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Sample records for polydimethylsiloxane-based conducting composites

  1. Polydimethylsiloxane-based conducting composites and their applications in microfluidic chip fabrication

    PubMed Central

    Gong, Xiuqing; Wen, Weijia

    2009-01-01

    This paper reviews the design and fabrication of polydimethylsiloxane (PDMS)-based conducting composites and their applications in microfluidic chip fabrication. Owing to their good electrical conductivity and rubberlike elastic characteristics, these composites can be used variously in soft-touch electronic packaging, planar and three-dimensional electronic circuits, and in-chip electrodes. Several microfluidic components fabricated with PDMS-based composites have been introduced, including a microfluidic mixer, a microheater, a micropump, a microdroplet controller, as well as an all-in-one microfluidic chip. PMID:19693388

  2. Polydimethylsiloxane-based self-healing composite and coating materials

    NASA Astrophysics Data System (ADS)

    Cho, Soo Hyoun

    This thesis describes the science and technology of a new class of autonomic polymeric materials which mimic some of the functionalities of biological materials. Specifically, we demonstrate an autonomic self-healing polymer system which can heal damage in both coatings and bulk materials. The new self-healing system we developed greatly extends the capability of self-healing polymers by introducing tin catalyzed polycondensation of hydroxyl end-functionalited polydimethylsiloxane and polydiethoxysiloxane based chemistries. The components in this system are widely available and comparatively low in cost, and the healing chemistry also remains stable in humid or wet environments. These achievements significantly increase the probability that self-healing could be extended not only to polymer composites but also to coatings and thin films in harsh environments. We demonstrate the bulk self-healing property of a polymer composite composed of a phase-separated PDMS healing agent and a microencapsulated organotin catalyst by chemical and mechanical testing. Another significant research focus is on self-healing polymer coatings which prevent corrosion of a metal substrate after deep scratch damage. The anti-corrosion properties of the self-healing polymer on metal substrates are investigated by corrosion resistance and electrochemical tests. Even after scratch damage into the substrate, the coating is able to heal, while control samples which do not include all the necessary healing components reveal rapid corrosion propagation. This self-healing coating solution can be easily applied to most substrate materials, and is compatible with most common polymer matrices. Self-healing has the potential to extend the lifetime and increase the reliability of thermosetting polymers used in a wide variety of applications ranging from microelectronics to aerospace.

  3. Bioinspired polydimethylsiloxane-based composites with high shear resistance against wet tissue.

    PubMed

    Fischer, Sarah C L; Levy, Oren; Kroner, Elmar; Hensel, René; Karp, Jeffrey M; Arzt, Eduard

    2016-08-01

    Patterned microstructures represent a potential approach for improving current wound closure strategies. Microstructures can be fabricated by multiple techniques including replica molding of soft polymer-based materials. However, polymeric microstructures often lack the required shear resistance with tissue needed for wound closure. In this work, scalable microstructures made from composites based on polydimethylsiloxane (PDMS) were explored to enhance the shear resistance with wet tissue. To achieve suitable mechanical properties, PDMS was reinforced by incorporation of polyethylene (PE) particles into the pre-polymer and by coating PE particle reinforced substrates with parylene. The reinforced microstructures showed a 6-fold enhancement, the coated structures even a 13-fold enhancement in Young׳s modulus over pure PDMS. Shear tests of mushroom-shaped microstructures (diameter 450µm, length 1mm) against chicken muscle tissue demonstrate first correlations that will be useful for future design of wound closure or stabilization implants. PMID:26849031

  4. Thermal Stability and Ablation Behavior of Modified Polydimethylsiloxane-Based Polyurethane Composites Reinforced with Polyhedral Oligomeric Silsesquioxane.

    PubMed

    Han, Zhongyou; Xi, Yukun; Kwon, Younghwan

    2016-02-01

    Series of polydimethylsiloxane (PDMS)-based polyurethane (PU)/polyhedral oligomeric silsesquioxane (POSS) composites are prepared using ether or polyether modified diol/polyol PDMS prepolymers, isophorone diisocyanate (IPDI) and either non-reactive or reactive POSS. The effect of POSS incorporated chemically or physically, number of ethylene oxide units and crosslinking on PDMS based PU is investigated in terms of thermal stability and ablation properties. The ablation property is measured using an oxyacetylene torch test, and the ablation rate is evaluated. The results show that POSS molecules make a considerable influence on the ablative resistance, because they act as protective silica forming precursors under oxyacetylene condition. POSS molecules, especially methyl POSS, in PU matrix leads to the formation of densely accumulated spherical silica layers on the top of the ablated surface, resulting in improved ablation resistance. PMID:27433703

  5. Conducting Compositions of Matter

    NASA Technical Reports Server (NTRS)

    Viswanathan, Tito (Inventor)

    1999-01-01

    The invention provides conductive compositions of matter, as well as methods for the preparation of the conductive compositions of matter, solutions comprising the conductive compositions of matter, and methods of preparing fibers or fabrics having improved anti-static properties employing the conductive compositions of matter.

  6. Conducting compositions of matter

    NASA Technical Reports Server (NTRS)

    Viswanathan, Tito (Inventor)

    2000-01-01

    The invention provides conductive compositions of matter, as well as methods for the preparation of the conductive compositions of matter, solutions comprising the conductive compositions of matter, and methods of preparing fibers or fabrics having improved anti-static properties employing the conductive compositions of matter.

  7. Electrically conductive cellulose composite

    DOEpatents

    Evans, Barbara R.; O'Neill, Hugh M.; Woodward, Jonathan

    2010-05-04

    An electrically conductive cellulose composite includes a cellulose matrix and an electrically conductive carbonaceous material incorporated into the cellulose matrix. The electrical conductivity of the cellulose composite is at least 10 .mu.S/cm at 25.degree. C. The composite can be made by incorporating the electrically conductive carbonaceous material into a culture medium with a cellulose-producing organism, such as Gluconoacetobacter hansenii. The composites can be used to form electrodes, such as for use in membrane electrode assemblies for fuel cells.

  8. Electrically conductive composite material

    DOEpatents

    Clough, Roger L.; Sylwester, Alan P.

    1989-01-01

    An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistant pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like.

  9. Electrically conductive composite material

    DOEpatents

    Clough, R.L.; Sylwester, A.P.

    1988-06-20

    An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistent pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like. 2 figs.

  10. High conductivity composite metal

    DOEpatents

    Zhou, Ruoyi; Smith, James L.; Embury, John David

    1998-01-01

    Electrical conductors and methods of producing them, where the conductors possess both high strength and high conductivity. Conductors are comprised of carbon steel and a material chosen from a group consisting of copper, nickel, silver, and gold. Diffusion barriers are placed between these two materials. The components of a conductor are assembled and then the assembly is subjected to heat treating and mechanical deformation steps.

  11. High conductivity composite metal

    DOEpatents

    Zhou, R.; Smith, J.L.; Embury, J.D.

    1998-01-06

    Electrical conductors and methods of producing them are disclosed, where the conductors possess both high strength and high conductivity. Conductors are comprised of carbon steel and a material chosen from a group consisting of copper, nickel, silver, and gold. Diffusion barriers are placed between these two materials. The components of a conductor are assembled and then the assembly is subjected to heat treating and mechanical deformation steps. 10 figs.

  12. Lightweight, Thermally Conductive Composite Material

    NASA Technical Reports Server (NTRS)

    Sharp, G. Richard; Loftin, Timothy A.

    1990-01-01

    Aluminum reinforced with carbon fibers superior to copper in some respects. Lightweight composite material has high thermal conductivity. Consists of aluminum matrix containing graphite fibers, all oriented in same direction. Available as sheets, tubes, and bars. Thermal conductivity of composite along fibers rises above that of pure copper over substantial range of temperatures. Graphite/aluminum composite useful in variety of heat-transfer applications in which reduction of weight critical. Used to conduct heat in high-density, high-speed integrated-circuit packages for computers and in base plates for electronic equipment. Also used to carry heat away from leading edges of wings in high-speed airplanes.

  13. Conductive Composites Made Less Expensively

    NASA Technical Reports Server (NTRS)

    Gaier, James R.

    2005-01-01

    The use of electrically conductive composite structures for electrostatic dissipation, electromagnetic interference shielding, and ground return planes could save between 30 and 90 percent of the mass of the structure, in comparison to aluminum. One strategy that has been shown to make conducting composites effectively uses intercalated graphite fiber as the reinforcement. Intercalation--the insertion of guest atoms or molecules between the graphene planes--can lower the electrical resistivity of graphite fibers by as much as a factor of 10, without sacrificing mechanical or thermal properties.

  14. Transparent conductive nano-composites

    DOEpatents

    Geohegan, David Bruce; Ivanov, Ilia N.; Puretzky, Alexander A.; Jesse, Stephen; Hu, Bin; Garrett, Matthew; Zhao, Bin

    2011-04-12

    The present invention, in one embodiment, provides a method of forming an organic electric device that includes providing a plurality of carbon nanostructures; and dispersing the plurality of carbon nanostructures in a polymeric matrix to provide a polymeric composite, wherein when the plurality of carbon nanostructures are present at a first concentration an interface of the plurality of carbon nanostructures and the polymeric matrix is characterized by charge transport when an external energy is applied, and when the plurality of carbon nanostructures are present at a second concentration the interface of the plurality of carbon nanostructures and the polymeric matrix are characterized by exciton dissociation when an external energy is applied, wherein the first concentration is less than the second concentration.

  15. Transparent conductive nano-composites

    DOEpatents

    Geohegan, David Bruce; Ivanov, Ilia N; Puretzky, Alexander A; Jesse, Stephen; Hu, Bin; Garrett, Matthew; Zhao, Bin

    2013-09-24

    The present invention, in one embodiment, provides a method of forming an organic electric device that includes providing a plurality of carbon nanostructures; and dispersing the plurality of carbon nanostructures in a polymeric matrix to provide a polymeric composite, wherein when the plurality of carbon nanostructures are present at a first concentration an interface of the plurality of carbon nanostructures and the polymeric matrix is characterized by charge transport when an external energy is applied, and when the plurality of carbon nanostructures are present at a second concentration the interface of the plurality of carbon nanostructures and the polymeric matrix are characterized by exciton dissociation when an external energy is applied, wherein the first concentration is less than the second concentration.

  16. Ionic conduction in polymer composite electrolytes

    NASA Astrophysics Data System (ADS)

    Dam, Tapabrata; Tripathy, Satya N.; Paluch, M.; Jena, S.; Pradhan, D. K.

    2016-05-01

    Conductivity and structural relaxation has been explored from modulus and dielectric loss formalisms respectively for a series of polymer composite electrolytes with zirconia as filler. The temperature dependence of conductivity followed Vogel-Tamman-Fulcher (VTF) behavior, which suggested a close correlation between conductivity and the segmental relaxation process in polymer electrolytes. Vogel temperature (T0) plays significant role in ion conduction process in these kind of materials.

  17. Composite Solid Electrolyte Containing Li+- Conducting Fibers

    NASA Technical Reports Server (NTRS)

    Appleby, A. John; Wang, Chunsheng; Zhang, Xiangwu

    2006-01-01

    Improved composite solid polymer electrolytes (CSPEs) are being developed for use in lithium-ion power cells. The matrix components of these composites, like those of some prior CSPEs, are high-molecular-weight dielectric polymers [generally based on polyethylene oxide (PEO)]. The filler components of these composites are continuous, highly-Li(+)-conductive, inorganic fibers. PEO-based polymers alone would be suitable for use as solid electrolytes, were it not for the fact that their room-temperature Li(+)-ion conductivities lie in the range between 10(exp -6) and 10(exp -8) S/cm, too low for practical applications. In a prior approach to formulating a CSPE, one utilizes nonconductive nanoscale inorganic filler particles to increase the interfacial stability of the conductive phase. The filler particles also trap some electrolyte impurities. The achievable increase in conductivity is limited by the nonconductive nature of the filler particles.

  18. Electronically conductive polymer composites and microstructures

    SciTech Connect

    Van Dyke, L.S.

    1993-01-01

    Composites of electronically conductive polymers with insulating host materials are investigated. A template synthesis method was developed for the production of electronically conductive polymer microstructures. In template synthesis the pores of a porous host membrane act as templates for the polymerization of a conductive polymer. The template synthetic method can be used to form either solid microfibrils or hollow microtubules. The electrochemical properties of conductive polymers produced via the template synthesis method are superior to those of conventionally synthesized conductive polymers. Electronically conductive polymers are used to impart conductivity to non-conductive materials. Two different approaches are used. First, thin film composites of conductive polymers with fluoropolymers are made by the polymerization of conductive polymers onto fluoropolymer films. Modification of the fluoropolymer surface prior to conductive polymer polymerization is necessary to obtain good adhesion between the two materials. The difference in adhesion of the conductive polymer to the modified and unmodified fluoropolymer surfaces can be used to pattern the conductive polymer coating. Patterning of the conductive polymer coating can alternatively be done via UV laser ablation of the conductive polymer. The second method by which conductive polymers were used to impart conductivity to an insulating polymer was via the formation of a graft copolymer. In this approach, heterocyclic monomers grafted to an insulating polyphosphazene backbone were polymerized to yield semiconductive materials. Finally the measurement of electrolyte concentration in polypyrrole and the effects of hydroxide anion on the electrochemical and electrical properties of polypyrrole are described. It is shown that treatment of polypyrrole with hydroxide anion increases the potential window over which polypyrrole is a good electronic conductor.

  19. Thermal Conductivity of Carbon Nanotube Composite Films

    NASA Technical Reports Server (NTRS)

    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.

  20. Effective thermal conductivity of damaged composites

    NASA Astrophysics Data System (ADS)

    Graham, Samuel, Jr.

    Ceramic matrix composites (CMCs) are susceptible to matrix cracking, fiber-matrix debonding, and oxidation processes as result of their application environments. These damage mechanisms act to degrade thermal conductivity and is a concern for many CMC applications. Prediction of this degradation relies on an accurate understanding of damage and thermal conductivity, and the development of analytical or numerical models. An experimental investigation into the degradation of thermal conductivity of CMCs was performed. In addition, an assessment was made of current micromechanics models for predicting thermal conductivity degradation. Experiments were performed on unidirectional reinforced Nicalon-LAS II glass-ceramic composites. Thermal conductivity was determined through flash diffusivity experiments. This procedure was also modified to treat orthotropic composite materials. Samples were subjected to mechanical loading-, oxidation-, and thermal shock-induced damage. The results showed that mechanical loading-induced damage resulted in no change in thermal conductivity transverse to the fiber axis and up to a 3.5% change parallel to the fibers. Mechanical loading followed by oxidation resulted in thermal conductivity degradation up to 26% and 10% transverse and parallel to the fibers, respectively. These data show the importance of the fiber-matrix interface in controlling both the longitudinal and transverse thermal conductivities of damaged composites. Predictions of thermal conductivity degradation parallel to the fiber direction were made with a shear-lag type micromechanics model. Results were in excellent agreement with experimental data. Thermal diffusivity data from isothermal oxidation and thermal shock experiments showed that this procedure is an effective nondestructive monitoring method. An assessment of transverse thermal conductivity rnicromechanics models was made through comparison with numerical solutions for random fiber inclusions with random

  1. Conductive polypyrrole/viscose fiber composites.

    PubMed

    Wang, Ning; Li, Guodong; Yu, Zhuo; Zhang, Xingxiang; Qi, Xiaoling

    2015-08-20

    Polypyrrole (PPy) was polymerized with pyrrole (Py) as the monomer, FeCl3 as an oxidant and sodium dodecyl benzene sulfonate (SDBS) as the dopant on the surface of viscose fiber (VCF) to prepare the conductive PPy/VCF composites. Fourier transform infrared spectra (FT-IR), thermal gravimetric analysis (TGA) and X-ray photoelectron spectroscope (XPS) proved that the interaction between PPy and VCF formed in the PPy/VCF composites. Three structures of N atoms (imine, amine and cationic atoms) were found in PPy of PPy/VCF composites. The influence of reaction conditions including reaction time, Py concentration, FeCl3 concentration and SDBS concentration on the morphology and the conductivity of PPy/VCF composites was investigated in detail. The orthogonal experiments were designed to determine the optimal reaction conditions: reaction time 5h, Py concentration 0.1 mol/L and FeCl3 concentration 0.25 mol/L. When PPy/VCF composite was washed 50 times in water, the conductivity still kept at 1.5S/cm, and this value was stable for more washing. PMID:25965491

  2. Thermal conductivity of hybrid short fiber composites

    SciTech Connect

    Dunn, M.L.; Taya, M.; Hatta, H.; Takei, T.; Nakajima, Y. Inst. of Space and Astronautical Science, Sagamihara Three-D Composites Research, Tsukuba Tohoku Univ., Sendai )

    1993-01-01

    A combined analytical/experimental study has been undertaken to investigate the effective thermal conductivity of hybrid composite materials. The analysis utilizes the equivalent inclusion approach for steady state heat conduction (Hatta and Taya, 1986) through which the interaction between the various reinforcing phases at finite concentrations is approximated by the Mori-Tanaka (1973) mean field approach. The multiple reinforcing phases of the composite are modeled as ellipsoidal in shape and thus can simulate a wide range of microstructural geometries ranging from thin platelet to continuous fiber reinforcement. The case when one phase of the composite is penny-shaped microcracks is studied in detail. Multiphase composites consisting of a Kerimid matrix and Al2O3 short fibers and Si3N4 whiskers were fabricated and, after a careful study of their microstructure, their thermal conductivities were measured. Analytical predictions are shown to be in good agreement with experimental results obtained for the Al2O3/Si3N4/Kerimid short fiber composites. 26 refs.

  3. Bipolar Battery Using Conductive-Fiber Composite

    NASA Technical Reports Server (NTRS)

    Rippel, Wally E.

    1989-01-01

    Improved version of lead/sulfuric acid battery, electrically-conducting fiber/polymer composite substrates used in place of metallic substrates. Sealing and corrosion problems reduced. Benefits include halving of weight, increased energy and power densities, and lower gassing rate. Important for electric-vehicle development.

  4. Thermal Conductivity of Al-Salt Composites

    NASA Astrophysics Data System (ADS)

    Li, Peng; Zhang, Mei; Wang, Lijun; Seetharaman, Seshadri

    2015-11-01

    With a view to examine the possibility of estimating the content of entrapped metallic aluminium in the salt cake from aluminium remelting, the thermal diffusivity of reference composites of KCl-NaCl-Al was measured as a function of aluminium metal content at room temperature. The thermal conductivity of the reference composites was found to increase with the metallic Al content. The lumped parameter model approach was carried out to discuss the influence of different geometry arrangements of each phase, viz. air, salts and metallic aluminium on the thermal conductivity. Application of the present results to industrial samples indicates that factors such as the interfacial condition of metallic Al particles have to be considered in order to estimate the amount of entrapped Al in the salt cake.

  5. Highly Conducting Graphite Epoxy Composite Demonstrated

    NASA Technical Reports Server (NTRS)

    Gaier, James R.

    1999-01-01

    Weight savings as high as 80 percent could be achieved if graphite polymer composites could replace aluminum in structures such as electromagnetic interference shielding covers and grounding planes. This could result in significant cost savings, especially for the mobile electronics found in spacecraft, aircraft, automobiles, and hand-held consumer electronics. However, such composites had not yet been fabricated with conductivity sufficient to enable these applications. To address this lack, a partnership of the NASA Lewis Research Center, Manchester College, and Applied Sciences, Inc., fabricated nonmetallic composites with unprecedented electrical conductivity. For these composites, heat-treated, vapor-grown graphite fibers were selected which have a resistivity of about 80 mW-cm, more than 20 times more conductive than typical carbon fibers. These fibers were then intercalated with iodine bromide (IBr). Intercalation is the insertion of guest atoms or molecules between the carbon planes of the graphite fibers. Since the carbon planes are not highly distorted in the process, intercalation has little effect on mechanical and thermal properties. Intercalation does, however, lower the carbon fiber resistivity to less than 10 mW-cm, which is comparable to that of metal fibers. Scaleup of the reaction was required since the initial intercalation experiments would be carried out on 20-mg quantities of fibers, and tens of grams of intercalated fibers would be needed to fabricate even small demonstration composites. The reaction was first optimized through a time and temperature study that yielded fibers with a resistivity of 8.7 2 mW-cm when exposed to IBr vapor at 114 C for 24 hours. Stability studies indicated that the intercalated fibers rapidly lost their conductivity when exposed to temperatures as low as 40 C in air. They were not, however, susceptible to degradation by water vapor in the manner of most graphite intercalation compounds. The 1000-fold scaleup

  6. Conductive ceramic composition and method of preparation

    DOEpatents

    Smith, James L.; Kucera, Eugenia H.

    1991-01-01

    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.

  7. Conductive ceramic composition and method of preparation

    DOEpatents

    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.

  8. Effective thermal conductivity of a thin composite material

    SciTech Connect

    Phelan, P.E.; Niemann, R.C.

    1996-12-31

    The thermal conductivity of a randomly oriented composite material is modeled using a probabilistic approach in order to determine if a size effect exists for the thermal conductivity at small composite thickness. The numerical scheme employs a random number generator to position the filler elements, which have a relatively high thermal conductivity, within a matrix having a relatively low thermal conductivity. Results indicate that, below some threshold thickness, the composite thermal conductivity increases with decreasing thickness, while above the threshold the thermal conductivity is independent of thickness. The threshold thickness increases for increasing filler fraction and increasing k{sub f}/k{sub m}, the ratio between filler and matrix thermal conductivities.

  9. Effective thermal conductivity of a thin, randomly oriented composite material

    SciTech Connect

    Phelan, P.E.; Niemann, R.C.

    1997-10-01

    The thermal conductivity of a randomly oriented composite material is modeled using a probabilistic approach in order to determine if a size effect exists for the thermal conductivity at small composite thicknesses. The numerical scheme employs a random number generator to position the filler elements, which have a relatively high thermal conductivity, within a matrix having a relative low thermal conductivity. The results indicate that, below some threshold thickness, the composite thermal conductivity is independent of thickness. The threshold thickness increases for increasing filler fraction and increasing k{sub f}/k{sub m}, the ratio between the filler and matrix thermal conductivities.

  10. Method of forming an electrically conductive cellulose composite

    DOEpatents

    Evans, Barbara R.; O'Neill, Hugh M.; Woodward, Jonathan

    2011-11-22

    An electrically conductive cellulose composite includes a cellulose matrix and an electrically conductive carbonaceous material incorporated into the cellulose matrix. The electrical conductivity of the cellulose composite is at least 10 .mu.S/cm at 25.degree. C. The composite can be made by incorporating the electrically conductive carbonaceous material into a culture medium with a cellulose-producing organism, such as Gluconoacetobacter hansenii. The composites can be used to form electrodes, such as for use in membrane electrode assemblies for fuel cells.

  11. Anion-conducting polymer, composition, and membrane

    DOEpatents

    Pivovar, Bryan S.; Thorn, David L.

    2011-11-22

    Anion-conducing polymers and membranes with enhanced stability to aqueous alkali include a polymer backbone with attached sulfonium, phosphazenium, phosphazene, and guanidinium residues. Compositions also with enhanced stability to aqueous alkali include a support embedded with sulfonium, phosphazenium, and guanidinium salts.

  12. Anion-conducting polymer, composition, and membrane

    DOEpatents

    Pivovar, Bryan S.; Thorn, David L.

    2010-12-07

    Anion-conducing polymers and membranes with enhanced stability to aqueous alkali include a polymer backbone with attached sulfonium, phosphazenium, phosphazene, and guanidinium residues. Compositions also with enhanced stability to aqueous alkali include a support embedded with sulfonium, phosphazenium, and guanidinium salts.

  13. Anion-conducting polymer, composition, and membrane

    DOEpatents

    Pivovar, Bryan S.; Thorn, David L.

    2009-09-01

    Anion-conducing polymers and membranes with enhanced stability to aqueous alkali include a polymer backbone with attached sulfonium, phosphazenium, phosphazene, and guanidinium residues. Compositions also with enhanced stability to aqueous alkali include a support embedded with sulfonium, phosphazenium, and guanidinium salts.

  14. Anion-Conducting Polymer, Composition, and Membrane

    SciTech Connect

    Pivovar, Bryan S.; Thorn, David L.

    2008-10-21

    Anion-conducing polymers and membranes with enhanced stability to aqueous alkali include a polymer backbone with attached sulfonium, phosphazenium, phosphazene, and guanidinium residues. Compositions also with enhanced stability to aqueous alkali include a support embedded with sulfonium, phosphazenium, and guanidinium salts.

  15. Conductive polymeric compositions for lithium batteries

    DOEpatents

    Angell, Charles A.; Xu, Wu

    2009-03-17

    Novel chain polymers comprising weakly basic anionic moieties chemically bound into a polyether backbone at controllable anionic separations are presented. Preferred polymers comprise orthoborate anions capped with dibasic acid residues, preferably oxalato or malonato acid residues. The conductivity of these polymers is found to be high relative to that of most conventional salt-in-polymer electrolytes. The conductivity at high temperatures and wide electrochemical window make these materials especially suitable as electrolytes for rechargeable lithium batteries.

  16. Conductivity of carbon nanotube polymer composites

    SciTech Connect

    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.

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

    DOEpatents

    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.

  18. Strength of VGCF/Al Composites for High Thermal Conductivity

    NASA Astrophysics Data System (ADS)

    Fukuchi, Kohei; Sasaki, Katsuhiko; Imanishi, Terumitsu; Katagiri, Kazuaki; Kakitsuji, Atsushi; Shimizu, Akiyuki

    In this paper, the evaluation of the strength of the VGCF/Aluminum composites which have high thermal conductivity is reported. VGCF (Vapor Growth Carbon Fiber) is a kind of the Carbon nanotube (CNT) which has very high thermal conductivity as well as CNT. The composites are made by spark plasma sintering. The stress-strain curves of the composites are obtained by the tensile tests and show that the composites have brittle behavior. The brittleness of the composites increases with increase in the volume fraction of VGCF. A numerical simulation based on the micromechanics is conducted to estimate nonlinear behavior in the elastic deformation and plastic deformation of the stress-strain relations of the composites. The theories of Eshelby, Mori-Tanaka, Weibull, and Ramberg-Osgood are employed for the numerical simulation. The simulations give some information of the microstructural change in the composite related to the volume fraction of VGCF.

  19. Electrical conductivity and rheology of carbon black composites under elongation

    NASA Astrophysics Data System (ADS)

    Starý, Zdeněk

    2015-04-01

    Electrical properties of conductive polymer composites are governed by filler particle structures which are formed in the material during the mixing. Therefore, knowledge of the behavior of conductive particle structures under defined conditions of deformation is necessary to produce materials with balanced electrical and rheological properties. Whereas the electrical conductivity evolution under shear can be nowadays studied even with the commercial rheometers, the investigations under elongation were not performed up to now. In this work simultaneous electrical and rheological measurements in elongation on polystyrene/carbon black composites are introduced. Such kind of experiment can help in understanding the relationships between processing conditions and properties of conductive polymer composites.

  20. Thermal Conductivity of Alumina-Toughened Zirconia Composites

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Zhu, Dong-Ming

    2003-01-01

    10-mol% yttria-stabilized zirconia (10YSZ)-alumina composites containing 0 to 30 mol% alumina were fabricated by hot pressing at 1500 C in vacuum. Thermal conductivity of the composites, determined at various temperatures using a steady-state laser heat flux technique, increased with increase in alumina content. Composites containing 0, 5, and 10-mol% alumina did not show any change in thermal conductivity with temperature. However, those containing 20 and 30-mol% alumina showed a decrease in thermal conductivity with increase in temperature. The measured values of thermal conductivity were in good agreement with those calculated from simple rule of mixtures.

  1. Fabrication of Ketjen black-polybenzoxazine superhydrophobic conductive composite coatings

    NASA Astrophysics Data System (ADS)

    Shen, Lie; Ding, Hongliang; Wang, Wen; Guo, Qipeng

    2013-03-01

    Superhydrophobic conductive Ketjen black-polybenzoxazine (KB-PBZ) composite coatings were prepared by a simple drop casting method with high static water contact angle (˜160°), low sliding angle (˜3°), and low sheet resistance (103 Ω/sq). The relationship between Ketjen black amounts and the structure and properties of the composite coatings was investigated. Under appropriate conditions, the composite coatings showed hierarchically structured roughness and possessed superhydrophobicity over the whole range of pH values. These coatings exhibited excellent thermal and environmental stability. Moreover, the superhydrophobic conductive composite coatings also can be obtained on various substrates such as wood, aluminum foil, paper, polyethylene terephthalate film and fabric.

  2. Effective thermal conductivity of composites with fibre-matrix debonding

    NASA Technical Reports Server (NTRS)

    Fadale, T. D.; Taya, M.

    1991-01-01

    Debonding of the fiber-matrix interface is a major cause for the degradation of the mechanical properties and the loss of thermal conductivity of fiber-reinforced composites. This paper discusses two analytical approaches for modeling the thermal conduction problem of composites. One is based on the concept of modeling the thermal barrier by an equivalent heat transfer coefficient at the fiber-matrix interface, as described by Hasselman and Johnson (1987) and Benveniste and Miloh (1986). The other approach, suggested by Hatta and Taya (1986), is by treating a composite with debonded interface as a coated-fiber composite. The major advantage of the latter aproach is that the thickness of the fiber coating can be realistically modeled depending upon the extent of degradation of the composite with the thermal conductivity of the coating as that of air.

  3. Thermal Conductivity behavior of MWCNT based PMMA and PC composites

    NASA Astrophysics Data System (ADS)

    Dubey, Girija; Jindal, Prashant; Bhandari, Rajiv; Dhiman, Neha; Bajaj, Chetan; Jindal, Vijay

    Poly methyl methacrylate (PMMA) and Polycarbonate (PC) are low cost polymer materials which can be easily transformed into desired shapes for various applications. However they have poor mechanical, thermal and electrical properties which are required to be enhanced to widen their scope of applications specifically where along with high strength, rapid heat transfer is essential. Multi Walled Carbon nanotubes (MWCNTs) are excellent new materials having extraordinary mechanical and transport properties. We will report results of fabricating composites of varying compositions of MWCNTs with PMMA and PC and their thermal conductivity behaviour using simple transient heat flow methods. The samples in disk shapes of around 2 cm diameters and 0.2 cm thickness with MWCNT compositions varying up to 10 wt% were fabricated. We found that both PMMA and PC measured high thermal conductivity with increase in the composition of CNTs. The thermal conductivity of 10wt% MWCNT/PMMA composite increased by nearly two times in comparison to pure PMMA.

  4. Process for fabricating composite material having high thermal conductivity

    DOEpatents

    Colella, Nicholas J.; Davidson, Howard L.; Kerns, John A.; Makowiecki, Daniel M.

    2001-01-01

    A process for fabricating a composite material such as that having high thermal conductivity and having specific application as a heat sink or heat spreader for high density integrated circuits. The composite material produced by this process has a thermal conductivity between that of diamond and copper, and basically consists of coated diamond particles dispersed in a high conductivity metal, such as copper. The composite material can be fabricated in small or relatively large sizes using inexpensive materials. The process basically consists, for example, of sputter coating diamond powder with several elements, including a carbide forming element and a brazeable material, compacting them into a porous body, and infiltrating the porous body with a suitable braze material, such as copper-silver alloy, thereby producing a dense diamond-copper composite material with a thermal conductivity comparable to synthetic diamond films at a fraction of the cost.

  5. Three-dimensional compressible and stretchable conductive composites.

    PubMed

    Yu, You; Zeng, Jifang; Chen, Chaojian; Xie, Zhuang; Guo, Ruisheng; Liu, Zhilu; Zhou, Xuechang; Yang, Yong; Zheng, Zijian

    2014-02-01

    Three-dimensional (3D) conductive composites with remarkable flexibility, compressibility, and stretchability are fabricated by solution deposition of thin metal coatings on chemically modified, macroscopically continuous, 3D polyurethane sponges, followed by infiltration of the metallic sponges with polydimethylsiloxane (PDMS). These low-cost conductive composites are used as high-performance interconnects for flexible and stretchable light-emitting diode (LED) arrays, even with severe surface abrasion or cutting. PMID:24307070

  6. Modeling the thermal conductivity of fiber-reinforced ceramic composites

    SciTech Connect

    Beecher, S.C.; Dinwiddie, R.B.

    1993-06-01

    A review of models for the prediction of the thermal conductivity of uni-directional fiber-reinforced composites will be presented. The ability of these models to give an accurate prediction of the composite thermal conductivity depends on the amount of information known about the constituent phase properties under the assumption that these properties do not change as a result of processing. Also presented are models that take into account the effects of fiber coatings.

  7. Thermal Conductivity Changes in Titanium-Graphene Composite upon Annealing

    NASA Astrophysics Data System (ADS)

    Jagannadham, Kasichainula

    2016-02-01

    Ti-graphene composite films were prepared on polished Ti substrates by deposition of graphene platelets from suspension followed by deposition of Ti by magnetron sputtering. The films were annealed at different temperatures up to 1073 K (800 °C) and different time periods in argon atmosphere. The annealed films were characterized by X-ray diffraction for phase identification, scanning electron microscopy for microstructure, energy-dispersive spectrometry for chemical analysis, atomic force microscopy for surface roughness, and transient thermoreflectance for thermal conductivity and interface thermal conductance. The results showed that the interface between the composite film and Ti substrate remained continuous with the absence of voids. Oxygen concentration in the composite films has increased for higher temperature and time of annealing. TiO2 and TiC phases are formed only in the film annealed at 1073 K (800 °C). The thermal conductivity of the composite film decreased with increasing oxygen concentration. The effective thermal conductance of the film annealed at 1073 K (800 °C) was significantly lower. The interface thermal conductance between the composite film and the Ti substrate is also reduced for higher oxygen concentration. Formation of microscopic TiO2 phase bound by interface boundaries and oxygen incorporation is considered responsible for the lower thermal conductance of the Ti-graphene composite annealed at 1073 K (800 °C).

  8. Thermal Conductivity of Alumina-reinforced Zirconia Composites

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.

    2005-01-01

    10-mol% yttria-stabilized zirconia (10SZ) - alumina composites containing 0-30 mol% alumina were fabricated by hot pressing at 1500 C in vacuum. Thermal conductivity was determined at various temperatures using a steady-state laser heat flux technique. Thermal conductivity of the composites increased with increase in alumina content. Composites containing 0, 5, and 10-mol% alumina did not show any change in thermal conductivity with temperature. However, those containing 20 and 30-mol% alumina showed a decrease in thermal conductivity with increase in temperature. The measured values of thermal conductivity were in good agreement with those calculated from the Maxwell-Eucken model where one phase is uniformly dispersed within a second major continuous phase.

  9. Cu/Diamond composite heat-conducting shims

    NASA Astrophysics Data System (ADS)

    Galashov, E. N.; Yusuf, A. A.; Mandrik, E. M.

    2015-11-01

    Composite material with high thermal conductivity was obtained by the method of thermal sintering of a diamond (50 - 75%) with a size of 20 to 250 μm in a matrix of copper.Coefficient of thermal conductivity of copper diamond composite materials was measured and is 450 - 650 W·m-1·K-1. The coefficient of thermal expansion CTE was measured and is 5.5 - 7.5 · 10-6/°C. The obtained copper diamond composite materials are promising objects for use in THz and microwave devices.

  10. Electrostatic Discharge Sensitivity and Electrical Conductivity of Composite Energetic Materials

    SciTech Connect

    Michael A. Daniels; Daniel J. Prentice; Chelsea Weir; Michelle L. Pantoya; Gautham Ramachandran; Tim Dallas

    2013-02-01

    Composite energetic material response to electrical stimuli was investigated and a correlation between electrical conductivity and ignition sensitivity was examined. The composites consisted of micrometer particle aluminum combined with another metal, metal oxide, or fluoropolymer. Of the nine tested mixtures, aluminum with copper oxide was the only mixture to ignite by electrostatic discharge with minimum ignition energy (MIE) of 25 mJ and an electrical conductivity of 1246.25 nS; two orders of magnitude higher than the next composite. This study showed a similar trend in MIE for ignition triggered by a discharged spark compared with a thermal hot wire source.

  11. Electroactivity of transparent composite films from conducting poly(thiophenes)

    SciTech Connect

    Roncali, J.; Garnier, F.

    1988-02-11

    Conducting composite films containing an electropolymerizable conducting polymer such as poly(3-methylthiophene) (PMeT) alloyed with poly(vinyl chloride) (PVC) have been prepared in a one-step process from synthesis media already containing dissolved PVC. This procedure based on the simultaneous electropolymerization and dip-cutting processes allows a large control of the composition, morphology, optical transmittance, conductivity, and electroactivity of the composite films. The growth of PMeT in synthesis media containing dissolved PVC has been analyzed. Increasing the PVC concentration produces a slight decrease of the MeT electropolymerization rate with no apparent modification of the polymerization mechanism. The electrochemical properties of the composite films have been investigated in acetonitrile by using cyclic voltammetry and chronoamperometry. At low scan rate (10 mV/s), the electrochemical responses of the composite films are identical with that of bare PMeT films prepared under the same conditions. At higher scan rates, a dependence of the electroactivity of the films on their PVC content is observed and the electrochemical response turns progressively from an adsorption-like behavior to a diffusion-controlled one. It is shown that the electrolyte concentration used for the synthesis of the composite films is the key factor controlling their electrochemical behavior. The incorporation of PMeT within the PVC matrix does not affect its spectroelectrochemical properties and furthermore leads to an improved electrochemical stability of the film under redox cycling.

  12. Electrical Properties of Conductive Nylon66/Graphene Oxide Composite Nanofibers.

    PubMed

    Nirmala, R; Navamathavan, R; Kim, Hak Yong; Park, Soo-Jin

    2015-08-01

    In this paper, we report on the structural and electrical properties of graphene oxide (GO) incorporated Nylon66 (N66) composite nanofibers prepared via electrospinning technique. Different types of composite nanofibers were electrospun by varying the weight percentage of GO in the polymer solution. Scanning electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy, as well as current-voltage (I-V) measurements were used to characterize the N66/GO composite nanofibers. The morphology of the N66/GO composite nanofibers exhibited densely arranged mesh-like ultrafine nanofibers which were strongly bound in between the main fibers. The I-V characteristics of the N66/GO composite nanofibers demonstrated that the blending of GO in to N66 nanofibers led to a dramatic improvement of the electrical conduction compared to that of pristine N66 nanofibers which can be utilized for the various technological applications. PMID:26369144

  13. High conductivity, low cost aluminum composite for thermal management

    SciTech Connect

    Sommer, J.L.

    1997-04-01

    In order to produce an inexpensive packaging material that exhibits high thermal conductivity and low CTE, Technical Research Associates, Inc. (TRA) has shown in Phase I the feasibility of incorporating natural flake graphite in an aluminum matrix. TRA has developed a proprietary coating technique where graphite flakes have been coated with a thin layer of molybdenum/molybdenum carbide (approximately 0.2 microns). This barrier coating can protect the graphite flake from chemical reaction and high temperature degradation in molten aluminum silicon alloys. Methods to successfully vacuum infiltrate coated flake with molten aluminum alloys were developed. The resulted metal matrix composites exhibited lower CTE than aluminum metal. The CTE of the composites were significantly lower than aluminum and its alloys. The CTE can potentially be tailored for specific applications. The in plane thermal conductivity was higher than the aluminum matrix alloy. The thermal conductivity and CTE of the composite may be significantly improved by improving the bond strength of the molybdenum coating on the graphite flake. The flake can potentially be incorporated in the molten aluminum and pressure die cast to align the flakes within the aluminum matrix. By preferentially aligning high conductivity graphite flakes within a plane or direction, the thermal conductivity of the resulting composite will be above pure aluminum in the alignment direction.

  14. A High Conducting Oxide Sulfide Composite Lithium Superionic Conductor

    SciTech Connect

    Rangasamy, Ezhiylmurugan; Keum, Jong Kahk; Sahu, Gayatri; Rondinone, Adam Justin; Dudney, Nancy J; Liang, Chengdu

    2014-01-01

    A hybrid superionic conductor was fabricated utilizing the space charge effect between the LLZO and LPS interfaces. This space-charge effect resulted in an improvement over the individual bulk conductivities of the two systems. Sample with higher weight fractions of LLZO are limited by the porosity and grain boundary resistance arising from non-sintered membranes. By combining the properties of LLZO and LPS, the high temperature sintering step has been avoided thus facilitating easier materials processing. The interfacial resistances were also measured to be minimal at ambient conditions. This procedure thus opens a new avenue for improving the ionic conductivity and electrochemical properties of existing solid state electrolytes. High frequency impedance analyses could aid in resolving the ionic conductivity contributions from the space charge layer in the higher conducting composites while mechanical property investigations could illustrate an improvement in the composite electrolyte in comparison with the crystalline LPS membranes.

  15. Pulsed terahertz inspection of non-conducting sandwich composites

    NASA Astrophysics Data System (ADS)

    Lopato, P.; Chady, T.

    2013-01-01

    Pulsed terahertz inspection enables accurate, contactless and safe for operating personnel evaluation of non-conducting structures. In this paper we present results of pulsed terahertz testing of various sandwich composite structures incorporating glass and basalt fibers based skin materials and spherecore and balsa wood based core materials. Various Time-Frequency Distributions (TFD) are utilized in order to obtain most valuable defects response.

  16. Electrically conductive bulk composites through a contact-connected aggregate.

    PubMed

    Nawroj, Ahsan I; Swensen, John P; Dollar, Aaron M

    2013-01-01

    This paper introduces a concept that allows the creation of low-resistance composites using a network of compliant conductive aggregate units, connected through contact, embedded within the composite. Due to the straight-forward fabrication method of the aggregate, conductive composites can be created in nearly arbitrary shapes and sizes, with a lower bound near the length scale of the conductive cell used in the aggregate. The described instantiation involves aggregate cells that are approximately spherical copper coils-of-coils within a polymeric matrix, but the concept can be implemented with a wide range of conductor elements, cell geometries, and matrix materials due to its lack of reliance on specific material chemistries. The aggregate cell network provides a conductive pathway that can have orders of magnitude lower resistance than that of the matrix material--from 10(12) ohm-cm (approx.) for pure silicone rubber to as low as 1 ohm-cm for the silicone/copper composite at room temperature for the presented example. After describing the basic concept and key factors involved in its success, three methods of implementing the aggregate into a matrix are then addressed--unjammed packing, jammed packing, and pre-stressed jammed packing--with an analysis of the tradeoffs between increased stiffness and improved resistivity. PMID:24349239

  17. Electrically Conductive Bulk Composites through a Contact-Connected Aggregate

    PubMed Central

    Nawroj, Ahsan I.; Swensen, John P.; Dollar, Aaron M.

    2013-01-01

    This paper introduces a concept that allows the creation of low-resistance composites using a network of compliant conductive aggregate units, connected through contact, embedded within the composite. Due to the straight-forward fabrication method of the aggregate, conductive composites can be created in nearly arbitrary shapes and sizes, with a lower bound near the length scale of the conductive cell used in the aggregate. The described instantiation involves aggregate cells that are approximately spherical copper coils-of-coils within a polymeric matrix, but the concept can be implemented with a wide range of conductor elements, cell geometries, and matrix materials due to its lack of reliance on specific material chemistries. The aggregate cell network provides a conductive pathway that can have orders of magnitude lower resistance than that of the matrix material - from 1012 ohm-cm (approx.) for pure silicone rubber to as low as 1 ohm-cm for the silicone/copper composite at room temperature for the presented example. After describing the basic concept and key factors involved in its success, three methods of implementing the aggregate into a matrix are then addressed – unjammed packing, jammed packing, and pre-stressed jammed packing – with an analysis of the tradeoffs between increased stiffness and improved resistivity. PMID:24349239

  18. Carbon Nanotubes - Polymer Composites with Enhanced Conductivity using Functionalized Nanotubes

    NASA Astrophysics Data System (ADS)

    Ramasubramaniam, Rajagopal; Chen, Jian; Gupta, Rishi

    2003-03-01

    Individual carbon nanotubes show superior electrical, mechanical and thermal properties [1]. Composite materials using carbon nanotubes as fillers are predicted to show similar superior properties. However, realization of such composites has been plagued by poor dispersion of carbon nanotubes in solvents and in polymer matrices. We have developed a method to homogenously disperse carbon nanotubes in polymer matrices using functionalized nanotubes [2]. Thin films of functionalized single walled nanotubes (SWNT) - polystyrene composites and functionalized SWNT - polycarbonate composites were prepared using solution evaporation and spin coating. Both of the composites show several orders of magnitude increase in conductivity for less than 1 wt thresholds of the composites are less than 0.2 wt nanotubes. We attribute the enhanced conduction to the superior dispersion of the functionalized nanotubes in the polymer matrix and to the reduced nanotube waviness resulting from the rigid backbone of the conjugated polymer. References: [1]. R. H. Baughman, A. A. Zakhidov and W. A. de Heer, Science v297, p787 (2002); [2]. J. Chen, H. Liu, W. A. Weimer, M. D. Halls, D. H. Waldeck and G. C. Walker, J. Am. Chem. Soc. v124, p9034 (2002).

  19. Thermally Conductive Metal-Tube/Carbon-Composite Joints

    NASA Technical Reports Server (NTRS)

    Copeland, Robert J.

    2004-01-01

    An improved method of fabricating joints between metal and carbon-fiber-based composite materials in lightweight radiators and heat sinks has been devised. Carbon-fiber-based composite materials have been used in such heat-transfer devices because they offer a combination of high thermal conductivity and low mass density. Metal tubes are typically used to carry heat-transfer fluids to and from such heat-transfer devices. The present fabrication method helps to ensure that the joints between the metal tubes and the composite-material parts in such heat-transfer devices have both (1) the relatively high thermal conductances needed for efficient transfer of heat and (2) the flexibility needed to accommodate differences among thermal expansions of dissimilar materials in operation over wide temperature ranges. Techniques used previously to join metal tubes with carbon-fiber-based composite parts have included press fitting and bonding with epoxy. Both of these prior techniques have been found to yield joints characterized by relatively high thermal resistances. The present method involves the use of a solder (63 percent Sn, 37 percent Pb) to form a highly thermally conductive joint between a metal tube and a carbon-fiber-based composite structure. Ordinarily, the large differences among the coefficients of thermal expansion of the metal tube, solder, and carbon-fiber-based composite would cause the solder to pull away from the composite upon post-fabrication cooldown from the molten state. In the present method, the structure of the solder is modified (see figure) to enable it to deform readily to accommodate the differential thermal expansion.

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

    PubMed

    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. PMID:20665629

  1. Smart conducting polymer composites having zero temperature coefficient of resistance

    NASA Astrophysics Data System (ADS)

    Chu, Kunmo; Lee, Sung-Chul; Lee, Sangeui; Kim, Dongearn; Moon, Changyoul; Park, Sung-Hoon

    2014-12-01

    Zero temperature coefficient of resistance (TCR) is essential for the precise control of temperature in heating element and sensor applications. Many studies have focused on developing zero-TCR systems with inorganic compounds; however, very few have dealt with developing zero-TCR systems with polymeric materials. Composite systems with a polymer matrix and a conducting filler show either a negative (NTC) or a positive temperature coefficient (PTC) of resistance, depending on several factors, e.g., the polymer nature and the filler shape. In this study, we developed a hybrid conducting zero-TCR composite having self-heating properties for thermal stability and reliable temperature control. The bi-layer composites consisted of a carbon nanotube (CNT)-based layer having an NTC of resistance and a carbon black (CB)-based layer having a PTC of resistance which was in direct contact with electrodes to stabilize the electrical resistance change during electric Joule heating. The composite showed nearly constant resistance values with less than 2% deviation of the normalized resistance until 200 °C. The CB layer worked both as a buffer and as a distributor layer against the current flow from an applied voltage. This behavior, which was confirmed both experimentally and theoretically, has been rarely reported for polymer-based composite systems.Zero temperature coefficient of resistance (TCR) is essential for the precise control of temperature in heating element and sensor applications. Many studies have focused on developing zero-TCR systems with inorganic compounds; however, very few have dealt with developing zero-TCR systems with polymeric materials. Composite systems with a polymer matrix and a conducting filler show either a negative (NTC) or a positive temperature coefficient (PTC) of resistance, depending on several factors, e.g., the polymer nature and the filler shape. In this study, we developed a hybrid conducting zero-TCR composite having self

  2. Electrically Conductive Multiphase Polymer Blend Carbon-Based Composites

    NASA Astrophysics Data System (ADS)

    Brigandi, Paul James

    The use of multiphase polymer blends provides unique morphologies and properties to reduce the percolation concentration and increase conductivity of carbon-based polymer composites. These systems offer improved conductivity, temperature stability and selective distribution of the conductive filler through unique morphologies at significantly lower conductive filler concentration. In this work, the kinetic and thermodynamic effects on a series of multiphase conductive polymer composites were investigated. The polymer blend phase morphology, filler distribution, electrical conductivity, and rheological properties of CB-filled PP/PMMA/EAA conductive polymer composites were determined. Thermodynamic and kinetic parameters were found to influence the morphology development and final composite properties. The morphology and CB distribution were found to be kinetically driven when annealed for a short period of time following the shear-intensive mixing process, whereas the three-phase polymer blend morphology is driven by thermodynamics when given sufficient time under high temperature annealing conditions in the melt state. At short annealing times, the CB distribution was influenced by the compounding sequence where the CB was added after being premixed with one of the polymer phases or directly added to the three phase polymer melt, but again was thermodynamically driven at longer annealing times with the CB migrating to the EAA phase. The resistivity was found to decrease by a statistically significant amount to similar levels for all of the composite systems with increasing annealing time, providing evidence of gradual phase coalescence to a tri-continuous morphology and CB migration. The addition of CB via the PP and EAA masterbatch results in significantly faster percolation and lower resistivity compared to when added direct to the system during compounding after 30 minutes annealing by a statistically significant amount. Dynamic oscillatory shear rheology using

  3. Ac conduction in conducting poly pyrrole-poly vinyl methyl ether polymer composite materials

    SciTech Connect

    Saha, S.K.; Mandal, T.K.; Mandal, B.M.; Chakravorty, D.

    1997-03-01

    Composite materials containing conducting polypyrrole and insulating poly (vinyl methyl ether) (PVME) have been synthesized by oxidative polymerization of pyrrole in ethanol using FeCl{sub 3} oxidant in the presence of PVME. The ac conductivity measurements have been carried out in the frequency range of 100 Hz to 10 MHz and in the temperature range of 110 to 350 K. The frequency dependent conductivity has been explained on the basis of a small polaron tunnelling mechanism. {copyright} {ital 1997 American Institute of Physics.}

  4. Strain sensing conductive polymer composites: Sensitivity and stability

    NASA Astrophysics Data System (ADS)

    Deng, Hua; Du, Rongni; Duan, Linyan; Fu, Qiang

    2016-03-01

    The effect of conductive network morphology and interfacial interaction on the strain sensing capability of conductive polymer composites (CPCs) is thought as crucial. Nevertheless, the stability in strain sensing behavior has barely been investigated. Herein, the resistivity-strain behavior in terms of stability and sensitivity of CPCs based on poly(styrene-butadiene-styrene) (SBS) containing multiwalled carbon nanotubes (MWCNTs) are studied. It is shown that the preparation method has an important influence on the resistivity-strain behavior of these CPCs. The sensitivity increases with decreasing filler content for both composites under linear uniaxial strain, showing higher strain sensitivity near the percolation threshold. A higher and wider range of sensitivities is obtained for melt mixed SBS/MWCNT. Meanwhile, resistivity downward drifting and shoulder peaks are shown for composites from melt mixing under dynamic strain. Interestingly, linear relationships and reversible resistivity in every cycle are observed for composites from solution mixing, showing good electromechanical consistency, stability and durability. From the TEM, rheology, SEM, SAXS, Raman microscopy and analytical modeling studies, the difference in morphology is thought to be responsible for such resistivity-strain behavior. As more disordered and less densely packed conductive networks in melt mixed CPCs are more easily destroyed under strain, evenly distributed and densely packed networks in solution mixed CPCs are more stable during cyclic stretching. Finally, different human motions have been detected using these CPCs, demonstrating the potential application of these CPCs as movement sensors.

  5. Nuclear alkylated pyridine aldehyde polymers and conductive compositions thereof

    NASA Technical Reports Server (NTRS)

    Rembaum, A.; Singer, S. (Inventor)

    1970-01-01

    A thermally stable, relatively conductive polymer was disclosed. The polymer was synthesized by condensing in the presence of catalyst a 2, 4, or 6 nuclear alklylated 2, 3, or 4 pyridine aldehyde or quaternary derivatives thereof to form a polymer. The pyridine groups were liked by olefinic groups between 2-4, 2-6, 2-3, 3-4, 3-6 or 4-6 positions. Conductive compositions were prepared by dissolving the quaternary polymer and an organic charge transfer complexing agent such as TCNQ in a mutual solvent such as methanol.

  6. Electromagnetic interference shielding effectiveness of polypropylene/conducting fiber composites

    NASA Astrophysics Data System (ADS)

    Lee, Pyoung-Chan; Kim, Bo-Ram; Jeoung, Sun Kyoung; Kim, Yeung Keun

    2016-03-01

    Electromagnetic released from the automotive electronic parts is harmful to human body. Electromagnetic interference (EMT) shielding refers to the reflection and/or adsorption of electromagnetic radiation by a material, which thereby acts as a shield against the penetration of the radiation through the shield. Polypropylene (PP)/conductive micro fiber composites containing various fiber contents and fiber length were injection-molded. The effect of fiber content and length on electrical properties of the composites was studied by electrical resistivity and EMT shielding measurements. The through-plane electrical conductivity and dielectric permittivity were obtained by measuring dielectric properties. The EMT shielding effectiveness (SE) was investigated by using S-parameter in the range of 100 ~ 1500 MHz. Reflection, absorption and multiple-reflection are the EMT attenuation mechanisms. From the measurement of S-Parameters, the absorption coefficient, reflection coefficient, and the shielding efficiency of the materials were calculated. The EMT SE of PP/conducing fiber composites is 40 dB over a wide frequency range up to 1.5 GHz, which is higher than that of PP/talc composite used automotive parts, viz. 0 dB.

  7. Conducting polymer composite materials for smart microwave windows

    NASA Astrophysics Data System (ADS)

    Barnes, Alan; Lees, K.; Wright, Peter V.; Chambers, Barry

    1999-07-01

    Samples of poly(aniline)-silver-polymer electrolyte particulate composites have been characterized at microwave frequencies when small d.c. electric fields are applied across them in both coaxial line and waveguide measurement test sets. The experimental data shows that the initial conductivity of the materials is dependent on the concentration of sliver metal and suggest that changes in resistance due to chemical switching take place, at least in part, in the manufacture of the composites. When silver is used as the electrodes, the experimental data show that changes in the slope of the cyclic voltammograms coincide with large changes in microwave reflectivity or transmission consistent with increasing conductivity of the composites when fields are applied. The reverse change occurs when the fields are removed. Measurements have shown that the composites are able to switch between the two impedance stats in times of less than one second for well over a million cycles with no apparent depreciation in material properties. Large area films have also been prepared and studied using the 'free space' technique.

  8. Processable Conducting Polyaniline, Carbon Nanotubes, Graphene and Their Composites

    NASA Astrophysics Data System (ADS)

    Wang, Kan

    Good processability is often required for applications of conducting materials like polyaniline (PANI), carbon nanotubes (CNTs) and graphene. This can be achieved by either physical stabilization or chemical functionalization. Functionalization usually expands the possible applications for the conducting materials depending on the properties of the functional groups. Processable conducting materials can also be combined with other co-dissolving materials to prepare composites with desired chemical and physical properties. Polyanilines (PANI) doped with dodecylbenzenesulfonic acid (DBSA) are soluble in many organic solvents such as chloroform and toluene. Single wall carbon nanotubes (SWCNTs) can be dispersed into PANI/DBSA to form homogeneous solutions. PANI/DBSA functions as a conducting surfactant for SWCNTs. The mixture can be combined with two-parts polyurethanes that co-dissolve in the organic solvent to produce conducting polymer composites. The composite mixtures can be applied onto various substrates by simple spray-on methods to obtain transparent and conducting coatings. Graphene, a single layer of graphite, has drawn intense interest for its unique properties. Processable graphene has been produced in N-methyl-2-pyrrolidone (NMP) by a one-step solvothermal reduction of graphite oxide without the aid of any reducing reagent and/or surfactant. The as-synthesized graphene disperses well in a variety of organic solvents such as dimethylsulfoxide (DMSO), ethanol and tetrahydrogenfuran (THF). The conductivity of solvothermal reduced graphite oxide is comparable to hydrazine reduced graphite oxide. Attempts were made to create intrinsically conducting glue comparable to mussel adhesive protiens using polyaniline and graphene. Mussels can attach to a variety of substrates under water. Catechol residue in 3,4-dihydroxyphenylalanine (L-DOPA) is the key to the wet adhesion. Tyrosine and phosphoserine with primary alkyl amine groups also participate in adhesion. A

  9. Development and characterization of a new conducting carbon composite electrode.

    PubMed

    Barsan, Madalina M; Pinto, Edilson M; Florescu, Monica; Brett, Christopher M A

    2009-03-01

    A new conducting composite flexible material prepared from cellulose acetate (CA) polymer and graphite has been developed and used for the fabrication of electrodes, which were then characterized by cyclic voltammetry and electrochemical impedance spectroscopy. Scanning electron microscopy (SEM) was used to provide information concerning the morphology of the composite electrode surface. The potential window, background currents and capacitance were evaluated by cyclic voltammetry in the pH range from 4.6 to 8.2. The voltammetry of model electroactive species demonstrates a close to reversible electrochemical behaviour, under linear diffusion control. The electroactive area of the composite electrodes increases after appropriate electrode polishing and electrochemical pre-treatment. The electrodes were used as substrate for the electropolymerisation of the phenazine dye neutral red, for future use as redox mediator in electrochemical biosensors. The composite electrodes were also successfully used for the amperometric detection of ascorbate at 0.0 V vs. SCE, and applied to the measurement of ascorbate in Vitamin C tablets; the sensor exhibits high sensitivity and a low detection limit of 7.7 microM. Perspectives for use as a versatile, mechanically flexible and robust composite electrode of easily adaptable dimensions are indicated. PMID:19200481

  10. Synthesis of Conductive Nanofillers/Nanofibers and Electrical Properties of their Conductive Polymer Composites

    NASA Astrophysics Data System (ADS)

    Sarvi, Ali

    Thanks to their corrosion resistance, light weight, low cost, and ease of processing, electrically conducting polymer composites (CPCs) have received significant attention for the replacement of metals and inorganic materials for sensors, actuators, supercapacitors, and electromagnetic interference (EMI) shields. In this PhD thesis, high aspect ratio conductive nanofillers namely copper nanowires (CuNWs) and multiwall carbon nanotubes (MWCNTs) were coated with polyaniline (PANi) using solution mixing and in-situ polymerization method, respectively. Transmission electron microscopy (TEM) showed a smooth polyaniline nano-coating between 5--18 nm in thickness on the nanofillers' surface. The coating thickness and; consequently, electrical conductivity was controlled and tuned by polyaniline/aniline concentration in solution. Composites with tunable conductivity may be used as chemisensors, electronic pressure sensors and switches. Coated nanofillers demonstrated better dispersion in polystyrene (PS) and provided lower electrical percolation threshold. Dispersion of nanofillers in PS was investigated using rheological measurements and confirmed with electron micrographs and nano-scale images of CPCs. Polyaniline (PANi), when used as a coating layer, was able to attenuate electromagnetic (EM) waves via absorption and store electrical charges though pseudocapacitance mechanism. The dielectric measurements of MWCNT-PANi/PS composites showed one order of magnitude increase in real electrical permittivity compared to that of MWCNT/PS composites making them suitable for charge storage purposes. Incorporation of PANi also brought a new insight into conductive network formation mechanism in electrospun mats where the orientation of conductive high aspect ratio nanofillers is a major problem. Conductive nanofibers of poly(vinylidene fluoride) (PVDF) filled with coated multiwall carbon nanotubes (MWCNTs) were fabricated using electrospinning. These highly oriented PVDF

  11. Ignition Sensitivity and Electrical Conductivity of a Composite Energetic Material with Conductive Nanofillers

    SciTech Connect

    Eric S. Collins; Brandon R. Skelton; Michelle L. Pantoya; Fahmida Irin; Micah J. Green; Michael A. Daniels

    2014-12-01

    The safe handling of powdered composite energetic materials requires an understanding of their response to electrostatic ignition stimuli. A binary composite comprised of Al and polytetrafluoroethylene (PTFE) was tailored for ESD ignition sensitivity with varied concentrations of highly conductive nanofillers. The goal was to control the ESD ignition response of the Al+PTFE with small concentrations of nanofillers that may not significantly affect the overall combustion performance of the mixture. The nanofillers examined include carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs). Adding CNTs created percolation at a lower volumetric percentage than GNPs and were found to be the controlling nanofiller, creating percolation for the mixture containing both CNTs and GNPs. Various mixing methods were examined. Ignition was achieved only for adding nanofillers at a volumetric percentage and mixing method that led to a bulk conductivity of approximately 5x10-3 ?S/cm.

  12. Thermal conductivity prediction of mesoporous composites (Cu/MCM-41)

    NASA Astrophysics Data System (ADS)

    Huang, Congliang; Feng, Yanhui; Zhang, Xinxin; Wang, Ge

    2014-06-01

    The thermal conductivity of the mesoporous composites Cu/MCM-41 was studied to provide some useful data for promising applications. Both of the lattice and electronic thermal conductivities of Cu nanowires with different size were predicted. With the shell of the matrix MCM-41 and the air confined in the mesochannels considered, the effective thermal conductivity (EffTC) of composites Cu/MCM-41 was obtained. The EffTC shows a great anisotropy. The EffTC along the Z direction (axial of the mesochannel) is much lower than that along directions perpendicular to the axial. It is unnecessary to further raise the filling ratio of Cu nanowires for improving the EffTC along the directions perpendicular to the axial, since the filling ratio 20% is high enough. As long as there is a void space in the mesochannel, the EffTC along the Z direction will be as low as the thermal conductivity of the matrix MCM-41, due to the large thermal resistance of the void space in mesochannels.

  13. Shear induced electrical behaviour of conductive polymer composites

    NASA Astrophysics Data System (ADS)

    Starý, Zdeněk; Krückel, Johannes; Schubert, Dirk W.

    2013-04-01

    The time-dependent electrical resistance of polymethylmethacrylate containing carbon black was measured under oscillatory shear in the molten state. The electrical signal was oscillating exactly at the doubled frequency of the oscillatory shear deformation. Moreover, the experimental results gave a hint to the development of conductive structures in polymer melts under shear deformation. It was shown that the flow induced destruction of conductive paths dominates over the flow induced build-up in the beginning of the shear deformations. However, for longer times both competitive effects reach a dynamic equilibrium and only the thermally induced build-up of pathways influences the changes in the composite resistance during the shear. Furthermore, the oscillating electrical response depends clearly on the deformation amplitude applied. A simple physical model describing the behaviour of conductive pathways under shear deformation was derived and utilized for the description of the experimental data.

  14. Single-walled carbon nanotube networks in conductive composite materials.

    PubMed

    Bârsan, Oana A; Hoffmann, Günter G; van der Ven, Leo G J; de With, G Bert

    2014-01-01

    Electrically conductive composite materials can be used for a wide range of applications because they combine the advantages of a specific polymeric material (e.g., thermal and mechanical properties) with the electrical properties of conductive filler particles. However, the overall electrical behaviour of these composite materials is usually much below the potential of the conductive fillers, mainly because by mixing two different components, new interfaces and interphases are created, changing the properties and behaviours of both. Our goal is to characterize and understand the nature and influence of these interfaces on the electrical properties of composite materials. We have improved a technique based on the use of sodium carboxymethyl cellulose (CMC) to disperse single-walled carbon nanotubes (SWCNTs) in water, followed by coating glass substrates, and drying and removing the CMC with a nitric acid treatment. We used electron microscopy and atomic force microscopy techniques to characterize the SWCNT films, and developed an in situ resistance measurement technique to analyse the influence of both the individual components and the mixture of an epoxy/amine system on the electrical behaviour of the SWCNTs. The results showed that impregnating a SWCNT network with a polymer is not the only factor that affects the film resistance; air exposure, temperature, physical and chemical properties of the individual polymer components, and also the formation of a polymeric network, can all have an influence on the macroscopic electrical properties of the initial SWCNT network. These results emphasize the importance of understanding the effects that each of the components can have on each other before trying to prepare an efficient polymer composite material. PMID:25430670

  15. Fabrication, Modelling and Application of Conductive Polymer Composites

    NASA Astrophysics Data System (ADS)

    Price, Aaron David

    Electroactive polymers (EAP) are an emerging branch of smart materials that possess the capability to change shape in the presence of an electric field. Opportunities for the advancement of knowledge were identified in the branch of EAP consisting of inherently electrically conductive polymers. This dissertation explores methods by which the unique properties of composite materials having conductive polymers as a constituent may be exploited. Chapter 3 describes the blending of polyaniline with conventional thermoplastics. Processing these polyblends into foams yielded a porous conductive material. The effect of blend composition and processing parameters on the resulting porous morphology and electrical conductivity was investigated. These findings represent the first systematic study of porous conductive polymer blends. In Chapter 4, multilayer electroactive polymer actuators consisting of polypyrrole films electropolymerized on a passive polymer membrane core were harnessed as actuators. The membrane is vital in the transport of ionic species and largely dictates the stiffness of the layered configuration. The impact of the mechanical properties of the membrane on the actuation response of polypyrrole-based trilayer bending actuators was investigated. Candidate materials with distinct morphologies were identified and their mechanical properties were evaluated. These results indicated that polyvinylidene difluoride membranes were superior to the other candidates. An electrochemical synthesis procedure was proposed, and the design of a novel polymerization vessel was reported. These facilities were utilized to prepare actuators under a variety of synthesis conditions to investigate the impact of conductive polymer morphology on the electromechanical response. Characterization techniques were implemented to quantitatively assess physical and electrochemical properties of the layered composite. Chapter 5 proposes a new unified multiphysics model that captures the

  16. Conductive PVDF-HFP/CNT composites for strain sensing

    NASA Astrophysics Data System (ADS)

    Hu, Bin; Liu, Yaolu; Hu, Ning; Wu, Liangke; Ning, Huiming; Zhang, Jianyu; Fu, Shaoyun; Tang, Shang; Xu, Chaohe; Liu, Feng; Alamusi; Yuan, Weifeng

    2016-02-01

    A strain sensor based on the composites of poly (vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) filled by multi-walled carbon nanotube (MWNT) was prepared using a proposed fabrication process. Three kinds of MWNT loadings, i.e., 1.0wt.%, 2.0wt.% and 3.0wt.% were employed. Due to good dispersion state of MWNT in PVDF-HFP matrix, which was characterized by scanning electron microscope (SEM), this sensor was found to be of high sensitivity and stable performance. The sensor’s piezoresistivity varied in a weak nonlinear pattern, which was probably caused by the tunneling effect among neighboring MWNTs. The gauge factor of the sensor of 1.0wt.% MWNT loading was identified to be the highest, i.e., 33. This sensor gauge factor decreased gradually with the increase of addition amount of MWNT, which was 5 for the sensor of 3.0wt.% MWNT loading. This gauge factor was still higher than that of conventional metal-foil strain sensors. The electrical conductivity of PVDF-HFP/MWNT composites was also studied. It was found that with the increase of the addition amount of MWNT, the electrical conductivity of the PVDF-HFP/MWNT composites varied in a perfect percolation pattern with a very low percolation threshold, i.e., 0.77 vol.%, further indicating the very good dispersion of MWNT in the PVDF-HFP matrix.

  17. Atomistic Modeling of Thermal Conductivity of Epoxy Nanotube Composites

    NASA Astrophysics Data System (ADS)

    Fasanella, Nicholas A.; Sundararaghavan, Veera

    2016-05-01

    The Green-Kubo method was used to investigate the thermal conductivity as a function of temperature for epoxy/single wall carbon nanotube (SWNT) nanocomposites. An epoxy network of DGEBA-DDS was built using the `dendrimer' growth approach, and conductivity was computed by taking into account long-range Coulombic forces via a k-space approach. Thermal conductivity was calculated in the direction perpendicular to, and along the SWNT axis for functionalized and pristine SWNT/epoxy nanocomposites. Inefficient phonon transport at the ends of nanotubes is an important factor in the thermal conductivity of the nanocomposites, and for this reason discontinuous nanotubes were modeled in addition to long nanotubes. The thermal conductivity of the long, pristine SWNT/epoxy system is equivalent to that of an isolated SWNT along its axis, but there was a 27% reduction perpendicular to the nanotube axis. The functionalized, long SWNT/epoxy system had a very large increase in thermal conductivity along the nanotube axis (~700%), as well as the directions perpendicular to the nanotube (64%). The discontinuous nanotubes displayed an increased thermal conductivity along the SWNT axis compared to neat epoxy (103-115% for the pristine SWNT/epoxy, and 91-103% for functionalized SWNT/epoxy system). The functionalized system also showed a 42% improvement perpendicular to the nanotube, while the pristine SWNT/epoxy system had no improvement over epoxy. The thermal conductivity tensor is averaged over all possible orientations to see the effects of randomly orientated nanotubes, and allow for experimental comparison. Excellent agreement is seen for the discontinuous, pristine SWNT/epoxy nanocomposite. These simulations demonstrate there exists a threshold of the SWNT length where the best improvement for a composite system with randomly oriented nanotubes would transition from pristine SWNTs to functionalized SWNTs.

