WorldWideScience
1

Effect of carbon nano-fibers (CNFs) content on thermal and mechanical properties of CNFs/SiC nano-composites  

Energy Technology Data Exchange (ETDEWEB)

Carbon nano-fibers dispersed {beta}-SiC (CNFs/SiC) nano-composites were prepared by hot-pressing via a transient eutectic phase route at 1900 C for 1 h under 20 MPa in Ar. The effects of additional CNFs content between 1 and 10 wt.% were investigated, based on densification, microstructure, thermal and mechanical properties. The CNFs/SiC nano-composites by the CNFs contents below 5 wt.% exhibited excellent relative densities over 98% with well dispersed CNFs. However, the CNFs/SiC nano-composites containing the CNFs of 10 wt.% possessed a relative density of 92%, accompanying CNFs agglomerates and many pores located inside the agglomerates. The three point bending strength gradually decreased with the increase of CNFs content, but the indentation fracture toughness increased to 5.7 MPa m{sup 1/2} by the CNFs content of 5 wt.% The thermal conductivity was enhanced with the increase of CNFs content and represented a maximum value of 80 W/mK at the CNFs content of 5 wt.%. (authors)

Shimoda, Kazuya [CEA Saclay, DEN DANS DMN SRMA, F-91191 Gif Sur Yvette (France); Shimoda, Kazuya; Hinoki, Tatsuya; Kohyama, Akira [Kyoto Univ, Inst Adv Energy, Kyoto 6110011 (Japan); Kohyama, Akira [Muroran Inst Technol, Dept Mat Sci and Engn, Muroran, Hokkaido 0508585 (Japan)

2010-07-01

2

Effect of carbon nano-fibers (CNFs) content on thermal and mechanical properties of CNFs/SiC nano-composites  

International Nuclear Information System (INIS)

Carbon nano-fibers dispersed ?-SiC (CNFs/SiC) nano-composites were prepared by hot-pressing via a transient eutectic phase route at 1900 C for 1 h under 20 MPa in Ar. The effects of additional CNFs content between 1 and 10 wt.% were investigated, based on densification, microstructure, thermal and mechanical properties. The CNFs/SiC nano-composites by the CNFs contents below 5 wt.% exhibited excellent relative densities over 98% with well dispersed CNFs. However, the CNFs/SiC nano-composites containing the CNFs of 10 wt.% possessed a relative density of 92%, accompanying CNFs agglomerates and many pores located inside the agglomerates. The three point bending strength gradually decreased with the increase of CNFs content, but the indentation fracture toughness increased to 5.7 MPa m1/2 by the CNFs content of 5 wt.% The thermal conductivity was enhanced with the increase of CNFs content and represented a maximum value of 80 W/mK at the CNFs content of 5 wt.%. (authors)

3

Laccase Biosensor Based on Electrospun Copper/Carbon Composite Nanofibers for Catechol Detection  

OpenAIRE

The study compared the biosensing properties of laccase biosensors based on carbon nanofibers (CNFs) and copper/carbon composite nanofibers (Cu/CNFs). The two kinds of nanofibers were prepared by electrospinning and carbonization under the same conditions. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy were employed to investigate the morphologies and structures of CNFs and Cu/CNFs. The amperometric results indicated that the Cu/CNFs/laccase(Lac)/Nafion/gla...

Jiapeng Fu; Hui Qiao; Dawei Li; Lei Luo; Ke Chen; Qufu Wei

2014-01-01

4

Optical properties of carbon nanofiber photonic crystals.  

Science.gov (United States)

Carbon nanofibers (CNFs) are used as components of planar photonic crystals. Square and rectangular lattices and random patterns of vertically aligned CNFs were fabricated and their properties studied using ellipsometry. We show that detailed information such as symmetry directions and the band structure of these novel materials can be extracted from considerations of the polarization state in the specular beam. The refractive index of the individual nanofibers was found to be n(CNF) = 4.1. PMID:20972321

Rehammar, R; Magnusson, R; Fernandez-Dominguez, A I; Arwin, H; Kinaret, J M; Maier, S A; Campbell, E E B

2010-11-19

5

Optical properties of carbon nanofiber photonic crystals  

Energy Technology Data Exchange (ETDEWEB)

Carbon nanofibers (CNFs) are used as components of planar photonic crystals. Square and rectangular lattices and random patterns of vertically aligned CNFs were fabricated and their properties studied using ellipsometry. We show that detailed information such as symmetry directions and the band structure of these novel materials can be extracted from considerations of the polarization state in the specular beam. The refractive index of the individual nanofibers was found to be n{sub CNF} = 4.1.

Rehammar, R; Kinaret, J M [Department of Applied Physics, Chalmers University of Technology, Gothenburg SE-412 96 (Sweden); Magnusson, R; Arwin, H [Department of Physics, Chemistry and Biology, Linkoeping University, Linkoeping SE-581 83 (Sweden); Fernandez-Dominguez, A I; Maier, S A [Department of Physics, Imperial College London, London SW7 2AZ (United Kingdom); Campbell, E E B, E-mail: robert.rehammar@chalmers.se [EaStCHEM, School of Chemistry, Edinburgh University, Edinburgh EH9 3JJ (United Kingdom)

2010-11-19

6

Optical properties of carbon nanofiber photonic crystals  

OpenAIRE

Carbon nanofibers (CNFs) are used as components of planar photonic crystals. Square and rectangular lattices and random patterns of vertically aligned CNFs were fabricated and their properties studied using ellipsometry. We show that detailed information such as symmetry directions and the band structure of these novel materials can be extracted from considerations of the polarization state in the specular beam. The refractive index of the individual nanofibers was found to be n(CNF) = 4.1.

Rehammar, R.; Magnusson, Roger; Fernandez-dominguez, A. I.; Arwin, Hans; Kinaret, J. M.; Maier, S. A.; Campbell, E. E. B.

2010-01-01

7

Optical properties of carbon nanofiber photonic crystals  

International Nuclear Information System (INIS)

Carbon nanofibers (CNFs) are used as components of planar photonic crystals. Square and rectangular lattices and random patterns of vertically aligned CNFs were fabricated and their properties studied using ellipsometry. We show that detailed information such as symmetry directions and the band structure of these novel materials can be extracted from considerations of the polarization state in the specular beam. The refractive index of the individual nanofibers was found to be nCNF = 4.1.

8

Functionalized carbon nanotubes and nanofibers for biosensing applications  

OpenAIRE

This review summarizes recent advances in electrochemical biosensors based on carbon nanotubes (CNTs) and carbon nanofibers (CNFs) with an emphasis on applications of CNTs. CNTs and CNFs have unique electric, electrocatalytic and mechanical properties, which make them efficient materials for developing electrochemical biosensors.

Wang, Jun; Lin, Yuehe

2008-01-01

9

Preparation and Catalytic Activity of Carbon Nanofibers Anchored Metallophthalocyanine in Decomposing Acid Orange 7  

OpenAIRE

Amine-modified CNFs (AN-CNFs) were first obtained through the Billups reaction from carbon nanofibers (CNFs), and were used as supports of cobalt tetracarboxylphthalocyanine (CoTCPc) for the catalytic oxidation of Acid Orange 7 (AO7) in the CoTCPc-AN-CNFs/H2O2 system. CNFs, AN-CNFs and CoTCPc-AN-CNFs were characterized by X-ray photoelectron spectroscopy, thermogravimetric analysis, transmission electron microscopy and N2 adsorption-desorption. The oxidative decoloration of AO7 in the presenc...

Baocheng Zhou; Wenxing Chen

2014-01-01

10

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

OpenAIRE

Carbon nanofibers (CNFs) randomly embedded in poly (lactic-co-glycolic-acid) (PLGA) composites have recently been shown to promote cardiomyocyte growth when compared with conventional PLGA without CNFs. It was shown then that PLGA:CNF composites were conductive and that conductivity increased as greater amounts of CNFs were added to pure PLGA. Moreover, tensile tests showed that addition of CNFs increased the tensile strength of the PLGA composite to mimic that of natural heart tissue. Most i...

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

2014-01-01

11

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

International Nuclear Information System (INIS)

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.

12

Modification of powdered activated carbon for the production of carbon nano fibers (CNFs)  

International Nuclear Information System (INIS)

Full text: In the present work, powdered activated carbon (PAC) was modified and used for the production of carbon nano fibers (CNFs). The modification of PAC was done by the impregnation of nickel on the surface of the activated carbon using the wet impregnation method. Variable weight percentage ratios of the catalyst (nickel) ratio were used. The nano fibers were synthesized on the surface of modified PAC by using the Chemical Vapor Deposition (CVD) method at a temperature of ?680 degree Celsius for one hour in the presence of acetylene as a carbon source. FESEM, TEM, and TGA were used for the characterization of the product. (author)

13

The effect of embedded carbon nanotubes on the morphological evolution during the carbonization of poly(acrylonitrile) nanofibers  

International Nuclear Information System (INIS)

Hybrid nanofibers with different concentrations of multi-walled carbon nanotubes (MWCNTs) in polyacrylonitrile (PAN) were fabricated using the electrospinning technique and subsequently carbonized. The morphology of the fabricated carbon nanofibers (CNFs) at different stages of the carbonization process was characterized by transmission electron microscopy and Raman spectroscopy. The polycrystalline nature of the CNFs was shown, with increasing content of ordered crystalline regions having enhanced orientation with increasing content of MWCNTs. The results indicate that embedded MWCNTs in the PAN nanofibers nucleate the growth of carbon crystals during PAN carbonization

14

Use of facile mechanochemical method to functionalize carbon nanofibers with nanostructured polyaniline and their electrochemical capacitance  

OpenAIRE

A facile approach to functionalize carbon nanofibers [CNFs] with nanostructured polyaniline was developed via in situ mechanochemical polymerization of polyaniline in the presence of chemically treated CNFs. The nanostructured polyaniline grafting on the CNF was mainly in a form of branched nanofibers as well as rough nanolayers. The good dispersibility and processability of the hybrid nanocomposite could be attributed to its overall nanostructure which enhanced its accessibility to the elect...

Du, Xusheng; Liu, Hong-yuan; Cai, Guipeng; Mai, Yiu-wing; Baji, Avinash

2012-01-01

15

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

Science.gov (United States)

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.

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

2012-10-01

16

Electrospun carbon nanofibers decorated with Ag-Pt bimetallic nanoparticles for selective detection of dopamine.  

Science.gov (United States)

Electrospun nanoporous carbon nanofibers (pCNFs) decorated with Ag-Pt bimetallic nanoparticles have been successfully synthesized by combining template carbonization and seed-growth reduction approach. Porous-structured polyacrylonitrile (PAN) nanofibers (pPAN) were first prepared by electrospinning PAN/polyvinylpyrrolidone (PVP) blend solution, followed by subsequent water extraction and heat treatment to obtain pCNFs. Ag-Pt/pCNFs were then obtained by using pCNFs as support for bimetallic nanoparticle loading. Thus, the obtained Ag-Pt/pCNFs were used to modify glassy carbon electrode (GCE) for selective detection of dopamine (DA) in the presence of uric acid (UA) and ascorbic acid (AA). This novel sensor exhibits fast amperometric response and high sensitivity toward DA with a wide linear concentration range of 10-500 ?M and a low detection limit of 0.11 ?M (S/N = 3), wherein the interference of UA and AA can be eliminated effectively. PMID:25029608

Huang, Yunpeng; Miao, Yue-E; Ji, Shanshan; Tjiu, Weng Weei; Liu, Tianxi

2014-08-13

17

Electrospun MgO-loaded carbon nanofibers: Enhanced field electron emission from the fibers in vacuum  

Science.gov (United States)

MgO-loaded electrospun carbon nanofibers (MgO/CNFs) were prepared by electrospinning a magnesium acetate containing polyacrylonitrile composite followed by stabilization under an air atmosphere at 280 °C and carbonization under a nitrogen atmosphere at 800 °C. In addition to investigating the morphological and material features of the nanofibers, the field emission (FE) characteristics of the carbonized NFs (CNFs), performed in an ultra-high vacuum chamber utilizing scanning electron microscopy (SEM), were determined. The results of the investigation show that the MgO/CNFs (195.5% enhancement) display enhanced field electron emission as compared to that of pure CNFs as a result of the existence of a MgO phase. Consequently, it appears that the graphitic structures of CNFs can be tuned, a finding that has significance in studies aimed at developing new field electron emission devices.

Aykut, Yakup

2013-02-01

18

Carbon nanotubes nucleate the growth of graphitic layers during carbonization.of electrospun poly(acrylonitrile) nanofibers.  

Science.gov (United States)

Hybrid nanofibers with varying concentration of multiwalled carbon nanotubes (MWCNTs) in polyacrylonitrile (PAN) were fabricated using the electrospinning technique and subsequently carbonized. The morphology of the fabricated carbon nanofibers (CNFs) at different stages of the carbonization process was characterized by high-resolution transmission electron microscopy (HRTEM) and Raman spectroscopy. In-situ morphological changes during heating were followed by HRTEM using a heated stage. The polycrystalline nature of the CNFs was shown, with increasing content of ordered crystalline regions having enhanced orientation with increasing content of MWCNTs. The results indicate that MWCNTs embedded within the PAN nanofibers nucleate the growth of graphitic layers during PAN carbonization.

Prilutsky, Sabina; Cohen, Yachin; Zussman, Eyal

2009-03-01

19

Carbon nanotubes grown on electrospun polyacrylonitrile-based carbon nanofibers via chemical vapor deposition  

Science.gov (United States)

Carbon nanotubes (CNTs) grown on electrospun polyacrylonitrile-based carbon nanofibers (CNFs) via chemical vapor deposition were studied in this paper. Analyses of Raman spectra and X-ray diffraction patterns revealed that incorporation of CNTs could improve the crystalline and structure integrity of the obtained CNFs/CNTs composite. About 7.4 wt% of CNTs were grown on the electrospun CNFs confirmed by thermal gravimetric analysis. The electrochemical results showed that the surface activity and the cycle retention of the CNFs/CNTs composite were enhanced due to its three-dimensional nanostructure, enhanced pore distribution, and good conductivity. The CNFs/CNTs composite offers a great potential for high-performance lithium-ion batteries as the electrode.

Zhao, Liang; Li, Yu; Zhao, Yunhui; Feng, Yiyu; Feng, Wei; Yuan, Xiaoyan

2012-03-01

20

Enhanced field electron emission from electrospun co-loaded activated porous carbon nanofibers.  

Science.gov (United States)

Highly porous, Co-loaded, activated carbon nanofibers (Co/AP-CNFs) were prepared by electrospinning a CoCl2-containing polyacrylonitrile composite, followed by thermal treatment processes under air and inert atmospheres. Observations show that carbon nanofibers (CNFs) generated in this fashion have a dramatically large porosity that results in an increase in the specific surface area from 193.5 to 417.3 m(2) g(-1)as a consequence of the presence of CoCl2 in PAN/CoCl2 precursor nanofibers. The nanofibers have a larger graphitic structure, which is enhanced by the addition of the cobaltous phase during the carbonization process. Besides evaluating the morphological and material features of the fibers, we have also carried out a field electron emission investigation of the fibers. The results show that an enhancement in the field electron emission of Co/AP-CNFs occurs as a result of the existence of cobalt in the carbon nanofibers, which results in a greater graphitization, increased specific total surface area and porosity of the carbon nanofibers. Overall, the Co/AP-CNFs are prepared in a facile manner and exhibit an enhanced field electron emission (54.79%) compared to that of pure CNFs, a feature that suggests their potential application to field electron emission devices. PMID:22720751

Aykut, Yakup

2012-07-25

21

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

Science.gov (United States)

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

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

2015-03-01

22

Growth of carbon nanofibers on metal-catalyzed substrates by pulsed laser ablation of graphite  

International Nuclear Information System (INIS)

Carbon nanofibers (CNFs) were grown on metal-catalyzed Si substrates by pulsed laser ablation of graphite. Metal catalysts, Ni, NiCo, Pd and PdNi, were respectively deposited on Si substrates with a SiO2 layer of 200-nm thickness by a dip coat method, and the substrates placed in a laser oven apparatus. By pulsed laser ablation of graphite for 2 hours, CNFs were grown at oven temperatures ? 1000deg. C. Diameters of grown CNFs were about 20-30 nm by scanning electron microscopy, and increased with oven temperature. The difference of CNF growth by the catalysts was shown. Pd-contained catalysts grew thicker CNFs than the other catalysts; while PdNi and NiCo yielded a higher number density of CNFs than the other catalysts. CNF diameter and length changed according to the substrate position from the target. We also discussed the growth mechanism of CNFs with this method

23

High performance supercapacitor based on Ni3S2/carbon nanofibers and carbon nanofibers electrodes derived from bacterial cellulose  

Science.gov (United States)

The Ni3S2 nanoparticles have been successfully grown on the carbon nanofibers (CNFs) derived from bacterial cellulose via a hydrothermal method, which the as-prepared composite exhibited high specific capacitance (883 F g-1 at 2 A g-1), much more than CNFs (108 F g-1 at 2 A g-1), and good cycle stability. The asymmetric supercapacitor was designed to contain the CNFs coated Ni3S2 nanoparticles (Ni3S2/CNFs) as positive electrode and CNFs as negative electrode in 2 M KOH electrolyte. Due to the synergistic effects of the two electrodes, asymmetric cell showed superior electrochemical performances. The optimized asymmetric supercapacitor gave a operating potential of 1.7 V in 2 M KOH aqueous solution, exhibiting a high specific capacitance of 56.6 F g-1 at 1 A g-1 and considerably high energy density of 25.8 Wh kg-1 at a power density of 425 W kg-1. Meanwhile, Ni3S2/CNFs//CNFs asymmetric supercapacitor showed excellent cycling stability with 97% specific capacitance retained after 2500 cycles.

Yu, Wendan; Lin, Worong; Shao, Xiaofeng; Hu, Zhaoxia; Li, Ruchun; Yuan, Dingsheng

2014-12-01

24

In2S3/carbon nanofibers/Au ternary synergetic system: Hierarchical assembly and enhanced visible-light photocatalytic activity.  

Science.gov (United States)

In this paper, carbon nanofibers (CNFs) were successfully synthesized by electrospinning technique. Next, Au nanoparticles (NPs) were assembled on the electrospun CNFs through in situ reduction method. By using the obtained Au NPs modified CNFs (CNFs/Au) as hard template, the In2S3/CNFs/Au composites were synthesized through hydrothermal technique. The results showed that the super long one-dimensional (1D) CNFs (about 306nm in average diameter) were well connected to form a nanofibrous network; and, the Au NPs with 18nm in average diameter and In2S3 nanosheets with 5-10nm in thickness were uniformly grown onto the surface of CNFs. Photocatalytic studies revealed that the In2S3/CNFs/Au composites exhibited highest visible-light photocatalytic activities for the degradation of Rhodamine B (RB) compared with pure In2S3 and In2S3/CNFs. The enhanced photocatalytic activity might arise from the high separation efficiency of photogenerated electron-hole pairs based on the positive synergetic effect between In2S3, CNFs and Au components in this ternary photocatalytic system. Meanwhile, the In2S3/CNFs/Au composites with hierarchical structure possess a strong adsorption ability towards organic dyes, which also contributed to the enhancement of photocatalytic activity. Moreover, the In2S3/CNFs/Au composites could be recycled easily by sedimentation due to their nanofibrous network structure. PMID:25464301

Zhang, Xin; Shao, Changlu; Li, Xinghua; Lu, Na; Wang, Kexin; Miao, Fujun; Liu, Yichun

2015-02-11

25

A catechol biosensor based on electrospun carbon nanofibers  

Science.gov (United States)

Summary Carbon nanofibers (CNFs) were prepared by combining electrospinning with a high-temperature carbonization technique. And a polyphenol biosensor was fabricated by blending the obtained CNFs with laccase and Nafion. Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscope (FE-SEM) were, respectively, employed to investigate the structures and morphologies of the CNFs and of the mixtures. Cyclic voltammetry and chronoamperometry were employed to study the electrocatalysis of the catechol biosensor. The results indicated that the sensitivity of the biosensor was 41 µA·mM?1, the detection limit was 0.63 µM, the linear range was 1–1310 µM and the response time was within 2 seconds, which excelled most other laccase-based biosensor reported. Furthermore, the biosensor showed good repeatability, reproducibility, stability and tolerance to interferences. This novel biosensor also demonstrated its promising application in detecting catechol in real water samples. PMID:24778958

Li, Dawei; Pang, Zengyuan; Chen, Xiaodong; Luo, Lei; Cai, Yibing

2014-01-01

26

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

OpenAIRE

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 recog...

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

2014-01-01

27

Graphene nanoribbons hybridized carbon nanofibers: remarkably enhanced graphitization and conductivity, and excellent performance as support material for fuel cell catalysts  

Science.gov (United States)

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 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. Electronic supplementary information (ESI) available: Experimental Section; IR; Raman spectra. See DOI: 10.1039/c3nr04663j

Wang, Chaonan; Gao, Hongrong; Li, Hong; Zhang, Yiren; Huang, Bowen; Zhao, Junhong; Zhu, Yan; Yuan, Wang Zhang; Zhang, Yongming

2014-01-01

28

Acetylene decomposition to helical carbon nanofibers over supported copper catalysts  

International Nuclear Information System (INIS)

The helical carbon nanofibers (CNFs), synthesized at relatively low temperatures (lower than 250 deg. C) by using Cu as a catalyst, SiO2, TiO2, Al2O3, MgO as supports and acetylene as gas source, has been investigated. The products were characterized by field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD). The morphologies of obtained products influenced by the types of supports and weight ratios (Cu/support = 1:1, 1:5, and 1:10) were discussed. The average diameter of the helical CNFs was about 80 nm, and these CNFs had the same coil pitch, and coil diameter

29

Fabrication of a carbon nanofiber sheet as a micro-porous layer for proton exchange membrane fuel cells  

Energy Technology Data Exchange (ETDEWEB)

A carbon nanofiber sheet (CNFS) has been prepared by electrospinning, stabilisation and subsequent carbonisation processes. Imaging with scanning electron microscope (SEM) indicates that the CNFS is formed by nonwoven nanofibers with diameters between 400 and 700 nm. The CNFS, with its three-dimensional pores, shows excellent electrical conductivity and hydrophobicity. In addition, it is found that the CNFS can be successfully applied as a micro-porous layer (MPL) in the cathode gas diffusion layer (GDL) of a proton exchange membrane fuel cell (PEMFC). The GDL with the CNFS as a MPL has higher gas permeability than a conventional GDL. Moreover, the resultant cathode GDL exhibits excellent fuel cell performance with a higher peak power density than that of a cathode GDL fabricated with a conventional MPL under the same test condition. (author)

Duan, Qiongjuan; Wang, Jiong; Lu, Yonggen [College of Material Science and Engineering, Donghua University, Shanghai 201620 (China); Wang, Biao; Wang, Huaping [State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University, Shanghai 201620 (China); College of Material Science and Engineering, Donghua University, Shanghai 201620 (China)

2010-12-15

30

Electrical properties of carbon nanofiber reinforced multiscale polymer composites  

International Nuclear Information System (INIS)

Carbon nanofiber (CNF) reinforced epoxy matrix nanocomposites and CNF reinforced glass hollow particle filled syntactic foams are studied for electrical properties. The effect of CNF weight fraction, hollow particle volume fraction, and hollow particle wall thickness on impedance and dielectric constant are characterized. The results show that the impedance decreases and the dielectric constant increases with increasing CNF content in the composites. Nanocomposites containing 10 wt.% CNFs showed significantly higher dielectric constant because of the presence of a continuous network of CNFs in the composite. CNF reinforced syntactic foams showed higher dielectric constant than the neat resin. The CNF content had a more prominent effect on the dielectric constant than the glass hollow particle volume fraction and wall thickness. The Maxwell–Garnett and the Jayasundere–Smith models are modified to include the effect of hollow particle wall thickness and obtain predictions of dielectric constants of syntactic foams. The semi-empirical predictions obtained from Maxwell–Garnett models are closer to the experimental values. Lightweight syntactic foams, tailored for electrical properties, can be useful in electronic packaging applications. - Highlights: • Using carbon nanofibers (CNFs) and glass hollow particles in multiphase composites. • The dielectric constant (?) of composites increases with CNF content. • Interconnected network of CNFs at high volume fraction exponentially increases ?. • Two theoretical models accurately predicted data trends of CNF/syntactic foams

31

Carbon nanofibers grown on activated carbon fiber fabrics as electrode of supercapacitors  

Science.gov (United States)

Carbon nanofibers (CNFs) were grown directly on activated carbon fiber fabric (ACFF), which was then used as the electrode of supercapacitors. Cyclic voltammetry and ac impedance were used to characterize the electrochemical properties of ACFF and CNF/ACFF electrodes in both aqueous and organic electrolytes. ACFF electrodes show higher specific capacitance than CNF/ACFF electrodes due to larger specific surface area. However, the spaces formed between the CNFs in the CNF/ACFF electrodes are more easily accessed than the slit-type pores of ACFF, and much higher electrical-double layer capacitance was obtained for CNF/ACFF electrodes.

Ko, Tse-Hao; Hung, Kai-Hsuan; Tzeng, Shinn-Shyong; Shen, Jin-Wei; Hung, Cheng-Hsin

2007-12-01

32

Carbon nanofibers grown on activated carbon fiber fabrics as electrode of supercapacitors  

International Nuclear Information System (INIS)

Carbon nanofibers (CNFs) were grown directly on activated carbon fiber fabric (ACFF), which was then used as the electrode of supercapacitors. Cyclic voltammetry and ac impedance were used to characterize the electrochemical properties of ACFF and CNF/ACFF electrodes in both aqueous and organic electrolytes. ACFF electrodes show higher specific capacitance than CNF/ACFF electrodes due to larger specific surface area. However, the spaces formed between the CNFs in the CNF/ACFF electrodes are more easily accessed than the slit-type pores of ACFF, and much higher electrical-double layer capacitance was obtained for CNF/ACFF electrodes

33

Fabrication and electron field-emission of carbon nanofibers grown on silicon nanoporous pillar array  

International Nuclear Information System (INIS)

Highlights: ? Carbon nanofibers were grown on silicon nanoporous pillar array by a CVD method.? Low turn-on field, high density and stable FE current were obtained in CNTs/Si-NPA.? Defects in CNTs and Si array substrate contributes the excellent FE property. - Abstract: Random orientation carbon nanofibers (CNFs) were grown on silicon nanoporous pillar array (Si-NPA) by thermal chemical vapor deposition (CVD) method with acetylene (C2H2) as carbon precursor and Ni as the catalyst. The synthesized CNFs were mainly composed of amorphous carbon and disordered graphite layers with a core–shell like structure. And, the tangled CNFs and the regular silicon-pillar array formed a nanometer-micron hierarchy structure. The electron field-emission (FE) property of CNFs/Si-NPA was measured and low turn-on field, high-density and stable FE current, high enhancement factor were obtained. The outstanding FE performance of the CNFs/Si-NPA emitters was attributed to the random orientation and defects of CNFs, the undulate surface of the Si-NPA substrate.

34

Fabrication and electron field-emission of carbon nanofibers grown on silicon nanoporous pillar array  

Energy Technology Data Exchange (ETDEWEB)

Highlights: Black-Right-Pointing-Pointer Carbon nanofibers were grown on silicon nanoporous pillar array by a CVD method. Black-Right-Pointing-Pointer Low turn-on field, high density and stable FE current were obtained in CNTs/Si-NPA. Black-Right-Pointing-Pointer Defects in CNTs and Si array substrate contributes the excellent FE property. - Abstract: Random orientation carbon nanofibers (CNFs) were grown on silicon nanoporous pillar array (Si-NPA) by thermal chemical vapor deposition (CVD) method with acetylene (C{sub 2}H{sub 2}) as carbon precursor and Ni as the catalyst. The synthesized CNFs were mainly composed of amorphous carbon and disordered graphite layers with a core-shell like structure. And, the tangled CNFs and the regular silicon-pillar array formed a nanometer-micron hierarchy structure. The electron field-emission (FE) property of CNFs/Si-NPA was measured and low turn-on field, high-density and stable FE current, high enhancement factor were obtained. The outstanding FE performance of the CNFs/Si-NPA emitters was attributed to the random orientation and defects of CNFs, the undulate surface of the Si-NPA substrate.

Wang Haiyan, E-mail: wanghaiyan@zzuli.edu.cn [Department of Technological Physics, Zhengzhou University of Light Industry, Zhengzhou 450002 (China); Wang Yongqiang; Xue Renzhong [Department of Technological Physics, Zhengzhou University of Light Industry, Zhengzhou 450002 (China); Kang Liping [Department of Technological Physics, Zhengzhou University of Light Industry, Zhengzhou 450002 (China); Department of Physics and Laboratory of Materials Physics, Zhengzhou University, Zhengzhou 450052 (China); Li Xinjian [Department of Physics and Laboratory of Materials Physics, Zhengzhou University, Zhengzhou 450052 (China)

2012-11-15

35

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

Science.gov (United States)

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

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

2013-03-01

36

Structure, mechanical properties and friction behavior of UHMWPE/HDPE/carbon nanofibers  

International Nuclear Information System (INIS)

Effects of untreated and pretreated carbon nanofibers (CNFs) on the crystallization behavior, friction behavior, and mechanical properties of ultra high molecular weight polyethylene (UHMWPE)/high density polyethylene (HDPE) nanocomposites prepared by a twin-screw extrusion were studied. The differential scanning calorimetry and wide angle X-ray diffraction measurements indicated that the addition of CNFs impacted the temperature of crystallization, but had no significant effects on the crystalline structure of the UHMWPE/HDPE blend. The degree of crystallinity, and the tensile strength and modulus of the UHMWPE/HDPE systems exhibited an increasing trend initially with addition of CNFs, followed by a decrease at higher contents. With the increase of untreated CNF content, the friction coefficient of UHMWPE/HDPE was decreasing and displayed less change in the process of friction. The microstructure features on the fracture surfaces and friction surfaces of the polymer blend and the nanocomposites were analyzed in detail by scanning electron microscope observations. The degree of crystallinity of the nanocomposites with the pretreated CNFs exhibited a decrease due to the better interface adhesion compared to that in the nanocomposites with the same loading untreated CNFs. The enhancement in tensile strength of nanocomposites containing 0.5 wt% treated CNFs was four times higher (32%) than that of the nanocomposites containing untreated CNFs (8%) over that of the pure potreated CNFs (8%) over that of the pure polymer

37

Formation of positronium in cup-stacked carbon nanofibers  

Energy Technology Data Exchange (ETDEWEB)

The positron-lifetime spectrum for cup-stacked carbon nanofibers (CNFs) is composed of three components: 0.125 ns (fixed) (6%), 0.345 ns (75%), 1.21 ns (19%). The longest-lived component assigned to ortho-positronium (o-Ps) verifies a prominent yield of o-Ps, which is in contrast with the fact that no o-Ps is detected for uncapped cylindrical multi-walled carbon nanotubes. CNFs heat-treated to 1073 K in vacuo showed a positron-lifetime spectrum the same as that of untreated CNFs, which demonstrates that the thermal detachment of some functional groups from the surface of the CNFs does not change the Ps yield. The yield is found almost independent of temperature between 10 and 280 K. A single CNF, ca. 50 nm in outer diameter, observed by transmission electron-microscopy, comprises stacked cups of 9{proportional_to}12 truncated conical graphene sheets at ca. 20 with respect to the fiber axis, so that all edges of graphene sheets are found on the zigzag outer- as well as inner-surfaces of the fiber. The Raman spectrum for CNFs exhibits a band of a disorder-induced mode at 1349 cm{sup -1} (D-band) and a band of the E{sub 2g2} in-plane mode at 1577 cm{sup -1} (G-band). The intensity-ratios of a D-band to a G-band are 0.17, 0.25 and 0 for a mat of CNFs, the edge plane and the basal plane of a highly oriented pyrolitic graphite block, respectively. For graphite materials, Ps is formed from the positrons trapped in the defects originating from edges of graphene sheets. (orig.)

Murakami, H. [Dept. of Physics, Faculty of Education, Tokyo Gakugei Univ., Koganei, Tokyo (Japan); Hiejima, T. [Dept. of Applied Chemistry, Faculty of Engineering, Tokyo Inst. of Polytechnics, Atsugi, Kanagawa (Japan); Sano, M. [Dept. of Chemistry, Div. of Natural Sciences, International Christian Univ., Tokyo (Japan)

2004-07-01

38

Formation of positronium in cup-stacked carbon nanofibers  

International Nuclear Information System (INIS)

The positron-lifetime spectrum for cup-stacked carbon nanofibers (CNFs) is composed of three components: 0.125 ns (fixed) (6%), 0.345 ns (75%), 1.21 ns (19%). The longest-lived component assigned to ortho-positronium (o-Ps) verifies a prominent yield of o-Ps, which is in contrast with the fact that no o-Ps is detected for uncapped cylindrical multi-walled carbon nanotubes. CNFs heat-treated to 1073 K in vacuo showed a positron-lifetime spectrum the same as that of untreated CNFs, which demonstrates that the thermal detachment of some functional groups from the surface of the CNFs does not change the Ps yield. The yield is found almost independent of temperature between 10 and 280 K. A single CNF, ca. 50 nm in outer diameter, observed by transmission electron-microscopy, comprises stacked cups of 9?12 truncated conical graphene sheets at ca. 20 with respect to the fiber axis, so that all edges of graphene sheets are found on the zigzag outer- as well as inner-surfaces of the fiber. The Raman spectrum for CNFs exhibits a band of a disorder-induced mode at 1349 cm-1 (D-band) and a band of the E2g2 in-plane mode at 1577 cm-1 (G-band). The intensity-ratios of a D-band to a G-band are 0.17, 0.25 and 0 for a mat of CNFs, the edge plane and the basal plane of a highly oriented pyrolitic graphite block, respectively. For graphite materials, Ps is formed from the positrons trapped in the defects originating from edges of graphene sheets. (origing from edges of graphene sheets. (orig.)

39

Textural and electrochemical characterization of porous carbon nanofibers as electrodes for supercapacitors  

Energy Technology Data Exchange (ETDEWEB)

Porous carbon nanofibers (CNFs) enriched with the graphitic structure were synthesized by thermal decomposition from a mixture containing polyethylene glycol and nickel chloride (catalyst). The textural and electrochemical properties of porous CNFs were systematically compared with those of commercially available multi-walled carbon nanotubes (MWCNTs). The high ratio of mesopores and large amount of open edges of porous CNFs with a higher specific surface area, very different from that of MWCNTs, are favorable for the penetration of electrolytes meanwhile the graphene layers of porous CNFs serve as a good electronic conductive medium of electrons. The electrochemical properties of porous CNFs and MWCNTs were characterized for the application of supercapacitors using cyclic voltammetry, galvanostatic charge-discharge method, and electrochemical impedance spectroscopic analyses. The porous CNFs show better capacitive performances (C{sub S} = 98.4 F g{sup -1} at 25 mV s{sup -1} and an onset frequency of behaving as a capacitor at 1.31 kHz) than that of MWCNTs (C{sub S} = 17.8 F g{sup -1} and an onset frequency at 1.01 kHz). This work demonstrates the promising capacitive properties of porous CNFs for the application of electrochemical supercapacitors. (author)

Huang, Chao-Wei; Wu, Yung-Tai; Hu, Chi-Chang; Li, Yuan-Yao [Department of Chemical Engineering, National Chung Cheng University, Chia-Yi 621 (China)

2007-10-11

40

Direct production of carbon nanofibers decorated with Cu2O by thermal chemical vapor deposition on Ni catalyst electroplated on a copper substrate  

Directory of Open Access Journals (Sweden)

Full Text Available  Carbon nanofibers (CNFs decorated with Cu2O particles were grown on a Ni catalyst layer deposited on a Cu substrate by thermal. chemical vapor deposition from liquid petroleum gas. Ni catalyst nanoparticles with different sizes were produced in an electroplating system at 35?C. These nanoparticles provide the nucleation sites for CNF growth, removing the need for a buffer layer. High temperature surface segregation of the Cu substrate into the Ni catalyst layer and its exposition to O2 at atmospheric environment, during the CNFs growth, lead to the production of CNFs decorated with Cu2O particles. The surface morphology of the Ni catalyst films and grown CNFs over it was studied by scanning electron microscopy. Transmission electron microscopy and Raman spectroscopy revealed the formation of CNFs. The selected area electron diffraction pattern and electron diffraction studies show that these CNFs were decorated with Cu2O nanoparticles.

MA Vesaghi

2012-12-01

41

Fabrication of carbon nanofiber-reinforced aluminum matrix composites assisted by aluminum coating formed on nanofiber surface by in situ chemical vapor deposition  

Science.gov (United States)

The van der Waals agglomeration of carbon nanofibers (CNFs) and the weight difference and poor wettability between CNFs and aluminum hinder the fabrication of dense CNF-reinforced aluminum matrix composites with superior properties. In this study, to improve this situation, CNFs were coated with aluminum by a simple and low-cost in situ chemical vapor deposition (in situ CVD). Iodine was used to accelerate the transport of aluminum atoms. The coating layer formed by the in situ CVD was characterized using scanning electron microscopy, transmission electron microscopy, x-ray diffraction, Fourier transform-infrared spectroscopy, and x-ray photoelectron spectroscopy. The results confirmed that the CNFs were successfully coated with aluminum. The composites were fabricated to investigate the effect of the aluminum coating formed on the CNFs. The dispersion of CNFs, density, Vickers micro-hardness and thermal conductivity of the composites fabricated by powder metallurgy were improved. Pressure-less infiltration experiments were conducted to fabricate composites by casting. The results demonstrated that the wettability and infiltration were dramatically improved by the aluminum coating layer on CNFs. The aluminum coating formed by the in situ CVD technique was proved to be effective for the fabrication of CNF-reinforced aluminum matrix composites.

Ogawa, Fumio; Masuda, Chitoshi

2015-01-01

42

Catalytic Growth of Macroscopic Carbon Nanofibers Bodies with Activated Carbon  

Science.gov (United States)

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° C for an hour in each step. The catalytic growth of nanocarbon in C2H4/H2 was carried out at temperature of 550° C for 2 hrs with different rotating angle in the fluidization system. SEM and N2 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.

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

2009-06-01

43

Catalytic Growth of Macroscopic Carbon Nanofibers Bodies with Activated Carbon  

International Nuclear Information System (INIS)

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 C2H4/H2 was carried out at temperature of 550 deg. C for 2 hrs with different rotating angle in the fluidization system. SEM and N2 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.

44

Processing and Structure of Carbon Nanofiber Paper  

Directory of Open Access Journals (Sweden)

Full Text Available A unique concept of making nanocomposites from carbon nanofiber paper was explored in this study. The essential element of this method was to design and manufacture carbon nanofiber paper with well-controlled and optimized network structure of carbon nanofibers. In this study, carbon nanofiber paper was prepared under various processing conditions, including different types of carbon nanofibers, solvents, dispersants, and acid treatment. The morphologies of carbon nanofibers within the nanofiber paper were characterized with scanning electron microscopy (SEM. In addition, the bulk densities of carbon nanofiber papers were measured. It was found that the densities and network structures of carbon nanofiber paper correlated to the dispersion quality of carbon nanofibers within the paper, which was significantly affected by papermaking process conditions.

Zhongfu Zhao

2009-01-01

45

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

Science.gov (United States)

Carbon nanofibers (CNFs) randomly embedded in poly (lactic-co-glycolic-acid) (PLGA) composites have recently been shown to promote cardiomyocyte growth when compared with conventional PLGA without CNFs. It was shown then that PLGA:CNF composites were conductive and that conductivity increased as greater amounts of CNFs were added to pure PLGA. Moreover, tensile tests showed that addition of CNFs increased the tensile strength of the PLGA composite to mimic that of natural heart tissue. Most importantly, throughout all cytocompatibility experiments, cardiomyocytes were viable and expressed important biomarkers that were greatest on 50:50 wt% CNF:PLGA composites. The increased selective adsorption of fibronectin and vitronectin (critical proteins that mediate cardiomyocyte function) onto such composites proved to be the mechanism of action. However, the natural myocardium is anisotropic in terms of mechanical and electrical properties, which was not emulated in these prior PLGA:CNF composites. Thus, the aim of this in vitro study was to create and characterize CNFs aligned in PLGA composites (at 50:50 wt%, including their mechanical and electrical properties and cardiomyocyte density), comparing such results with randomly oriented CNFs in PLGA. Specifically, CNFs were added to soluble biodegradable PLGA (50:50 PGA:PLA weight ratio) and aligned by applying a voltage and then allowing the polymer to cure. CNF surface micron patterns (20 ?m wide) on PLGA were then fabricated through a mold method to further mimic myocardium anisotropy. The results demonstrated anisotropic mechanical and electrical properties and significantly improved cardiomyocyte density for up to 5 days on CNFs aligned in PLGA compared with being randomly oriented in PLGA. These results indicate that CNFs aligned in PLGA should be further explored for improving cardiomyocyte density, which is necessary in numerous cardiovascular applications. PMID:25489241

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

2014-01-01

46

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

Science.gov (United States)

Carbon nanofibers (CNFs) randomly embedded in poly (lactic-co-glycolic-acid) (PLGA) composites have recently been shown to promote cardiomyocyte growth when compared with conventional PLGA without CNFs. It was shown then that PLGA:CNF composites were conductive and that conductivity increased as greater amounts of CNFs were added to pure PLGA. Moreover, tensile tests showed that addition of CNFs increased the tensile strength of the PLGA composite to mimic that of natural heart tissue. Most importantly, throughout all cytocompatibility experiments, cardiomyocytes were viable and expressed important biomarkers that were greatest on 50:50 wt% CNF:PLGA composites. The increased selective adsorption of fibronectin and vitronectin (critical proteins that mediate cardiomyocyte function) onto such composites proved to be the mechanism of action. However, the natural myocardium is anisotropic in terms of mechanical and electrical properties, which was not emulated in these prior PLGA:CNF composites. Thus, the aim of this in vitro study was to create and characterize CNFs aligned in PLGA composites (at 50:50 wt%, including their mechanical and electrical properties and cardiomyocyte density), comparing such results with randomly oriented CNFs in PLGA. Specifically, CNFs were added to soluble biodegradable PLGA (50:50 PGA:PLA weight ratio) and aligned by applying a voltage and then allowing the polymer to cure. CNF surface micron patterns (20 ?m wide) on PLGA were then fabricated through a mold method to further mimic myocardium anisotropy. The results demonstrated anisotropic mechanical and electrical properties and significantly improved cardiomyocyte density for up to 5 days on CNFs aligned in PLGA compared with being randomly oriented in PLGA. These results indicate that CNFs aligned in PLGA should be further explored for improving cardiomyocyte density, which is necessary in numerous cardiovascular applications. PMID:25489241

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

2014-01-01

47

Effects of the catalyst and substrate thickness on the carbon nanotubes/nanofibers as supercapacitor electrodes  

International Nuclear Information System (INIS)

The different growth conditions of carbon nanotubes (CNTs)/carbon nanofibers (CNFs) which lead to different characteristics when used as supercapacitor electrodes are reported. A layer of SiO2 was coated onto the Si substrate and then a layer of Ti was evaporated as a current collector. CNTs/CNFs were synthesized on the Ti surface via a water-assisted chemical vapor deposition method at 800 °C and 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. The effects of different thicknesses of the catalyst (5 and 10 nm) and Ti substrate layer (10, 30 and 150 nm) on the specific capacitance of the CNFs were studied and the capacitance of the CNTs/CNFs-based device was dependent on CNT/CNF morphology of the CNFs that varied for different combinations of the catalyst and Ti layer thicknesses. The characterization of CNTs/CNFs was carried out using scanning electron microscopy, electron dispersive spectroscopy, transmission electron microscopy and electron diffraction. The specific capacitance was measured using cyclic voltammetry via a three-electrode system. The highest specific capacitance (60 F g-1) was obtained in the sample grown with 5 nm of Fe catalyst onto 10 nm of Ti substrate.

48

Extraction of contact resistance in carbon nanofiber via interconnects with varying lengths  

Science.gov (United States)

A method to extract the contact resistance and bulk resistivity of vertically grown carbon nanofibers (CNFs) or similar one-dimensional nanostructures is described. Using a silicon-compatible process to fabricate a terrace test structure needed for the CNF length variation, the contact resistance is extracted by measuring in situ the resistances of individual CNFs with different lengths and within a small range of diameters using a nanoprober inside a scanning electron microscope. Accurate determination of contact resistances for various combinations of catalysts and underlayer metals can lead to eventual optimization of materials' growth and device fabrication processes for CNF via interconnects.

Li, Ke; Wu, Raymond; Wilhite, Patrick; Khera, Vinit; Krishnan, Shoba; Sun, Xuhui; Yang, Cary Y.

2010-12-01

49

Reticular Sn nanoparticle-dispersed PAN-based carbon nanofibers for anode material in rechargeable lithium-ion batteries  

Energy Technology Data Exchange (ETDEWEB)

Reticular tin nanoparticle-dispersed carbon (Sn/C) nanofibers (CNFs) were fabricated by stabilization of electrospun SnCl{sub 4}/PAN (PAN stands for nanoceria-polyacrylonitrile) composite fibers and subsequent carbonization at different temperatures. These Sn/C composite nanofibers used as anode materials for rechargeable lithium-ion batteries (LIBs) show that the Sn/C nanofibers at 700 and 850 C present much higher charge (785.8 and 811 mA h g{sup -1}) and discharge (1211.7 and 993 mA h g{sup -1}) capacities than those at 550 and 1000 C and the as-received CNFs at 850 C, corresponding to coulombic efficiencies of 64.9% and 81.7%, respectively. The superior electrochemical properties of the intriguing Sn/C nanofibers indicate a promising application in high performance Li-ion batteries. (author)

Yu, Yunhua; Yang, Qing; Teng, Donghua; Yang, Xiaoping [Key Laboratory of Carbon Fiber and Functional Polymers, Ministry of Education, Beijing University of Chemical Technology, Beijing 100029 (China); Ryu, Seungkon [Department of Chemical Engineering, Chungnam National University, Daejeon 305764 (Korea)

2010-09-15

50

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

Directory of Open Access Journals (Sweden)

Full Text Available Abdullah M Asiri,1 Hadi M Marwani,1 Sher Bahadar Khan,1 Thomas J Webster1,2 1Center of Excellence for Advanced Materials Research, King Abdulaziz University, Jeddah, Saudi Arabia; 2Department of Chemical Engineering, Northeastern University, Boston, MA, USA Abstract: 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 ?-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. Keywords: cardiomyocytes, poly(lactic-co-glycolic acid, carbon nanofibers, aligned, nanotechnology, anisotropy, mechanism, vitronectin, fibronectin, laminin

Asiri AM

2014-12-01

51

Voltammetry at carbon nanofiber electrodes  

OpenAIRE

Carbon nanofibers with diameters in the range 10-500 nm have been evaluated as novel electrode materials for electrochemical applications. Compared with other forms of nanostructured carbons, such as aerogels or activated charcoal, carbon nanofibers exhibit low BET surface areas, 50 vs. 500 m 2 g -1, because their surfaces are not readily penetrated by gaseous nitrogen. But somewhat surprisingly, they exhibit higher electrochemical capacit...

Marken, F.; Gerrard, Ml; Mellor, Im; Mortimer, Rj; Madden, Ce; Fletcher, S.; Holt, K.; Foord, Js; Dahm, Rh; Page, F.

2001-01-01

52

Characterization of field emission from carbon nanofibers on a metal tip  

International Nuclear Information System (INIS)

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 ?A was strongly dependent on emitter-anode distance, and the dominant field electrons were emitted within an angular spread of ???25 deg., 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=2x109 A/m2.

53

Characterization of field emission from carbon nanofibers on a metal tip  

Science.gov (United States)

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 ?A was strongly dependent on emitter-anode distance, and the dominant field electrons were emitted within an angular spread of ?? ˜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.

Sakai, Y.; Tone, D.; Nagatsu, S.; Endo, T.; Kita, S.; Okuyama, F.

2009-08-01

54

Encapsulation of MnO Nanocrystals in Electrospun Carbon Nanofibers as High-Performance Anode Materials for Lithium-Ion Batteries  

OpenAIRE

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 ...

Bin Liu; Xianluo Hu; Henghui Xu; Wei Luo; Yongming Sun; Yunhui Huang

2014-01-01

55

Surface coating on carbon nanofibers with alumina precursor by different synthesis routes  

OpenAIRE

Abstract Alumina-reinforced carbon nanofiber nanocomposites were prepared using different routes; powders mixture, colloidal route and sol-gel process followed by spark plasma sintering (SPS). CNFs/xAl2O3 (x=10-50 vol.%) were prepared through nanopowders mixing in a high-energy attrition milling. The main limitations in the preparation of this kind of nanocomposites are related to the difficulty in obtaining materials with a homogeneous distribution of both phases and the different...

Borrell Toma?s, Mari?a Amparo; Rocha, Victoria G.; Torrecillas San Milla?n, Ramo?n; Ferna?ndez Valde?s, Adolfo

2011-01-01

56

Direct growth of carbon nanofibers to generate a 3D porous platform on a metal contact to enable an oxygen reduction reaction.  

Science.gov (United States)

For carbon nanotube-based electronics to achieve their full performance potential, it is imperative to minimize the contact resistance between macroscale metal contacts and the carbon nanotube (CNT) nanoelectrodes. We have developed a three-dimensional electrode platform that consists of carbon nanofibers (CNFs) that are directly grown on a metal contact, such as copper (Cu). Carbon nanofiber morphology can be tailored by adjusting the annealing time of a thin electrochemically deposited nickel catalyst layer on copper. We demonstrate that increasing the annealing time increases the amount of copper infused into the nickel catalyst layer. This reduces the carbon deposition rate, and consequently a more well-defined CNF 3D architecture can be fabricated. This direct growth of CNFs on a Cu substrate yields an excellent electron transfer pathway, with contact resistance between CNFs and Cu being comparable to that of a Cu-Cu interface. Furthermore, the excellent bonding strength between CNFs and Cu can be maintained over prolonged periods of ultrasonication. The porous 3D platform affixed with intertwined CNFs allows facile surface functionalization. Using a simple solution soaking procedure, the CNF surface has been successfully functionalized with iron(II) phthalocyanine (FePc). FePc functionalized CNFs exhibit excellent oxygen reduction capability, equivalent to platinum-carbon electrodes. This result demonstrates the technological promise of this new 3D electrode platform that can be exploited in other applications that include sensing, battery, and supercapacitors. PMID:23171171

Pan, David; Ombaba, Matthew; Zhou, Zhi-You; Liu, Yang; Chen, Shaowei; Lu, Jennifer

2012-12-21

57

The study of controlling pore size on electrospun carbon nanofibers for hydrogen adsorption.  

Science.gov (United States)

Polyacrylonitrile (PAN)-based carbon nanofibers (CNFs) were prepared by using electrospinning method and heat treatment to get the media for hydrogen adsorption storage. Potassium hydroxide and zinc chloride activations were conducted to increase specific surface area and pore volume of CNFs. To investigate the relation between pore structure and the capacity of hydrogen adsorption, textural properties of activated CNFs were studied with micropore size distribution, specific surface area, and total pore volume by using BET (Brunauer-Emmett-Teller) surface analyzer apparatus and the capacity of hydrogen adsorption was evaluated by PCT (pressure-composition-temperature) hydrogen adsorption analyzer apparatus with volumetric method. The surface morphology of activated CNFs was observed by SEM (scanning electron microscope) images to investigate the surface change through activation. Even though specific surface area and total pore volume were important factors for increasing the capacity of hydrogen adsorption, the pore volume which has pore width (0.6-0.7 nm) was a much more effective factor than specific surface area and pore volume in PAN-based electrospun activated CNFs. PMID:17988675

Im, Ji Sun; Park, Soo-Jin; Kim, Tae Jin; Kim, Young Ho; Lee, Young-Seak

2008-02-01

58

Free-standing porous carbon nanofiber/ultrathin graphite hybrid for flexible solid-state supercapacitors.  

Science.gov (United States)

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

Qin, Kaiqiang; Kang, Jianli; Li, Jiajun; Shi, Chunsheng; Li, Yuxiang; Qiao, Zhijun; Zhao, Naiqin

2015-01-27

59

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

Science.gov (United States)

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 ?-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

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

2015-01-01

60

Maghemite nanoparticles on electrospun CNFs template as prospective lithium-ion battery anode.  

