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Sample records for conducting carbon ceramic

  1. Proton conducting cerate ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Coffey, G.W.; Pederson, L.R.; Armstrong, T.R.; Bates, J.L.; Weber, W.J. [Pacific Northwest Lab., Richland, WA (United States)

    1995-08-01

    Cerate perovskites of the general formula AM{sub x}Ce{sub 1-x}O{sub 3-{delta}}, where A = Sr or Ba and where M = Gd, Nd, Y, Yb or other rare earth dopant, are known to conduct a protonic current. Such materials may be useful as the electrolyte in a solid oxide fuel cell operating at intermediate temperatures, as an electrochemical hydrogen separation membrane, or as a hydrogen sensor. Conduction mechanisms in these materials were evaluated using dc cyclic voltammetry and mass spectrometry, allowing currents and activation energies for proton, electron, and oxygen ion contributions to the total current to be determined. For SrYb{sub 0.05}Ce{sub 0.95}O{sub 3-{delta}}, one of the best and most environmentally stable compositions, proton conduction followed two different mechanisms: a low temperature process, characterized by an activation energy of 0.42{+-}0.04 eV, and a high temperature process, characterized by an activation energy of 1.38{+-}0.13 eV. It is believed that the low temperature process is dominated by grain boundary conduction while bulk conduction is responsible for the high temperature process. The activation energy for oxygen ion conduction (0.97{+-}0.10 eV) agrees well with other oxygen conductors, while that for electronic conduction, 0.90{+-}0.09 eV, is affected by a temperature-dependent electron carrier concentration. Evaluated by direct measurement of mass flux through a dense ceramic with an applied dc field, oxygen ions were determined to be the majority charge carrier except at the lowest temperatures, followed by electrons and then protons.

  2. Conductive ceramic composition and method of preparation

    Science.gov (United States)

    Smith, J.L.; Kucera, E.H.

    1991-04-16

    A ceramic anode composition is formed of a multivalent metal oxide or oxygenate such as an alkali metal, transition metal oxygenate. The anode is prepared as a non-stoichiometric crystalline structure by reaction and conditioning in a hydrogen gas cover containing minor proportions of carbon dioxide and water vapor. The structure exhibits a single phase and substantially enhanced electrical conductivity over that of the corresponding stoichiometric structure. Unexpectedly, such oxides and oxygenates are found to be stable in the reducing anode fuel gas of a molten carbonate fuel cell. 4 figures.

  3. Proton-conducting cerate ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Pederson, L.R.; Coffey, G.W.; Bates, J.L.; Weber, W.J. [Pacific Northwest National Lab., Richland, WA (United States)

    1996-08-01

    Single-cell solid oxide fuel cells were constructed using strontium cerate as the electrolyte and their performance tested. Like certain zirconates, hafnates, and tantalates, the cerate perovskites are among a class of solid electrolytes that conduct protons at elevated temperatures. Depending on the temperature and chemical environment, these ceramics also support electronic and oxygen ion currents. A maximum power output of {approx}100 mW per cm{sup 2} electrolyte surface area was obtained at 900{degrees}C using 4% hydrogen as the fuel and air as the oxidant. A series of rare earth/ceria/zirconia were prepared and their electrical properties characterized. Rare earth dopants included ytterbia, yttria, terbia, and europia. Ionic conductivities were highest for rare earth/ceria and rare earth zirconia compositions; a minimum in ionic conductivity for all series were found for equimolar mixtures of ceria and zirconia. Cerium oxysulfide is of interest in fossil energy applications because of its high chemical stability and refractory nature. An alternative synthesis route to preparing cerium oxysulfide powders has been developed using combustion techniques.

  4. Proton conducting ceramic membranes for hydrogen separation

    Science.gov (United States)

    Elangovan, S [South Jordan, UT; Nair, Balakrishnan G [Sandy, UT; Small, Troy [Midvale, UT; Heck, Brian [Salt Lake City, UT

    2011-09-06

    A multi-phase proton conducting material comprising a proton-conducting ceramic phase and a stabilizing ceramic phase. Under the presence of a partial pressure gradient of hydrogen across the membrane or under the influence of an electrical potential, a membrane fabricated with this material selectively transports hydrogen ions through the proton conducting phase, which results in ultrahigh purity hydrogen permeation through the membrane. The stabilizing ceramic phase may be substantially structurally and chemically identical to at least one product of a reaction between the proton conducting phase and at least one expected gas under operating conditions of a membrane fabricated using the material. In a barium cerate-based proton conducting membrane, one stabilizing phase is ceria.

  5. Carbon nanofillers for machining insulating ceramics

    Directory of Open Access Journals (Sweden)

    Olivier Malek

    2011-10-01

    Full Text Available The implementation of ceramics in emerging applications is principally limited by the final machining process necessary for producing microcomponents with complex geometries. The addition of carbon nanotubes greatly enhances the electrical properties of insulating ceramics allowing electrical discharge machining to be used to manufacture intricate parts. Meanwhile other properties of the ceramic may be either preserved or even improved. For the first time, a silicon nitride/carbon nanotubes microgear is electrically discharge machined with a remarkably high material removal rate, low surface roughness, and low tool wear. This offers unprecedented opportunities for the manufacture of complicated ceramic parts by adding carbon nanotubes for new engineering and biomedical applications.

  6. Proton conducting ceramics in membrane separations

    Science.gov (United States)

    Brinkman, Kyle S; Korinko, Paul S; Fox, Elise B; Chen, Frank

    2015-04-14

    Perovskite materials of the general formula SrCeO.sub.3 and BaCeO.sub.3 are provided having improved conductivity while maintaining an original ratio of chemical constituents, by altering the microstructure of the material. A process of making Pervoskite materials is also provided in which wet chemical techniques are used to fabricate nanocrystalline ceramic materials which have improved grain size and allow lower temperature densification than is obtainable with conventional solid-state reaction processing.

  7. Proton conducting ceramics in membrane separations

    Energy Technology Data Exchange (ETDEWEB)

    Brinkman, Kyle S; Korinko, Paul S; Fox, Elise B; Chen, Frank

    2015-04-14

    Perovskite materials of the general formula SrCeO.sub.3 and BaCeO.sub.3 are provided having improved conductivity while maintaining an original ratio of chemical constituents, by altering the microstructure of the material. A process of making Pervoskite materials is also provided in which wet chemical techniques are used to fabricate nanocrystalline ceramic materials which have improved grain size and allow lower temperature densification than is obtainable with conventional solid-state reaction processing.

  8. Studies and Properties of Ceramics with High Thermal Conductivity

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The sintering technology of the AlN ceramics power were discussed. It is discussed that the compound sintering aids is consistent with the enhancement of the the thermal conductivity of AlN ceramics, and sintering technics is helped to the improvement of density. It is analyzed how to sinter machinable AlN ceramics with high thermal conductivity. And the microstructure of compound ceramics based on AlN was studied.

  9. Preparation of Ceramic-Bonded Carbon Block for Blast Furnace

    Science.gov (United States)

    Li, Yiwei; Li, Yawei; Sang, Shaobai; Chen, Xilai; Zhao, Lei; Li, Yuanbing; Li, Shujing

    2014-01-01

    Traditional carbon blocks for blast furnaces are mainly produced with electrically calcined anthracite owing to its good hot metal corrosion resistance. However, this kind of material shows low thermal conductivity and does not meet the demands for cooling of the hearth and the bottom of blast furnaces. In this article, a new kind of a high-performance carbon block has been prepared via ceramic-bonded carbon (CBC) technology in a coke bed at 1673 K (1400 °C) using artificial graphite aggregate, alumina, metallic aluminum, and silicon powders as starting materials. The results showed that artificial graphite aggregates were strongly bonded by the three-dimensional network of ceramic phases in carbon blocks. In this case, the good resistance of the CBC blocks against erosion/corrosion by the hot metal is provided by the ceramic matrix and the high thermal conductivity by the graphite aggregates. The microstructure of this carbon block resembles that of CBC composites with a mean pore size of less than 0.1 μm, and up to 90 pct of the porosity shows a pore size <1 μm. Its thermal conductivity is higher than 30 W · m-1 · K-1 [293 K (20 °C)]. Meanwhile, its hot metal corrosion resistance is better than that of traditional carbon blocks.

  10. Thermal Conductivity Measurement and Analysis of Fully Ceramic Microencapsulated fuel

    Energy Technology Data Exchange (ETDEWEB)

    Lee, H. G.; Kim, D. J.; Park, J. Y.; Kim, W. J. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Lee, S. J. [KEPCO Nuclear Fuel, Daejeon (Korea, Republic of)

    2015-10-15

    FCM nuclear fuel is composed of tristructural isotropic(TRISO) fuel particle and SiC ceramic matrix. SiC ceramic matrix play an essential part in protecting fission product. In the FCM fuel concept, fission product is doubly protected by TRISO coating layer and SiC ceramic matrix in comparison with the current commercial UO2 fuel system of LWR. In addition to a safety enhancement of FCM fuel, thermal conductivity of SiC ceramic matrix is better than that of UO2 fuel. Because the centerline temperature of FCM fuel is lower than that of the current UO2 fuel due to the difference of thermal conductivity of fuel, an operational release of fission products from the fuel can be reduced. SiC ceramic has attracted for nuclear fuel application due to its high thermal conductivity properties with good radiation tolerant properties, a low neutron absorption cross-section and a high corrosion resistance. Thermal conductivity of ceramic matrix composite depends on the thermal conductivity of each component and the morphology of reinforcement materials such as fibers and particles. There are many results about thermal conductivity of fiber-reinforced composite like as SiCf/SiC composite. Thermal conductivity of SiC ceramics and FCM pellets with the volume fraction of TRISO particles were measured and analyzed by analytical models. Polycrystalline SiC ceramics and FCM pellets with TRISO particles were fabricated by hot press sintering with sintering additives. Thermal conductivity of the FCM pellets with TRISO particles of 0 vol.%, 10 vol.%, 20 vol.%, 30 vol.% and 40 vol.% show 68.4, 52.3, 46.8, 43.0 and 34.5 W/mK, respectively. As the volume fraction of TRISO particles increased, the measured thermal conductivity values closely followed the prediction of Maxwell's equation.

  11. Development of an Innovative High-Thermal Conductivity UO2 Ceramic Composites Fuel Pellets with Carbon Nano-Tubes Using Spark Plasma Sintering

    Energy Technology Data Exchange (ETDEWEB)

    Subhash, Ghatu [Univ. of Florida, Gainesville, FL (United States); Wu, Kuang-Hsi [Florida International Univ. (FIU), Miami, FL (United States); Tulenko, James [Univ. of Florida, Gainesville, FL (United States)

    2014-03-10

    Uranium dioxide (UO2) is the most common fuel material in commercial nuclear power reactors. Despite its numerous advantages such as high melting point, good high-temperature stability, good chemical compatibility with cladding and coolant, and resistance to radiation, it suffers from low thermal conductivity that can result in large temperature gradients within the UO2 fuel pellet, causing it to crack and release fission gases. Thermal swelling of the pellets also limits the lifetime of UO2 fuel in the reactor. To mitigate these problems, we propose to develop novel UO2 fuel with uniformly distributed carbon nanotubes (CNTs) that can provide high-conductivity thermal pathways and can eliminate fuel cracking and fission gas release due to high temperatures. CNTs have been investigated extensively for the past decade to explore their unique physical properties and many potential applications. CNTs have high thermal conductivity (6600 W/mK for an individual single- walled CNT and >3000 W/mK for an individual multi-walled CNT) and high temperature stability up to 2800°C in vacuum and about 750°C in air. These properties make them attractive candidates in preparing nano-composites with new functional properties. The objective of the proposed research is to develop high thermal conductivity of UO2–CNT composites without affecting the neutronic property of UO2 significantly. The concept of this goal is to utilize a rapid sintering method (5–15 min) called spark plasma sintering (SPS) in which a mixture of CNTs and UO2 powder are used to make composites with different volume fractions of CNTs. Incorporation of these nanoscale materials plays a fundamentally critical role in controlling the performance and stability of UO2 fuel. We will use a novel in situ growth process to grow CNTs on UO2 particles for rapid sintering and develop UO2-CNT composites. This method is expected to provide a uniform distribution of CNTs at various volume fractions so that a high

  12. Cupric Hexacyanoferrate Nanoparticle Modified Carbon Ceramic Composite Electrodes

    Institute of Scientific and Technical Information of China (English)

    WANG,Peng(王鹏); ZHU,Guo-Yi(朱果逸)

    2002-01-01

    Graphite powder-supported cupric hexacyanoferrate (CuHCF)nanoparticles were dispersed into methyltrimethoxysilane-based gels to produce a conducting carbon ceramic composite, which was used as electrode material to fabricate surface-renewable CuHCF-modified electrodes. Electrochemical behavior of the CuHCF-modified carbon ceramic composite electrodes was characterized using cyclic and square-wave voitammetry.Cyclic voltammograms at various scan rates indicated that peak currents were surface-confined at low scan rates. In the presence of glutathione, a clear electrocatalytic response was observed at the CuHCF-modified composite electrodes. In addition, the electrodes exhibited a distinct advantage of reproducible surface-renewal by simple mechanical polishing on emery paper, as well as ease of preparation, and good chemical and mechanical stability in a flowing stream.

  13. Cupric Hexacyanoferrate Nanoparticle Modified Carbon Ceramic Composite Electrodes

    Institute of Scientific and Technical Information of China (English)

    WANG,Peng; ZHU,Guo-Yi

    2002-01-01

    Graphite powder-supported cupric hexacyanoferrate(CuHCF) nanoparticles were dispersed into methyltrimethoxysilane-based gels to produce a conducting carbon ceramic composite,which was used as electrode materials to fabricate surface-renewable CuHCF-modified electrodes.Electrochemical behavior of the CuHCF-modified carbon ceramic composite electrodes was characterized using cyclic and square-wave voltammetry. Cyclinc voltammograms at various scan rates indicated that peak currents were suface-confined at low scan rates.In the presence of glutathione,a clear electrocatalytic response was observed at the CuHCF-modified composite electrodes.In addition,the electrodes exhibited a distinct advantage of reproducible surface-renewal by simple mechanical polishing on emery paper,as well as ease of preparation,and good chemical and mechanical stability in a flowing stream.

  14. Development of high-thermal-conductivity silicon nitride ceramics

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    You Zhou

    2015-09-01

    Full Text Available Silicon nitride (Si3N4 with high thermal conductivity has emerged as one of the most promising substrate materials for the next-generation power devices. This paper gives an overview on recent developments in preparing high-thermal-conductivity Si3N4 by a sintering of reaction-bonded silicon nitride (SRBSN method. Due to the reduction of lattice oxygen content, the SRBSN ceramics could attain substantially higher thermal conductivities than the Si3N4 ceramics prepared by the conventional gas-pressure sintering of silicon nitride (SSN method. Thermal conductivity could further be improved through increasing the β/α phase ratio during nitridation and enhancing grain growth during post-sintering. Studies on fracture resistance behaviors of the SRBSN ceramics revealed that they possessed high fracture toughness and exhibited obvious R-curve behaviors. Using the SRBSN method, a Si3N4 with a record-high thermal conductivity of 177 Wm−1K−1 and a fracture toughness of 11.2 MPa m1/2 was developed. Studies on the influences of two typical metallic impurity elements, Fe and Al, on thermal conductivities of the SRBSN ceramics revealed that the tolerable content limits for the two impurities were different. While 1 wt% of impurity Fe hardly degraded thermal conductivity, only 0.01 wt% of Al caused large decrease in thermal conductivity.

  15. Thermal conductivity of single crystal and ceramic AlN

    Science.gov (United States)

    AlShaikhi, A.; Srivastava, G. P.

    2008-04-01

    We have applied the Callaway theory and used a detailed account of three-phonon scattering processes to calculate the thermal conductivity of three AlN single crystal samples containing different amounts of oxygen and two AlN ceramic samples with different grain sizes and oxygen contamination levels. The N-drift contribution to the total conductivity has been quantified. The influence on the thermal conductivity of oxygen-related defects, and grain boundaries in ceramic samples, has been investigated. The theoretical results obtained from this work are in good agreement with available experimental data. Our calculations suggest that the "effective" boundary length is greater than the reported grain size for each of the two ceramic samples studied by Watari et al. [J. Mater. Res. 17, 2940 (2002)].

  16. Thermal conductivity analysis of SiC ceramics and fully ceramic microencapsulated fuel composites

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hyeon-Geun, E-mail: hglee@kaeri.re.kr [Korea Atomic Energy Research Institute, 989-111 Daedeok-daero, Yuseong-gu, Daejeon (Korea, Republic of); Kim, Daejong [Korea Atomic Energy Research Institute, 989-111 Daedeok-daero, Yuseong-gu, Daejeon (Korea, Republic of); Lee, Seung Jae [KEPCO Nuclear Fuel, 242, Daedeok-daero, Yuseong-gu, Daejeon (Korea, Republic of); Park, Ji Yeon; Kim, Weon-Ju [Korea Atomic Energy Research Institute, 989-111 Daedeok-daero, Yuseong-gu, Daejeon (Korea, Republic of)

    2017-01-15

    Highlights: • Thermal conductivity of SiC ceramics and FCM pellets was measured and discussed. • Thermal conductivity of FCM pellets was analyzed by the Maxwell-Eucken equation. • Effective thermal conductivity of TRISO particles applied in this study was assumed. - Abstract: The thermal conductivity of SiC ceramics and FCM fuel composites, consisting of a SiC matrix and TRISO coated particles, was measured and analyzed. SiC ceramics and FCM pellets were fabricated by hot press sintering with Al{sub 2}O{sub 3} and Y{sub 2}O{sub 3} sintering additives. Several factors that influence thermal conductivity, specifically the content of sintering additives for SiC ceramics and the volume fraction of TRISO particles and the matrix thermal conductivity of FCM pellets, were investigated. The thermal conductivity values of samples were analyzed on the basis of their microstructure and the arrangement of TRISO particles. The thermal conductivity of the FCM pellets was compared to that predicted by the Maxwell-Eucken equation and the thermal conductivity of TRISO coated particles was calculated. The thermal conductivity of FCM pellets in various sintering conditions was in close agreement to that predicted by the Maxwell-Eucken equation with the fitted thermal conductivity value of TRISO particles.

  17. Ionic conductivity enhancement of polymer electrolytes with ceramic nanowire fillers.

    Science.gov (United States)

    Liu, Wei; Liu, Nian; Sun, Jie; Hsu, Po-Chun; Li, Yuzhang; Lee, Hyun-Wook; Cui, Yi

    2015-04-08

    Solid-state electrolytes provide substantial improvements to safety and electrochemical stability in lithium-ion batteries when compared with conventional liquid electrolytes, which makes them a promising alternative technology for next-generation high-energy batteries. Currently, the low mobility of lithium ions in solid electrolytes limits their practical application. The ongoing research over the past few decades on dispersing of ceramic nanoparticles into polymer matrix has been proved effective to enhance ionic conductivity although it is challenging to form the efficiency networks of ionic conduction with nanoparticles. In this work, we first report that ceramic nanowire fillers can facilitate formation of such ionic conduction networks in polymer-based solid electrolyte to enhance its ionic conductivity by three orders of magnitude. Polyacrylonitrile-LiClO4 incorporated with 15 wt % Li0.33La0.557TiO3 nanowire composite electrolyte exhibits an unprecedented ionic conductivity of 2.4 × 10(-4) S cm(-1) at room temperature, which is attributed to the fast ion transport on the surfaces of ceramic nanowires acting as conductive network in the polymer matrix. In addition, the ceramic-nanowire filled composite polymer electrolyte shows an enlarged electrochemical stability window in comparison to the one without fillers. The discovery in the present work paves the way for the design of solid ion electrolytes with superior performance.

  18. Electronic Conductivity of Vanadium-Tellurite Glass-Ceramics

    DEFF Research Database (Denmark)

    Kjeldsen, Jonas; Yue, Yuanzheng; Bragatto, Caio B.

    2013-01-01

    In this paper, we investigate the electronic conductivity of 2TeO2-V2O5 glass-ceramics with crystallinity ranging from 0 to 100 wt.%, i.e., from entirely amorphous to completely crystalline. The glass is prepared by the melt quenching technique, and the crystal is prepared by subsequent heat trea...... as percolation theory. This work implies that, based on its electronic conductivity, vitreous 2TeO2-V2O5 is more suitable as a cathode material in secondary batteries compared to a 2TeO2-V2O5 glass-ceramic.......In this paper, we investigate the electronic conductivity of 2TeO2-V2O5 glass-ceramics with crystallinity ranging from 0 to 100 wt.%, i.e., from entirely amorphous to completely crystalline. The glass is prepared by the melt quenching technique, and the crystal is prepared by subsequent heat...... treatment thereof. Glass-ceramics are prepared by mixing glass and crystal powder, followed by a sintering procedure. Activation energies for electronic conduction in the glass and in the crystal are determined by fitting the Mott-Austin equation to the electronic conductivity data obtained by impedance...

  19. Thermal conductivity peaks in old and new ceramic superconductors

    Science.gov (United States)

    Williams, Wendell S.

    1993-07-01

    A sharp peak in the thermal conductivity curve of high Tc ceramic superconductors below Tc found by many workers is compared with a similar but even larger effect found earlier for niobium carbide — an older ceramic superconductor — by Radosevich and Williams. The interpretation of this peak given in the literature for the high Tc materials — reduced phonon-electron scattering below Tc as the superconducting energy gap opens — is the same as that established earlier for niobium carbide, which can be treated by BCS/BRT theory, thus lending support to this view. The role of point defects (vacancies) in both materials is also emphasized.

  20. Mixed oxygen ion/electron-conducting ceramics for oxygen separation

    Energy Technology Data Exchange (ETDEWEB)

    Stevenson, J.W.; Armstrong, T.R.; Armstrong, B.L. [Pacific Northwest National Lab., Richland, WA (United States)

    1996-08-01

    Mixed oxygen ion and electron-conducting ceramics are unique materials that can passively separate high purity oxygen from air. Oxygen ions move through a fully dense ceramic in response to an oxygen concentration gradient, charge-compensated by an electron flux in the opposite direction. Compositions in the system La{sub 1{minus}x}M{sub x}Co{sub 1{minus}y{minus}z}Fe{sub y}N{sub z}O{sub 3{minus}{delta}}, perovskites where M=Sr, Ca, and Ba, and N=Mn, Ni, Cu, Ti, and Al, have been prepared and their electrical, oxygen permeation, oxygen vacancy equilibria, and catalytic properties evaluated. Tubular forms, disks, and asymmetric membrane structures, a thin dense layer on a porous support of the same composition, have been fabricated for testing purposes. In an oxygen partial gradient, the passive oxygen flux through fully dense structures was highly dependent on composition. An increase in oxygen permeation with increased temperature is attributed to both enhanced oxygen vacancy mobility and higher vacancy populations. Highly acceptor-doped compositions resulted in oxygen ion mobilities more than an order of magnitude higher than yttria-stabilized zirconia. The mixed conducting ceramics have been utilized in a membrane reactor configuration to upgrade methane to ethane and ethylene. Conditions were established to balance selectivity and throughput in a catalytic membrane reactor constructed from mixed conducting ceramics.

  1. Carbon-Nanotube-Reinforced Polymer-Derived Ceramic Composites

    Energy Technology Data Exchange (ETDEWEB)

    An, Linan; Xu, Weixing; Rajagopalan, Sudhir; Wang, Chong M.; Wang, Hsin; Fan, Yi; Zhang, Ligong; Jiang, Dapeng; Kapat, Jay; Chow, Louis; Guo, Baohua; Liang, Ji; Vaidyanathan, Raj

    2004-12-09

    Carbon nanotube reinforced ceramic composites were synthesized by using recently developed polymer-derived ceramics as matrices. Multi-wall carbon nanotubes, treated with a surfactant, were first dispersed in a liquid polymer precursor by sonication and mechanical stirring. The solution was then converted to fully dense ceramic composites with pressure-assist pyrolysis technique. Microstructural observation revealed that nanotubes were homogeneously dispersed throughout the ceramic matrix. Significant increases in mechanical and thermal properties were observed by adding only {approx}6vol% nanotubes. Strong nanotube pullout revealed by SEM observation suggested that the composites could possess high fracture toughness.

  2. Cast Steel Filtration Trials Using Ceramic-Carbon Filters

    Directory of Open Access Journals (Sweden)

    Lipowska B.

    2014-12-01

    Full Text Available Trials of cast steel filtration using two types of newly-developed foam filters in which carbon was the phase binding ceramic particles have been conducted. In one of the filters the source of carbon was flake graphite and coal-tar pitch, while in the other one graphite was replaced by a cheaper carbon precursor. The newly-developed filters are fired at 1000°C, i.e. at a much lower temperature than the currently applied ZrO2-based filters. During filtration trials the filters were subjected to the attack of a flowing metal stream having a temperature of 1650°C for 30 seconds.

  3. Pre-Combustion Carbon Dioxide Capture by a New Dual Phase Ceramic-Carbonate Membrane Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Jerry

    2014-09-30

    This report documents synthesis, characterization and carbon dioxide permeation and separation properties of a new group of ceramic-carbonate dual-phase membranes and results of a laboratory study on their application for water gas shift reaction with carbon dioxide separation. A series of ceramic-carbonate dual phase membranes with various oxygen ionic or mixed ionic and electronic conducting metal oxide materials in disk, tube, symmetric, and asymmetric geometric configurations was developed. These membranes, with the thickness of 10 μm to 1.5 mm, show CO2 permeance in the range of 0.5-5×10-7 mol·m-2·s-1·Pa-1 in 500-900oC and measured CO2/N2 selectivity of up to 3000. CO2 permeation mechanism and factors that affect CO2 permeation through the dual-phase membranes have been identified. A reliable CO2 permeation model was developed. A robust method was established for the optimization of the microstructures of ceramic-carbonate membranes. The ceramic-carbonate membranes exhibit high stability for high temperature CO2 separations and water gas shift reaction. Water gas shift reaction in the dual-phase membrane reactors was studied by both modeling and experiments. It is found that high temperature syngas water gas shift reaction in tubular ceramic-carbonate dual phase membrane reactor is feasible even without catalyst. The membrane reactor exhibits good CO2 permeation flux, high thermal and chemical stability and high thermal shock resistance. Reaction and separation conditions in the membrane reactor to produce hydrogen of 93% purity and CO2 stream of >95% purity, with 90% CO2 capture have been identified. Integration of the ceramic-carbonate dual-phase membrane reactor with IGCC process for carbon dioxide capture was analyzed. A methodology was developed to identify optimum operation conditions for a membrane tube of given dimensions that would treat coal syngas with targeted performance. The calculation results show that the dual-phase membrane reactor could

  4. Pre-Combustion Carbon Dioxide Capture by a New Dual Phase Ceramic-Carbonate Membrane Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Jerry Y. S. [Arizona State Univ., Tempe, AZ (United States)

    2015-01-31

    This report documents synthesis, characterization and carbon dioxide permeation and separation properties of a new group of ceramic-carbonate dual-phase membranes and results of a laboratory study on their application for water gas shift reaction with carbon dioxide separation. A series of ceramic-carbonate dual phase membranes with various oxygen ionic or mixed ionic and electronic conducting metal oxide materials in disk, tube, symmetric, and asymmetric geometric configurations was developed. These membranes, with the thickness of 10 μm to 1.5 mm, show CO2 permeance in the range of 0.5-5×10-7 mol·m-2·s-1·Pa-1 in 500-900°C and measured CO2/N2 selectivity of up to 3000. CO2 permeation mechanism and factors that affect CO2 permeation through the dual-phase membranes have been identified. A reliable CO2 permeation model was developed. A robust method was established for the optimization of the microstructures of ceramic-carbonate membranes. The ceramic-carbonate membranes exhibit high stability for high temperature CO2 separations and water gas shift reaction. Water gas shift reaction in the dual-phase membrane reactors was studied by both modeling and experiments. It is found that high temperature syngas water gas shift reaction in tubular ceramic-carbonate dual phase membrane reactor is feasible even without catalyst. The membrane reactor exhibits good CO2 permeation flux, high thermal and chemical stability and high thermal shock resistance. Reaction and separation conditions in the membrane reactor to produce hydrogen of 93% purity and CO2 stream of >95% purity, with 90% CO2 capture have been identified. Integration of the ceramic-carbonate dual-phase membrane reactor with IGCC process for carbon dioxide capture was analyzed. A methodology was developed to identify optimum operation conditions for a

  5. In situ measurement of ceramic vacuum chamber conductive coating quality

    Energy Technology Data Exchange (ETDEWEB)

    Doose, C.; Harkay, K.; Kim, S.; Milton, S.

    1997-08-01

    A method for measuring the relative surface resistivity and quality of conductive coatings on ceramic vacuum chambers was developed. This method is unique in that it allows one to test the coating even after the ceramic chamber is installed in the accelerator and under vacuum; furthermore, the measurement provides a localized surface reading of the coating conductance. The method uses a magnetic probe is calibrated using the measured DC end-to-end resistance of the tube under test and by comparison to a high quality test surface. The measurement method has also been verified by comparison to high frequency impedance measurements. A detailed description, results, and sensitivity of the technique are given here.

  6. Physical meaning of conductivity spectra for ZnO ceramics

    Institute of Scientific and Technical Information of China (English)

    Cheng Peng-Fei; Li Sheng-Tao; Li Jian-Ying; Ding Can; Yang Yan

    2012-01-01

    With the help of broadband dielectric spectroscopy in a wide temperature and frequency range,the conductivity spectra of ZnO polycrystalline ceramics are measured and the direct-current-like (DC-like) conductivity and relaxation polarization conductivity are observed successively along the frequency axis.According to the classical Debye theory and Cole-Cole equation,the physical meanings of the two conductivities are discussed.It is found that the DC-like conductivity corresponds to electron transportation over the Schottky barrier at the grainboundary.The relaxation polarization conductivity corresponds to electronic trap relaxation of intrinsic point defects (zinc interstitial and oxygen vacancy).When in the high frequency region,the relaxation conductivity obeys the universal law with the index n equal to the index α in the Cole-Cole equation as an indictor of disorder degree.

  7. Fabrication of low specific resistance ceramic carbon composites by slip casting

    Directory of Open Access Journals (Sweden)

    Rahul Kumar

    2015-09-01

    Full Text Available Ceramic carbon composites (CCCs utilize carbon as the conducting phase and can be used as resistors for high voltage electrical applications. To obtain superior mechanical properties it is desired to minimize the amount of carbon yet achieve desired electrical conductivity. Thus, electrically conducting nanosized carbon like carbon black (CB was used with the matrix materials. Uniform dispersion of CB in ceramic matrix leading to a percolating network at lowest possible volume fraction is a challenge. The present work reports colloidal processing approach to overcome these challenges. Fabrication of CCCs was done by slip casting. Two types of slurries, CB slurry and alumina–clay slurry, were made independently and mixed together at a later stage to make CCCs. Electrical, thermal and mechanical properties of the CCCs have been studied.

  8. Synthesis and sintering of ceramic nanocomposites with high mixed conductivity

    Directory of Open Access Journals (Sweden)

    Zyryanov V.V.

    2005-01-01

    Full Text Available Metastable solid solutions of complex oxides with fluorite and perovskite structures are obtained by mechanosynthesis. Dense ceramics on the base of these metastable phases was obtained by thermal sintering of nanopowders due to kinetic stabilization. Different degrees of a chemical interaction (interdiffusion are observed during sintering of "perovskite+fluorite" and "perovskite+perovskite" composites. It is shown, that optimization of the composition, mixing conditions of individual phases and their sintering, preparation of ceramic composites with mixed conductivity for use in catalytic membrane reactors is possible. Unusual behavior of complex perovskites and fluorites is discovered during sintering, enabling determination of an optimum sintering temperature and time for which a qualitative explanation is given. It is established that rearrangement of fine crystalline particles as a whole plays a key role in shrinkage.

  9. Anionic conducting oxide ceramics: Microstructure - property relations of BiCuVOx ceramics. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Berrera, T.P.; Dunn, B.; Fuqua, P.D.; Leininger, J.; Mackenzie, J.D.

    1996-06-14

    The bismuth vanadate composition, Bi4V2O11, is the parent compound for a new family of oxygen ion conductors. The substitution of various metallic ions for vanadium stabilizes the high temperature gamma-phase and leads to a series of compounds which possess the highest oxygen ion conductivities observed for temperatures below 400 deg C. This paper reports the first studies on the processing, densification and transport properties of copper-doped bismuth vanadate ceramics. Phase-pure materials with densities above 95% of theoretical were obtained using standard ceramic processing approaches. Ionic conductivities in the range of 1 x 10(exp {minus}2) S/cm at 400 deg C were observed for a variety of sintered samples.

  10. An accurate way to determine the ionic conductivity of mixed ionic-electronic conducting (MIEC) ceramics

    NARCIS (Netherlands)

    Chen, W.; Nauels, N.; Bouwmeester, H.J.M.; Nijmeijer, A.; Winnubst, A.J.A.

    2015-01-01

    Measuring oxygen transport through dense, mixed ion–electron conducting, ceramic membranes is usually performed in a lab-scale permeationset-up where feed and sweep gas are directly flushed to the membrane surface. Due to concentration gradients, the oxygen partial pressure PO2 measured at the outle

  11. Porous alumina and zirconia ceramics with tailored thermal conductivity

    Science.gov (United States)

    Gregorová, E.; Pabst, W.; Sofer, Z.; Jankovský, O.; Matějíček, J.

    2012-11-01

    The thermal conductivity of porous ceramics can be tailored by slip casting and uniaxial dry pressing, using either fugitive pore formers (saccharides) or partial sintering. Porous alumina and zirconia ceramics have been prepared using appropriate powder types (ungranulated for casting, granulated for pressing) and identical firing regimes (but different maximum temperatures in the case of partial sintering). Thermal diffusivities have been measured by the laser- and xenon-flash method and transformed into relative thermal conductivities, which enable a temperature-independent comparison between different materials. While the porosity can be controlled in a similar way for both materials when using pore formers, partial sintering exhibits characteristic differences between alumina and zirconia (for alumina porosities below 45 %, full density above 1600 °C, for zirconia porosities below 60 %, full density above 1300 °C). The different compaction behavior of alumina and zirconia (porosity after pressing 0.465 and 0.597, respectively) is reflected in the fact that for alumina the relative conductivity data of partially sintered materials are below the exponential prediction, while for zirconia they coincide with the latter. Notwithstanding these characteristic differences, for both alumina and zirconia it is possible to tailor the thermal conductivity from 100 % down to approx. 15 % of the solid phase value.

  12. Modelling of diffusion and conductivity relaxation of oxide ceramics

    Science.gov (United States)

    Preis, Wolfgang

    2016-12-01

    A two-dimensional square grain model has been applied to simulate simultaneously the diffusion process and relaxation of the dc conduction of polycrystalline oxide materials due to a sudden change of the oxygen partial pressure of the surrounding gas phase. The numerical calculations are performed by employing the finite element approach. The grains are squares of equal side length (average grain size) and the grain boundaries may consist of thin slabs of uniform thickness. An additional (space charge) layer adjacent to the grain boundary cores (thin slabs) either blocking (depletion layer) or highly conductive for electronic charge carriers may surround the grains. The electronic transport number of the mixed ionic-electronic conducting oxide ceramics may be close to unity (predominant electronic conduction). If the chemical diffusion coefficient of the neutral mobile component (oxygen) of the grain boundary core regions is assumed to be higher by many orders of magnitude than that in the bulk, the simulated relaxation curves for mass transport (diffusion) and dc conduction can deviate remarkably from each other. Deviations between the relaxation of mass transport and dc conduction are found in the case of considerably different electronic conductivities of grain boundary core regions, space charge layers, and bulk. On the contrary, the relaxation curves of mass transport and electronic conductivity are in perfect coincidence, when either effective medium diffusion occurs or the effective conductivity is unaffected by the individual conductivities of core regions and possible space charge layers, i.e. the grain boundary resistivity is negligible.

  13. Mixed ionic and electronic conducting ceramic membranes for hydrocarbon processing

    Science.gov (United States)

    Van Calcar, Pamela; Mackay, Richard; Sammells, Anthony F.

    2002-01-01

    The invention relates to mixed phase materials for the preparation of catalytic membranes which exhibit ionic and electronic conduction and which exhibit improved mechanical strength compared to single phase ionic and electronic conducting materials. The mixed phase materials are useful for forming gas impermeable membranes either as dense ceramic membranes or as dense thin films coated onto porous substrates. The membranes and materials of this invention are useful in catalytic membrane reactors in a variety of applications including synthesis gas production. One or more crystalline second phases are present in the mixed phase material at a level sufficient to enhance the mechanical strength of the mixture to provide membranes for practical application in CMRs.

  14. Electrical Conductivity of the Carbon Fiber Conductive Concrete

    Institute of Scientific and Technical Information of China (English)

    HOU Zuofu; LI Zhuoqiu; WANG Jianjun

    2007-01-01

    This paper discussed two methods to enhance the electrical conductivity of the carbon fiber(CF) electrically conductive concrete. The increase in the content of stone and the amount of water used to dissolve the methylcellulose and marinate the carbon fibers can decrease the electrical resistivity of the electrically conductive concrete effectively. Based on these two methods, the minimum CF content of the CF electrically conductive concrete for deicing or snow-melting application and the optimal ratio of the amount of water to dissolve the methylcellulose and marinate the carbon fibers were obtained.

  15. Protonic Conducting Ceramic for 300-400 C

    Science.gov (United States)

    Sayir, Ali

    2007-03-01

    Combining high protonic conductivity with thermodynamic stability is considered to be a key problem for high temperature protonic conducting ceramic (HTPC) membranes for electrochemical applications. The objective was to gain an understanding of the relationship of crystallite size, grain boundaries and defect chemistry on proton conduction and thermodynamic stability. We developed an analytical method using concurrent techniques of high-resolution transmission electron microscopy, impedance spectroscopy and nuclear microprobe to reveal spatial distribution of hydrogen. In our recent work, we shown that high-density of defects exist in the microstructure can reduce the level of proton incorporation. The results showed that hydrogen is concentrated at the grain boundaries where the hydrogen mobility is low. Perovskite structure BaCe1-xYxO3-δ (BCY) and BaZr1-xYxO3-δ films were deposited using pulsed laser deposition system on porous structures to provide mechanical strength. The ease with which the stoichiometry of a multi-component system can be maintained in the deposited films using pulsed laser deposition approach offered a significant advantage over other conventional film deposition techniques. Impedance spectroscopy was used to investigate protonic conductivity of high-density BaCe1-xYxO3-δ (BCY) and BaZr1-xYxO3-δ (BZY) films (2 - 5 μm). The crystallite size, grain boundaries and defect chemistry were characterized by XRD, SEM, TEM and HRTEM which showed the adverse effect of grain and domain boundaries. Variation of the process parameters, in particular of the substrate temperature, induced changes in the microstructure of the films and in their conductivity. Columnar grains enclosing reduced density of defects were seen to yield the best proton conductivities.

  16. Lower-Conductivity Ceramic Materials for Thermal-Barrier Coatings

    Science.gov (United States)

    Bansal, Narottam P.; Zhu, Dongming

    2006-01-01

    Doped pyrochlore oxides of a type described below are under consideration as alternative materials for high-temperature thermal-barrier coatings (TBCs). In comparison with partially-yttria-stabilized zirconia (YSZ), which is the state-of-the-art TBC material now in commercial use, these doped pyrochlore oxides exhibit lower thermal conductivities, which could be exploited to obtain the following advantages: For a given difference in temperature between an outer coating surface and the coating/substrate interface, the coating could be thinner. Reductions in coating thicknesses could translate to reductions in weight of hot-section components of turbine engines (e.g., combustor liners, blades, and vanes) to which TBCs are typically applied. For a given coating thickness, the difference in temperature between the outer coating surface and the coating/substrate interface could be greater. For turbine engines, this could translate to higher operating temperatures, with consequent increases in efficiency and reductions in polluting emissions. TBCs are needed because the temperatures in some turbine-engine hot sections exceed the maximum temperatures that the substrate materials (superalloys, Si-based ceramics, and others) can withstand. YSZ TBCs are applied to engine components as thin layers by plasma spraying or electron-beam physical vapor deposition. During operation at higher temperatures, YSZ layers undergo sintering, which increases their thermal conductivities and thereby renders them less effective as TBCs. Moreover, the sintered YSZ TBCs are less tolerant of stress and strain and, hence, are less durable.

  17. Methods of enhancing conductivity of a polymer-ceramic composite electrolyte

    Science.gov (United States)

    Kumar, Binod (Inventor)

    2003-01-01

    Methods for enhancing conductivity of polymer-ceramic composite electrolytes are provided which include forming a polymer-ceramic composite electrolyte film by a melt casting technique and uniaxially stretching the film from about 5 to 15% in length. The polymer-ceramic composite electrolyte is also preferably annealed after stretching such that it has a room temperature conductivity of from 10.sup.-4 S cm.sup.-1 to 10.sup.-3 S cm.sup.-1. The polymer-ceramic composite electrolyte formed by the methods of the present invention may be used in lithium rechargeable batteries.

  18. Polymer-derived ceramic composite fibers with aligned pristine multiwalled carbon nanotubes.

    Science.gov (United States)

    Sarkar, Sourangsu; Zou, Jianhua; Liu, Jianhua; Xu, Chengying; An, Linan; Zhai, Lei

    2010-04-01

    Polymer-derived ceramic fibers with aligned multiwalled carbon nanotubes (MWCNTs) are fabricated through the electrospinning of polyaluminasilazane solutions with well-dispersed MWCNTs followed by pyrolysis. Poly(3-hexylthiophene)-b-poly (poly (ethylene glycol) methyl ether acrylate) (P3HT-b-PPEGA), a conjugated block copolymer compatible with polyaluminasilazane, is used to functionalize MWCNT surfaces with PPEGA, providing a noninvasive approach to disperse carbon nanotubes in polyaluminasilazane chloroform solutions. The electrospinning of the MWCNT/polyaluminasilazane solutions generates polymer fibers with aligned MWCNTs where MWCNTs are oriented along the electrospun jet by a sink flow. The subsequent pyrolysis of the obtained composite fibers produces ceramic fibers with aligned MWCNTs. The study of the effect of polymer and CNT concentration on the fiber structures shows that the fiber size increases with the increment of polymer concentration, whereas higher CNT content in the polymer solutions leads to thinner fibers attributable to the increased conductivity. Both the SEM and TEM characterization of the polymer and ceramic fibers demonstrates the uniform orientation of CNTs along the fibers, suggesting excellent dispersion of CNTs and efficient CNT alignment via the electrospinning. The electrical conductivity of a ceramic fibers with 1.2% aligned MWCNTs is measured to be 1.58 x 10(-6) S/cm, which is more than 500 times higher than that of bulk ceramic (3.43 x 10(-9) S/cm). Such an approach provides a versatile method to disperse CNTs in preceramic polymer solutions and offers a new approach to integrate aligned CNTs in ceramics.

  19. High frequency conductivity in carbon nanotubes

    Directory of Open Access Journals (Sweden)

    S. S. Abukari

    2012-12-01

    Full Text Available We report on theoretical analysis of high frequency conductivity in carbon nanotubes. Using the kinetic equation with constant relaxation time, an analytical expression for the complex conductivity is obtained. The real part of the complex conductivity is initially negative at zero frequency and become more negative with increasing frequency, until it reaches a resonance minimum at ω ∼ ωB for metallic zigzag CNs and ω < ωB for armchair CNs. This resonance enhancement is indicative for terahertz gain without the formation of current instabilities induced by negative dc conductivity. We noted that due to the high density of states of conduction electrons in metallic zigzag carbon nanotubes and the specific dispersion law inherent in hexagonal crystalline structure result in a uniquely high frequency conductivity than the corresponding values for metallic armchair carbon nanotubes. We suggest that this phenomenon can be used to suppress current instabilities that are normally associated with a negative dc differential conductivity.

  20. Sodium-carbonate co-substituted hydroxyapatite ceramics

    Directory of Open Access Journals (Sweden)

    Zoltan Z. Zyman

    2013-12-01

    Full Text Available Powders of sodium-carbonate co-substituted hydroxyapatite, having sodium content in the range of 0.25–1.5 wt.% with a 0.25 wt.% step, were prepared by a precipitation-solid state reaction route. Compacts of the powders were sintered in a CO2 flow (4 mL/min at 1100 °C for 2 h. The sintered ceramics contained sodium and carbonate ions in the ranges of 0–1.5 wt.% and 1.3–6 wt.%, respectively, which are typical impurity concentrations in biological apatite. A relationship between sodium and carbonate contents and the type of carbonate substitution was found. The total carbonate content progressively increased with the sodium content. The obtained ceramics showed an AB-type carbonate substitution. However, the substitution became more B-type as the sodium content increased. As a result, the carbonation was almost B-type (94 % for the highest sodium content (1.5 wt.%.

  1. Application of Hot-wire Method for Measuring Thermal Conductivity of Fine Ceramics

    Directory of Open Access Journals (Sweden)

    Shangxi WANG

    2016-11-01

    Full Text Available Ceramic substrate is preferred in high density packaging due to its high electrical resistivity and moderate expansion coefficient. The thermal conductivity is a key parameter for packaging substrates. There are two common methods to measure the thermal conductivity, which are the hot-wire method and the laser-flash method. Usually, the thermal conductivities of porcelain is low and meet the measurement range of hot-wire method, and the measured value by hot-wire method has little difference with that by laser-flash method. In recent years, with the requirement of high-powered LED lighting, some kinds of ceramic substrates with good thermal conductivity have been developed and their thermal conductivity always measured by the means of laser flash method, which needs expensive instrument. In this paper, in order to detect the thermal conductivity of fine ceramic with convenience and low cost, the feasibility of replacing the laser flash method with hot wire method to measure thermal conductivity of ceramic composites was studied. The experiment results showed that the thermal conductivity value of fine ceramics measured by the hot-wire method is severely lower than that by the laser-flash method. However, there is a positive relationship between them. It is possible to measure the thermal conductivity of fine ceramic workpiece instantly by hot-wire method via a correction formula.DOI: http://dx.doi.org/10.5755/j01.ms.22.4.12543

  2. Novel sintered ceramic materials incorporated with EAF carbon steel slag

    Science.gov (United States)

    Karayannis, V.; Ntampegliotis, K.; Lamprakopoulos, S.; Papapolymerou, G.; Spiliotis, X.

    2017-01-01

    In the present research, novel sintered clay-based ceramic materials containing electric arc furnace carbon steel slag (EAFC) as a useful admixture were developed and characterized. The environmentally safe management of steel industry waste by-products and their valorization as secondary resources into value-added materials towards circular economy have attracted much attention in the last years. EAF Carbon steel slag in particular, is generated during the manufacture of carbon steel. It is a solid residue mainly composed of rich-in- Fe, Ca and Si compounds. The experimental results show that the beneficial incorporation of lower percentages of EAFC up to 6%wt. into ceramics sintered at 950 °C is attained without significant variations in sintering behavior and physico-mechanical properties. Further heating up to 1100 °C strongly enhances the densification of the ceramic microstructures, thus reducing the porosity and strengthening their mechanical performance. On the other side, in terms of thermal insulation behavior as well as energy consumption savings and production cost alleviation, the optimum sintering temperature appears to be 950 °C.

  3. Conductivity of single-walled carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Gets, A. V.; Krainov, V. P., E-mail: vpkrainov@mail.ru [Moscow Institute of Physics and Technology (Russian Federation)

    2016-12-15

    The conductivity of single-walled carbon nanotubes at low temperatures is calculated. It is shown that it is much higher than the well-known conductivity of a model 1D Fermi system. This is a purely quantum-mechanical effect.

  4. Conductance of AFM Deformed Carbon Nanotubes

    Science.gov (United States)

    Svizhenko, Alexei; Maiti, Amitesh; Anatram, M. P.; Biegel, Bryan (Technical Monitor)

    2002-01-01

    This viewgraph presentation provides information on the electrical conductivity of carbon nanotubes upon deformation by atomic force microscopy (AFM). The density of states and conductance were computed using four orbital tight-binding method with various parameterizations. Different chiralities develop bandgap that varies with chirality.

  5. Proton conducting ceramics for potentiometric hydrogen sensors for molten metals

    Energy Technology Data Exchange (ETDEWEB)

    Borland, H.; Llivina, L.; Colominas, S.; Abellà, J., E-mail: jordi.abella@iqs.edu

    2013-10-15

    Highlights: • Synthesis and chemical characterization of proton conductor ceramics. • Qualification of ceramics for hydrogen sensors in molten lithium–lead. • Ceramics have well-defined grains with a wide distribution of sizes. • Good agreement with predictions obtained with BaZrY, BaCeZrY and SrFeCo ceramics. -- Abstract: Tritium monitoring in lithium–lead eutectic (Pb–15.7Li) is of great importance for the performance of liquid blankets in fusion reactors. Also, tritium measurements will be required in order to proof tritium self-sufficiency in liquid metal breeding systems. On-line hydrogen (isotopes) sensors must be design and tested in order to accomplish these goals. Potentiometric hydrogen sensors for molten lithium–lead eutectic have been designed at the Electrochemical Methods Lab at Institut Quimic de Sarria (IQS) at Barcelona and are under development and qualification. The probes are based on the use of solid state electrolytes and works as proton exchange membranes (PEM). In this work the following compounds: BaZr{sub 0.9}Y{sub 0.1}O{sub 3}, BaCe{sub 0.6}Zr{sub 0.3}Y{sub 0.1}O{sub 3−α}, Sr(Ce{sub 0.6}-Zr{sub 0.4}){sub 0.9}Y{sub 0.1}O{sub 3−α} and Sr{sub 3}Fe{sub 1.8}Co{sub 2}O{sub 7} have been synthesized in order to be tested as PEM H-probes. Potentiometric measurements of the synthesized ceramic elements at 500 °C have been performed at a fixed hydrogen concentration. The sensors constructed using the proton conductor elements BaZr{sub 0.9}Y{sub 0.1}O{sub 3}, BaCe{sub 0.6}Zr{sub 0.3}Y{sub 0.1}O{sub 3−δ} and Sr{sub 3}Fe{sub 1.8}Co{sub 0.2}O{sub 7−δ} exhibited stable output potential and its value was close to the theoretical value calculated with the Nernst equation (deviation around 60 mV). In contrast, the sensor constructed using the proton conductor element Sr(Ce{sub 0.6}–Zr{sub 0.4}){sub 0.9}Y{sub 0.1}O{sub 3−δ} showed a deviation higher than 100 mV between experimental an theoretical data.

  6. Evaluation of porous carbon and ceramic supports for hyperfiltration

    Energy Technology Data Exchange (ETDEWEB)

    Cabellon, J.B.; Padia, A.K.; Whitesides, L.E. Jr.

    1971-03-24

    Porous carbon and ceramic tubes were evaluated as supports for dynamically formed zirconium (IV) hydrous oxide-polycarboxylic acid hyperfiltration membranes. The most promising membranes were formed on Union Carbide 6-C carbon tubes using a 150,000 molecular weight polyacrylic acid. Sodium chloride rejections as high as 97% were obtained at water fluxes of 80 gpd/ft{sup 2} compared with rejections of 90 to 95% and fluxes of 130 gpd/ft{sup 2} using the porous stainless steel-Acropor/Millipore supports. The effects of pressure, circulation velocity, and temperature on membrane flux and sodium chloride and Coalinga water rejections were studied. A small industrial module containing 6-C carbon supports with a 3.04 ft{sup 2} filtration surface gave a salt rejection of 86% and a product water flux of 60 gpd/ft{sup 2}.

  7. Porous Y2SiO5 Ceramic with Low Thermal Conductivity

    Institute of Scientific and Technical Information of China (English)

    Duanyang Li; Meishuan Li

    2012-01-01

    Porous Y2Si05 ceramic was fabricated by freeze casting with tert-butyl alcohol as solvent. The porous Y2SiO5 ceramic possessed long straight pore structure. With decreasing solid loading from 20 to 10 vol.%, the porosity of the Y2SiO5 ceramic increased linearly from 45% to Y2%, while the compressive strength declined from 23.2 to 3.2 MPa. The thermal conductivity of Y2SiO5 decreased from 2.34 W/mK for the dense bulk to 0.05 W/mK for the porous body with a porosity of 57%.

  8. Analysis of ionic conductance of carbon nanotubes

    NARCIS (Netherlands)

    Biesheuvel, P.M.; Bazant, M.Z.

    2016-01-01

    We use space-charge (SC) theory (also called the capillary pore model) to describe the ionic conductance, G, of charged carbon nanotubes (CNTs). Based on the reversible adsorption of hydroxyl ions to CNT pore walls, we use a Langmuir isotherm for surface ionization and make calculations as a

  9. Carbon nanotube-ceramic nanocomposites: Synthesis and characterization

    Science.gov (United States)

    Clark, Michael David

    Ceramic materials are widely used in modern society for a variety of applications including fuel cell electrolytes, bio-medical implants, and jet turbines. However, ceramics are inherently brittle making them excellent candidates for mechanical reinforcement. In this work, the feasibility of dispersing multi-walled carbon nanotubes into a silicon carbide matrix for mechanical property enhancement is explored. Prior to dispersing, nanotubes were purified using an optimized, three step methodology that incorporates oxidative treatment, acid sonication, and thermal annealing rendering near-superhydrophobic behavior in synthesized thin films. Alkyl functionalized nanotube dispersability was characterized in various solvents. Dispersability was contingent on fostering polar interactions between the functionalized nanotubes and solvent despite the purely dispersive nature of the aliphatic chains. Interpretation of these results yielded values of 45.6 +/- 1.2, 0.78 +/- 0.04, and 2 4 +/- 0.9 mJ/m2 for the Lifshitz-van der Waals, electron acceptor and electron donor surface energy components respectively. Aqueous nanotube dispersions were prepared using a number of surfactants to examine surfactant concentration and pH effects on nanotube dispersability. Increasing surfactant concentrations resulted in a solubility plateau, which was independent of the surfactant's critical micelle concentration. Deviations from neutral pH demonstrated negligible influence on non-ionic surfactant adsorption while, ionic surfactants showed substantial pH dependent behavior. These results were explained in the context of nanotube surface ionization and Debye length variation. Successful MWNT dispersion into a silicon carbide based matrix is reported by in-situ ceramic formation using two routes; sol-gel chemistry and pre-ceramic polymeric precursor workup. For the former, nanotube dispersion was assisted by PluronicRTM surfactants. Pyrolytic treatment and consolidation of formed powders

  10. Anionic conducting oxide ceramics. Final report, 15 April 1995--14 April 1998

    Energy Technology Data Exchange (ETDEWEB)

    Dunn, B.; Mackenzie, J.D.

    1998-04-01

    This program has emphasized the interrelationships among synthesis, microstructure and properties for oxygen ion conducting ceramics based on copper-substituted bismuth vanadate (Bi-V-Cu-O), known as BICUVOX. The authors showed that these materials readily formed dense ceramics with equiaxed microstructures and confirmed that they exhibited high ionic conductivity. Prolonged heat treatments at elevated temperatures did not cause significant changes in conductivity, an important consideration for electrochemical device operation. They also developed solution processing approaches for preparing thin films of the bismuth vanadate materials.

  11. Carbon nanotube based transparent conductive thin films.

    Science.gov (United States)

    Yu, X; Rajamani, R; Stelson, K A; Cui, T

    2006-07-01

    Carbon nanotube (CNT) based optically transparent and electrically conductive thin films are fabricated on plastic substrates in this study. Single-walled carbon nanotubes (SWNTs) are chemically treated with a mixture of concentrated sulfuric acid and nitric acid before being dispersed in aqueous surfactant-contained solutions. SWNT thin films are prepared from the stable SWNT solutions using wet coating techniques. The 100 nm thick SWNT thin film exhibits a surface resistivity of 6 kohms/square nanometer with an average transmittance of 88% on the visible light range, which is three times better than the films prepared from the high purity as-received SWNTs.

  12. Conductivity of carbon nanotube polymer composites

    Energy Technology Data Exchange (ETDEWEB)

    Wescott, J T; Kung, P; Maiti, A

    2006-11-20

    Dissipative Particle Dynamics (DPD) simulations were used to investigate methods of controlling the assembly of percolating networks of carbon nanotubes (CNTs) in thin films of block copolymer melts. For suitably chosen polymers the CNTs were found to spontaneously self-assemble into topologically interesting patterns. The mesoscale morphology was projected onto a finite-element grid and the electrical conductivity of the films computed. The conductivity displayed non-monotonic behavior as a function of relative polymer fractions in the melt. Results are compared and contrasted with CNT dispersion in small-molecule fluids and mixtures.

  13. Novel continuous carbon and ceramic nanofibers and nanocomposites

    Science.gov (United States)

    Wen, Yongkui

    2004-12-01

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

  14. Evidence of induced structural and conduction anisotropy in scandia-stabilized zirconia ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Barbashov, Vladimir; Nesova, Elizaveta; Pismenova, Natalia; Radionova, Olga [Donetsk Phys. Tech. Institute, N.A.S. Ukraine, R. Luxemburg St. 72, 83114 Donetsk (Ukraine)

    2012-04-15

    Evidence of current induced structural and conduction anisotropy was experimentally established in scandia-stabilized zirconia ceramics. It was found that these effects are observed only when the material is in the rhombohedral phase. It was shown using conductivity measurements and X-ray phase analysis that anisotropic behavior of polycrystalline ZrO{sub 2}-Sc{sub 2}O{sub 3} ceramics is induced by a low-amplitude alternating current in the temperature range corresponding to a rhombohedral-to-cubic phase transition. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. Thermal Conductivity of Carbon Nanotube Composite Films

    Science.gov (United States)

    Ngo, Quoc; Cruden, Brett A.; Cassell, Alan M.; Walker, Megan D.; Koehne, Jessica E.; Meyyappan, M.; Li, Jun; Yang, Cary Y.

    2004-01-01

    State-of-the-art ICs for microprocessors routinely dissipate power densities on the order of 50 W/sq cm. This large power is due to the localized heating of ICs operating at high frequencies, and must be managed for future high-frequency microelectronic applications. Our approach involves finding new and efficient thermally conductive materials. Exploiting carbon nanotube (CNT) films and composites for their superior axial thermal conductance properties has the potential for such an application requiring efficient heat transfer. In this work, we present thermal contact resistance measurement results for CNT and CNT-Cu composite films. It is shown that Cu-filled CNT arrays enhance thermal conductance when compared to as-grown CNT arrays. Furthermore, the CNT-Cu composite material provides a mechanically robust alternative to current IC packaging technology.

  16. Hot-Pressed BN-AlN Ceramic Composites of High Thermal Conductivity

    Science.gov (United States)

    Kanai, Takao; Tanemoto, Kei; Kubo, Hiroshi

    1990-04-01

    Hexagonal boron nitride-aluminum nitride (75-25 wt%) ceramic composites are synthesized by uniaxial hot pressing. High thermal conductivity, 247 W/(m\\cdotK), is attained for the perpendicular direction of the hot-pressing axis of the sintered body, by optimizing the amount of added sintering aid, calcium carbide. The composites have remarkable anisotropy with respect to structure and thermal conductivity. The revelation mechanism of high thermal conductivity is discussed.

  17. Structural morphology of amorphous conducting carbon film

    Indian Academy of Sciences (India)

    P N Vishwakarma; V Prasad; S V Subramanyam; V Ganesan

    2005-10-01

    Amorphous conducting carbon films deposited over quartz substrates were analysed using X-ray diffraction and AFM technique. X-ray diffraction data reveal disorder and roughness in the plane of graphene sheet as compared to that of graphite. This roughness increases with decrease in preparation temperature. The AFM data shows surface roughness of carbon films depending on preparation temperatures. The surface roughness increases with decrease in preparation temperature. Also some nucleating islands were seen on the samples prepared at 900°C, which are not present on the films prepared at 700°C. Detailed analysis of these islands reveals distorted graphitic lattice arrangement. So we believe these islands to be nucleating graphitic. Power spectrum density (PSD) analysis of the carbon surface indicates a transition from the nonlinear growth mode to linear surface-diffusion dominated growth mode resulting in a relatively smoother surface as one moves from low preparation temperature to high preparation temperature. The amorphous carbon films deposited over a rough quartz substrate reveal nucleating diamond like structures. The density of these nucleating diamond like structures was found to be independent of substrate temperature (700–900°C).

  18. Thermal Conductivity of Carbon Nanoreinforced Epoxy Composites

    Directory of Open Access Journals (Sweden)

    C. Kostagiannakopoulou

    2016-01-01

    Full Text Available The present study attempts to investigate the influence of multiwalled carbon nanotubes (MWCNTs and graphite nanoplatelets (GNPs on thermal conductivity (TC of nanoreinforced polymers and nanomodified carbon fiber epoxy composites (CFRPs. Loading levels from 1 to 3% wt. of MWCNTs and from 1 to 15% wt. of GNPs were used. The results indicate that TC of nanofilled epoxy composites increased with the increase of GNP content. Quantitatively, 176% and 48% increase of TC were achieved in nanoreinforced polymers and nanomodified CFRPs, respectively, with the addition of 15% wt. GNPs into the epoxy matrix. Finally, micromechanical models were applied in order to predict analytically the TC of polymers and CFRPs. Lewis-Nielsen model with optimized parameters provides results very close to the experimental ones in the case of polymers. As far as the composites are concerned, the Hashin and Clayton models proved to be sufficiently accurate for the prediction at lower filler contents.

  19. A novel approach for the fabrication of carbon nanofibre/ceramic porous structures

    KAUST Repository

    Walter, Claudia

    2013-11-01

    This paper describes the fabrication of hybrid ceramic/carbon scaffolds in which carbon nanofibres and multi-walled carbon nanotubes fully cover the internal walls of a microporous ceramic structure that provides mechanical stability. Freeze casting is used to fabricate a porous, lamellar ceramic (Al2O3) structure with aligned pores whose width can be controlled between 10 and 90μm. Subsequently, a two step chemical vapour deposition process that uses iron as a catalyst is used to grow the carbon nanostructures inside the scaffold. This catalyst remains in the scaffold after the growth process. The formation of the alumina scaffold and the influence of its structure on the growth of nanofibres and tubes are investigated. A set of growth conditions is determined to produce a dense covering of the internal walls of the porous ceramic with the carbon nanostructures. The limiting pore size for this process is located around 25μm. © 2013 Elsevier Ltd.

  20. A Novel Approach for the Effective Thermal Conductivity of Porous Ceramics

    Institute of Scientific and Technical Information of China (English)

    ZHU Qiang; ZHANG Fan-wei; ZHANG Yue; ZHANG Da-hai; LI Zhong-ping

    2006-01-01

    A new approach in combination of the effective medium theory with the equivalent unit in numerical simulation was developed to study the effective thermal conductivity of porous ceramics. The finite element method was used to simulate the heat transfer process which enables to acquire accurate results through highly complicated modeling and intensive computation. An alternative approach to mesh the material into small cells was also presented. The effective medium theory accounts for the effective thermal conductivity of cells while the equivalent unit is subsequently applied in numerical simulation to analyze the effective thermal conductivity of the porous ceramics. A new expression for the effective thermal conductivity, allowing for some structure factors such as volume fraction of pores and thermal conductivity, was put forward, and the results of its application was proved to be close to those of the mathematical simulation.

  1. A Spray Pyrolysis Method to Grow Carbon Nanotubes on Carbon Fibres, Steel and Ceramic Bricks.

    Science.gov (United States)

    Vilatela, Juan J; Rabanal, M E; Cervantes-Sodi, Felipe; García-Ruiz, Máximo; Jiménez-Rodríguez, José A; Reiband, Gerd; Terrones, Mauricio

    2015-04-01

    We demonstrate a spray pyrolysis method to grow carbon nanotubes (CNTs) with high degree of crystallinity, aspect ratio and degree of alignment on a variety of different substrates, such as conventional steel, carbon fibres (CF) and ceramics. The process consists in the chemical vapour deposition of both a thin SiO2 layer and CNTs that subsequently grow on this thin layer. After CNT growth, increases in specific surface by factors of 1000 and 30 for the steel and CF samples, respectively, are observed. CNTs growth on ceramic surfaces results in a surface resistance of 37.5 Ohm/sq. When using conventional steel as a rector tube, we observed CNTs growth rates of 0.6 g/min. Details of nanotube morphology and the growth mechanism are discussed. Since the method discussed here is highly versatile, it opens up a wide variety of applications in which specific substrates could be used in combination with CNTs.

  2. Creep Forming of Carbon-Reinforced Ceramic-Matrix Composites

    Science.gov (United States)

    Vaughn, Wallace L.; Scotti, Stephan J.; Ashe, Melissa P.; Connolly, Liz

    2007-01-01

    A set of lecture slides describes an investigation of creep forming as a means of imparting desired curvatures to initially flat stock plates of carbon-reinforced ceramic-matrix composite (C-CMC) materials. The investigation is apparently part of a continuing effort to develop improved means of applying small CCMC repair patches to reinforced carbon-carbon leading edges of aerospace vehicles (e.g., space shuttles) prior to re-entry into the atmosphere of the Earth. According to one of the slides, creep forming would be an intermediate step in a process that would yield a fully densified, finished C-CMC part having a desired size and shape (the other steps would include preliminary machining, finish machining, densification by chemical vapor infiltration, and final coating). The investigation included experiments in which C-CMC disks were creep-formed by heating them to unspecified high temperatures for time intervals of the order of 1 hour while they were clamped into single- and double-curvature graphite molds. The creep-formed disks were coated with an oxidation- protection material, then subjected to arc-jet tests, in which the disks exhibited no deterioration after exposure to high-temperature test conditions lasting 490 seconds.

  3. Conduction anisotropy in the Laplace pressure-induced rhombohedral phase of ScSZ ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Barbashov, Vladimir; Nesova, Elizaveta; Akimov, Gennady [Donetsk Phys. Tech. Institute, N.A.S. Ukraine, R. Luxemburg St. 72, 83114 Donetsk (Ukraine)

    2013-04-15

    Grain size effect on the phase composition of scandia stabilized zirconia ceramics was studied experimentally. It was established using X-ray phase analysis that the grain size decrease from 16 to 0.6 {mu}m results in the tetragonal-to-rhombohedral phase transition. It was shown that heating of the fine-grained material up to the 800 K in a weak electric field allows forming anisotropic behaviour of the ceramic electrolyte. The induced anisotropy is unambiguously reflected in temperature dependence of ionic conductivity. (copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Analysis of ionic conductance of carbon nanotubes

    CERN Document Server

    Biesheuvel, P M

    2016-01-01

    We use space-charge (SC) theory (also called the capillary pore model) to describe the ionic conductance, $G$, of charged carbon nanotubes (CNTs). Based on the reversible adsorption of hydroxyl ions to CNT pore walls, we use a Langmuir isotherm for surface ionization and make calculations as function of pore size, salt concentration $c$, and pH. Using realistic values for surface site density and pK, SC theory well describes published experimentally data on the conductance of CNTs. At extremely low salt concentration, when the electric potential becomes uniform across the pore, and surface ionization is low, we derive the scaling $G\\sim \\sqrt{c}$, while for realistic salt concentrations, SC theory does not lead to a simple power law for $G(c)$.

  5. Ceramic membranes for catalytic membrane reactors with high ionic conductivities and low expansion properties

    Science.gov (United States)

    Mackay, Richard; Sammells, Anthony F.

    2000-01-01

    Ceramics of the composition: Ln.sub.x Sr.sub.2-x-y Ca.sub.y B.sub.z M.sub.2-z O.sub.5+.delta. where Ln is an element selected from the fblock lanthanide elements and yttrium or mixtures thereof; B is an element selected from Al, Ga, In or mixtures thereof; M is a d-block transition element of mixtures thereof; 0.01.ltoreq.x.ltoreq.1.0; 0.01.ltoreq.y.ltoreq.0.7; 0.01.ltoreq.z.ltoreq.1.0 and .delta. is a number that varies to maintain charge neutrality are provided. These ceramics are useful in ceramic membranes and exhibit high ionic conductivity, high chemical stability under catalytic membrane reactor conditions and low coefficients of expansion. The materials of the invention are particularly useful in producing synthesis gas.

  6. An asymmetric tubular ceramic-carbonate dual phase membrane for high temperature CO2 separation.

    Science.gov (United States)

    Dong, Xueliang; Ortiz Landeros, José; Lin, Y S

    2013-10-25

    For the first time, a tubular asymmetric ceramic-carbonate dual phase membrane was prepared by a centrifugal casting technique and used for high temperature CO2 separation. This membrane shows high CO2 permeation flux and permeance.

  7. Ceramic silicon-boron-carbon fibers from organic silicon-boron-polymers

    Science.gov (United States)

    Riccitiello, Salvatore R. (Inventor); Hsu, Ming-Ta S. (Inventor); Chen, Timothy S. (Inventor)

    1993-01-01

    Novel high strength ceramic fibers derived from boron, silicon, and carbon organic precursor polymers are discussed. The ceramic fibers are thermally stable up to and beyond 1200 C in air. The method of preparation of the boron-silicon-carbon fibers from a low oxygen content organosilicon boron precursor polymer of the general formula Si(R2)BR(sup 1) includes melt-spinning, crosslinking, and pyrolysis. Specifically, the crosslinked (or cured) precursor organic polymer fibers do not melt or deform during pyrolysis to form the silicon-boron-carbon ceramic fiber. These novel silicon-boron-carbon ceramic fibers are useful in high temperature applications because they retain tensile and other properties up to 1200 C, from 1200 to 1300 C, and in some cases higher than 1300 C.

  8. Ceramic carbon electrode-based anodes for use in the copper-chlorine thermochemical cycle

    Energy Technology Data Exchange (ETDEWEB)

    Ranganathan, S.; Easton, E.B. [Univ. of Ontario Inst. of Technology, Oshawa, ON (Canada). Faculty of Science

    2009-07-01

    A thermochemical cycle is a process by which water is decomposed into hydrogen and oxygen through a series of chemical reactions. The chemicals that are used in these reactions are regenerated and recycled during the process. Sol-gel chemistry is becoming more common for the synthesis of electrode materials. The sol-gel reaction can be conducted in the presence of a carbon black to form a ceramic carbon electrode (CCE). The resultant CCE structure contains electronically conductive carbon particle pathways that are bound together through the ceramic binder, which can also promote ion transport. The CCE structure also has a high active surface area and is chemically and thermally robust. This paper presented an investigation of CCE materials prepared using 3-aminopropyl trimethoxysilane. Several electrochemical experiments including cyclic voltammetry and electrochemical impedance spectroscopy were performed to characterize their suitability as anode electrode materials for use in the electrochemical step of the copper-chlorine thermochemical cycle. Subsequent experiments included the manipulation of the relative ratio of organosilane carbon precursors to gauge its impact on electrode properties and performance. An overview of the materials characterization and electrochemical measurements were also presented. Specifically, the paper presented the experiment with particular reference to the CCE preparation; electrochemical experiments; thermal analysis; and scanning electron microscopy. Results were also provided. These included TGA analysis; scanning electron microscopy analysis; electrochemical characterization; and anodic polarization. Characterization of these CCE material demonstrated that they had good thermal stability, could be used at high temperatures, and were therefore, very promising anode materials. 15 refs., 7 figs.