  18. ac conductivity and dielectric constant of conductor-insulator composites

    NASA Astrophysics Data System (ADS)

    Murtanto, Tan Benny; Natori, Satoshi; Nakamura, Jun; Natori, Akiko

    2006-09-01

    We study the complex admittance (ac conductivity and dielectric constant) of conductor-insulator composite material, based on a two-dimensional square network consisting of randomly placed conductors and capacitors. We derived some exact analytical relations between the complex admittances of high and low frequencies and of complementary conductor concentrations. We calculate the complex admittance by applying a transfer-matrix method to a square network and study the dependence on both the frequency and the conductor concentration. The numerical results are compared with an effective-medium theory, and the range of applicability and limitation of the effective-medium theory are clarified.

  19. Silver nanowires/polycarbonate composites for conductive films

    NASA Astrophysics Data System (ADS)

    Moreno, I.; Navascues, N.; Irusta, S.; Santamaría, J.

    2012-09-01

    Silver nanowires (AgNW) with an aspect ratio of 85 were synthesized by a solvothermal process. The AgNW were characterized by SEM and XRD techniques. Nanocomposites of these silver nanowires in a polycarbonate matrix were prepared by simple solution mixing procedure in a concentration filler range 0-4.35 wt%. The obtained films were around 18 μm thick, optical microscopy and SEM characterization showed good dispersion of the nanowires in the polymeric matrix. The obtained composites presented low percolation threshold (0.04 wt%) and the maximum conductivity at 4.35 wt% filler loading was 2.3×10-2 S/cm.

  20. Electrically conductive nano graphite-filled bacterial cellulose composites.

    PubMed

    Erbas Kiziltas, Esra; Kiziltas, Alper; Rhodes, Kevin; Emanetoglu, Nuri W; Blumentritt, Melanie; Gardner, Douglas J

    2016-01-20

    A unique three dimensional (3D) porous structured bacterial cellulose (BC) can act as a supporting material to deposit the nanofillers in order to create advanced BC-based functional nanomaterials for various technological applications. In this study, novel nanocomposites comprised of BC with exfoliated graphite nanoplatelets (xGnP) incorporated into the BC matrix were prepared using a simple particle impregnation strategy to enhance the thermal properties and electrical conductivity of the BC. The flake-shaped xGnP particles were well dispersed and formed a continuous network throughout the BC matrix. The temperature at 10% weight loss, thermal stability and residual ash content of the nanocomposites increased at higher xGnP loadings. The electrical conductivity of the composites increased with increasing xGnP loading (attaining values 0.75 S/cm with the addition of 2 wt.% of xGnP). The enhanced conductive and thermal properties of the BC-xGnP nanocomposites will broaden applications (biosensors, tissue engineering, etc.) of BC and xGnP. PMID:26572457

  1. Bounds to the conductivity of some two-component composites

    NASA Astrophysics Data System (ADS)

    Helsing, Johan

    1993-02-01

    Calculation of third-order bounds to the conductivity of isotropic two-component composites is discussed. Coincidence of the Beran bounds and bounds derived using trial fields based on the solution of a single-body electrostatic boundary-value problem is demonstrated for a random distribution of impenetrable ellipsoids. This extends a proof of Beasley and Torquato [J. Appl. Phys. 60, 3576 (1986)]. A structural parameter related to third-order bounds is calculated for a face-centered cubic array of cubes in a matrix. For an array of rectangular blocks an upper bound in one direction is derived. This bound, and its two-dimensional analogs, become very sharp in the limit of strong inhomogeneity. Improved third- and fourth-order bounds for the three-dimensional checkerboard are presented.

  2. Fiber/Matrix Interfacial Thermal Conductance Effect on the Thermal Conductivity of SiC/SiC Composites

    SciTech Connect

    Nguyen, Ba Nghiep; Henager, Charles H.

    2013-04-20

    SiC/SiC composites used in fusion reactor applications are subjected to high heat fluxes and require knowledge and tailoring of their in-service thermal conductivity. Accurately predicting the thermal conductivity of SiC/SiC composites as a function of temperature will guide the design of these materials for their intended use, which will eventually include the effects of 14-MeV neutron irradiations. This paper applies an Eshelby-Mori-Tanaka approach (EMTA) to compute the thermal conductivity of unirradiated SiC/SiC composites. The homogenization procedure includes three steps. In the first step EMTA computes the homogenized thermal conductivity of the unidirectional (UD) SiC fiber embraced by its coating layer. The second step computes the thermal conductivity of the UD composite formed by the equivalent SiC fibers embedded in a SiC matrix, and finally the thermal conductivity of the as-formed SiC/SiC composite is obtained by averaging the solution for the UD composite over all possible fiber orientations using the second-order fiber orientation tensor. The EMTA predictions for the transverse thermal conductivity of several types of SiC/SiC composites with different fiber types and interfaces are compared to the predicted and experimental results by Youngblood et al.

  3. Highly conductive, multi-layer composite precursor composition to fuel cell flow field plate or bipolar plate

    SciTech Connect

    Jang, Bor Z.; Zhamu, Aruna; Guo, Jiusheng

    2011-02-15

    This invention provides a moldable, multiple-layer composite composition, which is a precursor to an electrically conductive composite flow field plate or bipolar plate. In one preferred embodiment, the composition comprises a plurality of conductive sheets and a plurality of mixture layers of a curable resin and conductive fillers, wherein (A) each conductive sheet is attached to at least one resin-filler mixture layer; (B) at least one of the conductive sheets comprises flexible graphite; and (C) at least one resin-filler mixture layer comprises a thermosetting resin and conductive fillers with the fillers being present in a sufficient quantity to render the resulting flow field plate or bipolar plate electrically conductive with a conductivity no less than 100 S/cm and thickness-direction areal conductivity no less than 200 S/cm.sup.2.

  4. Facile Method to Fabricate Highly Thermally Conductive Graphite/PP Composite with Network Structures.

    PubMed

    Feng, Changping; Ni, Haiying; Chen, Jun; Yang, Wei

    2016-08-01

    Thermally conductive polymer composites have aroused significant academic and industrial interest for several decades. Herein, we report a novel fabrication method of graphite/polypropylene (PP) composites with high thermal conductivity in which graphite flakes construct a continuous thermally conductive network. The thermal conductivity coefficient of the graphite/PP composites is markedly improved to be 5.4 W/mK at a graphite loading of 21.2 vol %. Such a great improvement of the thermal conductivity is ascribed to the occurrence of orientations of crystalline graphite flakes with large particles around PP resin particles and the formation of a perfect thermally conductive network. The model of Hashin-Shtrikman (HS) is adopted to interpret the outstanding thermally conductive property of the graphite/PP composites. This work provides a guideline for the easy fabrication of thermally conductive composites with network structures. PMID:27391206

  5. Extremely High Thermal Conductivity of Aligned Carbon Nanotube-Polyethylene Composites

    PubMed Central

    Liao, Quanwen; Liu, Zhichun; Liu, Wei; Deng, Chengcheng; Yang, Nuo

    2015-01-01

    The ultra-low thermal conductivity of bulk polymers may be enhanced by combining them with high thermal conductivity materials such as carbon nanotubes. Different from random doping, we find that the aligned carbon nanotube-polyethylene composites has a high thermal conductivity by non-equilibrium molecular dynamics simulations. The analyses indicate that the aligned composite not only take advantage of the high thermal conduction of carbon nanotubes, but enhance thermal conduction of polyethylene chains. PMID:26552843

  6. Extremely High Thermal Conductivity of Aligned Carbon Nanotube-Polyethylene Composites

    NASA Astrophysics Data System (ADS)

    Liao, Quanwen; Liu, Zhichun; Liu, Wei; Deng, Chengcheng; Yang, Nuo

    2015-11-01

    The ultra-low thermal conductivity of bulk polymers may be enhanced by combining them with high thermal conductivity materials such as carbon nanotubes. Different from random doping, we find that the aligned carbon nanotube-polyethylene composites has a high thermal conductivity by non-equilibrium molecular dynamics simulations. The analyses indicate that the aligned composite not only take advantage of the high thermal conduction of carbon nanotubes, but enhance thermal conduction of polyethylene chains.

  7. Conducting and non-conducting biopolymer composites produced by particle bonding

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In this report, we introduce two types of processes for the production of biopolymer composites: one is fabricated by bonding biopolymers with corn protein or wheat protein and the other by bonding starch with a synthetic polymer. These two types of biopolymer composites make use of the strong bon...

  8. Ionic Conduction in Lithium Ion Battery Composite Electrode Governs Cross-sectional Reaction Distribution

    PubMed Central

    Orikasa, Yuki; Gogyo, Yuma; Yamashige, Hisao; Katayama, Misaki; Chen, Kezheng; Mori, Takuya; Yamamoto, Kentaro; Masese, Titus; Inada, Yasuhiro; Ohta, Toshiaki; Siroma, Zyun; Kato, Shiro; Kinoshita, Hajime; Arai, Hajime; Ogumi, Zempachi; Uchimoto, Yoshiharu

    2016-01-01

    Composite electrodes containing active materials, carbon and binder are widely used in lithium-ion batteries. Since the electrode reaction occurs preferentially in regions with lower resistance, reaction distribution can be happened within composite electrodes. We investigate the relationship between the reaction distribution with depth direction and electronic/ionic conductivity in composite electrodes with changing electrode porosities. Two dimensional X-ray absorption spectroscopy shows that the reaction distribution is happened in lower porosity electrodes. Our developed 6-probe method can measure electronic/ionic conductivity in composite electrodes. The ionic conductivity is decreased for lower porosity electrodes, which governs the reaction distribution of composite electrodes and their performances. PMID:27193448

  9. Ionic Conduction in Lithium Ion Battery Composite Electrode Governs Cross-sectional Reaction Distribution

    NASA Astrophysics Data System (ADS)

    Orikasa, Yuki; Gogyo, Yuma; Yamashige, Hisao; Katayama, Misaki; Chen, Kezheng; Mori, Takuya; Yamamoto, Kentaro; Masese, Titus; Inada, Yasuhiro; Ohta, Toshiaki; Siroma, Zyun; Kato, Shiro; Kinoshita, Hajime; Arai, Hajime; Ogumi, Zempachi; Uchimoto, Yoshiharu

    2016-05-01

    Composite electrodes containing active materials, carbon and binder are widely used in lithium-ion batteries. Since the electrode reaction occurs preferentially in regions with lower resistance, reaction distribution can be happened within composite electrodes. We investigate the relationship between the reaction distribution with depth direction and electronic/ionic conductivity in composite electrodes with changing electrode porosities. Two dimensional X-ray absorption spectroscopy shows that the reaction distribution is happened in lower porosity electrodes. Our developed 6-probe method can measure electronic/ionic conductivity in composite electrodes. The ionic conductivity is decreased for lower porosity electrodes, which governs the reaction distribution of composite electrodes and their performances.

  10. Ionic Conduction in Lithium Ion Battery Composite Electrode Governs Cross-sectional Reaction Distribution.

    PubMed

    Orikasa, Yuki; Gogyo, Yuma; Yamashige, Hisao; Katayama, Misaki; Chen, Kezheng; Mori, Takuya; Yamamoto, Kentaro; Masese, Titus; Inada, Yasuhiro; Ohta, Toshiaki; Siroma, Zyun; Kato, Shiro; Kinoshita, Hajime; Arai, Hajime; Ogumi, Zempachi; Uchimoto, Yoshiharu

    2016-01-01

    Composite electrodes containing active materials, carbon and binder are widely used in lithium-ion batteries. Since the electrode reaction occurs preferentially in regions with lower resistance, reaction distribution can be happened within composite electrodes. We investigate the relationship between the reaction distribution with depth direction and electronic/ionic conductivity in composite electrodes with changing electrode porosities. Two dimensional X-ray absorption spectroscopy shows that the reaction distribution is happened in lower porosity electrodes. Our developed 6-probe method can measure electronic/ionic conductivity in composite electrodes. The ionic conductivity is decreased for lower porosity electrodes, which governs the reaction distribution of composite electrodes and their performances. PMID:27193448

  11. Revisiting the percolation phenomena in dielectric composites with conducting fillers

    NASA Astrophysics Data System (ADS)

    Zhang, Lin; Bass, Patrick; Cheng, Z.-Y.

    2014-07-01

    The composition (φ) dependence of the effective dielectric constant (ɛeff) on conductor-dielectric composites is widely described as ɛeff∝(φc-φ)-s. This relationship has been extensively used to fit experimental results for determining the percolation behavior (percolation threshold φc and power constant s). The equation was checked using experimental results from two 0-3 nanocomposite systems with uniform microstructures. It is found that the equation can be used to fit the experimental results, but the fitting constants (φc and s) do not reflect the percolation behavior: the values of both fitting constants are dependent on the frequency (f) and temperature selected. It is also found that the fitting constant φc increases with increasing frequency selected and it is believed that this arises from the critical phenomenon, ɛeff∝fγ-1, for composites close to the φc.

  12. Conducting molecular composites of polypyrrole with electroactive polymeric dopantions

    SciTech Connect

    Cameron, D.A.; Reynolds, J.R.

    1996-10-01

    Polypyrrole is one of the most widely used and studied electroactive polymers due to its good conductivity and stability in air. A variety of low molecular weight and polymeric ions have been used as charge compensating dopants in conductive polypyrrole in its oxidized state. In this work we report the electro-polymerization of polypyrrole films incorporating electroactive N-substituted polyaniline polyelectrolytes as dopant ions.

  13. Thermal-conductivity measurements of tungsten-fiber-reinforced superalloy composites using a thermal-conductivity comparator

    NASA Technical Reports Server (NTRS)

    Westfall, L. J.; Winsa, E. A.

    1979-01-01

    The thermal conductivity (TC) of tungsten-fiber-reinforced superalloys was determined for two composite systems by using a thermal conductivity standard from the National Bureau of Standards and a comparator and technique developed for that purpose. The results were compared with TC data for the nickel-base alloy MAR-M200. The technique lends itself to applications involving thin specimens, such as thin-walled turbine blades. The TC's of the composite systems were considerably higher in both the longitudinal and transverse directions than that of the monolithic superalloys used as the matrices.

  14. Electrical and thermal conductivities of reduced graphene oxide/polystyrene composites

    NASA Astrophysics Data System (ADS)

    Park, Wonjun; Hu, Jiuning; Jauregui, Luis A.; Ruan, Xiulin; Chen, Yong P.

    2014-03-01

    The author reports an experimental study of electrical and thermal transport in reduced graphene oxide (RGO)/polystyrene (PS) composites. The electrical conductivity (σ) of RGO/PS composites with different RGO concentrations at room temperature shows a percolation behavior with the percolation threshold of ˜0.25 vol. %. Their temperature-dependent electrical conductivity follows Efros-Shklovskii variable range hopping conduction in the temperature range of 30-300 K. The thermal conductivity (κ) of composites is enhanced by ˜90% as the concentration is increased from 0 to 10 vol. %. The thermal conductivity of composites approximately linearly increases with increasing temperature from 150 to 300 K. Composites with a higher concentration show a stronger temperature dependence in the thermal conductivity.

  15. Silver Nanoparticle-Deposited Boron Nitride Nanosheets as Fillers for Polymeric Composites with High Thermal Conductivity

    PubMed Central

    Wang, Fangfang; Zeng, Xiaoliang; Yao, Yimin; Sun, Rong; Xu, Jianbin; Wong, Ching-Ping

    2016-01-01

    Polymer composites with high thermal conductivity have recently attracted much attention, along with the rapid development of the electronic devices toward higher speed and performance. However, a common method to enhance polymer thermal conductivity through an addition of high thermally conductive fillers usually cannot provide an expected value, especially for composites requiring electrical insulation. Here, we show that polymeric composites with silver nanoparticle-deposited boron nitride nanosheets as fillers could effectively enhance the thermal conductivity of polymer, thanks to the bridging connections of silver nanoparticles among boron nitride nanosheets. The thermal conductivity of the composite is significantly increased from 1.63 W/m-K for the composite filled with the silver nanoparticle-deposited boron nitride nanosheets to 3.06 W/m-K at the boron nitride nanosheets loading of 25.1 vol %. In addition, the electrically insulating properties of the composite are well preserved. Fitting the measured thermal conductivity of epoxy composite with one physical model indicates that the composite with silver nanoparticle-deposited boron nitride nanosheets outperforms the one with boron nitride nanosheets, owning to the lower thermal contact resistance among boron nitride nanosheets’ interfaces. The finding sheds new light on enhancement of thermal conductivity of the polymeric composites which concurrently require the electrical insulation. PMID:26783258

  16. Silver Nanoparticle-Deposited Boron Nitride Nanosheets as Fillers for Polymeric Composites with High Thermal Conductivity.

    PubMed

    Wang, Fangfang; Zeng, Xiaoliang; Yao, Yimin; Sun, Rong; Xu, Jianbin; Wong, Ching-Ping

    2016-01-01

    Polymer composites with high thermal conductivity have recently attracted much attention, along with the rapid development of the electronic devices toward higher speed and performance. However, a common method to enhance polymer thermal conductivity through an addition of high thermally conductive fillers usually cannot provide an expected value, especially for composites requiring electrical insulation. Here, we show that polymeric composites with silver nanoparticle-deposited boron nitride nanosheets as fillers could effectively enhance the thermal conductivity of polymer, thanks to the bridging connections of silver nanoparticles among boron nitride nanosheets. The thermal conductivity of the composite is significantly increased from 1.63 W/m-K for the composite filled with the silver nanoparticle-deposited boron nitride nanosheets to 3.06 W/m-K at the boron nitride nanosheets loading of 25.1 vol %. In addition, the electrically insulating properties of the composite are well preserved. Fitting the measured thermal conductivity of epoxy composite with one physical model indicates that the composite with silver nanoparticle-deposited boron nitride nanosheets outperforms the one with boron nitride nanosheets, owning to the lower thermal contact resistance among boron nitride nanosheets' interfaces. The finding sheds new light on enhancement of thermal conductivity of the polymeric composites which concurrently require the electrical insulation. PMID:26783258

  17. Silver Nanoparticle-Deposited Boron Nitride Nanosheets as Fillers for Polymeric Composites with High Thermal Conductivity

    NASA Astrophysics Data System (ADS)

    Wang, Fangfang; Zeng, Xiaoliang; Yao, Yimin; Sun, Rong; Xu, Jianbin; Wong, Ching-Ping

    2016-01-01

    Polymer composites with high thermal conductivity have recently attracted much attention, along with the rapid development of the electronic devices toward higher speed and performance. However, a common method to enhance polymer thermal conductivity through an addition of high thermally conductive fillers usually cannot provide an expected value, especially for composites requiring electrical insulation. Here, we show that polymeric composites with silver nanoparticle-deposited boron nitride nanosheets as fillers could effectively enhance the thermal conductivity of polymer, thanks to the bridging connections of silver nanoparticles among boron nitride nanosheets. The thermal conductivity of the composite is significantly increased from 1.63 W/m-K for the composite filled with the silver nanoparticle-deposited boron nitride nanosheets to 3.06 W/m-K at the boron nitride nanosheets loading of 25.1 vol %. In addition, the electrically insulating properties of the composite are well preserved. Fitting the measured thermal conductivity of epoxy composite with one physical model indicates that the composite with silver nanoparticle-deposited boron nitride nanosheets outperforms the one with boron nitride nanosheets, owning to the lower thermal contact resistance among boron nitride nanosheets’ interfaces. The finding sheds new light on enhancement of thermal conductivity of the polymeric composites which concurrently require the electrical insulation.

  18. Thermal Conduction in Vertically Aligned Copper Nanowire Arrays and Composites.

    PubMed

    Barako, Michael T; Roy-Panzer, Shilpi; English, Timothy S; Kodama, Takashi; Asheghi, Mehdi; Kenny, Thomas W; Goodson, Kenneth E

    2015-09-01

    The ability to efficiently and reliably transfer heat between sources and sinks is often a bottleneck in the thermal management of modern energy conversion technologies ranging from microelectronics to thermoelectric power generation. These interfaces contribute parasitic thermal resistances that reduce device performance and are subjected to thermomechanical stresses that degrade device lifetime. Dense arrays of vertically aligned metal nanowires (NWs) offer the unique combination of thermal conductance from the constituent metal and mechanical compliance from the high aspect ratio geometry to increase interfacial heat transfer and device reliability. In the present work, we synthesize copper NW arrays directly onto substrates via templated electrodeposition and extend this technique through the use of a sacrificial overplating layer to achieve improved uniformity. Furthermore, we infiltrate the array with an organic phase change material and demonstrate the preservation of thermal properties. We use the 3ω method to measure the axial thermal conductivity of freestanding copper NW arrays to be as high as 70 W m(-1) K(-1), which is more than an order of magnitude larger than most commercial interface materials and enhanced-conductivity nanocomposites reported in the literature. These arrays are highly anisotropic, and the lateral thermal conductivity is found to be only 1-2 W m(-1) K(-1). We use these measured properties to elucidate the governing array-scale transport mechanisms, which include the effects of morphology and energy carrier scattering from size effects and grain boundaries. PMID:26284489

  19. Electrical and morphological properties of conducting layers formed from the silver-glass composite conducting powders prepared by spray pyrolysis.

    PubMed

    Jung, D S; Koo, H Y; Kang, Y C

    2010-03-01

    Ag-glass composite powders with various glass contents and excellent conducting properties were prepared by spray pyrolysis. Irrespective of the glass content, all the prepared powders were found to comprise spherical particles with nonaggregation characteristics. The crystal structure of the powder particles resembled that of pure Ag particles, irrespective of the glass content. Conducting layers formed from pure Ag did not melt even when sintered at 400 degrees C. On the other hand, conducting layers formed from composite powders containing 3 and 5 wt% glass melted when sintered at 400 degrees C. The optimum glass content of the composite powders was 3 wt% at sintering temperatures of 400 and 450 degrees C. However, the optimum glass content decreased to 1 wt% when the sintering temperature was increased to 550 degrees C. The lowest specific resistances of the conducting layers formed from the composite powders were 5.3 and 2.3 microohms-cm at sintering temperatures of 400 and 550 degrees C, respectively. PMID:20036371

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

    NASA Astrophysics Data System (ADS)

    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.

  1. A tactile sensor using a conductive graphene-sponge composite.

    PubMed

    Chun, Sungwoo; Hong, Ahyoung; Choi, Yeonhoi; Ha, Chunho; Park, Wanjun

    2016-04-28

    For sensors that emulate human tactile perception, we suggest a simple method for fabricating a highly sensitive force sensor using a conductive polyurethane sponge where graphene flakes are self-assembled into the porous structure of the sponge. The complete sensor device shows a sensitive and reliable detection response for a broad range of pressure and dynamic pressure that correspond to human tactile perception. Sensitivity of the sensor to detect vibration is also confirmed with vertical actuations due to slipping over micro-scale ridge structures attached on the sensors. Based on the sensor's ability to detect both pressure and vibration, the sensor can be utilized as a flexible tactile sensor. PMID:27076360

  2. Conductive polyurethane composites containing polyaniline-coated nano-silica.

    PubMed

    Liu, Bo-Tau; Syu, Jhan-Rong; Wang, De-Hua

    2013-03-01

    In this study, we used 1.2-Aminopropyltriethoxysilane (APTS) as a coupling agent to synthesize silica-polyaniline (PANI) core-shell nanoparticles. The core-shell nanoparticles and PANI oligomers were reacted with isocyanates to prepare the conductive polyurethane (PU)-PANI-silica nanocomposites. The core-shell-nanoparticle structure shows significant enhancement on electrical properties of the conductive nanocomposites even though only 0.0755-wt.% PANI was coated on the nano-silica. The surface resistance of the nanocomposite containing 5 wt.% PANI can reduce to ~10(8) Ω/sq, lowering two orders in contrast to the nanocomposite without the core-shell structure. In comparison with the neat PU, tensile strength and elongation of the nanocomposite containing silica-PANI core-shell nanoparticles can increase 3.1 and 3.8 times, respectively. We suspect that the extraordinary enhancement of electrical and mechanical properties may result from the fact that contact probability among PANI moieties and chemical bonding between particles and PU matrix increase due to the PANI coated on the surface of silica. PMID:23261334

  3. A tactile sensor using a conductive graphene-sponge composite

    NASA Astrophysics Data System (ADS)

    Chun, Sungwoo; Hong, Ahyoung; Choi, Yeonhoi; Ha, Chunho; Park, Wanjun

    2016-04-01

    For sensors that emulate human tactile perception, we suggest a simple method for fabricating a highly sensitive force sensor using a conductive polyurethane sponge where graphene flakes are self-assembled into the porous structure of the sponge. The complete sensor device shows a sensitive and reliable detection response for a broad range of pressure and dynamic pressure that correspond to human tactile perception. Sensitivity of the sensor to detect vibration is also confirmed with vertical actuations due to slipping over micro-scale ridge structures attached on the sensors. Based on the sensor's ability to detect both pressure and vibration, the sensor can be utilized as a flexible tactile sensor.For sensors that emulate human tactile perception, we suggest a simple method for fabricating a highly sensitive force sensor using a conductive polyurethane sponge where graphene flakes are self-assembled into the porous structure of the sponge. The complete sensor device shows a sensitive and reliable detection response for a broad range of pressure and dynamic pressure that correspond to human tactile perception. Sensitivity of the sensor to detect vibration is also confirmed with vertical actuations due to slipping over micro-scale ridge structures attached on the sensors. Based on the sensor's ability to detect both pressure and vibration, the sensor can be utilized as a flexible tactile sensor. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00774k

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

    NASA Technical Reports Server (NTRS)

    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.

  5. Transparent conductive multiwall carbon nanotubes-polymer composite for electrode applications.

    PubMed

    Nayak, Sasmita; Behura, Sanjay Kumar; Bhattacharjee, Sarama; Singh, Bimal P; Jani, Omkar; Mukhopadhyay, Indrajit

    2014-04-01

    Disperse Multiwall carbon nanotubes (MWCNTs) are incorporated aqueous N-hydroxy methyl acrylamide, which is subjected to crosslinking to develop a transparent conductive composite free standing film. The effects of the concentration of MWCNTs and temperature on optical and electrical properties of nano-composites are investigated. Interestingly, only 0.06 mg/ml of MWCNTs is sufficient to reach the percolation threshold (Phi) for transition in electrical conductivity up to 10(-4) S/cm, with a visible transmittance over 85%, which is well above the reported for such a low level of MWCNTs loading. The electrical conductivity of the composite was measured at 120 degrees C. It has been observed that electrical conductivity increases significantly with the increase in temperature, signifying the semiconducting nature of nano-composites. Finally, current-voltage (I-V) characteristics show liner behaviour, confirms Ohmic nature of nano-composites and metal contact. PMID:24734695

  6. High frequency characterization of conductive inks embedded within a structural composite

    NASA Astrophysics Data System (ADS)

    Pa, Peter; McCauley, Raymond; Larimore, Zachary; Mills, Matthew; Yarlaggada, Shridhar; Mirotznik, Mark S.

    2015-06-01

    Woven fabric composites provide an attractive platform for integrating electromagnetic functionality—such as conformal load-bearing antennas and frequency selective surfaces—into a structural platform. One practical fabrication method for integrating conductive elements within a woven fabric composite system involves using additive manufacturing systems such as screen printing. While screen printing is an inherently scalable, flexible and cost effective method, little is known about the high frequency electrical properties of its conductive inks when they are embedded within the woven fabric composite. Thus, we have completed numerical and experimental studies to determine the electrical conductivity of screen printable conductive inks that are embedded within this composite. We have also performed mechanical studies to evaluate how printing affects the structural performance of the composite.

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

    DOEpatents

    Kumar, Binod

    2003-12-02

    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.

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

    NASA Technical Reports Server (NTRS)

    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.

  9. Improved conductivity of carbon-nano-fiber (CNF)/polytetrafluoroethylene (PTFE) composite

    NASA Astrophysics Data System (ADS)

    Chandra, Sarita; Kalra, G. S.; Pushkar, Vinay K.; Panwar, Variz; Gill, Fateh Singh; Gupta, Himanshu; Pal, Pankaj K.; Pathak, Trilok K.; Purohit, L. P.

    2016-05-01

    A series of CNF/PTFE composite loaded with different weight % of CNFs as 0.01, 0.02, 0.03, 0.05, 1, 2, 3, 4, 5 into PTFE is fabricated. In this work, the 5wt% heat-treated CNFs were used as filler in PTFE. Current-voltage (I-V) study of the samples confirmed the samples as conducting composite. In scanning electron microscope (SEM) study, the conducting CNFs channels were observed from upper surface to inside throughout the polymer matrix. A sintered composite of 5wt% loading of CNFs showed an improved conductivity and SEM image exhibited a good binding of CNFs into PTFE.

  10. Monte Carlo Simulation of Thermal Conductivity in Randomly Distributed Nanowire Composites

    NASA Astrophysics Data System (ADS)

    Tian, W.; Yang, R.

    2007-03-01

    In this paper, we investigated the thermal conductivity of composites made of two types of randomly stacked nanowires with high contrast ratio of bulk thermal conductivity. Thermal conductivity predictions based on solving the phonon Boltzmann transport equation by using the Monte Carlo method are presented for different contrast ratios of thermal conductivity, sizes of nanowires and the volumetric fractions in the composites. For composites made of nanowires with high contrast ratio thermal conductivity, the thermal conductivity of the nanocomposites increase dramatically when the volumetric fraction of high thermal conductivity nanowire is higher than the geometry percolation threshold, although existing correlations in percolation theory do not fit the results due to the phonon interface scattering. On the other hand, when the the size of nanowires is small and the volumetric fraction of high thermal conductivity nanowire is less than percolation threshold, the thermal conductivity of the nanocomposites decreases with increasing the volumetric fraction of the high thermal conductivity nanowires. The results of this study may help the development of nanoscale thermoelectric materials in which the figure of merit is optimized by choosing appropriate nanowire size, property contrast and composition. RY acknowledges the funding support for this work by DoD/AFOSR MURI grant FA9550-06-1-0326. The simulation was conducted on a 24-node cluster supported by Intel Corporation and managed by Prof. Gang Chen and Mr. Lu Hu at MIT.

  11. Nanoscale electrical and mechanical characteristics of conductive polyaniline network in polymer composite films.

    PubMed

    Jafarzadeh, Shadi; Claesson, Per M; Sundell, Per-Erik; Pan, Jinshan; Thormann, Esben

    2014-11-12

    The presence and characteristics of a connected network of polyaniline (PANI) within a composite coating based on polyester acrylate (PEA) has been investigated. The bulk electrical conductivity of the composite was measured by impedance spectroscopy. It was found that the composite films containing PANI have an electrical conductivity level in the range of semiconductors (order of 10(-3) S cm(-1)), which suggests the presence of a connected network of the conductive phase. The nanoscopic distribution of such a network within the cured film was characterized by PeakForce tunneling atomic force microscopy (AFM). This method simultaneously provides local information about surface topography and nanomechanical properties, together with electrical conductivity arising from conductive paths connecting the metallic substrate to the surface of the coating. The data demonstrates that a PEA-rich layer exists at the composite-air interface, which hinders the conductive phase to be fully detected at the surface layer. However, by exposing the internal structure of the composites using a microtome, a much higher population of a conductive network of PANI, with higher elastic modulus than the PEA matrix, was observed and characterized. Local current-voltage (I-V) spectroscopy was utilized to investigate the conduction mechanism within the nanocomposite films, and revealed non-Ohmic characteristics of the conductive network. PMID:25295701

  12. Enhancing through thickness thermal conductivity of ultra-thin composite laminates. Final report

    SciTech Connect

    Ramani, K.; Vaidyanathan, A.

    1994-12-31

    The materials used in electronic applications have specific requirements for stiffness, thermal conductivity, and electromagnetic shielding making the choice of materials used very important. Electronic components are very sensitive to heat, hence the heat dissipation or cooling of the various components is necessary to prevent failure. Thus, any material used in the electronic industry must have a high thermal conductivity in addition to a specified thermal expansion, stiffness and strength properties. The purpose of this project was to design and manufacture composite panels which would conduct heat from an electronic chip attached to the top surface to a cooling liquid flowing at its lower surface. To maximize the heat conducted from the chip to the cooling liquid, the composite must have a high through thickness thermal conductivity. Further, design restrictions on the thickness of the composite panel had to be taken into account. It was found that the presence of excess resin adversely affects the conductivity of a woven fabric composite due to which the through thickness conductivity of the 400 {micro}m thick panel was better than the 500 {micro}m thick panel. The through thickness conductivity of the panel with short fibers alone was better than that of the woven cloth panel. The finite element model developed for a priori prediction of the through thickness thermal conductivity of the composite panels is a very powerful tool that can save enormous prototyping times an associates coats.

  13. High Temperature Characteristic in Electrical Breakdown and Electrical Conduction of Epoxy/Boron-nitride Composite

    NASA Astrophysics Data System (ADS)

    Takenaka, Yutaka; Kurimoto, Muneaki; Murakami, Yoshinobu; Nagao, Masayuki

    The power module for the electrical vehicle needs electrical insulation material with high thermal conductivity. Recently, the epoxy insulating material filled with boron-nitride particles (epoxy/boron-nitride composite) is focused as an effective solution. However, the insulation performance of epoxy/boron-nitride composite was not investigated enough especially at the high temperature in which the power module was used, i.e. more than 100°C. In this paper, we investigated high temperature characteristics in electrical breakdown and conduction current of epoxy/boron-nitride composite. Breakdown test under the application of DC lamp voltage and impulse voltage clarified that the epoxy/boron-nitride composite had the constant breakdown strength even in the high temperature. Comparison of the epoxy/boron-nitride composite with previous material, which was epoxy/alumina composite, indicated that the breakdown voltage of the epoxy/boron-nitride composite in the high temperature was found to be higher than that of epoxy/alumina composite under the same thermal-transfer quantity among them. Furthermore, conduction current measurement of epoxy/boron-nitride composite in the high temperature suggested the possibility of the ionic conduction mechanism.

  14. Highly conductive electrolyte composites containing glass and ceramic, and method of manufacture

    DOEpatents

    Hash, M.C.; Bloom, I.D.

    1992-10-13

    An electrolyte composite is manufactured by pressurizing a mixture of sodium ion conductive glass and an ionically conductive compound at between 12,000 and 24,000 pounds per square inch to produce a pellet. The resulting pellet is then sintered at relatively lower temperatures (800--1200 C), for example 1000 C, than are typically required (1400 C) when fabricating single constituent ceramic electrolytes. The resultant composite is 100 percent conductive at 250 C with conductivity values of 2.5 to 4[times]10[sup [minus]2](ohm-cm)[sup [minus]1]. The matrix exhibits chemical stability against sodium for 100 hours at 250 to 300 C. 1 figure.

  15. Composite material having high thermal conductivity and process for fabricating same

    DOEpatents

    Colella, N.J.; Davidson, H.L.; Kerns, J.A.; Makowiecki, D.M.

    1998-07-21

    A process is disclosed for fabricating a composite material such as that having high thermal conductivity and having specific application as a heat sink or heat spreader for high density integrated circuits. The composite material produced by this process has a thermal conductivity between that of diamond and copper, and basically consists of coated diamond particles dispersed in a high conductivity metal, such as copper. The composite material can be fabricated in small or relatively large sizes using inexpensive materials. The process basically consists, for example, of sputter coating diamond powder with several elements, including a carbide forming element and a brazeable material, compacting them into a porous body, and infiltrating the porous body with a suitable braze material, such as copper-silver alloy, thereby producing a dense diamond-copper composite material with a thermal conductivity comparable to synthetic diamond films at a fraction of the cost. 7 figs.

  16. Composite material having high thermal conductivity and process for fabricating same

    DOEpatents

    Colella, Nicholas J.; Davidson, Howard L.; Kerns, John A.; Makowiecki, Daniel M.

    1998-01-01

    A process for fabricating a composite material such as that having high thermal conductivity and having specific application as a heat sink or heat spreader for high density integrated circuits. The composite material produced by this process has a thermal conductivity between that of diamond and copper, and basically consists of coated diamond particles dispersed in a high conductivity metal, such as copper. The composite material can be fabricated in small or relatively large sizes using inexpensive materials. The process basically consists, for example, of sputter coating diamond powder with several elements, including a carbide forming element and a brazeable material, compacting them into a porous body, and infiltrating the porous body with a suitable braze material, such as copper-silver alloy, thereby producing a dense diamond-copper composite material with a thermal conductivity comparable to synthetic diamond films at a fraction of the cost.

  17. Thermal conductivity and thermal expansion of graphite fiber-reinforced copper matrix composites

    NASA Technical Reports Server (NTRS)

    Ellis, David L.; Mcdanels, David L.

    1993-01-01

    The high specific conductivity of graphite fiber/copper matrix (Gr/Cu) composites offers great potential for high heat flux structures operating at elevated temperatures. To determine the feasibility of applying Gr/Cu composites to high heat flux structures, composite plates were fabricated using unidirectional and cross-plied pitch-based P100 graphite fibers in a pure copper matrix. Thermal conductivity of the composites was measured from room temperature to 1073 K, and thermal expansion was measured from room temperature to 1050 K. The longitudinal thermal conductivity, parallel to the fiber direction, was comparable to pure copper. The transverse thermal conductivity, normal to the fiber direction, was less than that of pure copper and decreased with increasing fiber content. The longitudinal thermal expansion decreased with increasing fiber content. The transverse thermal expansion was greater than pure copper and nearly independent of fiber content.

  18. Thermal conductivity and thermal expansion of graphite fiber/copper matrix composites

    NASA Technical Reports Server (NTRS)

    Ellis, David L.; Mcdanels, David L.

    1991-01-01

    The high specific conductivity of graphite fiber/copper matrix (Gr/Cu) composites offers great potential for high heat flux structures operating at elevated temperatures. To determine the feasibility of applying Gr/Cu composites to high heat flux structures, composite plates were fabricated using unidirectional and cross-plied pitch-based P100 graphite fibers in a pure copper matrix. Thermal conductivity of the composites was measured from room temperature to 1073 K, and thermal expansion was measured from room temperature to 1050 K. The longitudinal thermal conductivity, parallel to the fiber direction, was comparable to pure copper. The transverse thermal conductivity, normal to the fiber direction, was less than that of pure copper and decreased with increasing fiber content. The longitudinal thermal expansion decreased with increasing fiber content. The transverse thermal expansion was greater than pure copper and nearly independent of fiber content.

  19. The Electrical and Thermal Conductivity of Woven Pristine and Intercalated Graphite Fiber-Polymer Composites

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Vandenburg, Yvonne Yoder; Berkebile, Steven; Stueben, Heather; Balagadde, Frederick

    2002-01-01

    A series of woven fabric laminar composite plates and narrow strips were fabricated from a variety of pitch-based pristine and bromine intercalated graphite fibers in an attempt to determine the influence of the weave on the electrical and thermal conduction. It was found generally that these materials can be treated as if they are homogeneous plates. The rule of mixtures describes the resistivity of the composite fairly well if it is realized that only the component of the fibers normal to the equipotential surface will conduct current. When the composite is narrow with respect to the fiber weave, however, there is a marked angular dependence of the resistance which was well modeled by assuming that the current follows only along the fibers (and not across them in a transverse direction), and that the contact resistance among the fibers in the composite is negligible. The thermal conductivity of composites made from less conductive fibers more closely followed the rule of mixtures than that of the high conductivity fibers, though this is thought to be an artifact of the measurement technique. Electrical and thermal anisotropy could be induced in a particular region of the structure by weaving together high and low conductivity fibers in different directions, though this must be done throughout all of the layers of the structure as interlaminar conduction precludes having only the top layer carry the anisotropy. The anisotropy in the thermal conductivity is considerably less than either that predicted by the rule of mixtures or the electrical resistivity.

  20. High thermal conductivity SiC/SiC composites for fusion applications -- 2

    SciTech Connect

    Kowbel, W.; Tsou, K.T.; Withers, J.C.; Youngblood, G.E.

    1998-03-01

    This report covers material presented at the IEA/Jupiter Joint International Workshop on SiC/SiC Composites for Fusion Structural Applications held in conjunction with ICFRM-8, Sendai, Japan, Oct. 23--24, 1997. An unirradiated SiC/SiC composite made with MER-developed CVR SiC fiber and a hybrid PIP/CVI SiC matrix exhibited room temperature transverse thermal conductivity of 45 W/mK. An unirradiated SiC/SiC composite made from C/C composite totally CVR-converted to a SiC/SiC composite exhibited transverse thermal conductivity values of 75 and 35 W/mK at 25 and 1000 C, respectively. Both types of SiC/SiC composites exhibited non-brittle failure in flexure testing.

  1. High strength-high conductivity Cu--Fe composites produced by powder compaction/mechanical reduction

    DOEpatents

    Verhoeven, John D.; Spitzig, William A.; Gibson, Edwin D.; Anderson, Iver E.

    1991-08-27

    A particulate mixture of Cu and Fe is compacted and mechanically reduced to form an "in-situ" Cu-Fe composite having high strength and high conductivity. Compaction and mechanical reduction of the particulate mixture are carried out at a temperature and time at temperature selected to avoid dissolution of Fe into the Cu matrix particulates to a harmful extent that substantially degrades the conductivity of the Cu-Fe composite.

  2. High strength-high conductivity Cu-Fe composites produced by powder compaction/mechanical reduction

    DOEpatents

    Verhoeven, J.D.; Spitzig, W.A.; Gibson, E.D.; Anderson, I.E.

    1991-08-27

    A particulate mixture of Cu and Fe is compacted and mechanically reduced to form an ''in-situ'' Cu-Fe composite having high strength and high conductivity. Compaction and mechanical reduction of the particulate mixture are carried out at a temperature and time at temperature selected to avoid dissolution of Fe into the Cu matrix particulates to a harmful extent that substantially degrades the conductivity of the Cu-Fe composite. 5 figures.

  3. Formation of conductive networks with both segregated and double-percolated characteristic in conductive polymer composites with balanced properties.

    PubMed

    Zhang, Shuangmei; Deng, Hua; Zhang, Qin; Fu, Qiang

    2014-05-14

    Morphological control of conductive networks involves the construction of segregated or double-percolated conductive networks is often reported to reduce the electrical percolation threshold of conductive polymer composites (CPCs) for better balance among electrical conductivity, mechanical properties, and filler content. Herein, the construction of conductive networks with both segregated and double-percolated characteristics is achieved based on polypropylene (PP)/polyethylene (PE) and multi-wall carbon nanotubes (CNTs). CNTs were firstly dispersed in PE; then PE/CNTs were compounded with PP particles well below the melting temperature of PP. It is observed that the percolation threshold (pc) decreases with increasing PP particle size (size 3.6 mm, pc=0.08 wt %), which agrees with previous theoretical prediction and experiment in much smaller particle size range. To further study this, the amount of CNTs in PE is varied. It is shown that the degree of PE/CNTs coating on PP particles varies with CNTs as well as PE content in these composites, and have significant influence on the final electrical property. Furthermore, a model combines classical percolation theory and model for segregated network has been proposed to analyze the effect of particle size, degree of coating and thickness of coating on the percolation behavior of these CPCs. In such a model the percolation of CNTs in PE phase as well as PENT phase in the segregated structure can be described. Overall, through such method, a much better balance among mechanical property, conductivity, and filler content is achieved in these CPCs comparing with the results in literature. PMID:24745303

  4. Thermally conductive polyamide 6/carbon filler composites based on a hybrid filler system

    NASA Astrophysics Data System (ADS)

    Ha, Sung Min; Kwon, O. Hwan; Gyeong Oh, Yu; Kim, Yong Seok; Lee, Sung-Goo; Won, Jong Chan; Cho, Kwang Soo; Gak Kim, Byoung; Yoo, Youngjae

    2015-12-01

    We explored the use of a hybrid filler consisting of graphite nanoplatelets (GNPs) and single walled carbon nanotubes (SWCNTs) in a polyamide 6 (PA 6) matrix. The composites containing PA 6, powdered GNP, and SWCNT were melt-processed and the effect of filler content in the single filler and hybrid filler systems on the thermal conductivity of the composites was examined. The thermal diffusivities of the composites were measured by the standard laser flash method. Composites containing the hybrid filler system showed enhanced thermal conductivity with values as high as 8.8 W (m · K)-1, which is a 35-fold increase compared to the thermal conductivity of pure PA 6. Thermographic images of heat conduction and heat release behaviors were consistent with the thermal conductivity results, and showed rapid temperature jumps and drops, respectively, for the composites. A composite model based on the Lewis-Nielsen theory was developed to treat GNP and SWCNT as two separate types of fillers. Two approaches, the additive and multiplicative approaches, give rather good quantitative agreement between the predicted values of thermal conductivity and those measured experimentally.

  5. Highly conductive composites for fuel cell flow field plates and bipolar plates

    DOEpatents

    Jang, Bor Z; Zhamu, Aruna; Song, Lulu

    2014-10-21

    This invention provides a fuel cell flow field plate or bipolar plate having flow channels on faces of the plate, comprising an electrically conductive polymer composite. The composite is composed of (A) at least 50% by weight of a conductive filler, comprising at least 5% by weight reinforcement fibers, expanded graphite platelets, graphitic nano-fibers, and/or carbon nano-tubes; (B) polymer matrix material at 1 to 49.9% by weight; and (C) a polymer binder at 0.1 to 10% by weight; wherein the sum of the conductive filler weight %, polymer matrix weight % and polymer binder weight % equals 100% and the bulk electrical conductivity of the flow field or bipolar plate is at least 100 S/cm. The invention also provides a continuous process for cost-effective mass production of the conductive composite-based flow field or bipolar plate.

  6. Silver-plated carbon nanotubes for silver/conducting polymer composites

    NASA Astrophysics Data System (ADS)

    Oh, Youngseok; Suh, Daewoo; Kim, Youngjin; Lee, Eungsuek; Mok, Jee Soo; Choi, Jaeboong; Baik, Seunghyun

    2008-12-01

    Carbon nanotubes (CNTs) have advantages as conductive fillers due to their large aspect ratio and excellent conductivity. In this study, a novel silver/conducting polymer composite was developed by the incorporation of silver-plated CNTs. It is important to achieve a homogeneous dispersion of nanotubes and to improve the interfacial bonding to utilize the excellent properties of reinforcements in the matrix material. The homogeneous dispersion of nanotubes was achieved by an acid treatment process, and the interfacial contact was improved by electroless silver plating around nanotubes. The resistivity of the silver/conducting polymer composite was decreased by 83% by the addition of silver-plated single-walled carbon nanotubes. Conductive bumps were also screen-printed to demonstrate the capability of the composite as electrical interconnects for multi-layer printed circuit boards.

  7. Silver-plated carbon nanotubes for silver/conducting polymer composites.

    PubMed

    Oh, Youngseok; Suh, Daewoo; Kim, Youngjin; Lee, Eungsuek; Mok, Jee Soo; Choi, Jaeboong; Baik, Seunghyun

    2008-12-10

    Carbon nanotubes (CNTs) have advantages as conductive fillers due to their large aspect ratio and excellent conductivity. In this study, a novel silver/conducting polymer composite was developed by the incorporation of silver-plated CNTs. It is important to achieve a homogeneous dispersion of nanotubes and to improve the interfacial bonding to utilize the excellent properties of reinforcements in the matrix material. The homogeneous dispersion of nanotubes was achieved by an acid treatment process, and the interfacial contact was improved by electroless silver plating around nanotubes. The resistivity of the silver/conducting polymer composite was decreased by 83% by the addition of silver-plated single-walled carbon nanotubes. Conductive bumps were also screen-printed to demonstrate the capability of the composite as electrical interconnects for multi-layer printed circuit boards. PMID:21730677

  8. Design of electrically and thermally conductive polymer composites for electronic packaging

    NASA Astrophysics Data System (ADS)

    Kim, Woo-Jin

    1998-09-01

    In designing electrically and thermally conductive polymer composites, one must know the fundamental knowledge of their macroproperty-microstructure relations. The macroproperties of interest in this study are the effective electrical and thermal conductivities. The key microstructural factors include filler shape, size, size distribution and geometric arrangement of fillers. The main tasks consist of processing, characterization and analytical modeling of silver flake/polymer matrix composites. Polymer composites are processed in various silver flake concentrations. Characterization includes the cure analysis, the microstucture examination, and the measurement of electrical and thermal conductivities. Four analytical models are constructed for predicting the effective electrical and thermal conductivities; (1) three-dimensional percolation model, (2) three-dimensional electrical resistor network model, (3) two-dimensional bond percolation model, and (4) three-dimensional thermal resistor network model. A three-dimensional percolation model predicts the threshold volume fraction of flake in terms of flake aspect ratio. A three-dimensional resistor network model is developed for the effective electrical resistivity, based on percolation and microscopic conduction mechanisms. It is found that flakes with larger aspect ratio, smaller mean value in size and broader size distribution yield smaller threshold volume fraction. The analytical predictions reasonably agree with the experimental results of silver flake/polymer matrix composites. A two-dimensional bond percolation model predicts the effect of filler arrangement on the composite resistivity. A composite with segregated distribution of conducting particles yields much smaller threshold volume fraction, comparing with random distribution. The analytical predictions are well matched with measured results of SiC particle/Sisb3Nsb4 composites. A three-dimensional thermal resistor network model is developed for the

  9. Thermal conductivity of polymer composites with the geometrical characteristics of graphene nanoplatelets

    PubMed Central

    Kim, Hyun Su; Bae, Hyun Sung; Yu, Jaesang; Kim, Seong Yun

    2016-01-01

    One of the most important physical factors related to the thermal conductivity of composites filled with graphene nanoplatelets (GNPs) is the dimensions of the GNPs, that is, their lateral size and thickness. In this study, we reveal the relationship between the thermal conductivity of polymer composites and the realistic size of GNP fillers within the polymer composites (measured using three-dimensional (3D) non-destructive micro X-ray CT analysis) while minimizing the effects of the physical parameters other than size. A larger lateral size and thickness of the GNPs increased the likelihood of the matrix-bonded interface being reduced, resulting in an effective improvement in the thermal conductivity and in the heat dissipation ability of the composites. The thermal conductivity was improved by up to 121% according to the filler size; the highest bulk and in-plane thermal conductivity values of the composites filled with 20 wt% GNPs were 1.8 and 7.3 W/m·K, respectively. The bulk and in-plane thermal conductivity values increased by 650 and 2,942%, respectively, when compared to the thermal conductivity values of the polymer matrix employed (0.24 W/m·K). PMID:27220415

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

    NASA Technical Reports Server (NTRS)

    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.

  11. An efficient multiple healing conductive composite via host-guest inclusion.

    PubMed

    Zhang, Da-Li; Ju, Xin; Li, Luo-Hao; Kang, Yang; Gong, Xiao-Lei; Li, Bang-Jing; Zhang, Sheng

    2015-04-14

    A self-healable conductive composite is developed by combining the small molecules and nanotubes through host-guest interactions. This material shows uniform conductivity, microwave absorption and humidity sensing properties, and can be rapidly healed to over 90% electrical and mechanical properties with the aid of water multiple times. In addition, the produced material is also remouldable and recyclable. PMID:25761433

  12. Investigations on Thermal Conductivities of Jute and Banana Fiber Reinforced Epoxy Composites

    NASA Astrophysics Data System (ADS)

    Pujari, Satish; Ramakrishna, Avasarala; Balaram Padal, Korabu Tulasi

    2016-01-01

    The Jute and Banana fibers are used as reinforcement in epoxy resin matrix for making partially green biodegradable material composite via hand lay-up technique. The thermal conductivity of the jute fiber epoxy composites and banana fiber epoxy composites at different volume fraction of the fiber is determined experimentally by using guarded heat flow meter method. The experimental results had shown that thermal conductivity of the composites decrease with an increase in the fiber content. Experimental results are compared with theoretical models (Series model, Hashin model and Maxwell model) to describe the variation of the thermal conductivity versus the volume fraction of the fiber. Good agreement between theoretical and experimental results is observed. Thermal conductivity of Banana fiber composite is less when compared to that of Jute composite which indicates banana is a good insulator and also the developed composites can be used as insulating materials in building, automotive industry and in steam pipes to save energy by reducing rate of heat transfer.

  13. Thermal diffusivity/conductivity of magnesium oxide/silicon carbide composites

    SciTech Connect

    Luo, J.; Stevens, R.; Taylor, R.

    1997-03-01

    SiC-particle-reinforced MgO composites have been fabricated by hot pressing, and the thermal diffusivities of the composites measured in the temperature range 200--1,000 C using a laser flash technique. The thermal conductivity of the composites was calculated by multiplying the diffusivity with density and with heat capacity. The Eshelby inclusion model has been examined, and an equation suitable for particulate composites with porosity has been derived using the multiphase Eshelby model. The model also considers the interfacial thermal condition. Good agreement was obtained between the predictions and the experimental results of the thermal conductivity of the composites, even for various levels of porosity in the composites. Crystal defects, observed in the composites, influenced the thermal conductivity, resulting in a deviation from isothermal interfacial condition. This was reflected in the interfacial thermal parameter, {beta}, used in the modeling, and the predicted value of {beta} was in the range of 3--10, depending on the thermal conductivity of SiC used for the calculations.

  14. Proton conducting, composite sulfonated polymer membrane for medium temperature and low relative humidity fuel cells

    NASA Astrophysics Data System (ADS)

    Shin, Dong Won; Kang, Na Rae; Lee, Kang Hyuck; Cho, Doo Hee; Kim, Ji Hoon; Lee, Won Hyo; Lee, Young Moo

    2014-09-01

    Inorganic-organic composite membranes are fabricated using zirconium acetylacetonate nanoparticles and biphenol-based sulfonated poly(arylene ether sulfone) as an inorganic, proton conducting nanomaterial and a polymer matrix, respectively. An amphiphilic surfactant (Pluronic®) induces distribution of the inorganic nanoparticles over the entire polymer membrane. The composite membranes are thermally stable up to 200 °C. Zirconium acetylacetonate improves inter-chain interactions and the robustness of polymer membranes resulting in excellent membrane mechanical properties. In addition, composite membranes show outstanding proton conductivity compared to that of the pristine membrane at medium temperatures (80-120 °C) and low relative humidity (<50%) conditions. This improvement is due to the presence of acetylacetonate anions, which bind water molecules and act as an additional proton conducting site and/or medium. Therefore, the composite membranes significantly outperform the pristine membrane in fuel cell performance tests at medium temperatures and low relative humidity.

  15. Modeling electric conduction in composite materials based on polypropylene and carbon black

    NASA Astrophysics Data System (ADS)

    Stepashkina, A. S.; Tsobkallo, E. S.; Moskalyuk, O. A.; Aleshin, A. N.

    2015-01-01

    We have created a composite material based on polypropylene (PP) with carbon black as the filler. The dependence of the electric resistivity of the composite on the filler mass fraction has been experimentally studied. It is established that this dependence has a threshold character and the material retains dielectric properties at filler concentrations below the percolation threshold. Above the threshold, the resistivity drops by from eight to ten orders of magnitude. A theoretical description of the electric conduction of the composite is proposed, and it is shown that theoretical values of the conductivity quite satisfactorily coincide with experimental data. The process of electric conduction of the composite material has been simulated in order to determine the percolation threshold by the Monte Carlo method.

  16. EMTA THERMAL CONDUCTIVITY PREDICTIONS FOR UNIRRADIATED AND IRRADIATED SIC/SIC COMPOSITES

    SciTech Connect

    Nguyen, Ba Nghiep; Henager, Charles H.; Kurtz, Richard J.

    2013-06-30

    The objective of this work is to achieve a predictive engineering tool to assess and tailor the thermophysical properties of unirradiated and irradiated SiC/SiC composites. Towards this objective, first, PNNL’s EMTA (Eshelby-Mori-Tanaka Approach) software was successfully applied to predict the thermal conductivity of unirradiated 2D SiC/SiC composites [1]. Next, we have extended the EMTA model reported in [1] to predict the thermal conductivity of these composites subjected to neutron irradiation at elevated temperatures and irradiation doses leading to defect saturation [2]. As EMTA thermal conductivity predictions compared well with the experimental results [1-2], in the future, a unified EMTA for SiC/SiC composites will be developed that addresses both thermal and mechanical properties.

  17. Preparation and Properties of Silver Nanowire-Based Transparent Conductive Composite Films

    NASA Astrophysics Data System (ADS)

    Tian, Ji-Li; Zhang, Hua-Yu; Wang, Hai-Jun

    2016-06-01

    Silver nanowire-based transparent conductive composite films with different structures were successfully prepared using various methods, including liquid polyol, magnetron sputtering and spin coating. The experimental results revealed that the optical transmittance of all different structural composite films decreased slightly (1-3%) compared to pure films. However, the electrical conductivity of all composite films had a great improvement. Under the condition that the optical transmittance was greater than 78% over the wavelength range of 400-800 nm, the AgNW/PVA/AgNW film became a conductor, while the AZO/AgNW/AZO film and the ITO/AgNW/ITO film showed 88.9% and 94% reductions, respectively, for the sheet resistance compared with pure films. In addition, applying a suitable mechanical pressure can improve the conductivity of AgNW-based composite films.

  18. UO2-UN composites with enhanced uranium density and thermal conductivity

    NASA Astrophysics Data System (ADS)

    Yang, Jae Ho; Kim, Dong-Joo; Kim, Keon Sik; Koo, Yang-Hyun

    2015-10-01

    A mixed ceramic composite composed of UO2-UN was studied to increase both the thermal conductivity and uranium density of the currently used UO2 pellet. UN powder was synthesized by hydriding and then nitriding spherical U metal powders. Disk-shaped mixed UO2-UN composites were fabricated by hot pressing UO2-UN powder mixtures within a temperature range of 1300 °C-1590 °C. A phase analysis was conducted using X-ray diffraction and a SEM analysis indicated that the sintered composite consists mainly of a mixture of UO2 and UN phases. Compared to pure UO2, the UO2-33vol% UN composite showed an increase in uranium density of 13% (10.91 g/cm3) and an increase in thermal conductivity of up to 100% (8.16 W/m k at 800 °C).

  19. Microcontact printing for patterning carbon nanotube/polymer composite films with electrical conductivity.

    PubMed

    Ogihara, Hitoshi; Kibayashi, Hiro; Saji, Tetsuo

    2012-09-26

    Patterned carbon nanotube (CNT)/acrylic resin composite films were prepared using microcontact printing (μCP). To prepare ink for μCP, CNTs were dispersed into propylene glycol monomethyl ether acetate (PGMEA) solution in which acrylic resin and a commercially available dispersant (Disperbyk-2001) dissolved. The resulting ink were spin-coated onto poly(dimethylsiloxane) (PDMS) stamps. By drying solvent components from the ink, CNT/polymer composite films were prepared over PDMS stamps. Contact between the stamps and glass substrates provided CNT/polymer composite patternings on the substrates. The transfer behavior of the CNT/polymer composite films depended on the thermal-treatment temperature during μCP; thermal treatment at temperatures near the glass-transition temperature (T(g)) of the acrylic resin was effective to form uniform patternings on substrates. Moreover, contact area between polymer and substrates also affect the transfer behavior. The CNT/polymer composite films showed high electrical conductivity, despite the nonconductivity of polymer components, because CNTs in the films were interconnected. The electrical conductivity of the composite films increased as CNT content in the film became higher; as a result, the composite patternings showed almost as high electrical conductivity as previously reported CNT/polymer bulk composites. PMID:22900673

  20. Electrical conductivity modeling and research of polypropylene composites filled with carbon black

    NASA Astrophysics Data System (ADS)

    Stepashkina, A. S.; Tsobkallo, E. S.; Alyoshin, A. N.

    2014-12-01

    Composites of polypropylene filled with carbon black (PP/CB composite) at different concentrations were prepared by melt mixing followed by compression molding. The dependence of electrical resistance on the filler mass fraction was experimentally received. It was shown that the received dependence had the threshold character. The composite kept dielectric properties at the filler concentration below the threshold and at the concentration above the threshold the electrical resistance decreased more than on 8-10 orders. The theoretical description of electrical conductivity of the composite was offered. Experimental data of the dependence between electrical resistance and the filler mass fraction agreed with the theoretical. The process of conductivity in the PP/CB composite was simulated by means of the Monte-Carlo method for threshold mass fraction estimation.

  1. Effective thermal conductivities of four metal ceramic composite coatings in hydrogen-oxygen rocket firings

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

    An experimental investigation was conducted to determine the effective conductivities of four plasma-arc-sprayed, metal-ceramic gradated coatings on hydrogen-oxygen thrust chambers. The effective thermal conductivities were not a function of pressure or oxidant-to-fuel ratio. The various materials that made up these composites do not seem to affect the thermal conductivity values as much as the differences in the thermal conductivities of the parent materials would lead one to expect. Contact resistance evolving from the spraying process seems to be the controlling factor. The thermal conductivities of all the composites tested fell in the range of 0.75 to 7.5 watts per meter kelvin.

  2. Mechanical Strength and Thermal Conductivity of Modified Expanded Vermiculite/Forsterite Composite Materials

    NASA Astrophysics Data System (ADS)

    Chen, Ding; Gu, Huazhi; Huang, Ao; Zhang, Meijie; Zhou, Fei; Wang, Chunfeng

    2016-01-01

    The mechanical and thermal insulation properties of expanded vermiculite (EV)/forsterite composite materials before and after the modification of EV by in situ alumina gel were characterized by three-point bending test, compressive strength test, and the flat-plate method for the determination of the thermal conductivity. The estimation method for the determination of the thermal conductivity of modified EV/forsterite composite materials was put forward, and the thermal conductivity in case of a high content of modified EV (the substitution rate of modified EV is more than 50 wt.%) is forecasted in this paper. The results show that, the mechanical properties and thermal insulation properties of the composite materials were significantly improved by increasing the modified EV content. When the substitution rate of modified EV was 50 wt.%, the flexural and compressive strength were 11.55 and 22.80 MPa, improved by 23.8 and 44.9%, respectively, compared with the unmodified sample; and the thermal conductivity was 0.169 W/m/K (at 1073 K), improved by 30.5%. The estimated thermal conductivities of modified EV/forsterite composite materials show good agreement with that of experiments, and the thermal conductivity of modified EV/forsterite composite materials was 0.157 W/m/K (at 1073 K) in case the substitution rate of modified EV was 100 wt.% through estimation.

  3. Conducting nanotubes or nanostructures based composites, method of making them and applications

    NASA Technical Reports Server (NTRS)

    Gupta, Mool C. (Inventor); Yang, Yonglai (Inventor); Dudley, Kenneth L. (Inventor); Lawrence, Roland W. (Inventor)

    2013-01-01

    An electromagnetic interference (EMI) shielding material includes a matrix of a dielectric or partially conducting polymer, such as foamed polystyrene, with carbon nanotubes or other nanostructures dispersed therein in sufficient concentration to make the material electrically conducting. The composite is formed by dispersing the nanotube material in a solvent in which the dielectric or partially conducting polymer is soluble and mixing the resulting suspension with the dielectric or partially conducting polymer. A foaming agent can be added to produce a lightweight foamed material. An organometallic compound can be added to enhance the conductivity further by decomposition into a metal phase.

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

    PubMed

    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

    2016-09-01

    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. PMID:27468781

  5. Influence of carbon fillers on the thermal conductivity of Poly (methyl methacrylate)/carbon composites

    NASA Astrophysics Data System (ADS)

    Chawla, Komal; Chauhan, Alok P. S.

    2016-04-01

    In the present research on carbon polymer composites, the effects of variation of the concentration of conductive fillers on the thermal conductivity of the resultant composite were studied. Carbon powders in the form of Carbon Fibers (CF) (200µm), Carbon Black (CB) (30-100 nm) and Graphite (75-100µm) were being considered as conductive fillers in the Poly (methyl methacrylate) (PMMA) matrix. Nielsen model was found to be the best proposed model that incorporated geometric configuration comprising of both the orientation and shape of fillers. It was established that the calculated values of thermal conductivity of PMMA composites with single fillers of CF were higher than those of CB followed by Graphite. Furthermore, a visible synergy was observed between the combinations of these fillers such as Graphite and CF, Graphite and CB, CF and CB, as well as CB and CF.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  7. Scratch-resistant, highly conductive, and high-strength carbon nanotube-based composite yarns.

    PubMed

    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. PMID:20831235

  8. DC conductivity and magnetic properties of piezoelectric-piezomagnetic composite system

    NASA Astrophysics Data System (ADS)

    Hemeda, O. M.; Tawfik, A.; A-Al-Sharif; Amer, M. A.; Kamal, B. M.; El Refaay, D. E.; Bououdina, M.

    2012-11-01

    A series of composites (1-x) (Ni0.8Zn0.2Fe2O4)+x (BaTiO3), where x=0%, 20%, 40%, 60%, 80% and 100% BT content, have been prepared by the standard ceramic technique, then sintered at 1200 °C for 8 h. X-ray diffraction analysis shows that the prepared composites consist of two phases, ferrimagnetic and ferroelectric. DC electrical resistivity, thermoelectric power, charge carriers concentration and charge carrier mobility have been studied at different temperatures. It was found that the DC electrical conductivity increases with increasing BT content. The values of the thermoelectric power were positive and negative for the composites indicating that there are two conduction mechanisms, hopping and band conduction, respectively. Using the values of DC electrical conductivity and thermoelectric power, the values of charge carrier mobility and the charge carrier concentration were calculated. Magnetic measurements (hysteresis loop and magnetic permeability) show that the magnetization decreases by increasing BT content. M-H loop of pure Ni0.6 Zn0.4 Fe2O4 composite indicates that it is paramagnetic at room temperature and that the magnetization is diluted by increasing the BT content in the composite system. The value of magnetoelectric coefficient for the composites decreases by increasing BT content for all the compositions except for 40% BT content, which may be due to the low resistivity of magnetic phase compared with the BT phase that causes a leakage of induced charges on the piezoelectric phase. Since both ferroelectric and magnetic phases preserve their basic properties in the bulk composite, the present BT-NZF composite are potential candidates for applications as pollution sensors and electromagnetic waves.

  9. Flexible multiwalled carbon nanotubes/conductive polymer composite electrode for supercapacitor applications

    NASA Astrophysics Data System (ADS)

    Lee, Ka Yeung Terence; Shi, HaoTian Harvey; Lian, Keryn; Naguib, Hani E.

    2015-11-01

    The electrode performance of three types of selected electrically conductive polymers (ECPs), namely polyaniline, polypyrrole (PPy) and poly(3, 4-ethylenedioxythiophene) PEDOT (PSS:PEDOT) composite with multiwalled carbon nanotubes (MWCNTs) were investigated in this study. The capacitor electrode performance has been examined in both three electrodes half-cell and two electrodes device setups. The nano-composites were fabricated via polymerization of pseudocapacitive conductive monomer onto the MWCNT surface through the in situ chemical polymerization approach. Stainless steel thin foils were used as a current collector as well as a flexible backbone. Graphite conductive ink was used as the binder with the composite powder to form a conductive electrode layer. Half-cell electrochemical study was conducted to optimize the weight proportion between MWCNT and ECP in this parametric study. Two-electrode cell electrochemical study assessed the potential performance for the device. MWCNT was found to serve as the framework for polymerization of the ECP into a tubular structure. Among the three composites, it was discovered that the PPy/MWCNT composite has superior capacitor performance up to scan rate of 500 mV s-1.

  10. Ac-conductivity and dielectric response of new zinc-phosphate glass/metal composites

    NASA Astrophysics Data System (ADS)

    Maaroufi, A.; Oabi, O.; Lucas, B.

    2016-07-01

    The ac-conductivity and dielectric response of new composites based on zinc-phosphate glass with composition 45 mol%ZnO-55 mol%P2O5, filled with metallic powder of nickel (ZP/Ni) were investigated by impedance spectroscopy in the frequency range from 100 Hz to 1 MHz at room temperature. A high percolating jump of seven times has been observed in the conductivity behavior from low volume fraction of filler to the higher fractions, indicating an insulator - semiconductor phase transition. The measured conductivity at higher filler volume fraction is about 10-1 S/cm and is frequency independent, while, the obtained conductivity for low filler volume fraction is around 10-8 S/cm and is frequency dependent. Moreover, the elaborated composites are characterized by high dielectric constants in the range of 105 for conductive composites at low frequencies (100 Hz). In addition, the distribution of the relaxation processes was also evaluated. The Debye, Cole-Cole, Davidson-Cole and Havriliak-Negami models in electric modulus formalism were used to model the observed relaxation phenomena in ZP/Ni composites. The observed relaxation phenomena are fairly simulated by Davidson-Cole model, and an account of the interpretation of results is given.

  11. Thermal conductivity prediction of magnetic composite sheet for near-field electromagnetic absorption

    SciTech Connect

    Lee, Joonsik; Nam, Baekil; Ko, Frank K.; Kim, Ki Hyeon

    2015-05-07

    The magnetic composite sheets were designed by using core-shell structured magnetic fillers instead of uncoated magnetic fillers to resolve concurrently the electromagnetic interference and thermal radiation problems. To predict the thermal conductivity of composite sheet, we calculated the thermal conductivity of the uncoated magnetic fillers and core-shell structured fillers. And then, the thermal conductivity of the magnetic composites sheet filled with core-shell structured magnetic fillers was calculated and compared with that of the uncoated magnetic fillers filled in composite sheet. The magnetic core and shell material are employed the typical Fe-Al-Si flake (60 μm × 60 μm × 1 μm) and 250 nm-thick AlN with high thermal conductivity, respectively. The longitudinal thermal conductivity of the core-shell structured magnetic composite sheet (2.45 W/m·K) enhanced about 33.4% in comparison with that of uncoated magnetic fillers (1.83 W/m·K) for the 50 vol. % magnetic filler in polymer matrix.

