu) and zinc (Zn) nanoparticles (NPs) were asymmetrically distributed in carbon nanofibers (CNFs) grown on an activated carbon fiber (ACF) substrate by chemical vapor deposition (CVD). The CVD conditions were chosen such that the Cu NPs moved along with the CNFs during tip-growth, while the Zn NPs remained adhered at the ACF. The bimetal-ACF/CNF composite material was characterized by the metal NP release profiles, in-vitro hemolytic and antibacterial activities, and bacterial cellular disruption and adhesion assay. The synergetic effects of the bimetal NPs distributed in the ACFs/CNFs resulted from the relatively slower release of the Cu NPs located at the tip of the CNFs and faster release of the Zn NPs dispersed in the ACF. The Cu/Zn-grown ACFs/CNFs inhibited the growth of the Gram negative Escherichia coli, Gram positive Staphylococcus aureus, and Methicillin resistance Staphylococcus aureus bacterial strains, with superior efficiency (instant and prolonged inhibition) than the Cu or Zn single metal-grown ACFs/CNFs. The prepared bimetal-carbon composite material in this study has potential to be used in different biomedical applications such as wound healing and antibiotic wound dressing. PMID:26652451

  16. Copper/zinc bimetal nanoparticles-dispersed carbon nanofibers: A novel potential antibiotic material.

    PubMed

    Ashfaq, Mohammad; Verma, Nishith; Khan, Suphiya

    2016-02-01

    Copper (Cu) and zinc (Zn) nanoparticles (NPs) were asymmetrically distributed in carbon nanofibers (CNFs) grown on an activated carbon fiber (ACF) substrate by chemical vapor deposition (CVD). The CVD conditions were chosen such that the Cu NPs moved along with the CNFs during tip-growth, while the Zn NPs remained adhered at the ACF. The bimetal-ACF/CNF composite material was characterized by the metal NP release profiles, in-vitro hemolytic and antibacterial activities, and bacterial cellular disruption and adhesion assay. The synergetic effects of the bimetal NPs distributed in the ACFs/CNFs resulted from the relatively slower release of the Cu NPs located at the tip of the CNFs and faster release of the Zn NPs dispersed in the ACF. The Cu/Zn-grown ACFs/CNFs inhibited the growth of the Gram negative Escherichia coli, Gram positive Staphylococcus aureus, and Methicillin resistance Staphylococcus aureus bacterial strains, with superior efficiency (instant and prolonged inhibition) than the Cu or Zn single metal-grown ACFs/CNFs. The prepared bimetal-carbon composite material in this study has potential to be used in different biomedical applications such as wound healing and antibiotic wound dressing.

  17. Growth of carbon nanofibers using resol-type phenolic resin and cobalt(II) catalyst.

    PubMed

    Kim, Taeyun; Mees, Karina; Park, Ho-Seon; Willert-Porada, Monika; Lee, Chang-Seop

    2013-11-01

    This study investigated carbon nanofibers (CNFs) grown on reticulated vitreous carbon (RVC) foam through catalytic deposition of ethylene. Before growing the CNFs, Co(II) on the RVC foam was expected to act as a catalyst by deposition. The preparation of the CNFs was a two-step process. The first step was preparing the RVC from polyurethane (PU) foam. Changes in weight over time were evaluated using two kinds of resol. The change in the mass and state of the sample with the change in temperature was studied during the carbonization process. The second step was to prepare the CNFs. An OH group was attached by the oxidation of the RVC foam. A change in the shape and mass of the sample was observed due to a change in nitric acid concentration and oxidation time. Then, cobalt was deposited to grow CNFs on the RVC foam. Hydrolysis helped to deposit the Co(ll) on the RVC foam. The appropriate time and temperature were investigated for the reduction process. In the last step, CNFs were prepared by the introducing ethylene gas. The resulting samples were analyzed using scanning electron microscopy, energy dispersive spectroscopy, N2-sorption, and X-ray photoelectron spectroscopy. PMID:24245253

  18. Electrospun carbon nanofibers from polyacrylonitrile blended with activated or graphitized carbonaceous materials for improving anodic bioelectrocatalysis.

    PubMed

    Patil, Sunil A; Chigome, Samuel; Hägerhäll, Cecilia; Torto, Nelson; Gorton, Lo

    2013-03-01

    The electrospun carbon nanofibers obtained from polyacrylonitrile (PAN) and PAN blends with either activated carbon (PAN-AC) or graphite (PAN-GR) were tested as anodes using Shewanella oneidensis MR-1. Extensive physico-chemical and electrochemical characterization confirmed their formation, their fibrous and porous nature, and their suitability as electrodes. N2 adsorption measurements revealed high specific surface area (229.8, 415.8 and 485.2m(2) g(-1)) and porosity (0.142, 0.202 and 0.239cm(3)g(-1)) for PAN, PAN-AC and PAN-GR, respectively. The chronoamperometric measurements showed a considerable decrease in start-up time and more than a 10-fold increase in the generation of current with these electrodes (115, 139 and 155μAcm(-2) for PAN, PAN-AC and PAN-GR, respectively) compared to the graphite electrode (11.5μAcm(-2)). These results indicate that the bioelectrocatalysis benefits from the blending of PAN with activated or graphitized carbonaceous materials, presumably due to the increased specific surface area, total pore volume and modification of the carbon microstructure. PMID:23399497

  19. Composite Materials with Magnetically Aligned Carbon Nanoparticles Having Enhanced Electrical Properties and Methods of Preparation

    NASA Technical Reports Server (NTRS)

    Hong, Haiping (Inventor); Peterson, G.P. (Bud) (Inventor); Salem, David R. (Inventor)

    2016-01-01

    Magnetically aligned carbon nanoparticle composites have enhanced electrical properties. The composites comprise carbon nanoparticles, a host material, magnetically sensitive nanoparticles and a surfactant. In addition to enhanced electrical properties, the composites can have enhanced mechanical and thermal properties.

  20. In situ encapsulation of germanium clusters in carbon nanofibers: high-performance anodes for lithium-ion batteries.

    PubMed

    Wang, Wei; Xiao, Ying; Wang, Xia; Liu, Bing; Cao, Minhua

    2014-10-01

    Alloyed anode materials for lithium-ion batteries (LIBs) usually suffer from considerable capacity losses during charge-discharge process. Herein, in situ-grown germanium clusters are homogeneously encapsulated into porous nitrogen-doped carbon nanofibers (N-CNFs) to form Ge/N-CNFs hybrids, using a facile electrospinning method followed by thermal treatment. When used as anode in LIBs, the Ge/N-CNFs hybrids exhibit excellent lithium storage performance in terms of specific capacity, cycling stability, and rate capability. The excellent electrochemical properties can be attributed to the unique structural features: the distribution of the germanium clusters, porous carbon nanofibers, and GeN chemical bonds all contribute to alleviating the large volume changes of germanium during the discharge-charge process, while at same time the unique porous N-CNFs not only increase the contact area between the electrode and the electrolyte, but also the conductivity of the hybrid.

  1. Third Harmonic Generation from Aligned Single-Wall Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Morris, Darius T., Jr.

    Optical properties of single-wall carbon nanotubes (SWCNTs) have been extensively studied during the last decade, and much basic knowledge has been accumulated on how light emission, scattering, and absorption occur in the realm of linear optics. However, their nonlinear optical properties remain largely unexplored. Here, we have observed strong third harmonic generation from highly aligned SWCNTs with intense mid-infrared radiation. Through power dependent experiments, we have determined the absolute value of the third-order nonlinear optical susceptibility, chi(3), of our SWCNT film to be 6.92 x 10--12 esu, which is three orders of magnitude larger than that of the fused silica reference sample we used. Furthermore, through polarization-dependent third harmonic generation experiments, all the nonzero tensor elements of chi(3) have also been extracted. The contribution of the weaker tensor elements to the overall chi (3) signal has been calculated to be approximately 1/6 of that of the dominant c3z zzz component. These results open up new possibilities for application of carbon nanotubes in optoelectronics.

  2. Pyrolytic carbon-coated silicon/carbon nanofiber composite anodes for high-performance lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Chen, Yanli; Hu, Yi; Shao, Jianzhong; Shen, Zhen; Chen, Renzhong; Zhang, Xiangwu; He, Xia; Song, Yuanze; Xing, Xiuli

    2015-12-01

    Pyrolytic carbon-coated Si/C nanofibers (Si/C-CNFs) composites have been prepared through the sucrose coating and secondary thermal treatment of Si/CNFs composites produced via electrospinning and carbonization. This results in a structure in which Si nanoparticles are distributed along the fibers, with the fiber surface being coated with an amorphous carbon layer through pyrolysis of the sucrose. This carbon coating not only limits the volume expansion of the exposed Si nanoparticles, preventing their direct contact with the electrolyte, but also creates a connection between the fibers that is beneficial to Li+ ion transport, structural integrity, and electrochemical conductivity. Consequently, the Si/C-CNFs composite exhibits a more stable cycle performance, better rate performance, and higher conductivity than Si/CNFs alone. The optimal level of performance was attained with a 20:200 mass ratio of sucrose to deionized water, with a high retained capacity of 1215.2 mAh g-1 after 50 cycles, thus indicating that it is a suitable anode material for Li-ion batteries.

  3. Vertically aligned carbon nanopillars with size and spacing control for a transparent field emission display.

    PubMed

    Lee, Seok Woo; Lee, Chang Hwa; Lee, Jung A; Lee, Seung S

    2013-01-18

    A top-down fabrication method is presented for vertically aligned carbon nanopillars (CNPs) using photolithography and pyrolysis. The modified backside exposure method of photolithography fabricates vertically aligned polymer (SU-8) nanopillars. The pyrolysis process, which transforms the polymer to amorphous carbon, reliably produces vertically aligned CNPs with widths ranging from 100 to 400 nm. The CNPs can be used as a transparent field emission cathode for a transparent display and light emission is observed.

  4. Dry shear aligning: a simple and versatile method to smooth and align the surfaces of carbon nanotube thin films

    NASA Astrophysics Data System (ADS)

    Tune, D. D.; Stolz, B. W.; Pfohl, M.; Flavel, B. S.

    2016-02-01

    We show that the application of lateral shear force on a randomly oriented thin film of carbon nanotubes, in the dry state, causes significant reordering of the nanotubes at the film surface. This new technique of dry shear aligning is applicable to carbon nanotube thin films produced by many of the established methods.We show that the application of lateral shear force on a randomly oriented thin film of carbon nanotubes, in the dry state, causes significant reordering of the nanotubes at the film surface. This new technique of dry shear aligning is applicable to carbon nanotube thin films produced by many of the established methods. Electronic supplementary information (ESI) available: Detailed experimental methods, table of nanotube details, absorption spectra, further SEM data, plots of sheet resistance, DC to optical conductivity, and 2D order parameter as a function of transmittance. See DOI: 10.1039/c5nr08784h

  5. Mechanical, thermal and morphological characterization of polycarbonate/oxidized carbon nanofiber composites produced with a lean 2-step manufacturing process.

    PubMed

    Lively, Brooks; Kumar, Sandeep; Tian, Liu; Li, Bin; Zhong, Wei-Hong

    2011-05-01

    In this study we report the advantages of a 2-step method that incorporates an additional process pre-conditioning step for rapid and precise blending of the constituents prior to the commonly used melt compounding method for preparing polycarbonate/oxidized carbon nanofiber composites. This additional step (equivalent to a manufacturing cell) involves the formation of a highly concentrated solid nano-nectar of polycarbonate/carbon nanofiber composite using a solution mixing process followed by melt mixing with pure polycarbonate. This combined method yields excellent dispersion and improved mechanical and thermal properties as compared to the 1-step melt mixing method. The test results indicated that inclusion of carbon nanofibers into composites via the 2-step method resulted in dramatically reduced ( 48% lower) coefficient of thermal expansion compared to that of pure polycarbonate and 30% lower than that from the 1-step processing, at the same loading of 1.0 wt%. Improvements were also found in dynamic mechanical analysis and flexural mechanical properties. The 2-step approach is more precise and leads to better dispersion, higher quality, consistency, and improved performance in critical application areas. It is also consistent with Lean Manufacturing principles in which manufacturing cells are linked together using less of the key resources and creates a smoother production flow. Therefore, this 2-step process can be more attractive for industry. PMID:21780388

  6. Mechanical, thermal and morphological characterization of polycarbonate/oxidized carbon nanofiber composites produced with a lean 2-step manufacturing process.

    PubMed

    Lively, Brooks; Kumar, Sandeep; Tian, Liu; Li, Bin; Zhong, Wei-Hong

    2011-05-01

    In this study we report the advantages of a 2-step method that incorporates an additional process pre-conditioning step for rapid and precise blending of the constituents prior to the commonly used melt compounding method for preparing polycarbonate/oxidized carbon nanofiber composites. This additional step (equivalent to a manufacturing cell) involves the formation of a highly concentrated solid nano-nectar of polycarbonate/carbon nanofiber composite using a solution mixing process followed by melt mixing with pure polycarbonate. This combined method yields excellent dispersion and improved mechanical and thermal properties as compared to the 1-step melt mixing method. The test results indicated that inclusion of carbon nanofibers into composites via the 2-step method resulted in dramatically reduced ( 48% lower) coefficient of thermal expansion compared to that of pure polycarbonate and 30% lower than that from the 1-step processing, at the same loading of 1.0 wt%. Improvements were also found in dynamic mechanical analysis and flexural mechanical properties. The 2-step approach is more precise and leads to better dispersion, higher quality, consistency, and improved performance in critical application areas. It is also consistent with Lean Manufacturing principles in which manufacturing cells are linked together using less of the key resources and creates a smoother production flow. Therefore, this 2-step process can be more attractive for industry.

  7. Measurement of Vertically Aligned Carbon Nanotube Array Compression Response

    NASA Astrophysics Data System (ADS)

    Cao, Changhong

    The use of carbon nanotubes (CNTs) in the form of vertically aligned arrays or films has been of interest due to the super-compressible response and the ability to be used as electrical and thermal contacts. CNT arrays have shown the remarkable ability to react as foam-like structures and exhibit localized, coordinated buckling within specific regions. An understanding of the buckling region evolution and the resulting effects on the bulk CNT array response are important, unanswered fundamental questions necessary for the future application of CNT arrays. Here, we report on the low-cycle compression of bulk vertically aligned CNT arrays to observe initiation and growth of the buckling as a function of compressive strain and the contacting substrate material. A critical strain of ˜5.5% is found above which the buckling region length increased and below which remained at or below the applied strain. The results are corroborated with nanoindentation on the surfaces, which indicate a stiffening of the near surface by 9.4%-16.5% with increasing applied strain. Also, contact counterfaces with different stiffness, lithium niobate and a polymer gel, were compared, which resulted in changes of ˜32% in total array height after cyclic compression. Raman spectroscopy on CNT arrays before and after compressive deformation was performed observing repeatable vibrational shifts in the strained regions. Also, to observe the applicability of CNT arrays as contact sensors, electrical resistance change during compression was measured and found to increase by 4 times in the parallel versus vertical direction. Observation and results of the buckling region nature and relationship with applied strain and contacting substrates are important for applying the nanotube arrays to energy absorbing cushions, tunable dampers, thermal contacts, contact sensing, chemical sensing, or in sliding contact.

  8. High performance transistors via aligned polyfluorene-sorted carbon nanotubes

    SciTech Connect

    Brady, Gerald J.; Joo, Yongho; Singha Roy, Susmit; Gopalan, Padma; Arnold, Michael S.

    2014-02-24

    We evaluate the performance of exceptionally electronic-type sorted, semiconducting, aligned single-walled carbon nanotubes (s-SWCNTs) in field effect transistors (FETs). High on-conductance and high on/off conductance modulation are simultaneously achieved at channel lengths which are both shorter and longer than individual s-SWCNTs. The s-SWCNTs are isolated from heterogeneous mixtures using a polyfluorene-derivative as a selective agent and aligned on substrates via dose-controlled, floating evaporative self-assembly at densities of ∼50 s-SWCNTs μm{sup −1}. At a channel length of 9 μm the s-SWCNTs percolate to span the FET channel, and the on/off ratio and charge transport mobility are 2.2 × 10{sup 7} and 46 cm{sup 2} V{sup −1} s{sup −1}, respectively. At a channel length of 400 nm, a large fraction of the s-SWCNTs directly span the channel, and the on-conductance per width is 61 μS μm{sup −1} and the on/off ratio is 4 × 10{sup 5}. These results are considerably better than previous solution-processed FETs, which have suffered from poor on/off ratio due to spurious metallic nanotubes that bridge the channel. 4071 individual and small bundles of s-SWCNTs are tested in 400 nm channel length FETs, and all show semiconducting behavior, demonstrating the high fidelity of polyfluorenes as selective agents and the promise of assembling s-SWCNTs from solution to create high performance semiconductor electronic devices.

  9. Thermal−Electrical Character of in Situ Synthesized Polyimide-Grafted Carbon Nanofiber Composites

    SciTech Connect

    Arlen, Michael J.; Wang, David; Jacobs, J. David; Justice, Ryan; Trionfi, Aaron; Hsu, Julia W.P.; Schaffer, Dale; Tan, Loon-Seng; Vaia, Richard A.

    2008-12-09

    Notwithstanding the success of polymer-carbon nanotube (CNT) nanocomposites, a solid understanding of the impact of external perturbations, including temperature and stress, on the electrical response, its reproducibility, and the subsequent relationship to the topology of the percolative morphology and molecular details of the CNT-CNT contact junction is not complete. Using an in situ synthesis approach, two series of polymide (CP2)-carbon nanofiber (CNF) composites are prepared with quantitatively (small-angle X-ray scattering) comparable CNF dispersions, but differing in the structure of the CNF-polymer interface. Amino-functionalized CNFs (FCNFs) enable direct formation of CP2 grafts onto the CNFs, whereas pristine CNFs (PCNFs) result in a relatively weak interface between the carbon nanofiber and CP2 matrix. In general, low-frequency ac impedance measurements are well described by the percolation bond model, yielding a percolation threshold below 1 vol % (0.24 and 0.68 vol % for PCNF-CP2 and FCNF-CP2, respectively). However, the design of the interface is determined to be crucial for controlling the electrical behavior in four substantial ways: magnitude of the limiting conductivity, linearity of the I-V response, magnitude and direction of temperature-dependent resistivity, and reproducibility of the absolute value of the resistivity with thermal cycling. These observations are consistent with a direct CNF-CNF contact limiting transport in the PCNF-CP2 system, where the CP2 grafts onto the FCNF from a dielectric layer, limiting transport within the FCNF-CP2 system. Furthermore, the grafted CP2 chains on the FCNF reduce local polymer dewetting at the CNF surfaces when the temperature exceeds the CP2 glass transition. This appears to stabilize the structure of the percolation network and associated conductivity. The general behavior of these interfacial extremes (pristine and fully functionalized CNFs) set important bounds on the design of interface

  10. Impact of carbon nanotube length on electron transport in aligned carbon nanotube networks

    SciTech Connect

    Lee, Jeonyoon; Stein, Itai Y.; Devoe, Mackenzie E.; Lewis, Diana J.; Lachman, Noa; Buschhorn, Samuel T.; Wardle, Brian L.; Kessler, Seth S.

    2015-02-02

    Here, we quantify the electron transport properties of aligned carbon nanotube (CNT) networks as a function of the CNT length, where the electrical conductivities may be tuned by up to 10× with anisotropies exceeding 40%. Testing at elevated temperatures demonstrates that the aligned CNT networks have a negative temperature coefficient of resistance, and application of the fluctuation induced tunneling model leads to an activation energy of ≈14 meV for electron tunneling at the CNT-CNT junctions. Since the tunneling activation energy is shown to be independent of both CNT length and orientation, the variation in electron transport is attributed to the number of CNT-CNT junctions an electron must tunnel through during its percolated path, which is proportional to the morphology of the aligned CNT network.