  9. Mesoporous Nitrogen Doped Carbon-Glass Ceramic Cathode for High Performance Lithium-Oxygen Battery

    Science.gov (United States)

    2012-06-01

    Hardwick, and J.- M. Tarascon, Nature Materials, vol. 11, pp 19-29, 2012. 2. Linden , D. (Ed), Handbook of Batteries , 2nd Edition, Mc-Graw-Hill, New...AFRL-RQ-WP-TP-2015-0053 MESOPOROUS NITROGEN DOPED CARBON-GLASS CERAMIC CATHODE FOR HIGH PERFORMANCE LITHIUM-OXYGEN BATTERY (POSTPRINT...DOPED CARBON-GLASS CERAMIC CATHODE FOR HIGH PERFORMANCE LITHIUM-OXYGEN BATTERY (POSTPRINT) 5a. CONTRACT NUMBER In-house 5b. GRANT NUMBER 5c

  10. Stabilisation dopant-dependent facilitation in ionic conductivity on millimeter-wave irradiation heating of zirconia-based ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Kishimoto, Akira, E-mail: kishim-a@cc.okayama-u.ac.jp; Hasunuma, Hideki; Teranishi, Takashi; Hayashi, Hidetaka

    2015-11-05

    Ionic conductivity was measured on scandia-, calcia-, and gadolinia-stabilised zirconia ceramics under quasi-millimeter-wave (MMW) irradiation heating and conventional heating. Conductivity enhancement was evaluated for these ceramics and compared with our previous report on yttria- and ytterbia-stabilised zirconia ceramics (YSZ and YbSZ, respectively). The ionic conduction for the various cation-substituted zirconia ceramics was enhanced under MMW irradiation heating. In the case of scandia-stabilisation, the optimal composition demonstrating maximum ionic conductivity was 12-mol% zirconia (ScSZ) under MMW irradiation heating, which was larger than under conventional heating. Such an optimal composition shift was similar to results for YSZ ceramics. These results are discussed in terms of the activation energies for vacancy–ion dissociation and ion transfer. - Highlights: • Under millimeter-wave irradiation heating ionic conductivity of zirconia ceramics was examined. • The optimal composition in scandium stabilized zirconia ceramics shifted the higher doping side. • MMW irradiation heated ScSZ showed the highest ionic conductivity value in zirconia ceramics ever reported. • The activation process was examined in relation to the non-thermal effects.

  11. Thermal conductivity of pressureless sintered Si3N4 ceramics with Li-exchanged zeolite

    Directory of Open Access Journals (Sweden)

    SNEZANA BOSKOVIC

    2004-09-01

    Full Text Available The effects of temperature on the thermal conductivity of Si3N4 sintered with Li-exchanged zeolite were investigated. The highest conductivity was measured for the ceramics sintered with 10 % of additive. The complete a->b-Si3N4 transformation and maximum density (> 98 % TD were attained with the sample sintered at 1650 ºC. However, the results show that Al and O from the additive dissolve into the b-Si3N4 structure which act as phonon scattering sites resulting in a lowering of the conductivity and a weaker temperature dependance of the conductivity.

  12. DC CONDUCTIVITY OF CERAMICS WITH CALCITE WASTE IN THE TEMPERATURE RANGE 20 - 1050C

    Directory of Open Access Journals (Sweden)

    Jan Ondruska

    2015-06-01

    Full Text Available The temperature dependences of the electrical DC conductivity of calcite waste, kaolinite and illite based ceramics were measured in the temperature range of 20 - 1050oC. The ceramic mass that was used was a mixture of 60 wt. % kaolinitic-illitic clay, 20 - 40 wt. % of this clay was fired at 1000oC for 90 min and 0, 10 and 20 wt. % of calcite waste. During heating, several processes take place - the release of the physically bound water, the burning of organic impurities, the dehydroxylation of kaolinite and illite, the decomposition of calcite, and the creation of anorthite and mullite. All of these processes were checked by means of differential thermal analysis (DTA, derivative thermogravimetry (DTG and thermodilatometry (TDA. At low temperatures (20 - 200oC, due to the release and decomposition of physically bound water, H+ and OH- are dominant charge carriers. After completion of release of physically bound water, up to the start of dehydroxylation at the temperature of ~ 450oC, the DC conductivity is dominated by a transport of Na+, K+, and Ca2+ ions. During dehydroxylation, H+ and OH- ions, which are released from kaolinite and illite lattices, contribute to the DC conductivity. Decomposition of calcite runs between ~ 700oC and 900oC. The glassy phase has a dominant influence on the DC conductivity in the fired ceramics. Its high conductivity is determined by the high mobility of Na+, K+, and Ca2+ ions.

  13. A novel processing of carbon nanotubes grown on molecular sieve coated porous ceramics

    Science.gov (United States)

    Mazumder, Sangram; Sarkar, Naboneeta; Park, Jung Gyu; Zhao, Wei; Kim, Sukyoung; Kim, Ik Jin

    2015-08-01

    The present study focuses on the growth of carbon nanotubes (CNTs) on Fe-containing zeolites coated porous ceramics by implementing three different and independent techniques, successively. Direct foaming-derived porous ceramics were subjected to hydrothermal reaction for on-site growth of NaA zeolites within it. The porous ceramics-zeolite composite was subjected to ion-exchange reaction to obtain the catalyst for CNT synthesis. Multi-walled CNTs (MWCNTs) were grown by catalytic chemical vapour deposition (CCVD) process using acetylene as carbon source. Microstructural, thermogravimetric and spectroscopic analyses showed distinctive differences in terms of hollow structural feature, yield and crystallinity of the MWCNTs with different reaction temperatures.

  14. Electrospinning of Ceramic Solid Electrolyte Nanowires for Lithium-Ion Batteries with Enhanced Ionic Conductivity

    Science.gov (United States)

    Yang, Ting

    Solid electrolytes have great potential to address the safety issues of Li-ion batteries, but better synthesis methods are still required for ceramics electrolytes such as lithium lanthanum titanate (LLTO) and lithium lanthanum zirconate (LLZO). Pellets made from ceramic nanopowders using conventional sintering can be porous due to the agglomeration of nanoparticles (NPs). Electrospinning is a simple and versatile technique for preparing oxide ceramic nanowires (NWs) and was used to prepare electrospun LLTO and LLZO NWs. Pellets prepared from the electrospun LLTO NWs had higher density, less void space, and higher Li+ conductivity compared to those comprised of LLTO prepared with conventional sol-gel methods, which demonstrated the potential that electrospinning can provide towards improving the properties of sol-gel derived ceramics. Cubic phase LLZO was stabilized at room temperature in the form of electrospun NWs without extrinsic dopants. Bulk LLZO with tetragonal structure was transformed to the cubic phase using particle size reduction via ball milling. Heating conditions that promoted particle coalescence and grain growth induced a transformation from the cubic to tetragonal phase in both types of nanostructured LLZO. Composite polymer solid electrolyte was fabricated using LLZO NWs as the filler and showed an improved ionic conductivity at room temperature. Nuclear magnetic resonance studies show that LLZO NWs partially modify the polymer matrix and create preferential pathways for Li+ conduction through the modified polymer regions. Doping did not have significant effect on improving the overall conductivity as the interfaces played a predominant role. By comparing fillers with different morphologies and intrinsic conductivities, it was found that both NW morphology and high intrinsic conductivity are desired.

  15. Improved ionic conductivity of lithium-zinc-tellurite glass-ceramic electrolytes

    Science.gov (United States)

    Widanarto, W.; Ramdhan, A. M.; Ghoshal, S. K.; Effendi, M.; Cahyanto, W. T.; Warsito

    An enhancement in the secondary battery safety demands the optimum synthesis of glass-ceramics electrolytes with modified ionic conductivity. To achieve improved ionic conductivity and safer operation of the battery, we synthesized Li2O included zinc-tellurite glass-ceramics based electrolytes of chemical composition (85-x)TeO2·xLi2O·15ZnO, where x = 0, 5, 10, 15 mol%. Samples were prepared using the melt quenching method at 800 °C followed by thermal annealing at 320 °C for 3 h and characterized. The effects of varying temperature, alternating current (AC) frequency and Li2O concentration on the structure and ionic conductivity of such glass-ceramics were determined. The SEM images of the annealed glass-ceramic electrolytes displayed rough surface with a uniform distribution of nucleated crystal flakes with sizes less than 1 μm. X-ray diffraction analysis confirmed the well crystalline nature of achieved electrolytes. Incorporation of Li2O in the electrolytes was found to generate some new crystalline phases including hexagonal Li6(TeO6), monoclinic Zn2Te3O8 and monoclinic Li2Te2O5. The estimated crystallite size of the electrolyte was ranged from ≈40 to 80 nm. AC impedance measurement revealed that the variation in the temperatures, Li2O contents, and high AC frequencies have a significant influence on the ionic conductivity of the electrolytes. Furthermore, electrolyte doped with 15 mol% of Li2O exhibited the optimum performance with an ionic conductivity ≈2.4 × 10-7 S cm-1 at the frequency of 54 Hz and in the temperature range of 323-473 K. This enhancement in the conductivity was attributed to the sizable alteration in the ions vibration and ruptures of covalent bonds in the electrolytes network structures.

  16. Enhanced thermal conductance of polymer composites through embeddingaligned carbon nanofibers

    Directory of Open Access Journals (Sweden)

    Dale K. Hensley

    2016-07-01

    Full Text Available The focus of this work is to find a more efficient method of enhancing the thermal conductance of polymer thin films. This work compares polymer thin films embedded with randomly oriented carbon nanotubes to those with vertically aligned carbon nanofibers. Thin films embedded with carbon nanofibers demonstrated a similar thermal conductance between 40–60 μm and a higher thermal conductance between 25–40 μm than films embedded with carbon nanotubes with similar volume fractions even though carbon nanotubes have a higher thermal conductivity than carbon nanofibers.

  17. Enhanced proton conductivity of yttrium-doped barium zirconate with sinterability in protonic ceramic fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Park, Ka-Young; Seo, Yongho; Kim, Ki Buem [HMC & Green Energy Research Institute, Department of Nanotechnology and Advanced Materials Engineering, Sejong University, Seoul 143-747 (Korea, Republic of); Song, Sun-Ju [Department of Materials Science and Engineering, Chonnam National University, Gwangju 550-749 (Korea, Republic of); Park, Byoungnam [Department of Materials Science and Engineering, Hongik University, Seoul 121-791 (Korea, Republic of); Park, Jun-Young, E-mail: jyoung@sejong.ac.kr [HMC & Green Energy Research Institute, Department of Nanotechnology and Advanced Materials Engineering, Sejong University, Seoul 143-747 (Korea, Republic of)

    2015-08-05

    Highlights: • Report effects of ceramic processing methods on the electrical conductivity of BZY. • Present effects of sintering aids on the conductivity and density of BZY. • CuO is the most effective sintering aid for the BZY. • Polymer gelation is the most effective method in terms of conductivity of BZY. • Grain boundary conductivity of the polymer gelation BZY is higher than others. - Abstract: In this study, we report the effects of various ceramic processing methods with different sintering aids on the relative density, crystallinity, microstructure, and electrical conductivity of proton conducting BaZr{sub 0.85}Y{sub 0.15}O{sub 3−δ} (BZY) pellets in details. First, the BZY ceramic pellets are fabricated by the solid-state reactive sintering by adding diverse sintering aids including CuO, NiO, ZnO, SnO, MgO, and Al{sub 2}O{sub 3}. Among these, CuO is found to be the most effective sintering aid in terms of the sintering temperature and total conductivity. However, transition metals as sintering aids have detrimental effects on the electrical conductivity of the BZY electrolytes. Second, the BZY electrolytes have been synthesized by four different methods: the solid-state, combustion, hydrothermal, and polymer gelation methods. The BZY pellets synthesized by the polymer gelation method exhibit dense microstructure with a high relative density of 95.3%. Moreover, the electrical conductivity of the BZY pellets synthesized by the polymer gelation method is higher than those prepared by the solid-state methods under the same test conditions: 1.28 × 10{sup −2} S cm{sup −1} (by the polymer gelation method) vs. 0.53 × 10{sup −2} S cm{sup −1} by the solid-state method at 600 °C in wet 5% H{sub 2} in Ar.

  18. Microchip electrophoresis in low-temperature co-fired ceramics technology with contactless conductivity measurement.

    Science.gov (United States)

    Fercher, Georg; Smetana, Walter; Vellekoop, Michiel J

    2009-07-01

    In this paper a novel micromachined contactless conductivity CE device produced in low temperature co-fired ceramics (LTCC) is introduced. The application of LTCC multilayer technology provides a promising method for the contactless detection of conductive compounds because of its increased dielectric constant compared with glass or plastics. The capacitive coupling of the excitation signal into the microchannel across the LTCC substrate is improved, resulting in better detection sensitivity. Two silver electrodes located externally at opposite sides at the end of the separation channel act as detector. Impedance variations in the channel are measured without galvanic contact between electrodes and fluid. Inorganic ions are separated in less than 1 min with this novel ceramic device. The limit of detection is 10 microM for potassium.

  19. Electrolytic process to produce sodium hypochlorite using sodium ion conductive ceramic membranes

    Energy Technology Data Exchange (ETDEWEB)

    Balagopal, Shekar; Malhotra, Vinod; Pendleton, Justin; Reid, Kathy Jo

    2012-09-18

    An electrochemical process for the production of sodium hypochlorite is disclosed. The process may potentially be used to produce sodium hypochlorite from seawater or low purity un-softened or NaCl-based salt solutions. The process utilizes a sodium ion conductive ceramic membrane, such as membranes based on NASICON-type materials, in an electrolytic cell. In the process, water is reduced at a cathode to form hydroxyl ions and hydrogen gas. Chloride ions from a sodium chloride solution are oxidized in the anolyte compartment to produce chlorine gas which reacts with water to produce hypochlorous and hydrochloric acid. Sodium ions are transported from the anolyte compartment to the catholyte compartment across the sodium ion conductive ceramic membrane. Sodium hydroxide is transported from the catholyte compartment to the anolyte compartment to produce sodium hypochlorite within the anolyte compartment.

  20. Life Cycle Assessment for Proton Conducting Ceramics Synthesized by the Sol-Gel Process

    Directory of Open Access Journals (Sweden)

    Soo-Sun Lee

    2014-09-01

    Full Text Available In this report, the environmental aspects of producing proton conducting ceramics are investigated by means of the environmental Life Cycle Assessment (LCA method. The proton conducting ceramics BaZr0.8Y0.2O3-δ (BZY, BaCe0.9Y0.1O2.95 (BCY10, and Sr(Ce0.9Zr0.10.95Yb0.05O3-δ (SCZY were prepared by the sol-gel process. Their material requirements and environmental emissions were inventoried, and their energy requirements were determined, based on actual production data. This latter point makes the present LCA especially worthy of attention as a preliminary indication of future environmental impact. The analysis was performed according to the recommendations of ISO norms 14040 and obtained using the Gabi 6 software. The performance of the analyzed samples was also compared with each other. The LCA results for these proton conducting ceramics production processes indicated that the marine aquatic ecotoxicity potential (MAETP made up the largest part, followed by fresh-water aquatic ecotoxicity potential (FAETP and Human Toxicity Potential (HTP. The largest contribution was from energy consumption during annealing and calcinations steps.

  1. Interpreting equilibrium-conductivity and conductivity-relaxation measurements to establish thermodynamic and transport properties for multiple charged defect conducting ceramics.

    Science.gov (United States)

    Zhu, Huayang; Ricote, Sandrine; Coors, W Grover; Kee, Robert J

    2015-01-01

    A model-based interpretation of measured equilibrium conductivity and conductivity relaxation is developed to establish thermodynamic, transport, and kinetics parameters for multiple charged defect conducting (MCDC) ceramic materials. The present study focuses on 10% yttrium-doped barium zirconate (BZY10). In principle, using the Nernst-Einstein relationship, equilibrium conductivity measurements are sufficient to establish thermodynamic and transport properties. However, in practice it is difficult to establish unique sets of properties using equilibrium conductivity alone. Combining equilibrium and conductivity-relaxation measurements serves to significantly improve the quantitative fidelity of the derived material properties. The models are developed using a Nernst-Planck-Poisson (NPP) formulation, which enables the quantitative representation of conductivity relaxations caused by very large changes in oxygen partial pressure.

  2. Thermo-mechanical test rig for experimental evaluation of thermal conductivity of ceramic pebble beds

    Energy Technology Data Exchange (ETDEWEB)

    Lo Frano, Rosa, E-mail: rosa.lofrano@ing.unipi.it; Aquaro, Donato; Pupeschi, Simone; Moscardini, Marigrazia

    2014-10-15

    Highlights: • Thermal conductivity values of bed as function of a material of known conductivity. • Minimizing the error caused by radial heat transfer. • Experimental evaluation of thermal conductivity of alumina pebble at different temperatures. • Experimental test with/without compression load. - Abstract: The experimental determination of mechanical and thermal properties of ceramic pebble beds, such as the lithium orthosilicate or lithium metatitanate, is a key issue in the framework of fusion power technology, for the reason that they are possible candidates in the design of breeder blankets. The paper deals with an experimental method for the evaluation of the thermal conductivity of ceramic pebble beds versus the temperature and compressive strain, based on a steady state heat flux through a material (alumina) of known conductivity. The alumina thermal conductivity is determined by means of the hot wire method. To assess the experimental method, a thermo-mechanical characterization of alumina pebble beds (a material largely available), having different diameters, considering a wide range of temperatures and compression forces has been carried out. Moreover preliminary tests have been performed on lithium orthosilicate and lithium metatitanate pebble beds.

  3. High-temperature electrically conductive ceramic composite and method for making same

    Energy Technology Data Exchange (ETDEWEB)

    Beck, D.E.; Gooch, J.G.; Holcombe, C.E. Jr.; Masters, D.R.

    1981-06-09

    The present invention relates to a metal-oxide ceramic composition useful in induction heating applications for treating uranium and uranium alloys. The ceramic composition is electrically conductive at room temperature and is nonreactive with molten uranium. The composition is prepared from a particulate admixture of 20 to 50 vol. % niobium and zirconium oxide which may be stabilized with an addition of a further oxide such as magnesium oxide, calcium oxide, or yttria. The composition is prepared by blending the powders, pressing or casting the blend into the desired product configuration, and then sintering the casting or compact in an inert atmosphere. In the casting operation, calcium aluminate is preferably added to the admixture in place of a like quantity of zirconia for providing a cement to help maintain the integrity of the sintered product.

  4. Multiwalled carbon nanotube-reinforced ceramic matrix composites as a promising structural material

    Energy Technology Data Exchange (ETDEWEB)

    Estili, Mehdi, E-mail: mehdiestili@gmail.co [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Department of Materials Processing, Graduate School of Engineering, Tohoku University, Sendai 980-8579 (Japan); Kwon, Hansang; Kawasaki, Akira; Cho, Seungchan; Takagi, Kenta; Kikuchi, Keiko [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Kawai, Masayoshi [Institute of Materials Structure Science, High Energy Accelerator Research Organization, Oho, Tsukuba, Ibaraki 305-0801 (Japan)

    2010-03-15

    In this paper, we introduce fully dense, multiwalled carbon nanotube (MWCNT)-reinforced ceramic matrix composites recently processed by a novel powder technology in our laboratory to be considered as a promising potential structural materials for employment in severe working conditions. A strategy is also offered to investigate the effect of working condition on the mechanical properties of MWCNTs embedded in the ceramic matrix for a reliable material selection for the working conditions needed.

  5. Ceramic Oxygen Generator for Carbon Dioxide Electrolysis Systems Project

    Data.gov (United States)

    National Aeronautics and Space Administration — In this SBIR Phase I proposal (Topic X9.01), NexTech Materials, Ltd. proposes to develop a high efficiency ceramic oxygen generation system which will separate O2...

  6. Ceramic separators based on Li+-conducting inorganic electrolyte for high-performance lithium-ion batteries with enhanced safety

    Science.gov (United States)

    Jung, Yun-Chae; Kim, Seul-Ki; Kim, Moon-Sung; Lee, Jeong-Hye; Han, Man-Seok; Kim, Duck-Hyun; Shin, Woo-Cheol; Ue, Makoto; Kim, Dong-Won

    2015-10-01

    Flexible ceramic separators based on Li+-conducting lithium lanthanum zirconium oxide are prepared as thin films and directly applied onto negative electrode to produce a separator-electrode assembly with good interfacial adhesion and low interfacial resistances. The ceramic separators show an excellent thermal stability and high ionic conductivity as compared to conventional polypropylene separator. The lithium-ion batteries assembled with graphite negative electrode, Li+-conducting ceramic separator and LiCoO2 positive electrode exhibit good cycling performance in terms of discharge capacity, capacity retention and rate capability. It is also demonstrated that the use of a ceramic separator can greatly improve safety over cells employing a polypropylene separator, which is highly desirable for lithium-ion batteries with enhanced safety.

  7. Theoretical and Experimental Analysis of Moisture-Dependent Thermal Conductivity of Lightweight Ceramic Bricks

    Science.gov (United States)

    Pavlík, Zbyšek; Fiala, Lukáš; Jerman, Miloš; Vejmelková, Eva; Pavlíková, Milena; Keppert, Martin; Černý, Robert

    2014-10-01

    The moisture-dependent thermal conductivity of two types of lightweight ceramic brick body is analyzed using both theoretical and experimental approaches. The basic physical properties are determined at first. Then, an impulse method is applied for the thermal-conductivity measurement. Initially, the material samples are dried, after that, they are exposed to liquid water for specific time intervals, and finally the moisture content is allowed to homogenize within the whole volume. The thermal-conductivity measurement is performed for different moisture contents achieved in this way. In the theoretical part, the homogenization principles are used for the calculation of the moisture-dependent thermal conductivity, utilizing the distribution functions based on the pore-size distribution measurement. Finally, a comparison of the measured and calculated data is done, and the validity of the applied effective media treatment is assessed.

  8. Structure degradation and conducting properties of the perovskite phase of yttrium ceramics

    CERN Document Server

    Kalanov, M U

    2002-01-01

    It is shown, that under normal conditions the perovskite phase of the yttrium ceramics of the [(Y,Ba)CuO sub 3 sub - subDELTA sub / sub 3] sub 3 is metastable and degrades in time. The degradation results in the YBa sub 2 Cu sub 3 O sub 7 sub - subdelta orthorhombic phase with transition into the superconducting state at T sub c = 91 K. The conductivity type changes thereby from the mixed metal-semiconductor character to the metallic one within the temperature interval of 100-300 K

  9. Examining the performance of refractory conductive ceramics as plasmonic materials: a theoretical approach

    OpenAIRE

    Kumar, Mukesh; Umezawa, Naoto; Ishii, Satoshi; Nagao, Tadaaki

    2015-01-01

    The main aim of this study is to scrutinize promising plasmonic materials by understanding their electronic structure and correlating them to the optical properties of selected refractory materials. For this purpose, the electronic and optical properties of the conductive ceramics TiC, ZrC, HfC, TaC, WC, TiN, ZrN, HfN, TaN, and WN are studied systematically by means of first-principles density functional theory. A full ab initio procedure to calculate plasma frequency from the electronic band...

  10. On the possibility of producing alumina ceramic with a slight electrical conductivity

    CERN Document Server

    Caspers, Fritz

    1989-01-01

    Antistatic alumina ceramic is desirable for certain particle accelerator applications. In general, highly insulating surface close to a charged particle beam must be avoided in order to prevent the formation of ion pockets and other unwanted electrical effects. For the AA vacuum chamber (UHV), an antistatic ferrite has been produced and successfully installed. The fabrication of antistatic alumina might be possible in a similar way. By using certain metal oxides in the cement, which holds the alumina particles together, a slight conductivity could be obtained after the firing and sintering process, without deteriorating the mechanical and outgassing properties of the alumina compound.

  11. Na+导电陶瓷的交流阻抗谱%AC Impedance Characteristics of Na+ Conductive Ceramic Electrodes

    Institute of Scientific and Technical Information of China (English)

    倪蕾蕾; 杨座国; 曾乐才; 刘宇; 祝铭

    2012-01-01

    以β″-Al2O3导电陶瓷为电解质,研究制备银/碳毡/低熔点钠盐电极(Ag/C/(NaNO3+NaNO2)),并选择银电极作为对比电极。测试条件为:温度275~400℃、频率12~105Hz。采用交流阻抗谱法(Ac)进行β″-Al2O3导电陶瓷与金属Na+界面兼容性和界面离子传导机理研究。结果表明:β″-Al2O3导电陶瓷的电导与温度关系服从于阿仑尼乌斯公式。比较两种电极可以发现,电极/电解质的界面接触对电极/电解质界面迁移阻抗和阻抗谱测试结果会有较大程度的影响。%Alumina conductive ceramic was used as solid electrolyte. Using the silver electrode as comparison one, a new electrode, silver / carbon felt / low melting sodium electrode (Ag/C/(NaNO3 + NaNO2)) as the test electrode was designed and prepared. The testing temperature ranged from 275 ℃ to 400℃ and frequency ranged from 12 Hz to 10^5Hz. The AC impedance spectroscopy was employed to study the compatibility and ion conduction mechanism between β″-Al2O3 ceramic and Na+. The results show that the conductivity of β″-Al2O3 ceramic and temperature obey the Arrhenius equation. In comparison of two electrodes, the contact between electrode and solid electrolyte plays an important role in electrode/ electrolyte interface transfer impedance and electrochemical impedance spectroscopy.

  12. Conductive polymers for carbon dioxide sensing

    NARCIS (Netherlands)

    Doan, T.C.D.

    2012-01-01

    Augmented levels of carbon dioxide (CO2) in greenhouses stimulate plant growth through photosynthesis. Wireless sensor networks monitoring CO2 levels in greenhouses covering large areas require preferably low power sensors to minimize energy consumption. Therefore, the main

  13. Modification of tubular ceramic membranes with carbon nanotubes using catalytic chemical vapor deposition.

    Science.gov (United States)

    Tran, Duc Trung; Thieffry, Guillemette; Jacob, Matthieu; Batiot-Dupeyrat, Catherine; Teychene, Benoit

    2015-01-01

    In this study, carbon nanotubes (CNTs) were successfully grown on tubular ceramic membranes using the catalytic chemical vapor deposition (CCVD) method. CNTs were synthesized at 650°C for 3-6 h under a 120 mL min(-1) flow of C2H6 on ceramic membranes impregnated with iron salt. The synthesis procedure was beforehand optimized in terms of catalyst amount, impregnation duration and reaction temperature, using small pieces of tubular ceramic membranes. The yield, size and structure of the CNTs produced were characterized using thermogravimetric analysis and microscopic imaging techniques. Afterwards, preliminary filtration tests with alginate and phenol were performed on two modified tubular membranes. The results indicate that the addition of CNTs on the membrane material increased the permeability of ceramic membrane and its ability to reject alginate and adsorb phenol, yet decreased its fouling resistance.

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

    Science.gov (United States)

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

    2008-01-01

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

  15. Electronic conduction in polymers, carbon nanotubes and graphene.

    Science.gov (United States)

    Kaiser, Alan B; Skákalová, Viera

    2011-07-01

    In the years since the discovery of organic polymers that exhibited electrical conductivities comparable to some metals, other novel carbon-based conductors have been developed, including carbon nanotubes and graphene (monolayers of carbon atoms). In this critical review, we discuss the common features and the differences in the conduction mechanisms observed in these carbon-based materials, which range from near ballistic and conventional metallic conduction to fluctuation-assisted tunnelling, variable-range hopping and more exotic mechanisms. For each category of material, we discuss the dependence of conduction on the morphology of the sample. The presence of heterogeneous disorder is often particularly important in determining the overall behaviour, and can lead to surprisingly similar conduction behaviour in polymers, carbon nanotube networks and chemically-derived graphene (122 references).

  16. Enhancement of ionic conductivity of PEO based polymer electrolyte by the addition of nanosize ceramic powders.

    Science.gov (United States)

    Wang, G X; Yang, L; Wang, J Z; Liu, H K; Dou, S X

    2005-07-01

    The ionic conductivity of polyethylene oxide (PEO) based solid polymer electrolytes (SPEs) has been improved by the addition of nanosize ceramic powders (TiO2 and AL2O3). The PEO based solid polymer electrolytes were prepared by the solution-casting method. Electrochemical measurement shows that the 10 wt% TiO2 PEO-LiClO4 polymer electrolyte has the best ionic conductivity (about 10(-4) S cm(-1) at 40-60 degrees C). The lithium transference number of the 10 wt% TiO2 PEO-LiClO4 polymer electrolyte was measured to be 0.47, which is much higher than that of bare PEO polymer electrolyte. Ac impedance testing shows that the interface resistance of ceramic-added PEO polymer electrolyte is stable. Linear sweep voltammetry measurement shows that the PEO polymer electrolytes are electrochemically stable in the voltage range of 2.0-5.0 V versus a Li/Li+ reference electrode.

  17. Space-charge impedance of rf-shielding wires with external ceramic and conducting pipes

    Science.gov (United States)

    Wang, Tai-Sen F.; Kurennoy, Sergey S.; Gluckstern, Robert L.

    2001-10-01

    We studied the electrostatic field due to a charged-particle beam with uniform particle density propagating inside an rf-shielding cage (rf cage) constructed from evenly spaced conducting wires. The beam and the rf cage are surrounded by a ceramic beam pipe positioned inside a conducting pipe concentric with the beam and the rf cage. The space-charge impedances in the long wavelength regime are investigated by considering the electrostatic fields due to the longitudinal and transverse perturbations on the density of the charged-particle beam. Shielding effects due to the rf cage are discussed and simple formulas are derived for estimating the space-charge impedances. Numerical examples are given for illustration. Comparisons between analytical estimates and the results produced by the field-solver computer program MAFIA show good agreement.

  18. Electrical conductivity improvement of aeronautical carbon fiber reinforced polyepoxy composites by insertion of carbon nanotubes

    OpenAIRE

    Lonjon, Antoine; Demont, Philippe; Dantras, Eric; Lacabanne, Colette

    2012-01-01

    International audience; An increase and homogenization of electrical conductivity is essential in epoxy carbon fiber laminar aeronautical composites. Dynamic conductivity measurements have shown a very poor transversal conductivity. Double wall carbon nanotubes have been introduced into the epoxy matrix to increase the electrical conductivity. The conductivity and the degree of dispersion of carbon nanotubes in epoxy matrix were evaluated. The epoxy matrix was filled with 0.4 wt.% of CNTs to ...

  19. Mixed Conduction in BaCe08Pr0.2O3- α Ceramic

    Institute of Scientific and Technical Information of China (English)

    Mao-yuan Wang; Li-gan Qiu

    2008-01-01

    BaCe0.8Pr0.2O3-α ceramic was synthesized by high temperature solid-state reaction. The structural char- acteristics and the phase purity of the crystal were determined using powder X-ray diffraction analysis. By using the methods of AC impedance spectroscopy, gas concentration cell and electrochemical pumping of hydrogen, the conductivity and ionic transport number of BaCe0.8Pr0.2O3-α were measured, and the elec- trical conduction behavior of the material was investigated in different gases in the temperature range of 500-900 ℃. The results indicate that the material was of a single perovskite-type orthorhombic phase. Prom 500 ℃ to 900 ℃, electronic-hole conduction was dominant in dry and wet oxygen, air or nitrogen, and the total conductivity of the material increased slightly with increasing oxygen partial pressure in the oxygen partial pressure range studied. Ionic conduction was dominant in wet hydrogen, and the total conductivity was about one or two orders of magnitude higher than that in hydrogen-free atmosphere (oxygen, air or nitrogen).

  20. Influence of gas pressure on the effective thermal conductivity of ceramic breeder pebble beds

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Weijing [School of Civil Engineering, The University of Sydney, Sydney (Australia); Pupeschi, Simone [Institute for Applied Materials, Karlsruhe Institute of Technology (KIT) (Germany); Hanaor, Dorian [School of Civil Engineering, The University of Sydney, Sydney (Australia); Institute for Materials Science and Technologies, Technical University of Berlin (Germany); Gan, Yixiang, E-mail: yixiang.gan@sydney.edu.au [School of Civil Engineering, The University of Sydney, Sydney (Australia)

    2017-05-15

    Highlights: • This study explicitly demonstrates the influence of the gas pressure on the effective thermal conductivity of pebble beds. • The gas pressure influence is shown to correlated to the pebble size. • The effective thermal conductivity is linked to thermal-mechanical properties of pebbles and packing structure. - Abstract: Lithium ceramics have been considered as tritium breeder materials in many proposed designs of fusion breeding blankets. Heat generated in breeder pebble beds due to nuclear breeding reaction must be removed by means of actively cooled plates while generated tritiums is recovered by purge gas slowly flowing through beds. Therefore, the effective thermal conductivity of pebble beds that is one of the governing parameters determining heat transport phenomenon needs to be addressed with respect to mechanical status of beds and purge gas pressure. In this study, a numerical framework combining finite element simulation and a semi-empirical correlation of gas gap conduction is proposed to predict the effective thermal conductivity. The purge gas pressure is found to vary the effective thermal conductivity, in particular with the presence of various sized gaps in pebble beds. Random packing of pebble beds is taken into account by an approximated correlation considering the packing factor and coordination number of pebble beds. The model prediction is compared with experimental observation from different sources showing a quantitative agreement with the measurement.

  1. Study on delayed cracking of conductive notch under electric field in PZT-5H ferroelectric ceramics

    Institute of Scientific and Technical Information of China (English)

    QIAO Guangli; SU Yanjing; QIAO Lijie; CHU Wuyang

    2006-01-01

    Electric-field-induced delay cracking of conducting notch in PZT-5H ferroelectric ceramics has been studied using a compact specimen with a notch filled in conductive silver paste. The critical electric field that induces instant failure of the PZT-5H specimen is shown to be EF = 14.7(3.2 kV/cm. When an electric field lower than EF, but higher than EDF = 9.9 kV/cm was applied, a micro-crack formed at the conductive notch tip instantly, propagating slowly until the specimen failure. When the electric field was lower than EDF, the micro-crack propagated a short distance, and then stopped. When the electric field was lower than EK=4.9 kV/cm, no cracks formed at the conductive notch tip instantly, however, a delay micro-crack would form and propagate. When the electric field was lower than EDK=2.4 kV/cm, no cracks formed and delay propagation occurred. A model for electric charge emission and concentration at a conductive notch is proposed to explain the delay cracking of conducting notch.

  2. Laser sintering of conductive carbon paste on plastic substrate

    Science.gov (United States)

    Kinzel, Edward C.; Kelkar, Rohan; Xu, Xianfan

    2010-02-01

    This work investigates fabrication of functional conductive carbon paste onto a plastic substrate using a laser. The method allows simultaneous sintering, patterning, and functionalization of the carbon paste. Experiments are carried out to optimize the laser processing parameters. It is shown that sheet resistance values obtained by laser sintering are close to the one specified by the manufacturer using conventional sintering method. Additionally, a heat transfer analysis using numerical methods is conducted to understand the relationship between the temperature during sintering and the sheet resistance values of sintered carbon wires. The process developed in this work has the potential of producing carbon-based electronic components on low cost plastic substrates.

  3. A Valence Electron Structure Criterion of Ionic Conductivity of Sr- and Mg-doped LaGaO3 Ceramics

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The valence electron structures of Sr- and Mg-doped LaGaO3 ceramics with different compositions were calculated by Empirical Electron Theory of Solids and Molecules (EET). A criterion for the ionic conductivity was proposed, i.e. the 1/(nAnB) increases with increasing the ionic conductivity when x or y≤20% (in molar fraction).

  4. The electrical conduction variation in stained carbon nanotubes

    Science.gov (United States)

    Sun, Shih-Jye; Wei Fan, Jun; Lin, Chung-Yi

    2012-01-01

    Carbon nanotubes become stained from coupling with foreign molecules, especially from adsorbing gas molecules. The charge exchange, which is due to the orbital hybridization, occurred in the stained carbon nanotube induces electrical dipoles that consequently vary the electrical conduction of the nanotube. We propose a microscopic model to evaluate the electrical current variation produced by the induced electrical dipoles in a stained zigzag carbon nanotube. It is found that stronger orbital hybridization strengths and larger orbital energy differences between the carbon nanotube and the gas molecules help increasing the induced electrical dipole moment. Compared with the stain-free carbon nanotube, the induced electrical dipoles suppress the current in the nanotube. In the carbon nanotubes with induced dipoles the current increases as a result of increasing orbital energy dispersion via stronger hybridization couplings. In particular, at a fixed hybridization coupling, the current increases with the bond length for the donor-carbon nanotube but reversely for the acceptor-carbon nanotube.

  5. Carbon nanotubes-porous ceramic composite by in situ CCVD growth of CNTs

    Energy Technology Data Exchange (ETDEWEB)

    Mazumder, Sangram; Sarkar, Naboneeta; Park, Jung Gyu [Institute of Processing and Application of Inorganic Materials (PAIM), Department of Materials Science and Engineering, Hanseo University, #360 Daegok-ri, Haemi-myeon, Seosan-si, Chungnam, 356-706 (Korea, Republic of); Han, In Sub [Korea Institute of Energy Research (KIER), #152 Gajeong-gu, Daejeon 305-343 (Korea, Republic of); Kim, Ik Jin, E-mail: ijkim@hanseo.ac.kr [Institute of Processing and Application of Inorganic Materials (PAIM), Department of Materials Science and Engineering, Hanseo University, #360 Daegok-ri, Haemi-myeon, Seosan-si, Chungnam, 356-706 (Korea, Republic of)

    2016-03-01

    A novel approach towards the formation of Carbon nanotubes-porous alumina ceramic composite was attempted by the application of three different reaction techniques. Porous alumina ceramics having micrometer pore dimensions were developed using the direct foaming technique. NaA zeolites were simultaneously synthesized and coated within the porous ceramics by an in situ hydrothermal process and were subjected to a simple ion exchange reaction for preparing the suitable catalyst material for Carbon nanotubes (CNTs) synthesis. The catalytic chemical vapour deposition (CCVD) technique was used to grow CNTs within the porous ceramics and the effect of growth time on the synthesized CNTs were investigated. Phase compositions of the samples were analysed by X-ray diffractometer (XRD). Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM) were used for morphology, surface quality and structural analysis. Crystallinity, defects and yield were studied by Raman spectroscopy and thermogravimetric analysis (TGA). - Highlights: • Novel processing route of MWCNTs grown on Cobalt-zeolites-porous ceramics by CCVD. • CCVD time of 120 min produced MWCNTs with most prominent tube-like structure. • 120 min produced highest yield (19.46%) of CNTs with an I{sub D}/I{sub G} ratio of 0.88.

  6. Fabrication of high thermal conductive Al-cBN ceramic sinters by high temperature high pressure method

    Science.gov (United States)

    Wang, P. F.; Li, Zh. H.; Zhu, Y. M.

    2011-05-01

    Al-cBN ceramic sinters were fabricated by sintering micro-powder mixture of Al and cBN under high temperature and high pressure condition. Differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electronic microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) elemental mapping analyses and laser flashing thermal conductivity measurements were performed to investigate the sintering properties and thermal conductivity of the Al-cBN ceramic sinters. XRD analysis revealed these Al-cBN ceramic sinters were composed of a large portion of cBN and of a small portion of AlN, and very little amount of AlB 12 and hBN. Formation of boundary phase resulted in the rapid densification of the sinters, as well as the increase of their relative density with increasing Al additions. The Al-cBN ceramic sinters have a maximum thermal conductivity of about 1.94 W/cm K at room temperature and a much higher value of about 2.04 W/cm K at 200 °C. Their high thermal conductivity over that of AlN-hBN composites promise Al-cBN ceramic sinters favorite candidates as high efficiency heat sink materials for wide band gap semiconductors.

  7. Thermal conductivity, electrical conductivity and specific heat of copper-carbon fiber composite

    Science.gov (United States)

    Kuniya, Keiichi; Arakawa, Hideo; Kanai, Tsuneyuki; Chiba, Akio

    1988-01-01

    A new material of copper/carbon fiber composite is developed which retains the properties of copper, i.e., its excellent electrical and thermal conductivity, and the property of carbon, i.e., a small thermal expansion coefficient. These properties of the composite are adjustable within a certain range by changing the volume and/or the orientation of the carbon fibers. The effects of carbon fiber volume and arrangement changes on the thermal and electrical conductivity, and specific heat of the composite are studied. Results obtained are as follows: the thermal and electrical conductivity of the composite decrease as the volume of the carbon fiber increases, and were influenced by the fiber orientation. The results are predictable from a careful application of the rule of mixtures for composites. The specific heat of the composite was dependent, not on fiber orientation, but on fiber volume. In the thermal fatigue tests, no degradation in the electrical conductivity of this composite was observed.

  8. Carbon nanotube and graphene nanoribbon-coated conductive Kevlar fibers.

    Science.gov (United States)

    Xiang, Changsheng; Lu, Wei; Zhu, Yu; Sun, Zhengzong; Yan, Zheng; Hwang, Chi-Chau; Tour, James M

    2012-01-01

    Conductive carbon material-coated Kevlar fibers were fabricated through layer-by-layer spray coating. Polyurethane was used as the interlayer between the Kevlar fiber and carbon materials to bind the carbon materials to the Kevlar fiber. Strongly adhering single-walled carbon nanotube coatings yielded a durable conductivity of 65 S/cm without significant mechanical degradation. In addition, the properties remained stable after bending or water washing cycles. The coated fibers were analyzed using scanning electron microcopy and a knot test. The as-produced fiber had a knot efficiency of 23%, which is more than four times higher than that of carbon fibers. The spray-coating of graphene nanoribbons onto Kevlar fibers was also investigated. These flexible coated-Kevlar fibers have the potential to be used for conductive wires in wearable electronics and battery-heated armors.

  9. Modeling Flow Rate to Estimate Hydraulic Conductivity in a Parabolic Ceramic Water Filter

    Directory of Open Access Journals (Sweden)

    Ileana Wald

    2012-01-01

    Full Text Available In this project we model volumetric flow rate through a parabolic ceramic water filter (CWF to determine how quickly it can process water while still improving its quality. The volumetric flow rate is dependent upon the pore size of the filter, the surface area, and the height of water in the filter (hydraulic head. We derive differential equations governing this flow from the conservation of mass principle and Darcy's Law and find the flow rate with respect to time. We then use methods of calculus to find optimal specifications for the filter. This work is related to the research conducted in Dr. James R. Mihelcic's Civil and Environmental Engineering Lab at USF.

  10. Thermal Conductivity of Carbon Nanotubes Embedded in Solids

    Institute of Scientific and Technical Information of China (English)

    CAO Bing-Yang; HOU Quan-Wen

    2008-01-01

    @@ A carbon-nanotube-atom fixed and activated scheme of non-equilibrium molecular dynamics simulations is put forward to extract the thermal conductivity of carbon nanotubes (CNTs) embedded in solid argon. Though a 6.5% volume fraction of CNTs increases the composite thermal conductivity to about twice as much as that of the pure basal material, the thermal conductivity of CNTs embedded in solids is found to be decreased by 1/8-1/5with reference to that of pure ones. The decrease of the intrinsic thermal conductivity of the solid-embedded CNTs and the thermal interface resistance are demonstrated to be responsible for the results.

  11. Grains and grain boundaries contribution to dielectric relaxations and conduction of Bi5Ti3FeO15 ceramics

    Science.gov (United States)

    Rehman, Fida; Li, Jing-Bo; Zhang, Jia-Song; Rizwan, Muhammad; Niu, Changlei; Jin, Hai-Bo

    2015-12-01

    Dielectric relaxation behaviors of Aurivillius Bi5Ti3FeO15 ceramics were investigated in a wide range of frequency and temperature via dielectric and impedance spectroscopies. We distinguished two dielectric relaxations using the combination of impedance and modulus analysis. Resistance of the grain boundary was found to be much larger than grains, whereas capacitance was at the same level. The kinetic analysis of dielectric data was carried out to evaluate the contributions of microstructure and defects to the relaxation and conduction. The possible relaxation-conduction mechanism in the ceramics was discussed. The results enable deep understanding of microstructure-defect-relaxation behaviors in Bi5Ti3FeO15 ceramics.

  12. A novel processing route for carbon nanotube reinforced glass-ceramic matrix composites

    Science.gov (United States)

    Dassios, Konstantinos G.; Bonnefont, Guillaume; Fantozzi, Gilbert; Matikas, Theodore E.

    2015-03-01

    The current study reports the establishment of a novel feasible way for processing glass- and ceramic- matrix composites reinforced with carbon nanotubes (CNTs). The technique is based on high shear compaction of glass/ceramic and CNT blends in the presence of polymeric binders for the production of flexible green bodies which are subsequently sintered and densified by spark plasma sintering. The method was successfully applied on a borosilicate glass / multi-wall CNT composite with final density identical to that of the full-dense ceramic. Preliminary non-destructive evaluation of dynamic mechanical properties such as Young's and shear modulus and Poisson's ratio by ultrasonics show that property improvement maximizes up to a certain CNT loading; after this threshold is exceeded, properties degrade with further loading increase.

  13. Improvement of strength of carbon nanotube-dispersed Si3N4 ceramics by bead milling and adding lower-temperature sintering aids

    Directory of Open Access Journals (Sweden)

    Mitsuaki Matsuoka

    2014-09-01

    Full Text Available Studies on the dispersion of carbon nanotubes (CNTs in silicon nitride (Si3N4 ceramics to provide the latter with electrical conductivity have been carried out in recent years. The density and the strength of Si3N4 ceramics were degraded, however, because the CNTs prevented Si3N4 from densifying. The CNTs disappeared after firing at high temperatures owing to the reaction between CNTs and Si3N4 or SiO2, or both Si3N4 and SiO2. In order to improve the density and suppress the reaction, sintering aids for lower-temperature densification of Si3N4 are needed. In this study, we added HfO2 as a sintering aid to a Si3N4–Y2O3–Al2O3–AlN–TiO2 system to fabricate CNT-dispersed Si3N4 ceramics at lower temperatures. Furthermore, bead milling was applied to disperse the CNTs homogeneously. Agglomerates of CNTs were pulverized by bead milling without obvious changes in morphology to eliminate larger fracture origins in CNT-dispersed ceramics. As a result of both the addition of HfO2 and bead milling, we successfully fabricated dense CNT-dispersed Si3N4 ceramics with high strength and electrical conductivity.

  14. Dielectric, Impedance and Conduction Behavior of Double Perovskite Pr2CuTiO6 Ceramics

    Science.gov (United States)

    Mahato, Dev K.; Sinha, T. P.

    2016-08-01

    Polycrystalline Pr2CuTiO6 (PCT) ceramics exhibits dielectric, impedance and modulus characteristics as a possible material for microelectronic devices. PCT was synthesized through the standard solid-state reaction method. The dielectric permittivity, impedance and electric modulus of PCT have been studied in a wide frequency (100 Hz-1 MHz) and temperature (303-593 K) range. Structural analysis of the compound revealed a monoclinic phase at room temperature. Complex impedance Cole-Cole plots are used to interpret the relaxation mechanism, and grain boundary contributions towards conductivity have been estimated. From electrical modulus formalism polarization and conductivity relaxation behavior in PCT have been discussed. Normalization of the imaginary part of impedance (Z″) and the normalized imaginary part of modulus (M″) indicates contributions from both long-range and localized relaxation effects. The grain boundary resistance along with their relaxation frequencies are plotted in the form of an Arrhenius plot with activation energy 0.45 eV and 0.46 eV, respectively. The ac conductivity mechanism has been discussed.

  15. AC impedance spectroscopy and conductivity studies of Dy doped Bi4V2O11 ceramics

    Science.gov (United States)

    Bag, Sasmitarani; Das, Parthasarathi; Behera, Banarji

    2017-03-01

    The ac impedance and conductivity properties of Dy doped Bi4V2 - x Dy x O11 (x = 0.05, 0.10, 0.15 and 0.20) ceramics prepared by solid-state reaction technique, in a wide frequency range at different temperatures have been studied. All the samples exhibited β-type phase orthorhombic structure at room temperature. The Nyquist plot confirmed the presence of both grain and grain boundary effects for all Dy doped samples. Double relaxation behavior was also observed. The grain and grain boundary resistance decreases with rise in temperature for all the concentration and exhibits a typical negative temperature co-efficient of resistance (NTCR) behavior. An analysis of the electric modulus suggests the possible hopping mechanism for electrical transport processes of all the materials. The ac conductivity spectrum obeys Jonscher's universal power law. DC conductivity of the materials were also studied and values of the activation energy found to be 0.40, 0.49, 0.73 and 0.78 eV for the compositions x = 0.05, 0.10, 0.15 and 0.20, respectively, at different temperatures (150-375 °C).

  16. Thermal Conductivity and Water Vapor Stability of Ceramic HfO2-Based Coating Materials

    Science.gov (United States)

    Zhu, Dong-Ming; Fox, Dennis S.; Bansal, Narottam P.; Miller, Robert A.

    2004-01-01

    HfO2-Y2O3 and La2Zr2O7 are candidate thermal/environmental barrier coating materials for gas turbine ceramic matrix composite (CMC) combustor liner applications because of their relatively low thermal conductivity and high temperature capability. In this paper, thermal conductivity and high temperature phase stability of plasma-sprayed coatings and/or hot-pressed HfO2-5mol%Y2O3, HfO2-15mol%Y2O3 and La2Zr2O7 were evaluated at temperatures up to 1700 C using a steady-state laser heat-flux technique. Sintering behavior of the plasma-sprayed coatings was determined by monitoring the thermal conductivity increases during a 20-hour test period at various temperatures. Durability and failure mechanisms of the HfO2-Y2O3 and La2Zr2O7 coatings on mullite/SiC Hexoloy or CMC substrates were investigated at 1650 C under thermal gradient cyclic conditions. Coating design and testing issues for the 1650 C thermal/environmental barrier coating applications will also be discussed.

  17. Tritium Sequestration in Gen IV NGNP Gas Stream via Proton Conducting Ceramic Pumps

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Fanglin Frank [Univ. of South Carolina, Columbia, SC (United States); Adams, Thad M. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Brinkman, Kyle [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Reifsnider, Kenneth [Univ. of South Carolina, Columbia, SC (United States)

    2011-09-30

    Several types of high-temperature proton conductors based on SrCeO3 and BaCeO3 have been systematically investigated in this project for tritium separation in NGNP applications. One obstacle for the field application is the chemical stability issues in the presence of steam and CO2 for these proton conductors. Several strategies to overcome such issues have been evaluated, including A site doping and B site co-doping method for perovskite-structured proton conductors. Novel zirconium-free proton conductors have also been developed with improved electrical conductivity and enhanced chemical stability. Novel catalytic materials for the proton-conducting separation membranes have been investigated. A tubular geometry proton-conducting membrane has been developed for the proton separation membranes. Total dose rate estimated from tritium decay (beta emission) under realistic membrane operating conditions, combined with electron irradiation experiments, indicates that proton ceramic materials possess the appropriate radiation stability for this application.

  18. Dielectric, Impedance and Conduction Behavior of Double Perovskite Pr2CuTiO6 Ceramics

    Science.gov (United States)

    Mahato, Dev K.; Sinha, T. P.

    2017-01-01

    Polycrystalline Pr2CuTiO6 (PCT) ceramics exhibits dielectric, impedance and modulus characteristics as a possible material for microelectronic devices. PCT was synthesized through the standard solid-state reaction method. The dielectric permittivity, impedance and electric modulus of PCT have been studied in a wide frequency (100 Hz-1 MHz) and temperature (303-593 K) range. Structural analysis of the compound revealed a monoclinic phase at room temperature. Complex impedance Cole-Cole plots are used to interpret the relaxation mechanism, and grain boundary contributions towards conductivity have been estimated. From electrical modulus formalism polarization and conductivity relaxation behavior in PCT have been discussed. Normalization of the imaginary part of impedance ( Z″) and the normalized imaginary part of modulus ( M″) indicates contributions from both long-range and localized relaxation effects. The grain boundary resistance along with their relaxation frequencies are plotted in the form of an Arrhenius plot with activation energy 0.45 eV and 0.46 eV, respectively. The ac conductivity mechanism has been discussed.

  19. Pyroelectric properties and electrical conductivity in samarium doped BiFeO 3 ceramics

    KAUST Repository

    Yao, Yingbang

    2012-06-01

    Samarium (Sm 3+) doped BiFeO 3 (BFO) ceramics were prepared by a modified solid-state-reaction method which adopted a rapid heating as well as cooling during the sintering process. The pyroelectric coefficient increased from 93 to 137 μC/m 2 K as the Sm 3+ doping level increased from 1 mol% to 8 mol%. Temperature dependence of the pyroelectric coefficient showed an abrupt decrease above 80 °C in all samples, which was associated with the increase of electrical conductivity with temperature. This electrical conduction was attributed to oxygen vacancy existing in the samples. An activation energy of ∼0.7 eV for the conduction process was found to be irrespective of the Sm 3+ doping level. On the other hand, the magnetic Néel temperature (T N) decreased with increasing Sm 3+ doping level. On the basis of our results, the effects of Sm doping level on the pyroelectric and electrical properties of the BFO were revealed. © 2011 Elsevier Ltd. All rights reserved.

  20. Separation of Hydrogen from Carbon Dioxide through Porous Ceramics

    Directory of Open Access Journals (Sweden)

    Taro Shimonosono

    2016-11-01

    Full Text Available The gas permeability of α-alumina, yttria-stabilized zirconia (YSZ, and silicon carbide porous ceramics toward H2, CO2, and H2–CO2 mixtures were investigated at room temperature. The permeation of H2 and CO2 single gases occurred above a critical pressure gradient, which was smaller for H2 gas than for CO2 gas. When the Knudsen number (λ/r ratio, λ: molecular mean free path, r: pore radius of a single gas was larger than unity, Knudsen flow became the dominant gas transportation process. The H2 fraction for the mixed gas of (20%–80% H2–(80%–20% CO2 through porous Al2O3, YSZ, and SiC approached unity with decreasing pressure gradient. The high fraction of H2 gas was closely related to the difference in the critical pressure gradient values of H2 and CO2 single gas, the inlet mixed gas composition, and the gas flow mechanism of the mixed gas. Moisture in the atmosphere adsorbed easily on the porous ceramics and affected the critical pressure gradient, leading to the increased selectivity of H2 gas.

  1. Durable, High Thermal Conductivity Melt Infiltrated Ceramic Composites for Turbine Engine Applications Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Durable, creep-resistant ceramic composites are necessary to meet the increased operating temperatures targeted for advanced turbine engines. Higher operating...

  2. Mechanically stiff, electrically conductive composites of polymers and carbon nanotubes

    Science.gov (United States)

    Worsley, Marcus A.; Kucheyev, Sergei O.; Baumann, Theodore F.; Kuntz, Joshua D.; Satcher, Jr., Joe H.; Hamza, Alex V.

    2015-07-21

    Using SWNT-CA as scaffolds to fabricate stiff, highly conductive polymer (PDMS) composites. The SWNT-CA is immersing in a polymer resin to produce a SWNT-CA infiltrated with a polymer resin. The SWNT-CA infiltrated with a polymer resin is cured to produce the stiff and electrically conductive composite of carbon nanotube aerogel and polymer.

  3. Ambient effects on the electrical conductivity of carbon nanotubes

    DEFF Research Database (Denmark)

    Roch, Aljoscha; Greifzu, Moritz; Roch Talens, Esther

    2015-01-01

    We show that the electrical conductivity of single walled carbon nanotubes (SWCNT) networks is affected by oxygen and air humidity under ambient conditions by more than a magnitude. Later, we intentionally modified the electrical conductivity by functionalization with iodine and investigated...

  4. Analysis of All-Carbon Brick Bottom and Ceramic Cup Synthetic Hearth Bottom

    Institute of Scientific and Technical Information of China (English)

    ZHAO Hong-bo; CHENG Shu-sen; ZHAO Min-ge

    2007-01-01

    One of the bottlenecks of the blast furnace (BF) campaign is the life length of hearth bottom. The basic reason for the erosion of hearth bottom is its direct contact with hot metal. According to the theory of heat transfer, models of BF hearth bottom are built based on the actual examples using software and VC language, and the calculated results are in good agreement with the data of BF dissection after blowing out. The temperature distribution and the capability of the resistance to erosion for different structures of hearth bottom are analyzed, especially the two prevalent kinds of hearth bottom arrangements called "the method of heat transfer" for all-carbon brick bottom and "the method of heat isolation" for ceramic synthetic hearth bottom. Features of the two kinds of hearth bottoms are analyzed. Also the different ways of protecting the hearth bottom are clarified, according to some actual examples. After that, the same essence of prolonging life, and the fact that the existence of a "protective skull" with low thermal conductivity between the hot metal and brick layers is of utmost importance are shown.

  5. Mesoporous Nitrogen-Doped Carbon-Glass Ceramic Cathodes for Solid-State Lithium-Oxygen Batteries (Postprint)

    Science.gov (United States)

    2012-01-01

    A. C.; Swanson, S .; Wilcke, W. J. Phys. Chem. Lett. 2010, 1, 2193−2203. (3) In Handbook of Batteries and Fuel Cells, 2nd ed.; Linden , D., Ed...AFRL-RZ-WP-TP-2012-0057 MESOPOROUS NITROGEN-DOPED CARBON-GLASS CERAMIC CATHODES FOR SOLID-STATE LITHIUM−OXYGEN BATTERIES (Postprint...November 2011 4. TITLE AND SUBTITLE MESOPOROUS NITROGEN-DOPED CARBON-GLASS CERAMIC CATHODES FOR SOLID-STATE LITHIUM−OXYGEN BATTERIES (Postprint

  6. Prediction of Thermophysical and Thermomechanical Characteristics of Porous Carbon-Ceramic Composite Materials of the Heat Shield of Aerospace Craft

    Science.gov (United States)

    Reznik, S. V.; Prosuntsov, P. V.; Mikhailovskii, K. V.

    2015-05-01

    A procedure for predicting thermophysical and thermomechanical characteristics of porous carbon-ceramic composite materials of the heat shield of aerospace craft as functions of the type of reinforcement, porosity of the structure, and the characteristics of the material's components has been developed. Results of mathematical modeling of the temperature and stressed-strained states of representative volume elements for determining the characteristics of a carbon-ceramic composite material with account taken of its anisotropy have been given.

  7. Thermal Conductivity of Advanced Ceramic Thermal Barrier Coatings Determined by a Steady-state Laser Heat-flux Approach

    Science.gov (United States)

    Zhu, Dong-Ming; Miller, Robert A.

    2004-01-01

    The development of low conductivity and high temperature capable thermal barrier coatings requires advanced testing techniques that can accurately and effectively evaluate coating thermal conductivity under future high-performance and low-emission engine heat-flux conditions. In this paper, a unique steady-state CO2 laser (wavelength 10.6 microns) heat-flux approach is described for determining the thermal conductivity and conductivity deduced cyclic durability of ceramic thermal and environmental barrier coating systems at very high temperatures (up to 1700 C) under large thermal gradients. The thermal conductivity behavior of advanced thermal and environmental barrier coatings for metallic and Si-based ceramic matrix composite (CMC) component applications has also been investigated using the laser conductivity approach. The relationships between the lattice and radiation conductivities as a function of heat flux and thermal gradient at high temperatures have been examined for the ceramic coating systems. The steady-state laser heat-flux conductivity approach has been demonstrated as a viable means for the development and life prediction of advanced thermal barrier coatings for future turbine engine applications.

  8. Universal Features of Quantized Thermal Conductance of Carbon Nanotubes

    OpenAIRE

    Yamamoto, Takahiro; Watanabe, Satoshi; Watanabe, Kazuyuki

    2003-01-01

    The universal features of quantized thermal conductance of carbon nanotubes (CNTs) are revealed through theoretical analysis based on the Landauer theory of heat transport. The phonon-derived thermal conductance of semiconducting CNTs exhibits a universal quantization in the low temperature limit, independent of the radius or atomic geometry. The temperature dependence follows a single curve given in terms of temperature scaled by the phonon energy gap. The thermal conductance of metallic CNT...

  9. Impedance characterization of epoxy composite containing conductive hybrid carbon fillers

    Science.gov (United States)

    Othman, Raja Nor; Tawil, Siti Nooraya; Zailan, Suhaila

    2017-08-01

    Epoxy composites containg carbon fillers are prepared in this work with an intention to characterise their electrical properties. The performance of electrical conductivity of epoxy composites is assessed by adding various loadings of conductive carbon fillers into the neat epoxy. First, Carbon Black (CB) was incorporated within epoxy matrix at several loadings. The increase in the specific conductivity of more than five orders of magnitude was observed between 3 wt. % and 4 wt.% CB loading, recorded at 10 kHz frequency. As such, the critical percolation loading, pc was recorded in between 3 wt.% and 4 wt.%. For the samples containing CB at loading 4 wt.% and above, the conductivity remains independent of the frequency, indicating a purely ohmic behaviour. It is also observed that the specific conductivity values can be altered by increasing the hardener stirring time up to 15 minutes, where the pc was successfully lowered down to < 3 wt. % It was further intended to study the hybrid effects by adding CNT to the composites. The conductivity data showed that the composite becomes frequency independent, even at 2 wt. % carbon loading (1 wt. % CB + 1 wt. % CNT), demonstrating the roles contributed by high aspect ratio conductive CNT in enhancing the formation of percolated path at much lower loading.

  10. Specific-heat measurement of single metallic, carbon, and ceramic fibers at very high temperature

    Science.gov (United States)

    Pradère, C.; Goyhénèche, J. M.; Batsale, J. C.; Dilhaire, S.; Pailler, R.

    2005-06-01

    The main objective of this work is to present a method for measuring the specific heat of single metallic, carbon, and ceramic fibers at very high temperature. The difficulty of the measurement is due to the microscale of the fiber (≈10μm) and the important range of temperature (700-2700K). An experimental device, a modelization of the thermal behavior, and an analytic model have been developed. A discussion on the measurement accuracy yields a global uncertainty lower than 10%. The characterization of a tungsten filament with thermal properties identical to those of the bulk allows the validation of the device and the thermal estimation method. Finally, measurements on carbon and ceramic fibers have been done at very high temperature.

  11. Tribological properties of hard carbon films on zirconia ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Erdemir, A.; Bindal, C.; Fenske, G.R. [Argonne National Lab., IL (United States); Wilbur, P. [Colorado State Univ., Fort Collins, CO (United States)

    1995-12-31

    This study investigated the tribological properties of hard diamondlike carbon (DLC) films on magnesia-partially-stabilized zirconia (MgO-PSZ) substrates over a wide range of loads, speeds, temperatures, and counterface materials. The films were 2 {micro}m-thick and produced on by ion-beam deposition at room temperature. Tribological tests were conducted on a ball-on-disk machine in open air of 30 to 50% relative humidity under contact loads of 1 to 50 N, at sliding velocities of 0.1 to 6 m/s, and at temperatures to 400{degrees}C. A1{sub 2}O{sub 3} and Si{sub 3}N{sub 4} balls were also used and rubbed against the DLC-coated MgO-PSZ disks, primarily to assess and compare their friction and wear performance to that of MgO-PSZ balls. A series of long-duration lifetime tests was run at speeds of 1, 2, and 6 m/s under a 5-N load to assess the durability of these DLC films. Test results showed that the friction coefficients of MgO-PSZ balls sliding against MgO-PSZ disks were in the range of 0.5-0.8, and the average specific wear rates of MgO-PSZ balls ranged from 10{sup {minus}5} to 5 {times} 10{sup {minus}4} mm{sup 3}/N.m, depending on sliding velocity, contact load and ambient temperature. The friction coefficients of MgO-PSZ balls sliding against the DLC-coated-MgO-PSZ disks varied between 0.03 to 0.1. The average specific wear rates of MgO-PSZ balls were reduced by factors of three to four orders of magnitude when rubbed against the DLC coated disks. These DLC films could last 1.5 million to 4 million cycles, depending on sliding velocity. Scanning electron microscopy and micro-laser Raman Spectroscopy were used to elucidate the microstructural and chemical nature of DLC films and worn surfaces.

  12. Poly(borosiloxanes as precursors for carbon fiber ceramic matrix composites

    Directory of Open Access Journals (Sweden)

    Renato Luiz Siqueira

    2007-06-01

    Full Text Available Ceramic matrix composites (CMCs, constituted of a silicon boron oxycarbide (SiBCO matrix and unidirectional carbon fiber rods as a reinforcement phase, were prepared by pyrolysis of carbon fiber rods wrapped in polysiloxane (PS or poly(borosiloxane (PBS matrices. The preparation of the polymeric precursors involved hydrolysis/condensation reactions of alkoxysilanes in the presence and absence of boric acid, with B/Si atomic ratios of 0.2 and 0.5. Infrared spectra of PBS showed evidence of Si-O-B bonds at 880 cm-1, due to the incorporation of the crosslinker trigonal units of BO3 in the polymeric network. X ray diffraction analyses exhibited an amorphous character of the resulting polymer-derived ceramics obtained by pyrolysis up to 1000 °C under inert atmosphere. The C/SiBCO composites showed better thermal stability than the C/SiOC materials. In addition, good adhesion between the carbon fiber and the ceramic phase was observed by SEM microscopy

  13. The influence of sintering on the dispersion of carbon nanotubes in ceramic matrix composites

    Science.gov (United States)

    Tapasztó, Orsolya; Lemmel, Hartmut; Markó, Márton; Balázsi, Katalin; Balázsi, Csaba; Tapasztó, Levente

    2014-10-01

    Optimizing the dispersion of carbon nanostructures in ceramic matrix composites is a fundamental technological challenge. So far most efforts have been focused on improving the dispersion of nanostructures during the powder phase processing, due to the limited information and control on their possible redistribution during the sintering. Here, we address this issue by comparing multi-walled carbon nanotubes reinforced Si3N4 composites prepared from the same starting powder dispersion but sintered using two different techniques. We employ ultra-small angle neutron scattering measurements to gain reliable information on the dispersion of nanostructures allowing a direct comparison of their redistribution during the sintering.

  14. Tough ceramic coatings: Carbon nanotube reinforced silica sol-gel

    Energy Technology Data Exchange (ETDEWEB)

    Lopez, A.J., E-mail: antoniojulio.lopez@urjc.es [Dept. de Ciencia e Ingenieria de Materiales, ESCET, Universidad Rey Juan Carlos, C/Tulipan s/n, Mostoles 28933, Madrid (Spain); Rico, A.; Rodriguez, J.; Rams, J. [Dept. de Ciencia e Ingenieria de Materiales, ESCET, Universidad Rey Juan Carlos, C/Tulipan s/n, Mostoles 28933, Madrid (Spain)

    2010-08-15

    Silica coatings reinforced with carbon nanotubes were produced via sol-gel route using two mixing techniques of the sol-gel precursors, mechanical and ultrasonic mixing, and dip-coating as deposition process on magnesium alloy substrates. Effective incorporation and distribution of 0.1 wt.% of carbon nanotubes in the amorphous silica matrix of the coatings were achieved using both techniques. Fabrication procedure determines the morphological aspects of the coating. Only mechanical mixing process produced coatings dense and free of defects. Nanoindentation technique was used to examine the influence of the fabrication process in the mechanical features of the final coatings, i.e. indentation fracture toughness, Young's modulus and hardness. A maximum toughening effect of about 24% was achieved in silica coatings reinforced with carbon nanotubes produced by the mechanical mixing route. Scanning electron microscopy investigation revealed that the toughening of these reinforced coatings was mainly due to bridging effect of the reinforcement.

  15. Examining the performance of refractive conductive ceramics as plasmonic materials: a theoretical approach

    CERN Document Server

    Kumar, Mukesh; Ishii, Satoshi; Nagao, Tadaaki

    2016-01-01

    The main aim of the study is to scrutinize promising plasmonic materials by understanding and correlating the electronic structure to optical properties of selected refractory materials. For this purpose, the electronic and optical properties of conductive ceramics TiC, ZrC, HfC, TaC, WN, TiN, ZrN, HfN, TaN and WN are studied systematically by means of the first-principles density functional theory. A full ab-initio procedure to calculate plasma frequency from electronic band structure is discussed. The dielectric functions are calculated including both interband and intraband transitions. Our calculations confirmed that transition metal nitrides such as TiN, ZrN and HfN are the strongest candidates close to the performance of conventional noble metals in the visible to the near-infrared regions. On the other hand, carbides are not suitable for plasmonic applications due to very large losses in the same regions. By adopting the dielectric functions calculated from the calculations, the scattering and absorpti...

  16. Chemical Stability of Conductive Ceramic Anodes in LiCl–Li2O Molten Salt for Electrolytic Reduction in Pyroprocessing

    Directory of Open Access Journals (Sweden)

    Sung-Wook Kim

    2016-08-01

    Full Text Available Conductive ceramics are being developed to replace current Pt anodes in the electrolytic reduction of spent oxide fuels in pyroprocessing. While several conductive ceramics have shown promising electrochemical properties in small-scale experiments, their long-term stabilities have not yet been investigated. In this study, the chemical stability of conductive La0.33Sr0.67MnO3 in LiCl–Li2O molten salt at 650°C was investigated to examine its feasibility as an anode material. Dissolution of Sr at the anode surface led to structural collapse, thereby indicating that the lifetime of the La0.33Sr0.67MnO3 anode is limited. The dissolution rate of Sr is likely to be influenced by the local environment around Sr in the perovskite framework.