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

    PubMed

    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. PMID:24758290

  13. Thermal Conductivity of Epoxy Resin Composites Filled with Combustion Synthesized h-BN Particles.

    PubMed

    Chung, Shyan-Lung; Lin, Jeng-Shung

    2016-01-01

    The thermal conductivity of epoxy resin composites filled with combustion-synthesized hexagonal boron nitride (h-BN) particles was investigated. The mixing of the composite constituents was carried out by either a dry method (involving no use of solvent) for low filler loadings or a solvent method (using acetone as solvent) for higher filler loadings. It was found that surface treatment of the h-BN particles using the silane 3-glycidoxypropyltrimethoxysilane (GPTMS) increases the thermal conductivity of the resultant composites in a lesser amount compared to the values reported by other studies. This was explained by the fact that the combustion synthesized h-BN particles contain less -OH or active sites on the surface, thus adsorbing less amounts of GPTMS. However, the thermal conductivity of the composites filled with the combustion synthesized h-BN was found to be comparable to that with commercially available h-BN reported in other studies. The thermal conductivity of the composites was found to be higher when larger h-BN particles were used. The thermal conductivity was also found to increase with increasing filler content to a maximum and then begin to decrease with further increases in this content. In addition to the effect of higher porosity at higher filler contents, more horizontally oriented h-BN particles formed at higher filler loadings (perhaps due to pressing during formation of the composites) were suggested to be a factor causing this decrease of the thermal conductivity. The measured thermal conductivities were compared to theoretical predictions based on the Nielsen and Lewis theory. The theoretical predictions were found to be lower than the experimental values at low filler contents (< 60 vol %) and became increasing higher than the experimental values at high filler contents (> 60 vol %). PMID:27213325

  14. Electrical conductivity and electromagnetic interference shielding characteristics of multiwalled carbon nanotube filled polyurethane composite films

    NASA Astrophysics Data System (ADS)

    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%.

  15. Network model for thermal conductivities of unidirectional fiber-reinforced composites

    NASA Astrophysics Data System (ADS)

    Wang, Yang; Peng, Chaoyi; Zhang, Weihua

    2014-12-01

    An empirical network model has been developed to predict the in-plane thermal conductivities along arbitrary directions for unidirectional fiber-reinforced composites lamina. Measurements of thermal conductivities along different orientations were carried out. Good agreement was observed between values predicted by the network model and the experimental data; compared with the established analytical models, the newly proposed network model could give values with higher precision. Therefore, this network model is helpful to get a wider and more comprehensive understanding of heat transmission characteristics of fiber-reinforced composites and can be utilized as guidance to design and fabricate laminated composites with specific directional or specific locational thermal conductivities for structures that simultaneously perform mechanical and thermal functions, i.e. multifunctional structures (MFS).

  16. Thermal Conductivity on the Nanofluid of Graphene and Silver Nanoparticles Composite Material.

    PubMed

    Myekhlai, Munkhshur; Lee, Taejin; Baatar, Battsengel; Chung, Hanshik; Jeong, Hyomin

    2016-02-01

    The composite material consisted of graphene (GN) and silver nanoparticles (AgNPs) has been essential topic in science and industry due to its unique thermal, electrical and antibacterial proper- ties. However, there are scarcity studies based on their thermal properties of nanofluids. Therefore, GN-AgNPs composite material was synthesized using facile and environment friendly method and further nanofluids were prepared by ultrasonication in this study. The morphological and structural investigations were carried out using scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffractometer (XRD) as well as ultra violet (UV)-visible spectroscopy. Furthermore, thermal conductivity measurements were performed for as-prepared nanofluids. As a result of thermal conductivity study, GN-AgNPs composite material was considerably enhanced the thermal conductivity of base fluid (water) by to 6.59% for the nanofluid (0.2 wt% GN and 0.4 wt% AgNPs). PMID:27433636

  17. Improvement of thermal conductivity of nano MgO/epoxy composites for electrical insulation materials

    NASA Astrophysics Data System (ADS)

    Majeed, Kawakib Jassim

    2013-12-01

    In the present study the dielectric and thermal properties of nano and micro MgO / Epoxy composites were studied with different weight percentage ratios, aiming at the development of electrical insulating materials with high thermal conductivity, this can be achieved by adding a low concentration of thermally conducting but electrically insulating nanofillers such as MgO nanoparticles, the results are discussed by determining the relative permittivity, tan delta and the thermal conductivity of the tested specimens. The obtained results showed improvement in the thermal conductivity values without deteriorating the dielectric properties.

  18. A study of conductive hydrogel composites of pH-responsive microgels and carbon nanotubes.

    PubMed

    Cui, Zhengxing; Zhou, Mi; Greensmith, Paula J; Wang, Wenkai; Hoyland, Judith A; Kinloch, Ian A; Freemont, Tony; Saunders, Brian R

    2016-05-14

    Conductive gel composites are attracting considerable attention because of their interesting electrical and mechanical properties. Here, we report conductive gel composites constructed using only colloidal particles as building blocks. The composites were prepared from mixed dispersions of vinyl-functionalised pH-responsive microgel particles (MGs) and multi-walled carbon nanotubes (CNTs). MGs are crosslinked pH-responsive polymer colloid particles that swell when the pH approaches the pKa of the particles. Two MG systems were used which contained ethyl acrylate (EA) or methyl acrylate (MA) and around 30 mol% of methacrylic acid (MAA). The MA-based MG is a new pH-responsive system. The mixed MG/CNT dispersions formed thixotropic physical gels. Those gels were transformed into covalent interlinked electrically conducting doubly crosslinked microgel/CNT composites (DX MG/CNT) by free-radical reaction. The MGs provided the dual roles of dispersant for the CNTs and macro-crosslinker for the composite. TEM data showed evidence for strong attraction between the MG and the CNTs which facilitated CNT dispersion. An SEM study confirmed CNT dispersion throughout the composites. The mechanical properties of the composites were studied using dynamic rheology and uniaxial compression measurements. Surprisingly, both the ductility and the modulus of the gel composites increased with increasing CNT concentration used for their preparation. Human adipose-derived mesenchymal stem cells (AD-MSCs) exposed to DX MG/CNT maintained over 99% viability with metabolic activity retained over 7 days, which indicated non-cytotoxicity. The results of this study suggest that our approach could be used to prepare other DX MG/CNT gel composites and that these materials may lead to future injectable gels for advanced soft-tissue repair. PMID:27067636

  19. High Thermal Conductivity NARloy-Z-Diamond Composite Combustion Chamber Liner For Advanced Rocket Engines

    NASA Technical Reports Server (NTRS)

    Bhat, Biliyar N.; Ellis, David; Singh, Jogender

    2014-01-01

    Advanced high thermal conductivity materials research conducted at NASA Marshall Space Flight Center (MSFC) with state of the art combustion chamber liner material NARloy-Z showed that its thermal conductivity can be increased significantly by adding diamond particles and sintering it at high temperatures. For instance, NARloy-Z containing 40 vol. percent diamond particles, sintered at 975C to full density by using the Field assisted Sintering Technology (FAST) showed 69 percent higher thermal conductivity than baseline NARloy-Z. Furthermore, NARloy-Z-40vol. percent D is 30 percent lighter than NARloy-Z and hence the density normalized thermal conductivity is 140 percent better. These attributes will improve the performance and life of the advanced rocket engines significantly. By one estimate, increased thermal conductivity will directly translate into increased turbopump power up to 2X and increased chamber pressure for improved thrust and ISP, resulting in an expected 20 percent improvement in engine performance. Follow on research is now being conducted to demonstrate the benefits of this high thermal conductivity NARloy-Z-D composite for combustion chamber liner applications in advanced rocket engines. The work consists of a) Optimizing the chemistry and heat treatment for NARloy-Z-D composite, b) Developing design properties (thermal and mechanical) for the optimized NARloy-Z-D, c) Fabrication of net shape subscale combustion chamber liner, and d) Hot fire testing of the liner for performance. FAST is used for consolidating and sintering NARlo-Z-D. The subscale cylindrical liner with built in channels for coolant flow is also fabricated near net shape using the FAST process. The liner will be assembled into a test rig and hot fire tested in the MSFC test facility to determine performance. This paper describes the development of this novel high thermal conductivity NARloy-Z-D composite material, and the advanced net shape technology to fabricate the combustion

  20. A Chemically Polymerized Electrically Conducting Composite of Polypyrrole Nanoparticles and Polyurethane for Tissue Engineering

    PubMed Central

    Broda, Christopher R.; Lee, Jae Y.; Sirivisoot, Sirinrath; Schmidt, Christine E.; Harrison, Benjamin S.

    2011-01-01

    A variety of cell types respond to electrical stimuli, accordingly many conducting polymers (CPs) have been used as tissue engineering (TE) scaffolds, one such CP is polypyrrole (PPy). PPy is a well studied biomaterial with potential TE applications due to its electrical conductivity and many other beneficial properties. Combining its characteristics with an elastomeric material, such as polyurethane (PU), may yield a hybrid scaffold with electrical activity and significant mechanical resilience. Pyrrole was in situ polymerized within a PU emulsion mixture in weight ratios of 1:100, 1:20, 1:10 and 1:5, respectively. Morphology, electrical conductivity, mechanical properties and cytocompatibility with C2C12 myoblast cells were characterized. The polymerization resulted in a composite with a principle base of PU interspersed with an electrically percolating network of PPy nanoparticles. As the mass ratio of PPy to PU increased so did electrical conductivity of the composites. In addition, as the mass ratio of PPy to PU increased, stiffness of the composite increased while maximum elongation length decreased. Ultimate tensile strength was reduced by approximately 47% across all samples with the addition of PPy to the PU base. Cytocompatibility assay data indicated no significant cytotoxic effect from the composites. Static cellular seeding of C2C12 cells and subsequent differentiation showed myotube formation on the composite materials. PMID:21681943

  1. Method of forming a dense, high temperature electronically conductive composite layer on a porous ceramic substrate

    DOEpatents

    Isenberg, Arnold O.

    1992-01-01

    An electrochemical device, containing a solid oxide electrolyte material and an electrically conductive composite layer, has the composite layer attached by: (A) applying a layer of LaCrO.sub.3, YCrO.sub.3 or LaMnO.sub.3 particles (32), on a portion of a porous ceramic substrate (30), (B) heating to sinter bond the particles to the substrate, (C) depositing a dense filler structure (34) between the doped particles (32), (D) shaving off the top of the particles, and (E) applying an electronically conductive layer over the particles (32) as a contact.

  2. Method of forming a dense, high temperature electronically conductive composite layer on a porous ceramic substrate

    DOEpatents

    Isenberg, A.O.

    1992-04-21

    An electrochemical device, containing a solid oxide electrolyte material and an electrically conductive composite layer, has the composite layer attached by: (A) applying a layer of LaCrO[sub 3], YCrO[sub 3] or LaMnO[sub 3] particles, on a portion of a porous ceramic substrate, (B) heating to sinter bond the particles to the substrate, (C) depositing a dense filler structure between the doped particles, (D) shaving off the top of the particles, and (E) applying an electronically conductive layer over the particles as a contact. 7 figs.

  3. Solvent-free fabrication of thermally conductive insulating epoxy composites with boron nitride nanoplatelets as fillers

    NASA Astrophysics Data System (ADS)

    Wang, Zifeng; Fu, Yuqiao; Meng, Wenjun; Zhi, Chunyi

    2014-11-01

    A solvent-free method for the fabrication of thermally conductive epoxy-boron nitride (BN) nanoplatelet composite material is developed in this study. By this method, polymer composites with nearly any filler fractions can be easily fabricated. The maximum thermal conductivity reaches 5.24 W/mK, which is 1,600% improvement in comparison with that of pristine epoxy material. In addition, the as-fabricated samples exhibit excellent overall performances with great mechanical property and thermal stability well preserved.

  4. Solvent-free fabrication of thermally conductive insulating epoxy composites with boron nitride nanoplatelets as fillers

    PubMed Central

    2014-01-01

    A solvent-free method for the fabrication of thermally conductive epoxy-boron nitride (BN) nanoplatelet composite material is developed in this study. By this method, polymer composites with nearly any filler fractions can be easily fabricated. The maximum thermal conductivity reaches 5.24 W/mK, which is 1,600% improvement in comparison with that of pristine epoxy material. In addition, the as-fabricated samples exhibit excellent overall performances with great mechanical property and thermal stability well preserved. PMID:25489292

  5. Solvent-free fabrication of thermally conductive insulating epoxy composites with boron nitride nanoplatelets as fillers.

    PubMed

    Wang, Zifeng; Fu, Yuqiao; Meng, Wenjun; Zhi, Chunyi

    2014-01-01

    A solvent-free method for the fabrication of thermally conductive epoxy-boron nitride (BN) nanoplatelet composite material is developed in this study. By this method, polymer composites with nearly any filler fractions can be easily fabricated. The maximum thermal conductivity reaches 5.24 W/mK, which is 1,600% improvement in comparison with that of pristine epoxy material. In addition, the as-fabricated samples exhibit excellent overall performances with great mechanical property and thermal stability well preserved. PMID:25489292

  6. Filler geometry and interface resistance of carbon nanofibres: Key parameters in thermally conductive polymer composites

    NASA Astrophysics Data System (ADS)

    Gharagozloo-Hubmann, Kati; Boden, André; Czempiel, Gregor J. F.; Firkowska, Izabela; Reich, Stephanie

    2013-05-01

    The thermal conductivity of polymer composites is measured for several tubular carbon nanofillers (nanotubes, fibres, and whiskers). The highest enhancement in the thermal conductivity is observed for functionalized multiwalled carbon nanotubes (90% enhancement for 1 vol. %) and Pyrograf carbon fibres (80%). We model the experimental data using an effective thermal medium theory and determine the thermal interface resistance (RK) at the filler-matrix interface. Our results show that the geometry of the nanofibres and the interface resistance are two key factors in engineering heat transport in a composite.

  7. Fabrication of polyaniline/polyimide composite fibers with electrically conductive properties

    NASA Astrophysics Data System (ADS)

    Lv, Pengxia; Zhao, Yong; Liu, Fangfang; Li, Guomin; Dai, Xuemin; Ji, Xiangling; Dong, Zhixin; Qiu, Xuepeng

    2016-03-01

    A series of polyaniline/polyimide (PANi/PI) composite fibers was prepared via dry-jet wet spinning followed by in situ polymerization growth. The resultant composite fibers showed good mechanical properties with a tensile strength of 0.90 GPa, a tensile modulus of 6.79 GPa, and an elongation at break of 14.63%. Thermogravimetric and thermal mechanical analyses revealed that the composite fibers had considerably good thermal stabilities in air and nitrogen atmospheres, as well as good size stabilities at 50-150 °C. Current-voltage curves indicated the transformation from electric insulation to electrical conductivity along the fiber axial direction. The composite fibers exhibited a sensitive response to immersion in solutions with different pH values. This work provides a simple approach to fabricate PANi/PI composite fibers that could be applied in the antistatic textile and military industries.

  8. Atmospheric-Pressure Processed Silver Nanowire (Ag-NW)/ZnO Composite Transparent Conducting Contacts

    SciTech Connect

    Perkins, John D.; Aggarwal, Shruti; van Hest, Maikel F. A. M.; Ginley, David S.

    2015-06-14

    Composite transparent contacts (TCs) based on metal nanowires and metal oxide matrix materials hold great promise for high performance transparent contacts for photovoltaics and opto-electronic technologies with the potential of all-atmospheric pressure processing. The metal nanowire mesh can provide both electrical conductivity and mechanical robustness against bending while the matrix material can both control the electrical interface and protect the metal nanowires. Here, we demonstrate all atmospheric pressure processed Ag-NW/ZnO composite TCs that are 90% transparent in the visible with sheet resistance Rs ~= 10 Ohms/sq. In addition, the composite TCs have higher infrared transmission than conventional TCO films with the same sheet resistance.

  9. Estimation of composite thermal conductivity of a heterogeneousmethane hydrate sample using iTOUGH2

    SciTech Connect

    Gupta, Arvind; Kneafsey, Timothy J.; Moridis, George J.; Seol,Yongkoo; Kowalsky, Michael B.; Sloan Jr., E.D.

    2006-05-15

    We determined the composite thermal conductivity (ktheta) ofa porous methanehydrate sample (composedof hydrate, water, and methan egas) as a function of density using iTOUGH2. X-ray computed tomography(CT) was used to visualize and quantify the density changes that occurredduring hydrate formation from granular ice. The composite thermalconductivity was estimated and validated by minimizing the differencesbetween the observed and the predicted thermal response using historymatching. The estimated density-dependent composite thermal conductivityranged between 0.25 and 0.58 W/m/K.

  10. Highly Thermally Conductive Composite Papers Prepared Based on the Thought of Bioinspired Engineering.

    PubMed

    Yao, Yimin; Zeng, Xiaoliang; Sun, Rong; Xu, Jian-Bin; Wong, Ching-Ping

    2016-06-22

    The rapid development of modern electronics and three-dimensional integration sets stringent requirements for efficient heat removal of thermal-management materials to ensure the long lifetime of the electronics. However, conventional polymer composites that have been used widely as thermal-management materials suffer from undesired thermal conductivity lower than 10 W m(-1) K(-1). In this work, we report a novel thermally conductive composite paper based on the thought of bioinspired engineering. The advantage of the bioinspired papers over conventional composites lies in that they possess a very high in-plane thermal conductivity up to 21.7 W m(-1) K(-1) along with good mechanical properties and high electrical insulation. We attribute the high thermal conductivity to the improved interfacial interaction between assembled components through the introduction of silver nanoparticles and the oriented structure based on boron nitride nanosheets and silicon carbide nanowires. This thought based on bioinspired engineering provides a creative opportunity for design and fabrication of novel thermally conductive materials, and this kind of composite paper has potential applications in powerful integrated microelectronics. PMID:27253387

  11. Electrical Conductance Tuning and Bistable Switching in Poly(N-vinylcarbazole)-Carbon Nanotube Composite Films.

    PubMed

    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. PMID:19485330

  12. Composition and Manufacturing Effects on Electrical Conductivity of Li/FeS 2 Thermal Battery Cathodes

    DOE PAGESBeta

    Reinholz, Emilee L.; Roberts, Scott A.; Apblett, Christopher A.; Lechman, Jeremy B.; Schunk, P. Randall

    2016-06-11

    The electrical conductivity is key to the performance of thermal battery cathodes. In this work we present the effects of manufacturing and processing conditions on the electrical conductivity of Li/FeS2 thermal battery cathodes. Finite element simulations were used to compute the conductivity of three-dimensional microcomputed tomography cathode microstructures and compare results to experimental impedance spectroscopy measurements. A regression analysis reveals a predictive relationship between composition, processing conditions, and electrical conductivity; a trend which is largely erased after thermally-induced deformation. Moreover, the trend applies to both experimental and simulation results, although is not as apparent in simulations. This research is amore » step toward a more fundamental understanding of the effects of processing and composition on thermal battery component microstructure, properties, and performance.« less

  13. Highly conductive electrolyte composites containing glass and ceramic, and method of manufacture

    DOEpatents

    Hash, Mark C.; Bloom, Ira D.

    1992-01-01

    An electrolyte composite is manufactured by pressurizing a mixture of sodium ion conductive glass and an ionically conductive compound at between 12,000 and 24,000 pounds per square inch to produce a pellet. The resulting pellet is then sintered at relatively lower temperatures (800.degree. C.-1200.degree. C.), for example 1000.degree. C., than are typically required (1400.degree. C.) when fabricating single constituent ceramic electrolytes. The resultant composite is 100 percent conductive at 250.degree. C. with conductivity values of 2.5 to 4.times.10.sup.-2 (ohm-cm).sup.-1. The matrix exhibits chemical stability against sodium for 100 hours at 250.degree. to 300.degree. C.

  14. Thermally Conductive-Silicone Composites with Thermally Reversible Cross-links.

    PubMed

    Wertz, J T; Kuczynski, J P; Boday, D J

    2016-06-01

    Thermally conductive-silicone composites that contain thermally reversible cross-links were prepared by blending diene- and dienophile-functionalized polydimethylsiloxane (PDMS) with an aluminum oxide conductive filler. This class of thermally conductive-silicones are useful as thermal interface materials (TIMs) within Information Technology (IT) hardware applications to allow rework of valuable components. The composites were rendered reworkable via retro Diels-Alder cross-links when temperatures were elevated above 130 °C and required little mechanical force to remove, making them advantageous over other TIM materials. Results show high thermal conductivity (0.4 W/m·K) at low filler loadings (45 wt %) compared to other TIM solutions (>45 wt %). Additionally, the adhesion of the material was found to be ∼7 times greater at lower temperatures (25 °C) and ∼2 times greater at higher temperatures (120 °C) than commercially available TIMs. PMID:27224959

  15. Thermal Conductivity Database of Various Structural Carbon-Carbon Composite Materials

    NASA Technical Reports Server (NTRS)

    Ohlhorst, Craig W.; Vaughn, Wallace L.; Ransone, Philip O.; Tsou, Hwa-Tsu

    1997-01-01

    Advanced thermal protection materials envisioned for use on future hypersonic vehicles will likely be subjected to temperatures in excess of 1811 K (2800 F) and, therefore, will require the rapid conduction of heat away from the stagnation regions of wing leading edges, the nose cap area, and from engine inlet and exhaust areas. Carbon-carbon composite materials are candidates for use in advanced thermal protection systems. For design purposes, high temperature thermophysical property data are required, but a search of the literature found little thermal conductivity data for carbon-carbon materials above 1255 K (1800 F). Because a need was recognized for in-plane and through-the-thickness thermal conductivity data for carbon-carbon composite materials over a wide temperature range, Langley Research Center (LaRC) embarked on an effort to compile a consistent set of thermal conductivity values from room temperature to 1922 K (3000 F) for carbon-carbon composite materials on hand at LaRC for which the precursor materials and thermal processing history were known. This report documents the thermal conductivity data generated for these materials. In-plane thermal conductivity values range from 10 to 233 W/m-K, whereas through-the-thickness values range from 2 to 21 W/m-K.

  16. Effect of Liquid-Crystalline Epoxy Backbone Structure on Thermal Conductivity of Epoxy-Alumina Composites

    NASA Astrophysics Data System (ADS)

    Giang, Thanhkieu; Kim, Jinhwan

    2016-06-01

    In a series of papers published recently, we clearly demonstrated that the most important factor governing the thermal conductivity of epoxy-Al2O3 composites is the backbone structure of the epoxy. In this study, three more epoxies based on diglycidyl ester-terminated liquid-crystalline epoxy (LCE) have been synthesized to draw conclusions regarding the effect of the epoxy backbone structure on the thermal conductivity of epoxy-alumina composites. The synthesized structures were characterized by proton nuclear magnetic resonance (1H-NMR) and Fourier-transform infrared (FT-IR) spectroscopy. Differential scanning calorimetry, thermogravimetric analysis, and optical microscopy were also employed to examine the thermal and optical properties of the synthesized LCEs and the cured composites. All three LCE resins exhibited typical liquid-crystalline behaviors: clear solid crystalline state below the melting temperature (T m), sharp crystalline melting at T m, and transition to nematic phase above T m with consequent isotropic phase above the isotropic temperature (T i). The LCE resins displayed distinct nematic liquid-crystalline phase over a wide temperature range and retained liquid-crystalline phase after curing, with high thermal conductivity of the resulting composite. The thermal conductivity values ranged from 3.09 W/m-K to 3.89 W/m-K for LCE-Al2O3 composites with 50 vol.% filler loading. The steric effect played a governing role in the difference. The neat epoxy resin thermal conductivity was obtained as 0.35 W/m-K to 0.49 W/m-K based on analysis using the Agari-Uno model. The results clearly support the objective of this study in that the thermal conductivity of the LCE-containing networks strongly depended on the epoxy backbone structure and the degree of ordering in the cured network.

  17. High thermal conductivity SiC/SiC composites for fusion applications

    SciTech Connect

    Withers, J.C.; Kowbel, W.; Loutfy, R.O.

    1997-04-01

    SiC/SiC composites are considered for fusion applications due to their neutron irradiation stability, low activation, and good mechanical properties at high temperatures. The projected magnetic fusion power plant first wall and the divertor will operate with surface heat flux ranges of 0.5 to 1 and 4 to 6 MW/m{sup 2}, respectively. To maintain high thermal performance at operating temperatures the first wall and divertor coolant channels must have transverse thermal conductivity values of 5 to 10 and 20 to 30 W/mK, respectively. For these components exposed to a high energy neutron flux and temperatures perhaps exceeding 1000{degrees}C, SiC/SiC composites potentially can meet these demanding requirements. The lack of high-purity SiC fiber and a low through-the-thickness (transverse) thermal conductivity are two key technical problems with currently available SiC/SiC. Such composites, for example produced from Nicalon{trademark} fiber with a chemical vapor infiltrated (CVI) matrix, typically exhibit a transverse conductivity value of less than 8 W/mK (unirradiated) and less than 3 W/mK after neutron irradiation at 800{degrees}C. A new SiC/SiC composite fabrication process has been developed at MER Corp. This paper describes this process, and the thermal and mechanical properties which are observed in this new composite material.

  18. The development of electrically conductive polycaprolactone fumarate-polypyrrole composite materials for nerve regeneration.

    PubMed

    Runge, M Brett; Dadsetan, Mahrokh; Baltrusaitis, Jonas; Knight, Andrew M; Ruesink, Terry; Lazcano, Eric A; Lu, Lichun; Windebank, Anthony J; Yaszemski, Michael J

    2010-08-01

    Electrically conductive polymer composites composed of polycaprolactone fumarate and polypyrrole (PCLF-PPy) have been developed for nerve regeneration applications. Here we report the synthesis and characterization of PCLF-PPy and in vitro studies showing PCLF-PPy materials support both PC12 cell and dorsal root ganglia (DRG) neurite extension. PCLF-PPy composite materials were synthesized by polymerizing pyrrole in preformed PCLF scaffolds (M(n) 7,000 or 18,000 g mol(-1)) resulting in interpenetrating networks of PCLF-PPy. Chemical compositions and thermal properties were characterized by ATR-FTIR, XPS, DSC, and TGA. PCLF-PPy materials were synthesized with five different anions (naphthalene-2-sulfonic acid sodium salt (NSA), dodecylbenzenesulfonic acid sodium salt (DBSA), dioctyl sulfosuccinate sodium salt (DOSS), potassium iodide (I), and lysine) to investigate effects on electrical conductivity and to optimize chemical composition for cellular compatibility. PCLF-PPy materials have variable electrical conductivity up to 6 mS cm(-1) with bulk compositions ranging from 5 to 13.5 percent polypyrrole. AFM and SEM characterization show microstructures with a root mean squared (RMS) roughness of 1195 nm and nanostructures with RMS roughness of 8 nm. In vitro studies using PC12 cells and DRG show PCLF-PPy materials synthesized with NSA or DBSA support cell attachment, proliferation, neurite extension, and are promising materials for future studies involving electrical stimulation. PMID:20483452

  19. The Development of Electrically Conductive Polycaprolactone Fumarate-Polypyrrole Composite Materials for Nerve Regeneration

    PubMed Central

    Runge, M. Brett; Dadsetan, Mahrokh; Baltrusaitis, Jonas; Knight, Andrew M.; Ruesink, Terry; Lazcano, Eric; Lu, Lichun; Windebank, Anthony J.; Yaszemski, Michael J.

    2010-01-01

    Electrically conductive polymer composites composed of polycaprolactone fumarate and polypyrrole (PCLF-PPy) have been developed for nerve regeneration applications. Here we report the synthesis and characterization of PCLF-PPy and in vitro studies showing PCLF-PPy materials support both PC12 cell and dorsal root ganglia (DRG) neurite extension. PCLF-PPy composite materials were synthesized by polymerizing pyrrole in pre-formed PCLF scaffolds (Mn 7,000 or 18,000 g mol−1) resulting in interpenetrating networks of PCLF-PPy. Chemical compositions and thermal properties were characterized by ATR-FTIR, XPS, DSC, and TGA. PCLF-PPy materials were synthesized with five different anions (naphthalene-2-sulfonic acid sodium salt (NSA), dodecylbenzenesulfonic acid sodium salt (DBSA), dioctyl sulfosuccinate sodium salt (DOSS), potassium iodide (I), and lysine) to investigate effects on electrical conductivity and to optimize chemical composition for cellular compatibility. PCLF-PPy materials have variable electrical conductivity up to 6 mS cm−1 with bulk compositions ranging from 5 to 13.5 percent polypyrrole. AFM and SEM characterization show microstructures with a root mean squared (RMS) roughness of 1195 nm and nanostructures with RMS roughness of 8 nm. In vitro studies using PC12 cells and DRG show PCLF-PPy materials synthesized with NSA or DBSA support cell attachment, proliferation, neurite extension, and are promising materials for future studies involving electrical stimulation. PMID:20483452

  20. Enhancement of thermal conductive pathway of boron nitride coated polymethylsilsesquioxane composite.

    PubMed

    Kim, Gyungbok; Ryu, Seung Han; Lee, Jun-Tae; Seong, Ki-Hun; Lee, Jae Eun; Yoon, Phil-Joong; Kim, Bum-Sung; Hussain, Manwar; Choa, Yong-Ho

    2013-11-01

    We report here in the fabrication of enhanced thermal conductive pathway nanocomposites of boron nitride (BN)-coated polymethylsilsesquioxane (PMSQ) composite beads using isopropyl alcohol (IPA) as a mixing medium. Exfoliated and size-reduced boron nitride particles were successfully coated on the PMSQ beads and explained by surface charge differences. A homogeneous dispersion and coating of BN on the PMSQ beads using IPA medium was confirmed by SEM. Each condition of the composite powder was carried into the stainless still mould and then hot pressed in an electrically heated hot press machine. Three-dimensional percolation networks and conductive pathways created by exfoliated BN were precisely formed in the nanocomposites. The thermal conductivity of nanocomposites was measured by multiplying specific gravity, specific heat, and thermal diffusivity, based upon the laser flash method. Densification of the composite resulted in better thermal properties. For an epoxy reinforced composite with 30 vol% BN and PMSQ, a thermal conductivity of nine times higher than that of pristine PMSQ was observed. PMID:24245317

  1. Effective properties analysis of a piezoelectric composite including conducting phase using a numerical homogenization approach

    NASA Astrophysics Data System (ADS)

    Zhang, Hongming; He, Xiaodong; Wang, Rongguo; Hao, Lifeng

    2011-11-01

    Piezoelectric composites find increasing applications in the field of smart materials, mainly as sensors and transducer. However, accurately predicting its performance is still a challenging task. In this paper, we analyzed the electromechanical properties of a three-phase piezoelectric composite with titanate piezoelectric ceramics powders (PZT-5H) and carbon black embedded in an epoxy matrix by a finite element numerical method. A homogenizing micromechanical model is applied, which is capable to provide various property parameters of the piezoelectric composite, such as dielectric constant, piezoelectric constant. The calculation verifies that the electric network formed by the conducting-phase carbon black(CB) can effectively improve the electromechanical performance of the piezoelectric composites. The effect of different content of the carbon black is also taken in consideration in the simulation. A good fit between the calculation and the experimental results clearly shows that the homogenizing modeling is able to accurately predict the electromechanical properties of the three-phase piezoelectric composite. This work will contribute to optimize the material function design and analyze the effect of conduct phase on the piezoelectric composites.

  2. Effective properties analysis of a piezoelectric composite including conducting phase using a numerical homogenization approach

    NASA Astrophysics Data System (ADS)

    Zhang, Hongming; He, Xiaodong; Wang, Rongguo; Hao, Lifeng

    2012-04-01

    Piezoelectric composites find increasing applications in the field of smart materials, mainly as sensors and transducer. However, accurately predicting its performance is still a challenging task. In this paper, we analyzed the electromechanical properties of a three-phase piezoelectric composite with titanate piezoelectric ceramics powders (PZT-5H) and carbon black embedded in an epoxy matrix by a finite element numerical method. A homogenizing micromechanical model is applied, which is capable to provide various property parameters of the piezoelectric composite, such as dielectric constant, piezoelectric constant. The calculation verifies that the electric network formed by the conducting-phase carbon black(CB) can effectively improve the electromechanical performance of the piezoelectric composites. The effect of different content of the carbon black is also taken in consideration in the simulation. A good fit between the calculation and the experimental results clearly shows that the homogenizing modeling is able to accurately predict the electromechanical properties of the three-phase piezoelectric composite. This work will contribute to optimize the material function design and analyze the effect of conduct phase on the piezoelectric composites.

  3. Thermal contact conductance between aligned, unidirectional carbon/epoxy resin composites under vacuum conditions

    SciTech Connect

    Rhoades, M.E.; Moses, W.M. Mercer Univ., Macon, GA )

    1991-01-01

    This paper investigates the thermal contact conductance across carbon fiber/epoxy resin composites under vacuum conditions at discrete contact pressures. Samples with unidirectional, continuous fibers oriented at 0 and 90 degrees to the contact interface are analyzed in 0/0 and 90/90 test configurations. Experimental results are compared with analytical data obtained using theory developed for homogeneous, isotropic, metallic contacts. As with earlier experiments in air, variations in the experimental data show the importance of material anisotropy and heterogeneity in governing thermal contact conductance between composites. While metallic theory can incorporate the anisotropic influence of fiber orientation, it fails to account for the distinct contributions of both fiber and matrix to the composite contact problem. 21 refs.

  4. Dielectric properties and electrical conductivity of flat micronic graphite/polyurethane composites

    NASA Astrophysics Data System (ADS)

    Plyushch, Artyom; Macutkevic, Jan; Kuzhir, Polina P.; Banys, Juras; Fierro, Vanessa; Celzard, Alain

    2016-03-01

    Results of broadband dielectric spectroscopy of flat micronic graphite (FMG)/polyurethane (PU) resin composites are presented in a wide temperature range (25-450 K). The electrical percolation threshold was found to lie between 1 and 2 vol. % of FMG. Above the percolation threshold, the composites demonstrated a huge hysteresis of properties on heating and cooling from room temperature up to 450 K, along with extremely high values of dielectric permittivity and electrical conductivity. Annealing proved to be a very simple but powerful tool for significantly improving the electrical properties of FMG-based composites. In order to explain this effect, the distributions of relaxation times were calculated by the complex impedance formalism. Below room temperature, both dielectric permittivity and electrical conductivity exhibited a very low temperature dependence, mainly caused by the different thermal properties of FMG and pure PU matrix.

  5. Magnetic assembly of transparent and conducting graphene-based functional composites

    NASA Astrophysics Data System (ADS)

    Le Ferrand, Hortense; Bolisetty, Sreenath; Demirörs, Ahmet F.; Libanori, Rafael; Studart, André R.; Mezzenga, Raffaele

    2016-06-01

    Innovative methods producing transparent and flexible electrodes are highly sought in modern optoelectronic applications to replace metal oxides, but available solutions suffer from drawbacks such as brittleness, unaffordability and inadequate processability. Here we propose a general, simple strategy to produce hierarchical composites of functionalized graphene in polymeric matrices, exhibiting transparency and electron conductivity. These are obtained through protein-assisted functionalization of graphene with magnetic nanoparticles, followed by magnetic-directed assembly of the graphene within polymeric matrices undergoing sol-gel transitions. By applying rotating magnetic fields or magnetic moulds, both graphene orientation and distribution can be controlled within the composite. Importantly, by using magnetic virtual moulds of predefined meshes, graphene assembly is directed into double-percolating networks, reducing the percolation threshold and enabling combined optical transparency and electrical conductivity not accessible in single-network materials. The resulting composites open new possibilities on the quest of transparent electrodes for photovoltaics, organic light-emitting diodes and stretchable optoelectronic devices.

  6. Evaluation of different conductive nanostructured particles as filler in smart piezoresistive composites

    PubMed Central

    2012-01-01

    This work presents a comparison between three piezoresistive composite materials based on nanostructured conductive fillers in a polydimethylsiloxane insulating elastomeric matrix for sensing applications. Without any mechanical deformation upon an applied bias, the prepared composites present an insulating electric behavior, while, when subjected to mechanical load, the electric resistance is reduced exponentially. Three different metal fillers were tested: commercial nickel and copper spiky-particles and synthesized highly-pointed gold nanostars. These particles were chosen because of their high electrical conductivity and especially for the presence of nanosized sharp tips on their surface. These features generate an enhancement of the local electric field increasing the tunneling probability between the particles. Different figures of merit concerning the morphology of the fillers were evaluated and correlated with the corresponding functional response of the composite. PMID:22721506

  7. Development and characterization of novel electrically conductive PANI-PGS composites for cardiac tissue engineering applications.

    PubMed

    Qazi, Taimoor H; Rai, Ranjana; Dippold, Dirk; Roether, Judith E; Schubert, Dirk W; Rosellini, Elisabetta; Barbani, Niccoletta; Boccaccini, Aldo R

    2014-06-01

    Cardiovascular diseases, especially myocardial infarction, are the leading cause of morbidity and mortality in the world, also resulting in huge economic burdens on national economies. A cardiac patch strategy aims at regenerating an infarcted heart by providing healthy functional cells to the injured region via a carrier substrate, and providing mechanical support, thereby preventing deleterious ventricular remodeling. In the present work, polyaniline (PANI) was doped with camphorsulfonic acid and blended with poly(glycerol-sebacate) at ratios of 10, 20 and 30vol.% PANI content to produce electrically conductive composite cardiac patches via the solvent casting method. The composites were characterized in terms of their electrical, mechanical and physicochemical properties. The in vitro biodegradability of the composites was also evaluated. Electrical conductivity increased from 0Scm(-1) for pure PGS to 0.018Scm(-1) for 30vol.% PANI-PGS samples. Moreover, the conductivities were preserved for at least 100h post fabrication. Tensile tests revealed an improvement in the elastic modulus, tensile strength and elasticity with increasing PANI content. The degradation products caused a local drop in pH, which was higher in all composite samples compared with pure PGS, hinting at a buffering effect due to the presence of PANI. Finally, the cytocompatibility of the composites was confirmed when C2C12 cells attached and proliferated on samples with varying PANI content. Furthermore, leaching of acid dopants from the developed composites did not have any deleterious effect on the viability of C2C12 cells. Taken together, these results confirm the potential of PANI-PGS composites for use as substrates to modulate cellular behavior via electrical stimulation, and as biocompatible scaffolds for cardiac tissue engineering applications. PMID:24561709

  8. Electrical conductivity of sulfonated poly(ether ether ketone) based composite membranes containing sulfonated polyhedral oligosilsesquioxane

    NASA Astrophysics Data System (ADS)

    Celso, Fabricio; Mikhailenko, Serguei D.; Rodrigues, Marco A. S.; Mauler, Raquel S.; Kaliaguine, Serge

    2016-02-01

    Composite proton exchange membranes (PEMs) intended for fuel cell applications were prepared by embedding of various amounts of dispersed tri-sulfonic acid ethyl POSS (S-Et-POSS) and tri-sulfonic acid butyl POSS (S-Bu-POSS) in thin films of sulfonated poly ether-ether ketone. The electrical properties of the PEMs were studied by Impedance spectroscopy and it was found that their conductivity σ changes with the filler content following a curve with a maximum. The water uptake of these PEMs showed the same dependence. The investigation of initial isolated S-POSS substances revealed the properties of typical electrolytes, which however in both cases possessed low conductivities of 1. 17 × 10-5 S cm-1 (S-Et-POSS) and 3.52 × 10-5 S cm-1 (S-Bu-POSS). At the same time, the insoluble in water S-POSS was found forming highly conductive interface layer when wetted with liquid water and hence producing a strong positive impact on the conductivity of the composite PEM. Electrical properties of the composites were analysed within the frameworks of effective medium theory and bounding models, allowing to evaluate analytically the range of possible conductivity values. It was found that these approaches produced quite good approximation of the experimental data and constituted a fair basis for interpretation of the observed relationship.

  9. The potential for damage from the accidental release of conductive carbon fibers from aircraft composites

    NASA Technical Reports Server (NTRS)

    Bell, V. L.

    1980-01-01

    Carbon and graphite fibers are known to be electrically conductive. The rapidly accelerating use of carbon fibers as the reinforcement in filamentary composite materials brought up the possibility of accidental release of carbon fibers from the burning of crashed commercial airliners with carbon composite parts. Such release could conceivably cause widespread damage to electrical and electronic equipment. The experimental and analytical results of a comprehensive investigation of the various elements necessary to assess the extent of such potential damage in terms of annual expected costs and maximum losses at low probabilities of occurrence are presented. A review of NASA materials research program to provide alternate or modified composite materials to overcome any electrical hazards from the use of carbon composites in aircraft structures is described.

  10. New composite composed of boron carbide and carbon fiber with high thermal conductivity for first wall

    NASA Astrophysics Data System (ADS)

    Jimbou, R.; Saidoh, M.; Nakamura, K.; Akiba, M.; Suzuki, S.; Gotoh, Y.; Suzuki, Y.; Chiba, A.; Yamaki, T.; Nakagawa, M.; Morita, K.; Tsuchiya, B.

    1996-10-01

    A new composite was created from B 4C powder and carbon fiber by hot-pressing at 1700°C or more. The composite sintered at 1700°C with 20-35 vol% B 4C shows a thermal conductivity of 250 W/m·K at 25°C which is slightly lower than the felt type C/C, but its value becomes higher than the C/C at temperatures above 400°C. The composite with 40 at% B shows more controllable recycling properties than B 4C. The erosion yield for the composite is about half the yield for graphite at 800 K. After electron beam irradiation in order to test heat resistance no cracks were detected up to 22-23 MW/m 2 leading to a surface temperature of 2500°C.

  11. A new modified conducting carbon composite electrode as sensor for ascorbate and biosensor for glucose.

    PubMed

    Barsan, Madalina M; Brett, Christopher M A

    2009-09-01

    A new carbon-based conducting composite has been developed as electrochemical sensor and biosensor for the amperometric detection of ascorbate and glucose. Electrocatalytic oxidation of ascorbate has been done successfully at unmodified cellulose acetate-graphite composite electrodes, the sensor being highly sensitive, selective and with a low detection limit at 0.0 V vs. SCE and was successfully applied for ascorbate determination in commercial fruit juice samples. An interference free glucose biosensor has also been developed, based on the immobilisation of glucose oxidase by cross-linking with glutaraldehyde on poly (neutral red) modified composite electrodes. The biosensor exhibits a higher sensitivity of 31.5+/-1.7 microA cm(-2) mM(-1) than other carbon-composite-based glucose biosensors, a detection limit of 20.3 microM and a very short response time. PMID:19349215

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

    DOEpatents

    Beck, David E.; Gooch, Jack G.; Holcombe, Jr., Cressie E.; Masters, David R.

    1983-01-01

    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.

  13. EMI shielding and conductivity of carbon nanotube-polymer composites at terahertz frequency.

    PubMed

    Polley, Debanjan; Barman, Anjan; Mitra, Rajib Kumar

    2014-03-15

    We investigate the shielding effectiveness and complex conductivity of single-walled carbon nanotubes (SWNT) distributed in a polyvinyl alcohol (PVA) matrix in the THz frequency range. SWNTs are dispersed in PVA matrices with varying SWNT content (keeping the thickness of SWNT/PVA film constant) using a slow-drying method, and terahertz time-domain spectroscopy (THz-TDS) is performed at room temperature in transmission geometry in the frequency range of 0.3-2.1 THz. The transmittance spectra show a possible application of SWNT/PVA composites as low-bandpass filters in the THz frequency region. Shielding effectiveness of all the samples is measured, and, at a particular probing frequency, they tend to follow a linear relationship with SWNT weight fraction in the polymer matrices. THz conductivity of the composite system is described in the light of a.c. hopping conduction. PMID:24690833

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

    NASA Astrophysics Data System (ADS)

    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.

  15. Effects of neutron irradiation on thermal conductivity of SiC-based composites and monolithic ceramics

    SciTech Connect

    Senor, D.J.; Youngblood, G.E.; Moore, C.E.; Trimble, D.J.; Woods, J.J.

    1996-06-01

    A variety of SiC-based composites and monolithic ceramics were characterized by measuring their thermal diffusivity in the unirradiated, thermal annealed, and irradiated conditions over the temperature range 400 to 1,000 C. The irradiation was conducted in the EBR-II to doses of 33 and 43 dpa-SiC (185 EFPD) at a nominal temperature of 1,000 C. The annealed specimens were held at 1,010 C for 165 days to approximately duplicate the thermal exposure of the irradiated specimens. Thermal diffusivity was measured using the laser flash method, and was converted to thermal conductivity using density data and calculated specific heat values. Exposure to the 165 day anneal did not appreciably degrade the conductivity of the monolithic or particulate-reinforced composites, but the conductivity of the fiber-reinforced composites was slightly degraded. The crystalline SiC-based materials tested in this study exhibited thermal conductivity degradation of irradiation, presumably caused by the presence of irradiation-induced defects. Irradiation-induced conductivity degradation was greater at lower temperatures, and was typically more pronounced for materials with higher unirradiated conductivity. Annealing the irradiated specimens for one hour at 150 C above the irradiation temperature produced an increase in thermal conductivity, which is likely the result of interstitial-vacancy pair recombination. Multiple post-irradiation anneals on CVD {beta}-SiC indicated that a portion of the irradiation-induced damage was permanent. A possible explanation for this phenomenon was the formation of stable dislocation loops at the high irradiation temperature and/or high dose that prevented subsequent interstitial/vacancy recombination.

  16. Effects of neutron irradiation on thermal conductivity of SiC-based composites and monolithic ceramics

    SciTech Connect

    Senor, D.J.; Youngblood, G.E.; Moore, C.E.; Trimble, D.J.; Woods, J.J.

    1997-05-01

    A variety of SiC-based composites and monolithic ceramics were characterized by measuring their thermal diffusivity in the unirradiated, thermal annealed, and irradiated conditions over the temperature range 400 to 1,000 C. The irradiation was conducted in the EBR-II to doses of 33 and 43 dpa-SiC (185 EFPD) at a nominal temperature of 1,000 C. The annealed specimens were held at 1,010 C for 165 days to approximately duplicate the thermal exposure of the irradiated specimens. Thermal diffusivity was measured using the laser flash method, and was converted to thermal conductivity using density data and calculated specific heat values. Exposure to the 165 day anneal did not appreciably degrade the conductivity of the monolithic or particulate-reinforced composites, but the conductivity of the fiber-reinforced composites was slightly degraded. The crystalline SiC-based materials tested in this study exhibited thermal conductivity degradation after irradiation, presumably caused by the presence of irradiation-induced defects. Irradiation-induced conductivity degradation was greater at lower temperatures, and was typically more pronounced for materials with higher unirradiated conductivity. Annealing the irradiated specimens for one hour at 150 C above the irradiation temperature produced an increase in thermal conductivity, which is likely the result of interstitial-vacancy pair recombination. Multiple post-irradiation anneals on CVD {beta}-SiC indicated that a portion of the irradiation-induced damage was permanent. A possible explanation for this phenomenon was the formation of stable dislocation loops at the high irradiation temperature and/or high dose that prevented subsequent interstitial/vacancy recombination.

  17. Synthesis of Conductive Polyurethane/Graphite Composites for Electromagnetic Interference Shielding

    NASA Astrophysics Data System (ADS)

    Puri, Pooja; Mehta, Rajeev; Rattan, Sunita

    2015-11-01

    Among various nanofillers for composite systems, carbon-based fillers such as graphite, carbon fibers, carbon black, carbon nanotubes, graphene, etc. are attracting great attention in both academia and industry for the advent of highly integrated electronic devices. The objective in fabricating such composite materials is to obtain distinct properties evolved from the synergistic effects of the component materials that may be exploited for various applications such as electronics and optical devices. In the present work, polyurethane/graphite composites have been synthesized with the aim of using them for electromagnetic shielding applications. The polyurethane/graphite composites were prepared through an in situ polymerization method in the presence of graphite nanoparticles. The prepared composites were characterized by scanning electron microscope, transmission electron microscope (TEM), and x-ray diffraction techniques. The shifting of the major peak of graphite nanoplatelets (GNPs) in prepared nanocomposites towards the left from 26.336° d-spacing = 3.381 Å to 25.374° d-spacing = 3.507 Å on a 2 θ scale indicates the intercalation type of dispersion in the prepared nanocomposites. This was further validated with the TEM characterization. The introduction of GNPs in polyurethane (PU) during in situ polymerization creates an electrical network in the resulting composite, which therefore makes it highly conductive. The prepared nanocomposite showed an electrical network at 2.2 vol.% of the percolation threshold in DC condition and a similar percolation threshold was found at 100 Hz in AC conditions. The maximum conductivity found at 6.5 vol.% of filler loading was 0.01 S/cm. The resulting composites were evaluated for electromagnetic interference (EMI) shielding at different filler loadings. The prepared PU/GNPs composites were found to be highly effective with shielding effectiveness of 19.34 dB, and with electromagnetic interference shielding materials at 0

  18. Micromechanics model for predicting anisotropic electrical conductivity of carbon fiber composite materials

    NASA Astrophysics Data System (ADS)

    Haider, Mohammad Faisal; Haider, Md. Mushfique; Yasmeen, Farzana

    2016-07-01

    Heterogeneous materials, such as composites consist of clearly distinguishable constituents (or phases) that show different electrical properties. Multifunctional composites have anisotropic electrical properties that can be tailored for a particular application. The effective anisotropic electrical conductivity of composites is strongly affected by many parameters including volume fractions, distributions, and orientations of constituents. Given the electrical properties of the constituents, one important goal of micromechanics of materials consists of predicting electrical response of the heterogeneous material on the basis of the geometries and properties of the individual phases, a task known as homogenization. The benefit of homogenization is that the behavior of a heterogeneous material can be determined without resorting or testing it. Furthermore, continuum micromechanics can predict the full multi-axial properties and responses of inhomogeneous materials, which are anisotropic in nature. Effective electrical conductivity estimation is performed by using classical micromechanics techniques (composite cylinder assemblage method) that investigates the effect of the fiber/matrix electrical properties and their volume fractions on the micro scale composite response. The composite cylinder assemblage method (CCM) is an analytical theory that is based on the assumption that composites are in a state of periodic structure. The CCM was developed to extend capabilities variable fiber shape/array availability with same volume fraction, interphase analysis, etc. The CCM is a continuum-based micromechanics model that provides closed form expressions for upper level length scales such as macro-scale composite responses in terms of the properties, shapes, orientations and constituent distributions at lower length levels such as the micro-scale.

  19. Development of ammonia sensors by using conductive polymer/hydroxyapatite composite materials.

    PubMed

    Huixia, Li; Yong, Liu; Lanlan, Luo; Yanni, Tan; Qing, Zhang; Kun, Li

    2016-02-01

    In order to improve the gas sensing properties, hydroxyapatite (HAp)-based composites were prepared by mixing with different contents of conductive polymers: polypyrrole (PPy) and polyaniline (PAni). The compositions, microstructures and phase constitutions of polymer/HAp composites were characterized, and the sensing properties were studied using a chemical gas sensing (CGS-8) system. The results showed that, compared to pure HAp, the sensitivities of the composites to ammonia were improved significantly. 5%PPy/HAp and 20%PAni/HAp composites exhibited the best sensitivities to ammonia, and the sensitivities at 500ppm were 86.72% and 86.18%, respectively. Besides, the sensitivity of 5%PPy/HAp at 1000ppm was up to 90.7%. Compared to pure PPy and PAni, the response and the recovery time of 5%PPy/HAp and 20%PAni/HAp at 200ppm were shortened several times, and they were 24s/245s and 15s/54s, respectively. In addition, the composites showed a very high selectivity to ammonia. The mechanism for the enhancement of the sensitivity to ammonia was also discussed. The polymer/HAp composites are very promising in applications of ammonia sensors. PMID:26652394

  20. High Thermal and Electrical Conductivity of Template Fabricated P3HT/MWCNT Composite Nanofibers.

    PubMed

    Smith, Matthew K; Singh, Virendra; Kalaitzidou, Kyriaki; Cola, Baratunde A

    2016-06-15

    Nanoporous alumina membranes are filled with multiwalled carbon nanotubes (MWCNTs) and then poly(3-hexylthiophene-2,5-diyl) (P3HT) melt, resulting in nanofibers with nanoconfinement induced coalignment of both MWCNT and polymer chains. The simple sonication process proposed here can achieve vertically aligned arrays of P3HT/MWCNT composite nanofibers with 3 wt % to 55 wt % MWCNT content, measured using thermogravimetric methods. Electrical and thermal transport in the composite nanofibers improves drastically with increasing carbon nanotube content where nanofiber thermal conductivity peaks at 4.7 ± 1.1 Wm(-1)K(-1) for 24 wt % MWCNT and electrical percolation occurs once 20 wt % MWCNT content is surpassed. This is the first report of the thermal conductivity of template fabricated composite nanofibers and the first proposed processing technique to enable template fabrication of composite nanofibers with high filler content and long aspect ratio fillers, where enhanced properties can also be realized on the macroscale due to vertical alignment of the nanofibers. These materials are interesting for thermal management applications due to their high thermal conductivity and temperature stability. PMID:27200459

  1. Mechanism of direct current electrical charge conduction in p-toluenesulfonate doped polypyrrole/carbon composites

    SciTech Connect

    Kumar, Amit; Singh, Rajiv K.; Singh, Hari K.; Singh, Ramadhar; Srivastava, Pankaj

    2014-03-14

    Polypyrrole/carbon (PPy/C) composites have been synthesized using varying concentration of p-toluenesulfonate (pTS) dopant by surface initiated in-situ chemical oxidative polymerization. The synthesis and influence of pTS on the structure of the PPy/C composites are confirmed by Fourier transform infrared studies and the morphological features have been examined by scanning electron microscopy. X-ray photoelectron spectroscopy, employed to examine the surface composition and doping level of these composites, confirms the anionic doping into the polymer backbone. Electron spin resonance measurement has been carried out on these samples to identify the nature of the charge carriers and their concentration at different doping levels. The dc electrical conductivity of these composites has been measured in the temperature range ∼10–305 K. The observed results have been analyzed in the framework of existing theoretical models. Different Mott's parameters, such as characteristic temperature (T{sub 0}), density of states at the Fermi level (N(E{sub F})), average hopping distance (R), and average hopping energy (W), evaluated from dc conductivity data supports the applicability of Mott's three dimensional variable range hopping mechanism in this system.

  2. Electrical conductivity and electromagnetic interference shielding characteristics of multiwalled carbon nanotube filled polyacrylate composite films

    NASA Astrophysics Data System (ADS)

    Li, Yong; Chen, Changxin; Zhang, Song; Ni, Yuwei; Huang, Jie

    2008-07-01

    Multiwalled carbon nanotubes (MWCNTs) were homogeneously dispersed in pure acrylic emulsion by ultrasonication to prepare MWCNT/polyacrylate composites applied on building interior wall for electromagnetic interference (EMI) shielding applications. The structure and surface morphology of the MWCNTs and MWCNT/polyacrylate composites were studied by field emission scanning microscopy (FESEM) and transmission electron microscopy (TEM). The electrical conductivity at room temperature and EMI shielding effectiveness (SE) of the composite films on concrete substrate with different MWCNT loadings were investigated and the measurement of EMI SE was carried out in two different frequency ranges of 100-1000 MHz (radio frequency range) and 8.2-12.4 GHz (X-band). The experimental results show that a low mass concentration of MWCNTs could achieve a high conductivity and the EMI SE of the MWCNT/polyacrylate composite films has a strong dependence on MWCNTs content in both two frequency ranges. The SE is higher in X-band than that in radio frequency range. For the composite films with 10 wt.% MWCNTs, the EMI SE of experiment agrees well with that of theoretical prediction in far field.

  3. Ferroelectric/ferromagnetic ceramic composite and its hybrid permittivity stemming from hopping charge and conductivity inhomogeneity

    NASA Astrophysics Data System (ADS)

    Zheng, Hui; Li, Lu; Xu, Zhaojun; Weng, Wenjian; Han, Gaorong; Ma, Ning; Du, Piyi

    2013-01-01

    Exploring the nature of multiferroic ceramic composite with dual high performances is much important to take full advantage of its novel dielectric properties. In this paper, Ni0.5Zn0.5291Fe2O4/BaTiO3 ceramic composite is proposed and successfully prepared from BTO and NZFO powders which are obtained by sol-gel process and citric acid combustion method, respectively. Results show that with increasing BTO content from 0 to 25 vol. % in the matrix of NZFO, the permittivity of the composite decreases from 220 k to 100 k at low frequencies (˜40 Hz) and contrarily from 20 to 100 at high frequencies (˜100 MHz). It is mainly ascribed to the instant polarization in NZFO at low frequencies and the polarization in the perovskite phase of BTO at sufficiently high frequencies. The permittivity of the ferrite and composite is shown to be compatible with a hybrid model proposed, which concerns hopping charges between Fe2+ and Fe3+, conductivity heterogeneity at the grain boundaries of the ferrite, and changes in the conductivities of the two phases induced by interdiffusion of the ions between the two phases. The composition dependence of the permittivity is agreeable with Kirkpatrick's compound law with the percolation threshold of NZFO to be about 55 vol. %.

  4. Thermal Conductivity and Erosion Durability of Composite Two-Phase Air Plasma Sprayed Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Schmitt, Michael P.; Rai, Amarendra K.; Zhu, Dongming; Dorfman, Mitchell R.; Wolfe, Douglas E.

    2015-01-01

    To enhance efficiency of gas turbines, new thermal barrier coatings (TBCs) must be designed which improve upon the thermal stability limit of 7 wt% yttria stabilized zirconia (7YSZ), approximately 1200 C. This tenant has led to the development of new TBC materials and microstructures capable of improved high temperature performance. This study focused on increasing the erosion durability of cubic zirconia based TBCs, traditionally less durable than the metastable t' zirconia based TBCs. Composite TBC microstructures composed of a low thermal conductivity/high temperature stable cubic Low-k matrix phase and a durable t' Low-k secondary phase were deposited via APS. Monolithic coatings composed of cubic Low-k and t' Low-k were also deposited, in addition to a 7YSZ benchmark. The thermal conductivity and erosion durability were then measured and it was found that both of the Low-k materials have significantly reduced thermal conductivities, with monolithic t' Low-k and cubic Low-k improving upon 7YSZ by approximately 13 and approximately 25%, respectively. The 40 wt% t' Low-k composite (40 wt% t' Low-k - 60 wt% cubic Low-k) showed a approximately 22% reduction in thermal conductivity over 7YSZ, indicating even at high levels, the t' Low-k secondary phase had a minimal impact on thermal in the composite coating. It was observed that a mere 20 wt% t' Low-k phase addition can reduce the erosion of a cubic Low-k matrix phase composite coating by over 37%. Various mixing rules were then investigated to assess this non-linear composite behavior and suggestions were made to further improve erosion durability.

  5. Composite electrolyte with proton conductivity for low-temperature solid oxide fuel cell

    SciTech Connect

    Raza, Rizwan; Ahmed, Akhlaq; Akram, Nadeem; Saleem, Muhammad; Niaz Akhtar, Majid; Ajmal Khan, M.; Abbas, Ghazanfar; Alvi, Farah; Yasir Rafique, M.; Sherazi, Tauqir A.; Shakir, Imran; Mohsin, Munazza; Javed, Muhammad Sufyan; Zhu, Bin E-mail: zhubin@hubu.edu.cn

    2015-11-02

    In the present work, cost-effective nanocomposite electrolyte (Ba-SDC) oxide is developed for efficient low-temperature solid oxide fuel cells (LTSOFCs). Analysis has shown that dual phase conduction of O{sup −2} (oxygen ions) and H{sup +} (protons) plays a significant role in the development of advanced LTSOFCs. Comparatively high proton ion conductivity (0.19 s/cm) for LTSOFCs was achieved at low temperature (460 °C). In this article, the ionic conduction behaviour of LTSOFCs is explained by carrying out electrochemical impedance spectroscopy measurements. Further, the phase and structure analysis are investigated by X-ray diffraction and scanning electron microscopy techniques. Finally, we achieved an ionic transport number of the composite electrolyte for LTSOFCs as high as 0.95 and energy and power density of 90% and 550 mW/cm{sup 2}, respectively, after sintering the composite electrolyte at 800 °C for 4 h, which is promising. Our current effort toward the development of an efficient, green, low-temperature solid oxide fuel cell with the incorporation of high proton conductivity composite electrolyte may open frontiers in the fields of energy and fuel cell technology.

  6. Effect of heat treatment on microstructure and thermal conductivity of carbon/carbon-copper composites

    NASA Astrophysics Data System (ADS)

    Yang, Peng'ao; Yin, Jian; Zhang, Hongbo; Xiong, Xiang

    2016-03-01

    Using 2.5-dimensional carbon fiber fabrics as the reinforcement, porous carbon/carbon(C/C) substrates were firstly fabricated by impregnation/carbonization (I/C) technique with furan resin and then treated at 2000, 2300 and 3000 °C, respectively. Finally, carbon fiber reinforced carbon and copper(C/C-Cu) composites were prepared by infiltrating melt copper alloy into C/C substrates under pressure. The effects of treating temperatures on microstructures and thermal conductivities of the composites were investigated. The results show that heat treatment plays an important role in the microstructure and thermal conductivity of C/C-Cu composites. It is conducive not only to rearrange the carbon crystallite of resin-based carbon in oriented layer structure, but also to improve the content and connectivity of copper alloy. The thermal conductivity increases with the increase in heat treatment temperature in both parallel and perpendicular direction; the thermal conductivity in parallel direction is evidently superior to that in perpendicular direction.

  7. Composition suitable for use as inert electrode having good electrical conductivity and mechanical properties

    DOEpatents

    Ray, S.P.; Rapp, R.A.

    1984-06-12

    An improved inert electrode composition is suitable for use as an inert electrode in the production of metals such as aluminum by the electrolytic reduction of metal oxide or metal salt dissolved in a molten salt bath. The composition comprises one or more metals or metal alloys and metal compounds which may include oxides of the metals comprising the alloy. The alloy and metal compounds are interwoven in a network which provides improved electrical conductivity and mechanical strength while preserving the level of chemical inertness necessary for such an electrode to function satisfactorily. 8 figs.

  8. Composition suitable for use as inert electrode having good electrical conductivity and mechanical properties

    DOEpatents

    Ray, Siba P.; Rapp, Robert A.

    1984-01-01

    An improved inert electrode composition is suitable for use as an inert electrode in the production of metals such as aluminum by the electrolytic reduction of metal oxide or metal salt dissolved in a molten salt bath. The composition comprises one or more metals or metal alloys and metal compounds which may include oxides of the metals comprising the alloy. The alloy and metal compounds are interwoven in a network which provides improved electrical conductivity and mechanical strength while preserving the level of chemical inertness necessary for such an electrode to function satisfactorily.

  9. Fabrication of high thermal conductivity arrays of carbon nanotubes and their composites

    DOEpatents

    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.

  10. MODELING THE TRANSVERSE THERMAL CONDUCTIVITY OF 2-D SICF/SIC COMPOSITES MADE WITH WOVEN FABRIC

    SciTech Connect

    Youngblood, Gerald E; Senor, David J; Jones, Russell H

    2004-06-01

    The hierarchical two-layer (H2L) model describes the effective transverse thermal conductivity (Keff) of a 2D-SiCf/SiC composite plate made from stacked and infiltrated woven fabric layers in terms of constituent properties and microstructural and architectural variables. The H2L model includes the effects of fiber-matrix interfacial conductance, high fiber packing fractions within individual tows and the non-uniform nature of 2D fabric/matrix layers that usually include a significant amount of interlayer porosity. Previously, H2L model Keff-predictions were compared to measured values for two versions of 2D Hi-Nicalon/PyC/ICVI-SiC composite, one with a “thin” (0.11m) and the other with a “thick” (1.04m) pyrocarbon (PyC) fiber coating, and for a 2D Tyranno SA/”thin” PyC/FCVI-SIC composite. In this study, H2L model Keff-predictions were compared to measured values for a 2D-SiCf/SiC composite made using the ICVI-process with Hi-Nicalon type S fabric and a “thin” PyC fiber coating. The values of Keff determined for the latter composite were significantly greater than the Keff-values determined for the composites made with either the Hi-Nicalon or the Tyranno SA fabrics. Differences in Keff-values were expected for the different fiber types, but major differences also were due to observed microstructural and architectural variations between the composite systems, and as predicted by the H2L model.

  11. Al-Ca and Al-Fe metal-metal composite strength, conductivity, and microstructure relationships

    SciTech Connect

    Kim, Hyong June

    2011-01-01

    Deformation processed metal-metal composites (DMMC’s) are composites formed by mechanical working (i.e., rolling, swaging, or wire drawing) of two-phase, ductile metal mixtures. Since both the matrix and reinforcing phase are ductile metals, the composites can be heavily deformed to reduce the thickness and spacing of the two phases. Recent studies have shown that heavily drawn DMMCs can achieve anomalously high strength and outstanding combinations of strength and conductivity. In this study, Al-Fe wire composite with 0.07, 0.1, and 0.2 volume fractions of Fe filaments and Al-Ca wire composite with 0.03, 0.06, and 0.09 volume fractions of Ca filaments were produced in situ, and their mechanical properties were measured as a function of deformation true strain. The Al-Fe composites displayed limited deformation of the Fe phase even at high true strains, resulting in little strengthening effect in those composites. Al-9vol%Ca wire was deformed to a deformation true strain of 13.76. The resulting Ca second-phase filaments were deformed to thicknesses on the order of one micrometer. The ultimate tensile strength increased exponentially with increasing deformation true strain, reaching a value of 197 MPa at a true strain of 13.76. This value is 2.5 times higher than the value predicted by the rule of mixtures. A quantitative relationship between UTS and deformation true strain was determined. X-ray diffraction data on transformation of Al + Ca microstructures to Al + various Al-Ca intermetallic compounds were obtained at the Advanced Photon Source at Argonne National Laboratory. Electrical conductivity was measured over a range of true strains and post-deformation heat treatment schedules.

  12. Fabrication of Al2O3/glass/Cf Composite Substrate with High Thermal Conductivity

    NASA Astrophysics Data System (ADS)

    Wang, S. X.; Liu, G. S.; Ouyang, X. Q.; Wang, Y. D.; Zhang, D.

    2016-02-01

    In this paper, carbon fiber with high thermal conductivity was introduced into the alumina-based composites. To avoid oriented alignment of carbon fibers (Cf) and carbothermal reactions during the sintering process, the Al2O3/glass/Cf substrate was hot-pressed under a segmental-pressure procedure at 1123 K. Experimental results show that carbon fibers randomly distribute and form a bridging structure in the matrix. The three-dimensional network of Cf in Al2O3/glass/Cf substrate brings excellent heat conducting performance due to the heat conduction by electrons. The thermal conductivity of Al2O3/30%glass/30%Cf is as high as 28.98 W mK-1, which is 4.56 times larger than that of Al2O3/30%glass.

  13. An analytical solution for transverse thermal conductivities of unidirectional fibre composites with thermal barrier

    NASA Astrophysics Data System (ADS)

    Zou, Mingqing; Yu, Boming; Zhang, Duanming

    2002-08-01

    In this paper, an analytical expression for transverse thermal conductivities of unidirectional fibre composites with thermal barrier is derived based on the electrical analogy technique and on the cylindrical filament-square packing array unit cell model (C-S model). The present analytical expressions both with and without thermal barrier between fibre and matrix are presented. The present theoretical predictions without thermal barrier are found to be in excellent agreement with the existing analytical model and nomogram from the finite difference method (FDM), and in good agreement with existing experimental data. Furthermore, the present analytical predictions with thermal barrier can best fit the experimental data and can provide a higher accuracy than the finite element method (FEM). The validity of the present analytical solution is thus verified for transverse thermal conductivities of unidirectional fibre composites with thermal barrier.

  14. Conducting polymer and its composite materials based electrochemical sensor for Nicotinamide Adenine Dinucleotide (NADH).

    PubMed

    Omar, Fatin Saiha; Duraisamy, Navaneethan; Ramesh, K; Ramesh, S

    2016-05-15

    Nicotinamide Adenine Dinucleotide (NADH) is an important coenzyme in the human body that participates in many metabolic reactions. The impact of abnormal concentrations of NADH significantly causes different diseases in human body. Electrochemical detection of NADH using bare electrode is a challenging task especially in the presence of main electroactive interferences such as ascorbic acid (AA), uric acid (UA) and dopamine (DA). Modified electrodes have been widely explored to overcome the problems of poor sensitivity and selectivity occurred from bare electrodes. This review gives an overview on the progress of using conducting polymers, polyelectrolyte and its composites (co-polymer, carbonaceous, metal, metal oxide and clay) based modified electrodes for the sensing of NADH. In addition, developments on the fabrication of numerous conducting polymer composites based modified electrodes are clearly described. PMID:26774092

  15. Thermal Conductivity of 3D CNT-Polymer Composites with Controlled Dispersion

    NASA Astrophysics Data System (ADS)

    Klittich, Mena; Wang, Xue; Dhinojwala, Ali

    The high thermal conductivity of isolated carbon nanotubes (CNTs) has inspired its use as a thermal filler for insulative polymers. However, the performance of these composites has consistently been sub par. Extensive analyses of these complex systems have resulted in the conclusion that resistance at the CNT/polymer interface due to phonon mismatch and poor physical binding, as well as the weakly bonded tube-tube interactions restrict the effectiveness of CNTs in practice. Experimental comparisons of CNT treatments, coatings, functionalization, and interactions with various polymers have proved challenging, due to the interconnected nature of the composite properties. Here, we have reversed the paradigm and used a constant CNT structure that is then modified post-growth to allow for direct comparisons of polymer composites.

  16. Carbon black and carbon black-conducting polymer composites for environmental applications

    SciTech Connect

    Rajeshwar, K.; Wampler, W.A.; Goeringer, S.; Gerspacher, M.

    1996-12-31

    A large fraction of the carbon black commercially produced in the U. S. and other parts of the world goes into the automobile tire industry and other rubber applications. However, specialty applications of this material are expected to grow in the future. The present study explores the applicability of composites of carbon black and an electronically conductive polymer, polypyrrole, in environmental pollution abatement scenarios. Chromium was used as a model environmental pollutant for demonstration of our approach.