Science.gov (United States)

In this work, maghemite (?-Fe2O3) nanoparticles were uniformly coated on carbon nanofibers (CNFs) by a hybrid synthesis procedure combining an electrospinning technique and hydrothermal method. Polyacrylonitrile nanofibers fabricated by the electrospinning technique serve as a robust support for iron oxide precursors during the hydrothermal process and successfully limit the aggregation of nanoparticles at the following carbonization step. The best materials were optimized under a carbonization condition of 600 °C for 12 h. X-ray diffraction and electron microscopy studies confirm the formation of a maghemite structure standing on the surface of CNFs. The average size of ?-Fe2O3 nanoparticles is below 100 nm, whereas CNFs are ?150 nm in diameter. In comparison with aggregated bare iron oxide nanoparticles, the as-prepared carbon-maghemite nanofibers exhibit a higher surface area and greatly improved electrochemical performance (>830 mAh g(-1) at 50 mA g(-1) for 40 cycles and high rate capacity up to 5 A g(-1) in the voltage range of 0.005-3 V vs Li). The greatly enhanced electrochemical performance is attributed to the unique one-dimensional nanostructure and the limited aggregation of nanoparticles. PMID:24383672

Wu, Yongzhi; Zhu, Peining; Reddy, M V; Chowdari, B V R; Ramakrishna, S

2014-02-12

61

Fabrication of Uniform Au–Carbon Nanofiber by Two-Step Low Temperature Decomposition  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract This paper presents a facile and efficient way to prepare carbon nanofibers ornamented with Au nanoparticles (Au/CNFs. Gold nanoparticles were first deposited in the channels of an anodized aluminum oxide (AAO membrane by thermal decomposition of HAuCl4and then carbon nanofibers were produced in the same channels loaded with the Au nanoparticles by decomposition of sucrose at 230 °C. An electron microscopy study revealed that the carbon nanofibers, ~10 nm thick and 6 ?m long, were decorated with Au nanoparticles with a diameter of 10 nm. This synthetic route can produce uniform Au nanoparticles on CNF surfaces without using any additional chemicals to modify the AAO channels or the CNF surfaces.

Lee Myeongsoon

2009-01-01

62

Fabrication of uniform au-carbon nanofiber by two-step low temperature decomposition.  

Science.gov (United States)

This paper presents a facile and efficient way to prepare carbon nanofibers ornamented with Au nanoparticles (Au/CNFs). Gold nanoparticles were first deposited in the channels of an anodized aluminum oxide (AAO) membrane by thermal decomposition of HAuCl4and then carbon nanofibers were produced in the same channels loaded with the Au nanoparticles by decomposition of sucrose at 230 °C. An electron microscopy study revealed that the carbon nanofibers, ~10 nm thick and 6 ?m long, were decorated with Au nanoparticles with a diameter of 10 nm. This synthetic route can produce uniform Au nanoparticles on CNF surfaces without using any additional chemicals to modify the AAO channels or the CNF surfaces. PMID:20596484

Lee, Myeongsoon; Hong, Seong-Cheol; Kim, Don

2009-01-01

63

Manufacturing of high performance polymer nanocomposites containing carbon nanotubes and carbon nanofibers using ultrasound assisted extrusion process  

Science.gov (United States)

The major objective of this study was to investigate the effect of ultrasonic treatment on the state of dispersion and properties of carbon nanotubes (CNTs) and carbon nanofibers (CNFs) in polymer matrices. In order to achieve this objective, an ultrasonic single screw extruder operating at a frequency of 20 kHz and an amplitude of upto 10 microm and an ultrasonic twin screw extruder operating at a frequency of 40 kHz and an amplitude of upto 6.0 microm, were used to process highly viscous materials and disperse these nanofillers homogeneously in a polymer matrix at residence times of order of seconds. High temperature thermoplastic resins including polyetherimide (PEI), liquid crystalline polymer (LCP) and polyetheretherketone (PEEK) were used. Multiwalled carbon nanotubes (MWNTs) and CNFs were used as reinforcing fillers. The effect of nanofiller loading and ultrasonic amplitudes on rheological, mechanical, electrical, thermal and morphological properties of the nanocomposites was studied. Ultrasonic treatment showed a tremendous decrease in die pressure. Morphological studies showed that ultrasonic treatment improved dispersion of CNFs and CNTs in polymer matrices. PEI/CNFs and PEI/MWNTs nanocomposites were prepared using ultrasound assisted single and twin screw extruder, respectively. A permanent increase in the viscosity, storage and loss modulus and decrease in tan delta was observed with ultrasonic treatment. Ultrasonically treated PEI/CNFs nanocomposites showed a decrease in electrical percolation threshold value as compared to the untreated ones. Breakage of CNFs was observed primarily due to extrusion process alone. In case of PEI/MWNTs nanocomposites, percolation threshold value was found to be between 1 and 2 wt% loading of CNTs for both treated and untreated samples. LCP/CNFs nanocomposites were prepared using ultrasound assisted twin screw extruder with separate feeding of CNFs in the polymer melt. In contrast to behavior of PEI/CNFs and PEI/MWNTs nanocomposites, the rheological behavior of LCP/CNFs nanocomposites practically was not affected with the ultrasonic treatment due to a reduction in fibrillation of LCP matrix in the presence of CNFs. Similar to PEI/CNFs nanocomposites; ultrasonically treated samples showed a decrease in the electrical percolation threshold value as compared to the untreated ones. Due to reduction in fibrillation of LCP no improvement in the mechanical properties was observed on addition of CNFs. After introducing the orientation by fiber spinning of LCP/CNFs nanocomposites, a tremendous increase in the mechanical properties of fibers was observed with increase in the draw down ratio. PEEK/MWNTs nanocomposites were prepared using ultrasonic single screw extruder. In contrast to PEI/CNFs and PEI/MWNTs nanocomposites, ultrasonically treated PEEK/MWNTs nanocomposites showed decrease in the complex viscosity, storage modulus. Loss modulus and increase in tan delta as compared to untreated ones. This could be due to the competition between increased dispersion of CNTs and a possible degradation of the polymeric chains in the presence of CNTs and a possible reduction of CNTs length on application of ultrasound. Due to above effects, ultrasonic treatment reduced the physical contacts between the CNTs and hence increased the volume resistivity near the percolation threshold. No degradation of pure PEEK matrix upon application of ultrasound was observed.

Kumar, Rishi

64

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

International Nuclear Information System (INIS)

Highlights: ? The CNFs improve the infiltration rate and thermal properties of carbon/carbon composites. ? The densification rate increases with the CNF content increasing at the beginning of infiltration. ? 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.%.

65

Enhancement of the effects of exfoliated carbon nanofibers by bone morphogenetic protein in a rat femoral fracture model.  

Science.gov (United States)

Exfoliated carbon nanofibers (ExCNFs) are expected to serve as excellent scaffolds for promoting and guiding bone-tissue regeneration. We aimed to enhance the effects of ExCNFs with bone morphogenetic proteins (BMPs) and examine their feasibility and safety in clinical applications using a rat femoral fracture model. Group I (n?=?16) animals were implanted with control MedGEL. Group II (n?=?17) animals were implanted with MedGEL containing ExCNFs. Group III (n?=?15) animals were implanted with MedGEL containing 1??g rhBMP-2. Group IV (n?=?15) animals were implanted with MedGEL containing 1??g rhBMP-2 and ExCNFs. The rats were euthanized after 6 weeks, and their fractured femurs were explanted and assessed by manual palpation, radiographs, and high-resolution microcomputerized tomography (micro-CT); the femurs were also subjected to biomechanical and histological analysis. The fusion rates in Group IV (73.3%) were considerably higher than those in Groups I (25.0%), II (52.9%), and III (46.7%). The results demonstrated the enhancement of the bone repair effects of ExCNFs by BMP in a rat femoral fracture model. Our results suggest that the enhancement of the effects of ExCNFs by BMP makes the combination a possible attractive therapy for various orthopedic surgeries. © 2014 Orthopaedic Research Society. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:185-192, 2015. PMID:25346439

Miyazaki, Masashi; Toyoda, Masahiro; Yoshiiwa, Toyomi; Kawano, Masanori; Kaku, Nobuhiro; Tsumura, Hiroshi

2015-02-01

66

Synthesis of Carbon Nanofibers Based on Resol Type Phenol Resin and Fe(III) Catalysts  

Energy Technology Data Exchange (ETDEWEB)

The carbon nanofibers (CNFs) used in this study were synthesized with an iron catalyst and ethylene as a carbon source. A concentration of 30 wt % iron(III) acetylacetonate was dissolved in resol type phenol resin and polyurethane foam was put into the solution. The sample was calendered after being cured at 80 .deg. C in air for 24 h. Stabilization and carbonization of the resol type phenol resin and reduction of the Fe{sup 3+} were completed in a high-temperature furnace by the following steps: heating to 600 .deg. C at a rate of 10 .deg. C/min with a mixture of H{sub 2}/N{sub 2} for 4 h to reduce the Fe{sup 3+} to Fe; heating to 1000 .deg. C in N{sub 2} at a rate 10 .deg. C/min for 30 minutes for pyrolysis; synthesizing CNFs in a mixture of 20.1% ethylene and H{sub 2}/N{sub 2} at 700 .deg. C for 2 h using a CVD process. Finally, the structural characterization of the CNFs was performed by scanning electron microscopy and a synthesis analysis was carried out using energy dispersive spectroscopy and X-ray photoelectron spectroscopy. Specific surface area analysis of the CNFs was also performed by N{sub 2}-sorption.

Hyun, Yura; Lee, Changseop [Keimyung Univ., Daegu (Korea, Republic of); Kim, Haesik [Korea E and S Co. Ltd., Daegu (Korea, Republic of)

2012-10-15

67

Efficient synthesis of Pt nanoparticles supported on hydrophobic graphitized carbon nanofibers for electrocatalysts using noncovalent functionalization  

Energy Technology Data Exchange (ETDEWEB)

As an alternative to the oxidative acid treatment, a noncovalent {pi}-{pi} interaction method is employed to deposit Pt electrocatalysts on highly hydrophobic carbon nanofibers (CNFs) for the application of polymer electrolyte membrane (PEM) fuel cells. Three different functionalization agents, namely benzyl mercaptan (BM), 1-aminopyrene (AP), and 1-pyrenecarboxylic acid (PCA), are used to functionalize CNFs and the effect of these groups on the electrochemical properties is examined. While the BM and AP act as a poison to Pt catalyst, the functionalization of CNF with PCA improves the distribution and loading of Pt as well as reducing the sintering of Pt particles. From the carbon corrosion test, unlike the oxidative acid treatment, the PCA treatment sustains the corrosion resistance of CNFs because it preserves the intrinsic properties of CNFs without damaging their surface structure. Therefore, the PCA treatment is a very effective way to prepare catalysts for PEM fuel cells and also extended to the fabrication of graphitized-carbon-supported catalysts of other precious metal for various applications. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Oh, Hyung-Suk; Kim, Hansung [Department of Chemical and Biomolecular Engineering, Yonsei University, 134 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749 (Korea, Republic of)

2011-10-21

68

Synthesis of Carbon Nanofibers Based on Resol Type Phenol Resin and Fe(III) Catalysts  

International Nuclear Information System (INIS)

The carbon nanofibers (CNFs) used in this study were synthesized with an iron catalyst and ethylene as a carbon source. A concentration of 30 wt % iron(III) acetylacetonate was dissolved in resol type phenol resin and polyurethane foam was put into the solution. The sample was calendered after being cured at 80 .deg. C in air for 24 h. Stabilization and carbonization of the resol type phenol resin and reduction of the Fe3+ were completed in a high-temperature furnace by the following steps: heating to 600 .deg. C at a rate of 10 .deg. C/min with a mixture of H2/N2 for 4 h to reduce the Fe3+ to Fe; heating to 1000 .deg. C in N2 at a rate 10 .deg. C/min for 30 minutes for pyrolysis; synthesizing CNFs in a mixture of 20.1% ethylene and H2/N2 at 700 .deg. C for 2 h using a CVD process. Finally, the structural characterization of the CNFs was performed by scanning electron microscopy and a synthesis analysis was carried out using energy dispersive spectroscopy and X-ray photoelectron spectroscopy. Specific surface area analysis of the CNFs was also performed by N2-sorption

69

In situ growth cupric oxide nanoparticles on carbon nanofibers for sensitive nonenzymatic sensing of glucose  

International Nuclear Information System (INIS)

Highlights: • CuO nanoparticles were directly and homogeneously grown on carbon nanofibers. • The obtained nanocomposite showed high electrooxidize activity to glucose. • A nonenzymatic glucose sensor was constructed based on the functional nanocomposite. • This sensor showed good performance to glucose. • The proposed sensor was successfully applied in detection of glucose in blood serum. -- Abstract: A novel method was employed to directly and homogeneously attaching cupric oxide nanoparticles (CuONPs) on carbon nanofibers (CNFs) for sensitive amperometric nonenzymatic sensing of glucose. The obtained CuONPs-CNFs nanocomposite was characterized by transmission electron microscopy and X-ray diffraction. The CuONPs-CNFs nanocomposite modified glassy carbon electrode showed high electrocatalytic activity toward the oxidation of glucose in alkaline media and a nonenzymatic glucose sensor was constructed based on the functional nanocomposite modified electrode. Under optimal experimental conditions, the designed sensor exhibited a wide linear response to glucose ranging from 5.0 × 10?7 to 1.1 × 10?2 M with a high sensitivity of 2739 ?A mM?1 cm?2 and a low detection limit down to 0.2 ?M at the signal to noise ratio of 3. This sensor showed good accuracy, acceptable precision and reproducibility. Moreover, the proposed sensor was successfully applied in the detection of glucose in human blood serum indicating its possibility in practical application

70

Direct synthesis of carbon nanofibers from South African coal fly ash  

Science.gov (United States)

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

2014-01-01

71

Effect of added nickel nitrate on the physical, thermal and morphological characteristics of polyacrylonitrile-based carbon nanofibers  

International Nuclear Information System (INIS)

Porous carbon nanofibers (CNFs) with enhanced physical, thermal and morphological properties are desirable in many areas like catalyst support in fuel cells and supercapacitors as electrode material. This research addresses the effect of added nickel nitrate in 1, 3 and 5 wt% into polyacrylonitrile (PAN) precursor solution to produce CNF webs using electrospinning method. Based on the quantitative data obtained from field emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM) images, we can notice that CNFs were formed with diameters in the size range of 100-300 nm after carbonization at 1000 deg. C. Fiber diameter of the random CNFs was decreased by increasing the nickel nitrate contents along with dramatic improvements in porosity and specific surface areas. This study indicated that the optimal nickel nitrate concentration of 5 wt% has produced CNFs with enhanced physical and thermo-chemical properties. The high resolution X-ray diffraction (HR-XRD) showed an increase in intensity of 0 0 2 peak of the CNFs due to the catalytic function of nickel oxide in the carbonized web and these observations are in agreement with the thermal gravimetric data.

72

Electrochemical properties for high surface area and improved electrical conductivity of platinum-embedded porous carbon nanofibers  

Science.gov (United States)

Four different types of carbon nanofibers (CNFs) for electrical double-layer capacitors (EDLCs), porous and non-porous CNFs with and without Pt metal nanoparticles, are synthesized by an electrospinning method and their performance in electrical double-layer capacitors (EDLCs) is characterized. In particular, the Pt-embedded porous CNFs (PCNFs) exhibit a high specific surface area of 670 m2 g-1, a large mesopore volume of 55.7%, and a low electrical resistance of 1.7 × 103. The synergistic effects of the high specific surface area with a large mesopore volume, and superior electrical conductivity result in an excellent specific capacitance of 130.2 F g-1, a good high-rate performance, superior cycling durability, and high energy density of 16.9-15.4 W h kg-1 for the performance of EDLCs.

An, Geon-Hyoung; Ahn, Hyo-Jin; Hong, Woong-Ki

2015-01-01

73

Using Converter Dust to Produce Low Cost Cementitious Composites by in situ Carbon Nanotube and Nanofiber Synthesis  

OpenAIRE

Carbon nanotubes (CNTs) and nanofibers (CNFs) were synthesized on clinker and silica fume particles in order to create a low cost cementitious nanostructured material. The synthesis was carried out by an in situ chemical vapor deposition (CVD) process using converter dust, an industrial byproduct, as iron precursor. The use of these materials reduces the cost, with the objective of application in large-scale nanostructured cement production. The resulting products were analyzed by scanning el...

Péter Ludvig; Calixto, Jose? M.; Ladeira, Luiz O.; Gaspar, Ivan C. P.

2011-01-01

74

Influence of the nature of the metal hydroxide in the porosity development of carbon nanofibers.  

Science.gov (United States)

In this study, highly porous carbon nanofibers (CNFs) were prepared by chemical activation in order to develop promising energy storage materials. The activation was performed at a temperature of 850 degrees C by using different metal hydroxides as the activating agents. Pore structures of the CNFs were analyzed using N(2)/77K adsorption isotherms. The presence of oxygen groups was analyzed by means of acid-base titration. The structural order (crystallinity) of the materials was studied by XRD and TGA analysis and the morphology and diameter distributions by means of TEM. The use of hydroxide of alkaline metals of low melting and boiling points (K, Rb, and Cs) led to the best results of porosity development. On the contrary, the pore opening was lower if the alkaline metal had a high boiling point (Na) or when alkali earth cations were used as activating agents. After the activation, the porous CNFs showed a decrease in diameter and scratches on their surfaces, as a consequence of the surface oxidation and opening of the graphitic layers, respectively. It was found that the specific surface area of the porous CNFs prepared using KOH and RbOH was more than 400 and 280 m(2) g(-1), respectively, without loss of their fiber shape. PMID:19419731

Jiménez, Vicente; Sánchez, Paula; de Lucas, Antonio; Valverde, José Luis; Romero, Amaya

2009-08-01

75

Structure and electrochemical applications of boron-doped graphitized carbon nanofibers  

International Nuclear Information System (INIS)

Boron-doped graphitized carbon nanofibers (CNFs) were prepared by optimizing CNFs preparation, surface treatment, graphitization and boron-added graphitization. The interlayer spacing (d002) of the boron-doped graphitized CNFs reached 3.356 ?, similar to that of single-crystal graphite. Special platelet CNFs (PCNFs), for which d002 is less than 3.400 ?, were selected for further heat treatment. The first heat treatment of PCNFs at 2800?°C yielded a d002 between 3.357 and 3.365 ?. Successive nitric acid treatment and a second heat treatment with boric acid reduced d002 to 3.356 ?. The resulting boron-doped PCNFs exhibited a high discharge capacity of 338 mAh g?1 between 0 and 0.5 V versus Li/Li+ and 368 mAh g?1 between 0 and 1.5 V versus Li/Li+. The first-cycle Coulombic efficiency was also enhanced to 71–80%. Such capacity is comparable to that of natural graphite under the same charge/discharge conditions. The boron-doped PCNFs also exhibited improved rate performance with twice the capacity of boron-doped natural graphite at a discharge rate of 5 C. (paper)

76

Sensitivity of Dielectric Properties to Wear Process on Carbon Nanofiber/High-Density Polyethylene Composites  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract We examined the correlation of wear effects with dielectric properties of carbon nanofibers (CNFs; untreated and organosilane-treated-reinforced high-density polyethylene (HDPE composites. Wear testing for the nanocomposites over up to 120 h was carried out, and then, dielectric permittivity and dielectric loss factor of the polymer composites with the increased wear time were studied. Scanning electron microscope and optical microscope observations were made to analyze the microstructure features of the nanocomposites. The results reveal that there exist approximate linear relationships of permittivity with wear coefficient for the nanocomposites. Composites containing silanized CNFs with the sufficiently thick coating exhibited high wear resistance. The change in permittivity was more sensitive to the increased wear coefficient for the nanocomposites with lower wear resistance. This work provides potential for further research on the application of dielectric signals to detect the effects of wear process on lifetime of polymeric materials.

Liu Tian

2011-01-01

77

Electromechanically tunable carbon nanofiber photonic crystal.  

Science.gov (United States)

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. PMID:23272804

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

2013-02-13

78

Phosphorus-doped tin oxides/carbon nanofibers webs as lithium-ion battery anodes with enhanced reversible capacity  

Science.gov (United States)

Phosphorus-doped tin oxides/carbon nanofibers (P-SnOx/CNFs) composite materials are prepared via electrospinning of a mixed solution composed of polyacrylonitrile (PAN), N,N-dimethyl formamide (DMF), tin tetrachloride, ethylene glycol and phosphoric acid as well as subsequent thermal treatments. The P-SnOx/CNFs samples with tunable P-doping contents are directly used as anodes for lithium-ion batteries without any binders and conductors, exhibiting enhanced reversible capacities and cycling stabilities in comparison with pristine undoped SnOx/CNFs (0P-SnOx/CNFs). In a controlled experiment, the 0.25P-SnOx/CNFs anode with the atomic ratio of P:Sn = 0.25:1 shows the highest specific reversible capacity of 676 mA h g-1 at 200 mA g-1 after 100 cycles. Even at a higher current density of 2000 mA g-1, it still maintains a superior specific reversible capacity of 288 mA h g-1. The improved electrochemical performances are attributed to the P-doping effects such as inducement of a stable structural protection for tin particles, and enhancement of lithium ion diffusion coefficient and electron kinetics of electrode materials.

Liu, Xiaowei; Teng, Donghua; Li, Ting; Yu, Yunhua; Shao, Xiaohong; Yang, Xiaoping

2014-12-01

79

In situ characterization of vertically oriented carbon nanofibers for three-dimensional nano-electro-mechanical device applications  

International Nuclear Information System (INIS)

We have performed mechanical and electrical characterization of individual as-grown, vertically oriented carbon nanofibers (CNFs) using in situ techniques, where such high-aspect-ratio, nanoscale structures are of interest for three-dimensional (3D) electronics, in particular 3D nano-electro-mechanical-systems (NEMS). Nanoindentation and uniaxial compression tests conducted in an in situ nanomechanical instrument, SEMentor, suggest that the CNFs undergo severe bending prior to fracture, which always occurs close to the bottom rather than at the substrate-tube interface, suggesting that the CNFs are well adhered to the substrate. This is also consistent with bending tests on individual tubes which indicated that bending angles as large as ? 700 could be accommodated elastically. In situ electrical transport measurements revealed that the CNFs grown on refractory metallic nitride buffer layers were conducting via the sidewalls, whereas those synthesized directly on Si were electrically unsuitable for low-voltage dc NEMS applications. Electrostatic actuation was also demonstrated with a nanoprobe in close proximity to a single CNF and suggests that such structures are attractive for nonvolatile memory applications. Since the magnitude of the actuation voltage is intimately dictated by the physical characteristics of the CNFs, such as diameter and length, we also addressed the ability to tune these parameters, to some extent, by adjusting the plasma-enhanced xtent, by adjusting the plasma-enhanced chemical vapor deposition growth parameters with this bottom-up synthesis approach.

80

Performance of carbon nanofiber-cement composites subjected to accelerated decalcification  

Directory of Open Access Journals (Sweden)

Full Text Available The effect of decalcification on the chemo-mechanical behavior of carbon nanofiber (CNF-cement composites was studied. Portland cement pastes with and without 0.2% CNFs were subjected to accelerated decalcification by exposure to ammonium nitrate solutions. The influence of microstructural alterations during decalcification on the physical and mechanical properties of the composites was examined. The presence of CNF agglomerates influenced the chemo-mechanical behavior of the composite during decalcification. Precipitation of secondary hydrates within the agglomerates during decalcification resulted in a decrease in local porosity, which strengthened the composite and slowed the loss of flexural strength.

Arnold J.

2013-07-01

81

Stabilization and carbonization of mesophase pitch nanofiber  

Science.gov (United States)

Mesophase pitch nanofibers were made with diameters of several hundred nanometers to a few microns. Thermogravimetric analysis showed the stabilization reaction in air began at a temperature below 200^oC, and produced a 6% weight gain. Changes intensity of aliphatic C-H (2850-3000 and 1400-1450 cm-1) and carbonyl -CO- (1690-1750 cm-1) peaks in Fourier transform infrared spectra were observed as a result of stabilization. The intensities of aryl alkyl ether peaks at 1200-1275 cm-1 increased with stabilization in air. Solid state NMR results confirmed these changes. Carbonization in inert gas began when the temperature reached 300^oC. There was a 25% weight loss during the carbonization. Element analysis showed that the only carbon remained. The structures of pitch nanofibers, stabilized nanofibers and the resulting carbon nanofibers were investigated with scanning electron microscopy, transmission electron microscopy and X-ray diffraction.

Fong, Hao; Reneker, Darrell H.

2000-03-01

82

In situ formation of hollow graphitic carbon nanospheres in electrospun amorphous carbon nanofibers for high-performance Li-based batteries  

Science.gov (United States)

We report on in situ formation of hollow graphitic carbon nanospheres (HGCNs) in amorphous carbon nanofibers (ACNFs) by a combination of electrospinning, calcination and acid treatment. The prepared carbon nanofibers contain many HGCNs on which defects such as discontinuous graphene sheets with a large d-spacing in their wall exist and provide extra sites for Li+ storage and serve as buffers for withstanding large volume expansion and shrinkage during the Li insertion and extraction procedure. Furthermore, some exposed HGCNs on the surface of the ACNFs as well as hollow structures are favorable for lithium ion diffusion from different orientations and sufficient contact between active material and electrolyte. In addition, the high conductivity architectures facilitate collection and transport of electrons during the cycling process. As a result, the ACNFs/HGCNs display a high reversible specific gravimetric capacity of ~750 mA h g-1 and volumetric capacity of ~1.1 A h cm-3 with outstanding rate capability and good cycling stability, which is superior to those of carbon nanofibers (CNFs), carbon nanotubes (CNTs), porous ACNFs, graphene nanosheets (GNSs), GNSs/CNFs, hollow carbon nanospheres and graphite. The synthesis process is simple, low-cost and environmentally friendly, providing new avenues for the rational engineering of high-energy carbon-based anode materials.

Chen, Yuming; Lu, Zhouguang; Zhou, Limin; Mai, Yiu-Wing; Huang, Haitao

2012-10-01

83

Lithium aluminosilicate reinforced with carbon nanofiber and alumina for controlled-thermal-expansion materials  

International Nuclear Information System (INIS)

Materials with a very low or tailored thermal expansion have many applications ranging from cookware to the aerospace industry. Among others, lithium aluminosilicates (LAS) are the most studied family with low and negative thermal expansion coefficients. However, LAS materials are electrical insulators and have poor mechanical properties. Nanocomposites using LAS as a matrix are promising in many applications where special properties are achieved by the addition of one or two more phases. The main scope of this work is to study the sinterability of carbon nanofiber (CNFs)/LAS and CNFs/alumina/LAS nanocomposites, and to adjust the ratio among components for obtaining a near-zero or tailored thermal expansion. Spark plasma sintering of nanocomposites, consisting of commercial CNFs and alumina powders and an ad hoc synthesized ?-eucryptite phase, is proposed as a solution to improving mechanical and electrical properties compared with the LAS ceramics obtained under the same conditions. X-ray diffraction results on phase compositions and microstructure are discussed together with dilatometry data obtained in a wide temperature range (?150 to 450 °C). The use of a ceramic LAS phase makes it possible to design a nanocomposite with a very low or tailored thermal expansion coefficient and exceptional electrical and mechanical properties.

84

Immobilization of nanofibrous A- or B-site substituted LaMnO3 perovskite-type oxides on macroscopic fiber with carbon nanofibers templates  

International Nuclear Information System (INIS)

The immobilization of nanofibrous A- or B-site substituted LaMnO3 perovskite-type oxides on macroscopic silica fiber via a unique and facile carbon nanofibers (CNFs) template-based method was reported. Field emission scanning electron microscopy (FE-SEM), coupled with X-ray diffraction (XRD) analysis confirmed the template effect and the existence of nanofibrous materials immobilized on silica fiber.

85

Controlled Growth of NiCo2O4 Nanorods and Ultrathin Nanosheets on Carbon Nanofibers for High-performance Supercapacitors  

OpenAIRE

Two one-dimensional hierarchical hybrid nanostructures composed of NiCo2O4 nanorods and ultrathin nanosheets on carbon nanofibers (CNFs) are controllably synthesized through facile solution methods combined with a simple thermal treatment. The structure of NiCo2O4 can be easily controlled to be nanorods or nanosheets by using different additives in the synthesis. These two different nanostructures are evaluated as electrodes for high performance supercapacitors, in view of their apparent adva...

Zhang, Genqiang; Lou, Xiong Wen

2013-01-01

86

Surface Characterization and Functionalization of Carbon Nanofibers  

Energy Technology Data Exchange (ETDEWEB)

Carbon nanofibers are high-aspect ratio graphitic materials that have been investigated for numerous applications due to their unique physical properties such as high strength, low density, metallic conductivity, tunable morphology, chemical and environmental stability, as well as compatibility with organochemical modification. Surface studies are extremely important for nanomaterials because not only is the surface structurally and chemically quite different from the bulk, but its properties tend to dominate at the nanoscale due to the drastically increased surface-to-volume ratio. This review surveys recent developments in surface analysis techniques used to characterize the surface structure and chemistry of carbon nanofibers and related carbon materials. These techniques include scanning probe microscopy, infrared and electron spectroscopy, electron microscopy, ion spectrometry, temperature programmed desorption and atom probe analysis. In addition, this article evaluates the methods used to modify the surface of carbon nanofibers in order to enhance their functionality to perform across an exceedingly diverse application space.

Klein, Kate L [ORNL; Melechko, Anatoli Vasilievich [ORNL; McKnight, Timothy E [ORNL; Retterer, Scott T [ORNL; Rack, Philip D [ORNL; Fowlkes, Jason Davidson [ORNL; Joy, David Charles [ORNL; Simpson, Michael L [ORNL

2008-01-01

87

Mechanical and Electrical Characterization of Entangled Networks of Carbon Nanofibers  

Directory of Open Access Journals (Sweden)

Full Text Available Entangled networks of carbon nanofibers are characterized both mechanically and electrically. Results for both tensile and compressive loadings of the entangled networks are presented for various densities. Mechanically, the nanofiber ensembles follow the micromechanical model originally proposed by van Wyk nearly 70 years ago. Interpretations are given on the mechanisms occurring during loading and unloading of the carbon nanofiber components.

Arash K. Mousavi

2014-06-01

88

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

Science.gov (United States)

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.

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

2013-01-01

89

From Carbon Nanotube Dispersion to Composite Nanofibers  

Science.gov (United States)

Composite polymer nanofibers containing single-walled carbon nanotubes (SWCNT) are fabricated by electrospinning. We describe the path from dispersing individual SWCNTs or thin bundles in water using amphiphilic polymers, through a structural characterization of the polymer conformation in the SWCNT/polymer hybrid to the characteristics of the electrospun composite nanofibers. An alternating copolymer of styrene and sodium maleate (PSSty) and gum arabic (GA)-a highly branched natural polysaccharide were successfully used to produce stable aqueous dispersions. Measurements of small angle neutron scattering (SANS) show that both polymers form a thick corona of adsorbed coils on the nanotubes. The large coils introduce a significant steric barrier stabilizing the dispersions, in addition to electrostatic repulsion by charged groups. The composite nanofibers showed good distribution and alignment of the SWCNTs in the poly(ethylene oxide) (PEO) nanfubers, as revealed by transmission electron microscopy. X-ray diffraction demonstrated a high degree of orientation of the PEO crystals in the electrospun nanofibers. Enhanced tensile properties were achieved due to the high degree of alignment of both nanotubes and polymer crystals, and a strong interface, especially with PSSty. The morphology and possible applications of these composite nanofibers will be discussed.

Cohen, Yachin; Pyckhout-Hintzen, Wim

2005-03-01

90

Dielectric transition of polyacrylonitrile derived carbon nanofibers  

Science.gov (United States)

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.

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

2014-09-01

91

One-step preparation of hydrophilic carbon nanofiber containing magnetic Ni nanoparticles materials and their application in drug delivery.  

Science.gov (United States)

A one-step process for the synthesis of hydrophilic carbon nanofibers (CNFs) through CO2 hydrogenation on NiNa/Al2O3 was developed for the loading and targeted delivery of the anticancer drug doxorubicin (DOX). CNFs that were synthesized on NiNa/Al2O3 for 9h at 500°C exhibited an adequate magnetic response and a large content of hydrophilic oxygen-containing functional groups on the carbon surface, resulting in excellent colloidal solution. The CNF material exhibited a highly efficient capacity for DOX adsorption, particularly at pH 9.0. The loading and release of DOX was strongly pH dependent, possibly due to electrostatic and ?-? stacking interactions between DOX and CNF sample. The Langmuir isotherm and pseudo second-order kinetics of DOX-loaded CNFs were well-modeled for the process of DOX adsorption. DOX-loaded CNF targeted cancer cells more selectively and effectively than free DOX and exhibited a marked tendency to kill HeLa cancer cells and reduced toxicity to normal human primary fibroblast (HPF) cells. PMID:25460704

Wang, Chih-Jen; Chen, Tse-Ching; Lin, Jarrn-Horng; Huang, Pei-Rong; Tsai, Hsing-Jui; Chen, Ching-Shiun

2015-02-15

92

Carbon nanofibers decorated with platinum nanoparticles: a novel three-dimensional platform for non-enzymatic sensing of hydrogen peroxide  

International Nuclear Information System (INIS)

We have developed a 3-dimensional (3-D) electrochemical sensor for highly sensitive detection of hydrogen peroxide (H2O2). Porous 3-D carbon nanofibers (CNFs), prepared by electrospinning, served as scaffold on a glassy carbon electrode. The 3-D CNFs were functionalized with platinum nanoparticles (Pt-NPs) by in-situ gas-phase decomposition of platinum salts at high temperature. The Pt-NPs act as an electrocatalyst for the decomposition of H2O2. TEM revealed that large amounts of Pt-NPs are deposited in the electrospun CNFs electrode even without using any stabilizer or reducing reagent. The sensor was investigated by cyclic voltammetry and amperometry and displays a good response to H2O2 with a linear range between 10 ?M and 15 mM (R?=?0.9994), a low detection limit (3.4 ?M at a signal-to-noise ratio of 3), and a response time of 3 s. The sensor shows excellent stability and selectivity. (author)

93

Enhanced electrical capacitance of porous carbon nanofibers derived from polyacrylonitrile and boron trioxide  

International Nuclear Information System (INIS)

Carbon nanofibers (CNFs) containing boron and nitrogen are prepared from polyacrylonitrile and boron trioxide (B2O3) by using simple electrospinning. The B2O3 introduction into a PAN solution causes a porous structure with stabilized [O]BN functional groups to develop in the processes of stabilization and carbonization. The pore structure and the functional groups such as B atoms and [O]BN introduce synergistic effects by not only increasing the power density but also the energy density, as shown by the results. The energy storage capabilities of the electrode prepared from 20 wt% B2O3 added to the PAN solution are as follows: a capacitance of 184.0 F g?1 and an energy density of 18.7–25.2 Wh kg?1 in the respective power density range of 400–10,000 W kg?1 in 6 M KOH electrolyte. Hence, these CNFs exhibit a very promising potential as electrode materials for electrical double-layer capacitors due to their unique microstructure and proper proportion of heteroatoms

94

Interweaved Si@C/CNTs and CNFs composites as anode materials for Li-ion batteries  

Energy Technology Data Exchange (ETDEWEB)

Graphical abstract: In summary, a serious of high-energy wet ball milling, closed spray drying and subsequent chemical vapor deposition methods were introduced successfully to fabricated novel Si@C/CNTs and CNFs composites with carbon nanotubes and carbon nanofibres interweaved with carbon coated silicon spherical composites as superior anodes in lithium-ion batteries. The core-shell structure of Si@C composites can accommodate the volume change of electrode during charge and discharge. Meanwhile, the citric acid pyrolyzed carbon was coated on the surface of the silicon perfectly and constructs the connection network of nano silicon particles. Moreover, the carbon nanotubes and carbon nanofibres, which is interweaved with nano-silicon, also allows high electrical conductivity, improved solid–electrolyte interface formation and structural integrity. Compared with pure silicon and Si@C composites, the novel Si@C/CNTs and CNFs composites had the best combination of reversible capacity and cycleablity, and this anode materials exhibited excellent electrochemical performance. The Si/C composite had a fairly high initial discharge capacity of 2168.7 mA h g{sup ?1} with an efficiency of 73%, and the discharge capacity of the 50th cycle maintained surprisingly of 1194.9 mA h g{sup ?1}. Meanwhile, spray drying and chemical vapor deposition are environmentally friendly, economical, and relatively high-yield method for the production of the Si@C/CNTs and CNFs composites in large quantities. Consequently, the novel Si@C/CNTs and CNFs composite electrodes may be a potential alternative to graphite for high energy density lithium ion batteries. Highlights: • The core/shell structured silicon/carbon composites were prepared by a facile way. • The as-prepared Si@C/CNTs and CNFs composites shows excellent electrochemical performance. • The preparation method has mild experiment conditions and high production rate. • The structure benefited electronic transfer and accommodated volume expansion. -- Abstract: Novel silicon@ carbon/carbon nanotubes and carbon nanofibres (Si@C/CNTs and CNFs) composites have been successfully synthesized by a serious of high-energy wet ball milling, closed spray drying and subsequently chemical vapor deposition methods, in which carbon nanotubes and carbon nanofibers are interweaved with carbon coated silicon (Si@C) spherical composites. As anode materials for lithium-ion batteries, the Si@C/CNTs and CNFs composites demonstrate a high first discharge capacity and excellent cycle ability. The high initial specific discharge capacity is approximately 2169 mA h g{sup ?1} and a reversible specific capacity approached 1195 mA h g{sup ?1} after 50 cycles at a high current density of 300 mA g{sup ?1}.

Zhang, Miao [School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510006 (China); Hou, Xianhua, E-mail: houxh@scnu.edu.cn [School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510006 (China); Engineering Research Center of Materials and Technology for Electrochemical Energy Storage Ministry of Education, Guangzhou 510006 (China); Wang, Jie; Li, Min [School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510006 (China); Hu, Shejun [School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510006 (China); Engineering Research Center of Materials and Technology for Electrochemical Energy Storage Ministry of Education, Guangzhou 510006 (China); Shao, Zongping [Nanjing University of Technology, College of Chemistry and Chemical Engineering, Nanjing 210009 (China); Liu, Xiang [Institute of Advanced Materials, Nanjing University of Technology, Nanjing 210009 (China)

2014-03-05

95

Carbon nanofibers: a versatile catalytic support  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english The aim of this article is present an overview of the promising results obtained while using carbon nanofibers based composites as catalyst support for different practical applications: hydrazine decomposition, styrene synthesis, direct oxidation of H2S into elementary sulfur and as fuel-cell electr [...] odes. We have also discussed some prospects of the use of these new materials in total combustion of methane and in ammonia decomposition. The macroscopic carbon nanofibers based composites were prepared by the CVD method (Carbon Vapor Deposition) employing a gaseous mixture of hydrogen and ethane. The results showed a high catalytic activity and selectivity in comparison to the traditional catalysts employed in these reactions. The fact was attributed, mainly, to the morphology and the high external surface of the catalyst support.

Nelize Maria de Almeida, Coelho; Jomar Livramento Barros, Furtado; Cuong, Pham-Huu; Ricardo, Vieira.

2008-09-01

96

Carbon nanofiber/polyethylene nanocomposite: Processing behavior, microstructure and electrical properties  

International Nuclear Information System (INIS)

Highlights: • Electrically conductive CNF/HDPE nanocomposite were prepared by melt compounding. • The effect of processing on the nanocomposites macro and micro structures was analyzed. • 1.4 vol% CNF were required to construct a conductive network within the HDPE matrix. • An EMI SE of 42 dB was reported for 15 vol% CNF/HDPE nanocomposite. • An empirical model was developed to estimate the EMI SE. - Abstract: Electrically conductive polymer nanocomposite of high density polyethylene (HDPE) filled with carbon nanofibers (CNFs) were prepared by melt compounding in a batch mixer. The nanocomposite processing behavior was studied by monitoring the mixing torque vs. time as function of filler content. Scanning electron microscopy and optical microscopy were used to investigate the nanocomposite dispersion of nanofiller and the adhesion between the nanofiller and polymer matrix. The electrical and electromagnetic interference (EMI) shielding behaviors of the nanocomposite were reported as function of nanofibers concentration, and an empirical correlation related the EMI SE to the nanocomposite’s electrical resistivity was developed. Good level of CNF dispersion was evident despite the poor adhesion exhibited between the nanofibers and the HDPE matrix. At 1.5 vol% CNF loading, the nanocomposite exhibited an electrical volume resistivity of 105 ?·cm. EMI shielding effectiveness was found to increase with increase in nanofiller concentration. In the 0.1–1.5 GHz frequency range, 2 mm thick plate made of 5 vol% CNF/HDPE nanocomposite exhibits an EMI shielding effectiveness of 20 dB

97

Structural characteristics of carbon nanofibers for on-chip interconnect applications  

International Nuclear Information System (INIS)

In this letter, we compare the structures of plasma-enhanced chemical vapor deposition of Ni-catalyzed and Pd-catalyzed carbon nanofibers (CNFs) synthesized for on-chip interconnect applications with scanning transmission electron microscopy (STEM). The Ni-catalyzed CNF has a conventional fiberlike structure and many graphitic layers that are almost parallel to the substrate at the CNF base. In contrast, the Pd-catalyzed CNF has a multiwall nanotubelike structure on the sidewall spanning the entire CNF. The microstructure observed in the Pd-catalyzed fibers at the CNF-metal interface has the potential to lower contact resistance significantly, as our electrical measurements using current-sensing atomic force microscopy indicate. A structural model is presented based on STEM image analysis

98

Structural characteristics of carbon nanofibers for on-chip interconnect applications  

Science.gov (United States)

In this letter, we compare the structures of plasma-enhanced chemical vapor deposition of Ni-catalyzed and Pd-catalyzed carbon nanofibers (CNFs) synthesized for on-chip interconnect applications with scanning transmission electron microscopy (STEM). The Ni-catalyzed CNF has a conventional fiberlike structure and many graphitic layers that are almost parallel to the substrate at the CNF base. In contrast, the Pd-catalyzed CNF has a multiwall nanotubelike structure on the sidewall spanning the entire CNF. The microstructure observed in the Pd-catalyzed fibers at the CNF-metal interface has the potential to lower contact resistance significantly, as our electrical measurements using current-sensing atomic force microscopy indicate. A structural model is presented based on STEM image analysis.

Ominami, Yusuke; Ngo, Quoc; Austin, Alexander J.; Yoong, Hans; Yang, Cary Y.; Cassell, Alan M.; Cruden, Brett A.; Li, Jun; Meyyappan, M.

2005-12-01

99

Functionalization of carbon nanofibers with elastomeric block copolymer using carbodiimide chemistry  

International Nuclear Information System (INIS)

Surface functionalization of carbon nanofibers (CNFs) with aminopropyl terminated polydimethylsiloxane [(PDMS-NH2)] and other organic diamines was achieved using carbodiimide chemistry. The carbodiimide chemistry provides faster reaction rate so that the reaction occurs at lower temperature compared to amidation and acylation-amidation chemistry. CNF functionalized with PDMS-NH2 fibers were further functionalized with oligomer of polyimide (6FDA-BisP) using imidization reaction. The formation of block copolymer on the surface of CNF is proposed as an effective method to engineer the interphase between the fiber and the polymer, which is essential to modulate and enhance the properties of the nanocomposite. The efficiency of the carbodiimide chemistry to functionalize amine terminated groups on CNF and the functionalization of block copolymer was characterized using thermal gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and UV-vis spectroscopy.

100

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

Science.gov (United States)

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

Zou, Mingzhong; Li, Jiaxin; Wen, WeiWei; Chen, Luzhuo; Guan, Lunhui; Lai, Heng; Huang, Zhigao

2014-12-01

101

Carbon nanofiber/cobalt oxide nanopyramid core-shell nanowires for high-performance lithium-ion batteries  

Science.gov (United States)

Carbon nanofiber (CNF)/Co3O4 nanopyramid core-shell nanowires (NWs) are synthesized using an electrospinning method followed by reduction and hydrothermal treatment in order to improve the capacity, cycle stability, and high-rate capability of the electrodes in Li ion batteries (LIBs). The morphology, crystal structure, and chemical states of all samples are investigated by means of field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and thermogravimetric analysis. For comparison, conventional CNFs, octahedral Co3O4, and Co3O4/CNF composite electrodes are prepared. LIB cells fabricate with the CNF/Co3O4 nanopyramid core-shell NWs exhibit superb discharge capacity (1173 mAh g-1 at the 1st cycle), cycle stability (795 mAh g-1 at 50 cycles), high initial Coulombic efficiency (84.8%), and high-rate capability (570 mAh g-1 at a current density of 700 mA g-1) as compared to the conventional CNF, octahedral Co3O4, and Co3O4/CNF composite electrodes. The performance improvement is owing to the introduction of one-dimensional CNFs relative to efficient electron transport in the core region, extensive utilization of Co3O4 nanopyramids with high capacity grown closely on the CNFs in the shell region, and the network structures of the electrode relative to the improvement of Li ion diffusion.

An, Geon-Hyoung; Ahn, Hyo-Jin

2014-12-01

102

Long-term cycling studies on electrospun carbon nanofibers as anode material for lithium ion batteries.  

Science.gov (United States)

Electrospun carbon nanofibers (CNF) have been prepared at different calcination temperatures for a prolonged time (12 h) derived from electrospun polyacrylonitrile (PAN) membranes. They are studied as anode materials in lithium ion batteries due to their high reversible capacity, improved long-term cycle performance, and good rate capacity. The fibrous morphologies of fresh electrodes and tested samples for more than 550 cycles have been compared; cyclic voltammogram (CV) has also been studied to understand the lithium intercalation/deintercalation mechanism of 1D nanomaterials. CNFs demonstrate interesting galvanostatic performance with fading capacity after the first few cycles, and the capacity increases during long-term cycling. The increasing capacity is observed accompanied by volumetric expansion on the nanofibers' edge. Results of rate capacity have also been explored for all CNF samples, and their stable electrochemical performances are further analyzed by the galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy (EIS). CNF carbonized at 800 °C is found to have a larger lithium ion storage ability and better cyclic stability than that carbonized at 600 and 1000 °C. PMID:24171411

Wu, Yongzhi; Reddy, M V; Chowdari, B V R; Ramakrishna, S

2013-11-27

103

Copper-doped Li4Ti5O12/carbon nanofiber composites as anode for high-performance sodium-ion batteries  

Science.gov (United States)

Lithium titanium oxide (Li4Ti5O12) is a promising anode material, owing to its superior safety and reliability. However, the main challenge of Li4Ti5O12 is the low material conductivity which restricts its electrochemical performance. In order to use Li4Ti5O12 in practical sodium-ion batteries, copper-doped Li4Ti5O12 (Li4-xCuxTi5O12, x = 0, 0.05, 0.1) nanoparticles were prepared to enhance the electronic conductivity. Copper-doped Li4Ti5O12 nanoparticles were then embedded in continuous carbon nanofibers (CNFs), which gave rise to fast electron transfer along the fiber direction. After copper-doping and CNF embedding, the resultant copper-doped Li4Ti5O12/CNFs achieved excellent reversible capacity (158.1 mAh g-1) at 30 mA g-1, high coulombic efficiency (99.87%), and good capacity retention (91%) after 150 cycles. In addition, copper-doped Li4Ti5O12/CNFs also exhibited good rate capability. It is, therefore, demonstrated that copper-doped Li4Ti5O12/CNFs are promising anode candidate.

Ge, Yeqian; Jiang, Han; Fu, Kun; Zhang, Changhuan; Zhu, Jiadeng; Chen, Chen; Lu, Yao; Qiu, Yiping; Zhang, Xiangwu

2014-12-01

104

The synthesis of titanium carbide-reinforced carbon nanofibers  

International Nuclear Information System (INIS)

Tailoring hard materials into nanoscale building blocks can greatly extend the applications of hard materials and, at the same time, also represents a significant challenge in the field of nanoscale science. This work reports a novel process for the preparation of carbon-based one-dimensional hard nanomaterials. The titanium carbide-carbon composite nanofibers with an average diameter of 90 nm are prepared by an electrospinning technique and a high temperature pyrolysis process. A composite solution containing polyacrylonitrile and titanium sources is first electrospun into the composite nanofibers, which are subsequently pyrolyzed to produce the desired products. The x-ray diffraction pattern and transmission electron microscopy results show that the main phase of the as-synthesized nanofibers is titanium carbide. The Raman analyses show that the composite nanofibers have low graphite clusters in comparison with the pure carbon nanofibers originating from the electrospun polyacrylonitrile nanofibers. The mechanical property tests demonstrate that the titanium carbide-carbon nanofiber membranes have four times higher tensile strength than the carbon nanofiber membranes, and the Young's modulus of the titanium carbide-carbon nanofiber membranes increases in direct proportion to the titanium quantity.

105

The synthesis of titanium carbide-reinforced carbon nanofibers  

Science.gov (United States)

Tailoring hard materials into nanoscale building blocks can greatly extend the applications of hard materials and, at the same time, also represents a significant challenge in the field of nanoscale science. This work reports a novel process for the preparation of carbon-based one-dimensional hard nanomaterials. The titanium carbide-carbon composite nanofibers with an average diameter of 90 nm are prepared by an electrospinning technique and a high temperature pyrolysis process. A composite solution containing polyacrylonitrile and titanium sources is first electrospun into the composite nanofibers, which are subsequently pyrolyzed to produce the desired products. The x-ray diffraction pattern and transmission electron microscopy results show that the main phase of the as-synthesized nanofibers is titanium carbide. The Raman analyses show that the composite nanofibers have low graphite clusters in comparison with the pure carbon nanofibers originating from the electrospun polyacrylonitrile nanofibers. The mechanical property tests demonstrate that the titanium carbide-carbon nanofiber membranes have four times higher tensile strength than the carbon nanofiber membranes, and the Young's modulus of the titanium carbide-carbon nanofiber membranes increases in direct proportion to the titanium quantity.

Zhu, Pinwen; Hong, Youliang; Liu, Bingbing; Zou, Guangtian

2009-06-01

106

The synthesis of titanium carbide-reinforced carbon nanofibers  

Energy Technology Data Exchange (ETDEWEB)

Tailoring hard materials into nanoscale building blocks can greatly extend the applications of hard materials and, at the same time, also represents a significant challenge in the field of nanoscale science. This work reports a novel process for the preparation of carbon-based one-dimensional hard nanomaterials. The titanium carbide-carbon composite nanofibers with an average diameter of 90 nm are prepared by an electrospinning technique and a high temperature pyrolysis process. A composite solution containing polyacrylonitrile and titanium sources is first electrospun into the composite nanofibers, which are subsequently pyrolyzed to produce the desired products. The x-ray diffraction pattern and transmission electron microscopy results show that the main phase of the as-synthesized nanofibers is titanium carbide. The Raman analyses show that the composite nanofibers have low graphite clusters in comparison with the pure carbon nanofibers originating from the electrospun polyacrylonitrile nanofibers. The mechanical property tests demonstrate that the titanium carbide-carbon nanofiber membranes have four times higher tensile strength than the carbon nanofiber membranes, and the Young's modulus of the titanium carbide-carbon nanofiber membranes increases in direct proportion to the titanium quantity.