  17. Recent advances in understanding the reinforcing ability and mechanism of carbon nanotubes in ceramic matrix composites

    Science.gov (United States)

    Estili, Mehdi; Sakka, Yoshio

    2014-12-01

    Since the discovery of carbon nanotubes (CNTs), commonly referred to as ultimate reinforcement, the main purpose for fabricating CNT-ceramic matrix composites has been mainly to improve the fracture toughness and strength of the ceramic matrix materials. However, there have been many studies reporting marginal improvements or even the degradation of mechanical properties. On the other hand, those studies claiming noticeable toughening measured using indentation, which is an indirect/unreliable characterization method, have not demonstrated the responsible mechanisms applicable to the nanoscale, flexible CNTs; instead, those studies proposed those classical methods applicable to microscale fiber/whisker reinforced ceramics without showing any convincing evidence of load transfer to the CNTs. Therefore, the ability of CNTs to directly improve the macroscopic mechanical properties of structural ceramics has been strongly questioned and debated in the last ten years. In order to properly discuss the reinforcing ability (and possible mechanisms) of CNTs in a ceramic host material, there are three fundamental questions to our knowledge at both the nanoscale and macroscale levels that need to be addressed: (1) does the intrinsic load-bearing ability of CNTs change when embedded in a ceramic host matrix?; (2) when there is an intimate atomic-level interface without any chemical reaction with the matrix, could one expect any load transfer to the CNTs along with effective load bearing by them during crack propagation?; and (3) considering their nanometer-scale dimensions, flexibility and radial softness, are the CNTs able to improve the mechanical properties of the host ceramic matrix at the macroscale when individually, intimately and uniformly dispersed? If so, how? Also, what is the effect of CNT concentration in such a defect-free composite system? Here, we briefly review the recent studies addressing the above fundamental questions. In particular, we discuss the new

  18. Recent advances in understanding the reinforcing ability and mechanism of carbon nanotubes in ceramic matrix composites

    Science.gov (United States)

    Estili, Mehdi; Sakka, Yoshio

    2014-01-01

    Since the discovery of carbon nanotubes (CNTs), commonly referred to as ultimate reinforcement, the main purpose for fabricating CNT–ceramic matrix composites has been mainly to improve the fracture toughness and strength of the ceramic matrix materials. However, there have been many studies reporting marginal improvements or even the degradation of mechanical properties. On the other hand, those studies claiming noticeable toughening measured using indentation, which is an indirect/unreliable characterization method, have not demonstrated the responsible mechanisms applicable to the nanoscale, flexible CNTs; instead, those studies proposed those classical methods applicable to microscale fiber/whisker reinforced ceramics without showing any convincing evidence of load transfer to the CNTs. Therefore, the ability of CNTs to directly improve the macroscopic mechanical properties of structural ceramics has been strongly questioned and debated in the last ten years. In order to properly discuss the reinforcing ability (and possible mechanisms) of CNTs in a ceramic host material, there are three fundamental questions to our knowledge at both the nanoscale and macroscale levels that need to be addressed: (1) does the intrinsic load-bearing ability of CNTs change when embedded in a ceramic host matrix?; (2) when there is an intimate atomic-level interface without any chemical reaction with the matrix, could one expect any load transfer to the CNTs along with effective load bearing by them during crack propagation?; and (3) considering their nanometer-scale dimensions, flexibility and radial softness, are the CNTs able to improve the mechanical properties of the host ceramic matrix at the macroscale when individually, intimately and uniformly dispersed? If so, how? Also, what is the effect of CNT concentration in such a defect-free composite system? Here, we briefly review the recent studies addressing the above fundamental questions. In particular, we discuss the new

  19. Development of mixed-conducting ceramic membranes for converting methane to syngas

    Energy Technology Data Exchange (ETDEWEB)

    Balachandran, U.; Maiya, P.S.; Ma, B.; Dusek, J.T.; Mieville, R.L.; Picciolo, J.J.

    1997-04-01

    The abundantly available natural gas (mostly methane) discovered in remote areas has stimulated considerable research on upgrading this gas to high-value-added clean-burning fuels such as dimethyl ether and alcohols and to pollution-fighting additives. Of the two routes to convert methane to valuable products direct and indirect, the direct route involving partial oxidation of methane to syngas (CO + H{sub 2}) by air is preferred. Syngas is the key intermediate product used to form a variety of petrochemicals and transportation fuels. This paper is concerned with the selective transport of oxygen from air for converting methane to syngas by means of a mixed-conducting ceramic oxide membrane prepared from Sr-Fe-Co-O oxide. While both perovskite and nonperovskite type Sr-Fe-Co-O oxides permeate large amounts of oxygen when the membrane tube is subjected to oxygen pressure gradients, the work shows that the nonperovskite SrFeCo{sub 0.5}O{sub x} exhibits remarkable stability during oxygen permeation. More particularly, extruded and sintered tubes from SrFeCo{sub 0.5}O{sub x} have been evaluated in a reactor operating at {approx} 850 C for conversion of methane into syngas in the presence of a reforming catalyst. Methane conversion efficiencies of {approx} 99% were observed. In addition, oxygen permeability of SrFeCo{sub 0.5}O{sub x} was measured as a function of oxygen partial pressure gradient and temperature in a gas-tight electrochemical cell. Oxygen permeability has also been calculated from conductivity data and the results are compared and discussed.

  20. Thermal Conductivity of Polyimide/Carbon Nanofiller Blends

    Science.gov (United States)

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

    2007-01-01

    In efforts to improve the thermal conductivity (TC) of Ultem(TM) 1000, it was compounded with three carbon based nano-fillers. Multiwalled carbon nanotubes (MWCNT), vapor grown carbon nanofibers (CNF) and expanded graphite (EG) were investigated. Ribbons were extruded to form samples in which the nano-fillers were aligned. Samples were also fabricated by compression molding in which the nano-fillers were randomly oriented. The thermal properties were evaluated by DSC and TGA, and the mechanical properties of the aligned samples were determined by tensile testing. The degree of dispersion and alignment of the nanoparticles were investigated with high-resolution scanning electron microscopy. The thermal conductivity of the samples was measured in both the direction of alignment as well as perpendicular to that direction using the Nanoflash technique. The results of this study will be presented.

  1. Carbon nanotube and conducting polymer composites for supercapacitors

    Institute of Scientific and Technical Information of China (English)

    Chuang Peng; Shengwen Zhang; Daniel Jewell; George Z. Chen

    2008-01-01

    Composites of carbon nanotubes and conducting polymers can be prepared via chemical synthesis, electrochemical deposition on pre-formed carbon nanotube electrodes, or by electrochemical co-deposition. The composites combine the large pseudocapacitance of the conducting polymers with the fast charging/discharging double-layer capacitance and excellent mechanical properties of the carbon nanotubes. The electrochemically co-deposited composites are the most homogeneous and show an unusual interaction between thepolymer and nanotubes, giving rise to a strengthened electron delocalisation and conjugation along the polymer chains. As a result they exhibit excellent electrochemical charge storage properties and fast charge/discharge switching, making them promising electrode mate-rials for high power supercapacitors.

  2. Carbon nanotube yarns as strong flexible conductive capacitive electrodes

    NARCIS (Netherlands)

    Liu, F.; Wagterveld, R.M.; Gebben, B.; Otto, M.J.; Biesheuvel, P.M.; Hamelers, H.V.M.

    2015-01-01

    Carbon nanotube (CNT) yarn, consisting of 23 µm diameter CNT filaments, can be used as capacitive electrodes that are long, flexible, conductive and strong, for applications in energy and electrochemical water treatment. We measure the charge storage capacity as function of salt concentration, and u

  3. MORPHOLOGY, CONDUCTIVITY AND ELECTROCHEMICAL PROPERTIES OF HYDROTHERMAL CARBONIZED POROUS CARBON MATERIALS

    Directory of Open Access Journals (Sweden)

    N. I. Nagirna

    2016-07-01

    Full Text Available The paper studies the morphology, conductivity and electrochemical properties of carbon materials, obtained from raw plant materials at different condition of hydrothermal carbonization, using low-temperature porometry, impedance spectroscopy and galvanostatic charge/discharge. It is set, that in porous structure of carbon materials micropores are dominant; when carbonization temperature increased the specific surface and pore volume decrease more than 10 times. The temperature growth results in increasing the electrical conductivity of the carbon material more than 6 orders. It is found, that the maximal value of specific capacity (1138 mА·h/g has an electrochemical system based on porous carbon carbonized at 1023 K.

  4. Thermal Protection of Carbon Fiber-Reinforced Composites by Ceramic Particles

    Directory of Open Access Journals (Sweden)

    Baljinder Kandola

    2016-06-01

    Full Text Available The thermal barrier efficiency of two types of ceramic particle, glass flakes and aluminum titanate, dispersed on the surface of carbon-fiber epoxy composites, has been evaluated using a cone calorimeter at 35 and 50 kW/m2, in addition to temperature gradients through the samples’ thicknesses, measured by inserting thermocouples on the exposed and back surfaces during the cone tests. Two techniques of dispersing ceramic particles on the surface have been employed, one where particles were dispersed on semi-cured laminate and the other where their dispersion in a phenolic resin was applied on the laminate surface, using the same method as used previously for glass fiber composites. The morphology and durability of the coatings to water absorption, peeling, impact and flexural tension were also studied and compared with those previously reported for glass-fiber epoxy composites. With both methods, uniform coatings could be achieved, which were durable to peeling or water absorption with a minimal adverse effect on the mechanical properties of composites. While all these properties were comparable to those previously observed for glass fiber composites, the ceramic particles have seen to be more effective on this less flammable, carbon fiber composite substrate.

  5. Composite yarns of multiwalled carbon nanotubes with metallic electrical conductivity.

    Science.gov (United States)

    Randeniya, Lakshman K; Bendavid, Avi; Martin, Philip J; Tran, Canh-Dung

    2010-08-16

    Unique macrostructures known as spun carbon-nanotube fibers (CNT yarns) can be manufactured from vertically aligned forests of multiwalled carbon nanotubes (MWCNTs). These yarns behave as semiconductors with room-temperature conductivities of about 5 x 10(2) S cm(-1). Their potential use as, for example, microelectrodes in medical implants, wires in microelectronics, or lightweight conductors in the aviation industry has hitherto been hampered by their insufficient electrical conductivity. In this Full Paper, the synthesis of metal-CNT composite yarns, which combine the unique properties of CNT yarns and nanocrystalline metals to obtain a new class of materials with enhanced electrical conductivity, is presented. The synthesis is achieved using a new technique, self-fuelled electrodeposition (SFED), which combines a metal reducing agent and an external circuit for transfer of electrons to the CNT surface, where the deposition of metal nanoparticles takes place. In particular, the Cu-CNT and Au-CNT composite yarns prepared by this method have metal-like electrical conductivities (2-3 x 10(5) S cm(-1)) and are mechanically robust against stringent tape tests. However, the tensile strengths of the composite yarns are 30-50% smaller than that of the unmodified CNT yarn. The SFED technique described here can also be used as a convenient means for the deposition of metal nanoparticles on solid electrode supports, such as conducting glass or carbon black, for catalytic applications.

  6. Bioelectrocatalytic mediatorless dioxygen reduction at carbon ceramic electrodes modified with bilirubin oxidase

    Energy Technology Data Exchange (ETDEWEB)

    Nogala, Wojciech; Celebanska, Anna; Szot, Katarzyna [Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw (Poland); Wittstock, Gunther, E-mail: gunther.wittstock@uni-oldenburg.d [Carl von Ossietzky University of Oldenburg, Faculty of Mathematics and Science, Center of Interface Science (CIS), Department of Pure and Applied Chemistry, D-26111 Oldenburg (Germany); Opallo, Marcin, E-mail: mopallo@ichf.edu.p [Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw (Poland)

    2010-08-01

    Carbon ceramic electrodes were prepared by sol-gel processing of a hydrophobic precursor - methyltrimethoxysilane (MTMOS) - together with dispersed graphite microparticles according to a literature procedure. Bilirubin oxidase (BOx) was adsorbed on this electrode from buffer solution and this process was followed by atomic force microscopy (AFM). The electrodes exhibited efficient mediatorless electrocatalytic activity towards dioxygen reduction. The activity depends on the time of adsorption of the enzyme and the pH. The electrode remains active in neutral solution. The bioelectrocatalytic activity is further increased when a fraction of the carbon microparticles is replaced by sulfonated carbon nanoparticles (CNPs). This additive enhances the electrical communication between the enzyme and the electronic conductor. At pH 7 the carbon ceramic electrode modified with bilirubin oxidase retains ca. half of its highest activity. The role of the modified nanoparticles is confirmed by experiments in which a film embedded in a hydrophobic silicate matrix also exhibited efficient mediatorless biocatalytic dioxygen reduction. Scanning electrochemical microscopy (SECM) of the studied electrodes indicated a rather even distribution of the catalytic activity over the electrode surface.

  7. Thermochemical ablation of carbon/carbon composites with non-linear thermal conductivity

    Directory of Open Access Journals (Sweden)

    Li Wei-Jie

    2014-01-01

    Full Text Available Carbon/carbon composites have been typically used to protect a rocket nozzle from high temperature oxidizing gas. Based on the Fourier’s law of heat conduction and the oxidizing ablation mechanism, the ablation model with non-linear thermal conductivity for a rocket nozzle is established in order to simulate the one-dimensional thermochemical ablation rate on the surface and the temperature distributions by using a written computer code. As the presented results indicate, the thermochemical ablation rate of a solid rocket nozzle calculated by using actual thermal conductivity, which is a function of temperature, is higher than that by a constant thermal conductivity, so the effect of thermal conductivity on the ablation rate of a solid rocket nozzle made of carbon/carbon composites cannot be neglected.

  8. Lattice Thermal Conductivity of Ultra High Temperature Ceramics ZrB2 and HfB2 from Atomistic Simulations

    Science.gov (United States)

    Lawson, John W.; Murray, Daw S.; Bauschlicher, Charles W., Jr.

    2011-01-01

    Atomistic Green-Kubo simulations are performed to evaluate the lattice thermal conductivity for single crystals of the ultra high temperature ceramics ZrB2 and HfB2 for a range of temperatures. Recently developed interatomic potentials are used for these simulations. Heat current correlation functions show rapid oscillations which can be identified with mixed metal-Boron optical phonon modes. Agreement with available experimental data is good.

  9. Thermography Used to Test Conductivity of Carbon Based Cloth

    Science.gov (United States)

    Craven, Paul

    2012-01-01

    Testing of the ability of carbon fiber to radiatively cool a heat source. The carbon fibers are attached to a heat source. The heat conducts into the fiber than along the fiber away from the heat source. The test are done in a vacuum chamber (10-5 Torr typical). The IR camera is viewing the fiber through a ZnSe window. A thermocouple (TC) in contact with the fiber is at the top right hand side of the area of interest and one is near the bottom. Thin shielding fins, seen edge on, are just above the top thermocouple.

  10. Nanodomain Structure and Energetics of Carbon Rich SiCN and SiBCN Polymer-Derived Ceramics

    OpenAIRE

    Gao, Yan

    2014-01-01

    This Ph.D. thesis focuses on the synthesis, processing, solid state structure, nanodomain structure, structural evolution, thermodynamic stability, and functional properties of carbon rich SiCN and SiBCN ceramics derived from preceramic polymers with tailored compositions and structures. The main objective of the studies is to better understand the effects of the composition and structure of the starting precursors, on the behavior of the resultant ceramics. First, a set of preceramic pol...

  11. Laser Processing of Carbon Nanotube Transparent Conducting Films

    Science.gov (United States)

    Mann, Andrew

    Transparent conducting films, or TCFs, are 2D electrical conductors with the ability to transmit light. Because of this, they are used in many popular electronics including smart phones, tablets, solar panels, and televisions. The most common material used as a TCF is indium tin oxide, or ITO. Although ITO has great electrical and optical characteristics, it is expensive, brittle, and difficult to pattern. These limitations have led researchers toward other materials for the next generation of displays and touch panels. The most promising material for next generation TCFs is carbon nanotubes, or CNTs. CNTs are cylindrical tubes of carbon no more than a few atoms thick. They have different electrical and optical properties depending on their atomic structure, and are extremely strong. As an electrode, they conduct electricity through an array of randomly dispersed tubes. The array is highly transparent because of gaps between the tubes, and size and optical properties of the CNTs. Many research groups have tried making CNT TCFs with opto-electric properties similar to ITO but have difficultly achieving high conductivity. This is partly attributed to impurities from fabrication and a mix of different tube types, but is mainly caused by low junction conductivity. In functionalized nanotubes, junction conductivity is impaired by covalently bonded molecules added to the sidewalls of the tubes. The addition of this molecule, known as functionalization, is designed to facilitate CNT dispersion in a solvent by adding properties of the molecule to the CNTs. While necessary for a good solution, functionalization decreases the conductivity in the CNT array by creating defects in the tube's structures and preventing direct inter-carbon bonding. This research investigates removing the functional coating (after tube deposition) by laser processing. Laser light is able to preferentially heat the CNTs because of their optical and electrical properties. Through local conduction

  12. Characterization of silicon-silicon carbide ceramic derived from carbon-carbon silicon carbide composites

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, Vijay K. [Indian Institute of Technology, Varanasi (India). Dept. of Mechanical Engineering; Krenkel, Walter [Univ. of Bayreuth (Germany). Dept. of Ceramic Materials Engineering

    2013-04-15

    The main objective of the present work is to process porous silicon - silicon carbide (Si - SiC) ceramic by the oxidation of carboncarbon silicon carbide (C/C - SiC) composites. Phase studies are performed on the oxidized porous composite to examine the changes due to the high temperature oxidation. Further, various characterization techniques are performed on Si- SiC ceramics in order to study the material's microstructure. The effects of various parameters such as fiber alignment (twill weave and short/chopped fiber) and phenolic resin type (resol and novolak) are characterized.

  13. Conductive Behaviors of Carbon Nanofibers Reinforced Epoxy Composites

    Institute of Scientific and Technical Information of China (English)

    MEI Qilin; WANG Jihui; WANG Fuling; HUANG Zhixiong; YANG Xiaolin; WEI Tao

    2008-01-01

    By means of ultrasonic dispersion,carbon nanofibers reinforced epoxy resin composite was prepared in the lab,the electrical conductivity of composite with different carbon nanofibers loadings were studied,also the voltage-current relationship,resistance-temperature properties and mechano-electric effect were investigated.Results show that the resistivity of composite decreases in geometric progression with the increasing of carbon nanofibers,and the threshold ranges between 0.1 wt%-0.2 wt%.The voltage-current relationship is in good conformity with the Ohm's law,both positive temperature coefficient and negative temperature coefficient can be found at elevated temperature.In the course of stretching,the electrical resistance of the composites increases with the stress steadily and changes sharply near the breaking point,which is of importance for the safety monitor and structure health diagnosis.

  14. Improved Electrical Conductivity of Carbon/Polyvinyl Alcohol Electrospun Nanofibers

    Directory of Open Access Journals (Sweden)

    Nader Shehata

    2015-01-01

    Full Text Available Carbon nanofibers (CNFs gained much interest in the last few years due to their promising electrical, chemical, and mechanical characteristics. This paper investigates a new nanocomposite composed of carbon nanofibers hosted by PVA and both are integrated in one electrospun nanofibers web. This technique shows a simple and cheap way to offer a host for CNFs using traditional deposition techniques. The results show that electrical conductivity of the formed nanofibers has been improved up to 1.63 × 10−4 S/cm for CNFs of weight 2%. The peak temperature of mass loss through TGA measurements has been reduced by 2.3%. SEM images show the homogeneity of the formed PVA and carbon nanofibers in one web, with stretched CNFs after the electrospinning process. The formed nanocomposite can be used in wide variety of applications including nanoelectronics and gas adsorption.

  15. Active carbon-ceramic sphere as support of ruthenium catalysts for catalytic wet air oxidation (CWAO) of resin effluent.

    Science.gov (United States)

    Liu, Wei-Min; Hu, Yi-Qiang; Tu, Shan-Tung

    2010-07-15

    Active carbon-ceramic sphere as support of ruthenium catalysts were evaluated through the catalytic wet air oxidation (CWAO) of resin effluent in a packed-bed reactor. Active carbon-ceramic sphere and ruthenium catalysts were characterized by N(2) adsorption and chemisorption measurements. BET surface area and total pore volume of active carbon (AC) in the active carbon-ceramic sphere increase with increasing KOH-to-carbon ratio, and AC in the sample KC-120 possesses values as high as 1100 m(2) g(-1) and 0.69 cm(3) g(-1) (carbon percentage: 4.73 wt.%), especially. Active carbon-ceramic sphere supported ruthenium catalysts were prepared using the RuCl(3) solution impregnation onto these supports, the ruthenium loading was fixed at 1-5 wt.% of AC in the support. The catalytic activity varies according to the following order: Ru/KC-120>Ru/KC-80>Ru/KC-60>KC-120>without catalysts. It is found that the 3 wt.% Ru/KC-120 catalyst displays highest stability in the CWAO of resin effluent during 30 days. Chemical oxygen demand (COD) and phenol removal were about 92% and 96%, respectively at the reaction temperature of 200 degrees C, oxygen pressure of 1.5 MPa, the water flow rate of 0.75 L h(-1) and the oxygen flow rate of 13.5 L h(-1).

  16. Thermochemical ablation of carbon/carbon composites with non-linear thermal conductivity

    OpenAIRE

    2014-01-01

    Carbon/carbon composites have been typically used to protect a rocket nozzle from high temperature oxidizing gas. Based on the Fourier’s law of heat conduction and the oxidizing ablation mechanism, the ablation model with non-linear thermal conductivity for a rocket nozzle is established in order to simulate the one-dimensional thermochemical ablation rate on the surface and the temperature distributions by using a written computer code. As the presented re...

  17. Thermally Conductive Tape Based on Carbon Nanotube Arrays

    Science.gov (United States)

    Kashani, Ali

    2011-01-01

    To increase contact conductance between two mating surfaces, a conductive tape has been developed by growing dense arrays of carbon nanotubes (CNTs, graphite layers folded into cylinders) on both sides of a thermally conductive metallic foil. When the two mating surfaces are brought into contact with the conductive tape in between, the CNT arrays will adhere to the mating surface. The van der Waals force between the contacting tubes and the mating surface provides adhesion between the two mating surfaces. Even though the thermal contact conductance of a single tube-to-tube contact is small, the tremendous amount of CNTs on the surface leads to a very large overall contact conductance. Interface contact thermal resistance rises from the microroughness and the macroscopic non-planar quality of mating surfaces. When two surfaces come into contact with each other, the actual contact area may be much less than the total area of the surfaces. The real area of contact depends on the load, the surface roughness, and the elastic and inelastic properties of the surface. This issue is even more important at cryogenic temperatures, where materials become hard and brittle and vacuum is used, which prevents any gas conduction through the interstitial region. A typical approach to increase thermal contact conductance is to use thermally conducting epoxies or greases, which are not always compatible with vacuum conditions. In addition, the thermal conductivities of these compounds are often relatively low. The CNTs used in this approach can be metallic or semiconducting, depending on the folding angle and diameter. The electrical resistivity of multiwalled carbon nanotubes (MWCNTs) has been reported. MWCNTs can pass a current density and remain stable at high temperatures in air. The thermal conductivity of a MWCNT at room temperature is measured to be approximately 3,000 W/m-K, which is much larger than that of diamond. At room temperature, the thermal conductance of a 0.3 sq cm

  18. Predicting the effective thermal conductivity of carbon nanotube based nanofluids

    Energy Technology Data Exchange (ETDEWEB)

    Sastry, N N Venkata; Bhunia, Avijit; Sundararajan, T; Das, Sarit K [Department of Mechanical Engineering, Indian Institute of Technology, Madras, Chennai 600 036 (India)

    2008-02-06

    Adding a small volume fraction of carbon nanotubes (CNTs) to a liquid enhances the thermal conductivity significantly. Recent experimental findings report an anomalously wide range of enhancement values that continue to perplex the research community and remain unexplained. In this paper we present a theoretical model based on three-dimensional CNT chain formation (percolation) in the base liquid and the corresponding thermal resistance network. The model considers random CNT orientation and CNT-CNT interaction forming the percolating chain. Predictions are in good agreement with almost all available experimental data. Results show that the enhancement critically depends on the CNT geometry (length), volume fraction, thermal conductivity of the base liquid and the nanofluid (CNT-liquid suspension) preparation technique. Based on the physical mechanism of heat conduction in the nanofluid, we introduce a new dimensionless parameter that alone characterizes the nanofluid thermal conductivity with reasonable accuracy ({approx} {+-} 5%)

  19. Predicting the effective thermal conductivity of carbon nanotube based nanofluids.

    Science.gov (United States)

    Venkata Sastry, N N; Bhunia, Avijit; Sundararajan, T; Das, Sarit K

    2008-02-06

    Adding a small volume fraction of carbon nanotubes (CNTs) to a liquid enhances the thermal conductivity significantly. Recent experimental findings report an anomalously wide range of enhancement values that continue to perplex the research community and remain unexplained. In this paper we present a theoretical model based on three-dimensional CNT chain formation (percolation) in the base liquid and the corresponding thermal resistance network. The model considers random CNT orientation and CNT-CNT interaction forming the percolating chain. Predictions are in good agreement with almost all available experimental data. Results show that the enhancement critically depends on the CNT geometry (length), volume fraction, thermal conductivity of the base liquid and the nanofluid (CNT-liquid suspension) preparation technique. Based on the physical mechanism of heat conduction in the nanofluid, we introduce a new dimensionless parameter that alone characterizes the nanofluid thermal conductivity with reasonable accuracy (∼ ± 5%).

  20. High conductivity transparent carbon nanotube films deposited from superacid

    Energy Technology Data Exchange (ETDEWEB)

    Hecht, David S; Lee, Roland; Hu Liangbing [Unidym Incorporated, 1244 Reamwood Drive, Sunnyvale, CA 94089 (United States); Heintz, Amy M; Moore, Bryon; Cucksey, Chad; Risser, Steven, E-mail: dhecht@gmail.com [Battelle, 505 King Avenue, Columbus, OH 43201 (United States)

    2011-02-18

    Carbon nanotubes (CNTs) were deposited from a chlorosulfonic superacid solution onto PET substrates by a filtration/transfer method. The sheet resistance and transmission (at 550 nm) of the films were 60 {Omega}/sq and 90.9% respectively, which corresponds to a DC conductivity of 12 825 S cm{sup -1} and a DC/optical conductivity ratio of 64.1. This is the highest DC conductivity reported for CNT thin films to date, and attributed to both the high quality of the CNT material and the exfoliation/doping by the superacid. This work demonstrates that CNT transparent films have not reached the conductivity limit; continued improvements will enable these films to be used as the transparent electrode for applications in solid state lighting, LCD displays, touch panels, and photovoltaics.

  1. High conductivity transparent carbon nanotube films deposited from superacid.

    Science.gov (United States)

    Hecht, David S; Heintz, Amy M; Lee, Roland; Hu, Liangbing; Moore, Bryon; Cucksey, Chad; Risser, Steven

    2011-02-18

    Carbon nanotubes (CNTs) were deposited from a chlorosulfonic superacid solution onto PET substrates by a filtration/transfer method. The sheet resistance and transmission (at 550 nm) of the films were 60 Ω/sq and 90.9% respectively, which corresponds to a DC conductivity of 12,825 S cm(-1) and a DC/optical conductivity ratio of 64.1. This is the highest DC conductivity reported for CNT thin films to date, and attributed to both the high quality of the CNT material and the exfoliation/doping by the superacid. This work demonstrates that CNT transparent films have not reached the conductivity limit; continued improvements will enable these films to be used as the transparent electrode for applications in solid state lighting, LCD displays, touch panels, and photovoltaics.

  2. Carbon nanotube dispersed conductive network for microbial fuel cells

    Science.gov (United States)

    Matsumoto, S.; Yamanaka, K.; Ogikubo, H.; Akasaka, H.; Ohtake, N.

    2014-08-01

    Microbial fuel cells (MFCs) are promising devices for capturing biomass energy. Although they have recently attracted considerable attention, their power densities are too low for practical use. Increasing their electrode surface area is a key factor for improving the performance of MFC. Carbon nanotubes (CNTs), which have excellent electrical conductivity and extremely high specific surface area, are promising materials for electrodes. However, CNTs are insoluble in aqueous solution because of their strong intertube van der Waals interactions, which make practical use of CNTs difficult. In this study, we revealed that CNTs have a strong interaction with Saccharomyces cerevisiae cells. CNTs attach to the cells and are dispersed in a mixture of water and S. cerevisiae, forming a three-dimensional CNT conductive network. Compared with a conventional two-dimensional electrode, such as carbon paper, the three-dimensional conductive network has a much larger surface area. By applying this conductive network to MFCs as an anode electrode, power density is increased to 176 μW/cm2, which is approximately 25-fold higher than that in the case without CNTs addition. Maximum current density is also increased to approximately 8-fold higher. These results suggest that three-dimensional CNT conductive network contributes to improve the performance of MFC by increasing surface area.

  3. Excess conductivity and the pseudogap state in Hf-doped YBa2Cu3O7-δ ceramics

    Science.gov (United States)

    Savich, S. V.; Samoilov, A. V.; Vovk, R. V.; Dobrovolskiy, O. V.; Kamchatna, S. N.; Dolgopolova, Ya. V.; Chernovol-Tkachenko, O. A.

    2016-12-01

    The electrical conductivity of hafnium (Hf)-doped YBa2Cu3O7-δ ceramics is investigated. Hf doping has been revealed to lead to an increase of the number of effective scattering centers for the normal charge carriers. In a broad temperature range, the excess conductivity of the investigated samples obeys an exponential temperature dependence, while near Tc it is satisfactorily described by the Aslamazov-Larkin model. Meanwhile, Hf doping has been shown to lead to a notable broadening of the temperature range for the manifestation of the pseudogap anomaly in the ab-plane.

  4. Phase Stability and Thermal Conductivity of Composite Environmental Barrier Coatings on SiC/SiC Ceramic Matrix Composites

    Science.gov (United States)

    Benkel, Samantha; Zhu, Dongming

    2011-01-01

    Advanced environmental barrier coatings are being developed to protect SiC/SiC ceramic matrix composites in harsh combustion environments. The current coating development emphasis has been placed on the significantly improved cyclic durability and combustion environment stability in high-heat-flux and high velocity gas turbine engine environments. Environmental barrier coating systems based on hafnia (HfO2) and ytterbium silicate, HfO2-Si nano-composite bond coat systems have been processed and their stability and thermal conductivity behavior have been evaluated in simulated turbine environments. The incorporation of Silicon Carbide Nanotubes (SiCNT) into high stability (HfO2) and/or HfO2-silicon composite bond coats, along with ZrO2, HfO2 and rare earth silicate composite top coat systems, showed promise as excellent environmental barriers to protect the SiC/SiC ceramic matrix composites.

  5. Electrically conducting nanobiocomposites using carbon nanotubes and collagen waste fibers

    Energy Technology Data Exchange (ETDEWEB)

    Meiyazhagan, Ashokkumar; Thangavel, Saravanamoorthy [Advanced Materials Laboratory, Center for Leather Apparel & Accessories Development, Central Leather Research Institute (Council of Scientific and Industrial Research), Adyar, Chennai 600020 (India); Hashim, Daniel P.; Ajayan, Pulickel M. [Department of Materials Science and NanoEngineering, Rice University, Houston, TX 77005 (United States); Palanisamy, Thanikaivelan, E-mail: thanik8@yahoo.com [Advanced Materials Laboratory, Center for Leather Apparel & Accessories Development, Central Leather Research Institute (Council of Scientific and Industrial Research), Adyar, Chennai 600020 (India)

    2015-05-01

    Electrically conducting hybrid biocomposite films were prepared using a simple and cost-effective method by incorporating different types of carbon nanotubes (XCNTs) viz., few walled carbon nanotube (FWCNT) and boron doped carbon nanotube (BCNT) into biopolymers. Collagen extracted from animal skin wastes was blended with guar gum and XCNTs in varying proportions to form flexible and electrically conducting hybrid films. We found that the electrical conductivity of both types of hybrid films increases radically as the XCNT loading increases. BCNT incorporated hybrid films show better electrical conductivity (3.0 × 10{sup −1} S/cm) than their FWCNT loaded counter parts (4.8 × 10{sup −4} S/cm) at a dosage of 2 wt.%. On the other hand, mechanical and other physical properties such as transparency, flexibility and surface smoothness of the developed hybrid films were affected as a function of XCNT concentration. We also demonstrated that the developed hybrid films lit up a LED lamp when inserted between batteries and the brightness of the emitted light depended on the XCNT loading. These results suggest a new way to transform an industrial biowaste into innovative advanced materials for applications in fields related to biomedicine, biosensors and electronics. - Highlights: • Hybrid nanobiocomposite films prepared using collagen, guar gum and CNTs. • Examined the effect of CNT doping on the properties of hybrid biocomposite films. • Higher CNT loading improved the conductivity radically, especially for BCNT. • The ability of developed hybrid films to lit up a LED lamp was demonstrated. • The results suggest a new way to transform biowaste into advanced materials.

  6. New Effective Material Couple--Oxide Ceramic and Carbon Nanotube-- Developed for Aerospace Microsystem and Micromachine Technologies

    Science.gov (United States)

    Miyoshi, Kazuhisa; VanderWal, Randall L.; Tomasek, Aaron J.; Sayir, Ali; Farmer, Serene C.

    2004-01-01

    lubrication task because of their potential for superior friction and wearf properties in air and in an ultrahigh vacuum, spacelike environment. At the NASA Glenn Research Center, two-phase oxide ceramic eutectics, Al2O3/ZrO2(Y2O3), were directionally solidified using the laser-float-zone process, and carbon nanotubes were synthesized within a high-temperature tube furnace at 800 C. Physical vapor deposition was used to coat all quartz substrates with 5-nm-thick iron as catalyst and bondcoat, which formed iron islands resembling droplets and serving as catalyst particles on the quartz. A series of scanning electron micrographs showing multiwalled carbon nanotubes directionally grown as aligned "nanograss" on quartz is presented. Unidirectional sliding friction eperiments were conducted at Glenn with the two-layered CNT coatings in contact with the two-phase Al2O3/ZrO2(Y2O3) eutectics in air and in ultrachigh vacuum. The main criteria for judging the performance of the materials couple for solid lubrication and antistick applications in a space environment were the coefficient of friction and the wear resistance (reciprocal of wear rate), which had to be less than 0.2 and greater than 10(exp 5) N(raised dot)/cubic millimetes, respectively, in ultrahigh vacuum. In air, the coefficient of friction for the CNT coatings in contact with Al2O3/ZrO2 (Y2O3) eutectics was 0.04, one-fourth of that for quartz. In an ultrahigh vacuum, the coefficient of friction for CNT coatings in contact with Al2O3/ZrO2 (Y2O3) was one-third of that for quartz. The two-phase Al2O3/ZrO2 (Y2O3) eutectic coupled with the two-layered CNT coating met the coefficient of friction and wear resistance criteria both in air and in an ultrahigh vacuum, spacelike environment. This material's couple can dramatically improve the stiction (or adhesion), friction, and wear resistance of the contacting surfaces, which are major issues for microdevices and micromachines.

  7. Local thermal conductivity of polycrystalline AlN ceramics measured by scanning thermal microscopy and complementary scanning electron microscopy techniques

    Institute of Scientific and Technical Information of China (English)

    Zhang Yue-Fei; Wang Li; R. Heiderhoff; A. K. Geinzer; Wei Bin; Ji Yuan; Han Xiao-Dong; L. J. Balk; Zhang Ze

    2012-01-01

    The local thermal conductivity of polycrystalline aluminum nitride (AlN) ceramics is measured and imaged by using a scanning thermal microscope (SThM) and complementary scanning electron microscope (SEM) based techniques at room temperature.The quantitative thermal conductivity for the AlN sample is gained by using a SThM with a spatial resolution of sub-micrometer scale through using the 3w method.A thermal conductivity of 308 W/m·K withingrains corresponding to that of high-purity single crystal AlN is obtained.The slight differences in thermal conduction between the adjacent grains are found to result from crystallographic misorientations,as demonstrated in the electron backscattered diffraction.A much lower thermal conductivity at the grain boundary is due to impurities and defects enriched in these sites,as indicated by energy dispersive X-ray spectroscopy.

  8. Reliability and effective thermal conductivity of three metallic-ceramic composite insulating coatings on cooled hydrogen-oxygen rockets

    Science.gov (United States)

    Price, H. G., Jr.; Schacht, R. L.; Quentmeyer, R. J.

    1973-01-01

    An experimental investigation of the structural integrity and effective thermal conductivity of three metallic-ceramic composite coatings was conducted. These coatings were plasma sprayed onto the combustion side of water-cooled, 12.7-centimeter throat diameter, hydrogen-oxygen rocket thrust chambers operating at 2.07 to 4.14 meganewtons per square meter chamber pressure. The metallic-ceramic composites functioned for six to 17 cycles and for as long as 213 seconds of rocket operations and could have probably provided their insulating properties for many additional cycles. The effective thermal conductivity of all the coatings was in the range of 0.7472 to 4.483 w/(m)(K), which makes the coatings a very effective thermal barrier. Photomicrographic studies of cross-sectioned coolant tubes seem to indicate that the effective thermal conductivity of the coatings is controlled by contact resistance between the particles, as a result of the spraying process, and not the thermal conductivity of the bulk materials.

  9. Conductive paper from lignocellulose wood microfibers coated with a nanocomposite of carbon nanotubes and conductive polymers

    Energy Technology Data Exchange (ETDEWEB)

    Agarwal, Mangilal; Xing Qi; Lvov, Yuri [Institute for Micromanufacturing, Louisiana Tech University, Ruston, LA 71272 (United States); Shim, Bong Sup; Kotov, Nicholas [Chemical Engineering Department, University of Michigan, Ann Arbor, MI 48109 (United States); Varahramyan, Kody [Electrical and Computer Engineering Department, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202 (United States)], E-mail: agarwal@iupui.edu

    2009-05-27

    Composite nanocoating of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) and aqueous dispersion of carbon nanotubes (CNT-PSS) on lignocellulose wood microfibers has been developed to make conductive microfibers and paper sheets. To construct the multilayers on wood microfibers, cationic poly(ethyleneimine) (PEI) has been used in alternate deposition with anionic conductive PEDOT-PSS and solubilized CNT-PSS. Using a Keithley microprobe measurement system, current-voltage measurements have been carried out on single composite microfibers after deposition of each layer to optimize the electrical properties of the coated microfibers. The conductivity of the resultant wood microfibers was in the range of 10{sup -2}-2 S cm{sup -1} depending on the architecture of the coated layer. Further, the conductivity of the coated wood microfibers increased up to 20 S cm{sup -1} by sandwiching multilayers of conductive co-polymer PEDOT-PSS with CNT-PSS through a polycation (PEI) interlayer. Moreover, paper hand sheets were manufactured from these coated wood microfibers with conductivity ranging from 1 to 20 S cm{sup -1}. A paper composite structure consisting of conductive/dielectric/conductive layers that acts as a capacitor has also been fabricated and is reported.

  10. Hydraulic conductivities of fractures and matrix in Slovenian carbonate aquifers

    Directory of Open Access Journals (Sweden)

    Timotej Verbovšek

    2008-12-01

    Full Text Available Hydraulic conductivities and specific storage coefficients of fractures and matrix in Slovenian carbonate aquifers were determined by Barker’s method for pumping test analysis, based on fractional flow dimension. Values are presented for limestones and mainly for dolomites, and additionally for separate aquifers, divided by age andlithology in several groups. Data was obtained from hydrogeological reports for 397 water wells, and among these, 79 pumping tests were reinterpreted. Hydraulic conductivities of fractures are higher than the hydraulic conductivities of matrix, and the differences are highly statistically significant. Likewise, differences are significant for specific storage, and the values of these coefficients are higher in the matrix. Values of all coefficients vary in separate aquifers, and the differences can be explained by diagenetic effects, crystal size, degree of fracturing, andcarbonate purity. Comparison of the methods, used in the reports, and the Barker’s method (being more suitable for karstic and fractured aquifers, shows that the latter fits real data better.

  11. Magnetoresistance, electrical conductivity, and Hall effect of glassy carbon

    Energy Technology Data Exchange (ETDEWEB)

    Baker, D.F.

    1983-02-01

    These properties of glassy carbon heat treated for three hours between 1200 and 2700/sup 0/C were measured from 3 to 300/sup 0/K in magnetic fields up to 5 tesla. The magnetoresistance was generally negative and saturated with reciprocal temperature, but still increased as a function of magnetic field. The maximum negative magnetoresistance measured was 2.2% for 2700/sup 0/C material. Several models based on the negative magnetoresistance being proportional to the square of the magnetic moment were attempted; the best fit was obtained for the simplest model combining Curie and Pauli paramagnetism for heat treatments above 1600/sup 0/C. Positive magnetoresistance was found only in less than 1600/sup 0/C treated glassy carbon. The electrical conductivity, of the order of 200 (ohm-cm)/sup -1/ at room temperature, can be empirically written as sigma = A + Bexp(-CT/sup -1/4) - DT/sup -1/2. The Hall coefficient was independent of magnetic field, insensitive to temperature, but was a strong function of heat treatment temperature, crossing over from negative to positive at about 1700/sup 0/C and ranging from -0.048 to 0.126 cm/sup 3//coul. The idea of one-dimensional filaments in glassy carbon suggested by the electrical conductivity is compatible with the present consensus view of the microstructure.

  12. Formation of conducting nanochannels in diamond-like carbon films

    Science.gov (United States)

    Evtukh, A.; Litovchenko, V.; Semenenko, M.; Yilmazoglu, O.; Mutamba, K.; Hartnagel, H. L.; Pavlidis, D.

    2006-09-01

    A sharp increase of the emission current at high electric fields and a decrease of the threshold voltage after pre-breakdown conditioning of diamond-like carbon (DLC) films have been measured. This effect was observed for DLC-coated silicon tips and GaAs wedges. During electron field emission (EFE) at high electric fields the energy barriers caused by an sp3 phase between sp2 inclusions can be broken, resulting in the formation of conducting nanochannels between the semiconductor-DLC interface and the surface of the DLC film. At high current densities and the resulting local heating, the diamond-like sp3 phase transforms into a conducting graphite-like sp2 phase. As a result an electrical conducting nanostructured channel is formed in the DLC film. The diameter of the conducting nanochannel was estimated from the reduced threshold voltage after pre-breakdown conditioning to be in the range of 5-25 nm. The presence of this nanochannel in an insulating matrix leads to a local enhancement of the electric field and a reduced threshold voltage for EFE. Based on the observed features an efficient method of conducting nanochannel matrix formation in flat DLC films for improved EFE efficiency is proposed. It mainly uses a silicon tip array as an upper electrode in contact with the DLC film. The formation of nanochannels starts at the interface between the tips and the DLC film. This opens new possibilities of aligned and high-density conducting channel formation.

  13. Relaxation dynamics of the conductive processes in BaTiO{sub 3} ceramics at high temperature

    Energy Technology Data Exchange (ETDEWEB)

    Leyet, Y., E-mail: yuri@cnt.uo.edu.cu [Departamento de Fisica, Facultad de Ciencias Naturales. Universidad de Oriente, Santiago de Cuba, C.P. 90500 (Cuba); Guerrero, F. [Departamento de Fisica, Facultad de Ciencias Naturales. Universidad de Oriente, Santiago de Cuba, C.P. 90500 (Cuba); Perez de la Cruz, J. [INESCPorto, Rua do Campo Alegre, 687, 4169-007, Porto (Portugal)

    2010-07-25

    The temperature and frequency dependences of the undoped BaTiO{sub 3} ceramics dielectric properties were measured between 25 deg. C and 700 deg. C and 100 Hz to 10 MHz, respectively. A dielectric anomaly was observed at low frequencies in the temperature range of 400-700 deg. C. This anomaly was associated to a low frequency dispersion process taking place at high temperature. The relaxation dynamics of the conductive process in BaTiO{sub 3} ceramics was investigated. A relaxation function in the time domain ({Phi}(t)) was determined from the frequency dependence of the dielectric modulus, using a relaxation function in the frequency domain (F*({omega})). In BaTiO{sub 3} ceramics context, the best relaxation functions (F*({omega})), in the temperature ranges of 220-400 deg. C and 425 deg. C and 630 deg. C, were found to be a Cole-Cole and Davidson-Cole distribution functions, respectively. The relaxation function (f(t)) obtained by the time domain method was found to be a Kohlrausch-Williams-Watts (KWW) function type. The activation energy values (0.72 eV and 0.8 eV) reveal a mechanism correlated with the movement of single ionized oxygen vacancies and electrons of the second level of ionization, probably due to the formation of a titanium liquid phase during the sintering process.

  14. Electrical conductance of carbon nanotubes with misaligned ends

    Energy Technology Data Exchange (ETDEWEB)

    Pantano, Antonio, E-mail: antonio.pantano@unipa.it; Muratore, Giuseppe; Montinaro, Nicola [Universita degli Studi di Palermo, Dipartimento di Ingegneria Chimica, Gestionale, Informatica e Meccanica (Italy)

    2013-09-15

    During a manufacturing process, when a straight carbon nanotube is placed on a substrate, e.g., production of transistors, its two ends are often misaligned. In this study, we investigate the effects of multiwall carbon nanotubes' (MWCNTs) outer diameter and chirality on the change in conductance due to misalignment of the two ends. The length of the studied MWCNTs was 120 nm, while the diameters ranged between 4 and 7 nm. A mixed finite element-tight-binding approach was carefully designed to realize reduction in computational time by orders of magnitude in calculating the deformation-induced changes in the electrical transport properties of the nanotubes. Numerical results suggest that armchair MWCNTs of small diameter should work better if used as conductors, while zigzag MWCNTs of large diameter are more suitable for building sensors.Graphical Abstract.

  15. Oxidation of Carbon Fibers in a Cracked Ceramic Matrix Composite Modeled as a Function of Temperature

    Science.gov (United States)

    Halbig, Michael C.; Cawley, James D.; Eckel, Andrew J.

    2003-01-01

    The oxidation model simulates the oxidation of the reinforcing carbon fibers within a ceramic matrix composite material containing as-fabricated microcracks. The physics-based oxidation model uses theoretically and experimentally determined variables as input for the model. The model simulates the ingress of oxygen through microcracks into a two-dimensional plane within the composite material. Model input includes temperature, oxygen concentration, the reaction rate constant, the diffusion coefficient, and the crack opening width as a function of the mechanical and thermal loads. The model is run in an iterative process for a two-dimensional grid system in which oxygen diffuses through the porous and cracked regions of the material and reacts with carbon in short time steps. The model allows the local oxygen concentrations and carbon volumes from the edge to the interior of the composite to be determined over time. Oxidation damage predicted by the model was compared with that observed from microstructural analysis of experimentally tested composite material to validate the model for two temperatures of interest. When the model is run for low-temperature conditions, the kinetics are reaction controlled. Carbon and oxygen reactions occur relatively slowly. Therefore, oxygen can bypass the carbon near the outer edge and diffuse into the interior so that it saturates the entire composite at relatively high concentrations. The kinetics are limited by the reaction rate between carbon and oxygen. This results in an interior that has high local concentrations of oxygen and a similar amount of consumed carbon throughout the cross section. When the model is run for high-temperature conditions, the kinetics are diffusion controlled. Carbon and oxygen reactions occur very quickly. The carbon consumes oxygen as soon as it is supplied. The kinetics are limited by the relatively slow rate at which oxygen is supplied in comparison to the relatively fast rate at which carbon and

  16. Measurements of Thermal Conductivity and Thermal Diffusivity of Molten Carbonates

    OpenAIRE

    Wicaksono, Hendro; Zhang, Xing; Fujiwara, Seiji; Fujii, Motoo

    2001-01-01

    The thermal conductivity and thermal diffusivity of molten carbonates (Li_2CO_3/K_2CO_3 and Li_2CO_3/Na_2CO_3) were measured using the transient short-hot-wire method in the temperature range from 530 to 670℃. Two types of probes were examined. One was a platinum short-hot-wire probe coated with alumina (Al_2O_3) thin film to prevent current leakage and corrosion. The other was a bare gold short-hot-wire probe. For the platinum probe, the quality of coating reduces gradually during the measur...

  17. Thermal conductance of carbon nanotube contacts: Molecular dynamics simulations and general description of the contact conductance

    Science.gov (United States)

    Salaway, Richard N.; Zhigilei, Leonid V.

    2016-07-01

    The contact conductance of carbon nanotube (CNT) junctions is the key factor that controls the collective heat transfer through CNT networks or CNT-based materials. An improved understanding of the dependence of the intertube conductance on the contact structure and local environment is needed for predictive computational modeling or theoretical description of the effective thermal conductivity of CNT materials. To investigate the effect of local structure on the thermal conductance across CNT-CNT contact regions, nonequilibrium molecular dynamics (MD) simulations are performed for different intertube contact configurations (parallel fully or partially overlapping CNTs and CNTs crossing each other at different angles) and local structural environments characteristic of CNT network materials. The results of MD simulations predict a stronger CNT length dependence present over a broader range of lengths than has been previously reported and suggest that the effect of neighboring junctions on the conductance of CNT-CNT junctions is weak and only present when the CNTs that make up the junctions are within the range of direct van der Waals interaction with each other. A detailed analysis of the results obtained for a diverse range of intertube contact configurations reveals a nonlinear dependence of the conductance on the contact area (or number of interatomic intertube interactions) and suggests larger contributions to the conductance from areas of the contact where the density of interatomic intertube interactions is smaller. An empirical relation accounting for these observations and expressing the conductance of an arbitrary contact configuration through the total number of interatomic intertube interactions and the average number of interatomic intertube interactions per atom in the contact region is proposed. The empirical relation is found to provide a good quantitative description of the contact conductance for various CNT configurations investigated in the MD

  18. Magnetoresponsive conductive colloidal suspensions with magnetized carbon nanotubes

    Science.gov (United States)

    Abdalla, Ahmed M.; Abdel Fattah, Abdel Rahman; Ghosh, Suvojit; Puri, Ishwar K.

    2017-01-01

    We synthesize a novel and hitherto unreported class of colloidal suspensions for which the dispersed phase, which consists of multiwall carbon nanotubes (MWNTs) decorated with magnetic nanoparticles (MNPs), is both magnetoresponsive and electrically conductive. Synthesis of the dispersed phase merges processes for producing ferrofluids and magnetic MWNTs (mMWNTs). We explore means to tune the properties of these magnetic conductive colloids (MCCs) by varying the (1) MNP material composition, and (2) MNP:MWNT (w/w) magnetization weight ratio (γ). The mMWNTs are examined using XRD, TEM, EDX and SQUID and MCCs are by measuring their zeta potential and electric conductivity. Magnetite (Fe3O4) MNPs, which possess a high Curie temperature, produce mMWNTs with high saturation magnetization that respond relatively weakly to temperature variations. Mn0.2Cu0.2Zn0.6Fe2O4 and Cu0.4Zn0.6Fe2O4 MNPs with lower Curie temperatures are more sensitive to changing temperature. Increasing the MNP Cu content improves the electric conductivity of the corresponding MCC while increasing γ enhances its magnetic response. After γ is raised above a threshold value, mMWNT decoration on the CNT surface becomes nonuniform since the MNPs now agglomerate perpendicular to the nanotube surface. These colloidal suspensions are a promising new class of material that can be manipulated with a magnetic field to tune their electrical conductivity.

  19. Fabrication of highly conductive carbon nanotube fibers for electrical application

    Science.gov (United States)

    Guo, Fengmei; Li, Can; Wei, Jinquan; Xu, Ruiqiao; Zhang, Zelin; Cui, Xian; Wang, Kunlin; Wu, Dehai

    2015-09-01

    Carbon nanotubes (CNTs) have great potential for use as electrical wires because of their outstanding electrical and mechanical properties. Here, we fabricate lightweight CNT fibers with electrical conductivity as high as that of stainless steel from macroscopic CNT films by drawing them through diamond wire-drawing dies. The entangled CNT bundles are straightened by suffering tension, which improves the alignment of the fibers. The loose fibers are squeezed by the diamond wire-drawing dies, which reduces the intertube space and contact resistance. The CNT fibers prepared by drawing have an electrical conductivity as high as 1.6 × 106 s m-1. The fibers are very stable when kept in the air and under cyclic tensile test. A prototype of CNT motor is demonstrated by replacing the copper wires with the CNT fibers.

  20. Multiscale Modeling of Thermal Conductivity of Polymer/Carbon Nanocomposites

    Science.gov (United States)

    Clancy, Thomas C.; Frankland, Sarah-Jane V.; Hinkley, Jeffrey A.; Gates, Thomas S.

    2010-01-01

    Molecular dynamics simulation was used to estimate the interfacial thermal (Kapitza) resistance between nanoparticles and amorphous and crystalline polymer matrices. Bulk thermal conductivities of the nanocomposites were then estimated using an established effective medium approach. To study functionalization, oligomeric ethylene-vinyl alcohol copolymers were chemically bonded to a single wall carbon nanotube. The results, in a poly(ethylene-vinyl acetate) matrix, are similar to those obtained previously for grafted linear hydrocarbon chains. To study the effect of noncovalent functionalization, two types of polyethylene matrices. -- aligned (extended-chain crystalline) vs. amorphous (random coils) were modeled. Both matrices produced the same interfacial thermal resistance values. Finally, functionalization of edges and faces of plate-like graphite nanoparticles was found to be only modestly effective in reducing the interfacial thermal resistance and improving the composite thermal conductivity

  1. Conducting polymer/carbon nanocoil composite electrodes for efficient supercapacitors

    KAUST Repository

    Baby, Rakhi Raghavan

    2012-01-01

    Herein, we report for the first time, conducting polymer (polyaniline (PANI) and polypyrrole (PPY)) coated carbon nanocoils (CNCs) as efficient binder-free electrode materials for supercapacitors. CNCs act as a perfect backbone for the uniform distribution of the conducting polymers in the composites. In two electrode configuration, the samples exhibited high specific capacitance with the values reaching up to 360 and 202 F g -1 for PANI/CNCs and PPY/CNCs respectively. The values obtained for specific capacitance and maximum storage energy per unit mass of the composites were found to be comparable to one of the best reported values for polymer coated multi-walled carbon nanotubes. In addition, the fabricated PANI/CNC based supercapacitors exhibited a high value of 44.61 Wh kg -1 for maximum storage energy per unit mass. Although the devices exhibit an initial capacitance loss due to the instability of the polymer, the specific capacitance stabilizes at a fixed value after 500 charge-discharge cycles. © 2012 The Royal Society of Chemistry.

  2. Semi-conducting carbon nanotube as variable capacitor

    Science.gov (United States)

    Ozmaian, M.; Naghdabadi, R.

    2013-12-01

    This paper proposes a novel, one-part, variable capacitor, using semi-conducting carbon nanotube (CNT). This variable capacitor works based on the change in the electronic structure of CNTs under applied voltage and deformations. Positive and negative charges are stored at both ends of a non-zero band gap nanotube which works as metallic electrodes in parallel plate capacitors. Also the neutral strip in the middle acts as the dielectric part of a conventional capacitor under the influence of an external electric field. Mechanical strains on carbon nanotube change its band gap energy and thus the length of neutral strip and charged regions. The lengths of these parts are primarily dependent on the nanotube chirality, deformation mode and applied voltage. This way, different parts of a conventional cantilever, parallel plate or bridge capacitor are reduced to a one part semi-conducting CNT capacitor. Analytical calculations based on classical electrostatics and density of states (DOS) relations are employed to investigate the effect of CNTs geometry, applied voltage and deformations on capacitive features. The proposed CNT-variable-capacitor can be useful for nano-electromechanical systems (NEMS), including displacement measurement sensors and tunable capacitor in integrated circuits.

  3. Proton conductivity in tungsten and antimony-modified titania ceramics prepared by the sol-gel method

    Energy Technology Data Exchange (ETDEWEB)

    Vichi, Flavio Maron [Departamento de Quimica Fundamental, Instituto de Quimica, Universidade de Sao Paulo, Av. Prof, Lineu Prestes, 748, Butanta, Sao Paulo, SP (Brazil); Tejedor-Tejedor, Maria Isabel; Anderson, Marc A. [Environmental Chemistry and Technology Program, University of Wisconsin-Madison, 660 N. Park St., Madison, WI 53706 (United States)

    2005-03-15

    Titania ceramic materials modified with 5% antimony and 5% tungsten were prepared by the sol-gel method. For the antimony-modified material, a treatment with H{sub 2}O{sub 2} was also performed, in order to obtain antimonic acid. The electric conductivity of the xerogels was measured at 25 {sup o}C in the relative humidity (RH) range 33-81%. At 25 {sup o}C, the electrical conductivity of the 'as prepared' 5% Sb ceramic varies from 2.02x10{sup -5} S cm{sup -1} at 33% RH to 1.12x10{sup -2} S cm{sup -1} at 81% R.H. For the material treated with H{sub 2}O{sub 2}, the conductivity varies from 1.56x10{sup -5} to 2.37x10{sup -2} S cm{sup -1} for 33% and 81% R.H., respectively. For the tungsten-modified material, the conductivity varies from 1.02x10{sup -5} to 2.66x10{sup -3} S cm{sup -1} for 33% and 81% R.H., respectively. The activation energies observed for proton conduction were 23.5 kJ mol{sup -1} for TiO{sub 2}/W 5%, 22.9 kJ mol{sup -1} for TiO{sub 2}/Sb 5% and 20.6 kJ mol{sup -1} for the material treated with H{sub 2}O{sub 2}. The highest activation energy was observed for untreated TiO{sub 2}:24.8 kJ mol{sup -1}. The conductivity values for the Sb-modified ceramics are superior to those reported previously for antimonic acid films, and approach the values reported for proton-conducting polymers, such as Nafion(R), making them a potential candidate for application as electrolytes in fuel cell systems.

  4. APPLICATION OF THE THERMAL CONDUCTIVITY CRITERION IN THE DESIGN OF FOAM-CERAMIC CONCRETES BASED ON THE OPAL-CRYSTOBALITE ROCK

    Directory of Open Access Journals (Sweden)

    Korolev Evgeniy Valerevich

    2012-10-01

    Full Text Available Design method of the foam-ceramic concrete with the pre-set value of thermal conductivity is proposed. Computed dependencies between the thermal conductivity, strength and generalized structural criterion - porosity - are presented. As a result of the research, it was identified that local input materials are ecological and easy to extract, and that they may be used as the mineral basis for the manufacturing of effective foam-glass ceramic materials that demonstrate their porous structure, similar to the one of the foam-ceramic concrete. The employment of the proposed approach to the design of the composition of foam-glass ceramic materials may substantially improve the most important properties of this material, namely, it may reduce the sorption capacity and improve the strength, if compared with the benchmark composition.

  5. Fracture characteristics of carbon fibre, ceramic and non-palladium endodontic post systems at monotonously increasing loads.

    Science.gov (United States)

    Ottl, P; Hahn, L; Lauer, H Ch; Fay, M

    2002-02-01

    A carbon fibre post system, three non-palladium and one palladium metal post systems, two ceramic post systems, and a metal post system with a ceramic core were studied in vitro. The control group consisted of root-filled test teeth without posts. The test teeth were identical artificial roots of an upper central incisor made from a posterior composite whose module of elasticity was similar to that of natural dentine. All posts were cemented in the roots using Panavia 21 TC. Subsequently, standardized full crowns were cemented onto all roots. On a universal testing machine, the test teeth were loaded palatally at monotonously increasing loads until root fracture. The highest mean fracture loads were found for the carbon fibre post system (312.5 +/- 58.8 N). The fracture load of non-palladium metal posts (242.3-300.4 N) did not differ significantly from that of the Perma-dor post (265.9 N), which does contain palladium. Values of 300.3 +/- 89.3 N (aluminium oxide ceramics) and 193.5 +/-57.0 N (zirconia ceramics) were found for the ceramic posts. The control group exhibited a fracture load of 228.8 +/- 35.7 N. The mean distance between the vestibular end of the fracture gap and the point of force application was between 10.1 +/- 2.3 and 14.7 +/- 1.2 mm.

  6. Highly Conductive Wire: Cu Carbon Nanotube Composite Ampacity and Metallic CNT Buckypaper Conductivity

    Science.gov (United States)

    de Groh, Henry C.

    2017-01-01

    NASA is currently working on developing motors for hybrid electric propulsion applications in aviation. To make electric power more feasible in airplanes higher power to weight ratios are sought for electric motors. One facet to these efforts is to improve (increase) the conductivity and (lower) density of the magnet wire used in motors. Carbon nanotubes (CNT) and composites containing CNT are being explored as a possible way to increase wire conductivity and lower density. Presented here are measurements of the current carrying capacity (ampacity) of a composite made from CNT and copper. The ability of CNT to improve the conductivity of such composites is hindered by the presence of semiconductive CNT (s-CNT) that exist in CNT supplies naturally, and currently, unavoidably. To solve this problem, and avoid s-CNT, various preferential growth and sorting methods are being explored. A supply of sorted 95 metallic CNT (m-CNT) was acquired in the form of thick film Buckypaper (BP) as part of this work and characterized using Raman spectroscopy, resistivity, and density measurements. The ampacity (Acm2) of the Cu-5volCNT composite was 3.8 lower than the same gauge pure Cu wire similarly tested. The lower ampacity in the composite wire is believed to be due to the presence of s-CNT in the composite and the relatively low (proper) level of longitudinal cooling employed in the test method. Although Raman spectroscopy can be used to characterize CNT, a strong relation between the ratios of the primary peaks GGand the relative amounts of m-CNT and s-CNT was not observed. The average effective conductivity of the CNT in the sorted, 95 m-CNT BP was 2.5 times higher than the CNT in the similar but un-sorted BP. This is an indication that improvements in the conductivity of CNT composites can be made by the use of sorted, highly conductive m-CNT.

  7. Ablation Property of Ceramics/Carbon Fibers/Resin Novel Super-hybrid Composite

    Institute of Scientific and Technical Information of China (English)

    Jun QIU; Xiaoming CAO; Chong TIAN; Jinsong ZHANG

    2005-01-01

    A novel super-hybrid composite (NSHC) is prepared with three-dimension reticulated SiC ceramic (3DRC), high performance carbon fibers and modified phenolic resin (BPR) in this paper. Ablation performance of super-hybrid composite is studied. The results show that the NSHC has less linear ablation rate compared with pure BPR and CF/BPR composite, for example, its linear ablation rate is 50% of CF/BPR at the same fiber content. Mass ablation rate of the NSHC is slightly lower than that of pure BPR and CF/BPR composite because of their difference in the density. Scanning electron microscopic analysis indicates that 3DRC can increase anti-erosion capacity of materials because its special reticulated structure can control the deformation of materials and strengthen the stability of integral structure.

  8. Ceramic Carbon/Polypyrrole Materials for the Construction of Bienzymatic Amperometric Biosensor for Glucose

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A novel amperometric glucose biosensor was constructed by electrochemical formation of a polypyrrole (PPy) membrane in the presence of glucose oxidase (GOD) on the surface of a horseradish peroxidase (HRP) modified ferrocenecarboxylic acid (FCA) mediated sol-gel derived ceramic carbon electrode. The amperometric detection of glucose was carried out at +0.16 V (vs. SCE) in 0.1 mol/L phosphate buffer solution (pH 6.9) with a linear response range between 8.0×10-5 and 1.3×10-3 mol/L of glucose. The biosensor showed a good suppression of inter- ference and a negligible deviation in the amperometric detection.

  9. Oxidation Kinetics and Strength Degradation of Carbon Fibers in a Cracked Ceramic Matrix Composite

    Science.gov (United States)

    Halbig, Michael C.

    2003-01-01

    Experimental results and oxidation modeling will be presented to discuss carbon fiber susceptibility to oxidation, the oxidation kinetics regimes and composite strength degradation and failure due to oxidation. Thermogravimetric Analysis (TGA) was used to study the oxidation rates of carbon fiber and of a pyro-carbon interphase. The analysis was used to separately obtain activation energies for the carbon constituents within a C/SiC composite. TGA was also conducted on C/SiC composite material to study carbon oxidation and crack closure as a function of temperature. In order to more closely match applications conditions C/SiC tensile coupons were also tested under stressed oxidation conditions. The stressed oxidation tests show that C/SiC is much more susceptible to oxidation when the material is under an applied load where the cracks are open and allow for oxygen ingress. The results help correlate carbon oxidation with composite strength reduction and failure.

  10. High frequency conductivity of hot electrons in carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Amekpewu, M., E-mail: mamek219@gmail.com [Department of Applied Physics, University for Development Studies, Navrongo (Ghana); Mensah, S.Y. [Department of Physics, College of Agriculture and Natural Sciences, U.C.C. (Ghana); Musah, R. [Department of Applied Physics, University for Development Studies, Navrongo (Ghana); Mensah, N.G. [Department of Mathematics, College of Agriculture and Natural Sciences, U.C.C. (Ghana); Abukari, S.S.; Dompreh, K.A. [Department of Physics, College of Agriculture and Natural Sciences, U.C.C. (Ghana)

    2016-05-01

    High frequency conductivity of hot electrons in undoped single walled achiral Carbon Nanotubes (CNTs) under the influence of ac–dc driven fields was considered. We investigated semi-classically Boltzmann's transport equation with and without the presence of the hot electrons’ source by deriving the current densities in CNTs. Plots of the normalized current density versus frequency of ac-field revealed an increase in both the minimum and maximum peaks of normalized current density at lower frequencies as a result of a strong injection of hot electrons. The applied ac-field plays a twofold role of suppressing the space-charge instability in CNTs and simultaneously pumping an energy for lower frequency generation and amplification of THz radiations. These have enormous promising applications in very different areas of science and technology.

  11. High frequency conductivity of hot electrons in carbon nanotubes

    Science.gov (United States)

    Amekpewu, M.; Mensah, S. Y.; Musah, R.; Mensah, N. G.; Abukari, S. S.; Dompreh, K. A.

    2016-05-01

    High frequency conductivity of hot electrons in undoped single walled achiral Carbon Nanotubes (CNTs) under the influence of ac-dc driven fields was considered. We investigated semi-classically Boltzmann's transport equation with and without the presence of the hot electrons' source by deriving the current densities in CNTs. Plots of the normalized current density versus frequency of ac-field revealed an increase in both the minimum and maximum peaks of normalized current density at lower frequencies as a result of a strong injection of hot electrons. The applied ac-field plays a twofold role of suppressing the space-charge instability in CNTs and simultaneously pumping an energy for lower frequency generation and amplification of THz radiations. These have enormous promising applications in very different areas of science and technology.

  12. Electrically conductive, optically transparent polymer/carbon nanotube composites

    Science.gov (United States)

    Connell, John W. (Inventor); Smith, Jr., Joseph G. (Inventor); Harrison, Joycelyn S. (Inventor); Park, Cheol (Inventor); Watson, Kent A. (Inventor); Ounaies, Zoubeida (Inventor)

    2011-01-01

    The present invention is directed to the effective dispersion of carbon nanotubes (CNTs) into polymer matrices. The nanocomposites are prepared using polymer matrices and exhibit a unique combination of properties, most notably, high retention of optical transparency in the visible range (i.e., 400-800 nm), electrical conductivity, and high thermal stability. By appropriate selection of the matrix resin, additional properties such as vacuum ultraviolet radiation resistance, atomic oxygen resistance, high glass transition (T.sub.g) temperatures, and excellent toughness can be attained. The resulting nanocomposites can be used to fabricate or formulate a variety of articles such as coatings on a variety of substrates, films, foams, fibers, threads, adhesives and fiber coated prepreg. The properties of the nanocomposites can be adjusted by selection of the polymer matrix and CNT to fabricate articles that possess high optical transparency and antistatic behavior.

  13. Conductive polymer foams with carbon nanofillers – Modeling percolation behavior

    Directory of Open Access Journals (Sweden)

    O. Maxian

    2017-05-01

    Full Text Available A new numerical model considering nanofiller random distribution in a porous polymeric matrix was developed to predict electrical percolation behavior in systems incorporating 1D-carbon nanotubes (CNTs and/or 2D-graphene nanoplatelets (GNPs. The numerical model applies to porous systems with closed-cell morphology. The percolation threshold was found to decrease with increasing porosity due to filler repositioning as a result of foaming. CNTs were more efficient in forming a percolative network than GNPs. High-aspect ratio (AR and randomly oriented fillers were more prone to form a network. Reduced percolation values were determined for misaligned fillers as they connect better in a network compared to aligned ones. Hybrid CNT-GNP fillers show synergistic effects in forming electrically conductive networks by comparison with single fillers.

  14. Unusual microstructures in TiO2 ceramic pellets with asymmetrical electrical conductivity

    Science.gov (United States)

    Shinozaki, S. S.; Donlon, W. T.; Meitzler, A. H.

    1982-11-01

    Ceramic pellets of TiO2 (rutile), with embedded Pt wire electrodes, have been heat treated in a manner that changed the normal electrical properties of rutile at room temperature from those of an insulator to those of a semiconductor with rectifying characteristics. This change in electrical properties was accompanied by the development of unusual microstructures in the rutile grains which were analyzed by a combination of techniques including transmission electron microscopy and scanning transmission electron microscopy. These analyses indicated that, under the applied conditions of heat treatment, Pt diffused into the rutile and reacted initially with the TiO2 at oxygen vacancy sites to form point-defect agglomerates and that these point defects blocked the normal formation of crystallographic shear planes. As the process proceeded by continued Pt diffusion, thin planar precipitates of PtTi3 were formed in epitaxial relation to the surrounding rutile matrix.

  15. Effects of Copper Doping on Dielectric and A.C. Conductivity in Layered Sodium Tri-Titanate Ceramic

    Science.gov (United States)

    Shripal; Dwivedi, Shailja; Singh, Rakesh; Tandon, R. P.

    2013-09-01

    Electron paramagnetic resonance (EPR) spectra of 0.01, 0.1 and 1.0 molar percentage (mp) of CuO doped derivatives of layered Na2Ti3O7 ceramic have been reported. The results show that copper substitutes as Cu2+ at Ti4+ octahedral sites. From the dependence of loss tangent (tan δ) and the relative permittivity (ɛ‧) on temperature and frequency, it is concluded that all the derivatives are of polar nature. The relaxation peaks at lower temperatures have been attributed to the presence of different types of dipoles, whereas peaks in the higher temperature region indicate possible ferroelectric phase transition. The dependence of conductivity on temperature show that electron hopping (polaron) conduction exists in a wide span of temperature range. However, the associated interlayer ionic conduction exists in a small temperature range. Interlayer alkali ion hopping mechanism of conduction has been proposed toward higher temperatures. The conductivity versus frequency plots reveal that the polaron conduction plays a prominent role toward the lower temperature side that diminishes with the rise in temperature. The most probable relaxation times for 0.01 and 0.1 mp CuO doped derivatives are almost same but it records an increased value for 1.0 mp doped material. This again attributes to the possible change in the symmetry of copper environment.

  16. Analysis of the Thermal Conductivity of Polymer Nanocomposites Filled with Carbon Nanotubes and Carbon Black

    Directory of Open Access Journals (Sweden)

    R.V. Dinzhos

    2014-04-01

    Full Text Available Experimental results and theoretical studies of thermophysical characteristics crystalline polyethylene nanocomposites containing from 0.3 to 2.5 wt. % carbon black and nanocomposites containing from 0.2 to 1.5 wt. % carbon nanotubes is done in the article. The fundamentals of the effective medium theory and percolation theory and how they correlate with the experimental data is shown. The features of the structure’s influence of polymer composites on their thermal properties is studied. A comparative analysis of the thermal conductivity of the compositions according to the geometry of the filler is done.