  17. Preparation and ion conductivity of composite films AgI-ZnO

    NASA Astrophysics Data System (ADS)

    Fateev, Sergey S.; Tveryanovich, Yu S.; Tomaev, V. V.; Fokina, Svetlana V.

    2015-05-01

    It has been proven that with laser deposition silver iodide retains its chemical composition and structure. A film has been produced with the help of laser deposition, consisting of finely divided crystals of ZnO and AgI. Its structure has been reviewed using X-Ray phase analysis, and its electric conductivity has been reviewed using impedance measurement. Special attention has been given to the effect of phase interaction on ion transport.

  18. Highly efficient flexible optoelectronic devices using metal nanowire-conducting polymer composite transparent electrode

    NASA Astrophysics Data System (ADS)

    Jung, Eui Dae; Nam, Yun Seok; Seo, Houn; Lee, Bo Ram; Yu, Jae Choul; Lee, Sang Yun; Kim, Ju-Young; Park, Jang-Ung; Song, Myoung Hoon

    2015-09-01

    Here, we report a comprehensive analysis of the electrical, optical, mechanical, and surface morphological properties of composite nanostrutures based on silver nanowires (AgNW) and PEDOT:PSS conducting polymer for the use as flexible and transparent electrodes. Compared to ITO or the single material of AgNW or PEDOT:PSS, the AgNW/PEDOT:PSS composite electrode showed high electrical conductivity with a low sheet resistance of 26.8 Ω/sq at 91% transmittance (at 550 nm), improves surface smoothness, and enhances mechanical properties assisted by an amphiphilic fluoro-surfactant. The polymeric light-emitting diodes (PLEDs) and organic solar cells (OSCs) using the AgNW/PEDOT:PSS composite electrode showed higher device performances than those with AgNW and PEDOT:PSS electrodes and excellent flexibility under bending test. These results indicates that the AgNW/PEDOT:PSS composite presented is a good candidate as next-generation transparent elelctrodes for applications into flexible optoelectronic devices. [Figure not available: see fulltext.

  19. Silicone Membranes to Inhibit Water Uptake into Thermoset Polyurethane Shape-Memory Polymer Conductive Composites

    PubMed Central

    Yu, Ya-Jen; Infanger, Stephen; Grunlan, Melissa A.; Maitland, Duncan J.

    2014-01-01

    Electroactive shape memory polymer (SMP) composites capable of shape actuation via resistive heating are of interest for various biomedical applications. However, water uptake into SMPs will produce a depression of the glass transition temperature (Tg) resulting in shape recovery in vivo. While water actuated shape recovery may be useful, it is foreseen to be undesirable during early periods of surgical placement into the body. Silicone membranes have been previously reported to prevent release of conductive filler from an electroactive polymer composite in vivo. In this study, a silicone membrane was used to inhibit water uptake into a thermoset SMP composite containing conductive filler. Thermoset polyurethane (PU) SMPs were loaded with either 5 wt% carbon black (CB) or 5 wt% carbon nanotubes (CNT) and subsequently coated with either an Al2O3- or silica-filled silicone membrane. It was observed that the silicone membranes, particularly the silica-filled membrane, reduced the rate of water absorption (37 °C) and subsequent Tg depression versus uncoated composites. In turn, this led to a reduction in the rate of recovery of the permanent shape when exposed to water at 37 °C. PMID:25663711

  20. Quantitative Conductive Atomic Force Microscopy on Single-Walled Carbon Nanotube-Based Polymer Composites.

    PubMed

    Bârsan, Oana A; Hoffmann, Günter G; van der Ven, Leendert G J; de With, Gijsbertus

    2016-08-01

    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. PMID:27404764

  1. Advancement in conductive cotton fabrics through in situ polymerization of polypyrrole-nanocellulose composites.

    PubMed

    Hebeish, A; Farag, S; Sharaf, S; Shaheen, Th I

    2016-10-20

    Current research was undertaking with a view to innovate a new approach for development of conductive - coated textile materials through coating cotton fabrics with nanocellulose/polypyrrole composites. The study was designed in order to have a clear understanding of the role of nanocellulose as well as modified composite thereof under investigation. It is anticipated that incorporation of nanocellulose in the pyrrole/cotton fabrics/FeCl3/H2O system would form an integral part of the composites with mechanical, electrical or both properties. Three different nanocellulosic substrates are involved in the oxidation polymerization reaction of polypyrrole (Ppy) in presence of cotton fabrics. Polymerization was subsequently carried out by admixing at various ratios of FeCl3 and pyrrole viz. Ppy1, Ppy2 and pp3. The conductive, mechanical and thermal properties of cotton fabrics coated independently with different nanocellulose/polypyrrole were investigated. FTIR, TGA, XRD, SEM and EDX were also used for further characterization. Results signify that, the conductivity of cotton fabrics increases exponentially with increasing the dose of pyrrole and oxidant irrespective of nanocellulose substrate used. While, the mechanical properties of cotton fabrics are not significantly affected by the oxidant treatment. PMID:27474547

  2. ac and dc percolative conductivity of magnetite-cellulose acetate composites

    SciTech Connect

    Chiteme, C.; McLachlan, D. S.; Sauti, G.

    2007-03-01

    ac and dc conductivity results for a percolating system, which consists of a conducting powder (magnetite) combined with an 'insulating' powder (cellulose acetate), are presented. Impedance and modulus spectra are obtained in a percolation system. The temperature dependence of the resistivity of the cellulose acetate is such that at 170 deg. C, it is essentially a conductor at frequencies below 0.059{+-}0.002 Hz, and a dielectric above. The percolation parameters, from the dc conductivity measured at 25 and 170 deg. C, are determined and discussed in relation to the ac results. The experimental results scale as a function of composition, temperature, and frequency. An interesting result is the correlation observed between the scaling parameter (f{sub ce}), obtained from a scaling of the ac measurements, and the peak frequency (f{sub cp}) of the arcs, obtained from impedance spectra, above the critical volume fraction. Scaling at 170 deg. C is not as good as at 25 deg. C, probably indicating a breakdown in scaling at the higher temperature. The modulus plots show the presence of two materials: a conducting phase dominated by the cellulose acetate and the isolated conducting clusters below the critical volume fraction {phi}{sub c}, as well as the interconnected conducting clusters above {phi}{sub c}. These results are confirmed by computer simulations using the two exponent phenomenological percolation equation. These results emphasize the need to analyze ac conductivity results in terms of both impedance and modulus spectra in order to get more insight into the behavior of composite materials.

  3. Latest Progress In Novel High Conductivity And Highly Stable Composite Structure Developments For Satellite Applications

    NASA Astrophysics Data System (ADS)

    Klebor, Maximillian; Reichmann, Olaf; Pfeiffer, Ernst K.; Ihle, Alexander; Linke, Stefan; Tschepe, Christoph; Roddecke, Susanne; Richter, Ines; Berrill, Mark; Santiago-Prowald, Julian

    2012-07-01

    Materials such as aluminium, titanium and carbon fibre based composites are indispensable in space business. However, special demands on spaceborne applications require both new ideas and new concepts but also powerful novel materials. These days the trend is to substitute aluminium for CFRP basically in order to safe mass or to decrease thermal expansions. Nevertheless there are upcoming requirements that cannot be met using standard CFRP materials. In this connection innovative composites have to be introduced. In the frame of this paper three major applications for such material requests are considered, i.e.: • antennas • satellite platform structural panels • radiators. The new composites need to cope with the following challenges and demands: high operational temperature range, high stiffness, high strength, high thermal conductivity, vacuum compatibility, low mass, high in- orbit stability, compatibility with metallic parts and many more. Some of these demands have to be fulfilled in conjunction. Herein the innovative composites cover new raw materials and their combination, manufacturing process enhancement as well as new inspection and test methods. It has been observed that by using the developed CFRPs it is possible to satisfy and excel the needs. However, these materials feature a different behaviour than conventional composites which has to be taken into account during future design.

  4. Characterization and modeling of piezo-resistive properties of carbon nanotube-based conductive polymer composites

    NASA Astrophysics Data System (ADS)

    Pham, Giang Truong

    Electrically conductive polymers (ECPs), offering capabilities such as electrostatic discharge protection and electromagnetic interference shielding, have been the subject of intensive research and development both in academia and industry. The emergence of new conductive nano-fillers in recent decades, particularly carbon nanotubes (CNTs), further fuels more enthusiasm. Thanks to CNTs' excellent mechanical, thermal, and electrical/electronic properties, CNT-filled polymers possess not only conductive properties, but a range of other properties desirable for multi-functional and high performance applications. In order to fully exploit the benefits of CNT-based conductive polymers (CNT-ECPs), researchers have conducted diverse studies primarily to characterize the electrical conductivity of the composites. A crucial area that is less studied is the piezoresistive behaviors of CNT-ECPs, that is, the change in material conductive properties due to an applied stress or strain. Given broad usage of ECPs, it would be reasonable to assume that ECP products commonly operate under certain stress or strain conditions. For instance, an electrostatic discharge (ESD)-protected conductive coating for spacecraft would be affected by strain induced by mechanical or aerodynamic loads. A more systematic understanding of the materials' piezoresistivity, therefore, is instrumental in ensuring satisfactory conductive performance of those material applications. Additionally, knowledge of conductive characteristics of the CNT-ECPs against stress/strain can open the door to newer material applications, e.g., strain gage or multifunctional conductive coating with strain-sensing capability. This research aims to achieve a more fundamental understanding of the mechanism of piezoresistive property of CNT-ECPs, and to develop a model that permits quantifying the structure-property relationships of CNT-ECPs' piezoresistivity. In this research, expanded experimental studies with various

  5. Continuous electrodeposition for lightweight, highly conducting and strong carbon nanotube-copper composite fibers.

    PubMed

    Xu, Geng; Zhao, Jingna; Li, Shan; Zhang, Xiaohua; Yong, Zhenzhong; Li, Qingwen

    2011-10-01

    Carbon nanotube (CNT) fiber is a promising candidate for lightweight cables. The introduction of metal particles on a CNT fiber can effectively improve its electrical conductivity. However, the decrease in strength is observed in CNT-metal composite fibers. Here we demonstrate a continuous process, which combines fiber spinning, CNT anodization and metal deposition, to fabricate lightweight and high-strength CNT-Cu fibers with metal-like conductivities. The composite fiber with anodized CNTs exhibits a conductivity of 4.08 × 10(4)-1.84 × 10(5) S cm(-1) and a mass density of 1.87-3.08 g cm(-3), as the Cu thickness is changed from 1 to 3 μm. It can be 600-811 MPa in strength, as strong as the un-anodized pure CNT fiber (656 MPa). We also find that during the tensile tests there are slips between the inner CNTs and the outer Cu layer, leading to the drops in electrical conductivity. Therefore, there is an effective fiber strength before which the Cu layer is robust. Due to the improved interfacial bonding between the Cu layer and the anodized CNT surfaces, such effective strength is still high, up to 490-570 MPa. PMID:21879118

  6. Stretchable conducting gold films prepared with composite MWNT/PDMS substrates

    NASA Astrophysics Data System (ADS)

    Manzoor, M. U.; Lemoine, P.; Dixon, D.; Hamilton, J. W. J.; Maguire, P. D.

    2015-10-01

    Novel stretchable conducting films were prepared by depositing gold layers onto polymer nano-composites substrates formed by in-situ crosslinking of polydimethylsiloxane (PDMS) in the presence of multiwall carbon nanotubes (MWNT). The MWNT content interferes with the PDMS cure reaction giving variations in thermal degradation, solvent swelling, mechanical and electrical properties. Tensile cycling experiments were carried out on the gold-coated PDMS and nano-composite substrates SEM analysis and electrical measurements demonstrated that the crack widening and increased electrical resistance observed during strain cycling were reversible. The inclusion of 8 % MWNT into PDMS brought more micro-cracking in the gold layer yet reduced the electrical resistance of the gold-coated samples by 172X at 5 % strain, 38X at 10 % strain and 19X at 20 %. Hence, this improvement in conduction is attributed to assisted-conduction through the MWNT loaded substrate. This mechanism results in a more stable and reproducible electrical behaviour, making electrical conduction less critically dependent on defects in the gold layer.

  7. Bioinspired modification of h-BN for high thermal conductive composite films with aligned structure.

    PubMed

    Shen, Heng; Guo, Jing; Wang, Hao; Zhao, Ning; Xu, Jian

    2015-03-18

    With the development of microelectronic technology, the demand of insulating electronic encapsulation materials with high thermal conductivity is ever growing and much attractive. Surface modification of chemical inert h-BN is yet a distressing issue which hinders its applications in thermal conductive composites. Here, dopamine chemistry has been used to achieve the facile surface modification of h-BN microplatelets by forming a polydopamine (PDA) shell on its surface. The successful and effective preparation of h-BN@PDA microplatelets has been confirmed by SEM, EDS, TEM, Raman spectroscopy, and TGA investigations. The PDA coating increases the dispersibility of the filler and enhances its interaction with PVA matrix as well. Based on the combination of surface modification and doctor blading, composite films with aligned h-BN@PDA are fabricated. The oriented fillers result in much higher in-plane thermal conductivities than the films with disordered structures produced by casting or using the pristine h-BN. The thermal conductivity is as high as 5.4 W m(-1) K(-1) at 10 vol % h-BN@PDA loading. The procedure is eco-friendly, easy handling, and suitable for the practical application in large scale. PMID:25707681

  8. Electrical conduction and dielectric relaxation in p-type PVA/CuI polymer composite

    PubMed Central

    Makled, M.H.; Sheha, E.; Shanap, T.S.; El-Mansy, M.K.

    2012-01-01

    PVA/CuI polymer composite samples have been prepared and subjected to characterizations using FT-IR spectroscopy, DSC analysis, ac spectroscopy and dc conduction. The FT-IR spectral analysis shows remarkable variation of the absorption peak positions whereas DSC illustrates a little decrease of both glass transition temperature, Tg, and crystallization fraction, χ, with increasing CuI concentration. An increase of dc conductivity for PVA/CuI nano composite by increasing CuI concentration is recoded up to 15 wt%, besides it obeys Arhenuis plot with an activation energy in the range 0.54–1.32 eV. The frequency dependence of ac conductivity showed power law with an exponent 0.33 < s < 0.69 which predicts hopping conduction mechanism. The frequency dependence of both dielectric permittivity and dielectric loss obeys Debye dispersion relations in wide range of temperatures and frequency. Significant values of dipole relaxation time obtained which are thermally activated with activation energies in the range 0.33–0.87 eV. A significant value of hopping distance in the range 3.4–1.2 nm is estimated in agreement with the value of Bohr radius of the exciton. PMID:25685462

  9. The empirical evaluation of thermal conduction coefficient of some liquid composite heat insulating materials

    NASA Astrophysics Data System (ADS)

    Anisimov, M. V.; Rekunov, V. S.; Babuta, M. N.; Bach Lien, Nguyen Thi Hong

    2016-02-01

    We experimentally determined the coefficients of thermal conductivity of some ultra thin liquid composite heat insulating coatings, for sample #1 λ = 0.086 W/(m·°C), for sample #2 λ = 0.091 W/(m·°C). We performed the measurement error calculation. The actual thermal conduction coefficient of the studied samples was higher than the declared one. The manufactures of liquid coatings might have used some "ideal" conditions when defining heat conductivity in the laboratory or the coefficient was obtained by means of theoretical solution of heat conduction problem in liquid composite insulating media. However, liquid insulating coatings are of great interest to builders, because they allow to warm objects of complex geometric shapes (valve chambers, complex assemblies, etc.), which makes them virtually irreplaceable. The proper accounting of heating qualities of paints will allow to avoid heat loss increase above the specified limits in insulated pipes with heat transfer materials or building structures, as well as protect them from possible thawing in the period of subzero weather.

  10. Facile Synthesis and Electrical Conductivity of Carbon Nanotube Reinforced Nanosilver Composite

    NASA Astrophysics Data System (ADS)

    Pal, Hemant; Sharma, Vimal; Kumar, Rajesh; Thakur, Nagesh

    2012-12-01

    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.

  11. Ionic conductivity of stabilized zirconia networks in compositeSOFC electrodes

    SciTech Connect

    Yamahara, Keiji; Sholklapper, Tal Z.; Jacobson, Craig P.; Visco,Steven J.; De Jonghe, Lutgard C.

    2004-03-01

    The effective oxygen conductivities in the zirconia networks of porous LSM-YSZ and LSM-SYSZ composites [i.e. La0.85Sr0.15MnO3(Y2O3)0.08(ZrO2)0.92 and La0.85Sr0.15MnO3(c2O3)0.1(Y2O3)0.01(ZrO2)0.89,respectively] were evaluated by an AC impedance technique using specimens in which LSM was removed by hydrochloric acid leaching. The oxygen conductivities of porous YSZ and SYSZ alone followed a Koh-Fortini relationship. LSM-containing zirconia network conductivities were additionally decreased by the presence of the LSM, presumably by increased grain boundary resistances. Constriction resistances were estimated to have a minor effect.

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

    SciTech Connect

    Li, Jinsong; Luo, Ruiying; Yan, Ying

    2011-09-15

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

  13. Final Scientific Report, New Proton Conductive Composite Materials for PEM Fuel Cells

    SciTech Connect

    Lvov, Serguei

    2010-11-08

    This project covered one of the main challenges in present-day PEM fuel cell technology: to design a membrane capable of maintaining high conductivity and mechanical integrity when temperature is elevated and water vapor pressure is severely reduced. The DOE conductivity milestone of 0.1 S cm-1 at 120 degrees C and 50 % relative humidity (RH) for designed membranes addressed the target for the project. Our approach presumed to develop a composite membrane with hydrophilic proton-conductive inorganic material and the proton conductive polymeric matrix that is able to “bridge” the conduction paths in the membrane. The unique aspect of our approach was the use of highly functionalized inorganic additives to benefit from their water retention properties and high conductivity as well. A promising result turns out that highly hydrophilic phosphorsilicate gels added in Nafion matrix improved PEM fuel cell performance by over 50% compared with bare Nafion membrane at 120 degrees C and 50 % RH. This achievement realizes that the fuel cell operating pressure can be kept low, which would make the PEM fuel cell much more cost efficient and adaptable to practical operating conditions and facilitate its faster commercialization particularly in automotive and stationary applications.

  14. Improvement of the thermal conductivity of SiC{sub F}/SiC composite

    SciTech Connect

    Youngblood, G.E.; Kowbel, W.

    1996-04-01

    The methods, high temperature annealing and doping, were examined for improving the thermal conductivity of simulated CVI/{Beta}-SiC matrix material. For instance, a two hour 1500{degrees}C anneal led to the increase of the room temperature (RT) thermal conductivity from 38 to 59 W.mK. Be doping was even more effective in causing the thermal conductivity to increase with RT conductivity values up to 160 W/mK attained. To further optimize the thermal conductivity, hot-pressed SiC materials with carefully controlled amounts of Be-and B{sub 4}C-doping were investigated. Although a small improvement ({approx} 8%) was achieved with 2.0 wt % Be-doping, the effort to refine the amount of doping needed was largely unsuccessful. Apparently, hot-pressing SiC introduced numerous substructural stacking faults which effectively scattered phonons on the intermediate temperature range and nullified the benefits of doping. Nevertheless, Be and B{sub 4}C-doping and/or thermal treatments appear to be promising strategies to achieve the goal of eventually improving the thermal conductivity of SiC{sub f}/SiC composite.

  15. Styrene-Butadiene Co-Polymer Based Highly Conducting and Flexible Polymer Composite Film with Low Percolation Threshold

    NASA Astrophysics Data System (ADS)

    Mathew, Anisha Mary; Neena, P.

    2011-10-01

    Conducting polymer composites are finding novel applications in various fields especially in device technology. In this work an effort has been made to synthesize polyaniline-synthetic rubber (Styrene-butadiene rubber) composite via ex-situ technique and its electrochemical properties are investigated. Highly conducting emeraldine form of polyaniline (20 S/cm) is prepared by the oxidative polymerization of aniline in aqueous acidic (CSA) media using ammonium peroxydisulfate as oxidizing agent. These composite films are characterized by UV-Visible spectroscopy to investigate their optical properties. The dc conductivity studies indicate that these composite films show extremely low percolation threshold.

  16. Poly (vinylidene fluoride)/graphene nano-platelets electrically conductive composite foam for thermoelectric applications

    NASA Astrophysics Data System (ADS)

    Sun, Yu-Chen; Terakita, Daryl; Tseng, Alex C.; Naguib, Hani E.

    2015-04-01

    In this paper, we present the next generation of polymer based composite foam material fabricated from poly(vinylidene fluoride) (PVDF) and graphene nano-platelets (GNPs) as secondary fillers. We discovered that such composite material has thermoelectric properties and has the potential to be used in energy harvesting applications. The samples were fabricated though melt blending methods, which is a cheaper, simpler process and can be easily scaled up to industrial level for mass production. Our results indicate that melt blending processes can produce either similar or superior results compared to traditional solvent casting methods. In addition, we utilized a novel batch foaming method and successfully created closed-cell structure for the composite material. Our results also show that the thermal conductivity of PVDF/GNP foam samples have approximately an order of magnitude drop compared to solid samples, which is desired for thermoelectric materials. Furthermore, we observed a change in the electrical conductivity threshold of the GNP fillers after foaming. We report a Seebeck coefficient of 217 μV/K for 15 wt% GNP/PVDF foam samples, which is approximately 10 times higher than values reported previously.

  17. Magnetic assembly of transparent and conducting graphene-based functional composites.

    PubMed

    Le Ferrand, Hortense; Bolisetty, Sreenath; Demirörs, Ahmet F; Libanori, Rafael; Studart, André R; Mezzenga, Raffaele

    2016-01-01

    Innovative methods producing transparent and flexible electrodes are highly sought in modern optoelectronic applications to replace metal oxides, but available solutions suffer from drawbacks such as brittleness, unaffordability and inadequate processability. Here we propose a general, simple strategy to produce hierarchical composites of functionalized graphene in polymeric matrices, exhibiting transparency and electron conductivity. These are obtained through protein-assisted functionalization of graphene with magnetic nanoparticles, followed by magnetic-directed assembly of the graphene within polymeric matrices undergoing sol-gel transitions. By applying rotating magnetic fields or magnetic moulds, both graphene orientation and distribution can be controlled within the composite. Importantly, by using magnetic virtual moulds of predefined meshes, graphene assembly is directed into double-percolating networks, reducing the percolation threshold and enabling combined optical transparency and electrical conductivity not accessible in single-network materials. The resulting composites open new possibilities on the quest of transparent electrodes for photovoltaics, organic light-emitting diodes and stretchable optoelectronic devices. PMID:27354243

  18. Multilayer Graphene Enables Higher Efficiency in Improving Thermal Conductivities of Graphene/Epoxy Composites.

    PubMed

    Shen, Xi; Wang, Zhenyu; Wu, Ying; Liu, Xu; He, Yan-Bing; Kim, Jang-Kyo

    2016-06-01

    The effects of number of graphene layers (n) and size of multilayer graphene sheets on thermal conductivities (TCs) of their epoxy composites are investigated. Molecular dynamics simulations show that the in-plane TCs of graphene sheets and the TCs across the graphene/epoxy interface simultaneously increase with increasing n. However, such higher TCs of multilayer graphene sheets will not translate into higher TCs of bulk composites unless they have large lateral sizes to maintain their aspect ratios comparable to the monolayer counterparts. The benefits of using large, multilayer graphene sheets are confirmed by experiments, showing that the composites made from graphite nanoplatelets (n > 10) with over 30 μm in diameter deliver a TC of ∼1.5 W m(-1) K(-1) at only 2.8 vol %, consistently higher than those containing monolayer or few-layer graphene at the same graphene loading. Our findings offer a guideline to use cost-effective multilayer graphene as conductive fillers for various thermal management applications. PMID:27140423

  19. Low power, lightweight vapor sensing using arrays of conducting polymer composite chemically-sensitive resistors

    NASA Technical Reports Server (NTRS)

    Ryan, M. A.; Lewis, N. S.

    2001-01-01

    Arrays of broadly responsive vapor detectors can be used to detect, identify, and quantify vapors and vapor mixtures. One implementation of this strategy involves the use of arrays of chemically-sensitive resistors made from conducting polymer composites. Sorption of an analyte into the polymer composite detector leads to swelling of the film material. The swelling is in turn transduced into a change in electrical resistance because the detector films consist of polymers filled with conducting particles such as carbon black. The differential sorption, and thus differential swelling, of an analyte into each polymer composite in the array produces a unique pattern for each different analyte of interest, Pattern recognition algorithms are then used to analyze the multivariate data arising from the responses of such a detector array. Chiral detector films can provide differential detection of the presence of certain chiral organic vapor analytes. Aspects of the spaceflight qualification and deployment of such a detector array, along with its performance for certain analytes of interest in manned life support applications, are reviewed and summarized in this article.

  20. Magnetic assembly of transparent and conducting graphene-based functional composites

    PubMed Central

    Le Ferrand, Hortense; Bolisetty, Sreenath; Demirörs, Ahmet F.; Libanori, Rafael; Studart, André R.; Mezzenga, Raffaele

    2016-01-01

    Innovative methods producing transparent and flexible electrodes are highly sought in modern optoelectronic applications to replace metal oxides, but available solutions suffer from drawbacks such as brittleness, unaffordability and inadequate processability. Here we propose a general, simple strategy to produce hierarchical composites of functionalized graphene in polymeric matrices, exhibiting transparency and electron conductivity. These are obtained through protein-assisted functionalization of graphene with magnetic nanoparticles, followed by magnetic-directed assembly of the graphene within polymeric matrices undergoing sol–gel transitions. By applying rotating magnetic fields or magnetic moulds, both graphene orientation and distribution can be controlled within the composite. Importantly, by using magnetic virtual moulds of predefined meshes, graphene assembly is directed into double-percolating networks, reducing the percolation threshold and enabling combined optical transparency and electrical conductivity not accessible in single-network materials. The resulting composites open new possibilities on the quest of transparent electrodes for photovoltaics, organic light-emitting diodes and stretchable optoelectronic devices. PMID:27354243

  1. Nitrite Oxidation with Copper-Cobalt Nanoparticles on Carbon Nanotubes Doped Conducting Polymer PEDOT Composite.

    PubMed

    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. PMID:26183223

  2. Electrochemical properties of a thermally expanded magnetic graphene composite with a conductive polymer.

    PubMed

    Ahmed, Mahmoud M M; Imae, Toyoko

    2016-04-21

    A magnetic graphene composite derived from stage-1 FeCl3-graphite intercalation compounds was thermally treated for up to 75 min at 400 °C or for 2 min at high temperatures up to 900 °C. These heat-treatments of the magnetic graphene composite gave rise to the cubical expansion of graphene with the enlargement of inter-graphene distances. The specific capacitance of the magnetic graphene composite increased upon heating and reached 42 F g(-1) at a scan rate of 5 mV s(-1) in 1.0 M NaCl, after being treated for 2 min at 900 °C. This value corresponds to 840% increase in the capacitance activity superior to that (5 F g(-1)) of the pristine magnetic graphene composite before heat-treatment. This capacitance enhancement can play a significant role in the increase of the surface area that reached 17.2 m(2) g(-1) during the non-defective inter-graphene exfoliation. Moreover, the magnetic graphene composite heated at 900 °C was hybridized with polyaniline by in situ polymerization of aniline to reach a specific capacitance of 253 F g(-1) at 5 mV s(-1). The current procedure of heat-treatment and hybridization with a conductive polymer can be an effective method for attaining a well-expanded magnetic graphene composite possessing an enhanced electrochemical activity with a relatively high energy density (141 W h kg(-1) in 1.0 M NaCl) and an excellent stability (99% after 9000 cycles of 20 A g(-1)). PMID:27030519

  3. Effect of interfacial thermal conductance and fiber orientation on the thermal diffusivity/conductivity of unidirectional fiber-reinforced ceramic matrix composites

    NASA Astrophysics Data System (ADS)

    Bhatt, Hemanshu Devshankar

    The role of an interfacial barrier at the fiber-matrix interface in the heat conduction behavior of a uniaxial silicon nitride and the effect of fiber orientation on the heat conduction characteristics of carbon fiber-reinforced borosilicate glass was investigated. A composite with fibers having a carbon-rich coating of about 3 microns was chosen as the reference material. The fiber-matrix interface was then modified using fibers with no carbon coating and using hot-isostatic-pressure (HIP) after nitridation. The formation of an interfacial gap at the interface resulted in the dependence of thermal diffusivity/conductivity on the surrounding atmosphere. However, no atmospheric effects were observed for composites with fibers without the carbon coating. HIP'ing increased the thermal diffusivity/conductivity of the composites due to densification of the matrix, crystallization of the fibers and increased physical contact at the interface. Removal of the interfacial carbon layer lowered the interfacial conductance considerably, due to decrease in the direct thermal contact between the fibers and the matrix. Interfacial contact conductance increased rapidly with increasing temperature in accordance with interfacial gap closure. These observations indicate that the heat conduction behavior was strongly affected by the existence of an interfacial thermal barrier. An analysis was conducted to determine the expression for the effective thermal conductivity of a uniaxially reinforced finite composite strip with insulated edges as a function of the angle between the fiber direction and the temperature gradient. Three carbon fiber-reinforced aluminoborosilicate glass composite specimens were used: thin, angled and thick rectangular. The thin specimens and the angled specimens represented the case of a composite infinite in extent. The thick rectangular specimens were expected to behave like a finite composite strip. For thin and angled specimens, the thermal conductivity

  4. Mo6S3I6-Au composites: synthesis, conductance, and applications.

    PubMed

    Zhang, Renyun; Hummelgård, Magnus; Dvorsek, Damjan; Mihailovic, Dragan; Olin, Håkan

    2010-08-15

    A single-step, premixing method was used to directly deposit gold nanoparticles on Mo(6)S(3)I(6) (MSI) molecular wire bundles. Gold nanoparticles with different sizes and densities were coated on the MSI by changing the concentration of the gold containing salt, HAuCl(4). TEM, SEM, and EDX characterization showed deposition of gold nanoparticles on the MSI nanowire surface. The electrical resistance of these MSI-Au composites was more than 100 times lower than that for pure MSI, and was mainly dependent on the density of the deposited gold nanoparticles. Furthermore, we immobilized thiol group-labeled oligonucleotide on the composites and then hybridized with a fully matched sequence. The resistance of the MSI-Au composites increased during the thiol step, while it decreased by hybridizing, due to the conductance difference between single- and double-stranded DNA chains. These results indicate that this new kind of MSI-Au composite could be used as a platform for different applications, including biosensors. PMID:20494366

  5. Strong and electrically conductive graphene-based composite fibers and laminates

    SciTech Connect

    Vlassiouk, Ivan V.; Polyzos, Georgios; Cooper, Ryan C.; Ivanov, Ilia N.; Keum, Jong Kahk; Paulauskas, Felix L.; Datskos, Panos G.; Smirnov, Sergei

    2015-04-28

    In this study, graphene is an ideal candidate for lightweight, high-strength composite materials given its superior mechanical properties (specific strength of 130 GPa and stiffness of 1 TPa). To date, easily scalable graphene-like materials in a form of separated flakes (exfoliated graphene, graphene oxide, and reduced graphene oxide) have been investigated as candidates for large-scale applications such as material reinforcement. These graphene-like materials do not fully exhibit all the capabilities of graphene in composite materials. In this study, we show that macro (2 inch × 2 inch) graphene laminates and fibers can be produced using large continuous sheets of single-layer graphene grown by chemical vapor deposition. The resulting composite structures have potential to outperform the current state-of-the-art composite materials in both mechanical properties and electrical conductivities (>8 S/cm with only 0.13% volumetric graphene loading and 5 × 103 S/cm for pure graphene fibers) with estimated graphene contributions of >10 GPa in strength and 1 TPa in stiffness.

  6. Anomalous hopping conduction in nanocrystalline/amorphous composites and amorphous semiconductor thin films

    NASA Astrophysics Data System (ADS)

    Kakalios, James; Bodurtha, Kent

    Composite nanostructured materials consisting of nanocrystals (nc) embedded within a thin film amorphous matrix can exhibit novel opto-electronic properties. Composite films are synthesized in a dual-chamber co-deposition PECVD system capable of producing nanocrystals of material A and embedding then within a thin film matrix of material B. Electronic conduction in composite thin films of hydrogenated amorphous silicon (a-Si:H) containing nc-germanium or nc-silicon inclusions, as well as in undoped a-Si:H, does not follow an Arrhenius temperature dependence, but rather is better described by an anomalous hopping expression (exp[-(To/T)3/4) , as determined from the ``reduced activation energy'' proposed by Zabrodskii and Shlimak. This temperature dependence has been observed in other thin film resistive materials, such as ultra-thin disordered films of Ag, Bi, Pb and Pd; carbon-black polymer composites; and weakly coupled Au and ZnO quantum dot arrays. There is presently no accepted theoretical understanding of this expression. The concept of a mobility edge, accepted for over four decades, appears to not be necessary to account for charge transport in amorphous semiconductors. Supported by NSF-DMR and the Minnesota Nano Center.

  7. Strong and electrically conductive graphene-based composite fibers and laminates

    DOE PAGESBeta

    Vlassiouk, Ivan V.; Polyzos, Georgios; Cooper, Ryan C.; Ivanov, Ilia N.; Keum, Jong Kahk; Paulauskas, Felix L.; Datskos, Panos G.; Smirnov, Sergei

    2015-04-28

    In this study, graphene is an ideal candidate for lightweight, high-strength composite materials given its superior mechanical properties (specific strength of 130 GPa and stiffness of 1 TPa). To date, easily scalable graphene-like materials in a form of separated flakes (exfoliated graphene, graphene oxide, and reduced graphene oxide) have been investigated as candidates for large-scale applications such as material reinforcement. These graphene-like materials do not fully exhibit all the capabilities of graphene in composite materials. In this study, we show that macro (2 inch × 2 inch) graphene laminates and fibers can be produced using large continuous sheets of single-layermore » graphene grown by chemical vapor deposition. The resulting composite structures have potential to outperform the current state-of-the-art composite materials in both mechanical properties and electrical conductivities (>8 S/cm with only 0.13% volumetric graphene loading and 5 × 103 S/cm for pure graphene fibers) with estimated graphene contributions of >10 GPa in strength and 1 TPa in stiffness.« less

  8. Doped SnO₂ transparent conductive multilayer thin films explored by continuous composition spread.

    PubMed

    Lee, Jin Ju; Ha, Jong-Yoon; Choi, Won-Kook; Cho, Yong Soo; Choi, Ji-Won

    2015-04-13

    Mn-doped SnO₂ thin films were fabricated by a continuous composition spread (CCS) method on a glass substrate at room temperature to find optimized compositions. The fabricated materials were found to have a lower resistivity than pure SnO₂ thin films because of oxygen vacancies generated by Mn doping. As Mn content was increased, resistivity was found to decrease for limited doping concentrations. The minimum thin film resistivity was 0.29 Ω-cm for a composition of 2.59 wt % Mn-doped SnO₂. The Sn-O vibrational stretching frequency in FT-IR showed a blue shift, consistent with oxygen deficiency. Mn-doped SnO₂/Ag/Mn-doped SnO₂ multilayer structures were fabricated using this optimized composition deposited by an on-axis radio frequency (RF) sputter. The multilayer transparent conducting oxide film had a resistivity of 7.35 × 10⁻⁵ Ω-cm and an average transmittance above 86% in the 550 nm wavelength region. PMID:25761303

  9. The effect of composition anomalies on the conductivity and density of seawater

    NASA Astrophysics Data System (ADS)

    Pawlowicz, R. A.; Wright, D.; Millero, F. J.

    2010-12-01

    As seawater circulates through the global ocean, its relative composition undergoes small variations. This results in changes to the conductivity/salinity/density relationship, which is currently well-defined only for Standard Seawater obtained from a particular area in the North Atlantic. Although these changes have been ignored for 30 years, they are in fact the largest source of errors in the determination of the thermodynamic properties of real seawater using the equation of state (either EOS80 or the newer TEOS-10). Here we describe a theoretical model that relates seawater composition, conductivity, and density. A numerical implementation of the model can be used to predict density anomalies resulting from observed conductivities, carbonate-system parameters, and nutrient concentrations. Predictions of density anomalies made this way for a number of hydrographic sections are shown below. Calculations replicate direct observations of density anomalies in both laboratory experiments and in the open ocean. Theoretical analysis suggests that a hierarchy of salinity variables are required to fully describe the effects of anomalous seawater, but numerical experimentation shows that simple conversion factors can be used to relate them all in typical open-ocean situations. These results are incorporated into the new seawater manual (IOC, SCOR, and IAPSO, The International Thermodynamic Equation of Seawater - 2010: Calculation and Use of Thermodynamic Properties,UNESCO, 2010, also at www.teos-10.org) and should be useful in future attempts to understand and model global ocean circulation. Model-calculated density anomalies over several trans-oceanic sections

  10. NEW PROTON CONDUCTIVE COMPOSITE MATERIALS WITH INORGANIC AND STYRENE GRAFTED AND SULFONATED VDF/CTFE FLUOROPOLYMERS

    SciTech Connect

    Lvov, Serguei; Payne, Terry L

    2008-01-01

    Creation of new membrane materials for proton exchange membrane fuel cells (PEMFCs) operating at elevated temperature and low relative humidity (RH) is one of the major challenges in the implementation of the fuel cell technology. New candidate membrane materials are required to efficiently conduct protons at 120oC and RH down to 15%. Based on these criteria, we are working on the development of new membrane materials, which are composites of inorganic proton conductors with a functionalized and cross-linkable Teflon-type polymer. The synthesis of crosslinkable P(VDF-CTFE) copolymer with controllable structure, molecular weight and terminal and side chain silane groups was described in [1]. The chemistry of the synthesis was centered on a specifically designed functional borane initiator containing silane groups. The major role of polymer matrix is to maintain the continuity of charge transfer and to ensure membrane integrity. The primary considerations include sufficient proton conductivity, thermal and chemical stability at elevated temperature, mechanical strength, compatibility with inorganic particulate phases, processibility to form uniform thin film, and cost effectiveness. Several classes of inorganic proton conductors with high water retention capability, including mesoporous materials (sulfated and/or sulfonated alumina, zirconia, titania) and zirconium phosphate of different structure have been chosen as candidate components for the new composite membranes for PEMFC operation at elevated temperatures and reduced RH. The primary requirement to the inorganic phases is the ability to provide high proton conductivity with the minimum amount of water (reduced humidity).

  11. Superhydrophobic and conductive carbon nanofiber/PTFE composite coatings for EMI shielding.

    PubMed

    Das, Arindam; Hayvaci, Harun T; Tiwari, Manish K; Bayer, Ilker S; Erricolo, Danilo; Megaridis, Constantine M

    2011-01-01

    This paper presents a solvent-based, mild method to prepare superhydrophobic, carbon nanofiber/PTFE-filled polymer composite coatings with high electrical conductivity and reports the first data on the effectiveness of such coatings as electromagnetic interference (EMI) shielding materials. The coatings are fabricated by spraying dispersions of carbon nanofibers and sub-micron PTFE particles in a polymer blend solution of poly(vinyledene fluoride) and poly(methyl methacrylate) on cellulosic substrates. Upon drying, coatings display static water contact angles as high as 158° (superhydrophobic) and droplet roll-off angles of 10° indicating self-cleaning ability along with high electrical conductivities (up to 309 S/m). 100 μm-thick coatings are characterized in terms of their EMI shielding effectiveness in the X-band (8.2-12.4 GHz). Results show up to 25 dB of shielding effectiveness, which changed little with frequency at a fixed composition, thus indicating the potential of these coatings for EMI shielding applications and other technologies requiring both extreme liquid repellency and high electrical conductivity. PMID:20889160

  12. Ion-Electron-Conducting Polymer Composites: Promising Electromagnetic Interference Shielding Material.

    PubMed

    Vyas, Manoj Kumar; Chandra, Amita

    2016-07-20

    Polymer nanocomposites consisting of poly(vinylidenefluoride-co-hexafluoropropylene) PVdF-HFP, inorganic salt (LiBF4), organic salt (EMIMBF4), multiwalled carbon nanotubes (MWCNTs), and Fe3O4 nanoparticles were prepared as electromagnetic shield material. Improvement in conductivity and dielectric property due to the introduction of EMIMBF4, LiBF4, and MWCNTs was confirmed by complex impedance spectroscopy. The highest conductivity obtained is ∼1.86 mS/cm. This is attributed to the high ionic conductivity of the ionic liquids and the formation of a connecting network by the MWCNTs facilitating electron conduction. The total electromagnetic interference (EMI) shielding effectiveness has a major contribution to it due to absorption. Although the total shielding effectiveness in the Ku band (12.4-18 GHz) of pure ion-conducting system was found to be ∼19 dB and that for the polymer composites which are mixed (ion + electron) conductors is ∼46 dB, the contributions due to absorption are ∼16 and ∼42 dB, respectively. PMID:27351810

  13. Applications of high thermal conductivity composites to electronics and spacecraft thermal design

    NASA Technical Reports Server (NTRS)

    Sharp, G. Richard; Loftin, Timothy A.

    1990-01-01

    Recently, high thermal conductivity continuous graphite fiber reinforced metal matrix composites (MMC's) have become available that can save much weight over present methods of heat conduction. These materials have two or three times higher thermal conductivity in the fiber direction than the pure metals when compared on a thermal conductivity to weight basis. Use of these materials for heat conduction purposes can result in weight savings of from 50 to 70 percent over structural aluminum. Another significant advantage is that these materials can be used without the plumbing and testing complexities that accompany the use of liquid heat pipes. A spinoff of this research was the development of other MMC's as electronic device heat sinks. These use particulates rather than fibers and are formulated to match the coefficient of thermal expansion of electronic substrates in order to alleviate thermally induced stresses. The development of both types of these materials as viable weight saving substitutes for traditional methods of thermal control for electronics packaging and also for spacecraft thermal control applications are the subject of this report.

  14. Highly conductive and flexible polymer composites with improved mechanical and electromagnetic interference shielding performances

    NASA Astrophysics Data System (ADS)

    Chen, Mengting; Zhang, Ling; Duan, Shasha; Jing, Shilong; Jiang, Hao; Luo, Meifang; Li, Chunzhong

    2014-03-01

    New flexible and conductive materials (FCMs) comprising a quartz fiber cloth (QFC) reinforced multi-walled carbon nanotubes (MWCNTs)-carbon aerogel (QMCA) and poly(dimethylsiloxane) (PDMS) have been successfully prepared. The QMCA-PDMS composite with a very low loading of MWCNTs (~1.6 wt%) demonstrates enhanced performance in tensile strength (129.6 MPa), modulus (3.41 GPa) and electromagnetic interference (EMI) shielding efficiency (SE) (~16 dB in X-band (8.2-12.4 GHz) region). Compared to the QC (where MWCNTs were simply deposited on the QFCs without forming aerogel networks) based PDMS composite, a ~120%, 330% and 178% increase of tensile strength, modulus, and EMI SE was obtained, respectively. Moreover, the EMI SE of the QMCA-PDMS composite can further reach 20 dB (a SE level needed for commercial applications) with only 2 wt% MWCNTs. Furthermore, the conductivity of the QMCA-PDMS laminate can reach 1.67 S cm-1 even with very low MWCNTs (1.6 wt%), which still remains constant even after 5000 times bending and exhibits an increase of ~170% than that of MWCNT-carbon aerogel (MCA)-PDMS at 20% strain. Such intriguing performances are mainly attributed to their unique networks in QMCA-PDMS composites. In addition, these features can also protect electronics against harm from external forces and EMI, giving the brand-new FCMs huge potential in next-generation devices, like E-skin, robot joints and so on.New flexible and conductive materials (FCMs) comprising a quartz fiber cloth (QFC) reinforced multi-walled carbon nanotubes (MWCNTs)-carbon aerogel (QMCA) and poly(dimethylsiloxane) (PDMS) have been successfully prepared. The QMCA-PDMS composite with a very low loading of MWCNTs (~1.6 wt%) demonstrates enhanced performance in tensile strength (129.6 MPa), modulus (3.41 GPa) and electromagnetic interference (EMI) shielding efficiency (SE) (~16 dB in X-band (8.2-12.4 GHz) region). Compared to the QC (where MWCNTs were simply deposited on the QFCs without forming

  15. Stability test of conduction-cooled LTS/HTS composite coil

    NASA Astrophysics Data System (ADS)

    Cui, Ying Min; Wang, Yin Shun; Lv, Gang; Pi, Wei

    2016-06-01

    A small LTS/HTS composite coil made of NbTi/Cu and YBCO, with an inner diameter of 80 mm, an outer diameter of 88mm, a height of 50 mm, and an inductance of 5.5 μH, was designed to test its heat disturbance performance in a GM cryocooler. For comparison, a conventional LTS coil of a similar size made of NbTi/Cu wire was also tested. Transport current was applied from 50 A to 700 A at 8 K and 8.5 K, respectively. The two coils’ heat disturbance, minimum quench energy and quench propagation velocity performance were investigated and simulated. The results indicate that the LTS/HTS composite coil shows better thermal stability and is more fit for operation in conductive cryocooler systems compared to LTS coils.

  16. Strength and conductivity of unidirectional copper composites reinforced by continuous SiC fibers

    NASA Astrophysics Data System (ADS)

    Kimmig, S.; Allen, I.; You, J. H.

    2013-09-01

    A SiC long fiber-reinforced copper composite offers a beneficial combination of high strength and high thermal conductivity at elevated temperatures. Both properties make the composite a promising material for the heat sink of high-heat-flux components. In this work, we developed a novel Cu/SiCf composite using the Sigma fiber. Based on HIP technique, a metallurgical process was established for fabricating high quality specimens using a TiC interface coating. Extensive tensile tests were conducted on the unidirectionally reinforced composite at 20 °C and 300 °C for a wide range of fiber volume fraction (Vf). In this paper, a large amount of test data is presented. The transversal thermal conductivity varies from 260 to 130 W/mK at 500 °C as Vf is increased from 13% to 37%. The tensile strength reached up to 1246 MPa at 20 °C for Vf = 37.6%, where the fracture strain was limited to 0.8%. The data of both elastic modulus and ultimate strength exhibited a good agreement with the rule-of-mixture predictions indicating a high quality of the materials. The strength of the composite with the Sigma fibers turned out to be superior to those of the SCS6 fibers at 300 °C, although the SCS6 fiber actually has a higher strength than the Sigma fiber. The fractographic pictures of tension test and fiber push-out test manifested a sufficient interfacial bonding. Unidirectional copper composite reinforced by long SiC fibers was fabricated using the Sigma SM1140+ fiber for a wide range of fiber volume fraction from 14% to 40%. Extensive tensile tests were carried out at RT and 300 °C. The data of ultimate strength as well as elastic modulus exhibited a good agreement with the rule-of-mixture predictions indicating a high quality of the materials. In terms of the tensile strength, the Cu/Sigma composite turned out to be superior to the previous Cu/SCS6 composite at 300 °C, while comparable at RT, although the SCS6 fiber has a higher strength than the Sigma fiber. Such a

  17. Nano-engineered Multiwall Carbon Nanotube-copper Composite Thermal Interface Material for Efficient Heat Conduction

    NASA Technical Reports Server (NTRS)

    Ngo, Quoc; Cruden, Brett A.; Cassell, Alan M.; Sims, Gerard; Li, Jun; Meyyappa, M.; Yang, Cary Y.

    2005-01-01

    Efforts in integrated circuit (IC) packaging technologies have recently been focused on management of increasing heat density associated with high frequency and high density circuit designs. While current flip-chip package designs can accommodate relatively high amounts of heat density, new materials need to be developed to manage thermal effects of next-generation integrated circuits. Multiwall carbon nanotubes (MWNT) have been shown to significantly enhance thermal conduction in the axial direction and thus can be considered to be a candidate for future thermal interface materials by facilitating efficient thermal transport. This work focuses on fabrication and characterization of a robust MWNT-copper composite material as an element in IC package designs. We show that using vertically aligned MWNT arrays reduces interfacial thermal resistance by increasing conduction surface area, and furthermore, the embedded copper acts as a lateral heat spreader to efficiently disperse heat, a necessary function for packaging materials. In addition, we demonstrate reusability of the material, and the absence of residue on the contacting material, both novel features of the MWNT-copper composite that are not found in most state-of-the-art thermal interface materials. Electrochemical methods such as metal deposition and etch are discussed for the creation of the MWNT-Cu composite, detailing issues and observations with using such methods. We show that precise engineering of the composite surface affects the ability of this material to act as an efficient thermal interface material. A thermal contact resistance measurement has been designed to obtain a value of thermal contact resistance for a variety of different thermal contact materials.

  18. Highly conductive and flexible polymer composites with improved mechanical and electromagnetic interference shielding performances.

    PubMed

    Chen, Mengting; Zhang, Ling; Duan, Shasha; Jing, Shilong; Jiang, Hao; Luo, Meifang; Li, Chunzhong

    2014-04-01

    New flexible and conductive materials (FCMs) comprising a quartz fiber cloth (QFC) reinforced multi-walled carbon nanotubes (MWCNTs)-carbon aerogel (QMCA) and poly(dimethylsiloxane) (PDMS) have been successfully prepared. The QMCA-PDMS composite with a very low loading of MWCNTs (∼1.6 wt%) demonstrates enhanced performance in tensile strength (129.6 MPa), modulus (3.41 GPa) and electromagnetic interference (EMI) shielding efficiency (SE) (∼16 dB in X-band (8.2-12.4 GHz) region). Compared to the QC (where MWCNTs were simply deposited on the QFCs without forming aerogel networks) based PDMS composite, a ∼120%, 330% and 178% increase of tensile strength, modulus, and EMI SE was obtained, respectively. Moreover, the EMI SE of the QMCA-PDMS composite can further reach 20 dB (a SE level needed for commercial applications) with only 2 wt% MWCNTs. Furthermore, the conductivity of the QMCA-PDMS laminate can reach 1.67 S cm(-1) even with very low MWCNTs (1.6 wt%), which still remains constant even after 5000 times bending and exhibits an increase of ∼170% than that of MWCNT-carbon aerogel (MCA)-PDMS at 20% strain. Such intriguing performances are mainly attributed to their unique networks in QMCA-PDMS composites. In addition, these features can also protect electronics against harm from external forces and EMI, giving the brand-new FCMs huge potential in next-generation devices, like E-skin, robot joints and so on. PMID:24577052

  19. Carbon nanotubes filled polymer composites: A comprehensive study on improving dispersion, network formation and electrical conductivity

    NASA Astrophysics Data System (ADS)

    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

  20. Conducting polymer composite film incorporated with aligned carbon nanotubes for transparent, flexible and efficient supercapacitor

    PubMed Central

    Lin, Huijuan; Li, Li; Ren, Jing; Cai, Zhenbo; Qiu, Longbin; Yang, Zhibin; Peng, Huisheng

    2013-01-01

    Polyaniline composite films incorporated with aligned multi-walled carbon nanotubes (MWCNTs) are synthesized through an easy electrodeposition process. These robust and electrically conductive films are found to function as effective electrodes to fabricate transparent and flexible supercapacitors with a maximum specific capacitance of 233 F/g at a current density of 1 A/g. It is 36 times of bare MWCNT sheet, 23 times of pure polyaniline and 3 times of randomly dispersed MWCNT/polyaniline film under the same conditions. The novel supercapacitors also show a high cyclic stability. PMID:23443325

  1. Transparent, conductive, and printable composites consisting of TEMPO-oxidized nanocellulose and carbon nanotube.

    PubMed

    Koga, Hirotaka; Saito, Tsuguyuki; Kitaoka, Takuya; Nogi, Masaya; Suganuma, Katsuaki; Isogai, Akira

    2013-04-01

    Ultrastrong, transparent, conductive and printable nanocomposites were successfully prepared by mixing single-walled carbon nanotubes (CNTs) with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibrils (TOCNs) with abundant sodium carboxyl groups on the crystalline nanocellulose surfaces. The surface-anionic cellulose nanofibrils had reinforcing and nanodispersing effects on the CNTs both in water used as the dispersed medium and in the dried composite film, providing highly conductive and printable nanocomposites with a small amount of CNTs. TOCNs are therefore expected as an effective flexible matrix that can be used as an alternative to conventional polymers for various electrical materials, when nanocomposited with CNTs and also graphene. Our findings provide a promising route to realize green and flexible electronics. PMID:23428212

  2. Applications of high thermal conductivity composites to electronics and spacecraft thermal design

    NASA Technical Reports Server (NTRS)

    Sharp, G. Richard; Loftin, Timothy A.

    1990-01-01

    Recently, high thermal conductivity graphite fiber-reinforced metal matrix composites (MMCs) have become available that can save weight over present methods of heat conduction. Another significant advantage is that these materials can be used without the plumbing and testing complexities that accompany the use of liquid heat pipes. A spinoff of this research was the development of other MMCs as electronic device heat sinks. These use particulates rather than fibers and are formulated to match the coefficient of thermal expansion of electronic substrates in order to alleviate thermally induced stresses. The development of both types of these materials as viable weight-saving substitutes for the traditional methods of thermal control for electronics packaging and also for spacecraft thermal control applications are the subjects of this report.

  3. The Origin of High Thermal Conductivity and Ultralow Thermal Expansion in Copper-Graphite Composites.

    PubMed

    Firkowska, Izabela; Boden, André; Boerner, Benji; Reich, Stephanie

    2015-07-01

    We developed a nanocomposite with highly aligned graphite platelets in a copper matrix. Spark plasma sintering ensured an excellent copper-graphite interface for transmitting heat and stress. The resulting composite has superior thermal conductivity (500 W m(-1) K(-1), 140% of copper), which is in excellent agreement with modeling based on the effective medium approximation. The thermal expansion perpendicular to the graphite platelets drops dramatically from ∼20 ppm K(-1) for graphite and copper separately to 2 ppm K(-1) for the combined structure. We show that this originates from the layered, highly anisotropic structure of graphite combined with residual stress under ambient conditions, that is, strain-engineering of the thermal expansion. Combining excellent thermal conductivity with ultralow thermal expansion results in ideal materials for heat sinks and other devices for thermal management. PMID:26083322

  4. Effects of neutron irradiation on thermal conductivity of SiC-based composites and monolithic ceramics

    SciTech Connect

    Senor, D.J.; Youngblood, G.E.; Moore, C.E.; Trimble, D.J.; Newsome, G.A.; Woods, J.J.

    1996-12-31

    A variety of SiC-based composites and monolithic ceramics were characterized by measuring their thermal diffusivity in the unirradiated, thermal annealed, and irradiated conditions over the temperature range 400 to 1000{degree}C. The irradiation was conducted in the FBR-II to doses of 33 and 43 dpa-SiC at a nominal temperature of 1000{degree}C. The annealed specimens were held at 1010{degree}C for 165 days to approximately duplicate the thermal exposure of the irradiated specimens. Thermal diffusivity was measured using the laser flash method, and was converted to thermal conductivity using density data and calculated specific heat values. 24 refs., 16 figs., 1 tab.

  5. Separation of conductivity and distance measurements for eddy current nondestructive inspection of graphite composite materials

    NASA Astrophysics Data System (ADS)

    Dufour, Isabelle; Placko, Dominique

    1993-06-01

    This article deals with the study of a process based on the principle of eddy current sensors for the nondestructive evaluation of graphite composite plates. This research has been carried out in the Laboratoire d'Electricitd Signaux et Robotique by the team working on datacollecting sensors for robotics in collaboration with Aerospatiale. Eddy current sensors are characterized by their impedance, which varies when a conducting material is approached in their sensitive area. For a given sensor, the output signal depends directly on the electrical and geometrical properties of the object. In the case discussed here, the interesting data are the distance between the sensor and the object, and its local conductivity. In order to invert the relationships between the sensor signal and the properties of the material, an external parametrical model has been developed. A scanning of the surface with a sensor designed for good spatial resolution measurements gives two accurate maps of the useful data.

  6. Thermal conductivity and retention characteristics of composites made of boron carbide and carbon fibers with extremely high thermal conductivity for first wall armour

    NASA Astrophysics Data System (ADS)

    Jimbou, R.; Kodama, K.; Saidoh, M.; Suzuki, Y.; Nakagawa, M.; Morita, K.; Tsuchiya, B.

    1997-02-01

    The thermal conductivity of the composite hot-pressed at 2100°C including B 4C and carbon fibers with a thermal conductivity of 1100 W/ m· K was nearly the same as that of the composite including carbon fibers with a thermal conductivity of 600 W/ m· K. This resulted from the higher amount of B diffused into the carbon fibers through the larger interface. The B 4C content in the composite can be reduced from 35 to 20 vol% which resulted from the more uniform distribution of B 4C by stacking the flat cloth woven of carbon fibers (carbon fiber plain fabrics) than in the composite with 35 vol% B 4C including curled carbon fiber plain fabrics. The decrease in the B 4C content does not result in the degradation of D (deuterium)-retention characteristics or D-recycling property, but will bring about the decreased amount of the surface layer to be melted under the bombardment of high energy hydrogen ions such as disruptions because of higher thermal conduction of the composite.

  7. Computational investigation on thermal conductivity behavior of Al 6061-SiC-Gr hybrid metal matrix composites

    NASA Astrophysics Data System (ADS)

    Krishna, S. A. Mohan; Shridhar, T. N.; Krishnamurthy, L.

    2015-10-01

    Metal matrix composites (MMCs) are regarded to be one of the most principal classifications in composite materials. The thermal characterization of hybrid MMCs has become increasingly important in a wide range of applications. Thermal conductivity is one of the most important properties of MMCs. Since nearly all MMCs are used in various temperature ranges, measurement of thermal conductivity as a function of temperature is necessary in order to know the behavior of the material. In the present research, evaluation of thermal conductivity has been accomplished for aluminum alloy (Al) 6061, silicon carbide (SiC) and graphite (Gr) hybrid MMCs from room temperature to 300∘C. Al-based composites reinforced with SiC and Gr particles have been prepared by stir casting technique. The thermal conductivity behavior of hybrid composites with different percentage compositions of reinforcements has been investigated using laser flash technique. The results have indicated that the thermal conductivity of the different compositions of hybrid MMCs decreases by the addition of Gr with SiC and Al 6061. Few empirical models have been validated concerning with the evaluation of thermal conductivity of composites. Using the experimental values namely density, thermal conductivity, specific heat capacity and enthalpy at varying temperature ranges, computational investigation has been carried out to evaluate the thermal gradient and thermal flux.

  8. Towards tunable sensitivity of electrical property to strain for conductive polymer composites based on thermoplastic elastomer.

    PubMed

    Lin, Lin; Liu, Siyao; Zhang, Qi; Li, Xiaoyu; Ji, Mizhi; Deng, Hua; Fu, Qiang

    2013-06-26

    The use of conductive polymer composites (CPCs) as strain sensors has been widely investigated and various resistivity-strain sensitivities are desirable for different applications. In this study, the use of mixed carbon fillers and functionalized carbon nanotubes was demonstrated to be vital for preparing thermoplastic polyurethane (TPU)-based strain sensors with tunable sensitivity. To understand the strain sensing behavior, we carried out scanning electron microscopy (SEM), Raman spectroscopy, wide-angle X-ray diffraction (WAXD), mechanical test, and rheology-electrical measurement. Hybrid fillers of multi-walled carbon nanotubes (MWNTs) and carbon black (CB) could reduce the entanglement in conductive network structure, thus increase the resistivity-strain sensitivity. Furthermore, incorporation of additional functionalized MWNTs in the CPCs could enhance the interfacial interaction between nanofillers and TPU, leading to further increase in sensitivity. Through such a simple method, strain sensors could be efficiently fabricated with large strain-sensing capability (strain as large as 200%) and a wide range of strain sensitivity (gauge factor ranging from 5 to 140238). Finally, the exponential revolution of resistive response to strain was fitted with a model based on tunneling theory by Simmons. It was observed that the change in tunneling distance and the number of conductive pathways could be accelerated significantly by adjusting conductive network structure and interfacial interaction. This study provides a guideline for the preparation of high-performance CPC strain sensors with a large range of resistivity-strain sensitivity. PMID:23713404

  9. An addressable conducting network for autonomic structural health management of composite structures

    NASA Astrophysics Data System (ADS)

    Takahashi, Kosuke; Park, Jong Se; Hahn, H. Thomas

    2010-10-01

    The electrical resistance change method (ERCM) has long been an area of interest as an in-service health monitoring system. To apply the ERCM to existing structures, a new concept, the addressable conducting network (ACN), is proposed for autonomic structural health management of graphite/polymer composites. The ACN consists of two sets of conducting lines normal to each other, where one set resides on the top surface of the laminate and the other on the bottom surface. Damage can be detected by monitoring the resistance change 'through the laminate thickness' between two lines. By using a thermally mendable polymer as the matrix, the same conducting lines can be used to supply the electric current needed for resistive heating, thereby allowing the detected damage to be healed. As shown experimentally, the electrical resistance change method using an ACN distinguishes between laminates made of properly and improperly cured prepreg as well as revealing damage generated during three-point bending tests. Finite element analysis was performed to examine the feasibility of the ACN and indicated that the damage can be easily located from the spatial distribution of resistance changes and that the damaged area can be locally heated by supplying a large amount of current to selected conducting lines.

  10. Design and characterization of a conductive nanostructured polypyrrole-polycaprolactone coated magnesium/PLGA composite for tissue engineering scaffolds.

    PubMed

    Liu, Haixia; Wang, Ran; Chu, Henry K; Sun, Dong

    2015-09-01

    A novel biodegradable and conductive composite consisting of magnesium (Mg), polypyrrole-block-ploycaprolactone (PPy-PCL), and poly(lactic-co-glycolic acid) (PLGA) is synthesized in a core-shell-skeleton manner for tissue engineering applications. Mg particles in the composite are first coated with a conductive nanostructured PPy-PCL layer for corrosion resistance via the UV-induced photopolymerization method. PLGA matrix is then added to tailor the biodegradability of the resultant composite. Composites with different composition ratios are examined through experiments, and their material properties are characterized. The in vitro experiments on culture of 293FT-GFP cells show that the composites are suitable for cell growth and culture. Biodegradability of the composite is also evaluated. By adding PLGA matrix to the composite, the degrading time of the composite can last for more than eight weeks, hence providing a longer period for tissue formation as compared to Mg composites or alloys. The findings of this research will offer a new opportunity to utilize a conductive, nanostructured-coated Mg/PLGA composite as the scaffold material for implants and tissue regeneration. PMID:25690806

  11. High Thermal Conductivity Polymer Matrix Composites (PMC) for Advanced Space Radiators

    NASA Technical Reports Server (NTRS)

    Shin, E. Eugene; Bowman, Cheryl; Beach, Duane

    2007-01-01

    High temperature polymer matrix composites (PMC) reinforced with high thermal conductivity (approx. 1000 W/mK) pitch-based carbon fibers are evaluated for a facesheet/fin structure of large space radiator systems. Significant weight reductions along with improved thermal performance, structural integrity and space durability toward its metallic counterparts were envisioned. Candidate commercial resin systems including Cyanate Esters, BMIs, and polyimide were selected based on thermal capabilities and processability. PMC laminates were designed to match the thermal expansion coefficient of various metal heat pipes or tubes. Large, but thin composite panels were successfully fabricated after optimizing cure conditions. Space durability of PMC with potential degradation mechanisms was assessed by simulated thermal aging tests in high vacuum, 1-3 x 10(exp -6) torr, at three temperatures, 227 C, 277 C, and 316 C for up to one year. Nanocomposites with vapor-grown carbon nano-fibers and exfoliated graphite flakes were attempted to improve thermal conductivity (TC) and microcracking resistance. Good quality nanocomposites were fabricated and evaluated for TC and durability including radiation resistance. TC was measured in both in-plan and thru-the-thickness directions, and the effects of microcracks on TC are also being evaluated. This paper will discuss the systematic experimental approaches, various performance-durability evaluations, and current subcomponent design and fabrication/manufacturing efforts.

  12. Modeling the transverse thermal conductivity of 3D-SICF/ SIC composites

    SciTech Connect

    Youngblood, Gerald E; Jones, Russell H; Yamada, Reiji

    2004-06-30

    Our previously developed hierarchical two-layer (H2L) model was modified to describe the effective transverse thermal conductivity (Keff) of a three-dimensional (3D) SiC/SiC composite plate made with cross-layered and Z-stitched X:Y:Z uniaxial fiber tow sub-units. As before, the model describes Keff in terms of constituent, microstructural and architectural properties that include the expected effects of fiber-matrix interfacial conductance, of high fiber packing fractions within individual tow sub-units and of the non-uniform porosity contents, shapes and orientations within these sub-units. Model predictions were obtained for two versions of a 3D-Tyranno SA/PyC/ICVI-SiC composite that had similar fiber/matrix pyrocarbon (PyC) interfaces, relatively high bulk densities (~2.88 g/cc), and an X:Y configuration with fiber content ratios 1:1. The only major difference between the two versions was their Z-stitch fiber content where the relative fiber ratios were 0.1 and 1.2 in the Z sub-units.

  13. Alternating current conductivity and dielectric relaxation of PANI:PVDF composites

    NASA Astrophysics Data System (ADS)

    Saïdi, Sami; Mannaî, Aymen; Bouzitoun, Mouna; Belhadj Mohamed, Abdellatif

    2014-04-01

    In this work, PANI:PVDF composites films were prepared with different PANI contents (p = 1, 2, 3, 4 and 5%). The resulting films were dried at various temperatures such as 30, 90 and 120 °C. The alternating current mechanisms and dielectric relaxation and of PANI:PVDF films were studied using complex impedance spectroscopy over a wide range of temperature (303-453 K) and a frequency range (1 kHz to 1 MHz). We found that the ac conductivity in PANI:PVDF composite is governed by correlated barrier hopping (CBH) model. In dielectric loss modulus study, two relaxation processes were identified. The first peak was associated to Maxwell Wagner-Sillas (MWS) relaxation whereas the second one which obtained at higher frequency was attributed to the αc relaxation. For PANI:PVDF film which dried at 30 °C, the MWS relaxation appears only at higher temperature. The temperature dependence of αc relaxation was suitably fitted according to Vogel Flucher Temman model whereas MWS relaxation follows Arrhenius type behavior. The effect of drying temperature on microstructure and phase crystallization of PVDF in the composites was carried out using atomic force microscopy (AFM) and Fourier transform infrared (FTIR) spectroscopy. These results were used to find a reasonable correlation between microstructure and electrical properties.

  14. Evolution of composition, molar mass, and conductivity during the free radical copolymerization of polyelectrolytes.

    PubMed

    Alb, Alina M; Paril, Ahmet; Catalgil-Giz, Huceste; Giz, Ahmet; Reed, Wayne F

    2007-07-26

    Despite their importance in biological and technological contexts, copolymeric polyelectrolytes (or "copolyelectrolytes") continue to present challenges to theorists and experimentalists. The first results of a unified approach to the kinetics and mechanisms of copolyelectrolyte synthesis and the physical characteristics of the resulting polymers are presented. The free radical copolymerization of 4-vinylbenzenesulfonic acid sodium salt and acrylamide was monitored using automatic continuous online monitoring of polymerization reactions (ACOMP), from which the average bivariate composition and mass distributions were determined. Composition drift was related to the evolution of conductivity. In some cases bimodal populations of copolyelectrolyte and homopolymeric poly(acrylamide) resulted, i.e., blends of copolyelectrolyte and neutral homopolymer. The end-product scattering behavior depended on whether the end-product was bimodal or not, as demonstrated using automatic continuous mixing (ACM) in conjunction with light scattering and viscosity. Negative light-scattering third virial coefficients were found for bimodal end-products. This combined approach may allow connecting the synthesis kinetics to the resulting "trivariate" distribution of composition, molar mass, and linear charge density, which in turn controls the properties of end-product solutions, such as chain conformations, interparticle interactions, viscosity, interactions with colloids and other polymers, phase separation, etc. Unified results may allow testing and improvement of existing polyelectrolyte theories, development of new quantitative physicochemical models, provide advanced characterization methods, set the stage for studying more complex copolyelectrolytes, such as hydrophobically modified ones, and provide tools for ultimately controlling and tailoring the synthesis and properties of copolyelectrolytes. PMID:17441756

  15. Electrical conduction and photoresponses of gamma-ray-irradiated single-stranded DNA/single-walled carbon nanotube composite systems

    NASA Astrophysics Data System (ADS)

    Hong, W.; Lee, E. M.; Kim, D. W.; Lee, Cheol Eui

    2015-04-01

    Effects of gamma-ray irradiation on the electrical conductivity and photoresponse have been studied for single-stranded DNA (ssDNA)/single-walled carbon nanotube (SWNT) composite films. The temperature-dependent electrical conductivity of the ssDNA/SWNT composite films, well described by a fluctuation-induced tunneling model, indicated modification of the barrier for thermally activated conduction by the gamma-ray irradiation. Besides, the photoresponse measurements indicated modified photoexcited charge carrier generation and oxygen photodesorption in the composite systems due to the gamma-ray irradiation.