Zhu Pinwen; Hong Youliang; Liu Bingbing; Zou Guangtian [State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China)], E-mail: ylhong@jlu.edu.cn

2009-06-24

107

Effect of carbon nanofiber surface groups on oxygen reduction reaction of supported Pt electrocatalyst  

International Nuclear Information System (INIS)

Highlights: ? We studied the effect of oxygen-groups on the particle size and deposition of Pt particles. ? Pt/CNF-OH exhibits smaller Pt mean particle size compared with Pt/CNF-OX. ? Pt/CNF-OH/GC electrode exhibits a better ORR activity than Pt/CNF-OX/GC electrode. -- Abstract: Pt nanoparticles supported on the acid-treated carbon nanofiber (CNF-OX) and LiAlH4-treated carbon nanofiber (CNF-OH) are synthesized via ethylene glycol reduction method. The nature of oxygen-containing surface groups on the CNF-OX and CNF-OH is investigated by potentiometric titration and XPS characterization. Titration of the support materials shows that LiAlH4 can effectively convert the carboxylic acid groups (from 0.21 mmol g?1 to 0.06 mmol g?1) to hydroxyl groups (from 0.09 mmol g?1 to 0.17 mmol g?1), which is agreed well with the results of XPS characterization. High resolution transmission electron microscopy (HRTEM) characterization shows that the Pt nanoparticles are highly dispersed on the two modified CNFs, and the Pt nanoparticles supported on the CNF-OH have a smaller particle size and a more uniform particle size distribution. Rotating disk electrode (RDE) analysis reveals that Pt/CNF-OH exhibits a better activity for ORR than Pt/CNF-OX, and this may be associated with the smaller particle size and better dispersion of Pt nanoparticles on the CNF-OH

108

The role of carbon nanofiber defects on the electrical and mechanical properties of CNF-based resins  

International Nuclear Information System (INIS)

Heat treatment of carbon nanofibers has proven to be an effective method in removing defects from carbon nanofibers, causing a strong increase in their structural perfection and thermal stability. It affects the bonding states of carbon atoms in the nanofiber structure and causes a significant transformation in the hybridization state of the bonded carbon atoms. Nanofilled resins made of heat-treated CNF show significant increases in their electrical conductivity even at low concentrations. This confirms that enhancement in the perfection of the fiber structure with consequent change in the morphological features plays a prominent role in affecting the electrical properties. Indeed heat-treated CNFs display a stiff structure and a smooth surface which tends to lower the thickness of the unavoidable insulating epoxy layer formed around the CNF which, in turn, plays a fundamental role in the electrical transport properties along the conducting clusters. This might be very beneficial in terms of electrical conductivity but might have negligible effect on the mechanical properties. (paper)

109

IN-SITU SYNCHROTRON SAXS/WAXD STUDIES DURING MELT SPINNING OF MODIFIED CARBON NANOFIBER AND ISOTACTIC POLYPROPYLENE NANOCOMPOSITE  

International Nuclear Information System (INIS)

The structural development of a nanocomposite, containing 95 wt% isotactic polypropylene (iPP) and 5 wt% modified carbon nanofiber (MCNF), during fiber spinning was investigated by in situ synchrotron small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) techniques. The modification of carbon nanofibers (CNFs) was accomplished by a chemical surface treatment using in situ polymerization of olefin segments to enhance its compatibility with iPP, where the iPP/MCNF nanocomposite was prepared by twostep blending to ensure the dispersion of MCNF. X-ray results showed that at low spin-draw ratios, the iPP/MCNF nanocomposite fiber exhibited much higher iPP crystalline orientation than the control iPP fiber. At higher spin-draw ratios, the crystalline orientation of the nanocomposite fiber and that of the pure iPP fiber was about the same. The crystallinity of the composite fiber was higher than that of the control iPP fiber, indicating the nucleating effect of the modified carbon nanofibers. The nanocomposite fiber also showed larger long periods at low spin-draw ratios. Measurements of mechanical properties indicated that the nanocomposite fiber with 5 wt% MCNF had much higher tensile strength, modulus and longer elongation to break. The mechanical enhancement can be attributed to the dispersion of MCNF in the matrix, which was confirmed by SEM results

110

Development of bimetal-grown multi-scale carbon micro-nanofibers as an immobilizing matrix for enzymes in biosensor applications  

International Nuclear Information System (INIS)

This study describes the development of a novel bimetal (Fe and Cu)-grown hierarchical web of carbon micro-nanofiber-based electrode for biosensor applications, in particular to detect glucose in liquids. Carbon nanofibers (CNFs) are grown on activated carbon microfibers (ACFs) by chemical vapor deposition (CVD) using Cu and Fe as the metal catalysts. The transition metal-fiber composite is used as the working electrode of a biosensor applied to detect glucose in liquids. In such a bi-nanometal-grown multi-scale web of ACF/CNF, Cu nanoparticles adhere to the ACF-surface, whereas Fe nanoparticles used to catalyze the growth of nanofibers attach to the CNF tips. By ultrasonication, Fe nanoparticles are dislodged from the tips of the CNFs. Glucose oxidase (GOx) is subsequently immobilized on the tips by adsorption. The dispersion of Cu nanoparticles at the substrate surface results in increased conductivity, facilitating electron transfer from the glucose solution to the ACF surface during the enzymatic reaction with glucose. The prepared Cu-ACF/CNF/GOx electrode is characterized for various surface and physicochemical properties by different analytical techniques, including scanning electron microscopy (SEM), electron dispersive X-ray analysis (EDX), Fourier-transform infrared spectroscopy (FTIR), BET surface area analysis, and transmission electron microscopy (TEM). The electrochemical tests show that the prepared electrode has fast response current, electrochemical stability, and high electron transfer rate, corroborated by CV and calibration curves. The prepared transition metal-based carbon electrode in this study is cost-effective, simple to develop, and has a stable immobilization matrix for enzymes. - Graphical abstract: A novel bimetal (Fe and Cu)-grown hierarchical web of carbon micro-nanofiber-based electrode is synthesized for biosensor applications, in particular to detect glucose in liquids. Carbon nanofibers are grown on activated carbon microfibers by chemical vapor deposition using Cu and Fe as the metal catalysts. In such a bi-nanometal-grown multi-scale web of ACF/CNF, Cu nanoparticles adhere to the ACF-surface, whereas Fe nanoparticles used to catalyze the growth of nanofibers attach to the CNF tips. Following ultrasonication, Fe nanoparticles are dislodged and replaced with glucose oxidase. The electrochemical tests show that the prepared electrode has fast response current, electrochemical stability, and high electron transfer rate, corroborated by its CV and calibration curves. Highlights: • Fe–Cu-grown web of carbon micro-nanofiber-based electrode was prepared. • The carbon electrode was applied to detect glucose in liquids. • It has electrochemical stability and high electron transfer rate. • The electrode is cost-effective and simple to develop. • It has a stable immobilization matrix for enzymes

111

Development of bimetal-grown multi-scale carbon micro-nanofibers as an immobilizing matrix for enzymes in biosensor applications  

Energy Technology Data Exchange (ETDEWEB)

This study describes the development of a novel bimetal (Fe and Cu)-grown hierarchical web of carbon micro-nanofiber-based electrode for biosensor applications, in particular to detect glucose in liquids. Carbon nanofibers (CNFs) are grown on activated carbon microfibers (ACFs) by chemical vapor deposition (CVD) using Cu and Fe as the metal catalysts. The transition metal-fiber composite is used as the working electrode of a biosensor applied to detect glucose in liquids. In such a bi-nanometal-grown multi-scale web of ACF/CNF, Cu nanoparticles adhere to the ACF-surface, whereas Fe nanoparticles used to catalyze the growth of nanofibers attach to the CNF tips. By ultrasonication, Fe nanoparticles are dislodged from the tips of the CNFs. Glucose oxidase (GOx) is subsequently immobilized on the tips by adsorption. The dispersion of Cu nanoparticles at the substrate surface results in increased conductivity, facilitating electron transfer from the glucose solution to the ACF surface during the enzymatic reaction with glucose. The prepared Cu-ACF/CNF/GOx electrode is characterized for various surface and physicochemical properties by different analytical techniques, including scanning electron microscopy (SEM), electron dispersive X-ray analysis (EDX), Fourier-transform infrared spectroscopy (FTIR), BET surface area analysis, and transmission electron microscopy (TEM). The electrochemical tests show that the prepared electrode has fast response current, electrochemical stability, and high electron transfer rate, corroborated by CV and calibration curves. The prepared transition metal-based carbon electrode in this study is cost-effective, simple to develop, and has a stable immobilization matrix for enzymes. - Graphical abstract: A novel bimetal (Fe and Cu)-grown hierarchical web of carbon micro-nanofiber-based electrode is synthesized for biosensor applications, in particular to detect glucose in liquids. Carbon nanofibers are grown on activated carbon microfibers by chemical vapor deposition using Cu and Fe as the metal catalysts. In such a bi-nanometal-grown multi-scale web of ACF/CNF, Cu nanoparticles adhere to the ACF-surface, whereas Fe nanoparticles used to catalyze the growth of nanofibers attach to the CNF tips. Following ultrasonication, Fe nanoparticles are dislodged and replaced with glucose oxidase. The electrochemical tests show that the prepared electrode has fast response current, electrochemical stability, and high electron transfer rate, corroborated by its CV and calibration curves. Highlights: • Fe–Cu-grown web of carbon micro-nanofiber-based electrode was prepared. • The carbon electrode was applied to detect glucose in liquids. • It has electrochemical stability and high electron transfer rate. • The electrode is cost-effective and simple to develop. • It has a stable immobilization matrix for enzymes.

Hood, Amit R. [Department of Chemical Engineering, Indian Institute of Technology, Kanpur (India); Saurakhiya, Neelam; Deva, Dinesh [DST Unit on Nanosciences, Kanpur, 208016 (India); Sharma, Ashutosh [Department of Chemical Engineering, Indian Institute of Technology, Kanpur (India); DST Unit on Nanosciences, Kanpur, 208016 (India); Verma, Nishith, E-mail: nishith@iitk.ac.in [Department of Chemical Engineering, Indian Institute of Technology, Kanpur (India); Center for Environmental Science and Engineering, Kanpur 208016 (India)

2013-10-15

112

ADSORPTION OF MULTIWALLED CARBON NANOTUBES ON ELECTROSPUN POLYCAPROLACTON NANOFIBERS  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: English Abstract in english Polycaprolacton (PCL) and multiwalled carbon nanotubes/PCL (P-MWNT/PCL) were prepared by electrospinning technique. The average diameter of the nanofibers was below 400 nm. The mechanical properties of the P-MWNT/PCL nanofibers were higher than that of neat PCL nanofibers. It was also found that the [...] mechanical properties of the composite nanofibers were decreased as increased the amount of P-MWNTs, which were due to the poor dispersion of the P-MWNTs in the PCL matrix or agglomeration of MWNTs at high concentration. The thermal stability of the P-MWNT/PCL nanofibers was higher than PCL nanofibers. The conductivity of the adsorbed P-MWNT on PCL (

KHALID, SAEED; PARK, SOO-YOUNG; MOHAMMAD, ISHAQ.

2009-12-01

113

Potential applications of nanofiber textile covered by carbon coatings  

Directory of Open Access Journals (Sweden)

Full Text Available Purpose: Nanospider technology is modified electrospinning method for production nanofiber textile from polymer solutions. This material can be used as wound dressing and filter materials for example. Carbon coatings deposited onto surface of polymer nanofiber textiles are predicted to improve filtration effectivity of filters and bioactivity of wound dressings. Carbon coatings have been produced by Microwave Radio Frequency Plasma Assisted Chemical Vapor Deposition (MW/RF PACVD method.Design/methodology/approach: Carbon coatings were deposited on polymer nanofiber textile by MW/RF PACVD method. Nanocomposite obtained in this way was characterized by the contact angle studies and by scanning electron microscope (SEM.Findings: Carbon coatings can be deposited on the polymer nanofibers by MW/RF PACVD method. Content of diamond phase in produced carbon coatings has been confirmed by wetability test. A SEM microscopic images have shown that the spaces between the nanofibers have not been closed by the material of the film.Research limitations/implications: MW/RF PACVD makes carbon coating synthesis possible in lower temperature, what is essential in case of applying the polymer substrate. Use of any other method than MW/RF PACVD for deposition of carbon coatings onto polymer nanofiber textile is not covered in this paper.Practical implications: Nanofiber textile produced by Nanospider is very good mechanical filter. Carbon onto surface of nanofibers can cause from this material active filter. Since this nanocomposite enables the transport of oxygen and exudate, simultaneously is impenetrable for bacteria or even viruses, it can be used for wound dressing.Originality/value: It is our belief that we are first to have deposited carbon coatings on nanofiber textile. We hope that in this way we have prepared very good material for filtration of air and for wound dressing.

Z. Ro?ek

2008-03-01

114

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

OpenAIRE

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 ...

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

2014-01-01

115

On Compiling Structured CNFs to OBDDs  

OpenAIRE

We present new results on the size of OBDD representations of structurally characterized classes of CNF formulas. First, we identify a natural sufficient condition, which we call the few subterms property, for a class of CNFs to have polynomial OBDD size; we then prove that CNFs whose incidence graphs are variable convex have few subterms (and hence have polynomial OBDD size), and observe that the few subterms property also explains the known fact that classes of CNFs of bou...

Bova, Simone; Slivovsky, Friedrich

2014-01-01

116

Evaluation of carbon fiber composites modified by in situ incorporation of carbon nanofibers  

Directory of Open Access Journals (Sweden)

Full Text Available Nano-carbon materials, such as carbon nanotubes and carbon nanofibers, are being thought to be used as multifunctional reinforcement in composites. The growing of carbon nanofiber at the carbon fiber/epoxy interface results in composites having better electrical properties than conventional carbon fiber/epoxy composites. In this work, carbon nanofibers were grown in situ over the surface of a carbon fiber fabric by chemical vapor deposition. Specimens of carbon fiber/nanofiber/epoxy (CF/CNF/epoxy composites were molded and electrical conductivity was measured. Also, the CF/CNF/epoxy composites were tested under flexure and interlaminar shear. The results showed an overall reduction in mechanical properties as a function of added nanofiber, although electrical conductivity increased up to 74% with the addition of nanofibers. Thus CF/CNF/epoxy composites can be used as electrical dissipation discharge materials.

André Navarro de Miranda

2011-12-01

117

Preparation of a new adsorbent from activated carbon and carbon nanofiber (AC/CNF for manufacturing organic-vacbpour respirator cartridge  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract In this study a composite of activated carbon and carbon nanofiber (AC/CNF was prepared to improve the performance of activated carbon (AC for adsorption of volatile organic compounds (VOCs and its utilization for respirator cartridges. Activated carbon was impregnated with a nickel nitrate catalyst precursor and carbon nanofibers (CNF were deposited directly on the AC surface using catalytic chemical vapor deposition. Deposited CNFs on catalyst particles in AC micropores, were activated by CO2 to recover the surface area and micropores. Surface and textural characterizations of the prepared composites were investigated using Brunauer, Emmett and Teller’s (BET technique and electron microscopy respectively. Prepared composite adsorbent was tested for benzene, toluene and xylene (BTX adsorption and then employed in an organic respirator cartridge in granular form. Adsorption studies were conducted by passing air samples through the adsorbents in a glass column at an adjustable flow rate. Finally, any adsorbed species not retained by the adsorbents in the column were trapped in a charcoal sorbent tube and analyzed by gas chromatography. CNFs with a very thin diameter of about 10-20 nm were formed uniformly on the AC/CNF. The breakthrough time for cartridges prepared with CO2 activated AC/CNF was 117 minutes which are significantly longer than for those cartridges prepared with walnut shell- based activated carbon with the same weight of adsorbents. This study showed that a granular form CO2 activated AC/CNF composite could be a very effective alternate adsorbent for respirator cartridges due to its larger adsorption capacities and lower weight.

Forushani Abbas Rahimi

2013-01-01

118

Preparation of a new adsorbent from activated carbon and carbon nanofiber (AC/CNF) for manufacturing organic-vacbpour respirator cartridge.  

Science.gov (United States)

In this study a composite of activated carbon and carbon nanofiber (AC/CNF) was prepared to improve the performance of activated carbon (AC) for adsorption of volatile organic compounds (VOCs) and its utilization for respirator cartridges. Activated carbon was impregnated with a nickel nitrate catalyst precursor and carbon nanofibers (CNF) were deposited directly on the AC surface using catalytic chemical vapor deposition. Deposited CNFs on catalyst particles in AC micropores, were activated by CO2 to recover the surface area and micropores. Surface and textural characterizations of the prepared composites were investigated using Brunauer, Emmett and Teller's (BET) technique and electron microscopy respectively. Prepared composite adsorbent was tested for benzene, toluene and xylene (BTX) adsorption and then employed in an organic respirator cartridge in granular form. Adsorption studies were conducted by passing air samples through the adsorbents in a glass column at an adjustable flow rate. Finally, any adsorbed species not retained by the adsorbents in the column were trapped in a charcoal sorbent tube and analyzed by gas chromatography. CNFs with a very thin diameter of about 10-20 nm were formed uniformly on the AC/CNF. The breakthrough time for cartridges prepared with CO2 activated AC/CNF was 117 minutes which are significantly longer than for those cartridges prepared with walnut shell- based activated carbon with the same weight of adsorbents. This study showed that a granular form CO2 activated AC/CNF composite could be a very effective alternate adsorbent for respirator cartridges due to its larger adsorption capacities and lower weight. PMID:23369424

Jahangiri, Mehdi; Adl, Javad; Shahtaheri, Seyyed Jamaleddin; Rashidi, Alimorad; Ghorbanali, Amir; Kakooe, Hossein; Forushani, Abbas Rahimi; Ganjali, Mohammad Reza

2013-01-01

119

Growth of carbon nanostructures on carbonized electrospun nanofibers with palladium nanoparticles  

Science.gov (United States)

This paper studies the mechanism of the formation of carbon nanostructures on carbon nanofibers with Pd nanoparticles by using different carbon sources. The carbon nanofibers with Pd nanoparticles were produced by carbonizing electrospun polyacrylonitrile (PAN) nanofibers including Pd(Ac)2. Such PAN-based carbon nanofibers were then used as substrates to grow hierarchical carbon nanostructures. Toluene, pyridine and chlorobenzine were employed as carbon sources for the carbon nanostructures. With the Pd nanoparticles embedded in the carbonized PAN nanofibers acting as catalysts, molecules of toluene, pyridine or chlorobenzine were decomposed into carbon species which were dissolved into the Pd nanoparticles and consequently grew into straight carbon nanotubes, Y-shaped carbon nanotubes or carbon nano-ribbons on the carbon nanofiber substrates. X-ray diffraction analysis and transmission electron microscopy (TEM) were utilized to capture the mechanism of formation of Pd nanoparticles, regular carbon nanotubes, Y-shaped carbon nanotubes and carbon nano-ribbons. It was observed that the Y-shaped carbon nanotubes and carbon nano-ribbons were formed on carbonized PAN nanofibers containing Pd-nanoparticle catalyst, and the carbon sources played a crucial role in the formation of different hierarchical carbon nanostructures.

Lai, Chuilin; Guo, Qiaohui; Wu, Xiang-Fa; Reneker, Darrell H.; Hou, Haoqing

2008-05-01

120

Growth of carbon nanostructures on carbonized electrospun nanofibers with palladium nanoparticles  

Energy Technology Data Exchange (ETDEWEB)

This paper studies the mechanism of the formation of carbon nanostructures on carbon nanofibers with Pd nanoparticles by using different carbon sources. The carbon nanofibers with Pd nanoparticles were produced by carbonizing electrospun polyacrylonitrile (PAN) nanofibers including Pd(Ac){sub 2}. Such PAN-based carbon nanofibers were then used as substrates to grow hierarchical carbon nanostructures. Toluene, pyridine and chlorobenzine were employed as carbon sources for the carbon nanostructures. With the Pd nanoparticles embedded in the carbonized PAN nanofibers acting as catalysts, molecules of toluene, pyridine or chlorobenzine were decomposed into carbon species which were dissolved into the Pd nanoparticles and consequently grew into straight carbon nanotubes, Y-shaped carbon nanotubes or carbon nano-ribbons on the carbon nanofiber substrates. X-ray diffraction analysis and transmission electron microscopy (TEM) were utilized to capture the mechanism of formation of Pd nanoparticles, regular carbon nanotubes, Y-shaped carbon nanotubes and carbon nano-ribbons. It was observed that the Y-shaped carbon nanotubes and carbon nano-ribbons were formed on carbonized PAN nanofibers containing Pd-nanoparticle catalyst, and the carbon sources played a crucial role in the formation of different hierarchical carbon nanostructures.

Lai Chuilin; Guo Qiaohui; Hou Haoqing [Chemistry College of Jiangxi Normal University, Nanchang 330027 (China); Wu Xiangfa [Department of Engineering Mechanics, University of Nebraska-Lincoln, Lincoln, NE 68588-0526 (United States); Reneker, Darrell H [Department of Polymer Science, University of Akron, Akron, OH 44325 (United States)], E-mail: haoqing@jxnu.edu.cn

2008-05-14

121

Growth of carbon nanostructures on carbonized electrospun nanofibers with palladium nanoparticles  

International Nuclear Information System (INIS)

This paper studies the mechanism of the formation of carbon nanostructures on carbon nanofibers with Pd nanoparticles by using different carbon sources. The carbon nanofibers with Pd nanoparticles were produced by carbonizing electrospun polyacrylonitrile (PAN) nanofibers including Pd(Ac)2. Such PAN-based carbon nanofibers were then used as substrates to grow hierarchical carbon nanostructures. Toluene, pyridine and chlorobenzine were employed as carbon sources for the carbon nanostructures. With the Pd nanoparticles embedded in the carbonized PAN nanofibers acting as catalysts, molecules of toluene, pyridine or chlorobenzine were decomposed into carbon species which were dissolved into the Pd nanoparticles and consequently grew into straight carbon nanotubes, Y-shaped carbon nanotubes or carbon nano-ribbons on the carbon nanofiber substrates. X-ray diffraction analysis and transmission electron microscopy (TEM) were utilized to capture the mechanism of formation of Pd nanoparticles, regular carbon nanotubes, Y-shaped carbon nanotubes and carbon nano-ribbons. It was observed that the Y-shaped carbon nanotubes and carbon nano-ribbons were formed on carbonized PAN nanofibers containing Pd-nanoparticle catalyst, and the carbon sources played a crucial role in the formation of different hierarchical carbon nanostructures

122

Friction of partially embedded vertically aligned carbon nanofibers inside elastomers  

International Nuclear Information System (INIS)

Vertically aligned carbon nanofibers partially embedded inside polyurethane (eVACNFs) are proposed as a robust high friction fibrillar material with a compliant backing. Carbon nanofibers with 50-150 nm in diameter and 20-30 ?m in length are vertically grown on silicon and transferred completely inside an elastomer by vacuum molding. By using time controlled and selective oxygen plasma etching, fibers are partially released up to 5 ?m length. Macroscale friction experiments show that eVACNFs exhibit reproducible effective friction coefficients up to 1. Besides high friction, the proposed fabrication method improves fiber-substrate bond strength, and enables uniform height nanofibers with a compliant backing

123

Carbon nanofiber reinforced epoxy matrix composites and syntactic foams - mechanical, thermal, and electrical properties  

Science.gov (United States)

The tailorability of composite materials is crucial for use in a wide array of real-world applications, which range from heat-sensitive computer components to fuselage reinforcement on commercial aircraft. The mechanical, electrical, and thermal properties of composites are highly dependent on their material composition, method of fabrication, inclusion orientation, and constituent percentages. The focus of this work is to explore carbon nanofibers (CNFs) as potential nanoscale reinforcement for hollow particle filled polymer composites referred to as syntactic foams. In the present study, polymer composites with high weight fractions of CNFs, ranging from 1-10 wt.%, are used for quasi-static and high strain rate compression analysis, as well as for evaluation and characterization of thermal and electrical properties. It is shown that during compressive characterization of vapor grown carbon nanofiber (CNF)/epoxy composites in the strain rate range of 10-4-2800 s-1, a difference in the fiber failure mechanism is identified based on the strain rate. Results from compression analyses show that the addition of fractions of CNFs and glass microballoons varies the compressive strength and elastic modulus of epoxy composites by as much as 53.6% and 39.9%. The compressive strength and modulus of the syntactic foams is also shown to generally increase by a factor of 3.41 and 2.96, respectively, with increasing strain rate when quasi-static and high strain rate testing data are compared, proving strain rate sensitivity of these reinforced composites. Exposure to moisture over a 6 month period of time is found to reduce the quasi-static and high strain rate strength and modulus, with a maximum of 7% weight gain with select grades of CNF/syntactic foam. The degradation of glass microballoons due to dealkalization is found to be the primary mechanism for reduced mechanical properties, as well as moisture diffusion and weight gain. In terms of thermal analysis results, the coefficient of thermal expansion (CTE) of CNF/epoxy and CNF/syntactic foam composites reinforced with glass microballoons decrease by as much as 11.6% and 38.4%. The experimental CTE values for all of the composites also fit within the bounds of established analytical models predicting the CTE of fiber and particle-reinforced composites. Further thermal studies through dynamic mechanical analysis demonstrated increased thermal stability and damping capability, where the maximum use and glass transition temperatures increase as much as 27.1% and 25.0%, respectively. The electrical properties of CNF reinforced composites are evaluated as well, where the electrical impedance decreases and the dielectric constant increases with addition of CNFs. Such behavior occurs despite the presence of epoxy and glass microballoons, which serve as insulative phases. Such results are useful in design considerations of lightweight composite materials used in weight saving, compressive strength, and damage tolerance applications, such as lightweight aircraft structure reinforcement, automobile components, and buoyancy control with marine submersibles. The results of the analyses have also evaluated certain factors for environmental exposure and temperature extremes, as well as considerations for electronics packaging, all of which have also played a role in shaping avant-garde composite structure designs for efficient, versatile, and long-life service use.

Poveda, Ronald Leonel

124

Facilitated transport channels in carbon nanotube/carbon nanofiber hierarchical composites decorated with manganese dioxide for flexible supercapacitors  

Science.gov (United States)

Freestanding carbon nanotube/carbon nanofiber (CNT/CNF) composites are prepared using electrospun CNFs as skeletons in a tubular chemical vapor deposition system. The obtained CNT/CNF composites show a hierarchical structure with a high special surface area, a high conductance (1250 S cm-1 for a 10 mm × 20 mm sample), and a high flexibility. After coated with manganese dioxide (MnO2) via an in-situ redox deposition for 0.5 h (?0.33 mg), the CNT/CNF/MnO2 electrodes show a high specific capacitance of 517 F g-1 at a scan rate of 5 mV s-1, which is about 5.6 time higher than that CNF/MnO2-0.25 h ones with MnO2 of ?0.36 mg. Moreover, this CNT/CNF/MnO2 electrodes show a much higher rate capability (57% at current density of 14 A g-1) than CNF/MnO2 ones (24% at 14 A g-1), and also show a higher cycling stability (maintaining 75% of the initial capacitance at cycle number of 1000). In addition, the symmetric supercapacitor assembled using two piece CNT/CNF/MnO2 electrodes shows their maximum energy density of 3.88 Wh kg-1 at power density of 7000 W kg-1. The capacitance of the assembled capacitor maintains 70% after 100 bending cycles, indicating a good flexibility. These enhancements in EC performances should be due to our designed hierarchical structures. It is suggested that such freestanding flexible CNFs/CNTs/MnO2 hierarchical composites are highly promising for high-performance flexible supercapacitors.

Wang, Tao; Song, Dengfei; Zhao, Hao; Chen, Jiayi; Zhao, Changhui; Chen, Lulu; Chen, Wanjun; Zhou, Jinyuan; Xie, Erqing

2015-01-01

125

Controlled growth of NiCo?O? nanorods and ultrathin nanosheets on carbon nanofibers for high-performance supercapacitors.  

Science.gov (United States)

Two one-dimensional hierarchical hybrid nanostructures composed of NiCo2O4 nanorods and ultrathin nanosheets on carbon nanofibers (CNFs) are controllably synthesized through facile solution methods combined with a simple thermal treatment. The structure of NiCo2O4 can be easily controlled to be nanorods or nanosheets by using different additives in the synthesis. These two different nanostructures are evaluated as electrodes for high performance supercapacitors, in view of their apparent advantages, such as high electroactive surface area, ultrathin and porous features, robust mechanical strength, shorter ion and electron transport path. Their electrochemical performance is systematically studied, and both of these two hierarchical hybrid nanostructures exhibit high capacitance and excellent cycling stability. The remarkable electrochemical performance will undoubtedly make these hybrid structures attractive for high-performance supercapacitors with high power and energy densities. PMID:23503561

Zhang, Genqiang; David Lou, Xiong Wen

2013-01-01

126

Interfacial engineering of carbon nanofiber-graphene-carbon nanofiber heterojunctions in flexible lightweight electromagnetic shielding networks.  

Science.gov (United States)

Lightweight carbon materials of effective electromagnetic interference (EMI) shielding have attracted increasing interest because of rapid development of smart communication devices. To meet the requirement in portable electronic devices, flexible shielding materials with ultrathin characteristic have been pursued for this purpose. In this work, we demonstrated a facile strategy for scalable fabrication of flexible all-carbon networks, where the insulting polymeric frames and interfaces have been well eliminated. Microscopically, a novel carbon nanofiber-graphene nanosheet-carbon nanofiber (CNF-GN-CNF) heterojunction, which plays the dominant role as the interfacial modifier, has been observed in the as-fabricated networks. With the presence of CNF-GN-CNF heterojunctions, the all-carbon networks exhibit much increased electrical properties, resulting in the great enhancement of EMI shielding performance. The related mechanism for engineering the CNF interfaces based on the CNF-GN-CNF heterojunctions has been discussed. Implication of the results suggests that the lightweight all-carbon networks, whose thickness and density are much smaller than other graphene/polymer composites, present more promising potential as thin shielding materials in flexible portable electronics. PMID:24914611

Song, Wei-Li; Wang, Jia; Fan, Li-Zhen; Li, Yong; Wang, Chan-Yuan; Cao, Mao-Sheng

2014-07-01

127

Co3O4 nanoparticles decorated carbon nanofiber mat as binder-free air-cathode for high performance rechargeable zinc-air batteries.  

Science.gov (United States)

An efficient, durable and low cost air-cathode is essential for a high performance metal-air battery for practical applications. Herein, we report a composite bifunctional catalyst, Co3O4 nanoparticles-decorated carbon nanofibers (CNFs), working as an efficient air-cathode in high performance rechargeable Zn-air batteries (ZnABs). The particles-on-fibers nanohybrid materials were derived from electrospun metal-ion containing polymer fibers followed by thermal carbonization and a post annealing process in air at a moderate temperature. Electrochemical studies suggest that the nanohybrid material effectively catalyzes oxygen reduction reaction via an ideal 4-electron transfer process and outperforms Pt/C in catalyzing oxygen evolution reactions. Accordingly, the prototype ZnABs exhibit a low discharge-charge voltage gap (e.g. 0.7 V, discharge-charge at 2 mA cm(-2)) with higher stability and longer cycle life compared to their counterparts constructed using Pt/C in air-cathode. Importantly, the hybrid nanofiber mat readily serves as an integrated air-cathode without the need of any further modification. Benefitting from its efficient catalytic activities and structural advantages, particularly the 3D architecture of highly conductive CNFs and the high loading density of strongly attached Co3O4 NPs on their surfaces, the resultant ZnABs show significantly improved performance with respect to the rate capability, cycling stability and current density, promising good potential in practical applications. PMID:25522330

Li, Bing; Ge, Xiaoming; Goh, F W Thomas; Hor, T S Andy; Geng, Dongsheng; Du, Guojun; Liu, Zhaolin; Zhang, Jie; Liu, Xiaogang; Zong, Yun

2015-01-22

128

Alumina-carbon nanofibers nanocomposites obtained by spark plasma sintering for proton exchange membrane fuel cell bipolar plates  

Energy Technology Data Exchange (ETDEWEB)

There is an increasing demand of multifunctional materials for a wide variety of technological developments. Bipolar plates for proton exchange membrane fuel cells are an example of complex functionality components that must show among other properties high mechanical strength, electrical, and thermal conductivity. The present research explored the possibility of using alumina-carbon nanofibers (CNFs) nanocomposites for this purpose. In this study, it was studied for the first time the whole range of powder compositions in this system. Homogeneous powders mixtures were prepared and subsequently sintered by spark plasma sintering. The materials obtained were thoroughly characterized and compared in terms of properties required to be used as bipolar plates. The control on material microstructure and composition allows designing materials where mechanical or electrical performances are enhanced. A 50/50 vol.% alumina-CNFs composite appears to be a very promising material for this kind of application. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Borrell, A.; Torrecillas, R. [Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN) Consejo Superior de Investigaciones Cientificas, Universidad de Oviedo, Principado de Asturias, Parque Tecnologico de Asturias, Llanera Asturias (Spain); Rocha, V.G.; Fernandez, A. [ITMA Materials Technology, Parque Tecnologico de Asturias, Llanera Asturias (Spain)

2012-08-15

129

Structural transformation of vapor grown carbon nanofibers studied by HRTEM  

International Nuclear Information System (INIS)

Vapor grown carbon nanofibers have been extensively manufactured and investigated in recent years. In this study commercially available vapor grown carbon nanofibers subjected to different processing and post processing conditions were studied employing high resolution TEM images. The analysis showed that the fibers consist primarily of conical nanofibers, but can contain a significant amount of bamboo nanofibers. Most conical nanofibers were found to consist of an ordered inner layer and a disordered outer layer, with the cone angle distribution of the inner layers indicating that these cannot have a stacked cone structure but are compatible with a cone-helix structure. Fibers that have been heat treated to temperatures above 1,500 oC undergo a structural transformation with the ordered inner layers changing from a cone-helix structure to a highly ordered multiwall stacked cone structure. The bamboo nanofibers were found to have a tapered multiwall nanotube structure for the wall and a multishell fullerene structure for the cap of each segment, surrounded by a disordered outer layer. When these fibers are heat treated the disordered outer layers transform to an ordered multiwall nanotube structure and merge with the wall of each segment. The end caps of each segment transform from a smooth multiwall fullerene structure to one consisting of disjointed graphene planes. A reaction-diffusion mechanism is proposed to explain the growth and structure of the bambplain the growth and structure of the bamboo nanofibers.

130

Formation and electrochemical performance of copper/carbon composite nanofibers  

Energy Technology Data Exchange (ETDEWEB)

Copper-loaded carbon nanofibers are fabricated by thermally treating electrospun Cu(CH{sub 3}COO){sub 2}/polyacrylonitrile nanofibers and utilized as an energy-storage material for rechargeable lithium-ion batteries. These composite nanofibers deliver more than 400 mA g{sup -1} reversible capacities at 50 and 100 mA g{sup -1} current densities and also maintain clear fibrous morphology and good structural integrity after 50 charge/discharge cycles. The relatively high capacity and good cycling performance of these composite nanofibers, stemmed from the integrated combination of metallic copper and disordered carbon as well as their unique textures and surface properties, make them a promising electrode candidate for next-generation lithium-ion batteries.

Ji Liwen; Lin Zhan; Zhou Rui; Shi Quan; Toprakci, Ozan; Medford, Andrew J.; Millns, Christopher R. [Fiber and Polymer Science Program, Department of Textile Engineering, Chemistry and Science, North Carolina State University, Raleigh, NC 27695-8301 (United States); Zhang Xiangwu, E-mail: xiangwu_zhang@ncsu.ed [Fiber and Polymer Science Program, Department of Textile Engineering, Chemistry and Science, North Carolina State University, Raleigh, NC 27695-8301 (United States)

2010-02-01

131

Characterization of small-scale batch-fabricated carbon nanofiber probes  

Energy Technology Data Exchange (ETDEWEB)

Linear-shaped single carbon nanofibers (CNFs) were batch-grown onto commercially available Si cantilevers for atomic force microscope by the Ar{sup +}-ion-irradiation method (9 cantilevers/batch). The force-curve measurements revealed that the long CNF probes ({approx} 1 {mu}m in length) were as flexible as the carbon nanotubes probes, whereas the short CNF probes ({approx} 400 nm in length) were characterized by the rigid nature similar to the Si probes. Thus, the mechanical properties of CNF probes were controllable by the CNF length. The ion-induced CNF probes were metallic in electrical property, and the higher resolution images in scanning spreading resistance microscopy was attained by the CNF probes than by conventional conductive diamond probes, due to the small tip radius, high aspect ratio and the durability of the CNF probes. Because the small-scale batch-fabricated CNF probes showed good uniformity in the size, mechanical and electrical properties, it was concluded that they are promising as practical conductive SPM probes.

Kitazawa, M; Ohta, R [Olympus Co. Ltd., 6666 Inatomi, Tatsuno, Kami-Ina-Gun, Nagano 399-0495 (Japan); Sugita, Y; Tanaka, J; Tanemura, M [Department of Environmental Technology, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan)], E-mail: ma_kitazawa@ot.olympus.co.jp

2008-03-15

132

Characterization of small-scale batch-fabricated carbon nanofiber probes  

International Nuclear Information System (INIS)

Linear-shaped single carbon nanofibers (CNFs) were batch-grown onto commercially available Si cantilevers for atomic force microscope by the Ar+-ion-irradiation method (9 cantilevers/batch). The force-curve measurements revealed that the long CNF probes (? 1 ?m in length) were as flexible as the carbon nanotubes probes, whereas the short CNF probes (? 400 nm in length) were characterized by the rigid nature similar to the Si probes. Thus, the mechanical properties of CNF probes were controllable by the CNF length. The ion-induced CNF probes were metallic in electrical property, and the higher resolution images in scanning spreading resistance microscopy was attained by the CNF probes than by conventional conductive diamond probes, due to the small tip radius, high aspect ratio and the durability of the CNF probes. Because the small-scale batch-fabricated CNF probes showed good uniformity in the size, mechanical and electrical properties, it was concluded that they are promising as practical conductive SPM probes

133

Synthesis, characterization and activity pattern of carbon nanofibers based copper/zirconia catalysts for carbon dioxide hydrogenation to methanol: Influence of calcination temperature  

Science.gov (United States)

A series of novel carbon nanofibers (CNFs) supported bimetallic copper/zirconia catalysts are synthesized by deposition precipitation method and calcined at different temperatures. Calcined catalysts are characterized by various techniques like X-ray diffraction, N2 adsorption-desorption, N2O chemisorption, high resolution transmission electron microscopy, temperature programmed reduction, X-ray photoelectron spectroscopy and temperature programmed desorption (CO2 & NH3). The structure-activity correlation is discussed in details. The results demonstrate 450 °C as optimum calcination temperature for methanol synthesis rate with CO2/H2 feed volume ratio of 1:3. CO2 conversion is found to be directly proportional to copper metallic surface area (SCu), while a linear relationship is observed between methanol synthesis rate and fraction of dispersed Cu.

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

2015-01-01

134

Numerical analysis of electron emission site distribution of carbon nanofibers for field emission properties.  

Science.gov (United States)

To obtain optimal field emission (FE) properties, it is important to evaluate FE parameters including the electron emission site ? and the field enhancement factor ?. However, it is difficult to evaluate ? quantitatively because the emitting electrons cannot be observed directly. The authors have aimed to analyze this site using an original architecture with a computation system tool based on the surface charge method, and a three-dimensional model has been employed to calculate FE properties with high accuracy. In this study, to analyze ? for determining FE properties, each carbon nanofiber (CNF) model separated by Cr islands which include the minimum area for calculating electric fields by the surface charge method was constructed on the surface of a Ni catalyst. The FE current was simulated with a Fowler-Nordheim formula using the calculated electric fields, followed by a simulation performed using all CNFs on a field emitter cathode. The electron emission site ? was determined by comparing the simulation and experimental results of the FE current. It was found that ? depends on the morphology of the CNF bundles, and a close quantitative correspondence between the experimental and the computation results of FE properties was obtained. In summary, a method of analyzing FE properties was established using an original architecture, making it possible to predict FE properties with a computational tool based on the surface charge method. PMID:23273149

Shimoi, Norihiro; Tanaka, Shun-ichiro

2013-02-01

135

Fabrication and electromagnetic characteristics of microwave absorbers containing carbon nanofibers and magnetic metals  

Science.gov (United States)

The ultimate aim of this study is the development of microwave absorbers containing both dielectric and magnetic lossy materials. Carbon nanofibers (CNFs) were used as dielectric lossy materials and NiFe particles were used as magnetic lossy materials. Total twelve specimens for the three types such as dielectric, magnetic and mixed radar absorbing materials (RAMs) were fabricated. Their complex permittivities and permeabilities in the range of 2~18 GHz were measured using the transmission line technique. The parametric studies in the X-band (8.2~12.4 GHz) for reflection loss characteristics of each specimen to design the single-layered RAMs were performed. The mixed RAMs generally showed the improved absorbing characteristics with thinner matching thickness. One of the mixed RAMs, S09 with the thickness of 2.00 mm had the 10 dB absorbing bandwidth of 4.0 GHz in the X-band. The experimental results for selected specimens were in very good agreements with simulation ones in terms of the overall reflection loss characteristics and 10 dB absorbing bandwidth.

Park, Ki-Yeon; Han, Jae-Hung; Lee, Sang-Bok; Kim, Jin-Bong; Yi, Jin-Woo; Lee, Sang-Kwan

2008-03-01

136

Health effects of exposure to carbon nanofibers: Systematic review, critical appraisal, meta analysis and research to practice perspectives  

International Nuclear Information System (INIS)

Background: Literature reviews examining the relationship between exposure to carbon nanofibers (CNFs) and health consequences are qualitative in nature and do not employ an evidence-based assessment. Objective: This research deals with a systematic review, critical appraisal, and meta-analysis designed to examine the potential health effects associated with exposure to CNFs. The utilization of research findings into practice is also explored. Methods: Published articles were obtained from a search of electronic databases and bibliographies of identified articles. A critical appraisal was conducted using an 'Experimental Appraisal Instrument' developed in this study. The meta-analysis was established using statistical techniques with/without the incorporation of overall study quality. The likelihood of utilizing research findings into practice (i.e., from research to practice) was computed using a four-step algorithm based on the criteria of: strength of association, consistency among studies, temporality, biological gradient, type of experimental unit, type of CNF (single- and multi-wall nanotubes), CNF grade (commercial or altered), exposure dose, exposure duration, and support by analogy from the published literature. Results: Twenty-one experimental studies satisfied the inclusion criteria and were performed on human cells, experimental animal models and animal cells as experimental units. The methodological qualities of published studies ranged from 'very poor' tublished studies ranged from 'very poor' to 'excellent', with 'overall study description' scoring 'good' and 'study execution' equal to 'moderate'. The random-effects model was applied in the meta-analysis calculations as heterogeneity was significant at the 10% for all outcomes reported. The mean standardized meta-estimates for the experimental groups were significantly lower than those for the control groups for cell viability and cell death, respectively. Incorporating the effect of overall study quality score widened the gap between the experimental and control groups. Assessment of research findings on the basis of the four-step algorithm revealed that the likelihood of the results to occur in practice is 'somewhat possible' at this time. That is, if exposure conditions to CNF in the reported studies are similar to those in nano-manufacturing plants, it is somewhat possible that CNFs alter the function of human cells resulting in loss of cell viability and cell death. Conclusions: Our findings suggest that it is 'somewhat possible' for the CNF to penetrate the human cells in the targeted organs and to cause cellular damage. Although the weight of evidence is not sufficient, it is advisable that actions be taken to ensure the protection of workers exposed to CNFs, that is, (a) engineering controls should be established to contain exposure to CNF, and (b) simultaneously rigorous personnel protective equipment should be planned to further minimize the risk of CNF exposure.

137

Co3O4 nanoparticles decorated carbon nanofiber mat as binder-free air-cathode for high performance rechargeable zinc-air batteries  

Science.gov (United States)

An efficient, durable and low cost air-cathode is essential for a high performance metal-air battery for practical applications. Herein, we report a composite bifunctional catalyst, Co3O4 nanoparticles-decorated carbon nanofibers (CNFs), working as an efficient air-cathode in high performance rechargeable Zn-air batteries (ZnABs). The particles-on-fibers nanohybrid materials were derived from electrospun metal-ion containing polymer fibers followed by thermal carbonization and a post annealing process in air at a moderate temperature. Electrochemical studies suggest that the nanohybrid material effectively catalyzes oxygen reduction reaction via an ideal 4-electron transfer process and outperforms Pt/C in catalyzing oxygen evolution reactions. Accordingly, the prototype ZnABs exhibit a low discharge-charge voltage gap (e.g. 0.7 V, discharge-charge at 2 mA cm-2) with higher stability and longer cycle life compared to their counterparts constructed using Pt/C in air-cathode. Importantly, the hybrid nanofiber mat readily serves as an integrated air-cathode without the need of any further modification. Benefitting from its efficient catalytic activities and structural advantages, particularly the 3D architecture of highly conductive CNFs and the high loading density of strongly attached Co3O4 NPs on their surfaces, the resultant ZnABs show significantly improved performance with respect to the rate capability, cycling stability and current density, promising good potential in practical applications.An efficient, durable and low cost air-cathode is essential for a high performance metal-air battery for practical applications. Herein, we report a composite bifunctional catalyst, Co3O4 nanoparticles-decorated carbon nanofibers (CNFs), working as an efficient air-cathode in high performance rechargeable Zn-air batteries (ZnABs). The particles-on-fibers nanohybrid materials were derived from electrospun metal-ion containing polymer fibers followed by thermal carbonization and a post annealing process in air at a moderate temperature. Electrochemical studies suggest that the nanohybrid material effectively catalyzes oxygen reduction reaction via an ideal 4-electron transfer process and outperforms Pt/C in catalyzing oxygen evolution reactions. Accordingly, the prototype ZnABs exhibit a low discharge-charge voltage gap (e.g. 0.7 V, discharge-charge at 2 mA cm-2) with higher stability and longer cycle life compared to their counterparts constructed using Pt/C in air-cathode. Importantly, the hybrid nanofiber mat readily serves as an integrated air-cathode without the need of any further modification. Benefitting from its efficient catalytic activities and structural advantages, particularly the 3D architecture of highly conductive CNFs and the high loading density of strongly attached Co3O4 NPs on their surfaces, the resultant ZnABs show significantly improved performance with respect to the rate capability, cycling stability and current density, promising good potential in practical applications. Electronic supplementary information (ESI) available: TGA curves of as electrospun Co(ii)-PAN fiber and C-CoPAN900 EDX and XPS spectra of the C-CoPAN900 photo of a home-built Zn-air cell and the preparation method of conventional catalyst electrode; polarization curves and corresponding power density plots of the battery using conventional type cathode of C-CoPN900 and commercial Pt/C catalyst; the electrocatalytic properties of hybrid CNFs obtained from varied weight ratios of PAN to cobalt acetate, e.g. 16 : 1 and 8 : 1, and their corresponding TGA curves; a comparison of the Zn-air battery performance of this work with recent literatures. See DOI: 10.1039/c4nr05988c

Li, Bing; Ge, Xiaoming; Goh, F. W. Thomas; Hor, T. S. Andy; Geng, Dongsheng; Du, Guojun; Liu, Zhaolin; Zhang, Jie; Liu, Xiaogang; Zong, Yun

2015-01-01

138

Reversible electrowetting of vertically aligned superhydrophobic carbon nanofibers.  

Science.gov (United States)

Reversible electrostatically induced wetting (electrowetting) of vertically aligned superhydrophobic carbon nanofibers has been investigated. Carbon nanofibers on a 5 x 5 microm pitch were grown on Si substrates, electrically insulated with a conformal dielectric, and hydrophobized with fluoropolymer. This nanostructured scaffold exhibited superhydrophobic behavior for saline (theta approximately 160 degrees). Electrowetting induced a contact angle reduction to theta approximately 100 degrees. Competitive two-liquid (dodecane/saline) electrowetting exhibited reversibility on the same nanostructured scaffold. Without applied bias, ultra-fine-point tip (approximately 25 nm radius) nanofibers result in effectively zero capacitance with the overlying saline layer. Complete electrowetting of the substrate is confirmed as capacitance values increase by several orders of magnitude with increased wetting. These results demonstrate the applicability of reversible electrowetting on nanostructured scaffolds and use of nanofabricated structures that can be integrated with various micro- and nanoelectronic technologies. PMID:17014150

Dhindsa, Manjeet S; Smith, Neil R; Heikenfeld, Jason; Rack, Philip D; Fowlkes, Jason D; Doktycz, Mitchel J; Melechko, Anatoli V; Simpson, Michael L

2006-10-10

139

Preparation and electrochemistry of carbon nanofibers and treated graphites  

Science.gov (United States)

Secondary lithium ion batteries commonly contain a carbon based electrode and a lithiated transition metal oxide based electrode, where electrochemical charging is lithium ion uptake at the carbon electrode. Since their commercial introduction in the 1990s, lithium ion battery research has flourished, however fully understanding the electrochemistry of the carbon electrode has remained an elusive challenge. Notably, many previous studies have been industrially motivated, and designed to optimize carbon performance rather than to fundamentally understand carbon electrochemistry. Several studies designed to explore carbon structure-function relationships are presented here. Small scale, benchtop techniques were utilized to systematically prepare families of related carbons similar in some aspects and different in others. The novel carbons were then characterized to relate physical and chemical properties to lithium ion battery electrochemistries. Chapter 1 discusses this strategy in more detail. Chapters 2 and 3 involve novel carbon nanofibers. Chapter 2 describes the synthesis of granular and acicular iron particles, and their catalytic use in the formation of carbon nanofibers. Chapter 3 describes further characterization of the carbon nanofibers relative to commercially available synthetic graphite and carbon black, where the potential application of carbon nanofibers for high rate applications is noted. Chapters 4 and 5 involve novel treatments of synthetic graphite. Chapter 4 describes the heat treatment of synthetic graphite in flowing CO2(g) , where short term aging of CO2 treated graphite was found to have a notable effect on irreversible capacity. Chapter 5 describes heat treatment in flowing Ar(g) to systematically affect particle and crystallite dimensions, where significant effects on irreversible capacity were observed.

Marschilok, Amy Catherine

140

Preparation of a New Adsorbent from Activated Carbon and Carbon Nanofiber (AC/CNF for Manufacturing Organic-Vacbpour Respirator Cartridge  

Directory of Open Access Journals (Sweden)

Full Text Available In this study a composite of activated carbon and carbon nanofiber (AC/CNF was prepared to improve the performance of activated carbon (AC for adsorption of volatile organic compounds (VOCs and its utilization for respirator cartridges. Activated carbon was impregnated with a nickel nitrate catalyst precursor and carbonnanofibers (CNF were deposited directly on the AC surface using catalytic chemical vapor deposition. Deposited CNFs on catalyst particles in AC micropores, were activated by CO2 to recover the surface area and micropores.Surface and textural characterizations of the prepared composites were investigated using Brunauer, Emmett andTeller’s (BET technique and electron microscopy respectively. Prepared composite adsorbent was tested forbenzene, toluene and xylene (BTX adsorption and then employed in an organic respirator cartridge in granularform. Adsorption studies were conducted by passing air samples through the adsorbents in a glass column at an adjustable flow rate. Finally, any adsorbed species not retained by the adsorbents in the column were trapped in a charcoal sorbent tube and analyzed by gas chromatography. CNFs with a very thin diameter of about 10-20 nmwere formed uniformly on the AC/CNF. The breakthrough time for cartridges prepared with CO2 activated AC/CNF was 117 minutes which are significantly longer than for those cartridges prepared with walnut shell- based activated carbon with the same weight of adsorbents. This study showed that a granular form CO2 activated AC/CNF composite could be a very effective alternate adsorbent for respirator cartridges due to its larger adsorption capacities and lower weight.

Mehdi Jahangiri

2013-01-01

141

Surface functionalization of carbon nanofibers by sol gel coating of zinc oxide  

Science.gov (United States)

In this paper the functional carbon nanofibers were prepared by the carbonization of ZnO coated PAN nanofibers to expand the potential applications of carbon nanofibers. Polyacrylonitrile (PAN) nanofibers were obtained by electrospinning. The electrospun PAN nanofibers were then used as substrates for depositing the functional layer of zinc oxide (ZnO) on the PAN nanofiber surfaces by sol-gel technique. The effects of coating, pre-oxidation and carbonization on the surface morphology and structures of the nanofibers were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Scanning electron microscopy (SEM), respectively. The results of SEM showed a significant increase of the size of ZnO nanograins on the surface of nanofibers after the treatments of coating, pre-oxidation and carbonization. The observations by SEM also revealed that ZnO nanoclusters were firmly and clearly distributed on the surface of the carbon nanofibers. FTIR examination also confirmed the deposition of ZnO on the surface of carbon nanofibers. The XRD analysis indicated that the crystal structure of ZnO nanograins on the surface of carbon nanofibers.

Shao, Dongfeng; Wei, Qufu; Zhang, Liwei; Cai, Yibing; Jiang, Shudong

2008-08-01

142

Surface functionalization of carbon nanofibers by sol-gel coating of zinc oxide  

International Nuclear Information System (INIS)

In this paper the functional carbon nanofibers were prepared by the carbonization of ZnO coated PAN nanofibers to expand the potential applications of carbon nanofibers. Polyacrylonitrile (PAN) nanofibers were obtained by electrospinning. The electrospun PAN nanofibers were then used as substrates for depositing the functional layer of zinc oxide (ZnO) on the PAN nanofiber surfaces by sol-gel technique. The effects of coating, pre-oxidation and carbonization on the surface morphology and structures of the nanofibers were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Scanning electron microscopy (SEM), respectively. The results of SEM showed a significant increase of the size of ZnO nanograins on the surface of nanofibers after the treatments of coating, pre-oxidation and carbonization. The observations by SEM also revealed that ZnO nanoclusters were firmly and clearly distributed on the surface of the carbon nanofibers. FTIR examination also confirmed the deposition of ZnO on the surface of carbon nanofibers. The XRD analysis indicated that the crystal structure of ZnO nanograins on the surface of carbon nanofibers

143

Morphology and internal structure of polymeric and carbon nanofibers  

Science.gov (United States)

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 a cheap raw material, graphitic fibers appear to be another useful starting material for mass production of graphene sheets.