  11. Effect of filler surface properties on stress relaxation behavior of carbon nanofiber/polyurethane nanocomposites

    NASA Astrophysics Data System (ADS)

    Sedat Gunes, I.; Jimenez, Guillermo; Jana, Sadhan

    2009-03-01

    The effect of carbon nanofiber (CNF) surface properties on tensile stress relaxation behavior of CNF/polyurethane (PU) nanocomposites was analyzed. PU was synthesized from methylene diisocyanate, polypropylene glycol (PPG diol), and butanediol. CNF, oxidized CNF (ox-CNF), and PPG diol grafted CNF (ol-CNF) were selected as fillers. ol-CNF was obtained by grafting PPG diol onto ox-CNF by reacting it with the carboxyl groups present on ox-CNF surface. The atomic ratios of oxygen to carbon present on the filler surfaces were 0.13 and 0.18 on ox-CNF and on ol-CNF as compared to 0.015 on CNF, mostly due to the presence oxygen containing polar groups on the surfaces of the former. The composites were prepared by in-situ polymerization and melt mixing in a chaotic mixer. The stress relaxation behavior of composites was determined at room temperature after inducing a tensile strain of 100%. The presence of fillers augmented the rate of stress relaxation in composites which was highest in the presence of CNF. The results suggested that relatively weak polymer-filler interactions in composites of CNF promoted higher stress relaxation.

  12. Direct synthesis of carbon nanofibers from South African coal fly ash

    NASA Astrophysics Data System (ADS)

    Hintsho, Nomso; Shaikjee, Ahmed; Masenda, Hilary; Naidoo, Deena; Billing, Dave; Franklyn, Paul; Durbach, Shane

    2014-08-01

    Carbon nanofibers (CNFs), cylindrical nanostructures containing graphene, were synthesized directly from South African fly ash (a waste product formed during the combustion of coal). The CNFs (as well as other carbonaceous materials like carbon nanotubes (CNTs)) were produced by the catalytic chemical vapour deposition method (CCVD) in the presence of acetylene gas at temperatures ranging from 400°C to 700°C. The fly ash and its carbonaceous products were characterized by transmission electron microscopy (TEM), thermogravimetric analysis (TGA), laser Raman spectroscopy and Brunauer-Emmett-Teller (BET) surface area measurements. It was observed that as-received fly ash was capable of producing CNFs in high yield by CCVD, starting at a relatively low temperature of 400°C. Laser Raman spectra and TGA thermograms showed that the carbonaceous products which formed were mostly disordered. Small bundles of CNTs and CNFs observed by TEM and energy-dispersive spectroscopy (EDS) showed that the catalyst most likely responsible for CNF formation was iron in the form of cementite; X-ray diffraction (XRD) and Mössbauer spectroscopy confirmed these findings.

  13. Carbon nanofiber-based counter electrodes for low cost dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Sebastián, D.; Baglio, V.; Girolamo, M.; Moliner, R.; Lázaro, M. J.; Aricò, A. S.

    2014-03-01

    Carbon materials represent an attractive alternative to platinum in dye-sensitized solar cells (DSSC) counter electrodes to contribute to an efficient conversion of solar energy into electricity. The use of highly graphitic carbon nanofibers (CNFs) is investigated by analyzing the effect of the filament diameter, surface area and graphitization degree on the DSSC cathode performance. To this purpose, transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy and physisorption analysis are used to characterize the main properties of the CNFs. The behavior of CNFs as counter electrodes in DSSC is investigated by polarization experiments and electrochemical impedance spectroscopy. Among the different materials, the CNF characterized by the highest surface area (183 m2 g-1), thinnest filament size (24 nm) and highest density of surface defects shows the best performance in terms of efficiency, open circuit potential and short circuit current density. Further investigation of the electrode thickness together with series and charge transfer resistance cross-analysis evidences the key role played by the surface area and surface graphitization to obtain a suitable performance. Compared to literature, so-obtained CNFs represent an interesting alternative to manufacture low cost DSSC cathodes.

  14. Direct synthesis of carbon nanofibers from South African coal fly ash

    PubMed Central

    2014-01-01

    Carbon nanofibers (CNFs), cylindrical nanostructures containing graphene, were synthesized directly from South African fly ash (a waste product formed during the combustion of coal). The CNFs (as well as other carbonaceous materials like carbon nanotubes (CNTs)) were produced by the catalytic chemical vapour deposition method (CCVD) in the presence of acetylene gas at temperatures ranging from 400°C to 700°C. The fly ash and its carbonaceous products were characterized by transmission electron microscopy (TEM), thermogravimetric analysis (TGA), laser Raman spectroscopy and Brunauer-Emmett-Teller (BET) surface area measurements. It was observed that as-received fly ash was capable of producing CNFs in high yield by CCVD, starting at a relatively low temperature of 400°C. Laser Raman spectra and TGA thermograms showed that the carbonaceous products which formed were mostly disordered. Small bundles of CNTs and CNFs observed by TEM and energy-dispersive spectroscopy (EDS) showed that the catalyst most likely responsible for CNF formation was iron in the form of cementite; X-ray diffraction (XRD) and Mössbauer spectroscopy confirmed these findings. PMID:25177215

  15. The Leidenfrost temperature increase for impacting droplets on carbon-nanofiber surfaces.

    PubMed

    Nair, Hrudya; Staat, Hendrik J J; Tran, Tuan; van Houselt, Arie; Prosperetti, Andrea; Lohse, Detlef; Sun, Chao

    2014-04-01

    Droplets impacting on a superheated surface can either exhibit a contact boiling regime, in which they make direct contact with the surface and boil violently, or a film boiling regime, in which they remain separated from the surface by their own vapor. The transition from the contact to the film boiling regime depends not only on the temperature of the surface and the kinetic energy of the droplet, but also on the size of the structures fabricated on the surface. Here we experimentally show that surfaces covered with carbon-nanofibers delay the transition to film boiling to much higher temperatures compared to smooth surfaces. We present physical arguments showing that, because of the small scale of the carbon fibers, they are cooled by the vapor flow just before the liquid impact, thus permitting contact boiling up to much higher temperatures than on smooth surfaces. We also show that as long as the impact is in the film boiling regime, the spreading factor of impacting droplets is consistent with the We(3/10) scaling (with We being the Weber number) as predicted for large We by a scaling analysis.

  16. NiCu Alloy Nanoparticle-Loaded Carbon Nanofibers for Phenolic Biosensor Applications

    PubMed Central

    Li, Dawei; Lv, Pengfei; Zhu, Jiadeng; Lu, Yao; Chen, Chen; Zhang, Xiangwu; Wei, Qufu

    2015-01-01

    NiCu alloy nanoparticle-loaded carbon nanofibers (NiCuCNFs) were fabricated by a combination of electrospinning and carbonization methods. A series of characterizations, including SEM, TEM and XRD, were employed to study the NiCuCNFs. The as-prepared NiCuCNFs were then mixed with laccase (Lac) and Nafion to form a novel biosensor. NiCuCNFs successfully achieved the direct electron transfer of Lac. Cyclic voltammetry and linear sweep voltammetry were used to study the electrochemical properties of the biosensor. The finally prepared biosensor showed favorable electrocatalytic effects toward hydroquinone. The detection limit was 90 nM (S/N = 3), the sensitivity was 1.5 µA µM−1, the detection linear range was 4 × 10−7–2.37 × 10−6 M. In addition, this biosensor exhibited satisfactory repeatability, reproducibility, anti-interference properties and stability. Besides, the sensor achieved the detection of hydroquinone in lake water. PMID:26610505

  17. Localized surface grafting reactions on carbon nanofibers induced by gamma and e-beam irradiation

    NASA Astrophysics Data System (ADS)

    Evora, M. C.; Araujo, J. R.; Ferreira, E. H. M.; Strohmeier, B. R.; Silva, L. G. A.; Achete, C. A.

    2015-04-01

    Electron beam and gamma-ray irradiation have potential application to modify the carbon fiber nanostructures in order to produce useful defects in the graphitic structure and create reactive sites. In this study, the methodology to functionalize carbon nanofiber (CNF), via a radiation process and using acrylic acid as a source of oxygen functional groups, was investigated. The samples were submitted to a direct grafting radiation process with electron beam and gamma-ray source. Several parameters were changed such as: acrylic acid concentration, radiation dose and percentage of inhibitor necessary to achieve functionalization, with higher percentage of oxygen functional groups on CNF surface, and better dispersion. The better results achieved were when mixing CNF in a solution of acrylic acid with 6% of inhibitor (FeSO4·7H2O) and irradiated at 100 kGy. The samples were characterized by X-ray photoelectron spectroscopy and the surface composition (atomic%) showed a significant increase of oxygen content for the samples after irradiation. Also, the dispersion of the functionalized CNF in water was stable during months which may be a good indication that the functionalization process of CNF via ionizing radiation was successful.

  18. Electrospun carbon nanofibers/electrocatalyst hybrids as asymmetric electrodes for vanadium redox flow battery

    NASA Astrophysics Data System (ADS)

    Wei, Guanjie; Fan, Xinzhuang; Liu, Jianguo; Yan, Chuanwei

    2015-05-01

    To improve the electrochemical activity of polyacrylonitrile (PAN)-based electrospun carbon nanofibers (ECNFs) toward vanadium redox couples, the multi-wall carbon nanotubes (CNTs) and Bi-based compound as electrocatalyst have been embedded in the ECNFs to make composite electrode, respectively. The morphology and electrochemical properties of pristine ECNFs, CNTs/ECNFs and Bi/ECNFs have been characterized. Among the three kinds of electrodes, the CNTs/ECNFs show best electrochemical activity toward VO2+/VO2+ redox couple, while the Bi/ECNFs present the best electrochemical activity toward V2+/V3+ redox couple. Furthermore, the high overpotential of hydrogen evolution on Bi/ECNFs makes the side-reaction suppressed. Because of the large property difference between the two composite electrodes, the CNTs/ECNFs and Bi/ECNFs are designed to act as positive and negative electrode for vanadium redox flow battery (VRFB), respectively. It not only does improve the kinetics of two electrode reactions at the same time, but also reduce the kinetics difference between them. Due to the application of asymmetric electrodes, performance of the cell is improved greatly.

  19. Hierarchical Graphene-Containing Carbon Nanofibers for Lithium-Ion Battery Anodes.

    PubMed

    Dufficy, Martin K; Khan, Saad A; Fedkiw, Peter S

    2016-01-20

    We present a method to produce composite anodes consisting of thermally reduced graphene oxide-containing carbon nanofibers (TRGO/CNFs) via electrospinning a dispersion of polyacrylonitrile (PAN) and graphene oxide (GO) sheets in dimethylformamide followed by heat treatment at 650 °C. A range of GO (1-20 wt % GO relative to polymer concentration) was added to the polymer solution, with each sample comprising similar polymer chain packing and subsequent CNF microstructure, as assessed by X-ray diffraction. An increase from 0 to 20 wt % GO in the fibers led to carbonized nonwovens with enhanced electronic conductivity, as TRGO sheets conductively connected the CNFs. Galvanostatic half-cell cycling revealed that TRGO addition enhanced the specific discharge capacity of the fibers. The optimal GO concentration of 5 wt % GO enhanced first-cycle discharge capacities at C/24 rates (15.6 mA g(-1)) 150% compared to CNFs, with a 400% capacity increase at 2-C rates (750 mA g(-1)). We attribute the capacity enhancement to a high degree of GO exfoliation. The TRGO/CNFs also experienced no capacity fade after 200 cycles at 2-C rates. Impedance spectroscopy of the composite anodes demonstrated that charge-transfer resistances decreased as GO content increased, implying that high GO loadings result in more electrochemically active material.

  20. Highly Flexible Freestanding Porous Carbon Nanofibers for Electrodes Materials of High-Performance All-Carbon Supercapacitors.

    PubMed

    Liu, Ying; Zhou, Jinyuan; Chen, Lulu; Zhang, Peng; Fu, Wenbin; Zhao, Hao; Ma, Yufang; Pan, Xiaojun; Zhang, Zhenxing; Han, Weihua; Xie, Erqing

    2015-10-28

    Highly flexible porous carbon nanofibers (P-CNFs) were fabricated by electrospining technique combining with metal ion-assistant acid corrosion process. The resultant fibers display high conductivity and outstanding mechanical flexibility, whereas little change in their resistance can be observed under repeatedly bending, even to 180°. Further results indicate that the improved flexibility of P-CNFs can be due to the high graphitization degree caused by Co ions. In view of electrode materials for high-performance supercapacitors, this type of porous nanostructure and high graphitization degree could synergistically facilitate the electrolyte ion diffusion and electron transportation. In the three electrodes testing system, the resultant P-CNFs electrodes can exhibit a specific capacitance of 104.5 F g(-1) (0.2 A g(-1)), high rate capability (remain 56.5% at 10 A g(-1)), and capacitance retention of ∼94% after 2000 cycles. Furthermore, the assembled symmetric supercapacitors showed a high flexibility and can deliver an energy density of 3.22 Wh kg(-1) at power density of 600 W kg(-1). This work might open a way to improve the mechanical properties of carbon fibers and suggests that this type of freestanding P-CNFs be used as effective electrode materials for flexible all-carbon supercapacitors.

  1. Aligned Single Wall Carbon Nanotube Polymer Composites Using an Electric Field

    NASA Technical Reports Server (NTRS)

    Park, Cheol; Wiklinson, John; Banda, Sumanth; Ounaies, Zoubeida; Wise, Kristopher E.; Sauti, Godfrey; Lillehei, Peter T.; Harrison, Joycelyn S.

    2005-01-01

    While high shear alignment has been shown to improve the mechanical properties of single wall carbon nanotubes (SWNT)-polymer composites, it is difficult to control and often results in degradation of the electrical and dielectric properties of the composite. Here, we report a novel method to actively align SWNTs in a polymer matrix, which allows for control over the degree of alignment of SWNTs without the side effects of shear alignment. In this process, SWNTs are aligned via field-induced dipolar interactions among the nanotubes under an AC electric field in a liquid matrix followed by immobilization by photopolymerization while maintaining the electric field. Alignment of SWNTs was controlled as a function of magnitude, frequency, and application time of the applied electric field. The degree of SWNT alignment was assessed using optical microscopy and polarized Raman spectroscopy and the morphology of the aligned nanocomposites was investigated by high resolution scanning electron microscopy. The structure of the field induced aligned SWNTs is intrinsically different from that of shear aligned SWNTs. In the present work, SWNTs are not only aligned along the field, but also migrate laterally to form thick, aligned SWNT percolative columns between the electrodes. The actively aligned SWNTs amplify the electrical and dielectric properties in addition to improving the mechanical properties of the composite. All of these properties of the aligned nanocomposites exhibited anisotropic characteristics, which were controllable by tuning the applied field conditions.

  2. Modelling clustering of vertically aligned carbon nanotube arrays

    PubMed Central

    Schaber, Clemens F.; Filippov, Alexander E.; Heinlein, Thorsten; Schneider, Jörg J.; Gorb, Stanislav N.

    2015-01-01

    Previous research demonstrated that arrays of vertically aligned carbon nanotubes (VACNTs) exhibit strong frictional properties. Experiments indicated a strong decrease of the friction coefficient from the first to the second sliding cycle in repetitive measurements on the same VACNT spot, but stable values in consecutive cycles. VACNTs form clusters under shear applied during friction tests, and self-organization stabilizes the mechanical properties of the arrays. With increasing load in the range between 300 µN and 4 mN applied normally to the array surface during friction tests the size of the clusters increases, while the coefficient of friction decreases. To better understand the experimentally obtained results, we formulated and numerically studied a minimalistic model, which reproduces the main features of the system with a minimum of adjustable parameters. We calculate the van der Waals forces between the spherical friction probe and bunches of the arrays using the well-known Morse potential function to predict the number of clusters, their size, instantaneous and mean friction forces and the behaviour of the VACNTs during consecutive sliding cycles and at different normal loads. The data obtained by the model calculations coincide very well with the experimental data and can help in adapting VACNT arrays for biomimetic applications. PMID:26464787

  3. Modelling clustering of vertically aligned carbon nanotube arrays.

    PubMed

    Schaber, Clemens F; Filippov, Alexander E; Heinlein, Thorsten; Schneider, Jörg J; Gorb, Stanislav N

    2015-08-01

    Previous research demonstrated that arrays of vertically aligned carbon nanotubes (VACNTs) exhibit strong frictional properties. Experiments indicated a strong decrease of the friction coefficient from the first to the second sliding cycle in repetitive measurements on the same VACNT spot, but stable values in consecutive cycles. VACNTs form clusters under shear applied during friction tests, and self-organization stabilizes the mechanical properties of the arrays. With increasing load in the range between 300 µN and 4 mN applied normally to the array surface during friction tests the size of the clusters increases, while the coefficient of friction decreases. To better understand the experimentally obtained results, we formulated and numerically studied a minimalistic model, which reproduces the main features of the system with a minimum of adjustable parameters. We calculate the van der Waals forces between the spherical friction probe and bunches of the arrays using the well-known Morse potential function to predict the number of clusters, their size, instantaneous and mean friction forces and the behaviour of the VACNTs during consecutive sliding cycles and at different normal loads. The data obtained by the model calculations coincide very well with the experimental data and can help in adapting VACNT arrays for biomimetic applications. PMID:26464787

  4. Visible Aligned Carbon Nanotube-MoS2 Hybrids

    NASA Astrophysics Data System (ADS)

    Wang, Rui; Hong, Tu; Wang, Tianjiao; Ali, Ahmad Iffat; Chani, Devpaul Singh; Xu, Yaqiong

    Single-walled carbon nanotubes (SWNTs) have gained great interest due to their excellent electrical, mechanical and thermal properties. Recent progress in two-dimensional (2D) materials has opened up new horizons in the realm of physics and engineering that could lead to the revolution of future electronics and optoelectronics. Various hybrid structures have been developed for different applications. Here we report a facile method to synthesize ultrathin 2D hybrids between horizontally-aligned SWNT and monolayer molybdenum sulfide (MoS2) through chemical vapor deposition (CVD). These hybrid structures can be imaged under an optical microscope; and their Raman mapping indicates that MoS2 flakes are partially grown on top of SWNTs. Moreover, strong photocurrent signals have been observed in SWNT-MoS2 hybrids through scanning photocurrent measurements. These fundamental studies may provide a new way to fabricate 2D hybrids for future electronics and optoelectronics. Department of Electrical Engineering & Computer Science, Vanderbilt University, Nashville, TN 37235, USA.

  5. In situ assembly of well-dispersed Ag nanoparticles (AgNPs) on electrospun carbon nanofibers (CNFs) for catalytic reduction of 4-nitrophenol.