  16. Strain and damage self-sensing cement composites with conductive graphene nanoplatelet

    NASA Astrophysics Data System (ADS)

    Pang, Sze Dai; Gao, Hongchen J.; Xu, Chunying; Quek, Ser Tong; Du, Hongjian

    2014-04-01

    A novel cement composite containing graphene nanoplatelet (GNP) which can sense its own strain and damage is introduced in this paper. Piezoresistive strain sensing was investigated for mortar specimens with GNP under both cyclic and monotonically increasing compressive and tensile strain. Under compression, the electrical resistance decreased with increasing strain and the normalized resistance can be described by a bilinear curve with a kink at about 400 microstrain. At low strain, a high gauge factor exceeding 103 in magnitude was obtained and it increased almost linearly with the GNP content. This can be attributed primarily to the reducing interfacial distance and forming of better contacts between GNP and cement paste when the composite was initially loaded. At higher compressive strain beyond 400 microstrain, the gauge factor is consistently about 102 for GNP content exceeding the percolation threshold. A different response was observed for specimens under tension due to the formation and propagation of microcracks even at low tensile strain due to the brittleness of the material. The initial gauge factor is of the order 102 for tensile strain up to 100 microstrain and it increases exponentially beyond that. The damage self-sensing capability of this conductive cement composites is explored using electric potential method. Closed form expression for the assessment of damage are derived based on the mathematical analogy between the electrostatic field and the elastostatic field under anti-plane shear loading. The derived expression provide a quick and accurate assessment of the damage of this conductive material which is characterized by its change in compliance.

  17. Correlation between Raman spectroscopy and electrical conductivity of graphite/polyaniline composites reacted with hydrogen peroxide

    NASA Astrophysics Data System (ADS)

    Aymen, Mannai; Sami, Saidi; Ahmed, Souissi; Fethi, Gmati; Abdellatif, Belhadj Mohamed

    2013-08-01

    The aim of this work is to correlate the Raman spectroscopic studies to the electrical properties of graphite/polyaniline composites (G/PANI) reacted with hydrogen peroxide. Raman spectroscopic studies have been performed for G/PANI composites with different graphite weight concentrations (y% = 0, 10, 20, 50). As expected, Raman bands situated at 1350 and 1580 cm-1 coming from graphite lattice appear, and their intensity increases with increasing graphite concentrations. The measured Raman region (1170-1800 cm-1) of PANI reacted with hydrogen peroxide was convoluted and fitted with seven Lorentzian curves. Three Lorentzian curves centred at 1609, 1578 and 1336 cm-1 are investigated. We find that the band at 1578 cm-1 attributed to the C=C stretching vibration in the quinonoid ring (Q) is slightly shifted to 1584 cm-1 and its intensity increases during the reaction with hydrogen peroxide. However, the peaks at 1609 and 1336 cm-1 attributed respectively to the C-C stretching of the benzenoid ring (B) and C-N+. vibration of delocalized polaronic structures (protonation band—PB), keep the same position and their intensities decrease. This could be interpreted as a deprotonation of imines nitrogen atoms in PANI. These results were correlated with the electrical percolation behaviour which occurs in the composite. Indeed, the electrical conductivity of G/PANI composites treated with H2O2 increases with increasing G weight concentration, only when this later becomes higher than a critical concentration yc known as the percolation threshold. We find that the percolation behaviour is linked to the intensity decrease of B and PB bands and to the intensity increase of Q band.

  18. Highly sensitive piezo-resistive graphite nanoplatelet-carbon nanotube hybrids/polydimethylsilicone composites with improved conductive network construction.

    PubMed

    Zhao, Hang; Bai, Jinbo

    2015-05-13

    The constructions of internal conductive network are dependent on microstructures of conductive fillers, determining various electrical performances of composites. Here, we present the advanced graphite nanoplatelet-carbon nanotube hybrids/polydimethylsilicone (GCHs/PDMS) composites with high piezo-resistive performance. GCH particles were synthesized by the catalyst chemical vapor deposition approach. The synthesized GCHs can be well dispersed in the matrix through the mechanical blending process. Due to the exfoliated GNP and aligned CNTs coupling structure, the flexible composite shows an ultralow percolation threshold (0.64 vol %) and high piezo-resistive sensitivity (gauge factor ∼ 10(3) and pressure sensitivity ∼ 0.6 kPa(-1)). Slight motions of finger can be detected and distinguished accurately using the composite film as a typical wearable sensor. These results indicate that designing the internal conductive network could be a reasonable strategy to improve the piezo-resistive performance of composites. PMID:25898271

  19. Electrical properties of polypropylene-based composites controlled by multilayered distribution of conductive particles.

    PubMed

    Gao, Wanli; Zheng, Yu; Shen, Jiabin; Guo, Shaoyun

    2015-01-28

    Materials consisting of alternating layers of pure polypropylene (PP) and carbon black filled polypropylene (PPCB) were fabricated in this work. The electrical behaviors of the multilayered composites were investigated from two directions: (1) Parallel to interfaces. The confined layer space allowed for a more compact connection between CB particles, while the conductive pathways tended to be broken up with increasing number of layers leading to a distinct enhancement of the electrical resistivity due to the separation of insulated PP layers. (2) Vertical to interfaces. The alternating assemblies of insulated and conductive layers like a parallel-plate capacitor made the electrical conductivity become frequency dependent. Following the layer multiplication process, the dielectric permittivity was significantly enhanced due to the accumulation of electrical charges at interfaces. Thus, as a microwave was incident on the dielectric medium, the interfacial polarization made the main contribution to inherent dissipation of microwave energy, so that the absorbing peak became strengthened when the material had more layers. Furthermore, the layer interfaces in the multilayered system were also effective to inhibit the propagation of cracks in the stretching process, leading to a larger elongation at the break than that of the PP/CB conventional system, which provided a potential route to fabricate electrical materials with optimal mechanical properties. PMID:25549245

  20. Effects of Compression and Filler Particle Coating on the Electrical Conductivity of Thermoplastic Elastomer Composites

    NASA Astrophysics Data System (ADS)

    Albers, Willem M.; Karttunen, Mikko; Wikström, Lisa; Vilkman, Taisto

    2013-10-01

    Elastomeric polymers can be filled with metallic micro- or nanoparticles to obtain electrical conductivity, in which the conductivity is largely determined by the intrinsic conductivity of and contact resistance between the particles. Electrons will flow through the material effectively when the percolation threshold for near-neighbor contacts is exceeded and sufficiently close contacts between the filler particles are realized for electron tunneling to occur. Silver-coated glass microparticles of two types (fibers and spheres) were used as fillers in a thermoplastic elastomer composite based on styrene-ethylene-butylene-styrene copolymer, and the direct-current (DC) resistance and radiofrequency impedance were significantly reduced by coating the filler particles with octadecylmercaptan. Not only was the resistance reduced but also the atypical positive piezoresistivity effect observed in these elastomers was strongly reduced, such that resistivity values below 0.01 Ω cm were obtained for compression ratios up to 20%. In the DC measurements, an additional decrease of resistivity was obtained by inclusion of π-extended aromatic compounds, such as diphenylhexatriene. Some qualitative theories are presented to illuminate the possible mechanisms of action of these surface coatings on the piezoresistivity.

  1. Design Guidelines for Shielding Effectiveness, Current Carrying Capability, and the Enhancement of Conductivity of Composite Materials

    NASA Technical Reports Server (NTRS)

    Evans, R. W.

    1997-01-01

    These guidelines address the electrical properties of composite materials which may have an effect on electromagnetic compatibility (EMC). The main topics of the guidelines include the electrical shielding, fault current return, and lightning protection capabilities of graphite reinforced polymers, since they are somewhat conductive but may require enhancement to be adequate for EMC purposes. Shielding effectiveness depends heavily upon the conductivity of the material. Graphite epoxy can provide useful shielding against RF signals, but it is approximately 1,000 times more resistive than good conductive metals. The reduced shielding effectiveness is significant but is still useful in many cases. The primary concern is with gaps and seams in the material just as it is with metal. Current carrying capability of graphite epoxy is adequate for dissipation static charges, but fault currents through graphite epoxy may cause fire at the shorting contact and at joints. The effect of lightning on selected graphite epoxy material and mating surfaces is described, and protection methods are reviewed.

  2. Thermal conductivity and expansion of cross-ply composites with matrix cracks

    NASA Astrophysics Data System (ADS)

    Lu, T. J.; Hutchinson, J. W.

    1995-08-01

    Theoretical models are developed for heat conduction and thermal expansion in a fiber-reinforced ceramic cross-ply laminate containing an array of parallel transverse matrix cracks. Two stages of the transverse matrix cracks are considered: Stage-I with tunnel cracks in the 90 ° plies aligned parallel to the fibers, and Stage-II with cracks extended across both the 90 and 0 ° plies with intact fibers bridging the matrix in the 0 ° plies. The effect of debonded fiber-matrix interfaces in the 0 ° plies is also considered in Stage-II. Approximate closed form solutions for the overall in-plane thermal conductivities and coefficients of thermal expansion (CTEs) as functions of matrix crack spacing and constituent properties are obtained using an approach which combines an analysis akin to a shear-lag analysis with finite element results. Emphasis is placed on the important class of composites whose fiber expansivity is smaller than that of the matrix. For this class, matrix cracking and interfacial debonding results in reduced thermal expansivity. Interfacial debonding has a significant effect on both longitudinal conductivity and thermal expansivity, especially the latter. Comparisons between the present model predictions and numerical and experimental results are provided where these are available.

  3. Study on effective thermal conductivity of silicone/phosphor composite and its size effect by Lattice Boltzmann method

    NASA Astrophysics Data System (ADS)

    Li, Lan; Zheng, Huai; Yuan, Chao; Hu, Run; Luo, Xiaobing

    2016-02-01

    The silicone/phosphor composite is widely used in light emitting diode (LED) packaging. The composite thermal properties, especially the effective thermal conductivity, strongly influence the LED performance. In this paper, a lattice Boltzmann model was presented to predict the silicone/phosphor composite effective thermal conductivity. Based on the present lattice Boltzmann model, a random generation method was established to describe the phosphor particle distribution in composite. Benchmarks were conducted by comparing the simulation results with theoretical solutions for simple cases. Then the model was applied to analyze the effective thermal conductivity of the silicone/phosphor composite and its size effect. The deviations between simulation and experimental results are <7 %, when the phosphor volume fraction varies from 0.038 to 0.45. The simulation results also indicate that effective thermal conductivity of the composite with larger particles is higher than that with small particles at the same volume fraction. While mixing these two sizes of phosphor particles provides an extra enhancement for the effective thermal conductivity.

  4. Fractal dendrite-based electrically conductive composites for laser-scribed flexible circuits

    PubMed Central

    Yang, Cheng; Cui, Xiaoya; Zhang, Zhexu; Chiang, Sum Wai; Lin, Wei; Duan, Huan; Li, Jia; Kang, Feiyu; Wong, Ching-Ping

    2015-01-01

    Fractal metallic dendrites have been drawing more attentions recently, yet they have rarely been explored in electronic printing or packaging applications because of the great challenges in large-scale synthesis and limited understanding in such applications. Here we demonstrate a controllable synthesis of fractal Ag micro-dendrites at the hundred-gram scale. When used as the fillers for isotropically electrically conductive composites (ECCs), the unique three-dimensional fractal geometrical configuration and low-temperature sintering characteristic render the Ag micro dendrites with an ultra-low electrical percolation threshold of 0.97 vol% (8 wt%). The ultra-low percolation threshold and self-limited fusing ability may address some critical challenges in current interconnect technology for microelectronics. For example, only half of the laser-scribe energy is needed to pattern fine circuit lines printed using the present ECCs, showing great potential for wiring ultrathin circuits for high performance flexible electronics. PMID:26333352

  5. Investigation into conductivity of silver-coated cenosphere composites prepared by a modified electroless process

    NASA Astrophysics Data System (ADS)

    Cao, Xiao Guo; Zhang, Hai Yan

    2013-01-01

    Silver-coated cenosphere composites are successfully fabricated by a modified electroless plating process that is modified by replacing the conventional pretreatment and sensitization steps by only using surface hydroxylation step to simplify the steps and reduce the overall cost of the coating process. Furthermore, the activation and electroless plating steps are merged into one step. The cenosphere particles are characterized by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction analysis (XRD) before and after the coating process. The relatively continuous and compact coating is obtained under the given coating conditions. The results indicated that the conductivity of Ag-coated cenospheres was improved with increasing the AgNO3 solution dosage and reaction time. It was also found that the optimum AgNO3 solution concentration was 0.05 mol/L, and the optimum range of reaction temperature was from 50 °C to 65 °C.

  6. A highly sensitive pressure sensor using conductive composite elastomers with wavy structures

    NASA Astrophysics Data System (ADS)

    Sun, Rujie; Zhang, Xiao-Chong; Rossiter, Jonathan; Scarpa, Fabrizio

    2016-05-01

    Flexible pressure sensors are crucial components for the next generation wearable devices to monitor human physiological conditions. In this paper, we present a novel resistive pressure sensor based on hybrid composites made from carbon nanotube (CNT) for the conductive coating layer and polydimethylsiloxane (PDMS) elastomers as the substrate. The high sensitivity of these sensors is attributed to the change of contact resistance caused by the variation of the contact areas between the wavy film and the electrodes. Porous electrodes were designed to increase the roughness of the interfaces, thus further enhancing the pressure sensitivity. The developed device was verified through a series of tests, and the sensor exhibited a high sensitivity of 2.05 kPa-1 under a low pressure of 35.6 Pa.

  7. Electrically Conducting Polymer-Copper Sulphide Composite Films, Preparation by Treatment of Polymer-Copper (2) Acetate Composites with Hydrogen Sulfide

    NASA Technical Reports Server (NTRS)

    Yamamoto, Takakazu; Kamigaki, Takahira; Kubota, Etsuo

    1988-01-01

    Polymer copper sulfide composite films were prepared by treatment of polymer poly(vinyl chloride), poly(acrylonitrile), copolymer of vinyl chloride and vinyl acetate (90:10), and ABS resin copper (2) acetate composites with hydrogen sulfide. The films showed electrical conductivity higher than 0.015 S/cm when they contained more than 20 wt percent of copper sulfide. A poly(acrylonitrile)-copper sulfide composite film containing 40 to 50 wt percent of copper sulfide showed electrical conductivity of 10 to 150.0 S/cm and had relatively high mechanical strength to be used in practical purposes.

  8. An investigation of electrochemomechanical actuation of conductive Polyacrylonitrile (PAN) nanofiber composites

    NASA Astrophysics Data System (ADS)

    Gonzalez, Mark A.; Walter, Wayne W.

    2014-03-01

    A polymer-based nanofiber composite actuator designed for contractile actuation was fabricated by electrospinning, stimulated by electrolysis, and characterized by electrochemical and mechanical testing to address performance limitations and understand the activation processing effects on actuation performance. Currently, Electroactive polymers (EAPs) have provided uses in sensory and actuation technology, but have either low force output or expand rather than contract, falling short in capturing the natural kinetics and mechanics of muscle needed to provide breakthroughs in the bio-medical and robotic fields. In this study, activated Polyacrylonitrile (PAN) fibers have demonstrated biomimetic functionalities similar to the sarcomere contraction responsible for muscle function. Activated PAN has also been shown to contract and expand by electrolysis when in close vicinity to the anode and cathode, respectively. PAN nanofibers (~500 nm) especially show faster response to changes in environmental pH and improved mechanical properties compared to larger diameter fibers. Tensile testing was conducted to examine changes in mechanical properties between annealing and hydrolysis processing. Voltage driven transient effects of localized pH were examined to address pHdefined actuation thresholds of PAN fibers. Electrochemical contraction rates of the PAN/Graphite composite actuator demonstrated up to 25%/min. Strains of 58.8%, ultimate stresses up to 77.1 MPa, and moduli of 0.21 MPa were achieved with pure PAN nanofiber mats, surpassing mechanical properties of natural muscles. Further improvements, however, to contraction rates and Young's moduli were found essential to capture the function and performance of skeletal muscles appropriately.

  9. Surface modification of fibers by conducting polymers and their use in composites

    NASA Astrophysics Data System (ADS)

    Yavuz, Hande; Girard, Gregory; Bai, Jinbo; Lab. PPSM, CNRS UMR 8531, ENS Cachan, 94235, Cachan Cedex Collaboration; Acxys Technologies France Collaboration

    2013-09-01

    Due to the discovery of their incredible functional properties, carbon nanotubes (CNTs) have drawn a great deal of interest from both academic and industrial research teams in the past few years. Since novel materials are to be integrated in structural and functional applications in several fields, inclusion of CNTs as a reinforcement component in polymer matrix composites (PMC) could bring new solutions. However, in order to obtain more advanced CNTs composites, the amount of strong bonding between CNTs and matrix must be realized to ensure the effective stress transfer in a PMC. This research aims to establish an efficient dielectric barrier discharge technique for the surface modification of CNTs grafted carbon fibers (CNTs-CF) with plasma polypyrrole (PPPy) in order to be used in PMC. It is found that response surface methodology can be applicable in modeling to evaluate the effects of important process variables on electrical resistivity of CNTs-CF. From low to high plasma powers, X-ray Photoelectron Spectroscopy studies revealed the loss of α- and β-carbons in pyrrole ring. The higher the plasma power the lower the electrical conductivity and the higher the mechanical properties. This research was supported under ANR PROCOM Project (EADS-IW). The financial support from French Government and Ecole Centrale Paris are gratefully acknowledged.

  10. Flexible and Conducting Metal-Fabric Composites Using the Flame Spray Process for the Production of Li-Ion Batteries

    NASA Astrophysics Data System (ADS)

    Voyer, Joel

    2013-06-01

    The wire flame spray process was used to produce electrically conductive and flexible Al coatings onto diverse textile fabrics. The investigation studied the influence of the spraying parameters and fabric materials on the electrical conductivity of the metal-fabric composites. Furthermore, this study showed that the production of flexible Li-ion batteries having good electrical properties based on the use of such flame-sprayed aluminium cathode current collectors is viable. Results show that a coating quantity threshold of about 20 mg/cm2 exists to obtain a sufficient electrical surface conductivity for a commercial use of the produced metal-fabric composites. An excellent electrical surface conductivity of the composites (about 500 SA) could be achieved through an adequate optimization of the spraying parameters. This conductivity increase enabled a reduction of the coating quantity and thus the flexibility of the fabric materials is better conserved, rendering the use of such composites for flexible batteries even more interesting. This study showed that the production of electrically conductive and flexible metal-fabric composites having sufficient electrical conductivity for the manufacture of flexible Li ions batteries is possible. This new method of producing such batteries represents an alternative to other chemically based processes which are hazardous to the environment because of their chemical nature.

  11. Composite lead for conducting an electrical current between 75-80K and 4.5K temperatures

    DOEpatents

    Negm, Yehia; Zimmerman, George O.; Powers, Jr., Robert E.; McConeghy, Randy J.; Kaplan, Alvaro

    1994-12-27

    A composite lead is provided which electrically links and conducts a current between about 75-80K. and liquid helium temperature of about 4.5K. The composite lead may be employed singly or in multiples concurrently to provide conduction of electrical current from normal conductors and semi-conductors at room temperature to superconductors operating at 4.5K. In addition, a variety of organizationl arrangements and assemblies are provided by which the mechanical strength and electrical reliability of the composite lead is maintained.

  12. Composite lead for conducting an electrical current between 75--80K and 4. 5K temperatures

    DOEpatents

    Negm, Y.; Zimmerman, G.O.; Powers, R.E. Jr.; McConeghy, R.J.; Kaplan, A.

    1994-12-27

    A composite lead is provided which electrically links and conducts a current between about 75-80K and liquid helium temperature of about 4.5K. The composite lead may be employed singly or in multiples concurrently to provide conduction of electrical current from normal conductors and semi-conductors at room temperature to superconductors operating at 4.5K. In addition, a variety of organizational arrangements and assemblies are provided by which the mechanical strength and electrical reliability of the composite lead is maintained. 12 figures.

  13. A poly(vinylidene fluoride) composite with added self-passivated microaluminum and nanoaluminum particles for enhanced thermal conductivity

    PubMed Central

    Zhou, Yongcun; Wang, Hong; Xiang, Feng; Zhang, Hu; Yu, Ke; Chen, Liang

    2011-01-01

    A polymer composite was prepared by embedding fillers made of self-passivated aluminum particles in two kind of sizes, micrometer size and nanometer size with different volume proportions into polyvinylidene fluoride matrix. The thermal conductivity and dielectric properties of the composite were studied. The results showed that the thermal conductivity of composites was significantly increased to 3.258 W∕mK when the volume proportion of micrometer size Al particles to nanometer size Al particles is at 20:1, also the relative permittivity was about 75.8 at 1 MHz. The effective simulation model values were in good accordance with experimental results. PMID:21629564

  14. Lead titanate/cyclic carbonate dependence on ionic conductivity of ferro/acrylate blend polymer composites

    NASA Astrophysics Data System (ADS)

    Jayaraman, R.; Vickraman, P.; Subramanian, N. M. V.; Justin, A. Simon

    2016-05-01

    Impedance, XRD, DSC and FTIR studies had been carried out for PVdF-co-HFP/LIBETI based system for three plasticizer (EC/DMC) - filler (PbTiO3) weight ratios. The enhanced conductivity 4.18 × 10-5 Scm-1 was noted for 57.5 wt% -7.5 wt% plasticizer - filler. while blending PEMA to PVdF-co-HFP respectively 7.5: 22.5 wt % (3/7), 15 wt%: 15 wt % (5/5) and 22.5wt %: 7.5 wt % (7/3), the improved conductivity was noted for 3/7 ratio 1.22 × 10-5 S cm-1 and its temperature dependence abide Arrhenius behavior. The intensity of peaks in XRD diffractogram registered dominance of lead titanate, from 2θ = 10° to 80° and absence of VdF crystallites (α+β phase) was noted. In DSC studies, the presence of the exotherm events, filler effect was distinctively seen exhibiting recrystallization of VdF crystallites. In blending PEMA, however, no trace of exotherms was found suggestive of PEMA better inhibiting recrystallization. FTIR study confirmed molecular interactions of various constituents in the vibrational band 500 - 1000 cm-1 both in pristine PVdF-co-HFP and PEMA blended composites with reference to C-F stretching, C-H stretching and C=O carbonyl bands.

  15. Computational prediction of electrical and thermal conductivities of disklike particulate composites

    NASA Astrophysics Data System (ADS)

    Qiu, J.; Yi, Y. B.; Guo, X.

    2015-07-01

    The effective conductivities are determined for randomly oriented disklike particles using an efficient computational algorithm based on the finite element method. The pairwise intersection criteria of disks are developed using a set of vector operations. An element partition scheme has been implemented to connect the elements on different disks across the lines of intersection. The computed conductivity is expressed as a function of the disk density and size. It is further expressed in a power-law form with the key parameters determined from curve fitting. The particle number and the trial number of simulations vary with the disk size to minimize the computational effort in search of the percolation paths. The estimated percolation threshold agrees very well with the result reported in the literature. It has been confirmed that the statistical invariant for percolation is a cubic function of the characteristic size, and that the definition of percolation threshold is consistent with that of the equivalent system containing spherical particles. Binary dispersions of disks of different radii have also been investigated to study the effect of the size distribution. The approximate solutions in the power-law function have potential applications in advanced composites with embedded graphene nanoplatelets (GNPs).

  16. The Role of Alloy Composition and T7 Heat Treatment in Enhancing Thermal Conductivity of Aluminum High Pressure Diecastings

    NASA Astrophysics Data System (ADS)

    Lumley, Roger N.; Deeva, Natalia; Larsen, Robert; Gembarovic, Jozef; Freeman, Joe

    2013-02-01

    The thermal conductivity of some common and experimental high pressure diecasting (HPDC) Al-Si-Cu alloys is evaluated. It is shown that the thermal conductivity of some compositions may be increased by more than 60 pct by utilizing T7 heat treatments. This may have substantial performance and cost benefits for applications where thermal management is a key design parameter.

  17. Styrene-butadiene-styrene copolymer compatibilized carbon black/polypropylene/polystyrene composites with tunable morphology, electrical conduction and rheological stabilities.

    PubMed

    Song, Yihu; Xu, Chunfeng; Zheng, Qiang

    2014-04-21

    We report a facile kinetic strategy in combination with styrene-butadiene-styrene (SBS) copolymer compatibilizers for preparing carbon black (CB) filled immiscible polypropylene (PP)/polystyrene (PS) (1/1) blends with finely tuned morphologies and show the important role of location and migration of CB nanoparticles in determining the electrical conductivity and rheological behaviour of the composites. A novel method of mixing a SBS/CB (5/3) masterbatch with the polymers allowed producing composites with CB aggregates dispersed partially in the unfavorable PP phase and partially in the PP side of the interface to exhibit diverse phase connectivity and electrical conductivity depending on the compounding sequences. A cocontinuous morphology with CB enrichment along the interface was formed in the composite prepared by mixing the SBS/CB masterbatch with the premixed PP/PS blend, giving rise to a highest electrical conductivity and dynamic moduli at low frequencies. On the other hand, mixing the masterbatch with one and then with another polymer yielded droplet (PS)-in-matrix (filled PP) composites. The composites underwent phase coalescence and CB redistribution accompanied by marked dynamic electrical conduction and modulus percolations as a function of time during thermal annealing at 180 °C. The composites with the initial droplet-in-matrix morphology progressed anomalously into the cocontinuous morphology, reflecting a common mechanism being fairly nonspecific for understanding the processing of filled multicomponent composites with tailored performances of general concern. PMID:24647801

  18. Ice-Templated Assembly Strategy to Construct 3D Boron Nitride Nanosheet Networks in Polymer Composites for Thermal Conductivity Improvement.

    PubMed

    Zeng, Xiaoliang; Yao, Yimin; Gong, Zhengyu; Wang, Fangfang; Sun, Rong; Xu, Jianbin; Wong, Ching-Ping

    2015-12-01

    Owing to the growing heat removal issue of modern electronic devices, polymer composites with high thermal conductivity have drawn much attention in the past few years. However, a traditional method to enhance the thermal conductivity of the polymers by addition of inorganic fillers usually creates composite with not only limited thermal conductivity but also other detrimental effects due to large amount of fillers required. Here, novel polymer composites are reported by first constructing 3D boron nitride nanosheets (3D-BNNS) network using ice-templated approach and then infiltrating them with epoxy matrix. The obtained polymer composites exhibit a high thermal conductivity (2.85 W m(-1) K(-1)), a low thermal expansion coefficient (24-32 ppm K(-1)), and an increased glass transition temperature (T(g)) at relatively low BNNSs loading (9.29 vol%). These results demonstrate that this approach opens a new avenue for design and preparation of polymer composites with high thermal conductivity. The polymer composites are potentially useful in advanced electronic packaging techniques, namely, thermal interface materials, underfill materials, molding compounds, and organic substrates. PMID:26479262

  19. Effects of Electric Discharge Plasma Treatment on the Thermal Conductivity of Polymer-Metal Nitride/Carbide Composites

    NASA Astrophysics Data System (ADS)

    Parali, Levent; Kurbanov, Mirza A.; Bayramov, Azad A.; Tatardar, Farida N.; Sultanakhmedova, Ramazanova I.; Xanlar, Huseynova Gulnara

    2015-11-01

    High-density polymer composites with semiconductor or dielectric fillers such as aluminum nitride (AIN), aluminum oxide (Al2O3), titanium carbide (TiC), titanium nitride (TiN), boron nitride (BN), silicon nitride (Si3N4), and titanium carbonitride (TiCN) were prepared by the hot pressing method. Each powder phase of the composites was exposed to an electric discharge plasma process before composite formation. The effects of the electric discharge plasma process and the filler content (volume fraction) on the thermal conductivity, volt-ampere characteristics, thermally stimulated depolarization current, as well as electrical and mechanical strength were investigated. The results of the study indicate that, with increasing filler volume fraction, the thermal conductivity of the samples also increased. Furthermore, the thermal conductivity, and electrophysical and mechanical properties of the high-density polyethylene + 70% BN composite modified using the electric discharge plasma showed improvement when compared with that without electric discharge plasma treatment.

  20. Design of electrical conductive composites: tuning the morphology to improve the electrical properties of graphene filled immiscible polymer blends.

    PubMed

    Mao, Cui; Zhu, Yutian; Jiang, Wei

    2012-10-24

    Polystyrene (PS) and poly(methyl methacrylate) (PMMA) blends filled with octadecylamine-functionalized graphene (GE-ODA) have been fabricated to obtain conductive composites with a lower electrical percolation threshold according to the concept of double percolation. The dependence of the electrical properties of the composites on the morphology is examined by changing the proportion of PS and PMMA. Our results reveal that the electrical conductivity of the composites can be optimal when PS and PMMA phases form a cocontinuous structure and GE-ODA nanosheets are selectively located and percolated in the PS phase. For the PS/PMMA blend (50w/50w), the composites exhibit an extremely low electrical percolation threshold (0.5 wt %) because of the formation of a perfect double percolated structure. Moreover, the rheological properties of the composites are also measured to gain a fundamental understanding of the relationship between microstructure and electrical properties. PMID:22950786

  1. What if the Electrical Conductivity of Graphene Is Significantly Deteriorated for the Graphene-Semiconductor Composite-Based Photocatalysis?

    PubMed

    Weng, Bo; Xu, Yi-Jun

    2015-12-23

    The extraordinary electrical conductivity of graphene has been widely regarded as the bible in literature to explain the activity enhancement of graphene-semiconductor composite photocatalysts. However, from the viewpoint of an entire composite-based artificial photosynthetic system, the significant matter of photocatalytic performance of graphene-semiconductor composite system is not just a simple and only issue of excellent electrical conductivity of graphene. Herein, the intentional design of melamine resin monomers functionalized three-dimensional (3D) graphene (donated as MRGO) with significantly deteriorated electrical conductivity enables us to independently focus on studying the geometry effect of MRGO on the photocatalytic performance of graphene-semiconductor composite. By coupling semiconductor CdS with graphene, including MRGO and reduced graphene oxide (RGO), it was found that the CdS-MRGO composites exhibit much higher visible light photoactivity than CdS-RGO composites although the electrical conductivity of MRGO is remarkably much lower than that of RGO. The comparison characterizations evidence that such photoactivity enhancement is predominantly attributed to the restacking-inhibited 3D architectural morphology of MRGO, by which the synergistic effects of boosted separation and transportation of photogenerated charge carriers and increased adsorption capacity can be achieved. Our work highlights that the significant matter of photocatalytic performance of graphene-semiconductor composite is not a simple issue on how to harness the electrical conductivity of graphene but the rational ensemble design of graphene-semiconductor composite, which includes the integrative optimization of geometrical and electrical factors of individual component and the interface composition. PMID:26624808

  2. Continuous Carbon Nanotube-Ultrathin Graphite Hybrid Foams for Increased Thermal Conductivity and Suppressed Subcooling in Composite Phase Change Materials.

    PubMed

    Kholmanov, Iskandar; Kim, Jaehyun; Ou, Eric; Ruoff, Rodney S; Shi, Li

    2015-12-22

    Continuous ultrathin graphite foams (UGFs) have been actively researched recently to obtain composite materials with increased thermal conductivities. However, the large pore size of these graphitic foams has resulted in large thermal resistance values for heat conduction from inside the pore to the high thermal conductivity graphitic struts. Here, we demonstrate that the effective thermal conductivity of these UGF composites can be increased further by growing long CNT networks directly from the graphite struts of UGFs into the pore space. When erythritol, a phase change material for thermal energy storage, is used to fill the pores of UGF-CNT hybrids, the thermal conductivity of the UGF-CNT/erythritol composite was found to increase by as much as a factor of 1.8 compared to that of a UGF/erythritol composite, whereas breaking the UGF-CNT bonding in the hybrid composite resulted in a drop in the effective room-temperature thermal conductivity from about 4.1 ± 0.3 W m(-1) K(-1) to about 2.9 ± 0.2 W m(-1) K(-1) for the same UGF and CNT loadings of about 1.8 and 0.8 wt %, respectively. Moreover, we discovered that the hybrid structure strongly suppresses subcooling of erythritol due to the heterogeneous nucleation of erythritol at interfaces with the graphitic structures. PMID:26529570

  3. Investigation into the effect of heat treatment on the thermal conductivity of 3-D carbon/carbon fiber composites

    SciTech Connect

    Dinwiddie, R.B.; Burchell, T.D. ); Baker, C.F. )

    1991-01-01

    The material used in this study was a carbon-carbon fiber composite manufactured from precursor yarn and petroleum based pitch through a process of repetitive densification of a woven preform. The resultant high temperature-high strength material exhibits relatively high thermal conductivity and is thus of interest to the fusion energy, plasma materials interactions (PMI) and plasma facing components (PFC) communities. Carbon-carbon fiber composite manufacture involves two distinct processes, preform weaving and component densification. In this study three samples were subjected to an additional heat treatment of 2550, 2750 or 3000{degree}C at Oak Ridge National Laboratory (ORNL) subsequent to their fourth graphitization at 2400{degree}C. It should be noted that no effort was made to optimize the composite for thermal conductivity, but rather only to provide a material with which to evaluate the effect of the final heat treatment temperature on the thermal conductivity. The fiber is the primary source of heat conduction in the composite. Consequently, increasing the fiber volume fraction, and/or the fiber thermal conductivity is expected to increase the composite thermal conductivity. 3 refs., 1 fig.

  4. Fabrication of High Thermal Conductivity NARloy-Z-Diamond Composite Combustion Chamber Liner for Advanced Rocket Engines

    NASA Technical Reports Server (NTRS)

    Bhat, Biliyar N.; Greene, Sandra E.; Singh, Jogender

    2016-01-01

    This paper describes the process development for fabricating a high thermal conductivity NARloy-Z-Diamond composite (NARloy-Z-D) combustion chamber liner for application in advanced rocket engines. The fabrication process is challenging and this paper presents some details of these challenges and approaches used to address them. Prior research conducted at NASA-MSFC and Penn State had shown that NARloy-Z-40%D composite material has significantly higher thermal conductivity than the state of the art NARloy-Z alloy. Furthermore, NARloy-Z-40 %D is much lighter than NARloy-Z. These attributes help to improve the performance of the advanced rocket engines. Increased thermal conductivity will directly translate into increased turbopump power, increased chamber pressure for improved thrust and specific impulse. Early work on NARloy-Z-D composites used the Field Assisted Sintering Technology (FAST, Ref. 1, 2) for fabricating discs. NARloy-Z-D composites containing 10, 20 and 40vol% of high thermal conductivity diamond powder were investigated. Thermal conductivity (TC) data. TC increased with increasing diamond content and showed 50% improvement over pure copper at 40vol% diamond. This composition was selected for fabricating the combustion chamber liner using the FAST technique.

  5. A study on the DC-electrical and thermal conductivities of epoxy/ZnO composites doped with carbon black

    NASA Astrophysics Data System (ADS)

    Juwhari, Hassan K.; Zihlif, Awwad; Elimat, Ziad; Ragosta, Giuseppe

    2014-06-01

    Thermo-electrical characterizations of hybrid polymer composites, made of epoxy matrix filled with various zinc oxide (ZnO) concentrations (0, 4.9, 9.9, 14.9, and 19.9 wt%), and reinforced with conductive carbon black (CB) nanoparticles (0.1 wt%), have been investigated as a function of ZnO concentration and temperature. Both the measured DC-electrical and thermal conductivities showed ZnO concentration and temperature dependencies. Increasing the temperature and filler concentrations were reflected in a negative temperature coefficient of resistivity and enhancement of the electrical conductivity as well. The observed increase in the DC conductivity and decrease in the determined activation energy were explained based on the concept of existing paths and connections between the ZnO particles and the conductive CB nanoparticles. Alteration of ZnO concentration with a fixed content of CB nanoparticles and/or temperature was found to be crucial in the thermal conductivity behavior. The addition of CB nanoparticles to the epoxy/ZnO matrix was found to enhance the electrical conduction resulting from the electronic and impurity contributions. Also, the thermal conductivity enhancement was mostly attributed to the heat transferred by phonons and electrons hopping to higher energy levels throughout the thermal processes. Scanning electron microscopy and energy-dispersive spectroscopy were used to observe the morphology and elements' distribution in the composites. The observed thermal conductivity behavior was found to correlate well with that of the DC-electrical conductivity as a function of the ZnO content. The overall enhancements in both the measured DC- and thermal conductivities of the prepared hybrid composites are mainly produced through mutual interactions between the filling conductive particles and also from electrons tunneling in the composite's bulk as well.

  6. The Effects of Various Conductive Additive and Polymeric Binder Contents on the Performance of a Lithium-ion Composite

    SciTech Connect

    Stevenson, Cynthia; Liu, G.; Zheng, H.; Kim, S.; Deng, Y.; Minor, A.M.; Song, X.; Battaglia, V.S.

    2008-08-07

    Fundamental electrochemical methods, cell performance tests, and physical characterization tests such as electron microscopy were used to study the effects of levels of the inert materials (acetylene black (AB), a nano-conductive additive, and polyvinylidene difluoride (PVDF), a polymer binder) on the power performance of lithium-ion composite cathodes. The electronic conductivity of the AB/PVDF composites at different compositions was measured with a four-point probe direct current method. The electronic conductivity was found to increase rapidly and plateau at a AB:PVDF ratio 0.2:1 (by weight), with 0.8:1 being the highest conductivity composition. AB:PVDF compositions along the plateau of 0.2:1, 0.4:1, 0.6:1 and 0.8:1 were investigated. Electrodes of each of those compositions were fabricated with different fractions of AB/PVDF to active material. It was found that at the 0.8:1 AB:PVDF, the rate performance improved with increases in the AB/PVDF loading, whereas at the 0.2:1 AB:PVDF, the rate performance improved with decreases in the AB/PVDF loading. The impedance of electrodes made with 0.6:1 AB:PVDF was low and relatively invariant.

  7. Mechanisms of greater cardiomyocyte functions on conductive nanoengineered composites for cardiovascular application

    PubMed Central

    Stout, David A; Yoo, Jennie; Santiago-Miranda, Adriana Noemi; Webster, Thomas J

    2012-01-01

    of natural heart tissue, ie, 0.15 MPa for 100% PLGA to 5.41 MPa for the 50:50 (PLGA to CNF [wt%:wt%]) ratio at 0.025 g/mL. Atomic force microscopy indicated that the addition of CNF to PLGA increased the material surface area from 10% (100:0 [PLGA to carbon nanofiber (wt%:wt%)]) to over 60% (50:50 [PLGA to carbon nanofibers (wt%:wt%)]). Lastly, the adsorption of specific proteins (fibronectin and vitronectin) showed significantly more adsorption for the 50:50 PLGA to CNF (wt%:wt%) ratio at 0.025 g/mL PLGA compared with pure PLGA, which may be why cardiomyocyte function increased on CNF-enriched composites. Conclusion This study demonstrates that cardiomyocyte function was enhanced on 50:50 PLGA to CNF (wt%:wt%) composite ratios at 0.025 g/mL PLGA densities because they mimicked native heart tissue tensile strength/conductivity and increased the adsorption of proteins known to promote cardiomyocyte function. PMID:23180962

  8. Correction of NPL-2013 estimate of the Boltzmann constant for argon isotopic composition and thermal conductivity

    NASA Astrophysics Data System (ADS)

    de Podesta, Michael; Yang, Inseok; Mark, Darren F.; Underwood, Robin; Sutton, Gavin; Machin, Graham

    2015-10-01

    In 2013, a team from NPL, Cranfield University and SUERC published an estimate of the Boltzmann constant based on precision measurements of the speed of sound in argon. A key component of our results was an estimate of the molar mass of the argon gas used in our measurements. To achieve this we made precision comparison measurements of the isotope ratios found in our experimental argon against the ratios of argon isotopes found in atmospheric air. We then used a previous measurement of the atmospheric argon isotope ratios to calibrate the relative sensitivity of the mass spectrometer to different argon isotopes. The previous measurement of the atmospheric argon isotope ratios was carried out at KRISS using a mass spectrometer calibrated using argon samples of known isotopic composition, which had been prepared gravimetrically. We report here a new measurement made at KRISS in October 2014, which directly compared a sample of our experimental gas against the same gravimetrically-prepared argon samples. We consider that this direct comparison has to take precedence over our previous more indirect comparison. This measurement implies a molar mass which is 2.73(60) parts in 106 lighter than our 2013 estimate, a shift which is seven times our 2013 estimate of the uncertainty in the molar mass. In this paper we review the procedures used in our 2013 estimate of molar mass; describe the 2014 measurement; highlight some questions raised by the large change in our estimate of molar mass; and describe how we intend to address the inconsistencies between them. We also consider the effect of a new estimate of the low pressure thermal conductivity of argon at 273.16 K. Finally we report our new best estimate of the Boltzmann constant with revised uncertainty, taking account of the new estimates for the molar mass and the thermal conductivity of the argon.

  9. Microstructure effects on proton conductivity in EVOH based ionic polymer-metal composites actuator

    NASA Astrophysics Data System (ADS)

    Dai, Lijun; Li, Lei; Zhang, Yujun

    2007-07-01

    The ionomer of sulfonated ethylene vinyl alcohol copolymers (EVOH) modified by poly (ethylene glycol) (PEG) (EVOH-g-SPEG) has been synthesized by the following process, EVOH was grafted by PEG through the Williamson reaction and sulfonic groups were introduced onto the end of PEG side chain by the open ring reaction of 1,3-propane sultone and the hydroxyl groups in EVOH. The crystalline structure and phase images of EVOH-g-SPEG membrane were characterized by X-ray diffraction (XRD) and atomic force microscope (AFM), and the ion conductivity is measured by a.c. impedance. XRD indicates that the water in EVOH-g-SPEG membrane region could destroy the membrane crystalline structure and the water absorption membranes are nearly amorphous. AFM phase images of the hydration membranes clearly show the hydrophilic domains, with sizes increasing from 10 to 35 nm as a function of the side chain length and the phase inversion could also be observed when n>=5 (n, numbers of grafting PEG side chain), which was consistent with a rapid increasing in water absorption. The a.c. impedance tests indicate that the comb-like EVOH-g-SPEG grafting with 2 PEG side chain provides the highest ionic conductivity (1.65×10 -3Scm -1). Moreover, the tip displacement and the bending stress of ionic polymer-metal composites (IPMC) prepared by electroless deposition of argentum were gained by electro-deformation tests. Its results show that the tip bending stress increased with the increasing input voltage and reached to its maximum under the applied voltage of 3.6V~4.4V. IPMC based on the EVOH-g-SPEG membrane exhibits higher bending stress with its maximum value of 6.20MPa.

  10. Si3N4/fused quartz composite crucible with enhanced thermal conductivity for multicrystalline silicon ingot growth

    NASA Astrophysics Data System (ADS)

    Zhao, Lili; Lv, Tiezheng; Zhu, Qingsong

    2015-04-01

    Two popular materials for multicrystalline Si ingot growth of the PV industry, Si3N4 and fused quartz, are working as composited material, tested and used to make industrial scale crucible. The main purpose of this composite material is to working as crucible for overcoming the low thermal conductivity of single fused quartz crucible during Si ingot process. Certain ceramic properties tests of the composite material, like porosity, density, are done with various percent of Si3N4/fused quartz, and thermal shock test did as well. These results prove that our composite material is feasible to make square crucible for Si ingot process. Thus we simulate multicrystalline Si ingot growth and experiments are done by industrial scale G5 crucible made by the composite material with optimal ratio of Si3N4/fused quartz. These results show that since composite crucible has higher thermal conductivity, the more heat flux could penetrate the bottom of crucible for Si directional solidification, correspondingly the temperature distribution, interface of solid-liquid Si, growth speed and grain structure, these kinds of key features of Si ingot process can be improved. The thermal profile analysis and photoluminescence picture show the improvement of Si ingot process using this composite crucible. Finally the considerations of industrial mass production using this kind of composite crucible are discussed.

  11. A simple, low-cost conductive composite material for 3D printing of electronic sensors.

    PubMed

    Leigh, Simon J; Bradley, Robert J; Purssell, Christopher P; Billson, Duncan R; Hutchins, David A

    2012-01-01

    3D printing technology can produce complex objects directly from computer aided digital designs. The technology has traditionally been used by large companies to produce fit and form concept prototypes ('rapid prototyping') before production. In recent years however there has been a move to adopt the technology as full-scale manufacturing solution. The advent of low-cost, desktop 3D printers such as the RepRap and Fab@Home has meant a wider user base are now able to have access to desktop manufacturing platforms enabling them to produce highly customised products for personal use and sale. This uptake in usage has been coupled with a demand for printing technology and materials able to print functional elements such as electronic sensors. Here we present formulation of a simple conductive thermoplastic composite we term 'carbomorph' and demonstrate how it can be used in an unmodified low-cost 3D printer to print electronic sensors able to sense mechanical flexing and capacitance changes. We show how this capability can be used to produce custom sensing devices and user interface devices along with printed objects with embedded sensing capability. This advance in low-cost 3D printing with offer a new paradigm in the 3D printing field with printed sensors and electronics embedded inside 3D printed objects in a single build process without requiring complex or expensive materials incorporating additives such as carbon nanotubes. PMID:23185319

  12. A unified model for the permittivity and thermal conductivity of epoxy based composites

    NASA Astrophysics Data System (ADS)

    Tsekmes, I. A.; Kochetov, R.; Morshuis, P. H. F.; Smit, J. J.

    2014-10-01

    In this paper, three-dimensional models are presented that were developed for both the relative permittivity and the thermal conductivity of composites based on epoxy in an attempt to understand the way in which modified fillers interact with epoxy. Various ceramics were used as fillers, namely magnesium oxide, aluminium nitride, aluminium oxide, hexagonal boron nitride and cubic boron nitride with an average particle size between 22 and 150 nm. The concept of the models is mainly based on two competing mechanisms, i.e., polymer re-organization and water uptake. These were realized in the models by assuming two interfacial layers around the particles, an inner and an outer layer. The former refers to water uptake and the latter demonstrates the influence of the matrix by the presence of surface modified particles and exhibits different properties than both the filler and polymer matrix. The thickness of the inner layer is constant while the outer layer thickness has a dynamic behaviour which strongly depends on the interparticle distance and thus, on the filler content. The same assumptions were made for both models and an accurate fit was achieved between the experimental data and model results.

  13. Polymer/Pristine graphene based composites: from emulsions to strong, electrically conducting foams

    SciTech Connect

    Woltornist, Steven J.; Carrillo, Jan-Michael Y.; Xu, Thomas O.; Dobrynin, Andrey V.; Adamson, Douglas H.

    2015-01-21

    The unique electrical, thermal, and mechanical properties of graphene make it a perfect candidate for applications in graphene/graphite based polymer composites, yet challenges due to the lack of solubility of pristine graphene/graphite in water and common organic solvents have limited its practical utilization. In this paper, we report a scalable and environmentally friendly technique to form water-in-oil type emulsions stabilized by overlapping pristine graphene sheets, enabling the synthesis of open cell foams containing a continuous graphitic network. Our approach utilizes the insolubility of graphene/graphite in both water and organic solvents and so does not require oxidation, reduction, surfactants, high boiling solvents, chemical functionalization, or the input of large amounts of mechanical energy or heat. At the heart of our technique is the strong attraction of graphene to high-energy oil and water interfaces. This allows for the creation of stable water-in-oil emulsions with controlled droplet size and overlapping graphene sheets playing the role of surfactant by covering the droplet surface and stabilizing the interfaces with a thin graphitic skin. Finally, these emulsions are used as templates for the synthesis of open cell foams with densities below 0.35 g/cm3 that exhibit remarkable mechanical and electrical properties including compressive moduli up to ~100 MPa, compressive strengths of over 8.3 MPa (1200 psi), and bulk conductivities approaching 7 S/m.

  14. Polymer/Pristine Graphene Based Composites: From Emulsions to Strong, Electrically Conducting Foams

    NASA Astrophysics Data System (ADS)

    Woltornist, Steven; Carrillo, Jan-Michael; Xu, Thomas; Dobrynin, Andrey; Adamson, Douglas

    2015-03-01

    The unique electrical, thermal and mechanical properties of graphene make it a perfect candidate for applications in graphene/graphite based polymer composites, yet challenges due to the lack of solubility of pristine graphene/graphite in water, common organic solvents, and polymer solutions and melts have limited its practical utilization. Here we report a scalable and environmentally friendly technique to form water-in-oil type emulsions stabilized by a graphitic skin consisting of overlapping pristine graphene sheets that enables the synthesis of open cell foams containing a continuous graphitic skin network. At the heart of our technique is the strong attraction of graphene to high-energy oil and water interfaces. This allows for the creation of stable water-in-oil emulsions with controlled droplet size and overlapping graphene sheets playing the role of surfactant by covering the droplet surface and stabilizing the interfaces with a thin graphitic skin. These emulsions are used as templates for the synthesis of the open cell foams with densities below 0.35 g/cm3 and exhibiting remarkable mechanical and electrical properties including compressive moduli up to ~ 100 MPa, compressive strengths of over 8.3 MPa, and bulk conductivities approaching 7 S/m.

  15. Polymer/Pristine graphene based composites: from emulsions to strong, electrically conducting foams

    DOE PAGESBeta

    Woltornist, Steven J.; Carrillo, Jan-Michael Y.; Xu, Thomas O.; Dobrynin, Andrey V.; Adamson, Douglas H.

    2015-01-21

    The unique electrical, thermal, and mechanical properties of graphene make it a perfect candidate for applications in graphene/graphite based polymer composites, yet challenges due to the lack of solubility of pristine graphene/graphite in water and common organic solvents have limited its practical utilization. In this paper, we report a scalable and environmentally friendly technique to form water-in-oil type emulsions stabilized by overlapping pristine graphene sheets, enabling the synthesis of open cell foams containing a continuous graphitic network. Our approach utilizes the insolubility of graphene/graphite in both water and organic solvents and so does not require oxidation, reduction, surfactants, high boilingmore » solvents, chemical functionalization, or the input of large amounts of mechanical energy or heat. At the heart of our technique is the strong attraction of graphene to high-energy oil and water interfaces. This allows for the creation of stable water-in-oil emulsions with controlled droplet size and overlapping graphene sheets playing the role of surfactant by covering the droplet surface and stabilizing the interfaces with a thin graphitic skin. Finally, these emulsions are used as templates for the synthesis of open cell foams with densities below 0.35 g/cm3 that exhibit remarkable mechanical and electrical properties including compressive moduli up to ~100 MPa, compressive strengths of over 8.3 MPa (1200 psi), and bulk conductivities approaching 7 S/m.« less

  16. Surface Plasmon Resonance Sensing Detection of Mercury and Lead Ions Based on Conducting Polymer Composite

    PubMed Central

    Abdi, Mahnaz M.; Abdullah, Luqman Chuah; Sadrolhosseini, Amir R.; Mat Yunus, Wan Mahmood; Moksin, Mohd Maarof; Tahir, Paridah Md.

    2011-01-01

    A new sensing area for a sensor based on surface plasmon resonance (SPR) was fabricated to detect trace amounts of mercury and lead ions. The gold surface used for SPR measurements were modified with polypyrrole-chitosan (PPy-CHI) conducting polymer composite. The polymer layer was deposited on the gold surface by electrodeposition. This optical sensor was used for monitoring toxic metal ions with and without sensitivity enhancement by chitosan in water samples. The higher amounts of resonance angle unit (ΔRU) were obtained for PPy-CHI film due to a specific binding of chitosan with Pb2+ and Hg2+ ions. The Pb2+ ion bind to the polymer films most strongly, and the sensor was more sensitive to Pb2+ compared to Hg2+. The concentrations of ions in the parts per million range produced the changes in the SPR angle minimum in the region of 0.03 to 0.07. Data analysis was done by Matlab software using Fresnel formula for multilayer system. PMID:21931763

  17. Steady-state heat conduction in multilayered composite plates and shells

    NASA Technical Reports Server (NTRS)

    Noor, A. K.; Burton, W. S.

    1991-01-01

    A study is made of a predictor-corrector procedure for the accurate determination of the temperature and heat flux distributions in thick multilayered composite plates and shells. A linear through-the-thickness temperature distribution is used in the predictor phase. The functional dependence of temperature on the thickness coordinate is then calculated a posteriori and used in the corrector phase. Extensive numerical results are presented for linear steady-state heat conduction problems, showing the effects of variation in the geometric and lamination parameters on the accuracy of the thermal response predictions of the predictor-corrector approach. Both antisymmetrically laminated anisotropic plates and multilayered orthotropic cylinders are considered. The solutions are assumed to be periodic in the surface coordinates. For each problem the standard of comparison is taken to be the analytic three-dimensional solution based on treating each layer as a homogeneous anisotropic medium. The potential of the predictor-corrector approach for predicting the thermal response of multilayered plates and shells with complicated geometry is discussed.

  18. A Simple, Low-Cost Conductive Composite Material for 3D Printing of Electronic Sensors

    PubMed Central

    Leigh, Simon J.; Bradley, Robert J.; Purssell, Christopher P.; Billson, Duncan R.; Hutchins, David A.

    2012-01-01

    3D printing technology can produce complex objects directly from computer aided digital designs. The technology has traditionally been used by large companies to produce fit and form concept prototypes (‘rapid prototyping’) before production. In recent years however there has been a move to adopt the technology as full-scale manufacturing solution. The advent of low-cost, desktop 3D printers such as the RepRap and Fab@Home has meant a wider user base are now able to have access to desktop manufacturing platforms enabling them to produce highly customised products for personal use and sale. This uptake in usage has been coupled with a demand for printing technology and materials able to print functional elements such as electronic sensors. Here we present formulation of a simple conductive thermoplastic composite we term ‘carbomorph’ and demonstrate how it can be used in an unmodified low-cost 3D printer to print electronic sensors able to sense mechanical flexing and capacitance changes. We show how this capability can be used to produce custom sensing devices and user interface devices along with printed objects with embedded sensing capability. This advance in low-cost 3D printing with offer a new paradigm in the 3D printing field with printed sensors and electronics embedded inside 3D printed objects in a single build process without requiring complex or expensive materials incorporating additives such as carbon nanotubes. PMID:23185319

  19. Mesoporous carbon/zirconia composites: a potential route to chemically functionalized electrically-conductive mesoporous materials.

    PubMed

    Oh, Jung-Min; Kumbhar, Amar S; Geiculescu, Olt; Creager, Stephen E

    2012-02-14

    Mesoporous nanocomposite materials in which nanoscale zirconia (ZrO(2)) particles are embedded in the carbon skeleton of a templated mesoporous carbon matrix were prepared, and the embedded zirconia sites were used to accomplish chemical functionalization of the interior surfaces of mesopores. These nanocomposite materials offer a unique combination of high porosity (e.g., ∼84% void space), electrical conductivity, and surface tailorability. The ZrO(2)/carbon nanocomposites were characterized by thermogravimetric analysis, nitrogen-adsorption porosimetry, helium pychnometry, powder X-ray diffraction, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. Comparison was made with templated mesoporous carbon samples prepared without addition of ZrO(2). Treatment of the nanocomposites with phenylphosphonic acid was undertaken and shown to result in robust binding of the phosphonic acid to the surface of ZrO(2) particles. Incorporation of nanoscale ZrO(2) surfaces in the mesoporous composite skeleton offers unique promise as a means for anchoring organophosphonates inside of pores through formation of robust covalent Zr-O-P bonds. PMID:22248432

  20. Studies on the activation energy from the ac conductivity measurements of rubber ferrite composites containing manganese zinc ferrite

    NASA Astrophysics Data System (ADS)

    Hashim, Mohd.; Alimuddin; Kumar, Shalendra; Shirsath, Sagar E.; Mohammed, E. M.; Chung, Hanshik; Kumar, Ravi

    2012-11-01

    Manganese zinc ferrites (MZF) have resistivities between 0.01 and 10 Ω m. Making composite materials of ferrites with either natural rubber or plastics will modify the electrical properties of ferrites. The moldability and flexibility of these composites find wide use in industrial and other scientific applications. Mixed ferrites belonging to the series Mn(1-x)ZnxFe2O4 were synthesized for different ‘x’ values in steps of 0.2, and incorporated in natural rubber matrix (RFC). From the dielectric measurements of the ceramic manganese zinc ferrite and rubber ferrite composites, ac conductivity and activation energy were evaluated. A program was developed with the aid of the LabVIEW package to automate the measurements. The ac conductivity of RFC was then correlated with that of the magnetic filler and matrix by a mixture equation which helps to tailor properties of these composites.

  1. EFFECTS OF SURFACE AREA DENSITY OF ALUMINUM FOAMS ON THERMAL CONDUCTIVITY OF ALUMINUM FOAM-PHASE CHANGE MATERIAL COMPOSITES

    SciTech Connect

    Hong, Sung-tae; Herling, Darrell R.

    2007-07-01

    The effects of the surface area density of open-cell aluminum foams on the effective thermal conductivity of aluminum foam-phase change material (PCM) composites were investigated. Paraffin was selected as the PCM. The experimental results show that the effective thermal conductivity increases as the temperature increases. The experimental results suggest that the effective thermal conductivities can be different for different surface area densities of foams even though the relative densities of foams are similar. Therefore, for an accurate estimation of the effective thermal conductivity, a correlation including the surface area density effect is needed.

  2. A multi-core-shell structured composite cathode material with a conductive polymer network for Li-S batteries.

    PubMed

    Wang, Mengjia; Wang, Weikun; Wang, Anbang; Yuan, Keguo; Miao, Lixiao; Zhang, Xiaolin; Huang, Yaqin; Yu, Zhongbao; Qiu, Jingyi

    2013-11-11

    A multi-core-shell with a conductive network structured C-PANI-S@PANI composite with high sulfur content up to 87% was synthesized. The composite cathode delivers higher specific capacity and excellent cycle stability, retaining a reversible discharge capacity of 835 mA h g(-1) after 100 cycles when the sulfur loading of the cathode was above 6 mg cm(-2). PMID:23999983

  3. Investigation on Temperature-Dependent Electrical Conductivity of Carbon Nanotube/Epoxy Composites for Sustainable Energy Applications.

    PubMed

    Njuguna, Michael K; Galpaya, Dilini; Yan, Cheng; Colwell, John M; Will, Geoffrey; Hu, Ning; Yarlagadda, Prasad; Bell, John M

    2015-09-01

    Composites with carbon nanotubes are becoming increasingly used in energy storage and electronic devices, due to incorporated excellent properties from carbon nanotubes and polymers. Although their properties make them more attractive than conventional smart materials, their electrical properties have been found to be temperature-dependent which is important to consider for the design of devices. To study the effects of temperature in electrically conductive multi-wall carbon nanotube/epoxy composites, thin films were prepared and the effect of temperature on the resistivity, thermal properties and Raman spectral characteristics of the composite films was evaluated. Resistivity-temperature profiles showed three distinct regions in as-cured samples and only two regions in samples whose thermal histories had been erased. In the vicinity of the glass transition temperature, the as-cured composites exhibited pronounced resistivity and enthalpic relaxation peaks, which both disappeared after erasing the composites' thermal histories by temperature cycling. Combined DSC, Raman spectroscopy, and resistivity-temperature analyses indicated that this phenomenon can be attributed to the physical aging of the epoxy matrix and that, in the region of the observed thermal history-dependent resistivity peaks, structural rearrangement of the conductive carbon nanotube network occurs through a volume expansion/relaxation process. These results have led to an overall greater understanding of the temperature-dependent behaviour of conductive carbon nanotube/epoxy composites, including the positive temperature coefficient effect. PMID:26716268

  4. Preparation of composite polymer electrolytes by electron beam-induced grafting: Proton- and lithium ion-conducting membranes

    NASA Astrophysics Data System (ADS)

    Nasef, M. M.; Saidi, H.; Dahlan, K. Z. M.

    2007-12-01

    Two classes of composite polymer electrolyte membranes, one conducting lithium ions (Li +) and the other conducting protons (H +) were prepared using simultaneous electron beam-induced grafting. Porous poly(vinylidene fluoride) (PVDF) films were impregnated with styrene and subjected to electron beam (EB) irradiation to obtain polystyrene (PS) filled PVDF precursor films that were subsequently treated with either chlorosulfonic acid/1,1,2,2-tetrachloroethane mixture to obtain H +-conducting composite membranes or LiPH 6/EC/DEC liquid electrolyte to obtain Li +-conducting composite membranes. The properties of the obtained membranes were evaluated using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and AC impedance measurements. The obtained membranes were found to achieve grafting content up to 46% with superior Li +-conductivity of 1.91 × 10 -3 S/cm and H +-conductivity of 5.95 × 10 -2 S/cm. The results of this work show that simultaneous radiation-induced grafting with EB is a promising method to prepare high quality ion-conducting membranes for possible use in fuel cells and lithium batteries.

  5. Tailoring percolating conductive networks of natural rubber composites for flexible strain sensors via a cellulose nanocrystal templated assembly.

    PubMed

    Wang, Shuman; Zhang, Xinxing; Wu, Xiaodong; Lu, Canhui

    2016-01-21

    Conductive polymer composites (CPCs) just above the percolation threshold exhibit a unique strain-reversible electric response upon application of tensile strain, which can be used to prepare strain sensors. However, it is difficult to balance the electric conductivity which is fundamental to a stable output signal and the strain sensing sensitivity due to the relatively dense conductive pathways of the traditional CPCs. Constructing a "brittle" but effective conductive network structure in CPCs is the essential foundation of a desirable sensing material. Here, we demonstrate for the first time that highly flexible, stretchable, sensitive, and reversible strain sensors can be fabricated by a facile latex assembly approach, in which nontoxic, sustainable and biodegradable cellulose nanocrystals played a key role in tailoring the percolating network of conductive natural rubber (NR)/carbon nanotube (CNT) composites. The resulting nanocomposites with a continuous 3D conductive structure exhibited a very low electrical conductivity percolation threshold (4-fold lower than that of the conventional NR/CNT composites), high resistivity and sensitivity (gauge factor ≈ 43.5) and meanwhile good reproducibility of up to 100% strain. The proposed materials and principles in this study open up a novel practical approach to design high performance flexible sensors for a broad range of multifunctional applications. PMID:26542376

  6. The influence of reduced graphene oxide on electrical conductivity of LiFePO4-based composite as cathode material

    NASA Astrophysics Data System (ADS)

    Arifin, Muhammad; Aimon, Akfiny Hasdi; Winata, Toto; Abdullah, Mikrajuddin; Iskandar, Ferry

    2016-02-01

    LiFePO4 is fascinating cathode active materials for Li-ion batteries application because of their high electrochemical performance such as a stable voltage at 3.45 V and high specific capacity at 170 mAh.g-1. However, their low intrinsic electronic conductivity and low ionic diffusion are still the hindrance for their further application on Li-ion batteries. Therefore, the efforts to improve their conductivity are very important to elevate their prospecting application as cathode materials. Herein, we reported preparation of additional of reduced Graphene Oxide (rGO) into LiFePO4-based composite via hydrothermal method and the influence of rGO on electrical conductivity of LiFePO4-based composite by varying mass of rGO in composition. Vibration of LiFePO4-based composite was detected on Fourier Transform Infrared Spectroscopy (FTIR) spectra, while single phase of LiFePO4 nanocrystal was observed on X-Ray Diffraction (XRD) pattern, it furthermore, Scanning Electron Microscopy (SEM) images showed that rGO was distributed around LiFePO4-based composite. Finally, the 4-point probe measurement result confirmed that the optimum electrical conductivity is in additional 2 wt% rGO for range 1 to 2 wt% rGO.

  7. Building up graphene-based conductive polymer composite thin films using reduced graphene oxide prepared by γ-ray irradiation.

    PubMed

    Xie, Siyuan; Zhang, Bowu; Wang, Chunlei; Wang, Ziqiang; Li, Linfan; Li, Jingye

    2013-01-01

    In this paper, reduced graphene oxide (RGO) was prepared by means of γ -ray irradiation of graphene oxide (GO) in a water/ethanol mix solution, and we investigated the influence of reaction parameters, including ethanol concentration, absorbed dose, and dose rate during the irradiation. Due to the good dispersibility of the RGO in the mix solution, we built up flexible and conductive composite films based on the RGO and polymeric matrix through facile vacuum filtration and polymer coating. The electrical and optical properties of the obtained composite films were tested, showing good electrical conductivity with visible transmittance but strong ultraviolet absorbance. PMID:24170985

  8. Microwave absorption properties of conducting polymer composite with barium ferrite nanoparticles in 12.4-18 GHz

    NASA Astrophysics Data System (ADS)

    Ohlan, Anil; Singh, Kuldeep; Chandra, Amita; Dhawan, S. K.

    2008-08-01

    Conducting polymer nanocomposites of polyphenyl amine with barium ferrite nanoparticles (50-70nm) have been synthesized via emulsion polymerization. The complex permittivity, permeability, and microwave absorption properties of the composite were studied in the 12.4-18GHz (Ku band) frequency range. The composite has shown high shielding effectiveness due to absorption (SEA) of 28.9dB (˜99.9%), which strongly depends on dielectric loss, magnetic permeability, and volume fraction of barium ferrite nanoparticles. The high value of SEA suggests that these composites can be used as a promising radar absorbing materials.

  9. Thermal conductivity of thermally-isolating polymeric and composite structural support materials between 0.3 and 4 K

    NASA Astrophysics Data System (ADS)

    Runyan, M. C.; Jones, W. C.

    2008-09-01

    We present measurements of the low-temperature thermal conductivity of a number of polymeric and composite materials from 0.3 to 4 K. The materials measured are Vespel SP-1, Vespel SP-22, unfilled PEEK, 30% carbon fiber-filled PEEK, 30% glass-filled PEEK, carbon fiber Graphlite composite rod, Torlon 4301, G-10/FR-4 fiberglass, pultruded fiberglass composite, Macor ceramic, and graphite rod. These materials have moderate to high elastic moduli making them useful for thermally-isolating structural supports.

  10. Prediction of Thermal Conductivity for Irradiated SiC/SiC Composites by Informing Continuum Models with Molecular Dynamics Data

    SciTech Connect

    Nguyen, Ba Nghiep; Gao, Fei; Henager, Charles H.; Kurtz, Richard J.

    2014-05-01

    This article proposes a new method to estimate the thermal conductivity of SiC/SiC composites subjected to neutron irradiation. The modeling method bridges different scales from the atomic scale to the scale of a 2D SiC/SiC composite. First, it studies the irradiation-induced point defects in perfect crystalline SiC using molecular dynamics (MD) simulations to compute the defect thermal resistance as a function of vacancy concentration and irradiation dose. The concept of defect thermal resistance is explored explicitly in the MD data using vacancy concentrations and thermal conductivity decrements due to phonon scattering. Point defect-induced swelling for chemical vapor deposited (CVD) SiC as a function of irradiation dose is approximated by scaling the corresponding MD results for perfect crystal β-SiC to experimental data for CVD-SiC at various temperatures. The computed thermal defect resistance, thermal conductivity as a function of grain size, and definition of defect thermal resistance are used to compute the thermal conductivities of CVD-SiC, isothermal chemical vapor infiltrated (ICVI) SiC and nearly-stoichiometric SiC fibers. The computed fiber and ICVI-SiC matrix thermal conductivities are then used as input for an Eshelby-Mori-Tanaka approach to compute the thermal conductivities of 2D SiC/SiC composites subjected to neutron irradiation within the same irradiation doses. Predicted thermal conductivities for an irradiated Tyranno-SA/ICVI-SiC composite are found to be comparable to available experimental data for a similar composite ICVI-processed with these fibers.

  11. Alignment of carbon iron into polydimethylsiloxane to create conductive composite with low percolation threshold and high piezoresistivity

    NASA Astrophysics Data System (ADS)

    Dong, Shuai; Wang, R.; Wang, Xiaojie

    2016-04-01

    With the development of soft materials for applications in flexible tactile sensors, metal particles/insulated polymer composites have been studied for many years. This article proposes a method to prepare carbon iron particles (CIPs)/polydimethylsiloxane (PDMS) conductive composite with low percolation threshold and highly piezoresistive stain sensitivity. CIPs-PDMS composites with various filler volume fraction were cured under a magnetic field over 1.0 T to create chain-like structure resulting in anisotropy of conductive materials. The electrical resistivity for the longitudinal direction were measured as a function of filler volume fraction to understand the electrical percolation behavior. In this study, the percolation threshold of CIPs-PDMS composite cured under a magnetic field can be as low as 0.1 vol.%, which is much less than most of those studies in particulate composites. Meanwhile, the effects of compressive strain on the electrical properties of CIPs-PDMS composites were also investigated. The strain sensitivity depends on filler volume fraction and decreases with the increasing of compressive strain. It has been found that the composites containing a small amount of CI particles curing under a magnetic field exhibit a high strain sensitivity of over 150. The microstructures were measured by using a scanning electron microscope (SEM), and the results were also reported in this paper.

  12. Development of novel multifunctional biobased polymer composites with tailored conductive network of micro-and-nano-fillers

    NASA Astrophysics Data System (ADS)

    Leung, Siu N.; Ghaffari, Shahriar; Naguib, Hani E.

    2013-04-01

    Biobased/green polymers and nanotechnology warrant a multidisciplinary approach to promote the development of the next generation of materials, products, and processes that are environmentally sustainable. The scientific challenge is to find the suitable applications, and thereby to create the demand for large scale production of biobased/green polymers that would foster sustainable development of these eco-friendly materials in contrast to their petroleum/fossil fuel derived counterparts. In this context, this research aims to investigate the synergistic effect of green materials and nanotechnology to develop a new family of multifunctional biobased polymer composites with promoted thermal conductivity. For instance, such composite can be used as a heat management material in the electronics industry. A series of parametric studies were conducted to elucidate the science behind materials behavior and their structure-toproperty relationships. Using biobased polymers (e.g., polylactic acid (PLA)) as the matrix, heat transfer networks were developed and structured by embedding hexagonal boron nitride (hBN) and graphene nanoplatelets (GNP) in the PLA matrix. The use of hybrid filler system, with optimized material formulation, was found to promote the composite's effective thermal conductivity by 10-folded over neat PLA. This was achieved by promoting the development of an interconnected thermally conductive network through structuring hybrid fillers. The thermally conductive composite is expected to afford unique opportunities to injection mold three-dimensional, net-shape, lightweight, and eco-friendly microelectronic enclosures with superior heat dissipation performance.