Zhong, Zhenxin

144

Optimizing the synthesis of carbon nano?ber based electrocatalysts for fuel cells  

OpenAIRE

This work deals with an optimization of the platinum dispersion on low surface area carbon nanofibers (CNFs) by using different synthesis procedures and its electrocatalytic activity towards oxygen reduction. The selected CNFs were characterized by a BET surface area of ca. 100 m2 g-1 and were in-house synthesized by the decomposition of CH4 at 700ºC. Pt nanoparticles were deposited by using four different synthesis routes. A metal concentration of 20 wt% was confirmed by EDX ...

Sebastia?n Del Ri?o, David; Suelves Laiglesia, Isabel; Moliner A?lvarez, Rafael; La?zaro Elorri, Mari?a Jesu?s; Stassi, Alessandro; Baglio, Vincenzo; Arico?, Antonino Salvatore

2012-01-01

145

High density carbon materials obtained at relatively low temperature by spark plasma sintering of carbon nanofibers  

Energy Technology Data Exchange (ETDEWEB)

Graphitic materials obtained at low temperatures are interesting for a wide range of industrial applications including bipolar plates. In this work, graphite based nanocomposites have been obtained starting from carbon nanofibers and a mixture of carbon nanofibers with 20 vol.% of alumina nanopowders. High density carbon components were obtained by using Spark Plasma Sintering at temperatures as low as 1500-1800 C for this kind of materials. The effect of spark plasma sintering parameters on the final density, and the mechanical and electrical properties of resulting nanocomposites have been investigated. Pure carbon nanofibers with around 90% of theoretical density and fracture strength of 60 MPa have been obtained at temperatures as low as 1500 C applying a pressure of 80 MPa during sintering. It has been proved that attrition milling is a suitable method for preparing homogeneous mixtures of carbon nanofibers and alumina powders. (orig.)

Borrell, Amparo; Torrecillas, Ramon [Nanomaterials and Nanotechnology Research Center (CINN), Principado de Asturias - Consejo Superior de Investigaciones Cientificas (CSIC), Univ. de Oviedo, Parque Tecnologico de Asturias, Llanera (Spain); Fernandez, Adolfo [Fundacion ITMA, Parque Tecnologico de Asturias, Llanera (Spain); Merino, Cesar [Grupo Antolin Ingenieria, Burgos (Spain)

2010-01-15

146

Effects of increasing carbon nanofiber density in polyurethane composites for inhibiting bladder cancer cell functions.  

Science.gov (United States)

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 their decreased expression of NMP-22, tumor necrosis factor alpha, and VEGF. Moreover, the adhesion of HUC increased on composites containing more CNF than PU. Overall levels of NMP-22 were significantly lower in HUC than in cancerous UMUC and SCaBER cells on PU:CNF composites. Thus, this study provided a novel nanocomposite consisting of CNF and PU that should be further studied for inhibiting the return of cancerous bladder tissue and for promoting normal non-cancerous bladder tissue formation. PMID:21417694

Tsang, Melissa; Chun, Young Wook; Im, Yeon Min; Khang, Dongwoo; Webster, Thomas J

2011-07-01

147

Improved bioactivity of PAN-based carbon nanofibers decorated with bioglass nanoparticles.  

Science.gov (United States)

Composite nanofibers composed of polyacrylonitrile (PAN)-based carbon nanofibers and bioactive glass (BG) nanoparticles have been prepared by electrospinning and in situ sintering. Morphology observation showed that the BG nanoparticles of size 20-50?nm were uniformly distributed on the surface of composite nanofibers with 350?nm average diameter after carbonization. Biological mineralization indicated the formation of apatite-like layer on the surface of composite nanofibers, in which the composition of carbonate hydroxyapatite was proved by FTIR and XRD analysis. Cell growth dynamics according to cellular morphology, CCK-8 assay, and alkaline phosphatase activity assay exhibited better cell adhesion, proliferation, and osteogenic induction of bone marrow-derived mesenchymal stem cells cultured on the composite nanofibers, which suggested the higher bioactivity of composite nanofibers compared to pure PAN-based carbon nanofibers. PMID:24266838

Han, Bing; Zhang, Xuehui; Liu, Haiyang; Deng, Xuliang; Cai, Qing; Jia, Xiaolong; Yang, Xiaoping; Wei, Yan; Li, Gang

2014-01-01

148

Platinum on Carbon Nanofibers as Catalyst for Cinnamaldehyde Hydrogenation  

OpenAIRE

The aim of the work described in this thesis was to investigate the role and nature of nanostructured carbon materials, oxygen surface groups and promoters on platinum-based catalysts for the selective hydrogenation of cinnamaldehyde. The selective hydrogenation of cinnamaldehyde to cinnamyl alcohol was chosen as a showcase. To establish structure-activity relations, it is crucial to prepare well-defined carbon nanofibers (CNF) supports and well-defined catalytic metal phases on these support...

Plomp, A. J.

2009-01-01

149

Carbon Nanofibers as Catalyst Support for Noble Metals  

OpenAIRE

In the quest for new and well-defined support materials for heterogeneous catalysts we explored the potential of carbon nanofibers (CNF). CNF belongs to the by now extensive family of synthetic graphite-like carbon materials with advantageous and tunable physico-chemical properties. Aim of the work described in this thesis has been the exploration of the potential of CNF as catalyst support material, notably for platinum and ruthenium, and its role in the performance of these catalysts in hyd...

Toebes, M. L.

2004-01-01

150

Silver-functionalized carbon nanofiber composite electrodes for ibuprofen detection  

Science.gov (United States)

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.

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

2012-06-01

151

Controlled Growth of NiCo2O4 Nanorods and Ultrathin Nanosheets on Carbon Nanofibers for High-performance Supercapacitors  

Science.gov (United States)

Two one-dimensional hierarchical hybrid nanostructures composed of NiCo2O4 nanorods and ultrathin nanosheets on carbon nanofibers (CNFs) are controllably synthesized through facile solution methods combined with a simple thermal treatment. The structure of NiCo2O4 can be easily controlled to be nanorods or nanosheets by using different additives in the synthesis. These two different nanostructures are evaluated as electrodes for high performance supercapacitors, in view of their apparent advantages, such as high electroactive surface area, ultrathin and porous features, robust mechanical strength, shorter ion and electron transport path. Their electrochemical performance is systematically studied, and both of these two hierarchical hybrid nanostructures exhibit high capacitance and excellent cycling stability. The remarkable electrochemical performance will undoubtedly make these hybrid structures attractive for high-performance supercapacitors with high power and energy densities. PMID:23503561

Zhang, Genqiang; (David) Lou, Xiong Wen

2013-01-01

152

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

Science.gov (United States)

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. PMID:25244060

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

2014-10-15

153

Design of Two-Dimensional, Ultrathin MoS2 Nanoplates Fabricated Within One-Dimensional Carbon Nanofibers With Thermosensitive Morphology: High-Performance Electrocatalysts For The Hydrogen Evolution Reaction.  

Science.gov (United States)

Two-dimensional MoS2 nanoplates within carbon nanofibers (CNFs) with monolayer thickness, nanometer-scale dimensions and abundant edges are fabricated. This strategy provides a well-defined pathway for the precise design of MoS2 nanomaterials, offering control over the evolution of MoS2 morphology from nanoparticles to nanoplates as well as from mono- to several-layer structures, over a lateral dimension range of 5 to 70 nm. CNFs play an important role in confining the growth of MoS2 nanoplates, leading to increases in the amount of exposed edge sites while hindering the stacking and aggregation of MoS2 layers, and accelerating electron transfer. The controlled growth of MoS2 nanoplates embedded in CNFs is leveraged to demonstrate structure-dependent catalytic activity in the hydrogen evolution reaction (HER). The results suggest that increases in the number of layers and the lateral dimension result in a decrease in HER activity as a general rule. Single-layer MoS2 nanoplates with abundant edges and a lateral dimension of 7.3 nm demonstrated the lowest hydrogen evolution reaction overpotential of 93 mV (J = 10 mA/cm(2)), the highest current density of 80.3 mA/cm(2) at ? = 300 mV and the smallest Tafel slope of 42 mV/decade. The ability of MoS2-CNFs hybrids to act as nonprecious metal catalysts indicates their promise for use in energy-related electrocatalytic applications. PMID:25420219

Zhu, Han; Lyu, FengLei; Du, MingLiang; Zhang, Ming; Wang, QingFa; Yao, JuMing; Guo, BaoChun

2014-12-24

154

Designing an ultrathin silica layer for highly durable carbon nanofibers as the carbon support in polymer electrolyte fuel cells  

Science.gov (United States)

A critical issue for maintaining long-term applications of polymer electrolyte fuel cells (PEFCs) is the development of an innovative technique for the functionalization of a carbon support that preserves their exceptional electrical conductivity and robustly enriches their durability. Here, we report for the first time how the formation of a partially coated, ultrathin, hydrophobic silica layer around the surfaces of the carbon nanofiber (CNF) helps improve the durability of the CNF without decreasing the significant electrical conductivity of the virgin CNF. The synthesis involved the adsorption of polycarbomethylsilane (PS) on the CNF's sidewalls, followed by high temperature pyrolysis of PS, resulting in a highly durable, conductive carbon support in PEFCs. The Pt nanoparticles are in direct contact with the surface of the carbon in the empty spaces between unevenly coated silica layers, which are not deposited directly onto the silica layer. The presence of a Pt nanoparticle layer that was thicker than the silica layer would be a quite advantageous circumstance that provides contact with other neighboring CNFs without having a significant adverse effect that deeply damages the electrical conductivity of the neighboring CNF composites with the silica layer. Furthermore, the ultrathin, hydrophobic silica layer around the surfaces of the CNF provides great potential to reduce the presence of water molecules in the vicinity of the carbon supports and the &z.rad;OH radicals formed on the surface of the Pt catalyst. As a result, the CNF with a 5 wt% silica layer that we prepared has had extremely high initial performance and durability under severe carbon corrosion conditions, starting up with 974 mA cm-2 at 0.6 V and ending up with more than 58% of the initial performance (i.e., 569 mA cm-2 at 0.6 V) after a 1.6 V holding test for 6 h. The beginning-of-life and end-of-life performances based on the virgin CNF without the silica layer were 981 and 340 mA cm-2 at 0.6 V, respectively. The CNF having a silica layer had long-term durability which was superior to that of the virgin CNF.

Hwang, Sun-Mi; Park, Jae-Hyun; Lim, Seongyop; Jung, Doo-Hwan; Guim, Hwanuk; Yoon, Young-Gi; Yim, Sung-Dae; Kim, Tae-Young

2014-09-01

155

Small-scale batch fabrication of carbon nanofiber probes  

Energy Technology Data Exchange (ETDEWEB)

The batch-growth of linear-shaped single CNFs onto commercially available Si cantilevers (3-9 chips / batch) using the ion-irradiation method was challenged, and the growth parameters were optimized in terms of the sample temperature (up to 70deg. C) and the ion-irradiation time. In every growth condition tested here, the batch-fabrication of CNF probes was achieved. The length and the growth direction of CNFs were controllable well with the ion-irradiation time and the ion-incidence angle, respectively. Thus, oriented and linear-shaped single CNFs, even longer than 1 {mu}m in length, were attainable. Under the optimized growth condition, CNFs were batch-grown uniformly in length with the standard deviation of less than {approx}10 %. CNFs showed almost no temperature dependence in growth rate, and fine CNFs tended to grow for short irradiation duration. Since AFM images of Si grating were attained repeatedly with a good image resolution using CNF probes thus batch-fabricated, the ion-irradiation method was believed to be quite promising to prepare practical CNF probes.

Tanaka, J [Department of Environmental Technology, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Kitazawa, M [Department of Environmental Technology, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Tanemura, M [Department of Environmental Technology, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Ohta, R [Olympus Co. Ltd., 6666 Inatomi, Tatsuno, Kami-Ina-Gun, Nagano 399-0495 (Japan)

2007-04-15

156

Oxygen adsorption-induced surface segregation of titanium oxide by activation in carbon nanofibers for maximizing photocatalytic performance.  

Science.gov (United States)

This research demonstrates a simple method for synthesizing titanium dioxide nanoparticle-decorated carbon nanofibers. These nanofibers showed highly efficient degradation of methylene blue under UV light because of the synergistic effects of the large surface-active sites of titanium dioxide nanoparticles and the carbon nanofibers on the photocatalytic properties. PMID:25575123

Lee, Sung-In; Jo, Seong-Mu; Joh, Han-Ik; Lee, Myong-Hoon; Lee, Sungho

2015-01-29

157

Detection of ricin using a carbon nanofiber based biosensor.  

Science.gov (United States)

We report ricin detection using antibody and aptamer probes immobilized on a nanoelectrode array (NEA) consisting of vertically aligned carbon nanofibers (VACNFs). These biosensor chips are fabricated on a wafer scale using steps common in integrated circuit manufacturing. Electrochemical impedance spectroscopy is used to characterize the detection event and the results indicate that the electron transfer resistance changes significantly after the ricin protein binds to the probe. Further confirmation is obtained from evaluation of the electrode surface by atomic force microscopy which clearly shows a change in height from the bare electrode to the surface bound by the probe-protein. PMID:21852102

Periyakaruppan, Adaikkappan; Arumugam, Prabhu U; Meyyappan, M; Koehne, Jessica E

2011-10-15

158

A hybrid functional nanomaterial: POSS functionalized carbon nanofiber  

Energy Technology Data Exchange (ETDEWEB)

A hybrid functional nanomaterial was synthesized by functionalizing carbon nanofibers (CNF) with polyhedral oligomeric silsesquioxane (POSS). The reaction between CNF and the amine group of ocataminophenyl POSS was achieved using carbodiimide chemistry. The CNF-POSS hybrids were designed to increase the reactivity of CNF without affecting its inherent properties. The reactive amine groups of CNF-POSS were further modified with an oligomer of polyimide polymer to improve the interaction with the polymer matrix, thus forming a nanocomposite with enhanced multifunctional properties. Functionalization was characterized using thermal gravimetric analysis (TGA), x-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM).

Iyer, Pallavi; Mapkar, Javed A; Coleman, Maria R, E-mail: maria.coleman6@utoledo.ed [Department of Chemical and Environmental Engineering, University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606 (United States)

2009-08-12

159

Ellipsometric investigations of photonic crystals based on carbon nanofibers  

CERN Document Server

Carbon nanofibers (CNF) are used as components of planar photonic crystals (PC). Square and rectangular lattices as well as random patterns of vertically aligned CNF were fabricated and their properties studied using ellipsometry. Conventional methods of ellipsometric analysis used in thin film ellipsometry are not applicable to these samples due to their nanostructured nature. We show that detailed information such as symmetry directions and the band structure of these novel materials can be extracted from considerations of the polarization state in the specular beam.

Rehammar, R; Arwin, H; Kinaret, J M; Campbell, E E B

2010-01-01

160

Health effects of exposure to carbon nanofibers: Systematic review, critical appraisal, meta analysis and research to practice perspectives  

Energy Technology Data Exchange (ETDEWEB)

Background: Literature reviews examining the relationship between exposure to carbon nanofibers (CNFs) and health consequences are qualitative in nature and do not employ an evidence-based assessment. Objective: This research deals with a systematic review, critical appraisal, and meta-analysis designed to examine the potential health effects associated with exposure to CNFs. The utilization of research findings into practice is also explored. Methods: Published articles were obtained from a search of electronic databases and bibliographies of identified articles. A critical appraisal was conducted using an 'Experimental Appraisal Instrument' developed in this study. The meta-analysis was established using statistical techniques with/without the incorporation of overall study quality. The likelihood of utilizing research findings into practice (i.e., from research to practice) was computed using a four-step algorithm based on the criteria of: strength of association, consistency among studies, temporality, biological gradient, type of experimental unit, type of CNF (single- and multi-wall nanotubes), CNF grade (commercial or altered), exposure dose, exposure duration, and support by analogy from the published literature. Results: Twenty-one experimental studies satisfied the inclusion criteria and were performed on human cells, experimental animal models and animal cells as experimental units. The methodological qualities of published studies ranged from 'very poor' to 'excellent', with 'overall study description' scoring 'good' and 'study execution' equal to 'moderate'. The random-effects model was applied in the meta-analysis calculations as heterogeneity was significant at the 10% for all outcomes reported. The mean standardized meta-estimates for the experimental groups were significantly lower than those for the control groups for cell viability and cell death, respectively. Incorporating the effect of overall study quality score widened the gap between the experimental and control groups. Assessment of research findings on the basis of the four-step algorithm revealed that the likelihood of the results to occur in practice is 'somewhat possible' at this time. That is, if exposure conditions to CNF in the reported studies are similar to those in nano-manufacturing plants, it is somewhat possible that CNFs alter the function of human cells resulting in loss of cell viability and cell death. Conclusions: Our findings suggest that it is 'somewhat possible' for the CNF to penetrate the human cells in the targeted organs and to cause cellular damage. Although the weight of evidence is not sufficient, it is advisable that actions be taken to ensure the protection of workers exposed to CNFs, that is, (a) engineering controls should be established to contain exposure to CNF, and (b) simultaneously rigorous personnel protective equipment should be planned to further minimize the risk of CNF exposure.

Genaidy, Ash, E-mail: world_tek_inc@yahoo.com [University of Cincinnati, College of Engineering, Cincinnati, Ohio (United States); WorldTek Inc, Cincinnati (United States); Tolaymat, Thabet [U.S. EPA Office of Research and Development. Cincinnati, Ohio (United States); Sequeira, Reynold [University of Cincinnati, College of Engineering, Cincinnati, Ohio (United States); Rinder, Magda [WorldTek Inc, Cincinnati (United States); Dionysiou, Dion [University of Cincinnati, College of Engineering, Cincinnati, Ohio (United States)

2009-06-01

161

Soft-templated synthesis of mesoporous carbon nanospheres and hollow carbon nanofibers  

Science.gov (United States)

Using coal tar pitch based amphiphilic carbonaceous materials (ACMs) as the precursor and amphiphilic triblock copolymer Plutonic P123 as the only soft template, carbon nanospheres with partially ordered mesopores and hollow carbon nanofibers were synthesized. The concentration of P123, cp, and the mass ratio of P123 to ACM, r, are the key parameters of controlling the shape of the as-prepared products. Mesoporous carbon nanospheres with diameter of 30-150 nm were prepared under the condition of cp = 13.3 g/L and r = 1.2. When cp = 26.7 g/L and r = 2, hollow carbon nanofibers with diameters of 50-200 nm and mesopores/macropores were obtained. Carbon nanospheres and hollow carbon fibers were amorphous materials. The mesoporous carbon nanospheres show good stability in the cyclic voltammograms and their specific capacitance at 10 mV s-1 is 172.1 F/g.

Cheng, Youliang; Li, Tiehu; Fang, Changqing; Zhang, Maorong; Liu, Xiaolong; Yu, Ruien; Hu, Jingbo

2013-10-01

162

Electromagnetic Properties of Novel Carbon Nanofibers  

OpenAIRE

Carbonized bacterial cellulose (CBC) with a three dimensional net-linked framework were synthesized from carbonized bacterial cellulose and investigated by X-ray diffraction, Raman spectrum and Transmission electron microscopy. The complex permittivity and permeability of CBC/paraffin wax composite with certain ratio of the composite were measured by vector network analysis in the frequency range of 0.1–18 GHz. It is found that the composite has high permittivity and dielectric loss, es...

Wang Gai-hua, Dai Bo

2013-01-01

163

EFFECT OF CELLULOSE NANOFIBERS ISOLATED FROM BAMBOO PULP RESIDUE ON VULCANIZED NATURAL RUBBER  

OpenAIRE

Nanocomposites were prepared using two bioresources, viz., cellulose nanofibers (CNFs) extracted from bamboo paper-pulp waste as the reinforcing phase and natural rubber (NR) as the matrix phase. CNFs with diameters up to 50 nm were isolated from bamboo pulp waste, and nanocomposites with 5 and 10% CNFs were obtained via two-roll mill mixing of solid natural rubber with a master batch containing 20 wt% CNFs. The NR phase was cross-linked using sulphur vulcanization. The morphology studies sho...

P. M. Visakh,; Sabu Thomas,; Kristiina Oksman,; Mathew, Aji P.

2012-01-01

164

One-step facile construction of high aspect ratio Fe3O4 decorated CNFs with distinctive porous morphology: potential multiuse expectations.  

Science.gov (United States)

The objective of our study was to develop a new class of Fe3O4 nanocrystals decorated CNFs with characteristic porous morphology by straightforward approach. The utilized CNFs-Fe3O4 hybrid was prepared by sol-gel electrospinning employing polyacrylonitrile and iron (III) nitrate nonahydrate as precursors. Scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy and X-ray diffraction techniques were employed to characterize novel CNFs-Fe3O4 composite. Nanofibers are having porous morphology, diameter size in the range of ~260±20 nm. In order to demonstrate the broad applicability of CNFs-Fe3O4 scaffold, we performed different analysis. The antibacterial activity was tested using Escherichia coli as model organism. With NIH 3T3 mouse fibroblasts, cytotoxicity of prepared high aspect ratio CNFs-Fe3O4 composite was evaluated by thiazoyl blue tetrazolium-bromide (MTT) assay, and fibroblast cell growth behavior with electrospun porous scaffolds was also examined. Interestingly, the prepared nanofibers exhibited enhanced bactericidal performance (minimum inhibition concentrations (MIC) from 5 ?g/mL to 80 ?g/mL) and CNFs-Fe3O4 composite as scaffolds indicated favorable enhancement in cell proliferation. Results from this study suggest that CNFs-Fe3O4 scaffold with small diameters coincidence with unique porous configuration can mimic the natural extracellular matrix (ECM) well and provide potential promises for applications in the fields of tissue engineering and regenerative medicine. Our findings clearly suggest wide application potentials of this (CNFs-Fe3O4) multifunctional composite and the nanofiberous mat can be a very good candidate as a filter for water purification, antibiofouling filtration and ECM for tissue engineering. PMID:23434708

Shamshi Hassan, M; Amna, Touseef; Hwang, I H; Khil, Myung-Seob

2013-06-01

165

Formation of carbon nanofibers from decacyclene by ion beam irradiation  

Energy Technology Data Exchange (ETDEWEB)

Amorphous carbon nanofibers with lengths of 1-20 {mu}m, uniform diameters of 20-100 nm were generated by ion beam-irradiation of decacyclene whiskers that were prepared on a flat plate of any material during vapor-deposition of decacyclene, a polycyclic aromatic compound, in vacuum for only a few minutes. The length of the whiskers did not depend on the duration of the vapor-deposition, whereas the number density of the whiskers increased with increasing the duration and reached 6.9 x 10{sup 7} cm{sup -2} at 4.5 min after starting the vapor-deposition. Irradiation of more than 10{sup 16} ions/cm{sup 2} with a 200 keV N{sup +} ion beam converted the whiskers to carbon nanofibers with the electrical conductivity comparable to that of graphite. This novel method of preparation is advantageous for aligning the fibers on a desired location, since the fibers are generated only on the irradiated part at ambient temperature without catalyst.

Kimura, Takahide [Division of Materials Chemistry, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628 (Japan); Koizumi, Hitoshi [Division of Materials Chemistry, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628 (Japan); Kinoshita, Hiroshi [Center for Advanced Research of Energy Conversion Materials, Hokkaido University, Sapporo 060-8628 (Japan); Ichikawa, Tsuneki [Division of Materials Chemistry, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628 (Japan)]. E-mail: ichikawa@eng.hokudai.ac.jp

2005-07-01

166

Formation of carbon nanofibers from decacyclene by ion beam irradiation  

International Nuclear Information System (INIS)

Amorphous carbon nanofibers with lengths of 1-20 ?m, uniform diameters of 20-100 nm were generated by ion beam-irradiation of decacyclene whiskers that were prepared on a flat plate of any material during vapor-deposition of decacyclene, a polycyclic aromatic compound, in vacuum for only a few minutes. The length of the whiskers did not depend on the duration of the vapor-deposition, whereas the number density of the whiskers increased with increasing the duration and reached 6.9 x 107 cm-2 at 4.5 min after starting the vapor-deposition. Irradiation of more than 1016 ions/cm2 with a 200 keV N+ ion beam converted the whiskers to carbon nanofibers with the electrical conductivity comparable to that of graphite. This novel method of preparation is advantageous for aligning the fibers on a desired location, since the fibers are generated only on the irradiated part at ambient temperature without catalyst

167

Carbon Nanofibers Synthesized on Selective Substrates for Nonvolatile Memory and 3D Electronics  

Science.gov (United States)

A plasma-enhanced chemical vapor deposition (PECVD) growth technique has been developed where the choice of starting substrate was found to influence the electrical characteristics of the resulting carbon nanofiber (CNF) tubes. It has been determined that, if the tubes are grown on refractory metallic nitride substrates, then the resulting tubes formed with dc PECVD are also electrically conducting. Individual CNFs were formed by first patterning Ni catalyst islands using ebeam evaporation and liftoff. The CNFs were then synthesized using dc PECVD with C2H2:NH3 = [1:4] at 5 Torr and 700 C, and approximately equal to 200-W plasma power. Tubes were grown directly on degenerately doped silicon substrates with resistivity rho approximately equal to 1-5 meterohm-centimeter, as well as NbTiN. The approximately equal to 200-nanometer thick refractory NbTiN deposited using magnetron sputtering had rho approximately equal to 113 microohm-centimeter and was also chemically compatible with CNF synthesis. The sample was then mounted on a 45 beveled Al holder, and placed inside a SEM (scanning electron microscope). A nanomanipulator probe stage was placed inside the SEM equipped with an electrical feed-through, where tungsten probes were used to make two-terminal electrical measurements with an HP 4156C parameter analyzer. The positive terminal nanoprobe was mechanically manipulated to physically contact an individual CNF grown directly on NbTiN as shown by the SEM image in the inset of figure (a), while the negative terminal was grounded to the substrate. This revealed the tube was electrically conductive, although measureable currents could not be detected until approximately equal to 6 V, after which point current increased sharply until compliance (approximately equal to 50 nA) was reached at approximately equal to 9.5 V. A native oxide on the tungsten probe tips may contribute to a tunnel barrier, which could be the reason for the suppressed transport at low biases. Currents up to approximately 100 nA could be cycled, which are likely to propagate via the tube surface, or sidewalls, rather than the body, which is shown by the I-V in figure (a). Electrical conduction via the sidewalls is a necessity for dc NEMS (nanoelectromechanical system) applications, more so than for the field emission applications of such tubes. During the tests, high conductivity was expected, because both probes were shorted to the substrate, as shown by curve 1 in the I-V characteristic in figure (b). When a tube grown on NbTiN was probed, the response was similar to the approximately equal to 100 nA and is represented by curve 2 in figure (b), which could be cycled and propagated via the tube surface or the sidewalls. However, no measureable currents for the tube grown directly on Si were observed as shown by curve 3 in figure (b), even after testing over a range of samples. This could arise from a dielectric coating on the sidewalls for tubes on Si. As a result of the directional nature of ion bombardment during dc PECVD, Si from the substrate is likely re-sputtered and possibly coats the sidewalls.

Kaul, Anupama B.; Khan, Abdur R.

2011-01-01

168

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

Science.gov (United States)

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

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

2012-07-11

169

Preparation and Application of Carbon Nanofibers-supported Palladium Nanoparticles Catalysts Based on Electrospinning  

OpenAIRE

Carbon nanofibers-supported palladium nanoparticle catalysts were prepared by electrospinning, chemical reduction and the subsequent high temperature carbonization methods. The experiments were carried out to investigate the influence of different reducing agents (sodium borohydride, hydrazine hydrate and hydrogen gas) on morphology of palladium nanoparticles and carbon nanofibers in detail. Catalysts were characterized by UV-Vis spectra, X-ray diffraction, fourier transform infrared spectrum...

Guo Li-ping, Bai Jie

2014-01-01

170

Pt/carbon nanofibers electrocatalysts for fuel cells: effect of the support oxidizing treatment  

OpenAIRE

Different Pt-based electrocatalysts supported on carbon nanofibers and carbon black (Vulcan XC-72R) have been prepared using a polymermediated synthesis. The electrocatalysts have been characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and cyclic voltammetry. The effect of carbon nanofibers treatment with HNO3 solution on Pt particle size and electroactive area has been analyzed. Highly dispersed Pt with homogeneous particle size and an electroactive area arou...

Zaragoza Marti?n, Francisco; Sopen?a Escario, Daniel; Morallo?n Nu?n?ez, Emilia; Salinas Marti?nez Lecea, Concepcio?n

2007-01-01

171

The copper-carbon nanofibers composite  

OpenAIRE

Cu/CNF (Carbon Nano Fiber) composite materials can be used as heat sink in power electronic devices. They can substitute Copper by combining a high thermal conductivity and a coefficient of thermal expansion close to the printed circuit one (alumina or aluminum nitride). After studying the properties of Copper matrix and CNF, three methods were set up for the elaboration of the Cu/CNF composite materials. It was first synthesized by a simple powder metallurgy process. Second, in order to obta...

Vincent, Ce?cile

2008-01-01

172

Hybrid Carbon Silica Nanofibers through Sol-Gel Electrospinning.  

Science.gov (United States)

A controlled sol-gel synthesis incorporated with electrospinning is employed to produce polyacrylonitrile-silica (PAN-silica) fibers. Hybrid fibers are obtained with varying amounts of silica precursor (TEOS in DMF catalyzed by HCl) and PAN. Solution viscosity, conductivity, and surface tension are found to relate strongly to the electrospinnability of PAN-silica solutions. TGA and DSC analyses of the hybrids indicate strong intermolecular interactions, possibly between the -OH group of silica and -CN of PAN. Thermal stabilization of the hybrids at 280 °C followed by carbonization at 800 °C transforms fibers to carbon-silica hybrid nanofibers with smooth morphology and diameter ranging from 400 to 700 nm. FTIR analysis of the fibers confirms the presence of silica in the as-spun as well as the carbonized material, where the extent of carbonization is also estimated by confirming the presence of -C?C and -C?O peaks in the carbonized hybrids. The graphitic character of the carbon-silica fibers is confirmed through Raman studies, and the role of silica in the disorder of the carbon structure is discussed. PMID:25474752

Pirzada, Tahira; Arvidson, Sara A; Saquing, Carl D; Shah, S Sakhawat; Khan, Saad A

2014-12-30

173

Fabrication of a compacted aluminum-carbon nanofiber material by hot pressing  

Science.gov (United States)

The aluminum-carbon nanofiber compacted materials fabricated by hot pressing are studied. The carbon content and the compacting temperature are shown to affect the hardness of the aluminum-carbon nanofiber compacted composite material: the hardness increases from 30 to 57 HB when the carbon nanofiber concentration increases from 0 to 1.5 wt %. The chemical state of the composite components is studied by X-ray photoelectron spectroscopy. Carbon nanofibers transform into an amorphous modification at a temperature of 980°C, which corresponds to the decrease in the hardness. Aluminum carbide Al4C3 is found to form, and its content increases monotonically in the hot pressing temperature range from 720 to 1370°C.

Kol'tsova, T. S.; Shakhov, F. M.; Voznyakovskii, A. A.; Lyashkov, A. I.; Tolochko, O. V.; Nasibulin, A. G.; Rudskoi, A. I.; Mikhailov, V. G.

2014-11-01

174

Electromagnetic Properties of Novel Carbon Nanofibers  

Directory of Open Access Journals (Sweden)

Full Text Available Carbonized bacterial cellulose (CBC with a three dimensional net-linked framework were synthesized from carbonized bacterial cellulose and investigated by X-ray diffraction, Raman spectrum and Transmission electron microscopy. The complex permittivity and permeability of CBC/paraffin wax composite with certain ratio of the composite were measured by vector network analysis in the frequency range of 0.1–18 GHz. It is found that the composite has high permittivity and dielectric loss, especially at the low frequency. The electromagnetic characteristics of the CBC/Fe3O4 complex absorbers synthesized by mixing a small quantity of CBC with Fe3O4 were also studied, aiming at improving the microwave absorbing properties of Fe3O4/Wax composite. When the sample’s thickness was 1.2 mm, the reflection loss reached a minimal value of –21 dB for CBC - Fe3O4/Wax and of –2 dB for Fe3O4/Wax as well.

WANG Gai-Hua, DAI Bo, MA Yong-Jun, REN Yong

2013-04-01

175

Imaging, spectroscopy, mechanical, alignment and biocompatibility studies of electrospun medical grade polyurethane (Carbothane™ 3575A) nanofibers and composite nanofibers containing multiwalled carbon nanotubes.  

Science.gov (United States)

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

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

2015-01-01

176

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

Science.gov (United States)

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

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

2012-07-01

177

Hierarchical core-shell carbon nanofiber@ZnIn?S? composites for enhanced hydrogen evolution performance.  

Science.gov (United States)

Improvement of hydrogen evolution ability is an urgent task for developing advanced catalysts. As one of the promising visible-light photocatalysts, ZnIn2S4 suffers from the ultrafast recombination of photoinduced charges, which limits its practical application for efficient solar water splitting. Herein, we reported a two-step method to prepare hierarchical core-shell carbon nanofiber@ZnIn2S4 composites. One-dimensional carbon nanofibers were first prepared by electrospinning and carbonization in N2. The subsequent solvothermal process led to the in situ growth of ZnIn2S4 nanosheets on the carbon nanofibers to fabricate hierarchical structure composites. The hierarchical core-shell configuration structure can help to form an intimate contact between the ZnIn2S4 nanosheet shell and the carbon nanofiber backbone compared with the equivalent physical mixture and can facilitate the interfacial charge transfer driven by the excitation of ZnIn2S4 under visible-light irradiation. Meanwhile, the ultrathin ZnIn2S4 nanosheets were uniformly grown on the surface of the carbon nanofibers, which can avoid agglomeration of ZnIn2S4. These synergistic effects made this unique hierarchical structure composite exhibit a significantly higher visible-light photocatalytic activity toward hydrogen evolution reaction compared with pure ZnIn2S4 or a physical mixture of ZnIn2S4 and carbon nanofibers in the absence of noble metal cocatalysts. PMID:25057818

Chen, Yajie; Tian, Guohui; Ren, Zhiyu; Pan, Kai; Shi, Yunhan; Wang, Jiaqi; Fu, Honggang

2014-08-27

178

Direct Electron Transfer of Hemoglobin on Manganese III Oxide-Ag Nanofibers Modified Glassy Carbon Electrode  

OpenAIRE

We investigated the electrochemical behavior of hemoglobin by glassy carbon electrode modified with Mn2O3-Ag nanofibers. The Mn2O3-Ag nanofibers were used as facilitator electron transfer between Hb and glassy-carbon-modified electrode. The Mn2O3-Ag nanofibers are studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The hemoglobin showed a quasireversible electrochemical redox behavior with a formal potential of ?49?mV (versus Ag/AgCl) in 0.1?M potas...

Fariba Pishbin; Mojdeh Khosravian-hemami; Saeed Rezaei-Zarchi; Mohammad Mahdi Saadatmand; Roya Malekzadeh; Somyyeh Rad; Mohammadreza Hadi; Gholamreza Mazaheri; Masoud Negahdary

2012-01-01

179

Effect of carbon nanofibers on tensile and compressive characteristics of hollow particle filled composites  

International Nuclear Information System (INIS)

The effect of presence of carbon nanofibers on the tensile and compressive properties of hollow particle filled composites is studied. Such composites, called syntactic foams, are known to have high specific modulus and low moisture absorption capabilities and are finding applications as core materials in aerospace and marine sandwich structures. The results of this study show that addition of 0.25 wt.% carbon nanofibers results in improvement in tensile modulus and strength compared to similar syntactic foam compositions that did not contain nanofibers. Compressive modulus decreased and strength remained largely unchanged for most compositions. Tensile and compressive failure features are analyzed using scanning electron microscopy.

180

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

Science.gov (United States)

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 cm(2) 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

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

2014-05-01

181

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

Science.gov (United States)

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.

Wang, Jiuyang

182

Electrospun vanadium pentoxide/carbon nanofiber composites for supercapacitor electrodes  

International Nuclear Information System (INIS)

The vanadium pentoxide (V2O5)/carbon nanofiber composites (CNFCs) were prepared from polyacrylonitrile/V2O5 in N,N-dimethylformamide by a simple electrospinning method, and their electrochemical properties as supercapacitor electrodes were investigated. Different loadings of V2O5, the microstructures of the CNFCs (e.g., nanometer-size diameters, high specific surface areas, narrow pore size distributions, and tunable porosities) were changed, and the textural parameters significantly affected the electrochemical properties of the composites. The CNFC capacitors delivered the high specific capacitances of 150.0 F g?1 for the CNFCs in an aqueous, with promising energy densities of 18.8 Wh kg?1, over a power density range of 400–20,000 W kg?1. The CNFCs simultaneously exhibited excellent capacity retention.

183

Structural changes in fibrous carbon nanomaterials produced by adding sulfur during chemical vapor deposition.  

Science.gov (United States)

Vapor-grown carbon fibers (VGCFs), platelet graphite nanofibers (PGNFs), turbostratic carbon nanofibers (CNFs), and carbon spheres were continuously produced by the thermal decomposition of ethanol in the presence of an Fe catalyst and a sulfur promoter at 1100 degrees C under a nitrogen/hydrogen atmosphere in a vertical chemical vapor deposition reactor. The sulfur concentration dramatically affected the morphology and microstructure of the carbon materials produced. A large amount of sulfur in the catalytic precursor led to the direct pyrolysis of hydrocarbons and the formation of carbon spheres (Fe:S = 1:10) while a lower amount of sulfur led to the formation of fibrous carbon materials, including VGCFs (Fe:S = 1:0.2), PGNFs (Fe:S = 1:2), and turbostratic CNFs (Fe:S = 1:5). The degree of poisoning of the catalysts determined the precipitation of the graphene layers, allowing the different types of carbon material to form. PMID:21121328

Wu, Hung-Chih; Li, Yuan-Yao

2010-12-01

184

Ni-catalysed carbon nanotubes and nanofibers assemblies grown on TiN/Si(1 0 0) substrates using hot-filaments combined with d.c. plasma CVD  

Science.gov (United States)

Different carbon nanotubes or nanofibers (CNTs or CNFs) assemblies were obtained using Ni catalyst deposited by Pulsed Laser Deposition (PLD) on TiN/Si(1 0 0) substrate from a H2/C2H2 mixture using plasma emerging from triode configured electrodes with two pairs of intercalated incandescent filaments at 1 kPa and 700 °C. In the presence of a relative intense plasma (54 W power), a dense CNT carpet was grown. The TEM images revealed the presence of elongated yet contorted 10-15 nm diameter CNTs with encapsulated Ni particles at their tips. Using a low plasma power (8 W) in similar conditions and from the same catalyst, a different morphology resulted: few self-sustained long fibrils (diameter around 1 ?m) which are curved under the action of their own weight containing compacted CNTs/CNFs and (only in the confined zones near the lateral edges) 50-200 nm thick filaments presenting buds-like structures and Y-shape junctions.

Fleaca, Claudiu Teodor; Le Normand, François

2014-02-01

185

Adsorption of toluene on carbon nanofibers prepared by electrospinning.  

Science.gov (United States)

This paper reports the novel results of activated carbon nanofibers (ACNF) used to improve the toluene adsorption capacity. The ACNF was prepared by stabilization, carbonization and activation after electrospinning the polymer solution of polyacrylonitrile (PAN) in N, N-dimethylformamide. The average diameter of the ACNF was approximately 300 nm, ranging from 200 to 500 nm. The toluene adsorption capacity of ACNF10 activated at 1000 degrees C increased to 65 g-toluene/100 g-ACNF. This was attributed to the high specific surface area (1403 m(2)/g), large micropore volume (0.505 cm(3)/g), and narrow average pore diameter (6.0 A). The oxygen to carbon ratio (O/C ratio) in ACNF10 was 1.8%. This O/C ratio appears to induce a higher toluene adsorption capacity, which originates from a non-polar interaction between the ACNF surface and toluene. In conclusion, the electrospun ACNF prepared in this study promotes the adsorption of toluene through the high specific surface area, large pore volume, narrow pore diameter and low O/C ratio. PMID:18262599

Oh, Gil-Young; Ju, Young-Wan; Kim, Mi-Young; Jung, Hong-Ryun; Kim, Hyung Jin; Lee, Wan-Jin

2008-04-15

186

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

Science.gov (United States)

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

2014-01-01

187

Development of radiation processing to functionalize carbon nanofiber to use in nanocomposite for industrial application  

International Nuclear Information System (INIS)

Radiation can be used to modify and improve the properties of materials. Electron beam and gamma ray irradiation has potential application in modifying the structure of carbon fibers in order to produce useful defects in the graphite structure and create reactive sites. In this study was investigated a methodology for radiation grafting processing to modify carbon nanofiber surfaces by grafting acrylic acid. The samples were submitted to direct radiation process. Several parameters were changed such as acrylic acid concentration, radiation dose and percentage of inhibitor to achieve functionalization with higher percentage of oxygen functional groups on carbon nanofiber surface and better dispersion. The samples were characterized by X-ray Photoelectron Spectroscopy and the dispersion stability upon storage was visually investigated. Carbon nanofiber directed irradiated with electron beam and gamma ray in a solution of acrylic acid with 6% of inhibitor (FeSO4.7H2O) and irradiated at 100 kGy had an increase of 20% of oxygen content onto carbon nanofiber surface. The Auger D-parameter for the samples direct irradiated grafted ranged between 17.0-17.7 compared to 21.1-18.9 of the unirradiated ones. This indicated that these samples had less sp2 and more sp3 bonding characteristics than unirradiated samples. This can be an indication of C=C bond breaking leading to the formation of new sp3 carbon atoms on carbon nanofiber surface with oxygen functional groups grafted. The samples grafted presented a good and stable dispersion. (author)

188

Relationship between Single Walled Carbon Nanotubes Individual Dispersion Behavior and Properties of Electrospun Nanofibers  

OpenAIRE

The dispersion stability behavior of single walled carbon nanotube (SWCNT) has important effects on morphological and mechanical properties of SWCNT/polymer composite nanofibers. The effects of SWCNTs incorporation on the morphological and structural developments and the relation between this develop-ments and mechanical properties of the polyacrylonitrile (PAN) nanofibers were demonstrated. The uni-form, stable dispersion and well oriented SWCNT within the PAN matrix were achieved through us...

Haji A.; Nasouri K.; Mousavi Shoushtari A.; Kaflou A.

2013-01-01

189

Electrospun carbon-tin oxide composite nanofibers for use as lithium ion battery anodes.  

Science.gov (United States)

Composite carbon-tin oxide (C-SnO(2)) nanofibers are prepared by two methods and evaluated as anodes in lithium-ion battery half cells. Such an approach complements the long cycle life of carbon with the high lithium storage capacity of tin oxide. In addition, the high surface-to-volume ratio of the nanofibers improves the accessibility for lithium intercalation as compared to graphite-based anodes, while eliminating the need for binders or conductive additives. The composite nanofibrous anodes have first discharge capacities of 788 mAh g(-1) at 50 mA g(-1) current density, which are greater than pure carbon nanofiber anodes, as well as the theoretical capacity of graphite (372 mAh g(-1)), the traditional anode material. In the first protocol to fabricate the C-SnO(2) composites, tin sulfate is directly incorporated within polyacrylonitrile (PAN) nanofibers by electrospinning. During a thermal treatment the tin salt is converted to tin oxide and the polymer is carbonized, yielding carbon-SnO(2) nanofibers. In the second approach, we soak the nanofiber mats in tin sulfate solutions prior to the final thermal treatment, thereby loading the outer surfaces with SnO(2) nanoparticles and raising the tin content from 1.9 to 8.6 wt %. Energy-dispersive spectroscopy and X-ray diffraction analyses confirm the formation of conversion of tin sulfate to tin oxide. Furthermore, analysis with Raman spectroscopy reveals that the additional salt soak treatment from the second fabrication approach increases in the disorder of the carbon structure, as compared to the first approach. We also discuss the performance of our C-SnO(2) compared with its theoretical capacity and other nanofiber electrode composites previously reported in the literature. PMID:21615138

Bonino, Christopher A; Ji, Liwen; Lin, Zhan; Toprakci, Ozan; Zhang, Xiangwu; Khan, Saad A

2011-07-01

190

The influence of a fibrous carbon envelope on the formation of CoFe nanoparticles for durable electrocatalytic oxygen evolution.  

Science.gov (United States)

Co oxides are known to be active and stable alternative anode electrocatalysts possessing the potential to replace the best performing but most expensive Ir and Ru oxides in alkaline water electrolysis. Of late, Co oxides loaded on various carbon supports have been reported as a way to outperform Ir or Ru catalysts by improving the utilization efficiency. In this study, we introduce Co and Fe nanoparticles embedded carbon nanofibers (CoFe-CNFs), fabricated through electrospinning and pyrolysis of a polymer mixed with Co and Fe precursors. This method is a facile route for simultaneously making Co and Fe nanoparticles as well as the stable accommodation of the CoFe nanoparticles in the carbon support. We demonstrate the potential of the CoFe-CNFs as active and stable electrocatalysts for the oxygen evolution reaction (OER) in alkaline media. We conducted detailed physico-chemical characterizations to elucidate the effect of the CNFs on the OER activity and stability of the CoFe-CNFs. It is suggested that the CNFs are a medium in which OER-active CoFe alloy nanoparticles are formed homogeneously, and that carbon layers surrounding the nanoparticles are beneficial to the stability of the CoFe-CNFs in the OER. PMID:24879319

Jeong, Beomgyun; Shin, Dongyoon; Lee, Jae Kwang; Kim, Dae Han; Kim, Young Dok; Lee, Jaeyoung

2014-07-21

191

Electrospun single-walled carbon nanotube/polyvinyl alcohol composite nanofibers: structure-property relationships  

International Nuclear Information System (INIS)

Polyvinyl alcohol (PVA) nanofibers and single-walled carbon nanotube (SWNT)/PVA composite nanofibers have been produced by electrospinning. An apparent increase in the PVA crystallinity with a concomitant change in its main crystalline phase and a reduction in the crystalline domain size were observed in the SWNT/PVA composite nanofibers, indicating the occurrence of a SWNT-induced nucleation crystallization of the PVA phase. Both the pure PVA and SWNT/PVA composite nanofibers were subjected to the following post-electrospinning treatments: (i) soaking in methanol to increase the PVA crystallinity, and (ii) cross-linking with glutaric dialdehyde to control the PVA morphology. Effects of the PVA morphology on the tensile properties of the resultant electrospun nanofibers were examined. Dynamic mechanical thermal analyses of both pure PVA and SWNT/PVA composite electrospun nanofibers indicated that SWNT-polymer interaction facilitated the formation of crystalline domains, which can be further enhanced by soaking the nanofiber in methanol and/or cross-linking the polymer with glutaric dialdehyde

192

Electrospun single-walled carbon nanotube/polyvinyl alcohol composite nanofibers: structure-property relationships  

Energy Technology Data Exchange (ETDEWEB)

Polyvinyl alcohol (PVA) nanofibers and single-walled carbon nanotube (SWNT)/PVA composite nanofibers have been produced by electrospinning. An apparent increase in the PVA crystallinity with a concomitant change in its main crystalline phase and a reduction in the crystalline domain size were observed in the SWNT/PVA composite nanofibers, indicating the occurrence of a SWNT-induced nucleation crystallization of the PVA phase. Both the pure PVA and SWNT/PVA composite nanofibers were subjected to the following post-electrospinning treatments: (i) soaking in methanol to increase the PVA crystallinity, and (ii) cross-linking with glutaric dialdehyde to control the PVA morphology. Effects of the PVA morphology on the tensile properties of the resultant electrospun nanofibers were examined. Dynamic mechanical thermal analyses of both pure PVA and SWNT/PVA composite electrospun nanofibers indicated that SWNT-polymer interaction facilitated the formation of crystalline domains, which can be further enhanced by soaking the nanofiber in methanol and/or cross-linking the polymer with glutaric dialdehyde.

Naebe, Minoo; Lin Tong; Wang Xungai [Centre for Material and Fibre Innovation, Deakin University, Geelong, VIC 3217 (Australia); Staiger, Mark P [Department of Mechanical Engineering, University of Canterbury, Christchurch (New Zealand); Dai Liming [Department of Chemical and Materials Engineering, University of Dayton, Dayton, OH 45469 (United States)], E-mail: tong.lin@deakin.edu.au

2008-07-30

193

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

Science.gov (United States)

In this study, parallel-aligned poly(propylene carbonate) (PPC) microfibers with a fiber diameter of 1.48±0.42?m were prepared by electrospinning and modified by oxygen plasma treatment. Next, chitosan nanofibers with a fiber diameter size of 278±98nm were introduced into the PPC fiber mats by freeze drying. Morphological analyses showed that the PPC scaffolds treated with 0.05mg/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. PMID:25498720

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

2015-03-01

194

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

Science.gov (United States)

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 that the time scale of single bubble growth is much shorter than the time over which the foam grows. The single bubble growth model was deemed to be applicable to low loadings of carbon nanofiber, where the bubble size distribution in the final foam is narrow.

Calebrese, Christopher

195

Carbonized Micro- and Nanostructures: Can Downsizing Really Help?  

Directory of Open Access Journals (Sweden)

Full Text Available In this manuscript, we discuss relationships between morphology and mechanical strength of carbonized structures, obtained via pyrolysis of polymeric precursors, across multiple length scales, from carbon fibers (CFs with diameters of 5–10 µm to submicron thick carbon nanofibers (CNFs. Our research points to radial inhomogeneity, skin–core structure, as a size-dependent feature of polyacrylonitrile-based CFs. This inhomogeneity is a surface effect, caused by suppressed diffusion of oxygen and stabilization byproducts during stabilization through skin. Hence, reducing the precursor diameters from tens of microns to submicron appears as an effective strategy to develop homogeneous carbonized structures. Our research establishes the significance of this downsizing in developing lightweight structural materials by comparing intrinsic strength of radially inhomogeneous CFs with that of radially homogeneous CNF. While experimental studies on the strength of CNFs have targeted randomly oriented turbostratic domains, via continuum modeling, we have estimated that strength of CNFs can reach 14 GPa, when the basal planes of graphitic domains are parallel to nanofiber axis. The CNFs in our model are treated as composites of amorphous carbon (matrix, reinforced with turbostratic domains, and their strength is predicted using Tsai–Hill criterion. The model was calibrated with existing experimental data.

Mohammad Naraghi

2014-05-01

196

Preparation and Application of Carbon Nanofibers-supported Palladium Nanoparticles Catalysts Based on Electrospinning  

Directory of Open Access Journals (Sweden)

Full Text Available Carbon nanofibers-supported palladium nanoparticle catalysts were prepared by electrospinning, chemical reduction and the subsequent high temperature carbonization methods. The experiments were carried out to investigate the influence of different reducing agents (sodium borohydride, hydrazine hydrate and hydrogen gas on morphology of palladium nanoparticles and carbon nanofibers in detail. Catalysts were characterized by UV-Vis spectra, X-ray diffraction, fourier transform infrared spectrum, scanning electron microscope, field emission transmission electron microscope. Results show that the palladium nanoparticles are distributed uniformly on the carbon nanofibers with dimension of about 7 nm, and the catalyst is relatively flexible by using hydrogen gas as reducing agent. Then it was applied to the Heck coupling reaction to test catalytic properties and recyclability. Results indicate that the catalyst possesses excellent stability and recyclability.

GUO Li-Ping, BAI Jie, LIANG Hai-Ou, LI Chun-Ping, SUN Wei-Yan, MENG Qing-Run

2014-08-01

197

Solvent-free acetylation of cellulose nanofibers for improving compatibility and dispersion.  