  17. Fast-ion conducting glass and glass-ceramics for the pH sensor Ionic conductivity

    CERN Document Server

    Niyompan, A

    2002-01-01

    Fast-ion conducting glasses of the compositions Na sub 1 sub + sub x M sub 2 sub - sub x sub / sub 3 Si sub x P sub 3 sub - sub x O sub 1 sub 2 sub - sub 2 sub x sub / sub 3 (0<= x <=3), where M = Zr, Ti, were studied to determine their structural arrangement, physical properties and ionic conductivity. Glass samples were prepared using the conventional melt-quench method in the melting temperature range, 1550 deg C to 1650 deg C. Glass products were characterised by XRD, DTA, dilatometry and density measurement. Solid state MAS NMR experiments of three accessible nuclei, sup 2 sup 3 Na, sup 2 sup 9 Si and sup 3 sup 1 P were used to determine short-range order arrangement in the glasses. XRD confirms the amorphicity of glasses for the compositions of x in range 0-3. Glass transition temperatures, T sub g , TEC, and molar volume are controlled by glass composition. The MAS NMR results suggest that glass structure could be visualised as the silicate network modified by Na sup + and Zr sup 4 sup + or Ti su...

  18. Electrical conduction mechanism in bulk ceramic insulators at high voltages until dielectric breakdown

    Science.gov (United States)

    Neusel, C.; Jelitto, H.; Schneider, G. A.

    2015-04-01

    In order to develop and verify a dielectric breakdown model for bulk insulators thicker than 100 μm, the knowledge of the dominating conduction mechanism at high electric fields, or respectively voltages, is necessary. The dielectric breakdown is the electrical failure of an insulator. In some existing breakdown models, ohmic conduction is assumed as dominating conduction mechanism. For verification, the dominating dc conduction mechanism of bulk insulators at room temperature was investigated by applying high voltages up to 70 kV to the insulator until dielectric breakdown occurs. Four conduction models, namely, ohmic, space charge limited, Schottky, and Poole-Frenkel conduction, were employed to identify the dominating conduction mechanism. Comparing the calculated permittivities from the Schottky and Poole-Frenkel coefficients with experimentally measured permittivity, Schottky and Poole-Frenkel conduction can be excluded as dominating conduction mechanism. Based on the current density voltage characteristics (J-V-curve) and the thickness-dependence of the current density, space charge limited conduction (SCLC) was identified to be the dominating conduction mechanism at high voltages leading to dielectric breakdown. As a consequence, breakdown models based on ohmic conduction are not appropriate to explain the breakdown of the investigated bulk insulators. Furthermore, the electrical failure of the examined bulk insulators can only be described correctly by a breakdown model which includes SCLC as conduction mechanism.

  19. Ultrasonic absorption characteristics of porous carbon-carbon ceramics with random microstructure for passive hypersonic boundary layer transition control

    Science.gov (United States)

    Wagner, Alexander; Hannemann, Klaus; Kuhn, Markus

    2014-06-01

    Preceding studies in the high enthalpy shock tunnel Göttingen of the German Aerospace Center (DLR) revealed that carbon fibre reinforced carbon ceramic (C/C) surfaces can be utilized to damp hypersonic boundary layer instabilities leading to a delay of boundary layer transition onset. To assess the ultrasonic absorption properties of the material, a test rig was set up to measure the reflection coefficient at ambient pressures ranging from 0.1 × 105 to 1 × 105 Pa. For the first time, broadband ultrasonic sound transducers with resonance frequencies of up to 370 kHz were applied to directly cover the frequency range of interest with respect to the second-mode instabilities observed in previous experiments. The reflection of ultrasonic waves from three flat plate test samples with a porous layer thickness between 5 and 30 mm was investigated and compared to an ideally reflecting surface. C/C was found to absorb up to 19 % of the acoustic power transmitted towards the material. The absorption characteristics were investigated theoretically by means of the quasi-homogeneous absorber theory. The experimental results were found to be in good agreement with the theory.

  20. Using multi-walled carbon nanotubes in spark plasma sintered Pb(Zr0.47Ti0.53)O3 ceramics for tailoring dielectric and tunability properties

    Science.gov (United States)

    Ciomaga, Cristina E.; Padurariu, Leontin; Curecheriu, Lavinia P.; Lupu, Nicoleta; Lisiecki, Isabelle; Deluca, Marco; Tascu, Sorin; Galassi, Carmen; Mitoseriu, Liliana

    2014-10-01

    The addition of small amounts (below 0.1 wt. %) of multi-walled carbon nanotubes (MWCNTs) to Pb(Zr0.47Ti0.53)O3 (PZT) ceramics prepared by spark plasma sintering is proposed as a method of tailoring the electrical properties, which are expected to be modified with respect to the pure PZT, both as result of the presence of 1-D conductive fillers in the ceramic product and via the microstructural modifications of ceramics induced during the sintering. The addition of even small amounts of carbon nanotubes strongly reduced the sinterability of PZT ceramics and resulted in the porous and fine-grained microstructures (relative density of 73% for a MWCNT addition of 0.5 vol. % by comparison with 91% in the pure PZT, produced in the same conditions). A monotonous decrease of permittivity with increasing the MWCNT level from ˜830 in pure PZT to ˜627 for x = 0.5 vol. %, at a fixed frequency f = 1kHz, and low dielectric losses below 2% have been observed. Tunability increases with respect to the values of dense PZT for small concentration of MWCNT as high as 0.0625 vol. % and then monotonically decreases for higher additions. Calculations by finite element modeling demonstrated that by addition of 1-D conductive fillers with compositions below the percolation limits to porous microstructures, the major role in changing the electrical properties via local field modification is related to the induced porosity rather than to the influence of the small amounts of MWCNTs survived after sintering and post-annealing treatment. The reduced permittivity with about 14% combined with low losses and higher tunability than in the pure PZT ceramics obtained at reasonable fields, makes the idea of using the addition of MWCNTs to ferroelectric ceramics an interesting approach in searching new structures for tunability properties.

  1. Heat conduction in double-walled carbon nanotubes with intertube additional carbon atoms.

    Science.gov (United States)

    Cui, Liu; Feng, Yanhui; Tan, Peng; Zhang, Xinxin

    2015-07-07

    Heat conduction of double-walled carbon nanotubes (DWCNTs) with intertube additional carbon atoms was investigated for the first time using a molecular dynamics method. By analyzing the phonon vibrational density of states (VDOS), we revealed that the intertube additional atoms weak the heat conduction along the tube axis. Moreover, the phonon participation ratio (PR) demonstrates that the heat transfer in DWCNTs is dominated by low frequency modes. The added atoms cause the mode weight factor (MWF) of the outer tube to decrease and that of the inner tube to increase, which implies a lower thermal conductivity. The effects of temperature, tube length, and the number and distribution of added atoms were studied. Furthermore, an orthogonal array testing strategy was designed to identify the most important structural factor. It is indicated that the tendencies of thermal conductivity of DWCNTs with added atoms change with temperature and length are similar to bare ones. In addition, thermal conductivity decreases with the increasing number of added atoms, more evidently for atom addition concentrated at some cross-sections rather than uniform addition along the tube length. Simultaneously, the number of added atoms at each cross-section has a considerably more remarkable impact, compared to the tube length and the density of chosen cross-sections to add atoms.

  2. On the addition of conducting ceramic nanoparticles in solvent-free ionic liquid electrolyte for dye-sensitized solar cells

    KAUST Repository

    Lee, Chuan-Pei

    2009-08-01

    Titanium carbide (TiC) is an extremely hard conducting ceramic material often used as a coating for titanium alloys as well as steel and aluminum components to improve their surface properties. In this study, conducting ceramic nanoparticles (CCNPs) have been used, for the first time, in dye-sensitized solar cells (DSSCs), and the incorporation of TiC nanoparticles in a binary ionic liquid electrolyte on the cell performance has been investigated. Cell conversion efficiency with 0.6 wt% TiC reached 1.68%, which was higher than that without adding TiC (1.18%); however, cell efficiency decreased when the TiC content reached 1.0 wt%. The electrochemical impedance spectroscopy (EIS) technique was employed to analyze the interfacial resistance in DSSCs, and it was found that the resistance of the charge-transfer process at the Pt counter electrode (Rct1) decreased when up to 1.0 wt% TiC was added. Presumably, this was due to the formation of the extended electron transfer surface (EETS) which facilitates electron transfer to the bulk electrolyte, resulting in a decrease of the dark current, whereby the open-circuit potential (VOC) could be improved. Furthermore, a significant increase in the fill factor (FF) for all TiC additions was related to the decrease in the series resistance (RS) of the DSSCs. However, at 1.0 wt% TiC, the largest charge-transfer resistance at the TiO2/dye/electrolyte interface was observed and resulted from the poor penetration of the electrolyte into the porous TiO2. The long-term stability of DSSCs with a binary ionic liquid electrolyte, which is superior to that of an organic solvent-based electrolyte, was also studied. © 2009 Elsevier B.V. All rights reserved.

  3. In vitro degradation and cell response of calcium carbonate composite ceramic in comparison with other synthetic bone substitute materials

    Energy Technology Data Exchange (ETDEWEB)

    He, Fupo [Department of Biomedical Engineering, School of Basic Sciences, Guangzhou Medical University, Guangzhou 510182 (China); Zhang, Jing [School of Materials Science and Engineering, South China University of Technology, Guangzhou 510641 (China); Yang, Fanwen; Zhu, Jixiang; Tian, Xiumei [Department of Biomedical Engineering, School of Basic Sciences, Guangzhou Medical University, Guangzhou 510182 (China); Chen, Xiaoming, E-mail: xmchenw@126.com [Department of Biomedical Engineering, School of Basic Sciences, Guangzhou Medical University, Guangzhou 510182 (China)

    2015-05-01

    The robust calcium carbonate composite ceramics (CC/PG) can be acquired by fast sintering calcium carbonate at a low temperature (650 °C) using a biocompatible, degradable phosphate-based glass (PG) as sintering agent. In the present study, the in vitro degradation and cell response of CC/PG were assessed and compared with 4 synthetic bone substitute materials, calcium carbonate ceramic (CC), PG, hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) ceramics. The degradation rates in decreasing order were as follows: PG, CC, CC/PG, β-TCP, and HA. The proliferation of rat bone mesenchymal stem cells (rMSCs) cultured on the CC/PG was comparable with that on CC and PG, but inferior to HA and β-TCP. The alkaline phosphatase (ALP) activity of rMSCs on CC/PG was lower than PG, comparable with β-TCP, but higher than HA. The rMSCs on CC/PG and PG had enhanced gene expression in specific osteogenic markers, respectively. Compared to HA and β-TCP, the rMSCs on the CC/PG expressed relatively lower level of collagen I and runt-related transcription factor 2, but showed more considerable expression of osteopontin. Although CC, PG, HA, and β-TCP possessed impressive performances in some specific aspects, they faced extant intrinsic drawbacks in either degradation rate or mechanical strength. Based on considerable compressive strength, moderate degradation rate, good cell response, and being free of obvious shortcoming, the CC/PG is promising as another choice for bone substitute materials. - Highlights: • A calcium carbonate composite ceramic (CC/PG) was acquired. • The in vitro degradation and cell response of CC/PG were compared to 4 materials. • The CC/PG showed moderate degradation rate. • The CC/PG exhibited good cell response. • The CC/PG was free of obvious drawback compared to other materials.

  4. In Situ Synthesis of Ceramic Reinforcements for Carbon/CuCrZr Joints Brazed with Composite Fillers

    Science.gov (United States)

    Mao, Yangwu; Yu, Si; Deng, Quanrong; Zhao, Pei

    2016-12-01

    Brazing of two kinds of carbon materials including graphite and carbon fiber-reinforced carbon composites to copper alloys has been realized with CuTiH2 + BN composite fillers. The microstructure characterization reveals that the ceramic reinforcements containing TiN particles and TiB whiskers have been synthesized by in situ reaction of BN additives with Ti discomposed from TiH2 in the composite filler. The filler layer of the joints is mainly composed of Cu-based solid solutions [Cu (ss)] and Ti-Cu intermetallics along with ceramic reinforcements. Furthermore, a continuous thin reaction layer mainly containing TiC is developed at the interface close to the carbon substrates. The growth of TiC layer is mainly controlled by the diffusion of carbon from the substrates into the liquid filler through the TiC layer formed. The interface evolution of the graphite/CuCrZr joints has been discussed. The electrical resistivity of the joining area is relatively low, which highly meets the requirement for the carbon commutator applications.

  5. Influence of raw materials composition on firing shrinkage, porosity, heat conductivity and microstructure of ceramic tiles

    Science.gov (United States)

    Kurovics, E.; Buzimov, A. Y.; Gömze, L. A.

    2016-04-01

    In this work some new raw material compositions from alumina, conventional brick-clays and sawdust were mixed, compacted and heat treated by the authors. Depending on raw material compositions and firing temperatures the specimens were examined on shrinkage, water absorption, heat conductivity and microstructures. The real raised experiments have shown the important role of firing temperature and raw material composition on color, heat conductivity and microstructure of the final product.

  6. Mixed polaronic-ionic conduction in lithium borate glasses and glass-ceramics containing copper oxide

    Science.gov (United States)

    Khalil, M. M. I.

    2007-03-01

    The effect of electric field strength on conduction in lithium borate glasses doped with CuO with different concentration was studied and the value of the jump distance of charge carrier was calculated. The conductivity measurements indicate that the conduction is due to non-adiabatic hopping of polarons and the activation energies are found to be temperature and concentration dependent. Lithium borate glasses are subjected to carefully-programmed thermal treatments which cause the nucleation and growth of crystalline phases. X-ray diffraction analysis confirmed the amorphous nature for the investigated glass sample and the formation of crystalline phase for annealed samples at 650 °C. The main separated crystalline phase is Li2B8O13. The scanning electron micrographs of some selected glasses showed a significant change in the morphology of the films investigated due to heat treatment of the glass samples. It was found that the dc-conductivity decreases with an increase of the HT temperature. The decrease of dc conductivity, with an increase of the HT temperature, can be related to the decrease in the number of free ions in the glass matrix. There is deviation from linearity at high temperature regions in the logσ-1/T plots for all investigated doped samples at a certain temperature at which the transition from polaronic to ionic conduction occurs. The hopping of small polarons is dominant at low temperatures, whereas the hopping of Li+ ions dominates at high temperatures.

  7. Mixed polaronic-ionic conduction in lithium borate glasses and glass-ceramics containing copper oxide

    Energy Technology Data Exchange (ETDEWEB)

    Khalil, M.M.I. [National Center for Radiation Research and Technology, Radiation Physics Department, Cairo (Egypt)

    2007-03-15

    The effect of electric field strength on conduction in lithium borate glasses doped with CuO with different concentration was studied and the value of the jump distance of charge carrier was calculated. The conductivity measurements indicate that the conduction is due to non-adiabatic hopping of polarons and the activation energies are found to be temperature and concentration dependent. Lithium borate glasses are subjected to carefully-programmed thermal treatments which cause the nucleation and growth of crystalline phases. X-ray diffraction analysis confirmed the amorphous nature for the investigated glass sample and the formation of crystalline phase for annealed samples at 650 C. The main separated crystalline phase is Li{sub 2}B{sub 8}O{sub 13}. The scanning electron micrographs of some selected glasses showed a significant change in the morphology of the films investigated due to heat treatment of the glass samples. It was found that the dc-conductivity decreases with an increase of the HT temperature. The decrease of dc conductivity, with an increase of the HT temperature, can be related to the decrease in the number of free ions in the glass matrix. There is deviation from linearity at high temperature regions in the log{sigma}-1/T plots for all investigated doped samples at a certain temperature at which the transition from polaronic to ionic conduction occurs. The hopping of small polarons is dominant at low temperatures, whereas the hopping of Li{sup +} ions dominates at high temperatures. (orig.)

  8. Thermal Conductivity of Ultem(TradeMark)/Carbon Nanofiller Blends

    Science.gov (United States)

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

    2006-01-01

    In an effort to improve polymer thermal conductivity (TC), Ultem(TradeMark) 1000 was compounded with nano-fillers of carbon allotropes. Ultem(TradeMark) 1000 was selected since it is both solution and melt processable. As-received and modified multiwalled carbon nanotubes (MWCNTs), vapor grown carbon nanofibers (CNF) and expanded graphite (EG) were investigated. MWCNTs were modified by functionalizing the surface through oxidization with concentrated acids, mixing with an alkyl bromide, and addition of alkyl and phosphorus compounds after initial treatment with n-butyl lithium. Functionalization was performed to improve the TC compatibility between the resin and MWCNTs. It was postulated that this may provide an improved interface between the MWCNT and the polymer which would result in enhanced TC. The nano-fillers were mixed with Ultem(TradeMark) 1000 in the melt and in solution at concentrations ranging from 5 to 40 wt%. Ribbons were extruded from the blends to form samples where the nano-fillers were aligned to some degree in the extrusion direction. Samples were also fabricated by compression molding resulting in random orientation of the nano-fillers. Thermal properties of the samples were evaluated by Differential Scanning Calorimetry (DSC) and Thermal Gravimetric Analyzer (TGA). Tensile properties of aligned samples were determined at room temperature. The specimens were cut from the ribbons in the extrusion direction; hence the nano-fillers are somewhat aligned in the direction of stress. Typically it was observed that melt mixed samples exhibited superior mechanical properties compared to solution mixed samples. As expected, increased filler loading led to increased modulus and decreased elongation with respect to the neat polymer. The degree of dispersion and alignment of the nano-fillers was determined by high-resolution scanning electron microscopy (HRSEM). HRSEM of the ribbons revealed that the MWCNTs and CNFs were predominantly aligned in the flow

  9. Enhancing thermal conductivity of fluids with graphite nanoparticles and carbon nanotube

    Science.gov (United States)

    Zhang, Zhiqiang; Lockwood, Frances E.

    2008-03-25

    A fluid media such as oil or water, and a selected effective amount of carbon nanomaterials necessary to enhance the thermal conductivity of the fluid. One of the preferred carbon nanomaterials is a high thermal conductivity graphite, exceeding that of the neat fluid to be dispersed therein in thermal conductivity, and ground, milled, or naturally prepared with mean particle size less than 500 nm, and preferably less than 200 nm, and most preferably less than 100 nm. The graphite is dispersed in the fluid by one or more of various methods, including ultrasonication, milling, and chemical dispersion. Carbon nanotubes with graphitic structure is another preferred source of carbon nanomaterial, although other carbon nanomaterials are acceptable. To confer long term stability, the use of one or more chemical dispersants is preferred. The thermal conductivity enhancement, compared to the fluid without carbon nanomaterial, is proportional to the amount of carbon nanomaterials (carbon nanotubes and/or graphite) added.

  10. High Conductivity Carbon-Carbon Heat Pipes for Light Weight Space Power System Radiators

    Science.gov (United States)

    Juhasz, Albert J.

    2008-01-01

    Based on prior successful fabrication and demonstration testing of a carbon-carbon heat pipe radiator element with integral fins this paper examines the hypothetical extension of the technology via substitution of high thermal conductivity composites which would permit increasing fin length while still maintaining high fin effectiveness. As a result the specific radiator mass could approach an ultimate asymptotic minimum value near 1.0 kg/m2, which is less than one fourth the value of present day satellite radiators. The implied mass savings would be even greater for high capacity space and planetary surface power systems, which may require radiator areas ranging from hundreds to thousands of square meters, depending on system power level.

  11. Dual percolation behaviors of electrical and thermal conductivity in metal-ceramic composites

    Science.gov (United States)

    Sun, K.; Zhang, Z. D.; Qian, L.; Dang, F.; Zhang, X. H.; Fan, R. H.

    2016-02-01

    The thermal and electrical properties including the permittivity spectra in radio frequency region were investigated for copper/yttrium iron garnet (Cu/YIG) composites. Interestingly, the percolation behaviors in electrical and thermal conductivity were obtained due to the formation of copper particles' networks. Beyond the electrical percolation threshold, negative permittivity was observed and plasmon frequency was reduced by several orders of magnitude. With the increase in copper content, the thermal conductivity was gradually increased; meanwhile, the phonon scattering effect and thermal resistance get enhanced, so the rate of increase in thermal conductivity gradually slows down. Hopefully, Cu/YIG composites with tunable electrical and thermal properties have great potentials for electromagnetic interference shielding and electromagnetic wave attenuation.

  12. Dual percolation behaviors of electrical and thermal conductivity in metal-ceramic composites

    Energy Technology Data Exchange (ETDEWEB)

    Sun, K.; Zhang, Z. D.; Qian, L.; Dang, F.; Zhang, X. H., E-mail: zhangxh@sdu.edu.cn, E-mail: fan@sdu.edu.cn; Fan, R. H., E-mail: zhangxh@sdu.edu.cn, E-mail: fan@sdu.edu.cn [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan 250061 (China)

    2016-02-08

    The thermal and electrical properties including the permittivity spectra in radio frequency region were investigated for copper/yttrium iron garnet (Cu/YIG) composites. Interestingly, the percolation behaviors in electrical and thermal conductivity were obtained due to the formation of copper particles' networks. Beyond the electrical percolation threshold, negative permittivity was observed and plasmon frequency was reduced by several orders of magnitude. With the increase in copper content, the thermal conductivity was gradually increased; meanwhile, the phonon scattering effect and thermal resistance get enhanced, so the rate of increase in thermal conductivity gradually slows down. Hopefully, Cu/YIG composites with tunable electrical and thermal properties have great potentials for electromagnetic interference shielding and electromagnetic wave attenuation.

  13. Ionic conductivity of co-doped Sc2O3-ZrO2 ceramics

    DEFF Research Database (Denmark)

    Omar, Shobit; bin Najib, Waqas; Chen, Weiwu

    2012-01-01

    The oxide ionic conductivity of Sc0.18Zr0.82O1.91 doped with 0.5 mol.% of both Yb2O3 and In2O3 is evaluated at various temperatures in air. Among various co-doped compositions, In0.02Sc0.18Zr0.80O1.90 exhibits the highest grain ionic conductivity followed by Yb0.02Sc0.18Zr0.80O1.90 at 500°C. Howe...

  14. Ceramic Methyltrioxorhenium

    CERN Document Server

    Herrmann, R; Eickerling, G; Helbig, C; Hauf, C; Miller, R; Mayr, F; Krug von Nidda, H A; Scheidt, E W; Scherer, W; Herrmann, Rudolf; Troester, Klaus; Eickerling, Georg; Helbig, Christian; Hauf, Christoph; Miller, Robert; Mayr, Franz; Nidda, Hans-Albrecht Krug von; Scheidt, Ernst-Wilhelm; Scherer, Wolfgang

    2006-01-01

    The metal oxide polymeric methyltrioxorhenium [(CH3)xReO3] is an unique epresentative of a layered inherent conducting organometallic polymer which adopts the structural motifs of classical perovskites in two dimensions (2D) in form of methyl-deficient, corner-sharing ReO5(CH3) octahedra. In order to improve the characteristics of polymeric methyltrioxorhenium with respect to its physical properties and potential usage as an inherentconducting polymer we tried to optimise the synthetic routes of polymeric modifications of 1 to obtain a sintered ceramic material, denoted ceramic MTO. Ceramic MTO formed in a solvent-free synthesis via auto-polymerisation and subsequent sintering processing displays clearly different mechanical and physical properties from polymeric MTO synthesised in aqueous solution. Ceramic MTO is shown to display activated Re-C and Re=O bonds relative to MTO. These electronic and structural characteristics of ceramic MTO are also reflected by a different chemical reactivity compared with its...

  15. Crystallisation behavior and electronic conductivity of vanadium tellurite glass-ceramics

    DEFF Research Database (Denmark)

    Kjeldsen, Jonas; Yue, Yuanzheng; Rodrigues, A.C.M.

    2012-01-01

    The electrodes of secondary batteries degrade during consecutive intercalation cycles, thus reducing the units’ capacity. The amorphous nature of an electrode could theoretically lower the degree of such degradation. Since a vanadium tellurite system exhibit high electronic conductivity and the a...

  16. Boride ceramics covalent functionalization and its effect on the thermal conductivity of epoxy composites

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Zhi-Qiang, E-mail: yuzhiqiang@fudan.edu.cn [Department of Materials Science, Fudan University, 200433 Shanghai (China); Wu, Yicheng [Department of Materials Science, Fudan University, 200433 Shanghai (China); Wei, Bin; Baier, Horst [Institute of Lightweight Structures, Technical University Munich (TUM), Boltzmannstr. 15, D-85747 Garching (Germany)

    2015-08-15

    Zirconium diboride/aluminium oxide (ZrB{sub 2}/Al{sub 2}O{sub 3}) composite particles were functionalized with epoxide functionalized γ-glycidoxypropyltrimethoxysilane by the covalent bonding approach to improve the interfacial compatibility of composite particles in epoxy matrix. The composites of epoxy resin filled with functionalized ZrB{sub 2}/Al{sub 2}O{sub 3} were prepared by in situ bulk condensation polymerization of bisphenol A and epichlorohydrin in the presence of ZrB{sub 2}/Al{sub 2}O{sub 3}. The heat-conducting properties of composites were investigated by the finite element method (FEM) and the thermal conductivity test. The finite-element program ANSYS was used for this numerical analysis, and three-dimensional spheres-in-cube lattice array models were built to simulate the microstructure of composite materials for different filler contents. The thermal conductivity of composites was determined by laser flash method (LFA447 Nanoflash), using the measured heat capacity and thermal diffusivity, with separately entered density data. The results show that the effective chemical bonds are formed between ZrB{sub 2}/Al{sub 2}O{sub 3} and γ-glycidoxypropyltrimethoxysilane after the surface functionalization. The interfacial compatibility and bonding of modified particles with the epoxy matrix are improved. The thermal conductivities of functionalized composites with 3 vol% and 5 vol% loading are increased by 8.3% and 12.5% relative to the unmodified composites, respectively. Comparison of experimental values and calculated values of the thermal conductivity, the average relative differences are under 5%. The predictive values of thermal conductivity of epoxy composites are in reasonable agreement with the experimental values. - Highlights: • The surfaces of ZrB{sub 2}/Al{sub 2}O{sub 3} were functionalized by silane coupling agents. • The thermal conductivity (TC) of modified epoxy composites is improved significantly. • The FEM values of TC are in

  17. In situ formation of low friction ceramic coatings on carbon steel by plasma electrolytic oxidation in two types of electrolytes

    Science.gov (United States)

    Wang, Yunlong; Jiang, Zhaohua

    2009-04-01

    In situ formation of ceramic coatings on Q235 carbon steel was achieved by plasma electrolytic oxidation (PEO) in carbonate electrolyte and silicate electrolyte, respectively. The surface and cross-section morphology, phase and elemental composition of PEO coatings were examined by means of scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS). The bond strength of the coating was determined using a direct pull-off test. The hardness as well as tribological properties of the ceramic coating was primarily studied. The results indicated that the coating obtained in carbonate electrolyte was Fe 3O 4, while the coating achieved from silicate electrolyte was proved to be amorphous. Both kinds of coatings showed coarse and porous surface. The Fe 3O 4 coatings obtained in carbonate electrolyte showed a high bonding strength to the substrate up to 20 ± 2 MPa and the value was 15 ± 2 MPa for the amorphous coatings obtained in carbonate electrolyte. The micro hardness of the amorphous coating and the Fe 3O 4 coating was 1001 Hv and 1413 Hv, respectively, which was more than two and three times as that of the Q235 alloy substrate (415 Hv). The friction coefficient exhibited by amorphous coating and Fe 3O 4 coating was 0.13 and 0.11, respectively, both lower than the uncoated Q235 substrate which ranged from 0.17 to 0.35.

  18. Preparation,Electrochemical Behavior and Electrocatalytic Activity of a Copper Hexacyanoferrate Modified Ceramic Carbon Electrode

    Institute of Scientific and Technical Information of China (English)

    YU,Hao; ZHENG,Jian-Bin

    2007-01-01

    A copper hexacyanoferrate modified ceramic carbon electrode(CuHCF/CCE)had been prepared by two-step sol-gel technique and characterized using electrochemical methods.The resulting modified electrode showed a pair of well-defined surface waves in the potential range of 0.40 to 1.0 V with the formal potential of 0.682 V (vs.SCE)in 0.050 mol·dm-3 HOAc-NaOAc buffer containing 0.30 mol·dm-3 KCI.The charge transfer coefficient (α) and charge transfer rate constant(Ks)for the modified electrode were calculated.The electrocatalytic activity of this modified electrode to hydrazine was also investigated,and chronoamperometry was exploited to conveniently determine the diffusion coefficient(D)of hydrazine in solution and the catalytic rate constant(Kcat).Finally,hydrazine was determined with amperometry using the resulting modified electrode.The calibration plot for hydrazine determination was linear in 3.0×10-6-7.5×10-4 mol·dm-3 with the detection limit of 8.0×10-7 mol·dm-3.This modified electrode had some advantages over the modified film electrodes constructed by the conventional methods,such as renewable surface,good long-term stability,excellent catalytic activity and short response time to hydrazine.

  19. Full Polymer Dielectric Elastomeric Actuators (DEA Functionalised with Carbon Nanotubes and High-K Ceramics

    Directory of Open Access Journals (Sweden)

    Tilo Köckritz

    2016-09-01

    Full Text Available Dielectric elastomer actuators (DEA are special devices which have a simple working and construction principle and outstanding actuation properties. The DEAs consist of a combination of different materials for the dielectric and electrode layers. The combination of these layers causes incompatibilities in their interconnections. Dramatic differences in the mechanical properties and bad adhesion of the layers are the principal causes for the reduction of the actuation displacement and strong reduction of lifetime. Common DEAs achieve actuation displacements of 2% and a durability of some million cycles. The following investigations represent a new approach to solving the problems of common systems. The investigated DEA consists of only one basic raw polymer, which was modified according to the required demands of each layer. The basic raw polymer was modified with single-walled carbon nanotubes or high-k ceramics, for example, lead magnesium niobate-lead titanate. The development of the full polymer DEA comprised the development of materials and technologies to realise a reproducible layer composition. It was proven that the full polymer actuator worked according to the theoretical rules. The investigated system achieved actuation displacements above 20% regarding thickness, outstanding interconnections at each layer without any failures, and durability above 3 million cycles without any indication of an impending malfunction.

  20. Liquid spreading on ceramic-coated carbon nanotube films and patterned microstructures

    Science.gov (United States)

    Zhao, Hangbo; Hart, A. John

    2015-11-01

    We study the capillary-driven liquid spreading behavior on films and microstructures of ceramic-coated vertically aligned carbon nanotubes (CNTs) fabricated on quartz substrates. The nanoscale porosity and micro-scale dimensions of the CNT structures, which can be precisely varied by the fabrication process, enable quantitative measurements that can be related to analytical models of the spreading behavior. Moreover, the conformal alumina coating by atomic layer deposition (ALD) prevents capillary-induced deformation of the CNTs upon meniscus recession, which has complicated previous studies of this topic. Washburn-like liquid spreading behavior is observed on non-patterned CNT surfaces, and is explained using a scaling model based on the balance of capillary driving force and the viscous drag force. Using these insights, we design patterned surfaces with controllable spreading rates and study the contact line pinning-depinning behavior. The nanoscale porosity, controllable surface chemistry, and mechanical stability of coated CNTs provide significantly enhanced liquid-solid interfacial area compared to solid microstructures. As a result, these surface designs may be useful for applications such as phase-change heat transfer and electrochemical energy storage. Funding for this project is provided by the National Institutes of Health and the MIT Center for Clean Water and Clean Energy supported by the King Fahd University of Petroleum and Minerals.

  1. The Production and Characterization of Ceramic Carbon Electrode Materials for CuCl-HCl Electrolysis

    Science.gov (United States)

    Edge, Patrick

    Current H2 gas supplies are primarily produced through steam methane reforming and other fossil fuel based processes. This lack of viable large scale and environmentally friendly H2 gas production has hindered the wide spread adoption of H2 fuel cells. A potential solution to this problem is the Cu-Cl hybrid thermochemical cycle. The cycle captures waste heat to drive two thermochemical steps creating CuCl as well as O2 gas and HCl from CuCl2 and water. The CuCl is oxidized in HCl to produce H2 gas and regenerate CuCl2, this process occurs at potentials well below those required for water electrolysis. The electrolysis process occurs in a traditional PEM fuel-cell. In the aqueous anolyte media Cu(I) will form anionic complexes such as CuCl 2 - or CuCl32-. The slow transport of these species to the anode surface limits the overall electrolysis process. To improve this transport process we have produced ceramic carbon electrode (CCE) materials through a sol-gel method incorporating a selection of amine containing silanes with increasing numbers of primary and secondary amines. When protonated these amines allow for improved transport of anionic copper complexes. The electrochemical and physical characterization of these CCE materials in a half and full-cell electrolysis environment will be presented. Electrochemical analysis was performed using cell polarization, cyclic voltammetry, and electrochemical impedance spectroscopy.

  2. The Measurement of Thermal Conductivities of Silica and Carbon Black Powders at Different pressures by Thermal COnductivity Probe

    Institute of Scientific and Technical Information of China (English)

    X.G.Liang; X.S.Ge; 等

    1992-01-01

    This investigation was done to study the gas filled powder insulation and thermal conductivity probe for the measurent of thermal conductivity of powders.The mathematical analysis showed that the heat capacity of the probe itself and the thermal rsistance between the probe and powder must be considered .The authors developed a slender probe and measured the effective thermal conductivity of sillca and carbon black powders under a variety of conditions.

  3. Ceramic Membrane combined with Powdered Activated Carbon (PAC) or Coagulation for Treatment of Impaired Quality Waters

    KAUST Repository

    Hamad, Juma Z.

    2013-08-29

    Ceramic membranes (CM) are robust membranes attributed with high production, long life span and stability against critical conditions. While capital costs are high, these are partially offset by lower operation and maintenance costs compared to polymeric membranes. Like any other low-pressure membrane (LPM), CM faces problems of fouling, low removal of organic matter and poor removal of trace organic compounds (TOrCs). Current pretreatment approaches that are mainly based on coagulation and adsorption can remove some organic matter but with a low removal of the biopolymers component which is responsible for fouling. Powdered activated carbon (PAC) accompanied with a LPM maintains good removal of TOrCs. However, enhanced removal of TOrCs to higher level is required. Submicron powdered activated carbon (SPAC), obtained after crushing commercial activated carbon into very fine particle, and novel activated carbon (KCU 6) which is characterized with larger pores and high surface area were employed. A pre-coating approach, which provides intimated contact between PAC and contaminants, was adopted for wastewater and (high DOC) surface water treatment. For seawater, in-line coagulation with iron III chloride was adopted. Both SPAC and KCU 6 showed good removal of biopolymers at a dose of 30 mg/L with > 85 % and 90 %, respectively. A dose of 40 mg/L of SPAC and 30 mg/L KCU 6 pre-coats were successful used in controlling membrane fouling. SPAC is suggested to remove biopolymers by physical means and adsorption while KCU 6 removed biopolymers through adsorption. Both KCU 6 and SPAC attained high removal of TOrCs whereas KCU 6 showed outstanding performance. Out of 29 TOrCs investigated, KCU 6 showed > 87 % TOrCs rejection for 28 compounds. In seawater pretreatment, transparent exopolymer particles (TEP) were found to be an important foulant. TEP promoted both reversible and irreversible fouling. TEP are highly electronegative while alumina CM is positively charged which

  4. ANALYSIS OF DAMAGE NEAR A CONDUCTING CRACK IN A PIEZOELECTRIC CERAMIC

    Institute of Scientific and Technical Information of China (English)

    YangXinhua; ChenChuanyao; HuYuantai

    2003-01-01

    The finite element formulation for analyzing static damage near a conducting crack in a thin piezoelectric plate is established from the virtual work principle of piezoelectricity. The damage fields under various mechanical and electrical loads are calculated carefully by using an effective iterative procedure. The numerical results show that all the damage fields around a crack tip are fan-shaped and the electric field applied has great influence on the mechanical damage,which is related to the piezoelectric properties.

  5. High-Conductance Thermal Interfaces Based on Carbon Nanotubes Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to develop a novel thermal interface material (TIM) that is based on an array of vertical carbon nanotubes (CNTs) for high heat flux applications. For...

  6. Quantum Mechanics Studies of Fuel Cell Catalysts and Proton Conducting Ceramics with Validation by Experiment

    Science.gov (United States)

    Tsai, Ho-Cheng

    /Os core-shell). We found that Pt2ML/Os has the highest activity (compared to pure Pt and to the Pt3Os alloy) because the 0.37 eV barrier decreases to 0.23 eV. To understand what aspects of the core shell structure lead to this improved performance, we considered the effect on ORR of compressing the alloy slab to the dimensions of pure Pt. However this had the same RDS barrier 0.37 eV. Experimental materials characterization proves the core-shell feature of our catalyst. In part II, we used QM calculations to study methane stream reforming on a Ni-alloy catalyst surfaces for solid oxide fuel cell (SOFC) application. SOFC has wide fuel adaptability but the coking and sulfur poisoning will reduce its stability. We carried out QM calculations on surface segregation and found that the most stable configuration for Ni4Fe has a Fe atom distribution of (0%, 50%, 25%, 25%, 0%) starting at the bottom layer. We calculated that the binding of C atoms on the Ni4Fe surface is 142.9 Kcal/mol, which is about 10 Kcal/mol weaker compared to the pure Ni surface. This result confirms the experimental observation. The reaction energy barriers for CH x decomposition and C binding on various alloy surface, Ni4X (X=Fe, Co, Mn, and Mo), showed Ni4Fe, Ni4Co, and Fe4Mn all have better coking resistance than pure Ni, but that only Ni4Fe and Fe4Mn have (slightly) improved activity compared to pure Ni. In part III, we used QM to examine the proton transport in doped perovskite-ceramics. Here we used a 2x2x2 supercell of perovskite with composition Ba8X 7M1(OH)1O23 where X=Ce or Zr and M=Y, Gd, or Dy. Thus in each case a 4+ X is replace by a 3 + M plus a proton on one O. Here we predicted the barriers for proton diffusion allowing both includes intra-octahedron and inter-octahedra proton transfer. Without any restriction, we only observed the inter-octahedra proton transfer with similar energy barrier as previous computational work but 0.2 eV higher than experimental result for Y doped zirconate

  7. New tunnel schottky SiC devices using mixed conduction ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Cerda, J. [S-SENCE and Div. of Applied Physics, Linkoeping Univ., Linkoeping (Sweden); Electronic Materials and Engineering, Electronics Dept., Univ. of Barcelona, Barcelona (Spain); Morante, J.R. [Electronic Materials and Engineering, Electronics Dept., Univ. of Barcelona, Barcelona (Spain); Lloyd Spetz, A. [S-SENCE and Div. of Applied Physics, Linkoeping Univ., Linkoeping (Sweden)

    2003-07-01

    A new tunnel Schottky diode based on SiC and a mixed conductor of BaSnO{sub 3} as the gate has been investigated. I-V curves at different operating temperatures and two different gas atmospheres have been measured. The device shows sensitivity to oxygen, with maximum at 400 C. A model that describes the behaviour of the device is proposed, which takes into account the different types of conduction of the BaSnO{sub 3} due to the temperature. (orig.)

  8. Comparison of two modified coal ash ferric-carbon micro-electrolysis ceramic media for pretreatment of tetracycline wastewater.

    Science.gov (United States)

    Yang, Kunlun; Jin, Yang; Yue, Qinyan; Zhao, Pin; Gao, Yuan; Wu, Suqing; Gao, Baoyu

    2017-05-01

    Application of modified sintering ferric-carbon ceramics (SFC) and sintering-free ferric-carbon ceramics (SFFC) based on coal ash and scrap iron for pretreatment of tetracycline (TET) wastewater was investigated in this article. Physical property, morphological character, toxic metal leaching content, and crystal component were studied to explore the application possibility of novel ceramics in micro-electrolysis reactors. The influences of operating conditions including influent pH, hydraulic retention time (HRT), and air-water ratio (A/W) on the removal of tetracycline were studied. The results showed that SFC and SFFC were suitable for application in micro-electrolysis reactors. The optimum conditions of SFC reactor were pH of 3, HRT of 7 h, and A/W of 10. For SFFC reactor, the optimum conditions were pH of 2, HRT of 7 h, and A/W of 15. In general, the TET removal efficiency of SFC reactor was better than that of SFFC reactor. However, the harden resistance of SFFC was better than that of SFC. Furthermore, the biodegradability of TET wastewater was improved greatly after micro-electrolysis pretreatment for both SFC and SFFC reactors.

  9. Conductive network formation of carbon nanotubes in elastic polymer microfibers and its effect on the electrical conductance: Experiment and simulation.

    Science.gov (United States)

    Cho, Hyun Woo; Kim, Sang Won; Kim, Jeongmin; Kim, Un Jeong; Im, Kyuhyun; Park, Jong-Jin; Sung, Bong June

    2016-05-21

    We investigate how the electrical conductance of microfibers (made of polymers and conductive nanofillers) decreases upon uniaxial deformation by performing both experiments and simulations. Even though various elastic conductors have been developed due to promising applications for deformable electronic devices, the mechanism at a molecular level for electrical conductance change has remained elusive. Previous studies proposed that the decrease in electrical conductance would result from changes in either distances or contact numbers between conductive fillers. In this work, we prepare microfibers of single walled carbon nanotubes (SWCNTs)/polyvinyl alcohol composites and investigate the electrical conductance and the orientation of SWCNTs upon uniaxial deformation. We also perform extensive Monte Carlo simulations, which reproduce experimental results for the relative decrease in conductance and the SWCNTs orientation. We investigate the electrical networks of SWCNTs in microfibers and find that the decrease in the electrical conductance upon uniaxial deformation should be attributed to a subtle change in the topological structure of the electrical network.

  10. Synthesis and Thermal Conductivity of Exfoliated Hexagonal Boron Nitride/Alumina Ceramic Composite

    Science.gov (United States)

    Hung, Ching-cheh; Hurst, Janet; Santiago, Diana; Lizcano, Maricela; Kelly, Marisabel

    2017-01-01

    Exfoliated hexagonal boron nitride (hBN)/alumina composite can be fabricated by following the process of (1) heating a mixture of hBN, AlCl3, and NaF in nitrogen for intercalation; (2) heating the intercalated product in air for exfoliation and at the same time converting the intercalate (AlCl3) into Al2O3, (3) rinsing the oxidized product, (4) coating individual exfoliated hBN platelets that contain Al2O3 with new layers of aluminum oxide, and finally, (5) hot pressing the product into the composite. The composite thus obtained has a composition of approximately 60 percent by weight hBN and 40 percent by weight alumina. Its in-plane and through-plane thermal conductivity were measured to be 86 and 18 watts per meter Kelvin, respectively, at room temperature.

  11. Characteristic Analysis of the Solid Oxide Fuel Cell with Proton Conducting Ceramic Electrolyte

    Institute of Scientific and Technical Information of China (English)

    谭小耀; 孟波; 杨乃涛; K.Li

    2005-01-01

    An electrolyte model for the solid oxide fuel cell (SOFC) with proton conducting perovskite electrolyte is developed in this study, in which four types of charge carriers including proton, oxygen vacancy (oxide ion), free electron and electron hole are taken into consideration. The electrochemical process within the SOFC with hydrogen as the fuel is theoretically analyzed. With the present model, the effects of some parameters, such as the thickness of electrolyte, operating temperature and gas composition, on the ionic transport (or gas permeation) through the electrolyte and the electrical performance, i.e., the electromotive force (EMF) and internal resistance of the cell, are investigated in detail. The theoretical results are tested partly by comparing with the experimental data obtained from SrCe0.05M0.05O3-α(M=Yb, Y) cells.

  12. Synthesis and metrology of conducting carbon nanotube assemblies

    Science.gov (United States)

    Longson, Timothy Jay

    Since its discovery, the carbon nanotube (CNT) has been proposed as one of the ultimate materials for its electrical, thermal and mechanical properties due to its incredibly strong sp2 bonds, low defect density, and large aspect ratio. Many experimental results on individual CNTs have confirmed these outstanding theoretically predicted properties. However, scaling these properties to the macroscopic regime has proved to be challenging. This work focused on the synthesis and measurement of highly conducting, macroscopic, CNT assemblies. Scaling up the synthesis of vertically aligned multiwalled CNT (MWNT) forests was investigated through the development of a large, 100mm, wafer scale, cold wall chemical vapor deposition chamber. In addition to the synthesis, two distinct CNT assemblies have been investigated. A linear morphology where CNTs are strung in series for electrical transport (CNT wires) and a massively parallel 2D array of vertically aligned CNTs for Thermal Interface Material (TIM) applications. Poymer-CNT wire composites have been fabricated by developing a coaxial CNT core-polymer shell electrospinning technique. The core-shell interactions in this system have been studied by way of Hansen's solubility parameters. The most well defined CNT core was achieved using a core solvent that is semi-immiscible with the shell solution, yet still a solvent of the shell polymer. Electrical characterization of the resulting CNT core has shown a two orders of magnitude increase in conductivity over traditional, homogeneously mixed, electrospun CNT wires. A number of vertically aligned MWNT assemblies were studied for their thermal interface properties. Double-sided Silicon substrate (MWNT-Si-MWNT) TIM assemblies were characterized using a DC, 1D reference bar, thermal measurement technique. While attempts to control MWNT density via a micelle template technique produced only 'spaghetti like' CNTs, sputter deposited catalyst provided stark variations in array density

  13. The Influence of Unidirectional Pressure on Electrical Conductivity of Carbon Black Filled Polyethylene

    Institute of Scientific and Technical Information of China (English)

    WANG Ke; ZHANG Guo; ZHAO Zhudi; PENG Yi; DI Weihua; DU Chuang

    2006-01-01

    High density polyethylene filled with conductive carbon black was prepared by conventional melt-mixing method. The effect of unidirectional pressure on the conductivity was studied. Wide angle X-ray diffraction (WAXD) was used to show the influence of pressure on the aggregate structure of the polymer filled with carbon black (CB) fillers. A model on the basis of the formation and destruction of conductive networks was proposed to explain the change in the conductivity with the application of pressure.

  14. Y{sub 3-x}Er{sub x}Al{sub 5}O{sub 12} aluminate ceramics: preparation, thermal properties and theoretical model of thermal conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yan-Gai; Peng, Peng; Fang, Minghao; Huang, Zhaohui [School of Materials Science and Technology, China University of Geosciences, Beijing (China)

    2012-03-15

    Rare-earth aluminate ceramics for thermal-barrier coatings (TBCs) are synthesized. The Young's modulus and thermal properties decrease with erbium additive increasing. The Y{sub 3-x}Er{sub x}Al{sub 5}O{sub 12} ceramics (x=1,3) possess a much-lower thermal conductivity compared with 8YSZ. The lower Young's modulus and thermal-expansion coefficient are due to the larger atomic weight of the Er substitutional atom. Additional phonon-scattering effects also contribute to the lower thermal conductivity. The results indicate that Y{sub 3-x}Er{sub x}Al{sub 5}O{sub 12} can be explored as a candidate material for TBC systems. A theoretical model that describes the influence of point defects on the thermal conductivity is discussed. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. Chemical stability of conductive ceramic anodes in LiCl–Li{sub 2}O molten salt for electrolytic reduction in pyroprocessing

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sung Wook; Kang, Hyun Woo; Jeon, Min Ku; Lee, Sang Kwon; Choi, Eun Young; Park, Woo Shin; Hong, Sun Seok; Oh, Seung Chul; Hur, Jin Mok [Nuclear Fuel Cycle Process Development Group, Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2016-08-15

    Conductive ceramics are being developed to replace current Pt anodes in the electrolytic reduction of spent oxide fuels in pyroprocessing. While several conductive ceramics have shown promising electrochemical properties in small-scale experiments, their long-term stabilities have not yet been investigated. In this study, the chemical stability of conductive La{sub 0.33}Sr{sub 0.67}MnO{sub 3} in LiCl–Li{sub 2}O molten salt at 650°C was investigated to examine its feasibility as an anode material. Dissolution of Sr at the anode surface led to structural collapse, thereby indicating that the lifetime of the La{sub 0.33}Sr{sub 0.67}MnO{sub 3} anode is limited. The dissolution rate of Sr is likely to be influenced by the local environment around Sr in the perovskite framework.

  16. Performance and cycle life of carbon- and conductive-based air electrodes for rechargeable Zn-air battery applications

    Science.gov (United States)

    Chellapandi Velraj, Samgopiraj

    The development of high-performance, cyclically stable bifunctional air electrodes are critical to the commercial deployment of rechargeable Zn-air batteries. The carbon material predominantly used as support material in the air electrodes due to its higher surface area and good electrical conductivity suffers from corrosion at high oxygen evolution overpotentials. This study addresses the carbon corrosion issues and suggests alternate materials to replace the carbon as support in the air electrode. In this study, Sm0.5Sr0.5CoO3-delta with good electrochemical performance and cyclic lifetime was identified as an alternative catalyst material to the commonly used La0.4Ca 0.6CoO3 catalyst for the carbon-based bifunctional electrodes. Also, a comprehensive study on the effects of catalyst morphology, testing conditions on the cycle life as well as the relevant degradation mechanism for the carbon-based electrode was conducted in this dissertation. The cyclic life of the carbon-based electrodes was strongly dependent on the carbon support material, while the degradation mechanisms were entirely controlled by the catalyst particle size/morphology. Some testing conditions like resting time and electrolyte concentration did not change the cyclic life or degradation mechanism of the carbon-based electrode. The current density used for cyclic testing was found to dictate the degradation mechanism leading to the electrode failure. An alternate way to circumvent the carbon corrosion is to replace the carbon support with a suitable electrically-conductive ceramic material. In this dissertation, LaNi0.9Mn0.1O3, LaNi 0.8Co0.2O3, and NiCo2O4 were synthesized and evaluated as prospective support materials due to their good electrical conductivity and their ability to act as the catalyst needed for the bifunctional electrode. The carbon-free electrodes had remarkably higher catalytic activity for oxygen evolution reaction (OER) when compared to the carbon-based electrode. However

  17. AC Conductivity and Impedance Properties of 0.65Pb(Mg1/3Nb2/3O3-0.35PbTiO3 Ceramics

    Directory of Open Access Journals (Sweden)

    Banarji Behera

    2009-01-01

    impedance spectroscopy technique. The impedance and electric permittivity were strongly temperature and frequency dependent. The activation energy, calculated from the temperature dependence of AC conductivity of the ceramics was found to be ∼0.5 eV. The relaxation process in the ceramics was found to be of non-Debye type. The nature of Cole-Cole diagram reveals the contribution of grain (bulk and grain boundary permittivity in the ceramics.

  18. Stretchable Conductive Networks of Carbon Nanotubes Using Plasticised Colloidal Templates

    Directory of Open Access Journals (Sweden)

    Patnarin eWorajittiphon

    2015-03-01

    Full Text Available We present a study of the behavior of highly ordered, segregated single-wall carbon nanotube networks under applied strain. Polymer latex templates induce self-assembly of carbon nanotubes into hexagonal (2D and honeycomb (3D networks within the matrix. Using mechanical and spectroscopic analysis, we have studied the strain transfer mechanisms between the carbon nanotube network and the polymer matrix. Axial deformation of the nanotube network under applied strain is indicated by downshifts in the 2D mode in the Raman spectra, as well as variation in the Radial Breathing modes. The slippage within nanotube bundles at high strain is indicated by a reduction in the 2D mode rate of change. The fractional resistance change of the composites with strain obeys power law dependence. We present a model for the behavior of carbon nanotube bundles under strain informed by these measurements, and potential applications for such composite materials in elastic electronic devices that can tolerate high strain.

  19. Ion conducting fluoropolymer carbonates for alkali metal ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    DeSimone, Joseph M.; Pandya, Ashish; Wong, Dominica; Balsara, Nitash P.; Thelen, Jacob; Devaux, Didier

    2017-09-05

    Liquid or solid electrolyte compositions are described that comprise a homogeneous solvent system and an alkali metal salt dissolved in said solvent system. The solvent system may comprise a fluoropolymer, having one or two terminal carbonate groups covalently coupled thereto. Batteries containing such electrolyte compositions are also described.

  20. Electrical conductivity of metal–carbon nanotube structures: Effect of length and doping

    Indian Academy of Sciences (India)

    R Nigam; S Habeeb; A Priyadarshi; N Jaggi

    2014-08-01

    The electrical properties of asymmetric metal–carbon nanotube (CNT) structures have been studied using density functional theory and non-equilibrium Green’s function method with Atomistix tool kit. The models with asymmetric metal contacts and carbon nanotube bear resemblance to experimental set-ups. The study shows the effect of varying length of carbon nanotube on electronic transmission and conductance of various structures. The effects of silicon doping on CNT-based structures have also been studied. The conductance of structure with longer CNT is more compared with shorter CNT. Silicon doping increases the conductivity of carbon nanotube-based structure.

  1. The dependence of the electronic conductivity of carbon molecular sieve electrodes on their charging states.

    Science.gov (United States)

    Pollak, Elad; Genish, Isaschar; Salitra, Gregory; Soffer, Abraham; Klein, Lior; Aurbach, Doron

    2006-04-13

    The dependence of the electronic conductivity of activated carbon electrodes on their potential in electrolyte solutions was examined. Kapton polymer films underwent carbonization (1000 degrees C), followed by a mild oxidation process (CO(2) at 900 degrees C) for various periods of time, to obtain carbons of different pore structures. A specially designed cell was assembled in order to measure the conductivity of carbon electrodes at different potentials in solutions. When the carbon electrodes possessed molecular sieving properties, a remarkable dependence of their conductivity on their charging state was observed. Aqueous electrolyte solutions containing ions of different sizes were used in order to demonstrate this phenomenon. As the average pore size of the activated carbons was larger, their molecular sieving ability was lower, and the dependence of their conductivity on their charging state regained its classical form. This behavior is discussed herein.

  2. Anisotropic conductance of the multiwall carbon nanotube array/silicone elastomer composite film

    Energy Technology Data Exchange (ETDEWEB)

    Yao Yuan; Liu Changhong; Fan Shoushan [Tsinghua-Foxconn Nanotechnology Research Center and Department of Physics, Tsinghua University, Beijing 100084 (China)

    2006-09-14

    Multiwall carbon nanotube array/silicone elastomer composite films have been fabricated with an in situ injection modelling method. The transverse conductivity of the composite films is larger than the lateral conductivity because the aligned carbon nanotube array is embedded into the polymer matrix. The nonlinear I-V curve has been analysed and the temperature-dependent transport behaviour has been investigated.

  3. Mechanically robust, electrically conductive ultralow-density carbon nanotube-based aerogels

    Energy Technology Data Exchange (ETDEWEB)

    Worsley, Marcus A.; Baumann, Theodore F.; Satcher, Jr., Joe H.

    2016-10-04

    Disclosed here is a device comprising a porous carbon aerogel or composite thereof as an energy storage material, catalyst support, sensor or adsorbent, wherein the porous carbon aerogel comprises a network of interconnected struts comprising carbon nanotube bundles covalently crosslinked by graphitic carbon nanoparticles, wherein the carbon nanotubes account for 5 to 95 wt. % of the aerogel and the graphitic carbon nanoparticles account for 5 to 95 wt. % of the aerogel, and wherein the aerogel has an electrical conductivity of at least 10 S/m and is capable of withstanding strains of more than 10% before fracture.

  4. Ultra-small Palladium Nanoparticle Decorated Carbon Nanotubes: Conductivity and Reactivity.

    Science.gov (United States)

    Li, Xiuting; Batchelor-McAuley, Christopher; Tschulik, Kristina; Shao, Lidong; Compton, Richard G

    2015-08-03

    Carbon nanotubes decorated with ultra-small metal nanoparticles are of great value in catalysis. We report that individual multiwalled carbon nanotubes decorated with ultra-small palladium nanoparticles can be detected by using the nano-impacts method. The high conductivity and reactivity of each decorated carbon nanotube is directly evidenced; this is achieved through studying the proton-reduction reaction for the underpotential deposition of hydrogen onto the nanoparticles decorated on the carbon nanotube walls. The reductive spikes from current amplification are analyzed to estimate the approximate length of the decorated carbon nanotubes, revealing that the decorated carbon nanotubes are electroactive along its entire length of several micrometers.

  5. Thermal Conductivity and Raman Spectra of Carbon Fibers

    Science.gov (United States)

    Liu, Xuebo; Dong, Hua; Li, Yan; Mei, Ning

    2017-10-01

    Due to its unique physical properties, carbon fiber (CF) has been widely studied for extensive application in aerospace and machinery. In this study, the thermal diffusivity of three kinds of CF sample is characterized by the transient electrothermal technique at room temperature. By subtracting the effect of radiative losses, the effective thermal diffusivity of CFs can be calculated as 6.46× 10^{-6} m2\\cdot s^{-1}, 6.58× 10^{-6} m2\\cdot s^{-1} and 2.01× 10^{-4} m2\\cdot s^{-1}, respectively. For the first time, the emissivity coefficient of carbon fiber is calibrated as 0.78. Combined with Raman spectra and phonon scattering, we found that the better crystalline structure and low defect in CF have an obvious impact on its thermal diffusivity.

  6. Activated carbon is an electron-conducting amphoteric ion adsorbent

    CERN Document Server

    Biesheuvel, P M

    2015-01-01

    Electrodes composed of activated carbon (AC) particles can desalinate water by ion electrosorption. To describe ion electrosorption mathematically, accurate models are required for the structure of the electrical double layers (EDLs) that form within electrically charged AC micropores. To account for salt adsorption also in uncharged ACs, an "attraction term" was introduced in modified Donnan models for the EDL structure in ACs. Here it will be shown how instead of using an attraction term, chemical information of the surface structure of the carbon-water interface in ACs can be used to construct an alternative EDL model for ACs. This EDL model assumes that ACs contain both acidic groups, for instance due to carboxylic functionalities, and basic groups, due to the adsorption of protons to the carbon basal planes. As will be shown, this "amphoteric Donnan" model accurately describes various data sets for ion electrosorption in ACs, for solutions of NaCl, of CaCl2, and mixtures thereof, as function of the exter...

  7. Humidifier for fuel cell using high conductivity carbon foam

    Science.gov (United States)

    Klett, James W.; Stinton, David P.

    2006-12-12

    A method and apparatus of supplying humid air to a fuel cell is disclosed. The extremely high thermal conductivity of some graphite foams lends itself to enhance significantly the ability to humidify supply air for a fuel cell. By utilizing a high conductivity pitch-derived graphite foam, thermal conductivity being as high as 187 W/m.dot.K, the heat from the heat source is more efficiently transferred to the water for evaporation, thus the system does not cool significantly due to the evaporation of the water and, consequently, the air reaches a higher humidity ratio.

  8. Investigating the Inter-Tube Conduction Mechanism in Polycarbonate Nanocomposites Prepared with Conductive Polymer-Coated Carbon Nanotubes.

    Science.gov (United States)

    Ventura, Isaac Aguilar; Zhou, Jian; Lubineau, Gilles

    2015-12-01

    A well-known strategy to improve the electrical conductivity of polymers is to dope them with high-aspect-ratio and conductive nanoparticles such as carbon nanotubes (CNTs). However, these nanocomposites also exhibit undesirable properties such as damage-sensitive and history-dependent conductivity because their macroscopic electrical conductivity is largely determined by the tunneling effect at the tube/tube interface. To reduce these issues, new nanocomposites have been developed with CNTs that have been coated with a conductive layer of poly(3,4-ethylenedioxythiophene)poly(styrenesulfonate) (PEDOT/PSS). It has been posited that the insulating region between the CNTs is replaced by a conductive polymer bridge; this has not been proven up to now. We propose here to investigate in-depth how the macroscopic conductivity of these materials is changing when (1) varying the frequency of the electrical loading (impedance spectroscopy), (2) varying the mechanical hydrostatic pressure, and (3) varying the voltage of the electrical loading. The response is systematically compared to the one of conventional carbon nanotube/polycarbonate (CNT/PC) nanocomposites so we can clarify how efficiently the tunneling effect is suppressed from these composites. The objective is to elucidate further the mechanism for conduction in such material formulations.

  9. Investigating the Inter-Tube Conduction Mechanism in Polycarbonate Nanocomposites Prepared with Conductive Polymer-Coated Carbon Nanotubes

    KAUST Repository

    Ventura, Isaac Aguilar

    2015-12-16

    A well-known strategy to improve the electrical conductivity of polymers is to dope them with high-aspect-ratio and conductive nanoparticles such as carbon nanotubes (CNTs). However, these nanocomposites also exhibit undesirable properties such as damage-sensitive and history-dependent conductivity because their macroscopic electrical conductivity is largely determined by the tunneling effect at the tube/tube interface. To reduce these issues, new nanocomposites have been developed with CNTs that have been coated with a conductive layer of poly(3,4-ethylenedioxythiophene)poly(styrenesulfonate) (PEDOT/PSS). It has been posited that the insulating region between the CNTs is replaced by a conductive polymer bridge; this has not been proven up to now. We propose here to investigate in-depth how the macroscopic conductivity of these materials is changing when (1) varying the frequency of the electrical loading (impedance spectroscopy), (2) varying the mechanical hydrostatic pressure, and (3) varying the voltage of the electrical loading. The response is systematically compared to the one of conventional carbon nanotube/polycarbonate (CNT/PC) nanocomposites so we can clarify how efficiently the tunneling effect is suppressed from these composites. The objective is to elucidate further the mechanism for conduction in such material formulations.

  10. Testing the Chemical/Structural Stability of Proton Conducting Perovskite Ceramic Membranes by in Situ/ex Situ Autoclave Raman Microscopy.

    Science.gov (United States)

    Slodczyk, Aneta; Zaafrani, Oumaya; Sharp, Matthew D; Kilner, John A; Dabrowski, Bogdan; Lacroix, Olivier; Colomban, Philippe

    2013-10-25

    Ceramics, which exhibit high proton conductivity at moderate temperatures, are studied as electrolyte membranes or electrode components of fuel cells, electrolysers or CO2 converters. In severe operating conditions (high gas pressure/high temperature), the chemical activity towards potentially reactive atmospheres (water, CO2, etc.) is enhanced. This can lead to mechanical, chemical, and structural instability of the membranes and premature efficiency loss. Since the lifetime duration of a device determines its economical interest, stability/aging tests are essential. Consequently, we have developed autoclaves equipped with a sapphire window, allowing in situ Raman study in the 25-620 °C temperature region under 1-50 bar of water vapor/gas pressure, both with and without the application of an electric field. Taking examples of four widely investigated perovskites (BaZr0.9Yb0.1O3-δ, SrZr0.9Yb0.1O3-δ, BaZr0.25In0.75O3-δ, BaCe0.5Zr0.3Y0.16Zn0.04O3-δ), we demonstrate the high potential of our unique set-up to discriminate between good/stable and instable electrolytes as well as the ability to detect and monitor in situ: (i) the sample surface reaction with surrounding atmospheres and the formation of crystalline or amorphous secondary phases (carbonates, hydroxides, hydrates, etc.); and (ii) the structural modifications as a function of operating conditions. The results of these studies allow us to compare quantitatively the chemical stability versus water (corrosion rate from ~150 µm/day to less than 0.25 µm/day under 200-500 °C/15-80 bar PH2O) and to go further in comprehension of the aging mechanism of the membrane.

  11. Magneli phase titanium sub-oxide conductive ceramic TinO2n-1 as support for electrocatalyst toward oxygen reduction reaction with high activity and stability

    Institute of Scientific and Technical Information of China (English)

    伍秋美; 阮建明; 周忠诚; 桑商斌

    2015-01-01

    Magneli phase titanium sub-oxide conductive ceramic TinO2n-1 was used as the support for Pt due to its excellent resistance to electrochemical oxidation, and Pt/TinO2n-1 composites were prepared by the impregnation-reduction method. The electrochemical stability of TinO2n-1 was investigated and the results show almost no change in the redox region after oxidation for 20 h at 1.2 V (vs NHE) in 0.5 mol/L H2SO4 aqueous solution. The catalytic activity and stability of the Pt/TinO2n-1 toward the oxygen reduction reaction (ORR) in 0.5 mol/L H2SO4 solution were investigated through the accelerated aging tests (AAT), and the morphology of the catalysts before and after the AAT was observed by transmission electron microscopy. At the potential of 0.55 V (vs SCE), the specific kinetic current density of the ORR on the Pt/TinO2n-1 is about 1.5 times that of the Pt/C. The LSV curves for the Pt/C shift negatively obviously with the half-wave potential shifting about 0.02 V after 8000 cycles AAT, while no obvious change takes place for the LSV curves for the Pt/TinO2n-1. The Pt particles supported on the carbon aggregate obviously, while the morphology of the Pt supported on TinO2n-1 remains almost unchanged, which contributes to the electrochemical surface area loss of Pt/C being about 2 times that of the Pt/TinO2n-1. The superior catalytic stability of Pt/TinO2n-1 toward the ORR could be attributed to the excellent stability of the TinO2n-1 and the electronic interaction between the metals and the support.

  12. Screen printing of electro-conductive ceramics for the development of microheater devices; Siebdruck von elektrisch leitfaehigen Keramiken zur Entwicklung heizbarer keramischer Mikrokomponenten

    Energy Technology Data Exchange (ETDEWEB)

    Stolz, S.

    2004-07-01

    The objective of the current work was the development of electro-conductive ceramic screen printing pastes. By screen printing these pastes on ceramic substrates microstructured ceramic heating elements were developed, covering the temperature range from room temperature up to about 1000 C. Until now, no commercial pastes are available for this high temperature region. The scope of the work comprises the development of screen printing pastes of three different materials: Al{sub 2}O{sub 3}/TiN, Si{sub 3}N{sub 4}/TiN and Indium-Tin-Oxide (In{sub 2-x}Sn{sub x}O{sub 3}). The paste optimisation was conducted to accomplish the prerequisites for a dense sintered microstructure of the layers leading to reproducible electrical properties. Furthermore the rheological properties of the pastes were adjusted in order to yield an optimised printing result. Microstructured ceramic resistance heating elements, screen printed onto alumina substrates could be realized for the material combination Al{sub 2}O{sub 3}/TiN and for In{sub 2-x}Sn{sub x}O{sub 3}, whereas Si3N4/TiN showed severe deficiencies. Different types of heating elements were developed and examined with respect to their heating characteristics. It could be shown that the heaters can be operated up to temperatures of 1000 C. Potential applications for these devices are igniters, heating elements for sensors or for micro reaction technology components. Due to the linear temperature versus electrical resistance correlation they can also be used as temperature monitoring units. As a first application a heating concept for a ceramic microreactor was developed and built. The objective was a localized inductive heating of the reaction zone. It was possible to reach a temperature of 1000 C at the reaction zone, whereas the gas in- and outlet parts showed a temperature below 500 C. (orig.)

  13. Effect of carbon on wettability and interface reaction between melt superalloy and ceramic material

    Directory of Open Access Journals (Sweden)

    Chen Xiaoyan

    2014-01-01

    Full Text Available Effect of C on wettability and interface reaction between a nickel based superalloy and ceramic material was investigated by using a sessile drop method. It was found that the content of C in the alloy is able to influence the wettability and interface reaction. Alloys with C content lower than 0.1wt.% are stable on ceramic material and no interface reaction generates at the alloy-ceramic interface. However, when C content is higher than 0.1wt.%, the interface reaction occurs and the wetting angle decreases quickly. The product of interface reaction is discontinuous and composed of 9Al2O3 ⋅Cr2O3. Such result indicates that Cr in the alloy is impossible to react with the ceramic material and form Cr2O3 without the assistance of C. It is suggested that C in the alloy deoxidizes SiO2 in the ceramic material and produces SiO and CO. SiO is unstable and it can release active O atom at the interface. Cr at the interface combines with free O atom and forms Cr2O3. Al2O3 in the ceramic material and Cr2O3 finally forms 9Al2O3 ⋅Cr2O3.

  14. Lattice Thermal Conductivity of Ultra High Temperature Ceramics (UHTC) ZrB2 and HfB2 from Atomistic Simulations

    Science.gov (United States)

    Lawson, JOhn W.; Daw, Murray S.; Bauschlicher, Charles W.

    2011-01-01

    Ultra high temperature ceramics (UHTC) including ZrB2 and HfB2 are candidate materials for applications in extreme environments because of their high melting point, good mechanical properties and reasonable oxidation resistance. Unlike many ceramics, these materials have high thermal conductivity which can be advantageous, for example, to reduce thermal shock. Recently, we developed Tersoff style interatomic potentials for both ZrB2 and HfB2 appropriate for atomistic simulations. As an application, Green-Kubo molecular dynamics simulations were performed to evaluate the lattice thermal conductivity for single crystals of ZrB2 and HfB2. The atomic mass difference in these binary compounds leads to oscillations in the time correlation function of the heat current. Results at room temperature and at elevated temperatures will be reported.

  15. Anaerobic acidogenic digestion of olive mill wastewaters in biofilm reactors packed with ceramic filters or granular activated carbon.

    Science.gov (United States)

    Bertin, Lorenzo; Lampis, Silvia; Todaro, Daniela; Scoma, Alberto; Vallini, Giovanni; Marchetti, Leonardo; Majone, Mauro; Fava, Fabio

    2010-08-01

    Four identically configured anaerobic packed bed biofilm reactors were developed and employed in the continuous acidogenic digestion of olive mill wastewaters to produce volatile fatty acids (VFAs), which can be exploited in the biotechnological production of polyhydroxyalkanoates. Ceramic porous cubes or granular activated carbon were used as biofilm supports. Aside packing material, the role of temperature and organic loading rate (OLR) on VFA production yield and mixture composition were also studied. The process was monitored through a chemical, microbiological and molecular biology integrated procedure. The highest wastewater acidification yield was achieved with the ceramic-based technology at 25 degrees C, with an inlet COD and an OLR of about 17 g/L and 13 g/L/day, respectively. Under these conditions, about the 66% of the influent COD (not including its VFA content) was converted into VFAs, whose final amount represented more than 82% of the influent COD. In particular, acetic, propionic and butyric acids were the main VFAs by composing the 55.7, 21.5 and 14.4%, respectively, of the whole VFA mixture. Importantly, the relative concentrations of acetate and propionate were affected by the OLR parameter. The nature of the packing material remarkable influenced the process performances, by greatly affecting the biofilm bacterial community structure. In particular, ceramic cubes favoured the immobilization of Firmicutes of the genera Bacillus, Paenibacillus and Clostridium, which were probably involved in the VFA producing process.