  13. Inorganic-based proton conductive composite membranes for elevated temperature and reduced relative humidity PEM fuel cells

    NASA Astrophysics Data System (ADS)

    Wang, Chunmei

    Proton exchange membrane (PEM) fuel cells are regarded as highly promising energy conversion systems for future transportation and stationary power generation and have been under intensive investigations for the last decade. Unfortunately, cutting edge PEM fuel cell design and components still do not allow economically commercial implementation of this technology. The main obstacles are high cost of proton conductive membranes, low-proton conductivity at low relative humidity (RH), and dehydration and degradation of polymer membranes at high temperatures. The objective of this study was to develop a systematic approach to design a high proton conductive composite membrane that can provide a conductivity of approximately 100 mS cm-1 under hot and dry conditions (120°C and 50% RH). The approach was based on fundamental and experimental studies of the proton conductivity of inorganic additives and composite membranes. We synthesized and investigated a variety of organic-inorganic Nafion-based composite membranes. In particular, we analyzed their fundamental properties, which included thermal stability, morphology, the interaction between inorganic network and Nafion clusters, and the effect of inorganic phase on the membrane conductivity. A wide range of inorganic materials was studied in advance in order to select the proton conductive inorganic additives for composite membranes. We developed a conductivity measurement method, with which the proton conductivity characteristics of solid acid materials, zirconium phosphates, sulfated zirconia (S-ZrO2), phosphosilicate gels, and Santa Barbara Amorphous silica (SBA-15) were discussed in detail. Composite membranes containing Nafion and different amounts of functionalized inorganic additives (sulfated inorganics such as S-ZrO2, SBA-15, Mobil Composition of Matter MCM-41, and S-SiO2, and phosphonated inorganic P-SiO2) were synthesized with different methods. We incorporated inorganic particles within Nafion clusters

  14. Flexible touchpads based on inductive sensors using embedded conductive composite polymer

    NASA Astrophysics Data System (ADS)

    Rahbar, A.; Rahbar, M.; Gray, B. L.

    2014-04-01

    We present the design, fabrication, and preliminary testing of a flexible array of sensor switches intended for applications in wearable electronics and sensor systems. The touch pad sensor arrays feature flexible printed circuit board (flexible PCB) substrates and/or flexible conductive composite polymer (CCP) structures, resulting in highly flexible switch arrays. Each switch consists of 4 elements: fascia, target, spacer and a sensor coil. The user presses the fascia, bringing the target in contact with the sensor coil. Any change in the position of the target changes the coil inductance due to the generation of eddy currents, which are detected by an electronic circuit and custom software. Contact between the target and coil also measurably changes the inductance of the coils. Different sizes and geometries (square, circular, hexagonal and octagonal) of coils in both flexible PCB metal (copper) and CCP were investigated to determine which couple best with the CCP that forms the target for the inductive coils. We describe techniques for patterning two-layer inductive coils on flexible PCBs. Using this process, we demonstrate coil trace thicknesses of 200 micrometers. We also present a new low cost microfabrication technique to create inductive flexible coils using embedded CCP in polydimethylsiloxane (PDMS) as an alternative to flexible PCB metal coils. We further describe an electronic circuit that accurately measures inductances as low as 500 nH that is used to detect the change in the inductance of a sensor's coil when the user presses the target element of the sensor. The inductance for a sensor composed of CCP square coils and CCP target was measured to be approximately 35 μH before being pressed. When pressed, the inductance dropped to 3.8 μH, a change which was easily detected.

  15. Ionic conductivity and electrochemical characterization of novel microporous composite polymer electrolytes

    SciTech Connect

    Xu, W.; Siow, K.S.; Gao, Z.; Lee, S.Y.

    1999-12-01

    Composite polymer electrolytes (CPEs) have been prepared by encapsulating electrolyte solutions of inorganic lithium salts dissolved in a plasticizer or mixture of plasticizers such as ethylene carbonate (EC), propylene carbonate (PC), {gamma}-butyrolactone (BL) and dimethyl carbonate (DMC), into porous polymer membranes. These polymer membranes are obtained from microemulsion polymerization of the microemulsion system of acrylonitrile, 4-vinylbenzenesulfonic acid lithium salt, ethylene glycol dimethacrylate (as cross-linker), {omega}-methoxy poly(ethyleneoxy){sub 40} undecyl-{alpha}-methacrylate (as surfactant), and water. These CPEs exhibit conductivities of 3.1 x 10{sup {minus}4} to 1.2 x 10{sup {minus}3} S cm{sup {minus}1} at room temperature. The lithium ion transference number, measured using a dc polarization method coupled with ac impedance spectroscopy, is found to be ca. 0.45. Cyclic voltammetry of the CPEs on stainless steel electrodes shows electrochemical stability windows extending up to 3.9, 4.0, and 4.4 V vs. Li{sup +}/Li for CPEs with 1 M LiSO{sub 3}CF{sub 3}/EC-PC (1:1 by volume), 1 M LiBF{sub 4}/BL and 1 M LiClO{sub 4}/EC-DMC (1:1 by volume), respectively. The impedance of the Li/CPE interface for the CPE with 1 M LiClO{sub 4}/EC-DMC under open circuit conditions is found to increase over storage time. Preliminary charge-discharge tests of prototype Li/CPE/LiMn{sub 2}O{sub 4} cells show an initial discharge capacity of ca. 118 mAh g{sup {minus}1} of LiMn{sub 2}O{sub 4} at a discharge current rate of 0.10 mA cm{sup {minus}2}, and promising cyclability.

  16. Copper Nanoparticle/Multiwalled Carbon Nanotube Composite Films with High Electrical Conductivity and Fatigue Resistance Fabricated via Flash Light Sintering.

    PubMed

    Hwang, Hyun-Jun; Joo, Sung-Jun; Kim, Hak-Sung

    2015-11-18

    In this work, multiwalled carbon nanotubes (MWNTs) were employed to improve the conductivity and fatigue resistance of flash light sintered copper nanoparticle (NP) ink films. The effect of CNT weight fraction on the flash light sintering and the fatigue characteristics of Cu NP/CNT composite films were investigated. The effect of carbon nanotube length was also studied with regard to enhancing the conductivity and fatigue resistance of flash light sintered Cu NP/CNT composite films. The flash light irradiation energy was optimized to obtain high conductivity Cu NP/CNT composite films. Cu NP/CNT composite films fabricated via optimized flash light irradiation had the lowest resistivity (7.86 μΩ·cm), which was only 4.6 times higher than that of bulk Cu films (1.68 μΩ·cm). It was also demonstrated that Cu NP/CNT composite films had better durability and environmental stability than those of Cu NPs only. PMID:26505908

  17. Conductive ZnO:Zn Composites for High-Rate Sputtering Deposition of ZnO Thin Films

    NASA Astrophysics Data System (ADS)

    Zhou, Li Qin; Dubey, Mukul; Simões, Raul; Fan, Qi Hua; Neto, Victor

    2015-02-01

    We report an electrically conductive composite prepared by sintering ZnO and metallic Zn powders. Microstructure analysis combined with electrical conductivity studies indicated that when the proportion of metallic Zn reached a threshold (˜20 wt.%), a metal matrix was formed in accordance with percolation theory. This composite has potential as a sputtering target for deposition of high-quality ZnO. Use of the ZnO:Zn composite completely eliminates target poisoning effects in reactive sputtering of the metal, and enables deposition of thin ZnO films at rates much higher than those obtained by sputtering of pure ZnO ceramic targets. The optical transmittance of the ZnO films prepared by use of this composite is comparable with that of films produced by radio frequency sputtering of pure ZnO ceramic targets. The sputtering characteristics of the conductive ZnO:Zn composite target are reported, and possible mechanisms of the high rate of deposition are also discussed.

  18. Enhanced thermal conductivity of uranium dioxide-silicon carbide composite fuel pellets prepared by Spark Plasma Sintering (SPS)

    NASA Astrophysics Data System (ADS)

    Yeo, S.; Mckenna, E.; Baney, R.; Subhash, G.; Tulenko, J.

    2013-02-01

    Uranium dioxide (UO2)-10 vol% silicon carbide (SiC) composite fuel pellets were produced by oxidative sintering and Spark Plasma Sintering (SPS) at a range of temperatures from 1400 to 1600 °C. Both SiC whiskers and SiC powder particles were utilized. Oxidative sintering was employed over 4 h and the SPS sintering was employed only for 5 min at the highest hold temperature. It was noted that composite pellets sintered by SPS process revealed smaller grain size, reduced formation of chemical products, higher density, and enhanced interfacial contact compared to the pellets made by oxidative sintering. For given volume of SiC, the pellets with powder particles yielded a smaller grain size than pellets with SiC whiskers. Finally thermal conductivity measurements at 100 °C, 500 °C, and 900 °C revealed that SPS sintered UO2-SiC composites exhibited an increase of up to 62% in thermal conductivity compared to UO2 pellets, while the oxidative sintered composite pellets revealed significantly inferior thermal conductivity values. The current study points to the improved processing capabilities of SPS compared to oxidative sintering of UO2-SiC composites.

  19. Conductive Circuit Containing a Polymer Composition Containing Thermally Exfoliated Graphite Oxide and Method of Making the Same

    NASA Technical Reports Server (NTRS)

    Prud'Homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor)

    2014-01-01

    A conductive circuit containing a polymer composite, which contains at least one polymer and a modified graphite oxide material, containing thermally exfoliated graphite oxide having a surface area of from about 300 m(sup.2)/g to 2600 m(sup.2)/g, and a method of making the same.

  20. Mechanically durable and highly conductive elastomeric composites from long single-walled carbon nanotubes mimicking the chain structure of polymers.

    PubMed

    Ata, Seisuke; Kobashi, Kazufumi; Yumura, Motoo; Hata, Kenji

    2012-06-13

    By using long single-walled carbon nanotubes (SWNTs) as a filler possessing the highest aspect ratio and small diameter, we mimicked the chain structure of polymers in the matrix and realized a highly conductive elastomeric composite (30 S/cm) with an excellent mechanical durability (4500 strain cycles until failure), far superior to any other reported conductive elastomers. This exceptional mechanical durability was explained by the ability of long and traversing SWNTs to deform in concert with the elastomer with minimum stress concentration at their interfaces. The conductivity was sufficient to operate many active electronics components, and thus this material would be useful for practical stretchable electronic devices. PMID:22546049

  1. Electrically conductive LCP-carbon composite with low carbon content for bipolar plate application in polymer electrolyte membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Wolf, H.; Willert-Porada, M.

    Lightweight polymer-carbon composites with high specific electrical conductivity at a carbon content below 40 vol.% were developed. The electrical and mechanical properties and the hydrogen permeability of carbon fiber and particle reinforced liquid crystalline polymers were examined. Vectra ® A 950, SIGRAFIL ® carbon fibers and Vulcan ® XC 72 R carbon black were employed. The composites are found to have sufficient mechanical properties and a hydrogen permeability low enough to be utilised as bipolar plate material in fuel cell applications. The density of the new composite is 20% lower than the density of commercial bipolar plates made from carbon reinforced polymeric composite materials, due to the lower carbon content. The current density at 0.5 V in an operating fuel cell is only 20% lower compared to commercial materials with more than 80 vol.% carbon content and meets the requirements for bipolar plate application.

  2. Enhanced proton conductivity by the influence of modified montmorillonite on poly (vinyl alcohol) based blend composite membranes

    NASA Astrophysics Data System (ADS)

    Palani, P. Bahavan; Abidin, K. Sainul; Kannan, R.; Rajashabala, S.; Sivakumar, M.

    2016-05-01

    The highest proton conductivity value of 0.0802 Scm-1 is obtained at 6wt% of protonated MMT added to the PVA/PEG blends. The polymer blend composite membranes are prepared with varied concentration of Poly vinyl alcohol (PVA), Poly ethylene glycol (PEG) and Montmorillonite (MMT) by solution casting method. The Na+ MMT was modified (protonated) to H+ MMT with ion exchange process. The prepared membranes were characterized by using TGA, FTIR, XRD, Ion Exchange Capacity, Water/Methanol uptake, swelling ratio and proton conductivity. The significant improvements in the hydrolytic stability were observed. In addition, thermal stability of the composite membranes were improved and controlled by the addition of MMT. All the prepared membranes are shown appreciable values of proton conductivity at room temperature with 100% relative humidity.

  3. Electric properties of carbon nano-onion/polyaniline composites: a combined electric modulus and ac conductivity study

    NASA Astrophysics Data System (ADS)

    Papathanassiou, Anthony N.; Mykhailiv, Olena; Echegoyen, Luis; Sakellis, Ilias; Plonska-Brzezinska, Marta E.

    2016-07-01

    The complex electric modulus and the ac conductivity of carbon nano-onion/polyaniline composites were studied from 1 mHz to 1 MHz at isothermal conditions ranging from 15 K to room temperature. The temperature dependence of the electric modulus and the dc conductivity analyses indicate a couple of hopping mechanisms. The distinction between thermally activated processes and the determination of cross-over temperature were achieved by exploring the temperature dependence of the fractional exponent of the dispersive ac conductivity and the bifurcation of the scaled ac conductivity isotherms. The results are analyzed by combining the granular metal model (inter-grain charge tunneling of extended electron states located within mesoscopic highly conducting polyaniline grains) and a 3D Mott variable range hopping model (phonon assisted tunneling within the carbon nano-onions and clusters).

  4. A novel biocompatible conducting polyvinyl alcohol (PVA)-polyvinylpyrrolidone (PVP)-hydroxyapatite (HAP) composite scaffolds for probable biological application.

    PubMed

    Chaudhuri, B; Mondal, B; Ray, S K; Sarkar, S C

    2016-07-01

    We have prepared biocompatible composites of 80wt% polyvinyl alcohol (PVA)-(20wt%) polyvinylpyrrolidone (PVP) blend with different concentrations of bioactive nanohydroxyapatite, Ca10(PO4)6(HO)2 (HAP). The composite films demonstrated maximum effective conductivity (σ∼1.64×10(-4)S/m) and effective dielectric constant (ε∼290) at percolation threshold concentration (∼10wt% HAP) at room temperature. These values of σ and ε are much higher than those of PVA, PVP or HAP. Our preliminary observation indicated excellent biocompatibility of the electrospun fibrous meshes of two of these composites with different HAP contents (8.5 and 5wt% within percolation threshold concentration) using NIH 3T3 fibroblast cell line. Cells viability on the well characterized composite fibrous scaffolds was determined by MTT [3-(4,5-di-methylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay analysis. Enhancement of σ, due to HAP addition, was found to show increased biocompatibility of the fibrous scaffold. Enhanced σ value of the PVA/PVP-HAP composite provided supporting cues for the increased cell viability and biocompatibility of the composite fibrous meshes. Excellent biocompatibility these electrospun composite scaffolds made them to plausible potential candidates for tissue engineering or other biomedical applications. PMID:26998868

  5. Symmetry transformation in the problem of the conductivity of anisotropic composites

    SciTech Connect

    Balagurov, B. Ya.

    2013-11-15

    A transformation of the coordinates, current density, and electric field strength has been proposed such that holds the direct-current equations. One of the components of a composite can be made isotropic by choosing the coefficients of the transformation. This allows the generalization of the standard theory of the effective medium to the case of an anisotropic composite with inclusions of an arbitrary shape.

  6. The different fate of satellite cells on conductive composite electrospun nanofibers with graphene and graphene oxide nanosheets.

    PubMed

    Mahmoudifard, Matin; Soleimani, Masoud; Hatamie, Shadie; Zamanlui, Soheila; Ranjbarvan, Parviz; Vossoughi, Manouchehr; Hosseinzadeh, Simzar

    2016-04-01

    Electrospinning of composite polymer solutions provides fantastic potential to prepare novel nanofibers for use in a variety of applications. The addition of graphene (G) and graphene oxide (GO) nanosheets to bioactive polymers was found to enhance their conductivity and biocompatibility. Composite conductive nanofibers of polyaniline (PANI) and polyacrylonitrile (PAN) with G and GO nanosheets were prepared by an electrospinning process. The fabricated membranes were investigated by physical and chemical examinations including scanning electron microscopy (SEM), Raman spectroscopy, x-ray diffraction (XRD) and tensile assay. The muscle satellite cells enriched by a pre-plating technique were cultured in the following and their proliferation and differentiation behavior studied by MTT, Real-Time PCR assays and 4', 6-diamidino-2-phenylindole (DAPI) staining. The cultured cells on composite nanofibrous PAN/PANI-CSA/G confirmed a higher proliferation and differentiation value compared to other groups including PAN/PANI-CSA/GO and PAN/PANI-CSA scaffolds. Furthermore, the higher stiffness of the former scaffold showed a lower cell spreading as a function of stem cell activation into more proliferative cells. It is supposed that the enhanced conductivity value in addition to relative higher stiffness of the PAN/PANI-CSA/G composite nanofibers plays a favorable role for proliferation and differentiation of satellite cells. PMID:26962722

  7. Fabrication and characterization of poly(lactic acid)/acetyl tributyl citrate/carbon black as conductive polymer composites.

    PubMed

    Yu, Jiugao; Wang, Ning; Ma, Xiaofei

    2008-03-01

    By using acetyl tributyl citrate (ATBC) as the plasticizer of poly(lactic acid) (PLA) and carbon black (CB) as conductive filler, electrically conductive polymer composites (CPC) with different CB and ATBC contents were prepared. FTIR revealed that the interaction existed between PLA/ATBC matrix and CB filler and ATBC could improve this interaction. The rheology showed that ATBC could obviously decrease the shear viscosity and improve the fluidity of the composites but just the reverse for CB. With the increasing of CB contents, the enforcement effect, storage modulus, and glass-transition temperature increased but the elongation at break decreased. PLA/ATBC/CB composites exhibited the low electrical percolation thresholds of 0.516, 1.20, 2.46, and 2.74 vol % CB at 30, 20, 10, and 0 wt % ATBC. The conductivity of the composite containing 3.98 vol % CB and 30 wt % ATBC reached 1.60 S/cm. Scanning electron microscopy revealed that the addition of ATBC facilitated the dispersion of the CB in the PLA matrix. Water vapor permeability (WVP) showed that, at the same CB contents, the more ATBC contents there were, the less the values of WVP were. PMID:18290627

  8. Proton conductivity of CsH{sub 2}PO{sub 4}WPA composites at intermediate temperatures

    SciTech Connect

    Insani, Evan Kamaratul; Nguyen, Van H.; Kawamura, Go; Hamagami, Jun-ichi; Sakai, Mototsugu; Matsuda, Atsunori; Yuliarto, Brian

    2010-10-24

    CsH{sub 2}PO{sub 4} and H{sub 3}PW{sub 12}O{sub 40}6H{sub 2}O (WPA6H{sub 2}O) were mechanically milled by using planetary ball mill to obtain xCsH{sub 2}PO{sub 4}--(1-x)WPA6H{sub 2}O(%mol) composites. Characterizations of the composites indicate that there were changes of structure of CsH{sub 2}PO{sub 4}WPA composite after mechanical milling. {sup 1}H MAS NMR measurements suggested a hydrogen bond was newly developed between CsH{sub 2}PO{sub 4} and WPA which correlated with conductivity of the composites. 95CsH{sub 2}PO{sub 4}5WPA shows the highest conductivity at 70-170 deg. C range of temperature. The mechanical milling succeed to increase the conductivity under non-humidified atmosphere and intermediate temperature.

  9. Interfacial characteristics of diamond/aluminum composites with high thermal conductivity fabricated by squeeze-casting method

    SciTech Connect

    Jiang, Longtao; Wang, Pingping; Xiu, Ziyang; Chen, Guoqin; Lin, Xiu; Dai, Chen; Wu, Gaohui

    2015-08-15

    In this work, aluminum matrix composites reinforced with diamond particles (diamond/aluminum composites) were fabricated by squeeze casting method. The material exhibited a thermal conductivity as high as 613 W / (m · K). The obtained composites were investigated by scanning electron microscope and transmission electron microscope in terms of the (100) and (111) facets of diamond particles. The diamond particles were observed to be homogeneously distributed in the aluminum matrix. The diamond{sub (111)}/Al interface was found to be devoid of reaction products. While at the diamond{sub (100)}/Al interface, large-sized aluminum carbides (Al{sub 4}C{sub 3}) with twin-crystal structure were identified. The interfacial characteristics were believed to be responsible for the excellent thermal conductivity of the material. - Graphical abstract: Display Omitted - Highlights: • Squeeze casting method was introduced to fabricate diamond/Al composite. • Sound interfacial bonding with excellent thermal conductivity was produced. • Diamond{sub (111)}/ aluminum interface was firstly characterized by TEM/HRTEM. • Physical combination was the controlling bonding for diamond{sub (111)}/aluminum. • The growth mechanism of Al{sub 4}C{sub 3} was analyzed by crystallography theory.

  10. Conductivity degradation of polyvinylidene fluoride composite binder during cycling: Measurements and simulations for lithium-ion batteries

    DOE PAGESBeta

    Grillet, Anne M.; Humplik, Thomas; Stirrup, Emily K.; Roberts, Scott A.; Barringer, David A.; Snyder, Chelsea M.; Janvrin, Madison R.; Apblett, Christopher A.

    2016-07-02

    The polymer-composite binder used in lithium-ion battery electrodes must both hold the electrodes together and augment their electrical conductivity while subjected to mechanical stresses caused by active material volume changes due to lithiation and delithiation. We have discovered that cyclic mechanical stresses cause significant degradation in the binder electrical conductivity. After just 160 mechanical cycles, the conductivity of polyvinylidene fluoride (PVDF):carbon black binder dropped between 45–75%. This degradation in binder conductivity has been shown to be quite general, occurring over a range of carbon black concentrations, with and without absorbed electrolyte solvent and for different polymer manufacturers. Mechanical cycling ofmore » lithium cobalt oxide (LiCoO2) cathodes caused a similar degradation, reducing the effective electrical conductivity by 30–40%. Mesoscale simulations on a reconstructed experimental cathode geometry predicted the binder conductivity degradation will have a proportional impact on cathode electrical conductivity, in qualitative agreement with the experimental measurements. Lastly, ohmic resistance measurements were made on complete batteries. Direct comparisons between electrochemical cycling and mechanical cycling show consistent trends in the conductivity decline. This evidence supports a new mechanism for performance decline of rechargeable lithium-ion batteries during operation – electrochemically-induced mechanical stresses that degrade binder conductivity, increasing the internal resistance of the battery with cycling.« less

  11. Statistical Continuum Theory for the Effective Conductivity of Fiber Filled Polymer Composites: Effect of Orientation Distribution and Aspect Ratio

    SciTech Connect

    Mikdam, Amed; Makradi, A.; Ahzi, Said; Garmestani, Hamid; Li, Dongsheng; Remond, Y.

    2010-03-01

    Effective conductivity of polymer composites, filled with conducting fibers such as carbon nanotubes, is studied using statistical continuum theory. The fiber orientation distribution in the matrix plays a very important role on their effective properties. To take into account their orientation, shape and distribution, two-point and three-point probability distribution functions are used. The effect of fibers orientation is illustrated by comparing the effective conductivity of microstructures with oriented and non-oriented fibers. The randomly oriented fibers result in an isotropic effective conductivity. The increased fiber orientation distribution can lead to higher anisotropy in conductivity. The effect of fiber’s aspect ratio on the effective conductivity is studied by comparing microstructures with varying degrees of fiber orientation distribution. Results show that the increase in anisotropy leads to higher conductivity in the maximum fiber orientation distribution direction and lower conductivity in the transverse direction. These results are in agreement with various models from the literature that show the increase of the aspect ratio of fibers improves the electrical and thermal conductivity.

  12. Conduction mechanism in Polyaniline-flyash composite material for shielding against electromagnetic radiation in X-band & Ku band

    NASA Astrophysics Data System (ADS)

    Singh, Avanish Pratap; Anoop Kumar, S.; Chandra, Amita; Dhawan, S. K.

    2011-06-01

    β-Naphthalene sulphonic acid (β-NSA) doped polyaniline (PANI)-flyash (FA) composites have been prepared by chemical oxidative polymerization route whose conductivity lies in the range 2.37-21.49 S/cm. The temperature dependence of electrical conductivity has also been recorded which shows that composites follow Mott's 3D-VRH model. SEM images demonstrate that β-NSA leads to the formation of the tubular structure with incorporated flyash phase. TGA studies show the improvement in thermal stability of composites with increase in loading level of flyash. Complex parameters i.e. permittivity (ɛ* = ɛ'- iɛ″) and permeability (μ*=μ'- iμ″) of PANI-FA composites have been calculated from experimental scattering parameters (S11 & S21) using theoretical calculations given in Nicholson-Ross and Weir algorithms. The microwave absorption properties of the composites have been studied in X-band (8.2 - 12.4 GHz) & Ku-Band (12.4 - 18 GHz) frequency range. The maximum shielding effectiveness observed was 32dB, which strongly depends on dielectric loss and volume fraction of flyash in PANI matrix.

  13. Light-Weight Silver Plating Foam and Carbon Nanotube Hybridized Epoxy Composite Foams with Exceptional Conductivity and Electromagnetic Shielding Property.

    PubMed

    Xu, Yu; Li, Ying; Hua, Wei; Zhang, Aiming; Bao, Jianjun

    2016-09-14

    Herein, light-weight and exceptionally conductive epoxy composite foams were innovatively fabricated for electromagnetic interference (EMI) shielding applications using multiwalled carbon nanotubes (MWCNTs) and 3D silver-coated melamine foam (SF) as conductive frameworks. A novel and nontraditional polymer microsphere was used to reduce the material density. The preformed, highly porous, and electrically conductive SF provided channels for fast electron transport. The MWCNTs were used to offset the decrease in conductive pathways due to the crystal defects of the silver layer and the insulating epoxy resin. Consequently, an exceptional conductivity of 253.4 S m(-1), a remarkable EMI shielding effectiveness of above 68 dB at 0.05-18 GHz, and a thermal conductivity of 0.305 W mK(-1) were achieved in these novel foams employing only 2 wt % of MWCNTs and 3.7 wt % of silver due to the synergistic effects that originated in the MWCNT and SF. These parameters are substantially higher than that achieved for the foam containing 2 wt % MWCNTs. Also, the SF exhibited little weakening in the foamability of the epoxy blends and the compression properties of resulting foams. All the results indicated that this effort provided a novel, simple, low-cost, and easily industrialized concept for fabricating light-weight, high-strength epoxy composite foams for high-performance EMI shielding applications. PMID:27553528

  14. Highly conductive quasi-coaxial electrospun quaternized polyvinyl alcohol nanofibers and composite as high-performance solid electrolytes

    NASA Astrophysics Data System (ADS)

    Liao, Guan-Ming; Li, Pin-Chieh; Lin, Jia-Shiun; Ma, Wei-Ting; Yu, Bor-Chern; Li, Hsieh-Yu; Liu, Ying-Ling; Yang, Chun-Chen; Shih, Chao-Ming; Lue, Shingjiang Jessie

    2016-02-01

    Electrospun quaternized polyvinyl alcohol (Q-PVA) nanofibers are prepared, and a potassium hydroxide (KOH)-doped nanofiber mat demonstrates enhanced ionic conductivity compared with a dense Q-PVA film with KOH doping. The Q-PVA composite containing 5.98% electrospun Q-PVA nanofibers exhibits suppressed methanol permeability. Both the high conductivity and suppressed methanol permeability are attributed to the quasi-coaxial structure of the electrospun nanofibers. The core of the fibers exhibits a more amorphous region that forms highly conductive paths, while the outer shell of the nanofibers contains more polymer crystals that serve as a hard sheath surrounding the soft core. This shell induces mass transfer resistance and creates a tortuous fuel pathway that suppresses methanol permeation. Such a Q-PVA composite is an effective solid electrolyte that makes the use of alkaline fuel cells viable. In a direct methanol alkaline fuel cell operated at 60 °C, a peak power density of 54 mW cm-2 is obtained using the electrospun Q-PVA composite, a 36.4% increase compared with a cell employing a pristine Q-PVA film. These results demonstrate that highly conductive coaxial electrospun nanofibers can be prepared through a single-opening spinneret and provide a possible approach for high-performance electrolyte fabrication.

  15. Fabrication of High Thermal Conductivity NARloy-Z-Diamond Composite Combustion Chamber Liner for Advanced Rocket Engines

    NASA Technical Reports Server (NTRS)

    Bhat, Biliyar N.; Greene, Sandra E.; Singh, Jogender

    2016-01-01

    NARloy-Z alloy (Cu-3 percent, Ag-0.5 percent, Zr) is a state of the art alloy currently used for fabricating rocket engine combustion chamber liners. Research conducted at NASA-MSFC and Penn State – Applied Research Laboratory has shown that thermal conductivity of NARloy-Z can be increased significantly by adding diamonds to form a composite (NARloy-Z-D). NARloy-Z-D is also lighter than NARloy-Z. These attributes make this advanced composite material an ideal candidate for fabricating combustion chamber liner for an advanced rocket engine. Increased thermal conductivity will directly translate into increased turbopump power and increased chamber pressure for improved thrust and specific impulse. This paper describes the process development for fabricating a subscale high thermal conductivity NARloy-Z-D combustion chamber liner using Field Assisted Sintering Technology (FAST). The FAST process uses a mixture of NARloy-Z and diamond powders which is sintered under pressure at elevated temperatures. Several challenges were encountered, i.e., segregation of diamonds, machining the super hard NARloy-Z-D composite, net shape fabrication and nondestructive examination. The paper describes how these challenges were addressed. Diamonds coated with copper (CuD) appear to give the best results. A near net shape subscale combustion chamber liner is being fabricated by diffusion bonding cylindrical rings of NARloy-Z-CuD using the FAST process.

  16. Effect of Applied Potential on the Electrochemical Deposition of Styrene-Butadiene Co-Polymer Based Conducting Polymer Composite

    NASA Astrophysics Data System (ADS)

    Mathew, Anisha Mary; Neena, P.

    2011-10-01

    Homogeneous conducting polymer composite films with improved electrical properties are synthesized via electrochemical polymerization of polyaniline on Styrene butadiene rubber coated steel electrode. The electrochemical polymerization is carried out by potentiostatic method using an aqueous solution of 0.2 M aniline and 1.5 M sulphuric acid as electrolyte in a single compartment electrochemical cell. The optical studies show successful incorporation of polyaniline into the matrix polymer film. The effect of applied potential on the electrodeposition of composite is studied by cyclic voltammetry and by impedance spectroscopic measurements.

  17. Method of making composition suitable for use as inert electrode having good electrical conductivity and mechanical properties

    DOEpatents

    Ray, S.P.; Rapp, R.A.

    1986-04-22

    An improved inert electrode composition is suitable for use as an inert electrode in the production of metals such as aluminum by the electrolytic reduction of metal oxide or metal salt dissolved in a molten salt bath. The composition comprises one or more metals or metal alloys and metal compounds which may include oxides of the metals comprising the alloy. The alloy and metal compounds are interwoven in a network which provides improved electrical conductivity and mechanical strength while preserving the level of chemical inertness necessary for such an electrode to function satisfactorily. 8 figs.

  18. Method of making composition suitable for use as inert electrode having good electrical conductivity and mechanical properties

    DOEpatents

    Ray, Siba P.; Rapp, Robert A.

    1986-01-01

    An improved inert electrode composition is suitable for use as an inert electrode in the production of metals such as aluminum by the electrolytic reduction of metal oxide or metal salt dissolved in a molten salt bath. The composition comprises one or more metals or metal alloys and metal compounds which may include oxides of the metals comprising the alloy. The alloy and metal compounds are interwoven in a network which provides improved electrical conductivity and mechanical strength while preserving the level of chemical inertness necessary for such an electrode to function satisfactorily.

  19. Workshop for Conducting Phase 2 of the INTEC Glass Composition Variation Study

    SciTech Connect

    B. A. Staples; C. A. Musick

    1999-06-01

    During March 30-31, 1999, the Phase 2 Idaho Nuclear Technology and Engineering Center (INTEC) Glass Composition Variation Study Workshop was held at the Shilo Inn in Idaho Falls, Idaho. The workshop had the purpose of establishing a preparation and characterization protocol for the phase 2b glasses of the INTEC composition variation study. The workshop also had the purpose of reviewing the most recent estimates of INTEC high-level waste compositions for their impacts on the vitrification of these wastes. Waste composition estimates discussed included those of the various calcine types and of the high activity waste fractions from the calcine dissolution/separations process. Persons from the Idaho National Engineering and Environmental Laboratory, Pacific Northwest Laboratories, and Savannah River Technology Center participated in this workshop. As a result of the workshop, details for the preparation and characterization of the phase 2b matrix of glasses were completed. The impac ts on vitrification of updated waste composition estimates were discussed. Actions for the preparation and characterization of the glasses and development of the separations flowsheet were established.

  20. Preparation and application of conducting polymer/Ag/clay composite nanoparticles formed by in situ UV-induced dispersion polymerization

    PubMed Central

    Zang, Limin; Qiu, Jianhui; Yang, Chao; Sakai, Eiichi

    2016-01-01

    In this work, composite nanoparticles containing polypyrrole, silver and attapulgite (PPy/Ag/ATP) were prepared via UV-induced dispersion polymerization of pyrrole using ATP clay as a templet and silver nitrate as photoinitiator. The effects of ATP concentration on morphology, structure and electrical conductivity were studied. The obtained composite nanoparticles with an interesting beads-on-a-string morphology can be obtained in a short time (10 min), which indicates the preparation method is facile and feasible. To explore the potential applications of the prepared PPy/Ag/ATP composite nanoparticles, they were served as multifunctional filler and blended with poly(butylene succinate) (PBS) matrix to prepare biodegradable composite material. The distribution of fillers in polymer matrix and the interfacial interaction between fillers and PBS were confirmed by scanning electron microscope, elemental mapping and dynamic mechanical analysis. The well dispersed fillers in PBS matrix impart outstanding antibacterial property to the biodegradable composite material as well as enhanced storage modulus due to Ag nanoparticles and ATP clay. The biodegradable composite material also possesses modest surface resistivity (106 ~ 109 Ω/◻). PMID:26839126

  1. Preparation and application of conducting polymer/Ag/clay composite nanoparticles formed by in situ UV-induced dispersion polymerization.

    PubMed

    Zang, Limin; Qiu, Jianhui; Yang, Chao; Sakai, Eiichi

    2016-01-01

    In this work, composite nanoparticles containing polypyrrole, silver and attapulgite (PPy/Ag/ATP) were prepared via UV-induced dispersion polymerization of pyrrole using ATP clay as a templet and silver nitrate as photoinitiator. The effects of ATP concentration on morphology, structure and electrical conductivity were studied. The obtained composite nanoparticles with an interesting beads-on-a-string morphology can be obtained in a short time (10 min), which indicates the preparation method is facile and feasible. To explore the potential applications of the prepared PPy/Ag/ATP composite nanoparticles, they were served as multifunctional filler and blended with poly(butylene succinate) (PBS) matrix to prepare biodegradable composite material. The distribution of fillers in polymer matrix and the interfacial interaction between fillers and PBS were confirmed by scanning electron microscope, elemental mapping and dynamic mechanical analysis. The well dispersed fillers in PBS matrix impart outstanding antibacterial property to the biodegradable composite material as well as enhanced storage modulus due to Ag nanoparticles and ATP clay. The biodegradable composite material also possesses modest surface resistivity (10(6)~ 10(9) Ω/◻). PMID:26839126

  2. Preparation and application of conducting polymer/Ag/clay composite nanoparticles formed by in situ UV-induced dispersion polymerization

    NASA Astrophysics Data System (ADS)

    Zang, Limin; Qiu, Jianhui; Yang, Chao; Sakai, Eiichi

    2016-02-01

    In this work, composite nanoparticles containing polypyrrole, silver and attapulgite (PPy/Ag/ATP) were prepared via UV-induced dispersion polymerization of pyrrole using ATP clay as a templet and silver nitrate as photoinitiator. The effects of ATP concentration on morphology, structure and electrical conductivity were studied. The obtained composite nanoparticles with an interesting beads-on-a-string morphology can be obtained in a short time (10 min), which indicates the preparation method is facile and feasible. To explore the potential applications of the prepared PPy/Ag/ATP composite nanoparticles, they were served as multifunctional filler and blended with poly(butylene succinate) (PBS) matrix to prepare biodegradable composite material. The distribution of fillers in polymer matrix and the interfacial interaction between fillers and PBS were confirmed by scanning electron microscope, elemental mapping and dynamic mechanical analysis. The well dispersed fillers in PBS matrix impart outstanding antibacterial property to the biodegradable composite material as well as enhanced storage modulus due to Ag nanoparticles and ATP clay. The biodegradable composite material also possesses modest surface resistivity (106 ~ 109 Ω/◻).

  3. Structuring and electric conductivity of polymer composites pyrolysed at high temperatures

    NASA Astrophysics Data System (ADS)

    Aneli, J. N.; Natriashvili, T. M.; Zaikov, G. E.

    2014-05-01

    On the basis of mixes of phenolformaldehide and epoxy resins at presence of some silicon organic compounds and fiber glasses annealed in vacuum and hydrogen media the new conductive monolithic materials have been created. There were investigated the conductive, magnetic and some other properties of these materials. It is established experimentally that the obtained products are characterized by semiconducting properties, the level of conductivity of which are regulated by selection of technological conditions. The density and mobility of charge carriers increase at increasing of annealing temperature up to definite levels. The temperature dependence of the electrical conductivity and charge mobility describe by Mott formulas. It is established that at annealing free radicals and other paramagnetic centers are formed. Iit is proposed that charge transport between conducting clusters provides by mechanism of charge jumping with alternative longevity of the jump.

  4. The role of MgBr2 to enhance the ionic conductivity of PVA/PEDOT:PSS polymer composite

    PubMed Central

    Sheha, Eslam M.; Nasr, Mona M.; El-Mansy, Mabrouk K.

    2014-01-01

    A solid polymer electrolyte system based on poly(vinyl alcohol) (PVA) and poly(3,4-Etylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) complexed with magnesium bromide (MgBr2) salt was prepared using solution cast technique. The ionic conductivity is observed to increase with increasing MgBr2 concentration. The maximum conductivity was found to be 9.89 × 10−6 S/cm for optimum polymer composite film (30 wt.% MgBr2) at room temperature. The increase in the conductivity is attributed to the increase in the number of ions as the salt concentration is increased. This has been proven by dielectric studies. The increase in conductivity is also attributable to the increase in the fraction of amorphous region in the electrolyte films as confirmed by their structural, thermal, electrical and optical properties. PMID:26199746

  5. An Improved Thermal Conductivity Polyurethane Composite for a Space Borne 20KV Power Supply

    NASA Technical Reports Server (NTRS)

    Shapiro, Andrew A.; Haque, Inam

    2005-01-01

    This effort was designed to find a way to reduce the temperature rise of critical components of a 20KV High Voltage Power Supply (HVPS) by improving the overall thermal conductivity of the encapsulated modules. Three strategies were evaluated by developing complete procedures, preparing samples, and performing tests. The three strategies were: 1. Improve the thermal conductivity of the polyurethane encapsulant through the addition of thermally conductive powder while minimizing impact on other characteristics of the encapsulant. 2. Improve the thermal conductivity of the polyurethane encapsulated assembly by the addition of a slab of thermally conductive, electrically insulating material, which is to act as a heat spreader. 3. Employ a more thermally conductive substrate (Al203) with the existing encapsulation scheme. The materials were chosen based on the following criteria: high dielectric breakdown strength; high thermal conductivity, ease of manufacturing, high compliance, and other standard space qualified materials properties (low out-gassing, etc.). An optimized cure was determined by a statistical design of experiments for both filled and unfilled materials. The materials were characterized for the desired properties and a complete process was developed and tested. The thermal performance was substantially improved and the strategies may be used for space flight.

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

    NASA Technical Reports Server (NTRS)

    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.

  7. Influence of matching solubility parameter of polymer matrix and CNT on electrical conductivity of CNT/rubber composite

    PubMed Central

    Ata, Seisuke; Mizuno, Takaaki; Nishizawa, Ayumi; Subramaniam, Chandramouli; Futaba, Don N.; Hata, Kenji

    2014-01-01

    We report a general approach to fabricate elastomeric composites possessing high electrical conductivity for applications ranging from wireless charging interfaces to stretchable electronics. By using arbitrary nine kinds of rubbers as matrices, we experimentally demonstrate that the matching the solubility parameter of CNTs and the rubber matrix is important to achieve higher electrical conductivity in CNT/rubber composite, resulting in continuous conductive pathways leading to electrical conductivities as high as 15 S/cm with 10 vol% CNT in fluorinated rubber. Further, using thermodynamic considerations, we demonstrate an approach to mix CNTs to arbitrary rubber matrices regardless of solubility parameter of matrices by adding small amounts of fluorinated rubber as a polymeric-compatibilizer of CNTs. We thereby achieved electrical conductivities ranging from 1.2 to 13.8 S/cm (10 vol% CNTs) using nine varieties of rubber matrices differing in chemical structures and physical properties. Finally, we investigated the components of solubility parameter of CNT by using Hansen solubility parameters, these findings may useful for controlling solubility parameter of CNTs. PMID:25434701

  8. 7Li NMR spectroscopy and ion conduction mechanism in mesoporous silica (SBA-15) composite poly(ethylene oxide) electrolyte

    NASA Astrophysics Data System (ADS)

    Reddy, M. Jaipal; Chu, Peter P.

    A composite of mesoporous silica (SBA-15) with a polyethylene oxide (PEO) polymer electrolyte is examined for use in various electrochemical devices. Incorporation of SBA-15 in a PEO:LiClO 4 polymer electrolyte facilitates salt dissociation, enhances ion conductivity, and improves miscibility between organic and inorganic moieties. Optimized conductivity is found at 10 wt.% SBA-15 composition, above this concentration the conductivity is reduced due to aggregation of a SBA-15:Li rich phase. Heating above melt temperature of PEO allows more of the polymer segments to interact with SBA-15. This results in a greater degree of disorder upon cooling, and the ion conductivity is enhanced. A 7Li MAS NMR study reveals three types of lithium-ion coordination. Two major types of conduction mechanism can be identified: one through conventional amorphous PEO; a second via hopping in a sequential manner by replacing the nearby vacancies ('holes') on the surface (both interior and exterior) of the SBA-15 channels.

  9. Epoxy Composites with Added Aluminum with Binary Particle Size Distribution for Enhanced Dielectric Properties and Thermal Conductivity

    NASA Astrophysics Data System (ADS)

    Sui, Xuezhen; Zhou, Wenying; Dong, Lina; Wang, Zijun; Wu, Peng; Zuo, Jing; Cai, Huiwu; Liu, Xiangrong

    2016-08-01

    Three kinds of hybrid aluminum (Al) particles with binary particle size distribution, i.e., [2 μm/50 μm], [2 μm/18 μm] and [18 μm/50 μm], were added in epoxy (EP) to prepare hybrid Al/EP composites with enhanced dielectric properties and thermal conductivity for embedded capacitor applications. The dielectric permittivity, dissipation factor, and thermal conductivity of three types of hybrid Al/EP composites were investigated as a function of relative volume fraction of smaller-size Al of hybrid Al particles (V s) at a total filler content of 60 wt.%, respectively. The results indicate that dielectric permittivity and thermal conductivity of the hybrid Al/EP mainly depend on two factors, such as the type of hybrid filler and the V s. The maximum dielectric permittivity of 48 appears at V s = V 18μm/V (18μm+50μm) = 35%. While, the above two factors have a negligible influence on the dissipation factor, which is as low as 0.022. The highest thermal conductivity of 1.28 W/m K is obtained at V s = V 18μm/V (18μm+50μm) = 50%. The maximum thermal conductivity for three hybrid systems shifts towards lower V s with decreasing the size ratio of a larger Al to a smaller one.

  10. Optimization of Acetylene Black Conductive Additive andPolyvinylidene Difluoride Composition for High Power RechargeableLithium-Ion Cells

    SciTech Connect

    Liu, G.; Zheng, H.; Battaglia, V.S.; Simens, A.S.; Minor, A.M.; Song, X.

    2007-07-01

    Fundamental electrochemical methods were applied to study the effect of the acetylene black (AB) and the polyvinylidene difluoride (PVDF) polymer binder on the performance of high-power designed rechargeable lithium ion cells. A systematic study of the AB/PVDF long-range electronic conductivity at different weight ratios is performed using four-probe direct current tests and the results reported. There is a wide range of AB/PVDF ratios that satisfy the long-range electronic conductivity requirement of the lithium-ion cathode electrode; however, a significant cell power performance improvement is observed at small AB/PVDF composition ratios that are far from the long-range conductivity optimum of 1 to 1.25. Electrochemical impedance spectroscopy (EIS) tests indicate that the interfacial impedance decreases significantly with increase in binder content. The hybrid power pulse characterization results agree with the EIS tests and also show improvement for cells with a high PVDF content. The AB to PVDF composition plays a significant role in the interfacial resistance. We believe the higher binder contents lead to a more cohesive conductive carbon particle network that results in better overall all local electronic conductivity on the active material surface and hence reduced charge transfer impedance.

  11. Thermal Conductivity and Thermal Gradient Cyclic Behavior of Refractory Silicate Coatings on SiC/SiC Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Lee, Kang N.; Miller, Robert A.

    2001-01-01

    Plasma-sprayed mullite and BSAS coatings have been developed to protect SiC/SiC ceramic matrix composites from high temperature environmental attack. In this study, thermal conductivity and thermal barrier functions of these coating systems are evaluated using a laser high-heat-flux test rig. The effects of water vapor on coating thermal conductivity and durability are studied by using alternating furnace and laser thermal gradient cyclic tests. The influence of laser high thermal-gradient cycling on coating failure modes is also investigated.

  12. Numerical stability of an explicit finite difference scheme for the solution of transient conduction in composite media

    NASA Technical Reports Server (NTRS)

    Campbell, W.

    1981-01-01

    A theoretical evaluation of the stability of an explicit finite difference solution of the transient temperature field in a composite medium is presented. The grid points of the field are assumed uniformly spaced, and media interfaces are either vertical or horizontal and pass through grid points. In addition, perfect contact between different media (infinite interfacial conductance) is assumed. A finite difference form of the conduction equation is not valid at media interfaces; therefore, heat balance forms are derived. These equations were subjected to stability analysis, and a computer graphics code was developed that permitted determination of a maximum time step for a given grid spacing.

  13. Effect of composition and temperature on viscosity and electrical conductivity of borosilicate glasses for Hanford nuclear waste immobilization

    SciTech Connect

    Hrma, P.; Piepel, G.F.; Smith, D.E.; Redgate, P.E.; Schweiger, M.J.

    1993-04-01

    Viscosity and electrical conductivity of 79 simulated borosilicate glasses in the expected range of compositions to be produced in the Hanford Waste Vitrification Plant were measured within the temperature span from 950 to 1250[degree]C. The nine major oxide components were SiO[sub 2], B[sub 2]O[sub 3], Li[sub 2]O, Na[sub 2]O, CaO, MgO, Fe[sub 2]O[sub 3], Al[sub 2]O[sub 3], and ZrO[sub 2]. The test compositions were generated statistically. The data were fitted by Fulcher and Arrhenius equations with temperature coefficients being multilinear functions of the mass fractions of the oxide components. Mixture models were also developed for the natural logarithm of viscosity and that of electrical conductivity at 1150[degree]C. Least squares regression was used to obtain component coefficients for all the models.

  14. Resistive switching memory devices based on electrical conductance tuning in poly(4-vinyl phenol)-oxadiazole composites.

    PubMed

    Sun, Yanmei; Miao, Fengjuan; Li, Rui; Wen, Dianzhong

    2015-11-28

    Nonvolatile memory devices, based on electrical conductance tuning in thin films of poly(4-vinyl phenol) (PVP) and 2-(4-tert-butylphenyl)-5-(4-biphenylyl)-1,3,4-oxadiazole (PBD) composites, are fabricated. The current-voltage characteristics of the fabricated devices show different electrical conductance behaviors, such as the write-once read-many-times (WORM) memory effect, the rewritable flash memory effect and insulator behavior, which depend on the content of PBD in the PVP + PBD composites. The OFF and ON states of the WORM and rewritable flash memory devices are stable under a constant voltage stress or a continuous pulse voltage stress at a read voltage. The memory mechanism is deduced from the modeling of the nature of currents in both states in the devices. PMID:26490192

  15. Effect of Copper/Graphite Addition on Electrical Conductivity and Thermal Insulation of Unsaturated Polyester/Jute Composites

    NASA Astrophysics Data System (ADS)

    Biswas, Bhabatosh; Chabri, Sumit; Mitra, Bhairab Chandra; Das, Kunal; Bandyopadhyay, Nil Ratan; Sinha, Arijit

    2016-02-01

    Jute fibre along with Cu particle reinforced unsaturated polyester composites having different filler loading viz. 2, 5, 10 and 15 wt% were fabricated by compression molding technique. In present investigation, it was observed that with fillers (Jute and Cu) incorporation, the electrical conductivity was monotonically increased up to 10 wt% of filler content followed by saturation at 15 wt% of filler content. It was further observed that along with fillers (Jute and Cu) incorporation, the thermal insulation was decreased monotonically up to 10 wt% of filler content and achieved a saturation at 15 wt% of filler content. A similar trend was observed with the variation of electrical conductivity and thermal insulation after incorporation of graphite within copper reinforced UP/Jute composites. Structural investigation through SEM, XRD and FTIR confirm the dispersion of fillers. An improvement of crystallinity of the matrix with fillers addition was observed from XRD analyses. The interfacial bonding between fillers and matrix was studied from FTIR pattern.

  16. Composite lithium metal anode by melt infusion of lithium into a 3D conducting scaffold with lithiophilic coating.

    PubMed

    Liang, Zheng; Lin, Dingchang; Zhao, Jie; Lu, Zhenda; Liu, Yayuan; Liu, Chong; Lu, Yingying; Wang, Haotian; Yan, Kai; Tao, Xinyong; Cui, Yi

    2016-03-15

    Lithium metal-based battery is considered one of the best energy storage systems due to its high theoretical capacity and lowest anode potential of all. However, dendritic growth and virtually relative infinity volume change during long-term cycling often lead to severe safety hazards and catastrophic failure. Here, a stable lithium-scaffold composite electrode is developed by lithium melt infusion into a 3D porous carbon matrix with "lithiophilic" coating. Lithium is uniformly entrapped on the matrix surface and in the 3D structure. The resulting composite electrode possesses a high conductive surface area and excellent structural stability upon galvanostatic cycling. We showed stable cycling of this composite electrode with small Li plating/stripping overpotential (<90 mV) at a high current density of 3 mA/cm(2) over 80 cycles. PMID:26929378

  17. Precise 3D printing of micro/nanostructures using highly conductive carbon nanotube-thiol-acrylate composites

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Xiong, W.; Jiang, L. J.; Zhou, Y. S.; Lu, Y. F.

    2016-04-01

    Two-photon polymerization (TPP) is of increasing interest due to its unique combination of truly three-dimensional (3D) fabrication capability and ultrahigh spatial resolution of ~40 nm. However, the stringent requirements of non-linear resins seriously limit the material functionality of 3D printing via TPP. Precise fabrication of 3D micro/nanostructures with multi-functionalities such as high electrical conductivity and mechanical strength is still a long-standing challenge. In this work, TPP fabrication of arbitrary 3D micro/nanostructures using multi-walled carbon nanotube (MWNT)-thiolacrylate (MTA) composite resins has been developed. Up to 0.2 wt% MWNTs have been incorporated into thiol-acrylate resins to form highly stable and uniform composite photoresists without obvious degradation for one week at room temperature. Various functional 3D micro/nanostructures including woodpiles, micro-coils, spiral-like photonic crystals, suspended micro-bridges, micro-gears and complex micro-cars have been successfully fabricated. The MTA composite resin offers significant enhancements in electrical conductivity and mechanical strength, and on the same time, preserving high optical transmittance and flexibility. Tightly controlled alignment of MWNTs and the strong anisotropy effect were confirmed. Microelectronic devices including capacitors and resistors made of the MTA composite polymer were demonstrated. The 3D micro/nanofabrication using the MTA composite resins enables the precise 3D printing of micro/nanostructures of high electrical conductivity and mechanical strength, which is expected to lead a wide range of device applications, including micro/nano-electromechanical systems (MEMS/NEMS), integrated photonics and 3D electronics.

  18. Highly stretchable resistive pressure sensors using a conductive elastomeric composite on a micropyramid array.

    PubMed

    Choong, Chwee-Lin; Shim, Mun-Bo; Lee, Byoung-Sun; Jeon, Sanghun; Ko, Dong-Su; Kang, Tae-Hyung; Bae, Jihyun; Lee, Sung Hoon; Byun, Kyung-Eun; Im, Jungkyun; Jeong, Yong Jin; Park, Chan Eon; Park, Jong-Jin; Chung, U-In

    2014-06-01

    A stretchable resistive pressure sensor is achieved by coating a compressible substrate with a highly stretchable electrode. The substrate contains an array of microscale pyramidal features, and the electrode comprises a polymer composite. When the pressure-induced geometrical change experienced by the electrode is maximized at 40% elongation, a sensitivity of 10.3 kPa(-1) is achieved. PMID:24536023

  19. The potential for damage from the accidental release of conductive carbon fibers from burning composites

    NASA Technical Reports Server (NTRS)

    Bell, V. L.

    1980-01-01

    The potential damage to electrical equipment caused by the release of carbon fibers from burning commercial airliners is assessed in terms of annual expected costs and maximum losses at low probabilities of occurrence. A materials research program to provide alternate or modified composite materials for aircraft structures is reviewed.

  20. Simultaneously improving electrical conductivity and thermopower of polyaniline composites by utilizing carbon nanotubes as high mobility conduits.

    PubMed

    Wang, Hong; Yi, Su-in; Pu, Xiong; Yu, Choongho

    2015-05-13

    Electrical conductivity and thermopower of isotropic materials typically have inversely proportional correlation because both are strongly affected in the opposite way by the electronic carrier concentration. This behavior has been one of the major hurdles in developing high-performance thermoelectrics whose figure-of-merit enhances with large thermopower and high electrical conductivity. Here we report a promising method of simultaneously improving both properties with polyaniline (PANI) composites filled by carbon nanotubes (CNTs). With addition of double-wall CNTs (DWCNTs), the electronic mobility of PANI doped with camphorsulfonic acid (PANI-CSA) was raised from ∼0.15 to ∼7.3 cm(2)/(V s) (∼50 time improvement) while the carrier concentration was decreased from ∼2.1 × 10(21) to ∼5.6 × 10(20) cm(-3) (∼4 time reduction). The larger increase of mobility increased electrical conductivity despite the carrier concentration reduction that enlarges thermopower. The improvement in the carrier mobility could be attributed to the band alignment that attracts hole carriers to CNTs whose mobility is much higher than that of PANI-CSA. The electrical conductivity of the PANI-CSA composites with 30-wt % DWCNTs was measured to be ∼610 S/cm with a thermopower value of ∼61 μV/K at room temperature, resulting in a power factor value of ∼220 μW/(m K(2)), which is more than two orders higher than that of PANI-CSA as well as the highest among those of the previously reported PANI composites. Further study may result in high performance thermoelectric organic composites uniquely offering mechanical flexibility, light weight, low toxicity, and easy manufacturing. unlike conventional inorganic semiconductors. PMID:25894982

  1. Modeling the Transverse Thermal Conductivity of 2-D SiCf/SiC Composites Made with Woven Fabric

    SciTech Connect

    Youngblood, Gerald E.; Senor, David J.; Jones, Russell H.

    2004-06-30

    The hierarchical two-layer (H2L) model was developed to describe the effective transverse thermal conductivity, Keff, of a 2D-SiCf/SiC composite made from stacked and infiltrated woven fabric layers in terms of constituent properties and microstructural and architectural variables. The H2L model includes the expected effects of fiber-matrix interfacial conductance as well as the effects of high fiber packing fractions within individual tows and the non-uniform nature of 2D-fabric layers that usually include a significant amount of interlayer porosity. Previously, H2L model predictions were compared to measured values of Keff for two versions of DuPont 2D-Hi NicalonÔ/PyC/ICVI-SiC composite, one with a “thin” (0.110 μm) and the other with a “thick” (1.040 μm) pyrocarbon (PyC) fiber coating, and for a 2D-TyrannoÔ SA/”thin” PyC/FCVI-SIC composite made by ORNL. In this study, H2L model predictions are compared to measured Keff-values for a 2D-SiCf/SiC composite made by GE Power Systems (formerly DuPont Lanxide) using the ICVI-process with Hi-NicalonÔ type S fabric. The values of Keff determined for the composite made with the Hi-NicalonÔ type S fabric were significantly greater than Keff-values determined for the composites made with either the Hi-NicalonÔor the TyrannoÔ SA fabrics. Differences in Keff-values were expected for using different fiber types, but major differences also were due to observed microstructural variations between the systems, and as predicted by the H2L model.

  2. Characterization of smart microwave window materials based on conducting polymer composites: coaxial line, waveguide, and cyclic voltammetry measurements

    NASA Astrophysics Data System (ADS)

    Barnes, Alan; Wright, Peter V.; Despotakis, Anthony; Lees, K.; Chambers, Barry

    1998-07-01

    Discs of polyaniline-silver-polymer electrolyte composites exhibit rapid and reversible changes in their microwave impedance when small electric fields are applied across then in a resonant coaxial line test set. The experimental data show that the initial conductivity of the materials is dependent on the concentration of silver metal and suggests that changes in resistance due to chemical switching take plane, at least in part, in the manufacture of the composites. The experimental data show that changes in the gradient of the cyclic voltammograms coincide with large changes in microwave reflectivity consistent with increasing conductivity of the composite when fields are applied. The reverse change occurs when the fields are removed. Measurements of the switching speed have shown that the composites are able to switch between the different states at in times of less than a second for more than one million switching operations with no depreciation of the material. Large area films have also been studied in the front of waveguide devices and measured in a microwave transmission mode. The results show that large changes in microwave impedance occur with the application of small electric fields (~ 15 V cm-1).

  3. Boron Nitride Nanosheets (BNNSs) Chemically Modified by "Grafting-From" Polymerization of Poly(caprolactone) for Thermally Conductive Polymer Composites.

    PubMed

    Lee, Jinseong; Jung, Haejong; Yu, Seunggun; Man Cho, Suk; Tiwari, Vimal K; Babu Velusamy, Dhinesh; Park, Cheolmin

    2016-07-01

    To meet the growing demand for rapid heat dissipation in electronic devices to ensure their reliable performance with a high level of safety, many polymer composites with thermally conductive but electrically insulating 2D boron nitride nanosheets (BNNSs) are being developed. Here we present an efficient way to enhance the thermal conductivity (TC) of a polymer composite by means of "grafting-from" polymerization of a poly(caprolactone) (PCL) onto BNNSs. The BNNSs, which were exfoliated from bulk BN by means of ultra-sonication, were prepared by means of radical oxidation. These oxidized BNNSs (oxi-BNNSs) were employed as initiators for subsequent ring-opening polymerization of PCL, which successfully resulted in PCL chemically grafted onto BNNSs (PCL-g-BNNSs). The excellent dispersion of PCL-g-BNNSs in common solvents allowed us to readily fabricate a polymer composite that contained PCL-g-BNNSs embedded in a PCL matrix, and the composite showed TC values that were five and nine times greater in the out-of-plane and in-plane mode, respectively, than those of pristine PCL. PMID:27283727

  4. Novel composite proton-exchange membrane based on proton-conductive glass powders and sulfonated poly (ether ether ketone)

    NASA Astrophysics Data System (ADS)

    Di, Zhigang; Xie, Qiang; Li, Haibin; Mao, Dali; Li, Ming; Zhou, Daowu; Li, Lu

    2015-01-01

    The SiO2-Nafion/sulfonated poly (ether ether ketone) (SPEEK) composite membranes are fabricated by using the simple mechanical ball-milling process to combine SiO2 glass powders with small portion of Nafion, in which SiO2 glass powders are prepared by modified sol-gel progress and Nafion is embedded in situ into a highly porous silica network. The morphology, thermal and mechanical properties, pore structure, proton conductivity and fuel cell performance of the SiO2-Nafion/SPEEK composite membranes are investigated. The poor miscibility of Nafion and sulfonated aromatic polymer is solved by fixing Nafion into SiO2 glass powders. The composite membranes perform well even if the proportion of inorganic component in membranes is as high as 40 wt.%. A maximum of proton conductivity, 0.018 S cm-1, is obtained from the membrane of 4(8Si-2N)/6SPEEK at 80 °C and 90% relative humidity, which is owing to its enhanced hygroscopicity and highly dispersed Nafion clusters. In addition, a single fuel cell equipped with the composite membrane shows a peak power density of 589.2 mW cm-2 at 70 °C.

  5. A comprehensive study of sulfonated carbon materials as conductive composites for polymer solar cells.

    PubMed

    Ji, Ting; Tan, Licheng; Hu, Xiaotian; Dai, Yanfeng; Chen, Yiwang

    2015-02-14

    Sulfonated carbon nanotubes (S-CNTs) and sulfonated graphene (S-Gra) with superior dispersibility were successfully prepared to modify poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) for applications in polymer solar cells (PSCs). The synergetic effect between S-CNTs/S-Gra and PEDOT:PSS could remove excess insulating PSS chains leading to an obvious phase separation between the PEDOT and PSS chains, which allows the formation of more conductive PEDOT channels. The PEDOT:PSS (Clevios PH 4083):S-CNTs with well-matched work function, favorable morphology, optimized hydrophobicity and superior hole mobility is demonstrated to be an excellent hole transport layer (HTL) for PSCs. However, the PEDOT:PSS (Clevios PH 4083) modified by sulfonated graphene with stacked and wrinkled lamellae as an HTL renders a rough morphology and has a negative impact on the morphology of the active layer, consequently resulting in a poor device performance. Excitingly, PEDOT:PSS (Clevios PH 1000) modified with S-Gra shows high conductivity, because the sulfonated graphene lamellae contribute to the connection between the insulator and conductive PEDOT islands and improves the charge conduction. The PH1000:S-Gra with multiple layers presents excellent electrical conductive properties and a high transmittance (sheet resistance of ∼45 Ω sq(-1) and transmittance of ∼85.5% at 550 nm), which possess great potential for its application as a transparent conductive and flexible electrode in organic electronics. PMID:25563771

  6. Proton conductance and fatty acyl composition of liver mitochondria correlates with body mass in birds.

    PubMed Central

    Brand, Martin D; Turner, Nigel; Ocloo, Augustine; Else, Paul L; Hulbert, A J

    2003-01-01

    The proton conductance of isolated liver mitochondria correlates significantly with body mass in mammals, but not in ectotherms. To establish whether the correlation in mammals is general for endotherms or mammal-specific, we measured proton conductance in mitochondria from birds, the other main group of endotherms, using birds varying in mass over a wide range (nearly 3000-fold), from 13 g zebra finches to 35 kg emus. Respiratory control ratios were higher in mitochondria from larger birds. Mitochondrial proton conductance in liver mitochondria from birds correlated strongly with body mass [respiration rate per mg of protein driving proton leak at 170 mV being 44.7 times (body mass in g)(-0.19)], thus suggesting a general relationship between body mass and proton conductance in endotherms. Mitochondria from larger birds had the same or perhaps greater surface area per mg of protein than mitochondria from smaller birds. Hence, the lower proton conductance was caused not by surface area changes but by some change in the properties of the inner membrane. Liver mitochondria from larger birds had phospholipid fatty acyl chains that were less polyunsaturated and more monounsaturated when compared with those from smaller birds. Phospholipid fatty acyl polyunsaturation correlated positively and monounsaturation correlated negatively with proton conductance. These correlations echo those seen in mammalian liver mitochondria, suggesting that they too are general for endotherms. PMID:12943530

  7. In situ synthesis of robust conductive cellulose/polypyrrole composite aerogels and their potential application in nerve regeneration.

    PubMed

    Shi, Zhuqun; Gao, Huichang; Feng, Jiao; Ding, Beibei; Cao, Xiaodong; Kuga, Shigenori; Wang, Yingjun; Zhang, Lina; Cai, Jie

    2014-05-19

    Nanostructured conductive polymers can offer analogous environments for extracellular matrix and induce cellular responses by electric stimulation, however, such materials often lack mechanical strength and tend to collapse under small stresses. We prepared electrically conductive nanoporous materials by coating nanoporous cellulose gels (NCG) with polypyrrole (PPy) nanoparticles, which were synthesized in situ from pyrrole monomers supplied as vapor. The resulting NCG/PPy composite hydrogels were converted to aerogels by drying with supercritical CO2, giving a density of 0.41-0.53 g cm(-3), nitrogen adsorption surface areas of 264-303 m(2) g(-1), and high mechanical strength. The NCG/PPy composite hydrogels exhibited an electrical conductivity of up to 0.08 S cm(-1). In vitro studies showed that the incorporation of PPy into an NCG enhances the adhesion and proliferation of PC12 cells. Electrical stimulation demonstrated that PC12 cells attached and extended longer neurites when cultured on NCG/PPy composite gels with DBSA dopant. These materials are promising candidates for applications in nerve regeneration, carbon capture, catalyst supports, and many others. PMID:24711342

  8. Structural, electrical conductivity and dielectric behavior of Na2SO4–LDT composite solid electrolyte

    PubMed Central

    Iqbal, Mohd Z.; Rafiuddin

    2015-01-01

    A series of composite materials of general molecular formula (1 − x) Na2SO4 − (x) LDT was prepared by solid state reaction method. The phase structure and functionalization of these materials were defined by X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR) respectively. Differential thermal analysis (DTA) revealed that the hump of phase transition at 250 °C has decreased while its thermal stability was enhanced. Scanning electron microscopy signifies the presence of improved rigid surfaces and interphases that are accountable for the high ionic conduction due to dispersion of LDT particles in the composite systems. Arrhenius plots of the conductance show the maximum conductivity, σ = 4.56 × 10−4 S cm−1 at 500 °C for the x = 0.4 composition with the lowest activation energy 0.34 eV in the temperature range of 573–773 K. The value of dielectric constant was decreased with increasing frequency and follows the usual trend. PMID:26843979

  9. DC conductivity, cationic exchange capacity, and specific surface area related to chemical composition of pore lining chlorites.

    PubMed

    Henn, François; Durand, Claudine; Cerepi, Adrian; Brosse, Etienne; Giuntini, J C

    2007-07-15

    Low resistivity in argillaceous sandstone reservoirs may be attributed either to the effect of microporosity, or to specific effects due to intrinsic clays' conducting properties or to other conducting minerals. In order to distinguish these effects, cation exchange capacity, specific surface areas, and dc conductivity of various pore lining chlorite-bearing sandstones from different hydrocarbon reservoir measurements are investigated. Cation exchange capacity and specific surface area are measured on whole rocks as well as on size-separated fractions. Both sets of values are low, in agreement with the structural and textural observations. The conductivity of these chlorites, measured in air conditions and after dehydration, is investigated by means of complex impedance spectroscopy on size-separated fractions as a function of temperature and compared to that of reference clays. The results show a large influence of moisture, applied electric field frequency, and temperature on the electrical properties. The magnitude of the dehydrated clays' conductivity is such that its influence on the conductivity of argillaceous sandstone is lower than that related to the presence of water or brine by several orders of magnitude. The dc conductivity and the related activation energy of the dehydrated samples appear to be related to the chemical composition of the clays. More specifically, a clear correlation occurs with the electrical charges of the clay network, that is to say with the location, i.e., tetrahedral or octahedral sites, of the substituting trivalent elements. PMID:17433348

  10. Metal matrix-metal nanoparticle composites with tunable melting temperature and high thermal conductivity for phase-change thermal storage.

    PubMed

    Liu, Minglu; Ma, Yuanyu; Wu, Hsinwei; Wang, Robert Y

    2015-02-24

    Phase-change materials (PCMs) are of broad interest for thermal storage and management applications. For energy-dense storage with fast thermal charging/discharging rates, a PCM should have a suitable melting temperature, large enthalpy of fusion, and high thermal conductivity. To simultaneously accomplish these traits, we custom design nanocomposites consisting of phase-change Bi nanoparticles embedded in an Ag matrix. We precisely control nanoparticle size, shape, and volume fraction in the composite by separating the nanoparticle synthesis and nanocomposite formation steps. We demonstrate a 50-100% thermal energy density improvement relative to common organic PCMs with equivalent volume fraction. We also tune the melting temperature from 236-252 °C by varying nanoparticle diameter from 8.1-14.9 nm. Importantly, the silver matrix successfully prevents nanoparticle coalescence, and no melting changes are observed during 100 melt-freeze cycles. The nanocomposite's Ag matrix also leads to very high thermal conductivities. For example, the thermal conductivity of a composite with a 10% volume fraction of 13 nm Bi nanoparticles is 128 ± 23 W/m-K, which is several orders of magnitude higher than typical thermal storage materials. We complement these measurements with calculations using a modified effective medium approximation for nanoscale thermal transport. These calculations predict that the thermal conductivity of composites with 13 nm Bi nanoparticles varies from 142 to 47 W/m-K as the nanoparticle volume fraction changes from 10 to 35%. Larger nanoparticle diameters and/or smaller nanoparticle volume fractions lead to larger thermal conductivities. PMID:25610944

  11. Synthesis of proton conducting mesoporous materials and composite membranes for high temperature proton exchange membrane (PEM) fuel cells

    NASA Astrophysics Data System (ADS)

    Feng, Fangxia

    Tungstosilicate mesoporous materials (WMM) were synthesized using the ionic surfactant cetyltrimethylammonium bromide (C16H33N +(CH3)3Br- CTMABr) and non-ionic surfactants, including C12H25(OCH2CH 2)10OH (Brij 22, C12EO10OH), C 16H33(OCH2CH2)10OH (Brij 56, C16EO10OH), and C18H37(OCH 2CH2)10OH (Brij 76, C18EO10OH). The proton conductivities were measured by AC impedance spectroscopy. Using CTMABr, the highest W/Si ratio achieved for the molecular sieve product was 0.03. The conductivity ranged from 0.5 to 2.2 x 10-2 S/cm, where the highest conductivity was observed with the H3PO 4 based preparation. Non-ionic surfactants produced materials with a W/Si ratio as high as 0.05 without any dense WO3 impurities. These samples showed thicker pore walls (39A), higher thermal stability, and higher proton conductivity (4.0 x 10-2 S/cm). The WMMs were also employed to make a composite membrane with linear polyethyleneimine (PEI), 3-glycidoxypropyltrimethoxysilane (GLYMO), bis(trifluoromethanesulfonyl)imide (HTFSI). At 100°C and 100% relative humidity, the composite membrane with 30 wt.% calcined (at 500°C) WMM showed the highest conductivity of 6.1 x 10-2 S/cm. At 130°C and 20% relative humidity, the highest conductivity of 6.4 x 10-3 S/cm was obtained for the composite membrane with 30 wt.% as-synthesized WMM. Transparent free-standing mesoporous silica (MS) films were synthesized from a system of TMOS-Brij-Acid-H2O. The non-ionic surfactants used included Brij 22 (Cl2EO10OH), Brij 56 (C16EO 10OH), and Brij 76 (C18EO10OH). The acids used include HCl, H3PO4, and CF3SO3H. The effect of synthesis parameters on the synthesis and the proton conductivity of mesoporous silica were investigated. The Brij 56/CF3SO 3H based product showed the highest conductivity of 6.5 x 10 -2 S/cm at room temperature. Composite was prepared by combing TMOS, Brij surfactant, acid (HCl, H3PO4, or CF 3SO3H), N-[3-(trimethoxysilyl)propyl]-ethylenediamine (EDATMS), 3-glycidoxypropylmethoxysilane (GLYMO

  12. Clear, Conductive, Transparent, Flexible Space Durable Composite Films for Electrostatic Charge Mitigation

    NASA Technical Reports Server (NTRS)

    Watson, Kent A.; Connell, John W.; Delozier, Donavon M.; Smith, Joseph G., Jr.