Science.gov (United States)

Cellulose nanofibers (CNFs), as bio-materials derived from wood or non-wood plants, have the advantages of being biodegradable, renewable, low cost, and having good mechanical properties compared to synthetic nanofibers. CNFs have been used as reinforcement in polymeric matrices, however, due to their polar surface, their dispersibility in non-polar solvents and compatibility with hydrophobic matrices are poor. In this work, the chemical modification of CNFs, using acetic anhydride in the presence of pyridine as a catalyst, was studied with the aim of changing the surface properties. Native and chemically modified CNFs were characterized in terms of dynamic absorption, thermal stability, surface chemistry, morphology, and crystal structure. The reaction of acetylation between the acetyl groups and the hydroxyl groups of the CNFs was examined using Fourier transform infrared (FT-IR) analysis, while its extent was assessed by titration. The ester content of CNFs was higher for the acetylated samples compared to the control samples. It was also shown that the crystallinity decreased moderately as a result of esterification. Thermal stability of the modified nanofibers was slightly increased. Unlike native CNFs, a stable aqueous suspension was obtained with the modified nanofibers in both ethanol and acetone. The contact angle measurements confirmed that the surface characteristics of acetylated CNFs were changed from hydrophilic to more hydrophobic. In addition, the obtained acetylated CNFs showed more hydrophobic surface, which is in favor of enhancing the hydrophobic non-polar mediums. PMID:24507293

Ashori, Alireza; Babaee, Mehran; Jonoobi, Mehdi; Hamzeh, Yahya

2014-02-15

198

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

Science.gov (United States)

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.

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

2012-05-01

199

Electrochemical stability of carbon nanofibers in proton exchange membrane fuel cells  

International Nuclear Information System (INIS)

This fundamental study deals with the electrochemical stability of several non-conventional carbon based catalyst supports, intended for low temperature proton exchange membrane fuel cell (PEMFC) cathodes. Electrochemical surface oxidation of raw and functionalized carbon nanofibers, and carbon black for comparison, was studied following a potential step treatment at 25.0 deg. C in acid electrolyte, which mimics the operating conditions of low temperature PEMFCs. Surface oxidation was characterized using cyclic voltammetry, X-ray photoelectron spectroscopy (XPS), and contact angle measurements. Cyclic voltammograms clearly showed the presence of the hydroquinone/quinone couple. Furthermore, identification of carbonyl, ether, hydroxyl and carboxyl surface functional groups were made by deconvolution of the XPS spectra. The relative increase in surface oxides on carbon nanofibers during the electrochemical oxidation treatment is significantly smaller than that on carbon black. This suggests that carbon nanofibers are more resistant to the electrochemical corrosion than carbon black under the experimental conditions used in this work. This behaviour could be attributed to the differences found in the microstructure of both kinds of carbons. According to these results, carbon nanofibers possess a high potential as catalyst support to increase the durability of catalysts used in low temperature PEMFC applications.

200

Functionalization of carbon nanotube and nanofiber electrodes with biological macromolecules: Progress toward a nanoscale biosensor  

Science.gov (United States)

The integration of nanoscale carbon-based electrodes with biological recognition and electrical detection promises unparalleled biological detection systems. First, biologically modified carbon-based materials have been shown to have superior long-term chemical stability when compared to other commonly used materials for biological detection such as silicon, gold, and glass surfaces. Functionalizing carbon electrodes for biological recognition and using electrochemical methods to transduce biological binding information will enable real-time, hand-held, lower cost and stable biosensing devices. Nanoscale carbon-based electrodes allow the additional capability of fabricating devices with high densities of sensing elements, enabling multi-analyte detection on a single chip. We have worked toward the integration of these sensor components by first focusing on developing and characterizing the chemistry required to functionalize single-walled carbon nanotubes and vertically aligned carbon nanofibers with oligonucleotides and proteins for specific biological recognition. Chemical, photochemical and electrochemical methods for functionalizing these materials with biological molecules were developed. We determined, using fluorescence and colorimetric techniques, that these biologically modified nanoscale carbon electrodes are biologically active, selective, and stable. A photochemical functionalization method enabled facile functionalization of dense arrays vertically aligned carbon nanofiber forests. We found that much of the vertically aligned carbon nanofiber sidewalls were functionalized and biologically accessible by this method---the absolute number of DNA molecules hybridized to DNA-functionalized nanofiber electrodes was ˜8 times higher than the number of DNA molecules hybridized to flat glassy carbon electrodes and implies that nanofiber forest sensors may facilitate higher sensitivity to target DNA sequences per unit area. We also used the photochemical method for surface chemistry for linking cytochrome c to nanofiber electrodes, and the resulting immobilized protein was determined to be active and was detected electrochemically using no electrochemical mediators. Additionally, we have developed an electrochemical functionalization method which allows for electrically-addressable biomolecular functionalization of patterned nanotubes and nanofibers. This method has enabled us to discretely functionalize individual sub-micron nanofiber regions with different DNA sequences on the same chip using no microfluidics, and will be useful for detection of multiple analytes on a single chip.

Baker, Sarah E.

201

Conductivity of carbon nanofiber/polypyrrole conducting nanocomposites  

Energy Technology Data Exchange (ETDEWEB)

Carbon nanofiber (CNF) / Polypyrrole (Ppy) composite materials were fabricated by two newly invented processes - filtering, washing and drying the mixture of CNF dispersion and Ppy-NMP solution (FWP process) and heating an aqueous solution of CNF (SH process). CNF/Ppy composite materials have never been reported before in any other research papers. Conductivities of the composite films were obtained by using a four-probe method. To compare the conductivity of CNF/Ppy with that of a pure single-walled carbon nanotube (SWNT), SWNT films were also fabricated and voltage was measured. SEM images were taken for both a surface and a cross-section of composite samples fabricated by the two processes. The CNF/Ppy by FWP was a little brittle because of the low solubility of Ppy in the NMP, and on the other hand, the same material by SH became flexible enough. The conductivity of the pure SWNT film was as high as double the similar case. The conductivity of the pure SWNT film was 20.11 S/cm and 0.013 cm thick. The CNF/Ppy composite films with the thicknesses of 0.062 cm and 0.085 cm gave a conductivity of 63.32 S/cm and 40.57 S/cm, respectively, which are higher than that of the pure SWNT film or SWNT/Polyaniline (PANi) film. The good conductivity of CNF/Ppy composites shows the improved potential for developing the materials for a small actuator

Kim, Cheol; Zhang, Shuai [Kyungpook National University, Daegu (Korea, Republic of)

2009-01-15

202

Conductivity of carbon nanofiber/polypyrrole conducting nanocomposites  

International Nuclear Information System (INIS)

Carbon nanofiber (CNF) / Polypyrrole (Ppy) composite materials were fabricated by two newly invented processes - filtering, washing and drying the mixture of CNF dispersion and Ppy-NMP solution (FWP process) and heating an aqueous solution of CNF (SH process). CNF/Ppy composite materials have never been reported before in any other research papers. Conductivities of the composite films were obtained by using a four-probe method. To compare the conductivity of CNF/Ppy with that of a pure single-walled carbon nanotube (SWNT), SWNT films were also fabricated and voltage was measured. SEM images were taken for both a surface and a cross-section of composite samples fabricated by the two processes. The CNF/Ppy by FWP was a little brittle because of the low solubility of Ppy in the NMP, and on the other hand, the same material by SH became flexible enough. The conductivity of the pure SWNT film was as high as double the similar case. The conductivity of the pure SWNT film was 20.11 S/cm and 0.013 cm thick. The CNF/Ppy composite films with the thicknesses of 0.062 cm and 0.085 cm gave a conductivity of 63.32 S/cm and 40.57 S/cm, respectively, which are higher than that of the pure SWNT film or SWNT/Polyaniline (PANi) film. The good conductivity of CNF/Ppy composites shows the improved potential for developing the materials for a small actuator

203

Carbon Nanotubes/Nanofibers by Plasma Enhanced Chemical Vapour Deposition  

Science.gov (United States)

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.

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

204

Graphenized carbon nanofiber: a novel light-trapping and conductive material to achieve an efficiency breakthrough in silicon solar cells.  

Science.gov (United States)

An innovative 1D material-graphenized carbon nanofiber-is designed and synthesized. The nanofiber exhibits superior light-scattering properties, ultralow absorption loss, and high electrical conductivity, and enables a wide range of applications. Simply integrating the nanofibers with the state-of-the-art silicon solar cells leads to a leaping efficiency boost of 3.8%, almost five times higher than the current world record. PMID:25363355

Chen, Xi; Jia, Baohua; Cai, Boyuan; Fang, Jia; Chen, Ze; Zhang, Xiaodan; Zhao, Ying; Gu, Min

2015-02-01

205

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

International Nuclear Information System (INIS)

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 expoage 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.

206

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

Science.gov (United States)

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.

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

2013-11-01

207

Direct measurement of bending stiffness and estimation of Young's modulus of vertically aligned carbon nanofibers  

Science.gov (United States)

The bending stiffness of individual, as-grown, vertically aligned carbon nanofibers was measured using a custom-built atomic force microscope placed inside a scanning electron microscope. The internal structure of the nanofiber was best modeled as dual-phase, composed of an inner graphitic core covered with a tapered amorphous carbon shell. It was found that the fibers have a relatively low bending stiffness, with Young's modulus values of about 10 GPa for the inner core and 65 GPa for the outer shell. The low Young's modulus of the inner core is attributed to a non-zero angle between the graphitic sheets and the nanofiber axis. The weak shear modulus between graphitic sheets thereby dominates the mechanical behaviour of the fibers.

Ghavanini, F. A.; Jackman, H.; Lundgren, P.; Svensson, K.; Enoksson, P.

2013-05-01

208

Direct Electron Transfer of Hemoglobin on Manganese III Oxide-Ag Nanofibers Modified Glassy Carbon Electrode  

Science.gov (United States)

We investigated the electrochemical behavior of hemoglobin by glassy carbon electrode modified with Mn2O3-Ag nanofibers. The Mn2O3-Ag nanofibers were used as facilitator electron transfer between Hb and glassy-carbon-modified electrode. The Mn2O3-Ag nanofibers are studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The hemoglobin showed a quasireversible electrochemical redox behavior with a formal potential of ?49?mV (versus Ag/AgCl) in 0.1?M potassium phosphate buffer solution at pH 7.0. The designed biosensor possesses good stability and reproducibility and achieves 95% of the steady-state current in less than five seconds. PMID:22550487

Negahdary, Masoud; Mazaheri, Gholamreza; Rad, Somyyeh; Hadi, Mohammadreza; Malekzadeh, Roya; Saadatmand, Mohammad Mahdi; Rezaei-Zarchi, Saeed; Pishbin, Fariba; Khosravian-hemami, Mojdeh

2012-01-01

209

The fabrication and electrochemical properties of electrospun nanofibers of a multiwalled carbon nanotube grafted by chitosan  

International Nuclear Information System (INIS)

Multiwalled carbon nanotubes (MWCNTs) were grafted by chitosan (CS); the product could disperse well in poly(vinyl alcohol) (PVA) aqueous solution with 2% (v/v) acetic acid solution. Because this product has potential in several biological fields, it was electrospun so as to enlarge the surface area. Raman spectra indicated that the electrospinning process did not severely alter the electron hybridization of carbon atoms within the nanotube framework. Moreover and interestingly, these nanofibers showed a novel sheath-core structure; the outer and inner diameters of these sheath-core nanofibers were about 200 nm and 100 nm, respectively. These nanofibers' electrochemical properties were characterized by detection of hydrogen peroxide and voltammetric responses of potassium ferricyanide. The electrospun fibers' web displayed faster electron transfer kinetics and better electrochemical properties than its cast film, which justified further applications in biological areas

210

The fabrication and electrochemical properties of electrospun nanofibers of a multiwalled carbon nanotube grafted by chitosan  

Energy Technology Data Exchange (ETDEWEB)

Multiwalled carbon nanotubes (MWCNTs) were grafted by chitosan (CS); the product could disperse well in poly(vinyl alcohol) (PVA) aqueous solution with 2% (v/v) acetic acid solution. Because this product has potential in several biological fields, it was electrospun so as to enlarge the surface area. Raman spectra indicated that the electrospinning process did not severely alter the electron hybridization of carbon atoms within the nanotube framework. Moreover and interestingly, these nanofibers showed a novel sheath-core structure; the outer and inner diameters of these sheath-core nanofibers were about 200 nm and 100 nm, respectively. These nanofibers' electrochemical properties were characterized by detection of hydrogen peroxide and voltammetric responses of potassium ferricyanide. The electrospun fibers' web displayed faster electron transfer kinetics and better electrochemical properties than its cast film, which justified further applications in biological areas.

Feng Wei; Wu Zigang; Li Yu; Feng Yiyu; Yuan Xiaoyan [School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China)], E-mail: weifeng@tju.edu.cn

2008-03-12

211

The fabrication and electrochemical properties of electrospun nanofibers of a multiwalled carbon nanotube grafted by chitosan  

Science.gov (United States)

Multiwalled carbon nanotubes (MWCNTs) were grafted by chitosan (CS); the product could disperse well in poly(vinyl alcohol) (PVA) aqueous solution with 2% (v/v) acetic acid solution. Because this product has potential in several biological fields, it was electrospun so as to enlarge the surface area. Raman spectra indicated that the electrospinning process did not severely alter the electron hybridization of carbon atoms within the nanotube framework. Moreover and interestingly, these nanofibers showed a novel sheath-core structure; the outer and inner diameters of these sheath-core nanofibers were about 200 nm and 100 nm, respectively. These nanofibers' electrochemical properties were characterized by detection of hydrogen peroxide and voltammetric responses of potassium ferricyanide. The electrospun fibers' web displayed faster electron transfer kinetics and better electrochemical properties than its cast film, which justified further applications in biological areas.

Feng, Wei; Wu, Zigang; Li, Yu; Feng, Yiyu; Yuan, Xiaoyan

2008-03-01

212

Electrochemical enzymatic biosensors using carbon nanofiber nanoelectrode arrays  

Science.gov (United States)

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 ?m 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.

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

2012-10-01

213

Electrochemical behavior of TiO2/carbon dual nanofibers  

International Nuclear Information System (INIS)

The charge transfer processes are favored in dual nanofibers composed by TiO2Rutile-Csemigraphitic/Csemigraphitic over other systems such as TiO2Anatase and Rutile-Camorphous/Camorphous and TiO2Rutile-Camorphous, dual and single nanofibers respectively. The study of electrochemical impedance spectroscopy (EIS) shows that the net of nanofibers presented a charge transfer resistance value (Rct) of 3.15 ?. The increased ability of these materials to favor the diffusion of electroactive species in individual nanofibers is that the junction between the n-type semiconductor TiO2 and the semigraphitic material can be of the ohmic kind. Moreover, this observation was supported by cyclic voltammetry (CV) and electrical conductivity studies by two-probe method. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) confirmed the continuity and duality in the morphology of these materials. The effect of heat treatment on crystallinity was evident in the results obtained from the X-Ray Diffraction (XRD) and Selected Area Electron Diffraction (SAED) studies. Due to the electrochemical performance and morphological features of TiO2Rutile-Csemigraphitic/Csemigraphitic dual nanofibers; this novel nanostructured material can be regarded as an excellent candidate for applications such as a base material for electronic devices, photocatalysis, among other similar technologies

214

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

Science.gov (United States)

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. PMID:25510199

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

215

High-performance lithium storage in nitrogen-enriched carbon nanofiber webs derived from polypyrrole  

International Nuclear Information System (INIS)

Highlights: • N-enriched carbon nanofiber webs are prepared via direct carbonization route with polyporrole as template. • The pyrolysis time plays an important role in N doping level and existing type. • Effect of N-doping on performance of the carbon anode material is investigated. • High reversible capacity of 238 mAh g?1 at 5 A g?1 is attained. -- Abstract: Nitrogen-doped carbon nanofiber webs (N-CNFWs) are prepared by direct pyrolyzation of polypyrrole (PPy) nanofiber webs at 600 °C. The structure and morphology of N-CNFWs are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), Raman spectra and elemental analysis. Both the doped N content and the N existing type in carbon, change with the pyrolysis time. As anode material for lithium-ion battery, the N-CNFWs show high capacity and good rate capability. The reversible capacity is up to 668 mAh g?1 at a current density of 0.1 A g?1 and 238 mAh g?1 at 5 A g?1, which can be ascribed to the nanofiber structure and high nitrogen content

216

Surface modified PLGA/carbon nanofiber composite enhances articular chondrocyte functions  

Science.gov (United States)

Since articular cartilage has a limited self regeneration capability, alternative methods are needed for repairing cartilage defects. The purpose of the present in vitro study was to explore the effects of material surface properties and external stimulation on chondrocyte (cartilage-synthesizing cell) functions. Based on this information, a goal of this research was to propose a scaffold composite material for enhancing articular chondrocyte function. To improve functions of chondrocytes, material (namely, poly(lactic-co-glycolic acid); PLGA) surfaces were modified via chemical (NaOH) etching techniques. Chondrocytes were cultured on surface-modified 2-D PLGA films and 3-D PLGA tissue engineering scaffolds, which were created by a salt-leaching method. Carbon nanofibers were imprinted on PLGA matrices in an aligned pattern for controlled electrically-active surface features. Electrical stimulation was applied to expedite and enhance chondrocyte functions. Results demonstrated that both NaOH-treated 2-D and 3-D substrates enhanced chondrocyte functions (cell numbers as well as extracellular matrix production) compared to non-treated PLGA substrates. Furthermore, chondrocytes preferred to attach along the carbon nanofiber patterns imprinted on PLGA. Electrical stimulation also enhanced chondrocyte functions on carbon nanofiber/PLGA composites. Underlying material properties that may have enhanced chondrocyte functions include a more hydrophilic surface, surface energy differences due to the presence of carbon nanofibers, increased surface area, altered porosity, and a greater degree of nanometer roughness. Moreover, these altered surface properties positively influenced select protein adsorption that controlled subsequent chondrocyte adhesion. Collectively, this study provided a scaffold model for osteochondral defects that can be synthesized using the above techniques and a layer by layer approach to accommodate the property differences in each layer of natural cartilage. Specifically, these results suggest that the superficial zone, middle zone, and deep zone of cartilage should be composed of carbon nanofibers aligned parallel to the surface in PLGA, randomly oriented carbon nanofibers in PLGA, and carbon nanofibers aligned perpendicular to the surface in PLGA, respectively. Clearly, such scaffolds may ultimately enhance the efficacy of scaffolds used for articular cartilage repair.

Park, Grace Eunseung

217

Transparent liquid-crystal-based microlens array using vertically aligned carbon nanofiber electrodes on quartz substrates  

Energy Technology Data Exchange (ETDEWEB)

A novel transparent liquid-crystal-based microlens array has been fabricated using an array of vertically aligned multi-wall carbon nanofibers (MWCNFs) on a quartz substrate and its optical characteristics investigated. Electron beam lithography was used for the catalyst patterning on a quartz substrate to grow the MWCNF array of electrodes. The structure of the electrode array was determined through simulation to achieve the best optical performance. Both the patterned catalyst and growth parameters were optimized for optimal MWCNF properties. We report an in-depth optical characterization of these reconfigurable hybrid liquid crystal and nanofiber microlens arrays.

Dai Qing; Rajasekharan, Ranjith; Butt, Haider; Won, Kanghee; Wang Xiaozhi; Wilkinson, Timothy D; Amaragtunga, Gehan, E-mail: qd205@cam.ac.uk [Department of Engineering (Division B), Cape Building, University of Cambridge, 9 J J Thomson Avenue, Cambridge CB3 0FA (United Kingdom)

2011-03-18

218

Transparent liquid-crystal-based microlens array using vertically aligned carbon nanofiber electrodes on quartz substrates  

International Nuclear Information System (INIS)

A novel transparent liquid-crystal-based microlens array has been fabricated using an array of vertically aligned multi-wall carbon nanofibers (MWCNFs) on a quartz substrate and its optical characteristics investigated. Electron beam lithography was used for the catalyst patterning on a quartz substrate to grow the MWCNF array of electrodes. The structure of the electrode array was determined through simulation to achieve the best optical performance. Both the patterned catalyst and growth parameters were optimized for optimal MWCNF properties. We report an in-depth optical characterization of these reconfigurable hybrid liquid crystal and nanofiber microlens arrays.

219

The Optical Excitation of Zigzag Carbon Nanotubes with Photons Guided in Nanofibers  

CERN Document Server

We consider the excitation of electrons in semiconducting carbon nanotubes by photons from the evanescent field created by a subwavelength-diameter optical fiber. The strongly changing evanescent field of such nanofibers requires dropping the dipole approximation. We show that this leads to novel effects, especially a high dependence of the photon absorption on the relative orientation and geometry of the nanotube-nanofiber setup in the optical and near infrared domain. In particular, we calculate photon absorption probabilities for a straight nanotube and nanofiber depending on their relative angle. Nanotubes orthogonal to the fiber are found to perform much better than parallel nanotubes when they are short. As the nanotube gets longer the absorption of parallel nanotubes is found to exceed the orthogonal nanotubes and approach 100% for extremely long nanotubes. In addition, we show that if the nanotube is wrapped around the fiber in an appropriate way the absorption is enhanced. We find that optical and ne...

Broadfoot, S; Jaksch, D

2011-01-01

220

Fabrication of transition metal oxide-carbon nanofibers with novel hierarchical architectures.  

Science.gov (United States)

We report a facile two-step methodology; electrospinning followed by high temperature treatment, to produce manganese oxide-based nanofibers with well-controlled nanoscale architectures. Electrospinning of manganese acetate-based solution (MnOx precursor) has been utilized to fabricate meso-porous manganese oxide nanofibers. These fibers have diameters of about 200-300 nm and fiber mats have been shown to have specific surface area of over 12 m2/g. Scanning and transmission electron microscopy results show that electrospinning has been successfully utilized to create nanofibers with deep inter-connected internal meso-pores for high surface area. In addition, fibers have been spun in a co-axial arrangement to fabricate hollow meso-porous nanofibers, or to develop core-shell nanofibers with nanoparticles of manganese oxides decorated over current conducting carbon core. X-ray diffraction analysis of the oxide fibers confirms the presence of manganese oxides (MnO2, Mn3O4) after calcination at 700 degrees C. These architectures, we believe, are potentially favorable for use in Li-ion batteries, Li-air batteries and supercapacitors. PMID:24758057

Hu, Alice; Curran, Chris; Tran, Chau; Kapllani, Alda; Kalra, Vibha

2014-07-01

221

DC Plasma Synthesis of Vertically Aligned Carbon Nanofibers for Biointerfacing  

Science.gov (United States)

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 flexible polydimethylesiloxane (PDMS) is presented. A process has been developed that involves synthesizing fibers on aluminum, followed by spin coating a thin layer of PDMS and then dissolving the underlying aluminum with KOH. Finally, a method of fiber synthesis using just air and acetone as the process gases is presented, enabling the possibility of inatmosphere, large scale VACNF synthesis. It is envisioned that these advancements should assist the viability of large scale VACNF related technologies and will help to bridge the gap between experimental applications and industrial adoption.

Pearce, Ryan Christopher

222

Durability of Carbon Nanofiber (CNF) & Carbon Nanotube (CNT) as Catalyst Support for Proton Exchange Membrane Fuel Cells  

OpenAIRE

Durability issues have recently been given much attention in Proton Exchange Membrane Fuel Cell (PEMFC) research. It gives fundamental definition for cell life time, capital cost, system stability and technique reliability. Loss of catalyst surface area due to corrosion of supporting material (normally carbon black) is one of the essential degradation mechanisms during cell operation. In this work, durability of Carbon Nanofibers (CNF) & Carbon Nanotubes (CNT) as alternative platinum catalyst...

Andersen, Shuang Ma; Borghei, Maryam; Lund, Peter; Elina, Yli-rantala; Pasanen, Antti; Kauppinen, Esko; Ruiz, Virginia; Kauranen, Pertti; Skou, Eivind Morten

2013-01-01

223

Hollow carbon-nanotube/carbon-nanofiber hybrid anodes for Li-ion batteries.  

Science.gov (United States)

By a novel in situ chemical vapor deposition, activated N-doped hollow carbon-nanotube/carbon-nanofiber composites are prepared having a superhigh specific Brunauer–Emmett–Teller (BET) surface area of 1840 m(2) g(–1) and a total pore volume of 1.21 m(3) g(–1). As an anode, this material has a reversible capacity of ~1150 mAh g(–1) at 0.1 A g(–1) (0.27 C) after 70 cycles. At 8 A g(–1) (21.5 C), a capacity of ~320 mAh g(–1) fades less than 20% after 3500 cycles, which makes it a superior anode material for a Li-ion battery. PMID:24144455

Chen, Yuming; Li, Xiaoyan; Park, Kyusung; Song, Jie; Hong, Jianhe; Zhou, Limin; Mai, Yiu-Wing; Huang, Haitao; Goodenough, John B

2013-11-01

224

Decomposition of Fe5C2 catalyst particles in carbon nanofibers during TEM observation  

Directory of Open Access Journals (Sweden)

Full Text Available The effect of an electron beam on nanoparticles of two Fe carbide catalysts inside a carbon nanofiber was investigated in a transmission electron microscope. Electron beam exposure does not result in significant changes for cementite (?-Fe3C. However, for Hägg carbide nanoparticles (?-Fe5C2, explosive decay is observed after exposure for 5–10 s. This produces small particles of cementite and ?-Fe, each covered with a multilayer carbon shell, and significantly modifies the carbon-fiber structure. It is considered that the decomposition of Hägg carbide is mostly due to the damage induced by high-energy electron collisions with the crystal lattice, accompanied by the heating of the particle and by mechanical stress provided by the carbon layers of the nanofiber.

Vladimir D Blank, Boris A Kulnitskiy, Igor A Perezhogin, Yuriy L Alshevskiy and Nikita V Kazennov

2009-01-01

225

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

OpenAIRE

Carbon nanofiber (CNF), as one of the most important members of carbon fibers, has been investigated in both fundamental scientific research and practical applications. CNF composites are able to be applied as promising materials in many fields, such as electrical devices, electrode materials for batteries and supercapacitors and as sensors. In these applications, the electrical conductivity is always the first priority need to be considered. In fact, the electrical property of CNF composites...

Lichao Feng; Ning Xie; Jing Zhong

2014-01-01

226

Increased response/recovery lifetimes and reinforcement of Polyaniline Nanofiber Films using Carbon Nanotubes  

OpenAIRE

We have prepared high surface area, conductive, mechanically robust, responsive polyaniline-carbon nanotune composite films. These were produced by filtration from dilute dispersions of polyaniline nanofibers and single-walled carbon nanotubes. Unlike polyaniline alone, these composites are mechanically stable, maintain large intractable surfaces and exhibit greatly enhanced response/recovery behavior to changes in their local environment. This is illustrated by exposing the films to ammonia.

Coleman, Jonathan Nesbit; Blighe, Fiona

2012-01-01

227

Development of Electro-Mechanical Spinning for Controlled Deposition of Carbon Nanofibers  

Science.gov (United States)

In the past few decades the fields of nanotechnology and miniaturized devices had an exponentially growth of interest in academic and research environment, leading to breakthroughs discoveries that are envisioned to have a profound impact on our economy and society in the near future. Recently, the focus is moving toward the development of technologies that enable the production of micro- /nano-devices on a larger scale and at lower costs. Among the different micro- /nano-devices manufacturing challenges, in this dissertation the aim is to reliably fabricate suspend carbon micro- /nano-fibers between two carbon electrode walls in a way that can be mass produced at relatively low cost. The first part of this thesis provides an in depth overview of current methods used for the fabrication of carbon based micro devices (C-MEMS) and of electrospinning, a manufacturing technology that emerges as a simple and inexpensive approach to produce nanofibers. Electro-Mechanical Spinning (EMS) has been developed from electrospinning and optimized for the production of suspended carbon nanofibers, aiming to achieve greater deposition control at the single nanofiber level, while maintaining the low cost of electrospinning. After the successful development of EMS, the so fabricated carbon micro- /nano-fibers have been characterized, first from the electrical point of view, then from the mechanical one. The electrical characterization involves conductivity measurements of fibers with respect of different and controllable manufacturing processes steps. Variations of those manufacturing parameters have been proven to be capable of tailoring the carbon structure and, therefore, the conductivity of the fibers within a desired range. Further investigation regarding the electrical properties was also conducted to prevent (or control) current induced fiber breakdown. Finally, the Young's modulus of those fibers was investigated and observed to be dependent on the fibers thickness. Similarly to conductivity, variations in Young's modulus are also related to formation of a different carbon structure when fibers diameter is below certain values. In conclusion, appropriate combinations of EMS and C-MEMS processes were proven to be capable of fabricating controllable suspended carbon nanofibers with tuned conductivity and Young's modulus properties.

Canton, Giulia

228

The interfacial strength of carbon nanofiber epoxy composite using single fiber pullout experiments  

International Nuclear Information System (INIS)

Carbon nanotubes and nanofibers are extensively researched as reinforcing agents in nanocomposites for their multifunctionality, light weight and high strength. However, it is the interface between the nanofiber and the matrix that dictates the overall properties of the nanocomposite. The current trend is to measure elastic properties of the bulk nanocomposite and then compare them with theoretical models to extract the information on the interfacial strength. The ideal experiment is single fiber pullout from the matrix because it directly measures the interfacial strength. However, the technique is difficult to apply to nanocomposites because of the small size of the fibers and the requirement for high resolution force and displacement sensing. We present an experimental technique for measuring the interfacial strength of nanofiber-reinforced composites using the single fiber pullout technique and demonstrate the technique for a carbon nanofiber-reinforced epoxy composite. The experiment is performed in situ in a scanning electron microscope and the interfacial strength for the epoxy composite was measured to be 170 MPa.

229

Study on glow discharge effects on catalyst films for growing aligned carbon nanofibers in negative bias-enhanced hot filament chemical vapor deposition system  

International Nuclear Information System (INIS)

Aligned carbon nanofibers (ACNFs) were grown on silicon substrates coated with NiFe catalyst films by negative bias-enhanced hot filament chemical vapor deposition (CVD). The growth and structure of the aligned carbon nanofibers were investigated by scanning electron microscopy (SEM). The results indicate that the aligned carbon nanofibers could be synthesized after the glow discharge appears when the negative bias is higher than a certain value, while they are bent if the glow discharge does not appear. Furthermore, the diameters of the aligned carbon nanofibers are reduced and their lengths are increased with increasing the negative bias. It is shown that the glow discharge resulting from the negative bias plays an important role in the growth of aligned carbon nanofibers. Here, the effects of the glow discharge on the growth and structure of the aligned carbon nanofibers are discussed

230

Enhanced visible-light photocatalytic performance of electrospun carbon-doped TiO2/halloysite nanotube hybrid nanofibers.  

Science.gov (United States)

In this work, the effects of halloysite nanotubes (HNTs) on the visible-light photocatalytic ability of electrospun carbon doped TiO2/HNT (CTH) nanofibers have been explored. Structural and morphological investigations demonstrate that incorporation of HNTs into anatase CTH hybrid nanofibers was easily achieved by using sol-gel processing combined with electrospinning approach, thus HNTs could be uniformly embedded in the electrospun nanofibers. The visible-light photocatalytic efficiency of CTH hybrid on the degradation of methyl blue (MB) was greatly enhanced with the combination of moderate amount of HNTs (8%), which was 23 times higher than that of commercial anatase TiO2. Mechanism of the enhancing effect of HNTs has been explored by analyzing the dual-effect of adsorption and photocatalysis in various amounts of HNTs incorporated CTiO2 nanofibers. With nanotubular structure and considerable adsorption ability, incorporated HNTs functioned as porogen agent in CTH nanofibers. This simple incorporation approach increases the specific surface areas of nanofibers, which improves the mass transport of reactant into the nanofibers and the adsorption of visible-light by scattering, meanwhile may suppress the charge recombination and enhance photoinduced charge separation, thus efficiently enhancing visible-light photocatalytic performance of the CTH hybrid nanofibers. PMID:25463176

Jiang, Ling; Huang, Yunpeng; Liu, Tianxi

2015-02-01

231

Silicon nanoparticles encapsulated in hollow graphitized carbon nanofibers for lithium ion battery anodes  

Science.gov (United States)

Silicon (Si) is a promising material for lithium ion battery (LIB) anodes due to its high specific capacity. To overcome its shortcomings such as insulation property and large volume change during the charge-discharge process, a novel hybrid system, Si nanoparticles encapsulated in hollow graphitized carbon nanofibers, is studied. First, electrospun polyacrylonitrile (PAN)-Si hybrid nanofibers were obtained using water as the collector. The loose nanofiber lumps suspended in water have large inter-fiber distance, allowing in situ coating of a thin layer of polydopamine (PDA), the source for graphitized carbon, uniformly throughout the system. The designed morphology and structure were then realized by etching and calcination, and the morphology and structure were subsequently verified by various analytical techniques. Electrochemical measurements show that the resulting hollow hybrid nanofibers (C-PDA-Si NFs) exhibit much better cycling stability and rate capacity than conventional C/Si nanofibers derived by electrospinning of PAN-Si followed by calcination. For instance, the capacity of C-PDA-Si NFs is as high as 72.6% of the theoretical capacity after 50 cycles, and a high capacity of 500 mA h g-1 can be delivered at a current density of 5 A g-1. The significantly improved electrochemical properties of C-PDA-Si NFs are due to the excellent electrical conductivity of the carbonized PDA (C-PDA) shell that compensates for the insulation property of Si, the high electrochemical activity of C-PDA, which has a layered structure and is N-doped, the hollow nature of the nanofibers and small size of Si nanoparticles that ensure smooth insertion-extraction of lithium ions and more complete alloying with them, as well as the buffering effect of the remaining PAN-derived carbon around the Si nanoparticles, which stabilizes the structure.Silicon (Si) is a promising material for lithium ion battery (LIB) anodes due to its high specific capacity. To overcome its shortcomings such as insulation property and large volume change during the charge-discharge process, a novel hybrid system, Si nanoparticles encapsulated in hollow graphitized carbon nanofibers, is studied. First, electrospun polyacrylonitrile (PAN)-Si hybrid nanofibers were obtained using water as the collector. The loose nanofiber lumps suspended in water have large inter-fiber distance, allowing in situ coating of a thin layer of polydopamine (PDA), the source for graphitized carbon, uniformly throughout the system. The designed morphology and structure were then realized by etching and calcination, and the morphology and structure were subsequently verified by various analytical techniques. Electrochemical measurements show that the resulting hollow hybrid nanofibers (C-PDA-Si NFs) exhibit much better cycling stability and rate capacity than conventional C/Si nanofibers derived by electrospinning of PAN-Si followed by calcination. For instance, the capacity of C-PDA-Si NFs is as high as 72.6% of the theoretical capacity after 50 cycles, and a high capacity of 500 mA h g-1 can be delivered at a current density of 5 A g-1. The significantly improved electrochemical properties of C-PDA-Si NFs are due to the excellent electrical conductivity of the carbonized PDA (C-PDA) shell that compensates for the insulation property of Si, the high electrochemical activity of C-PDA, which has a layered structure and is N-doped, the hollow nature of the nanofibers and small size of Si nanoparticles that ensure smooth insertion-extraction of lithium ions and more complete alloying with them, as well as the buffering effect of the remaining PAN-derived carbon around the Si nanoparticles, which stabilizes the structure. Electronic supplementary information (ESI) available: The photo of an electrospinning setup with a liquid collector, the photos of a compact electrospun PAN mat and that with PDA coating, the XRD pattern and TGA profile of carbonized PAN-Si hybrid nanofibers, SEM images, FTIR and Raman spectra of hollow PDA nanofibers, the cycling capacity of C-PDA-Si NFs which are prepared

Kong, Junhua; Yee, Wu Aik; Wei, Yuefan; Yang, Liping; Ang, Jia Ming; Phua, Si Lei; Wong, Siew Yee; Zhou, Rui; Dong, Yuliang; Li, Xu; Lu, Xuehong

2013-03-01

232

Studies on the de/re-hydrogenation characteristics of nanocrystalline MgH2 admixed with carbon nanofibres  

Science.gov (United States)

In the present investigation, we have synthesized different morphologies of carbon nanofibres (CNFs) to investigate their catalytic effect on the hydrogenation characteristics of 25 h ball-milled MgH2 (nano MgH2). The TEM analysis reveals that 25 h of ball-milling leads to the formation of nanocrystalline particles with size ranging between 10 and 20 nm. Different morphologies of CNFs were synthesized by catalytic thermal decomposition of acetylene (C2H2) gas over LaNi5 alloy. Helical carbon nanofibers (HCNFs) were formed at a temperature 650 °C. By increasing the synthesis temperature to 750 °C, planar carbon nanofibres were formed. In order to explore the effectiveness of CNFs towards lowering the decomposition temperature, TPD experiments (at heating rate 5 °C/min) were performed for nano MgH2 with and without CNFs. It was found that the decomposition temperature is reduced to ~334 and ~300 °C from 367 °C for the PCNF and HCNF catalysed nano MgH2. It is also found that HCNF admixed nano MgH2 absorbs ~5.25 wt% within 10 min as compared with pristine nano MgH2, which absorbs only ~4.2 % within the same time and same condition of temperature and pressure. Thus the HCNF possesses better catalytic activity than PCNF. These different levels of improvement in hydrogenation properties of HCNF catalysed nano MgH2 is attributed to the morphology of the CNFs.

Shahi, Rohit R.; Raghubanshi, Himanshu; Shaz, M. A.; Srivastava, O. N.

2012-09-01

233

Fracture Toughness of Vapor Grown Carbon Nanofiber-Reinforced Polyethylene Composites  

OpenAIRE

The impact fracture behavior of a vapor grown carbon nanofiber (VGCNF) reinforced high-density polyethylene (PE) composite was evaluated. The samples consisting of pure PE and composites with 10?wt% and 20?wt% of VGCNFs were prepared by a combination of hot-pressing and extrusion methods. Extrusion was used to produce samples with substantially different shear histories. The fracture behavior of these samples was analyzed using the essential work of fracture (EWF) approa...

Adhikari, A. R.; Partida, E.; Petty, T. W.; Jones, R.; Lozano, K.; Guerrero, C.

2009-01-01

234

Carbon nanofiber aerogels for emergent cleanup of oil spillage and chemical leakage under harsh conditions  

OpenAIRE

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...

Zhen-Yu Wu; Chao Li; Hai-Wei Liang; Yu-Ning Zhang; Xin Wang,; Jia-Fu Chen; Shu-Hong Yu

2014-01-01

235

Conducting nanocomposites based on polyamide 6,6 and carbon nanofibers prepared by cryogenic grinding  

OpenAIRE

Nanocomposites based on polyamide 6,6 and carbon nanofiber have been obtained following a new procedure. It consists of the physical mixing of the polymer matrix, in the form of powder, and the corresponding amount of additive. Then, samples were prepared by compression molding and their structural characteristics, as well as their thermal and electrical properties were determined. The materials present good electrical conductivity at lower percolation thresholds than those correspondin...

Linares, A.; Canalda, J. C.; Cagiao, M. E.; Ezquerra, T. A.

2011-01-01

236

Solid-state NMR and EPR study of fluorinated carbon nanofibers  

International Nuclear Information System (INIS)

Carbon nanofibers were fluorinated in two manners, in pure fluorine gas (direct fluorination) and with a fluorinating agent (TbF4 during the so-called controlled fluorination). The resulting fluorinated nanofibers have been investigated by solid-state nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR). This underlines that the fluorination mechanisms differ since a (CF)n structural type is obtained, whatever the temperature, with the controlled reaction, whereas, during the direct process, a (C2F)n type is formed over a wide temperature range. Through a careful characterization of the products, i.e. density of dangling bonds (as internal paramagnetic centers), structural type (acting on molecular motion) and specific surface area (related to the amount of physisorbed O2), the effect of atmospheric oxygen molecules on the spin-lattice nuclear relaxation has been underlined. - Graphical abstract: Scheme of the fluorination process using F2 and TbF4 as fluorinating agent

237

Electrospun La0.8Sr0.2MnO3 nanofibers for a high-temperature electrochemical carbon monoxide sensor  

International Nuclear Information System (INIS)

Lanthanum strontium manganite (La0.8Sr0.2MnO3, LSM) nanofibers have been synthesized by the electrospinning method. The electrospun nanofibers are intact without morphological and structural changes after annealing at 1050?°C. The LSM nanofibers are employed as the sensing electrode of an electrochemical sensor with yttria-stabilized zirconia (YSZ) electrolyte for carbon monoxide detection at high temperatures over 500?°C. The electrospun nanofibers form a porous network electrode, which provides a continuous pathway for charge transport. In addition, the nanofibers possess a higher specific surface area than conventional micron-sized powders. As a result, the nanofiber electrode exhibits a higher electromotive force and better electro-catalytic activity toward CO oxidation. Therefore, the sensor with the nanofiber electrode shows a higher sensitivity, lower limit of detection and faster response to CO than a sensor with a powder electrode. (paper)

238

Electrospun La0.8Sr0.2MnO? nanofibers for a high-temperature electrochemical carbon monoxide sensor.  

Science.gov (United States)

Lanthanum strontium manganite (La(0.8)Sr(0.2)MnO(3), LSM) nanofibers have been synthesized by the electrospinning method. The electrospun nanofibers are intact without morphological and structural changes after annealing at 1050?°C. The LSM nanofibers are employed as the sensing electrode of an electrochemical sensor with yttria-stabilized zirconia (YSZ) electrolyte for carbon monoxide detection at high temperatures over 500?°C. The electrospun nanofibers form a porous network electrode, which provides a continuous pathway for charge transport. In addition, the nanofibers possess a higher specific surface area than conventional micron-sized powders. As a result, the nanofiber electrode exhibits a higher electromotive force and better electro-catalytic activity toward CO oxidation. Therefore, the sensor with the nanofiber electrode shows a higher sensitivity, lower limit of detection and faster response to CO than a sensor with a powder electrode. PMID:22751138

Zhi, Mingjia; Koneru, Anveeksh; Yang, Feng; Manivannan, Ayyakkannu; Li, Jing; Wu, Nianqiang

2012-08-01

239

Carbon nanotube-loaded electrospun LiFePO4/carbon composite nanofibers as stable and binder-free cathodes for rechargeable lithium-ion batteries.  

Science.gov (United States)

LiFePO(4)/CNT/C composite nanofibers were synthesized by using a combination of electrospinning and sol-gel techniques. Polyacrylonitrile (PAN) was used as the electrospinning media and carbon source. Functionalized CNTs were used to increase the conductivity of the composite. LiFePO(4) precursor materials, PAN and functionalized CNTs were dissolved or dispersed in N,N-dimethylformamide separately and they were mixed before electrospinning. LiFePO(4) precursor/CNT/PAN composite nanofibers were then heat-treated to obtain LiFePO(4)/CNT/C composite nanofibers. Fourier transform infrared spectroscopy measurements were done to demonstrate the functionalization of CNTs. The structure of LiFePO(4)/CNT/C composite nanofibers was determined by X-ray diffraction analysis. The surface morphology and microstructure of LiFePO(4)/CNT/C composite nanofibers were characterized using scanning electron microscopy and transmission electron microscopy. Electrochemical performance of LiFePO(4)/CNT/C composite nanofibers was evaluated in coin-type cells. Functionalized CNTs were found to be well-dispersed in the carbonaceous matrix and increased the electrochemical performance of the composite nanofibers. As a result, cells using LiFePO(4)/CNT/C composite nanofibers have good performance, in terms of large capacity, extended cycle life, and good rate capability. PMID:22301674

Toprakci, Ozan; Toprakci, Hatice A K; Ji, Liwen; Xu, Guanjie; Lin, Zhan; Zhang, Xiangwu

2012-03-01

240

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

Energy Technology Data Exchange (ETDEWEB)

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.

Kodumagulla, A [North Carolina State University; Varanasi, V [North Carolina State University; Pearce, Ryan [North Carolina State University; Wu, W-C [North Carolina State University; Hensley, Dale K [ORNL; Tracy, Joseph B [North Carolina State University; McKnight, Timothy E [ORNL; Melechko, Anatoli [North Carolina State University

2014-01-01

241

Characterization of poly(methyl methacrylate) and thermoplastic polyurethane-carbon nanofiber composites produced by chaotic mixing  

Science.gov (United States)

Chaotic mixing is a novel mixing technique offering high mixing efficiency even under mild shearing conditions. In this work, chaotic mixing was used to prepare composites of carbon nanofibers and two thermoplastic polymers---poly (methyl methacrylate) (PMMA) and thermoplastic polyurethanes (TPU)---and their electrical, mechanical, and thermal properties were evaluated. The TPU systems were based on the reaction products of 4,4'-diphenylmethane diisocyanate, (MDI), soft segment polyol, and 1,4-butanediol as chain extender. Soft segment polyols in the form of poly(propylene glycol) (PPG), and poly(epsilon-caprolactone)diol (PCL) were used to obtain respectively amorphous and crystalline soft segments. Of these, the TPU system based on crystalline soft segment exhibited shape memory effects. Both, as-received untreated carbon nanofibers (CNF) with a very low amount of atomic oxygen on the surface, and oxidized carbon nanofibers (CNFOX) were used. CNFOX was also modified by esterifying with PPG to produce a third type of carbon nanofiber named CNFOL. These carbon nanofibers were examined by X-ray photoelectron spectroscopy to determine the elemental composition of the surface, and by scanning electron microscopy and transmission electron microscopy to determine the surface morphology.

Jiminez, Guillermo A.

242

Metal nanoparticle-directed NiCo2O4 nanostructure growth on carbon nanofibers with high capacitance.  

Science.gov (United States)

Metal nanoparticles (Ni, Co) decorated on an electrospun carbon nanofiber surface directed the growth of NiCo2O4 into nanorod and nanosheet morphologies. These metal nanoparticles served as a transition layer to strengthen the interface and promote charge transfer between carbon and NiCo2O4 to achieve a high capacitance of 781 F g(-1). PMID:24935238

Chen, Long; Zhu, Jiahua

2014-08-01

243

A high performance silicon/carbon composite anode with carbon nanofiber for lithium-ion batteries  

Energy Technology Data Exchange (ETDEWEB)

The electrochemical performance of a composite of nano-Si powder and a pyrolytic carbon of polyvinyl chloride (PVC) with carbon nanofiber (CNF) was examined as an anode for lithium-ion batteries. CNF was incorporated into the composite by two methods; direct mixing of CNF with the nano-Si powder coated with carbon produced by pyrolysis of PVC (referred to as Si/C/CNF-1) and mixing of CNF, nano-Si powder, and PVC with subsequent firing (referred to as Si/C/CNF-2). The external Brunauer-Emmett-Teller (BET) surface area of Si/C/CNF-1 was comparable to that of Si/C/CNF-2. The micropore BET surface area of Si/C/CNF-2 (73.86 m{sup 2} g{sup -1}) was extremely higher than that of Si/C/CNF-1 (0.74 m{sup 2} g{sup -1}). The composites prepared by both methods exhibited high capacity and excellent cycling stability for lithium insertion and extraction. A capacity of more than 900 mA h g{sup -1} was maintained after 30 cycles. The coulombic efficiency of the first cycle for Si/C/CNF-1 was as low as 53%, compared with 73% for Si/C/CNF-2. Impedance analysis of cells containing these anode materials suggested that the charge transfer resistance for Si/C/CNF-1 was not changed by cycling, but that Si/C/CNF-2 had high charge transfer resistance after cycling. A composite electrode prepared by mixing Si/C/CNF-2 and CNF exhibited a high reversible capacity at high rate, excellent cycling performance, and a high coulombic efficiency during the first lithium insertion and extraction cycles. (author)

Si, Q.; Hanai, K.; Ichikawa, T.; Hirano, A.; Imanishi, N.; Takeda, Y.; Yamamoto, O. [Department of Chemistry, Faculty of Engineering, Mie University, 1577 Kurimamachiya-cho, Tsu, Mie 514-8507 (Japan)

2010-03-15

244

Effect of Carbon Nanofiber-Matrix Adhesion on Polymeric Nanocomposite Properties—Part II  

Directory of Open Access Journals (Sweden)

Full Text Available A successful integration of two independent phases with good adhesion is imperative for effective translation of superior carbon nanofiber filler properties into a physically superior carbon nanocomposite. Carbon nanofibers were subjected to electrochemical oxidation in 0.1 M nitric acid for varying times. The strength of adhesion between the nanofiber and an epoxy matrix was characterized by flexural strength and modulus. The surface functional groups formed and their concentration of nanofibers showed a dependence on the degree of oxidation. The addition of chemical functional groups on the nanofiber surface allows them to physically and chemically adhere to the continuous resin matrix. The chemical interaction with the continuous epoxy matrix results in the creation of an interphase region. The ability to chemically and physically interact with the epoxy region is beneficial to the mechanical properties of a carbon nanocomposite. A tailored degree of surface functionalization was found to increase adhesion to the matrix and increase flexural modulus.

Khalid Lafdi

2008-01-01

245

Destructive adsorption of Diazinon pesticide by activated carbon nanofibers containing Al2O3 and MgO nanoparticles.  

Science.gov (United States)

We report the destructive adsorption of Diazinon pesticide by porous webs of activated carbon nanofibers containing Al2O3 and MgO nanoparticles. The results show that, the presence of Al2O3 and MgO nanoparticles in the activated carbon nanofibers increases the amount of destructively adsorbed Diazinon pesticide by activated carbon nanofibers. Moreover, type, amount, and specific surface area of metal oxide nanoparticles affect the adsorption rate as well as the total destructively adsorbed Diazinon. Liquid chromatography proved the degradation of Diazinon by chemical reaction with Al2O3 and MgO nanoparticles. Liquid chromatography-mass spectrometry showed that the main product of reaction between Diazinon and the metal oxides is 2-isopropyl-6-methyl-4-pyrimidinol with less toxicity than Diazinon. PMID:23912227

Behnam, Roghaye; Morshed, Mohammad; Tavanai, Hossein; Ghiaci, Mehran

2013-10-01

246

Shape controlled synthesis of Cu2O and its catalytic application to synthesize amorphous carbon nanofibers  

International Nuclear Information System (INIS)

Octahedral Cu2O particles and Cu2O nanowires were synthesized by a simple solution-phase route using N2H4.H2O as reducing agent at room temperature. Amorphous carbon nanofibers were synthesized using octahedral Cu2O particles and an acetylene gas source at atmospheric pressure. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy and thermogravimetric (TG) analysis. SEM and TEM images indicated that most of the obtained octahedral Cu2O particles had an edge length of 400-700 nm. The obtained nanowires had uniform diameters of about 15 nm, and the length of the nanowires ranged from 5 to 10 ?m. The XRD result revealed the amorphous feature of the nanofibers. IR spectrum revealed that the nanofibers consist of -CH, -CH2, -C=C- and -CH3 groups. The concentrations of N2H4.H2O and NaOH played important roles in controlling the geometric shape of the Cu2O

247

Silicon solar cells: graphenized carbon nanofiber: a novel light-trapping and conductive material to achieve an efficiency breakthrough in silicon solar cells (adv. Mater. 5/2015).  

Science.gov (United States)

The large-scale deployment of solar energy has been severely hindered by the slow pace of the conversion efficiency advances. To solve this challenge, M. Gu and co-workers successfully synthesize a one-dimensional graphenized carbon nanofiber, as described on page 849. The nanofiber exhibits superior optical and electrical properties. Integrating the nanofibers with solar cells leads to a world-record highest efficiency boost. PMID:25645074

Chen, Xi; Jia, Baohua; Cai, Boyuan; Fang, Jia; Chen, Ze; Zhang, Xiaodan; Zhao, Ying; Gu, Min

2015-02-01

248

Preparation of Surface Adsorbed and Impregnated Multi-walled Carbon Nanotube/Nylon-6 Nanofiber Composites and Investigation of their Gas Sensing Ability  

OpenAIRE

We have prepared electrospun Nylon-6 nanofibers via electrospinning, and adsorbed multi-walled carbon nanotubes (MWCNTs) onto the surface of Nylon-6 fibers using Triton® X-100 to form a MWCNTs/Nylon-6 nanofiber composite. The dispersed MWCNTs have been found to be stable in hexafluoroisopropanol for several months without precipitation. A MWCNTs/Nylon-6 nanofiber composite based chemical sensor has demonstrated its responsiveness towards a wide range of solvent vapours at room tempera...

Velmurugan Thavasi; Lala, Neeta L.; Seeram Ramakrishna

2009-01-01

249

Preparation of macroporous carbon nanofibers with macroscopic openings in the surfaces and their applications  

International Nuclear Information System (INIS)

Macroporous carbon nanofibers with mesoscale surface openings were produced by electrospinning. During the electrospinning of polyacrylonitrile (PAN) solution including crosslinked polymer colloids, the polymer colloids were concentrated in the center of PAN fibers. Carbonization left interconnected spherical pores inside the carbon fibers and mesoscale openings in the fiber surfaces. The existence of surface openings facilitated inward diffusion of various solvent molecules, nanoparticles, and large molecules such as proteins. The porous fibers could be dispersed in both hydrophilic and hydrophobic solvents and materials, which enabled production of polymer composites in which the fibers and polymers were interpenetrating through the pores. Silica coating on the macroporous carbon fibers enriched the surface chemistry to effectively immobilize proteins helped by easy diffusion through surface openings.