    PubMed

    Zhang, Peng; Shao, Changlu; Zhang, Zhenyi; Zhang, Mingyi; Mu, Jingbo; Guo, Zengcai; Liu, Yichun

    2011-08-01

    Carbon nanofibers/silver nanoparticles (CNFs/AgNPs) composite nanofibers were fabricated by two steps consisting of the preparation of the CNFs by electrospinning and the hydrothermal growth of the AgNPs on the CNFs. The as-prepared nanofibers were characterized by scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, X-ray diffraction, resonant Raman spectra, thermal gravimetric and differential thermal analysis, and X-ray photoelectron spectroscopy, respectively. The results indicated that not only were AgNPs (25-50 nm) successfully grown on the CNFs but also the AgNPs were distributed without aggregation on the CNFs. Further more, by adjusting the parameters in hydrothermal processing, the content of silver supported on the CNFs could be easily controlled. The catalytic activities of the CNFs/AgNPs composite nanofibers to the reduction of 4-nitrophenol (4-NP) with NaBH(4) were tracked by UV-visible spectroscopy. It was suggested that the CNFs/AgNPs composite nanofibers exhibited high catalytic activity in the reduction of 4-NP, which might be attributed to the high surface areas of AgNPs and synergistic effect on delivery of electrons between CNFs and AgNPs. And, the catalytic efficiency was enhanced with the increasing of the content of silver on the CNFs/AgNPs composite nanofibers. Notably, the CNFs/AgNPs composite nanofibers could be easily recycled due to their one-dimensional nanostructural property.

  6. Extremely High Thermal Conductivity of Aligned Carbon Nanotube-Polyethylene Composites

    PubMed Central

    Liao, Quanwen; Liu, Zhichun; Liu, Wei; Deng, Chengcheng; Yang, Nuo

    2015-01-01

    The ultra-low thermal conductivity of bulk polymers may be enhanced by combining them with high thermal conductivity materials such as carbon nanotubes. Different from random doping, we find that the aligned carbon nanotube-polyethylene composites has a high thermal conductivity by non-equilibrium molecular dynamics simulations. The analyses indicate that the aligned composite not only take advantage of the high thermal conduction of carbon nanotubes, but enhance thermal conduction of polyethylene chains. PMID:26552843

  7. Surface optimization of high density polyethylene and carbon nanofiber composites for the improvement of electromagnetic shielding effectiveness

    NASA Astrophysics Data System (ADS)

    Jarvis, Brandon C.

    Nanoreinforced composites of High Density Polyethylene (HDPE) and Carbon Nanofibers (CNF) of varying nanofiber concentration were fabricated via melt mixing. Following fabrication, various metal and metal-nitride thin films were sputter deposited upon the substrates. Volume resistivity measurements of the composite substrates, as well as four point probe analysis of the composites and the deposited films were performed and are reported. Electromagnetic Interference (EMI) Shielding Effectiveness (SE) measurements were performed upon all samples in order to gauge the effects of percolation and the presence of the deposited film(s) upon overall SE. Comparisons of experimental measurements with analytical models available in the literature will be made in order to gain insight in to the dominant shielding mechanisms in the composite(s).

  8. Fabrication and characterization of polylactic acid and polylactic acid/multi-walled carbon nanotube nanofibers through centrifugal spinning

    NASA Astrophysics Data System (ADS)

    Patlan, Richard

    Biocompatible polymer nanofibers hold great potential in the biomedical engineering field. Their biodegradable nature and enhanced properties could help solve a wide array of health related problems, particularly in the areas of tissue regeneration, drug delivery, and biosensor design. The novel Forcespinning™ method allows the production of submicron fibers without many of the drawbacks found in electrospinning, while also providing a substantial increase in fiber production. The aim of the study was to utilize this method to fabricate non-woven nanofibrous mats composed of polylactic acid (PLA) and polylactic acid/multi-walled carbon nanotube composite fibers. The morphology, thermal properties, and crystalline structure of the resulting nanofibers were then characterized using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), and X-Ray Diffraction (XRD).

  9. Design and Synthesis of Bubble-Nanorod-Structured Fe2O3-Carbon Nanofibers as Advanced Anode Material for Li-Ion Batteries.

    PubMed

    Cho, Jung Sang; Hong, Young Jun; Kang, Yun Chan

    2015-04-28

    A structure denoted as a "bubble-nanorod composite" is synthesized by introducing the Kirkendall effect into the electrospinning method. Bubble-nanorod-structured Fe2O3-C composite nanofibers, which are composed of nanosized hollow Fe2O3 spheres uniformly dispersed in an amorphous carbon matrix, are synthesized as the target material. Post-treatment of the electrospun precursor nanofibers at 500 °C under 10% H2/Ar mixture gas atmosphere produces amorphous FeOx-carbon composite nanofibers. Post-treatment of the FeOx-carbon composite nanofibers at 300 °C under air atmosphere produces the bubble-nanorod-structured Fe2O3-C composite nanofibers. The solid Fe nanocrystals formed by the reduction of FeOx are converted into hollow Fe2O3 nanospheres during the further heating process by the well-known Kirkendall diffusion process. The discharge capacities of the bubble-nanorod-structured Fe2O3-C composite nanofibers and hollow bare Fe2O3 nanofibers for the 300th cycles at a current density of 1.0 A g(-1) are 812 and 285 mA h g(-1), respectively, and their capacity retentions measured from the second cycle are 84 and 24%, respectively. The hollow nanospheres accommodate the volume change that occurs during cycling. The unique structure of the bubble-nanorod-structured Fe2O3-C composite nanofibers results in their superior electrochemical properties by improving the structural stability during long-term cycling.

  10. Graphene nanoribbons hybridized carbon nanofibers: remarkably enhanced graphitization and conductivity, and excellent performance as support material for fuel cell catalysts

    NASA Astrophysics Data System (ADS)

    Wang, Chaonan; Gao, Hongrong; Li, Hong; Zhang, Yiren; Huang, Bowen; Zhao, Junhong; Zhu, Yan; Yuan, Wang Zhang; Zhang, Yongming

    2014-01-01

    High electronic conductivity of the support material and uniform distribution of the catalyst nanoparticles (NPs) are extremely desirable for electrocatalysts. In this paper, we present our recent progress on electrocatalysts for fuel cells with simultaneously improved conductivity of the supporting carbon nanofibers (CNFs) and distribution of platinum (Pt) NPs through facile incorporation of graphene nanoribbons (GNRs). Briefly, GNRs were obtained by the cutting and unzipping of multiwalled carbon nanotubes (MWCNTs) and subsequent thermal reduction and were first used as novel nanofillers in CNFs towards high performance support material for electrocatalysis. Through electrospinning and carbonization processes, GNR embedded carbon nanofibers (G-CNFs) with greatly enhanced graphitization and electronic conductivity were synthesized. Chemical deposition of Pt NPs onto G-CNFs generated a new Pt-G-CNF hybrid catalyst, with homogeneously distributed Pt NPs of ~3 nm. Compared to Pt-CNF (Pt on pristine CNFs) and Pt-M-CNF (Pt on MWCNT embedded CNFs), Pt-G-CNF hybrids exhibit significantly improved electrochemically active surface area (ECSA), better CO tolerance for electro-oxidation of methanol and higher electrochemical stability, testifying G-CNFs are promising support materials for high performance electrocatalysts for fuel cells.High electronic conductivity of the support material and uniform distribution of the catalyst nanoparticles (NPs) are extremely desirable for electrocatalysts. In this paper, we present our recent progress on electrocatalysts for fuel cells with simultaneously improved conductivity of the supporting carbon nanofibers (CNFs) and distribution of platinum (Pt) NPs through facile incorporation of graphene nanoribbons (GNRs). Briefly, GNRs were obtained by the cutting and unzipping of multiwalled carbon nanotubes (MWCNTs) and subsequent thermal reduction and were first used as novel nanofillers in CNFs towards high performance support material for

  11. Occupational Exposure Assessment in Carbon Nanotube and Nanofiber Primary and Secondary Manufacturers

    PubMed Central

    DAHM, MATTHEW M.; EVANS, DOUGLAS E.; SCHUBAUER-BERIGAN, MARY K.; BIRCH, M. EILEEN; FERNBACK, JOSEPH E.

    2015-01-01

    Research Significance Toxicological evidence suggests the potential for a wide range of health effects, which could result from exposure to carbon nanotubes (CNTs) and carbon nanofibers (CNFs). The National Institute for Occupational Safety and Health (NIOSH) has proposed a recommended exposure limit (REL) for CNTs/CNFs at the respirable size fraction. The current literature is lacking exposure information, with few studies reporting results for personal breathing zone (PBZ) samples in occupational settings. To address this gap, exposure assessments were conducted at six representative sites identified as CNT/CNF primary or secondary manufacturers. Methods Personal and area filter-based samples were collected for both the inhalable mass concentration and the respirable mass concentration of elemental carbon (EC) as well as CNT structure count analysis by transmission electron microscopy to assess exposures. When possible, full-shift PBZ samples were collected; area samples were collected on a task-based approach. Results The vast majority of samples collected in this study were below the proposed REL (7 μg m−3). Two of the three secondary manufacturers’ surveyed found concentrations above the proposed REL. None of the samples collected at primary manufacturers were found to be above the REL. Visual and microscopy-based evidence of CNTs/CNFs were found at all sites, with the highest CNT/CNF structure counts being found in samples collected at secondary manufacturing sites. The statistical correlations between the filter-based samples for the mass concentration of EC and CNT structure counts were examined. A general trend was found with a P-value of 0.01 and a corresponding Pearson correlation coefficient of 0.44. Conclusions CNT/CNF concentrations were above the proposed NIOSH REL for PBZ samples in two secondary manufacturing facilities that use these materials for commercial applications. These samples were collected during dry powder handling processes, such

  12. Preparation of novel carbon microfiber/carbon nanofiber-dispersed polyvinyl alcohol-based nanocomposite material for lithium-ion electrolyte battery separator.

    PubMed

    Sharma, Ajit K; Khare, Prateek; Singh, Jayant K; Verma, Nishith

    2013-04-01

    A novel nanocomposite polyvinyl alcohol precursor-based material dispersed with the web of carbon microfibers and carbon nanofibers is developed as lithium (Li)-ion electrolyte battery separator. The primary synthesis steps of the separator material consist of esterification of polyvinyl acetate to produce polyvinyl alcohol gel, ball-milling of the surfactant dispersed carbon micro-nanofibers, mixing of the milled micron size (~500 nm) fibers to the reactant mixture at the incipience of the polyvinyl alcohol gel formation, and the mixing of hydrophobic reagents along with polyethylene glycol as a plasticizer, to produce a thin film of ~25 μm. The produced film, uniformly dispersed with carbon micro-nanofibers, has dramatically improved performance as a battery separator, with the ion conductivity of the electrolytes (LiPF6) saturated film measured as 0.119 S-cm(-1), approximately two orders of magnitude higher than that of polyvinyl alcohol. The other primary characteristics of the produced film, such as tensile strength, contact angle, and thermal stability, are also found to be superior to the materials made of other precursors, including polypropylene and polyethylene, discussed in the literature. The method of producing the films in this study is novel, simple, environmentally benign, and economically viable.

  13. Synthesis and Application of Si/Carbon Nanofiber Composites Based on Ni and Mo Catalysts for Anode Material of Lithium Secondary Batteries.

    PubMed

    Jang, Eunyi; Park, Heal-Ku; Lee, Chang-Seop

    2016-05-01

    In this paper, carbon nanofibers (CNFs) and Si/carbon nanofiber composites were synthesized for use as the anode material of lithium secondary batteries. Catalysts were prepared based on Ni and Mo metals and CNFs were grown through chemical vapor deposition (CVD). In addition, the grown CNFs were mixed with silicon particles to synthesize Si/carbon nanofibers composites. The physiochemical characteristics of the synthesized CNFs and Si/carbon nanofiber composites were analyzed by SEM, EDS, XRD, Raman, BET and XPS. The electrochemical characteristics were investigated by using cyclic voltammetry and galvanostatic charge-discharge. Using CNFs and Si/carbon nanofiber composites as the anode material, three electrode cells were assembled and the electrochemical characteristics were measured using LiPF6 and LiClO4 as electrolytes. As a result of the galvanostatic charge-discharge of CNFs that were grown through catalysts with Ni and Mo concentration ratio of 6:4, the initial discharge capacity when using LiPF6 as the electrolyte was 570 mAh/g and the retention rate was 15.05%. In the case of using LiClO4 as the electrolyte, the initial discharge capacity was 263 mAh/g and the retention rate was 67.23%. PMID:27483824

  14. Adsorption of ciprofloxacin, bisphenol and 2-chlorophenol on electrospun carbon nanofibers: in comparison with powder activated carbon.

    PubMed

    Li, Xiaona; Chen, Shuo; Fan, Xinfei; Quan, Xie; Tan, Feng; Zhang, Yaobin; Gao, Jinsuo

    2015-06-01

    Carbon nanofibers (CNFs) were prepared by electrospun polyacrylonitrile (PAN) polymer solutions followed by thermal treatment. For the first time, the influence of stabilization procedure on the structure properties of CNFs was explored to improve the adsorption capacity of CNFs towards the environmental pollutants from aqueous solution. The adsorption of three organic chemicals including ciprofloxacin (CIP), bisphenol (BPA) and 2-chlorophenol (2-CP) on electrospun CNFs with high surface area of 2326m(2)/g and micro/mesoporous structure characteristics were investigated. The adsorption affinities were compared with that of the commercial powder activated carbon (PAC). The adsorption kinetics and isotherms showed that the maximum adsorption capacities (qm) of CNFs towards the three pollutants are sequenced in the order of CIP>BPA>2-CP, which are 2.6-fold (CIP), 1.6-fold (BPA) and 1.1-fold (2-CP) increase respectively in comparison with that of PAC adsorption. It was assumed that the micro/mesoporous structure of CNFs, molecular size of the pollutants and the π electron interaction play important roles on the high adsorption capacity exhibited by CNFs. In addition, electrostatic interaction and hydrophobic interaction also contribute to the adsorption of CNFs. This study demonstrates that the electrospun CNFs are promising adsorbents for the removal of pollutants from aqueous solutions.

  15. Highly sensitive and selective determination of methylergometrine maleate using carbon nanofibers/silver nanoparticles composite modified carbon paste electrode.

    PubMed

    Kalambate, Pramod K; Rawool, Chaitali R; Karna, Shashi P; Srivastava, Ashwini K

    2016-12-01

    A highly sensitive and selective voltammetric method for determination of Methylergometrine maleate (MM) in pharmaceutical formulations, urine and blood serum samples has been developed based on enhanced electrochemical response of MM at carbon nanofibers and silver nanoparticles modified carbon paste electrode (CNF-AgNP-CPE). The electrode material was characterized by various techniques viz., X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. The electrocatalytic response of MM at CNF-AgNP-CPE was studied by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). Under optimized conditions, the proposed sensor exhibits excellent electrochemical response towards MM. The DPV study shows greatly enhanced electrochemical signal for MM at CNF-AgNP-CPE lending high sensitivity to the proposed sensor for MM detection. The peak (Ip) current for MM is found to be rectilinear in the range 4.0×10(-8)-2.0×10(-5)M with a detection limit of 7.1×10(-9)M using DPV. The feasibility of the proposed sensor in analytical applications was investigated by conducting experiments on commercial pharmaceutical formulations, human urine and blood serum samples, which yielded satisfactory recoveries of MM. The proposed electrochemical sensor offers high sensitivity, selectivity, reproducibility and practical utility. We recommend it as an authentic and productive electrochemical sensor for successful determination of MM. PMID:27612735

  16. Highly sensitive and selective determination of methylergometrine maleate using carbon nanofibers/silver nanoparticles composite modified carbon paste electrode.

    PubMed

    Kalambate, Pramod K; Rawool, Chaitali R; Karna, Shashi P; Srivastava, Ashwini K

    2016-12-01

    A highly sensitive and selective voltammetric method for determination of Methylergometrine maleate (MM) in pharmaceutical formulations, urine and blood serum samples has been developed based on enhanced electrochemical response of MM at carbon nanofibers and silver nanoparticles modified carbon paste electrode (CNF-AgNP-CPE). The electrode material was characterized by various techniques viz., X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. The electrocatalytic response of MM at CNF-AgNP-CPE was studied by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). Under optimized conditions, the proposed sensor exhibits excellent electrochemical response towards MM. The DPV study shows greatly enhanced electrochemical signal for MM at CNF-AgNP-CPE lending high sensitivity to the proposed sensor for MM detection. The peak (Ip) current for MM is found to be rectilinear in the range 4.0×10(-8)-2.0×10(-5)M with a detection limit of 7.1×10(-9)M using DPV. The feasibility of the proposed sensor in analytical applications was investigated by conducting experiments on commercial pharmaceutical formulations, human urine and blood serum samples, which yielded satisfactory recoveries of MM. The proposed electrochemical sensor offers high sensitivity, selectivity, reproducibility and practical utility. We recommend it as an authentic and productive electrochemical sensor for successful determination of MM.

  17. Novel injectable biomimetic hydrogels with carbon nanofibers and self assembled rosette nanotubes for myocardial applications.

    PubMed

    Meng, Xiangling; Stout, David A; Sun, Linlin; Beingessner, Rachel L; Fenniri, Hicham; Webster, Thomas J

    2013-04-01

    The objective of the present in vitro study was to investigate cardiomyocyte functions, specifically their adhesion and proliferation, on injectable scaffolds containing RNT (rosette nanotubes) and CNF (carbon nanofibers) in a pHEMA (poly(2-hydroxyethyl methacrylate)) hydrogel to determine their potential for myocardial tissue engineering applications. RNTs are novel biocompatible nanomaterials assembled from synthetic analogs of DNA bases guanine and cytosine that self-assemble within minutes when placed in aqueous solutions at body temperatures. These materials could potentially improve cardiomyocyte functions and solidification time of pHEMA and CNF composites. Because heart tissue is conductive, CNFs were added to pHEMA to increase the composite's conductivity. Our results showed that cardiomyocyte density increased after 4 h, 1 day, and 3 days with greater amounts of CNFs and greater amounts of RNTs in pHEMA (up to 10 mg mL(-1) CNFs and 0.05 mg mL(-1) RNTs). Factors that may have increased cardiomyocyte functions include greater wettability, conductivity, and an increase in surface nanoroughness with greater amounts of CNFs and RNTs. In effect, contact angles measured on the surface of the composites decreased while the conductivity and surface roughness increased as CNFs and RNTs content increased. Lastly, the ultimate tensile modulus decreased for composites with greater amounts of CNFs. In summary, the properties of these injectable composites make them promising candidates for myocardial tissue engineering applications and should be further studied. PMID:23008178

  18. Multi-scale Performance and Durability of Carbon Nanofiber/Cement Composites

    NASA Astrophysics Data System (ADS)

    Sanchez, F.; Zhang, L.; Ince, C.

    This paper reports on recent work that is directed at understanding the fundamental controlling mechanisms of multi-scale, environmental weathering of nano-structured cement-based materials through an integrated experimental and computational program. The effect of surface treatment and admixture addition on the incorporation of carbon nanofibers (CNFs) in cement composites was studied. Silica fume and surface treatment with nitric acid facilitated CNF dispersion. The CNFs were found as individual fibers anchored in the hydration products throughout the cement pastes and as entangled networks in cavities. The presence of the CNFs did not modify the compressive or tensile strength of the composite but did provide it with a fair level of mechanical integrity post testing. Preliminary results on durability indicated a residual effect of the CNFs after decalcification of the composites as manifested by a slow load dissipation after peak load under compression. Molecular dynamics modeling of the reinforcing structure-cement phase interface demonstrated that manipulation of the interface characteristics may provide a method to control the composite properties.