  16. Carbon Nanotube-Conducting Polymer Composites Based Solar Cells

    Institute of Scientific and Technical Information of China (English)

    Prakash; R.Somani; M.Umeno

    2007-01-01

    1 Results Combination of carbon nanotubes (CN) with polymers is important for application towards value added composites,solar cells,fuel cells etc.Especially interesting is the combination of CN with π-conjugated polymers because of the potential interaction between the highly delocalized π-electrons of the CN and the π-electrons correlated with the lattice of polymer skeleton.Efficient exciton dissociation due to electron transfer from the photoexcited polymer to CN is of interest for photovoltaic app...

  17. Thermal and tensile strength testing of thermally-conductive adhesives and carbon foam

    Science.gov (United States)

    Chertok, M.; Fu, M.; Irving, M.; Neher, C.; Shi, M.; Tolfa, K.; Tripathi, M.; Vinson, Y.; Wang, R.; Zheng, G.

    2017-01-01

    Future collider detectors, including silicon tracking detectors planned for the High Luminosity LHC, will require components and mechanical structures providing unprecedented strength-to-mass ratios, thermal conductivity, and radiation tolerance. This paper studies carbon foam used in conjunction with thermally conductive epoxy and thermally conductive tape for such applications. Thermal performance and tensile strength measurements of aluminum-carbon foam-adhesive stacks are reported, along with initial radiation damage test results.

  18. Stability of Conductive Carbon Additives for High-voltage Li-ion Battery Cathodes

    OpenAIRE

    Nilssen, Benedicte Eikeland

    2014-01-01

    Conductive carbon additives are important constituents of the current state-of-the-art Li-ion battery cathodes, as the traditional active cathode materials are characterized by too low electronic conductivities. In high-voltage Li-ion batteries, these additives are subject for anion intercalation and electrolyte oxidation, which might cause changes in the conductive carbon network in the cathode, and hence the overall cycling performance of the electrode. This thesis has focused on study the ...

  19. Hydrogen Extraction Characteristics of Electrochemical Hydrogen Pump Using Proton-conducting Ceramics CaZr0.9In0.1O3-α

    Institute of Scientific and Technical Information of China (English)

    XIA; Ti-rui; YANG; Hong-guang; HE; Chang-shui; YANG; Li-ling; ZHAO; Wei-wei; LIU; Zhen-xing

    2013-01-01

    To develop high-efficiency and economical hydrogen isotope purification and recovery processes for a tritium extraction system in a fusion reactor,hydrogen extraction characteristics of an electrochemical hydrogen pump using a one-end closed tube made of proton-conducting ceramic CaZr0.9In0.1O3-α(effective electrode area was 160 cm2)were studied.The hydrogen pumping characteristics were evaluated over the

  20. A Study on Electrically Conducting Magnesia—carbon Bricks for DC EAF

    Institute of Scientific and Technical Information of China (English)

    TONGXiaojun; YANLiyi; 等

    1998-01-01

    This paper gives a brief introduction to a kind of special refractories for DC EAF-electrically conducting magnesia-carbon bricks.The application of the conductive magnesia-carbon brick as a hearth electrode is a trend of development in DC arc furnace hearth bootom because of its features of anti corrosion and easy repatching,This is a proven process already available abroad.After a study of teh effect of different amount of graphite added and pretreating temperatures on the eletric-conductivity of magnesia-carbon bricks it has been found that for a balance between electric and thermal conductivities,the proper amount of graphite to be added should be 8%-14% and the pretreatment at temperature of 1300-1500℃ will result in the formation inside the magnesia-carbon bricks of a continuous three-dimensional network of graphite and semi-coke,thus making the brick conductive.

  1. Effects of carbon content and solidification rate on thermal conductivity of grey cast iron

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The thermal conductivity or diffusivity of pearlitic grey irons with various carbon contents is investigated by the laser flash method. The materials are cast in controlled thermal environments and produced in three dissimilar cooling rates. The cooling rate together with the carbon content largely influence the thermal conductivity of grey iron. Linear relationships exist between the thermal conductivity and the carbon content, the carbon equivalent and the fraction of former primary solidified austenite transformed into pearlite. The work shows that optimal thermal transport properties are obtained at medium cooling rates. Equations describing the thermal conductivity of pearlite,solidified as pre-eutectic austenite, and the eutectic of grey iron are derived. The thermal conductivity of pearlitic grey iron is modeled at both room temperature and elevated temperature with good accuracy.

  2. Effects of Carbon Content and Solidification Rate on the Thermal Conductivity of Grey Cast Iron

    Institute of Scientific and Technical Information of China (English)

    Daniel Holmgren; Attila Diószegi; Ingvar L.Svensson

    2008-01-01

    The thermal conductivity/diffusivity of pearlitic grey irons with various carbon contents was investi- gated by the laser flash method. The materials were cast in controlled thermal environments producing three dissimilar cooling rates. The cooling rates together with the carbon content largely influence the thermal conductivity of grey iron. Linear relationships exist between the thermal conductivity and the carbon content, the carbon equivalent, and the fraction of the former primary solidified austenite transformed into pearlite. The results show that the optimal thermal transport properties are obtained at medium cooling rates. Equa- tions are given for the thermal conductivity of pearlite, solidified as pre-eutectic austenite, and the eutectic of grey iron. The thermal conductivity of pearlitic grey iron is modelled at both room temperature and elevated temperatures with good accuracy.

  3. Effects of carbon content and solidification rate on thermal conductivity of grey cast iron

    Directory of Open Access Journals (Sweden)

    Daniel Holmgren

    2007-08-01

    Full Text Available The thermal conductivity or diffusivity of pearlitic grey irons with various carbon contents is investigated by the laser flash method. The materials are cast in controlled thermal environments and produced in three dissimilar cooling rates. The cooling rate together with the carbon content largely influence the thermal conductivity of grey iron. Linear relationships exist between the thermal conductivity and the carbon content, the carbon equivalent and the fraction of former primary solidified austenite transformed into pearlite. The work shows that optimal thermal transport properties are obtained at medium cooling rates. Equations describing the thermal conductivity of pearlite,solidified as pre-eutectic austenite, and the eutectic of grey iron are derived. The thermal conductivity of pearlitic grey iron is modeled at both room temperature and elevated temperature with good accuracy.

  4. Preparation of a sol-gel-derived carbon nanotube ceramic electrode by microwave irradiation and its application for the determination of adenine and guanine

    Energy Technology Data Exchange (ETDEWEB)

    Abbaspour, Abdolkarim, E-mail: abbaspour@chem.susc.ac.i [Department of Chemistry, College of Sciences, Shiraz University, Shiraz, Fars 71456-85464 (Iran, Islamic Republic of); Ghaffarinejad, Ali [Department of Chemistry, College of Sciences, Shiraz University, Shiraz, Fars 71456-85464 (Iran, Islamic Republic of)

    2010-01-01

    In this study, microwave irradiation was used for the fast preparation (min) of a sol-gel-derived carbon nanotube ceramic electrode (MW-CNCE). For confirmation of the preparation of the ceramic by MW irradiation, Fourier transform infrared, X-ray diffraction spectra and scanning electron microscopy images of the produced ceramic were compared with those of conventional ceramic (which is produced by drying the ceramic in air for 48 h). The electrochemical behavior of MW-CNCE in nicotinamide adenine dinucleotide, L-cysteine, adenine and guanine was compared with that of a conventional sol-gel-derived carbon nanotube ceramic electrode (CNCE). In all systems, similar peak potentials and lower background currents were obtained with respect to CNCE. Finally, the MW-CNCE was used for the simultaneous determination of adenine and guanine using differential pulse voltammetry. The linear ranges of 0.1-10 and 0.1-20 muM were obtained for adenine and guanine, respectively. These results are comparable with some modified electrodes that have recently been reported for the determination of adenine and guanine, with the advantage that the proposed electrode did not contain modifier. In addition, the proposed electrode was successfully used for the oxidation of adenine and guanine in DNA, and the detection limit for this measurement was 0.05 mug mL{sup -1} DNA.

  5. Comparative study of apatite formation on CaSiO3 ceramics in simulated body fluids with different carbonate concentrations.

    Science.gov (United States)

    Iimori, Yusuke; Kameshima, Yoshikazu; Okada, Kiyoshi; Hayashi, Shigeo

    2005-01-01

    Apatite formation on CaSiO3 ceramics was investigated using two different simulated body fluids (SBF) proposed by Kokubo (1990) and Tas (2000) and three sample/SBF (S/S) ratios (1.0, 2.5 and 8.3 mg/ml) at 36.5 degrees C for 1-25 days. The CaSiO3 ceramic was prepared by firing coprecipitated gel with Ca/Si = 0.91 at 1400 degrees C. The bulk density was 2.14 g/cm3 and the relative density about 76%. The two SBF solutions contain different concentrations of HCO3- and Cl- ions, the concentrations of which are closer to human blood plasma in the Tas SBF formulation than in the Kokubo formulation. The pH values in the former solution are also more realistic. The CaSiO3 ceramics show apatite formation in SBF (Kokubo) after soaking for only 1 day at all S/S ratios whereas different phases were formed at each S/S ratio in SBF (Tas). The crystalline phases formed were mainly apatite at S/S = 1.0 mg/ml, carbonate-type apatite at 2.5 mg/ml and calcite at 8.3 mg/ml. At higher S/S ratios the increase in the Ca concentration became higher while the P concentration became lower in the reacted SBF. These changes in SBF concentrations and increasing pH occurred at higher S/S ratios, producing more favorable conditions in the SBF for the formation of carbonate bearing phases, finally leading to the formation of calcite instead of apatite in the higher HCO3- ion concentration SBF (Tas). Apatite is, however, formed in the lower HCO3- ion concentration SBF (Kokubo) even though the Ca and P concentrations change in a similar manner to SBF (Tas).

  6. In situ, controlled and reproducible attachment of carbon nanotubes onto conductive AFM tips

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Jianxun [International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Chinese Academy of Science Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafty, National Center for Nanoscience and Technology of China, No. 11, Bei yi tiao, Zhong Guan Cun, Beijing 100190 (China); Shingaya, Yoshitaka [International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Zhao, Yuliang [Chinese Academy of Science Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafty, National Center for Nanoscience and Technology of China, No. 11, Bei yi tiao, Zhong Guan Cun, Beijing 100190 (China); Nakayama, Tomonobu, E-mail: NAKAYAMA.Tomonobu@nims.go.jp [International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)

    2015-04-30

    Graphical abstract: - Highlights: • An effective and controllable method was developed to fabricate CNT AFM probes in-situ. • Individual carbon nanotube was assembled. • The alignment angle and protruding length of as-produced CNT probes are excellent. - Abstract: Owing to the small diameter, wear resistance, high aspect ratio of their cylindrical structure and outstanding young's modulus, carbon nanotubes are regarded as excellent probes for atomic force microscope (AFM) imaging and various applications. To take the best out of carbon nanotubes’ potentials as AFM probes, we present a facile and reliable method to attach a single carbon nanotube onto an AFM probe covered with conductive Au layer. The method involves the following steps: positioning the AFM probe exactly onto a designated multiple-walled carbon nanotube growing vertically on a conductive substrate, establishing physical contact of the probe apex to the carbon nanotube with an appropriate force, and finally flowing a DC current of typically 100 μA from the AFM probe to the substrate through the carbon nanotube. The current flow results in the fracture and attachment of the carbon nanotube onto the AFM probe. Our method is similar to that reported in previous studies to cut and assemble carbon nanotubes by flowing current under SEM, but by our method we succeed to achieve superior control of protruding length and reproducible attachment angle of the carbon nanotube in one step. Moreover, it is now possible to reliably prepare carbon nanotube probes in-situ during AFM experiments.

  7. Foam-structured Activated Carbon-ceramic as TiO2 Supports for Photocatalytic Degradation of Phenol

    Institute of Scientific and Technical Information of China (English)

    LIU Wei-min

    2013-01-01

    An activated foam-structured carbon-ceramic(AFCC) was prepared and investigated as TiO2 support for the photocatalytic degradation of phenol.AFCC and TiO2/AFCC catalysts were characterized by N2 adsorptiondesorption and X-ray diffraction(XRD).The effects of AFCC on the photocatalytic activity and the crystallinity of TiO2 were studied.The results show that the crystallinity and anatase/rutile ratio of TiO2 loaded on AFCC could be significantly influenced by the calcination temperature.The degradation rate of phenol benefited from the synergistic effects of the adsorption of activated carbon(AC) and the photocatalysis of TiO2,which suggests that a high surface area of AC is essential to achieve high degradation rates and efficiencies.It was found that the larger mean cell size of AFCC increased the light transmission within the foam.

  8. Enhanced Electrical Conductivity of Aluminum by Carbon Nanotube Hybrid Dilution

    Science.gov (United States)

    Stigers, Shelby; Savadelis, Alexader; Carruba, Kathryn; Johns, Kiley; Adu, Kofi

    2015-03-01

    Carbon nanotubes (CNTs) have been recognized as potential candidate for reinforcements in lightweight metals. A composite consisting of CNTs embedded in an Al-matrix might work as an ultra-low-resistive material with the potential of having a room-temperature resistivity far below Al, Cu and Ag. While several advances have been made in developing Al-CNT composites, three major challenges: (1) interfacial bond strength between CNT and the Al matrix, (2) homogeneous dispersion of the CNTs in the Al matrix and impurity (CNTs) scattering centers, continue to limit progress in Al-CNT composites. Several conventional methods including powder metallurgy, melting and solidification, thermal spray and electrochemical deposition have been used to process Al and CNT to form composites. We present preliminary results that address these challenges and demonstrate the fabrication of easily drawable Al-CNT composites into wires of diameter <= 1.0mm with ~ 18% +/- 2% reduction in the electrical resistivity of Al-CNT composite using CNT-hybrid as reinforcement and an inductive melting technique that takes advantage of the induced eddy current in the melt to provide in-situ stirring. This Work is Supported by Penn State Altoona Undergraduate Research Sponsored Program and Penn State Materials Research Institute, University Park.

  9. Extremely high thermal conductivity anisotropy of double-walled carbon nanotubes

    Directory of Open Access Journals (Sweden)

    Zhaoji Ma

    2017-06-01

    Full Text Available Based on molecular dynamics simulations, we reveal that double-walled carbon nanotubes can possess an extremely high anisotropy ratio of radial to axial thermal conductivities. The mechanism is basically the same as that for the high thermal conductivity anisotropy of graphene layers - the in-plane strong sp2 bonds lead to a very high intralayer thermal conductivity while the weak van der Waals interactions to a very low interlayer thermal conductivity. However, different from flat graphene layers, the tubular structures of carbon nanotubes result in a diameter dependent thermal conductivity. The smaller the diameter, the larger the axial thermal conductivity but the smaller the radial thermal conductivity. As a result, a DWCNT with a small diameter may have an anisotropy ratio of thermal conductivity significantly higher than that for graphene layers. The extremely high thermal conductivity anisotropy allows DWCNTs to be a promising candidate for thermal management materials.

  10. Extremely high thermal conductivity anisotropy of double-walled carbon nanotubes

    Science.gov (United States)

    Ma, Zhaoji; Guo, Zhengrong; Zhang, Hongwei; Chang, Tienchong

    2017-06-01

    Based on molecular dynamics simulations, we reveal that double-walled carbon nanotubes can possess an extremely high anisotropy ratio of radial to axial thermal conductivities. The mechanism is basically the same as that for the high thermal conductivity anisotropy of graphene layers - the in-plane strong sp2 bonds lead to a very high intralayer thermal conductivity while the weak van der Waals interactions to a very low interlayer thermal conductivity. However, different from flat graphene layers, the tubular structures of carbon nanotubes result in a diameter dependent thermal conductivity. The smaller the diameter, the larger the axial thermal conductivity but the smaller the radial thermal conductivity. As a result, a DWCNT with a small diameter may have an anisotropy ratio of thermal conductivity significantly higher than that for graphene layers. The extremely high thermal conductivity anisotropy allows DWCNTs to be a promising candidate for thermal management materials.

  11. 日用陶瓷的低碳制备技术%LOW-CARBON PREPARATION TECHNOLOGY OF CERAMICS

    Institute of Scientific and Technical Information of China (English)

    王慧; 刘晓红; 郑卫东; 曾令可

    2011-01-01

    Global warming has become one of the world's most pressing problems, how to effectively prevent the emission of greenhouse gases are serious challenges what countries around the worm must face. For the high energy consumption, carbon dioxide emissions large ceramic industry, to achieve low-carbon production of ceramics is an important way to improve the competitiveness of enterprises.%全球气候变暖已成为当今世界最为严峻的问题之一,如何有效地防止温室气体的排放也是世界各国必须面临的严峻挑战。对于高能耗、二氧化碳排放量较大的陶瓷行业来说,实现陶瓷的低碳生产,是提高企业竞争力的一条重要途径。

  12. Mechanically robust, electrically conductive ultralow-density carbon nanotube-based aerogels

    Science.gov (United States)

    Worsley, Marcus A; Baumann, Theodore F; Satcher, Jr., Joe H

    2014-04-01

    A method of making a mechanically robust, electrically conductive ultralow-density carbon nanotube-based aerogel, including the steps of dispersing nanotubes in an aqueous media or other media to form a suspension, adding reactants and catalyst to the suspension to create a reaction mixture, curing the reaction mixture to form a wet gel, drying the wet gel to produce a dry gel, and pyrolyzing the dry gel to produce the mechanically robust, electrically conductive ultralow-density carbon nanotube-based aerogel. The aerogel is mechanically robust, electrically conductive, and ultralow-density, and is made of a porous carbon material having 5 to 95% by weight carbon nanotubes and 5 to 95% carbon binder.

  13. Mechanically robust, electrically conductive ultralow-density carbon nanotube-based aerogels

    Energy Technology Data Exchange (ETDEWEB)

    Worsley, Marcus A.; Baumann, Theodore F.; Satcher, Jr, Joe H.

    2016-07-05

    A method of making a mechanically robust, electrically conductive ultralow-density carbon nanotube-based aerogel, including the steps of dispersing nanotubes in an aqueous media or other media to form a suspension, adding reactants and catalyst to the suspension to create a reaction mixture, curing the reaction mixture to form a wet gel, drying the wet gel to produce a dry gel, and pyrolyzing the dry gel to produce the mechanically robust, electrically conductive ultralow-density carbon nanotube-based aerogel. The aerogel is mechanically robust, electrically conductive, and ultralow-density, and is made of a porous carbon material having 5 to 95% by weight carbon nanotubes and 5 to 95% carbon binder.

  14. Broadband white light emission from Ce:AlN ceramics: High thermal conductivity down-converters for LED and laser-driven solid state lighting

    Science.gov (United States)

    Wieg, A. T.; Penilla, E. H.; Hardin, C. L.; Kodera, Y.; Garay, J. E.

    2016-12-01

    We introduce high thermal conductivity aluminum nitride (AlN) as a transparent ceramic host for Ce3+, a well-known active ion dopant. We show that the Ce:AlN ceramics have overlapping photoluminescent (PL) emission peaks that cover almost the entire visible range resulting in a white appearance under 375 nm excitation without the need for color mixing. The PL is due to a combination of intrinsic AlN defect complexes and Ce3+ electronic transitions. Importantly, the peak intensities can be tuned by varying the Ce concentration and processing parameters, causing different shades of white light without the need for multiple phosphors or light sources. The Commission Internationale de l'Eclairage coordinates calculated from the measured spectra confirm white light emission. In addition, we demonstrate the viability of laser driven white light emission by coupling the Ce:AlN to a readily available frequency tripled Nd-YAG laser emitting at 355 nm. The high thermal conductivity of these ceramic down-converters holds significant promise for producing higher power white light sources than those available today.

  15. Broadband white light emission from Ce:AlN ceramics: High thermal conductivity down-converters for LED and laser-driven solid state lighting

    Directory of Open Access Journals (Sweden)

    A. T. Wieg

    2016-12-01

    Full Text Available We introduce high thermal conductivity aluminum nitride (AlN as a transparent ceramic host for Ce3+, a well-known active ion dopant. We show that the Ce:AlN ceramics have overlapping photoluminescent (PL emission peaks that cover almost the entire visible range resulting in a white appearance under 375 nm excitation without the need for color mixing. The PL is due to a combination of intrinsic AlN defect complexes and Ce3+ electronic transitions. Importantly, the peak intensities can be tuned by varying the Ce concentration and processing parameters, causing different shades of white light without the need for multiple phosphors or light sources. The Commission Internationale de l’Eclairage coordinates calculated from the measured spectra confirm white light emission. In addition, we demonstrate the viability of laser driven white light emission by coupling the Ce:AlN to a readily available frequency tripled Nd-YAG laser emitting at 355 nm. The high thermal conductivity of these ceramic down-converters holds significant promise for producing higher power white light sources than those available today.

  16. Effect of micro-cracking on the thermal conductivity and thermal expansion of tialite (Al2TiO5 ceramics

    Directory of Open Access Journals (Sweden)

    Ramanathan Papitha

    2013-09-01

    Full Text Available The pure and magnesium silicate (Mg2+/Si4+ doped tialite ceramics were prepared from the homogenized mixture of alumina and titania by uniaxial pressing and pressure-less sintering at 1550 °C in air. Thermal conductivity and thermal expansion of the doped and undoped tialite ceramics were measured from 30 to 700 °C. The identical trend in the behaviour of these thermal properties most probably is influenced by the population, size and shape of microcracks present throughout the grain and grain boundaries as complemented by the microstructural observations. The observed decrease in thermal properties of the doped in comparison to the pure tialite can be attributed to the substitutional Mg2+ and Si4+ at Al3+ site in Al2TiO5 which promotes the phonon scattering and causes modifications in micro-crack density and the morphology of the cracks.

  17. Thermal and tensile strength testing of thermally-conductive adhesives and carbon foam

    CERN Document Server

    Chertok, Maxwell; Irving, Michael; Neher, Christian; Shi, Mengyao; Tolfa, Kirk; Tripathi, Mani; Vinson, Yasmeen; Wang, Ruby; Zheng, Gayle

    2016-01-01

    Future collider detectors, including silicon tracking detectors planned for the High Luminosity LHC, will require components and mechanical structures providing unprecedented strength-to-mass ratios, thermal conductivity, and radiation tolerance. This paper studies carbon foam used in conjunction with thermally conductive epoxy and thermally conductive tape for such applications. Thermal conductivity and tensile strength measurements of aluminum-carbon foam-adhesive stacks are reported. Initial radiation damage tests are also presented. These results can inform bonding method choices for future tracking detectors.

  18. Nanoporous palladium anode for direct ethanol solid oxide fuel cells with nanoscale proton-conducting ceramic electrolyte

    Science.gov (United States)

    Li, Yong; Wong, Lai Mun; Xie, Hanlin; Wang, Shijie; Su, Pei-Chen

    2017-02-01

    In this work, we demonstrate the operation of micro-solid oxide fuel cells (μ-SOFCs) with nanoscale proton-conducting Y-BaZrO3 (BZY) electrolyte to avoid the fuel crossover problem for direct ethanol fuel cells (DEFCs). The μ-SOFCs are operated with the direct utilisation of ethanol vapour as a fuel and Pd as anode at the temperature range of 300-400 °C. The nanoporous Pd anode is achieved by DC sputtering at high Ar pressure of 80 mTorr. The Pd-anode/BYZ-electrolyte/Pt-cathode cell show peak power densities of 72.4 mW/cm2 using hydrogen and 15.3 mW/cm2 using ethanol at 400 °C. No obvious carbon deposition is seen from XPS analysis after fuel cell test with ethanol fuel.

  19. Tailoring Thermal Conductivity of Single-stranded Carbon-chain Polymers through Atomic Mass Modification.

    Science.gov (United States)

    Liao, Quanwen; Zeng, Lingping; Liu, Zhichun; Liu, Wei

    2016-10-07

    Tailoring the thermal conductivity of polymers is central to enlarge their applications in the thermal management of flexible integrated circuits. Progress has been made over the past decade by fabricating materials with various nanostructures, but a clear relationship between various functional groups and thermal properties of polymers remains to be established. Here, we numerically study the thermal conductivity of single-stranded carbon-chain polymers with multiple substituents of hydrogen atoms through atomic mass modification. We find that their thermal conductivity can be tuned by atomic mass modifications as revealed through molecular dynamics simulations. The simulation results suggest that heavy homogeneous substituents do not assist heat transport and trace amounts of heavy substituents can in fact hinder heat transport substantially. Our analysis indicates that carbon chain has the biggest contribution (over 80%) to the thermal conduction in single-stranded carbon-chain polymers. We further demonstrate that atomic mass modifications influence the phonon bands of bonding carbon atoms, and the discrepancies of phonon bands between carbon atoms are responsible for the remarkable drops in thermal conductivity and large thermal resistances in carbon chains. Our study provides fundamental insight into how to tailor the thermal conductivity of polymers through variable substituents.

  20. Carbon nanotube: nanodiamond Li-ion battery cathodes with increased thermal conductivity

    Science.gov (United States)

    Salgado, Ruben; Lee, Eungiee; Shevchenko, Elena V.; Balandin, Alexander A.

    2016-10-01

    Prevention of excess heat accumulation within the Li-ion battery cells is a critical design consideration for electronic and photonic device applications. Many existing approaches for heat removal from batteries increase substantially the complexity and overall weight of the battery. Some of us have previously shown a possibility of effective passive thermal management of Li-ion batteries via improvement of thermal conductivity of cathode and anode material1. In this presentation, we report the results of our investigation of the thermal conductivity of various Li-ion cathodes with incorporated carbon nanotubes and nanodiamonds in different layered structures. The cathodes were synthesized using the filtration method, which can be utilized for synthesis of commercial electrode-active materials. The thermal measurements were conducted with the "laser flash" technique. It has been established that the cathode with the carbon nanotubes-LiCo2 and carbon nanotube layered structure possesses the highest in-plane thermal conductivity of 206 W/mK at room temperature. The cathode containing nanodiamonds on carbon nanotubes structure revealed one of the highest cross-plane thermal conductivity values. The in-plane thermal conductivity is up to two orders-of-magnitude greater than that in conventional cathodes based on amorphous carbon. The obtained results demonstrate a potential of carbon nanotube incorporation in cathode materials for the effective thermal management of Li-ion high-powered density batteries.

  1. The Effects of Radial Compression on Thermal Conductivity of Carbon and Boron Nitride Nanotubes

    OpenAIRE

    Haijun Shen

    2012-01-01

    By using molecular dynamics method, thermal conductivity of (10, 10) carbon and boron nitride (BN) nanotubes under radial compression was investigated, and the - (thermal conductivity versus temperature) curves of the two nanotubes were obtained. It is found that with the increase of temperature the thermal conductivity of two nanotubes decreases; the nanotubes, under both the local compression and whole compression, have lower thermal conductivity, and the larger the compressive deformat...

  2. Carbon nanotubes with silver nanoparticle decoration and conductive polymer coating for improving the electrical conductivity of polycarbonate composites

    KAUST Repository

    Patole, Archana S.

    2015-01-01

    We proposed a strategy to enhance the conductivity of polycarbonate by using three-phase hybrid metallic/non-metallic fillers. Ethylene diamine (EDA) functionalized multiwalled carbon nanotubes (MWCNT-EDA) are first decorated with silver nanoparticles. These Ag/ MWCNT-EDA fillers are then coated with a conductive layer of ethylene glycol treated PEDOT: PSS (poly [3,4-ethylenedioxythiophene]: poly [styrenesulfonate]) (EP). In such an approach, the MWCNT backbone is covered by a highly conductive coating made of Ag nanoparticles surrounded by EP. To understand how Ag and EP form a highly conductive coating, the effect of different wt% of Ag nanoparticles on EP was studied. Ag nanoparticles around the size of 128 ± 28 nmeffectively lowered the volume resistivity of bulk EP, resulting in a highly conducting Ag/EP blend. We found that in the final Ag/MWCNT-EDA/EP assembly, the EP coating enhances the electrical conductivity in two ways: (1) it is an efficient dispersing agent that helps in achieving a uniform dispersion of the Ag/MWCNT-EDA and (2) it acts as a conductive bridge between particles (Ag and MWCNT-EDA), reducing the particle to particle resistivity. When inserted into polycarbonate, this three-phase blend successfully reduced the volume resistivity of the polymer by two orders of magnitude compared with previous approaches.

  3. Remarkable enhancement of the electrical conductivity of carbon nanostructured thin films after compression.

    Science.gov (United States)

    Georgakilas, Vasilios; Koutsioukis, Apostolos; Petr, Martin; Tucek, Jiri; Zboril, Radek

    2016-06-01

    In this work, we demonstrate a significant improvement in the electrical conductivity of carbon nanostructured thin films, composed of graphene nanosheets and multiwalled carbon nanotubes, by compression/polishing. It is shown that the sheet resistance of compressed thin films of carbon nanostructures and hybrids is remarkably decreased in comparison with that of as-deposited films. The number of the interconnections, the distance between the nanostructures as well as their orientation are highly altered by the compression favoring the electrical conductivity of the compressed samples.

  4. Morphology and Electrical Conductivity of Carbon Nanocoatings Prepared from Pyrolysed Polymers

    Directory of Open Access Journals (Sweden)

    Marcin Molenda

    2014-01-01

    Full Text Available Conductive carbon nanocoatings (conductive carbon layers—CCL were formed on α-Al2O3 model support using three different polymer precursors and deposition methods. This was done in an effort to improve electrical conductivity of the material through creating the appropriate morphology of the carbon layers. The best electrical properties were obtained with use of a precursor that consisted of poly-N-vinylformamide modified with pyromellitic acid (PMA. We demonstrate that these properties originate from a specific morphology of this layer that showed nanopores (3-4 nm capable of assuring easy pathways for ion transport in real electrode materials. The proposed, water mediated, method of carbon coating of powdered supports combines coating from solution and solid phase and is easy to scale up process. The optimal polymer carbon precursor composition was used to prepare conductive carbon nanocoatings on LiFePO4 cathode material. Charge-discharge tests clearly show that C/LiFePO4 composites obtained using poly-N-vinylformamide modified with pyromellitic acid exhibit higher rechargeable capacity and longer working time in a battery cell than standard carbon/lithium iron phosphate composites.

  5. New Activated Carbon with High Thermal Conductivity and Its Microwave Regeneration Performance

    Institute of Scientific and Technical Information of China (English)

    GU Xuexian; SU Zhanjun; XI Hongxia

    2016-01-01

    Using a walnut shell as a carbon source and ZnCl2 as an activating agent, we resolved the temperature gradient problems of activated carbon in the microwave desorption process. An appropriate amount of silicon carbide was added to prepare the composite activated carbon with high thermal conductivity while developing VOC adsorption-microwave regeneration technology. The experimental results show that the coefficient of thermal conductivity of SiC-AC is three times as much as those of AC and SY-6. When microwave power was 480 W in its microwave desorption , the temperature of the bed thermal desorption was 10℃ to 30℃below that of normal activated carbon prepared in our laboratory. The toluene desorption activation energy was 16.05 kJ∙mol-1, which was 15% less than the desorption activation energy of commercial activated carbon. This study testified that the process could maintain its high adsorption and regeneration desorption performances.

  6. Electrochemical Properties of Cathode Composite Prepared using Carbon Wool Conducting Additives

    Science.gov (United States)

    Masuda, S.; Nakamura, T.; Yamada, Y.; Tabuchi, M.

    2011-05-01

    New carbon particles, carbon wool, were utilized as conducting additives for the cathode composite, and the electrochemical properties of the cathode composite were examined. The carbon wool particles exhibit good conductivity (~100S m-1), because they have large fraction (approximately 80%) of sp2 graphite-like component and three-dimensional network structure. Partial replacement of acetylene black with carbon wool has no affect on the low current rate performance but a negative influence on high current rate performance. However, a small addition of carbon wool to the appropriate amount of acetylene black leads to the improvement of high rate capability without a significant reduction of the cathode density. Therefore, it may give us a possibility to obtain the cathode having both high density and high power capability.

  7. Electrochemical Properties of Cathode Composite Prepared using Carbon Wool Conducting Additives

    Energy Technology Data Exchange (ETDEWEB)

    Masuda, S; Nakamura, T; Yamada, Y [Department of Electrical Engineering, Graduate School of Engineering, University of Hyogo, 2167 Shosha, Himeji, Hyogo, 671-2201 (Japan); Tabuchi, M, E-mail: tatsuya@eng.u-hyogo.ac.jp [National Institute of Advanced Industrial Science and Technology, Osaka, 563-8577 (Japan)

    2011-05-15

    New carbon particles, carbon wool, were utilized as conducting additives for the cathode composite, and the electrochemical properties of the cathode composite were examined. The carbon wool particles exhibit good conductivity ({approx}10{sup 0}S m{sup -1}), because they have large fraction (approximately 80%) of sp{sup 2} graphite-like component and three-dimensional network structure. Partial replacement of acetylene black with carbon wool has no affect on the low current rate performance but a negative influence on high current rate performance. However, a small addition of carbon wool to the appropriate amount of acetylene black leads to the improvement of high rate capability without a significant reduction of the cathode density. Therefore, it may give us a possibility to obtain the cathode having both high density and high power capability.

  8. Enhancing conductivity of metallic carbon nanotube networks by transition metal adsorption

    Science.gov (United States)

    Ketolainen, T.; Havu, V.; Puska, M. J.

    2015-02-01

    The conductivity of carbon nanotube thin films is mainly determined by carbon nanotube junctions, the resistance of which can be reduced by several different methods. We investigate electronic transport through carbon nanotube junctions in a four-terminal configuration, where two metallic single-wall carbon nanotubes are linked by a group 6 transition metal atom. The transport calculations are based on the Green's function method combined with the density-functional theory. The transition metal atom is found to enhance the transport through the junction near the Fermi level. However, the size of the nanotube affects the improvement in the conductivity. The enhancement is related to the hybridization of chromium and carbon atom orbitals, which is clearly reflected in the character of eigenstates near the Fermi level. The effects of chromium atoms and precursor molecules remaining adsorbed on the nanotubes outside the junctions are also examined.

  9. Enhancing conductivity of metallic carbon nanotube networks by transition metal adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Ketolainen, T., E-mail: tomi.ketolainen@aalto.fi; Havu, V.; Puska, M. J. [COMP, Department of Applied Physics, Aalto University, P.O. Box 11100, FI-00076 Aalto (Finland)

    2015-02-07

    The conductivity of carbon nanotube thin films is mainly determined by carbon nanotube junctions, the resistance of which can be reduced by several different methods. We investigate electronic transport through carbon nanotube junctions in a four-terminal configuration, where two metallic single-wall carbon nanotubes are linked by a group 6 transition metal atom. The transport calculations are based on the Green’s function method combined with the density-functional theory. The transition metal atom is found to enhance the transport through the junction near the Fermi level. However, the size of the nanotube affects the improvement in the conductivity. The enhancement is related to the hybridization of chromium and carbon atom orbitals, which is clearly reflected in the character of eigenstates near the Fermi level. The effects of chromium atoms and precursor molecules remaining adsorbed on the nanotubes outside the junctions are also examined.

  10. The Effects of Radial Compression on Thermal Conductivity of Carbon and Boron Nitride Nanotubes

    Directory of Open Access Journals (Sweden)

    Haijun Shen

    2012-01-01

    Full Text Available By using molecular dynamics method, thermal conductivity of (10, 10 carbon and boron nitride (BN nanotubes under radial compression was investigated, and the - (thermal conductivity versus temperature curves of the two nanotubes were obtained. It is found that with the increase of temperature the thermal conductivity of two nanotubes decreases; the nanotubes, under both the local compression and whole compression, have lower thermal conductivity, and the larger the compressive deformation is, the lower the thermal conductivity is; the whole compression has more remarkable effect on thermal conductivity than the local compression.

  11. Studies Conducted of Sodium Carbonate Contaminant Found on the Wing Leading Edge and the Nose Cap of the Space Shuttle Orbiter

    Science.gov (United States)

    Jacobson, Nathan S.; Palou, Jaime J.

    2003-01-01

    approach and was used by the NASA Kennedy Space Center when the deposits were first observed. The effect of case 2 is minimal and would actually restore the the Type A glass to its composition before carbonate formation. However, the problem with allowing the carbonate to remain leads to the third scenario, the deposit flowing onto other parts. A series of tests were conducted on unprotected SiC, and minimal effects were found in the short-term, but other ceramic and metal parts could be damaged by the molten sodium carbonate and would require close monitoring.

  12. Studies Conducted of Sodium Carbonate Contaminant Found on the Wing Leading Edge and the Nose Cap of the Space Shuttle Orbiter

    Science.gov (United States)

    Jacobson, Nathan S.; Palou, Jaime J.

    2003-01-01

    approach and was used by the NASA Kennedy Space Center when the deposits were first observed. The effect of case 2 is minimal and would actually restore the the Type A glass to its composition before carbonate formation. However, the problem with allowing the carbonate to remain leads to the third scenario, the deposit flowing onto other parts. A series of tests were conducted on unprotected SiC, and minimal effects were found in the short-term, but other ceramic and metal parts could be damaged by the molten sodium carbonate and would require close monitoring.

  13. Spark plasma sintering of silicon carbide, multi-walled carbon nanotube and graphene reinforced zirconium diboride ceramic composite

    Science.gov (United States)

    Balaraman Yadhukulakrishnan, Govindaraajan

    Scope and Method of Study: Space vehicles re-entering the earth's atmosphere experience very high temperatures due to aerodynamic heating. Ultra-high temperature ceramics (UHTC) with melting point higher than 3200°C are promising materials for thermal protection systems of such space vehicles re-entering the earth's atmosphere. Among several UHTC systems ZrB2 based ceramic composites are particularly important for thermal protection systems due to their better mechanical and thermoelectric properties and high oxidation resistance. In this study spark plasma sintering of SiC, carbon nanotubes (CNT) and graphene nano platelets (GNP) reinforced ZrB2 ultra-high temperature ceramic matrix composites is reported. Findings and Conclusions: Systematic investigations on the effect of reinforcement type (SiC, CNTs and GNP) and content (10-40 vol.% SiC, 2-6 vol.% CNTs and 2-6 vol.% GNP) on densification behavior, microstructure development, and mechanical properties (microhardness, bi-axial flexural strength, and indentation fracture toughness) are reported. With the similar SPS parameters near-full densification (>99% relative density) was achieved with 10-40 vol.% SiC, 4-6 vol.% CNT reinforced composites. Highly dense composites were obtained in 4-6 vol.% GNP reinforced composites. The SiC, CNT and GNP reinforcement improved the indentation fracture toughness of the composites through a range of toughening mechanisms, including particle shearing, crack deflection at the particle-matrix interface, and grain pull-outs for ZrB2-SiC composites, CNT pull-outs and crack deflection in ZrB2-CNT composites and crack deflection, crack bridging and GNP sheet pull-out for ZrB2 -GNP composites.

  14. Understanding Nanoscale Thermal Conduction an Mechanical Strength Correlation in High Temperature Ceramics with Improved Thermal Shock Resistance for Aerospace Applications

    Science.gov (United States)

    2012-08-08

    A.H.W. Ngan, Creep and strain burst in indium and aluminium during nanoindentation. Scripta Materialia, 2001. 45(8): p. 971-976. 23. Cao, Z.H., P.Y...Fahrenholtz, W.G., G.E. Hilmas, I.G. Talmy, and J.A. Zaykoski, Refractory diborides of zirconium and hafnium . J. Am. Ceram. Soc. , 2007. 90(5): p

  15. Electrical conductivity and thermal behavior of solid electrolytes based on alkali carbonates and sulfates

    NARCIS (Netherlands)

    Brosda, S.; Bouwmeester, Henricus J.M.; Guth, U.

    1997-01-01

    Both thermal stability and electrical conductivity of alkali ion conducting Na2CO3 and Na2SO4, were improved by adding alkaline earth carbonates and sulfates, respectively, as well as insulating materials like ¿-Al2O3. The admixing of divalent compounds causes two effects. First a more or less

  16. Effect of Filler Orientation on Thermal Conductivity of Polypropylene Matrix Carbon Nanofiber Composites

    Science.gov (United States)

    Enomoto, Kazuki; Fujiwara, Shu; Yasuhara, Toshiyuki; Murakami, Hiroya; Teraki, Junichi; Ohtake, Naoto

    2005-06-01

    Polypropylene matrix carbon nanofiber composites were obtained by injection molding after kneading with a batch-type twin-screw kneader. The thermal conductivity of the composites in the thickness direction was evaluated, with particular focus on the effects of carbon nanofiber (CNF) content and filler orientation. The thermal conductivity of the composites increased with increasing CNF content, and was obtained as 3.46 W/(m\\cdotK) when the CNF content was 50% in weight fraction and the CNFs were highly oriented along the measuring direction of thermal conductivity. This value is approximately seventeenfold higher than that of neat polypropylene.

  17. Tailoring Thermal Conductivity of Single-stranded Carbon-chain Polymers through Atomic Mass Modification

    CERN Document Server

    Liao, Quanwen; Liu, Zhichun; Liu, Wei

    2016-01-01

    Tailoring the thermal conductivity of polymers is central to enlarge their applications in the thermal management of flexible integrated circuits. Progress has been made over the past decade by fabricating materials with various nanostructures, but a clear relationship between various functional groups and thermal properties of polymers remains to be established. Here, we numerically study the thermal conductivity of single-stranded carbon-chain polymers with multiple substituents of hydrogen atoms through atomic mass modification. We find that their thermal conductivity can be tuned by atomic mass modifications as revealed through molecular dynamics simulations. The simulation results suggest that heavy homogeneous substituents do not assist heat transport and trace amounts of heavy substituents can in fact hinder heat transport substantially. Our analysis indicates that carbon chain has the biggest contribution (over 80%) to the thermal conduction in single-stranded carbon-chain polymers. We further demonst...

  18. Carbon doped PDMS: conductance stability over time and implications for additive manufacturing of stretchable electronics

    Science.gov (United States)

    Tavakoli, Mahmoud; Rocha, Rui; Osorio, Luis; Almeida, Miguel; de Almeida, Anibal; Ramachandran, Vivek; Tabatabai, Arya; Lu, Tong; Majidi, Carmel

    2017-03-01

    Carbon doped PDMS (cPDMS), has been used as a conductive polymer for stretchable electronics. Compared to liquid metals, cPDMS is low cost and is easier to process or to print with an additive manufacturing process. However, changes on the conductance of the carbon based conductive PDMS (cPDMS) were observed over time, in particular after integration of cPDMS and the insulating polymer. In this article we investigate the process parameters that lead to improved stability over conductance of the cPDMS over time. Slight modifications to the fabrication process parameters were conducted and changes on the conductance of the samples for each method were monitored. Results suggested that change of the conductance happens mostly after integration of a pre-polymer over a cured cPDMS, and not after integration of the cPDMS over a cured insulating polymer. We show that such changes can be eliminated by adjusting the integration priority between the conductive and insulating polymers, by selecting the right curing temperature, changing the concentration of the carbon particles and the thickness of the conductive traces, and when possible by changing the insulating polymer material. In this way, we obtained important conclusions regarding the effect of these parameters on the change of the conductance over time, that should be considered for additive manufacturing of soft electronics. Also, we show that these changes can be possibly due to the diffusion from PDMS into cPDMS.

  19. Thin film ceramic thermocouples

    Science.gov (United States)

    Gregory, Otto (Inventor); Fralick, Gustave (Inventor); Wrbanek, John (Inventor); You, Tao (Inventor)

    2011-01-01

    A thin film ceramic thermocouple (10) having two ceramic thermocouple (12, 14) that are in contact with each other in at least on point to form a junction, and wherein each element was prepared in a different oxygen/nitrogen/argon plasma. Since each element is prepared under different plasma conditions, they have different electrical conductivity and different charge carrier concentration. The thin film thermocouple (10) can be transparent. A versatile ceramic sensor system having an RTD heat flux sensor can be combined with a thermocouple and a strain sensor to yield a multifunctional ceramic sensor array. The transparent ceramic temperature sensor that could ultimately be used for calibration of optical sensors.

  20. Thermal Conductivity of Diamond Packed Electrospun PAN-Based Carbon Fibers Incorporated with Multi Wall Carbon Nanotubes.

    Science.gov (United States)

    Dong, Qi; Lu, Chunyuan; Tulugan, Kelimu; Jin, Chunzi; Yoon, Soo Jong; Park, Yeong Min; Kim, Tae Gyu

    2016-02-01

    Multi wall carbon nanotubes (MWCNTs) and diamond are renowned as superlative material due to their relatively high thermal conductivity and hardness while comparing with any bulk materials. In this research, polyacrylonitrile (PAN) solution incorporated with MWCNTs at an alteration of mass fractions (0 wt%, 0.6 wt%, 1 wt%, 2 wt%) were fabricated via electrospinning under optimized parameters. Dried composite nanofibers were stabilized and carbonized, after which water base polytrafluorethylene (PTFE) mixed with nano diamond powder solution was spin coated on them. Scanning electron microscopy, Raman spectroscopy, X-ray scattering and Laserflash thermal conductivity were used to characterize the composite nanofiber sheets. The result shows that the thermal conductivity increased to 4.825 W/m K from 2.061 W/mK. The improvement of thermal conductivities is suggesting the incorporation of MWCNTs.

  1. Molecular Dynamics Simulations of the Thermal Conductivity of Single-Wall Carbon Nanotubes

    Science.gov (United States)

    Osman, M.; Srivastava, Deepak; Govindan,T. R. (Technical Monitor)

    2000-01-01

    Carbon nanotubes (CNT) have very attractive electronic, mechanical. and thermal properties. Recently, measurements of thermal conductivity in single wall CNT mats showed estimated thermal conductivity magnitudes ranging from 17.5 to 58 W/cm-K at room temperature. which are better than bulk graphite. The cylinderical symmetry of CNT leads to large thermal conductivity along the tube axis, additionally, unlike graphite. CNTs can be made into ropes that can be used as heat conducting pipes for nanoscale applications. The thermal conductivity of several single wall carbon nanotubes has been calculated over temperature range from l00 K to 600 K using non-equilibrium molecular dynamics using Tersoff-Brenner potential for C-C interactions. Thermal conductivity of single wall CNTs shows a peaking behavior as a function of temperature. Dependence of the peak position on the chirality and radius of the tube will be discussed and explained in this presentation.

  2. Molecular Dynamics Simulations of the Thermal Conductivity of Single-Wall Carbon Nanotubes

    Science.gov (United States)

    Osman, M.; Srivastava, Deepak; Govindan,T. R. (Technical Monitor)

    2000-01-01

    Carbon nanotubes (CNT) have very attractive electronic, mechanical. and thermal properties. Recently, measurements of thermal conductivity in single wall CNT mats showed estimated thermal conductivity magnitudes ranging from 17.5 to 58 W/cm-K at room temperature. which are better than bulk graphite. The cylinderical symmetry of CNT leads to large thermal conductivity along the tube axis, additionally, unlike graphite. CNTs can be made into ropes that can be used as heat conducting pipes for nanoscale applications. The thermal conductivity of several single wall carbon nanotubes has been calculated over temperature range from l00 K to 600 K using non-equilibrium molecular dynamics using Tersoff-Brenner potential for C-C interactions. Thermal conductivity of single wall CNTs shows a peaking behavior as a function of temperature. Dependence of the peak position on the chirality and radius of the tube will be discussed and explained in this presentation.

  3. PREPARATION OF ACTIVATED CARBON FROM SILK COTTON WOOD AND COCONUT SHELL BY PYROLISIS WITH CERAMIC FURNACE

    Directory of Open Access Journals (Sweden)

    Winarto Haryadi

    2010-06-01

    Full Text Available Preparation of activated carbon from silk cotton wood and coconut shell has been done. Carbon was made by pyrolysis process in the Muchalal furnace with 3000 watt electric power. The electric power was increased gradually from 1000, 2000 and then 3000 watt with interval 2 hours during 7 hours. Carbon was activated in Muchalal furnace with 4000 watt electric power during 2 hours and flowed with nitrogen gas. Product of the activated carbon was compared to standart product with several analysis including the surface area, acetic acid adsorption, iod adsorption and vapour adsorption. The results of analysis showed that surface area for silk cotton wood carbon, coconut shell carbon, and E.Merck product were 288.8072 m2/g, 222.9387 m2/g and 610.5543 m2/g, respectively. Acetic acid adsorption for silk cotton wood carbon, coconut shell carbon, and standart product were 157.391 mg/g, 132.791 mg/g, and 186.911 mg/g, respectively. Iodine adsorption for cotton wood carbon, coconut shell carbon, and standart product were 251.685 mg/g, 207.270 mg/g and 310.905 mg/g, respectively. Vapour adsorption for cotton wood carbon, coconut shell carbon and standart product were 12%, 4%,and 14%., respectively Key words : Activated carbon, pyrolysis, Muchalal furnace

  4. Non-Ohmic conduction in In{sub 2}O{sub 3}–Bi{sub 2}O{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Glot, A.B., E-mail: alexglot@mixteco.utm.mx [Universidad Tecnológica de la Mixteca, Huajuapan de León, Oaxaca 69000 (Mexico); Mazurik, S.V. [Dniepropetrovsk National University, Dniepropetrovsk 49010 (Ukraine)

    2013-11-01

    The semiconductor In{sub 2}O{sub 3}–Bi{sub 2}O{sub 3} ceramics exhibit unusual behaviour: The current quasi-saturation (current limiting) in dc current–voltage characteristic is accompanied by low-frequency (∼1 Hz) current oscillations. In this paper some electrical properties of In{sub 2}O{sub 3}–Bi{sub 2}O{sub 3} ceramics are studied and a mechanism of non-Ohmic conduction in this material is suggested. The electrical conduction is controlled by the grain-boundary potential barriers. Assuming that the barrier heights at different grain boundaries in a sample are not identical, the current quasi-saturation is explained qualitatively by capture of electrons at the interface states and respective increase in the height of key barriers. A mechanism of current oscillations is related to the current quasi-saturation. An increase in the height of key barriers leads to a raise of the voltage drop at these barriers and to Joule heating of barrier regions followed by decrease in the barrier height. The suggested mechanism of non-Ohmic conduction is confirmed by the obtained experimental data.

  5. Fabrication and Electromagnetic Wave-Absorbing Property of Si3N4 Ceramics with Gradient Pyrolytic Carbon Distribution

    Science.gov (United States)

    Li, Xiangming; Gao, Mingjun

    2016-07-01

    A Si3N4 ceramic with gradient distribution of pyrolytic carbon (Gradient-PyC-Si3N4) was fabricated by a combined technique of precursor infiltration pyrolysis and directional oxidation. An electromagnetic wave could enter Gradient-PyC-Si3N4 with little reflection because of a weak impedance mismatch at its surface, and the electromagnetic wave entering Gradient-PyC-Si3N4 could propagate forward along the PyC changing belt and simultaneously be absorbed by PyC with little reflection. The electromagnetic reflectivity of the Gradient-PyC-Si3N4 with an absence of PyC could reach a low level of -12.1 dB, which means that about 94% of the incident energy is absorbed and so makes the Gradient-PyC-Si3N4 a promising electromagnetic absorbing material for covert action.

  6. Bioelectrocatalytic carbon ceramic gas electrode for reduction of dioxygen and its application in a zinc-dioxygen cell

    Energy Technology Data Exchange (ETDEWEB)

    Nogala, W.; Celebanska, A.; Opallo, M. [Institute of Physical Chemistry, Polish Academy of Sciences, ul. Kasprzaka 44/52, PL-01-224 Warszawa (Poland); Wittstock, G. [Faculty of Mathematics and Science, Department of Pure and Applied Chemistry, Carl von Ossietzky University of Oldenburg, Center of Interface Science (CIS), D-26111 Oldenburg (Germany)

    2010-12-15

    An enzyme-modified carbon ceramic electrode was constructed and studied that is capable to reduce dioxygen supplied from the gas phase. The permeation of the electrode material and its hydrophobic silicate component was studied by scanning electrochemical microscopy. The mass-transfer coefficient of dioxygen in methyltrimethoxysilane-based silicate was estimated to be 6.44 x 10{sup -5} cm{sup 2} s{sup -1}. After modification of the electrode with bilirubin oxidase and immersion in deareated aqueous electrolyte, the dioxygen bioelectrocatalytic reduction is observed with onset potential at 0.45 V. The constructed electrode was successfully applied as cathode in a zinc-dioxygen cell. (Copyright copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. Low-temperature SCR of NO{sub x} with NH{sub 3} over carbon-ceramic supported catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Valdes-Solis, Teresa; Marban, Gregorio; Fuertes, Antonio B. [Instituto Nacional del Carbon (CSIC), c/Francisco Pintado Fe No. 26, 33011 Oviedo (Spain)

    2003-11-10

    A new method for preparing vanadium oxide supported on carbon-ceramic cellular monoliths is described. This includes a support oxidation step with HNO{sub 3}, followed by ionic exchange with a NaOH solution, equilibrium adsorption impregnation of VO{sup 2+} and thermal treatment. As a result an active catalyst for low-temperature selective catalytic reduction (SCR) reaction is obtained. The V-catalyst is more resistant to SO{sub 2} poisoning than the previously developed Mn-catalyst. Inhibition by water is reversible for both types of catalysts. Testing of the vanadium catalyst after subjecting it to the outlet gas stream of a power plant shows fast deactivation until constant residual activity is reached. Deactivation seems to be caused by arsenic poisoning and the formation of superficial sulphates.

  8. RTA-treated carbon fiber/copper core/shell hybrid for thermally conductive composites.

    Science.gov (United States)

    Yu, Seunggun; Park, Bo-In; Park, Cheolmin; Hong, Soon Man; Han, Tae Hee; Koo, Chong Min

    2014-05-28

    In this paper, we demonstrate a facile route to produce epoxy/carbon fiber composites providing continuous heat conduction pathway of Cu with a high degree of crystal perfection via electroplating, followed by rapid thermal annealing (RTA) treatment and compression molding. Copper shells on carbon fibers were coated through electroplating method and post-treated via RTA technique to reduce the degree of imperfection in the Cu crystal. The epoxy/Cu-plated carbon fiber composites with Cu shell of 12.0 vol % prepared via simple compression molding, revealed 18 times larger thermal conductivity (47.2 W m(-1) K(-1)) in parallel direction and 6 times larger thermal conductivity (3.9 W m(-1) K(-1)) in perpendicular direction than epoxy/carbon fiber composite. Our novel composites with RTA-treated carbon fiber/Cu core/shell hybrid showed heat conduction behavior of an excellent polymeric composite thermal conductor with continuous heat conduction pathway, comparable to theoretical values obtained from Hatta and Taya model.

  9. The production of silicon carbon nitride ceramic fibres from poly-silazane polymers. Herstellung von Siliciumcarbonitrid-Keramikfasern aus Polysilazan-Polymeren

    Energy Technology Data Exchange (ETDEWEB)

    Holzinger, R.

    1994-07-14

    The investigations carried out in this work can be divided into two main points. One, the process technique branch, goes along the polymer precursor route. This includes the melt spinning of the poly-silazane polymers, the stabilisation of the green fibres and finally pyrolysis to silicon-carbon nitride ceramic fibres. Starting from the polymers, all the reactions and structural changes during the individual steps are examined. These experiments represent the second main part of the work. The optimisation criterion is always the tensile strength of the resulting ceramic fibres. (orig.)

  10. Temperature dependence of dc electrical conductivity of activated carbon-metal oxide nanocomposites. Some insight into conduction mechanisms

    Science.gov (United States)

    Barroso-Bogeat, Adrián; Alexandre-Franco, María; Fernández-González, Carmen; Sánchez-González, José; Gómez-Serrano, Vicente

    2015-12-01

    From a commercial activated carbon (AC) and six metal oxide (Al2O3, Fe2O3, SnO2, TiO2, WO3 and ZnO) precursors, two series of AC-metal oxide nanocomposites are prepared by wet impregnation, oven-drying at 120 °C, and subsequent heat treatment at 200 or 850 °C in inert atmosphere. The temperature-dependent dc electrical conductivity of AC and the as-prepared nanocomposites is measured from room temperature up to ca. 200 °C in air atmosphere by the four-probe method. The decrease in conductivity for the hybrid materials as compared to AC is the result of a complex interplay between several factors, including not only the intrinsic conductivity, crystallite size, content and chemical nature of the supported nanoparticles, which ultimately depend on the precursor and heat treatment temperature, but also the adsorption of oxygen and water from the surrounding atmosphere. The conductivity data are discussed in terms of a thermally activated process. In this regard, both AC and the prepared nanocomposites behave as semiconductors, and the temperature-dependent conductivity data have been interpreted on the basis of the classical model proposed by Mott and Davis. Because of its high content of heteroatoms, AC may be considered as a heavily doped semiconductor, so that conduction of thermally excited carriers via acceptor or donor levels is expected to be the dominant mechanism. The activation energies for the hybrid materials suggest that the supported metal oxide nanoparticles strongly modify the electronic band structure of AC by introducing new trap levels in different positions along its band gap. Furthermore, the thermally activated conduction process satisfies the Meyer-Neldel rule, which is likely connected with the shift of the Fermi level due to the introduction of the different metal oxide nanoparticles in the AC matrix.

  11. Sol-gel derived multiwalled carbon nanotubes ceramic electrode modified with molecularly imprinted polymer for ultra trace sensing of dopamine in real samples

    Energy Technology Data Exchange (ETDEWEB)

    Prasad, Bhim Bali, E-mail: prof.bbpd@yahoo.com [Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi 221 005 (India); Kumar, Deepak; Madhuri, Rashmi; Tiwari, Mahavir Prasad [Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi 221 005 (India)

    2011-08-01

    Highlights: > MWCNTs-CE was prepared by silane acrylate which provides a nanometer thin MIP film. > The sensor was modified by iniferter and MIP using 'surface grafting-from approach'. > A comparative study was performed between differentially designed ceramic electrodes. > The sensor can detect dopamine in real samples with LODs (0.143-0.154 ng mL{sup -1}). - Abstract: A new class of composite electrodes made of sol-gel derived ceramic-multiwalled carbon nanotubes is used for the growth of a nanometer thin film adopting 'surface grafting-from approach'. For this the multiwalled carbon nanotubes-ceramic electrode surface is first modified with an iniferter (benzyl N,N-diethyldithiocarbamate) and then dopamine imprinted polymer, under UV irradiation, for differential pulse anodic stripping voltammetric sensing of dopamine in aqueous, blood serum, cerebrospinal fluid, and pharmaceutical samples (detection limit 0.143-0.154 ng mL{sup -1}, 3{sigma}), without any cross reactivity, interferences and false-positive contributions. Such composite electrodes offer higher stability, electron kinetics, and renewable porous surface of larger electroactive area (with insignificant capacitance) than carbon ceramic electrodes. Additional cyclic voltammetry (stripping mode) and chronocoulometry experiments were performed to explore electrodics and kinetics of electro-oxidation of dopamine.

  12. Sensitivity of simulated terrestrial carbon assimilation and canopy transpiration to different stomatal conductance and carbon assimilation schemes

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Haishan [Nanjing University of Information Science and Technology, Key Laboratory of Meteorological Disaster of Ministry of Education, Nanjing (China); Georgia Institute of Technology, School of Earth and Atmospheric Sciences, Atlanta, GA (United States); Dickinson, Robert E. [Georgia Institute of Technology, School of Earth and Atmospheric Sciences, Atlanta, GA (United States); The University of Texas at Austin, Department of Geological Sciences, Austin, TX (United States); Dai, Yongjiu [Beijing Normal University, State Key Laboratory of Earth Surface Processes and Resource Ecology, School of Global Change and Earth System Science, Beijing (China); Zhou, Liming [Georgia Institute of Technology, School of Earth and Atmospheric Sciences, Atlanta, GA (United States)

    2011-03-15

    Accurate simulations of terrestrial carbon assimilation and canopy transpiration are needed for both climate modeling and vegetation dynamics. Coupled stomatal conductance and carbon assimilation (A - g{sub s}) models have been widely used as part of land surface parameterizations in climate models to describe the biogeophysical and biogeochemical roles of terrestrial vegetation. Differences in various A - g{sub s} schemes produce substantial differences in the estimation of carbon assimilation and canopy transpiration, as well as in other land-atmosphere fluxes. The terrestrial carbon assimilation and canopy transpiration simulated by two different representative A - g{sub s} schemes, a simple A-g{sub s} scheme adopted from the treatments of the NCAR model (Scheme I) and a two-big-leaf A - g{sub s} scheme newly developed by Dai et al. (J Clim 17:2281-2299, 2004) (Scheme II), are compared via some sensitivity experiments to investigate impacts of different A - g{sub s} schemes on the simulations. Major differences are found in the estimate of canopy carbon assimilation rate, canopy conductance and canopy transpiration between the two schemes, primarily due to differences in (a) functional forms used to estimate parameters for carbon assimilation sub-models, (b) co-limitation methods used to estimate carbon assimilation rate from the three limiting rates, and (c) leaf-to-canopy scaling schemes. On the whole, the differences in the scaling approach are the largest contributor to the simulation discrepancies, but the different methods of co-limitation of assimilation rate also impact the results. Except for a few biomes, the residual effects caused by the different parameter estimations in assimilation sub-models are relatively small. It is also noted that the two-leaf temperature scheme produces distinctly different sunlit and shaded leaf temperatures but has negligible impacts on the simulation of the carbon assimilation. (orig.)

  13. Preparation, microstructure and oxidation resistance of SiCN ceramic matrix composites with glass-like carbon interface

    Directory of Open Access Journals (Sweden)

    Yi Xia

    2009-02-01

    Full Text Available Glass-like carbon (GC interface was successfully introduced into carbon fiber-reinforced SiCN ceramic matrix composite (C/GC/SiCN by polymer infiltration and pyrolysis using phenolic resin as precursor. In order to highlight the Oxidation resistance of GC interface, the Oxidation behavior of GC, carbon fiber (Cf containing approximately 0.3 μm GC coating and C/GC/SiCN was investigated by means of weight changes and residual strength ratio before and after oxidizing, and the results were also compared with that of Cf containing Pyrocarbon (PyC coating and C/PyC/SiCN composite. Scanning electron microscopy displays homogeneous, adherent GC coating on Cf. Weight loss rate of Cf containing GC coating is lower than that of Cf containing PyC coating. The residual stress ratio of C/GC/SiCN was higher than that of C/PyC/SiCN. The results indicate that GC interface can improve anti-oxidation of Cf-reinforced composite than PyC interface.

  14. Spark plasma sintering of silicon carbide and multi-walled carbon nanotube reinforced zirconium diboride ceramic composite

    Energy Technology Data Exchange (ETDEWEB)

    Yadhukulakrishnan, Govindaraajan B.; Rahman, Arif; Karumuri, Sriharsha [School of Mechanical and Aerospace Engineering Oklahoma State University, Stillwater, OK 74078 (United States); Stackpoole, Margaret M. [ELORET Corporation, Moffett Field, CA 94035 (United States); Kalkan, A. Kaan; Singh, Raman P. [School of Mechanical and Aerospace Engineering Oklahoma State University, Stillwater, OK 74078 (United States); Harimkar, Sandip P., E-mail: sandip.harimkar@okstate.edu [School of Mechanical and Aerospace Engineering Oklahoma State University, Stillwater, OK 74078 (United States)

    2012-08-30

    Highlights: Black-Right-Pointing-Pointer Dense SiC and carbon nanotube reinforced ZrB{sub 2} composites were spark plasma sintered. Black-Right-Pointing-Pointer SiC and carbon nanotube reinforcement favored the densification of ZrB{sub 2} composites. Black-Right-Pointing-Pointer SiC and carbon nanotube reinforcement resulted in toughening of ZrB{sub 2} composites. Black-Right-Pointing-Pointer Carbon nanotubes were retained in the spark plasma sintered ZrB{sub 2} composites. - Abstract: In this paper spark plasma sintering (SPS) of silicon carbide and multi-walled carbon nanotube reinforced zirconium diboride ultra-high temperature ceramic matrix composites is reported. Systematic investigations on the effect of reinforcement type (SiC and CNTs) and content (10-40 vol.% SiC and 2-6 vol.% CNTs) on densification behavior, microstructure development, and mechanical properties (microhardness, bi-axial flexural strength, and indentation fracture toughness) are presented. With the similar SPS processing parameters (1900 Degree-Sign C, 70 MPa pressure, and 15 min soaking time), near-full densification (>99% relative density) was achieved with 10-40% SiC (in ZrB{sub 2}-SiC) and 4-6% CNT (in ZrB{sub 2}-CNT) reinforced composites. The SiC and CNT reinforcement further improved the indentation fracture toughness of the composites through a range of toughening mechanisms, including particle shearing, crack deflection at the particle-matrix interface, and grain pull-outs for ZrB{sub 2}-SiC composites, and CNT pull-outs and crack deflection in ZrB{sub 2}-CNT composites.

  15. Applications of Technology of Compound Lining of Semi—gr aphitized Self—baking Carbon Block Ceramic Brickwork in Large—sized Blast Furnaces

    Institute of Scientific and Technical Information of China (English)

    HAOYung-zhong; CHENQian-wan

    1994-01-01

    Based on the analyses of the lining technologies of the hot press formed carbon brick iu U.S.A., of the ce-ramic cup in France and of the creative self-baking car-bon brick in China,the technology of semi-graphitized car-bon block-ceramic brickwork has been studied and developed ,and has successfully ben used in No.7 blast furnace (2580m3) at Anshan Irom and Steel Company and in No.3 blast furnace (1200m3) at Taiyuan Iron and Steel Company,This paper puts fourward a feasible scheme for realization of long service lives of the bootms and the hearths of large-sized blast furaces in China.

  16. Analysis of energy consumption and carbon dioxide emissions in ceramic tile manufacture; Analisis de consumos energeticos y emisiones de dioxido de carbono en la fabricacion de baldosas ceramicas

    Energy Technology Data Exchange (ETDEWEB)

    Monfort, E.; Mezquita, A.; Granel, R.; Vaquer, E.; Escrig, A.; Miralles, A.; Zaera, V.

    2010-07-01

    The ceramic tile manufacturing process is energy intensive since it contains several stages in which the product is subject to thermal treatment. The thermal energy used in the process is usually obtained by combustion of natural gas, which is a fossil fuel whose oxidation produces emissions of carbon dioxide, a greenhouse gas. Energy costs account for 15% of the average direct manufacturing costs, and are strongly influenced by the price of natural gas, which has increased significantly in the last few years. Carbon dioxide emissions are internationally monitored and controlled in the frame of the Kyoto Protocol. Applicable Spanish law is based on the European Directive on emissions trading, and the assignment of emissions rights is based on historical values in the sectors involved. Legislation is scheduled to change in 2013, and the resulting changes will directly affect the Spanish ceramic tile manufacturing industry, since many facilities will become part of the emissions trading system. The purpose of this study is to determine current thermal energy consumption and carbon dioxide emissions in the ceramic tile manufacturing process. A comprehensive sectoral study has been carried out for this purpose on several levels: the first analyses energy consumption and carbon dioxide emissions in the entire industry; the second determines energy consumption and carbon dioxide emissions in industrial facilities over a long period of time (several months); while the third level breaks down these values, determining energy consumption and emissions in terms of the product made and the manufacturing stage. (Author) 8 refs.

  17. Use of sodium carbonate as a binder in ceramic tile compositions; Uso del carbonato sodico como ligante en composiciones de baldosas ceramicas

    Energy Technology Data Exchange (ETDEWEB)

    Quereda, F.; Sanchez, E.; Garcia-Ten, J.; Gozalbo, A.; Beltran, V.; Sanchez, J.; Sales, J.

    2010-07-01

    This study analyses, first, the influence of sodium carbonate content on the behaviour of the ceramic tile body composition during the different manufacturing process stages (preparation of the suspension, pressing, and firing), as well as on unfired tile mechanical strength. It has been verified that sodium carbonate can be used as a binder in ceramic tile compositions, since small percentages considerably enhance dry tile mechanical strength. It has furthermore been determined that for each composition there is an optimum addition content, with high increased mechanical strength (up to 70%), without this noticeably affecting the rheological behaviour of the suspension to be spray dried. These results are currently being patented (patent application P200930148). Once the binding effect of sodium carbonate had been verified, it was sought to establish its action mechanism. For this purpose, drops of mixtures of a standard ceramic composition and increasing quantities of sodium carbonate were prepared. The drops were rapidly dried and the granules were characterised by scanning electron microscopy. It was thus verified that the most likely sodium carbonate action mechanism was formation of solid bridges by crystallisation. (Author)

  18. Investigations on d.c. conductivity behaviour of milled carbon fibre reinforced epoxy graded composites

    Indian Academy of Sciences (India)

    Navin Chand; Archana Nigrawal

    2008-08-01

    This paper reports the d.c. conductivity behaviour of milled carbon fibre reinforced polysulphide modified epoxy gradient composites. Milled carbon fibre reinforced composites having 3 vol. % of milled carbon fibre and poly sulphide modified epoxy resin have been developed. D.C. conductivity measurements are conducted on the graded composites by using an Electrometer in the temperature range from 26°C to 150°C. D.C. conductivity increases with the increase of distance in the direction of centrifugal force, which shows the formation of graded structure with the composites. D.C. conductivity increases on increase of milled carbon fibre content from 0.45 to 1.66 vol.%. At 50°C, d.c. conductivity values were 1.85 × 10-11, 1.08 × 10-11 and 2.16 × 10-12 for samples 1, 2 and 3, respectively. The activation energy values for different composite samples 1, 2 and 3 are 0.489, 0.565 and 0.654 eV, respectively which shows decrease in activation energy with increase of fibre content.

  19. Diameter and Temperature Dependence of Thermal Conductivity of Single-Walled Carbon Nanotubes

    Institute of Scientific and Technical Information of China (English)

    PAN Rui-Qin

    2011-01-01

    Temperature and diameter dependence of the thermal conductivity of several armchair single-walled carbon nan-otubes (SWNTs) are studied by nonequilibrium molecular dynamics method with Brenner II potential. The thermal conductivities are calculated at temperatures from WOK to 600K. It is found that the thermal conductivity decreases as the temperature increases and increases as the diameter of SWNT increases. The results demonstrate that these two phenomena are due to the onset of the Umklapp process.%@@ Temperature and diameter dependence of the thermal conductivity of several armchair single-walled carbon nan- otubes (SWNTs) are studied by nonequilibrium molecular dynamics method with Brenner Ⅱ potential.The thermal conductivities are calculated at temperatures from 100K to 600K.It is found that the thermal con- ductivity decreases as the temperature increases and increases as the diameter of SWNT increases.The results demonstrate that these two phenomena are due to the onset of the Umklapp process.