250

Hydrogen desorption from NaAlH4 catalyzed by ball-milling with carbon nanofibers  

International Nuclear Information System (INIS)

The effect of ball-milling NaAlH4 with carbon nanofibers on the hydrogen desorption rates is reported. The rates are strongly dependent on the ball to powder ratio and milling time. The use of an Arrhenius equation corrected for the dependence of hydrogen pressure allows a comparison with other literature data, performed in different conditions. It shows that ball-milling at high energy is the most favorable route to increase the desorption rate and lower the activation energy for hydrogen desorption.

251

Preparation of graphitic carbon nanofibers with the use of water-soluble supports.  

Science.gov (United States)

Graphitic carbon nanofibers (GCNFs) are prepared from CO/H2 with a nickel-rich Fe-Ni (2:8) growth catalyst supported on three different water-soluble supports (Na4SiO4, Na2SiO3, and Na2CO3). GCNF products are formed with yield and crystallinity comparable to those of GCNF product produced with the same growth catalyst supported on fumed silica. Separation of GCNF product from the solid support is accomplished by aqueous dissolution of the support. This synthetic method extends the convenient isolation of GCNFs formed with supported growth catalysts to a wide variety of potential solid supports. PMID:12908314

Steigerwalt, Eve S; Lukehart, C M

2002-02-01

252

Carbon nanofiber aerogels for emergent cleanup of oil spillage and chemical leakage under harsh conditions  

Science.gov (United States)

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.

Wu, Zhen-Yu; Li, Chao; Liang, Hai-Wei; Zhang, Yu-Ning; Wang, Xin; Chen, Jia-Fu; Yu, Shu-Hong

2014-02-01

253

Hollow activated carbon nanofibers prepared by electrospinning as counter electrodes for dye-sensitized solar cells  

International Nuclear Information System (INIS)

Hollow activated carbon nanofibers (H-ACNF) were prepared by concentric electrospinning of poly(methyl methacrylate) (PMMA) as a pyrolytic core precursor and polyacrylonitrile (PAN) as a carbon shell precursor, followed by stabilization, carbonization, and activation. The H-ACNF with 190 and 270 nm for core and shell diameter showed excellent mesoporous structure, and 1-D conducting pathway in employing as catalysts of counter electrodes (CEs) for dye-sensitized solar cells (DSCs). The mesoporous structure of H-ACNF represented surface area of 1037.5 m2 g?1 with average mesopore diameter of 17.4 nm. The overall conversion efficiency of H-ACNF is comparable to that of Pt CE because its characteristics promotes the electron and ion transfer, decreases the resistance of charge transfer, and increases the contact area between liquid electrolyte and H-ACNF

254

Enhanced Pt performance with H2O plasma modified carbon nanofiber support  

Science.gov (United States)

The insufficient durability and catalytic activity in low loading of platinum (Pt) are main obstacles to the development of low-temperature fuel cells. Our study demonstrated an efficient way to simultaneously improve the durability and electro-catalytic activity of Pt catalysts on carbon supports by water vapor (H2O) plasma functionalization. We report the finding that H2O plasma modification can introduce hydroxyl groups on carbon nanofiber (CNF) surface, and at the same time, highly preserve the microstructure of carbon support. Pt/CNF-H2O electrode possesses ultra-low Pt loading and superior electro-catalytic activity, poisoning-resistance ability and stability, suggesting a good candidate for fuel cell applications.

Hu, Jue; Jiang, Lin; Zhang, Chengxu; Zhang, Xiaodong; Meng, Yuedong; Wang, Xiangke

2014-04-01

255

Controllable synthesis of Zn2TiO4-carbon core/shell nanofibers with high photocatalytic performance  

International Nuclear Information System (INIS)

Graphical abstract: We describe a controllable route to synthesize Zn2TiO4-carbon core/shell nanofibers with different thickness of carbon layers (from 2 to 8 nm) as high efficiency photocatalysts. Highlights: ? Synthesis of Zn2TiO4-carbon nanofibers with different thickness of carbon layers. ? Zn2TiO4-carbon NFs showed photocatalytic activity for the degradation of Rhodamine B. ? Easy photocatalyst separation and reuse. ? A general way to fabricate other carbon-coated core/shell photocatalysts. - Abstract: Zn2TiO4-carbon core/shell nanofibers (Zn2TiO4-C NFs) with different thickness of carbon layers (from 2 to 8 nm) were fabricated by combining the electrospinning technique and hydrothermal method. The results showed that a uniform carbon layer was formed around the electrospun Zn2TiO4 nanofiber (Zn2TiO4 NFs). By adjusting the hydrothermal fabrication parameters, the thickness of carbon layer varied linearly with the concentration of glucose. Furthermore, the core/shell structure formed between Zn2TiO4 and carbon enhanced the charge separation of pure Zn2TiO4 under ultraviolet excitation, as evidenced by photoluminescence spectra. The photocatalytic studies revealed that the Zn2TiO4-C NFs exhibited enhanced photocatalytic efficiency of photodeotocatalytic efficiency of photodegradation of Rhodamine B (RB) compared with the pure Zn2TiO4 NFs under ultraviolet excitation, which might be attributed to the high separation efficiency of photogenerated electrons and holes based on the synergistic effect between carbon and Zn2TiO4. Notably, the Zn2TiO4-C NFs could be recycled easily by sedimentation without a decrease of the photocatalytic activity.

256

Formation of carbon nanostructures containing single-crystalline cobalt carbides by ion irradiation method  

International Nuclear Information System (INIS)

Carbon nanofibers (CNFs) with a diameter of 17 nm, and carbon nanoneedles (CNNs) with sharp tips have been synthesized on graphite substrates by ion irradiation of argon ions with the Co supplies rate of 1 and 3.4 nm/min, respectively. Energy dispersive X-ray spectrometry, combined with selected area electron diffraction patterns has been used to identify the chemical composition and crystallinity of these carbon nanostructures. The CNFs were found to be amorphous in nature, while the structures of the CNNs consisted of cubic CoCx, orthorhombic Co2C and Co3C depending on the cobalt content in the CNNs. The diameter of the carbide crystals was almost as large as the diameter of the CNN. Compared to the ion-induced nickel carbides and iron carbides, the formation of single-crystalline cobalt carbides might be due to the high temperature produced by the irradiation.

257

Free-standing nitrogen-doped carbon nanofiber films as highly efficient electrocatalysts for oxygen reduction.  

Science.gov (United States)

Free-standing nitrogen-doped carbon nanofiber (NCNF) films based on polyacrylonitrile (PAN) were prepared simply by the combination of electrospinning and thermal treatment. We reused the nitrogen-rich gas generated as the byproduct of PAN at elevated temperature, mainly NH3, for surface etching and nitrogen doping. The as-obtained NCNFs exhibited a rougher surface and smaller diameter than pristine carbon nanofibers. Despite the decreased total N content, a significant increase in the content of pyrrolic-N was observed for the NCNFs. In application to electrochemistry, the free-standing NCNF films showed comparable catalytic activity with a close four-electron pathway to a commercial Pt/C catalyst in alkaline medium toward oxygen reduction reaction (ORR), which can be attributed to the nitrogen doping and high hydrophilicity. More importantly, the ORR current density on the NCNFs only dropped 6.6% after 10,000 s of continuous operation, suggesting an enhanced long-time durability. In addition, the NCNFs also showed better electrocatalytic selectivity than Pt/C. Our work reveals a facile but efficient approach for the synthesis of free-standing NCNF films as a promising alternative to Pt-based electrocatalysts in fuel cells. PMID:23986349

Liu, Dong; Zhang, Xueping; Sun, Zaicheng; You, Tianyan

2013-10-21

258

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

Science.gov (United States)

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 3×3 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

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

2014-09-15

259

Electrically conductive carbon nanofiber/paraffin wax composites for electric thermal storage  

International Nuclear Information System (INIS)

Highlights: ? Carbon nanofiber (CNF)/paraffin wax composite is found to be a promising electric thermal storage material. ? The thermal storage capacity of CNF/paraffin wax composite is five times of traditional electric thermal storage material. ? CNF is shown to be an effective conductive filler for the composite. - Abstract: The research of electric thermal storage (ETS) has attracted a lot of attention recently, which converts off-peak electrical energy into thermal energy and release it later at peak hours. In this study, new electric thermal storage composites are developed by employing paraffin wax as thermal storage media and carbon nanofiber (CNF) as conductive fillers. Electric heating and thermal energy release performances of the CNF/paraffin wax composites are experimentally investigated. Experimental results show that, when the composites are heated to about 70 °C, the developed electrically conductive CNF/paraffin wax composites present a thermal storage capacity of about 280 kJ/kg, which is five times of that of traditional thermal storage medium such as ceramic bricks (54 kJ/kg). The CNF/paraffin wax composites can also effectively store the thermal energy and release the thermal energy in later hours.

260

Fabrication of carbon nanofiber-driven electrodes from electrospun polyacrylonitrile/polypyrrole bicomponents for high-performance rechargeable lithium-ion batteries  

Energy Technology Data Exchange (ETDEWEB)

Carbon nanofibers were prepared through electrospinning a blend solution of polyacrylonitrile and polypyrrole, followed by carbonization at 700 C. Structural features of electrospun polyacrylonitrile/polypyrrole bicomponent nanofibers and their corresponding carbon nanofibers were characterized using scanning electron microscopy, differential scanning calorimeter, thermo-gravimetric analysis, wide-angle X-ray diffraction, and Raman spectroscopy. It was found that intermolecular interactions are formed between two different polymers, which influence the thermal properties of electrospun bicomponent nanofibers. In addition, with the increase of polypyrrole concentration, the resultant carbon nanofibers exhibit increasing disordered structure. These carbon nanofibers were used as anodes for rechargeable lithium-ion batteries without adding any polymer binder or conductive material and they display high reversible capacity, improved cycle performance, relatively good rate capability, and clear fibrous morphology even after 50 charge/discharge cycles. The improved electrochemical performance of these carbon nanofibers can be attributed to their unusual surface properties and unique structural features, which amplify both surface area and extensive intermingling between electrode and electrolyte phases over small length scales, thereby leading to fast kinetics and short pathways for both Li ions and electrons. (author)

Ji, Liwen; Yao, Yingfang; Toprakci, Ozan; Lin, Zhan; Liang, Yinzheng; Shi, Quan; Medford, Andrew J.; Millns, Christopher R.; Zhang, Xiangwu [Fiber and Polymer Science Program, Department of Textile Engineering, Chemistry and Science, North Carolina State University, 2401 Research Drive, Raleigh, NC 27695-8301 (United States)

2010-04-02

261

LiFePO4 - 3D carbon nanofiber composites as cathode materials for Li-ions batteries  

Science.gov (United States)

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.

Dimesso, L.; Spanheimer, C.; Jaegermann, W.; Zhang, Y.; Yarin, A. L.

2012-03-01

262

Radiation grafting of methacrylate onto carbon nanofiber surface  

International Nuclear Information System (INIS)

Radiation can be used to modify and improve the properties of materials. Electron beam irradiation has potential application in modifying the structure of carbon fibers in order to produce useful defects in the graphite structure and create reactive sites. In this study, vapor grown carbon nano fibers (VGCF) were irradiated with a high energy (3 MeV) electron beam in air to dose of 1000 kGy to create active sites and added to methyl methacrylate (MMA) dissolved in water/methanol (50% V). The irradiated samples were analyzed by X-Ray Photoelectron Spectroscopy (XPS) and Raman spectroscopy to assess the impact on surface and bulk properties. Oxygen was readily incorporated enhancing the dispersion of VGCF. Raman spectroscopy analyses indicated that the sample irradiated and preirradiated grafted sample with MMA had the intensity ratio increased. (author)

263

Effect of the nature the carbon precursor on the physico-chemical characteristics of the resulting activated carbon materials  

Energy Technology Data Exchange (ETDEWEB)

Carbon materials, including amorphous carbon, graphite, carbon nanospheres (CNSs) and different types of carbon nanofibers (CNFs) [platelet, herringbone and ribbon], were chemically activated using KOH. The pore structure of carbon materials was analyzed using N{sub 2}/77 K adsorption isotherms. The presence of oxygen groups was analyzed by temperature programmed desorption in He and acid-base titration. The structural order of the materials was studied by X-ray diffraction and temperature programmed oxidation. The morphology and diameter distribution of CNFs and CNSs were characterized by transmission electron microscopy. The materials were also characterized by temperature-desorption programmed of H{sub 2} and elemental composition. The ways in which the different structures were activated are described, showing the type of pores generated. Relationships between carbon yield, removed carbon, activation degree and graphitic character were also examined. The oxygen content in the form of oxygen-containing surface groups increased after the activation giving qualitative information about them. The average diameter of both CNFs and CNSs was decreased after the activation process as consequence of the changes produced on the material surface.

Jimenez, Vicente, E-mail: vicente.jimenez@uclm.es [Facultad de Ciencias Quimicas, Departamento de Ingenieria Quimica, Universidad de Castilla-La Mancha, 13071 Ciudad Real (Spain); Sanchez, Paula; Valverde, Jose Luis [Facultad de Ciencias Quimicas, Departamento de Ingenieria Quimica, Universidad de Castilla-La Mancha, 13071 Ciudad Real (Spain); Romero, Amaya [Escuela Tecnica Agricola, Departamento de Ingenieria Quimica, Universidad de Castilla-La Mancha, 13071 Ciudad Real (Spain)

2010-11-01

264

Effect of the nature the carbon precursor on the physico-chemical characteristics of the resulting activated carbon materials  

International Nuclear Information System (INIS)

Carbon materials, including amorphous carbon, graphite, carbon nanospheres (CNSs) and different types of carbon nanofibers (CNFs) [platelet, herringbone and ribbon], were chemically activated using KOH. The pore structure of carbon materials was analyzed using N2/77 K adsorption isotherms. The presence of oxygen groups was analyzed by temperature programmed desorption in He and acid-base titration. The structural order of the materials was studied by X-ray diffraction and temperature programmed oxidation. The morphology and diameter distribution of CNFs and CNSs were characterized by transmission electron microscopy. The materials were also characterized by temperature-desorption programmed of H2 and elemental composition. The ways in which the different structures were activated are described, showing the type of pores generated. Relationships between carbon yield, removed carbon, activation degree and graphitic character were also examined. The oxygen content in the form of oxygen-containing surface groups increased after the activation giving qualitative information about them. The average diameter of both CNFs and CNSs was decreased after the activation process as consequence of the changes produced on the material surface.

265

The influence of the dispersion method on the electrical properties of vapor-grown carbon nanofiber/epoxy composites  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract The influence of the dispersion of vapor-grown carbon nanofibers (VGCNF on the electrical properties of VGCNF/Epoxy composites has been studied. A homogenous dispersion of the VGCNF does not imply better electrical properties. In fact, it is demonstrated that the most simple of the tested dispersion methods results in higher conductivity, since the presence of well-distributed nanofiber clusters appears to be a key factor for increasing composite conductivity. PACS: 72.80.Tm; 73.63.Fg; 81.05.Qk

Covas José

2011-01-01

266

Nanographene derived from carbon nanofiber and its application to electric double-layer capacitors  

International Nuclear Information System (INIS)

The fascinating properties of graphene are attracting considerable attention in engineering fields such as electronics, optics, and energy engineering. These properties can be controlled by controlling graphene's structure, e.g., the number of layers and the sheet size. In this study, we synthesized nanosized graphene from a platelet-type carbon nanofiber. The thickness and size of nanographene oxide are around 1 nm and 60 nm and we obtained nanographene by hydrazine reduction of nanographene oxide. We applied the nanographene to an ionic-liquid electric double-layer capacitor (EDLC), which exhibited a much larger capacitance per specific surface area than an EDLC using conventional activated carbon. Furthermore, the capacitance increased significantly with increasing cycle time. After 30th cycle, the capacitance was achieved 130 F g?1, though the surface area was only 240 m2 g?1. These results suggest that nanographene structure induce the capacitance enhancement.

267

Imaging, spectroscopic, mechanical and biocompatibility studies of electrospun Tecoflex® EG 80A nanofibers and composites thereof containing multiwalled carbon nanotubes  

Science.gov (United States)

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.

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

268

EFFECT OF CELLULOSE NANOFIBERS ISOLATED FROM BAMBOO PULP RESIDUE ON VULCANIZED NATURAL RUBBER  

Directory of Open Access Journals (Sweden)

Full Text Available Nanocomposites were prepared using two bioresources, viz., cellulose nanofibers (CNFs extracted from bamboo paper-pulp waste as the reinforcing phase and natural rubber (NR as the matrix phase. CNFs with diameters up to 50 nm were isolated from bamboo pulp waste, and nanocomposites with 5 and 10% CNFs were obtained via two-roll mill mixing of solid natural rubber with a master batch containing 20 wt% CNFs. The NR phase was cross-linked using sulphur vulcanization. The morphology studies showed that the dispersion of CNF in NR matrix was not optimal, and some aggregates were visible on the fracture surface. The tensile strength and modulus at 50% elongation increased for the nanocomposites with the addition of CNFs, accompanied by a moderate decrease in elongation at break. The storage modulus of the natural rubber significantly increased above its glass-rubber transition temperature upon nanofiber addition. The addition of CNFs also had a synergistic impact on the thermal stability of natural rubber. The susceptibility to organic solvents decreased significantly for the nanocomposites compared to crosslinked NR, which indicated restriction of polymer chain mobility in the vicinity of the nanosized CNFs in the NR matrix.

P. M. Visakh,

2012-02-01

269

Morphological characterization of carbon nanofiber aerosol using tandem mobility and aerodynamic size measurements  

International Nuclear Information System (INIS)

Characterizing microstructural and transport properties of non-spherical particles, such as carbon nanofibers (CNF), is important for understanding their transport and deposition in human respiratory system and engineered devices such as particle filters. We describe an approach to obtain morphological information of non-spherical particles using a tandem system of differential mobility analyzer (DMA) and an electrical low-pressure impactor (ELPI). Effective density, dynamic shape factors (DSF), particle mass, and fractal dimension-like mass-scaling exponent of nanofibers were derived using the measured mobility and aerodynamic diameters, along with the known material density of CNF. Multiple charging of particles during DMA classification, which tends to bias the measured shape factors and particle mass toward higher values, was accounted for using a correction procedure. Particle mass derived from DMA–ELPI measurements agreed well with the direct mass measurements using an aerosol particle mass analyzer. Effective densities, based on mobility diameters, ranged from 0.32 to 0.67 g cm?3. The DSF of the CNF ranged from 1.8 to 2.3, indicating highly non-spherical particle morphologies.

270

Morphological characterization of carbon nanofiber aerosol using tandem mobility and aerodynamic size measurements  

Energy Technology Data Exchange (ETDEWEB)

Characterizing microstructural and transport properties of non-spherical particles, such as carbon nanofibers (CNF), is important for understanding their transport and deposition in human respiratory system and engineered devices such as particle filters. We describe an approach to obtain morphological information of non-spherical particles using a tandem system of differential mobility analyzer (DMA) and an electrical low-pressure impactor (ELPI). Effective density, dynamic shape factors (DSF), particle mass, and fractal dimension-like mass-scaling exponent of nanofibers were derived using the measured mobility and aerodynamic diameters, along with the known material density of CNF. Multiple charging of particles during DMA classification, which tends to bias the measured shape factors and particle mass toward higher values, was accounted for using a correction procedure. Particle mass derived from DMA-ELPI measurements agreed well with the direct mass measurements using an aerosol particle mass analyzer. Effective densities, based on mobility diameters, ranged from 0.32 to 0.67 g cm{sup -3}. The DSF of the CNF ranged from 1.8 to 2.3, indicating highly non-spherical particle morphologies.

Deye, Gregory J.; Kulkarni, Pramod, E-mail: pskulkarni@cdc.gov; Ku, Bon Ki [National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention (United States)

2012-09-15

271

How does surface modification aid in the dispersion of carbon nanofibers?  

Science.gov (United States)

Small-angle light scattering is used to assess the dispersion behavior of vapor-grown carbon nanofibers suspended in water. These data provide the first insights into the mechanism by which surface treatment promotes dispersion. Both acid-treated and untreated nanofibers exhibit hierarchical morphology consisting of small-scale aggregates (small bundles) that agglomerate to form fractal clusters that eventually precipitate. Although the morphology of the aggregates and agglomerates is nearly independent of surface treatment, their time evolution is quite different. The time evolution of the small-scale bundles is studied by extracting the size distribution from the angle-dependence of the scattered intensity, using the maximum entropy method in conjunction with a simplified tube form factor. The bundles consist of multiple tubes possibly aggregated side-by-side. Acid oxidation has little effect on this bundle morphology. Rather acid treatment inhibits agglomeration of the bundles. The time evolution of agglomeration is followed by fitting the scattering data to a generalized fractal model. Agglomerates appear immediately after cessation of sonication for untreated fibers but only after hours for treated fibers. Eventually, however, both systems precipitate. PMID:16375306

Zhao, Jian; Schaefer, Dale W; Shi, Donglu; Lian, Jie; Brown, Janis; Beaucage, Gregory; Wang, Lumin; Ewing, Rodney C

2005-12-15

272

Enhanced performances in primary lithium batteries of fluorinated carbon nanofibers through static fluorination  

International Nuclear Information System (INIS)

Using galvanostatic discharges, the electrochemical properties of fluorinated carbon nanofibers (CNF) have been investigated. Several methods of fluorination are compared, (i) direct process using a flux of pure molecular fluorine F2 (dynamic process), (ii) controlled fluorination using atomic fluorine released continuously by the thermal decomposition of a solid fluorinating agent (TbF4), and (iii) static fluorination by the filling of a closed reactor with undiluted molecular fluorine as reactive gas. Electrochemical performances of the resulting materials are compared highlighting significant improvement using the static method. The discharge potential increases from 2.27 V (vs. Li+/Li°) for materials obtained by the direct route to a medium 2.40 V by the static route resulting from a two steps discharge mechanism. Owing to a complete characterization of each fluorinated materials by X-ray diffraction (XRD), solid state nuclear magnetic resonance (NMR) and transmission electron microscopy (TEM), the increased average potential of fluorinated sample through the static way has been explained by the peculiar distribution of fluorine and carbon sites in the nanomaterial. Then, in order to understand the two steps discharge mechanism of the latter material, its discharge mechanism through galvanostatic measurements at different depths of discharge has been investigated in different electrolytes. The discharged materials have been studied owing to 19F MAS NMR, XRD and scanning electron microscopy characterizations. The texture and cristallinity of lithium fluoride particles are key parameters acting on the ionic diffusion of Li+ and F? ions and as a consequence on the electrochemical performances. Its high solubility in EC/PC/3DMC solvent mixture prevents from overvoltage phenomenon occurring during the discharge of fluorinated carbon nanofibers in primary lithium battery

273

Functional properties of electrospun NiO/RuO2 composite carbon nanofibers  

International Nuclear Information System (INIS)

Highlights: ? Fabrication of carbon nanofibers with nickel–ruthenium composites by electrospinning. ? An interesting observation of increase in capacitance with increase in the number of cycles for supercapacitor applications. ? Li ion battery testing showed a stable capacity ranging from 350 mAh g?1 to 400 mAh g?1. ? Lower impedance with the incorporation of 15 wt% Ru precursor than those without Ru. - Abstract: One-dimensional (1D) nickel oxide/ruthenium oxide (NiO/RuO2)–carbon composite nanofibers (NiRu–C–NFs) were fabricated via electrospinning of a homogenous mixture of polyacrylonitrile (PAN) and Ni/Ru salt precursors at different ratios followed by heat treatments. The 1D nanostructures of the composite material were characterized by field-emission scanning electron microscopy (FE-SEM), powder X-ray diffraction (XRD), Rietveld refinement and Brunauer–Emmett–Teller (BET) surface area measurements. Li-cycling properties were evaluated using cyclic voltammetry and galvanostatic properties. The asymmetric hybrid supercapacitor studies were carried out with activated carbon as a cathode and NiRu–C–NFs composites as anodes in the cycling range, 0.005–3.0 V using 1 M LiPF6 (EC;DMC) electrolyte. NiRu–C–NFs fabricated from 5 wt% nickel (II) and 15 wt% ruthenium (III) precursors showed a capacitance up to ?60 F g?1 after 30 cycles. Anodic Li-cycling studies of NiRu–C–NF-0 and NiRu–C–NF-2 composite samples showed a reversible capacity of 230 and 350 m Ahg?1 at current rate of 72 mA g?1 at the end of 40th cycle in the voltage range of 0.005–3.0 V. Electrochemical impedance studies (EIS) on NiRu–C–NFs showed lower impedance value for 15 wt% Ru than the bare sample.

274

Influence of oxygen-containing surface groups on the activity and selectivity of carbon nanofiber-supported ruthenium catalysts in the hydrogenation of cinnamaldehyde  

OpenAIRE

Carbon-nanofiber-supported ruthenium catalysts were employed to study the influence of oxygen-containing surface groups on catalytic performance in the liquid-phase hydrogenation of cinnamaldehyde. The carbon nanofibers were oxidized to introduce oxygen-containing groups and the metal precursor was applied using homogeneous deposition precipitation. After reduction the catalysts were heat-treated in nitrogen at different temperatures to tune the number of surface oxygen functional groups. TEM...

Toebes, M. L.; Prinsloo, F. F.; Bitter, J. H.; Dillen, A. J.; Jong, K. P.

2003-01-01

275

High power direct methanol fuel cell with a porous carbon nanofiber anode layer  

International Nuclear Information System (INIS)

Highlights: • This study demonstrates a novel porous carbon nanofiber anode (PNCF) layer. • PNFC anode layer DMFC presents power density of 23.0 mW cm?2. • This unit operates at room temperature and consumes low concentration of methanol. - Abstract: Three anode electrodes containing Pt–Ru Black as a catalyst were fabricated with a porous layer made with different carbon materials: carbon black (CB), carbon nanofiber (CNF) and a combination of both carbon materials (CB + CNF). The carbon-based porous layer was coated onto a carbon cloth with PTFE pre-treatment for delivering hydrophobic properties and applied in direct methanol fuel cells (DMFCs). Characterisation of electrochemical properties for three different anode electrodes was performed with cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) at room temperature in a half-cell configuration. The evolution of the surface morphology of diffusion layer and electrodes was characterised by using variable-pressure scanning electron microscopy (VP-SEM). The electrochemical results indicate that electrode with CNF layer showed the highest current densities compared to CB and CB + CNF with the same catalyst loading. VP-SEM measurements show the network formation within the structure, which could facilitate the methanol mass transfer and improve the catalyst efficiency. The electrodes were applied to a single-cell DMFC, and the cell performance was experimentally investigated under passive operating mode and room temperature. A maximum power density of 23.0 mW cm?2 at a current density of 88.0 mA cm?2 with a 3 M dilute methanol solution was achieved. The results show that the electrodes with a CNF layer could improve the performance of DMFC as compared with commercially used CB and prove it’s potentially application in DMFC technology especially for portable power source applications due to several advantages as followings: operating at low concentration of methanol, operating at room temperature, low catalyst loading in anode and cathode, cheaper, less hazardous and no parasitic load

276

A co-confined carbonization approach to aligned nitrogen-doped mesoporous carbon nanofibers and its application as an adsorbent.  

Science.gov (United States)

Nitrogen-doped carbon nanofibers (MCNFs) with an aligned mesoporous structure were synthesized by a co-confined carbonization method using anodic aluminum oxide (AAO) membrane and tetraethylorthosilicate (TEOS) as co-confined templates and ionic liquids as the precursor. The as-synthesized MCNFs with the diameter of 80-120nm possessed a bulk nitrogen content of 5.3wt% and bimodal mesoporous structure. The nitrogen atoms were mostly bound to the graphitic network in two forms, i.e. pyridinic and pyrrolic nitrogen, providing adsorption sites for acidic gases like SO2 and CO2. Cyclic experiments revealed a considerable stability of MCNFs over 20 runs of SO2 adsorption and 15 runs for CO2 adsorption. The MCNFs also have a preferable adsorption performance for Cd(2+). PMID:24887121

Chen, Aibing; Liu, Chao; Yu, Yifeng; Hu, Yongqi; Lv, Haijun; Zhang, Yue; Shen, Shufeng; Zhang, Jian

2014-07-15

277

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

Science.gov (United States)

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.

Kim, Chang Hyo; Kim, Bo-Hye

2015-01-01

278

Self-sensing of carbon nanofiber concrete columns subjected to reversed cyclic loading  

International Nuclear Information System (INIS)

Civil infrastructures are generally a country's most expensive investment, and concrete is the most widely used material in the construction of civil infrastructures. During a structure's service life, concrete ages and deteriorates, leading to substantial loss of structural integrity and potentially resulting in catastrophic disasters such as highway bridge collapses. A solution for preventing such occurrences is the use of structural health monitoring (SHM) technology for concrete structures containing carbon nanofibers (CNF). CNF concrete has many structural benefits. CNF restricts the growth of nanocracks in addition to yielding higher strength and ductility. Additionally, test results indicate a relationship between electrical resistance and concrete strain, which can be well utilized for SHM. A series of reinforced concrete (RC) columns were built and tested under a reversed cyclic loading using CNF as a SHM device. The SHM device detected and assessed the level of damage in the RC columns, providing a real-time health monitoring system for the structure's overall integrity

279

Carbon Nanofiber Reinforced and PU-toughened POM Ternary Composites: Friction, Wear and Creep Properties  

Directory of Open Access Journals (Sweden)

Full Text Available Composites composed of polyoxymethylene (POM, polyurethane (PU and carbon nanofiber (CNF were produced by water-mediated melt compounding. PU latex and/or aqueous CNF dispersion were introduced into the molten POM in laboratory kneader to prepare toughened and/or nanoreinforced POM composites. The dispersion of the CNF was inspected using scanning electron microscopy (SEM. The mechanical properties (friction, wear and creep strain of the composites were determined by roller (steel-on-plate (ROP and creep tensile tests. It was found that CNF worked as a reinforcement and improved the coefficient of friction (COF and wear. It was also found that, the creep resistance decreases with increasing time, temperature and addition of CNF.

Suchart Siengchin

2011-12-01

280

Preparation of Chitin Nanofibers-Gold Metallic Nanocomposite by Phase Transfer Method  

Science.gov (United States)

Chitin nanofibers (CNFs)-Au(0) nanoparticles (Au NPs) blends in dispersion, flakes and thin film or sheet forms were first prepared by mixing pre-organized Au NPs prepared in triblock copolymer with diluted CNFs suspension. Water soluble polymer triblock copolymer poly (methyl vinyl ether, PMVE) in the amount 0.6 wt.% was used to prepare NPs and 0.12 wt.% net chitin content was used as CNFs suspension to prepare the blended composite. Au NPs of size 4.4 nm (? = 1.2) were obtained when Au salt (HAuCl4?3H2O (hydrogen tetrachloroaurate (III) trihydrate) was reduced by 5 equivalents of NaBH4. PMVE polymer acted as a stabilizing or capping agent for pre-organized NPs. Completion of reaction was fast, all salt reduced to metallic form in just 15 min after the addition of NaBH4. CNFs (1 wt.% chitin) which was used to prepare CNFs-Au NPs blend composite were prepared from crab shell in never dried acidic condition by established combination of chemical and mechanical processes that gave 25-40 nm width and high aspect ratio CNFs. When polymer capped Au NPs mixed with CNF suspension, all Au NPs and 56% polymer were mass transferred from water phase to entangle with more polar moieties of CNFs-water suspension as no trace of Au NPs were noticed in water-polymer mother liquor after blending with CNFs suspension. Particles size of CNFs-Au NPs composite was measured by employing TEM, SAXS and SEM techniques. CNFs-Au NPs composite were characterized in solution and compressed dried sheet form by recording digital images, UV-vis and XRD spectroscopies. CNFs-Au NPs suspension had antibacterial activity against gram positive bacteria S. aureus.

Shervani, Zameer; Taisuke, Yukawa; Ifuku, Shinsuke; Saimoto, Hiroyuki; Morimoto, Minoru

2012-10-01

281

Durability of Carbon Nanofiber (CNF) & Carbon Nanotube (CNT) as Catalyst Support for Proton Exchange Membrane Fuel Cells  

DEFF Research Database (Denmark)

Durability issues have recently been given much attention in Proton Exchange Membrane Fuel Cell (PEMFC) research. It gives fundamental definition for cell life time, capital cost, system stability and technique reliability. Loss of catalyst surface area due to corrosion of supporting material (normally carbon black) is one of the essential degradation mechanisms during cell operation. In this work, durability of Carbon Nanofibers (CNF) & Carbon Nanotubes (CNT) as alternative platinum catalyst supports for Proton Exchange Membrane Fuel Cells (PEMFCs) was assessed. Platinized CNF and CNT using a standard polyol method were prepared and fabricated as cathodes of Membrane Electrode Assemblies (MEA) for PEMFC. Both the catalysts as such and the MEAs made out of them were evaluated regarding to thermal and electrochemical stability using traditional carbon black (Vulcan XC72) as a reference. Thermal gravimetric analysis (TGA), cyclic voltammetry (CV), polarization curve and impedance spectroscopy were applied on the samples under accelerated stress conditions. The carbon nano-materials demonstrated better stability as support for nano-sized platinum catalyst under PEMFC related operating conditions. Due to different morphology of the nano carbons compared to Vulcan XC 72 the electrode structures may still need optimization to improve overall cell performance.

Andersen, Shuang Ma; Borghei, Maryam

2013-01-01

282

Ultra-wide-range electrochemical sensing using continuous electrospun carbon nanofibers with high densities of states.  

Science.gov (United States)

Carbon-based sensors for wide-range electrochemical detection of redox-active chemical and biological molecules were fabricated by the electrospinning of polyacrylonitrile fibers directly onto a polyacrylonitrile-coated substrate followed by carbonization at 1200 °C. The resulting electrospun carbon nanofibers (ECNFs) were firmly attached to the substrate with good mesh integrity and had high densities of electronic states (DOS), which was achieved without need for further modifications or the use of any additives. The mass of ECNFs deposited, and thus the electroactive surface area (ESA) of the sensor, was adjusted by varying the electrospinning deposition time, thereby enabling the systematic manipulation of the dynamic range of the sensor. A standard redox probe (Fe(CN)6(3-/4-)) was used to demonstrate that the ECNF sensor exhibits strong electrocatalytic activity without current saturation at high analyte concentrations. Dopamine was used as a model analyte to evaluate the sensor performance; we find that the ECNF device exhibits a dynamic range ?10(5) greater than that of many existing carbon-based sensors. The ECNF sensors exhibited excellent sensitivity, selectivity, stability, and reproducibility for dopamine detection. PMID:24547786

Mao, Xianwen; Yang, Xiaoqing; Rutledge, Gregory C; Alan Hatton, T

2014-03-12

283

A nucleation and growth model of vertically-oriented carbon nanofibers or nanotubes by plasma-enhanced catalytic chemical vapor deposition.  

Science.gov (United States)

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. PMID:16792361

Cojocaru, C S; Senger, A; Le Normand, F

2006-05-01

284

Nitrogen-doped porous carbon nanofiber webs/sulfur composites as cathode materials for lithium-sulfur batteries  

International Nuclear Information System (INIS)

Nitrogen-doped porous carbon nanofiber webs-sulfur composites (N-CNFWs/S) were synthesized for the first time with sulfur (S) encapsulated into nitrogen-doped porous carbon nanofiber webs (N-CNFWs) via a modified oxidative template route, carbonization-activation and thermal treatment. The composites were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET), X-ray powder diffraction (XRD), and thermogravimetry (TG) measurements. The results show that sulfur is well dispersed and immobilized homogeneously in the micropores of nitrogen-doped porous carbon nanofiber webs (N-CNFWs) with high electrical conductivity, surface area and large pore volume. The electrochemical tests show that the N-CNFWs/S composites with 60 wt. % of S have a high initial discharge capacity of 1564 mA h g?1, a good cycling stability at the current density of 175 mA g?1, and excellent rate capability (reversible discharging capacity of above 400 mA h g?1 at 1600 mA g?1)

285

Effects of carbon nanoparticles on properties of thermoset polymer systems  

Science.gov (United States)

Polymer nanocomposites are novel materials in which at least one of the dimensions of the reinforcing material is on the order of 100 nm or less. While thermoplastic nanocomposites have been studied very widely, there are fewer studies concerning the effect of nanoparticles on thermoset systems. Low temperature cure thermoset systems are very important for many important applications. In this study, the processing, mechanical and thermal properties and reaction kinetics of carbon nanofiber (CNF) and/or carbon nanotubes (CNT) reinforced low temperature vinyl ester and epoxy nanocomposites were studied. In the first part, the processing challenge of incorporating CNFs into conventional fiber reinforced composites made by Vacuum infusion resin transfer molding (VARTM) was addressed by a new technique. The CNFs are pre-bound on the long fiber mats, instead of mixing them in the polymer resin, thereby eliminating several processing drawbacks. The resulting hybrid nanocomposites showed significant improvements in tensile, flexural and thermal properties. The effect of CNFs on the mold filling in VARTM was also studied and shown to follow the Darcy's law. In the second part, the effect of CNFs on the low temperature cure kinetics of vinyl ester and epoxy resins is studied using a thermal analysis technique, namely Differential scanning calorimetry (DSC). The effect of CNFs on the free radical polymerization of vinyl esters was found to be very complex as the CNFs interact with the various curing ingredients in the formulation. Specifically, the interaction effects of CNFs and the inhibitor were studied and a reaction mechanism was proposed to explain the observed phenomenon. The effect of surface modification of the carbon nanoparticles on the cure kinetics of wind-blade epoxy was studied. The surface functionalization reduced the activation energy of the epoxy reaction and was found to have an acceleration effect on the cure kinetics of epoxy resin at room temperature. In the final part, the preparation, properties and characterization of a thin film of carbon nanoparticles, also called a "nanopaper" was studied. Specifically, a new layer-by-layer multiparticle nanopaper was prepared and this layer-by-layer approach improved the mechanical properties of the stand alone nanopaper. The cure kinetics of epoxy resin in the presence of unmodified CNF paper and polyethyleneimine modified CNF paper were studied and modeled using an autocatalytic model. The nanopaper was also used as a functional coating in conventional fiber reinforced epoxy composites and improved several properties such as abrasion resistance and electromagnetic shielding effectiveness.

Movva, Siva Subramanyam

286

Consolidation of carbon nanofiber/copper composites by hot-pressing and spark plasma sintering: a comparative study.  

Science.gov (United States)

Vapour grown carbon nanofibers have been incorporated into a copper matrix at 20 and 40 volume fractions. The manufacturing route involves the dispersion of the carbon nanofibers and their subsequent coating by electroless plating with copper. The consolidation of the composite powders was performed by two different techniques: hot-pressing and spark plasma sintering. A comparative study of the two processes is reported, in terms of microstructure, dispersion and porosity. The consolidation by hot-pressing (at 900 degrees C, 30 MPa) led to poreless composites (relative density > 96%) and to a homogeneous microstructure. On the other hand, spark plasma sintering (at 400 degrees C, 75 MPa) led to lower densification (relative density < 96%) and heterogeneous microstructure. PMID:19435042

Barcena, Jorge; Martinez, Vladimir; Martinez, Ramon; Maudes, Jon; Sarries, Jose-Ignacio; Carol, Iñaki; Gonzalez, Javier-Jesus; Coleto, Javier

2009-03-01

287

Electrospun carbon nanofibers from polyacrylonitrile blended with activated or graphitized carbonaceous materials for improving anodic bioelectrocatalysis.  

Science.gov (United States)

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 155?Acm(-2) for PAN, PAN-AC and PAN-GR, respectively) compared to the graphite electrode (11.5?Acm(-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

Patil, Sunil A; Chigome, Samuel; Hägerhäll, Cecilia; Torto, Nelson; Gorton, Lo

2013-03-01

288

Au Coating of Carbon Nanofiber-Tipped SPM Probes for Immobilization of Thiolated Biomolecules  

International Nuclear Information System (INIS)

An argon-ion-induced carbon nanofiber (CNF) is expected to be an ideal nanocarbon for developing probes for scanning probe microscopes (SPM) owing to its superior physical properties and structures. To use this pristine CNF as a biofunctionalized SPM probe, its surface needs to be further modified with probing molecules that have specific biochemical affinities toward biological targets. In this study, using a carbon-coated Si wafer as a substitute for a CNF-tipped SPM probe, we investigated ion sputtering for the formation of an Au film on a carbon surface, followed by thermal annealing for making the Au-crystal orientation preferable for the chemisorption of thiolated biomolecules. Finally, we confirmed the biofunctionality of the immobilized thiolated oligonucleotide probe on the annealed Au film in order to hybridize it with the complementary oligonucleotide target. The hybrids were detected by fluorescence emitted from streptavidin-conjugated quantum dots tagged to the biotin molecules. From these results, it was shown that Au coating, thermal annealing, and the subsequent immobilization of thiolated biomolecules can be used for the development of new biofunctional CNF-tipped SPM probes.

289

Mechanical, thermal and morphological characterization of polycarbonate/oxidized carbon nanofiber composites produced with a lean 2-step manufacturing process.  

Science.gov (United States)

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

Lively, Brooks; Kumar, Sandeep; Tian, Liu; Li, Bin; Zhong, Wei-Hong

2011-05-01

290

Functional properties of electrospun NiO/RuO{sub 2} composite carbon nanofibers  

Energy Technology Data Exchange (ETDEWEB)

Highlights: Black-Right-Pointing-Pointer Fabrication of carbon nanofibers with nickel-ruthenium composites by electrospinning. Black-Right-Pointing-Pointer An interesting observation of increase in capacitance with increase in the number of cycles for supercapacitor applications. Black-Right-Pointing-Pointer Li ion battery testing showed a stable capacity ranging from 350 mAh g{sup -1} to 400 mAh g{sup -1}. Black-Right-Pointing-Pointer Lower impedance with the incorporation of 15 wt% Ru precursor than those without Ru. - Abstract: One-dimensional (1D) nickel oxide/ruthenium oxide (NiO/RuO{sub 2})-carbon composite nanofibers (NiRu-C-NFs) were fabricated via electrospinning of a homogenous mixture of polyacrylonitrile (PAN) and Ni/Ru salt precursors at different ratios followed by heat treatments. The 1D nanostructures of the composite material were characterized by field-emission scanning electron microscopy (FE-SEM), powder X-ray diffraction (XRD), Rietveld refinement and Brunauer-Emmett-Teller (BET) surface area measurements. Li-cycling properties were evaluated using cyclic voltammetry and galvanostatic properties. The asymmetric hybrid supercapacitor studies were carried out with activated carbon as a cathode and NiRu-C-NFs composites as anodes in the cycling range, 0.005-3.0 V using 1 M LiPF{sub 6} (EC;DMC) electrolyte. NiRu-C-NFs fabricated from 5 wt% nickel (II) and 15 wt% ruthenium (III) precursors showed a capacitance up to {approx}60 F g{sup -1} after 30 cycles. Anodic Li-cycling studies of NiRu-C-NF-0 and NiRu-C-NF-2 composite samples showed a reversible capacity of 230 and 350 m Ahg{sup -1} at current rate of 72 mA g{sup -1} at the end of 40th cycle in the voltage range of 0.005-3.0 V. Electrochemical impedance studies (EIS) on NiRu-C-NFs showed lower impedance value for 15 wt% Ru than the bare sample.

Wu Yongzhi [Healthcare and Energy Materials Laboratory, Nanoscience and Nanotechnology Initiative, National University of Singapore, Singapore 117576 (Singapore); Physics Department, National University of Singapore, Singapore 117542 (Singapore); NUS Graduate School for Integrated Science and Engineering, 10 Kent Ridge Crescent, National University of Singapore, Singapore 119260 (Singapore); Balakrishna, Rajiv [Healthcare and Energy Materials Laboratory, Nanoscience and Nanotechnology Initiative, National University of Singapore, Singapore 117576 (Singapore); Physics Department, National University of Singapore, Singapore 117542 (Singapore); Reddy, M.V., E-mail: phymvv@nus.edu.sg [Physics Department, National University of Singapore, Singapore 117542 (Singapore); Nair, A. Sreekumaran, E-mail: nniansn@nus.edu.sg [Healthcare and Energy Materials Laboratory, Nanoscience and Nanotechnology Initiative, National University of Singapore, Singapore 117576 (Singapore); Chowdari, B.V.R. [Physics Department, National University of Singapore, Singapore 117542 (Singapore); Ramakrishna, S. [Healthcare and Energy Materials Laboratory, Nanoscience and Nanotechnology Initiative, National University of Singapore, Singapore 117576 (Singapore); Kind Saud University, Riyadh 11451 (Saudi Arabia)

2012-03-15

291

Boosting the local anodic oxidation of silicon through carbon nanofiber atomic force microscopy probes.  

Science.gov (United States)

Many nanofabrication methods based on scanning probe microscopy have been developed during the last decades. Local anodic oxidation (LAO) is one of such methods: Upon application of an electric field between tip and surface under ambient conditions, oxide patterning with nanometer-scale resolution can be performed with good control of dimensions and placement. LAO through the non-contact mode of atomic force microscopy (AFM) has proven to yield a better resolution and tip preservation than the contact mode and it can be effectively performed in the dynamic mode of AFM. The tip plays a crucial role for the LAO-AFM, because it regulates the minimum feature size and the electric field. For instance, the feasibility of carbon nanotube (CNT)-functionalized tips showed great promise for LAO-AFM, yet, the fabrication of CNT tips presents difficulties. Here, we explore the use of a carbon nanofiber (CNF) as the tip apex of AFM probes for the application of LAO on silicon substrates in the AFM amplitude modulation dynamic mode of operation. We show the good performance of CNF-AFM probes in terms of resolution and reproducibility, as well as demonstration that the CNF apex provides enhanced conditions in terms of field-induced, chemical process efficiency. PMID:25671165

Rius, Gemma; Lorenzoni, Matteo; Matsui, Soichiro; Tanemura, Masaki; Perez-Murano, Francesc

2015-01-01

292

Electrochemical Protease Biosensor Based on Enhanced AC Voltammetry Using Carbon Nanofiber Nanoelectrode Arrays.  

Science.gov (United States)

We report an electrochemical method for measuring the activity of proteases using nanoelectrode arrays (NEAs) fabricated with vertically aligned carbon nanofibers (VACNFs). The VACNFs of ~150 nm in diameter and 3 to 5 ?m in length were grown on conductive substrates and encapsulated in SiO2 matrix. After polishing and plasma etching, controlled VACNF tips are exposed to form an embedded VACNF NEA. Two types of tetrapeptides specific to cancer-mediated proteases legumain and cathepsin B are covalently attached to the exposed VACNF tip, with a ferrocene (Fc) moiety linked at the distal end. The redox signal of Fc can be measured with AC voltammetry (ACV) at ~1 kHz frequency on VACNF NEAs, showing distinct properties from macroscopic glassy carbon electrodes due to VACNF's unique interior structure. The enhanced ACV properties enable the kinetic measurements of proteolytic cleavage of the surface-attached tetrapeptides by proteases, further validated with a fluorescence assay. The data can be analyzed with a heterogeneous Michaelis-Menten model, giving "specificity constant" kcat /Km as (4.3 ± 0.8) × 10(4) M(-1)s(-1) for cathepsin B and (1.13 ± 0.38) × 10(4) M(-1)s(-1) for legumain. This method could be developed as portable multiplex electronic techniques for rapid cancer diagnosis and treatment monitoring. PMID:23814632

Swisher, Luxi Z; Syed, Lateef U; Prior, Allan M; Madiyar, Foram R; Carlson, Kyle R; Nguyen, Thu A; Hua, Duy H; Li, Jun

2013-02-28

293

?-Fe2O3 nanoparticle-loaded carbon nanofibers as stable and high-capacity anodes for rechargeable lithium-ion batteries.  

Science.gov (United States)

?-Fe(2)O(3) nanoparticle-loaded carbon nanofiber composites were fabricated via electrospinning FeCl(3)·6H(2)O salt-polyacrylonitrile precursors in N,N-dimethylformamide solvent and the subsequent carbonization in inert gas. Scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and elemental analysis were used to study the morphology and composition of ?-Fe(2)O(3)-carbon nanofiber composites. It was indicated that ?-Fe(2)O(3) nanoparticles with an average size of about 20 nm have a homogeneous dispersion along the carbon nanofiber surface. The resultant ?-Fe(2)O(3)-carbon nanofiber composites were used directly as the anode material in rechargeable lithium half cells, and their electrochemical performance was evaluated. The results indicated that these ?-Fe(2)O(3)-carbon nanofiber composites have high reversible capacity, good capacity retention, and acceptable rate capability when used as anode materials for rechargeable lithium-ion batteries. PMID:22524417

Ji, Liwen; Toprakci, Ozan; Alcoutlabi, Mataz; Yao, Yingfang; Li, Ying; Zhang, Shu; Guo, Bingkun; Lin, Zhan; Zhang, Xiangwu

2012-05-01

294

Preparation of carbon nanoparticles and nanofibers by a simple microwave based method and studying the field emission properties  

Energy Technology Data Exchange (ETDEWEB)

Research highlights: {yields} A novel and simple microwave based method for preparation of carbon nanostructures were developed. {yields} The mw-plasma method can produce catalyst nanoparticles from a solid metallic source. {yields} The resulting nanostructure exhibit good field emission (FE) properties. {yields} Deposition of nanoparticles through the mw-plasma method improves field emission properties. - Abstract: A novel, simple and fast method for preparation of graphitic nanostructures such as nanofibers and nanospheres which uses a standard microwave oven is described. In this method polystyrene is used as carbon source and a solid metal such as nickel or iron provides both the trigger to initiate the plasma, as well as a source for sputtering catalyst particles which are required for formation of nanofibers. The mechanism of this process is discussed through analysis of different properties of the resulting products, by examining the effect of changing the microwave processing time and the nature of the metallic trigger/catalyst source. The effect of morphology of nanoparticles (nanofibers vs. nanospheres), as well as the effect of trigger/catalyst material and the deposition method on electron field emission properties of these samples, are also investigated.

Hojati-Talemi, Pejman, E-mail: mrpejman@yahoo.com [Department of Materials Engineering, Monash University, Clayton, Vic 3800 (Australia); Asghari-Khiavi, Mehdi [School of Chemistry, Monash University, Clayton, Vic 3800 (Australia); Simon, George [Department of Materials Engineering, Monash University, Clayton, Vic 3800 (Australia)

2011-05-16

295

Fabrication and characterization of polylactic acid and polylactic acid/multi-walled carbon nanotube nanofibers through centrifugal spinning  

Science.gov (United States)

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).

Patlan, Richard

296

Effect of Carbon Nanofiber Heat Treatment on Physical Properties of Polymeric Nanocomposites—Part I  

Directory of Open Access Journals (Sweden)

Full Text Available The definition of a nanocomposite material has broadened significantly to encompass a large variety of systems made of dissimilar components and mixed at the nanometer scale. The properties of nanocomposite materials also depend on the morphology, crystallinity, and interfacial characteristics of the individual constituents. In the current work, vapor-grown carbon nanofibers were subjected to varying heat-treatment temperatures. The strength of adhesion between the nanofiber and an epoxy (thermoset matrix was characterized by the flexural strength and modulus. Heat treatment to 1800C∘ demonstrated maximum improvement in mechanical properties over that of the neat resin, while heat-treatment to higher temperatures demonstrated a slight decrease in mechanical properties likely due to the elimination of potential bonding sites caused by the elimination of the truncated edges of the graphene layers. Both the electrical and thermal properties of the resulting nanocomposites increased in conjunction with the increasing heat-treatment temperature.

Emel Yildiz

2008-01-01

297

Nonenzymatic hydrogen peroxide sensor based on a glassy carbon electrode modified with electrospun PdO-NiO composite nanofibers  

International Nuclear Information System (INIS)

A glassy carbon electrode was modified with PdO-NiO composite nanofibers (PdO-NiO-NFs) and applied to the electrocatalytic reduction of hydrogen peroxide (H2O2). The PdO-NiO-NFs were synthesized by electrospinning and subsequent thermal treatment, and then characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Factors such as the composition and fraction of nanofibers, and of the applied potential were also studied. The sensor exhibits high sensitivity for H2O2 (583.43 ?A?·?mM?1?·?cm?2), a wide linear range (from 5.0 ?M to 19 mM), a low detection limit (2.94 ?M at an SNR of 3), good long term stability, and is resistant to fouling. (author)

298

Preparation of novel carbon microfiber/carbon nanofiber-dispersed polyvinyl alcohol-based nanocomposite material for lithium-ion electrolyte battery separator  

International Nuclear Information System (INIS)

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 ?m. 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. Highlights: ? A novel material as a potential Li-ion electrolyte battery separator is synthesized. ? Synthesis steps include esterification of polyvinyl acetate to produce PVA-gel. ? The film is in-situ incorporated (dispersed) with carbon micro and nanofibers. ? The produced film has improved performance as a battery separator

299

Preparation of novel carbon microfiber/carbon nanofiber-dispersed polyvinyl alcohol-based nanocomposite material for lithium-ion electrolyte battery separator  

Energy Technology Data Exchange (ETDEWEB)

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 ?m. The produced film, uniformly dispersed with carbon micro-nanofibers, has dramatically improved performance as a battery separator, with the ion conductivity of the electrolytes (LiPF{sub 6}) saturated film measured as 0.119 S-cm{sup ?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. Highlights: ? A novel material as a potential Li-ion electrolyte battery separator is synthesized. ? Synthesis steps include esterification of polyvinyl acetate to produce PVA-gel. ? The film is in-situ incorporated (dispersed) with carbon micro and nanofibers. ? The produced film has improved performance as a battery separator.