  19. A three-dimensionally chitin nanofiber/carbon nanotube hydrogel network for foldable conductive paper.

    PubMed

    Chen, Chuchu; Yang, Chuang; Li, Suiyi; Li, Dagang

    2015-12-10

    We reported a highly conductive nanocomposite made with multiwalled carbon nanotubes (MWCNTs) and chitin nanofibers (ChNFs). The MWCNTs were dispersed into ChNFs by the simple process of vacuum-filtration, forming a three-dimensional network structure. In this approach, MWCNT acted as a filler to introduce electron channel paths throughout the ChNF skeleton. And then, a hybrid hydrogel system (20 wt.% NaOH, -18 °C) was applied to prepare the ChNF/MWCNT gel-film followed with drying process. It is found that the resultant ChNF/MWCNT gel-film exposed much more MWCNT areas forming denser structure due to the shrinking of ChNFs after the gelation treatment. Compared with ChNF/MWCNT film, the one treated under hydrogel system (ChNF/MWCNT gel-film) exhibited almost twice higher conductivity (9.3S/cm for 50 wt.% MWCNTs in gel-film; whereas 4.7S/cm for 50 wt.% MWCNTs in film). Moreover, the facile and low-cost of this conductive paper may have great potential in development of foldable electronic devices.

  20. Hierarchically mesoporous CuO/carbon nanofiber coaxial shell-core nanowires for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Park, Seok-Hwan; Lee, Wan-Jin

    2015-05-01

    Hierarchically mesoporous CuO/carbon nanofiber coaxial shell-core nanowires (CuO/CNF) as anodes for lithium ion batteries were prepared by coating the Cu2(NO3)(OH)3 on the surface of conductive and elastic CNF via electrophoretic deposition (EPD), followed by thermal treatment in air. The CuO shell stacked with nanoparticles grows radially toward the CNF core, which forms hierarchically mesoporous three-dimensional (3D) coaxial shell-core structure with abundant inner spaces in nanoparticle-stacked CuO shell. The CuO shells with abundant inner spaces on the surface of CNF and high conductivity of 1D CNF increase mainly electrochemical rate capability. The CNF core with elasticity plays an important role in strongly suppressing radial volume expansion by inelastic CuO shell by offering the buffering effect. The CuO/CNF nanowires deliver an initial capacity of 1150 mAh g-1 at 100 mA g-1 and maintain a high reversible capacity of 772 mAh g-1 without showing obvious decay after 50 cycles.

  1. Multiwalled Carbon Nanotube/nanofiber Arrays as Conductive and Dry Adhesive Interface Materials

    NASA Technical Reports Server (NTRS)

    Tong, Tao; Zhao, Yang; Delzeit, Lance; Majumdar, Arun; Kashani, Ali

    2004-01-01

    We demonstrate the possibility of making conductive and dry adhesive interfaces between multiwalled carbon nanotube (MWNT) and nanofiber (MWNF) arrays grown by chemical vapor deposition with transition-metal as catalyst on highly Boron doped silicon substrates. The maximum observed adhesion force between MWNT and MWNF surfaces is 3.5 mN for an apparent contact area of 2 mm by 4 mm. The minimum contact resistance measured at the same time is approx.20 Omega. Contact resistances of MWNT-MWNT and MWNT-gold interfaces were also measured as pressure forces around several mN were applied at the interface. The resulting minimum contact resistances are on the same order but with considerable variation from sample to sample. For MWNT-MWNT contacts, a minimum contact resistance of approx.1 Omega is observed for a contact area of 2 mm by 1 mm. The relatively high contact resistances, considering the area density of the nanotubes, might be explained by the high cross-tube resistances at the contact interfaces.

  2. Polyaniline/carbon nanofiber and organic charge transfer complex based composite electrode for electroanalytical urea detection

    NASA Astrophysics Data System (ADS)

    Das, Gautam; Yoon, Hyon Hee

    2015-06-01

    A composite electrode based on polyaniline coated modified carbon nanofiber (PANI-mCNF), tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) and urease (Ur) enzyme was evaluated as biosensor for urea detection. Homogeneous coating of PANI on the surface of mCNF was achieved by oxidative polymerization of anilium ion. Fourier transform infrared (FTIR) spectroscopy and field-emission scanning electron microscopy (FESEM) were used to analyze the structural and morphological characteristics of PANI-mCNF nanocomposite. The biosensor showed excellent electroactivity in neutral and basic medium. A linear response to urea in the concentration range of 0.5-8.4 mM with a correlation coefficient of 0.998, good sensitivity (2.84 µA cm-2 mM-1) and a fast response time (ca. 4 s) was obtained for the biosensor. The minimum detection limit was found to be 3 µM. The biosensor was stable and showed minimal loss in sensitivity, even after two months of storage. The amalgamation of the PANI and CNF synergistically enhances the performance of the biosensor for electroanalytical detection of urea.

  3. Physicochemical and electrochemical properties of carbon nanotube/graphite nanofiber hybrid nanocomposites for supercapacitor

    NASA Astrophysics Data System (ADS)

    Ramli, Nurul Infaza Talalah; Abdul Rashid, Suraya; Sulaiman, Yusran; Mamat, Md Shuhazlly; Mohd Zobir, Syazwan Afif; Krishnan, Shutesh

    2016-10-01

    This work reports the combination of graphitic nanofibers (GNF) and carbon nanotubes (CNT) as the electrode material for supercapacitors. The hybrid CNT/GNF was prepared via a synthesis route that involved simple sonication and stirring. The loading of CNT was varied from 5 to 40% weight percentages. A specific capacitance of 174 Fg-1 has been obtained for 20 wt% CNT loading at 50 mV F g-1th 1 M H2SO4 aqueous solution as the electrolyte. The addition of 20 wt% CNT raised the specific capacitance by 87% more than the GNF electrodes. Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscope (TEM) reveals the random entanglement of CNT and GNF that create diffusion paths for ion transportation. Conformational changes were monitored by Raman spectroscopy, where two dominant peaks (D and G) showed strong intensities and sharp profiles. X-ray Diffraction spectroscopy (XRD) confirmed the purity of CNT/GNF hybrid nanocomposites. 20 wt% of CNT addition also shows an outstanding thermal stability. The marked improvement of the hybrid performance was attributed to the high conductivity of the two constituent materials, coupled with sufficient accessible active sites for electrochemical reactions that resulted in a synergistic behavior of the materials.

  4. A three-dimensionally chitin nanofiber/carbon nanotube hydrogel network for foldable conductive paper.

    PubMed

    Chen, Chuchu; Yang, Chuang; Li, Suiyi; Li, Dagang

    2015-12-10

    We reported a highly conductive nanocomposite made with multiwalled carbon nanotubes (MWCNTs) and chitin nanofibers (ChNFs). The MWCNTs were dispersed into ChNFs by the simple process of vacuum-filtration, forming a three-dimensional network structure. In this approach, MWCNT acted as a filler to introduce electron channel paths throughout the ChNF skeleton. And then, a hybrid hydrogel system (20 wt.% NaOH, -18 °C) was applied to prepare the ChNF/MWCNT gel-film followed with drying process. It is found that the resultant ChNF/MWCNT gel-film exposed much more MWCNT areas forming denser structure due to the shrinking of ChNFs after the gelation treatment. Compared with ChNF/MWCNT film, the one treated under hydrogel system (ChNF/MWCNT gel-film) exhibited almost twice higher conductivity (9.3S/cm for 50 wt.% MWCNTs in gel-film; whereas 4.7S/cm for 50 wt.% MWCNTs in film). Moreover, the facile and low-cost of this conductive paper may have great potential in development of foldable electronic devices. PMID:26428129

  5. Free-standing porous carbon nanofiber/ultrathin graphite hybrid for flexible solid-state supercapacitors.

    PubMed

    Qin, Kaiqiang; Kang, Jianli; Li, Jiajun; Shi, Chunsheng; Li, Yuxiang; Qiao, Zhijun; Zhao, Naiqin

    2015-01-27

    A micrometer-thin solid-state supercapacitor (SC) was assembled using two pieces of porous carbon nanofibers/ultrathin graphite (pCNFs/G) hybrid films, which were one-step synthesized by chemical vapor deposition using copper foil supported Co catalyst. The continuously ultrathin graphite sheet (∼ 25 nm) is mechanically compliant to support the pCNFs even after etching the copper foil and thus can work as both current collector and support directly with nearly ignorable fraction in a SC stack. The pCNFs are seamlessly grown on the graphite sheet with an ohmic contact between the pCNFs and the graphite sheet. Thus, the accumulated electrons/ions can duly transport from the pCNFs to graphite (current collector), which results in a high rate performance. The maximum energy density and power density based on the whole device are up to 2.4 mWh cm(-3) and 23 W cm(-3), which are even orders higher than those of the most reported electric double-layer capacitors and pseudocapacitors. Moreover, the specific capacitance of the device has 96% retention after 5000 cycles and is nearly constant at various curvatures, suggesting its wide application potential in powering wearable/miniaturized electronics. PMID:25567451

  6. Free-standing porous carbon nanofiber/ultrathin graphite hybrid for flexible solid-state supercapacitors.

    PubMed

    Qin, Kaiqiang; Kang, Jianli; Li, Jiajun; Shi, Chunsheng; Li, Yuxiang; Qiao, Zhijun; Zhao, Naiqin

    2015-01-27

    A micrometer-thin solid-state supercapacitor (SC) was assembled using two pieces of porous carbon nanofibers/ultrathin graphite (pCNFs/G) hybrid films, which were one-step synthesized by chemical vapor deposition using copper foil supported Co catalyst. The continuously ultrathin graphite sheet (∼ 25 nm) is mechanically compliant to support the pCNFs even after etching the copper foil and thus can work as both current collector and support directly with nearly ignorable fraction in a SC stack. The pCNFs are seamlessly grown on the graphite sheet with an ohmic contact between the pCNFs and the graphite sheet. Thus, the accumulated electrons/ions can duly transport from the pCNFs to graphite (current collector), which results in a high rate performance. The maximum energy density and power density based on the whole device are up to 2.4 mWh cm(-3) and 23 W cm(-3), which are even orders higher than those of the most reported electric double-layer capacitors and pseudocapacitors. Moreover, the specific capacitance of the device has 96% retention after 5000 cycles and is nearly constant at various curvatures, suggesting its wide application potential in powering wearable/miniaturized electronics.

  7. Hierarchically mesoporous CuO/carbon nanofiber coaxial shell-core nanowires for lithium ion batteries

    PubMed Central

    Park, Seok-Hwan; Lee, Wan-Jin

    2015-01-01

    Hierarchically mesoporous CuO/carbon nanofiber coaxial shell-core nanowires (CuO/CNF) as anodes for lithium ion batteries were prepared by coating the Cu2(NO3)(OH)3 on the surface of conductive and elastic CNF via electrophoretic deposition (EPD), followed by thermal treatment in air. The CuO shell stacked with nanoparticles grows radially toward the CNF core, which forms hierarchically mesoporous three-dimensional (3D) coaxial shell-core structure with abundant inner spaces in nanoparticle-stacked CuO shell. The CuO shells with abundant inner spaces on the surface of CNF and high conductivity of 1D CNF increase mainly electrochemical rate capability. The CNF core with elasticity plays an important role in strongly suppressing radial volume expansion by inelastic CuO shell by offering the buffering effect. The CuO/CNF nanowires deliver an initial capacity of 1150 mAh g−1 at 100 mA g−1 and maintain a high reversible capacity of 772 mAh g−1 without showing obvious decay after 50 cycles. PMID:25944615

  8. Carbon nanofiber-based composites for the construction of mediator-free biosensors.

    PubMed

    Lu, Xianbo; Zhou, Jianhua; Lu, Wu; Liu, Qing; Li, Jinghong

    2008-03-14

    Carbon nanofibers (CNFs), with typical diameters of approximately 80 nm and lengths of the order of micrometers, are extremely attractive in bioanalytical area as they can combine properties of high surface area, non-toxicity, acceptable biocompatibility, ease of fabrication, chemical and electrochemical stability, good electrical conductivity. In this work, CNF-based composites were successfully used as an immobilization matrix for the construction of a reagentless mediator-free hemoglobin-based H2O2 biosensor. The results revealed that hemoglobin retained its essential secondary structure in the CNF-based composite film. With the advantages of organic-inorganic hybrid materials, dramatically facilitated direct electron transfer of hemoglobin and good bioelectrocatalytic activity towards H2O2 were demonstrated. The biosensor displayed good performance along with good long-term stability. The CNF-based composites were proved to be a promising biosensing platform for the construction of mediator-free biosensors, and may find wide potential applications in biosensors, biocatalysis, bioelectronics and biofuel cell.

  9. Covalent immobilization of redox enzyme on electrospun nonwoven poly(acrylonitrile-co-acrylic acid) nanofiber mesh filled with carbon nanotubes: a comprehensive study.

    PubMed

    Wang, Zhen-Gang; Ke, Bei-Bei; Xu, Zhi-Kang

    2007-07-01

    In this work, novel conductive composite nanofiber mesh possessing reactive groups was electrospun from solutions containing poly(acrylonitrile-co-acrylic acid) (PANCAA) and multi-walled carbon nanotubes (MWCNTs) for redoxase immobilization, assuming that the incorporated MWCNTs could behave as electrons transferor during enzyme catalysis. The covalent immobilization of catalase from bovine liver on the neat PANCAA nanofiber mesh or the composite one was processed in the presence of EDC/NHS. Results indicated that both the amount and activity retention of bound catalase on the composite nanofiber mesh were higher than those on the neat PANCAA nanofiber mesh, and the activity increased up to 42%. Kinetic parameters, K(m) and V(max), for the catalases immobilized on the composite nanofiber mesh were lower and higher than those on the neat one, respectively. This enhanced activity might be ascribed to either promoted electron transfer through charge-transfer complexes and the pi system of carbon nanotubes or rendered biocompatibility by modified MWCNTs. Furthermore, the immobilized catalases revealed much more stability after MWCNTs were incorporated into the polymer nanofiber mesh. However, there was no significant difference in optimum pH value and temperature, thermal stability and operational stability between these two immobilized preparations, while the two ones appeared more advantageous than the free in these properties. The effect of MWCNTs incorporation on another redox enzyme, peroxidase, was also studied and it was found that the activity increased by 68% in comparison of composite one with neat preparation. PMID:17171660

  10. Electrospun Nanofibers for Regenerative Medicine**

    PubMed Central

    Liu, Wenying; Thomopoulos, Stavros

    2013-01-01

    This article reviews recent progress in applying electrospun nanofibers to the emerging field of regenerative medicine. We begin with a brief introduction to electrospinning and nanofibers, with a focus on issues related to the selection of materials, incorporation of bioactive molecules, degradation characteristics, control of mechanical properties, and facilitation of cell infiltration. We then discuss a number of approaches to fabrication of scaffolds from electrospun nanofibers, including techniques for controlling the alignment of nanofibers and for producing scaffolds with complex architectures. We also highlight applications of the nanofiber-based scaffolds in four areas of regenerative medicine that involve nerves, dural tissues, tendons, and the tendon-to-bone insertion site. We conclude this review with perspectives on challenges and future directions for design, fabrication, and utilization of scaffolds based on electrospun nanofibers. PMID:23184683

  11. Growth of long and aligned multi-walled carbon nanotubes on carbon and metal substrates

    NASA Astrophysics Data System (ADS)

    Delmas, M.; Pinault, M.; Patel, S.; Porterat, D.; Reynaud, C.; Mayne-L'Hermite, M.

    2012-03-01

    Well aligned, long and dense multi-walled carbon nanotubes (CNT) can be grown on both carbon fibres and any metal substrates compatible with the CNT synthesis temperature. The injection-CVD process developed involves two stages, including fibre pretreatment by depositing a SiO2-based sub-layer from an organometallic precursor followed by CNT growth from toluene/ferrocene precursor mixture. Carbon substrates, as well as metals, can easily be treated with this process, which takes place in the same reactor and does not need any handling in between the two stages. The aligned CNT carpets obtained are similar to the ones grown on reference quartz substrates. The CNT growth rate is fairly high (ca. 30 μm min-1) and it is possible to control CNT length by varying the CNT synthesis duration. The thickness of the SiO2-based sub-layer can be varied and is shown to have an influence on the CNT growth. This layer is assumed to play a diffusion barrier layer role between the substrate and the iron based catalyst nanoparticles producing CNT. The CNT anchorage to the carbon fibres has been checked and good overall adhesion proved, which is in favour of a good transfer of electrical charge and heat between the nanotubes and fibre.

  12. Superemission in vertically-aligned single-wall carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Khmelinskii, Igor; Makarov, Vladimir

    2016-09-01

    Presently we used two samples of vertically aligned single-wall carbon nanotubes (VA SWCNTs) with parallelepiped geometry, sized 0.02 cm × 0.2 cm × 1.0 cm and 0.2 cm × 0.2 cm × 1.0 cm. We report absorption and emission properties of the VA SWCNTs, including strong anisotropy in both their absorption and emission spectra. We found that the emission spectra extend from the middle-IR range to the near-IR range, with such extended spectra being reported for the first time. Pumping the VA SWCNTs in the direction normal to their axis, superemission (SE) was observed in the direction along their axis. The SE band maximum is located at 7206 ± 0.4 cm-1. The energy and the power density of the superemission were estimated, along with the diffraction-limited divergence. At the pumping energy of 3 mJ/pulse, the SE energy measured by the detector was 0.74 mJ/pulse, corresponding to the total SE energy of 1.48 mJ/pulse, with the energy density of 18.5 mJ cm-2/pulse and the SE power density of 1.2 × 105 W cm-2/pulse. We report that a bundle of VA SWCNTs is an emitter with a relatively small divergence, not exceeding 3.9 × 10-3 rad. We developed a theoretical approach to explain such absorption and emission spectra. The developed theory is based on the earlier proposed SSH theory, which we extended to include the exchange interactions between the closest SWCNT neighbors. The developed theoretical ideas were implemented in a homemade FORTRAN code. This code was successfully used to calculate and reproduce the experimental spectra and to determine the SWCNT species that originate the respective absorption bands, with acceptable agreement between theory and experiment.

  13. Alignment of muscle precursor cells on the vertical edges of thick carbon nanotube films.

    PubMed

    Holt, Ian; Gestmann, Ingo; Wright, Andrew C

    2013-10-01

    The development of scaffolds and templates is an essential aspect of tissue engineering. We show that thick (>0.5 mm) vertically aligned carbon nanotube films, made by chemical vapour deposition, can be used as biocompatible substrates for the directional alignment of mouse muscle cells where the cells grow on the exposed sides of the films. Ultra high resolution scanning electron microscopy reveals that the films themselves consist mostly of small diameter (10 nm) multi-wall carbon nanotubes of wavy morphology with some single wall carbon nanotubes. Our findings show that for this alignment to occur the nanotubes must be in pristine condition. Mechanical wiping of the films to create directional alignment is detrimental to directional bioactivity. Larger areas for study have been formed from a composite of multiply stacked narrow strips of nanotubes wipe-transferred onto elastomer supports. These composite substrates appear to show a useful degree of alignment of the cells.