    2004-01-01

    Space environmentally durable polymeric films with low color and sufficient electrical conductivity to mitigate electrostatic charge (ESC) build-up have been under investigation as part of a materials development activity. These materials have potential applications on advanced spacecraft, particularly on large, deployable, ultra-light weight Gossamer spacecraft. The approach taken to impart sufficient electrical conductivity into the polymer film while maintaining flexibility is to use single wall carbon nanotubes (SWNTs) as conductive additives. Approaches investigated in our lab involved an in-situ polymerization method, addition of SWNTs to a polymer containing reactive end-groups, and spray coating of polymer surfaces. The work described herein is a summary of the current status of this project. Surface conductivities (measured as surface resistance) in the range sufficient for ESC mitigation were achieved with minimal effects on the physical, thermal, mechanical and optical properties of the films. Additionally, the electrical conductivity was not affected by harsh mechanical manipulation of the films. The chemistry and physical properties of these nanocomposites will be discussed.

  13. Preparation of conductive PDDA/(PEDOT:PSS) multilayer thin film: influence of polyelectrolyte solution composition.

    PubMed

    Jurin, F E; Buron, C C; Martin, N; Filiâtre, C

    2014-10-01

    Self-assembled multilayer films made of PEDOT:PSS poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) and PDDA poly(diallyldimethylammonium chloride) were prepared using layer-by-layer method. In order to modify the growth regime of the multilayer, to fabricate an electrical conductive film and to control its thickness, the effects of pH, type of electrolyte, ionic strength and polyelectrolyte concentration were investigated. Optical reflectometry measurements show that the pH of the solutions has no effect on the film growth while the adsorbed amount increases more rapidly when BaCl2 is used instead of NaCl as electrolyte. An increase in the ionic strength (with NaCl) induces a change in the growth regime from a linear to an exponential one at low polyelectrolyte concentration. As UV-vis measurements indicate, no decomplexation of PEDOT was recorded after film preparation. With polyelectrolyte concentration below 1 g L(-1), no conductive films were obtained even if 50 bilayers were deposited. A conductive film was prepared with a polyelectrolyte concentration of 1 g L(-1) and the measured conductivity was 0.3 S m(-1). A slight increase in conductivity was recorded when BaCl2 was used probably due to a modification of the film structure. PMID:24984072

  14. A polyvinyl alcohol/ p-sulfonate phenolic resin composite proton conducting membrane

    NASA Astrophysics Data System (ADS)

    Wu, Chien-Shun; Lin, Fan-Yen; Chen, Chih-Yuan; Chu, Peter P.

    Membranes composed of poly(vinyl alcohol) (PVA) and a proton source polymer, sulfonated phenolic resin (s-Ph) displayed good proton conductivity of the order of 10 -2 S cm -1 at ambient temperatures. Upon cross-linking above 110 °C, covalent links between the sulfonate groups of the phenolic resin and the hydroxyl groups of the PVA were established. Although this sacrificed certain sulfonate groups, the conductivity value was still preserved at the 10 -2 S cm -1 level. In sharp contrast to Nafion, the current membrane (both before and after cross-linking) was also effective in reducing the methanol uptake where the swelling ratio decreased with increase of methanol concentration. Although both the methanol permeation and the proton conductivity were lower compared to Nafion, the conductivity/permeability ratio of 0.97 for the PVA/s-Ph is higher than that determined for Nafion. The results suggested the effectiveness of proton transport in the polymer-complex structure and the possibility that a high proton conductivity can be realized with less water.

  15. A study of the oriented composites with the conductive segregated structure obtained via solid-phase processing of the UHMWPE reactor powder mixed with the carbon nanofillers

    NASA Astrophysics Data System (ADS)

    Lebedev, Oleg V.; Kechek'yan, Alexander S.; Shevchenko, Vitaly G.; Kurkin, Tikhon S.; Golubev, Evgeny K.; Karpushkin, Evgeny A.; Sergeev, Vladimir G.; Ozerin, Alexander N.

    2016-05-01

    Electrically conductive oriented polymer nano-composites of different compositions, based on the reactor powder of ultra-high-molecular-weight polyethylene (UHMWPE) with a special morphology, filled with particles of nanostructured graphite (NG), multi-walled carbon nanotubes (MWCNTs), and electrically conductive carbon black (CB), were investigated. Polymer composites were obtained via compaction of the mechanical mixture of the polymer and filler powder, followed by uniaxial deformation of the material under homogeneous shear (HS) conditions (all of the processing stages were conducted at room temperature). Resulted composites possess a high tensile strength, high level of the electrical conductivity and low percolation threshold, owing it to the formation of the segregated conductive structure, The influence of the type of nanosized carbon filler, degree of the deformation under HS condition, temperature and etc. on the electrical conductivity and mechanical properties of strengthened conductive composites oriented under homogeneous shear conditions was investigated. Changes in the electrical conductivity of oriented composite materials during reversible "tension-shrinkage" cycles along the orientation axis direction were studied. A theoretical approach, describing the process of transformation of the conductive system as a response on polymer phase deformation and volume change, was proposed, based on the data received from the analysis of the conductivity behavior during the uniaxial deformation and thermal treatment of composites.

  16. Discontinuous anchoring transition and photothermal switching in composites of liquid crystals and conducting polymer nanofibers

    NASA Astrophysics Data System (ADS)

    Rasna, M. V.; Zuhail, K. P.; Manda, R.; Paik, P.; Haase, W.; Dhara, Surajit

    2014-05-01

    We prepared nanocomposites of a nematic liquid crystal and nanofibers of a conducting polymer (polyaniline). All the nanocomposites exhibit a discontinuous surface anchoring transition from planar to homeotropic in the nematic phase on a perfluoropolymer coated surface with a thermal hysteresis (≈5.3∘C). We observe a relatively large bistable conductivity and demonstrate a light driven switching of conductivity and dielectric constant in dye doped nanocomposites in the thermal hysteresis (bistable) region. The experimental results have been explained based on the reorientation of the nanofibers driven by the anchoring transition of the nematic liquid crystal. We show a significant enhancement of the bistable temperature range (≈13∘C) by an appropriate choice of compound in the binary system.

  17. Enhanced electrical conductivity and hardness of silver-nickel composites by silver-coated multi-walled carbon nanotubes.

    PubMed

    Lee, Dongmok; Sim, Jeonghyun; Kim, Wonyoung; Moon, Chuldong; Cho, Wookdong; Baik, Seunghyun

    2015-07-24

    We investigated electrical conductivity and Vickers hardness of Ag- and Ni-based composites prepared by powder metallurgy involving spark plasma sintering. The starting composition was Ag:Ni = 61:39 vol%, which provided an electrical conductivity of 3.30 × 10(5) S cm(-1) and a hardness of 1.27 GPa. The addition of bare multi-walled carbon nanotubes (MWNTs, 1.45 vol%) increased hardness (1.31 GPa) but decreased electrical conductivity (2.99 × 10(5) S cm(-1)) and carrier mobility (11 cm(2) V(-1) s(-1)) due to the formation of Ni3C in the interface between the MWNTs and Ni during spark plasma sintering. The formation of Ni3C was prevented by coating the surface of the nanotubes with Ag (nAgMWNTs), concomitantly increasing electrical conductivity (3.43 × 10(5) S cm(-1)) and hardness (1.37 GPa) of the sintered specimen (Ag:Ni:nAgMWNTs = 59.55:39:1.45 vol%). The electrical contact switching time (133 357) was also increased by 30%, demonstrating excellent feasibility as electrical contact materials for electric power industries. PMID:26133395

  18. Suppression of bulk conductivity in InAs/GaSb broken gap composite quantum wells

    SciTech Connect

    Charpentier, Christophe; Fält, Stefan; Reichl, Christian; Nichele, Fabrizio; Nath Pal, Atindra; Pietsch, Patrick; Ihn, Thomas; Ensslin, Klaus; Wegscheider, Werner

    2013-09-09

    The two-dimensional topological insulator state in InAs/GaSb quantum wells manifests itself by topologically protected helical edge channel transport relying on an insulating bulk. This work investigates a way of suppressing bulk conductivity by using gallium source materials of different degrees of impurity concentrations. While highest-purity gallium is accompanied by clear conduction through the sample bulk, intentional impurity incorporation leads to a bulk resistance over 1 MΩ, independent of applied magnetic fields. In addition, ultra high electron mobilities for GaAs/AlGaAs structures fabricated in a molecular beam epitaxy system used for the growth of Sb-based samples are reported.

  19. Electronic conduction and microstructure in polymer composites filled with carbonaceous particles

    NASA Astrophysics Data System (ADS)

    Mdarhri, A.; Brosseau, C.; Zaghrioui, M.; El Aboudi, I.

    2012-08-01

    Physical and physico-chemical properties of polymer filled with carbon black (CB) particles, namely, the microstructure dependence of these properties, are not only interesting on their own but are particularly important for electronic applications as they can impose limits on the sensitivity of a device. With this purpose, we report on an experimental study of the structural and electrical properties of semi-crystalline ethylene-co-butyl acrylate polymer filled with conductive CB nano-particles. We found that the value of the direct current conductivity exhibits a jump of 12 orders of magnitude over a small change in CB concentration and is due to a percolation-like behavior. To assess the temperature evolution of supercolative samples, we present measurements of the conductivity as function of temperature. Above the glass transition temperature of the polymer, the CB network restricts the motions of the polymer chains. This behavior was ascribed to the change in CB mesostructure in the polymer matrix as probed by scanning electron microscopy and atomic force microscopy as well as to the difference in the thermal expansion between the two phases. In addition to the observed conductivity increase, the effect of adding CB particles in the polymer matrix is to increase the thermal stability as is probed by thermogravimetric analysis tests. The room temperature alternating current conductivity, studied over the frequency range from 100 Hz to 15 MHz, is interpreted as arising mainly from inter-aggregate polarization effects. By considering carefully the CB content of the alternating current conductivity, we found that our experimental data agree well with the Sheng's model of fluctuation-induced tunnelling of charge carriers over nanometric gaps between adjacent CB aggregates. For studying the filler content dependence of the effective permittivity, several mixing laws and effective medium theories have been used. The observed discrepancies between our experimental

  20. High charge density conducting polymer/graphite fiber composite electrodes for battery applications

    SciTech Connect

    Coffey, B.; Madsen, P.V.; Poehler, T.O.; Searson, P.C.

    1995-02-01

    Novel composite electrode structures have been fabricated by single-step electropolymerization of polypyrrole onto a porous graphite fiber matrix. The graphite substrate provides a lightweight structure with high surface area. The available charge capacity of the composite electrodes was proportional to the electropolymerization time and the mass of electroactive polymer with reversible charge capacities in excess of 4.0 C/cm{sup 2} and a specific capacity of 90 mAh/g, independent of polymer mass. The rate of charge extraction was dependent on the polymer mass and the morphology of the polymer electrode. In test cells using a polypyrrole/graphite fiber anode and a polypyrrole-polystyrene sulfonate/graphite fiber cathode, the authors have demonstrated a capacity of more than 40 mAh/g based on the active mass of the undoped polymer on discharging the cell to 0.1 V over a 10 k{Omega} load. More than 70% of the available charge was extracted from the cell over 50 cycles with no degradation of cell performance.

  1. Green synthesis of high conductivity silver nanoparticle-reduced graphene oxide composite films

    NASA Astrophysics Data System (ADS)

    Dinh, D. A.; Hui, K. S.; Hui, K. N.; Cho, Y. R.; Zhou, Wei; Hong, Xiaoting; Chun, Ho-Hwan

    2014-04-01

    A green facile chemical approach to control the dimensions of Ag nanoparticles-graphene oxide (AgNPs/GO) composites was performed by the in situ ultrasonication of a mixture of AgNO3 and graphene oxide solutions with the assistance of vitamin C acting as an environmentally friendly reducing agent at room temperature. With decreasing ultrasonication time, the size of the Ag nanoparticles decreased and became uniformly distributed over the surface of the GO nanosheets. The as-prepared AgNPs/rGO composite films were then formed using a spin coating method and reduced at 500 °C under N2/H2 gas flow for 1 h. Four-point probe measurements showed that the sheet resistance of the AgNPs/rGO films decreased with decreasing AgNPs size. The lowest sheet resistance of 270 Ω/sq was obtained in the film corresponding to 1 min of ultrasonication, which showed a 40 times lower resistivity than the rGO film (10.93 kΩ/sq). The formation mechanisms of the as-prepared AgNPs/rGO films are proposed. This study provides a guide to controlling the dimensions of AgNPs/rGO films, which might hold promise as advanced materials for a range of analytical applications, such as catalysis, sensors and microchips.

  2. Development of Amperometric Biosensors Based on Nanostructured Tyrosinase-Conducting Polymer Composite Electrodes

    PubMed Central

    Lupu, Stelian; Lete, Cecilia; Balaure, Paul Cătălin; Caval, Dan Ion; Mihailciuc, Constantin; Lakard, Boris; Hihn, Jean-Yves; del Campo, Francisco Javier

    2013-01-01

    Bio-composite coatings consisting of poly(3,4-ethylenedioxythiophene) (PEDOT) and tyrosinase (Ty) were successfully electrodeposited on conventional size gold (Au) disk electrodes and microelectrode arrays using sinusoidal voltages. Electrochemical polymerization of the corresponding monomer was carried out in the presence of various Ty amounts in aqueous buffered solutions. The bio-composite coatings prepared using sinusoidal voltages and potentiostatic electrodeposition methods were compared in terms of morphology, electrochemical properties, and biocatalytic activity towards various analytes. The amperometric biosensors were tested in dopamine (DA) and catechol (CT) electroanalysis in aqueous buffered solutions. The analytical performance of the developed biosensors was investigated in terms of linear response range, detection limit, sensitivity, and repeatability. A semi-quantitative multi-analyte procedure for simultaneous determination of DA and CT was developed. The amperometric biosensor prepared using sinusoidal voltages showed much better analytical performance. The Au disk biosensor obtained by 50 mV alternating voltage amplitude displayed a linear response for DA concentrations ranging from 10 to 300 μM, with a detection limit of 4.18 μM. PMID:23698270

  3. Impedance spectroscopic analysis of composite electrode from activated carbon/conductive materials/ruthenium oxide for supercapacitor applications

    NASA Astrophysics Data System (ADS)

    Taer, E.; Deraman, M.; Talib, I. A.; Awitdrus, Farma, R.; Ishak, M. M.; Omar, R.; Dolah, B. N. M.; Basri, N. H.; Othman, M. A. R.; Kanwal, S.

    2015-04-01

    Activated carbon powders (ACP) were produced from the KOH treated pre-carbonized rubber wood sawdust. Different conductive materials (graphite, carbon black and carbon nanotubes (CNTs)) were added with a binder (polivinylidene fluoride (PVDF)) into ACP to improve the supercapacitive performance of the activated carbon (AC) electrodes. Symmetric supercapacitor cells, fabricated using these AC electrodes and 1 molar H2SO4 electrolyte, were analyzed using a standard electrochemical impedance spectroscopy technique. The addition of graphite, carbon black and CNTs was found effective in reducing the cell resistance from 165 to 68, 23 and 49 Ohm respectively, and increasing the specific capacitance of the AC electrodes from 3 to 7, 17, 32 F g-1 respectively. Since the addition of CNTs can produce the highest specific capacitance, CNTs were chosen as a conductive material to produce AC composite electrodes that were added with 2.5 %, 5 % and 10 % (by weight) electro-active material namely ruthenium oxide; PVDF binder and CNTs contents were kept at 5 % by weight in each AC composite produced. The highest specific capacitance of the cells obtained in this study was 86 F g-1, i.e. for the cell with the resistance of 15 Ohm and composite electrode consists of 5 % ruthenium oxide.

  4. Impedance spectroscopic analysis of composite electrode from activated carbon/conductive materials/ruthenium oxide for supercapacitor applications

    SciTech Connect

    Taer, E.; Awitdrus,; Farma, R.; Deraman, M. Talib, I. A.; Ishak, M. M.; Omar, R.; Dolah, B. N. M.; Basri, N. H.; Othman, M. A. R.; Kanwal, S.

    2015-04-16

    Activated carbon powders (ACP) were produced from the KOH treated pre-carbonized rubber wood sawdust. Different conductive materials (graphite, carbon black and carbon nanotubes (CNTs)) were added with a binder (polivinylidene fluoride (PVDF)) into ACP to improve the supercapacitive performance of the activated carbon (AC) electrodes. Symmetric supercapacitor cells, fabricated using these AC electrodes and 1 molar H{sub 2}SO{sub 4} electrolyte, were analyzed using a standard electrochemical impedance spectroscopy technique. The addition of graphite, carbon black and CNTs was found effective in reducing the cell resistance from 165 to 68, 23 and 49 Ohm respectively, and increasing the specific capacitance of the AC electrodes from 3 to 7, 17, 32 F g{sup −1} respectively. Since the addition of CNTs can produce the highest specific capacitance, CNTs were chosen as a conductive material to produce AC composite electrodes that were added with 2.5 %, 5 % and 10 % (by weight) electro-active material namely ruthenium oxide; PVDF binder and CNTs contents were kept at 5 % by weight in each AC composite produced. The highest specific capacitance of the cells obtained in this study was 86 F g{sup −1}, i.e. for the cell with the resistance of 15 Ohm and composite electrode consists of 5 % ruthenium oxide.

  5. Electrically conductive polyimide film containing gold (III) ions, composition, and process of making

    NASA Technical Reports Server (NTRS)

    Caplan, Maggie L. (Inventor); Stoakley, Diane M. (Inventor); St. Clair, Anne K. (Inventor)

    1996-01-01

    An electrically conductive, thermooxidatively stable poltimide, especially a film thereof, is prepared from an intimate admixture of a particular polyimide and gold (III) ions, in an amount sufficient to provide between 17 and 21 percent by weight of gold (III) ions, based on the weight of electrically conductive, thermooxidatively stable polyimide. The particular polyimide is prepared from a polyamic acid which has been synthesized from a dianhydride/diamine combination selected from the group consisting of 3,3',4,4'-benzophenonetetracarboxylic dianhydride and 2,2-bis[4-(4 -aminophenoxy)phenyl]hexafluoropropane; 3,3',4,4'-benzophenonetetracarboxylic dianhydride and 4,4'-oxydianiline; 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride and 4,4'-oxydianiline; and 3,3'4,4'-benzophenonetetracarboxylic dianhydride and 2,2-bis(3-aminophenyl)hexafluoropropane.

  6. Highly conductive thermoplastic composites for rapid production of fuel cell bipolar plates

    DOEpatents

    Huang, Jianhua [Blacksburg, VA; Baird, Donald G [Blacksburg, VA; McGrath, James E [Blacksburg, VA

    2008-04-29

    A low cost method of fabricating bipolar plates for use in fuel cells utilizes a wet lay process for combining graphite particles, thermoplastic fibers, and reinforcing fibers to produce a plurality of formable sheets. The formable sheets are then molded into a bipolar plates with features impressed therein via the molding process. The bipolar plates formed by the process have conductivity in excess of 150 S/cm and have sufficient mechanical strength to be used in fuel cells. The bipolar plates can be formed as a skin/core laminate where a second polymer material is used on the skin surface which provides for enhanced conductivity, chemical resistance, and resistance to gas permeation.

  7. Modeling of Interfacial Modification Effects on Thermal Conductivity of Carbon Nanotube Composites

    NASA Technical Reports Server (NTRS)

    Clancy, Thomas C.; Gates, Thomas S.

    2006-01-01

    The effect of functionalization of carbon nanotubes on the thermal conductivity of nanocomposites has been studied using a multi-scale modeling approach. These results predict that grafting linear hydrocarbon chains to the surface of a single wall carbon nanotube with covalent chemical bonds should result in a significant increase in the thermal conductivity of these nanocomposites. This is due to the decrease in the interfacial thermal (Kapitza) resistance between the single wall carbon nanotube and the surrounding polymer matrix upon chemical functionalization. The nanocomposites studied here consist of single wall carbon nanotubes in a bulk poly(ethylene vinyl acetate) matrix. The nanotubes are functionalized by end-grafting linear hydrocarbon chains of varying length to the surface of the nanotube. The effect which this functionalization has on the interfacial thermal resistance is studied by molecular dynamics simulation. Interfacial thermal resistance values are calculated for a range of chemical grafting densities and with several chain lengths. These results are subsequently used in an analytical model to predict the resulting effect on the bulk thermal conductivity of the nanocomposite.

  8. High-density interconnect substrates and device packaging using conductive composites

    NASA Astrophysics Data System (ADS)

    Gandhi, Pradeep; Gallagher, Catherine; Matijasevic, Goran

    1998-02-01

    High-end printed circuit board manufacturing technology is receiving increasing attention due to higher functionality in smaller form factors. This is evident from the industry efforts to produced reliable microvias and related trace features to pack as much circuit density as possible. Cost, density and performance requirements have prodded entry into a market that was mainly reserved for ceramic and molded packages for the last forty years. To successfully meet the demanding specifications of this market segment, a worldwide effort is underway for the development of new materials, processes and equipment. A novel base technology that is applicable to most of the major packaging and redistribution elements in an electronic module is presented.High density multilayer circuits with landless blind and buried vias can be fabricated by filling the conductor paste into photoimaged dielectrics and thermally processing it at a relatively lower temperature. Via layers are prepared directly on the inherently planarized circuit layer in an identical fashion. Because these composite materials are applied in an additive fabrication method, metal substrates can be employed for high thermal dissipation and excellent CTE control over a wide temperature range. The conductor material is based on interpenetrating polymer and metal networks that are formed in situ from metal particles and a thermosetting flux/binder. The metal network is formed when the alloy particles melt and react with adjacent high melting point metal particle. Interaction also occurs between the alloy particles and pad, lead or previous trace metallizations provided they are solderable by alloys of tin. The new alloy composition created by the interdiffusion process within the bulk material has a higher melting point than the original alloy and thus solidifies immediately upon formation. This metallurgical reaction, known as transient liquid phase sintering, is facilitated by the polymer mixture. INtegration of

  9. Evaluation of morphological indices and total body electrical conductivity to assess body composition in big brown bats

    USGS Publications Warehouse

    Pearce, R.D.; O'Shea, T.J.; Wunder, B.A.

    2008-01-01

    Bat researchers have used both morphological indices and total body electric conductivity (TOBEC) as proxies for body condition in a variety of studies, but have typically not validated these indices against direct measurement of body composition. We quantified body composition (total carcass lipids) to determine if morphological indices were useful predictors of body condition in big brown bats (Eptesicus fuscus). We also evaluated body composition indirectly by TOBEC using EM-SCAN?? technology. The most important predictors of body composition in multiple regression analysis were body mass-to-forearm ratio (partial r2 = 0.82, P < 0.001) followed by TOBEC measurement (partial r2 = 0.08, P < 0.001) and to a minor extent head length (partial r2 = 0.02, P < 0.05). Morphological condition indices alone may be adequate for some studies because of lower cost and effort. Marking bats with passive integrated transponder (PIT) tags affected TOBEC measurements. ?? Museum and Institute of Zoology PAS.

  10. A Numerical Study on the Thermal Conductivity of 3D Woven C/C Composites at High Temperature

    NASA Astrophysics Data System (ADS)

    Shigang, Ai; Rujie, He; Yongmao, Pei

    2015-12-01

    Experimental data for Carbon/Carbon (C/C) constituent materials are combined with a three dimensional steady state heat transfer finite element analysis to demonstrate the average in-plane and out-of-plane thermal conductivities (TCs) of C/C composites. The finite element analysis is carried out at two distinct length scales: (a) a micro scale comparable with the diameter of carbon fibres and (b) a meso scale comparable with the carbon fibre yarns. Micro-scale model calculate the TCs at the fibre yarn scale in the three orthogonal directions ( x, y and z). The output results from the micro-scale model are then incorporated in the meso-scale model to obtain the global TCs of the 3D C/C composite. The simulation results are quite consistent with the theoretical and experimental counterparts reported in references. Based on the numerical approach, TCs of the 3D C/C composite are calculated from 300 to 2500 K. Particular attention is given in elucidating the variations of the TCs with temperature. The multi-scale models provide an efficient approach to predict the TCs of 3D textile materials, which is helpful for the thermodynamic property analysis and structure design of the C/C composites.

  11. Thermal conductivity of tubular nanowire composites based on a thermodynamical model

    NASA Astrophysics Data System (ADS)

    Lebon, Georgy; Machrafi, Hatim

    2015-07-01

    A formula for the effective heat conductivity of a nanocomposite with cylindrical nanowire inclusions is derived. Both transversal and longitudinal heating along the wires are investigated. Several effects are examined: the volume fraction and sizes of the nanowires, the type of scattering at the particle-matrix interface and temperature. As illustration, silicon nanowires inclusions in a germanium matrix is considered; the results are shown to be in good agreement with other models and numerical solutions of the Boltzmann transport equation. Our main contribution consists of using extended irreversible thermodynamics to cope with the nano dimensions of the wires.

  12. Electrical conductivity studies of graphene wrapped nanocrystalline LiMnPO{sub 4} composite

    SciTech Connect

    Cheruku, Rajesh; D, Surya Bhaskaram; Govindaraj, G.; Vijayan, Lakshmi

    2015-06-24

    Nanocrystalline LiMnPO{sub 4} material was synthesized by template free sucrose assisted hydrothermal method. The material possesses the orthorhombic crystal structure with Pnma, space group having four formula units. The GO was prepared by the hummer’s method and it was reduced graphene oxide (rGO) with hydrazine hydrate in the presence of nitrogen atmosphere. LiMnPO{sub 4} material was wrapped by the rGO to increase its conductivity. The structural characterization was accomplished through X-ray diffraction, FT-IR and Raman spectroscopy. Morphology was identified by the SEM, Electrical characterization was done through impedance spectroscopy and the results were reported.

  13. Preparation and investigation of dc conductivity and relative permeability of epoxy/Li-Ni-Zn ferrite composites

    NASA Astrophysics Data System (ADS)

    Darwish, M. A.; Saafan, S. A.; El-Kony, D.; Salahuddin, N. A.

    2015-07-01

    Ferrite nanoparticles - having the compositions Li(x/2)(Ni0.5Zn0.5)(1-x)Fe(2+x/2)O4 (x=0, 0.2, 0.3) - have been prepared by the co-precipitation method. The prepared powders have been divided into groups and sintered at different temperatures (373 K, 1074 K and 1473 K). X-Ray diffraction analysis (XRD) for all samples has confirmed the formation of the desired ferrites with crystallite sizes within the nanoscale (<100 nm). The dc conductivity, the relative permeability and the magnetization of the ferrite samples have been investigated and according to the results, the sample Li0.15(Ni0.5Zn0.5)0.7 Fe2.15O4 sintered at 1473 K has been chosen to prepare the composites. The particle size of this sample has been recalculated by using JEOL JEM-100SX transmission electron microscope and it has been found about 64.7 nm. Then, a pure epoxy sample and four pristine epoxy resin /Li0.15(Ni0.5Zn0.5)0.7 Fe2.15O4 composites have been prepared using different ferrite contents (20%, 30%, 40%, and 50%) wt.%. These samples have been characterized by Fourier transform infrared (FTIR) spectroscopy and their dc conductivity, relative permeability and magnetization have also been investigated. The obtained results indicate that the investigated composites may be promising candidates for practical applications such as EMI suppressor and high frequency applications.

  14. Graphene, conducting polymer and their composites as transparent and current spreading electrode in GaN solar cells

    NASA Astrophysics Data System (ADS)

    Mahala, Pramila; Kumar, Ajay; Nayak, Sasmita; Behura, Sanjay; Dhanavantri, Chenna; Jani, Omkar

    2016-04-01

    Understanding the physics of charge carrier transport at graphene/p-GaN interface is critical for achieving efficient device functionality. Currently, the graphene/p-GaN interface is being explored as light emitting diodes, however this interface can be probed as a potential photovoltaic cell. We report the intimate interfacing of mechanically exfoliated graphene (EG), conducting polymer (PEDOT:PSS) and composite of reduced graphene oxide (rGO) and PEDOT:PSS with a wide band gap p-GaN layer. To explore their potential in energy harvesting, three heterojunction devices such as: (i) EG/p-GaN/sapphire, (ii) PEDOT:PSS/p-GaN/sapphire and (iii) PEDOT:PSS(rGO)/p-GaN/sapphire are designed and their photovoltaic characteristics are examined. It is interesting to observe that the EG/p-GaN/sapphire solar cell exhibits high open-circuit voltage of 0.545 V with low ideality factor and reverse saturation current. However, improved short circuit current density (13.7 mA/cm2) is noticed for PEDOT:PSS/p-GaN/sapphire solar cell because of enhanced conductivity accompanied by high transmittance for PEDOT:PSS. Further, the low series resistance for PEDOT:PSS(rGO)/p-GaN/sapphire is observed suggesting that the PEDOT:PSS and rGO composite is well dispersed and exhibits low interfacial resistances with p-GaN. The present investigation leverages the potential of graphene, conducting polymer and their composites as dual capability of (a) transparent and current spreading electrode and (b) an active top layer to make an intimate contact with wide bandgap p-type GaN for possible prospect towards high performance diodes, switches and solar cells.

  15. Atomic and Molecular Layer Deposition for Enhanced Lithium Ion Battery Electrodes and Development of Conductive Metal Oxide/Carbon Composites

    NASA Astrophysics Data System (ADS)

    Travis, Jonathan

    The performance and safety of lithium-ion batteries (LIBs) are dependent on interfacial processes at the positive and negative electrodes. For example, the surface layers that form on cathodes and anodes are known to affect the kinetics and capacity of LIBs. Interfacial reactions between the electrolyte and the electrodes are also known to initiate electrolyte combustion during thermal runaway events that compromise battery safety. Atomic layer deposition (ALD) and molecular layer deposition (MLD) are thin film deposition techniques based on sequential, self-limiting surface reactions. ALD and MLD can deposit ultrathin and conformal films on high aspect ratio and porous substrates such as composite particulate electrodes in lithium-ion batteries. The effects of electrode surface modification via ALD and MLD are studied using a variety of techniques. It was found that sub-nm thick coatings of Al2O 3 deposited via ALD have beneficial effects on the stability of LIB anodes and cathodes. These same Al2O3 ALD films were found to improve the safety of graphite based anodes through prevention of exothermic solid electrolyte interface (SEI) degradation at elevated temperatures. Ultrathin and conformal metal alkoxide polymer films known as "metalcones" were grown utilizing MLD techniques with trimethylaluminum (TMA) or titanium tetrachloride (TiCl4) and organic diols or triols, such as ethylene glycol (EG), glycerol (GL) or hydroquinone (HQ), as the reactants. Pyrolysis of these metalcone films under inert gas conditions led to the development of conductive metal oxide/carbon composites. The composites were found to contain sp2 carbon using micro-Raman spectroscopy in the pyrolyzed films with pyrolysis temperatures ≥ 600°C. Four point probe measurements demonstrated that the graphitic sp2 carbon domains in the metalcone films grown using GL and HQ led to significant conductivity. The pyrolysis of conformal MLD films to obtain conductive metal oxide/carbon composite films

  16. High-Frequency Testing of Composite Fan Vanes With Erosion-Resistant Coating Conducted

    NASA Technical Reports Server (NTRS)

    Bowman, Cheryl L.; Sutter, James K.; Naik, Subhash; Otten, Kim D.; Perusek, Gail P.

    2003-01-01

    The mechanical integrity of hard, erosion-resistant coatings were tested using the Structural Dynamics Laboratory at the NASA Glenn Research Center. Under the guidance of Structural Mechanics and Dynamics Branch personnel, fixturing and test procedures were developed at Glenn to simulate engine vibratory conditions on coated polymer-matrix- composite bypass vanes using a slip table in the Structural Dynamics Laboratory. Results from the high-frequency mechanical bench testing, along with concurrent erosion testing of coupons and vanes, provided sufficient confidence to engine-endurance test similarly coated vane segments. The knowledge gained from this program will be applied to the development of oxidation- and erosion-resistant coatings for polymer matrix composite blades and vanes in future advanced turbine engines. Fan bypass vanes from the AE3007 (Rolls Royce America, Indianapolis, IN) gas turbine engine were coated by Engelhard (Windsor, CT) with compliant bond coatings and hard ceramic coatings. The coatings were developed collaboratively by Glenn and Allison Advanced Development Corporation (AADC)/Rolls Royce America through research sponsored by the High-Temperature Engine Materials Technology Project (HITEMP) and the Higher Operating Temperature Propulsion Components (HOTPC) project. High-cycle fatigue was performed through high-frequency vibratory testing on a shaker table. Vane resonant frequency modes were surveyed from 50 to 3000 Hz at input loads from 1g to 55g on both uncoated production vanes and vanes with the erosion-resistant coating. Vanes were instrumented with both lightweight accelerometers and strain gauges to establish resonance, mode shape, and strain amplitudes. Two high-frequency dwell conditions were chosen to excite two strain levels: one approaching the vane's maximum allowable design strain and another near the expected maximum strain during engine operation. Six specimens were tested per dwell condition. Pretest and posttest

  17. Composition-dependent structural and transport properties of amorphous transparent conducting oxides

    NASA Astrophysics Data System (ADS)

    Khanal, Rabi; Buchholz, D. Bruce; Chang, Robert P. H.; Medvedeva, Julia E.

    2015-05-01

    Structural properties of amorphous In-based oxides, In -X -O with X =Zn , Ga, Sn, or Ge, are investigated using ab initio molecular dynamics liquid-quench simulations. The results reveal that indium retains its average coordination of 5.0 upon 20% X fractional substitution for In, whereas X cations satisfy their natural coordination with oxygen atoms. This finding suggests that the carrier generation is primarily governed by In atoms, in accord with the observed carrier concentration in amorphous In-O and In -X -O . At the same time, the presence of X affects the number of six-coordinated In atoms as well as the oxygen sharing between the InO6 polyhedra. Based on the obtained interconnectivity and spatial distribution of the InO6 and XO x polyhedra in amorphous In -X -O , composition-dependent structural models of the amorphous oxides are derived. The results help explain our Hall mobility measurements in In -X -O thin films grown by pulsed-laser deposition and highlight the importance of long-range structural correlations in the formation of amorphous oxides and their transport properties.

  18. Flexible transparent conducting composite films using a monolithically embedded AgNW electrode with robust performance stability.

    PubMed

    Im, Hyeon-Gyun; Jin, Jungho; Ko, Ji-Hoon; Lee, Jaemin; Lee, Jung-Yong; Bae, Byeong-Soo

    2014-01-21

    We report on the performance of an all-in-one flexible hybrid conducting film employing a monolithically embedded AgNW transparent electrode and a high-performance glass-fabric reinforced composite substrate (AgNW-GFRHybrimer film). Specifically, we perform in-depth investigations on the stability of the AgNW-GFRHybrimer film against heat, thermal oxidation, and wet chemicals to demonstrate the potential of the hybrid conducting film as a robust electrode platform for thin-film optoelectronic devices. With the ease of large-area processability, smooth surface topography, and robust performance stability, the AgNW-GFRHybrimer film can be a promising platform for high-performance optoelectronic devices. PMID:24284890

  19. Electrically Conductive, Optically Transparent Polymer/Carbon Nanotube Composites and Process for Preparation Thereof

    NASA Technical Reports Server (NTRS)

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

    2009-01-01

    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 hy selection of the polymer matrix and CNT to fabricate articles that possess high optical transparency and antistatic behavior.

  20. Composition Dependence of the Optical Conductivity of NiPt Alloys Determined by Spectroscopic Ellipsometry

    NASA Astrophysics Data System (ADS)

    Abdallah, Lina; Tawalbeh, Tarek; Vasiliev, Igor; Zollner, Stefan; Lavoie, Christian; Ozcan, Ahmet; Raymond, Mark

    2012-10-01

    The complex dielectric function of different Ni-Pt alloys (0% to 25% Pt concentration, 10nm thickness) was determined using spectroscopic ellipsometry over a broad photon energy range from 0.6 to 6.6eV. Data were fitted using basis spline functions as well as Drude-Lorentz oscillators to describe free carrier absorption and interband transitions. We found absorption peaks at 1.5 and 4.7 eV due to interband transitions. Results showed a broadening in the absorption peak of Nickel with increasing the Platinum concentration in the alloy. The experimental results were compared with ab initio density functional theory band structure calculations which showed that adding Platinum enhances the density of states of Nickel especially at low energies. Annealing the metals at 500^o C for 30 s increases the optical conductivity.

  1. Electrically Conductive, Optically Transparent Polymer/Carbon Nanotube Composites and Process for Preparation Thereof

    NASA Technical Reports Server (NTRS)

    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.

  2. Electrically conductive, optically transparent polymer/carbon nanotube composites and process for preparation thereof

    NASA Technical Reports Server (NTRS)

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

    2009-01-01

    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.

  3. Flexible transparent conducting composite films using a monolithically embedded AgNW electrode with robust performance stability

    NASA Astrophysics Data System (ADS)

    Im, Hyeon-Gyun; Jin, Jungho; Ko, Ji-Hoon; Lee, Jaemin; Lee, Jung-Yong; Bae, Byeong-Soo

    2013-12-01

    We report on the performance of an all-in-one flexible hybrid conducting film employing a monolithically embedded AgNW transparent electrode and a high-performance glass-fabric reinforced composite substrate (AgNW-GFRHybrimer film). Specifically, we perform in-depth investigations on the stability of the AgNW-GFRHybrimer film against heat, thermal oxidation, and wet chemicals to demonstrate the potential of the hybrid conducting film as a robust electrode platform for thin-film optoelectronic devices. With the ease of large-area processability, smooth surface topography, and robust performance stability, the AgNW-GFRHybrimer film can be a promising platform for high-performance optoelectronic devices.We report on the performance of an all-in-one flexible hybrid conducting film employing a monolithically embedded AgNW transparent electrode and a high-performance glass-fabric reinforced composite substrate (AgNW-GFRHybrimer film). Specifically, we perform in-depth investigations on the stability of the AgNW-GFRHybrimer film against heat, thermal oxidation, and wet chemicals to demonstrate the potential of the hybrid conducting film as a robust electrode platform for thin-film optoelectronic devices. With the ease of large-area processability, smooth surface topography, and robust performance stability, the AgNW-GFRHybrimer film can be a promising platform for high-performance optoelectronic devices. Electronic supplementary information (ESI) available: Further characteristics of AgNW-GFRHybrimer films and thermal oxidation of AgNW on glass. See DOI: 10.1039/c3nr05348b

  4. Sol-gel-derived composite antimony-doped, tin oxide-coated clay-silicate semitransparent and conductive electrodes.

    PubMed

    Sadeh, A; Sladkevich, S; Gelman, F; Prikhodchenko, P; Baumberg, I; Berezin, O; Lev, O

    2007-07-15

    A new form of conductive and transparent porous composite electrode is introduced. The electrode material is composed of antimony-doped, tin oxide (ATO)-coated mica platelets imbedded in sol-gel-derived silicate or methyl silicate network. The platelet clays self-align in a layered structure within the silicate film, an anisotropic construction that minimizes the ATO loading required to achieve electric percolation. Transparency and resistance as a function of clay loading is reported with typical values of 100 k Omega/square and 1.5 OD for a 20-microm-thick film. The transparency is lower as compared to sputtered ATO glasses, but this is, as far as we know, the best method for the low-temperature preparation of transparent, porous, and electrically conductive (as opposed to the amply reported ionically conductive) electrode materials. Permselectivity induced by the silicate and clay ingredients is demonstrated by permeation of positively charged methyl viologen compared to negatively charged ferricyanide. Prussian blue-modified ATO-coated platelets dispersed in sol-gel-derived silicate were used to demonstrate feasibility of a transparent and electrically conductive porous electrochromic material. PMID:17555295

  5. Development of glucose biosensors based on nanostructured graphene-conducting polyaniline composite.

    PubMed

    Feng, Xue; Cheng, Huijun; Pan, Yiwen; Zheng, Hao

    2015-08-15

    A biosensor was fabricated by immobilizing glucose oxidase (GOD) into nanostructured graphene (GRA)-conducting polyaniline (PANI) nanocomposite, which was based on electrochemical polymerization of aniline in GRA synthesized by using electrochemical expansion of graphite in propylene carbonate electrolyte. Scanning electron spectroscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to characterize the morphology and performance of the as-prepared biosensor, respectively. Amperometric measurements were carried out to optimize test conditions (pH and applied potential) of the biosensor. Under the optimal conditions, the biosensor showed a linear range from 10.0 μM to 1.48 mM (R(2)=0.9988) with a sensitivity of 22.1 μA mM(-1) cm(-2), and a detection limit of 2.769 μM (S/N=3). The apparent Michaelis-Menten constant (KM(a)) was estimated to be 3.26 mM. The interference from glycine (Gly), D-galactose (D-Gal), urea (Urea), L-phenylalanine (L-Phe), ascorbic acid (AA), and L-tyrosine (L-Tyr) was also investigated. The results indicated that the biosensor exhibit high sensitivity and superior selectivity, providing a hopeful candidate for glucose biosensing. PMID:25845333

  6. Facile synthesis and electrochemical properties of conducting SrRuO 3-RuO 2 composite nanofibre mats

    NASA Astrophysics Data System (ADS)

    Hyun, Tae-Seon; Kim, Ho-Gi; Kim, Il-Doo

    This study reports the facile synthesis of highly conductive SrRuO 3(SRO)-RuO 2 composite nanofibre mats and their potential suitability for application in electrochemical capacitors as an active electrode material. SRO-RuO 2/poly(vinyl acetate) composite nanofibre mats are electrospun on to a Au-coated SiO 2/Si substrate and a Ti substrate, subsequently thermocompressed at 60 °C, and calcined at various temperatures (from 350 to 850 °C). The calcined SRO-RuO 2 nanofibre mats exhibit porous morphologies and bundle shapes composed of multiple-fibrils with a nanoparticle diameter ranging from 20 to 50 nm. Single SRO-RuO 2 nanofibre and multiple SRO-RuO 2 nanofibre mats show high electrical conductivity of 476 and 40.8 S cm -1, respectively. Pseudocapacitors using SRO-RuO 2 nanofibre mats calcined at 350 °C exhibit a high specific capacitance of 192 F g -1 at a scan rate of 10 mV s -1. The superior capacitance retention (83.4%) of the SRO-RuO 2 nanofibre mats is maintained even at rapid scan rate of 1000 mV s -1.

  7. On-line vs off-line electrical conductivity characterization. Polycarbonate composites developed with multiwalled carbon nanotubes by compounding technology

    NASA Astrophysics Data System (ADS)

    Llorens-Chiralt, R.; Weiss, P.; Mikonsaari, I.

    2014-05-01

    Material characterization is one of the key steps when conductive polymers are developed. The dispersion of carbon nanotubes (CNTs) in a polymeric matrix using melt mixing influence final composite properties. The compounding becomes trial and error using a huge amount of materials, spending time and money to obtain competitive composites. Traditional methods to carry out electrical conductivity characterization include compression and injection molding. Both methods need extra equipments and moulds to obtain standard bars. This study aims to investigate the accuracy of the data obtained from absolute resistance recorded during the melt compounding, using an on-line setup developed by our group, and to correlate these values with off-line characterization and processing parameters (screw/barrel configuration, throughput, screw speed, temperature profile and CNTs percentage). Compounds developed with different percentages of multi walled carbon nanotubes (MWCNTs) and polycarbonate has been characterized during and after extrusion. Measurements, on-line resistance and off-line resistivity, showed parallel response and reproducibility, confirming method validity. The significance of the results obtained stems from the fact that we are able to measure on-line resistance and to change compounding parameters during production to achieve reference values reducing production/testing cost and ensuring material quality. Also, this method removes errors which can be found in test bars development, showing better correlation with compounding parameters.

  8. Development of Innovative Accident Tolerant High Thermal Conductivity UO2-Diamond Composite Fuel Pellets

    SciTech Connect

    Tulenko, James; Subhash, Ghatu

    2016-01-01

    The University of Florida (UF) evaluated a composite fuel consisting of UO2 powder mixed with diamond micro particles as a candidate as an accident-tolerant fuel (ATF). The research group had previous extensive experience researching with diamond micro particles as an addition to reactor coolant for improved plant thermal performance. The purpose of this research work was to utilize diamond micro particles to develop UO2-Diamond composite fuel pellets with significantly enhanced thermal properties, beyond that already being measured in the previous UF research projects of UO2 – SiC and UO2 – Carbon Nanotube fuel pins. UF is proving with the current research results that the addition of diamond micro particles to UO2 may greatly enhanced the thermal conductivity of the UO2 pellets producing an accident-tolerant fuel. The Beginning of life benefits have been proven and fuel samples are being irradiated in the ATR reactor to confirm that the thermal conductivity improvements are still present under irradiation.

  9. Modified carbon fibers to improve composite properties. [sizing fibers for reduced electrical conductivity and adhesion during combustion

    NASA Technical Reports Server (NTRS)

    Shepler, R. E.

    1979-01-01

    Thin coatings, 5 to 10 wt. percent, were applied to PAN-based carbon fibers. These coatings were intended to make the carbon fibers less electrically conductive or to cause fibers to stick together when a carbon fiber/epoxy composite burned. The effectiveness of the coatings in these regards was evaluated in burn tests with a test rig designed to simulate burning, impact and wind conditions which might release carbon fibers. The effect of the coatings on fiber and composite properties and handling was also investigated. Attempts at sizing carbon fibers with silicon dioxide, silicon carbide and boron nitride meet with varying degrees of success; however, none of these materials provided an electrically nonconductive coating. Coatings intended to stick carbon fibers together after a composite burned were sodium silicate, silica gel, ethyl silicate, boric acid and ammonium borate. Of these, only the sodium silicate and silica gel provided any sticking together of fibers. The amount of sticking was insufficient to achieve the desired objectives.

  10. A composite SWNT-collagen matrix: characterization and preliminary assessment as a conductive peripheral nerve regeneration matrix

    NASA Astrophysics Data System (ADS)

    Tosun, Z.; McFetridge, P. S.

    2010-12-01

    Unique in their structure and function, single-walled carbon nanotubes (SWNTs) have received significant attention due to their potential to create unique conductive materials. For neural applications, these conductive materials hold promise as they may enhance regenerative processes. However, like other nano-scaled biomaterials it is important to have a comprehensive understanding how these materials interact with cell systems and how the biological system responds to their presence. These investigations aim to further our understanding of SWNT-cell interactions by assessing the effect SWNT/collagen hydrogels have on PC12 neuronal-like cells seeded within and (independently) on top of the composite material. Two types of collagen hydrogels were prepared: (1) SWNTs dispersed directly within the collagen (SWNT/COL) and (2) albumin-coated SWNTs prepared using the surfactant 'sodium cholate' to improve dispersion (AL-SWNT/COL) and collagen alone serving as a control (COL). SWNT dispersion was significantly improved when using surfactant-assisted dispersion. The enhanced dispersion resulted in a stiffer, more conductive material with an increased collagen fiber diameter. Short-term cell interactions with PC12 cells and SWNT composites have shown a stimulatory effect on cell proliferation relative to plain collagen controls. In parallel to these results, p53 gene displayed normal expression levels, which indicates the absence of nanoparticle-induced DNA damage. In summary, these mechanically tunable SWNT-collagen scaffolds show the potential for enhanced electrical activity and have shown positive in vitro biocompatibility results offering further evidence that SWNT-based materials have an important role in promoting neuronal regeneration.

  11. Electrical conductivity studies in (Ag3AsS3)x(As2S3)1-x superionic glasses and composites

    NASA Astrophysics Data System (ADS)

    Studenyak, I. P.; Neimet, Yu. Yu.; Kranjčec, M.; Solomon, A. M.; Orliukas, A. F.; Kežionis, A.; Kazakevičius, E.; Šalkus, T.

    2014-01-01

    Compositional, frequency, and temperature studies of impedance and electrical conductivity in (Ag3AsS3)x(As2S3)1-x superionic glasses and composites were performed. Frequency range from 10 Hz to 3 × 109 Hz and temperature interval 300-400 K were used for the measurements. Compositional dependences of electrical conductivity and activation energy are analyzed; the most substantial changes are observed with the transition from (Ag3AsS3)0.4(As2S3)0.6 glass to (Ag3AsS3)0.5(As2S3)0.5 composite. With increase of Ag3AsS3 content, the investigated materials are found to have crystalline inclusions and show the two-phase composite nature. Addition of Ag3AsS3 leads to the increase of electrical conductivity whereas the activation energy decreases.

  12. Size effect of cubic ZrO2 nanoparticles on ionic conductivity of polyethylene oxide-based composite

    NASA Astrophysics Data System (ADS)

    Dey, Arup; Ghoshal, Tandra; Karan, S.; De, S. K.

    2011-08-01

    A solvent free solid composite polymer electrolyte (SCPE) film consisting of high molecular mass polyethylene oxide (PEO) with sodium perchlorate (NaClO4) as electrolytic salt and cubic zirconium oxide (ZrO2) nanoparticles as the filler has been prepared by solution casting technique to influence the transport properties. X-ray diffraction and Fourier transform infrared spectroscopy confirm the formation of the SCPE film, whereas atomic force microscopy reveals the presence of a network of interconnected nanoparticles forming uniform surface feature of relatively low roughness. The highest ionic conductivity (σ = 6.96 × 10-5 S-cm-1) for PEO25 - NaClO4 with 5 wt. % ZrO2 nanoparticles of the smallest size 4.5 nm is an order of magnitude higher than the pure PEO25 - NaClO4 at room temperature. The conductivity enhancement is due to the creation of additional sites and favorable conduction pathways for ionic transport through Lewis acid-base type interactions between the polar surface groups of the ceramic filler and the electrolyte ionic species.

  13. A novel composite conductive microfiltration membrane and its anti-fouling performance with an external electric field in membrane bioreactors.

    PubMed

    Huang, Jian; Wang, Zhiwei; Zhang, Junyao; Zhang, Xingran; Ma, Jinxing; Wu, Zhichao

    2015-01-01

    Membrane fouling remains an obstacle to wide-spread applications of membrane bioreactors (MBRs) for wastewater treatment and reclamation. Herein, we report a simple method to prepare a composite conductive microfiltration (MF) membrane by introducing a stainless steel mesh into a polymeric MF membrane and to effectively control its fouling by applying an external electric field. Linear sweep voltammetry and electrochemical impedance spectroscopy analyses showed that this conductive membrane had very good electrochemical properties. Batch tests demonstrated its anti-fouling ability in filtration of bovine serum albumin, sodium alginate, humic acid and silicon dioxide particles as model foulants. The fouling rate in continuous-flow MBRs treating wastewater was also decreased by about 50% for this conductive membrane with 2 V/cm electric field compared to the control test during long-term operation. The enhanced electrostatic repulsive force between foulants and membrane, in-situ cleaning by H2O2 generated from oxygen reduction, and decreased production of soluble microbial products and extracellular polymeric substances contributed to fouling mitigation in this MBR. The results of this study shed light on the control strategy of membrane fouling for achieving a sustainable operation of MBRs. PMID:25784160

  14. Cytocompatibility of a conductive nanofibrous carbon nanotube/poly (L-Lactic acid) composite scaffold intended for nerve tissue engineering

    PubMed Central

    Kabiri, Mahboubeh; Oraee-Yazdani, Saeed; Dodel, Masumeh; Hanaee-Ahvaz, Hana; Soudi, Sara; Seyedjafari, Ehsan; Salehi, Mohammad; Soleimani, Masoud

    2015-01-01

    The purpose of this study was to fabricate a conductive aligned nanofibrous substrate and evaluate its suitability and cytocompatibility with neural cells for nerve tissue engineering purposes. In order to reach these goals, we first used electrospinning to fabricate single-walled carbon-nanotube (SWCNT) incorporated poly(L-lactic acid) (PLLA) nanofibrous scaffolds and then assessed its cytocompatibility with olfactory ensheathing glial cells (OEC). The plasma treated scaffolds were characterized using scanning electron microscopy and water contact angle. OECs were isolated from olfactory bulb of GFP Sprague-Dawley rats and characterized using OEC specific markers via immunocytochemistry and flow cytometery. The cytocompatibility of the conductive aligned nano-featured scaffold was assessed using microscopy and MTT assay. We indicate that doping of PLLA polymer with SWCNT can augment the aligned nanosized substrate with conductivity, making it favorable for nerve tissue engineering. Our results demonstrated that SWCNT/PLLA composite scaffold promote the adhesion, growth, survival and proliferation of OEC. Regarding the ideal physical, topographical and electrical properties of the scaffold and the neurotrophic and migratory features of the OECs, we suggest this scaffold and the cell/scaffold construct as a promising platform for cell delivery to neural defects in nerve tissue engineering approaches. PMID:26600751

  15. Ionic conductivity in gem-quality single-crystal alkali feldspar from the Eifel: temperature, orientation and composition dependence

    NASA Astrophysics Data System (ADS)

    El Maanaoui, Hamid; Wilangowski, Fabian; Maheshwari, Aditya; Wiemhöfer, Hans-Dieter; Abart, Rainer; Stolwijk, Nicolaas A.

    2016-05-01

    We measured the ion conductivity of single-crystal alkali feldspar originating from two different locations in the Eifel/Germany, named Volkesfeld and Rockeskyller sanidine and having potassium site fractions C_K of 0.83 and 0.71, respectively. The dc conductivities resulting from electrochemical impedance spectroscopy over the temperature range of 300-900°C show a weak composition dependence but pronounced differences between the b-direction [perp (010)] and c^{*}-direction [perp (001)] of the monoclinic feldspar structure. Conductivity activation energies obtained from the observed linear Arrhenius plots are close to 1.2 eV in all cases, which is closely similar to the activation energies of the ^{22}Na tracer diffusivity in the same crystals. Taking into account literature data on K tracer diffusion and diffusion correlation effects, the present results point to a predominance of the interstitialcy mechanism over the vacancy mechanism in mass and charge transport on the alkali sublattice in potassium-rich alkali feldspar.

  16. Effects of TiO2 addition on ionic conductivity of PVC/PEMA blend based composite polymer electrolyte

    NASA Astrophysics Data System (ADS)

    Subban, R. H. Y.; Sukri, Nursyazwani

    2015-08-01

    PVC/PEMA blend based polymer electrolytes with lithium bistrifluoromethane sulfonimide (LiN(CF3SO2)2) and PVC/PEMA/(LiN(CF3SO2)2-TiO2 films were prepared by solution cast technique. The sample containing 35 wt. % LiN(CF3SO2)2 exhibited the highest conductivity of 1.75 × 10-5 Scm-1. The conductivity of the sample increased to 2.12 × 10-5 Scm-1 and 4.61 × 10-5 Scm-1 when 4 wt. % and 10 wt. % of titanium dioxide (TiO2) was added to the sample at 65 wt. % PVC/PEMA-35 wt. % LiN(CF3SO2)2 composition respectively. The low increase in conductivity is attributed to two competing factors: increase in crystallinity as accounted by X-Ray diffraction (XRD) and decrease in glass transition temperature as accounted by differential scanning calorimetry (DSC).

  17. A novel composite conductive microfiltration membrane and its anti-fouling performance with an external electric field in membrane bioreactors

    PubMed Central

    Huang, Jian; Wang, Zhiwei; Zhang, Junyao; Zhang, Xingran; Ma, Jinxing; Wu, Zhichao

    2015-01-01

    Membrane fouling remains an obstacle to wide-spread applications of membrane bioreactors (MBRs) for wastewater treatment and reclamation. Herein, we report a simple method to prepare a composite conductive microfiltration (MF) membrane by introducing a stainless steel mesh into a polymeric MF membrane and to effectively control its fouling by applying an external electric field. Linear sweep voltammetry and electrochemical impedance spectroscopy analyses showed that this conductive membrane had very good electrochemical properties. Batch tests demonstrated its anti-fouling ability in filtration of bovine serum albumin, sodium alginate, humic acid and silicon dioxide particles as model foulants. The fouling rate in continuous-flow MBRs treating wastewater was also decreased by about 50% for this conductive membrane with 2 V/cm electric field compared to the control test during long-term operation. The enhanced electrostatic repulsive force between foulants and membrane, in-situ cleaning by H2O2 generated from oxygen reduction, and decreased production of soluble microbial products and extracellular polymeric substances contributed to fouling mitigation in this MBR. The results of this study shed light on the control strategy of membrane fouling for achieving a sustainable operation of MBRs. PMID:25784160

  18. Effects of TiO{sub 2} addition on ionic conductivity of PVC/PEMA blend based composite polymer electrolyte

    SciTech Connect

    Subban, R. H. Y.; Sukri, Nursyazwani

    2015-08-28

    PVC/PEMA blend based polymer electrolytes with lithium bistrifluoromethane sulfonimide (LiN(CF{sub 3}SO{sub 2}){sub 2}) and PVC/PEMA/(LiN(CF{sub 3}SO{sub 2}){sub 2}-TiO{sub 2} films were prepared by solution cast technique. The sample containing 35 wt. % LiN(CF{sub 3}SO{sub 2}){sub 2} exhibited the highest conductivity of 1.75 × 10{sup −5} Scm{sup −1}. The conductivity of the sample increased to 2.12 × 10{sup −5} Scm{sup −1} and 4.61 × 10{sup −5} Scm{sup −1} when 4 wt. % and 10 wt. % of titanium dioxide (TiO{sub 2}) was added to the sample at 65 wt. % PVC/PEMA-35 wt. % LiN(CF{sub 3}SO{sub 2}){sub 2} composition respectively. The low increase in conductivity is attributed to two competing factors: increase in crystallinity as accounted by X-Ray diffraction (XRD) and decrease in glass transition temperature as accounted by differential scanning calorimetry (DSC)

  19. A novel composite conductive microfiltration membrane and its anti-fouling performance with an external electric field in membrane bioreactors

    NASA Astrophysics Data System (ADS)

    Huang, Jian; Wang, Zhiwei; Zhang, Junyao; Zhang, Xingran; Ma, Jinxing; Wu, Zhichao

    2015-03-01

    Membrane fouling remains an obstacle to wide-spread applications of membrane bioreactors (MBRs) for wastewater treatment and reclamation. Herein, we report a simple method to prepare a composite conductive microfiltration (MF) membrane by introducing a stainless steel mesh into a polymeric MF membrane and to effectively control its fouling by applying an external electric field. Linear sweep voltammetry and electrochemical impedance spectroscopy analyses showed that this conductive membrane had very good electrochemical properties. Batch tests demonstrated its anti-fouling ability in filtration of bovine serum albumin, sodium alginate, humic acid and silicon dioxide particles as model foulants. The fouling rate in continuous-flow MBRs treating wastewater was also decreased by about 50% for this conductive membrane with 2 V/cm electric field compared to the control test during long-term operation. The enhanced electrostatic repulsive force between foulants and membrane, in-situ cleaning by H2O2 generated from oxygen reduction, and decreased production of soluble microbial products and extracellular polymeric substances contributed to fouling mitigation in this MBR. The results of this study shed light on the control strategy of membrane fouling for achieving a sustainable operation of MBRs.

  20. EXACT SOLUTION OF HEAT CONDUCTION IN A TWO-DOMAIN COMPOSITE CYLINDER WITH AN ORTHOTROPIC OUTER LAYER.

    SciTech Connect

    C. AVILES-RAMOS; C. RUDY

    2000-11-01

    The transient exact solution of heat conduction in a two-domain composite cylinder is developed using the separation of variables technique. The inner cylinder is isotropic and the outer cylindrical layer is orthotropic. Temperature solutions are obtained for boundary conditions of the first and second kinds at the outer surface of the orthotropic layer. These solutions are applied to heat flow calorimeters modeling assuming that there is heat generation due to nuclear reactions in the inner cylinder. Heat flow calorimeter simulations are carried out assuming that the inner cylinder is filled with plutonium oxide powder. The first objective in these simulations is to predict the onset of thermal equilibrium of the calorimeter with its environment. Two types of boundary conditions at the outer surface of the orthotropic layer are used to predict thermal equilibrium. The procedure developed to carry out these simulations can be used as a guideline for the design of calorimeters. Another important application of these solutions is on the estimation of thermophysical properties of orthotropic cylinders. The thermal conductivities in the vertical, radial and circumferential directions of the orthotropic outer layer can be estimated using this exact solution and experimental data. Simultaneous estimation of the volumetric heat capacity and thermal conductivities is also possible. Furthermore, this solution has potential applications to the solution of the inverse heat conduction problem in this cylindrical geometry. An interesting feature of the construction of this solution is that two different sets of eigenfunctions need to be considered in the eigenfunction expansion. These eigenfunctions sets depend on the relative values of the thermal diffusivity of the inner cylinder and the thermal diffusivity in the vertical direction of the outer cylindrical layer.

  1. A flexible strain sensor based on a Conductive Polymer Composite for in situ measurement of parachute canopy deformation.

    PubMed

    Cochrane, Cédric; Lewandowski, Maryline; Koncar, Vladan

    2010-01-01

    A sensor based on a Conductive Polymer Composite (CPC), fully compatible with a textile substrate and its general properties, has been developed in our laboratory, and its electromechanical characterization is presented herein. In particular the effects of strain rate (from 10 to 1,000 mm/min) and of repeated elongation cycles on the sensor behaviour are investigated. The results show that strain rate seems to have little influence on sensor response. When submitted to repeated tensile cycles, the CPC sensor is able to detect accurately fabric deformations over each whole cycle, taking into account the mechanical behaviour of the textile substrate. Complementary information is given concerning the non-effect of aging on the global resistivity of the CPC sensor. Finally, our sensor was tested on a parachute canopy during a real drop test: the canopy fabric deformation during the critical inflation phase was successfully measured, and was found to be less than 9%. PMID:22163654

  2. Incorporation of cobalt-ferrite nanoparticles into a conducting polymer in aqueous micellar medium: strategy to get photocatalytic composites.

    PubMed

    Endrődi, Balázs; Hursán, Dorottya; Petrilla, Liliána; Bencsik, Gábor; Visy, Csaba; Chams, Amani; Maslah, Nabiha; Perruchot, Christian; Jouini, Mohamed

    2014-01-01

    In this study an easy strategy for conducting polymer based nanocomposite formation is presented through the deposition of cobalt-ferrite (CoFe(2)O(4)) containing poly(3,4-ethylenedioxythiophene) (PEDOT) thin layers. The electrochemical polymerization has been performed galvanostatically in an aqueous micellar medium in the presence of the nanoparticles and the surface active Triton X-100. The nanoparticles have been characterized by Transmission electron microscopy (TEM), the thin layers has been studied by applying Scanning electron microscopy (SEM), and X-ray diffraction (XRD), and the basic electrochemical properties have been also determined. Moreover, electrocatalytic activity of the composite was demonstrated in the electrooxidation reaction of dopamine (DA). The enhanced sensitivity - related to the cobalt-ferrite content - and the experienced photocatalyitic activity are promising for future application. PMID:25125121

  3. Implementation of a Thick-Film Composite Li-Ion Microcathode Using Carbon Nanotubes as the Conductive Filler

    NASA Technical Reports Server (NTRS)

    Lin, Qian; Harb, John N.

    2004-01-01

    This paper describes the development of a thick-film microcathode for use in Li-ion microbatteries in order to provide increased power and energy per area. These cathodes take advantage of a composite porous electrode structure, utilizing carbon nanotubes (CNT) as the conductive filler. The use of carbon nanotubes was found to significantly reduce the measured resistance of the electrodes, increase active material accessibility, and improve electrode performance. In particular, the cycling and power performance of the thick-film cathodes was significantly improved, and the need for compression was eliminated. Cathode thickness and CNT content were optimized to maximize capacity and power performance. Power capability of >50 mW/sq cm (17 mA/sq cm) with discharge capacity of >0.17 mAh/sq cm was demonstrated. The feasibility of fabricating thick-film microcathodes capable of providing the power and capacity needed for use in autonomous microsensor systems was also demonstrated.

  4. A Flexible Strain Sensor Based on a Conductive Polymer Composite for in situ Measurement of Parachute Canopy Deformation

    PubMed Central

    Cochrane, Cédric; Lewandowski, Maryline; Koncar, Vladan

    2010-01-01

    A sensor based on a Conductive Polymer Composite (CPC), fully compatible with a textile substrate and its general properties, has been developed in our laboratory, and its electromechanical characterization is presented herein. In particular the effects of strain rate (from 10 to 1,000 mm/min) and of repeated elongation cycles on the sensor behaviour are investigated. The results show that strain rate seems to have little influence on sensor response. When submitted to repeated tensile cycles, the CPC sensor is able to detect accurately fabric deformations over each whole cycle, taking into account the mechanical behaviour of the textile substrate. Complementary information is given concerning the non-effect of aging on the global resistivity of the CPC sensor. Finally, our sensor was tested on a parachute canopy during a real drop test: the canopy fabric deformation during the critical inflation phase was successfully measured, and was found to be less than 9%. PMID:22163654

  5. Prediction of body composition by total body electrical conductivity technique is affected by fat reserves of Japanese quail.

    PubMed

    Hyánková, L; Szebestová, Z

    2010-11-01

    The effect of fat accumulation on the prediction of in vivo body composition by a total body electrical conductivity (TOBEC) technique was evaluated using Japanese quail at 2 life periods (0 to 21 d and 28 to 70 d of age) that differ significantly in the fatness of birds. In total, 119 quail of 14 age categories were weighed and scanned by the TOBEC analyzer, and their carcasses were subjected to chemical analysis. The prediction equations for chemical composition (percentage of water, lipids, and lean tissue) and body masses (weight of body, water, lipids, and lean tissue) were obtained by linear regression analysis. The equations involved the E-value as the independent variable. In both growth phases, a high accuracy of estimation was found for the total body, lean, and water masses (0.85 ≤ R(2) ≤ 0.98), whereas a low accuracy of estimation was observed for percentages of lipids, lean tissue, and water (0.27 ≤ R(2) ≤ 0.64). Most of the variables showed a worse estimation in the late than in the early growth phase; the maximum difference was observed for the lipid mass (R(2) = 0.35 vs. 0.90, respectively). The correlations between analyzed variables and the residual error distributions of regression models demonstrated that the lower power of the models in the late versus early growth phase may be attributed to an enhanced fat accumulation in sexually mature birds. Their high fat reserves considerably decrease body hydration, which negatively influences the estimation of body composition based upon the TOBEC procedure. PMID:20952716

  6. Transparent conducting ITAZO anode films grown by a composite target RF magnetron sputtering at room temperature for organic solar cells

    NASA Astrophysics Data System (ADS)

    Sun, Nanhai; Fang, Guojia; Zheng, Qiao; Wang, Mingjun; Liu, Nishuang; Liu, Wei; Zhao, Xingzhong

    2009-08-01

    The preparation and characteristics of AZO co-sputtered ITO (ITAZO) electrodes grown on glass and flexible substrates using a specially designed composite target in organic solar cells are described. It was found that both the electrical and optical properties of the ITAZO films were critically dependent on the Ar/O2 flow ratio and sputtering power. In addition, all ITAZO electrodes show the amorphous structure due to the low substrate temperature. Even though the ITAZO electrode was prepared at room temperature, we can obtain the ITAZO electrode with the sheet resistance of 23 Ω/square (on a glass substrate) and 26 Ω/square (on a flexible substrate) and the average optical transmittance of 87.5% (on a glass substrate) and 86.3% (on a flexible substrate) in the region between 450 and 800 nm wavelength. In addition, the Ar ion treatment of the polyethylene terephthalate (PET) substrate could remove surface contamination and increase the adherence of the ITAZO film with the PET substrate. Furthermore, organic solar cells prepared on the ITAZO electrode under optimized conditions show the typical current density-voltage characteristics with the conversion power efficiency of 3.2%. This indicates that the composite target sputtering technique is a promising sputtering process for transparent conducting electrodes for low-cost solar cell applications.