Sharma, Ajit K.; Khare, Prateek [Department of Chemical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016 (India); Singh, Jayant K., E-mail: jayantks@iitk.ac.in [Department of Chemical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016 (India); Verma, Nishith, E-mail: nishith@iitk.ac.in [Department of Chemical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016 (India); Center for Environmental Science and Engineering, Indian Institute of Technology Kanpur, Kanpur 208016 (India)

2013-04-01

300

Preparation of Surface Adsorbed and Impregnated Multi-walled Carbon Nanotube/Nylon-6 Nanofiber Composites and Investigation of their Gas Sensing Ability  

Directory of Open Access Journals (Sweden)

Full Text Available We have prepared electrospun Nylon-6 nanofibers via electrospinning, and adsorbed multi-walled carbon nanotubes (MWCNTs onto the surface of Nylon-6 fibers using Triton® X-100 to form a MWCNTs/Nylon-6 nanofiber composite. The dispersed MWCNTs have been found to be stable in hexafluoroisopropanol for several months without precipitation. A MWCNTs/Nylon-6 nanofiber composite based chemical sensor has demonstrated its responsiveness towards a wide range of solvent vapours at room temperature and only mg quantities of MWCNTs were expended. The large surface area and porous nature of the electrospun Nylon-6/MWCNT nanofibers facilitates greater analyte permeability. The experimental analysis has indicated that the dipole moment, functional group and vapour pressure of the analytes determine the magnitude of the responsiveness.

Velmurugan Thavasi

2009-01-01

301

Development of antimicrobial biomaterials produced from chitin-nanofiber sheet/silver nanoparticle composites.  

Science.gov (United States)

BackgroundChitin nanofibers sheets (CNFSs) with nanoscale fiber-like surface structures are nontoxic and biodegradable biomaterials with large surface-to-mass ratio. CNFSs are widely applied as biomedical materials such as a functional wound dressing. This study aimed to develop antimicrobial biomaterials made up of CNFS-immobilized silver nanoparticles (CNFS/Ag NPs).Materials and methodsCNFSs were immersed in suspensions of Ag NPs (5.17¿±¿1.9 nm in diameter; mean¿±¿SD) for 30 min at room temperature to produce CNFS/Ag NPs. CNFS/Ag NPs were characterized by transmission electron microscopy (TEM) and then tested for antimicrobial activities against Escherichia (E.) coli, Pseudomonas (P.) aeruginosa, and H1N1 influenza A virus, three pathogens that represent the most widespread infectious bacteria and viruses. Ultrathin sectioning of bacterial cells also was carried out to observe the bactericidal mechanism of Ag NPs.ResultsThe TEM images indicated that the Ag NPs are dispersed and tightly adsorbed onto CNFSs. Although CNFSs alone have only weak antimicrobial activity, CNFS/Ag NPs showed much stronger antimicrobial properties against E. coli, P. aeruginosa, and influenza A virus, with the amount of immobilized Ag NPs onto CNFSs.ConclusionsOur results suggest that CNFS/Ag NPs interacting with those microbes exhibit stronger antimicrobial activities, and that it is possible to apply CNFS/Ag NPs as anti-virus sheets as well as anti-infectious wound dressings. PMID:25467525

Nguyen, Vinh; Ishihara, Masayuki; Kinoda, Jun; Hattori, Hidemi; Nakamura, Shingo; Ono, Takeshi; Miyahira, Yasushi; Matsui, Takemi

2014-12-01

302

Thin MoS2 nanoflakes encapsulated in carbon nanofibers as high-performance anodes for lithium-ion batteries.  

Science.gov (United States)

In this work, highly flexible MoS2-based lithium-ion battery anodes composed of disordered thin MoS2 nanoflakes encapsulated in amorphous carbon nanofibrous mats were fabricated for the first time through hydrothermal synthesis of graphene-like MoS2, followed by electrospinning and carbonization. X-ray diffraction as well as scanning and transmission electron microscopic studies show that the as-synthesized MoS2 nanoflakes have a thickness of about 5 nm with an expanded interlayer spacing, and their structure and morphology are well-retained after the electrospinning and carbonization. At relatively low MoS2 contents, the nanoflakes are dispersed and well-embedded in the carbon nanofibers. Consequently, excellent electrochemical performance, including good cyclability and high rate capacity, was achieved with the hybrid nanofibrous mat at the MoS2 content of 47%, which may be attributed to the fine thickness and multilayered structure of the MoS2 sheets with an expanded interlayer spacing, the good charge conduction provided by the high-aspect-ratio carbon nanofibers, and the robustness of the nanofibrous mat. PMID:24701987

Zhao, Chenyang; Kong, Junhua; Yao, Xiayin; Tang, Xiaosheng; Dong, Yuliang; Phua, Si Lei; Lu, Xuehong

2014-05-14

303

Nitrogen/phosphorus co-doped nonporous carbon nanofibers for high-performance supercapacitors  

Science.gov (United States)

This study demonstrates a facile and effective approach to prepare nitrogen/phosphorus co-doped nonporous carbon nanofibers (N/P-NPCNFs) through the electrospinning of the polyacrylonitrile and phosphoric acid precursor solutions and subsequent thermal treatment. X-ray photoelectron spectroscopy analyses show that the contents of phosphorus and pyrrol-like nitrogen in N/P-NPCNFs can be tuned by controlling the amount of phosphoric acid. The maximum specific capacitance of 224.9 F g-1 is achieved at 0.5 A g-1 in 1 M H2SO4. Furthermore, the specific capacitance could still remain 155.5 F g-1 at 30 A g-1 with a high capacitance retention ratio of 70%. It is worth noting that no capacitance loss is observed over 8000 charge/discharge cycles, clearly demonstrating a robust long-term stability. The excellent electrochemical performance can be attributed to the synergetic effect of nitrogen and phosphorus functionalities.

Yan, Xiaodong; Liu, Yuan; Fan, Xiaorong; Jia, Xiaolong; Yu, Yunhua; Yang, Xiaoping

2014-02-01

304

Vertically aligned carbon nanofiber architecture as a multifunctional 3-D neural electrical interface.  

Science.gov (United States)

Developing biomaterial constructs that closely mimic the natural tissue microenvironment with its complex chemical and physical cues is essential for improving the function and reliability of implantable devices, especially those that require direct neural-electrical interfaces. Here we demonstrate that free-standing vertically aligned carbon nanofiber (VACNF) arrays can be used as a multifunctional 3-D brush-like nanoengineered matrix that interpenetrates the neuronal network of PC12 cells. We found that PC12 neuron cells cultured on VACNF substrates can form extended neural network upon proper chemical and biochemical modifications. The soft 3-D VACNF architecture provides a new platform to fine-tune the topographical, mechanical, chemical, and electrical cues at subcellular nanoscale. This new biomaterial platform can be used for both fundamental studies of material-cell interactions and the development of chronically stable implantable neural devices. Micropatterned multiplex VACNF arrays can be selectively controlled by electrical and electrochemical methods to provide localized stimulation with extraordinary spatiotemporal resolution. Further development of this technology may potentially result in a highly multiplex closed-loop system with multifunctions for neuromodulation and neuroprostheses. PMID:17554831

Nguyen-Vu, T D Barbara; Chen, Hua; Cassell, Alan M; Andrews, Russell J; Meyyappan, M; Li, Jun

2007-06-01

305

Bending actuation in a single-layer carbon-nanofiber/polypyrrole composite film and its fabrication  

International Nuclear Information System (INIS)

Thin CNF/PPy composite single-layer films were produced by the electrophoretic deposition and polymerization process which was developed for this study. It was demonstrated that the films could generate a bending motion subjected to an actuating electric voltage even though they consisted of only single-layer. Carbon nanofiber and polypyrrole composite films were obtained from only one side of a working electrode. Several different CNF/PPy films were synthesized, as varying the CNF weight ratios from 3%, 5%, and 7% to 10%. Conductivity of pure PPy and CNF/PPy composite films were measured. Conductivity of the films is improved linearly from 77.9S/cm (pure PPy film) to 124.3 S/cm (10% CNF/PPy) as the CNF weight ratio increases. Adding CNF was effective for improving the conductivity of PPy. As results of electromechanical actuation tests with the films, it was noticed that the strain of the films was reduced a little as the CNF weight ratio increased. Bending motions were observed for both PPy and CNF/PPy films subjected to a voltage. The tip bending deflections was in the range of 0.5 mm to 2 mm. CNF/PPy films showed a great potential to be a good candidate for small light actuators

306

Size-selectivity and anomalous subdiffusion of nanoparticles through carbon nanofiber-based membranes  

International Nuclear Information System (INIS)

A simulation is presented here that serves the dual functions of generating a nanoporous membrane replica and executing the Brownian motion of nanoparticles through the virtual membrane. Specifically, the concentration profile of a dilute solution of fluorescent particles in a stochastic and SiO2-coated carbon nanofiber (oxCNF), nanoporous membrane was simulated. The quality of the simulated profile was determined by comparing the results with experimental concentration profiles. The experimental concentration profiles were collected adjacent to the oxCNF membrane surface from time-lapse fluorescence microscopy images. The simulation proved ideal as an accurate predictor of particle diffusion-the simulated concentration profile merged with the experimental profiles at the inlet/exit surfaces of the oxCNF membrane. In particular, the oxCNF barrier was found to hinder the transport of 50 and 100 nm particles and transmembrane trajectories were indicative of anomalous subdiffusion; the diffusion coefficient was found to be a function of time and space

307

Cellulose nanofiber/single-walled carbon nanotube hybrid non-woven macrofiber mats as novel wearable supercapacitors with excellent stability, tailorability and reliability  

Science.gov (United States)

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

Niu, Qingyuan; Gao, Kezheng; Shao, Ziqiang

2014-03-01

308

Monolithically Integrated, Mechanically Resilient Carbon-Based Probes for Scanning Probe Microscopy  

Science.gov (United States)

Scanning probe microscopy (SPM) is an important tool for performing measurements at the nanoscale in imaging bacteria or proteins in biology, as well as in the electronics industry. An essential element of SPM is a sharp, stable tip that possesses a small radius of curvature to enhance spatial resolution. Existing techniques for forming such tips are not ideal. High-aspect-ratio, monolithically integrated, as-grown carbon nanofibers (CNFs) have been formed that show promise for SPM applications by overcoming the limitations present in wet chemical and separate substrate etching processes.

Kaul, Anupama B.; Megerian, Krikor G.; Jennings, Andrew T.; Greer, Julia R.

2010-01-01

309

Synthesis of ruthenium oxide coated ordered mesoporous carbon nanofiber arrays as a catalyst for lithium oxygen battery  

Science.gov (United States)

Li-O2 batteries with super-high theoretical energy density are attracting extensive attention. However, the sluggish oxygen reduction/evolution reaction, the huge volume change from O2/Li2O2 conversion and the undesired electrolyte decomposition in cathode limit their performance. Herein we show design and synthesis of RuO2-coated ordered mesoporous carbon nanofiber arrays by using a natural crab shell template as a catalyst for Li-O2 battery, exhibiting several advantage features. First, the ordered mesopores in nanofibers facilitate electrolyte penetration and electron/ion transfer. In addition, the macro-sized voids between the nanofibers provide efficient buffer space for O2/Li2O2 accommodation and improve O2 diffusion. Furthermore, the uniform RuO2-coating layer alleviates undesired electrolyte decomposition and enhances the surface electronic conductivity. As a result, the battery displays high performance, including high capacity (20600 mAh g-1 at a current density of 100 mA g-1), high rate (9750 mAh g-1 at a current density of 1000 mA g-1) and long-life (300 cycles at a fixed capacity of 1000 mAh g-1).

Guo, Ziyang; Zhou, Dandan; Liu, Haijing; Dong, Xiaoli; Yuan, Shouyi; Yu, Aishui; Wang, Yonggang; Xia, Yongyao

2015-02-01

310

A facile route for controlled alignment of carbon nanotube-reinforced, electrospun nanofibers using slotted collector plates  

Directory of Open Access Journals (Sweden)

Full Text Available A facile route for controlled alignment of electrospun multiwalled carbon nanotube (MWCNT-reinforced Polyvinyl Alcohol (PVA nanofibers using slotted collector geometries has been realized. The process is based on analytical predictions using electrostatic field analysis for envisaging the extent of alignment of the electrospun fibers on varied collector geometries. Both the experimental and theoretical studies clearly indicate that the introduction of an insulating region into a conductive collector significantly influences the electrostatic forces acting on a charged fiber. Among various collector geometries, rectangular slotted collectors with circular ends showed good fiber alignment over a large collecting area. The electrospun fibers produced by this process were characterized by Atomic Force Microscopy (AFM, High Resolution Transmission Electron Microscopy (HRTEM, Scanning Electron Microscopy (SEM and Optical Microscopy. Effects of electrospinning time and slot widths on the fiber alignment have been analyzed. PVA-MWCNT nanofibers were found to be conducting in nature owing to the presence of reinforced MWCNTs in PVA matrix. The method can enable the direct integration of aligned nanofibers with controllable configurations, and significantly simplify the production of nanofibersbased devices.

G. R. Rakesh

2015-02-01

311

Biological adhesive based on carboxymethyl chitin derivatives and chitin nanofibers.  

Science.gov (United States)

Novel biological adhesives made from chitin derivatives were prepared and evaluated for their adhesive properties and biocompatibility. Chitin derivatives with acrylic groups, such as 2-hydroxy-3-methacryloyloxypropylated carboxymethyl chitin (HMA-CM-chitin), were synthesized and cured by the addition of an aqueous hydrogen peroxide solution as a radical initiator. The adhesive strength of HMA-CM-chitin increased when it was blended with chitin nanofibers (CNFs) or surface-deacetylated chitin nanofibers (S-DACNFs). HMA-CM-chitin/CNFs or HMA-CM-chitin/S-DACNFs have almost equal adhesive strength compared to that of a commercial cyanoacrylate adhesive. Moreover, quick adhesion and induction of inflammatory cells migration were observed in HMA-CM-chitin/CNF and HMA-CM-chitin/S-DACNF. These findings indicate that the composites prepared in this study are promising materials as new biological adhesives. PMID:25542790

Azuma, Kazuo; Nishihara, Masahiro; Shimizu, Haruki; Itoh, Yoshiki; Takashima, Osamu; Osaki, Tomohiro; Itoh, Norihiko; Imagawa, Tomohiro; Murahata, Yusuke; Tsuka, Takeshi; Izawa, Hironori; Ifuku, Shinsuke; Minami, Saburo; Saimoto, Hiroyuki; Okamoto, Yoshiharu; Morimoto, Minoru

2015-02-01

312

Stainless steel mesh supported nitrogen-doped carbon nanofibers for binder-free cathode in microbial fuel cells.  

Science.gov (United States)

In this communication, we report a binder-free oxygen reduction cathode for microbial fuel cells. The binder-free cathode is prepared by growth of nitrogen-doped carbon nanofibers (NCNFs) on stainless steel mesh (SSM) via simple pyrolysis of pyridine. The interaction force between NCNFs and SSM surface is very strong which is able to tolerate water flush. The NCNFs/SSM cathode shows high and stable electrocatalytic activity for oxygen reduction reaction, which is comparable to that of Pt/SSM and ferricyanide cathode. This study proposes a promising low-cost binder-free cathode for microbial fuel cells. PMID:22336437

Chen, Shuiliang; Chen, Yu; He, Guanghua; He, Shuijian; Schröder, Uwe; Hou, Haoqing

2012-04-15

313

CVD Growth of Carbon Nanostructures from Zirconia: Mechanisms and a Method for Enhancing Yield.  

Science.gov (United States)

By excluding metals from synthesis, growth of carbon nanostructures via unreduced oxide nanoparticle catalysts offers wide technological potential. We report new observations of the mechanisms underlying chemical vapor deposition (CVD) growth of fibrous carbon nanostructures from zirconia nanoparticles. Transmission electron microscope (TEM) observation reveals distinct differences in morphological features of carbon nanotubes and nanofibers (CNTs and CNFs) grown from zirconia nanoparticle catalysts versus typical oxide-supported metal nanoparticle catalysts. Nanofibers borne from zirconia lack an observable graphitic cage consistently found with nanotube-bearing metal nanoparticle catalysts. We observe two distinct growth modalities for zirconia: (1) turbostratic CNTs 2-3 times smaller in diameter than the nanoparticle localized at a nanoparticle corner, and (2) nonhollow CNFs with approximately the same diameter as the nanoparticle. Unlike metal nanoparticle catalysts, zirconia-based growth should proceed via surface-bound kinetics, and we propose a growth model where initiation occurs at nanoparticle corners. Utilizing these mechanistic insights, we further demonstrate that preannealing of zirconia nanoparticles with a solid-state amorphous carbon substrate enhances growth yield. PMID:25487041

Kudo, Akira; Steiner, Stephen A; Bayer, Bernhard C; Kidambi, Piran R; Hofmann, Stephan; Strano, Michael S; Wardle, Brian L

2014-12-24

314

High-yield harvest of nanofibers/mesoporous carbon composite by pyrolysis of waste biomass and its application for high durability electrochemical energy storage.  

Science.gov (United States)

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

Liu, Wu-Jun; Tian, Ke; He, Yan-Rong; Jiang, Hong; Yu, Han-Qing

2014-12-01

315

Dye-sensitized solar cells based on anatase TiO2/multi-walled carbon nanotubes composite nanofibers photoanode  

International Nuclear Information System (INIS)

Highlights: ? TiO2/multi-walled carbon nanotubes (MWCNTs) hybrid nanofibers are prepared via electrospinning. ? Dye-sensitized solar cells (DSSCs) are assembled using TiO2/MWCNTs nanofibers film as photoanode. ? Energy conversion efficiency of DSSCs is greatly dependent on the content of MWCNTs. ? Moderate MWCNTs incorporation can substantially enhance the performance of DSSCs. - Abstract: Anatase TiO2/multi-walled carbon nanotubes (TiO2/MWCNTs) hybrid nanofibers (NFs) film was prepared via a facile electrospinning method. Dye-sensitized solar cells (DSSCs) based on TiO2/MWCNTs composite NFs photoanodes with different contents of MWCNTs (0, 0.1, 0.3, 0.5, 1 wt.%) were assembled using N719 dye as sensitizer. Field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), X-ray diffractometer (XRD), and Raman spectrometer were used to characterize the TiO2/MWCNTs electrode films. The photocurrent–voltage (I–V) characteristic, incident photo-to-current conversion efficiency (IPCE) spectrum, and electrochemical impedance spectroscopy (EIS) measurements were carried out to evaluate the photoelectric properties of the DSSCs. The results reveal that the energy conversion efficiency is greatly dependent on the content of MWCNTs in the composite NFs film, and a moderate incorporation of MWCNTs can substantially enhance the performance of DSSCs. When the electrode containss. When the electrode contains 0.3 wt.% MWCNTs, the corresponding solar cell yield the highest efficiency of 5.63%. This efficiency value is approximately 26% larger than that of the unmodified counterpart.

316

Carbon nanotubes and nanofibers synthesized by CVD on nickel coatings deposited with a vacuum arc  

International Nuclear Information System (INIS)

Nanotubes and nanofibers were grown on Ni coatings deposited by plasma generated with a pulsed vacuum arc on silicon wafers using three different bias conditions: at floating potential (approximately +30 V respect to the grounded cathode); at ground potential; and at -60 V. An atomic force microscopy study showed that the Ni film morphology was affected by the bias condition of the substrate. The morphology of carbonaceous species depended on Ni-films characteristics. FE-SEM and TEM analyses have shown that nanofibers growth was favoured on Ni coatings deposited at -60 V whereas nanotubes grew mainly on Ni coatings obtained at floating and ground potentials. Hence, this new method to produce the precursor can be optimized to obtain nanotubes or nanofibers varying the substrate bias for the Ni deposition.

317

Mass production of multi-channeled porous carbon nanofibers and their application as binder-free electrodes for high-performance supercapacitors.  

Science.gov (United States)

A unique class of multi-channeled porous carbon nanofibers (MCPCNFs) are designed with dual-pathway ion transport capability via a modified electrospinning approach. Combined with other features including high conductivity and numerous functional groups for facilitating the formation of electric double-layer charges, the MCPCNFs exhibit excellent supercapacitive performance, holding great potential for high-performance supercapacitor electrode materials. PMID:25236751

He, Haiyong; Shi, Lin; Fang, Yan; Li, Xianglong; Song, Qi; Zhi, Linjie

2014-11-01

318

Electrospun silicon/carbon/titanium oxide composite nanofibers for lithium ion batteries  

Science.gov (United States)

Si/C/TiO2 composite nanofibers have been prepared via a facile electrospinning method combined with a sol-gel chemistry, whose electrochemical performance as anode materials in lithium-ion battery was evaluated. As-prepared nanofibers (NFs) were characterized using scanning electron microscopy, energy dispersive spectroscopy, powder X-ray diffraction and thermogravimetric analyzer to identify their morphology, phase, crystallinity and compositions. Rutile phase TiO2 nanofibers demonstrated a relatively low gravimetric specific capacity of ?83 mAh g-1 when discharged at 0.1C. In contrast, composite nanofibers possess a much higher gravimetric specific capacity. When the Si to C mass ratio is of 0.217, a specific capacity as high as 720 mAh g-1 can be attained, 94% of which can be maintained after 55 cycles. The enhanced cycling stability of micron silicon materials is attributed to the space confinement provided by the structurally stable TiO2. These findings can provide a beneficial guidance for future lithium ion battery electrode development.

Wu, Qingliu; Tran, Toan; Lu, Wenquan; Wu, Ji

2014-07-01

319

Photocatalysis of sub-ppm limonene over multiwalled carbon nanotubes/titania composite nanofiber under visible-light irradiation.  

Science.gov (United States)

This study was conducted under visible-light exposure to investigate the photocatalytic characteristics of a multiwalled carbon nanotube/titania (TiO2) composite nanofiber (MTCN) using a continuous-flow tubular reactor. The MTCN was prepared by a sol-gel process, followed by an electrospinning technique. The photocatalytic decomposition efficiency for limonene on the MTCN was higher than those obtained from reference TiO2 nanofibers or P25 TiO2, and the experimental results agreed well with the Langmuir-Hinshelwood model. The CO concentrations generated during the photocatalysis did not reach levels toxic to humans. The mineralization efficiency for limonene on the MTCN was also higher than that for P25 TiO2. Moreover, the mineralization efficiency obtained using the MTCN increased steeply from 8.3 to 91.1% as the residence time increased from 7.8 to 78.0s, compared to the increase in the decomposition efficiencies for limonene from 90.1 to 99.9%. Three gas-phase intermediates (methacrolein, acetic acid, and limonene oxide) were quantitatively determined for the photocatalysis for limonene over the MTCN, whereas only two intermediates (acetic acid and limonene oxide) were quantitatively determined over P25 TiO2. Other provisional gas-phase intermediates included cyclopropyl methyl ketone and 2-ethylbutanal. PMID:25464310

Jo, Wan-Kuen; Kang, Hyun-Jung

2015-02-11

320

Manufacturing and Shear Response Characterization of Carbon Nanofiber Modified CFRP Using the Out-of-Autoclave-Vacuum-Bag-Only Cure Process  

OpenAIRE

The interlaminar shear response is studied for carbon nanofiber (CNF) modified out-of-autoclave-vacuum-bag-only (OOA-VBO) carbon fiber reinforced plastic (CFRP). Commercial OOA-VBO prepregs were coated with a CNF modified epoxy solution and a control epoxy solution without CNF to make CNF modified samples and control samples, respectively. Tensile testingwas used to study the in-plane shear performance of [±45°]4s composite laminates. Significant difference in failure modes between the cont...

Mcdonald, Erin E.; Wallace, Landon F.; Hickman, Gregory J. S.; Kuang-Ting Hsiao

2014-01-01

321

Direct electrochemistry and electrocatalysis of heme-proteins immobilized in porous carbon nanofiber/room-temperature ionic liquid composite film  

Energy Technology Data Exchange (ETDEWEB)

The combination of porous carbon nanofiber (PCNF) and room-temperature ionic liquid (RTIL) provided a suitable microenvironment for heme-proteins to transfer electron directly. Hemoglobin, myoglobin, and cytochrome c incorporated in PCNF/RTIL films exhibited a pair of well-defined, quasi-reversible cyclic voltammetric peaks at about -0.28 V vs. SCE in pH 7.0 buffers, respectively, characteristic of the protein heme Fe(III)/Fe(II) redox couples. The cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the modified electrode. The heme/PCNF/RTIL/CHIT films were also characterized by UV-vis spectroscopy, indicating that heme-proteins in the composite film could retain its native structure. Oxygen, hydrogen peroxide, and nitrite were catalytically reduced at the heme/PCNF/RTIL/CHIT film modified electrodes, showing the potential applicability of the films as the new type of biosensors or bioreactors based on direct electrochemistry of the redox proteins.

Sheng Qinglin [Institute of Analytical Science/Shaanxi Provincial Key Laboratory of Electroanalytical Chemistry, Northwest University, Xi' an, Shaanxi 710069 (China); Zheng Jianbin, E-mail: zhengjb@nwu.edu.c [Institute of Analytical Science/Shaanxi Provincial Key Laboratory of Electroanalytical Chemistry, Northwest University, Xi' an, Shaanxi 710069 (China); Shangguan Xiaodong [Institute of Analytical Science/Shaanxi Provincial Key Laboratory of Electroanalytical Chemistry, Northwest University, Xi' an, Shaanxi 710069 (China); Lin Wanghua; Li Yuanyao [Department of Chemical Engineering, National Chung Cheng University, Chia-Yi 62102, Taiwan (China); Liu Ruixiao [Institute of Analytical Science/Shaanxi Provincial Key Laboratory of Electroanalytical Chemistry, Northwest University, Xi' an, Shaanxi 710069 (China)

2010-03-30

322

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

Science.gov (United States)

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

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

2014-08-01

323

Pd-Ni alloy nanoparticle/carbon nanofiber composites: preparation, structure, and superior electrocatalytic properties for sugar analysis.  

Science.gov (United States)

Novel Pd-Ni alloy nanoparticle/carbon nanofiber (Pd-Ni/CNF) composites were successfully prepared by a simple method involving electrospinning of precursor polyacrylonitrile/Pd(acac)2/Ni(acac)2 nanofibers, followed by a thermal process to reduce metals and carbonize polyacrylonitrile. The nanostructures of the resulting Pd-Ni/CNF nanocomposites were carefully examined by a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), high-angle annular dark field (HAADF)-scanning transmission electron microscopy (STEM), energy dispersive X-ray (EDX), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and X-ray photoelectron spectra (XPS). For all the nanocomposites, the Pd-Ni alloy nanoparticles (NPs) were dispersed uniformly and embedded firmly within the framework or on the surface of CNF. The size, composition, and alloy homogeneity of the Pd-Ni alloy NPs could be readily tailored by controlling the feed ratio of metal precursors and the thermal treatment process. Cyclic voltammetric studies showed enhanced redox properties for Pd-Ni/CNF-based electrodes relative to the Ni-metal electrode and significantly improved electrocatalytic activity for sugar (e.g., glucose, fructose, sucrose, and maltose) oxidation. The application potential of Pd-Ni/CNF-based electrodes in flow systems for sugars detection was explored. A very low limit of detection for sugars (e.g., 7-20 nM), high resistance to surface fouling, excellent signal stability and reproducibility, and a very wide detection linear range (e.g., 0.03-800 ?M) were revealed for this new type of Pd-Ni/CNF nanocomposite as the detecting electrode. Such detection performances of Pd-Ni/CNF-based electrodes are superior to those of state-of-the-art nonenzymatic sugar detectors that are commercially available or known in the literature. PMID:24837693

Guo, Qiaohui; Liu, Dong; Zhang, Xueping; Li, Libo; Hou, Haoqing; Niwa, Osamu; You, Tianyan

2014-06-17

324

Centrifugal spinning: A novel approach to fabricate porous carbon fibers as binder-free electrodes for electric double-layer capacitors  

Science.gov (United States)

Carbon nanofibers (CNFs), among various carbonaceous candidates for electric double-layer capacitor (EDLC) electrodes, draw extensive attention because their one-dimensional architecture offers both shortened electron pathways and high ion-accessible sites. Creating porous structures on CNFs yields larger surface area and enhanced capacitive performance. Herein, porous carbon nanofibers (PCNFs) were synthesized via centrifugal spinning of polyacrylonitrile (PAN)/poly(methyl methacrylate) (PMMA) solutions combined with thermal treatment and were used as binder-free EDLC electrodes. Three precursor fibers with PAN/PMMA weight ratios of 9/1, 7/3 and 5/5 were prepared and carbonized at 700, 800, and 900 °C, respectively. The highest specific capacitance obtained was 144 F g-1 at 0.1 A g-1 with a rate capability of 74% from 0.1 to 2 A g-1 by PCNFs prepared with PAN/PMMA weight ratio of 7/3 at 900 °C. These PCNFs also showed stable cycling performance. The present work demonstrates that PCNFs are promising EDLC electrode candidate and centrifugal spinning offers a simple, cost-effective strategy to produce PCNFs.

Lu, Yao; Fu, Kun; Zhang, Shu; Li, Ying; Chen, Chen; Zhu, Jiadeng; Yanilmaz, Meltem; Dirican, Mahmut; Zhang, Xiangwu

2015-01-01

325

Towards the control of the diameter of individualized single walled carbon nanotubes in CVD process at low temperature  

Energy Technology Data Exchange (ETDEWEB)

In the current work, we show that it is possible to favor the selective growth of single-walled carbon nanotubes (SWCNTs) with a narrow diameter distribution on supported catalyst particles with a broad size distribution. Carbon nanotubes were grown at 600 C on silicon substrates. The structure of carbon deposits was controlled by managing the carbon feedstock for adjusting the rate of carbon nanostructures formation on the surface of catalyst particles. Either carbon nanofibers (CNFs) carpets or isolated SWCNTs were obtained. With the fine tune of carbon feedstock, small isolated SWCNTs with a narrow diameter distribution were obtained by limiting the catalytic activity of the largest catalyst particles. HRTEM observations of nanotube embryos have suggested a possible mechanism of multi-walled carbon nanotubes (MWCNTs) formation that can explain why the growth of MWCNTs with parallel walls seems to be more difficult than SWCNTs or CNFs at low temperature. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Tsareva, Svetlana [Institut Jean Lamour UMR 7819, CNRS - Universite de Lorraine, Parc de Saurupt, 54011 Nancy (France); Structure et Reactivite des Systemes Moleculaires Complexes UMR 7565, CNRS - Universite de Lorraine, Vandoeuvre les Nancy (France); Devaux, Xavier [Institut Jean Lamour UMR 7819, CNRS - Universite de Lorraine, Parc de Saurupt, 54011 Nancy (France); Dossot, Manuel [Laboratoire de Chimie Physique et Microbiologie pour l' Environnement UMR 7564, CNRS - Universite de Lorraine, 54602 Villers les Nancy (France)

2012-12-15

326

Engineered magnetic core-shell SiO2/Fe microspheres and "medusa-like" microspheres of SiO2/iron oxide/carbon nanofibers or nanotubes.  

Science.gov (United States)

Iron oxide (IO) thin coatings of controlled thickness on SiO2 microspheres of narrow size distribution were prepared by decomposition at 160 °C of triiron dodecacarbonyl onto silica microspheres dispersed in diethylene glycol diethyl ether free of surfactant or stabilizer. The dried washed SiO2/IO core-shell microspheres were annealed at different temperatures and time periods under inert (Ar) or reducing (H2) atmosphere. The effect of temperature on the chemical composition, morphology, crystallinity, and magnetic properties of the IO and the elemental Fe nanoparticles type coatings onto the SiO2 core microspheres has been elucidated. "Medusa-like" SiO2/IO/carbon nanofibers and tubes particles were prepared by CVD of ethylene on the surface of the SiO2/IO microspheres at different temperatures. The morphology change of the grafted carbon nanofibers and tubes as a function of the CVD temperature was also elucidated. PMID:25089849

Mero, On; Sougrati, Moulay-Tahar; Jumas, Jean-Claude; Margel, Shlomo

2014-08-19

327

Mesoporous Li4Ti5O12/carbon nanofibers for high-rate lithium-ion batteries  

International Nuclear Information System (INIS)

Highlights: • Facile electrospinning method combined with soft-template self-assembly. • Abundant mesopores and large specific surface area. • Superior rate capability and excellent cycling stability. -- Abstract: Mesoporous Li4Ti5O12/carbon nanofibers (LTO/C NFs) are prepared by a facile electrospinning method combined with soft-template self-assembly. The morphology and structure are characterized by field-emission scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The diameter of as-prepared LTO/C NFs is approximately 400 nm with highly crystallinity LTO nanoparticle completely embedded in carbon framework. Nitrogen adsorption–desorption isotherms and corresponding pore size distribution reveal that the mesoporous LTO/C NFs exhibite high specific surface area (212.1 m2/g?1) and large pore volume. Compared with the regular LTO/C NFs, the mesoporous LTO/C NFs show much higher rate capability and better capacity retention. At a current rate of 5 C, the reversible capacity of the mesoporous LTO/C NFs electrode is up to 127.4 mA h g?1 and still remains at 122.7 mA h g?1 after 100 cycles. The excellent electrochemical performances are closedly related to well-defined one-dimensional (1D) mesoporous nanostructure with LTO nanoparticles embedded in the carbon framework, which efficiently shortened the path length of Li+ diffusion, enhanced electrolyte-active material contact area and facilitated rapid electron transfer

328

In situ fabrication of Ni(OH)2 nanofibers on polypyrrole-based carbon nanotubes for high-capacitance supercapacitors  

International Nuclear Information System (INIS)

Highlights: ? Facile surface decoration approach to highly porous Ni(OH)2/CNT composites. ? Polypyrrole-based CNTs form three-dimensional electron-transport channels. ? A high capacitance of 1118 F g?1 at 50 mA cm?2 is delivered. ? Ni(OH)2/CNT composites exhibit high discharge capability. - Abstract: Large-scale nickel hydroxide–carbon [Ni(OH)2/CNT] networks with three-dimensional electron-transport channels are synthesized via a facile and general surface-decoration approach, using polypyrrole-derived CNTs as the support. Flexible Ni(OH)2 nanofibers with a diameter of 5–10 nm and a length of 50–120 nm are intertwined and wrapped homogenously on carbon networks, leading to the formation of more complex networks. When used as supercapacitor electrodes, this designed architecture with large surface area, abundant pores and good electrical conductivity is very important in technology. It can promote the bulk accessibility of electrolyte OH? and diffusion rate within the redox phase. Consequently, an unusual specific capacitance of 1745 F g?1 can be obtained for Ni(OH)2/CNT composite at 30 mA cm?2. Even at a high rate (50 mA cm?2), the composite can also deliver a specific capacitance as high as 1118 F g?1, exhibiting the potential application for supercapacitors

329

Controllable growth of Prussian blue nanostructures on carboxylic group-functionalized carbon nanofibers and its application for glucose biosensing  

International Nuclear Information System (INIS)

Glucose detection is very important in biological analysis, clinical diagnosis and the food industry, and especially for the routine monitoring of diabetes. This work presents an electrochemical approach to the detection of glucose based on Prussian blue (PB) nanostructures/carboxylic group-functionalized carbon nanofiber (FCNF) nanocomposites. The hybrid nanocomposites were constructed by growing PB onto the FCNFs. The obtained PB–FCNF nanocomposites were characterized by scanning electron microscopy, x-ray diffraction and x-ray photoelectron spectroscopy. The mechanism of formation of PB–FCNF nanocomposites was investigated and is discussed in detail. The PB–FCNF modified glassy carbon electrode (PB–FCNF/GCE) shows good electrocatalysis toward the reduction of H2O2, a product from the reduction of O2 followed by glucose oxidase (GOD) catalysis of the oxidation of glucose to gluconic acid. Further immobilizing GOD on the PB–FCNF/GCE, an amperometric glucose biosensor was achieved by monitoring the generated H2O2 under a relatively negative potential. The resulting glucose biosensor exhibited a rapid response of 5 s, a low detection limit of 0.5 ?M, a wide linear range of 0.02–12 mM, a high sensitivity of 35.94 ?A cm?2 mM?1, as well as good stability, repeatability and selectivity. The sensor might be promising for practical application. (paper)

330

High pseudocapacitance from ultrathin V{sub 2}O{sub 5} films electrodeposited on self-standing carbon-nanofiber paper  

Energy Technology Data Exchange (ETDEWEB)

An ultrathin V{sub 2}O{sub 5} layer was electrodeposited by cyclic voltammetry on a self-standing carbon-nanofiber paper, which was obtained by stabilization and heat-treatment of an electrospun polyacrylonitrile (PAN)-based nanofiber paper. A very-high capacitance of 1308 F g{sup -1} was obtained in a 2 M KCl electrolyte when the contribution from the 3 nm thick vanadium oxide was considered alone, contributing to over 90% of the total capacitance (214 F g{sup -1}) despite the low weight percentage of the V{sub 2}O{sub 5} (15 wt%). The high capacitance of the V{sub 2}O{sub 5} is attributed to the large external surface area of the carbon nanofibers and the maximum number of active sites for the redox reaction of the ultrathin V{sub 2}O{sub 5} layer. This ultrathin layer is almost completely accessible to the electrolyte and thus results in maximum utilization of the oxide (i.e., minimization of dead volume). This hypothesis was experimentally evaluated by testing V{sub 2}O{sub 5} layers of different thicknesses. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Ghosh, Arunabha; Ra, Eun Ju; Jin, Meihua; Kim, Tae Hyung; Biswas, Chandan; Lee, Young Hee [BK21 Physics Division, Sungkyunkwan Advanced Institute of Nanotechnology, Department of Physics, Sungkyunkwan University (SKKU), Suwon (Korea, Republic of); Jeong, Hae-Kyung [Department of Physics, Daegu University, GyeonSan (Korea, Republic of)

2011-07-08

331

Factoring-in agglomeration of carbon nanotubes and nanofibers for better prediction of their toxicity versus asbestos  

Science.gov (United States)

Background Carbon nanotubes (CNT) and carbon nanofibers (CNF) are allotropes of carbon featuring fibrous morphology. The dimensions and high aspect ratio of CNT and CNF have prompted the comparison with naturally occurring asbestos fibers which are known to be extremely pathogenic. While the toxicity and hazardous outcomes elicited by airborne exposure to single-walled CNT or asbestos have been widely reported, very limited data are currently available describing adverse effects of respirable CNF. Results Here, we assessed pulmonary inflammation, fibrosis, oxidative stress markers and systemic immune responses to respirable CNF in comparison to single-walled CNT (SWCNT) and asbestos. Pulmonary inflammatory and fibrogenic responses to CNF, SWCNT and asbestos varied depending upon the agglomeration state of the particles/fibers. Foci of granulomatous lesions and collagen deposition were associated with dense particle-like SWCNT agglomerates, while no granuloma formation was found following exposure to fiber-like CNF or asbestos. The average thickness of the alveolar connective tissue - a marker of interstitial fibrosis - was increased 28 days post SWCNT, CNF or asbestos exposure. Exposure to SWCNT, CNF or asbestos resulted in oxidative stress evidenced by accumulations of 4-HNE and carbonylated proteins in the lung tissues. Additionally, local inflammatory and fibrogenic responses were accompanied by modified systemic immunity, as documented by decreased proliferation of splenic T cells ex vivo on day 28 post exposure. The accuracies of assessments of effective surface area for asbestos, SWCNT and CNF (based on geometrical analysis of their agglomeration) versus estimates of mass dose and number of particles were compared as predictors of toxicological outcomes. Conclusions We provide evidence that effective surface area along with mass dose rather than specific surface area or particle number are significantly correlated with toxicological responses to carbonaceous fibrous nanoparticles. Therefore, they could be useful dose metrics for risk assessment and management. PMID:22490147

2012-01-01

332

Wafer-scale fabrication of patterned carbon nanofiber nanoelectrode arrays: a route for development of multiplexed, ultrasensitive disposable biosensors.  

Science.gov (United States)

One of the major limitations in the development of ultrasensitive electrochemical biosensors based on one-dimensional nanostructures is the difficulty involved with reliably fabricating nanoelectrode arrays (NEAs). In this work, we describe a simple, robust and scalable wafer-scale fabrication method to produce multiplexed biosensors. Each sensor chip consists of nine individually addressable arrays that uses electron beam patterned vertically aligned carbon nanofibers (VACNFs) as the sensing element. To ensure nanoelectrode behavior with higher sensitivity, VACNFs were precisely grown on 100 nm Ni dots with 1 microm spacing on each micro pad. Pretreatments by the combination of soaking in 1.0 M HNO(3) and electrochemical etching in 1.0M NaOH dramatically improved the electrode performance, indicated by the decrease of redox peak separation in cyclic voltammogram (DeltaE(p)) to approximately 100 mV and an approximately 200% increase in steady-state currents. The electrochemical detection of the hybridization of DNA targets from E. coli O157:H7 onto oligonucleotide probes were successfully demonstrated. The 9 arrays within the chip were divided into three groups with triplicate sensors for positive control, negative control and specific hybridization. The proposed method has the potential to be scaled up to NxN arrays with N up to 10, which is ideal for detecting a myriad of organisms. In addition, such sensors can be used as a generic platform for many electroanalysis applications. PMID:19303281

Arumugam, Prabhu U; Chen, Hua; Siddiqui, Shabnam; Weinrich, Jarret A P; Jejelowo, Ayodeji; Li, Jun; Meyyappan, M

2009-05-15

333

Synthesis and properties of SiNx coatings as stable fluorescent markers on vertically aligned carbon nanofibers  

Directory of Open Access Journals (Sweden)

Full Text Available 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 predominantly Si and N. In fluorescent microscopy experiments, whereby VACNFs are interfaced to cell and tissue cultures for a variety of applications, it was observed that this material is broadly fluorescent. In this paper, we provide insight into nature of these silicon/nitrogen in-situ coatings. We propose a potential mechanism for deposition of SiNx coating on the sidewalls of VACNFs during PECVD synthesis and explore the origin of the coating’s fluorescence. It is most likely that the substrate reacts with process gases similar to reactive sputtering and chemical vapor deposition (CVD, forming silane and other silicon bearing compounds prior to isotropic deposition as a SiNx coating onto the VACNFs. The formation of Sinanoclusters (NCs is also implicated due to a combination of strong fluorescence and elemental analysis of the samples. These broadly luminescent fibers can prove useful as registry markers in fluorescent cellular studies and for tagging and tracing applications.

Ryan Pearce

2014-04-01

334

Quantitative electrochemical detection of cathepsin B activity in complex tissue lysates using enhanced AC voltammetry at carbon nanofiber nanoelectrode arrays.  

Science.gov (United States)

The proteolytic activity of a cancer-related enzyme cathepsin B is measured with alternating current voltammetry (ACV) using ferrocene (Fc) labeled tetrapeptides attached to nanoelectrode arrays (NEAs) fabricated with vertically aligned carbon nanofibers (VACNFs). This combination enables the use of high AC frequencies (~1kHz) with enhanced electrochemical signals. The specific proteolysis of the Fc-peptide by cathepsin B produces decay in the ACV peak current versus the reaction time. The exponential component of the raw data can be extracted and defined as the "extracted proteolytic signal" which allows consistent quantitative analyses using a heterogeneous Michaelis-Menten model. A "specificity constant" kcat/KM = (3.68 ± 0.50) × 10(4)M(-1)s(-1) for purified cathepsin B was obtained. The detections of cathepsin B activity in different concentrations of whole lysate of human breast tissue, tissue lysate spiked with varied concentrations of cathepsin B, and the tissue lysate after immunoprecipitation showed that there is ~13.4 nM higher cathepsin B concentration in 29.1 µg mL(-1) of whole tissue lysate than the immunoprecipitated sample. The well-defined regular VACNF NEAs by e-beam lithography show a much faster kinetics for cathepsin B proteolysis with kcat/KM = 9.2 × 10(4)M(-1)s(-1). These results illustrate the potential of this technique as a portable multiplex electronic system for cancer diagnosis by rapid protease profiling of serum or blood samples. PMID:24480132

Swisher, Luxi Z; Prior, Allan M; Shishido, Stephanie; Nguyen, Thu A; Hua, Duy H; Li, Jun

2014-06-15

335

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

Energy Technology Data Exchange (ETDEWEB)

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.

Pearce, Ryan [North Carolina State University; Klein, Kate L [ORNL; Ivanov, Ilia N [ORNL; Hensley, Dale K [ORNL; Meyer III, Harry M [ORNL; Melechko, Anatoli [North Carolina State University; McKnight, Timothy E [ORNL

2014-01-01

336

A novel electrochemical sensor of bisphenol A based on stacked graphene nanofibers/gold nanoparticles composite modified glassy carbon electrode  

International Nuclear Information System (INIS)

In this paper, a novel and convenient electrochemical sensor based on stacked graphene nanofibers (SGNF) and gold nanoparticles (AuNPs) composite modified glassy carbon electrode (GCE) was developed for the determination of bisphenol A (BPA). The AuNPs/SGNF modified electrode showed an efficient electrocatalytic role for the oxidation of BPA, and the oxidation overpotentials of BPA were decreased significantly and the peak current increased greatly compared with bare GCE and other modified electrode. The transfer electron number (n) and the charge transfer coefficient (?) were calculated with the result as n = 4, ? = 0.52 for BPA, which indicated the electrochemical oxidation of BPA on AuNPs/SGNF modified electrode was a four-electron and four-proton process. The effective surface areas of AuNPs/SGNF/GCE increased for about 1.7-fold larger than that of the bare GCE. In addition, the kinetic parameters of the modified electrode were calculated and the apparent heterogeneous electron transfer rate constant (ks) was 0.51 s?1. Linear sweep voltammetry was applied as a sensitive analytical method for the determination of BPA and a good linear relationship between the peak current and BPA concentration was obtained in the range from 0.08 to 250 ?M with a detection limit of 3.5 × 10?8 M. The modified electrode exhibited a high sensitivity, long-term stability and remarkable reproducible analytical performance and was successfully applied for the determination of BPA in baby bottles with satisfying results

337

75 FR 80819 - Draft Current Intelligence Bulletin “Occupational Exposure to Carbon Nanotubes and Nanofibers  

Science.gov (United States)

...strategies for controlling occupational exposure to carbon nanotubes...Interested parties should contact the NIOSH Docket Office...possible health risks of occupational exposure to carbon nanotubes...experimental data on the airborne characteristics of carbon...FURTHER INFORMATION CONTACT: Ralph D....

2010-12-23

338

Simple fabrication of flexible electrodes with high metal-oxide content: electrospun reduced tungsten oxide/carbon nanofibers for lithium ion battery applications  

Science.gov (United States)

A one-step and mass-production synthetic route for a flexible reduced tungsten oxide-carbon composite nanofiber (WOx-C-NF) film is demonstrated via an electrospinning technique. The WOx-C-NF film exhibits unprecedented high content of metal-oxides (~80 wt%) and good flexibility (the tensile strength of the specimen was 6.13 MPa) without the use of flexible support materials like CNTs or graphene. The WOx-C-NF film is directly used as an anode in a lithium ion battery (LIB). Compared with previously reported tungsten oxide electrodes, the WOx-C-NF film exhibits high reversible capacity (481 mA h g-1total electrode), stable cycle, and improved rate performance, without the use of additive carbon, a polymeric binder and a current collector. Moreover, control electrodes fabricated by conventional processes support the positive effects of both the freestanding electrode and metal-oxide embedded carbon 1-D nanofiber structure.A one-step and mass-production synthetic route for a flexible reduced tungsten oxide-carbon composite nanofiber (WOx-C-NF) film is demonstrated via an electrospinning technique. The WOx-C-NF film exhibits unprecedented high content of metal-oxides (~80 wt%) and good flexibility (the tensile strength of the specimen was 6.13 MPa) without the use of flexible support materials like CNTs or graphene. The WOx-C-NF film is directly used as an anode in a lithium ion battery (LIB). Compared with previously reported tungsten oxide electrodes, the WOx-C-NF film exhibits high reversible capacity (481 mA h g-1total electrode), stable cycle, and improved rate performance, without the use of additive carbon, a polymeric binder and a current collector. Moreover, control electrodes fabricated by conventional processes support the positive effects of both the freestanding electrode and metal-oxide embedded carbon 1-D nanofiber structure. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr01033g

Lee, Jaehyuk; Jo, Changshin; Park, Bangrock; Hwang, Woonbong; Lee, Hyung Ik; Yoon, Songhun; Lee, Jinwoo

2014-08-01

339

Development of Radiation Processing to Functionalize Carbon Nanofiber to Use in Nanocomposites for Industrial Application  

International Nuclear Information System (INIS)

The effects of ionizing radiation on carbon materials have been thoroughly investigated because of its importance in the fields of nuclear, medical, and materials science. Basically, the effect of ionizing radiation on carbon materials takes place as a displacement of carbon atoms from their amorphous or graphitic structures. For nanocarbon materials, only destructive effects were observed in early experiments involving bombardment of carbon nanotubes and fullerenes with ions. However, recent work reveals that radiation can exploit defect creation for novel materials development especially in electronic nanotechnology (Krasheninnikov et al., 2007)

340

Thermal Conductivity of Ethylene Vinyl Acetate Copolymer/Carbon Nanofiller Blends  

Science.gov (United States)

To reduce weight and increase the mobility, comfort, and performance of future spacesuits, flexible, thermally conductive fabrics and plastic tubes are needed for the Liquid Cooling and Ventilation Garment. Such improvements would allow astronauts to operate more efficiently and safely for extended extravehicular activities. As an approach to raise the thermal conductivity (TC) of an ethylene vinyl acetate copolymer (Elvax 260), it was compounded with three types of carbon based nanofillers: multi-walled carbon nanotubes (MWCNTs), vapor grown carbon nanofibers (CNFs), and expanded graphite (EG). In addition, other nanofillers including metallized CNFs, nickel nanostrands, boron nitride, and powdered aluminum were also compounded with Elvax 260 in the melt at various loading levels. In an attempt to improve compatibility between Elvax 260 and the nanofillers, MWCNTs and EG were modified by surface coating and through noncovalent and covalent attachment of organic molecules containing alkyl groups. Ribbons of the nanocomposites were extruded to form samples in which the nanofillers were aligned in the direction of flow. Samples were also fabricated by compression molding to yield nanocomposites in which the nanofillers were randomly oriented. Mechanical properties of the aligned samples were determined by tensile testing while the degree of dispersion and alignment of nanoparticles were investigated using high-resolution scanning electron microscopy. TC measurements were performed using a laser flash (Nanoflash ) technique. TC of the samples was measured in the direction of, and perpendicular to, the alignment direction. Additionally, tubing was also extruded from select nanocomposite compositions and the TC and mechanical flexibility measured.

Ghose, S.; Watson, K. A.; Working, D. C.; Connell, J. W.; Smith, J. G., Jr.; Lin, Y.; Sun, Y. P.

2007-01-01

341

Carbon nanostructure-derived polyaniline metacomposites: electrical, dielectric, and giant magnetoresistive properties.  