  14. Structure and Characterization of Vertically Aligned Single-Walled Carbon Nanotube Bundles

    DOE PAGES

    Márquez, Francisco; López, Vicente; Morant, Carmen; Roque-Malherbe, Rolando; Domingo, Concepción; Elizalde, Eduardo; Zamora, Félix

    2010-01-01

    Arrmore » ays of vertically aligned single-walled carbon nanotube bundles, SWCNTs, have been synthesized by simple alcohol catalytic chemical vapor deposition process, carried out at 800°C. The formed SWCNTs are organized in small groups perpendicularly aligned and attached to the substrate. These small bundles show a constant diameter of ca. 30 nm and are formed by the adhesion of no more than twenty individual SWCNTs perfectly aligned along their length.« less

  15. Cellulose nanofiber/single-walled carbon nanotube hybrid non-woven macrofiber mats as novel wearable supercapacitors with excellent stability, tailorability and reliability

    NASA Astrophysics Data System (ADS)

    Niu, Qingyuan; Gao, Kezheng; Shao, Ziqiang

    2014-03-01

    Non-woven macrofiber mats are prepared by simply controlling the extrusion patterns of cellulose nanofiber/single-walled carbon nanotube suspensions in an ethanol coagulation bath, and drying in air under restricted conditions. These novel wearable supercapacitors based on non-woven macrofiber mats are demonstrated to have excellent tailorability, electrochemical stability, and damage reliability.Non-woven macrofiber mats are prepared by simply controlling the extrusion patterns of cellulose nanofiber/single-walled carbon nanotube suspensions in an ethanol coagulation bath, and drying in air under restricted conditions. These novel wearable supercapacitors based on non-woven macrofiber mats are demonstrated to have excellent tailorability, electrochemical stability, and damage reliability. Electronic supplementary information (ESI) available: Experimental, TEM image, IR spectra, and XRD spectra of cellulose nanofibers, photograph of the cellulose nanofiber/single-walled carbon nanotube suspension, cellulose nanofiber/single-walled carbon nanotube non-woven macrofiber mat and non-woven macrofiber mat wearable supercapacitors. The electrochemical performance of the CNF/SWCNT hybrid fiber wearable supercapacitor. Photograph of the non-woven macrofiber mat wearable supercapacitors integrated within textiles. See DOI: 10.1039/c3nr05929d

  16. Nickel incorporated carbon nanotube/nanofiber composites as counter electrodes for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Joshi, Prakash; Zhou, Zhengping; Poudel, Prashant; Thapa, Amit; Wu, Xiang-Fa; Qiao, Qiquan

    2012-08-01

    A nickel incorporated carbon nanotube/nanofiber composite (Ni-CNT-CNF) was used as a low cost alternative to Pt as counter electrode (CE) for dye-sensitized solar cells (DSCs). Measurements based on energy dispersive X-rays spectroscopy (EDX) showed that the majority of the composite CE was carbon at 88.49 wt%, while the amount of Ni nanoparticles was about 11.51 wt%. Measurements based on electrochemical impedance spectroscopy (EIS) showed that the charge transfer resistance (Rct) of the Ni-CNT-CNF composite electrode was 0.71 Ω cm2, much lower than that of the Pt electrode (1.81 Ω cm2). Such a low value of Rct indicated that the Ni-CNT-CNF composite carried a higher catalytic activity than the traditional Pt CE. By mixing with CNTs and Ni nanoparticles, series resistance (Rs) of the Ni-CNT-CNF electrode was measured as 5.96 Ω cm2, which was close to the Rs of 5.77 Ω cm2 of the Pt electrode, despite the significant difference in their thicknesses: ~22 μm for Ni-CNT-CNF composite, while ~40 nm for Pt film. This indicated that use of a thick layer (tens of microns) of Ni-CNT-CNF counter electrode does not add a significant amount of resistance to the total series resistance (Rs-tot) in DSCs. The DSCs based on the Ni-CNT-CNF composite CEs yielded an efficiency of 7.96% with a short circuit current density (Jsc) of 15.83 mA cm-2, open circuit voltage (Voc) of 0.80 V, and fill factor (FF) of 0.63, which was comparable to the device based on Pt, that exhibited an efficiency of 8.32% with Jsc of 15.01 mA cm-2, Voc of 0.83, and FF of 0.67.

  17. Optimized electrospinning synthesis of iron-nitrogen-carbon nanofibers for high electrocatalysis of oxygen reduction in alkaline medium.

    PubMed

    Yan, Xingxu; Liu, Kexi; Wang, Xiangqing; Wang, Tuo; Luo, Jun; Zhu, Jing

    2015-04-24

    To achieve iron-nitrogen-carbon (Fe-N-C) nanofibers with excellent electrocatalysis for replacing high-cost Pt-based catalysts in the cathodes of fuel cells and metal-air batteries, we have investigated and evaluated the effects of polyacrylonitrile (PAN) concentration and the proportion of iron to PAN, along with voltage and flow rate during the electrospinning process, and thus proposed three criteria to optimize these parameters for ideal nanofiber catalysts. The best half-wave potential of an optimized catalysts is 0.82 V versus reversible hydrogen electrode in an alkaline medium, which reaches the best range of the non-precious-metal catalysts reported and is very close to that of commercial Pt/C catalysts. Furthermore, the electron-transfer number of our catalysts is superior to that of the Pt/C, indicating the catalysts undergo a four-electron process. The durability of the optimized Fe-N-C nanofibers is also better than that of the Pt/C, which is attributed to the homogeneous distribution of the active sites in our catalysts. PMID:25815586

  18. Optimized electrospinning synthesis of iron-nitrogen-carbon nanofibers for high electrocatalysis of oxygen reduction in alkaline medium

    NASA Astrophysics Data System (ADS)

    Yan, Xingxu; Liu, Kexi; Wang, Xiangqing; Wang, Tuo; Luo, Jun; Zhu, Jing

    2015-04-01

    To achieve iron-nitrogen-carbon (Fe-N-C) nanofibers with excellent electrocatalysis for replacing high-cost Pt-based catalysts in the cathodes of fuel cells and metal-air batteries, we have investigated and evaluated the effects of polyacrylonitrile (PAN) concentration and the proportion of iron to PAN, along with voltage and flow rate during the electrospinning process, and thus proposed three criteria to optimize these parameters for ideal nanofiber catalysts. The best half-wave potential of an optimized catalysts is 0.82 V versus reversible hydrogen electrode in an alkaline medium, which reaches the best range of the non-precious-metal catalysts reported and is very close to that of commercial Pt/C catalysts. Furthermore, the electron-transfer number of our catalysts is superior to that of the Pt/C, indicating the catalysts undergo a four-electron process. The durability of the optimized Fe-N-C nanofibers is also better than that of the Pt/C, which is attributed to the homogeneous distribution of the active sites in our catalysts.

  19. Electrospun polyamide 6/poly(allylamine hydrochloride) nanofibers functionalized with carbon nanotubes for electrochemical detection of dopamine.

    PubMed

    Mercante, Luiza A; Pavinatto, Adriana; Iwaki, Leonardo E O; Scagion, Vanessa P; Zucolotto, Valtencir; Oliveira, Osvaldo N; Mattoso, Luiz H C; Correa, Daniel S

    2015-03-01

    The use of nanomaterials as an electroactive medium has improved the performance of bio/chemical sensors, particularly when synergy is reached upon combining distinct materials. In this paper, we report on a novel architecture comprising electrospun polyamide 6/poly(allylamine hydrochloride) (PA6/PAH) nanofibers functionalized with multiwalled carbon nanotubes, used to detect the neurotransmitter dopamine (DA). Miscibility of PA6 and PAH was sufficient to form a single phase material, as indicated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), leading to nanofibers with no beads onto which the nanotubes could adsorb strongly. Differential pulse voltammetry was employed with indium tin oxide (ITO) electrodes coated with the functionalized nanofibers for the selective electrochemical detection of dopamine (DA), with no interference from uric acid (UA) and ascorbic acid (AA) that are normally present in biological fluids. The response was linear for a DA concentration range from 1 to 70 μmol L(-1), with detection limit of 0.15 μmol L(-1) (S/N = 3). The concepts behind the novel architecture to modify electrodes can be potentially harnessed in other electrochemical sensors and biosensors.

  20. Encapsulation of MnO Nanocrystals in Electrospun Carbon Nanofibers as High-Performance Anode Materials for Lithium-Ion Batteries

    PubMed Central

    Liu, Bin; Hu, Xianluo; Xu, Henghui; Luo, Wei; Sun, Yongming; Huang, Yunhui

    2014-01-01

    A novel and controllable approach is developed for the synthesis of MnO nanocrystals embedded in carbon nanofibers (MnO/CNFs) through an electrospinning process. The as-formed MnO/CNFs have a porous structure with diameters of 100–200 nm and lengths up to several millimeters. When used as an anode material for lithium-ion batteries, the resulting MnO/CNFs exhibit superior electrochemical performances with high specific capacity, good cyclability, and excellent rate capability. The unique porous carbon nanofibers (PCNFs) can not only improve the contact area between the electrode and the electrolyte, but also alleviate the impact of the large volume effect of MnO during the electrochemical cycling. It is expected that the present synthetic strategy can be extended to synthesize other nanostructured oxides encapsulated in carbon nanofibers for extensive energy transfer and storage applications. PMID:24598639

  1. Graphene Folding in Si Rich Carbon Nanofibers for Highly Stable, High Capacity Li-Ion Battery Anodes.

    PubMed

    Fei, Ling; Williams, Brian P; Yoo, Sang H; Kim, Jangwoo; Shoorideh, Ghazal; Joo, Yong Lak

    2016-03-01

    Silicon nanoparticles (Si NPs) wrapped by graphene in carbon nanofibers were obtained via electrospinning and subsequent thermal treatment. In this study, water-soluble poly(vinyl alcohol) (PVA) with low carbon yield is selected to make the process water-based and to achieve a high silicon yield in the composite. It was also found that increasing the amount of graphene helps keep the PVA fiber morphology after carbonization, while forming a graphene network. The fiber SEM and HRTEM images reveal that micrometer graphene is heavily folded into sub-micron scale fibers during electrospinning, while Si NPs are incorporated into the folds with nanospace in between. When applied to lithium-ion battery anodes, the Si/graphene/carbon nanofiber composites show a high reversible capacity of ∼2300 mAh g(-1) at a charging rate of 100 mA/g and a stable capacity of 1191 mAh g(-1) at 1 A/g after more than 200 cycles. The interconnected graphene network not only ensures the excellent conductivity but also serves as a buffering matrix for the mechanic stress caused by volume change; the nanospace between Si NPs and folded graphene provides the space needed for volume expansion. PMID:26853163

  2. Membranes of MnO Beading in Carbon Nanofibers as Flexible Anodes for High-Performance Lithium-Ion Batteries

    PubMed Central

    Zhao, Xin; Du, Yuxuan; Jin, Lei; Yang, Yang; Wu, Shuilin; Li, Weihan; Yu, Yan; Zhu, Yanwu; Zhang, Qinghua

    2015-01-01

    Freestanding yet flexible membranes of MnO/carbon nanofibers are successfully fabricated through incorporating MnO2 nanowires into polymer solution by a facile electrospinning technique. During the stabilization and carbonization processes of the as-spun membranes, MnO2 nanowires are transformed to MnO nanoparticles coincided with a conversion of the polymer from an amorphous state to a graphitic structure of carbon nanofibers. The hybrids consist of isolated MnO nanoparticles beading in the porous carbon and demonstrate superior performance when being used as a binder-free anode for lithium-ion batteries. With an optimized amount of MnO (34.6 wt%), the anode exhibits a reversible capacity of as high as 987.3 mAh g−1 after 150 discharge/charge cycles at 0.1 A g−1, a good rate capability (406.1 mAh g−1 at 3  A g−1) and an excellent cycling performance (655 mAh g−1 over 280 cycles at 0.5 A g−1). Furthermore, the hybrid anode maintains a good electrochemical performance at bending state as a flexible electrode. PMID:26374601

  3. Membranes of MnO Beading in Carbon Nanofibers as Flexible Anodes for High-Performance Lithium-Ion Batteries

    NASA Astrophysics Data System (ADS)

    Zhao, Xin; Du, Yuxuan; Jin, Lei; Yang, Yang; Wu, Shuilin; Li, Weihan; Yu, Yan; Zhu, Yanwu; Zhang, Qinghua

    2015-09-01

    Freestanding yet flexible membranes of MnO/carbon nanofibers are successfully fabricated through incorporating MnO2 nanowires into polymer solution by a facile electrospinning technique. During the stabilization and carbonization processes of the as-spun membranes, MnO2 nanowires are transformed to MnO nanoparticles coincided with a conversion of the polymer from an amorphous state to a graphitic structure of carbon nanofibers. The hybrids consist of isolated MnO nanoparticles beading in the porous carbon and demonstrate superior performance when being used as a binder-free anode for lithium-ion batteries. With an optimized amount of MnO (34.6 wt%), the anode exhibits a reversible capacity of as high as 987.3 mAh g-1 after 150 discharge/charge cycles at 0.1 A g-1, a good rate capability (406.1 mAh g-1 at 3  A g-1) and an excellent cycling performance (655 mAh g-1 over 280 cycles at 0.5 A g-1). Furthermore, the hybrid anode maintains a good electrochemical performance at bending state as a flexible electrode.

  4. Bicontinuous Structure of Li₃V₂(PO₄)₃ Clustered via Carbon Nanofiber as High-Performance Cathode Material of Li-Ion Batteries.

    PubMed

    Chen, Lin; Yan, Bo; Xu, Jing; Wang, Chunguang; Chao, Yimin; Jiang, Xuefan; Yang, Gang

    2015-07-01

    In this work, the composite structure of Li3V2(PO4)3 (LVP) nanoparticles with carbon nanofibers (CNF) is designed. The size and location of LVP particles, and the degree of graphitization and diameter of carbon nanofibers, are optimized by electrospinning and heat treatment. The bicontinuous morphologies of LVP/CNF are dependent on the carbonization of PVP and simultaneous growing of LVP, with the fibers shrunk and the LVP crystals grown toward the outside. LVP nanocystals clustered via carbon nanofibers guarantee improving the diffusion ability of Li(+), and the carbon fiber simultaneously guarantees the effective electron conductivity. Compared with the simple carbon-coated LVP and pure LVP, the particle-clustered structure guarantees high rate capability and long-life cycling stability of NF-LVP as cathode for LIBs. At 20 C rate in the range 3.0-4.3 V, NF-LVP delivers the initial capacity of 122.6 mAh g(-1) close to the theoretical value of 133 mAh g(-1), and maintains 97% of the initial capacity at the 1000th cycle. The bead-like structure of cathode material clustered via carbon nanofibers via electrospinning will be further applied to high-performance LIBs.

  5. Revealing the Role of Catalysts in Carbon Nanotubes and Nanofibers by Scanning Transmission X-ray Microscopy

    PubMed Central

    Gao, Jing; Zhong, Jun; Bai, Lili; Liu, Jinyin; Zhao, Guanqi; Sun, Xuhui

    2014-01-01

    The identification of effective components on the atomic scale in carbon nanomaterials which improve the performance in various applications remains outstanding challenges. Here the catalyst residues in individual carbon nanotube (CNT) and carbon nanofiber (CNF) were clearly imaged with a concurrent characterization of their electronic structure by nanoscale scanning transmission X-ray microscopy. Except for prominent catalyst nanoparticle at the tip, tiny catalyst clusters along the tube (fiber) were detected, indicating a migration of the catalysts with the growth of CNTs (CNFs). The observation provides the direct evidence on the atomic metal in CNT for oxygen reduction reported in the literature. Interaction between catalysts (Fe, Ni) and CNTs (CNFs) at the tip was also identified by comparing the X-ray absorption spectra. A deep understanding of catalyst residues such as Fe or Ni in carbon nanomaterials is very vital to growth mechanism development and practical applications. PMID:24398972

  6. Synthesis and characterization of radially-aligned carbon filaments spontaneously grown on a carbon yarn.

    PubMed

    Muradov, Nazim; Rahman, Zia Ur

    2008-09-01

    The synthesis and characterization of radially-aligned carbon filaments (RACF) produced from light hydrocarbons are reported. RACF grow spontaneously on the surface of a resistively heated (1100-1700 degrees C) carbon yarn exposed to C1-C3 hydrocarbons (methane, ethylene, propane) as carbon precursors. The diameter of the RACF depends on the temperature, exposure time, nature of hydrocarbon, and it ranges from 700 nm to 40 microm, with the length of the carbon filaments reaching up to 800 microm. The morphology and microstructure of the produced carbon filaments were analyzed by a number of materials characterization techniques, and it was shown that they feature a tree-ring type structure made of turbostratic carbon layers. RACF are characterized by the presence of cracks (50-100 nm in width) between the consecutive "tree-rings" and a crenulated structure of the exterior surface of the filaments. The RAFC growth mechanism is yet to be fully understood. Pros and cons for the catalytic versus non-catalytic growth models for the RACF are discussed in the paper. PMID:19049036

  7. Production of Aligned Carbon Nanotube Films and Nitrogen Doped Carbon Nanotube Films from the Pyrolysis of Styrene

    NASA Astrophysics Data System (ADS)

    Jin, Yi Zheng; Hsu, Wen Kuang; Zhu, Yan Qiu; Watts, Paul C. P.; Chueh, Yu Lun; Chou, Li Jen; Kroto, Harold W.; Walton, David R. M.

    2004-09-01

    Styrene is used as a carbon source in a CVD process to obtain aligned carbon nanotube films. Changing the carrier gas from argon to ammonia introduces nitrogen into the tubes. SEM, TEM and HRTEM show the well-aligned structures, which appear to exist as macrobundles. EELS analyses have verified the existence of 3.3 wt.% nitrogen in the tube. Irradiation experiments show that this technique can be used to manipulate NCNTs.

  8. Rational Design of Efficient Electrocatalysts for Hydrogen Evolution Reaction: Single Layers of WS2 Nanoplates Anchored to Hollow Nitrogen-Doped Carbon Nanofibers.

    PubMed

    Yu, Sunmoon; Kim, Jaehoon; Yoon, Ki Ro; Jung, Ji-Won; Oh, Jihun; Kim, Il-Doo

    2015-12-30

    To exploit the benefits of nanostructuring for enhanced hydrogen evolution reaction (HER), we employed coaxial electrospinning to synthesize single-layered WS2 nanoplates anchored to hollow nitrogen-doped carbon nanofibers (WS2@HNCNFs) as efficient electrocatalysts. For comparison, bulk WS2 powder and single layers of WS2 embedded in nitrogen-doped carbon nanofibers (WS2@NCNFs) were synthesized and electrochemically tested. The distinctive design of the WS2@HNCNFs enables remarkable electrochemical performances showing a low overpotential with reduced charge transfer resistance, a small Tafel slope, and excellent durability. The experimental results highlight the importance of nanostructure engineering in electrocatalysts for enhanced HER. PMID:26654256

  9. Unraveling the growth of vertically aligned multi-walled carbon nanotubes by chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Ramirez, A.; Royo, C.; Latorre, N.; Mallada, R.; Tiggelaar, R. M.; Monzón, A.

    2014-12-01

    The interaction between the main operational variables during the growth of vertically aligned multiwalled carbon nanotubes (VA-MWCNTs) by catalytic chemical vapor deposition is studied. In this contribution, we report the influence of the carbon source (i.e. acetylene, ethylene and propylene), the reaction/activation temperature, the rate of heating, the reaction time, the metal loading, and the metallic nanoparticle size and distribution on the growth and alignment of carbon nanotubes. Fe/Al thin films deposited onto silicon samples by electron-beam evaporation are used as catalyst. A phenomenological growth mechanism is proposed to explain the interaction between these multiple factors. Three different outcomes of the synthesis process are found: i) formation of forests of non-aligned, randomly oriented multi-walled carbon nanotubes, ii) growth of vertically aligned tubes with a thin and homogeneous carbonaceous layer on the top, and iii) formation of vertically aligned carbon nanotubes. This carbonaceous layer (ii) has not been reported before. The main requirements to promote vertically aligned carbon nanotube growth are determined.

  10. Carbon Nanotube and Nanofiber Exposure Assessments: An Analysis of 14 Site Visits

    PubMed Central

    Dahm, Matthew M.; Schubauer-Berigan, Mary K.; Evans, Douglas E.; Birch, M. Eileen; Fernback, Joseph E.; Deddens, James A.