  20. Carbon Nanotube-based Super Nanotube: Tailorable Thermal Conductivity at Three-dimensional

    CERN Document Server

    Zhan, Haifei; Gu, Yuantong

    2015-01-01

    The advancements of nanomaterials or nanostructures have enabled the possibility of fabricating multifunctional materials that hold great promises in engineering applications. The carbon nanotube (CNT)-based nanostructure is one representative building block for such multifunctional materials. Based on a series of in silico studies, we report the tailorability of the thermal conductivity of a three-dimensional CNT-based nanostructure, i.e., the single wall CNT (SWNT)-based super nanotube (ST). It is shown that the thermal conductivity of STs varies with different connecting carbon rings, and the ST with longer constituent SWNTs and larger diameter yield to a smaller thermal conductivity. Further results reveal that the inverse of the ST thermal conductivity exhibits a good linear relationship with the inverse of its length. Particularly, it is found that the thermal conductivity exhibits an approximately proportional relationship with the inverse of the temperature, but appears insensitive to the axial strain...

  1. Scalable nanomanufacturing of surfactant-free carbon nanotube inks for spray coatings with high conductivity

    Institute of Scientific and Technical Information of China (English)

    Colin Preston[1; Da Song[1; Jaiqi Dai[1; Zois Tsinas[2; John Bavier[3; John Cumings[1; Vince Ballarotto[3; Liangbing Hu[1

    2015-01-01

    Spray-coated carbon nanotube films offer a simple and printable solution for fabricating low cost, lightweight, and flexible thin-film electronics. However, current nanotube spray inks require either a disruptive surfactant or destructive surface functionalization to stabilize dispersions at the cost of the electrical properties of the deposited film. We demonstrate that high-purity few-walled carbon nanotubes may be stabilized in isopropanol after surface functionalization and that optimizing the ink stability dramatically enhances the conductivity of subsequent spray-coated thin films. We consequently report a surfactant-free carbon nanotube ink for spray-coated thin films with conductivities reaching 2,100 S/cm. Zeta-potential measurements, used to quantify the nanotube ink dispersion quality, directly demonstrate a positive correlation with the spray- coated film conductivity, which is the key metric for high-performance printed electronics.

  2. Graphene as conductive additives in binderless activated carbon electrodes for power enhancement of supercapacitor

    Science.gov (United States)

    Nor, N. S. M.; Deraman, M.; Suleman, M.; Norizam, M. D. M.; Basri, N. H.; Sazali, N. E. S.; Hamdan, E.; Hanappi, M. F. Y. M.; Tajuddin, N. S. M.; Othman, M. A. R.; Shamsudin, S. A.; Omar, R.

    2016-11-01

    Carbon based supercapacitor electrodes from composite of binderless activated carbon and graphene as a conductive additive were fabricated with various amount of graphene (0, 2, 4, 6, 8 and 10 wt%). Graphene was mixed in self-adhesive carbon grains produced from pre-carbonized powder derived from fibers of oil palm empty fruit bunches and converted into green monoliths (GMs). The GMs were carbonized (N2) and activated (CO2) to produce activated carbon monoliths (ACMs) electrodes. Porosity characterizations by nitrogen adsorption-desorption isotherm method shows that the pore characteristics of the ACMs are influenced by the graphene additive. The results of galvanostatic charge-discharge tests carried out on the supercapacitor cells fabricated using these electrodes shows that the addition of graphene additive (even in small amount) decreases the equivalent series resistance and enhances the specific power of the cells but significantly lowers the specific capacitance. The supercapacitor cell constructed with the electrode containing 4 wt % of graphene offers the maximum power (175 W kg-1) which corresponds to an improvement of 55%. These results demonstrate that the addition of graphene as conductive additive in activated carbon electrodes can enhance the specific power of the supercapacitor.

  3. Impedance and a.c. conductivity studies of Ba(Pr1/2Nb1/2)O3 ceramic

    Indian Academy of Sciences (India)

    K Amar Nath; K Prasad; K P Chandra; A R Kulkarni

    2013-08-01

    Impedance and electrical conduction studies of Ba(Pr1/2Nb1/2)O3 ceramic prepared through conventional ceramic fabrication technique are presented. The crystal symmetry, space group and unit cell dimensions were estimated using Rietveld analysis. X-ray diffraction analysis indicated the formation of a single-phase cubic structure with space group, $\\bar{3}$. EDAX and SEM studies were carried out to study the quality and purity of compound. To find a correlation between the response of the real system and idealized model circuit composed of discrete electrical components, the model fittings were presented using impedance data. Complex impedance as well as electric modulus analyses suggested dielectric relaxation to be of non-Debye type and negative temperature coefficient of resistance character. The correlated barrier hopping model was employed to successfully explain the mechanism of charge transport in Ba(Pr1/2Nb1/2)O3. The a.c. conductivity data were used to evaluate density of states at Fermi level, minimum hopping length and apparent activation energy.

  4. A practical dimensionless equation for the thermal conductivity of carbon nanotubes and CNT arrays

    Directory of Open Access Journals (Sweden)

    Qiang Chen

    2014-05-01

    Full Text Available Experimental results reported in the last decade on the thermal conductivity of carbon nanotubes (CNTs have shown a fairly divergent behavior. An underlying intrinsic consistency was believed to exist in spite of the divergence in the thermal conductivity data of various CNTs. A dimenisonless equation that describes the temperature dependence of thermal conductivity was derived by introducing reduced forms relative to a chosen reference point. This equation can serve as a practical approximation to characterize the conductivity of individual CNT with different structural parameters as well as bulk CNT arrays with different bundle configurations. Comparison of predictions by the equation and historical measurements showed good agreements within their uncertainties.

  5. High conductivity carbon nanotube wires from radial densification and ionic doping

    Science.gov (United States)

    Alvarenga, Jack; Jarosz, Paul R.; Schauerman, Chris M.; Moses, Brian T.; Landi, Brian J.; Cress, Cory D.; Raffaelle, Ryne P.

    2010-11-01

    Application of drawing dies to radially densify sheets of carbon nanotubes (CNTs) into bulk wires has shown the ability to control electrical conductivity and wire density. Simultaneous use of KAuBr4 doping solution, during wire drawing, has led to an electrical conductivity in the CNT wire of 1.3×106 S/m. Temperature-dependent electrical measurements show that conduction is dominated by fluctuation-assisted tunneling, and introduction of KAuBr4 significantly reduces the tunneling barrier between individual nanotubes. Ultimately, the concomitant doping and densification process leads to closer packed CNTs and a reduced charge transfer barrier, resulting in enhanced bulk electrical conductivity.

  6. Conductive Carbon Nanotube Inks for Use with Desktop Inkjet Printing Technology

    Science.gov (United States)

    Roberson, Luke; Williams, Martha; Tate, LaNetra; Fortier, Craig; Smith, David; Davia, Kyle; Gibson, Tracy; Snyder, Sarah

    2013-01-01

    Inkjet printing is a common commercial process. In addition to the familiar use in printing documents from computers, it is also used in some industrial applications. For example, wire manufacturers are required by law to print the wire type, gauge, and safety information on the exterior of each foot of manufactured wire, and this is typically done with inkjet or laser printers. The goal of this work was the creation of conductive inks that can be applied to a wire or flexible substrates via inkjet printing methods. The use of inkjet printing technology to print conductive inks has been in testing for several years. While researchers have been able to get the printing system to mechanically work, the application of conductive inks on substrates has not consistently produced adequate low resistances in the kilohm range. Conductive materials can be applied using a printer in single or multiple passes onto a substrate including textiles, polymer films, and paper. The conductive materials are composed of electrical conductors such as carbon nanotubes (including functionalized carbon nanotubes and metal-coated carbon nanotubes); graphene, a polycyclic aromatic hydrocarbon (e.g., pentacene and bisperipentacene); metal nanoparticles; inherently conductive polymers (ICP); and combinations thereof. Once the conductive materials are applied, the materials are dried and sintered to form adherent conductive materials on the substrate. For certain formulations, increased conductivity can be achieved by printing on substrates supported by low levels of magnetic field alignment. The adherent conductive materials can be used in applications such as damage detection, dust particle removal, smart coating systems, and flexible electronic circuitry. By applying alternating layers of different electrical conductors to form a layered composite material, a single homogeneous layer can be produced with improved electrical properties. It is believed that patterning alternate layers of

  7. Bioinspired Multifunctional Superhydrophobic Surfaces with Carbon-Nanotube-Based Conducting Pastes by Facile and Scalable Printing.

    Science.gov (United States)

    Han, Joong Tark; Kim, Byung Kuk; Woo, Jong Seok; Jang, Jeong In; Cho, Joon Young; Jeong, Hee Jin; Jeong, Seung Yol; Seo, Seon Hee; Lee, Geon-Woong

    2017-03-01

    Directly printed superhydrophobic surfaces containing conducting nanomaterials can be used for a wide range of applications in terms of nonwetting, anisotropic wetting, and electrical conductivity. Here, we demonstrated that direct-printable and flexible superhydrophobic surfaces were fabricated on flexible substrates via with an ultrafacile and scalable screen printing with carbon nanotube (CNT)-based conducting pastes. A polydimethylsiloxane (PDMS)-polyethylene glycol (PEG) copolymer was used as an additive for conducting pastes to realize the printability of the conducting paste as well as the hydrophobicity of the printed surface. The screen-printed conducting surfaces showed a high water contact angle (WCA) (>150°) and low contact angle hysteresis (WCA superhydrophobic surfaces also showed sticky superhydrophobic characteristics and were used to transport water droplets. Moreover, fabricated films on metal meshes were used for an oil/water separation filter, and liquid evaporation behavior was investigated on the superhydrophobic and conductive thin-film heaters by applying direct current voltage to the film.

  8. SINGLE IONIC CONDUCTION OF POLYSILOXANE CONTAINING PROPYLENE CARBONATE GROUP AND LITHIUM POLYMERIC SALTS

    Institute of Scientific and Technical Information of China (English)

    CHEN Xiwen; FANG Shibi; HAO Ning; JIANG Yingyan

    1996-01-01

    The polysiloxane containing propylene carbonate side group and several lithium polymeric salts were synthesized. The structure were confirmed by IR, NMR and XPS. The blending systems of polysiloxane containing propylene carbonate group with different lithium polymeric salts were studied by ion conductivity, XPS and DSC. Different lithium polymeric salts in the blending system lead to conductivity arranged in the following sequence:poly(lithium ethylenebenzene sulfonate methylsiloxane) > poly(lithium propionate methylsiloxane) > poly(lithium propylsulfonate methylsiloxane) > poly(lithium styrenesulfonate).In the blending system the best single ion conductivity was close to 10-5 Scm-1 at room temperature. XPS showed that at low lithium salt concentration the conductivity increased with the increasing content of lithium salt, in consequence of the increase of free ion and solvent separated ion pair. At high lithium salt concentration the free ion was absent and the solvent-separated ion pair functioned as carrier.

  9. The Thermal Conductivity of Carbon Nanotubes with Defects and Intramolecular Junctions

    Directory of Open Access Journals (Sweden)

    Qiaoli Zhou

    2013-01-01

    Full Text Available The thermal conductivity of various carbon nanotubes with defects or intramolecular junctions was studied using nonequilibrium molecular dynamics approach. The results show that the thermal conductivity of both armchair and zigzag carbon nanotubes increased with the decrease of the radius of the tube. The thermal conductivity of armchair tube is higher than that of zigzag tube when the radii of the two tubes are kept almost same. Discontinuities appear on the temperature profile along the tube axial at the region of IMJ, resulting in the large temperature gradient and thus lower thermal conductivity of (n,n/(m,0 tube with one IMJ and (m,0/(n,n/(m,0 tube with two IMJs. For the (m,0/(n,n/(m,0 tube with two IMJs, phonon mean free path of the middle (n,n tube is much smaller than that of the isolate (n,n tube.

  10. Giant Surface Conductivity Enhancement in a Carbon Nanotube Composite by Ultraviolet Light Exposure.

    Science.gov (United States)

    Long, Christian J; Orloff, Nathan D; Twedt, Kevin A; Lam, Thomas; Vargas-Lara, Fernando; Zhao, Minhua; Natarajan, Bharath; Scott, Keana C; Marksz, Eric; Nguyen, Tinh; Douglas, Jack F; McClelland, Jabez; Garboczi, Edward; Obrzut, Jan; Liddle, J Alexander

    2016-09-07

    Carbon nanotube composites are lightweight, multifunctional materials with readily adjustable mechanical and electrical properties-relevant to the aerospace, automotive, and sporting goods industries as high-performance structural materials. Here, we combine well-established and newly developed characterization techniques to demonstrate that ultraviolet (UV) light exposure provides a controllable means to enhance the electrical conductivity of the surface of a commercial carbon nanotube-epoxy composite by over 5 orders of magnitude. Our observations, combined with theory and simulations, reveal that the increase in conductivity is due to the formation of a concentrated layer of nanotubes on the composite surface. Our model implies that contacts between nanotube-rich microdomains dominate the conductivity of this layer at low UV dose, while tube-tube transport dominates at high UV dose. Further, we use this model to predictably pattern conductive traces with a UV laser, providing a facile approach for direct integration of lightweight conductors on nanocomposite surfaces.

  11. Spray-coated carbon nanotube carpets for creeping reduction of conducting polymer based artificial muscles

    Science.gov (United States)

    Simaite, Aiva; Delagarde, Aude; Tondu, Bertrand; Souères, Philippe; Flahaut, Emmanuel; Bergaud, Christian

    2017-01-01

    During cyclic actuation, conducting polymer based artificial muscles are often creeping from the initial movement range. One of the likely reasons of such behaviour is unbalanced charging during conducting polymer oxidation and reduction. To improve the actuation reversibility and subsequently the long time performance of ionic actuators, we suggest using spray-coated carbon nanotube (CNT) carpets on the surface of the conducting polymer electrodes. We show that carbon nanotubes facilitate a conducting polymer redox reaction and improve its reversibility. Consequently, in the long term, charge accumulation in the polymer film is avoided leading to a significantly improved lifetime performance during cycling actuation. To our knowledge, it is the first time a simple solution to an actuator creeping problem has been suggested.

  12. Development of a mixed-conductive ceramic membrane for syngas production; Developpement d'une membrane ceramique conductrice mixte pour la production de gaz de synthese

    Energy Technology Data Exchange (ETDEWEB)

    Etchegoyen, G

    2005-10-15

    Natural gas conversion into syngas (H{sub 2}+CO) is very attractive for hydrogen and clean fuel production via GTL technology by providing an alternative to oil products and reducing greenhouse gas emission. Syngas production, using a mixed ionic-electronic conducting ceramic membrane, is thought to be particularly promising. The purpose of this PhD thesis was to develop this type of membrane. Mixed-conducting oxide was synthesized, characterized and then, shaped via tape casting and co-sintered in order to obtain multilayer membranes with controlled architectures and microstructures. Oxygen permeation fluxes were measured with a specific device to evaluate membrane performances. As a result, the optimisation of architecture and microstructure made it possible to increase oxygen permeation flux by a factor 30. Additional researches were focused on the oxide composition in order to achieve higher dimensional stability. (author)

  13. Synthesis of refractory conductive niobium carbide nanowires within the inner space of carbon nanotube templates

    Science.gov (United States)

    Kobayashi, Keita; Kitaura, Ryo; Wang, Qing; Wakamori, Ikuya; Shinohara, Hisanori; Anada, Satoshi; Nagase, Takeshi; Saito, Takeshi; Kiyomiya, Masaharu; Yasuda, Hidehiro

    2014-01-01

    Conductive niobium carbide (NbC) nanowires with diameters of 1-3 nm were synthesized within the inner space of carbon nanotubes (CNTs) by exposing the CNTs to niobium (V) chloride vapor through hydrogen reduction. The NbC nanowires were found to have a NaCl-type crystal structure by transmission electron microscopy and transmission electron diffractometry. Results from electronic transport measurements imply that the electrical conductivity of the synthesized product was improved compared with that of empty CNTs.

  14. Conductivity and Ambient Stability of Halogen-Doped Carbon Nanotube Fibers

    Science.gov (United States)

    Gaier, J. R.; Chirino, C. M.; Chen, M.; Waters, D. L.; Tran, Mai Kim; Headrick, R.; Young, C. C.; Tsentalovich, D.; Whiting, B.; Pasquali, M.; Waarbeek, Ron ter; Otto, Marcin J.

    2014-01-01

    Carbon nanotube fibers were fabricated using a variety of spinning conditions and post-spinning processing with the goal of creating a high-conductivity yet environmentally stable fiber. These fiber variants were then doped with bromine, iodine, iodine chloride, or iodine bromide and their electrical and microstructural properties were characterized. Environmentally stable compounds were synthesized with electrical conductivity greater than 50,000 Scm.

  15. Fabrication of Aligned-Carbon-Nanotube-Composite Paper with High and Anisotropic Conductivity

    OpenAIRE

    Yuki Fujitsuka; Takahide Oya

    2012-01-01

    A functional carbon-nanotube (CNT)-composite paper is described in which the CNTs are aligned. This “aligned-CNT composite paper” is a flexible composite material that has CNT functionality (e.g., electrical conductivity) despite being a paper. An advanced fabrication method was developed to overcome the problem of previous CNT-composite papers, that is, reduced conductivity due to random CNT alignment. Aligning the CNTs by using an alternating current (AC) field was hypothesized to increase ...

  16. Effect of SiO2 on the Preparation and Properties of Pure Carbon Reaction Bonded Silicon Carbide Ceramics

    Institute of Scientific and Technical Information of China (English)

    WU Qi-de; GUO Bing-jian; YAN Yong-gao; ZHAO Xiu-jian; HONG Xiao-lin

    2004-01-01

    Effect of SiO2 content and sintering process on the composition and properties of Pure CarbonReaction Bonded Silicon Carbide (PCRBSC) ceramics prepared with C - SiO2 green body by infiltrating siliconwas presented. The infiltrating mechanism of C - SiO2 preform was also explored. The experimental results indicatethat the shaping pressure increases with the addition of SiO2 to the preform, and the pore size of the body turnedfiner and distributed in a narrower range, which is beneficial to decreasing the residual silicon content in the sin-tered materials and to avoiding shock off, thus increasing the conversion rate of SiC. SiO2 was deoxidized by car-bon at a high temperature and the gaseous SiO and CO produced are the main reason to the crack of the body atan elevated temperature. If the green body is deposited at 1800℃ in vacuum before infiltration crack will not beproduced in the preform and fully dense RBSC can be obtained. The ultimate material has the following properties:a density of3.05-3.12g/cm3 ,a strength of 580±32MPa and a hardness of (HRA)91-92.3.

  17. Improvement of anti-oxidation properties of carbon fibers by SiC/SiO2 ceramic coating.

    Science.gov (United States)

    Kim, Bo-Hye; Yang, Kap Seung; Woo, Hee-Gweon; Kim, Su Yeun

    2011-08-01

    To improve the anti-oxidation properties of carbon fibers (CFs), the sol-gel method followed by pyrolysis was used to coat CFs with SiC/SiO2 ceramic coatings. The SiO2 sol-gel coating was performed by dip coating a PAN(polyacrylonitrile)-based stabilized fiber (PSF) in a silica sol prepared by the polycondensation of tetraethylorthosilicate (TEOS) in the presence of an acidic catalyst. The PSF coated with SiO2 sol then underwent heat treatments at high temperatures in an inert atmosphere to deposit the SiC/SiO2 and carbonize the deposited fibers. The surface morphology of the CFs deposited with SiC/SiO2 was characterized using a scanning electron microscope (SEM). The relative oxidation resistance of the SiC/SiO2 layer deposited on the CFs was determined by the weight loss due to the use of a thermogravimetric analyzer (TGA) under flowing air, and the data were used to calculate the activation energies through an Arrhenius plot.

  18. Effect of aligned carbon nanotubes on electrical conductivity behaviour in polycarbonate matrix

    Indian Academy of Sciences (India)

    M M Larijani; E J Khamse; Z Asadollahi; M Asadi

    2012-06-01

    This article reports effects of alignment of embedded carbon nanotubes in a polycarbonate polymer matrix under magnetic, direct and alternating current electric fields on the electrical properties of the resulting nanocomposites. Composites consisting of different quantities of carbon nanotubes in a polycarbonate matrix have been prepared using a solution casting technique. The effects of field strength and nanotube concentration on the resulted network structure and conductivity of the composites were studied by in situ optical microscopy, transmission electron microscopy and four-point probe technique. The results showed that the composites prepared in the presence of field had better conductivity than those of as-prepared composites. It was also concluded that the application of alternating current electric field and magnetic field in this system led to the formation of relatively continuing networks while direct current electric field only prevented agglomeration of the carbon nanotubes in the polycarbonate matrix and created relatively uniform distribution of nanotubes in the matrix.

  19. Measuring the thermal conductivity of individual carbon nanotubes by the Raman shift method

    Energy Technology Data Exchange (ETDEWEB)

    Li Qingwei; Liu Changhong; Wang Xueshen; Fan Shoushan [Tsinghua-Foxconn Nanotechnology Research Center and Department of Physics, Tsinghua University, Beijing 100084 (China)], E-mail: chliu@mail.tsinghua.edu.cn

    2009-04-08

    The thermal contact resistance is a difficult problem that has puzzled many researchers in measuring the intrinsic thermal conductivity of an individual carbon nanotube (CNT). To avoid this problem, a non-contact Raman spectra shift method is introduced, by which we have successfully measured the thermal conductivity ({kappa}) of an individual single-walled carbon nanotube and a multi-walled carbon nanotube. The measured {kappa} values are 2400 W m{sup -1} K{sup -1} and 1400 W m{sup -1} K{sup -1}, respectively. The CNT was suspended over a trench and heated by electricity. The temperature difference between the middle and the two ends of the CNT indicated its intrinsic heat transfer capability. The temperature difference was determined by the temperature-induced shifts of its G band Raman spectra. This new method can eliminate the impact of the thermal contact resistance which was a Gordian knot in many previous measurements.

  20. Barium carbonate as an agent to improve the electrical properties of neodymium-barium-copper system at high temperature

    Energy Technology Data Exchange (ETDEWEB)

    Fernandes, J.P. [Post-Graduate Program in Chemical Engineering, Universidade Federal de Santa Catarina (UFSC), Florianópolis, SC, 88040-900 (Brazil); Duarte, G.W. [Post-Graduate Program in Chemical Engineering, Universidade Federal de Santa Catarina (UFSC), Florianópolis, SC, 88040-900 (Brazil); Research Group in Technology and Information, Centro Universitário Barriga Verde (UNIBAVE), Santa Catarina, SC (Brazil); Caldart, C. [Post-Graduate Program in Science and Materials Engineering, Universidade do Extremo Sul Catarinense (UNESC), Criciúma, SC, 88806-000 (Brazil); Kniess, C.T. [Post-Graduate Program in Professional Master in Management, Universidade Nove de Julho, São Paulo, SP (Brazil); Montedo, O.R.K.; Rocha, M.R. [Post-Graduate Program in Science and Materials Engineering, Universidade do Extremo Sul Catarinense (UNESC), Criciúma, SC, 88806-000 (Brazil); Riella, H.G. [Post-Graduate Program in Chemical Engineering, Universidade Federal de Santa Catarina (UFSC), Florianópolis, SC, 88040-900 (Brazil); Fiori, M.A., E-mail: fiori@unochapeco.edu.br [Post-Graduate Program in Environmental Science, Universidade Comunitária da Região de Chapecó (UNOCHAPECÓ), Chapecó, SC, 89809-000 (Brazil); Post-Graduate Program in Technology and Management of the Innovation, Universidade Comunitária da Região de Chapecó (UNOCHAPECÓ), Chapecó, SC, 89809-000 (Brazil)

    2015-11-15

    Specialized ceramics are manufactured under special conditions and contain specific elements. They possess unique electrical and thermal properties and are frequently used by the electronics industry. Ceramics containing neodymium-barium-copper (NBC) exhibit high conductivities at low temperatures. NBC-based ceramics are typically combined with oxides, i.e., NBCo produced from neodymium oxide, barium oxide and copper oxide. This study presents NBC ceramics that were produced with barium carbonate, copper oxide and neodymium oxide (NBCa) as starting materials. These ceramics have good electrical conductivities at room temperature. Their conductivities are temperature dependent and related to the starting amount of barium carbonate (w%). - Highlights: • The new crystalline structure were obtained due presence of the barium carbonate. • The NBCa compound has excellent electrical conductivity at room temperature. • The grain crystalline morphology was modified by presence of the barium carbonate. • New Phases α and β were introduced by carbonate barium in the NBC compound.

  1. Nanoscale Soldering of Positioned Carbon Nanotubes using Highly Conductive Electron Beam Induced Gold Deposition

    DEFF Research Database (Denmark)

    Madsen, Dorte Nørgaard; Mølhave, Kristian; Mateiu, Ramona Valentina

    2003-01-01

    We have developed an in-situ method for controlled positioning of carbon nanotubes followed by highly conductive contacting of the nanotubes, using electron beam assisted deposition of gold. The positioning and soldering process takes place inside an Environmental Scanning Electron Microscope (E...

  2. Conductance of Sidewall-Functionalized Carbon Nanotubes: Universal Dependence on Adsorption Sites

    DEFF Research Database (Denmark)

    García-Lastra, J.M.; Thygesen, Kristian Sommer; Strange, Mikkel

    2008-01-01

    We use density functional theory to study the effect of molecular adsorbates on the conductance of metallic carbon nanotubes (CNT). The five molecules considered (NO2, NH2, H, COOH, OH) lead to very similar scattering of the electrons. The adsorption of a single molecule suppresses one of the two...

  3. Improved conductivity and capacitance of interdigital carbon microelectrodes through integration with carbon nanotubes for micro-supercapacitors

    Institute of Scientific and Technical Information of China (English)

    Yanjuan Yang; Liang He; Chunjuan Tang; Ping Hu; Xufeng Hong; Mengyu Yan; Yixiao Dong

    2016-01-01

    In the last decade,pyrolyzed-carbon-based composites have attracted much attention for their applications in micro-supercapacitors.Although various methods have been investigated to improve the performance of pyrolyzed carbons,such as conductivity,energy storage density and cycling performance,effective methods for the integration and mass-production of pyrolyzed-carbonbased composites on a large scale are lacking.Here,we report the development of an optimized photolithographic technique for the fine micropatterning of photoresist/chitosan-coated carbon nanotube (CHIT-CNT) composite.After subsequent pyrolysis,the fabricated carbon/CHIT-CNT microelectrode-based micro-supercapacitor has a high capacitance (6.09 mF.cm-2) and energy density (4.5 mWh.cm-3) at a scan rate of 10 mV.s-1.Additionally,the micro-supercapacitor has a remarkable long-term cyclability,with 99.9% capacitance retention after 10,000 cyclic voltammetry cycles.This design and microfabrication process allow the application of carbon microelectromechanical system (C-MEMS)-based micro-supercapacitors due to their high potential for enhancing the mechanical and electrochemical performance of micro-supercapacitors.

  4. Electroanalysis of some common pesticides using conducting polymer/multiwalled carbon nanotubes modified glassy carbon electrode.

    Science.gov (United States)

    Manisankar, P; Sundari, Pl Abirama; Sasikumar, R; Palaniappan, Sp

    2008-09-15

    The cyclic voltammetric behaviour of three common pesticides such as isoproturon (ISO), voltage (VOL) and dicofol (DCF) was investigated at glassy carbon electrode (GCE), multiwalled carbon nanotubes modified GCE (MWCNTs/GCE), polyaniline (PANI) and polypyrrole (PPY) deposited MWCNT/GCE. The modified electrode film was characterized by scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). The electroactive behaviour of the pesticides was realized from the cyclic voltammetric studies. The differential pulse voltammetric principle was used to analyze the above-mentioned pesticides using MWCNT/GCE, PANI/MWCNT/GCE and PPY/MWCNT/GCE. Effects of accumulation potential, accumulation time, Initial scan potential, amplitude and pulse width were examined for the optimization of stripping conditions. The PANI/MWCNT/GCE performed well among the three electrode systems and the determination range obtained was 0.01-100 mgL(-1) for ISO, VOL and DCF respectively. The limit of detection (LOD) was 0.1 microgL(-1) for ISO, 0.01 microgL(-1) for VOL and 0.05 microgL(-1) for DCF on PANI/MWCNT/GCE modified system. It is significant to note that the PANI/MWCNT/GCE modified system results in the lowest LOD in comparison with the earlier reports. Suitability of this method for the trace determination of pesticide in spiked samples was also realized.

  5. Improvement of the electrical conductivity of carbon fibers through the growth of carbon nanofibers.

    Science.gov (United States)

    Moon, Cheol-Whan; Meng, Long-Yue; Im, Seung-Soon; Rhee, Kyong-Yop; Park, Soo-Jin

    2011-07-01

    In this work, carbon nanofibers (CNFs) were synthesized on carbon fiber (CF) surfaces precoated with metal-doped mesoporous silica films. Fe, Ni, and Co were doped in the mesoporous silica films and played the role of catalysts for the decomposition of acetylene to grow CNFs on the CF surfaces. The chemical composition and surface structure of CFs before and after the growth of the CNFs were investigated by EDX, N2 full isotherms, and SEM. The electrical property of the CFs was investigated using a four-probe volume resistivity tester. The SEM results indicated that the CNFs with diameters of 20-100 nm grew uniformly and densely on the CF surfaces. The diameter and length distributions of the CNFs were found to be dependent on the metal that was doped in the mesoporous silica films. The electrical properties of the CFs were enhanced after the CNFs' growth on the CF surfaces, and the CNFs grown over the Ni catalyst with the narrowest diameter distribution gave the lowest volume resistivity to the CFs.

  6. Polypropylene/Graphene and Polypropylene/Carbon Fiber Conductive Composites: Mechanical, Crystallization and Electromagnetic Properties

    Directory of Open Access Journals (Sweden)

    Chien-Lin Huang

    2015-11-01

    Full Text Available This study aims to examine the properties of composites that different carbon materials with different measurements can reinforce. Using a melt compounding method, this study combines polypropylene (PP and graphene nano-sheets (GNs or carbon fiber (CF to make PP/GNs and PP/CF conductive composites, respectively. The DSC results and optical microscopic observation show that both GNs and CF enable PP to crystalize at a high temperature. The tensile modulus of PP/GNs and PP/CF conductive composites remarkably increases as a result of the increasing content of conductive fillers. The tensile strength of the PP/GNs conductive composites is inversely proportional to the loading level of GNs. Containing 20 wt% of GNs, the PP/GNs conductive composites have an optimal conductivity of 0.36 S/m and an optimal EMI SE of 13 dB. PP/CF conductive composites have an optimal conductivity of 10−6 S/m when composed of no less than 3 wt% of CF, and an optimal EMI SE of 25 dB when composed of 20 wt% of CF.

  7. Iodine doped carbon nanotube cables exceeding specific electrical conductivity of metals

    Science.gov (United States)

    Zhao, Yao; Wei, Jinquan; Vajtai, Robert; Ajayan, Pulickel M.; Barrera, Enrique V.

    2011-09-01

    Creating highly electrically conducting cables from macroscopic aggregates of carbon nanotubes, to replace metallic wires, is still a dream. Here we report the fabrication of iodine-doped, double-walled nanotube cables having electrical resistivity reaching ~10-7 Ω.m. Due to the low density, their specific conductivity (conductivity/weight) is higher than copper and aluminum and is only just below that of the highest specific conductivity metal, sodium. The cables exhibit high current-carrying capacity of 104~105 A/cm2 and can be joined together into arbitrary length and diameter, without degradation of their electrical properties. The application of such nanotube cables is demonstrated by partly replacing metal wires in a household light bulb circuit. The conductivity variation as a function of temperature for the cables is five times smaller than that for copper. The high conductivity nanotube cables could find a range of applications, from low dimensional interconnects to transmission lines.

  8. Length Dependence of Thermal Conductivity of Single-Walled Carbon Nanotubes

    Institute of Scientific and Technical Information of China (English)

    PAN Rui-Qin; XU Zi-Jian; ZHU Zhi-Yuan

    2007-01-01

    Dependence of the thermal conductivity on the length of two armchair single-walled carbon nanotubes (SWNTs) is studied by the nonequilibrium molecular dynamics (MD) method with Brenner Ⅱ potential. The thermal conductivities are calculated for (5, 5) and (7, 7) SWNTs with lengths ranging from 22 to 155 nm. The results show that the thermal conductivity of SWNTs is sensitive to the length and it does not converge to a Unite value when the tube length increases up to 155 nm, however it obeys a power law relation.

  9. Improved thermal conductivity of Ag decorated carbon nanotubes water based nanofluids

    Science.gov (United States)

    Farbod, Mansoor; Ahangarpour, Ameneh

    2016-12-01

    The effect of Ag decoration of carbon nanotubes on thermal conductivity enhancement of Ag decorated MWCNTs water based nanofluids has been investigated. The pristine and functionalized MWCNTs were decorated with Ag nanoparticles by mass ratios of 1%, 2% and 4% and used to prepare water based nanofluids with 0.1 vol.%. An enhancement of 1-20.4 percent in thermal conductivity was observed. It was found that the decoration of functionalized MWCNTs can increase the thermal conductivity about 0.16-8.02 percent compared to the undecorated ones. The maximum enhancement of 20.4% was measured for the sample containing 4 wt.% Ag at 40 °C.

  10. Static conductivity and superconductivity of carbon nanotubes: Relations between tubes and sheets

    Energy Technology Data Exchange (ETDEWEB)

    Benedict, L.X.; Crespi, V.H.; Louie, S.G.; Cohen, M.L. [Department of Physics, University of California at Berkeley, Berkeley, California 94720 (United States)]|[Materials Sciences Division, Lawrence Berkeley Laboratory, Berkeley, California 94720 (United States)

    1995-11-15

    We relate the static conductivity of carbon nanotubes to the static in-plane conductivity of a graphite sheet and conclude that isolated single-wall nanotubes are excellent conductors. In contrast, multiwall tubes at low doping may possess conductivities substantially below that of the sum of the constituent tubes. The curvature of small tubes opens new electron-phonon scattering channels that are not available to sheets. This increases the electron-phonon coupling and yields superconducting transition temperatures for small doped tubes intermediate between those of intercalated graphite and alkali-metal-doped C{sub 60}.

  11. Carbon Microparticles from Organosolv Lignin as Filler for Conducting Poly(Lactic Acid

    Directory of Open Access Journals (Sweden)

    Janea Köhnke

    2016-05-01

    Full Text Available Carbon microparticles were produced from organosolv lignin at 2000 °C under argon atmosphere following oxidative thermostabilisation at 250 °C. Scanning electron microscopy, X-ray diffraction, small-angle X-ray scattering, and electro-conductivity measurements revealed that the obtained particles were electrically conductive and were composed of large graphitic domains. Poly(lactic acid filled with various amounts of lignin-derived microparticles showed higher tensile stiffness increasing with particle load, whereas strength and extensibility decreased. Electric conductivity was measured at filler loads equal to and greater than 25% w/w.

  12. Dispersion issues and thermal conductivity of polypropylene/multi wall carbon nanotube systems

    Science.gov (United States)

    Russo, Pietro; Patti, Antonella; Acierno, Domenico; Acierno, Stefano

    2016-05-01

    Three types of multiwall carbon nanotubes, one non-functionalized tubes and two functionalized with polar (amino and carboxyl) groups, were used as fillers in a polypropylene resin to develop nanocomposites with improved thermal conductivity. In particular, formulations containing up to 5% in volume of carbon nanotubes, prepared by melt blending, were analyzed in terms of dynamic rheological behavior of melts and thermal conductivity. The former can give information related to the build-up of internal network structures and to the level of dispersion of the fillers. Taking into account that the properties of nanocomposites are strictly related to these aspects, the enhancement of thermal conductivity with respect to the pristine matrix are discussed as a function of the filler content, dispersion of the filler and presence of internal structures.

  13. Fast and reliable method of conductive carbon nanotube-probe fabrication for scanning probe microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Dremov, Vyacheslav, E-mail: dremov@issp.ac.ru; Fedorov, Pavel; Grebenko, Artem [Institute of Solid State Physics, RAS, 142432 Chernogolovka (Russian Federation); Interdisciplinary Center for Basic Research, Moscow Institute of Physics and Technology, 141700 Dolgoprudniy (Russian Federation); Fedoseev, Vitaly [Institute of Solid State Physics, RAS, 142432 Chernogolovka (Russian Federation)

    2015-05-15

    We demonstrate the procedure of scanning probe microscopy (SPM) conductive probe fabrication with a single multi-walled carbon nanotube (MWNT) on a silicon cantilever pyramid. The nanotube bundle reliably attached to the metal-covered pyramid is formed using dielectrophoresis technique from the MWNT suspension. It is shown that the dimpled aluminum sample can be used both for shortening/modification of the nanotube bundle by applying pulse voltage between the probe and the sample and for controlling the probe shape via atomic force microscopy imaging the sample. Carbon nanotube attached to cantilever covered with noble metal is suitable for SPM imaging in such modulation regimes as capacitance contrast microscopy, Kelvin probe microscopy, and scanning gate microscopy. The majority of such probes are conductive with conductivity not degrading within hours of SPM imaging.

  14. Analysis of Percolation Behavior of Electrical Conductivity of the Systems Based on Polyethers and Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    E.A. Lysenkov

    2016-03-01

    Full Text Available The basic theoretical models of electrical conductivity of polymer nanocomposites and their accordance to experimental results are analysed for the systems based on polyethers and carbon nanotubes using the methods of mathematical simulation. It is set that models which are based on the effective medium approximation do not take into account existence of percolation threshold and can’t be using for exact definition of experimental data. It is discovered that the Fourier model demonstrats a good accordance with an experiment, however it is applicable only for the systems in which a large increase of conductivity under reaching the percolation threshold is observed, that systems with low own conductivity. It is set that the best accordance to experimental data was shown by the Kirkpatrick model and the generalized McLachlan model, which, except for the percolation threshold, structural descriptions of clusters which are formed from carbon nanotubes take into account.

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

    Science.gov (United States)

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

    2015-04-01

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

  16. Adhesion to carbon nanotube conductive scaffolds forces action-potential appearance in immature rat spinal neurons.

    Science.gov (United States)

    Fabbro, Alessandra; Sucapane, Antonietta; Toma, Francesca Maria; Calura, Enrica; Rizzetto, Lisa; Carrieri, Claudia; Roncaglia, Paola; Martinelli, Valentina; Scaini, Denis; Masten, Lara; Turco, Antonio; Gustincich, Stefano; Prato, Maurizio; Ballerini, Laura

    2013-01-01

    In the last decade, carbon nanotube growth substrates have been used to investigate neurons and neuronal networks formation in vitro when guided by artificial nano-scaled cues. Besides, nanotube-based interfaces are being developed, such as prosthesis for monitoring brain activity. We recently described how carbon nanotube substrates alter the electrophysiological and synaptic responses of hippocampal neurons in culture. This observation highlighted the exceptional ability of this material in interfering with nerve tissue growth. Here we test the hypothesis that carbon nanotube scaffolds promote the development of immature neurons isolated from the neonatal rat spinal cord, and maintained in vitro. To address this issue we performed electrophysiological studies associated to gene expression analysis. Our results indicate that spinal neurons plated on electro-conductive carbon nanotubes show a facilitated development. Spinal neurons anticipate the expression of functional markers of maturation, such as the generation of voltage dependent currents or action potentials. These changes are accompanied by a selective modulation of gene expression, involving neuronal and non-neuronal components. Our microarray experiments suggest that carbon nanotube platforms trigger reparative activities involving microglia, in the absence of reactive gliosis. Hence, future tissue scaffolds blended with conductive nanotubes may be exploited to promote cell differentiation and reparative pathways in neural regeneration strategies.

  17. Immobilization of carbon nanotubes and metallophthalocyanines on conductive surfaces by electrochemical means for electroanalytical purposes

    Energy Technology Data Exchange (ETDEWEB)

    Porras Gutierrez, A.; Gutierrez Granados, S. [Centre national de la recherche scientifique, Paris (France). Unite de Pharmacologie Chimique et Genetique; Guanajuato Univ. Guanajuato (Mexico). Inst. de Investigaciones Cientificas; Richard, C.; Griveau, S.; Bedioui, F. [Centre national de la recherche scientifique, Paris (France). Unite de Pharmacologie Chimique et Genetique; Zagal, J.H. [Santiago Univ. de Chile, Santiago (Chile)

    2008-07-01

    Carbon nanotubes (CNT) have been touted as viable candidates for the design of new electrode materials because of their high conductivity and high specific surface area. This study explored the use of electrochemical methods to immobilize single walled carbon nanotubes (SWCNT) on glassy carbon (GC) in a stable and controlled fashion. Two electrochemical routes were investigated to get the stable immobilization of nanotubes, notably (1) electropolymerization of conducting polymers in presence of SWCNT, and (2) the electrochemical grafting of diazonium salts in presence of SWCNT. The objective was to obtain chemically and mechanically stable composite GC/SWCNT electrodes. The electrochemical performances and reactivity of the electrodes were analyzed by voltammetry and by scanning electrochemical microscopy. The optimized immobilization methods were then applied to the conception of electrocatalysts hybrids, by co-immobilization of nanotubes with well-known redox catalyst metallocomplexes for activation of the electro-oxidation of biologically relevant thiol. The study showed that the nanocomposite material based on the combined use of metallophthalocynines, functionalized SWCNTs and electropolymerizable matrices enables the assembly of highly stable electrodes with better electrocatalytic oxidation of thiols. This fast procedure to modify glassy carbon (GC) electrode using commercially available cobalt phthalocyanine (CoPc) and tetrasulfonated nickel phthalocyanine (NiTSPc), oxidized single walled carbon nanotubes SWCNT and electropolymerized polypyrrole or diazonium derivatives. It was concluded that the electrodes are highly stable and the tailored hybrid surfaces improves electron transfer. 4 refs.

  18. Apparent Power Law Scaling of Variable Range Hopping Conduction in Carbonized Polymer Nanofibers

    Science.gov (United States)

    Kim, Kyung Ho; Lara-Avila, Samuel; Kang, Hojin; He, Hans; Eklӧf, Johnas; Hong, Sung Ju; Park, Min; Moth-Poulsen, Kasper; Matsushita, Satoshi; Akagi, Kazuo; Kubatkin, Sergey; Park, Yung Woo

    2016-11-01

    We induce dramatic changes in the structure of conducting polymer nanofibers by carbonization at 800 °C and compare charge transport properties between carbonized and pristine nanofibers. Despite the profound structural differences, both types of systems display power law dependence of current with voltage and temperature, and all measurements can be scaled into a single universal curve. We analyze our experimental data in the framework of variable range hopping and argue that this mechanism can explain transport properties of pristine polymer nanofibers as well.

  19. Portfolio: Ceramics.

    Science.gov (United States)

    Hardy, Jane; And Others

    1982-01-01

    Describes eight art activities using ceramics. Elementary students created ceramic tiles to depict ancient Egyptian and medieval European art, made ceramic cookie stamps, traced bisque plates on sketch paper, constructed clay room-tableaus, and designed clay relief masks. Secondary students pit-fired ceramic pots and designed ceramic Victorian…

  20. Portfolio: Ceramics.

    Science.gov (United States)

    Hardy, Jane; And Others

    1982-01-01

    Describes eight art activities using ceramics. Elementary students created ceramic tiles to depict ancient Egyptian and medieval European art, made ceramic cookie stamps, traced bisque plates on sketch paper, constructed clay room-tableaus, and designed clay relief masks. Secondary students pit-fired ceramic pots and designed ceramic Victorian…

  1. Spark plasma sintering and thermal conductivity of carbon nanotube bulk materials

    Science.gov (United States)

    Zhang, H. L.; Li, J.-F.; Yao, K. F.; Chen, L. D.

    2005-06-01

    Carbon nanotube (CNT) bulk samples were fabricated by spark plasma sintering (SPS), which, as a rapid consolidation technique, preserved the phase structure and diameter of cylindrical tubules of the CNTs even at high temperatures of up to 2000°C. The thermal conductivity of the resultant bulk samples was measured by the conventional laser-flash method, and the corresponding thermal conductivity was found to be as low as 4.2W/m/K at room temperature. This low thermal conductivity of the CNT bulk materials was explained on the basis of multiple physical elements including intensive tube-tube interactions. CNT bulk materials may find potential applications as thermoelectric materials that require low thermal conductivity, but high electrical conductivity.

  2. Electrically conductive carbon fibre-reinforced composite for aircraft lightning strike protection

    Science.gov (United States)

    Katunin, Andrzej; Krukiewicz, Katarzyna; Turczyn, Roman; Sul, Przemysław; Bilewicz, Marcin

    2017-05-01

    Aircraft elements, especially elements of exterior fuselage, are subjected to damage caused by lightning strikes. Due to the fact that these elements are manufactured from polymeric composites in modern aircraft, and thus, they cannot conduct electrical charges, the lightning strikes cause burnouts in composite structures. Therefore, the effective lightning strike protection for such structures is highly desired. The solution presented in this paper is based on application of organic conductive fillers in the form of intrinsically conducting polymers and carbon fabric in order to ensure electrical conductivity of whole composite and simultaneously retain superior mechanical properties. The presented studies cover synthesis and manufacturing of the electrically conductive composite as well as its characterization with respect to mechanical and electrical properties. The performed studies indicate that the proposed material can be potentially considered as a constructional material for aircraft industry, which characterizes by good operational properties and low cost of manufacturing with respect to current lightning strike protection materials solutions.

  3. Enhanced field-dependent conductivity of magnetorheological gels with low-doped carbon nanotubes

    Science.gov (United States)

    Qu, Hang; Yu, Miao; Fu, Jie; Yang, Pingan; Liu, Yuxuan

    2017-10-01

    Magnetorheological gels (MRG) exhibit field-dependent conductivity and controllable mechanical properties. In order to extend their application field, filling a large number of traditional conductive materials is the most common means to enhance the poor conductivity of MRG. In this study, the conductivity of MRG is improved by low-doped carbon nanotubes (CNTs). The influence of CNTs on the magnetoresistance of MRG is discussed from two aspects—the improvement in electrical conductivity and the magnetic sensitivity of conductivity variation. The percolation threshold of CNTs in MRG should be between 1 wt% and 2 wt%. The conductivity of a 4 wt% CNT-doped sample increases more than 28 000 times compared with pure MRG. However, there is a cliff-like drop for the range and rate of conductivity variation when the doping amount of CNTs is between 3 wt% and 4 wt%. Therefore, it is concluded that the optimal mass fraction of CNTs is 3%, which can maintain a suitable variation range and a strong conductivity. Compared with pure MRG, its conductivity increases by at least two orders of magnitude. Finally, a sketch of particle motion simulation is developed to understand the improving mechanism and the effect of CNTs.

  4. Properties of doped ZnO transparent conductive thin films deposited by RF magnetron sputtering using a series of high quality ceramic targets

    Institute of Scientific and Technical Information of China (English)

    LIN Wei; MA Ruixin; SHAO Wei; KANG Bo; WU Zhongliang

    2008-01-01

    To obtain high transmittance and low resistivity ZnO transparent conductive thin films,a series of ZnO ceramic targets (ZnO:Al,ZnO:(Al,Dy),ZnO:(Al,Gd),ZnO:(Al,Zr),ZnO:(Al,Nb),and ZnO:(Al,W)) were fabricated and used to deposit thin films onto glass substrates by radio frequency (RF) magnetron sputtering.X-ray diffraction (XRD) analysis shows that the films are polyerystalline fitting well with hexagonal wurtzite structure and have a preferred orientation of the (002) plane.The transmittance of above 86% as well as the lowest resistivity of 8.43 x 10-3 Ω·cm was obtained.

  5. AC conductivity and relaxation mechanism in (Nd1/2Li1/2)(Fe1/2V1/2)O3 ceramics

    Science.gov (United States)

    Nath, Susmita; Barik, Subrat Kumar; Choudhary, R. N. P.

    2016-05-01

    In the present study we have synthesized polycrystalline sample of (Nd1/2Li1/2)(Fe1/2V1/2)O3 ceramic by a standard high-temperature solid-state reaction technique. Studies of dielectric and electrical properties of the compound have been carried out in a wide range of temperature (RT - 400 °C) and frequency (1kHz - 1MHz) using complex impedance spectroscopic technique. The imaginary vs. real component of the complex impedance plot (Nyquist plot) of the prepared sample exhibits the existence of grain, grain boundary contributions in the complex electrical parameters and negative temperature coefficient of resistance (NTCR) type behavior like semiconductor. Details study of ac conductivity plot reveals that the material obeys universal Jonscher's power law.

  6. Thermal conductivity of carbon foams. Measurements and interpretation; Conductivite thermique de mousses de carbone. Mesures et interpretation

    Energy Technology Data Exchange (ETDEWEB)

    Bourret, F.; Fort, C.; Duffa, G. [CEA CESTA, 33 - Le Barp (France)

    1996-12-31

    This paper describes thermal diffusivity measurements performed with the flash method on carbon foams with open porosity at ambient and higher temperatures. The influence of gas inclusions in the pores has been studied too. In this type of highly insulating material, radiant heat transfer plays a major role. The experiments carried out are interpreted in terms of equivalent thermal conductivity and show the difficulties encountered, in particular the dependence with sample thickness. An interpretation based on a direct simulation with an equivalent periodical material is given with an estimation of the gaseous conductivity based on the kinetics theory of gases. This study demonstrates that the notion of equivalent thermal conductivity is not applicable to all experiments. (J.S.) 10 refs.

  7. Carbon Nanotubes Act as Conductive Additives in the cathode of Lithium Ion Batteries

    Institute of Scientific and Technical Information of China (English)

    Wang Guoping; Zhou Gumin; Qu MeiZhen; Wang Guixing; Wang Yunshi; Zhong Hong; Yu Zuolong

    2004-01-01

    The layered compounds LiCoO2, LiNiO2 and spinel compound LiMn2O4 have served as very effective cathode active materials in lithium ion rechargeable batteries. Generally, their high conductive resistance easily results in a serious polarization and poor utilization of active materials.In order to make full use of the active materials and increase the capacity, the charge-discharge rate and the cycle life of lithium ion batteries, conductive additives are often added into the above cathode materials to form a conductive network. Carbon materials, such as carbon black, graphite powders and chemical vapor deposit carbon fibers have been widely used as conductive additives owing to their high electrical conductivity and chemical inertness. To effectively utilize the active materials, the contents of these carbon additives in the cathode often reach up to 10~20wt%. This leads to a great need for binder, for example, 10wt% or more. It follows therefore a considerable increase in volume of the lithium batteries and lower energy density because of the large amount of carbon additives and binder in the cathode.By substituting carbon nanotubes (CNTs) for carbon black, graphite powders or chemical vapor deposit carbon fibers, much conductive additives and binder are saved, and the cathode with only 3~5wt% of conductive additives CNTs shows excellent rate capacity. At the discharge rate 0.5C,2.0C and 3.0C, the LiCoO2 cathode with CNTs exhibits discharge capacity up to 134mAh/g, 126 and 120mAh/g, respectively. The explanation is given as follows. Firstly, their microstructure and graphitic crystallinity are very important for electron transport. CNTs employed in the experiments comprise an array of complete graphite sheets seamlessly wrapped into cylindrical tubes which are concentrically nested like the rings of a tree trunk. Thus, the process of -electrons transport occurs in graphite sheet in super-conjugative manner when they move from one end to the other end in CNTs

  8. Comparative evaluation of electrical conductivity of hydroxyapatite ceramics densified through ramp and hold, spark plasma and post sinter Hot Isostatic Pressing routes.

    Science.gov (United States)

    Buchi Suresh, M; Biswas, P; Mahender, V; Johnson, Roy

    2017-01-01

    Hydroxyapatite ceramics synthesized through sonochemical route were processed and densified through ramp & hold (R&H) and Spark Plasma Sintering (SPS) routes. The effect of processing route on the relative density and electrical conductivity were studied. Further, the samples were Hot Isostatically Pressed (HIP) under argon pressure at elevated temperature to further densify the sample. All these samples processed under different conditions were characterized by X-ray diffraction, Scanning Electron Microscopy and AC Conductivity. The samples have exhibited hydroxyapatite phase; however, microstructures exhibited distinctly different grain morphologies and grain sizes. AC impedance spectroscopic measurement was carried out on hydroxyapatite samples processed through different routes and the corresponding spectra were analyzed by the analogy to equivalent circuit involving resistors and capacitors. SPS sintered sample after HIPing has exhibited the highest conductivity. This can be attributed to the higher density in combination with finer grain sizes. Activation energy based on Arrhenius equation is calculated and the prominent conduction mechanism is proposed. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Using graphene networks to build bioinspired self-monitoring ceramics

    Science.gov (United States)

    Picot, Olivier T.; Rocha, Victoria G.; Ferraro, Claudio; Ni, Na; D'Elia, Eleonora; Meille, Sylvain; Chevalier, Jerome; Saunders, Theo; Peijs, Ton; Reece, Mike J.; Saiz, Eduardo

    2017-02-01

    The properties of graphene open new opportunities for the fabrication of composites exhibiting unique structural and functional capabilities. However, to achieve this goal we should build materials with carefully designed architectures. Here, we describe the fabrication of ceramic-graphene composites by combining graphene foams with pre-ceramic polymers and spark plasma sintering. The result is a material containing an interconnected, microscopic network of very thin (20-30 nm), electrically conductive, carbon interfaces. This network generates electrical conductivities up to two orders of magnitude higher than those of other ceramics with similar graphene or carbon nanotube contents and can be used to monitor `in situ' structural integrity. In addition, it directs crack propagation, promoting stable crack growth and increasing the fracture resistance by an order of magnitude. These results demonstrate that the rational integration of nanomaterials could be a fruitful path towards building composites combining unique mechanical and functional performances.

  10. Comparative Studies of the Adsorption of Direct Dye on Activated Carbon and Conducting Polymer Composite

    Directory of Open Access Journals (Sweden)

    J. Raffiea Baseri

    2012-01-01

    Full Text Available This study analyses the feasibility of removing Direct Blue 71 from aqueous solution by different adsorbents such as activated carbon (TPAC and Poly pyrrole polymer composite (PPC prepared from Thevetia Peruviana. Batch mode adsorption was performed to investigate the adsorption capacities of these adsorbents by varying initial dye concentration, temperature, agitation time and pH. The performance of TPAC was compared with PPC. Among the adsorbents, PPC had more adsorption capacity (88.24% than TPAC (58.82% at an initial concentration of 50 mg/L and at 30°C. The experimental data best fitted with pseudo second order kinetic model. The adsorption data fitted well for Langmuir adsorption isotherm. Thermodynamic parameters for the adsorbents were also evaluated. The carbon embedded in conducting polymers matrix show better adsorptive properties than activated carbon.

  11. Synthesis of Porous and Mechanically Compliant Carbon Aerogels Using Conductive and Structural Additives

    Directory of Open Access Journals (Sweden)

    Carlos Macias

    2016-01-01

    Full Text Available We report the synthesis of conductive and mechanically compliant monolithic carbon aerogels prepared by sol-gel polycondensation of melamine-resorcinol-formaldehyde (MRF mixtures by incorporating diatomite and carbon black additives. The resulting aerogels composites displayed a well-developed porous structure, confirming that the polymerization of the precursors is not impeded in the presence of either additive. The aerogels retained the porous structure after etching off the siliceous additive, indicating adequate cross-linking of the MRF reactants. However, the presence of diatomite caused a significant fall in the pore volumes, accompanied by coarsening of the average pore size (predominance of large mesopores and macropores. The diatomite also prevented structural shrinkage and deformation of the as-prepared monoliths upon densification by carbonization, even after removal of the siliceous framework. The rigid pristine aerogels became more flexible upon incorporation of the diatomite, favoring implementation of binderless monolithic aerogel electrodes.

  12. Self-monitoring electrically conductive asphalt-based composite containing carbon fillers

    Institute of Scientific and Technical Information of China (English)

    WU Shao-peng; LIU Xiao-ming; YE Qun-shan; LI Ning

    2006-01-01

    A new novel function materials,structure self-monitoring asphalt-based composite was introduced. The results show that the output resistance of electrically conductive asphalt-based composites would change under cyclic loading and vehicle loading action. The resistance change of conductive asphalt-based composites was aroused by the variation of its interior structure. When the fatigue failure was studied,the larger cracks cut the continuous electrically conductive path and the electron is difficult to overcome the potential barrier of gap. In the early period,the slight deformation and microcrack may be recovered due to the viscoelasticity character of asphalt,which leads to some cracks close again,the output resistance changes a little. But with the shear process performs continuously,the cracks become larger and larger,which would cut the conductive path and block off the transition of electrons,and if the cracks are large enough,the pitch-matrix composites containing carbon fillers will lose electrically conductive function. When the rutting failure was studied,the flowage of conductive substance results in the decrease of substance due to electrically conducting and conductive path decreasing. The decrease of electron volume contribute to electrically conducting and large stone aggregate prevent the electron from transiting. In a word,the variation of output resistance is aroused by the variation of interior structure completely.

  13. Application of Pre-coated Microfiltration Ceramic Membrane with Powdered Activated Carbon for Natural Organic Matter Removal from Secondary Wastewater Effluent

    KAUST Repository

    Kurniasari, Novita

    2012-12-01

    Ceramic membranes offer more advantageous performances than conventional polymeric membranes. However, membrane fouling caused by Natural Organic Matters (NOM) contained in the feed water is still become a major problem for operational efficiency. A new method of ceramic membrane pre-coating with Powdered Activated Carbon (PAC), which allows extremely contact time for adsorbing aquatic contaminants, has been studied as a pre-treatment prior to ceramic microfiltration membrane. This bench scale study evaluated five different types of PAC (SA Super, G 60, KCU 6, KCU 8 and KCU 12,). The results showed that KCU 6 with larger pore size was performed better compared to other PAC when pre-coated on membrane surface. PAC pre-coating on the ceramic membrane with KCU 6 was significantly enhance NOM removal, reduced membrane fouling and improved membrane performance. Increase of total membrane resistance was suppressed to 96%. The removal of NOM components up to 92%, 58% and 56% for biopolymers, humic substances and building blocks, respectively was achieved at pre-coating dose of 30 mg/l. Adsorption was found to be the major removal mechanism of NOM. Results obtained showed that biopolymers removal are potentially correlated with enhanced membrane performance.

  14. Carbon-coated ceramic membrane reactor for the production of hydrogen by aqueous-phase reforming of sorbitol.

    Science.gov (United States)

    Neira D'Angelo, M F; Ordomsky, V; Schouten, J C; van der Schaaf, J; Nijhuis, T A

    2014-07-01

    Hydrogen was produced by aqueous-phase reforming (APR) of sorbitol in a carbon-on-alumina tubular membrane reactor (4 nm pore size, 7 cm long, 3 mm internal diameter) that allows the hydrogen gas to permeate to the shell side, whereas the liquid remains in the tube side. The hydrophobic nature of the membrane serves to avoid water loss and to minimize the interaction between the ceramic support and water, thus reducing the risks of membrane degradation upon operation. The permeation of hydrogen is dominated by the diffusivity of the hydrogen in water. Thus, higher operation temperatures result in an increase of the flux of hydrogen. The differential pressure has a negative effect on the flux of hydrogen due to the presence of liquid in the larger pores. The membrane was suitable for use in APR, and yielded 2.5 times more hydrogen than a reference reactor (with no membrane). Removal of hydrogen through the membrane assists in the reaction by preventing its consumption in undesired reactions.

  15. Growth of gallium nitride and indium nitride nanowires on conductive and flexible carbon cloth substrates.

    Science.gov (United States)

    Yang, Yi; Ling, Yichuan; Wang, Gongming; Lu, Xihong; Tong, Yexiang; Li, Yat

    2013-03-07

    We report a general strategy for synthesis of gallium nitride (GaN) and indium nitride (InN) nanowires on conductive and flexible carbon cloth substrates. GaN and InN nanowires were prepared via a nanocluster-mediated growth method using a home built chemical vapor deposition (CVD) system with Ga and In metals as group III precursors and ammonia as a group V precursor. Electron microscopy studies reveal that the group III-nitride nanowires are single crystalline wurtzite structures. The morphology, density and growth mechanism of these nanowires are determined by the growth temperature. Importantly, a photoelectrode fabricated by contacting the GaN nanowires through a carbon cloth substrate shows pronounced photoactivity for photoelectrochemical water oxidation. The ability to synthesize group III-nitride nanowires on conductive and flexible substrates should open up new opportunities for nanoscale photonic, electronic and electrochemical devices.

  16. Effect of conductive additives to gel electrolytes on activated carbon-based supercapacitors

    Directory of Open Access Journals (Sweden)

    Farshad Barzegar

    2015-09-01

    Full Text Available This article is focused on polymer based gel electrolyte due to the fact that polymers are cheap and can be used to achieve extended potential window for improved energy density of the supercapacitor devices when compared to aqueous electrolytes. Electrochemical characterization of a symmetric supercapacitor devices based on activated carbon in different polyvinyl alcohol (PVA based gel electrolytes was carried out. The device exhibited a maximum energy density of 24 Wh kg−1 when carbon black was added to the gel electrolyte as conductive additive. The good energy density was correlated with the improved conductivity of the electrolyte medium which is favorable for fast ion transport in this relatively viscous environment. Most importantly, the device remained stable with no capacitance lost after 10,000 cycles.

  17. Experimental Study on Deicing Performance of Carbon Fiber Reinforced Conductive Concrete

    Institute of Scientific and Technical Information of China (English)

    Zuquan TANG; Zhuoqiu LI; Jueshi QIAN; Kejin WANG

    2005-01-01

    Carbon fiber reinforced concrete (CFRC) is a kind of good electrothermal material. When connected to an external power supply, stable and uniform heat suitable for deicing application is generated in the CFRC slab. Electric heating and deicing experiments of carbon fiber reinforced concrete slab were carried out in laboratory, and the effect of the temperature and thickness of ice, the thermal conductivity of CFRC, and power output on deicing performance and energy consumption were investigated. The experimental results indicate that it is an effective method to utilize the thermal energy produced by CFRC slab to deice. The time to melt the ice completely decreases with increasing power output and ice temperature, and increases with increasing thickness of the ice. The energy consumption to ranges from -3℃ to -18℃. CFRC with good thermal conduction can reduce temperature difference in CFRC slab effectively.

  18. Transparent conducting film: Effect of mechanical stretching to optical and electrical properties of carbon nanotube mat

    Indian Academy of Sciences (India)

    Tsuyoshi Saotome; Hansang Kim; David Lashmore; H Thomas Hahn

    2011-07-01

    We describe in this paper a transparent conducting film (TCF). It is a fibrous layer of multiwalled carbon nanotubes (MWNTs), labeled a dilute CNT mat, that was prepared and unidirectionally stretched to improve both the optical and electrical properties. After stretching by 80% strain, transmittance at 550 nm wavelength was improved by 37% and sheet resistance was reduced to 71% of the original value. The improvement of the transmittance can be explained by increased area of the CNT mat after stretch, and the reduced sheet resistance can be explained by increased density of the CNT alignment in lateral direction due to contraction. Based on the microscopic observation before and after stretch, models to describe the phenomena are proposed. By further expanding on this method, it may be possible to obtain a transparent conducting carbon nanotube film which is crack-resistant for solar cell applications.

  19. Self-assembly of single walled carbon nanotubes onto cotton to make conductive yarn

    Institute of Scientific and Technical Information of China (English)

    Wei Zhang; Yee Yuan Tan; Chengwei Wu; S. Ravi P. Silva

    2012-01-01

    A simple,economical and scalable technique is demonstrated to make conductive yarn.Single walled carbon nanotubes (SWCNTs) are non-covalently functionalized with dye (Acid Red 91) and dispersed in water; while cotton yarn is treated with poly (ethylene imine).When the resulting yarn is immersed in the SWCNT dispersion,SWCNTs self-assemble onto the yarn due to electrostatic forces between the functionalized nanotubes and yarn.Scanning electron microscopy,transmission electron microscopy and Raman spectroscopy indicate the assembly of carbon nanotubes.The SWCNT functionalized yarn exhibits reasonable electrical conduction behaviour and are then used to make chemiresistors.The electrical resistance of the chemiresistors used as sensors increases on exposure to ammonia gas,which can be explained in terms of electron transfer between gas molecules and SWCNTs.

  20. Enhanced thermal conductivity of n-octadecane containing carbon-based nanomaterials

    Science.gov (United States)

    Motahar, Sadegh; Alemrajabi, Ali A.; Khodabandeh, Rahmatollah

    2016-08-01

    In the present study, carbon-based nanomaterials including multiwalled carbon nanotubes (MWCNTs) and vapor-grown carbon nanofibers (CNFs) were dispersed in n-octadecane as a phase change material (PCM) at various mass fractions of 0.5, 1, 2 and 5 wt% by the two-step method. The transient plane source technique was used to measure thermal conductivity of samples at various temperatures in solid (5-25 °C) and liquid (30-55 °C) phases. The experimental results showed that thermal conductivity of the composites increases with increasing the loading of the MWCNTs and CNFs. A maximum thermal conductivity enhancement of 36 % at 5 wt% MWCNTs and 5 °C as well as 50 % at 2 wt% and 55 °C were experimentally obtained for n-octadecane/MWCNTs samples. Dispersing CNFs into n-octadecane raised the thermal conductivity up to 18 % at 5 wt% and 10 °C and 21 % at 5 wt% and 55 °C. However, the average enhancement of 19 and 21 % for solid and liquid phases of MWCNTs composite as well as 33 and 46 % for solid and liquid phase of CNFs promised a better heat transfer characteristics of MWCNTs in n-octadecane. A comparison between results of the present work and available literature revealed a satisfactory enhancement of thermal conductivity. For the investigated n-octadecane/MWCNTs and n-octadecane/CNFs composites, a new correlation was proposed for predicting the thermal conductivity as a function of temperature and nanomaterials loading.

  1. Materials and Concepts for Full Ceramic SOFCs with Focus on Carbon Containing Fuels

    DEFF Research Database (Denmark)

    Holtappels, Peter; Sudireddy, Bhaskar Reddy; Veltzé, Sune

    , stability, and S- tolerance has been investigated. These results and an assessment on a 1 kW system level using CPOX reformed natural gas will be reviewed and further perspectives of the cell concept discussed, especially with respect to efficient operation on high carbon containing fuels....

  2. 77 FR 38082 - Certain Activated Carbon from China; Notice of Commission Determination To Conduct a Full Five...

    Science.gov (United States)

    2012-06-26

    ... COMMISSION Certain Activated Carbon from China; Notice of Commission Determination To Conduct a Full Five... Activated Carbon From China AGENCY: United States International Trade Commission. ACTION: Notice. SUMMARY... whether revocation of the antidumping duty order on certain activated carbon from China would be likely...

  3. Origin of conductivity cross over in entangled multi-walled carbon nanotube network filled by iron

    OpenAIRE

    Chimowa, George; Linganiso, Ella C.; Churochkin, Dmitry; Neil J. Coville; Bhattacharyya, Somnath

    2011-01-01

    A realistic transport model showing the interplay of the hopping transport between the outer shells of iron filled entangled multi-walled carbon nanotubes (MWNT) and the diffusive transport through the inner part of the tubes, as a function of the filling percentage, is developed. This model is based on low-temperature electrical resistivity and magneto-resistance (MR) measurements. The conductivity at low temperatures showed a crossover from Efros-Shklovski (E-S) variable range hopping (VRH)...

  4. Green's function embedding approach to quantum conductivity of single wall carbon nanotubes

    Science.gov (United States)

    Andriotis, Antonis N.; Menon, Madhu

    2001-08-01

    Quantum conductivity of carbon nanotubes is calculated using an efficient embedding Green's function formalism that allows for a realistic nanotube-metal lead contacts. The details of the contact geometry is found to profoundly influence the I-V characteristics. Furthermore, the primary effect of defects in nanotubes is to smooth out the steplike features of the corresponding I-V curve of the pristine tube.

  5. Bias-dependent amino-acid-induced conductance changes in short semi-metallic carbon nanotubes.

    Science.gov (United States)

    Abadir, G B; Walus, K; Pulfrey, D L

    2010-01-08

    We study the interaction between short semi-metallic carbon nanotubes and different amino acids using molecular dynamics and ab initio (density functional theory/non-equilibrium Green's function) simulations. We identify two different mechanisms of nanotube conductance change upon adsorption of amino acids: one due to the change of the coordinates of the nanotube arising from van der Waals forces of interaction with the adsorbed amino acid; and one due to electrostatic interactions, which appear only in the case of charged amino acids. We also find that the transport mechanism and the changes in the conductance of the tube upon amino acid adsorption are bias dependent.

  6. Thermal conductivity of vertically aligned carbon nanotube arrays: Growth conditions and tube inhomogeneity

    Science.gov (United States)

    Bauer, Matthew L.; Pham, Quang N.; Saltonstall, Christopher B.; Norris, Pamela M.

    2014-10-01

    The thermal conductivity of vertically aligned carbon nanotube arrays (VACNTAs) grown on silicon dioxide substrates via chemical vapor deposition is measured using a 3ω technique. For each sample, the VACNTA layer and substrate are pressed to a heating line at varying pressures to extract the sample's thermophysical properties. The nanotubes' structure is observed via transmission electron microscopy and Raman spectroscopy. The presence of hydrogen and water vapor in the fabrication process is tuned to observe the effect on measured thermal properties. The presence of iron catalyst particles within the individual nanotubes prevents the array from achieving the overall thermal conductivity anticipated based on reported measurements of individual nanotubes and the packing density.

  7. Electrothermal Performances of Poly(Vinylidiene Fluoride)/Fluorine Rubber Conductive Composite Filled with Carbon Black

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    @@ The conductive polymer composites and their corresponding resistors with PTC (positive temperature coefficient) characteristic can be manufactured by mixing conductive carbon blacks with poly(vinylidiene fluoride )matrix. The Joule heat can produce when alternative voltage is exerted on the composite resistors, and the resistors can produce when alternative voltage is exerted on the current from flowing at a high temperature because of their PTC effect, thus becoming a kind of important thermoelectric switching materials as heating, temperature-controlling and currentlinfiting element applications.