Science.gov (United States)

Polyaniline (PANI) nanocomposites incorporating different loadings of graphene and various other carbon nanostructures including carbon nanotubes (CNTs) and carbon nanofibers (CNFs) have been synthesized using a surface-initiated polymerization (SIP) method. Transmission electron microscopy (TEM) results indicate that the graphene has been exfoliated into a few layers (typically one, two, and three layers) during polymerization and has been uniformly dispersed in the PANI matrix. The graphene layer dispersion degree is quantified by a free-path spacing measurement (FPSM) method based on the TEM microstructures. The SIP method also demonstrates its feasibility for coating PANI on one-dimensional (1D) CNFs and CNTs without introducing additional surface functional groups. The effects of graphene size, loading level, and surface functionality on the electrical conductivity and dielectric permittivity of their corresponding nanocomposites have been systematically studied. The temperature-dependent conductivity behavior revealed a quasi-3D variable range hopping (VRH) electron transport mechanism for all the nanocomposites. Giant magnetoresistance (GMR) at room temperature is observed in pure PANI, which can be enhanced by the incorporation of a high loading of graphene (5%) due to the ?-? stacking-induced efficient electron transport at the PANI/graphene interface. More interestingly, negative permittivity is found in each composite which can be easily tuned by adjusting the filler loading, morphology, and surface functionality. PMID:22703477

Zhu, Jiahua; Gu, Hongbo; Luo, Zhiping; Haldolaarachige, Neel; Young, David P; Wei, Suying; Guo, Zhanhu

2012-07-10

342

Electrospinning of ceramic nanofibers  

Science.gov (United States)

Silicon Carbide (SiC) nanofibers of diameters as low as 20 nm are fabricated. The fibers were produced through the electrostatic spinning of the preceramic poly(carbomethylsilane) with pyrolysis to ceramic. A new technique was used where the preceramic was blended with polystyrene (PS) and, subsequent to electrospinning, was exposed to UV to crosslink the PS and prevent fibers flowing during pyrolysis. Electrospun SiC fibers were characterized by FTIR, TGA-DTA, SEM, TEM, XRD, and SAED. Fibers were shown to be polycrystalline and nanograined with alpha-SiC 15R polytype being dominant, where commercial fiber production methods form beta-SiC 3C. Pyrolysis of the bulk polymer blend to SiC produced alpha-SiC 15R as the dominant polytype with larger grains showing that electrospinning nanofibers affects resultant crystallinity. Fibers produced were shown to have a core-shell structure of an oxide scale that was variable by pyrolysis conditions. Metal oxide powders (chromium oxide, cobalt oxide, iron oxide, silicon oxide, tantalum oxide, titanium oxide, tungsten oxide, vanadium oxide, and zirconium oxide), were converted to metal carbide powders and metal nitride powders by the process of carbothermal reduction (CTR). Synthetic pitch was explored as an alternative to graphite which is a common carbon source for CTR. It was shown via characterization with XRD that pitch performs as well and in some cases better than graphite and is therefore a viable alternative in CTR. Conversion of metal oxide powders with pitch led to conversion of sol-gel based metal oxide nanofibers produced by electrospinning. Pitch was soluble in the solutions xv that were electrospun allowing for intimate contact between the sol-gel and the carbon source for CTR. This method became a two step processing method to produce metal carbide and nitride nanofibers: first electrospin sol-gel based metal oxide nanofibers and subsequently pyrolize them in the manner of CTR to transform them. Results indicate that this method was capable of transforming hafnium, niobium, tantalum, titanium, vanadium, and zirconium sol-gel nanofibers to metal carbides and nitrides.

Eick, Benjamin M.

343

Flexible, ultralight, porous superconducting yarns containing shell-core magnesium diboride-carbon nanotube nanofibers.  

Science.gov (United States)

Magnesium-diboride-coated carbon nanotube arrays are synthesized by templating carbon-nanotube aerogel sheets with boron and then converting the boron to MgB2 . The resultant MgB2 -CNT sheets are twisted into flexible, light-weight yarns that have a superconducting transition around 37.8 K and critical current and critical field comparable with those of existing MgB2 wires, but have about 20 times lower density than bulk MgB2 . PMID:25319360

Bykova, Julia S; Lima, Márcio Dias; Haines, Carter S; Tolly, Derrick; Salamon, M B; Baughman, Ray H; Zakhidov, Anvar A

2014-11-01

344

Introduction of aldehyde vs. carboxylic groups to cellulose nanofibers using laccase/TEMPO mediated oxidation.  

Science.gov (United States)

The chemo-enzymatic modification of cellulose nanofibers (CNFs) using laccase as biocatalysts and TEMPO or 4-Amino-TEMPO as mediators under mild aqueous conditions (pH 5, 30°C) has been investigated to introduce surface active aldehyde groups. 4-Amino TEMPO turned out to be kinetically 0.5-times (50%) more active mediator, resulting to oxoammonium cation intermediacy generated and its in situ regeneration during the modification of CNFs. Accordingly, beside of around 750mmol/kg terminally-located aldehydes, originated during CNFs isolation, the reaction resulted to about 140% increase of C6-located aldehydes at optimal conditions, without reducing CNFs crystallinity. While only the C6-aldehydes were wholly transformed into the carboxyls after additional post-treatment using NaOH according to the Cannizzaro reaction, the post-oxidation with air-oxygen in EtOH/water medium or NaClO2 resulted to no- or very small amounts of carboxyls created, respectively, at a simultaneous loss of all C6- and some terminal-aldehydes in the latter due to the formation of highly-resistant hemiacetal covalent linkages with available cellulose hydroxyls. The results indicated a new way of preparing and stabilizing highly reactive C6-aldehydes on cellulose, and their exploitation in the development of new nanocellulose-based materials. PMID:25458275

Jaušovec, Darja; Vogrin?i?, Robert; Kokol, Vanja

2015-02-13

345

Electrical, Mechanical, and Morphological Characterization of Carbon Nanotube filled Polymeric Nanofibers  

Science.gov (United States)

This work focuses on the inclusion of conductive nanotubes into polymeric matrices with the end goal of creating conductive nanocomposites. This investigation has been carried out by uniform dispersion of multi-walled carbon nanotubes in aqueous solutions of polyvinyl alcohol (PVA) and polyethylene oxide (PEO), which are inherently nonconductive polymers. To fabricate these structures we are using the electrospinning process encompassing an array of collection methods including parallel bars and a static plate. Carbon nanotubes are known to have excellent electrical conductivity and mechanical properties. This investigation shows that the inclusion of carbon nanotubes increases the electronic conduction in these polymers and enhances the mechanical properties of the composites. Dispersion of these nanotubes is the key factor in this process; gum Arabic and surfactants have been utilized for the dispersion of these nanotubes. Conductivity measurements have been carried out by two point probe method and by performing sensitive current and conductance measurements with a femtoammeter. Further morphological characterization has been performed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM).^1 Department of Textile Engineering, Chemistry, and Science ^2 Department of Physics

Gorga, Russell; Clarke, Laura; McCullen, Seth; Ojha, Satyajeet; Roberts, Wesley

2006-03-01

346

The Optimization of Electrical Conductivity Using Central Composite Design for Polyvinyl Alcohol/Multiwalled Carbon Nanotube-Manganese Dioxide Nanofiber Composites Synthesised by Electrospinning  

Directory of Open Access Journals (Sweden)

Full Text Available This research reports the characterization and statistical analysis of electrical conductivity optimization for polyvinyl alcohol (PVA/multiwalled carbon nanotube (MWCNT-manganese dioxide (MnO2 nanofiber composite. The Central Composite Design (CCD, the most common design of Response Surface Methodology (RSM had been used to optimise the synthesis process of PVA/MWCNT-MnO2 nanofiber composite. The process parameters studied were; applied voltage (16 kV - 30 kV, solution flow rate (3- 5 mL h-1 and surrounding temperature (17-30°C. Analysis of variance (ANOVA was used to analyse the experimental results. The prediction of optimum value and the clarification of the interactions between the specified range factors were done by using the quadratic model. The results revealed that at the parameter condition of 23 kV for applied voltage, 4 mL h-1 solution flow rate and 18°C of surrounding temperature, the highest electrical conductivity of 2.66x10-5 S cm-1 was obtained. The predicted (2.81 x10-5 S cm-1 value after optimization process was in good agreement with the experimental data (3.06 x10-5 S cm-1. The model was able to accurately predict the response of electrical conductivity with less than 10% error. Referring to ANOVA results, it was statistically found that the surrounding temperature parameter given significant effect to electrical conductivity of PVA/MWCNT-MnO2 nanofiber composite in both single parameter and interaction between parameter.

Ahmad Zuhairi Abdullah

2012-01-01

347

Synergetic role of nanoparticles and micro-scale short carbon fibers on the mechanical profiles of epoxy resin  

Directory of Open Access Journals (Sweden)

Full Text Available It was demonstrated in our previous work that the combined carbon nanofibers (CNFs and microsized short carbon fibers (SCFs in epoxy (EP leads to significant improvements in the mechanical properties of the matrix. In this work, the effect of nano-SiO2 particles, having an extremely different aspect ratio from CNFs, on the tensile property and fracture toughness of SCFs-filled EP was studied. It was revealed that the combined use of SCFs and silica nanoparticles exerts a synergetic effect on the mechanical and fracture properties of EP. Application of SCFs and the nanoparticles is an effective way to greatly enhance the modulus, strength and fracture toughness of the EP simultaneously. The synergetic role of the multiscale fillers was explained by prominent changes in the stress state near the microsized fillers and the plastic zone ahead of the crack tip. The synergetic role of multiscale fillers is expected to open up new opportunities to formulate highperformance EP composites.

2011-10-01

348

Polymethylsilsesquioxane-cellulose nanofiber biocomposite aerogels with high thermal insulation, bendability, and superhydrophobicity.  

Science.gov (United States)

Polymethylsilsesquioxane-cellulose nanofiber (PMSQ-CNF) composite aerogels have been prepared through sol-gel in a solvent containing a small amount of CNFs as suspension. Since these composite aerogels do not show excessive aggregation of PMSQ and CNF, the original PMSQ networks are not disturbed. Composite aerogels with low density (0.020 g cm(-3) at lowest), low thermal conductivity (15 mW m(-1) K(-1)), visible light translucency, bending flexibility, and superhydrophobicity thus have been successfully obtained. In particular, the lowest density and bending flexibility have been achieved with the aid of the physical supporting effect of CNFs, and the lowest thermal conductivity is comparable with the original PMSQ aerogels and standard silica aerogels. The PMSQ-CNF composite aerogels would be a candidate to practical high-performance thermal insulating materials. PMID:24865571

Hayase, Gen; Kanamori, Kazuyoshi; Abe, Kentaro; Yano, Hiroyuki; Maeno, Ayaka; Kaji, Hironori; Nakanishi, Kazuki

2014-06-25

349

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

Science.gov (United States)

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

Kim, So Yeun; Yang, Kap Seung; Kim, Bo-Hye

2015-01-01

350

Low-temperature self-assembled vertically aligned carbon nanofibers as counter-electrode material for dye-sensitized solar cells  

International Nuclear Information System (INIS)

Low-temperature AC–DC PECVD is employed for direct growth of vertically aligned carbon nanofibers (VACNFs) on ordinary transparent conductive glass as counter-electrode material for dye-sensitized solar cells (DSSCs). To the best of our knowledge, this is the first report on utilization of VACNFs grown directly on ordinary FTO-coated glass as a cost-effective catalyst material in DSSCs. According to the FESEM images, the as-grown arrays are well aligned and dense, and offer uniform coverage on the surface of the substrate. In-plane and out-of-plane conductivity measurements reveal their good electrical conductivity, and Raman spectroscopy suggests a high number of electrocatalytic active sites, favoring charge transport at the electrolyte/electrode interface. Hybrid VACNF/Pt electrodes are also fabricated for performance comparison with Pt and VACNF electrodes. X-ray diffraction results verify the crystallization of Pt in hybrid electrodes and further confirm the vertical alignment of carbon nanofibers. Electrochemical characterization indicates that VACNFs provide both high catalytic and good charge transfer capability, which can be attributed to their high surface area, defect-rich and one-dimensional structure, vertical alignment and low contact resistance. As a result, VACNF cells can achieve a comparable performance (?5.6%) to that of the reference Pt cells (?6.5%). Moreover, by combination of the excellent charge transport and catalytic ability of VACNFs and the high conductivity of Pt nanoparticles, hybrid VACNF/Pt cells can deliver a performance superior to that of the Pt cells (?7.2%), despite having a much smaller amount of Pt loading, which raises hopes for low-cost large-scale production of DSSCs in the future. (paper)

351

High-Frequency Characteristics of One-Dimensional Carbon Nanostructures  

Science.gov (United States)

The ever increasing demand for faster and more reliable chips depends largely on the performance of on-chip interconnects. Over ten years ago, copper became the preferred metal over aluminum as the on-chip interconnects material in the most advanced silicon chip technology. However, as copper interconnects scale down, its resistivity increases exponentially due to the degrading effect of surface scattering and grain-boundary scattering. Currently, the scaled-down copper interconnects suffer from reliability concerns due to electromigration in the sub-30 nm technology regime. In order to keep up with the International Technology Roadmap for Semiconductors (ITRS), copper must be replaced. Because of their superior properties, carbon-based nanostructures are the preferred choice to replace copper in next-generation integrated circuits. The principal objective of this work is to develop a methodology to investigate the high-frequency electrical conduction in one-dimensional carbon nanostructures, in particular, carbon nanofibers (CNFs) as a potential replacement for copper in next-generation on-chips interconnects. This work is divided into four parts. First, a high-frequency test structure with low transmission is designed and fabricated, allowing capacitances less than 1fF to be measured from 0.1 to 50 GHz. Second, S-parameters from 0.1 to 50 GHz are measured for the test structure and for the test structure connected by a CNF. Third, based on this data a frequency-independent parallel-RC network that models the CNF is proposed that matches the measured S-parameters. In this model the capacitance is the only fitting parameter. Finally, an analytical approach is developed that validates the frequency-independent RC -model, whose parameters are obtained directly from measurements without fitting. This simple RC-model takes into account the effect of both the contact impedance between the signal pads and the nanofiber, as well the impedance of the nanofiber.

Madriz Flores, Francisco R.

2010-11-01

352

In situ fabrication of Ni(OH){sub 2} nanofibers on polypyrrole-based carbon nanotubes for high-capacitance supercapacitors  

Energy Technology Data Exchange (ETDEWEB)

Highlights: ? Facile surface decoration approach to highly porous Ni(OH){sub 2}/CNT composites. ? Polypyrrole-based CNTs form three-dimensional electron-transport channels. ? A high capacitance of 1118 F g{sup ?1} at 50 mA cm{sup ?2} is delivered. ? Ni(OH){sub 2}/CNT composites exhibit high discharge capability. - Abstract: Large-scale nickel hydroxide–carbon [Ni(OH){sub 2}/CNT] networks with three-dimensional electron-transport channels are synthesized via a facile and general surface-decoration approach, using polypyrrole-derived CNTs as the support. Flexible Ni(OH){sub 2} nanofibers with a diameter of 5–10 nm and a length of 50–120 nm are intertwined and wrapped homogenously on carbon networks, leading to the formation of more complex networks. When used as supercapacitor electrodes, this designed architecture with large surface area, abundant pores and good electrical conductivity is very important in technology. It can promote the bulk accessibility of electrolyte OH{sup ?} and diffusion rate within the redox phase. Consequently, an unusual specific capacitance of 1745 F g{sup ?1} can be obtained for Ni(OH){sub 2}/CNT composite at 30 mA cm{sup ?2}. Even at a high rate (50 mA cm{sup ?2}), the composite can also deliver a specific capacitance as high as 1118 F g{sup ?1}, exhibiting the potential application for supercapacitors.

Fan, Jianzhang [School of Chemistry and Chemical Engineering, Xinjiang University, Urumqi 830046 (China); Mi, Hongyu, E-mail: mmihongyu@163.com [School of Chemistry and Chemical Engineering, Xinjiang University, Urumqi 830046 (China); Xu, Youlong, E-mail: ylxuxjtu@mail.xjtu.edu.cn [Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education, Xi’an Jiaotong University, Xi’an 710049 (China); Gao, Bo [Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Urumqi 830011 (China)

2013-03-15

353

Manufacturing and shear response characterization of carbon nanofiber modified CFRP using the out-of-autoclave-vacuum-bag-only cure process.  

Science.gov (United States)

The interlaminar shear response is studied for carbon nanofiber (CNF) modified out-of-autoclave-vacuum-bag-only (OOA-VBO) carbon fiber reinforced plastic (CFRP). Commercial OOA-VBO prepregs were coated with a CNF modified epoxy solution and a control epoxy solution without CNF to make CNF modified samples and control samples, respectively. Tensile testing was used to study the in-plane shear performance of [± 45°]4s composite laminates. Significant difference in failure modes between the control and CNF modified CFRPs was identified. The control samples experienced half-plane interlaminar delamination, whereas the CNF modified samples experienced a localized failure in the intralaminar region. Digital image correlation (DIC) surface strain results of the control sample showed no further surface strain increase along the delaminated section when the sample was further elongated prior to sample failure. On the other hand, the DIC results of the CNF modified sample showed that the surface strain increased relatively and uniformly across the CFRP as the sample was further elongated until sample failure. The failure mode evidence along with microscope pictures indicated that the CNF modification acted as a beneficial reinforcement inhibiting interlaminar delamination. PMID:24688435

McDonald, Erin E; Wallace, Landon F; Hickman, Gregory J S; Hsiao, Kuang-Ting

2014-01-01

354

Novos materiais à base de nanofibras de carbono como suporte de catalisador na decomposição da hidrazina / Carbon nanofibers a new catalyst support for hydrazine decomposition  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese [...] Abstract in english Today satellites propulsion is based on the use of monopropellant and/or bipropellant chemical systems. The maneuvering of satellite is based on the hydrazine decomposition micropropulsors catalyzed by metallic iridium supported on g-alumina. This reaction is a surface reaction and is strongly exoth [...] ermic and implies that the operation of the micropropulsor is controlled by the mass and heat diffusions. For this reason and for the fact that the propulsor operation is frequently in pulsed regime, the catalyst should support high pressure and temperature variations within a short time period. The performance and the durability of the commercial catalyst are jeopardized by the low thermal conductivity of the alumina. The low thermal conductivity of the alumina support restricts the heat diffusion and leads to the formation of hot spots on the catalyst surface causing the metal sintering and/or fractures of the support, resulting in loss of the activity and catalyst destruction. This work presents the synthesis and characterization of new carbon composite support for the active element iridium, in substitution of the commercial catalysts alumina based support. These supports are constituted of carbon nanofibers (30 to 40 nm diameter) supported on a macroscopic carbon felt. These materials present high thermal conductivity and mechanical resistance, as well as the easiness to be shaped with different macroscopic shapes. The mechanical stability and the performance of the iridium supported on the carbon composite support, evaluated in a laboratory scale test in hydrazine decomposition reaction, are superior compared to the commercial catalyst.

Ricardo, Vieira; Cuong, Pham-Huu; Nicolas, Keller; Marc J., Ledoux.

2003-10-01

355

Choline chloride-thiourea, a deep eutectic solvent for the production of chitin nanofibers.  

Science.gov (United States)

Deep eutectic solvents (DESs) consisting of the mixtures of choline halide (chloride/bromide)-urea and choline chloride-thiourea were used as solvents to prepare ?-chitin nanofibers (CNFs). CNFs of diameter 20-30 nm could be obtained using the DESs comprising of the mixture of choline chloride and thiourea (CCT 1:2); however, NFs could not be obtained using the DESs having urea (CCU 1:2) as hydrogen bond donor. The physicochemical properties of thus obtained NFs were compared with those obtained using a couple of imidazolium based ionic liquids namely, 1-butyl-3-methylimidazolium hydrogen sulphate [(Bmim)HSO4] and 1-methylimidazolium hydrogen sulphate [(Hmim)HSO4] as well as choline based bio-ILs namely, choline hydrogen sulphate [(Chol)HSO4] and choline acrylate. The CNFs obtained using the DES as a solvent were used to prepare calcium alginate bio-nanocomposite gel beads having enhanced elasticity in comparison to Ca-alginate beads. The bio-nanocomposite gel beads thus obtained were used to study slow release of 5-fluorouracil, an anticancer drug. PMID:24528755

Mukesh, Chandrakant; Mondal, Dibyendu; Sharma, Mukesh; Prasad, Kamalesh

2014-03-15

356

Mesoporous Li{sub 4}Ti{sub 5}O{sub 12}/carbon nanofibers for high-rate lithium-ion batteries  

Energy Technology Data Exchange (ETDEWEB)

Highlights: • Facile electrospinning method combined with soft-template self-assembly. • Abundant mesopores and large specific surface area. • Superior rate capability and excellent cycling stability. -- Abstract: Mesoporous Li{sub 4}Ti{sub 5}O{sub 12}/carbon nanofibers (LTO/C NFs) are prepared by a facile electrospinning method combined with soft-template self-assembly. The morphology and structure are characterized by field-emission scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The diameter of as-prepared LTO/C NFs is approximately 400 nm with highly crystallinity LTO nanoparticle completely embedded in carbon framework. Nitrogen adsorption–desorption isotherms and corresponding pore size distribution reveal that the mesoporous LTO/C NFs exhibite high specific surface area (212.1 m{sup 2}/g{sup ?1}) and large pore volume. Compared with the regular LTO/C NFs, the mesoporous LTO/C NFs show much higher rate capability and better capacity retention. At a current rate of 5 C, the reversible capacity of the mesoporous LTO/C NFs electrode is up to 127.4 mA h g{sup ?1} and still remains at 122.7 mA h g{sup ?1} after 100 cycles. The excellent electrochemical performances are closedly related to well-defined one-dimensional (1D) mesoporous nanostructure with LTO nanoparticles embedded in the carbon framework, which efficiently shortened the path length of Li{sup +} diffusion, enhanced electrolyte-active material contact area and facilitated rapid electron transfer.

Wang, Jie; Shen, Laifa; Li, Hongsen; Ding, Bing; Nie, Ping; Dou, Hui; Zhang, Xiaogang, E-mail: azhangxg@nuaa.edu.cn

2014-02-25

357

Synthesis of carbon nanofibres from a liquid solution containing both catalyst and polyethylene glycol  

International Nuclear Information System (INIS)

Carbon nanofibres (CNFs) exhibiting bamboo-like, hollow fibril morphology were prepared from a mixture of polyethylene glycol (PEG) and iron-based compounds such as Fe2(SO4)3·nH2O, Fe(NO3)·9H2O or FeO(OH) by a thermal process. These materials were well mixed in distilled water prior to thermal treatment in an air/nitrogen atmosphere. With increasing temperature, the mixture underwent solvent removal, dehydrogenation, thermal decomposition, carbonization and catalytic graphitization to form CNFs. Results show that CNFs can be formed with different PEG/catalyst ratios (100/1-1000/1 by weight) at 750 deg. C. The catalyst effect is discussed for the formation of bamboo-like CNFs. The diameter of the CNFs was about 30-50 nm while the length was a few micrometres

358

Synthesis of nano-Fe3O4-loaded tubular carbon nanofibers and their application as negative electrodes for Fe/air batteries  

Science.gov (United States)

Nano-Fe3O4-loaded tubular carbon nanofibers (nano-Fe3O4/TCNFs) were synthesized by adding TCNFs into the high-temperature solution-phase reactions of iron(III) acetylacetonate with 1,2-hexadecanediol in the presence of oleic acid and oleylamine. The morphology and structure of this material were investigated by transmission electron microscopy (TEM) and X-ray diffraction (XRD) measurements. TEM observation clarified that nano-sized Fe3O4 particles with a uniform diameter of several nanometers were distributed and loaded tightly on the TCNF surfaces (inside and outside). After being annealed at 500 °C in Ar gas flow, nano-Fe3O4/TCNFs were used as the active material of negative electrodes for Fe/air batteries. Using an alkaline aqueous electrolyte with K2S additive, a high specific capacity of 786 mAh g-1 and cycling efficiency of 76% at the 30th cycle were obtained. The downsizing of the conductive Fe3O4 nano-particles was considered to have contributed to the good electrochemical properties of the material.

Ito, Akisuke; Zhao, Liwei; Okada, Shigeto; Yamaki, Jun-ichi

2011-10-01

359

Anomalous capacity increase at high-rates in lithium-ion battery anodes based on silicon-coated vertically aligned carbon nanofibers  

Science.gov (United States)

This study reports of a multi-scale hierarchical lithium-ion battery (LIB) anode that shows a surprising increase in storage capacity at higher current rates from ?3C to ?8C. The anode, composed of forest-like vertically aligned carbon nanofibers coaxially coated with Si shells, is shown to obtain a storage capacity of 3000-3500 mAh (gSi)-1 and greater than 99% coulombic efficiency at a 1C (or C/1) rate, leading to remarkable stability over 500 charge-discharge cycles. In contrast to other studies, this hierarchical LIB anode shows superior high-rate capability where the capacity decreased by less than 7% from ?C/8 to ?3C rates and, more importantly, increased by a few percent from ?3C to ?8C rates, displaying a new phenomenon that becomes more evident after going through long cycles. Electron microscopy, Raman, and electrochemical impedance spectroscopy reveal that the electrode structure remains stable during long cycling and that this enhanced property is likely associated with the combination of the unique nanocolumnar microstructure of the Si coating and the vertical core-shell architecture. It reveals an exciting potential to develop high-performance lithium-ion batteries.

Klankowski, Steven A.; Pandey, Gaind P.; Cruden, Brett A.; Liu, Jianwei; Wu, Judy; Rojeski, Ronald A.; Li, Jun

2015-02-01

360

A template-free method for preparation of cobalt nanoparticles embedded in N-doped carbon nanofibers with a hierarchical pore structure for oxygen reduction.  

Science.gov (United States)

Designing and preparing porous materials without using any templates is a challenge. Herein, single-nozzle electrospinning technology coupled with post pyrolysis is applied to prepare cobalt nanoparticles embedded in N-doped carbon nanofibers with a hierarchical pore structure (HP-Co-NCNFs). The resultant HP-Co-NCNFs have lengths up to several millimeters with an average diameter of 200?nm and possess abundant micro/meso/macropores on both the surface and within the fibers. Such a microstructure endows the surface area as high as 115?m(2) ?g(-1) . When used as an electrocatalyst for the oxygen reduction reaction (ORR), the HP-Co-NCNFs exhibit outstanding electrochemical performance in terms of activity, methanol tolerance, and durability. The hierarchically porous structure and high surface area can effectively decrease the mass transport resistance and increase the exposed ORR active sites. The sufficient amount of exposed ORR active sites along with accessible transport channel and enhanced electrical conductivity may be responsible for the good electrocatalytic performance. PMID:25449793

Wang, Shuguang; Cui, Zhentao; Cao, Minhua

2015-01-26

361

Polymer crystallization-driven, periodic patterning on carbon nanotubes.  

Science.gov (United States)

We report herein a unique means to periodically pattern polymeric materials on individual carbon nanotubes (CNTs) using a controlled polymer crystallization method. One-dimensional (1D) CNTs were periodically decorated with polymer lamellar crystals, resulting in nano-hybrid shish-kebab (NHSK) structures. The periodicity of the polymer lamellae varies from 20 to 150 nm. The kebabs are approximately 5-10 nm thick (along CNT direction) with a lateral size of approximately 20 nm to micrometers, which can be readily controlled by varying crystallization conditions. Both polyethylene and Nylon 66 were successfully decorated on single-walled carbon nanotubes (SWNTs), multiwalled carbon nanotubes (MWNTs), as well as vapor grown carbon nanofibers (CNFs). The formation mechanism was attributed to "size-dependent soft epitaxy". Because NHSK formation conditions depend on CNT structures, it further provides a unique opportunity for CNT separation. The reported method opens a gateway to periodically patterning polymers and different functional groups on individual CNTs in an ordered and controlled manner, an attractive research field that is yet to be explored. PMID:16448143

Li, Lingyu; Li, Christopher Y; Ni, Chaoying

2006-02-01

362

Curvature, Hybridization and Contamination of Carbon Nanostructures Analysis Using Electron Microscopy and XANES Spectroscopy  

Directory of Open Access Journals (Sweden)

Full Text Available The ability to control the nanoscale shape of carbon nanostructures during wide-scale synthesis process is an essential goal in research for Nanotechnology applications. This paper reports a significant progress toward that goal. Variant CVD has been used for the synthesis of the samples studied. Curvature, hybridization and contamination are analyzed using Electron Microscopies and XANES spectroscopy. The investigations of the results show that four types of samples are obtained. They are carbon nanotubes (CNTs, carbon nanofibers (CNFs, carbon nanowalls (CNWs and carbon nanoparticles (CNPs. Almost all of them have catalyst nanoparticles (metal on top in top growth model or on base in base growth model and encapsulated or adsorbed in sidewalls. The orientation of tubular carbon nanomaterials depends on operating parameters. They are classified in three groups: the poorly oriented, the medium oriented and the highly oriented. Their contamination (radicals, atoms and molecules and hybridization are intrinsically related to the curvature of their graphene layers. XANES spectroscopy allows quantitative characterization of nanomaterials.

Rolant Eba Medjo

2014-02-01

363

Hydrogen storage in different carbon materials: Influence of the porosity development by chemical activation  

Science.gov (United States)

The hydrogen adsorption capacity of different types of carbon nanofibers (platelet, fishbone and ribbon) and amorphous carbon have been measured as a function of pressure and temperature. The results showed that the more graphitic carbon materials adsorbed less hydrogen than more amorphous materials. After a chemical activation process, the hydrogen storage capacities of the carbon materials increased markedly in comparison with the non-activated ones. BET surface area of amorphous carbon increased by a factor of 3.5 and the ultramicropore volume doubled, thus increasing the hydrogen adsorption by a factor of 2. However, BET surface area in platelet CNFs increased by a factor of 3 and the ultramicropore volume by a factor of 6, thus increasing the hydrogen storage by a factor of 4.5. The dependency of hydrogen storage capacity of carbon materials on the BET surface area was evaluated using both a condensation model and experimental results. Comparison of data suggests that the hydrogen adsorption capacity clearly depends on the pore structure and so, on the accessibility to the internal surface.

Jiménez, Vicente; Ramírez-Lucas, Ana; Sánchez, Paula; Valverde, José Luís; Romero, Amaya

2012-01-01

364

Electrostatic deposition of nanofibers for sensor application  

OpenAIRE

This work addresses the formation of nanofibers (with hundred of nanometers) by using electrospinning (electrostatic deposition) aiming at applications as sensors. Different quantities of a colloidal dispersion of graphite particles were blended with polyacrylonitrile (PAN) and N,N dimethylformamide (DMF), resulting in a series of solutions with carbon concentrations ranging from 0 to 25%. Precipitation was observed depending on the concentration of carbon added to the precursor blend. As a c...

Ana Neilde Rodrigues da Silva; Rogerio Furlan; Idalia Ramos; Jorge Juan Santiago-Avilés

2005-01-01

365

Study of the fire resistant behavior of unfilled and carbon nanofibers reinforced polybenzimidazole coating for structural applications:  

OpenAIRE

With increasing interest in epoxy-based carbon fiber composites for structural applications, it is important to improve the fire resistant properties of these materials. The fire resistant performance of these materials can be improved either by using high performance epoxy resin for manufacturing carbon fiber composite or by protecting the previously used epoxy-based composite with some fire resistant coating. In this context, work is carried out to evaluate the fire resistance performance o...

Iqbal, H. M. S.; Stec, A. A.; Patel, P.; Bhowmik, S.; Benedictus, R.

2013-01-01

366

Visible light photocatalytic activity of novel MWCNT-doped ZnO electrospun nanofibers  

OpenAIRE

Multi wall carbon nanotube (MWCNT) doped ZnO nanofibers were fabricated by electrospinning for the first time. We have successfully demonstrated the photocatalytic activity of doped nanofibers under visible light. Scanning electron microscopy showed that the diameter of MWCNT-doped ZnO nanofibers varied from 120 to 300 nm without agglomeration of MWCNT. Fourier transform infrared spectroscopy and X-ray diffraction studies proved the formation of ZnO bond and wurtzite structure with smaller cr...

Zanetti, Marco

2012-01-01

367

Rippling of polymer nanofibers  

Science.gov (United States)

This paper studies the evolution mechanism of surface rippling in polymer nanofibers under axial stretching. This rippling phenomenon has been detected in as-electrospun polyacrylonitrile in recent single-fiber tension tests, and in electrospun polyimide nanofibers after imidization. We herein propose a one-dimensional nonlinear elastic model that takes into account the combined effect of surface tension and nonlinear elasticity during the rippling initiation and its evolution in compliant polymer nanofibers. The polymer nanofiber is modeled as an incompressible, isotropically hyperelastic Mooney-Rivlin solid. The fiber geometry prior to rippling is considered as a long circular cylinder. The governing equation of surface rippling is established through linear perturbation of the static equilibrium state of the nanofiber subjected to finite axial prestretching. The critical stretch and ripple wavelength are determined in terms of surface tension, elastic property, and fiber radius. Numerical examples are demonstrated to examine these dependencies. In addition, a critical fiber radius is determined, below which the polymer nanofibers are intrinsically unstable. The present model, therefore, is capable of predicting the rippling condition in compliant nanofibers, and can be further used as a continuum mechanics approach for the study of surface instability and nonlinear wave propagation in compliant fibers and wires at the nanoscale.

Wu, Xiang-Fa; Kostogorova-Beller, Yulia Y.; Goponenko, Alexander V.; Hou, Haoqing; Dzenis, Yuris A.

2008-12-01

368

High-performance hybrid (electrostatic double-layer and faradaic capacitor-based) polymer actuators incorporating nickel oxide and vapor-grown carbon nanofibers.  

Science.gov (United States)

The electrochemical and electromechanical properties of polymeric actuators prepared using nickel peroxide hydrate (NiO2·xH2O) or nickel peroxide anhydride (NiO2)/vapor-grown carbon nanofibers (VGCF)/ionic liquid (IL) electrodes were compared with actuators prepared using solely VGCFs or single-walled carbon nanotubes (SWCNTs) and an IL. The electrode in these actuator systems is equivalent to an electrochemical capacitor (EC) exhibiting both electrostatic double-layer capacitor (EDLC)- and faradaic capacitor (FC)-like behaviors. The capacitance of the metal oxide (NiO2·xH2O or NiO2)/VGCF/IL electrode is primarily attributable to the EDLC mechanism such that, at low frequencies, the strains exhibited by the NiO2·xH2O/VGCF/IL and NiO2/VGCF/IL actuators primarily result from the FC mechanism. The VGCFs in the NiO2·xH2O/VGCF/IL and NiO2/VGCF/IL actuators strengthen the EDLC mechanism and increase the electroconductivity of the devices. The mechanism underlying the functioning of the NiO2·xH2O/VGCF/IL actuator in which NiO2·xH2O/VGCF = 1.0 was found to be different from that of the devices produced using solely VGCFs or SWCNTs, which exhibited only the EDLC mechanism. In addition, it was found that both NiO2 and VGCFs are essential with regard to producing actuators that are capable of exhibiting strain levels greater than those of SWCNT-based polymer actuators and are thus suitable for practical applications. Furthermore, the frequency dependence of the displacement responses of the NiO2·xH2O/VGCF and NiO2/VGCF polymer actuators were successfully simulated using a double-layer charging kinetic model. This model, which accounted for the oxidization and reduction reactions of the metal oxide, can also be applied to SWCNT-based actuators. The results of electromechanical response simulations for the NiO2·xH2O/VGCF and NiO2/VGCF actuators predicted the strains at low frequencies as well as the time constants of the devices, confirming that the model is applicable not only to EDLC-based actuator systems but also to the fabricated EDLC/FC system. PMID:25354668

Terasawa, Naohiro; Asaka, Kinji

2014-12-01

369

Optimisation of Arsenic Adsorption from Water by Carbon Nanofibres Grown on Powdered Activated Carbon Impregnated with Nickel  

OpenAIRE

Contamination of water due to arsenic (As) is increasing in many parts of the world. The removal of As from aqueous solution by using impregnated carbon nanofibres (CNFs) as the adsorbent is reported in this paper. The effects of pH, CNFs dosage, contact time and initial concentration of arsenic were studied at room temperature (±25°C). The interactions among the parameters were also investigated. The data obtained from the adsorption experiment were analysed using statistical software in o...

Mamun, A. A.; Ma’an, F. R.; Zahirah, A. K.; Yehya, M. A.; Mohammed, A. R. S.; Alam, M. Z.; Muyibi, S. A.; Faris, I. A.; Azni, I.

2009-01-01

370

Superhydrophobic terpolymer nanofibers containing perfluoroethyl alkyl methacrylate by electrospinning  

Science.gov (United States)

A new statistical terpolymer containing perfluoroethyl alkyl methacrylate (Zonyl-TM), methyl methacrylate and butyl acrylate, poly(Zonyl-TM-ran-MMA-ran-BA) was synthesized in supercritical carbon dioxide at 200 bar and 80 °C using AIBN as an initiator by heterogeneous free radical copolymerization. Nanofibers of this terpolymer were produced by electrospinning from its DMF solution. The structural and thermal properties of terpolymers and electrospun poly(Zonyl-TM-MMA-BA) nanofibers were analyzed using Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy and differential scanning calorimetry. Nanofiber morphology was investigated by scanning electron microscopy. Electrospun nanofiber layer was found to be superhydrophobic with a water contact angle of 172 ± 1° and highly oleophobic with hexadecane, glycerol and ethylene glycol contact angles of 70 ± 1°, 167 ± 1° and 163 ± 1° respectively. The change of the contact angle results on the electrospun fiber layer and flat terpolymer surfaces by varying feed monomer composition were compared and discussed in the text.

Cengiz, Ugur; Avci, Merih Z.; Erbil, H. Yildirim; Sarac, A. Sezai

2012-05-01

371

Superhydrophobic terpolymer nanofibers containing perfluoroethyl alkyl methacrylate by electrospinning  

International Nuclear Information System (INIS)

A new statistical terpolymer containing perfluoroethyl alkyl methacrylate (Zonyl-TM), methyl methacrylate and butyl acrylate, poly(Zonyl-TM-ran-MMA-ran-BA) was synthesized in supercritical carbon dioxide at 200 bar and 80 °C using AIBN as an initiator by heterogeneous free radical copolymerization. Nanofibers of this terpolymer were produced by electrospinning from its DMF solution. The structural and thermal properties of terpolymers and electrospun poly(Zonyl-TM-MMA-BA) nanofibers were analyzed using Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy and differential scanning calorimetry. Nanofiber morphology was investigated by scanning electron microscopy. Electrospun nanofiber layer was found to be superhydrophobic with a water contact angle of 172 ± 1° and highly oleophobic with hexadecane, glycerol and ethylene glycol contact angles of 70 ± 1°, 167 ± 1° and 163 ± 1° respectively. The change of the contact angle results on the electrospun fiber layer and flat terpolymer surfaces by varying feed monomer composition were compared and discussed in the text.

372

The preparation of mesoporous SnO2 nanotubes by carbon nanofibers template and their lithium storage properties  

International Nuclear Information System (INIS)

Mesoporous SnO2 nanotubes are prepared by templating against carbon fibers through a facile solution approach followed by calcination at 800 °C for 2 h. The nanotubes are characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and nitrogen adsorption. The electrochemical performances as the anodes of lithium-ions batteries are studied by the cyclic voltammogram (CV) and galvanostatic discharge–charge voltage tests. Because of its unique structure (the mesoporous wall, internal void and open ends), the as-obtained mesoporous SnO2 nanotubes demonstrate a reversible capacity of 585 mA h g?1 up to 50 cycles at a high current density of 400 mA g?1

373

Human umbilical vein endothelial cell interaction with phospholipid polymer nanofibers coated by micro-patterned diamond-like carbon (DLC)  

Science.gov (United States)

Blood-contacting medical devices should possess the surface properties with the following two important characteristics: The first is the anti-thrombogenicity of the material surface and the second is the re-endothelialization over the device surface after long-term implantation, because endothelial cells have excellent anticoagulant properties in blood vessels. To develop highly hemocompatible materials that could promote surface endothelialization, we investigated biocompatible polymers coated with thin diamond-like carbon (DLC) film. In this research, we examined the viability of human umbilical vein endothelial cells (HUVECs) for hydrophilic 2-methacryloyloxyethyl phosphorylcholine (MPC) fibers with DLC coatings, both of which were known to be anti-thrombogenic. DLC was synthesized on MPC by varying the ratio of covered area by patterned DLC. HUVECs were seeded on DLC-coated MPC for 6 days. The results indicated that the MPC surface with DLC did not disturb HUVEC proliferation in 6 days of culture. Additionally, we are currently making strong efforts to fabricate MPC fibers with bFGF which is an important growth factor involved in cell proliferation. MPC containing bFGF with DLC coatings could be extensively utilized for blood-contacting medical devices.

Yoshida, Soki; Hasebe, Terumitsu; Suzuki, Tetsuya; Hotta, Atsushi

2013-03-01

374

Characterization of nanocarbons (nanotubes and nanofibers) by Inverse Gas Chromatography  

International Nuclear Information System (INIS)

The adsorption of different alkanes (linear and cyclic), aromatics and chlorohydrocarbons on non-microporous carbons-carbon nanotubes (CNTs) and carbon nanofibres (CNFs)- was studied in this work by inverse gas chromatography (IGC). Capacity of adsorption was derived from the isotherms of adsorption, whereas thermodynamic properties (enthalpy of adsorption, surface free energy characteristics) have been determined from chromatographic retention data. CNTs present the highest adsorption capacity. From surface free energy data, enthalpies of adsorption of polar compounds were divided into dispersive and specific contributions. The interactions of cyclic (benzene and cyclohexane) and chlorinated compounds (trichloroethylene, tetrachloroethylene and chloroform) with the surfaces are mainly dispersive over all the carbons tested, being CNTs the material with the highest dispersive contribution. Adsorption parameters were correlated with morphological and chemical properties of the materials

375

Characterization of nanocarbons (nanotubes and nanofibers) by Inverse Gas Chromatography  

Science.gov (United States)

The adsorption of different alkanes (linear and cyclic), aromatics and chlorohydrocarbons on non-microporous carbons-carbon nanotubes (CNTs) and carbon nanofibres (CNFs)- was studied in this work by inverse gas chromatography (IGC). Capacity of adsorption was derived from the isotherms of adsorption, whereas thermodynamic properties (enthalpy of adsorption, surface free energy characteristics) have been determined from chromatographic retention data. CNTs present the highest adsorption capacity. From surface free energy data, enthalpies of adsorption of polar compounds were divided into dispersive and specific contributions. The interactions of cyclic (benzene and cyclohexane) and chlorinated compounds (trichloroethylene, tetrachloroethylene and chloroform) with the surfaces are mainly dispersive over all the carbons tested, being CNTs the material with the highest dispersive contribution. Adsorption parameters were correlated with morphological and chemical properties of the materials.

Díaz, E.; Ordóñez, S.; Vega, A.

2007-04-01

376

Nanomechanical testing of polymeric nanofibers  

Science.gov (United States)

Biodegradable polymeric nanofibrous scaffold comprises individual nanofibers where their stiffnesses can promote or undermine the various cellular functions as well as structural integrity of the scaffold. As such, there is a need to investigate the nanomechanical properties of these individual nanofibers. However, conducting mechanical tests of individual fibers at the nanometer scale can pose great challenges and difficulties. Here, we present novel techniques to perform nanomechanical testing of individual polymeric nanofibers. For demonstration of the nano tensile tests, polycaprolactone (PCL) nanofibers were produced via electrospinning. These fibers were deposited across two parallel edges of a cardboard frame so that a single nanofiber can be isolated for tensile test using a nano tensile tester. For nanoscale three-point bend test, a Poly (L-lactic acid) (PLLA) nanofiber was suspended across a microsized groove etched on a silicon wafer. An atomic force microscope (AFM) tip was then used to apply a point load on the mid-span of the suspended fiber. Beam bending theory was then used to calculate the elastic modulus of the nanofiber. For nanoindentation test, a PLLA nanofiber was deposited on a mica substrate and an AFM tip used to indent the nanofiber. Modified Hertz theory for normal contact was then used to evaluate the elastic modulus of the nanofiber.

Tan, E. P. S.; Lim, C. T.

2005-04-01

377

Electrostatic deposition of nanofibers for sensor application  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english This work addresses the formation of nanofibers (with hundred of nanometers) by using electrospinning (electrostatic deposition) aiming at applications as sensors. Different quantities of a colloidal dispersion of graphite particles were blended with polyacrylonitrile (PAN) and N,N dimethylformamide [...] (DMF), resulting in a series of solutions with carbon concentrations ranging from 0 to 25%. Precipitation was observed depending on the concentration of carbon added to the precursor blend. As a consequence, the relative viscosity decreases, due to PAN molecules removal from the solution by carbon particles adsorption, forming precipitates. The resulting fibers show an irregular shape, as observed by SEM and the diameters decrease with the increase of the carbon concentration in the precursor blend. The incorporation of carbon particles in the fibers was confirmed by FTIRS and Raman spectroscopy.

Ana Neilde Rodrigues da, Silva; Rogerio, Furlan; Idalia, Ramos; Jorge Juan, Santiago-Avilés.

2005-03-01

378

Electrostatic deposition of nanofibers for sensor application  

Directory of Open Access Journals (Sweden)

Full Text Available This work addresses the formation of nanofibers (with hundred of nanometers by using electrospinning (electrostatic deposition aiming at applications as sensors. Different quantities of a colloidal dispersion of graphite particles were blended with polyacrylonitrile (PAN and N,N dimethylformamide (DMF, resulting in a series of solutions with carbon concentrations ranging from 0 to 25%. Precipitation was observed depending on the concentration of carbon added to the precursor blend. As a consequence, the relative viscosity decreases, due to PAN molecules removal from the solution by carbon particles adsorption, forming precipitates. The resulting fibers show an irregular shape, as observed by SEM and the diameters decrease with the increase of the carbon concentration in the precursor blend. The incorporation of carbon particles in the fibers was confirmed by FTIRS and Raman spectroscopy.

Ana Neilde Rodrigues da Silva

2005-03-01

379

Tailored surface structure of LiFePO4/C nanofibers by phosphidation and their electrochemical superiority for lithium rechargeable batteries.  

Science.gov (United States)

We offer a brand new strategy for enhancing Li ion transport at the surface of LiFePO4/C nanofibers through noble Li ion conducting pathways built along reduced carbon webs by phosphorus. Pristine LiFePO4/C nanofibers composed of 1-dimensional (1D) LiFePO4 nanofibers with thick carbon coating layers on the surfaces of the nanofibers were prepared by the electrospinning technique. These dense and thick carbon layers prevented not only electrolyte penetration into the inner LiFePO4 nanofibers but also facile Li ion transport at the electrode/electrolyte interface. In contrast, the existing strong interactions between the carbon and oxygen atoms on the surface of the pristine LiFePO4/C nanofibers were weakened or partly broken by the adhesion of phosphorus, thereby improving Li ion migration through the thick carbon layers on the surfaces of the LiFePO4 nanofibers. As a result, the phosphidated LiFePO4/C nanofibers have a higher initial discharge capacity and a greatly improved rate capability when compared with pristine LiFePO4/C nanofibers. Our findings of high Li ion transport induced by phosphidation can be widely applied to other carbon-coated electrode materials. PMID:24786736

Lee, Yoon Cheol; Han, Dong-Wook; Park, Mihui; Jo, Mi Ru; Kang, Seung Ho; Lee, Ju Kyung; Kang, Yong-Mook

2014-06-25

380

Engineered Polymer Composites Through Electrospun Nanofiber Coating of Fiber Tows  

Science.gov (United States)

Composite materials offer significant weight savings in many aerospace applications. The toughness of the interface of fibers crossing at different angles often determines failure of composite components. A method for toughening the interface in fabric and filament wound components using directly electrospun thermoplastic nanofiber on carbon fiber tow is presented. The method was first demonstrated with limited trials, and then was scaled up to a continuous lab scale process. Filament wound tubes were fabricated and tested using unmodified baseline towpreg material and nanofiber coated towpreg.

Kohlman, Lee W.; Bakis, Charles; Williams, Tiffany S.; Johnston, James C.; Kuczmarski, Maria A.; Roberts, Gary D.

2014-01-01

381

Electrorheology of nanofiber suspensions  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Electrorheological (ER fluid, which can be transformed rapidly from a fluid-like state to a solid-like state under an external electric field, is considered to be one of the most important smart fluids. However, conventional ER fluids based on microparticles are subjected to challenges in practical applications due to the lack of versatile performances. Recent researches of using nanoparticles as the dispersal phase have led to new interest in the development of non-conventional ER fluids with improved performances. In this review, we especially focus on the recent researches on electrorheology of various nanofiber-based suspensions, including inorganic, organic, and inorganic/organic composite nanofibers. Our goal is to highlight the advantages of using anisotropic nanostructured materials as dispersal phases to improve ER performances.

Yin Jianbo

2011-01-01

382

Electrospinning of ceramic nanofibers  

OpenAIRE

Silicon Carbide (SiC) nanofibers of diameters as low as 20 nm are fabricated. The fibers were produced through the electrostatic spinning of the preceramic poly(carbomethylsilane) with pyrolysis to ceramic. A new technique was used where the preceramic was blended with polystyrene (PS) and, subsequent to electrospinning, was exposed to UV to crosslink the PS and prevent fibers flowing during pyrolysis. Electrospun SiC fibers were characterized by FTIR, TGA-DTA, SEM, TEM, XRD, and SAED. Fibers...

Eick, Benjamin M.

2008-01-01

383

Application of Nanofiber Technology to Nonwoven Thermal Insulation  

Directory of Open Access Journals (Sweden)

Full Text Available Nanofiber technology (fiber diameter less than 1 micrometer is under development for future Army lightweight protective clothing systems. Nanofiber applications for ballistic and chemical/biological protection are being actively investigated, but the thermal properties of nanofibers and their potential protection against cold environments are relatively unknown. Previous studies have shown that radiative heat transfer in fibrous battings is minimized at fiber diameters between 5 and 10 micrometers. However, the radiative heat transfer mechanism of extremely small diameter fibers of less than 1 micrometer diameter is not well known. Previous studies were limited to glass fibers, which have a unique set of thermal radiation properties governed by the thermal emissivity properties of glass. We are investigating the thermal transfer properties of high loft nanofiber battings composed of carbon fiber and various polymeric fibers such as polyacrylonitrile, nylon, and polyurethane. Thermal insulation battings incorporating nanofibers could decrease the weight and bulk of current thermal protective clothing, and increase mobility for soldiers in the battlefield.

Phillip W. Gibson, Ph.D

2007-07-01

384

Electrospinning highly aligned long polymer nanofibers on large scale by using a tip collector  

Science.gov (United States)

The authors developed a very simple alignment technique by which highly aligned polymer nanofibers of length >25cm were electrospun over a lateral range as large as 63cm. This technique is based on a modified configuration, application of a tip collector, and sideward ejection. The salient feature of the electrospinning process is the production of single nanofibers one by one, which was clearly confirmed by real-time images taken by a high-speed camera. Aligned polycaprolactone, polyacrylonitrile, and carbon nanofibers were prepared by this method.

Rafique, Javed; Yu, Jie; Yu, Jiliang; Fang, Gang; Wong, K. W.; Zheng, Z.; Ong, H. C.; Lau, W. M.

2007-08-01

385

Investigating Impact of The Interfacial Debonding on The Mechanical Propertiesof NanoFiber Reinforced Composites  

Directory of Open Access Journals (Sweden)

Full Text Available This work investigates the influence of the interfacial debonding in a nanofiber reinforced composite on the mechanical properties. Mainly, three dimensional-axisymmetric finite element analysis is adopted to study a representative volume element (RVE which is consist of carbon nanofiber confined by a polymeric matrix and subjected to axial tension. Besides, a longitudinal interfacial debonding is imposed along the interfacial nanofiber/matrix. The result of the FEA demonstrate a significant impact of the interfacial debonding on the Young’s modulus of the nanocomposite.

Waleed.K. Ahmed

2014-01-01

386

Metal oxide nanofiber gas sensor  

International Nuclear Information System (INIS)

There is much advancement on gas sensors with the growth in the synthesis of nanomaterials. In this age of industrialization, there is a key need to develop stable gas sensors with fast response and recovery time. In this study, Silicon dioxide (SiO2) nanofibers based gas sensors were developed and oxygen gas sensing properties were investigated with different oxygen gas environment. SiO2 nanofibers were synthesized through electrospinning process. Electrospinning being an efficient and versatile technique produced long nanofibers with 100 p?m length and 100-150 nm diameter. The characterization of nanofibers was done by Scanning Electron Microscopy. Nickel (Ni) contacts with 80 nm thickness were defined lithographically on glass substrate. The gas sensing performance was evaluated by AC and DC measurements. Devices based on Bi doped and undoped SiO2 nanofibers were fabricated. The fast response (time 51 secs) and recovery (time 34 secs) of SiO2 nanofibers based device had a strong potential for commercial use. The fast response and recovery time is attributed to the porous and high surface to volume ratio of nanofibers. (author)