    2015-01-01

    Recent evidence has suggested the potential for wide-ranging health effects that could result from exposure to carbon nanotubes (CNT) and carbon nanofibers (CNF). In response, the National Institute for Occupational Safety and Health (NIOSH) set a recommended exposure limit (REL) for CNT and CNF: 1 µg m−3 as an 8-h time weighted average (TWA) of elemental carbon (EC) for the respirable size fraction. The purpose of this study was to conduct an industrywide exposure assessment among US CNT and CNF manufacturers and users. Fourteen total sites were visited to assess exposures to CNT (13 sites) and CNF (1 site). Personal breathing zone (PBZ) and area samples were collected for both the inhalable and respirable mass concentration of EC, using NIOSH Method 5040. Inhalable PBZ samples were collected at nine sites while at the remaining five sites both respirable and inhalable PBZ samples were collected side-by-side. Transmission electron microscopy (TEM) PBZ and area samples were also collected at the inhalable size fraction and analyzed to quantify and size CNT and CNF agglomerate and fibrous exposures. Respirable EC PBZ concentrations ranged from 0.02 to 2.94 µg m−3 with a geometric mean (GM) of 0.34 µg m−3 and an 8-h TWA of 0.16 µg m−3. PBZ samples at the inhalable size fraction for EC ranged from 0.01 to 79.57 µg m−3 with a GM of 1.21 µg m−3. PBZ samples analyzed by TEM showed concentrations ranging from 0.0001 to 1.613 CNT or CNF-structures per cm3 with a GM of 0.008 and an 8-h TWA concentration of 0.003. The most common CNT structure sizes were found to be larger agglomerates in the 2–5 µm range as well as agglomerates >5 µm. A statistically significant correlation was observed between the inhalable samples for the mass of EC and structure counts by TEM (Spearman ρ = 0.39, P < 0.0001). Overall, EC PBZ and area TWA samples were below the NIOSH REL (96% were <1 μg m−3 at the respirable size fraction), while 30% of the inhalable PBZ EC

  11. Fe2O3 nanorods/carbon nanofibers composite: Preparation and performance as anode of high rate lithium ion battery

    NASA Astrophysics Data System (ADS)

    Wu, Chunyu; Li, Xiaoping; Li, Weishan; Li, Bin; Wang, Yaqiong; Wang, Yating; Xu, Mengqing; Xing, Lidan

    2014-04-01

    A novel Fe2O3/carbon composite is prepared using a facile one-step hydrothermal method. Its structure, morphology and performance as anode of lithium ion battery are investigated with X-ray diffraction, scanning electron microscopy, thermogravimetry, cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy. It is found that the as-prepared composite is composed of α-Fe2O3 nanorods of about 75 nm in diameter and 1 μm in length, which are enwrapped with soft and curly carbon nanofibers, and exhibits superior charge/discharge performance compared to bare α-Fe2O3 nanorods, especially at high current rate. The discharge capacity is 1069 mAh g-1 at the first cycle and remains 560 mAh g-1 after 30 cycles at 0.2C for the bare nanorods, but improved to 1278 mAh g-1 and 960 mAh g-1 for the composite. At 12C, the discharge capacity is only 798 mAh g-1 initially and becomes 98 mAh g-1 after 30 cycles for the bare nanorods, while 844 mAh g-1 and 292 mAh g-1 for the composite. The improved performance of the composite is attributed to the bondage from carbon nanofibers, which contributes to the improvement in electronic conductivity and structure stability of α-Fe2O3 nanorods.

  12. Aerosol Monitoring during Carbon Nanofiber Production: Mobile Direct-Reading Sampling

    PubMed Central

    Evans, Douglas E.; Ku, Bon Ki; Birch, M. Eileen; Dunn, Kevin H.

    2010-01-01

    Detailed investigations were conducted at a facility that manufactures and processes carbon nanofibers (CNFs). Presented research summarizes the direct-reading monitoring aspects of the study. A mobile aerosol sampling platform, equipped with an aerosol instrument array, was used to characterize emissions at different locations within the facility. Particle number, respirable mass, active surface area, and photoelectric response were monitored with a condensation particle counter (CPC), a photometer, a diffusion charger, and a photoelectric aerosol sensor, respectively. CO and CO2 were additionally monitored. Combined simultaneous monitoring of these metrics can be utilized to determine source and relative contribution of airborne particles (CNFs and others) within a workplace. Elevated particle number concentrations, up to 1.15 × 106 cm−3, were found within the facility but were not due to CNFs. Ultrafine particle emissions, released during thermal treatment of CNFs, were primarily responsible. In contrast, transient increases in respirable particle mass concentration, with a maximum of 1.1 mg m−3, were due to CNF release through uncontrolled transfer and bagging. Of the applied metrics, our findings suggest that particle mass was probably the most useful and practical metric for monitoring CNF emissions in this facility. Through chemical means, CNFs may be selectively distinguished from other workplace contaminants (Birch et al., in preparation), and for direct-reading monitoring applications, the photometer was found to provide a reasonable estimate of respirable CNF mass concentration. Particle size distribution measurements were conducted with an electrical low-pressure impactor and a fast particle size spectrometer. Results suggest that the dominant CNF mode by particle number lies between 200 and 250 nm for both aerodynamic and mobility equivalent diameters. Significant emissions of CO were also evident in this facility. Exposure control recommendations

  13. An amperometric uric acid biosensor based on chitosan-carbon nanotubes electrospun nanofiber on silver nanoparticles.

    PubMed

    Numnuam, Apon; Thavarungkul, Panote; Kanatharana, Proespichaya

    2014-06-01

    A novel amperometric uric acid biosensor was fabricated by immobilizing uricase on an electrospun nanocomposite of chitosan-carbon nanotubes nanofiber (Chi-CNTsNF) covering an electrodeposited layer of silver nanoparticles (AgNPs) on a gold electrode (uricase/Chi-CNTsNF/AgNPs/Au). The uric acid response was determined at an optimum applied potential of -0.35 V vs Ag/AgCl in a flow-injection system based on the change of the reduction current for dissolved oxygen during oxidation of uric acid by the immobilized uricase. The response was directly proportional to the uric acid concentration. Under the optimum conditions, the fabricated uric acid biosensor had a very wide linear range, 1.0-400 μmol L(-1), with a very low limit of detection of 1.0 μmol L(-1) (s/n = 3). The operational stability of the uricase/Chi-CNTsNF/AgNPs/Au biosensor (up to 205 injections) was excellent and the storage life was more than six weeks. A low Michaelis-Menten constant of 0.21 mmol L(-1) indicated that the immobilized uricase had high affinity for uric acid. The presence of potential common interfering substances, for example ascorbic acid, glucose, and lactic acid, had negligible effects on the performance of the biosensor. When used for analysis of uric acid in serum samples, the results agreed well with those obtained by use of the standard enzymatic colorimetric method (P > 0.05). PMID:24718436

  14. Aerosol monitoring during carbon nanofiber production: mobile direct-reading sampling.

    PubMed

    Evans, Douglas E; Ku, Bon Ki; Birch, M Eileen; Dunn, Kevin H

    2010-07-01

    Detailed investigations were conducted at a facility that manufactures and processes carbon nanofibers (CNFs). Presented research summarizes the direct-reading monitoring aspects of the study. A mobile aerosol sampling platform, equipped with an aerosol instrument array, was used to characterize emissions at different locations within the facility. Particle number, respirable mass, active surface area, and photoelectric response were monitored with a condensation particle counter (CPC), a photometer, a diffusion charger, and a photoelectric aerosol sensor, respectively. CO and CO(2) were additionally monitored. Combined simultaneous monitoring of these metrics can be utilized to determine source and relative contribution of airborne particles (CNFs and others) within a workplace. Elevated particle number concentrations, up to 1.15 x 10(6) cm(-3), were found within the facility but were not due to CNFs. Ultrafine particle emissions, released during thermal treatment of CNFs, were primarily responsible. In contrast, transient increases in respirable particle mass concentration, with a maximum of 1.1 mg m(-3), were due to CNF release through uncontrolled transfer and bagging. Of the applied metrics, our findings suggest that particle mass was probably the most useful and practical metric for monitoring CNF emissions in this facility. Through chemical means, CNFs may be selectively distinguished from other workplace contaminants (Birch et al., in preparation), and for direct-reading monitoring applications, the photometer was found to provide a reasonable estimate of respirable CNF mass concentration. Particle size distribution measurements were conducted with an electrical low-pressure impactor and a fast particle size spectrometer. Results suggest that the dominant CNF mode by particle number lies between 200 and 250 nm for both aerodynamic and mobility equivalent diameters. Significant emissions of CO were also evident in this facility. Exposure control

  15. Periodically striped films produced from super-aligned carbon nanotube arrays.

    PubMed

    Liu, Kai; Sun, Yinghui; Liu, Peng; Wang, Jiaping; Li, Qunqing; Fan, Shoushan; Jiang, Kaili

    2009-08-19

    We report a novel way to draw films from super-aligned carbon nanotube arrays at large drawing angles. The obtained super-aligned carbon nanotube films have a periodically striped configuration with alternating thinner and thicker film sections, and the width of the stripes is equal to the height of the original arrays. Compared with ordinary uniform films, the striped films provide a better platform for understanding the mechanism of spinning films from arrays because carbon nanotube junctions are easily observed and identified at the boundary of the stripes. Further studies show that the carbon nanotube junctions are bottleneck positions for thermal conduction and mechanical strength of the film, but do not limit its electrical conduction. These films can be utilized as striped and high-degree polarized light emission sources. Our results will be valuable for new applications and future large-scale production of tunable super-aligned carbon nanotube films. PMID:19636102

  16. High-yield harvest of nanofibers/mesoporous carbon composite by pyrolysis of waste biomass and its application for high durability electrochemical energy storage.

    PubMed

    Liu, Wu-Jun; Tian, Ke; He, Yan-Rong; Jiang, Hong; Yu, Han-Qing

    2014-12-01

    Disposal and recycling of the large scale biomass waste is of great concern. Themochemically converting the waste biomass to functional carbon nanomaterials and bio-oil is an environmentally friendly apporach by reducing greenhouse gas emissions and air pollution caused by open burning. In this work, we reported a scalable, "green" method for the synthesis of the nanofibers/mesoporous carbon composites through pyrolysis of the Fe(III)-preloaded biomass, which is controllable by adjustment of temperature and additive of catalyst. It is found that the coupled catalytic action of both Fe and Cl species is able to effectively catalyze the growth of the carbon nanofibers on the mesoporous carbon and form magnetic nanofibers/mesoporous carbon composites (M-NMCCs). The mechanism for the growth of the nanofibers is proposed as an in situ vapor deposition process, and confirmed by the XRD and SEM results. M-NMCCs can be directly used as electrode materials for electrochemical energy storage without further separation, and exhibit favorable energy storage performance with high EDLC capacitance, good retention capability, and excellent stability and durability (more than 98% capacitance retention after 10,000 cycles). Considering that biomass is a naturally abundant and renewable resource (over billions tons biomass produced every year globally) and pyrolysis is a proven technique, M-NMCCs can be easily produced at large scale and become a sustainable and reliable resource for clean energy storage. PMID:25372400

  17. High-yield harvest of nanofibers/mesoporous carbon composite by pyrolysis of waste biomass and its application for high durability electrochemical energy storage.

    PubMed

    Liu, Wu-Jun; Tian, Ke; He, Yan-Rong; Jiang, Hong; Yu, Han-Qing

    2014-12-01

    Disposal and recycling of the large scale biomass waste is of great concern. Themochemically converting the waste biomass to functional carbon nanomaterials and bio-oil is an environmentally friendly apporach by reducing greenhouse gas emissions and air pollution caused by open burning. In this work, we reported a scalable, "green" method for the synthesis of the nanofibers/mesoporous carbon composites through pyrolysis of the Fe(III)-preloaded biomass, which is controllable by adjustment of temperature and additive of catalyst. It is found that the coupled catalytic action of both Fe and Cl species is able to effectively catalyze the growth of the carbon nanofibers on the mesoporous carbon and form magnetic nanofibers/mesoporous carbon composites (M-NMCCs). The mechanism for the growth of the nanofibers is proposed as an in situ vapor deposition process, and confirmed by the XRD and SEM results. M-NMCCs can be directly used as electrode materials for electrochemical energy storage without further separation, and exhibit favorable energy storage performance with high EDLC capacitance, good retention capability, and excellent stability and durability (more than 98% capacitance retention after 10,000 cycles). Considering that biomass is a naturally abundant and renewable resource (over billions tons biomass produced every year globally) and pyrolysis is a proven technique, M-NMCCs can be easily produced at large scale and become a sustainable and reliable resource for clean energy storage.

  18. Growth and Characterization of Carbon Nanofibers on Fe/C-Fiber Textiles Coated by Deposition-Precipitation and Dip-Coating.

    PubMed

    Lee, Sang-Won; Lee, Chang-Seop

    2015-09-01

    This research was conducted to synthesize carbon nanofibers on C-fiber textiles, by thermal chemical vapor deposition (CVD) using Fe catalyst. The substrate, which was a carbon textile consisting of non-woven carbon fibers and attached graphite particles, was oxidized by nitric acid, before the deposition process. Hydroxyl groups were created on the C-fiber textile, due to the oxidization step. Fe(III) hydroxide was subsequently deposited on the oxidized surface of the C-fiber textile. To deposit ferric particles, two different methods were tested: (i) deposition-precipitation, and (ii) dip-coating. For the experiments using both types of catalyst deposition, the weight ratio of Fe to C-fiber textile was also varied. Ferric particles were reduced to iron after deposition, by using H2/N2 gas, and carbon nanofibers (CNFs) were grown by flowing ethylene gas. Properties of carbon nanofibers created like this were analyzed through Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), N2-sorption (BET), X-ray Diffraction (XRD), X-ray Photoelectron Spectoscopy (XPS), Thermal analysis (TG/DTA), and Raman spectroscopy. In the case of the deposition-precipitation method, the results show that the diameter of carbon nanofibers grew up to 40-60 nm and 30-55 nm, at which the weight ratios of Fe catalyst to C-fiber textiles were 1:30 and 1:70, respectively. When Fe particles were deposited by the dip-coating method, the diameter of carbon nanofibers grew up to 40-60 nm and 25-30 nm, for the ratios of Fe catalyst to C-fiber textiles of 1:10 and 1:30, respectively.

  19. Growth and Characterization of Carbon Nanofibers on Fe/C-Fiber Textiles Coated by Deposition-Precipitation and Dip-Coating.

    PubMed

    Lee, Sang-Won; Lee, Chang-Seop

    2015-09-01

    This research was conducted to synthesize carbon nanofibers on C-fiber textiles, by thermal chemical vapor deposition (CVD) using Fe catalyst. The substrate, which was a carbon textile consisting of non-woven carbon fibers and attached graphite particles, was oxidized by nitric acid, before the deposition process. Hydroxyl groups were created on the C-fiber textile, due to the oxidization step. Fe(III) hydroxide was subsequently deposited on the oxidized surface of the C-fiber textile. To deposit ferric particles, two different methods were tested: (i) deposition-precipitation, and (ii) dip-coating. For the experiments using both types of catalyst deposition, the weight ratio of Fe to C-fiber textile was also varied. Ferric particles were reduced to iron after deposition, by using H2/N2 gas, and carbon nanofibers (CNFs) were grown by flowing ethylene gas. Properties of carbon nanofibers created like this were analyzed through Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), N2-sorption (BET), X-ray Diffraction (XRD), X-ray Photoelectron Spectoscopy (XPS), Thermal analysis (TG/DTA), and Raman spectroscopy. In the case of the deposition-precipitation method, the results show that the diameter of carbon nanofibers grew up to 40-60 nm and 30-55 nm, at which the weight ratios of Fe catalyst to C-fiber textiles were 1:30 and 1:70, respectively. When Fe particles were deposited by the dip-coating method, the diameter of carbon nanofibers grew up to 40-60 nm and 25-30 nm, for the ratios of Fe catalyst to C-fiber textiles of 1:10 and 1:30, respectively. PMID:26716329

  20. Oriented nanofibers embedded in a polymer matrix

    NASA Technical Reports Server (NTRS)

    Barrera, Enrique V. (Inventor); Rodriguez-Macias, Fernando J. (Inventor); Lozano, Karen (Inventor); Chibante, Luis Paulo Felipe (Inventor); Stewart, David Harris (Inventor)

    2011-01-01

    A method of forming a composite of embedded nanofibers in a polymer matrix is disclosed. The method includes incorporating nanofibers in a plastic matrix forming agglomerates, and uniformly distributing the nanofibers by exposing the agglomerates to hydrodynamic stresses. The hydrodynamic said stresses force the agglomerates to break apart. In combination or additionally elongational flow is used to achieve small diameters and alignment. A nanofiber reinforced polymer composite system is disclosed. The system includes a plurality of nanofibers that are embedded in polymer matrices in micron size fibers. A method for producing nanotube continuous fibers is disclosed. Nanofibers are fibrils with diameters of 100 nm, multiwall nanotubes, single wall nanotubes and their various functionalized and derivatized forms. The method includes mixing a nanofiber in a polymer; and inducing an orientation of the nanofibers that enables the nanofibers to be used to enhance mechanical, thermal and electrical properties. Orientation is induced by high shear mixing and elongational flow, singly or in combination. The polymer may be removed from said nanofibers, leaving micron size fibers of aligned nanofibers.

  1. Noble Metal Decoration and Alignment of Carbon Nanotubes in Carboxymethyl Cellulose

    EPA Science Inventory

    A facile microwave (MW) method is described that accomplishes alignment and decoration of noble metals on carbon nanotubes wrapped with carboxymethyl cellulose (CMC). Carbon nanotubes (CNTs) such as single-wall (SWNT), multi-wall (MWNT) and Buckminsterfullerene (C-60) were well ...

  2. Flexible copper-stabilized sulfur-carbon nanofibers with excellent electrochemical performance for Li-S batteries

    NASA Astrophysics Data System (ADS)

    Zeng, Linchao; Jiang, Yu; Xu, Jun; Wang, Min; Li, Weihan; Yu, Yan

    2015-06-01

    By rational design, we fabricated a flexible and free-standing copper-immobilized sulfur-porous carbon nanofiber (denoted as S@PCNFs-Cu) electrode by simply impregnating sulfur into electrospun derived Cu embedded porous carbon nanofibers (PCNFs-Cu). The PCNF film with a 3D interconnected structure is used as a conducting matrix to encapsulate sulfur. In addition, the introduction of Cu leads to the formation of a chemical bond between Cu and S, preventing the dissolution of polysulfide during cycling. The micropores and mesopores of PCNF hosts provide free space to accommodate the volume change of S and polysulfide. When used as a cathode material for Li-S batteries, the S@PCNFs-Cu (S content: 52 wt%) exhibits much better electrochemical performance compared to the Cu-free S@PCNF electrode. The S@PCNFs-Cu displays high reversible capacity (680 mA h g-1 after 100 cycles at 50 mA g-1), excellent rate capability (415 mA h g-1 at 1 A g-1) and super Coulombic efficiency of 100%. This strategy of stabilizing S with a small amount of copper nanoparticles can be a very promising method to prepare free-standing cathode material for high-performance Li-S batteries.