  8. Electrothermal Performances of Poly(Vinylidiene Fluoride)/Fluorine Rubber Conductive Composite Filled with Carbon Black

    Institute of Scientific and Technical Information of China (English)

    LUO; YanLing

    2001-01-01

    The conductive polymer composites and their corresponding resistors with PTC (positive temperature coefficient) characteristic can be manufactured by mixing conductive carbon blacks with poly(vinylidiene fluoride )matrix. The Joule heat can produce when alternative voltage is exerted on the composite resistors, and the resistors can produce when alternative voltage is exerted on the current from flowing at a high temperature because of their PTC effect, thus becoming a kind of important thermoelectric switching materials as heating, temperature-controlling and currentlinfiting element applications.  ……

  9. Preparation of Conductive Coating Solutions by Blending Waterborne Acrylic Polyurethane Dispersion with Carbon Nanotube

    Energy Technology Data Exchange (ETDEWEB)

    Huh, Woo Young; Yun, Dong Gu; Song, Ki Chang [Konyang University, Nonsan (Korea, Republic of)

    2013-02-15

    Waterborne polyurethane dispersion (WPUD) was synthesized from polycarbonate diol (PCD), isophorone diisocyanate (IPDI) and dimethylol propionic acid (DMPA) as starting materials. Then, waterborne acrylic polyurethane dispersion (AUD) was synthesized by reacting the WPUD with an acrylate monomer, methyl methacrylate (MMA). Subsequently, the AUD was mixed with multi-walled carbon nanotube (MWCNT) to yield a conductive coating solution, and the mixture was coated on the polycarbonate substrate. With increasing the amount of MMA in the AUD, the pencil hardness, abrasion resistance and chemical resistance of the coating films were improved, but the electrical conductivity of the coating films was decreased. On the other hand, the pencil hardness, abrasion resistance and chemical resistance of coating films were decreased, but the electrical conductivity was enhanced with increasing the amount of MWCNT in the conductive coating solutions.

  10. Conductivity analysis of epoxy/carbon nanotubes composites by dipole relaxation and hopping models

    Science.gov (United States)

    Ramos, Airton; Pezzin, Sergio H.; Farias, Heric Denis; Becker, Daniela; Bello, Roger H.; Coelho, Luiz A. F.

    2016-10-01

    In this study it was used a numerical technique of successive approximations to estimate parameters of a conductivity model that includes the hopping process and the dipole relaxation for the purpose of describing the behavior of the conductivity measured on nanocomposites with carbon nanotubes in epoxy resin in the range of frequency of 100 Hz to 40 MHz. Two relaxation bands were detected, one with a response below 10 kHz and one above 10 MHz. For the first band, it was observed that the nanocomposites become more conductive, and its conductivity less temperature dependent, as the nanotube content increases. The second band is characterized by a large spread in relaxation time. The results show that the percolation threshold is below 0.15 vol% and that 'ac' hopping is the main transport process above 100 kHz, becoming dominant with respect to percolation at higher temperatures (>340 K).

  11. INTERACTION MODELS FOR EFFECTIVE THERMAL AND ELECTRIC CONDUCTIVITIES OF CARBON NANOTUBE COMPOSITES

    Institute of Scientific and Technical Information of China (English)

    Fei Deng; Quanshui Zheng

    2009-01-01

    The present article provides supplementary information of previous works of ana-lytic models for predicting conductivity enhancements of carbon nanotube composites. The mod-els, though fairly simple, are able to take account of the effects of conductivity anisotropy, non-straightness, and aspect ratio of the CNT additives on the conductivity enhancement of the com-posite and to give predictions agreeing well with existing experimental data. The omitted detailed derivation of this model is demonstrated in the present article with a more systematical analysis, which may help with further development in this direction. Furthermore, the effects of various orientation distributions of CNTs are reported here for the first time. The information may be useful in design or fabrication technology of CNT composites for better or specified conductivities.

  12. On the linear dependence of a carbon nanofiber thermal conductivity on wall thickness

    Directory of Open Access Journals (Sweden)

    Alexandros Askounis

    2016-11-01

    Full Text Available Thermal transport in carbon nanofibers (CNFs was thoroughly investigated. In particular, individual CNFs were suspended on T-type heat nanosensors and their thermal conductivity was measured over a range of temperatures. Unexpectedly, thermal conductivity was found to be dependent on CNF wall thickness and ranging between ca. 28 and 43 W/(m⋅K. Further investigation of the CNF walls with high resolution electron microscopy allowed us to propose a tentative description of how wall structure affects phonon heat transport inside CNFs. The lower thermal conductivities, compared to other CNTs, was attributed to unique CNF wall structure. Additionally, wall thickness is related to the conducting lattice length of each constituent graphene cone and comparable to the Umklapp length. Hence, as the wall thickness and thus lattice length increases there is a higher probability for phonon scattering to the next layer.

  13. Conductivity-Dependent Strain Response of Carbon Nanotube Treated Bacterial Nanocellulose

    Directory of Open Access Journals (Sweden)

    S. Farjana

    2013-01-01

    Full Text Available This paper reports the strain sensitivity of flexible, electrically conductive, and nanostructured cellulose which was prepared by modification of bacterial cellulose with double-walled carbon nanotubes (DWCNTs and multiwalled carbon nanotubes (MWCNTs. The electrical conductivity depends on the modifying agent and its dispersion process. The conductivity of the samples obtained from bacterial cellulose (BNC pellicles modified with DWCNT was in the range from 0.034 S·cm−1 to 0.39 S·cm−1, and for BNC pellicles modified with MWCNTs it was from 0.12 S·cm−1 to 1.6 S·cm−1. The strain-induced electromechanical response, resistance versus strain, was monitored during the application of tensile force in order to study the sensitivity of the modified nanocellulose. A maximum gauge factor of 252 was found from the highest conductive sample treated by MWCNT. It has been observed that the sensitivity of the sample depends on the conductivity of the modified cellulose.

  14. Fabrication of Aligned-Carbon-Nanotube-Composite Paper with High and Anisotropic Conductivity

    Directory of Open Access Journals (Sweden)

    Yuki Fujitsuka

    2012-01-01

    Full Text Available A functional carbon-nanotube (CNT-composite paper is described in which the CNTs are aligned. This “aligned-CNT composite paper” is a flexible composite material that has CNT functionality (e.g., electrical conductivity despite being a paper. An advanced fabrication method was developed to overcome the problem of previous CNT-composite papers, that is, reduced conductivity due to random CNT alignment. Aligning the CNTs by using an alternating current (AC field was hypothesized to increase the electrical conductivity and give the paper an anisotropic characteristic. Experimental results showed that a nonionic surfactant was not suitable as a CNT dispersant for fabricating aligned-CNT composite paper and that catechin with its six-membered rings and hydrophilic groups was suitable. Observation by scanning electron microscopy of samples prepared using catechin showed that the CNTs were aligned in the direction of the AC field on the paper fibers. Measurement of the electric conductivity showed that the surface resistance was different between the direction of the aligned CNTs (high conductivity and that of verticality (low. The conductivity of the aligned-CNT-composite paper samples was higher than that of nonaligned samples. This unique and functional paper, which has high and anisotropic conductivity, is applicable to a conductive material to control the direction of current.

  15. Preparation and performance of ZnO nanowires modified carbon fibers reinforced NiFe{sub 2}O{sub 4} ceramic matrix composite

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Lei, E-mail: jwlzl77@163.com; Jiao, Wanli

    2013-12-25

    Highlights: •Unlike existing chemical modification, the liquid growth remains fiber’s strength. •ZnO nanowires array are grown on carbon fibers with controllable morphology. •ZnO nanowires array modified carbon fibers can reinforce the strength of ceramic matrix composite. •This research will provide a means to produce multifunctional composites. -- Abstract: The surface of carbon fibers was modified by ZnO nanowires using the liquid growth method. NiFe{sub 2}O{sub 4} ceramic matrix composites reinforced by the modified carbon fibers were prepared by a high-temperature solid-state reaction method at 1300 °C for 5 h in N{sub 2} atmosphere. The influences of modified carbon fibers on the mechanical performances of NiFe{sub 2}O{sub 4} composites were investigated. The crystal structure of modified carbon fibers and the morphology of modified carbon fibers surface and the NiFe{sub 2}O{sub 4} composites fracture cross-section were observed by meaning of X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. The results showed that hexagonal wurtzite ZnO nanowires array grew from the surface of carbon fibers vertically, with nanowires diameters ranging from 170 nm to 380 nm and lengths up to 2.8 μm. Unlike existing chemical modification and high temperature oxidation method, the liquid growth allowed morphology control and maintained the single fiber tensile strength substantially unchanged under certain growth procedures. Compared to pure NiFe{sub 2}O{sub 4} ceramic and bare carbon fibers reinforced NiFe{sub 2}O{sub 4} composite, the bending strength of NiFe{sub 2}O{sub 4} composite reinforced with ZnO nanowires surface modified carbon fibers was shown to increase by up to 70% and 45%, respectively. The development of an interphase offering control over the morphology will provide a means to produce multifunctional composites.

  16. Electrical conductivity and chemical stability of BaCe0.8−AGd0.2O3− (A = In, Zr, Ta; = 0, 0.1) ceramics

    Indian Academy of Sciences (India)

    Xiao-Ming Liu; Yi-Jing Gu; Zhan-Guo Liu; Jia-Hu Ouyang; Fu-Yao Yan; Jun Xiang

    2013-06-01

    BaCe0.8−AGd0.2O3− (A = In, Zr, Ta; = 0, 0.1) ceramics were synthesized by solid-state reaction method. Microstructure and electrical properties of BaCe0.8−AGd0.2O3− ceramics were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and complex impedance analysis at intermediate temperatures of 573–1073 K in different atmospheres. BaCe0.8Gd0.2O3−, BaCe0.7In0.1Gd0.2O3− and BaCe0.7Zr0.1Gd0.2O3− ceramics exhibit a single cubic perovskite structure. BaCe0.7In0.1Gd0.2O3− ceramic has the highest conductivity of 4.6 × 10-2 S.cm-1 in air at 1073 K. BaCe0.7In0.1Gd0.2O3− and BaCe0.7Zr0.1Gd0.2O3− ceramics exhibit an excellent chemical stability against boiling water. Indium is a suitable doping element to promote the sintering densification and to enhance both electrical conductivity and chemical stability of Gd-doped BaCeO3 at operating temperatures.

  17. Analysis of neutron irradiation effects on thermal conductivity of SiC-based composites and monolithic ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Youngblood, G.E.; Senor, D.J. [Pacific Northwest National Lab., Richland, WA (United States)

    1997-08-01

    After irradiation of a variety of SiC-based materials to 33 or 43 dpa-SiC at 1000{degrees}C, their thermal conductivity values were degraded and became relatively temperature independent, which indicates that the thermal resistivity was dominated by point defect scattering. The magnitude of irradiation-induced conductivity degradation was greater at lower temperatures and typically was larger for materials with higher unirradiated conductivity. From these data, a K{sub irr}/K{sub unirr} ratio map which predicts the expected equilibrium thermal conductivity for most SiC-based materials as a function of irradiation temperature was derived. Due to a short-term EOC irradiation at 575{degrees} {+-} 60{degrees}C, a duplex irradiation defect structure was established. Based on an analysis of the conductivity and swelling recovery after post-irradiation anneals for these materials with the duplex defect structure, several consequences for irradiating SiC at temperatures of 1000{degrees}C or above are given. In particular, the thermal conductivity degradation in the fusion relevant 800{degrees}-1000{degrees}C temperature range may be more severe than inferred from SiC swelling behavior.

  18. A.C. Conductivity Investigations on Layered Na2-x-yLixKyTi3O7 Ceramics

    Directory of Open Access Journals (Sweden)

    Rakesh Singh

    2013-01-01

    Full Text Available Frequency and temperature dependence of a.c. electrical conductivity of layered mixed ionic alkali trititanates, Na1.89Li0.10K0.01Ti3O7, Na1.88Li0.10K0.02Ti3O7, Na1.86Li0.10K0.04Ti3O7, and Na1.85Li0.10K0.05Ti3O7, have been investigated over a wide temperature 350 K ≤T≥ 725 K and frequency 10 kHz to 1 MHz range. For this, Arrhenius plots are used for a.c. electrical conductivity of these compounds. The obtained conductivity plots have been divided into four distinct regions and discussed the relevant theory. According to slop variation, the conduction mechanisms occurring are different in different temperature regions. At lower temperatures, the hopping electron disorders the surroundings by moving to its neighboring Ti atoms from their equilibrium positions, causing structural defect in the polycrystalline network named small polaron. At higher temperatures, associated/unassociated interlayer ionic conduction occurs along with the alkali ions hopping through the interlayer space and electron hopping (small polaron conduction through Ti–Ti chains in these layered polar alkali titanates.

  19. The influence of low dose neutron irradiation on the thermal conductivity of Allcomp carbon foam

    Energy Technology Data Exchange (ETDEWEB)

    Burchell, Timothy D. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Porter, Wallace D. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); McDuffee, Joel Lee [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-03-01

    Oak Ridge National Laboratory was contracted via a Work for Others Agreement with Allcomp Inc. (NFE-14-05011-MSOF: Carbon Foam for Beam Stop Applications ) to determine the influence of low irradiation dose on the thermal conductivity of Allcomp Carbon Foam. Samples (6 mm dia. x 5 mm thick) were successfully irradiated in a rabbit capsule in a hydraulic tube in the target region of the High Flux Isotope Reactor at the Oak Ridge National Laboratory. The specimens were irradiated at Tirr = 747.5 C to a neutron damage dose of 0.2 dpa. There is a small dimensional and volume shrinkage and the mass and density appear reduced (we would expect density to increase as volume reduces at constant mass). The small changes in density, dimensions or volume are not of concern. At 0.2 dpa the irradiation shrinkage rate difference between the glassy carbon skeleton and the CVD coating was not sufficient to cause a large enough irradiation-induced strain to create any mechanical degradation. Similarly differential thermal expansion was not a problem. It appears that only the thermal conductivity was affected by 0.2 dpa. For the intended application conditions, i.e. @ 400 C and 0 DPA (start- up) the foam thermal conductivity is about 57 W/m.K and at 700 C and 0.2 DPA (end of life) the foam thermal conductivity is approx. 30.7 W/m.K. The room temp thermal conductivity drops from 100-120 W/m.K to approximately 30 W/m.K after 0.2 dpa of neutron irradiation.

  20. Electrical conductivity of activated carbon-metal oxide nanocomposites under compression: a comparison study.

    Science.gov (United States)

    Barroso-Bogeat, A; Alexandre-Franco, M; Fernández-González, C; Macías-García, A; Gómez-Serrano, V

    2014-12-01

    From a granular commercial activated carbon (AC) and six metal oxide (Al2O3, Fe2O3, SnO2, TiO2, WO3 and ZnO) precursors, two series of AC-metal oxide nanocomposites were prepared by wet impregnation, oven-drying at 120 °C, and subsequent heat treatment at 200 or 850 °C in an inert atmosphere. Here, the electrical conductivity of the resulting products was studied under moderate compression. The influence of the applied pressure, sample volume, mechanical work, and density of the hybrid materials was thoroughly investigated. The DC electrical conductivity of the compressed samples was measured at room temperature by the four-probe method. Compaction assays suggest that the mechanical properties of the nanocomposites are largely determined by the carbon matrix. Both the decrease in volume and the increase in density were relatively small and only significant at pressures lower than 100 kPa for AC and most nanocomposites. In contrast, the bulk electrical conductivity of the hybrid materials was strongly influenced by the intrinsic conductivity, mean crystallite size, content and chemical nature of the supported phases, which ultimately depend on the metal oxide precursor and heat treatment temperature. The supported nanoparticles may be considered to act as electrical switches either hindering or favouring the effective electron transport between the AC cores of neighbouring composite particles in contact under compression. Conductivity values as a rule were lower for the nanocomposites than for the raw AC, all of them falling in the range of semiconductor materials. With the increase in heat treatment temperature, the trend is toward the improvement of conductivity due to the increase in the crystallite size and, in some cases, to the formation of metals in the elemental state and even metal carbides. The patterns of variation of the electrical conductivity with pressure and mechanical work were slightly similar, thus suggesting the predominance of the pressure

  1. Thermal conductivity of freestanding single wall carbon nanotube sheet by Raman spectroscopy.

    Science.gov (United States)

    Sahoo, Satyaprakash; Chitturi, Venkateswara Rao; Agarwal, Radhe; Jiang, Jin-Wu; Katiyar, Ram S

    2014-11-26

    Thermal properties of single wall carbon nanotube sheets (SWCNT-sheets) are of significant importance in the area of thermal management, as an isolated SWCNT possesses high thermal conductivity of the value about 3000 W m(-1) K(-1). Here we report an indirect method of estimating the thermal conductivity of a nanometer thick suspended SWCNT-sheet by employing the Raman scattering technique. Tube diameter size is examined by the transmissions electron microscopy study. The Raman analysis of the radial breathing modes predicts narrow diameter size distribution with achiral (armchair) symmetry of the constituent SWCNTs. From the first order temperature coefficient of the A1g mode of the G band along with the laser power dependent frequency shifting of this mode, the thermal conductivity of the suspended SWCNT-sheet is estimated to be about ∼18.3 W m(-1) K(-1). Our theoretical study shows that the thermal conductivity of the SWCNT-sheet has contributions simultaneously from the intratube and intertube thermal transport. The intertube thermal conductivity (with contributions from the van der Waals interaction) is merely around 0.7 W m(-1) K(-1), which is three orders smaller than the intratube thermal conductivity, leading to an abrupt decrease in the thermal conductivity of the SWCNT-sheet as compared to the reported value for isolated SWCNT.

  2. Scratch-resistant, highly conductive, and high-strength carbon nanotube-based composite yarns.

    Science.gov (United States)

    Liu, Kai; Sun, Yinghui; Lin, Xiaoyang; Zhou, Ruifeng; Wang, Jiaping; Fan, Shoushan; Jiang, Kaili

    2010-10-26

    High-strength and conductive carbon nanotube (CNT) yarns are very attractive in many potential applications. However, there is a difficulty when simultaneously enhancing the strength and conductivity of CNT yarns. Adding some polymers into CNT yarns to enhance their strength will decrease their conductivity, while treating them in acid or coating them with metal nanoparticles to enhance their conductivity will reduce their strength. To overcome this difficulty, here we report a method to make high-strength and highly conductive CNT-based composite yarns by using a continuous superaligned CNT (SACNT) yarn as a conductive framework and then inserting polyvinyl alcohol (PVA) into the intertube spaces of the framework through PVA/dimethyl sulphoxide solution to enhance the strength of yarns. The as-produced CNT/PVA composite yarns possess very high tensile strengths up to 2.0 GPa and Young's moduli more than 120 GPa, much higher than those of the CNT/PVA yarns reported. The electric conductivity of as-produced composite yarns is as high as 9.2 × 10(4) S/m, comparable to HNO(3)-treated or Au nanoparticle-coated CNT yarns. These composite yarns are flexible, lightweight, scratch-resistant, very stable in the lab environment, and resistant to extremely humid ambient and as a result can be woven into high-strength and heatable fabrics, showing potential applications in flexible heaters, bullet-proof vests, radiation protection suits, and spacesuits.

  3. Carbon Nanotube/Conductive Additive/Space Durable Polymer Nanocomposite Films for Electrostatic Charge Dissipation

    Science.gov (United States)

    Smith, Joseph G., Jr.; Watson, Kent A.; Delozier, Donavon M.; Connell, John W.

    2003-01-01

    Thin film membranes of space environmentally stable polymeric materials possessing low color/solar absorptivity (alpha) are of interest for potential applications on Gossamer spacecraft. In addition to these properties, sufficient electrical conductivity is required in order to dissipate electrostatic charge (ESC) build-up brought about by the charged orbital environment. One approach to achieve sufficient electrical conductivity for ESC mitigation is the incorporation of single wall carbon nanotubes (SWNTs). However, when the SWNTs are dispersed throughout the polymer matrix, the nanocomposite films tend to be significantly darker than the pristine material resulting in a higher alpha. The incorporation of conductive additives in combination with a decreased loading level of SWNTs is one approach for improving alpha while retaining conductivity. Taken individually, the low loading level of conductive additives and SWNTs is insufficient in achieving the percolation level necessary for electrical conductivity. When added simultaneously to the film, conductivity is achieved through a synergistic effect. The chemistry, physical, and mechanical properties of the nanocomposite films will be presented.

  4. Unusual thermal conduction characteristics of phase change composites with single-walled carbon nanotube inclusion

    Science.gov (United States)

    Harish, Sivasankaran; Ishikawa, Kei; Chiashi, Shohei; Shiomi, Junichiro; Maruyama, Shigeo

    2013-03-01

    Thermal energy storage using phase transition materials is often employed in many engineering applications. However, the low thermal conductivity of such materials inhibits its use for large scale applications. Recently, Zheng et al. [Nature Comm. 2011] demonstrated an efficient technique using graphite suspensions to tune the thermal and electrical conductivity using temperature regulation. In this work, we report large contrasts in thermal conductivity enhancement of nano composites with single walled carbon nanotube (SWCNT) inclusions using first order phase transition process. SWCNTs synthesized by alcohol CVD were dispersed in n-octadecane by tip-sonication with sodium deoxycholate as the surfactant. Thermal conductivity measurements were carried out with transient hot-wire system [Mater. Express 2012]. Thermal conductivity enhancement in the liquid state was found to be nominal and is consistent with the predictions of Maxwell- Garnett type effective medium theory. However, in the frozen state nearly a 2.5 fold increase in thermal conductivity was observed. Similar temperature dependent thermal conductivity contrast was observed when exfoliated graphite nanoplatelets were used as the inclusions. Financial support from Grant-in-Aid for Scientific Research (22226006 and 19054003), Monbukagakusho Scholarship, Global Center of Excellence for Mechanical Systems Innovation

  5. Influence of O-2 and N-2 on the conductivity of carbon nanotube networks

    DEFF Research Database (Denmark)

    Mowbray, Duncan; Morgan, C.; Thygesen, Kristian Sommer

    2009-01-01

    We have performed experiments on single-wall carbon nanotube (SWNT) networks and compared with density-functional theory (DFT) calculations to identify the microscopic origin of the observed sensitivity of the network conductivity to physisorbed O-2 and N-2. Previous DFT calculations of the trans......We have performed experiments on single-wall carbon nanotube (SWNT) networks and compared with density-functional theory (DFT) calculations to identify the microscopic origin of the observed sensitivity of the network conductivity to physisorbed O-2 and N-2. Previous DFT calculations...... of the transmission function for isolated pristine SWNTs have found physisorbed molecules have little influence on their conductivity. However, by calculating the four-terminal transmission function of crossed SWNT junctions, we show that physisorbed O-2 and N-2 do affect the junction's conductance. This may...... be understood as an increase in tunneling probability due to hopping via molecular orbitals. We find the effect is substantially larger for O-2 than for N-2, and for semiconducting rather than metallic SWNTs junctions, in agreement with experiment....

  6. Preparation and Application of Conductive Textile Coatings Filled with Honeycomb Structured Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Filip Govaert

    2014-01-01

    Full Text Available Electrical conductive textile coatings with variable amounts of carbon nanotubes (CNTs are presented. Formulations of textile coatings were prepared with up to 15 wt % of CNT, based on the solid weight of the binder. The binders are water based polyacrylate dispersions. The CNTs were mixed into the binder dispersion starting from a commercially available aqueous CNT dispersion that is compatible with the binder dispersion. Coating formulations with variable CNT concentrations were applied on polyester and cotton woven and knitted fabrics by different textile coating techniques: direct coating, transfer coating, and screen printing. The coatings showed increasing electrical conductivity with increasing CNT concentration. The coatings can be regarded to be electrically conductive (sheet resistivity<103 Ohm/sq starting at 3 wt% CNT. The degree of dispersion of the carbon nanotubes particles inside the coating was visualized by scanning electron microscopy. The CNT particles form honeycomb structured networks in the coatings, proving a high degree of dispersion. This honeycomb structure of CNT particles is forming a conductive network in the coating leading to low resistivity values.

  7. Effect of conducting polypyrrole on the transport properties of carbon nanotube yarn

    Energy Technology Data Exchange (ETDEWEB)

    Foroughi, Javad, E-mail: foroughi@uow.edu.au [ARC Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute, University of Wollongong, Wollongong, NSW 2519 (Australia); Information and communication Technology Research Institute, University of Wollongong, Wollongong, NSW 2519 (Australia); Kimiaghalam, Bahram [Information and communication Technology Research Institute, University of Wollongong, Wollongong, NSW 2519 (Australia); Ghorbani, Shaban Reza [Department of Physics, Hakim Sabzevari University, P.O. Box 397, Sabzevar (Iran, Islamic Republic of); Safaei, Farzad [Information and communication Technology Research Institute, University of Wollongong, Wollongong, NSW 2519 (Australia); Abolhasan, Mehran [Faculty of Engineering and IT University of Technology Sydney, Sydney, NSW Australia (Australia)

    2012-10-01

    Experiments were conducted to measure the electrical conductivity in three types of pristine and carbon nanotube-polypyrrole (CNT-PPy) composite yarns and its dependence on over a wide temperature range. The experimental results fit well with the analytical models developed. The effective energy separation between localized states of the pristine CNT yarn is larger than that for both the electrochemically and chemically prepared CNT-PPy yarns. It was found that all samples are in the critical regime in the insulator-metal transition, or close to the metallic regime at low temperature. The electrical conductivity results are in good agreement with a Three Dimensional Variable Range Hopping model at low temperatures, which provides a strong indication that electron hopping is the main means of current transfer in CNT yarns at T < 100 K. We found that the two shell model accurately describes the electronic properties of CNT and CNT-PPy composite yarns in the temperature range of 5-350 K. - Highlights: Black-Right-Pointing-Pointer We developed hybrid carbon nanotube conducting polypyrrole composite yarns. Black-Right-Pointing-Pointer The main current transfer scheme in yarn is via three dimensional electrons hopping. Black-Right-Pointing-Pointer Two shell model describes well electronic properties of yarns in range of 5-350 K.

  8. Modeling the effects of electrical and non-electrical parameters on the material removal and surface integrity in case of µEDM of a non-conductive ceramic material using a combined fuzzy-AOM approach

    DEFF Research Database (Denmark)

    Puthumana, Govindan

    2016-01-01

    and surface integrity for a non-conductive ceramic material. The fuzzy logic modeling system is employed for predicting the μEDM process responses. The trends in the material removal rate and hardness values with the chosen electrical and non-electrical parameter for the model and obtained using AOM approach...

  9. A new approach to modeling the effective thermal conductivity of ceramics porous media using a generalized self-consistent method

    Science.gov (United States)

    Edrisi, Siroos; Bidhendi, Norollah Kasiri; Haghighi, Maryam

    2017-01-01

    Effective thermal conductivity of the porous media was modeled based on a self-consistent method. This model estimates the heat transfer between insulator surface and air cavities accurately. In this method, the pore size and shape, the temperature gradient and other thermodynamic properties of the fluid was taken into consideration. The results are validated by experimental data for fire bricks used in cracking furnaces at the olefin plant of Maroon petrochemical complexes well as data published for polyurethane foam (synthetic polymers) IPTM and IPM. The model predictions present a good agreement against experimental data with thermal conductivity deviating <1 %.

  10. Effect of HIPing on conductivity and impedance measurements of DyBi5Fe2Ti3O18 ceramics

    Indian Academy of Sciences (India)

    N V Prasad; G Prasad; Mahendra Kumar; S V Suryanarayana; T Bhimasankaram; G S Kumar

    2000-12-01

    X-ray diffraction, a.c. impedance and conductivity (a.c. and d.c.) have been used to characterize DyBi5Fe2Ti3O18. Samples were prepared by solid state double sintering method. A few samples were also subjected to hot isostatic pressing (HIP) at 800°C for 2 h at 100 MPa pressure. The data on XRD, impedance and conductivity of two sets of samples are compared to understand study of effect of HIPing on the properties of DyBi5Fe2Ti3O18.

  11. Facile synthesis and electrical conductivity of carbon nanotube reinforced nanosilver composite

    Energy Technology Data Exchange (ETDEWEB)

    Pal, Hemant [National Institute of Technology, Hamirpur (India). Dept. of Physics; Govt. College Chowari, Chamba (H.P.) (India). Dept. of Physics; Sharma, Vimal [National Institute of Technology, Hamirpur (India). Dept. of Physics; Kumar, Rajesh [Jaypee Univ. of Information and Technology, Solan (H.P.) (India). Dept. of Physics; Thakur, Nagesh [Himachal Pradesh Univ., Shimla (H.P.) (India). Dept. of Physics

    2012-12-15

    Metal matrix nanocomposites reinforced with carbon nanotubes (CNTs) have become popular in industrial applications. Due to their excellent thermophysical and mechanical properties, CNTs are considered as attractive filler for the improvement in properties of metals. In the present work, we have synthesized noncovalently functionalized CNT reinforced nanosilver composites by using a modified molecular level mixing method. The structure and morphology of nanocomposites are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy dispersive spectroscopy. The electrical conductivity of silver-CNT nanocomposites measured by the four-point probe method is found to be more than that of the pure nanosilver. The significant improvement in electrical conductivity of Ag/CNT nanocomposites stems from homogenous and embedded distribution of CNTs in a silver matrix with intact structure resulting from noncovalent functionalization. The low temperature sintering also enhances the electrical conductivity of Ag/CNT nanocomposites. (orig.)

  12. Heat Conductivity of One-Dimensional Carbon Chain in an External Potential

    Institute of Scientific and Technical Information of China (English)

    GE Yong; DONG Jin-Ming

    2007-01-01

    The heat transport in a one-dimensional (1D) carbon nanowire (CNW) lying in an external potential with different amplitudes and periods is studied by the non-equilibrium molecular dynamics method. It is found that the thermal conductivity of CNW is always anomalous, increasing with the CNW length and obeying the power law κ~ N, in which α decreases with the increasing external potential amplitude. The thermal conductivity could be enhanced by the external potential with rather larger amplitudes, which means that an applied external potential could be an efficient tool to improve the heat conductivity of a real 1D material. In addition, the effect of different periods of the external potential is studied, finding the external potential with an incommensurate period leads to the smaller α value.

  13. NONLINEAR CURRENT-VOLTAGE CHARACTERISTICS OF CONDUCTIVE POLYETHYLENE COMPOSITES WITH CARBON BLACK FILLED PET MICROFIBRILS

    Institute of Scientific and Technical Information of China (English)

    Qian-ying Chen; Jing Gao; Kun Dai; Huan Pang; Jia-zhuang Xu; Jian-hua Tang; Zhong-ming Li

    2013-01-01

    Current-voltage electrical behavior of in situ microfibrillar carbon black (CB)/poly(ethylene terephthalate)(PET)/polyethylene (PE) (m-CB/PET/PE) composites with various CB concentrations at ambient temperatures was studied under a direct-current electric field.The current-voltage (Ⅰ-Ⅴ) curves exhibited nonlinearity beyond a critical value of voltage.The dynamic random resistor network (DRRN) model was adopted to semi-qualitatively explain the nonlinear conduction behavior of m-CB/PET/PE composites.Macroscopic nonlinearity originated from the interracial interactions between CB/PET micro fibrils and additional conduction channels.Combined with the special conductive networks,an illustration was proposed to interpret the nonlinear Ⅰ-Ⅴ characteristics by a field emission or tunneling mechanism between CB particles in the CB/PET microfibers intersections.

  14. Inkjet printing of flexible high-performance carbon nanotube transparent conductive films by ``coffee ring effect''

    Science.gov (United States)

    Shimoni, Allon; Azoubel, Suzanna; Magdassi, Shlomo

    2014-09-01

    Transparent and flexible conductors are a major component in many modern optoelectronic devices, such as touch screens for smart phones, displays, and solar cells. Carbon nanotubes (CNTs) offer a good alternative to commonly used conductive materials, such as metal oxides (e.g. ITO) for flexible electronics. The production of transparent conductive patterns, and arrays composed of connected CNT ``coffee rings'' on a flexible substrate poly(ethylene terephthalate), has been reported. Direct patterning is achieved by inkjet printing of an aqueous dispersion of CNTs, which self-assemble at the rim of evaporating droplets. After post-printing treatment with hot nitric acid, the obtained TCFs are characterized by a sheet resistance of 156 Ω sq-1 and transparency of 81% (at 600 nm), which are the best reported values obtained by inkjet printing of conductive CNTs. This makes such films very promising as transparent conductors for various electronic devices, as demonstrated by using an electroluminescent device.

  15. Highly conductive, transparent flexible films based on open rings of multi-walled carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Ko, Wen-Yin; Su, Jun-Wei; Guo, Chian-Hua; Fu, Shu-Juan; Hsu, Chuen-Yuan; Lin, Kuan-Jiuh, E-mail: kjlin@dragon.nchu.edu.tw

    2011-09-01

    Open rings of multi-walled carbon nanotubes were stacked to form porous networks on a poly(ethylene terephthalate) substrate to form a flexible conducting film (MWCNT-PET) with good electrical conductivity and transparency by a combination of ultrasonic atomization and spin-coating technique. To enhance the electric flexibility, we spin-coated a cast film of poly(vinyl alcohol) onto the MWCNT-PET substrate, which then underwent a thermo-compression process. Field-emission scanning electron microscopy of the cross-sectional morphology illustrates that the film has a robust network with a thickness of {approx} 175 nm, and it remarkably exhibits a sheet resistance of approximately 370 {Omega}/sq with {approx} 77% transmittance at 550 nm even after 500 bending cycles. This electrical conductivity is much superior to that of other MWCNT-based transparent flexible films.

  16. Thermal Moore's law and near-field thermal conductance in carbon-based electronics

    Science.gov (United States)

    Rotkin, Slava V.

    2009-08-01

    The novel thermal conductance mechanism, theoretically predicted and experimentally measured in nanotube field-effect transistors (FET), is discussed with respect to the power dissipation problem of modern carbon-based electronics. Such an effect is due to the near-field coupling of the charge carriers in the transistor channel with the local electric field of the surface electromagnetic modes. The coupling leads to a quantum electrodynamic (QED) energy exchange between the hot electrons in FET channel and the optical polar phonon bath being in thermal equilibrium with the substrate. For an example of a NT on silica, this QED coupling mechanism is shown to exceed significantly the interface Kapitza conductance, that is, the classical phonon heat transport. The QED thermal conductance is proposed to play dominant role in the energy dissipation in nanoelectronics with a hetero-interface between the device channel and the polar substrate.

  17. Fabrication of flexible transparent conductive films from long double-walled carbon nanotubes

    Directory of Open Access Journals (Sweden)

    Naoki Imazu

    2014-04-01

    Full Text Available The fabrication of flexible transparent conducting films (TCFs is important for the development of the next-generation flexible devices. In this study, we used double-walled carbon nanotubes (DWCNTs as the starting material and described a fabrication method of flexible TCFs. We have determined in a quantitative way that the key factors are the length and the dispersion states of the DWCNTs as well as the weight-ratios of dispersant polymer/DWCNTs. By controlling such factors, we have readily fabricated a flexible highly transparent (94% transmittance and conductive (surface resistivity = 320 Ω sq−1 DWCNT film without adding any chemical doping that is often used to reduce the surface resistivity. By applying a wet coating, we have succeeded in the fabrication of large-scale conducting transparent DWCNT films based on the role-to-role method.

  18. Carbon nanotubes increase the electrical conductivity of fibroblast-seeded collagen hydrogels.

    Science.gov (United States)

    MacDonald, Rebecca A; Voge, Christopher M; Kariolis, Mihalis; Stegemann, Jan P

    2008-11-01

    Carbon nanotubes are attractive as additives in fiber-reinforced composites due to their high aspect ratio, strength and electrical conductivity. In the present study, solubilized collagen Type I was polymerized in the presence of dispersed single-walled carbon nanotubes (SWNT) and human dermal fibroblast cells (HDF) to produce collagen-SWNT composite biomaterials with HDF embedded directly in the matrix. The resulting constructs, with SWNT loadings of 0 (control), 0.8, 2.0 and 4.0 wt.% SWNT, were cultured and electrical properties were evaluated in the frequency range 5-500 kHz at days 3 and 7. All collagen-SWNT hydrogel matrices underwent HDF-mediated gel compaction over time in culture, but the presence of SWNT significantly decreased the rate and extent of gel compaction. Viability of HDF in all constructs was consistently high and cell morphology was not affected by the presence of SWNT. However, cell number at day 7 in culture decreased with increasing SWNT loading. Electrical conductivity of the constructs varied from 3 to 7 mS cm(-1), depending on SWNT loading level. Conductivity increased uniformly with increasing wt.% of SWNT (R=0.78) and showed a modest frequency dependence, suggesting that the electrical percolation threshold had not been reached in these materials. These data demonstrate that the electrical conductivity of cell-seeded collagen gels can be increased through the incorporation of carbon nanotubes. Protein-SWNT composite materials may have application as scaffolds for tissue engineering, as substrates to study electrical stimulation of cells, and as transducers or leads for biosensors.

  19. Third order optical nonlinear studies on highly conducting vertically aligned carbon nanoflakes

    Science.gov (United States)

    Singh, Mukesh; Kumar, Indrajeet; Khare, Alika; Agarwal, Pratima

    2016-12-01

    Third order optical nonlinearity of carbon nanoflakes were studied by modified single beam closed aperture Z-scan technique using a continuous wave He-Ne laser at 632.8 nm. Thin films of vertically aligned carbon nanoflakes were synthesized on corning glass substrate at substrate temperature of 400 °C by hot filament chemical vapor deposition. Films were characterized by scanning electron microscope and atomic force microscopy which confirmed that carbon nanoflakes were vertically aligned on the substrate. Temperature dependent electrical conductivity measurements in temperature range of 300-480 K under high vacuum (˜10-5 mbar) showed that conductivity of the films was increased almost linearly with increasing temperature with a weak temperature dependence. The negative temperature coefficient of resistance indicates semiconducting behavior of the films. Nonlinear refractive index coefficient (n 2) of the films was found to be of the order of 10-5 cm2 W-1, which can be important for the applications in the field of nonlinear photonics.

  20. Thermal Conductivity of Ethylene Vinyl Acetate Copolymer/Carbon Nanofiller Blends

    Science.gov (United States)

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

    2007-01-01

    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.

  1. Wrapping and dispersion of multiwalled carbon nanotubes improves electrical conductivity of protein-nanotube composite biomaterials.

    Science.gov (United States)

    Voge, Christopher M; Johns, Jeremy; Raghavan, Mekhala; Morris, Michael D; Stegemann, Jan P

    2013-01-01

    Composites of extracellular matrix proteins reinforced with carbon nanotubes have the potential to be used as conductive biopolymers in a variety of biomaterial applications. In this study, the effect of functionalization and polymer wrapping on the dispersion of multiwalled carbon nanotubes (MWCNT) in aqueous media was examined. Carboxylated MWCNT were wrapped in either Pluronic(®) F127 or gelatin. Raman spectroscopy and X-ray photoelectron spectroscopy showed that covalent functionalization of the pristine nanotubes disrupted the carbon lattice and added carboxyl groups. Polymer and gelatin wrapping resulted in increased surface adsorbed oxygen and nitrogen, respectively. Wrapping also markedly increased the stability of MWCNT suspensions in water as measured by settling time and zeta potential, with Pluronic(®)-wrapped nanotubes showing the greatest effect. Treated MWCNT were used to make 3D collagen-fibrin-MWCNT composite materials. Carboxylated MWCNT resulted in a decrease in construct impedance by an order of magnitude, and wrapping with Pluronic(®) resulted in a further order of magnitude decrease. Functionalization and wrapping also were associated with maintenance of fibroblast function within protein-MWCNT materials. These data show that increased dispersion of nanotubes in protein-MWCNT composites leads to higher conductivity and improved cytocompatibility. Understanding how nanotubes interact with biological systems is important in enabling the development of new biomedical technologies.

  2. The strengthening effect of 1D carbon materials on magnetorheological plastomers: mechanical properties and conductivity

    Science.gov (United States)

    Xu, Jiaqi; Xuan, Shouhu; Pang, Haoming; Gong, Xinglong

    2017-03-01

    This work reported novel multifunctional carbon filler-doped magnetorheological plastomers (CMRPs) and their magnetic–mechanical–conductive coupling properties. Here, the one-dimensional carbon fillers, such as carbon micro-fibers (CFs), carbon nanotubes (CNTs) and their mixtures (CFs and CNTs) were dispersed into the matrix for the final product. It was found that the CMRPs with 7.5 wt% CFs and 0.5 wt% CNTs had an excellent magnetorheological (MR) effect (2200%) and magnetic field dependent electrical property. Specifically, the resistance was reduced by two orders of magnitude with the magnetic field increasing from 0 to 900 mT. Moreover, the relationship between resistance and strain was also discovered. The resistance increased by three orders of magnitude due to the amplitude of oscillation, which was 10% in the absence of the magnetic field, while the resistance would decrease by three orders of magnitude under a 900 mT magnetic field. The variation range of the resistance increased with the increasing oscillation amplitude, and the period of the resistance was half of the period of the strain. To conclude, the possible mechanism for the multifunctional properties was discussed.

  3. Assessment of Interactions Between Stomatal Conductance, Evapotranspiration, Carbon and Irrigated Soil Salinity

    Science.gov (United States)

    Runkle, B.; Liang, X.

    2006-12-01

    Hydrological behavior and soil salinity are intricately linked in many agricultural environments. Fluxes of energy, water, and carbon dioxide are critical to the response of plants to soil salinity. A physically based plant water use model is developed to examine the problem of soil salinity as it relates to evapotranspiration and plant water uptake in an arid agricultural region. This model incorporates carbon dynamics and photosynthetic activity into the plant water use model, and examines the nonlinear manner in which plants respond to increased soil salinity. Higher soil osmotic pressure resulting from increased ionic presence increases the resistance to water flow through the plant; this change also impacts the assimilation of carbon dioxide through the stomatal opening. Canopy and ecosystem fluxes are now measured with such intensity as to allow comprehensive diurnal analysis of the effects of soil water and salt status on plant water, carbon, and energy fluxes. Initial results show that at higher salinity levels, non-linear and higher variable changes occur to stomatal conductance and evapotranspiration. Scaling these results to the daily or weekly level may be of great use to agricultural planners in their water management decisions.

  4. FIBROUS CERAMIC-CERAMIC COMPOSITE MATERIALS PROCESSING AND PROPERTIES

    OpenAIRE

    1986-01-01

    The introduction of continuous fibers in a ceramic matrix can improve its toughness, if the fiber-matrix bonding is weak enough, due to matrix microcracking and fiber pull-out. Ceramic-ceramic composite materials are processed according to liquid or gas phase techniques. The most important are made of glass, carbide, nitride or oxide matrices reinforced with carbon, SiC or Al2O3 fibers.

  5. Multiscale Modeling of Ultra High Temperature Ceramics (UHTC) ZrB2 and HfB2: Application to Lattice Thermal Conductivity

    Science.gov (United States)

    Lawson, John W.; Daw, Murray S.; Squire, Thomas H.; Bauschlicher, Charles W.

    2012-01-01

    We are developing a multiscale framework in computational modeling for the ultra high temperature ceramics (UHTC) ZrB2 and HfB2. These materials are characterized by high melting point, good strength, and reasonable oxidation resistance. They are candidate materials for a number of applications in extreme environments including sharp leading edges of hypersonic aircraft. In particular, we used a combination of ab initio methods, atomistic simulations and continuum computations to obtain insights into fundamental properties of these materials. Ab initio methods were used to compute basic structural, mechanical and thermal properties. From these results, a database was constructed to fit a Tersoff style interatomic potential suitable for atomistic simulations. These potentials were used to evaluate the lattice thermal conductivity of single crystals and the thermal resistance of simple grain boundaries. Finite element method (FEM) computations using atomistic results as inputs were performed with meshes constructed on SEM images thereby modeling the realistic microstructure. These continuum computations showed the reduction in thermal conductivity due to the grain boundary network.

  6. Lattice Thermal Conductivity of Ultra High Temperature Ceramics (UHTC) ZrB2 and HfB2 from Atomistic Simulations

    Science.gov (United States)

    Lawson, John W.; Daw, Murray S.; Bauschlicher, Charles W.

    2012-01-01

    Ultra high temperature ceramics (UHTC) including ZrB2 and HfB2 have a number of properties that make them attractive for applications in extreme environments. One such property is their high thermal conductivity. Computational modeling of these materials will facilitate understanding of fundamental mechanisms, elucidate structure-property relationships, and ultimately accelerate the materials design cycle. Progress in computational modeling of UHTCs however has been limited in part due to the absence of suitable interatomic potentials. Recently, we developed Tersoff style parameterizations of such potentials for both ZrB2 and HfB2 appropriate for atomistic simulations. As an application, Green-Kubo molecular dynamics simulations were performed to evaluate the lattice thermal conductivity for single crystals of ZrB2 and HfB2. The atomic mass difference in these binary compounds leads to oscillations in the time correlation function of the heat current, in contrast to the more typical monotonic decay seen in monoatomic materials such as Silicon, for example. Results at room temperature and at elevated temperatures will be reported.

  7. Microstructure and Electrical Conductivity of CNTs/PMMA Nanocomposite Foams Foaming by Supercritical Carbon Dioxide

    Institute of Scientific and Technical Information of China (English)

    YUAN Huan; XIONG Yuanlu; LUO Guoqiang; LI Meijuan; SHEN Qiang; ZHANG Lianmeng

    2016-01-01

    The carbon nanotubes (CNTs)/ polymethylmethacrylate (PMMA) nanocomposite foams were prepared by the anti-solvent precipitation and supercritical foaming method. The morphology and the electrical conductivity of the foams with different kinds of CNTs were investigated. The experimental results showed that all the foams had uniform cell structure, and the cell size changed from 1.9 to 10 μm when the foaming temperature ranged from 50℃ to 95℃. With small cell size (1.9-4.0 μm), the conductivities of the foams were 3.34×10-6-4.16×10-6 S/cm compared with the solid matrix since the introduction of micro cells did not destroy the conductive network. However, when the cell size was biger (4.5-10 μm), the aspect ratio of the CNTs played the dominant role of the conductivity. The foams with short CNTs had higher conductivity, since the short CNTs were hard to stretch and snap by the cells and can well-dispersed in the cell wall and cell edges. The results of this work provided a novel material design method for conductive foams based on the rule of both microstructure and aspect ratio of the CNTs.

  8. Conductivity study of PEO–LiClO4 polymer electrolyte doped with ZnO nanocomposite ceramic filler

    Indian Academy of Sciences (India)

    S U Patil; S S Yawale; S P Yawale

    2014-10-01

    The preparation and characterization of composite polymer electrolytes comprising PEO and LiClO4 with different concentrations of ZnO nanoparticles are studied. Conductivity measurements were carried out and discussed. In order to ascertain the thermal stability of the polymer electrolyte with maximum conductivity, films were subjected to TG/DTA analysis in the range of 298–823 K. In the present work, FTIR spectroscopy is used to study polymer structure and interactions between PEO and LiClO4, which can make changes in the vibrational modes of the atoms or molecules in the material. FTIR spectra show the complexation of LiClO4 with PEO. The SEM photographs indicated that electrolytes are miscible and homogeneous.

  9. Complex impedance, dielectric relaxation and electrical conductivity studies of Ba1-xSrxTiO3 ceramics

    Science.gov (United States)

    Elbasset, A.; Sayouri S, S.; Abdi, F.; Lamcharfi, T.; Mrharrab, L.

    2017-03-01

    In this work, we prepared series of Ba1-xSrxTiO3 (BSxT) powders, with different strontium concentrations (x = 0, 0.025, 0.75, 0.10, 0.125 and 0.15), by the sol-gel method. The variation of structure in the Ba1-xSrxTiO3 system was analyzed using XRD and Raman techniques. The field dependence of dielectric relaxation and conductivity was measured over a wide frequency range from room temperature to 400 °C. The activation energy, calculated from the thermal variation of the conductivity for different frequencies, showed that the Sr has significant effects on the properties of BaTiO3. Relaxation times extracted using the imaginary part of the complex impedance (Z’’(ω)) and the modulus (M’’(ω)) were also found to follow the Arrhenius law and showed an anomaly around the phase transition temperature.

  10. Mesophyll conductance and leaf carbon isotope composition of two high elevation conifers along an altitudinal gradient

    Science.gov (United States)

    Guo, J.; Beverly, D.; Cook, C.; Ewers, B.; Williams, D. G.

    2016-12-01

    Carbon isotope ratio values (δ13C) of conifer leaf material generally increases with elevation, potentially reflecting decreases in the leaf internal to ambient CO2 concentration ratio (Ci/Ca) during photosynthesis. Reduced stomatal conductance or increased carboxylation capacity with increasing elevation could account for these patterns. But some studies reported conifers δ13C increased with altitude consistently, but Ci/Ca did not significantly decrease and leaf nitrogen content remained constant with increasing of altitude in Central Rockies. Variation in leaf mesophyll conductance to CO2 diffusion, which influences leaf δ13C independently of effects related to stomatal conductance and carboxylation demand, might reconcile these conflicting observations. Leaf mass per unit area (LMA) increases with altitude and often correlates with δ13C and mesophyll conductance. Therefore, we hypothesized that increases in δ13C of conifers with altitude are controlled mainly by changes in mesophyll conductance. To test this hypothesis, leaf δ13C, photosynthetic capacity, leaf nitrogen content, LMA, and mesophyll conductance were determined on leaves of two dominant conifers (Pinus contorta and Picea engelmannii) along a 90-km transect in SE Wyoming at altitudes ranging from 2400 to 3200 m above sea level. Mesophyll conductance was determined by on-line 13C discrimination using isotope laser spectroscopy. We expected to observe relatively small differences in stomatal conductance and decreases in mesophyll conductance from lower and higher altitude sites. Such a pattern would have important implications for how differences in leaf δ13C values across altitude are interpreted in relation to forest water use and productivity from scaling of leaf-level water-use efficiency.

  11. Low temperature hall effect investigation of conducting polymer-carbon nanotubes composite network.

    Science.gov (United States)

    Bahrami, Afarin; Talib, Zainal Abidin; Yunus, Wan Mahmood Mat; Behzad, Kasra; M Abdi, Mahnaz; Din, Fasih Ud

    2012-11-14

    Polypyrrole (PPy) and polypyrrole-carboxylic functionalized multi wall carbon nanotube composites (PPy/f-MWCNT) were synthesized by in situ chemical oxidative polymerization of pyrrole on the carbon nanotubes (CNTs). The structure of the resulting complex nanotubes was characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The effects of f-MWCNT concentration on the electrical properties of the resulting composites were studied at temperatures between 100 K and 300 K. The Hall mobility and Hall coefficient of PPy and PPy/f-MWCNT composite samples with different concentrations of f-MWCNT were measured using the van der Pauw technique. The mobility decreased slightly with increasing temperature, while the conductivity was dominated by the gradually increasing carrier density.

  12. Transparent conducting film: Effect of vacuum filtration of carbon nanotube suspended in oleum

    Indian Academy of Sciences (India)

    Tsuyoshi Saotome; Hansang Kim; Zhe Wang; David Lashmore; H Thomas Hahn

    2011-07-01

    Vacuum filtration process to fabricate a transparent conducting carbon nanotube (CNT) film is reported. A CNT mat, which is a fibrous sheet of long multi-walled carbon nanotubes (MWNT), was prepared and dispersed in oleum by solution-sonication. The suspension was then vacuum filtered to obtain a thin MWNT layer with improved dispersion. Sheet resistance of the obtained MWNT layer was increased despite the improved dispersion. SEM micrographs and energy dispersive spectroscopy results indicated that the increase of the sheet resistance could be attributed to degradation and oxidation of the MWNT bundles. Though the chemical approach in this study did not improve the electrical property of the CNT mat, a mechanical approach proposed in our recent work was deemed suitable to enhance optical and electrical properties of the CNT mat.

  13. Structural stability of transparent conducting films assembled from length purified single-wall carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    J. M. Harris; G. R. S. Iyer; D. O. Simien; J. A. Fagan; J. Y. Huh; J. Y. Chung; S. D. Hudson; J. Obrzut; J. F. Douglas; C. M. Stafford; E. K. Hobbie

    2011-01-01

    Single-wall carbon nanotube (SWCNT) films show significant promise for transparent electronics applications that demand mechanical flexibility, but durability remains an outstanding issue. In this work, thin membranes of length purified single-wall carbon nanotubes (SWCNTs) are uniaxially and isotropically compressed by depositing them on prestrained polymer substrates. Upon release of the strain, the topography, microstructure, and conductivity of the films are characterized using a combination of optical/fluorescence microscopy, light scattering, force microscopy, electron microscopy, and impedance spectroscopy. Above a critical surface mass density, films assembled from nanotubes of well-defined length exhibit a strongly nonlinear mechanical response. The measured strain dependence reveals a dramatic softening that occurs through an alignment of the SWCNTs normal to the direction of prestrain, which at small strains is also apparent as an anisotropic increase in sheet resistance along the same direction. At higher strains, the membrane conductivities increase due to a compression-induced restoration of conductive pathways. Our measurements reveal the fundamental mode of elasto-plastic deformation in these films and suggest how it might be suppressed.

  14. Physico-mechanical and electrical properties of conductive carbon black reinforced chlorosulfonated polyethylene vulcanizates

    Directory of Open Access Journals (Sweden)

    2008-12-01

    Full Text Available The present work deals with the effect of conductive carbon black (Ensaco 350G on the physico-mechanical and electrical properties of chlorosulfonated polyethylene (CSM rubber vulcanizates. The physico-mechanical properties like tensile strength, tear strength, elongation at break, compression set, hardness and abrasion resistance have been studied before and after heat ageing. Up to 30 parts per hundred rubber (phr filler loading both tensile and tear strength increases beyond which it shows a decreasing trend whereas modulus gradually increases with the filler loading. Incorporation of carbon black increases the hysteresis loss of filled vulcanizates compared to gum vulcanizates. Unlike gum vulcanizate, in filled vulcanizates the rate of relaxation shows increasing trend. The bound rubber content is found to increase with increase in filler loading. Dielectric relaxation spectra were used to study the relaxation behavior as a function of frequency (100 to 106 Hz at room temperature. Variation in real and imaginary parts of electric modulus has been explained on the basis of interfacial polarization of fillers in the polymer medium. The percolation limit of the conductive black as studied by ac conductivity measurements has also been reported.

  15. Calculation of the transport properties of carbon dioxide. II. Thermal conductivity and thermomagnetic effects

    Science.gov (United States)

    Bock, Steffen; Bich, Eckard; Vogel, Eckhard; Dickinson, Alan S.; Vesovic, Velisa

    2004-05-01

    The transport properties of pure carbon dioxide have been calculated from the intermolecular potential using the classical trajectory method. Results are reported in the dilute-gas limit for thermal conductivity and thermomagnetic coefficients for temperatures ranging from 200 K to 1000 K. Three recent carbon dioxide potential energy hypersurfaces have been investigated. Since thermal conductivity is influenced by vibrational degrees of freedom, not included in the rigid-rotor classical trajectory calculation, a correction for vibration has also been employed. The calculations indicate that the second-order thermal conductivity corrections due to the angular momentum polarization (Bukowski et al. (1999) are in good agreement with the available experimental data. They underestimate the best experimental data at room temperature by 1% and in the range up to 470 K by 1%-3%, depending on the data source. Outside this range the calculated values, we believe, may be more reliable than the currently available experimental data. Our results are consistent with measurements of the thermomagnetic effect at 300 K only when the vibrational degrees of freedom are considered fully. This excellent agreement for these properties indicates that particularly the potential surface of Bukowski et al. provides a realistic description of the anisotropy of the surface.

  16. Electrical conduction in (Na0.125Bi0.125Ba0.65Ca0.1)(Nd0.065Ti0.87Nb0.065)O3 ceramic

    Indian Academy of Sciences (India)

    Syed Mahboob; G Prasad; G S Kumar

    2006-02-01

    Polycrystalline ceramic samples of sodium bismuth titanate with simultaneous doping at A and B sites have been studied for the influence of these dopants on the electrical conduction mechanism. A.C. conductivity measurements were done on the prepared sample in a wide range of frequency and temperature. These studies revealed that the conduction in the sample arises due to hopping of bound charges. Four-term power law is used to characterize the frequency dependence of a.c. conductivity. From the temperature dependence of the exponents, the a.c. conduction in the samples is explained.

  17. Fracture Toughness of Carbon Nanotube-Reinforced Metal- and Ceramic-Matrix Composites

    Directory of Open Access Journals (Sweden)

    Y. L. Chen

    2011-01-01

    Full Text Available Hierarchical analysis of the fracture toughness enhancement of carbon nanotube- (CNT- reinforced hard matrix composites is carried out on the basis of shear-lag theory and facture mechanics. It is found that stronger CNT/matrix interfaces cannot definitely lead to the better fracture toughness of these composites, and the optimal interfacial chemical bond density is that making the failure mode just in the transition from CNT pull-out to CNT break. For hard matrix composites, the fracture toughness of composites with weak interfaces can be improved effectively by increasing the CNT length. However, for soft matrix composite, the fracture toughness improvement due to the reinforcing CNTs quickly becomes saturated with an increase in CNT length. The proposed theoretical model is also applicable to short fiber-reinforced composites.

  18. Ceramic anode catalyst for dry methane type molten carbonate fuel cell

    Science.gov (United States)

    Tagawa, T.; Yanase, A.; Goto, S.; Yamaguchi, M.; Kondo, M.

    Oxide catalyst materials for methane oxidation were examined in order to develop the anode electrode for molten carbonate type fuel cell (MCFC). As a primary selection, oxides such as lanthanum (La 2O 3) and samarium (Sm 2O 3) were selected from screening experiments of TPD, TG and tubular reactor. Composite materials of these oxides with titanium fine powder were assembled into a cell unit for MCFC as the anode electrode. Steady-state activities were observed with these anode electrode materials when hydrogen was used as a fuel. When methane was directly charged to anode as a fuel (dry methane operation), a power generation with steady state was observed on both lanthanum and samarium composites after gradual decrease of open circuit electromotive force (OCV) and closed circuit current (CCI). The steady-state activity held as long as 144 h of continuous operation.

  19. 固态质子导电器件的研究综述%Solid State Protonic Devices Using Proton Conducting Ceramics

    Institute of Scientific and Technical Information of China (English)

    Hiroyasu Iwahara

    2004-01-01

    固体中质子运动的科学与技术称为质子学.本文纵览了基于质子导电陶瓷的种种可能的质子学器件.这些器件不仅有利于提高当前的科技质量,同时也将有助于构建未来的氢能系统.质子学器件按其应用方式可以分为两类,一类是利用其电动势,另一类利用质子优先传输性能.原电池型的氢传感器和燃料电池属于前者,氢泵、蒸汽电解器和膜反应器属于后者.原则上由上述器件可以推演开发出更多的改进型式.应用钙钛矿型氧化物高温质子导电陶瓷,已经制备了几种质子导电器件,虽然尚处于实验室规模但已证明具有肯定的技术功能.%"Science and technology" of protons in motion in solids is called protonics.This paper surveys the possible protonic devices using a proton-conducting ceramic. They will contribute not only to the enhancement of the quality of technology at present but also to the construction of a hydrogen energy system in the near future. The protonic devices are classified into two categories; the devices utilizing electromotive force and those utilizing preferential transport of protons. Galvanic cell type hydrogen sensors and fuel cells belong to the former, and hydrogen pump, steam electrolyzer and membrane reactors to the latter. Many kinds of modifications can be derived, in principle, from the devices described above. Using high temperature proton-conducting ceramics based on perovskitetype oxides, some of the devices were made on a laboratory-scale, and have been positively verified to work.

  20. Carbon Nanotube/Cu Nanowires/Epoxy Composite Mats with Improved Thermal and Electrical Conductivity.

    Science.gov (United States)

    Xing, Yajuan; Cao, Wei; Li, Wei; Chen, Hongyuan; Wang, Miao; Wei, Hanxing; Hu, Dongmei; Chen, Minghai; Li, Qingwen

    2015-04-01

    Polymer composites with carbon nanofillers have been regarded as a promising candidate for electronic package materials. The challenge for such materials is to increase the electrical and thermal conductivity of the composites. Herein, we reported an epoxy composite film with high thermal and electrical conductivity that were prepared by loading high volume fraction of well-dispersed multi-walled carbon nanotubes (MWCNTs, around 50 nm in diameter, 1-10 µm in length) and copper nanowires (Cu NWs, 60-70 nm in diameter, 1-5 µm in length) in epoxy matrix. The MWCNT-Cu NW hybrid mats were prepared by a vacuum filtration method with an optimum Cu NW content of 50 wt%. The hybrid mats was then impregnated by epoxy solution to prepare epoxy composite films. The epoxy was modified by the toughening agent to make the composite films tough and flexible. The loading fraction of MWCNTs and Cu NWs was tuned by controlling the viscosity of epoxy solution. A remarkable synergetic effect between the MWCNTs and Cu NWs in improving the electrical and thermal conductivity of epoxy composites was demonstrated. The results showed that the electrical conductivity of nanocomposites with 42.5 wt% epoxy was 1500 S/m, and the thermal conductivity was 2.83 W/m K, which was 10.1 times of the neat epoxy. Its thermal resistance was as low as 1% of the pure epoxy. And the mechanical properties of composites were also investigated. These robust and flexible nanocomposites showed prospective applications as thermal interface materials (TIMs) in the electronic industry.

  1. Conductive additive content balance in Li-ion battery cathodes: Commercial carbon blacks vs. in situ carbon from LiFePO{sub 4}/C composites

    Energy Technology Data Exchange (ETDEWEB)

    Palomares, Veronica; Goni, Aintzane; Muro, Izaskun Gil de; Rojo, Teofilo [Departamento de Quimica Inorganica, Universidad del Pais Vasco UPV/EHU, P.O. Box. 644, 48080, Bilbao (Spain); de Meatza, Iratxe; Bengoechea, Miguel [Energy Department, CIDETEC-IK4, P Miramon 196, Parque Tecnologico de San Sebastian, 20009, San Sebastian (Spain); Cantero, Igor [Departamento I+D+i Nuevas Tecnologias, CEGASA, Artapadura, 11, 01013 Vitoria-Gasteiz (Spain)

    2010-11-15

    Two samples of commercial conducting carbon black and the carbon generated in situ during LiFePO{sub 4}/C composite synthesis from citric acid are studied, with the aim of finding out whether carbon from the composite can fulfil the same function as carbon black in the electrode blend for a Li-ion battery. For this purpose, the carbon samples are analyzed by several techniques, such as X-ray diffraction, Raman spectroscopy, transmission electron microscopy, granulometry, BET specific area and conductivity measurements. Different cathode compositions and component proportions are tested for pellet and cast electrodes. Electrochemical results show that a moderate reduction of commercial carbon black content in both kinds of cathodes, by adding more LiFePO{sub 4}/C composite, enhanced the electrochemical behaviour by around 10%. In situ generated carbon can partially replace commercial conducting carbon black because its high specific surface probably enhances electrolyte penetration into the cathode, but it is always necessary to maintain a minimum amount of carbon black that provides better conductivity in order to obtain a good electrochemical response. (author)

  2. Electronic thermal conductivity of armchair graphene nanoribbons and zigzag carbon nanotubes

    Science.gov (United States)

    Mousavi, Hamze; Khodadadi, Jabbar; Kurdestany, Jamshid Moradi; Grabowski, Marek

    2017-01-01

    Through the Green's function formalism and tight-binding Hamiltonian model calculations, the temperature dependent electronic thermal conductivity (TC) for different diameters of zigzag carbon nanotubes and their corresponding unzipped armchair graphene nanoribbons is calculated. All functional temperature dependencies bear crossovers, for which, at higher temperatures, nanotubes have a slightly higher TC than their derived nanoribbons, while below that crossover, both systems exhibit a significant coincidence over a moderate range of lower temperatures. Noticeably, TC decreases with increasing the width or diameter of the corresponding systems. Also, at low temperatures TC is proportional to the density of states around the Fermi level, and thus increasing for metal or semiconductors of narrower gap cases.

  3. Fabrication of high thermal conductivity arrays of carbon nanotubes and their composites

    Science.gov (United States)

    Geohegan, David B [Knoxville, TN; Ivanov, Ilya N [Knoxville, TN; Puretzky, Alexander A [Knoxville, TN

    2010-07-27

    Methods and apparatus are described for fabrication of high thermal conductivity arrays of carbon nanotubes and their composites. A composition includes a vertically aligned nanotube array including a plurality of nanotubes characterized by a property across substantially all of the vertically aligned nanotube array. A method includes depositing a vertically aligned nanotube array that includes a plurality of nanotubes; and controlling a deposition rate of the vertically aligned nanotubes array as a function of an in situ monitored property of the plurality of nanotubes.

  4. Effect of Palmitic Acid on the Electrical Conductivity of Carbon Nanotubes−Epoxy Resin Composites

    OpenAIRE

    Barrau, Sophie; Demont, Philippe; Perez, Emile; Peigney, Alain; Laurent, Christophe; Lacabanne, Colette

    2003-01-01

    International audience; We found that the palmitic acid allows an efficient dispersion of carbon nanotubes in the epoxy matrix. We have set up an experimental protocol in order to enhance the CNTs dispersion in epoxy resin. Electrical conductivity is optimal using a 1:1 CNTs to palmitic acid weight ratio. The associated percolation threshold is found between 0.05 and 0.1 wt % CNTs, i.e., between 0.03 and 0.06 vol %. The SEM image shows essentially individual CNTs which is inagreement with con...

  5. Detection and quantized conductance of neutral atoms near a charged carbon nanotube.

    Science.gov (United States)

    Ristroph, Trygve; Goodsell, Anne; Golovchenko, J A; Hau, Lene Vestergaard

    2005-02-18

    We describe a novel single atom detector that uses the high electric field surrounding a charged single-walled carbon nanotube to attract and subsequently field-ionize neutral atoms. A theoretical study of the field-ionization tunneling rates for atomic trajectories in the attractive potential near a nanowire shows that a broadly applicable, high spatial resolution, low-power, neutral-atom detector with nearly 100% efficiency is realizable with present-day technology. Calculations also show that the system can provide the first opportunity to study quantized conductance phenomena when detecting cold neutral atoms with mean velocities less than 15 m/s.

  6. Effects of Structural Deformation and Tube Chirality on Electronic Conductance of Carbon Nanotubes

    Science.gov (United States)

    Svizhenko, Alexei; Maiti, Amitesh; Anantram, M. P.; Biegel, Bryan A. (Technical Monitor)

    2002-01-01

    A combination of large scale classical force-field (UFF), density functional theory (DFT), and tight-binding Green's function transport calculations is used to study the electronic properties of carbon nanotubes under the twist, bending, and atomic force microscope (AFM)-tip deformation. We found that in agreement with experiment a significant change in electronic conductance can be induced by AFM-tip deformation of metallic zigzag tubes and by twist deformation of armchair tubes. The effect is explained in terms of bandstructure change under deformation.

  7. Carbon nanotubes filled polymer composites: A comprehensive study on improving dispersion, network formation and electrical conductivity

    Science.gov (United States)

    Chakravarthi, Divya Kannan

    In this dissertation, we determine how the dispersion, network formation and alignment of carbon nanotubes in polymer nanocomposites affect the electrical properties of two different polymer composite systems: high temperature bismaleimide (BMI) and polyethylene. The knowledge gained from this study will facilitate optimization of the above mentioned parameters, which would further enhance the electrical properties of polymer nanocomposites. BMI carbon fiber composites filled with nickel-coated single walled carbon nanotubes (Ni-SWNTs) were processed using high temperature vacuum assisted resin transfer molding (VARTM) to study the effect of lightning strike mitigation. Coating the SWNTs with nickel resulted in enhanced dispersions confirmed by atomic force microscopy (AFM) and dynamic light scattering (DLS). An improved interface between the carbon fiber and Ni-SWNTs resulted in better surface coverage on the carbon plies. These hybrid composites were tested for Zone 2A lightning strike mitigation. The electrical resistivity of the composite system was reduced by ten orders of magnitude with the addition of 4 weight percent Ni-SWNTs (calculated with respect to the weight of a single carbon ply). The Ni-SWNTs - filled composites showed a reduced amount of damage to simulated lightning strike compared to their unfilled counterparts indicated by the minimal carbon fiber pull out. Methods to reduce the electrical resistivity of 10 weight percent SWNTs --- medium density polyethylene (MDPE) composites were studied. The composites processed by hot coagulation method were subjected to low DC electric fields (10 V) at polymer melt temperatures to study the effect of viscosity, nanotube welding, dispersion and, resultant changes in electrical resistivity. The electrical resistivity of the composites was reduced by two orders of magnitude compared to 10 wt% CNT-MDPE baseline. For effective alignment of SWNTs, a new process called Electric field Vacuum Spray was devised to

  8. In Situ Monitoring of Dispersion Dynamics of Carbon Nanotubes during Sonication Using Electrical Conductivity Measurements

    Directory of Open Access Journals (Sweden)

    Syed Sadiq Ali

    2015-01-01

    Full Text Available The main challenge in the fabrication of carbon nanotube- (CNT- based composite materials is the optimization of the sonication time in order to obtain homogenous and uniform dispersion of CNTs. Past studies mostly relied on postprocessing characterization techniques to address this issue. In the present, however, in situ monitoring of dispersion dynamics of CNTs in distilled water is carried out using instantaneous conductivity measurements. Using a computer controlled data acquisition system, the time evolution of the solution conductivity was carefully recorded. The data were then used to evaluate the intensity of turbulent fluctuations, which clearly highlighted the existence of three distinct sonication phases. During the first phase, the conductivity fluctuations initially increased attaining ultimately a maximum, thus indicating the occurrence of large agglomerates of CNTs. During the second phase of sonication, the solution conductivity showed a rather steep increase while fluctuations steadily declined. This phenomenon can be attributed to the breakdown of large CNT agglomerates, resulting in greater dispersion homogeneity of CNTs. During the third phase, after almost 650 kJ/L of sonication energy, the conductivity increase was almost negligible. The fluctuation intensity also remained constant during this phase signifying that the further sonication was no longer required.

  9. Electrical Conductance Tuning and Bistable Switching in Poly(N-vinylcarbazole)-Carbon Nanotube Composite Films.

    Science.gov (United States)

    Liu, Gang; Ling, Qi-Dan; Teo, Eric Yeow Hwee; Zhu, Chun-Xiang; Chan, D Siu-Hung; Neoh, Koon-Gee; Kang, En-Tang

    2009-07-28

    By varying the carbon nanotube (CNT) content in poly(N-vinylcarbazole) (PVK) composite thin films, the electrical conductance behavior of an indium-tin oxide/PVK-CNT/aluminum (ITO/PVK-CNT/Al) sandwich structure can be tuned in a controlled manner. Distinctly different electrical conductance behaviors, such as (i) insulator behavior, (ii) bistable electrical conductance switching effects (write-once read-many-times (WORM) memory effect and rewritable memory effect), and (iii) conductor behavior, are discernible from the current density-voltage characteristics of the composite films. The turn-on voltage of the two bistable conductance switching devices decreases and the ON/OFF state current ratio of the WORM device increases with the increase in CNT content of the composite film. Both the WORM and rewritable devices are stable under a constant voltage stress or a continuous pulse voltage stress, with an ON/OFF state current ratio in excess of 10(3). The conductance switching effects of the composite films have been attributed to electron trapping in the CNTs of the electron-donating/hole-transporting PVK matrix.