  7. Synthesis of highly conductive cotton fiber/nanostructured silver/polyaniline composite membranes for water sterilization application

    NASA Astrophysics Data System (ADS)

    Abu-Thabit, Nedal Y.; Basheer, Rafil A.

    2014-09-01

    Electrically conductive composite membranes (ECCMs) composed of cotton fibers, conductive polyaniline and silver nanostructures were prepared and utilized as electrifying filter membranes for water sterilization. Silver metal and polyaniline were formed in situ during the oxidative polymerization of aniline monomers in the presence of silver nitrate as weak oxidizing agent. The reaction was characterized by long induction period and the morphology of the obtained ECCMs contained silver nanoparticles and silver flakes of 500-1000 nm size giving a membrane electrical resistance in the range of 10-30 Ohm sq-1. However, when dimethylformamide (DMF) was employed as an auxiliary reducing agent to trigger and speed up the polymerization reaction, silver nanostructures such as wires, ribbons, plates were formed and were found to be embedded between polyaniline coating and cotton fibers. These ECCMs exhibited a slightly lower resistance in the range of 2-10 Ohm sq.-1 and, therefore, were utilized for the fabrication of a bacteria inactivation device. When water samples containing 107-108 CFU mL-1 E. coli bacteria were passed through the prepared ECCMs by gravity force, with a filtration rate of 0.8 L h-1 and at an electric potential of 20 V, the fabricated device showed 92% bacterial inactivation efficiency. When the treated solution was passed through the membrane for a second time under the same conditions, no E. coli bacteria was detected.

  8. Dielectric relaxations and conduction mechanisms in polyether-clay composite polymer electrolytes under high carbon dioxide pressure.

    PubMed

    Kitajima, Shunsuke; Bertasi, Federico; Vezzù, Keti; Negro, Enrico; Tominaga, Yoichi; Di Noto, Vito

    2013-10-21

    The composite material P(EO/EM)-Sa consisting of synthetic saponite (Sa) dispersed in poly[ethylene oxide-co-2-(2-methoxyethoxy)ethyl glycidyl ether] (P(EO/EM)) is studied by "in situ" measurements using broadband electrical spectroscopy (BES) under pressurized CO2 to characterize the dynamic behavior of conductivity and the dielectric relaxations of the ion host polymer matrix. It is revealed that there are three dielectric relaxation processes associated with: (I) the dipolar motions in the short oxyethylene side chains of P(EO/EM) (β); and (II) the segmental motion of the main chains comprising the polyether components (αfast, αslow). αslow is attributed to the slow α-relaxation of P(EO/EM) macromolecules, which is hindered by the strong coordination interactions with the ions. Two conduction processes are observed, σDC and σID, which are attributed, respectively, to the bulk conductivity and the interdomain conductivity. The temperature dependence of conductivity and relaxation processes reveals that αfast and αslow are strongly correlated with σDC and σID. The "in situ" BES measurements under pressurized CO2 indicate a fast decrease in σDC at the initial CO2 treatment time resulting from the decrease in the concentration of polyether-M(n+) complexes, which is driven by the CO2 permeation. The relaxation frequency (fR) of αslow at the initial CO2 treatment time increases and shows a steep rise with time with the same behavior of the αfast mode. It is demonstrated that the interactions between polyether chains of P(EO/EM) and cations in the polymer electrolyte layers embedded in Sa are probably weakened by the low permittivity of CO2 (ε = 1.08). Thus, the formation of ion pairs in the polymer electrolyte domains of P(EO/EM)-Sa occurs, with a corresponding reduction in the concentration of ion carriers. PMID:23963202

  9. FEM (finite element method) thermal modeling and thermal hydraulic performance of an enhanced thermal conductivity UO2/BeO composite fuel

    SciTech Connect

    Zhou, Wenzhong

    2011-03-24

    An enhanced thermal conductivity UO2-BeO composite nuclear fuel was studied. A methodology to generate ANSYS (an engineering simulation software) FEM (Finite Element Method) thermal models of enhanced thermal conductivity oxide nuclear fuels was developed. The results showed significant increase in the fuel thermal conductivities and have good agreement with the measured ones. The reactor performance analysis showed that the decrease in centerline temperature was 250-350K for the UO2-BeO composite fuel, and thus we can improve nuclear reactors' performance and safety, and high-level radioactive waste generation.

  10. The use of polyimide-modified aluminum nitride fillers in AlN@PI/Epoxy composites with enhanced thermal conductivity for electronic encapsulation

    PubMed Central

    Zhou, Yongcun; Yao, Yagang; Chen, Chia-Yun; Moon, Kyoungsik; Wang, Hong; Wong, Ching-ping

    2014-01-01

    Polymer modified fillers in composites has attracted the attention of numerous researchers. These fillers are composed of core-shell structures that exhibit enhanced physical and chemical properties that are associated with shell surface control and encapsulated core materials. In this study, we have described an apt method to prepare polyimide (PI)-modified aluminum nitride (AlN) fillers, AlN@PI. These fillers are used for electronic encapsulation in high performance polymer composites. Compared with that of untreated AlN composite, these AlN@PI/epoxy composites exhibit better thermal and dielectric properties. At 40 wt% of filler loading, the highest thermal conductivity of AlN@PI/epoxy composite reached 2.03 W/mK. In this way, the thermal conductivity is approximately enhanced by 10.6 times than that of the used epoxy matrix. The experimental results exhibiting the thermal conductivity of AlN@PI/epoxy composites were in good agreement with the values calculated from the parallel conduction model. This research work describes an effective pathway that modifies the surface of fillers with polymer coating. Furthermore, this novel technique improves the thermal and dielectric properties of fillers and these can be used extensively for electronic packaging applications. PMID:24759082

  11. The use of polyimide-modified aluminum nitride fillers in AlN@PI/epoxy composites with enhanced thermal conductivity for electronic encapsulation.

    PubMed

    Zhou, Yongcun; Yao, Yagang; Chen, Chia-Yun; Moon, Kyoungsik; Wang, Hong; Wong, Ching-Ping

    2014-01-01

    Polymer modified fillers in composites has attracted the attention of numerous researchers. These fillers are composed of core-shell structures that exhibit enhanced physical and chemical properties that are associated with shell surface control and encapsulated core materials. In this study, we have described an apt method to prepare polyimide (PI)-modified aluminum nitride (AlN) fillers, AlN@PI. These fillers are used for electronic encapsulation in high performance polymer composites. Compared with that of untreated AlN composite, these AlN@PI/epoxy composites exhibit better thermal and dielectric properties. At 40 wt% of filler loading, the highest thermal conductivity of AlN@PI/epoxy composite reached 2.03 W/mK. In this way, the thermal conductivity is approximately enhanced by 10.6 times than that of the used epoxy matrix. The experimental results exhibiting the thermal conductivity of AlN@PI/epoxy composites were in good agreement with the values calculated from the parallel conduction model. This research work describes an effective pathway that modifies the surface of fillers with polymer coating. Furthermore, this novel technique improves the thermal and dielectric properties of fillers and these can be used extensively for electronic packaging applications. PMID:24759082

  12. Mössbauer and electrical conduction investigations of LiFe(BaTi)(PO4) NASICON nano composite

    NASA Astrophysics Data System (ADS)

    Hassaan, M. Y.; Kaixin, Zhu; Wang, Junhu; Moustafa, M. G.

    2016-12-01

    NASICON glass sample with a composition of Li 1.3Fe 0.3(BaTi) 1.7(PO 4) 3 was prepared using the conventional melt-quenching technique at 1300 ∘C for one hour after two stages of calcination process at 300 ∘C and 600 ∘C respectively. DTA was used to determine (T g) and (T c) of the as-quenched glass sample. XRD was used to confirm the glassy state of the prepared sample. The as-quenched glass sample was heat treated near its onset crystallization temperature for different times 1, 2, 3, 4, and 5 hours. The gradual precipitation of the crystalline nano-particles with NASICON type structure was also confirmed using XRD. The as-prepared sample and the five heat treated (HT) samples were investigated using Mössbauer spectroscopy, DC and AC conductivities and dielectric permittivity. FTIR, density, and TEM measurements were also performed. After HT, XRD and FTIR measurements conformed the formation of NASICON phase. The results of the dielectric permittivity showed no maximum peak in the studied temperature and frequency ranges, which indicates the absence of ferroelectric behavior of the HT glass sample. Mössbauer data showed that the iron in the glass and its HT samples include two ionic states, Fe 3+ (O h) and Fe 2+ (O h) ions. It is observed that the DC conductivity of the HT glass for 5 h was almost two orders of magnitude higher than that of the parent glass.

  13. Conformal Pad-Printing Electrically Conductive Composites onto Thermoplastic Hemispheres: Toward Sustainable Fabrication of 3-Cents Volumetric Electrically Small Antennas.

    PubMed

    Wu, Haoyi; Chiang, Sum Wai; Yang, Cheng; Lin, Ziyin; Liu, Jingping; Moon, Kyoung-Sik; Kang, Feiyu; Li, Bo; Wong, Ching Ping

    2015-01-01

    Electrically small antennas (ESAs) are becoming one of the key components in the compact wireless devices for telecommunications, defence, and aerospace systems, especially for the spherical one whose geometric layout is more closely approaching Chu's limit, thus yielding significant bandwidth improvements relative to the linear and planar counterparts. Yet broad applications of the volumetric ESAs are still hindered since the low cost fabrication has remained a tremendous challenge. Here we report a state-of-the-art technology to transfer electrically conductive composites (ECCs) from a planar mould to a volumetric thermoplastic substrate by using pad-printing technology without pattern distortion, benefit from the excellent properties of the ECCs as well as the printing-calibration method that we developed. The antenna samples prepared in this way meet the stringent requirement of an ESA (ka is as low as 0.32 and the antenna efficiency is as high as 57%), suggesting that volumetric electronic components i.e. the antennas can be produced in such a simple, green, and cost-effective way. This work can be of interest for the development of studies on green and high performance wireless communication devices. PMID:26317999

  14. Conformal Pad-Printing Electrically Conductive Composites onto Thermoplastic Hemispheres: Toward Sustainable Fabrication of 3-Cents Volumetric Electrically Small Antennas

    PubMed Central

    Wu, Haoyi; Chiang, Sum Wai; Yang, Cheng; Lin, Ziyin; Liu, Jingping; Moon, Kyoung-Sik; Kang, Feiyu; Li, Bo; Wong, Ching Ping

    2015-01-01

    Electrically small antennas (ESAs) are becoming one of the key components in the compact wireless devices for telecommunications, defence, and aerospace systems, especially for the spherical one whose geometric layout is more closely approaching Chu’s limit, thus yielding significant bandwidth improvements relative to the linear and planar counterparts. Yet broad applications of the volumetric ESAs are still hindered since the low cost fabrication has remained a tremendous challenge. Here we report a state-of-the-art technology to transfer electrically conductive composites (ECCs) from a planar mould to a volumetric thermoplastic substrate by using pad-printing technology without pattern distortion, benefit from the excellent properties of the ECCs as well as the printing-calibration method that we developed. The antenna samples prepared in this way meet the stringent requirement of an ESA (ka is as low as 0.32 and the antenna efficiency is as high as 57%), suggesting that volumetric electronic components i.e. the antennas can be produced in such a simple, green, and cost-effective way. This work can be of interest for the development of studies on green and high performance wireless communication devices. PMID:26317999

  15. Impacts of pore- and petro-fabrics, mineral composition and diagenetic history on the bulk thermal conductivity of sandstones

    NASA Astrophysics Data System (ADS)

    Nabawy, Bassem S.; Géraud, Yves

    2016-03-01

    The present study aims to model the bulk thermal fabric of the highly porous (26.5 ≤ øHe ≤ 39.0%) siliceous Nubia sandstones in south Egypt, as well as their pore- and petro-anisotropy. The thermal fabric concept is used in the present study to describe the magnitude and direction of the thermal foliation 'F', lineation 'L' and anisotropy 'λ'. Cementation, pressure solution, compaction and the authigenic clay content are the main pore volume-controlling factors, whereas the cement dissolution and fracturing are the most important porosity-enhancing factors. The bulk thermal fabric of the Nubia sandstone is raised mostly from the contribution of the mineral composition and the pore volume. The kaolinite content and pore volume are the main reducing factors for the measured bulk thermal conductivity 'k', whereas the quartz content is the most important enhancing factors. The optical scanning technique, which is one of the most accurate and precise techniques, was applied for measuring the bulk thermal conductivity 'k' of the studied samples. For the dry state, the average thermal condutivity 'kav' in the NE-SW, NW-SE and vertical directions, varies from 1.53 to 2.40, 1.54 to 2.36 and from 1.31 to 2.20 W/(mK), respectively. On other hand, 'kav' for the saline water-saturated state for the NE-SW, NW-SE and vertical directions varies between 2.94 & 4.42, 2.90 & 4.31 and between 2.39 & 3.65 W/(mK), respectively. The present thermal pore fabric is slightly anisotropic, 'λ' varies from 1.10 to 1.41, refers mostly to the NW-SE direction (kmax direction, elongation direction), whereas the petro-fabric refers to NE-SW direction (kmax direction, elongation direction). This gives rise to a conclusion that the pore- and petro-fabrics have two different origins. Therefore, studying the thermal conductivity of the Nubia sandstone in 3-D indicates a pore fabric elongation fluctuating around the N-S direction.

  16. Ionic conductivity and the formation of cubic CaH{sub 2} in the LiBH{sub 4}–Ca(BH{sub 4}){sub 2} composite

    SciTech Connect

    Sveinbjörnsson, Dadi; Blanchard, Didier; Myrdal, Jon Steinar Gardarsson; Younesi, Reza; Viskinde, Rasmus; Riktor, Marit Dalseth; Norby, Poul; Vegge, Tejs

    2014-03-15

    LiBH{sub 4}–Ca(BH{sub 4}){sub 2} composites were prepared by ball milling. Their crystal structures and phase composition were investigated using synchrotron X-ray diffraction and Rietveld refinement, and their ionic conductivity was measured using impedance spectroscopy. The materials were found to form a physical mixture. The composites were composed of α-Ca(BH{sub 4}){sub 2}, γ-Ca(BH{sub 4}){sub 2} and orthorhombic LiBH{sub 4}, and the relative phase quantities of the Ca(BH{sub 4}){sub 2} polymorphs varied significantly with LiBH{sub 4} content. The formation of small amounts of orthorhombic CaH{sub 2} and cubic CaH{sub 2} in a CaF{sub 2}-like structure was observed upon heat treatment. Concurrent formation of elemental boron may also occur. The ionic conductivity of the composites was measured using impedance spectroscopy, and was found to be lower than that of ball milled LiBH{sub 4}. Electronic band structure calculations indicate that cubic CaH{sub 2} with hydrogen defects is electronically conducting. Its formation along with the possible precipitation of boron therefore has an effect on the measured conductivity of the LiBH{sub 4}–Ca(BH{sub 4}){sub 2} composites and may increase the risk of an internal short-circuit in the cells. -- Graphical abstract: An Arrhenius plot of the ionic conductivity of the LiBH{sub 4}–Ca(BH{sub 4}){sub 2} composites (red, blue, green). The ionic conductivity of ball milled (gray) and non-milled (black) LiBH{sub 4} is shown for comparison. The filled symbols are measured during heating runs and the empty symbols are measured during subsequent cooling runs. The conductivity of the composites is in all cases higher during cooling, most probably due to the formation of an electronically conducting layer containing defect-rich cubic CaH{sub 2}. Such layer formation could eventually lead to a short circuit in the cell and reveals a general issue of chemical stability that should be attended to in the development of solid

  17. Electrodeposition of chitosan/gelatin/nanosilver: A new method for constructing biopolymer/nanoparticle composite films with conductivity and antibacterial activity.

    PubMed

    Wang, Yifeng; Guo, Xuecheng; Pan, Ruihao; Han, Di; Chen, Tao; Geng, Zenghua; Xiong, Yanfei; Chen, Yanjun

    2015-08-01

    Electrodeposition of chitosan provides a controllable means to simultaneously assemble biological materials and nanoparticles for various applications. Here, we present a new method to construct biopolymer/nanoparticle composite films with conductivity and antibacterial activity by electrodeposition of chitosan/gelatin/nanosilver. Besides, this method can be employed to build biopolymer/nanoparticle composite hydrogels or coatings on various electrodes or conductive substrates. We initially use a simple approach to prepare the aqueous nanosilver that can be well-dispersed in water. Then, the codeposition mixture containing chitosan, gelatin and nanosilver is prepared, and it can be electrodeposited onto different electrodes or conductive substrates in response to imposed electrical signals. After electrodeposition, it is found that the deposited hydrogels and their dried films are smooth and homogeneous due to the elimination of H2 bubbles by addition of H2O2 in electrodeposition process. Importantly, the composite films are strong enough to completely and readily peel from the electrodes after they reacted with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC), which can build a type of biopolymer/nanoparticle film for further applications. Furthermore, the electrodeposition technique is able to offer controllable and convenient method to construct the composite films with diverse shapes. The composite films display improved conductivity and in vitro antibacterial activity against Escherichia coli and Staphylococcus aureus, which may provide attractive applications in biomedical fields such as artificial muscles, skin biomaterials and neuroprosthetic implants. PMID:26042710

  18. Methane oxidation over mixed-conducting SrFe(Al)O3-delta-SrAl2O4 composite.

    PubMed

    Yaremchenko, A A; Kharton, V V; Valente, A A; Veniaminov, S A; Belyaev, V D; Sobyanin, V A; Marques, F M B

    2007-06-01

    The steady-state CH4 conversion by oxygen permeating through mixed-conducting (SrFe)0.7(SrAl2)0.3Oz composite membranes, comprising strontium-deficient SrFe(Al)O3-delta perovskite and monoclinic SrAl2O4-based phases, occurs via different mechanisms in comparison to the dry methane interaction with the lattice oxygen. The catalytic behavior of powdered (SrFe)0.7(SrAl2)0.3Oz, studied by temperature-programmed reduction in dry CH4 at 523-1073 K, is governed by the level of oxygen nonstoichiometry in the crystal lattice of the perovskite component and is qualitatively similar to that of other perovskite-related ferrites, such as Sr0.7La0.3Fe0.8Al0.2O3-delta. While extensive oxygen release from the ferrite lattice at 700-900 K leads to predominant total oxidation of methane, significant selectivity to synthesis gas formation, with H2/CO ratios close to 2, is observed above 1000 K, when a critical value of oxygen deficiency is achieved. The steady-state oxidation over dense membranes at 1123-1223 K results, however, in prevailing total combustion, particularly due to excessive oxygen chemical potential at the membrane surface. In combination with surface-limited oxygen permeability, mass transport limitations in a porous layer at the membrane permeate side prevent reduction and enable stable operation of (SrFe)0.7(SrAl2)0.3Oz membranes under air/methane gradient. Taking into account the catalytic activity of SrFeO3-delta-based phases for the partial oxidation of methane to synthesis gas and the important role of mass transport-related effects, one promising approach for membrane development is the fabrication of thick layer of porous ferrite-based catalyst at the surface of dense (SrFe)0.7(SrAl2)0.3Oz composite. PMID:17627318

  19. The ionic transport mechanism and coupling between the ion conduction and segmental relaxation processes of PEO20-LiCF3SO3 based ion conducting polymer clay composites.

    PubMed

    Dam, Tapabrata; Jena, Sidhartha S; Pradhan, Dillip K

    2016-07-20

    A series of ion conducting polymer-clay composites has been prepared using a solution casting technique. Relaxation dynamics and the ionic transport mechanism are systematically studied employing broadband dielectric spectroscopy over a wide frequency and temperature range. Among different phenomenological and theoretical models for ion conduction in disordered ionic conductors, conductivity isotherm spectra are analysed using the modified Almond-West and random free energy barrier model. Conductivity scaling suggests that the ionic transport mechanism is independent of temperature, and a similar inference is also obtained using scaled electrical modulus spectra. DC conductivity along with conductivity and segmental relaxation time following the Vogel-Tammann-Fulcher relationship suggests coupling between the ionic transport and segmental relaxation processes. Electrical modulus and dielectric formalism are used to understand the conductivity and segmental relaxation processes, respectively. The presence of first and second universality in the ionic transport mechanism is discussed using the real part of conductivity spectra and dielectric loss spectra. The crossover between the first and second universality is explained using the Kramer-Krönig approach. The ion diffusion coefficient is investigated using Ratner's classical approach in combination with the modified Stokes-Einstein relationship to correlate the coupled nature of the ion conduction mechanism and polymer segmental motion. PMID:27399598

  20. Computer Simulation of Spatial Arrangement and Connectivity of Particles in Three-Dimensional Microstructure: Application to Model Electrical Conductivity of Polymer Matrix Composite

    NASA Technical Reports Server (NTRS)

    Louis, P.; Gokhale, A. M.

    1996-01-01

    Computer simulation is a powerful tool for analyzing the geometry of three-dimensional microstructure. A computer simulation model is developed to represent the three-dimensional microstructure of a two-phase particulate composite where particles may be in contact with one another but do not overlap significantly. The model is used to quantify the "connectedness" of the particulate phase of a polymer matrix composite containing hollow carbon particles in a dielectric polymer resin matrix. The simulations are utilized to estimate the morphological percolation volume fraction for electrical conduction, and the effective volume fraction of the particles that actually take part in the electrical conduction. The calculated values of the effective volume fraction are used as an input for a self-consistent physical model for electrical conductivity. The predicted values of electrical conductivity are in very good agreement with the corresponding experimental data on a series of specimens having different particulate volume fraction.

  1. Estimation of dc transport dynamics in strongly correlated (La,Pr,Ca)MnO{sub 3} film using an insulator-metal composite model for terahertz conductivity

    SciTech Connect

    Nguyen, T. V. A.; Hattori, A. N.; Nakamura, T.; Fujiwara, K.; Tanaka, H.; Nagai, M.; Ashida, M.

    2014-07-14

    Temperature-dependent conductivities at dc and terahertz (THz) frequency region (σ{sub THz}(ω,T)) were obtained for a strongly correlated (La{sub 0.275}Pr{sub 0.35}Ca{sub 0.375})MnO{sub 3} (LPCMO) film using THz time domain spectroscopy. A composite model that describes σ{sub THz}(ω,T) for LPCMO through the insulator-metal transition (IMT) was established by incorporating Austin-Mott model characterizing the hopping of localized electrons and Drude model explaining the behavior of free electrons. This model enables us to reliably investigate the dc transport dynamics from THz conductivity measurement, i.e., simultaneously evaluate the dc conductivity and the competing composition of metal and insulator phases through the IMT, reflecting the changes in microscopic conductivity of these phases.

  2. Latitudinal trends and temporal shifts in the catch composition of bottom trawls conducted on the eastern Bering Sea shelf

    NASA Astrophysics Data System (ADS)

    Stevenson, Duane E.; Lauth, Robert R.

    2012-06-01

    Latitudinal species diversity gradients are well known in both terrestrial and aquatic ecosystems throughout the world. However, trends in relative abundance and other shifts in community structure with latitude, which can be more sensitive to environmental shifts such as climate change, have received less attention. Here we investigate latitudinal trends in the seafloor community of the eastern Bering Sea using catches of fishes and epibenthic invertebrates in bottom trawl surveys conducted from 1982 to 2010. Our results indicate that the overall biomass of the epibenthic community declines with increasing latitude in the eastern Bering Sea. This latitudinal trend is primarily driven by declining fish catches in the northern Bering Sea, which in turn reflects changes in the structure of the fish community. The fish fauna in northern latitudes is increasingly dominated by gadids, though the species composition of the gadid fauna also changes with latitude, with smaller species becoming more common in the north. The biomass of the invertebrate megafauna remains relatively consistent throughout the eastern Bering Sea, but invertebrates make up a larger proportion of the catch in bottom trawls conducted at higher latitudes. The epibenthic invertebrate megafauna in the eastern Bering Sea is composed primarily of sea stars (Asteriidae) and oregoniid crabs (Chionoecetes and Hyas), though no clear latitudinal trends in the invertebrate community are evident. Limited trawl data from the eastern Chukchi Sea indicate that the fish community farther north is even more heavily dominated by gadids, and the epibenthic invertebrate community is dominated by asteriid sea stars. Temperature data from bottom trawl surveys in the southeastern Bering Sea over the past decade indicate that there was a distinct temperature shift around 2005, and the relatively warm years of 2001-2005 were followed by five relatively cold years. This shift in the summer temperature regime of the Bering

  3. Three-dimensional porous stretchable and conductive polymer composites based on graphene networks grown by chemical vapour deposition and PEDOT:PSS coating.

    PubMed

    Chen, Mengting; Duan, Shasha; Zhang, Ling; Wang, Zhihui; Li, Chunzhong

    2015-02-21

    We have manufactured a highly conductive and stretchable composite by backfilling the 3D graphene-PEDOT:PSS skeleton with poly(dimethylsiloxane) (PDMS). The electrical conductivity of our product can reach 24 S cm(-1) with only 1.5 wt% graphene and 1.5 wt% PEDOT:PSS loading, and its resistance increased only 35% when stretched to 80% strain. PMID:25605259

  4. The influence of SiC particle size and volume fraction on the thermal conductivity of spark plasma sintered UO2-SiC composites

    NASA Astrophysics Data System (ADS)

    Yeo, Sunghwan; Baney, Ronald; Subhash, Ghatu; Tulenko, James

    2013-11-01

    This study examines the influence of Silicon Carbide (SiC) particle addition on thermal conductivity of UO2-SiC composite pellets. UO2 powder and β-SiC particles of different sizes and of different volume fractions were mechanically mixed and sintered at 1350-1450 °C for 5 min by Spark Plasma Sintering (SPS). The particle size (0.6-55 μm diameter) and volume fraction (5-20%) of SiC were systematically varied to investigate their influence on the resulting UO2-SiC composite pellet microstructure and the thermal properties. It was found that SiC particle size less than 16.9 μm with larger volume fraction is more effective for improving the thermal conductivity of the fuel pellets. Scanning Electron Microscopy examination revealed micro-cracking and interfacial debonding in the composites containing larger size SiC particles (16.9 and 55 μm) which resulted in reduced thermal conductivity. For the UO2-SiC composite pellets containing 1 μm diameter SiC particles, the thermal conductivity increased almost linearly with volume fraction of particles. However, the addition of a larger volume fraction of SiC reduces the amount of heavy metal in the composite pellet and therefore a higher U-235 enrichment is necessary to compensate for the heavy metal loss. The experimental thermal conductivity values of the UO2-SiC composite pellets are in good agreement with the theoretical values based on the available model in the literature.

  5. Environmental effects on composite airframes: A study conducted for the ARM UAV Program (Atmospheric Radiation Measurement Unmanned Aerospace Vehicle)

    SciTech Connect

    Noguchi, R.A.

    1994-06-01

    Composite materials are affected by environments differently than conventional airframe structural materials are. This study identifies the environmental conditions which the composite-airframe ARM UAV may encounter, and discusses the potential degradation processes composite materials may undergo when subjected to those environments. This information is intended to be useful in a follow-on program to develop equipment and procedures to prevent, detect, or otherwise mitigate significant degradation with the ultimate goal of preventing catastrophic aircraft failure.

  6. Solid state {sup 31}P MAS NMR spectroscopy and conductivity measurements on NbOPO{sub 4} and H{sub 3}PO{sub 4} composite materials

    SciTech Connect

    Risskov Sørensen, Daniel; Nielsen, Ulla Gro; Skou, Eivind M.

    2014-11-15

    A systematic study of composite powders of niobium oxide phosphate (NbOPO{sub 4}) and phosphoric acid (H{sub 3}PO{sub 4}) has been performed in order to characterize the material's ability to perform as an electrolyte material in medium temperature fuel cells and electrolyzers. Powders of H{sub 3}PO{sub 4} contents between 13.1 and 74.2 M% were produced and characterized with powder X-ray diffraction, {sup 31}P MAS NMR and impedance spectroscopy. NMR revealed that a significant degree of dehydration and vaporization of H{sub 3}PO{sub 4} takes place above 200 °C, and increases with temperature. At 500 °C the NbOPO{sub 4} and H{sub 3}PO{sub 4} has reacted to form niobium pyrophosphate (Nb{sub 2}P{sub 4}O{sub 15}). Impedance spectroscopy showed an increase in conductivity with increasing acid concentration, whereas the conductivity decreased slightly with increasing temperature. The highest conductivity measured was 2.5·10{sup −3} S/cm for a sample containing 74.2 M% of H{sub 3}PO{sub 4}. Lastly, it was shown that NbOPO{sub 4} has no significant conductivity of its own. - Graphical abstract: Conductivity of NbOPO{sub 4}/H{sub 3}PO{sub 4} composites as a function of equivalent P{sub 2}O{sub 5} content. The conductivity is insignificant for pure NbOPO{sub 4}. - Highlights: • Composites have been made from NbOPO{sub 4} and H{sub 3}PO{sub 4}. • The composites composition has been investigated with solid state NMR. • The composites have shown clear signs of acid dehydration upon heating. • The conductivity of the composites increases for increasing acid content. • NbOPO{sub 4} has no significant conductivity of its own.

  7. High conductivity composite flip-chip joints and silver-indium bonding to bismuth telluride for high temperature applications

    NASA Astrophysics Data System (ADS)

    Lin, Wen P.

    Two projects are reported. First, the barrier layer and silver (Ag)-indium (In) transient liquid phase (TLP) bonding for thermoelectric (TE) modules at high temperature were studied, and followed with a survey of Ag microstructure and grain growth kinetics. Second, the high electrical conductivity joint materials bonded by both Ag-AgIn TLP and solid-state bonding processes for small size flip-chip applications were designed. In the first project, barrier and Ag-In TLP bonding layer for TE module at high temperature application were studied. Bismuth telluride (Bi2 Te3) and its alloys are used as materials for a TE module. A barrier/bonding composite was developed to satisfy the TE module for high temperature operation. Titanium (Ti)/ gold (Au) was chosen as the barrier layers and an Ag-rich Ag-In joint was chosen as the bonding layer. An electron-beam evaporated Ti layer was selected as the barrier layer. An Ag-In fluxless TLP bonding process was developed to bond the Bi 2Te3 chips to the alumina substrates for high temperature applications. To prepare for bonding, the Bi2Te3 chips were coated with a Ti/Au barrier layer followed by a Ag layer. The alumina substrates with titanium-tungsten (TiW)/Au were then electroplated with the Ag/In/Ag structure. These Bi2Te3 chips were bonded to alumina substrates at a bonding temperature of 180ºC with a static pressure as low as 100psi. The resulting void-free joint consists of five regions: Ag, (Ag), Ag2In, (Ag), and Ag, where (Ag) is Ag-rich solid solution with In atoms in it and Ag is pure Ag. This joint has a melting temperature higher than 660ºC, and it manages the coefficient of thermal expansion (CTE) mismatch between the Bi2Te3 and alumina substrate. The whole Ti/Au barrier layer and Ag-In bonding composite between Bi 2Te3 and alumina survived after an aging test at 250°C for 200 hours. The Ag-In joint transformed from Ag/(Ag)/Ag2In/(Ag)/Ag to a more reliable (Ag) rich layer after the aging test. Ag thin films were

  8. Study on ion conductivity and crystallinity of composite polymer electrolytes based on poly(ethylene oxide)/poly(acrylonitrile) containing nano-sized Al2O3 fillers.

    PubMed

    Kim, Mingyeong; Lee, Lyungyu; Jung, Yongju; Kim, Seok

    2013-12-01

    In this paper, composite polymer electrolytes were prepared by a blend of poly(ethylene oxide) (PEO) and poly(acrylonitrile) (PAN) as a polymer matrix, ethylene carbonate as a plasticizer, LiClO4 as a salt, and by containing a different content of nano-sized Al2O3. The composite films were prepared by using the solution casting method. The crystallinity and ionic conductivity of the polymer electrolytes was investigated using X-ray diffraction (XRD) and AC impedance method, respectively. The morphology of composite polymer electrolyte film was analyzed by SEM method. From the experimental results, by increasing the Al2O3 content, the crystallinity of PEO was reduced, and the ionic conductivity was increased. In particular, by a doping of 15 wt.% Al2O3 in PEO/PAN polymer blend, the CPEs showed the superior ionic conductivity. However, when Al2O3 content exceeds 15 wt.%, the ionic conductivity was decreased. From the surface morphology, it was concluded that the ionic conductivity was decreased because the CPEs showed a heterogenous morphology due to immiscibility or aggregation of the ceramic filler within the polymer matrix. PMID:24266154

  9. Effective thermal conductivity of metal and non-metal particulate composites with interfacial thermal resistance at high volume fraction of nano to macro-sized spheres

    SciTech Connect

    Faroughi, Salah Aldin; Huber, Christian

    2015-02-07

    In this study, we propose a theoretical model to compute the effective thermal conductivity of metal and dielectric spherical particle reinforced composites with interfacial thermal resistance. We consider a wide range of filler volume fraction with sizes ranging from nano- to macro-scale. The model, based on the differential effective medium theory, accounts for particle interactions through two sets of volume fraction corrections. The first correction accounts for a finite volume of composite and the second correction introduces a self-crowding factor that allows us to develop an accurate model for particle interaction even for high volume fraction of fillers. The model is examined to other published models, experiments, and numerical simulations for different types of composites. We observe an excellent agreement between the model and published datasets over a wide range of particle volume fractions and material properties of the composite constituents.

  10. The thermal conductivity of embedded nano-aluminum nitride-doped multi-walled carbon nanotubes in epoxy composites containing micro-aluminum nitride particles.

    PubMed

    Choi, Seran; Im, Hyungu; Kim, Jooheon

    2012-02-17

    Amino-functionalized nano-aluminum nitride (nano-AlN) particles were doped onto the surfaces of chlorinated multi-walled carbon nanotubes (MWCNTs) to act as fillers in thermally conducting composites. These synthesized materials were embedded in epoxy resin. Then, the untreated micro-aluminum nitride (micro-AlN) particles were added to this resin, whereby the composites filled with nano-AlN-doped MWCNTs (0, 0.5, 1, 1.5, 2 wt%) and micro-AlN (25.2, 44.1, 57.4 vol%) were fabricated. As a result, the thermal diffusivity and conductivity of all composites continuously improved with increasing nano-AlN-doped MWCNT content and micro-AlN filler loading. The thermal conductivity reached its maximum, which was 31.27 times that of the epoxy alone, when 2 wt% nano-AlN-doped MWCNTs and 57.4 vol% micro-AlN were added to the epoxy resin. This result is due to the high aspect ratio of the MWCNTs and the surface polarity of the doped nano-AlN and micro-AlN particles, resulting in the improved thermal properties of the epoxy composite. PMID:22248559

  11. The thermal conductivity of embedded nano-aluminum nitride-doped multi-walled carbon nanotubes in epoxy composites containing micro-aluminum nitride particles

    NASA Astrophysics Data System (ADS)

    Choi, Seran; Im, Hyungu; Kim, Jooheon

    2012-02-01

    Amino-functionalized nano-aluminum nitride (nano-AlN) particles were doped onto the surfaces of chlorinated multi-walled carbon nanotubes (MWCNTs) to act as fillers in thermally conducting composites. These synthesized materials were embedded in epoxy resin. Then, the untreated micro-aluminum nitride (micro-AlN) particles were added to this resin, whereby the composites filled with nano-AlN-doped MWCNTs (0, 0.5, 1, 1.5, 2 wt%) and micro-AlN (25.2, 44.1, 57.4 vol%) were fabricated. As a result, the thermal diffusivity and conductivity of all composites continuously improved with increasing nano-AlN-doped MWCNT content and micro-AlN filler loading. The thermal conductivity reached its maximum, which was 31.27 times that of the epoxy alone, when 2 wt% nano-AlN-doped MWCNTs and 57.4 vol% micro-AlN were added to the epoxy resin. This result is due to the high aspect ratio of the MWCNTs and the surface polarity of the doped nano-AlN and micro-AlN particles, resulting in the improved thermal properties of the epoxy composite.

  12. Improved wetting behavior and thermal conductivity of the three-dimensional nickel foam/epoxy composites with graphene oxide as interfacial modifier

    NASA Astrophysics Data System (ADS)

    Huang, Liang; Zhu, Pengli; Li, Gang; Sun, Rong

    2016-05-01

    The partial reduced graphene oxide (P-rGO) sheets-wrapped nickel foams (NF@P-rGO) were prepared by hydrothermal method, and then their epoxy composites were fabricated via a simple drop-wetting process. The P-rGO sheets on the metal networks could effectively improve the compatibility between nickel foam and epoxy resin, thus greatly accelerate the wetting of epoxy resin on the foams and avoid cracks in the network-polymer interface. Owing to the existence of high-efficiency conductive metal networks, the NF@P-rGO/epoxy composite has a high thermal conductivity of 0.584 W m-1 K-1, which is 2.6 times higher than that of neat epoxy resin. Additionally, owing to the improved wetting ability, NF@P-rGO-10 wt% boron nitride (BN) microsheets/epoxy composites could be fabricated and have a further higher thermal conductivity of 0.71 W m-1 K-1. We believe the use of P-rGO as a novel surface modifier and the following liquid polymer drop-wetting could be an effective method to obtain novel and outstanding metal foam/polymer composites.

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

    SciTech Connect

    Subhash, Ghatu; Wu, Kuang-Hsi; Tulenko, James

    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

  14. A Kinetics Study on Electrical Resistivity Transition of In Situ Polymer Aging Sensors Based on Carbon-Black-Filled Epoxy Conductive Polymeric Composites (CPCs)

    NASA Astrophysics Data System (ADS)

    Liang, Qizhen; Nyugen, Mark T.; Moon, Kyoung-Sik; Watkins, Ken; Morato, Lilian T.; Wong, Ching Ping

    2013-06-01

    Sensors based on carbon-black-filled bisphenol A-type epoxy conductive polymeric composites (CPCs) have been prepared and applied to monitor thermal oxidation aging of polymeric materials. Thermogravimetric analysis (TGA) is applied to characterize weight loss of epoxy resin in the aging process. By using a mathematical model based on the Boltzmann equation, a relationship between the electrical resistivity of the sensors based on epoxy/carbon black composites and aging time is established, making it possible to monitor and estimate the aging status of polymeric components in situ based on a fast and convenient electrical resistance measurement.

  15. Regeneration efficiency, shuttle heat loss and thermal conductivity in epoxy-composite annualr gap regenerators from 4K to 80K

    NASA Technical Reports Server (NTRS)

    Myrtle, K.; Cygax, S.; Plateel, C.; Winter, C.

    1983-01-01

    A test apparatus designed to simulate a section of a Stirling cycle cryocooler was built. Measurements of regeneration efficiency, shuttle heat loss and thermal conductivity reported for several regenerator test sections. The test composites were epoxy glass, epoxy glass with lead particles, epoxy glass with activated charcoal and epoxy graphite. Losses measured for these materials were approximately the same. Losses are in good agreement with those calculated theoretically for an epoxy glass (C-10) composite. The implications of these results on cryocooler design are discussed.

  16. Characterization and Development of BaZrO3 /NiO Composites for use as Anodes in Proton Conducting SOFCs

    NASA Astrophysics Data System (ADS)

    Khan, Islam; Dillon, Kelly; Camata, Renato; Genau, Amber

    2015-04-01

    Solid oxide fuel cells (SOFCs) are devices that convert chemical energy to electrical energy directly through oxidation of the fuel. The basic structure of SOFCs consists of three parts: an anode and a cathode that are separated by an electrolyte. The focus of this work is on developing and characterizing anode materials for proton-conducting SOFCs which use ceramic material BaZrO3 as the electrolyte. These anodes are made using a BaZrO3 -Ni composite, known as a cermet (ceramic and metal), which has shown potential as anode materials for these devices. The conventional method for making BaZrO3 -Ni cermets consist of an intermediate stage composite material BaZrO3 -NiO that have a strong influence on the final properties of the anode. Composites consisting of the two phases, BaZrO3 and NiO, with different weight ratios were made into pellets (0.5-inch diameter) using a mechanical mixing method followed by sintering at high temperatures. Optical microscopy image analysis showed grain growth in both phases as well as presence of porosity. The effect of sintering temperature on the densification of the composite powders was analyzed and the results showed that higher temperature enabled higher densification of the composites. Electrochemical impedance spectroscopy indicated there are two factors that contribute to the impedance in the structure of the composite materials, and possible sources for each factor are discussed. UAB College of Arts and Sciences.

  17. Deformation theory of an electro-conductive composite composed of entangled network of carbon nanotubes embedded in elastic polyurethane

    NASA Astrophysics Data System (ADS)

    Slobodian, Petr; Riha, Pavel; Olejnik, Robert; Saha, Petr

    2013-04-01

    A strain sensing polymer composite consisting of a network of entangled multi-walled carbon nanotubes in a thermoplastic polyurethane elastomer is tested by tensile and bending deformation. The composite is prepared by taking a non-woven polyurethane filter membrane, enmeshing it with carbon nanotubes and melding them together. The testing has shown that the material can be elongated as much as 400% during which the electrical resistance is increased more than 270 times. To describe the composite strain dependent resistance, a rheological model is proposed which takes into account a decrease of local contact forces between nanotubes as well as the reduction of number of contacts with deformation. The theory is used for description of sensing element deformation and resistance when simple elongation and repeated bending is exerted.

  18. Cyclophosphazene based conductive polymer-carbon nanotube composite as novel supporting material for methanol fuel cell applications.

    PubMed

    Prasanna, Dakshinamoorthy; Selvaraj, Vaithilingam

    2016-06-15

    This present study reports the development of novel catalyst support of amine terminated cyclophosphazene/cyclophosphazene/hexafluoroisopropylidenedianiline-carbon nanotube (ATCP/CP/HFPA-CNT) composite. The ATCP/CP/HFPA-CNT composite has been used as a catalyst support for platinum (Pt) and platinum-gold (Pt-Au) nanoparticles towards electrooxidation of methanol in alkaline medium. The obtained anode materials were characterized by X-ray diffraction, transmission electron microscope and energy dispersive X-ray analysis. Electrocatalytic performances of Pt/ATCP/CP/HFPA-CNT and Pt-Au/ATCP/CP/HFPA-CNT catalysts were investigated by cyclic voltammetry, CO stripping and chronoamperometric techniques. The electrooxidation of methanol and CO stripping results conclude that the metal nanocatalyst embedded with ATCP/CP/HFPA-CNT composite shows significantly higher anodic oxidation current, more CO tolerance and lower onset potential when compared to that of the Pt/CNT and Pt/C (Vulcan carbon) catalysts. PMID:27016917

  19. Preparation and characterization of nano-composites with carbon nanotubes and core-shell type polyaniline for the conductive colloidal ink

    NASA Astrophysics Data System (ADS)

    Lee, Jungmin; Varadan, Vijay K.

    2012-04-01

    Printing method for electronics elements fabrication has attractive advantages such as low material consumption, high speed fabrication, and low temperature process. The stable conductive ink is the most important factor for the fabrication of printed electronics elements with high resolution. These materials are widely used as fillers in conductive inks; metal particles, conductive polymers, and carbon materials. Among these materials, the carbon nanotubes (CNTs) are extremely attractive filler for printed electronics due to its superior electrical properties, extra high mechanical properties, and excellent chemical stability. In this research, nano-composites which are composed of multi wall carbon nanotubes (MWCNTs) and polyaniline core-shell type particles were synthesized and formulated into electrically conductive colloidal inks. The poly(acrylonitrile-co-itaconic acid-co-methylacrylate) nanoparticles were used as cores. And this core was coated with polyaniline. The surface treatments for MWCNTs were applied to make the stable nano-composites. The experimental conditions were optimized to achieve high miscibility between MWCNTs and polyaniline coated particles. Their structure and surface morphology of the nanocomposites were characterized by Scanning Electron Microscopy. And four point probe automatic resistivity meter was used to measure the conductivities of the nanocomposites.

  20. A technique for real-time detection, location and quantification of damage in large polymer composite structures made of electrically non-conductive fibers and carbon nanotube networks.

    PubMed

    Naghashpour, Ali; Van Hoa, Suong

    2013-11-15

    In this work, we have developed a novel, practical and real-time structural health monitoring (SHM) technique to detect, locate and quantify damage that occurs at one or more locations in large polymer composite structures (LPCSs) made of electrically non-conductive fibers and carbon nanotube networks. Our technique exploits the piezoresistive effect of multiwalled carbon nanotubes (MWCNTs) in epoxy resin. The electrically conductive epoxy resin was used to prepare glass fiber reinforced composite plates. The plates were marked with grid points where electrically conductive silver-epoxy pastes were deposited. The electrical resistances between the grid points were measured and used as a reference set. Two new concepts are introduced. One is uniformity of MWCNT distribution which gives rise to uniformity in electrical conductivity. The second is maximum sensitivity to change in electrical resistance due to the occurrence of damage. These issues are demonstrated as criteria to determine the optimal quantity of MWCNTs. This optimal quantity is used to assure damage detectability at any region in the large plates. Drilled holes and impact testing were conducted to simulate damage. The damage causes the electrical resistance between the contact points surrounding the damage to increase. This increase is used to detect, locate and quantify damage. PMID:24141251

  1. Electrical conduction mechanism and improved multiferroic properties of NFO/ (Pb0.50Sr0.50) TiO3 bilayer nanostructure composite thin film

    NASA Astrophysics Data System (ADS)

    Bala, Kanchan; Ram, Mast; Sharma, Hakikat; Negi, N. S.

    2016-05-01

    Multiferroic 2-2 type layered NFO/ (Pb0.50Sr0.50) TiO3 composite thin film on Pt/TiO2/Si substrate was prepared by novel metallo-Organic process using spin coating technique. The structural and surface morphology were confirmed by X-Ray diffraction (XRD) atomic force microscope (AFM). Significantly improved ferroelectric properties (Ps ˜ 8.69, Pr ˜ 3.19 µC/cm2 and Ec ˜ 419kV/cm) and magnetic properties (Ms), (Mr) and (Hc) is (104emu/cc, 0.8emu/cc and 25Oe.) were observed at room temperature. Our observation provides an effective way to manipulate the conduction behavior to understand the leakage current density of multiferroic composites film at the interface. Poole-Frankel tunneling conduction mechanism dominates the leakage current of films in the relatively high electric filed.

  2. Effects of irradiation and post-irradiation annealing on the thermal conductivity/diffusivity of monolithic SiC and f-SiC/SiC composites

    NASA Astrophysics Data System (ADS)

    Youngblood, G. E.; Senor, D. J.; Jones, R. H.

    2004-08-01

    Laser flash thermal diffusivity measurements were made on high-purity monolithic CVD-SiC and 2D f-SiC(Hi-Nicalon™)/ICVI-SiC composite samples before and after irradiation (250-800 °C, 4-8 dpa-SiC) and after post-irradiation annealing composite samples to 1200 °C. For irradiated CVD-SiC, the defect concentrations at saturation were estimated to range from 25 300 appm (250 °C) down to 940 appm (800 °C). The transverse thermal conductivity ratios after-to-before irradiation ( Kir/ Ko) determined at the irradiation temperatures ranged from: 0.044 (250 °C) up to 0.12 (800 °C) for irradiated CVD-SiC and 0.18 (330 °C) up to 0.29 (800 °C) for the irradiated Hi-Nicalon™ composite. Analysis of thermal diffusivity values for the Hi-Nicalon composite measured in air, argon, helium and vacuum indicated that thermal conductivity degradation occurred primarily due to point defect accumulation in the matrix component. After annealing to 1200 °C and cooling to ambient, fiber/matrix debonding occurred due to net shrinkage in the fiber and PyC interface components.

  3. Effects of irradiation and post-irradiation annealing on the thermal conductivity/diffusivity of monolithic SiC and f-SiC/SiC composites

    SciTech Connect

    Youngblood, Gerald E.; Senor, David J.; Jones, Russell H.

    2004-08-01

    Laser flash thermal diffusivity measurements were made on high-purity monolithic CVD-SiC and 2D f-SiC(Hi-Nicalon)/ICVI-SiC composite samples before and after irradiation (250 to 800C, 4-8 dpa-SiC) and after post-irradiation annealing composite samples to 1200C. For irradiated CVD-SiC, the defect concentrations at saturation were estimated to range from 25,300 appm (250C) down to 940 appm (800C). The transverse thermal conductivity ratios after-to-before irradiation (Kir/Ko) determined at the irradiation temperatures were: 0.044 up to 0.12 (250 up to 800C) for irradiated CVD-SiC and 0.18 up to 0.29 (330 up to 800C) for the irradiated Hi-Nicalon composite. Analysis of thermal diffusivity values for the Hi-Nicalon composite measured in air, argon, helium and vacuum indicated that thermal conductivity degradation occurred primarily due to point defect accumulation in the matrix component. After annealing to 1200C and cooling to the irradiation temperature, fiber/matrix debonding occurred due to net shrinkage in the fiber and PyC interface components.

  4. Preparation and conductivity of composite apatite La9.33Si6O26 (LSO) - Zr0.85Y0.15O1.925 (YSZ)

    NASA Astrophysics Data System (ADS)

    Noviyanti, Atiek Rostika; Irwansyah, Ferli S.; Hidayat, Sahrul; Hardian, Arie; Syarif, Dani Gustaman; Yuliyati, Yati B.; Hastiawan, Iwan

    2016-02-01

    A great challenge to reduce high operating temperature of solid oxide fuel cell (SOFC) to intermediate temperature SOFC (IT-SOFC, 500-750 °C), is the development of solid electrolyte materials with high ionic conductivity at intermediate temperature range. In response to this challenge, here we report a novel composite material La9.33Si6O26 (LSO)-Zr0.85Y0.15O1.925 (YSZ). LSO-YSZ composite synthesis was carried out by combining LSO with commercial YSZ (9:1, 8:2, 7:3) using hydrothermal method. In order to get dense pellet, all of the product were sintered at 1450 °C for 3 hours. X-ray diffraction pattern of the entire pellets show typical both of LSO and YSZ pattern which indicate that the composite was succesfully formed. The highest conductivity was detected in YSZ-7LSO (YSZ:LSO = 7: 3), i.e 1.72 × 10-4 Scm-1 at 700 °C and also has low activation energy (0.88 eV). This result suggests that the LSO-YSZ composite materials are good oxide ion conductor and potential to be used as an alternative solid electrolyte in IT-SOFC technology.

  5. Effect of mechanical activation on thermal and electrical conductivity of sintered Cu, Cr, and Cu/Cr composite powders

    NASA Astrophysics Data System (ADS)

    Rogachev, A. S.; Kuskov, K. V.; Moskovskikh, D. O.; Usenko, A. A.; Orlov, A. O.; Shkodich, N. F.; Alymov, M. I.; Mukasyan, A. S.

    2016-06-01

    The results of measurement of electric resistivity and thermal conductivity of materials obtained by spark plasma sintering from powders of Cu, Cr, and their mixtures in the range of 300-600 K are presented. It is shown that the grinding of powders in planetary mills results in a reasonably substantial change in the electric and thermal properties of materials: to increasing electric resistivity and decreasing thermal conductivity and temperature coefficients of electric resistivity. The possible causes of these effects are considered.

  6. Analysis of neutron irradiation effects on thermal conductivity of SiC-based composites and monolithic ceramics

    SciTech Connect

    Youngblood, G.E.; Senor, D.J.

    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.

  7. Hybrid absorbers composed of Fe3O4 thin film and magnetic composite sheet and enhancement of conduction noise absorption on a microstrip line

    NASA Astrophysics Data System (ADS)

    Kim, Sung-Soo

    2015-05-01

    In response to develop wide-band noise absorbers with an improved low-frequency performance, this study investigates hybrid absorbers that are composed of conductive Fe3O4 thin film and magnetic composite sheets. The Fe3O4 films prepared via reactive sputtering exhibit a typical value of electrical resistivity of ≃10-4 Ωm. Rubber composites with flaky Fe-Si-Al particles of a high permeability and high permittivity are used as the magnetic sheet functioning as an electromagnetic shield barrier. Microstrip lines with a characteristic impedance of 50 Ω are used to measure the noise absorbing properties. For the Fe3O4 film with a low surface resistance and covered by the magnetic sheet, approximately 80% power absorption can be obtained at 1 GHz, which is significantly higher than that of the original magnetic sheet or Fe3O4 film. The high power absorption of the hybrid absorber is attributed to the enhanced ohmic loss of the Fe3O4 film through increased electric field strength bounded by the upper magnetic composite sheet. The noise absorption is further enhanced through increasing the electrical conductivity of the film containing more conductive phase (Fe3O4 + Fe), which can be prepared in a reduced oxygen partial pressure during reactive sputtering.

  8. Gas sensing properties of conducting polymer/Au-loaded ZnO nanoparticle composite materials at room temperature

    PubMed Central

    2014-01-01

    In this work, a new poly (3-hexylthiophene):1.00 mol% Au-loaded zinc oxide nanoparticles (P3HT:Au/ZnO NPs) hybrid sensor is developed and systematically studied for ammonia sensing applications. The 1.00 mol% Au/ZnO NPs were synthesized by a one-step flame spray pyrolysis (FSP) process and mixed with P3HT at different mixing ratios (1:1, 2:1, 3:1, 4:1, and 1:2) before drop casting on an Al2O3 substrate with interdigitated gold electrodes to form thick film sensors. Particle characterizations by X-ray diffraction (XRD), nitrogen adsorption analysis, and high-resolution transmission electron microscopy (HR-TEM) showed highly crystalline ZnO nanoparticles (5 to 15 nm) loaded with ultrafine Au nanoparticles (1 to 2 nm). Film characterizations by XRD, field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray (EDX) spectroscopy, and atomic force microscopy (AFM) revealed the presence of P3HT/ZnO mixed phases and porous nanoparticle structures in the composite thick film. The gas sensing properties of P3HT:1.00 mol% Au/ZnO NPs composite sensors were studied for reducing and oxidizing gases (NH3, C2H5OH, CO, H2S, NO2, and H2O) at room temperature. It was found that the composite film with 4:1 of P3HT:1.00 mol% Au/ZnO NPs exhibited the best NH3 sensing performances with high response (approximately 32 to 1,000 ppm of NH3), fast response time (4.2 s), and high selectivity at room temperature. Plausible mechanisms explaining the enhanced NH3 response by composite films were discussed. PMID:25246871

  9. Particle Arrangement Design for Predicting the Percolation Threshold of Silver/Epoxy Composite for Electrically Conductive Adhesive Application

    NASA Astrophysics Data System (ADS)

    Zulkarnain, M.; Husaini, Muhammad; Mariatti, M.; Azid, I. A.

    2015-11-01

    The early use of electrically conductive adhesives (ECAs) provided an alternative to solder because of their several advantages, such as good electrical conductivity, low cost, extendability to fine pitch of interconnecting material and environmental friendliness. According to previous works, an optimal particle volume fraction became a major objective of many researchers in order to obtain highly conductive ECAs, realizing that the need for transitions from an insulator to a conductor is controlled by the geometric arrangement of particles. In the current study, particle arrangement models of ECAs are developed by establishing the effects of van der Waals' attraction energy and particle motion, which act as a kind of particle interaction to generate a conducting structure. The methodology is divided into three major parts: the formulation of a particle arrangement technique, and numerical and experimental studies. The formulation of particle arrangement is developed in an epoxy colloidal system. During verification, the particle arrangement model is validated by the theoretical fractal dimension and guided by a morphological study of the experimental assessments. The model was simulated through representative volume elements with the volume fraction factor, which was set in the range of 2-8 vol.%, while electrical conductivity was an observed parameter. The numerical results showed good agreement with the experiments in which the percolation threshold occurred between 4 and 6% of the volume of filler loading.

  10. Influence of composition nonstoichiometry on the electrical conductivity of LiNaGe4O9 crystals

    NASA Astrophysics Data System (ADS)

    Volnyanskii, M. D.; Trubitsyn, M. P.; Bibikova, O. A.

    2014-06-01

    The electrical conductivity σ of Li2 - x Na x Ge4O9 ( x = 1, 0.5, 0.2) crystals in an alternating-current electric field has been investigated at a frequency of 1 kHz in the temperature range of 300-800 K. A considerable anisotropy of the electrical conductivity has been revealed for crystals with a sodium concentration x = 1 at T > 500 K. It has been shown that the electrical conductivity σ along certain crystallographic directions increases by more than three orders of magnitude with a change in the sodium concentration from x = 1 to x = 0.2. The results have been discussed taking into account the specific features of the structure of the crystals under investigation. Presumably, the major charge carriers are interstitial Li ions migrating along channels of the framework structure of the Li2 - x Na x Ge4O9 crystals.

  11. Superstable transparent conductive Cu@Cu4Ni nanowire elastomer composites against oxidation, bending, stretching, and twisting for flexible and stretchable optoelectronics.

    PubMed

    Song, Jizhong; Li, Jianhai; Xu, Jiayue; Zeng, Haibo

    2014-11-12

    Low cost and high conductivity make copper (Cu) nanowire (NW) electrodes an attractive material to construct flexible and stretchable electronic skins, displays, organic light-emitting diodes (OLEDs), solar cells, and electrochromic windows. However, the vulnerabilities that Cu NW electrodes have to oxidation, bending, and stretching still present great challenges. This work demonstrates a new Cu@Cu4Ni NW conductive elastomer composite with ultrahigh stability for the first time. Cu@Cu4Ni NWs, facilely synthesized through a one-pot method, have highly crystalline alloyed shells, clear and abrupt interfaces, lengths more than 50 μm, and smooth surfaces. These virtues provide the NW-elastomer composites with a low resistance of 62.4 ohm/sq at 80% transparency, which is even better than the commercial ITO/PET flexible electrodes. In addition, the fluctuation amplitude of resistance is within 2 ohm/sq within 30 days, meaning that at ΔR/R0 = 1, the actual lifetime is estimated to be more than 1200 days. Neither the conductivity nor the performances of OLED with elastomers as conductive circuits show evident degradation during 600 cycles of bending, stretching, and twisting tests. These high-performance and extremely stable NW elastomeric electrodes could endow great chances for transparent, flexible, stretchable, and wearable electronic and optoelectronic devices. PMID:25302453

  12. Composition.

    ERIC Educational Resources Information Center

    Nemanich, Donald, Ed.

    1974-01-01

    The articles in this special issue of the "Illinois English Bulletin" concern the state of composition instruction at the secondary and college levels. The titles and authors are "Monologues or Dialogues? A Plea for Literacy" by Dr. Alfred J. Lindsey, "Teaching Composition: Curiouser and Curiouser" by Denny Brandon, and "Teaching Writing to High…

  13. A model for predicting changes in the electrical conductivity, practical salinity, and absolute salinity of seawater due to variations in relative chemical composition

    NASA Astrophysics Data System (ADS)

    Pawlowicz, R.

    2010-03-01

    Salinity determination in seawater has been carried out for almost 30 years using the Practical Salinity Scale 1978. However, the numerical value of so-called practical salinity, computed from electrical conductivity, differs slightly from the true or absolute salinity, defined as the mass of dissolved solids per unit mass of seawater. The difference arises because more recent knowledge about the composition of seawater is not reflected in the definition of practical salinity, which was chosen to maintain historical continuity with previous measures, and because of spatial and temporal variations in the relative composition of seawater. Accounting for these spatial variations in density calculations requires the calculation of a correction factor δSA, which is known to range from 0 to 0.03 g kg-1 in the world oceans. Here a mathematical model relating compositional perturbations to δSA is developed, by combining a chemical model for the composition of seawater with a mathematical model for predicting the conductivity of multi-component aqueous solutions. Model calculations for this estimate of δSA, denoted δSRsoln, generally agree with estimates of δSA based on fits to direct density measurements, denoted δSRdens, and show that biogeochemical perturbations affect conductivity only weakly. However, small systematic differences between model and density-based estimates remain. These may arise for several reasons, including uncertainty about the biogeochemical processes involved in the increase in Total Alkalinity in the North Pacific, uncertainty in the carbon content of IAPSO standard seawater, and uncertainty about the haline contraction coefficient for the constituents involved in biogeochemical processes. This model may then be important in constraining these processes, as well as in future efforts to improve parameterizations for δSA.

  14. A model for predicting changes in the electrical conductivity, practical salinity, and absolute salinity of seawater due to variations in relative chemical composition

    NASA Astrophysics Data System (ADS)

    Pawlowicz, R.

    2009-11-01

    Salinity determination in seawater has been carried out for almost 30 years using the 1978 Practical Salinity Standard. However, the numerical value of so-called practical salinity, computed from electrical conductivity, differs slightly from the true or absolute salinity, defined as the mass of dissolved solids per unit mass of seawater. The difference arises because more recent knowledge about the composition of seawater is not reflected in the definition of practical salinity, which was chosen to maintain historical continuity with previous measures, and because of spatial and temporal variations in the relative composition of seawater. Accounting for these variations in density calculations requires the calculation of a correction factor δSA, which is known to range from 0 to 0.03 g kg-1 in the world oceans. Here a mathematical model relating compositional perturbations to δSA is developed, by combining a chemical model for the composition of seawater with a mathematical model for predicting the conductivity of multi-component aqueous solutions. Model calculations generally agree with estimates of δSA based on fits to direct density measurements, and show that biogeochemical perturbations affect conductivity only weakly. However, small systematic differences between model and density-based estimates remain. These may arise for several reasons, including uncertainty about the biogeochemical processes involved in the increase in Total Alkalinity in the North Pacific, uncertainty in the carbon content of IAPSO standard seawater, and uncertainty about the haline contraction coefficient for the constituents involved in biogeochemical processes. This model may then be important in constraining these processes, as well as in future efforts to improve parameterizations for δSA.

  15. Robust conductive mesoporous carbon-silica composite films with highly ordered and oriented orthorhombic structures from triblock-copolymer template co-assembly

    SciTech Connect

    Song, Lingyan; Feng, Dan; Campbell, Casey G; Gu, Dong; Forster, Aaron M; Yager, Kevin G; Fredin, Nathaniel; Lee, Hae-Jeong; Jones, Ronald L; Zhao, Dongyuan; Vogt, Bryan D

    2012-07-11

    In this work, we describe a facile approach to improve the robustness of conductive mesoporous carbon-based thin films by the addition of silica to the matrix through the triconstituent organic-inorganic-organic co-assembly of resol (carbon precursor) and tetraethylorthosilicate (silica precursor) with triblock-copolymer Pluronic F127. The pyrolysis of the resol-silica-pluronic F127 film yields a porous composite thin film with well-defined mesostructure. X-Ray diffraction (XRD), grazing incidence small angle X-ray scattering (GISAXS), and electron microscopy measurements indicate that the obtained carbon-based thin films have a highly ordered orthorhombic mesostructure (Fmmm) with uniform large pore size (~3 nm). The orthorhombic mesostructure is oriented and the (010) plane is parallel to the silicon wafer substrate. The addition of silica to the matrix impacts the pore size, surface area, porosity, modulus and conductivity. For composite films with approximately 40 wt% silica, the conductivity is decreased by approximately an order of magnitude in comparison to a pure carbon mesoporous film, but the conductivity is comparable to typical printed carbon inks used in electrochemical sensing, {approx}10 S cm-1. The mechanical properties of these mesoporous silica-carbon hybrid films are similar to the pure carbon analogs with a Young's modulus between 10 GPa and 15 GPa, but the material is significantly more porous. Moreover, the addition of silica to the matrix appears to improve the adhesion of the mesoporous film to a silicon wafer. These mesoporous silica-carbon composite films have appropriate characteristics for use in sensing applications.

  16. Effects of type of binder and conducting phase on the performance of solid-state electrochemiluminescence composites.

    PubMed

    Safavi, A; Sedaghati, F; Shahbaazi, H

    2014-05-01

    The electrochemiluminescence (ECL) of tris(2,2-bipyridyl)ruthenium [Ru(bpy)3 ](2+) has received much attention. By immobilizing [Ru(bpy)3 ](2+) on an electrode surface, solid-state ECL has several advantages over solution-phase ECL, such as reduced amounts of costly reagent and a simplified experimental design. Herein, different types of solid-state ECL sensors were fabricated and the performances of paraffin oil and two ionic liquids (ILs) as the binders were compared for the construction of solid-state ECL. Scanning electron microscopy (SEM), CCD camera, UV-vis, fluorescence spectroscopy, electrochemistry and ECL were applied to characterize and evaluate the performance of the solid-state composites. According to the obtained results, Ru-graphite/IL octyl pyridinium hexaflurophosphate (OPPF6 ) was introduced as a new solid-state ECL with excellent properties such as simple preparation, low background current, fast electron-transfer rate and good reproducibility and stability. Moreover, for a study of the effect of carbon structure on the performance of the electrode, graphite was replaced by multi-walled carbon nanotubes (MWCNTs) and Ru-MWCNT/OPPF6 was constructed and its efficiency was compared with Ru-graphite/OPPF6 composite electrode. PMID:23760772

  17. Superconductivity of {open_quotes}conducting polymer-fullerene alkali metal{close_quotes} composites: Dreams and realities

    SciTech Connect

    Zakhidov, A.A.; Yoshino, K.

    1996-10-01

    Composites of fullerene C{sub 60} with conjugated polymers (CP) like polyalkylthiophene (PAT) and polyphenylene vinylene derivative (OO-PPV) have earlier demonstrated intensive charge transfer upon photoexcitation. Doping of CP/C{sub 60} composites by A metal vapors (A=K,Rb) is aimed at C{sub 60} induced SC, in which electrons of CP chains may participate in SC pairing, induced via hybridization with C{sub 60} molecules. We have found an SC phase experimentally both in PAT. (C{sub 60}) {sub y}K{sub x} and OO.PPV (C{sub 60}){sub y}K{sub x} by a sensitive method of low field microwave absorption (LFMA), and proved by SQUID. The SCT{sub c} ranges from 12 to 17 K, depending on y and x. This SC phase shows a granular behavior in LFMA, and thus originates from SC A{sub 3}C{sub 60} clusters weakly linked by Josephson junctions. True C{sub 60} induced SC might be masked by granular A{sub 3}C{sub 60}. Anomalous LFMA and paramagnetic Meissner effects observed in SQUID, indicate the existence of Josephson {pi}-junctions. CP is apparently involved in SC via spin carrying polarons P in CP chains, which play a role of {pi}-junctions. Strategies for further search of C{sub 60} induced SC are discussed.

  18. Proof of concept for a novel, binder-free and conducting carbon-free sulfur battery cathode: Composite electroformation of copper foil with incorporated polythiophene wrapped sulfur particles

    NASA Astrophysics Data System (ADS)

    Erhardt, Claudia; Sörgel, Şeniz; Meinhard, Sandra; Sörgel, Timo

    2015-11-01

    This work, for the first time, presents sulfur electrodes for lithium/sulfur (Li/S) batteries produced by a newly developed single-step electroforming process, which allows simultaneous sulfur incorporation during electroformation of an electrically conducting electrode. This metal is used as binding matrix for the sulfur particles and thereby makes any binder and conducting carbon additives redundant. Furthermore, it serves by itself as the current collector, so that all functionalities (current collector, binder and electrical conductor towards sulfur) are fulfilled by the electroformed metal, while modified sulfur particles are directly incorporated (composite electroformation). In this way, the sulfur cathode can be produced in a single continuous step in form of a metal foil with adjustable thickness and sulfur loading. The process requires functionalization of sulfur to improve its wettability, incorporation homogeneity and volume which is provided by wrapping sulfur particles with polythiophene. Electroformed copper-sulfur composite foils are chosen as a first proof of the new concept. The achieved battery capacity, cycling stability and coulombic efficiency are presented. It is shown that the electroformed copper-sulfur composite foil operates very well as a battery cathode and a discharge capacity of over 400 mAh g-1 at a rate of 0.5 C over 100 cycles is preserved.

  19. Crystalline-amorphous silicon nano-composites: Nano-pores and nano-inclusions impact on the thermal conductivity

    NASA Astrophysics Data System (ADS)

    Verdier, M.; Termentzidis, K.; Lacroix, D.

    2016-05-01

    The thermal conductivities of nanoporous and nanocomposite silicon with incorporated amorphous phases have been computed by molecular dynamics simulations. A systematic investigation of the porosity and the width of the amorphous shell contouring a spherical pore has been made. The impact of amorphous phase nanoinclusions in a crystalline matrix has also been studied with the same amorphous fraction as the porosity of nanoporous silicon to achieve comparison. The key parameter for all configurations with or without the amorphous phase is proved to be the interface (between the crystalline and amorphous phases or crystalline and void) to volume ratio. We obtain the sub-amorphous thermal conductivity for several configurations by combining pores, amorphous shell, and crystalline phase. These configurations are promising candidates for low cost and not toxic thermoelectric devices based on abundant semiconductors.

  20. Tunability of mobility and conductivity over large ranges in poly(3,3'''-didodecylquaterthiophene)/insulating polymer composites.

    PubMed

    Sun, J; Jung, B-J; Lee, T; Berger, L; Huang, J; Liu, Y; Reich, D H; Katz, H E

    2009-02-01

    Semiconducting polymers are currently being considered as active layers in field-effect transistors, in which high charge carrier mobility and low off conductivity are important. For other applications, such as certain spintronic mechanisms, the opposite characteristics are desirable. Blending such polymers with insulating polymers would be expected to lower the mobility. In this paper, we report that the use of hydrocarbon polymers such as polystyrene as insulators generally raises the mobility when the semiconducting polymer is poly(bisdodecylquaterthiophene). A high mobility value of nearly 0.1 cm(2)/V.s was obtained for an optimal blend. While this is counterintuitive, it is consistent with a few other recent reports. In order to lower the mobility significantly, a much more polar and irregular blending agent is needed. The further addition of tetrafluorotetracyanoquinodimethane as a dopant gave a rare low mobility/high conductivity combination of properties, with a charge carrier density on the order of 10(19) cm(-3). Thus, mobility and conductivity were tuned somewhat independently over 3 and 4 orders of magnitude, respectively. PMID:20353231