  3. Processing, wear, and mechanical properties of polyethylene composites prepared with pristine and organosilane-treated carbon nanofibers

    NASA Astrophysics Data System (ADS)

    Wood, Weston

    Polymers and nanocomposites have been increasingly used for tribological applications over the last few decades. In particular, ultrahigh molecular weight polyethylene (UHMWPE) is a high performance polymer with excellent strength, toughness, and wear resistance. Because of these properties, UHMWPE is an ideal material for a variety of applications including body armor, components of sporting goods such as skies and snowboards, and liners in total joint replacement. Though the toughness and wear resistance far exceed that of most other polymeric materials, there is a high demand for improving the tribological and mechanical properties of UHMWPE for many applications. The approach used in this work for improving such properties is through nanocomposite technology, specifically via the incorporation of carbon nanofibers. In order to obtain the full potential of nanocomposite technology, two critical issues need to be addressed: appropriate interactions between the filler and matrix and proper dispersion of the nano-reinforcement. These critical issues are particularly important for UHMWPE nanocomposites in that UHMWPE is an extremely viscous polymer and thus cannot be processed conventionally, typically resulting in dispersion issues far worse than that of other composite systems. Furthermore, UHMWPE is non-polar, so interactions between filler and matrix will be limited to Van der Waals forces for untreated nanofillers. Therefore, the research presented aims at solving these issues by using a paraffin-assisted processing method and applying appropriate surface treatment to the carbon nanofibers. Under optimized processing conditions, wear and mechanical properties of UHMWPE composites can be substantially improved.

  4. Facile electrospinning preparation of phosphorus and nitrogen dual-doped cobalt-based carbon nanofibers as bifunctional electrocatalyst

    NASA Astrophysics Data System (ADS)

    Wang, Zhuang; Zuo, Pengjian; Fan, Liquan; Han, Jianan; Xiong, Yueping; Yin, Geping

    2016-04-01

    A novel electrochemical catalyst of phosphorus and nitrogen dual-doped cobalt-based carbon nanofibers (Cosbnd Nsbnd P-CNFs) is prepared by a facile and cost-effective electrospinning technique. Excellent features of the porous carbon nanofibers with large amounts of Co atoms, N/P-doping effect, abundant pyridinic-N and Cosbnd Nx clusters as catalytic active sites, and the advantages of the structure and composition result in a high catalytic efficiency. In alkaline or acidic media, Cosbnd Nsbnd P-CNFs exhibits remarkable electrocatalytic activities and kinetics for oxygen reduction reaction (ORR), superior methanol tolerance and stability, and a similar four-electron pathway. In addition, Cosbnd Nsbnd P-CNFs also shows excellent performance for hydrogen evolution reaction (HER), offering a low onset potential of -0.216 V and a stable current density of 10 mA cm-2 at potential of -0.248 V. The mechanism of ORR and HER catalytic active site arises from the doping of N/P atoms in the Co-based CNFs, which is responsible for the excellent electrocatalytic performance. Due to the excellent catalytic efficiencies, Cosbnd Nsbnd P-CNFs act as a promising catalyst material for fuel cells and water splitting technologies.

  5. Flexible copper-stabilized sulfur-carbon nanofibers with excellent electrochemical performance for Li-S batteries.

    PubMed

    Zeng, Linchao; Jiang, Yu; Xu, Jun; Wang, Min; Li, Weihan; Yu, Yan

    2015-07-01

    By rational design, we fabricated a flexible and free-standing copper-immobilized sulfur-porous carbon nanofiber (denoted as S@PCNFs-Cu) electrode by simply impregnating sulfur into electrospun derived Cu embedded porous carbon nanofibers (PCNFs-Cu). The PCNF film with a 3D interconnected structure is used as a conducting matrix to encapsulate sulfur. In addition, the introduction of Cu leads to the formation of a chemical bond between Cu and S, preventing the dissolution of polysulfide during cycling. The micropores and mesopores of PCNF hosts provide free space to accommodate the volume change of S and polysulfide. When used as a cathode material for Li-S batteries, the S@PCNFs-Cu (S content: 52 wt%) exhibits much better electrochemical performance compared to the Cu-free S@PCNF electrode. The S@PCNFs-Cu displays high reversible capacity (680 mA h g(-1) after 100 cycles at 50 mA g(-1)), excellent rate capability (415 mA h g(-1) at 1 A g(-1)) and super Coulombic efficiency of 100%. This strategy of stabilizing S with a small amount of copper nanoparticles can be a very promising method to prepare free-standing cathode material for high-performance Li-S batteries. PMID:26059471

  6. Electrospun Pd nanoparticles loaded on Vulcan carbon/ conductive polymeric ionic liquid nanofibers for selective and sensitive determination of tramadol.

    PubMed

    Fathirad, Fariba; Mostafavi, Ali; Afzali, Daryoush

    2016-10-12

    In the present work a sensitive and selective electrochemical sensor was fabricated based on a glassy carbon electrode which has been modified with Pd nanoparticles loaded on Vulcan carbon/conductive polymeric ionic liquid composite nanofibers. The nanostructures were characterized by UV-Vis, FT-IR, FESEM, EDX and XRD techniques. The electrochemical study of the modified electrode, as well as its efficiency for the electrooxidation of tramadol was described in 0.1 M phosphate buffered solution (PBS) (pH 7.0) using cyclic voltammetry, linear sweep voltammetry, chronoamperometry and square wave voltammetry as diagnostic techniques. It has been found that application of the composite nanofibers result in a sensitivity enhancement and a considerable decrease in the anodic overpotential, leading to negative shifts about 200 mV in peak potential. The results exhibit a linear dynamic range from 0.05 μM to 200 μM and a detection limit of 0.015 μM for tramadol. Finally, the modified electrode was used for the determination of tramadol in pharmaceutical and biological samples.

  7. Electrospun Pd nanoparticles loaded on Vulcan carbon/ conductive polymeric ionic liquid nanofibers for selective and sensitive determination of tramadol.

    PubMed

    Fathirad, Fariba; Mostafavi, Ali; Afzali, Daryoush

    2016-10-12

    In the present work a sensitive and selective electrochemical sensor was fabricated based on a glassy carbon electrode which has been modified with Pd nanoparticles loaded on Vulcan carbon/conductive polymeric ionic liquid composite nanofibers. The nanostructures were characterized by UV-Vis, FT-IR, FESEM, EDX and XRD techniques. The electrochemical study of the modified electrode, as well as its efficiency for the electrooxidation of tramadol was described in 0.1 M phosphate buffered solution (PBS) (pH 7.0) using cyclic voltammetry, linear sweep voltammetry, chronoamperometry and square wave voltammetry as diagnostic techniques. It has been found that application of the composite nanofibers result in a sensitivity enhancement and a considerable decrease in the anodic overpotential, leading to negative shifts about 200 mV in peak potential. The results exhibit a linear dynamic range from 0.05 μM to 200 μM and a detection limit of 0.015 μM for tramadol. Finally, the modified electrode was used for the determination of tramadol in pharmaceutical and biological samples. PMID:27662760

  8. Array of aligned and dispersed carbon nanotubes and method of producing the array

    DOEpatents

    Ivanov, Ilia N; Simpson, John T; Hendricks, Troy R

    2013-06-11

    An array of aligned and dispersed carbon nanotubes includes an elongate drawn body including a plurality of channels extending therethrough from a first end to a second end of the body, where the channels have a number density of at least about 100,000 channels/mm.sup.2 over a transverse cross-section of the body. A plurality of carbon nanotubes are disposed in each channel, and the carbon nanotubes are sufficiently dispersed and aligned along a length of the channels for the array to comprise an average resistivity per channel of about 9700 .OMEGA.m or less.

  9. Array of aligned and dispersed carbon nanotubes and method of producing the array

    DOEpatents

    Ivanov, Ilia N.; Simpson, John T.; Hendricks, Troy R.

    2012-06-19

    An array of aligned and dispersed carbon nanotubes includes an elongate drawn body including a plurality of channels extending therethrough from a first end to a second end of the body, where the channels have a number density of at least about 100,000 channels/mm.sup.2 over a transverse cross-section of the body. A plurality of carbon nanotubes are disposed in each channel, and the carbon nanotubes are sufficiently dispersed and aligned along a length of the channels for the array to comprise an average resistivity per channel of about 9700 .OMEGA.m or less.

  10. Secondary nanotube growth on aligned carbon nanofibre arrays for superior field emission.

    PubMed

    Watts, Paul C P; Lyth, Stephen M; Henley, Simon J; Silva, S Ravi P

    2008-04-01

    We report substantial improvement of the field emission properties from aligned carbon nanotubes grown on aligned carbon nanofibres by a two-stage plasma enhanced chemical vapour deposition (PECVD) process. The threshold field decreased from 15.0 to 3.6 V/microm after the secondary growth. The field enhancement factor increased from 240 to 1480. This technique allows for superior emission of electrons for carbon nanotube/nanofibre arrays grown directly on highly doped silicon for direct integration in large area displays. PMID:18572626

  11. Quasi one dimensional transport in individual electrospun composite nanofibers

    SciTech Connect

    Avnon, A. Datsyuk, V.; Trotsenko, S.; Wang, B.; Zhou, S.

    2014-01-15

    We present results of transport measurements of individual suspended electrospun nanofibers Poly(methyl methacrylate)-multiwalled carbon nanotubes. The nanofiber is comprised of highly aligned consecutive multiwalled carbon nanotubes. We have confirmed that at the range temperature from room temperature down to ∼60 K, the conductance behaves as power-law of temperature with an exponent of α ∼ 2.9−10.2. The current also behaves as power law of voltage with an exponent of β ∼ 2.3−8.6. The power-law behavior is a footprint for one dimensional transport. The possible models of this confined system are discussed. Using the model of Luttinger liquid states in series, we calculated the exponent for tunneling into the bulk of a single multiwalled carbon nanotube α{sub bulk} ∼ 0.06 which agrees with theoretical predictions.

  12. Easy fabrication of aligned PLLA nanofibers-based 2D scaffolds suitable for cell contact guidance studies.

    PubMed

    Mohanraj, John; Puzzi, Luca; Capria, Ennio; Corvaglia, Stefania; Casalis, Loredana; Mestroni, Luisa; Sbaizero, Orfeo; Fraleoni-Morgera, Alessandro

    2016-05-01

    An easy, low-cost and fast wet processing-based method named ASB-SANS (Auxiliary Solvent-Based Sublimation-Aided NanoStructuring) has been used to fabricate poly(l-lactic acid) (PLLA) highly ordered and hierarchically organized 2D fibrillar patterns, with fiber widths between 40 and 500 nm and lengths exceeding tens of microns. A clear contact guidance effect of these nanofibrillar scaffolds with respect to HeLa and NIH-3T3 cells growth has been observed, on top of an overall good viability. For NIH-3T3 pronounced elongation of the cells was observed, as well as a remarkable ability of the patterns to guide the extension of pseudopodia. Moreover, SEM imaging revealed filopodia stemming from both sides of the pseudopodia and aligned with the secondary PLLA nanofibrous structures created by the ASB-SANS procedure. These results validate ASB-SANS as a technique capable to provide biocompatible 2D nanofibrillar patterns suitable for studying phenomena of contact guidance (and, more in general, the behavior of cells onto nanofibrous scaffolds), at very low costs and in an extremely easy way, accessible to virtually any laboratory. PMID:26952427

  13. Synthesis of Large Arrays of Well-Aligned Carbon Nanotubes on Glass

    SciTech Connect

    Bush, P. Siegal, M.P.; Huang, Z.P.; Provencio, P.N.; Ren, Z.F.; Wang, J.H.; Xu, J.W.

    1998-11-10

    Free-standing aligned carbon nanotubes have previously been grown above 7000C on mesoporous silica embedded with iron nanoparticles. Here, carbon nanotubes aligned over areas up to several square centimeters were grown on nickel-coated glass below 666oC by plasma-enhanced hot filament chemical vapor deposition. Acetylene (C2H2) gas was used as the carbon source and ammonia (NH3) gas was used as a catalyst and dilution gas. Nanotubes with controllable diameters from 20 to 400 nanometers and lengths from 0.1 to 50 micrometers were obtained. Using this method, large panels of aligned carbon nanotubes can be made under conditions that are suitable for device fabrication.

  14. Synthesis, Optimization, and Performance Demonstration of Electrospun Carbon Nanofiber-Carbon Nanotube Composite Sorbents for Point-of-Use Water Treatment.

    PubMed

    Peter, Katherine T; Vargo, John D; Rupasinghe, Thilini P; De Jesus, Aribet; Tivanski, Alexei V; Sander, Edward A; Myung, Nosang V; Cwiertny, David M

    2016-05-11

    We developed an electrospun carbon nanofiber-carbon nanotube (CNF-CNT) composite with optimal sorption capacity and material strength for point-of-use (POU) water treatment. Synthesis variables including integration of multiwalled carbon nanotubes (CNTs) and macroporosity (via sublimation of phthalic acid), relative humidity (20 and 40%), and stabilization temperature (250 and 280 °C) were used to control nanofiber diameter and surface area (from electron microscopy and BET isotherms, respectively), surface composition (from XPS), and strength (from AFM nanoindentation and tensile strength tests). Composites were then evaluated using kinetic, isotherm, and pH-edge sorption experiments with sulfamethoxazole (log Kow = 0.89) and atrazine (log Kow = 2.61), representative micropollutants chosen for their different polarities. Although CNFs alone were poor sorbents, integration of CNTs and macroporosity achieved uptake comparable to granular activated carbon. Through reactivity comparisons with CNT dispersions, we propose that increasing macroporosity exposes the embedded CNTs, thereby enabling their role as the primary sorbent in nanofiber composites. Because the highest capacity sorbents lacked sufficient strength, our optimal formulation (polyacrylonitrile 8 wt %, CNT 2 wt %, phthalic acid 2.4 wt %; 40% relative humidity; 280 °C stabilization) represents a compromise between strength and performance. This optimized sorbent was tested with a mixture of ten organic micropollutants at environmentally relevant concentrations in a gravity-fed, flow-through filtration system, where removal trends suggest that both hydrophobic and specific binding interactions contribute to micropollutant uptake. Collectively, this work highlights the promise of CNF-CNT filters (e.g., mechanical strength, ability to harness CNT sorption capacity), while also prioritizing areas for future research and development (e.g., improved removal of highly polar micropollutants, sensitivity to

  15. Synthesis, Optimization, and Performance Demonstration of Electrospun Carbon Nanofiber-Carbon Nanotube Composite Sorbents for Point-of-Use Water Treatment.

    PubMed

    Peter, Katherine T; Vargo, John D; Rupasinghe, Thilini P; De Jesus, Aribet; Tivanski, Alexei V; Sander, Edward A; Myung, Nosang V; Cwiertny, David M

    2016-05-11

    We developed an electrospun carbon nanofiber-carbon nanotube (CNF-CNT) composite with optimal sorption capacity and material strength for point-of-use (POU) water treatment. Synthesis variables including integration of multiwalled carbon nanotubes (CNTs) and macroporosity (via sublimation of phthalic acid), relative humidity (20 and 40%), and stabilization temperature (250 and 280 °C) were used to control nanofiber diameter and surface area (from electron microscopy and BET isotherms, respectively), surface composition (from XPS), and strength (from AFM nanoindentation and tensile strength tests). Composites were then evaluated using kinetic, isotherm, and pH-edge sorption experiments with sulfamethoxazole (log Kow = 0.89) and atrazine (log Kow = 2.61), representative micropollutants chosen for their different polarities. Although CNFs alone were poor sorbents, integration of CNTs and macroporosity achieved uptake comparable to granular activated carbon. Through reactivity comparisons with CNT dispersions, we propose that increasing macroporosity exposes the embedded CNTs, thereby enabling their role as the primary sorbent in nanofiber composites. Because the highest capacity sorbents lacked sufficient strength, our optimal formulation (polyacrylonitrile 8 wt %, CNT 2 wt %, phthalic acid 2.4 wt %; 40% relative humidity; 280 °C stabilization) represents a compromise between strength and performance. This optimized sorbent was tested with a mixture of ten organic micropollutants at environmentally relevant concentrations in a gravity-fed, flow-through filtration system, where removal trends suggest that both hydrophobic and specific binding interactions contribute to micropollutant uptake. Collectively, this work highlights the promise of CNF-CNT filters (e.g., mechanical strength, ability to harness CNT sorption capacity), while also prioritizing areas for future research and development (e.g., improved removal of highly polar micropollutants, sensitivity to

  16. Depressing the hydrogenation and decomposition reaction in H2O2 synthesis by supporting AuPD on oxygen functionalized carbon nanofibers

    DOE PAGES

    Villa, Alberto; Freakley, Simon J.; Schiavoni, Marco; Edwards, Jennifer K.; Hammond, Ceri; Wang, Wu; Wang, Di; Prati, Laura; Dimitratos, Nikolaos; Hutchings, Graham J.; et al

    2015-12-03

    In this work, we show that the introduction of acidic oxygen functionalities to the surface of carbon nanofibers serves to depress the hydrogenation and the decomposition of hydrogen peroxide during the direct synthesis of H2O2. Furthermore, the presence of acidic groups enhances the H2O2 productivity in the case of supported AuPd nanoparticles.

  17. Single-Walled Carbon Nanotubes, Carbon Nanofibers and Laser-Induced Incandescence

    NASA Technical Reports Server (NTRS)

    Schubert, Kathy (Technical Monitor); VanderWal, Randy L.; Ticich, Thomas M.; Berger, Gordon M.; Patel, Premal D.

    2004-01-01

    Laser induced incandescence applied to a heterogeneous, multi-element reacting flows is characterized by a) temporally resolved emission spectra, time-resolved emission at selected detection wavelengths and fluence dependence. Laser fluences above 0.6 Joules per square centimeter at 1064 nm initiate laser-induced vaporization, yielding a lower incandescence intensity, as found through fluence dependence measurements. Spectrally derived temperatures show that values of excitation laser fluence beyond this value lead to a super-heated plasma, well above the vaporization of temperature of carbon. The temporal evolution of the emission signal at these fluences is consistent with plasma dissipation processes, not incandescence from solid-like structures.

  18. A facile method to align carbon nanotubes on polymeric membrane substrate

    PubMed Central

    Zhao, Haiyang; Zhou, Zhijun; Dong, Hang; Zhang, Lin; Chen, Huanlin; Hou, Lian

    2013-01-01

    The alignment of carbon nanotubes (CNT) is the fundamental requirement to ensure their excellent functions but seems to be desolated in recent years. A facile method, hot-press combined with peel-off (HPPO), is introduced here, through which CNT can be successfully vertically aligned on the polymeric membrane substrate. Shear force and mechanical stretch are proposed to be the main forces to align the tubes perpendicular to the substrate surface during the peel-off process. The alignment of CNT keeps its orientation in a thin hybrid membrane by dip-coating cellulose acetate dope solution. It is expected that the stable alignment of CNT by HPPO would contribute to the realization of its potential applications. PMID:24326297

  19. A facile method to align carbon nanotubes on polymeric membrane substrate

    NASA Astrophysics Data System (ADS)

    Zhao, Haiyang; Zhou, Zhijun; Dong, Hang; Zhang, Lin; Chen, Huanlin; Hou, Lian

    2013-12-01

    The alignment of carbon nanotubes (CNT) is the fundamental requirement to ensure their excellent functions but seems to be desolated in recent years. A facile method, hot-press combined with peel-off (HPPO), is introduced here, through which CNT can be successfully vertically aligned on the polymeric membrane substrate. Shear force and mechanical stretch are proposed to be the main forces to align the tubes perpendicular to the substrate surface during the peel-off process. The alignment of CNT keeps its orientation in a thin hybrid membrane by dip-coating cellulose acetate dope solution. It is expected that the stable alignment of CNT by HPPO would contribute to the realization of its potential applications.