  10. Thermal conductivity of a film of single walled carbon nanotubes measured with infrared thermal imager

    Science.gov (United States)

    Feng, Ya; Inoue, Taiki; Xiang, Rong; Chiashi, Shohei; Maruyama, Shigeo

    Heat dissipation has restricted the modern miniaturization trend with the development of electronic devices. Theoretically proven to be with high axial thermal conductivity, single walled carbon nanotubes (SWNT) have long been expected to cool down the nanoscale world. Even though the tube-tube contact resistance limits the capability of heat transfer of the bulk film, the high intrinsic thermal conductivity of SWNT still glorify the application of films of SWNT network as a thermal interface material. In this work, we proposed a new method to straightly measure the thermal conductivity of SWNT film. We bridged two cantilevered Si thin plate with SWNT film, and kept a steady state heat flow in between. With the infrared camera to record the temperature distribution, the Si plates with known thermal conductivity can work as a reference to calculate the heat flux going through the SWNT film. Further, the thermal conductivity of the SWNT film can be obtained through Fourier's law after deducting the effect of thermal radiation. The sizes of the structure, the heating temperature, the vacuum degree and other crucial impact factors are carefully considered and analyzed. The author Y. F. was supported through the Advanced Integration Science Innovation Education and Research Consortium Program by the Ministry of Education, Culture, Sport, Science and Technology.

  11. Atomistic simulations, mesoscopic modeling, and theoretical analysis of thermal conductivity of bundles composed of carbon nanotubes

    Science.gov (United States)

    Volkov, Alexey N.; Salaway, Richard N.; Zhigilei, Leonid V.

    2013-09-01

    The propensity of carbon nanotubes (CNTs) to self-organize into continuous networks of bundles has direct implications for thermal transport properties of CNT network materials and defines the importance of clear understanding of the mechanisms and scaling laws governing the heat transfer within the primary building blocks of the network structures—close-packed bundles of CNTs. A comprehensive study of the thermal conductivity of CNT bundles is performed with a combination of non-equilibrium molecular dynamics (MD) simulations of heat transfer between adjacent CNTs and the intrinsic conductivity of CNTs in a bundle with a theoretical analysis that reveals the connections between the structure and thermal transport properties of CNT bundles. The results of MD simulations of heat transfer in CNT bundles consisting of up to 7 CNTs suggest that, contrary to the widespread notion of strongly reduced conductivity of CNTs in bundles, van der Waals interactions between defect-free well-aligned CNTs in a bundle have negligible effect on the intrinsic conductivity of the CNTs. The simulations of inter-tube heat conduction performed for partially overlapping parallel CNTs indicate that the conductance through the overlap region is proportional to the length of the overlap for CNTs and CNT-CNT overlaps longer than several tens of nm. Based on the predictions of the MD simulations, a mesoscopic-level model is developed and applied for theoretical analysis and numerical modeling of heat transfer in bundles consisting of CNTs with infinitely large and finite intrinsic thermal conductivities. The general scaling laws predicting the quadratic dependence of the bundle conductivity on the length of individual CNTs in the case when the thermal transport is controlled by the inter-tube conductance and the independence of the CNT length in another limiting case when the intrinsic conductivity of CNTs plays the dominant role are derived. An application of the scaling laws to bundles of

  12. Composite Polymer Electrolytes with Li7La3Zr2O12 Garnet-Type Nanowires as Ceramic Fillers: Mechanism of Conductivity Enhancement and Role of Doping and Morphology.

    Science.gov (United States)

    Yang, Ting; Zheng, Jin; Cheng, Qian; Hu, Yan-Yan; Chan, Candace K

    2017-07-05

    Composite polymer solid electrolytes (CPEs) containing ceramic fillers embedded inside a polymer-salt matrix show great improvements in Li(+) ionic conductivity compared to the polymer electrolyte alone. Lithium lanthanum zirconate (Li7La3Zr2O12, LLZO) with a garnet-type crystal structure is a promising solid Li(+) conductor. We show that by incorporating only 5 wt % of the ceramic filler comprising undoped, cubic-phase LLZO nanowires prepared by electrospinning, the room temperature ionic conductivity of a polyacrylonitrile-LiClO4-based composite is increased 3 orders of magnitude to 1.31 × 10(-4) S/cm. Al-doped and Ta-doped LLZO nanowires are also synthesized and utilized as fillers, but the conductivity enhancement is similar as for the undoped LLZO nanowires. Solid-state nuclear magnetic resonance (NMR) studies show that LLZO NWs partially modify the PAN polymer matrix and create preferential pathways for Li(+) conduction through the modified polymer regions. CPEs with LLZO nanoparticles and Al2O3 nanowire fillers are also studied to elucidate the role of filler type (active vs passive), LLZO composition (undoped vs doped), and morphology (nanowire vs nanoparticle) on the CPE conductivity. It is demonstrated that both intrinsic Li(+) conductivity and nanowire morphology are needed for optimal performance when using 5 wt % of the ceramic filler in the CPE.

  13. Piezoelectric, impedance, electric modulus and AC conductivity studies on (Bi0.5Na0.50.95Ba0.05TiO3 ceramic

    Directory of Open Access Journals (Sweden)

    Ansu K. Roy

    2013-06-01

    Full Text Available Lead-free piezoelectric perovskite ceramic (Bi0.5Na0.50.95Ba0.05TiO3 (BNT-BT0.05, prepared by conventional high temperature solid state reaction technique at 1160 °C/3h in air atmosphere, is investigated by impedance and modulus spectroscopy in a temperature range 35–400 °C, over a frequency range 100 Hz–1 MHz. The crystal structure, microstructure, and piezoelectric properties as well as the AC conductivity of the sample were studied. Powder X-ray diffraction pattern derived from the resulting data at the room temperature subjected to Rietveld refinements and Williamson-Hall plot analysis confirmed the formation of phase pure compound with monoclinic unit cells having a crystallite-size ~33.8 nm. Observed SEM micrograph showed a uniform distribution of grains inside the sample having an average grain size ~3 mm. Longitudinal piezoelectric charge coefficient of the sample poled under a DC electric field of ~ 2.5 kV/mm at 80 °C in a silicone oil bath was found to be equal to 95 pC/N. The frequency and temperature dependent electrical data analysed in the framework of AC conductivity, complex impedance as well as electric modulus formalisms showed negative temperature coefficient of resistance (NTCR character of the material and the dielectric relaxation in the material to be of non-Debye type. Double power law for the frequency-dependence of AC conductivity and Jump Relaxation Model (JRM were found to explain successfully the mechanism of charge transport in BNT-BT0.05.

  14. Auto-thermal reforming using mixed ion-electronic conducting ceramic membranes for a small-scale H₂ production plant.

    Science.gov (United States)

    Spallina, Vincenzo; Melchiori, Tommaso; Gallucci, Fausto; van Sint Annaland, Martin

    2015-03-18

    The integration of mixed ionic electronic conducting (MIEC) membranes for air separation in a small-to-medium scale unit for H2 production (in the range of 650-850 Nm3/h) via auto-thermal reforming of methane has been investigated in the present study. Membranes based on mixed ionic electronic conducting oxides such as Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) give sufficiently high oxygen fluxes at temperatures above 800 °C with high purity (higher than 99%). Experimental results of membrane permeation tests are presented and used for the reactor design with a detailed reactor model. The assessment of the H2 plant has been carried out for different operating conditions and reactor geometry and an energy analysis has been carried out with the flowsheeting software Aspen Plus, including also the turbomachines required for a proper thermal integration. A micro-gas turbine is integrated in the system in order to supply part of the electricity required in the system. The analysis of the system shows that the reforming efficiency is in the range of 62%-70% in the case where the temperature at the auto-thermal reforming membrane reactor (ATR-MR) is equal to 900 °C. When the electric consumption and the thermal export are included the efficiency of the plant approaches 74%-78%. The design of the reactor has been carried out using a reactor model linked to the Aspen flowsheet and the results show that with a larger reactor volume the performance of the system can be improved, especially because of the reduced electric consumption. From this analysis it has been found that for a production of about 790 Nm3/h pure H2, a reactor with a diameter of 1 m and length of 1.8 m with about 1500 membranes of 2 cm diameter is required.

  15. Electrical conductivity and electromagnetic interference shielding characteristics of multiwalled carbon nanotube filled polyurethane composite films

    Science.gov (United States)

    Son Hoang, Anh

    2011-06-01

    Multiwalled carbon nanotubes (MWCNTs) were homogeneously dispersed in a pure polyurethane resin by grinding in a planetary ball mill. The structure and surface morphology of the MWCNTs and MWCNT/polyurethane composites were studied by filed emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) methods. The electrical conductivity at room temperature and electromagnetic interference (EMI) shielding effectiveness (SE) of the composite films with different MWCNT loadings were investigated and the measurement of EMI SE was carried out in a frequency range of 8-12 GHz (X-band). The experimental results show that with a low MWCNT concentration the composite films could achieve a high conductivity and their EMI SE has a strong dependence on MWCNT content. For the composite films with 22 wt% of MWCNTs, the EMI SE attained an average value of 20 dB, so that the shielding effect reduced the penetrating power to 1%.

  16. Surface-conduction electron-emitter characteristics and fabrication based on vertically aligned carbon nanotube arrays

    Science.gov (United States)

    Shih, Yi-Ting; Li, Kuan-Wei; Honda, Shin-ichi; Lin, Pao-Hung; Huang, Ying-Sheng; Lee, Kuei-Yi

    2017-06-01

    The carbon nanotube (CNT) has replaced palladium oxide (PdO) as the electrode material for surface-conduction electron-emitter (SCE) applications. Vertically aligned CNT arrays with a delta-star arrangement were patterned and synthesized onto a quartz substrate using photolithography and thermal chemical vapor deposition. Delta-star shaped VACNT arrays with 20° tips are used as cathodes that easily emit electrons because of their high electrical field gradient. In order to improve the field emission and secondary electrons (SEs) in SCE applications, magnesium oxide (MgO) nanostructures were coated onto the VACNT arrays to promote the surface-conduction electron-emitter display (SED) efficiency (η). According to the definition of η in SCE applications, in this study, the η was stably maintained in the 75-85% range. The proposed design provides a facile new method for developing SED applications.

  17. An experimental study on thermal conductivity and viscosity of nanofluids containing carbon nanotubes

    Science.gov (United States)

    Sadri, Rad; Ahmadi, Goodarz; Togun, Hussein; Dahari, Mahidzal; Kazi, Salim Newaz; Sadeghinezhad, Emad; Zubir, Nashrul

    2014-03-01

    Recently, there has been considerable interest in the use of nanofluids for enhancing thermal performance. It has been shown that carbon nanotubes (CNTs) are capable of enhancing the thermal performance of conventional working liquids. Although much work has been devoted on the impact of CNT concentrations on the thermo-physical properties of nanofluids, the effects of preparation methods on the stability, thermal conductivity and viscosity of CNT suspensions are not well understood. This study is focused on providing experimental data on the effects of ultrasonication, temperature and surfactant on the thermo-physical properties of multi-walled carbon nanotube (MWCNT) nanofluids. Three types of surfactants were used in the experiments, namely, gum arabic (GA), sodium dodecylbenzene sulfonate (SDBS) and sodium dodecyl sulfate (SDS). The thermal conductivity and viscosity of the nanofluid suspensions were measured at various temperatures. The results showed that the use of GA in the nanofluid leads to superior thermal conductivity compared to the use of SDBS and SDS. With distilled water as the base liquid, the samples were prepared with 0.5 wt.% MWCNTs and 0.25% GA and sonicated at various times. The results showed that the sonication time influences the thermal conductivity, viscosity and dispersion of nanofluids. The thermal conductivity of nanofluids was typically enhanced with an increase in temperature and sonication time. In the present study, the maximum thermal conductivity enhancement was found to be 22.31% (the ratio of 1.22) at temperature of 45°C and sonication time of 40 min. The viscosity of nanofluids exhibited non-Newtonian shear-thinning behaviour. It was found that the viscosity of MWCNT nanofluids increases to a maximum value at a sonication time of 7 min and subsequently decreases with a further increase in sonication time. The presented data clearly indicated that the viscosity and thermal conductivity of nanofluids are influenced by the

  18. An experimental study on thermal conductivity and viscosity of nanofluids containing carbon nanotubes.

    Science.gov (United States)

    Sadri, Rad; Ahmadi, Goodarz; Togun, Hussein; Dahari, Mahidzal; Kazi, Salim Newaz; Sadeghinezhad, Emad; Zubir, Nashrul

    2014-01-01

    Recently, there has been considerable interest in the use of nanofluids for enhancing thermal performance. It has been shown that carbon nanotubes (CNTs) are capable of enhancing the thermal performance of conventional working liquids. Although much work has been devoted on the impact of CNT concentrations on the thermo-physical properties of nanofluids, the effects of preparation methods on the stability, thermal conductivity and viscosity of CNT suspensions are not well understood. This study is focused on providing experimental data on the effects of ultrasonication, temperature and surfactant on the thermo-physical properties of multi-walled carbon nanotube (MWCNT) nanofluids. Three types of surfactants were used in the experiments, namely, gum arabic (GA), sodium dodecylbenzene sulfonate (SDBS) and sodium dodecyl sulfate (SDS). The thermal conductivity and viscosity of the nanofluid suspensions were measured at various temperatures. The results showed that the use of GA in the nanofluid leads to superior thermal conductivity compared to the use of SDBS and SDS. With distilled water as the base liquid, the samples were prepared with 0.5 wt.% MWCNTs and 0.25% GA and sonicated at various times. The results showed that the sonication time influences the thermal conductivity, viscosity and dispersion of nanofluids. The thermal conductivity of nanofluids was typically enhanced with an increase in temperature and sonication time. In the present study, the maximum thermal conductivity enhancement was found to be 22.31% (the ratio of 1.22) at temperature of 45°C and sonication time of 40 min. The viscosity of nanofluids exhibited non-Newtonian shear-thinning behaviour. It was found that the viscosity of MWCNT nanofluids increases to a maximum value at a sonication time of 7 min and subsequently decreases with a further increase in sonication time. The presented data clearly indicated that the viscosity and thermal conductivity of nanofluids are influenced by the

  19. Electrochemical behaviour of ceramic yttria stabilized zirconia on carbon steel synthesized via sol-gel process

    Energy Technology Data Exchange (ETDEWEB)

    Crespo, M.A. Dominguez, E-mail: mdominguezc@ipn.m [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Unidad Altamira (CICATA-IPN) km 14.5 Carr. Tampico-Puerto Industrial, C.P. 89600, Altamira, Tamaulipas (Mexico); Murillo, A. Garcia; Torres-Huerta, A.M. [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Unidad Altamira (CICATA-IPN) km 14.5 Carr. Tampico-Puerto Industrial, C.P. 89600, Altamira, Tamaulipas (Mexico); Yanez-Zamora, C. [Estudiante del postgrado en Tecnologia Avanzada del CICATA-IPN, Unidad Altamira, km 14.5, Carr. Tampico-Puerto Industrial. C.P. 89600, Altamira, Tamaulipas (Mexico); Carrillo-Romo, F. de J [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Unidad Altamira (CICATA-IPN) km 14.5 Carr. Tampico-Puerto Industrial, C.P. 89600, Altamira, Tamaulipas (Mexico)

    2009-08-26

    Chromate conversion coatings have been widely applied for the corrosion of different metallic substrates. However, the waste containing Cr{sup 6+} has many limitations due to the environmental consideration and health hazards. An interesting alternative seems to be the deposition on metallic surface of thin layers of yttria or zirconia or both by the sol-gel process. In this study, Ytttria and Yttria stabilized zirconia (YSZ, 8% Y{sub 2}O{sub 3}) thin films were used for coating commercial carbon steel substrates by sol-gel method and the dip-coating process. The evolution of organic compounds up to crystallization process as a function of heat treatments was study by FT-IR spectroscopy. The structure and morphology of the coatings were analysed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The anticorrosion performance of the coatings has been evaluated by using electrochemical techniques in an aggressive media (3.5 wt.% NaCl). The corrosion behaviour of sol-gel method was compared with traditional chromate conversion coatings. Differences in the electrochemical behaviour of YSZ coatings are related to the development of microcracks during the sintering process and to the presence of organic compounds during growth film. Electrochemical results showed that sol-gel YSZ and Y{sub 2}O{sub 3} coatings can act as protective barriers against wet corrosion; however yttria films displayed low adhesion to substrate. The corrosion parameters provide an explanation of the role of each film and show a considerable increase in the corrosion resistance for coated samples in comparison to the bare steel samples.

  20. Enhancing the electrical conductivity of carbon-nanotube-based transparent conductive films using functionalized few-walled carbon nanotubes decorated with palladium nanoparticles as fillers.

    Science.gov (United States)

    Li, Yu-An; Tai, Nyan-Hwa; Chen, Swe-Kai; Tsai, Tsung-Yen

    2011-08-23

    This work demonstrates the processing and characterization of the transparent and highly electrically conductive film using few-walled carbon nanotubes (FWCNTs) decorated with Pd nanoparticles as fillers. The approach included functionalizing the FWCNTs, immersing them in an aqueous solution of palladate salts, and subsequently subjecting them to a reduction reaction in H(2). Field-emission scanning electron microscopy and transmission electron microscopy images showed that the functionalized FWCNTs (f-FWCNTs) were decorated with uniform and homogeneous Pd nanoparticles with an average diameter of 5 nm. A shift of the G-band to a higher frequency in the Raman spectra of the Pd-decorated f-FWCNTs (Pd@f-FWCNTs) illustrates that the p-type doping effect was enhanced. X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy showed that PdCl(2) was the primary decoration compound on the f-FWCNTs prior to the reduction reaction and that Pd nanoparticles were the only decorated nanoparticles after H(2) reduction. The contact resistance between the metallic materials and the semiconducting CNTs in FWCNTs, controlled by the Schottky barrier, was significantly decreased compared to the pristine FWCNTs. The decrease in contact resistance is attributed to the 0.26 eV increase of the work function of the Pd@f-FWCNTs. Extremely low sheet resistance of 274 ohm/sq of the poly(ethylene terephthalate) substrates coated with Pd@f-FWCNTs was attained, which was 1/25 the resistance exhibited by those coated with FWCNTs, whereas the same optical transmittance of 81.65% at a wavelength of 550 nm was maintained. © 2011 American Chemical Society

  1. Internal friction and microplasticity of carbon-fiber-reinforced SiC ceramics; Tanso sen`i kyoka SiC ceramics no hakai zenku katei ni okeru naibu masatsu

    Energy Technology Data Exchange (ETDEWEB)

    Ogawa, H.; Nishino, Y.; Asano, S. [Nagoya Institute of Technology, Nagoya (Japan)

    1995-08-20

    Mechanical responses of carbon-fiber-reinforced SiC ceramics before fracture were measured in the strain range below 2 {times} 10{sup {minus}3} by two experimental methods: mechanical hysteresis and internal friction. Load-deflection curves were obtained by the three-point bending deformation in loading-unloading cycles. A little permanent strain was found after the first cycle even in the range where fracture never occurred. A closed hysteresis loop was observed after several cycles and stabilized with a symmetrical shape after more than twenty cycles. Such a stabilized hysteresis loop is attributed to the steady-state microplastic deformation and may cause the amplitude-dependent internal friction. Internal friction was measured in the fundamental mode of free-free resonant vibration as a function of strain amplitude. With increasing the amount of prestrain in the bending deformation, internal friction increased and became sensitive to the strain amplitude. The amplitude-dependent internal friction in the composites is considered to originate from fiber pull-out or microcrack propagation. The internal friction data were analyzed on the basis of the microplasticity theory and converted into the plastic strain expressed as a function of stress. Therefore, it becomes possible to non-destructively study the forerunning process of fracture of the fiber-reinforced ceramics. 23 refs., 6 figs.

  2. Final Technical Report CONDUCTIVE COATINGS FOR SOLAR CELLS USING CARBON NANOTUBES

    Energy Technology Data Exchange (ETDEWEB)

    Paul J Glatkowski; Jorma Peltola; Christopher Weeks; Mike Trottier; David Britz

    2007-09-30

    US Department of Energy (DOE) awarded a grant for Eikos Inc. to investigate the feasibility of developing and utilizing Transparent Conducting Coatings (TCCs) based on carbon nanotubes (CNT) for solar cell applications. Conventional solar cells today employ metal oxide based TCCs with both Electrical Resistivity (R) and Optical Transparency (T), commonly referred to as optoelectronic (RT) performance significantly higher than with those possible with CNT based TCCs available today. Transparent metal oxide based coatings are also inherently brittle requiring high temperature in vacuum processing and are thus expensive to manufacture. One such material is indium tin oxide (ITO). Global demand for indium has recently increased rapidly while supply has diminished causing substantial spikes in raw material cost and availability. In contrast, the raw material, carbon, needed for CNT fabrication is abundantly available. Transparent Conducting Coatings based on CNTs can overcome not only cost and availability constraints while also offering the ability to be applied by existing, low cost process technologies under ambient conditions. Processes thus can readily be designed both for rigid and flexible PV technology platforms based on mature spray or dip coatings for silicon based solar cells and continuous roll to roll coating processes for polymer solar applications.

  3. Electrical conductivity and thermal properties of functionalized carbon nanotubes/polyurethane composites

    Directory of Open Access Journals (Sweden)

    Aline M. F. Lima

    2012-01-01

    Full Text Available Multi-walled carbon nanotubes (MWCNTs functionalized with amine and carboxyl groups were used to prepare polyurethane/MWCNT nanocomposites in two distinct concentrations: a lower value of 1 mass% (spray coating and a higher one of ~50 mass% (buckypaper based. The MWCNT-NH2 sample contained only 0.5 mass% of amine groups, whereas MWCNT-COOH contained 5 mass% of carboxyl groups. The MWCNT functionalized with low amine group content showed improved thermal properties when compared to neat thermoplastic polyurethane (TPU and MWCNT-COOH based nanocomposites. The electrical conductivity of the polyurethane elastomer was greatly increased from 10-12 to ~10-5 S cm-1in the 1 mass% nanotube composite and to 7 S cm-1for the MWCNT-NH2 buckypaper-based nanocomposite. Furthermore, the relative high content of functional groups in the MWCNT-COOH sample, which disrupt the sp²structure in the nanotube walls, led to inferior properties; for instance the conductivity of the buckypaper based composite is one order of magnitude lower when using MWCNT-COOH in comparison with the MWCNT-NH2. These results show the range of property design possibilities available with the elastomeric polyurethane nanocomposite by tailoring the functional group content and the carbon nanotube load.

  4. The thermal properties of a carbon nanotube-enriched epoxy: Thermal conductivity, curing, and degradation kinetics

    KAUST Repository

    Ventura, Isaac Aguilar

    2013-05-31

    Multiwalled carbon nanotube-enriched epoxy polymers were prepared by solvent evaporation based on a commercially available epoxy system and functionalized multiwalled carbon nanotubes (COOH-MWCNTs). Three weight ratio configurations (0.05, 0.5, and 1.0 wt %) of COOH-MWCNTs were considered and compared with neat epoxy and ethanol-treated epoxy to investigate the effects of nano enrichment and processing. Here, the thermal properties of the epoxy polymers, including curing kinetics, thermal conductivity, and degradation kinetics were studied. Introducing the MWCNTs increased the curing activation energy as revealed by differential scanning calorimetry. The final thermal conductivity of the 0.5 and 1.0 wt % MWCNT-enriched epoxy samples measured by laser flash technique increased by up to 15% compared with the neat material. The activation energy of the degradation process, investigated by thermogravimetric analysis, was found to increase with increasing CNT content, suggesting that the addition of MWCNTs improved the thermal stability of the epoxy polymers. © 2013 Wiley Periodicals, Inc.

  5. Conductivity and optical studies of plasticized solid polymer electrolytes doped with carbon nanotube

    Energy Technology Data Exchange (ETDEWEB)

    Ibrahim, Suriani, E-mail: sue_83@um.edu.my [Advanced Materials Research Laboratory, Department of Mechanical Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia); Ahmad, Roslina; Johan, Mohd Rafie [Advanced Materials Research Laboratory, Department of Mechanical Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia)

    2012-01-15

    Solid polymer electrolyte films based on Poly(ethylene oxide) (PEO) complexed with lithium hexafluorophosphate (LiPF{sub 6}), ethylene carbonate (EC) and amorphous carbon nanotube ({alpha}CNTs) were prepared by the solution cast technique. The conductivity increases from 10{sup -10} to 10{sup -5} Scm{sup -1} upon the addition of salt. The incorporation of EC and {alpha}CNTs to the salted polymer enhances the conductivity significantly to 10{sup -4} and 10{sup -3} Scm{sup -1}. The complexation of doping materials with polymer were confirmed by X-ray diffraction and infrared studies. Optical properties like direct band gap and indirect band gap were investigated for pure and doped polymer films in the wavelength range 200-400 nm. It was found that the energy gaps and band edge values shifted to lower energies on doping. - Highlights: > Optical band gap values show the decreasing trend with an increasing dopant concentration. > It is also observed that the absorption edge shifted to longer wavelength on doping. > Results of the optical measurements indicate the presence of a well-defined {pi}{yields}{pi}* transition associated with the formation of a conjugated C=O and/or C=O electronic structure.

  6. Nitrite Oxidation with Copper-Cobalt Nanoparticles on Carbon Nanotubes Doped Conducting Polymer PEDOT Composite.

    Science.gov (United States)

    Wang, Junjie; Xu, Guiyun; Wang, Wei; Xu, Shenghao; Luo, Xiliang

    2015-09-01

    Copper-cobalt bimetal nanoparticles (Cu-Co) have been electrochemically prepared on glassy carbon electrodes (GCEs), which were electrodeposited with conducting polymer nanocomposites of poly(3,4-ethylenedioxythiophene) (PEDOT) doped with carbon nanotubes (CNTs). Owing to their good conductivity, high mechanical strength, and large surface area, the PEDOT/CNTs composites offered excellent substrates for the electrochemical deposition of Cu-Co nanoparticles. As a result of their nanostructure and the synergic effect between Cu and Co, the Cu-Co/PEDOT/CNTs composites exhibited significantly enhanced catalytic activity towards the electrochemical oxidation of nitrite. Under optimized conditions, the nanocomposite-modified electrodes had a fast response time within 2 s and a linear range from 0.5 to 430 μm for the detection of nitrite, with a detection limit of 60 nm. Moreover, the Cu-Co/PEDOT/CNTs composites were highly stable, and the prepared nitrite sensors could retain more than 96 % of their initial response after 30 days.

  7. High adhesion transparent conducting films using graphene oxide hybrid carbon nanotubes

    Science.gov (United States)

    Da, Shi-Xun; Wang, Jie; Geng, Hong-Zhang; Jia, Song-Lin; Xu, Chun-Xia; Li, Lin-Ge; Shi, Pei-Pei; Li, Guangfen

    2017-01-01

    Flexible transparent conducting films (TCFs) with carbon nanotubes (CNTs) have attracted more and more attention for their wide range of potential applications. While, there are still some problems to be solved on several aspects. In this study, a graphene oxide/carbon nanotube (GO/CNT) hybrid TCF was fabricated through the simple spray coating method. GO sheets were introduced to form new electron transporting channels. It was found that the best optoelectronic property films were fabricated when the ratio of GO/CNT is 1.5:1.0, which the sheet resistance of the film was found to be 146 Ω/sq at the transmittance of 86.0%. Due to the two-dimensional structure and the oxidation groups of GO sheets, flatness and wettability of the electrode surface was improved obviously. Adhesion factor of the TCFs was calculated by the change of transparent and sheet resistance after trial test, the addition of GO sheets enhanced the adhesion dramatically and the mechanism was analyzed. Improvements of conductivity, flatness, wettability and adhesion above are all advantageous for the solution-based processing of organic electronics for spraying and printing.

  8. First-Principles Design of Conductance Switching in Functionalized Carbon Nanotubes

    Science.gov (United States)

    Li, Elise; Poilvert, Nicolas; Marzari, Nicola

    2010-03-01

    Functionalization of SWNT through addition reactions represents an effective method to engineer or manipulate carbon nanotubes. For armchair CNTs,the conductivity is often decreased by orders of magnitude by the introduction of monovalent functional groups which disrupt the conjugated π network, whereas in [1+2] cycloadditions of carbenes or nitrenes, the sp^2 environment and therefore CNT metallicity can be recovered due to the sidewall bond breakage induced by the cyclopropane strain. In real systems, this bond cleavage depends heavily on the chirality and curvature of the tube, and the chemical nature of the addends. Here we explore the underlying mechanism of bond-cleavage chemistry in [1+2] cycloadditions on armchair carbon nanotubes using first-principles calculations. We find the high strain energy in cyclopropane moiety can be compensated by a through space π orbital interaction between the addend and the CNT which lowers the HOMO energy significantly in closed-bond configuration. A bond opening or closing switch marked by large conductance change can therefore be devised by modulating the proximity of the addend π system and the tube surface via optical or electrochemical control, which potentially has extensive applications in nanoscale devices.

  9. Optimization of stomatal conductance for maximum carbon gain under dynamic soil moisture

    Science.gov (United States)

    Manzoni, Stefano; Vico, Giulia; Palmroth, Sari; Porporato, Amilcare; Katul, Gabriel

    2013-12-01

    Optimization theories explain a variety of forms and functions in plants. At the leaf scale, it is often hypothesized that carbon gain is maximized, thus providing a quantifiable objective for a mathematical definition of optimality conditions. Eco-physiological trade-offs and limited resource availability introduce natural bounds to this optimization process. In particular, carbon uptake from the atmosphere is inherently linked to water losses from the soil as water is taken up by roots and evaporated. Hence, water availability in soils constrains the amount of carbon that can be taken up and assimilated into new biomass. The problem of maximizing photosynthesis at a given water availability by modifying stomatal conductance, the plant-controlled variable to be optimized, has been traditionally formulated for short time intervals over which soil moisture changes can be neglected. This simplification led to a mathematically open solution, where the undefined Lagrange multiplier of the optimization (equivalent to the marginal water use efficiency, λ) is then heuristically determined via data fitting. Here, a set of models based on different assumptions that account for soil moisture dynamics over an individual dry-down are proposed so as to provide closed analytical expressions for the carbon gain maximization problem. These novel solutions link the observed variability in λ over time, across soil moisture changes, and at different atmospheric CO2 concentrations to water use strategies ranging from intensive, in which all soil water is consumed by the end of the dry-down period, to more conservative, in which water stress is avoided by reducing transpiration.

  10. Bimodal Latex Effect on Spin-Coated Thin Conductive Polymer-Single-Walled Carbon Nanotube Layers.

    Science.gov (United States)

    Moradi, Mohammad-Amin; Larrakoetxea Angoitia, Katalin; van Berkel, Stefan; Gnanasekaran, Karthikeyan; Friedrich, Heiner; Heuts, Johan P A; van der Schoot, Paul; van Herk, Alex M

    2015-11-10

    We synthesize two differently sized poly(methyl methacrylate-co-tert-butyl acrylate) latexes by emulsion polymerization and mix these with a sonicated single-walled carbon nanotube (SWCNT) dispersion, in order to prepare 3% SWCNT composite mixtures. We spin-coat these mixtures at various spin-speed rates and spin times over a glass substrate, producing a thin, transparent, solid, conductive layer. Keeping the amount of SWCNTs constant, we vary the weight fraction of our smaller 30-nm latex particles relative to the larger 70-nm-sized ones. We find a maximum in the electrical conductivity up to 370 S/m as a function of the weight fraction of smaller particles, depending on the overall solid content, the spin speed, and the spin time. This maximum occurs at 3-5% of the smaller latex particles. We also find a more than 2-fold increase in conductivity parallel to the radius of spin-coating than perpendicular to it. Atomic force microscopy points at the existence of lanes of latex particles in the spin-coated thin layer, while large-area transmission electron microscopy demonstrates that the SWCNTs are aligned over a grid fixed on the glass substrate during the spin-coating process. We extract the conductivity distribution on the surface of the thin film and translate this into the direction of the SWCNTs in it.

  11. Conductivity of carbonate- and perfluoropolyether-based electrolytes in porous separators

    Science.gov (United States)

    Devaux, Didier; Chang, Yu H.; Villaluenga, Irune; Chen, X. Chelsea; Chintapalli, Mahati; DeSimone, Joseph M.; Balsara, Nitash P.

    2016-08-01

    In lithium batteries, a porous separator filled with an electrolyte is placed in between the electrodes. Properties of the separator such as porosity and wettability strongly influence the conductivity of the electrolyte-separator composite. This study focuses on three commercial separators: a single layer polypropylene (Celgard 2500), a trilayer polypropylene-polyethylene-polypropylene (PP-PE-PP), and a porous polytetrafluoroethylene (PTFE). Electron microscopy was used to characterize the pore structure, and these experiments reveal large differences in pore morphology. The separators were soaked in both carbonate- and perfluoropolyether-based electrolytes. The conductivity of the neat electrolytes (σ0) varied from 6.46 × 10-6 to 1.76 × 10-2 S cm-1. The porosity and wettability of the separator affect the electrolyte uptake that in turn affect the conductivity of electrolyte-separator composites. The conductivity of the electrolyte-separator composites (σ) was found to follow a master equation, σ = 0.51·σ0·ϕc3.2±0.2, where ϕc is the volume fraction of the electrolyte in each separator.

  12. Thermal Conductivity of Epoxy Resin Reinforced with Magnesium Oxide Coated Multiwalled Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Fei-Peng Du

    2013-01-01

    Full Text Available Magnesium oxide coated multiwalled carbon nanotubes (MgO@MWNT were fabricated and dispersed into epoxy matrix. The microstructures of MgO@MWNT and epoxy/MgO@MWNT nanocomposites were characterized by TEM and SEM. Electrical resistivity and thermal conductivity of epoxy nanocomposites were investigated with high resistance meter and thermal conductivity meter, respectively. MgO@MWNT has core-shell structure with MgO as shell and nanotube as core, and the thickness of MgO shell is ca. 15 nm. MgO@MWNT has been dispersed well in the epoxy matrix. MgO@MWNT loaded epoxy nanocomposites still retain electrical insulation inspite of the filler content increase. However, thermal conductivity of epoxy was increased with the MgO@MWNT content increasing. When MgO@MWNT content reached 2.0 wt.%, thermal conductivity was increased by 89% compared to neat epoxy, higher than that of unmodified MWNT nanocomposites with the same loading content.

  13. Carbon nanotube-coated silicone as a flexible and electrically conductive biomedical material

    Energy Technology Data Exchange (ETDEWEB)

    Matsuoka, Makoto, E-mail: matsuoka@den.hokudai.ac.jp [Department of Oral and Maxillofacial Surgery, Graduate School of Dental Medicine, Hokkaido University, Kita 13 Nishi 7, Kita-ku, Sapporo 060-8586 (Japan); Japan Society for the Promotion of Science (Japan); Akasaka, Tsukasa [Department of Dental Materials and Engineering, Graduate School of Dental Medicine, Hokkaido University, Kita 13 Nishi 7, Kita-ku, Sapporo 060-8586 (Japan); Totsuka, Yasunori [Department of Oral and Maxillofacial Surgery, Graduate School of Dental Medicine, Hokkaido University, Kita 13 Nishi 7, Kita-ku, Sapporo 060-8586 (Japan); Watari, Fumio [Department of Dental Materials and Engineering, Graduate School of Dental Medicine, Hokkaido University, Kita 13 Nishi 7, Kita-ku, Sapporo 060-8586 (Japan)

    2012-04-01

    Artificial cell scaffolds that support cell adhesion, growth, and organization need to be fabricated for various purposes. Recently, there have been increasing reports of cell patterning using electrical fields. We fabricated scaffolds consisting of silicone sheets coated with single-walled (SW) or multi-walled (MW) carbon nanotubes (CNTs) and evaluated their electrical properties and biocompatibility. We also performed cell alignment with dielectrophoresis using CNT-coated sheets as electrodes. Silicone coated with 10 {mu}g/cm{sup 2} SWCNTs exhibited the least sheet resistance (0.8 k{Omega}/sq); its conductivity was maintained even after 100 stretching cycles. CNT coating also improved cell adhesion and proliferation. When an electric field was applied to the cell suspension introduced on the CNT-coated scaffold, the cells became aligned in a pearl-chain pattern. These results indicate that CNT coating not only provides electro-conductivity but also promotes cell adhesion to the silicone scaffold; cells seeded on the scaffold can be organized using electricity. These findings demonstrate that CNT-coated silicone can be useful as a biocompatible scaffold. - Highlights: Black-Right-Pointing-Pointer We fabricated a CNT-coated silicone which has conductivity and biocompatibility. Black-Right-Pointing-Pointer The conductivity was maintained after 100 cycles of stretching. Black-Right-Pointing-Pointer CNT coatings enabled C2C12 cells adhere to the silicone surface. Black-Right-Pointing-Pointer Cells were aligned with dielectrophoresis between CNT-coated silicone surfaces.

  14. Preparation of conductive polypyrrole (PPy) composites under supercritical carbon dioxide conditions

    Institute of Scientific and Technical Information of China (English)

    LI Gang; LIAO Xia; SUN Xinghua; YU Jian; HE Jiasong

    2007-01-01

    Electrically conductive composites were prepared via the chemical oxidative polymerization of the pyrrole monomer in polystyrene (PS) and zinc neutralized sulfonated polystyrene (Zn-SPS) films under supercritical carbon dioxide (SC-CO2) conditions.The strong swelling effect of SCCO2 made polypyrrole (PPy) particles not only form on the surface,but also become incorporated into the film,resulting in a homogeneous structure with a relatively higher conductivity.By comparison,the composite prepared in aqueous solutions shows a skin-core structure and a conductivity of 3 to 4 orders of magnitude lower than that of the former due to the diffusion-controlled process of the pyrrole monomer.The percolation thresholds of PS/PPy and Zn-SPS/PPy composites were 6.2% and 2.7% of the volume fraction of PPy,respectively,much lower than the theoretically predicted value of 16%.Moreover,the conductive composites prepared under SC-CO2 conditions showed higher thermal stability,especially in the high-temperature region.

  15. Improved thermal conductivity of Ag decorated carbon nanotubes water based nanofluids

    Energy Technology Data Exchange (ETDEWEB)

    Farbod, Mansoor, E-mail: farbod_m@scu.ac.ir; Ahangarpour, Ameneh

    2016-12-16

    The effect of Ag decoration of carbon nanotubes on thermal conductivity enhancement of Ag decorated MWCNTs water based nanofluids has been investigated. The pristine and functionalized MWCNTs were decorated with Ag nanoparticles by mass ratios of 1%, 2% and 4% and used to prepare water based nanofluids with 0.1 vol.%. An enhancement of 1–20.4 percent in thermal conductivity was observed. It was found that the decoration of functionalized MWCNTs can increase the thermal conductivity about 0.16–8.02 percent compared to the undecorated ones. The maximum enhancement of 20.4% was measured for the sample containing 4 wt.% Ag at 40 °C. - Highlights: • MWCNTs were decorated with Ag nanoparticles by the mass ratios of 1, 2 and 4%. • The decorated CNTs were used to prepare water based nanofluids with 0.1 Vol.%. • 1–20.4% increase was observed in thermal conductivity (TC) compared to pure water. • Ag decorated CNTs increased TC of nanofluid up to 8% compared to CNTs nanofluid.

  16. Electrically conductive strain sensing polyurethane nanocomposites with synergistic carbon nanotubes and graphene bifillers

    Science.gov (United States)

    Liu, Hu; Gao, Jiachen; Huang, Wenju; Dai, Kun; Zheng, Guoqiang; Liu, Chuntai; Shen, Changyu; Yan, Xingru; Guo, Jiang; Guo, Zhanhu

    2016-06-01

    Thermoplastic polyurethane (TPU) based conductive polymer composites (CPCs) with a reduced percolation threshold and tunable resistance-strain sensing behavior were obtained through the addition of synergistic carbon nanotubes (CNT) and graphene bifillers. The percolation threshold of graphene was about 0.006 vol% when the CNT content was fixed at 0.255 vol% that is below the percolation threshold of CNT/TPU nanocomposites. The synergistic effect between graphene and CNT was identified using the excluded volume theory. Graphene acted as a `spacer' to separate the entangled CNTs from each other and the CNT bridged the broad gap between individual graphene sheets, which was beneficial for the dispersion of CNT and formation of effective conductive paths, leading to better electrical conductivity at a lower conductive filler content. Compared with the dual-peak response pattern of the CNT/TPU based strain sensors, the CPCs with hybrid conductive fillers displayed single-peak response patterns under small strain, indicating good tunability with the synergistic effect of CNT and graphene. Under larger strain, prestraining was adopted to regulate the conductive network, and better tunable single-peak response patterns were also obtained. The CPCs also showed good reversibility and reproductivity under cyclic extension. This study paves the way for the fabrication of CPC based strain sensors with good tunability.Thermoplastic polyurethane (TPU) based conductive polymer composites (CPCs) with a reduced percolation threshold and tunable resistance-strain sensing behavior were obtained through the addition of synergistic carbon nanotubes (CNT) and graphene bifillers. The percolation threshold of graphene was about 0.006 vol% when the CNT content was fixed at 0.255 vol% that is below the percolation threshold of CNT/TPU nanocomposites. The synergistic effect between graphene and CNT was identified using the excluded volume theory. Graphene acted as a `spacer' to separate the

  17. Conductive surface modification of LiFePO4 with nitrogen doped carbon layers for lithium-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Sukeun [ORNL; Liao, Chen [ORNL; Sun, Xiao-Guang [ORNL; Bridges, Craig A [ORNL; Unocic, Raymond R [ORNL; Nanda, Jagjit [ORNL; Dai, Sheng [ORNL; Paranthaman, Mariappan Parans [ORNL

    2012-01-01

    The LiFePO4 rod surface modified with nitrogen doped carbon layer has been prepared using hydrothermal processing followed by post-annealing in the presence of an ionic liquid. The coated LiFePO4 rod exhibits good capacity retention and high rate capability as the nitrogen doped carbon improves conductivity and prevents aggregation of the rod during cycling.

  18. Using the carbon nanotube (CNT)/CNT interaction to obtain hybrid conductive nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Santos, J.; Silva, A.; Bretas, R., E-mail: joaopaulofsbrasil@hotmail.com, E-mail: bretas@ufscar.br [Department of Materials Engineering, Federal University of São Carlos, Rod. Washington Luís, Km 235, PO Box 676, São Carlos, SP, 13565-905 (Brazil)

    2015-05-22

    Carbon nanotubes (CNTs) combine unique physical, electrical, chemical, thermal and mechanical properties with a huge surface area that qualify them to a broad range of applications. These potential applications, however, are often limited due to the strong inter-tubes van der Waals interactions, which results in poor dispersion in polymeric matrixes or solvents in general. Thus, the goal of this work was to use this limitation as an advantage, to produce novel conductive hybrid nanostructures, which consist of nonwoven Nylon 6 (PA6) mats of electrospun nanofibers with a large amount of multiwall carbon nanotubes (MWCNT) strongly attached and adsorbed on the nanofibers´ surfaces. To produce such structures, the MWCNT were previously functionalized with carboxylic groups and subsequently incorporated in the nanofibers by two subsequent steps: i) preparation of nonwoven mats of PA6/MWCNT by electrospinning and ii) treatment of the mats in an aqueous dispersion of MWCNT/Triton X–100. Analyses of UV-visible light showed that carboxylic groups were actually inserted in the MWCNT. Thermogravimetric analyzes (TGA) showed that the amount of adsorbed MWCNT on the fibers´ surfaces at the end of the procedure was approximately 12 times higher than after the first step. Micrographs obtained by scanning electron microscopy (SEM) confirmed this result and electrical conductivities measurements of the MWCNT/PA6, after the treatment in the aqueous solution, showed that these structures had conductivity of 10-2 S/m. It was concluded that the adhesion of CNTs at the surface of the nanofibers occurred due a combination of two types of bonding: hydrogen bonds between the carboxylic groups of the functionalized CNT and the PA6 and van der Waals interactions between the CNTs.

  19. Using the carbon nanotube (CNT)/CNT interaction to obtain hybrid conductive nanostructures

    Science.gov (United States)

    Santos, J.; Silva, A.; Bretas, R.

    2015-05-01

    Carbon nanotubes (CNTs) combine unique physical, electrical, chemical, thermal and mechanical properties with a huge surface area that qualify them to a broad range of applications. These potential applications, however, are often limited due to the strong inter-tubes van der Waals interactions, which results in poor dispersion in polymeric matrixes or solvents in general. Thus, the goal of this work was to use this limitation as an advantage, to produce novel conductive hybrid nanostructures, which consist of nonwoven Nylon 6 (PA6) mats of electrospun nanofibers with a large amount of multiwall carbon nanotubes (MWCNT) strongly attached and adsorbed on the nanofiberś surfaces. To produce such structures, the MWCNT were previously functionalized with carboxylic groups and subsequently incorporated in the nanofibers by two subsequent steps: i) preparation of nonwoven mats of PA6/MWCNT by electrospinning and ii) treatment of the mats in an aqueous dispersion of MWCNT/Triton X-100. Analyses of UV-visible light showed that carboxylic groups were actually inserted in the MWCNT. Thermogravimetric analyzes (TGA) showed that the amount of adsorbed MWCNT on the fiberś surfaces at the end of the procedure was approximately 12 times higher than after the first step. Micrographs obtained by scanning electron microscopy (SEM) confirmed this result and electrical conductivities measurements of the MWCNT/PA6, after the treatment in the aqueous solution, showed that these structures had conductivity of 10-2 S/m. It was concluded that the adhesion of CNTs at the surface of the nanofibers occurred due a combination of two types of bonding: hydrogen bonds between the carboxylic groups of the functionalized CNT and the PA6 and van der Waals interactions between the CNTs.

  20. Thermal conductivity mapping of pyrolytic carbon and silicon carbide coatings on simulated fuel particles by time-domain thermoreflectance

    Energy Technology Data Exchange (ETDEWEB)

    Lopez-Honorato, E. [Materials Science Centre, School of Materials, University of Manchester, Grosvenor Street, Manchester M1 7HS (United Kingdom); Chiritescu, C. [Department of Materials Science and Engineering, Frederick Seitz Materials Research Laboratory, University of Illinois, Urbana, IL 61801 (United States); Xiao, P. [Materials Science Centre, School of Materials, University of Manchester, Grosvenor Street, Manchester M1 7HS (United Kingdom)], E-mail: Ping.xiao@manchester.ac.uk; Cahill, David G. [Department of Materials Science and Engineering, Frederick Seitz Materials Research Laboratory, University of Illinois, Urbana, IL 61801 (United States); Marsh, G.; Abram, T.J. [Nexia Solutions Ltd., Springfields PR4 0XJ (United Kingdom)

    2008-08-15

    Thermal conductivity of pyrolytic carbon and silicon carbide coatings on spherical particles has been mapped using time-domain thermoreflectance. The thermal conductivities measured for pyrolytic carbon ranged between 3.4 and 13.5 W/m K. The effect of porosity, pore-size distribution, anisotropy, in-plane disorder and domain sizes is discussed. A thermal conductivity of 168 W/m K was obtained for SiC. Mapping of the thermal conductivity of coated fuel particles provides useful data for modeling fuel performance during the operation of nuclear reactors.

  1. 陶瓷-活性炭球为载体的CWAO催化剂%Ceramic-activated carbon sphere supported catalyst for catalytic wet air oxidation(CWAO)

    Institute of Scientific and Technical Information of China (English)

    刘卫民

    2012-01-01

    Ceramic-activated carbon sphere as support of ruthenium catalysts were evaluated through the catalytic wet air oxidation(CWAO) of resin effluent.The effects of the preparation conditions,such as ceramic-activated carbon sphere support,Ru loading,macro-pore diameter of ceramic sphere,etc.on the catalytic activity and stability were investigated.The results show that the catalytic activity varies according to the following order: Ru/KC-120 Ru/KC-80 Ru/KC-60 KC-120 without catalysts.It is found that the 3% Ru/KC-120 catalyst displayed highest stability in the CWAO of resin effluent during 120 min.Chemical oxygen demand(COD) and phenol removal were about 91% and 96%,respectively,at the reaction temperature of 200℃,oxygen pressure of 1.5 MPa.%以陶瓷-活性炭球为载体制备载Ru催化剂,用于催化湿式氧化(CWAO)法处理酚醛树脂废水,考察了陶瓷-活性炭球载体、Ru负载量和陶瓷球宏孔孔径等对催化剂的催化活性和稳定性的影响。实验结果表明,催化剂催化活性的顺序为:Ru/KC-120〉Ru/KC-80〉Ru/KC-60〉KC-120〉无催化剂。在200℃,氧气分压为1.5 MPa等条件下,催化湿式氧化酚醛树脂废水,3%Ru/KC-120催化剂表现良好的催化活性与稳定性,在120 min内,COD和苯酚去除率分别达到91%和96%。

  2. Effects of Lithium Oxide Addition on Sintering Behavior and Electrical Conductivity of Ce0.8Gd0.2O1.9 Ceramics Prepared by Commercial Powders.

    Science.gov (United States)

    Seo, Seung-Woo; Park, Min-Woo; Lee, Joo-Sin

    2016-05-01

    The densification behavior and electrical conductivity of Ce0.8Gd0.2O1.9 ceramics with lithium oxide concentrations ranging from 0 to 7 mol% were investigated. The sintered density was found to increase with increasing Li2O content up to 2 mol% and then to decrease somewhat upon further Li20 addition. Dense Ce0.8Gd0.2O1.9 ceramics with 97% of the theoretical density could be obtained by sintering the milled mixture with 2 mol% Li2O addition at 1250 degrees C for 5 h. The conductivity of the 2 mol% Li2O-added specimen showed a maximum value of 4.99 x 10(-3) Ω(-1) x cm(-1) at 700 degrees C. Pure Ce0.8Gd0.2O1.9 ceramics needed to be sintered at 1550 degrees C in order to obtain an equivalent theoretical density and conductivity. The addition of Li2O was found to promote the sintering properties and electrical conductivities of Gd2O3-doped CeO2.

  3. Press-Printed Conductive Carbon Black Nanoparticle Films for Molecular Detection at the Microscale.

    Science.gov (United States)

    Della Pelle, Flavio; Vázquez, Luis; Del Carlo, Michele; Sergi, Manuel; Compagnone, Dario; Escarpa, Alberto

    2016-08-26

    Carbon black nanoparticle (CBNP) press-transferred film-based transducers for the molecular detection at the microscale level were proposed for the first time. Current-sensing atomic force microscopy (CS-AFM) revealed that the CBNP films were effectively press-transferred, retaining their good conductivity. A significant correlation between the morphology and the resistance was observed. The highest resistance was localized at the top of the press-transferred film protrusions, whereas low values are usually obtained at the deep crevices or grooves. The amount of press-transferred CBNPs is the key parameter to obtain films with improved conductivity, which is in good agreement with the electrochemical response. In addition, the conductivity of such optimum films was not only Ohmic; in fact, tunneling/hopping contributions were observed, as assessed by CS-AFM. The CBNP films acted as exclusive electrochemical transducers as evidenced by using two classes of molecules, that is, neurotransmitters and environmental organic contaminants. These results revealed the potential of these CBNP press-transferred films for providing new options in microfluidics and other related micro- and nanochemistry applications.

  4. Conductive Graphitic Carbon Nitride as an Ideal Material for Electrocatalytically Switchable CO2 Capture.

    Science.gov (United States)

    Tan, Xin; Kou, Liangzhi; Tahini, Hassan A; Smith, Sean C

    2015-12-01

    Good electrical conductivity and high electron mobility of the sorbent materials are prerequisite for electrocatalytically switchable CO2 capture. However, no conductive and easily synthetic sorbent materials are available until now. Here, we examined the possibility of conductive graphitic carbon nitride (g-C4N3) nanosheets as sorbent materials for electrocatalytically switchable CO2 capture. Using first-principle calculations, we found that the adsorption energy of CO2 molecules on g-C4N3 nanosheets can be dramatically enhanced by injecting extra electrons into the adsorbent. At saturation CO2 capture coverage, the negatively charged g-C4N3 nanosheets achieve CO2 capture capacities up to 73.9 × 10(13) cm(-2) or 42.3 wt%. In contrast to other CO2 capture approaches, the process of CO2 capture/release occurs spontaneously without any energy barriers once extra electrons are introduced or removed, and these processes can be simply controlled and reversed by switching on/off the charging voltage. In addition, these negatively charged g-C4N3 nanosheets are highly selective for separating CO2 from mixtures with CH4, H2 and/or N2. These predictions may prove to be instrumental in searching for a new class of experimentally feasible high-capacity CO2 capture materials with ideal thermodynamics and reversibility.

  5. Simulations of water transport through carbon nanotubes: how different water models influence the conduction rate.

    Science.gov (United States)

    Liu, L; Patey, G N

    2014-11-14

    The conduction rate of water through (8,8) and (9,9) carbon nanotubes at 300 K and a pressure difference of 220 MPa is investigated using molecular dynamics simulations. The TIP3P, SPC/E, and TIP4P/2005 water models are considered. The pressure-driven flow rate is found to be strongly model dependent for both nanotubes. The fastest model (TIP3P) has a flow rate that is approximately five times faster than the slowest (TIP4P/2005). It is shown that the flow rate is significantly influenced by the structure taken on by the water molecules confined in the nanotube channels. The slower models, TIP4P/2005 and SPC/E, tend to favor stacked ring arrangements, with the molecules of a ring moving together through the nanotube, in what we term a "cluster-by-cluster" conduction mode. Confined TIP3P water has a much weaker tendency to form ring structures, and those that do form are fragile and break apart under flow conditions. This creates a much faster "diffusive" conduction mode where the water molecules mainly move through the tube as individual particles, rather than as components of a larger cluster. Our results demonstrate that water models developed to describe the properties of bulk water can behave very differently in confined situations.

  6. A morphological investigation of conductive networks in polymers loaded with carbon nanotubes

    KAUST Repository

    Lubineau, Gilles

    2017-01-13

    Loading polymers with conductive nanoparticles, such as carbon nanotubes, is a popular approach toward improving their electrical properties. Resultant materials are typically described by the weight or volume fractions of their nanoparticles. Because these conductive particles are only capable of charge transfer over a very short range, most do not interact with the percolated paths nor do they participate to the electrical transfer. Understanding how these particles are arranged is necessary to increase their efficiency. It is of special interest to understand how these particles participate in creating percolated clusters, either in a specific or in all directions, and non-percolated clusters. For this, we present a computational modeling strategy based on a full morphological analysis of a network to systematically analyse conductive networks and show how particles are arranged. This study provides useful information for designing these types of materials and examples suitable for characterizing important features, such as representative volume element, the role of nanotube tortuosity and the role of tunneling cutoff distance.

  7. Quantitative Conductive Atomic Force Microscopy on Single-Walled Carbon Nanotube-Based Polymer Composites.

    Science.gov (United States)

    Bârsan, Oana A; Hoffmann, Günter G; van der Ven, Leendert G J; de With, Gijsbertus

    2016-08-03

    Conductive atomic force microscopy (C-AFM) is a valuable technique for correlating the electrical properties of a material with its topographic features and for identifying and characterizing conductive pathways in polymer composites. However, aspects such as compatibility between tip material and sample, contact force and area between the tip and the sample, tip degradation and environmental conditions render quantifying the results quite challenging. This study aims at finding the suitable conditions for C-AFM to generate reliable, reproducible, and quantitative current maps that can be used to calculate the resistance in each point of a single-walled carbon nanotube (SWCNT) network, nonimpregnated as well as impregnated with a polymer. The results obtained emphasize the technique's limitation at the macroscale as the resistance of these highly conductive samples cannot be distinguished from the tip-sample contact resistance. Quantitative C-AFM measurements on thin composite sections of 150-350 nm enable the separation of sample and tip-sample contact resistance, but also indicate that these sections are not representative for the overall SWCNT network. Nevertheless, the technique was successfully used to characterize the local electrical properties of the composite material, such as sample homogeneity and resistance range of individual SWCNT clusters, at the nano- and microscale.

  8. A three-dimensionally chitin nanofiber/carbon nanotube hydrogel network for foldable conductive paper.

    Science.gov (United States)

    Chen, Chuchu; Yang, Chuang; Li, Suiyi; Li, Dagang

    2015-12-10

    We reported a highly conductive nanocomposite made with multiwalled carbon nanotubes (MWCNTs) and chitin nanofibers (ChNFs). The MWCNTs were dispersed into ChNFs by the simple process of vacuum-filtration, forming a three-dimensional network structure. In this approach, MWCNT acted as a filler to introduce electron channel paths throughout the ChNF skeleton. And then, a hybrid hydrogel system (20 wt.% NaOH, -18 °C) was applied to prepare the ChNF/MWCNT gel-film followed with drying process. It is found that the resultant ChNF/MWCNT gel-film exposed much more MWCNT areas forming denser structure due to the shrinking of ChNFs after the gelation treatment. Compared with ChNF/MWCNT film, the one treated under hydrogel system (ChNF/MWCNT gel-film) exhibited almost twice higher conductivity (9.3S/cm for 50 wt.% MWCNTs in gel-film; whereas 4.7S/cm for 50 wt.% MWCNTs in film). Moreover, the facile and low-cost of this conductive paper may have great potential in development of foldable electronic devices.

  9. Carbonate apatite formation on novel multiphase CaO-SiO2-P2O5-MgO glass-ceramics in TRIS-HCl buffer

    Directory of Open Access Journals (Sweden)

    Lachezar Radev

    2016-06-01

    Full Text Available The main purpose of the presented article is the preparation of novel glass-ceramics in CaO-SiO2-P2O5-MgO system and evaluation of carbonate apatite formation after soaking in TRIS-HCl buffer solution for 14 days. The investigated samples were prepared via sol-gel method and structure of the obtained samples was studied using XRD, FTIR, SEM, XPS and ICP-AES. XRD of the thermally treated samples showed that the presence of some crystalline phases is depended on the gel composition. FTIR revealed the existence of all characteristic bands for the observed crystalline phases. SEM monitored the presence of particles with different morphology. After soaking in TRIS-HCl solution, FTIR confirmed that carbonate apatite was formed on the soaked surface. The obtained data are in a good agreement with XPS analysis. The change of ions concentrations in TRIS-HCl buffer solution after immersion of the prepared glass-ceramics was recorded by ICP-AES measurements.

  10. On Ceramics.

    Science.gov (United States)

    School Arts, 1982

    1982-01-01

    Presents four ceramics activities for secondary-level art classes. Included are directions for primitive kiln construction and glaze making. Two ceramics design activities are described in which students make bizarrely-shaped lidded jars, feet, and footwear. (AM)

  11. Electrical conductivity modeling of multiple carbon fillers in liquid crystal polymer composites for fuel cell bipolar plate applications

    Energy Technology Data Exchange (ETDEWEB)

    Barton, R.L.; Keith, J.M.; King, J.A. [Michigan Technological Univ., Houghton, MI (United States). Dept. of Chemical Engineering

    2008-08-15

    This study modelled the electrical conductivity of a single filler composite system using a general effective media (GEM) equation. The aim of the study was to investigate the use of synthetic graphite and carbon fiber in liquid crystal polymers for fuel cell bipolar plate applications. The polymer consisted of 73 mole per cent hydroxybenzoic acid and 27 mole per cent hydroxynaphthoic acid. Composites of various concentrations of single and multiple filler combinations were tested. A volumetric in-plane electrical conductivity test was conducted on all samples in order to measure voltage drop. A through-plane conductivity test was conducted to measure resistivity. The GEM equation was then used to model the conductivity data obtained during the tests. Results of the study showed that at 45 vol per cent, the electrical conductivity of the multiple filler composite was comparable to data obtained from single filler electrical conductivities. The electrical conductivity of the multiple filler composite at 60 per cent graphite and 10 per cent carbon fiber was comparable to the single filler carbon fiber composite, but lower than the single filler synthetic graphite composite. Results also showed that the GEM equation provided excellent agreement with results obtained during the experiments. It was concluded that the percolation threshold of the multiple filler composite was almost identical to the single carbon fiber filler, but lower than the single synthetic graphite composite. 35 refs., 3 tabs., 2 figs.

  12. Structural, nanomechanical and variable range hopping conduction behavior of nanocrystalline carbon thin films deposited by the ambient environment assisted filtered cathodic jet carbon arc technique

    Energy Technology Data Exchange (ETDEWEB)

    Panwar, O.S., E-mail: ospanwar@mail.nplindia.ernet.in [Polymorphic Carbon Thin Films Group, Physics of Energy Harvesting Division, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi - 110 012 (India); Rawal, Ishpal; Tripathi, R.K. [Polymorphic Carbon Thin Films Group, Physics of Energy Harvesting Division, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi - 110 012 (India); Srivastava, A.K. [Electron and Ion Microscopy, Sophisticated and Analytical Instruments, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi - 110 012 (India); Kumar, Mahesh [Ultrafast Opto-Electronics and Tetrahertz Photonics Group, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi - 110 012 (India)

    2015-04-15

    Highlights: • Nanocrystalline carbon thin films are grown by filtered cathodic jet carbon arc process. • Effect of gaseous environment on the properties of carbon films has been studied. • The structural and nanomechanical properties of carbon thin films have been studied. • The VRH conduction behavior in nanocrystalline carbon thin films has been studied. - Abstract: This paper reports the deposition and characterization of nanocrystalline carbon thin films by filtered cathodic jet carbon arc technique assisted with three different gaseous environments of helium, nitrogen and hydrogen. All the films are nanocrystalline in nature as observed from the high resolution transmission electron microscopic (HRTEM) measurements, which suggests that the nanocrystallites of size ∼10–50 nm are embedded though out the amorphous matrix. X-ray photoelectron spectroscopic studies suggest that the film deposited under the nitrogen gaseous environment has the highest sp{sup 3}/sp{sup 2} ratio accompanied with the highest hardness of ∼18.34 GPa observed from the nanoindentation technique. The film deposited under the helium gaseous environment has the highest ratio of the area under the Raman D peak to G peak (A{sub D}/A{sub G}) and the highest conductivity (∼2.23 S/cm) at room temperature, whereas, the film deposited under the hydrogen environment has the lowest conductivity value (2.27 × 10{sup −7} S/cm). The temperature dependent dc conduction behavior of all the nanocrystalline carbon thin films has been analyzed in the light of Mott’s variable range hopping (VRH) conduction mechanism and observed that all the films obey three dimension VRH conduction mechanism for the charge transport.

  13. Electronic structure and conductivity of nanocomposite metal (Au,Ag,Cu,Mo)-containing amorphous carbon films

    Energy Technology Data Exchange (ETDEWEB)

    Endrino, Jose L.; Horwat, David; Gago, Raul; Andersson, Joakim; Liu, Y.S.; Guo, Jinghua; Anders, Andre

    2008-05-14

    In this work, we study the influence of the incorporation of different metals (Me = Au, Ag, Cu, Mo) on the electronic structure of amorphous carbon (a-C:Me) films. The films were produced at room temperature using a novel pulsed dual-cathode arc deposition technique. Compositional analysis was performed with secondary neutral mass spectroscopy whereas X-ray diffraction was used to identify the formation of metal nanoclusters in the carbon matrix. The metal content incorporated in the nanocomposite films induces a drastic increase in the conductivity, in parallel with a decrease in the band gap corrected from Urbach energy. The electronic structure as a function of the Me content has been monitored by x-ray absorption near edge structure (XANES) at the C K-edge. XANES showed that the C host matrix has a dominant graphitic character and that it is not affected significantly by the incorporation of metal impurities, except for the case of Mo, where the modifications in the lineshape spectra indicated the formation of a carbide phase. Subtle modifications of the spectral lineshape are discussed in terms of nanocomposite formation.

  14. 25th anniversary article: carbon nanotube- and graphene-based transparent conductive films for optoelectronic devices.

    Science.gov (United States)

    Du, Jinhong; Pei, Songfeng; Ma, Laipeng; Cheng, Hui-Ming

    2014-04-02

    Carbon nanotube (CNT)- and graphene (G)-based transparent conductive films (TCFs) are two promising alternatives for commonly-used indium tin oxide-based TCFs for future flexible optoelectronic devices. This review comprehensively summarizes recent progress in the fabrication, properties, modification, patterning, and integration of CNT- and G-TCFs into optoelectronic devices. Their potential applications and challenges in optoelectronic devices, such as organic photovoltaic cells, organic light emitting diodes and touch panels, are discussed in detail. More importantly, their key characteristics and advantages for use in these devices are compared. Despite many challenges, CNT- and G-TCFs have demonstrated great potential in various optoelectronic devices and have already been used for some products like touch panels of smartphones. This illustrates the significant opportunities for the industrial use of CNTs and graphene, and hence pushes nanoscience and nanotechnology one step towards practical applications.

  15. Efficient coating of transparent and conductive carbon nanotube thin films on plastic substrates

    Energy Technology Data Exchange (ETDEWEB)

    Ng, M H Andrew; Hartadi, Lysia T; Tan Huiwen; Poa, C H Patrick [Institute of Materials Research and Engineering, 3 Research Link, 117602 (Singapore)], E-mail: patrick-poa@imre.a-star.edu.sg

    2008-05-21

    Optically transparent and electrically conductive single-walled carbon nanotube (SWNT) thin films were fabricated at room temperature using a dip-coating technique. The film transparency and sheet resistance can be easily tailored by controlling the number of coatings. Aminopropyltriethoxysilane (APTS) was used as an adhesion promoter and, together with surfactant Triton X-100, greatly improved the SWNTs coating. Only five coats were required to obtain a sheet resistance of 2.05 {omega}{open_square} and film transparency of 84 %T. The dip-coated film after post-deposition treatment with nitric acid has a sheet resistance as low as 130 {omega}{open_square} at 69 %T. This technique is suitable for large-scale SWNT coating at room temperature and can be used on different types of substrates such as glass and plastics. This paper will discuss the role of the adhesion promoter and surfactant in the coating process.

  16. Synthesis and characterization of conducting composites of polyaniline and carbon black with high thermal stability

    Directory of Open Access Journals (Sweden)

    Fabio R. Simões

    2009-01-01

    Full Text Available In this work, a detailed chemical route to prepare thermally stable polyaniline (PANI/carbon black (CB composites is described. The syntheses were performed by chemical polymerization of aniline over CB particles, using different PANI/CB mass ratios. The thermal and electrical properties were characterized. Composites with mass ratio up to 65:35 (PANI:CB showed excellent thermal stability maintaining their conducting properties when thermally treated at 230 °C for two hours, which is adequate to process these materials. Moreover, the results showed an important reduction in the surface area of the composites which have a good relationship with the improvement of the rheological properties in melt processing.

  17. Highly Conductive Carbon Fiber Reinforced Concrete for Icing Prevention and Curing

    Directory of Open Access Journals (Sweden)

    Oscar Galao

    2016-04-01

    Full Text Available This paper aims to study the feasibility of highly conductive carbon fiber reinforced concrete (CFRC as a self-heating material for ice formation prevention and curing in pavements. Tests were carried out in lab ambient conditions at different fixed voltages and then introduced in a freezer at −15 °C. The specimens inside the freezer were exposed to different fixed voltages when reaching +5 °C for prevention of icing and when reaching the temperature inside the freezer, i.e., −15 °C, for curing of icing. Results show that this concrete could act as a heating element in pavements with risk of ice formation, consuming a reasonable amount of energy for both anti-icing (prevention and deicing (curing, which could turn into an environmentally friendly and cost-effective deicing method.

  18. Electrically Conductive, Optically Transparent Polymer/Carbon Nanotube Composites and Process for Preparation Thereof

    Science.gov (United States)

    Connell, John W. (Inventor); Smith, Joseph G. (Inventor); Harrison, Joycelyn S. (Inventor); Park, Cheol (Inventor); Watson, Kent A. (Inventor); Ounaies, Zoubeida (Inventor)

    2011-01-01

    The present invention is directed to the effective dispersion of carbon nanotubes (CNTs) into polymer matrices. The nanocomposites are prepared using polymer matrices and exhibit a unique combination of properties, most notably, high retention of optical transparency in the visible range (i.e., 400-800 nm), electrical conductivity, and high thermal stability. By appropriate selection of the matrix resin, additional properties such as vacuum ultraviolet radiation resistance, atomic oxygen resistance, high glass transition (T.sub.g) temperatures, and excellent toughness can be attained. The resulting nanocomposites can be used to fabricate or formulate a variety of articles such as coatings on a variety of substrates, films, foams, fibers, threads, adhesives and fiber coated prepreg. The properties of the nanocomposites can be adjusted by selection of the polymer matrix and CNT to fabricate articles that possess high optical transparency and antistatic behavior.

  19. Morphology and Cure Behavior of Multi-walled Carbon Nanotubes-based Thermally Conductive Adhesive

    Institute of Scientific and Technical Information of China (English)

    WANG Junxia; YAN Shilin; HE Yunban; YAN Fei; XIE Beiping

    2014-01-01

    We evaluated the cure behavior of multi-walled carbon nanotubes (MWCNTs) based thermally conductive adhesive by comprehensively thermal analysis, which presented extremely complicated variability of conversion ratioαas a function of temperature with synergistic action of positive effect and negative volume-blocking effect of MWCNTs and cross-linked network of cured polymer molecules. Due to the decomposition of MWCNTs and degradation of polymer, the mass drop is dramatically obvious over the temperature range of 330-370℃. Binary resins filled with acid-treated MWCNTs present similar reaction interval as neat epoxy and matrix resins, which is distinct from the material filled with raw MWCNTs. The alteration of the crystalline temperature and cure temperature of resins is attributed to heterogeneous nucleation of MWCNTs in matrix resins. The-COOH group of acid-treated MWCNTs reacts with epoxy groups and thus generates cross-linking, accelerates the reaction rate and reduces the cure temperature.

  20. Simultaneous measurement of thermal conductivity and thermal contact resistance of individual carbon fibers using Raman spectroscopy.

    Science.gov (United States)

    Liu, Jinhui; Wang, Haidong; Ma, Weigang; Zhang, Xing; Song, Yan

    2013-04-01

    In this paper, a new method employing Raman spectroscopy to determine thermal conductivity (TC) and thermal contact resistance (TCR) of an individual fiber was developed. Laser absorption is accounted for, but there is no need to be determined in this method. The local temperatures along the fiber longitudinal direction were determined by Raman shift. Two independent equations related to TC and TCR were established through measuring the temperature variation induced by changing electrical heating power at the center of the sample and the local temperature rise induced by a focused laser heating from Raman spectroscopy at two different positions on the sample, respectively. By solving the two equations, TC and TCR can then be obtained. This method has been validated by measuring two suspended carbon fibers.