  20. Direct synthesis of mesostructured carbon nanofibers decorated with silver-nanoparticles as a multifunctional membrane for water treatment

    NASA Astrophysics Data System (ADS)

    Aboueloyoun Taha, Ahmed

    2015-12-01

    One-dimensional (1D) porous carbon nanofibers (CNFs) decorated by silver (Ag) nanoparticles (NPs) were prepared using a one-pot/self-template synthesis strategy by combining electrospinning and carbonization methods. The characterization results revealed that AgNPs were homogenously distributed along the CNFs and possessed a relatively uniform nano-size of about 12 nm. The novel membrane distinctively displayed enhanced photocatalytic activity under visible-light irradiation. The membrane exhibited excellent dye degradation and bacteria disinfection in batch experiments. The high photocatalytic activity can be attributed to the highly accessible surface areas, good light absorption capability, and high separation efficiency of photogenerated electron-hole pairs. The as-prepared membranes can be easily recycled because of their 1D property.

  1. Antimony nanoparticles anchored on interconnected carbon nanofibers networks as advanced anode material for sodium-ion batteries

    NASA Astrophysics Data System (ADS)

    Hou, Hongshuai; Jing, Mingjun; Yang, Yingchang; Zhang, Yan; Song, Weixin; Yang, Xuming; Chen, Jun; Chen, Qiyuan; Ji, Xiaobo

    2015-06-01

    Interconnected carbon nanofibers networks (ICNNs) prepared through the carbonization of polypyrrole (PPy) precursor are utilized as conductive pathways and buffer to improve the Na storage performance of antimony (Sb) as anode for sodium-ion batteries (SIBs). The as-obtained Sb/ICNNs composite exhibits excellent cycle stability. The reversible capacity can remain 542.5 mAh g-1 with a high capacity retention of 96.7% after 100 cycles at a current density of 100 mA g-1. And the superior rate performance is also observed, the reversible capacity can still reach 325 mAh g-1 at a high current density of 3200 mA g-1. These great electrochemical performances observed above suggest that this type of composite can be a nice option for advanced SIBs anode materials and may be extended to other active materials/ICNNs composite electrode.

  2. Highly flexible NiCo2O4/CNTs doped carbon nanofibers for CO2 adsorption and supercapacitor electrodes.

    PubMed

    Iqbal, Nousheen; Wang, Xianfeng; Ahmed Babar, Aijaz; Yu, Jianyong; Ding, Bin

    2016-08-15

    Controllable synthesis of carbon nanofibers (CNFs) with hierarchical porosity and high flexibility are extremely desirable for CO2 adsorption and energy storage applications. Herein, we report a nickel cobaltite/carbon nanotubes doped CNFs (NiCo2O4/CNTs CNFs) mesoporous membrane that shows well-developed flexibility, tailored pore structure, hydrophobic character, and high stability. Ascribed to these unique features, NiCo2O4/CNTs CNFs membrane shows high CO2 capture of 1.54mmol/g at 25°C and 1.0bar, and electrochemical measurements for supercapacitors exhibit good performance with specific capacitances of 220F/g (in 1M KOH) at a current density of 1A/g. The successful synthesis of such hybrid membrane provides new insight into development of various multifunctional applications. PMID:27209394

  3. Preparation of polyacrylnitrile (PAN)/ Manganese oxide based activated carbon nanofibers (ACNFs) for adsorption of Cadmium (II) from aqueous solution

    NASA Astrophysics Data System (ADS)

    Abdullah, N.; Yusof, N.; Jaafar, J.; Ismail, AF; Che Othman, F. E.; Hasbullah, H.; Salleh, W. N. W.; Misdan, N.

    2016-06-01

    In this work, activated carbon nanofibers (ACNFs) from precursor polyacrylnitrile (PAN) and manganese oxide (MnO2) were prepared via electrospinning process. The electrospun PAN/MnO2-based ACNFs were characterised in term of its morphological structure and specific surface area using SEM and BET analysis respectively. The comparative adsorption study of cadmium (II) ions from aqueous solution between the neat ACNFs, composite ACNFs and commercial granular activated carbon was also conducted. SEM analysis illustrated that composite ACNFs have more compact fibers with presence of MnO2 beads with smaller fiber diameter of 437.2 nm as compared to the neat ACNFs which is 575.5 nm. BET analysis elucidated specific surface area of ACNFs/MnO2 to be 67 m2/g. Under adsorption study, it was found out that Cd (II) removal by ACNFs/MnO2 was the highest (97%) followed by neat ACNFs (96%) and GAC (74%).

  4. Effects of increasing carbon nanofiber density in polyurethane composites for inhibiting bladder cancer cell functions.

    PubMed

    Tsang, Melissa; Chun, Young Wook; Im, Yeon Min; Khang, Dongwoo; Webster, Thomas J

    2011-07-01

    Polyurethane (PU) is a versatile elastomer that is commonly used in biomedical applications. In turn, materials derived from nanotechnology, specifically carbon nanofibers (CNFs), have received increasing attention for their potential use in biomedical applications. Recent studies have shown that the dispersion of CNFs in PU significantly enhances composite nanoscale surface roughness, tensile properties, and thermal stability. Although there have been studies concerning normal primary cell functions on such nanocomposites, there have been few studies detailing cancer cell responses. Since many patients who require bladder transplants have suffered from bladder cancer, the ideal bladder prosthetic material should not only promote normal primary human urothelial cell (HUC) function, but also inhibit the return of bladder cancerous cell activity. This study examined the correlation between transitional (UMUC) and squamous (or SCaBER) urothelial carcinoma cells and HUC on PU:CNF nanocomposites of varying PU and CNF weight ratios (from pure PU to 4:1 [PU:CNF volume ratios], 2:1, 1:1, 1:2, and 1:4 composites to pure CNF). Composites were characterized for mechanical properties, wettability, surface roughness, and chemical composition by atomic force microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and goniometry. The adhesion and proliferation of UMUC and SCaBER cancer cells were assessed by MTS assays. Cellular responses were further quantified by measuring the amounts of nuclear mitotic protein 22 (NMP-22), vascular endothelial growth factor (VEGF), and tumor necrosis factor alpha. Results demonstrated that both UMUC and SCaBER cell proliferation rates decreased over time on substrates with increased CNF in PU. In addition, with the exception of VEGF from UMUC (which was the same across all materials), composites containing the most CNF activated cancer cells (UMUC and SCaBER) the least, as shown by

  5. Ultrafast laser orthogonal alignment and patterning of carbon nanotube-polymer composite films

    NASA Astrophysics Data System (ADS)

    Murphy, Ryan D.; Abere, Michael J.; Zhang, Huanan; Sun, Haiping; Torralva, Ben; Mansfield, John F.; Kotov, Nicholas A.; Yalisove, Steven M.

    2012-11-01

    Dual orthogonal alignment of carbon nanotubes (CNTs) within the plane and perpendicular to a substrate is essential for many applications but difficult to obtain. Here, we demonstrate that it is possible using a combination of layer-by-layer deposition and ultrafast laser irradiation. Single-wall CNT-polymer composites preferentially aligned within the plane are irradiated with ultrafast laser pulses. After irradiation with distinct fluences at ambient conditions, morphology is seen where CNTs are formed into bundled CNTs with some orthogonal alignment. A model is presented to account for thermal expansion of the polymer and the formation of CNT bundles.

  6. Preparation of core-shell nanofibers with selectively localized CNTs from Shish Kebab-like hierarchical composite micelles.

    PubMed

    Liu, Chang-Lei; Wang, Mei-Jia; Wu, Gang; You, Jiao; Chen, Si-Chong; Liu, Ya; Wang, Yu-Zhong

    2014-08-01

    A novel and facile bottom-up strategy for preparing core-shell nanofibers with selectively localized carbon nanotubes is developed using hierarchical composite micelles of crystalline-coil copolymer and carbon nanotubes as the building blocks. An amphiphilic di-block copolymer of poly (p-dioxanone) (PPDO) and PEG (polyethylene glycol) functionalized with pyrene moieties at the chain ends of PPDO blocks (Py-PPDO-b-PEG) is designed for constructing composite micelles with multiwalled carbon nanotubes (MWCNTs). The self-assembly of Py-PPDO-b-PEG and MWCNTs is co-induced by the crystallization of PPDO blocks and the π-π stacking interactions between pyrene moieties and MWCNTs, resulting in composite micelles with "shish kebab"-like nanostructure. A mixture of composite micelles and polyvinyl alcohol (PVA) water solution is then used as the spinning solution for preparing electrospun nanofibers. The morphologies of the nanofibers with different composition are investigated by SEM and TEM. The results suggest that the MWCNTs selectively localized in the core of the nanofibers of MWCNTs/Py-PPDO-b-PEG/PVA. The alignment and interfusion of composite micelles during the formation of nanofibers may confine the carbon nanotubes in the hydrophobic core region. In contrast, the copolymer without pyrene moieties cannot form composite micelles, thus these nanofibers show selective localization of MWCNTs in the PVA shell region. PMID:25048154

  7. Imaging, Spectroscopic, Mechanical and Biocompatibility Studies of Electrospun Tecoflex(®) EG 80A Nanofibers and Composites Thereof Containing Multiwalled Carbon Nanotubes.

    PubMed

    Macossay, Javier; Sheikh, Faheem A; Cantu, Travis; Eubanks, Thomas M; Salinas, M Esther; Farhangi, Chakavak S; Ahmad, Hassan; Hassan, M Shamshi; Khil, Myung-Seob; Maffi, Shivani K; Kim, Hern; Bowlin, Gary L

    2014-12-01

    The present study discusses the design, development and characterization of electrospun Tecoflex(®) EG 80A class of polyurethane nanofibers and the incorporation of multiwalled carbon nanotubes (MWCNTs) to these materials. Scanning electron microscopy results confirmed the presence of polymer nanofibers, which showed a decrease in fiber diameter at 0.5% wt. and 1% wt. MWCNTs loadings, while transmission electron microscopy showed evidence of the MWCNTs embedded within the polymer matrix. The fourier transform infrared spectroscopy and Raman spectroscopy were used to elucidate the polymer-MWCNTs intermolecular interactions, indicating that the C-N and N-H bonds in polyurethanes are responsible for the interactions with MWCNTs. Furthermore, tensile testing indicated an increase in the Young's modulus of the nanofibers as the MWCNTs concentration was increased. Finally, NIH 3T3 fibroblasts were seeded on the obtained nanofibers, demonstrating cell biocompatibility and proliferation. Therefore, the results indicate the successful formation of polyurethane nanofibers with enhanced mechanical properties, and demonstrate their biocompatibility, suggesting their potential application in biomedical areas. PMID:25435600

  8. Imaging, spectroscopic, mechanical and biocompatibility studies of electrospun Tecoflex® EG 80A nanofibers and composites thereof containing multiwalled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Macossay, Javier; Sheikh, Faheem A.; Cantu, Travis; Eubanks, Thomas M.; Salinas, M. Esther; Farhangi, Chakavak S.; Ahmad, Hassan; Hassan, M. Shamshi; Khil, Myung-seob; Maffi, Shivani K.; Kim, Hern; Bowlin, Gary l.

    2014-12-01

    The present study discusses the design, development, and characterization of electrospun Tecoflex® EG 80A class of polyurethane nanofibers and the incorporation of multiwalled carbon nanotubes (MWCNTs) to these materials. Scanning electron microscopy results confirmed the presence of polymer nanofibers, which showed a decrease in fiber diameter at 0.5% wt. and 1% wt. MWCNTs loadings, while transmission electron microscopy showed evidence of the MWCNTs embedded within the polymer matrix. The Fourier transform infrared spectroscopy and Raman spectroscopy were used to elucidate the polymer-MWCNTs intermolecular interactions, indicating that the C-N and N-H bonds in polyurethanes are responsible for the interactions with MWCNTs. Furthermore, tensile testing indicated an increase in the Young's modulus of the nanofibers as the MWCNTs concentration was increased. Finally, NIH 3T3 fibroblasts were seeded on the obtained nanofibers, demonstrating cell biocompatibility and proliferation. Therefore, the results indicate the successful formation of polyurethane nanofibers with enhanced mechanical properties, and demonstrate their biocompatibility, suggesting their potential application in biomedical areas.

  9. Imaging, Spectroscopic, Mechanical and Biocompatibility Studies of Electrospun Tecoflex® EG 80A Nanofibers and Composites Thereof Containing Multiwalled Carbon Nanotubes

    PubMed Central

    Macossay, Javier; Sheikh, Faheem A.; Cantu, Travis; Eubanks, Thomas M.; Salinas, M. Esther; Farhangi, Chakavak S.; Ahmad, Hassan; Hassan, M. Shamshi; Khil, Myung-seob; Maffi, Shivani K.; Kim, Hern; Bowlin, Gary l.

    2014-01-01

    The present study discusses the design, development and characterization of electrospun Tecoflex® EG 80A class of polyurethane nanofibers and the incorporation of multiwalled carbon nanotubes (MWCNTs) to these materials. Scanning electron microscopy results confirmed the presence of polymer nanofibers, which showed a decrease in fiber diameter at 0.5% wt. and 1% wt. MWCNTs loadings, while transmission electron microscopy showed evidence of the MWCNTs embedded within the polymer matrix. The fourier transform infrared spectroscopy and Raman spectroscopy were used to elucidate the polymer-MWCNTs intermolecular interactions, indicating that the C-N and N-H bonds in polyurethanes are responsible for the interactions with MWCNTs. Furthermore, tensile testing indicated an increase in the Young’s modulus of the nanofibers as the MWCNTs concentration was increased. Finally, NIH 3T3 fibroblasts were seeded on the obtained nanofibers, demonstrating cell biocompatibility and proliferation. Therefore, the results indicate the successful formation of polyurethane nanofibers with enhanced mechanical properties, and demonstrate their biocompatibility, suggesting their potential application in biomedical areas. PMID:25435600

  10. Carbon/SnO2/carbon core/shell/shell hybrid nanofibers: tailored nanostructure for the anode of lithium ion batteries with high reversibility and rate capacity

    NASA Astrophysics Data System (ADS)

    Kong, Junhua; Liu, Zhaolin; Yang, Zhengchun; Tan, Hui Ru; Xiong, Shanxin; Wong, Siew Yee; Li, Xu; Lu, Xuehong

    2012-01-01

    A carbon/SnO2/carbon core/shell/shell hybrid nanofibrous mat was successfully prepared via single-spinneret electrospinning followed by carbonization and hydrothermal treatment. The morphology and structure of carbon/SnO2/carbon hybrid nanofibers were characterized by field-emission scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, wide-angle X-ray diffraction and X-ray photoelectron spectroscopy, and their electrochemical properties were studied as an anode in lithium ion batteries (LIBs). It is shown that the designed hybrid nanofibrous mat exhibits excellent electrochemical properties, including high reversible capacity with high columbic efficiency and impressive rate capacity. The greatly enhanced electrochemical performance is mainly due to the morphological stability and reduced diffusion resistance, which are induced by both the carbon core and deposited carbon skin. Furthermore, the embedded and de-aggregated SnO2 nanoparticles in the carbon phase, which are less than 10 nm in size, provide large numbers of reaction sites for lithium ions and ensure complete alloying with them.A carbon/SnO2/carbon core/shell/shell hybrid nanofibrous mat was successfully prepared via single-spinneret electrospinning followed by carbonization and hydrothermal treatment. The morphology and structure of carbon/SnO2/carbon hybrid nanofibers were characterized by field-emission scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, wide-angle X-ray diffraction and X-ray photoelectron spectroscopy, and their electrochemical properties were studied as an anode in lithium ion batteries (LIBs). It is shown that the designed hybrid nanofibrous mat exhibits excellent electrochemical properties, including high reversible capacity with high columbic efficiency and impressive rate capacity. The greatly enhanced electrochemical performance is mainly due to the morphological stability and reduced diffusion

  11. Hydrogen evolution on hydrophobic aligned carbon nanotube arrays.

    PubMed

    Misra, Abha; Giri, Jyotsnendu; Daraio, Chiara

    2009-12-22

    We investigate for the first time hydrophobic carbon nanotube-based electrochemical cells as an alternative solution to hydrogen sorting. We show that the electrically conducting surface of the nanotube arrays can be used as a cathode for hydrogen generation and absorption by electrolyzing water. We support our findings with Raman and gas chromatography measurements. These results suggest that carbon nanotube forests, presenting a unique combination of hydrophobicity and conductivity, are suitable for application in fuel cells and microelectromechanical devices.

  12. Carbon-Confined SnO2-Electrodeposited Porous Carbon Nanofiber Composite as High-Capacity Sodium-Ion Battery Anode Material.

    PubMed

    Dirican, Mahmut; Lu, Yao; Ge, Yeqian; Yildiz, Ozkan; Zhang, Xiangwu

    2015-08-26

    Sodium resources are inexpensive and abundant, and hence, sodium-ion batteries are promising alternative to lithium-ion batteries. However, lower energy density and poor cycling stability of current sodium-ion batteries prevent their practical implementation for future smart power grid and stationary storage applications. Tin oxides (SnO2) can be potentially used as a high-capacity anode material for future sodium-ion batteries, and they have the advantages of high sodium storage capacity, high abundance, and low toxicity. However, SnO2-based anodes still cannot be used in practical sodium-ion batteries because they experience large volume changes during repetitive charge and discharge cycles. Such large volume changes lead to severe pulverization of the active material and loss of electrical contact between the SnO2 and carbon conductor, which in turn result in rapid capacity loss during cycling. Here, we introduce a new amorphous carbon-coated SnO2-electrodeposited porous carbon nanofiber (PCNF@SnO2@C) composite that not only has high sodium storage capability, but also maintains its structural integrity while ongoing repetitive cycles. Electrochemical results revealed that this SnO2-containing nanofiber composite anode had excellent electrochemical performance including high-capacity (374 mAh g(-1)), good capacity retention (82.7%), and large Coulombic efficiency (98.9% after 100th cycle). PMID:26252051

  13. Carbon-Confined SnO2-Electrodeposited Porous Carbon Nanofiber Composite as High-Capacity Sodium-Ion Battery Anode Material.

    PubMed

    Dirican, Mahmut; Lu, Yao; Ge, Yeqian; Yildiz, Ozkan; Zhang, Xiangwu

    2015-08-26

    Sodium resources are inexpensive and abundant, and hence, sodium-ion batteries are promising alternative to lithium-ion batteries. However, lower energy density and poor cycling stability of current sodium-ion batteries prevent their practical implementation for future smart power grid and stationary storage applications. Tin oxides (SnO2) can be potentially used as a high-capacity anode material for future sodium-ion batteries, and they have the advantages of high sodium storage capacity, high abundance, and low toxicity. However, SnO2-based anodes still cannot be used in practical sodium-ion batteries because they experience large volume changes during repetitive charge and discharge cycles. Such large volume changes lead to severe pulverization of the active material and loss of electrical contact between the SnO2 and carbon conductor, which in turn result in rapid capacity loss during cycling. Here, we introduce a new amorphous carbon-coated SnO2-electrodeposited porous carbon nanofiber (PCNF@SnO2@C) composite that not only has high sodium storage capability, but also maintains its structural integrity while ongoing repetitive cycles. Electrochemical results revealed that this SnO2-containing nanofiber composite anode had excellent electrochemical performance including high-capacity (374 mAh g(-1)), good capacity retention (82.7%), and large Coulombic efficiency (98.9% after 100th cycle).

  14. Photocatalysis of sub-ppm limonene over multiwalled carbon nanotubes/titania composite nanofiber under visible-light irradiation.

    PubMed

    Jo, Wan-Kuen; Kang, Hyun-Jung

    2015-01-01

    This study was conducted under visible-light exposure to investigate the photocatalytic characteristics of a multiwalled carbon nanotube/titania (TiO2) composite