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Sample records for li3ca2c6 intercalated graphite

  1. Intercalated Graphite Fiber Conductor.

    DTIC Science & Technology

    1980-12-01

    Lightweight electrical conductors were developed from graphitic fibers inter- calated with highly electrophilic intercalants. Conductance increases of...intercalated with highly electrophilic molecules ("intercalants") to en- hance their electrical conductivity. Evaluation of the elec- trical resistance of two...corrosion resistant to fluorine containing chemicals. Since the moisture permeability of the TFE is much less than that of the FEP, attempts were made to

  2. Intercalated graphite electrical conductors

    NASA Technical Reports Server (NTRS)

    Banks, B. A.

    1983-01-01

    For years NASA has wanted to reduce the weight of spacecraft and aircraft. Experiments are conducted to find a lightweight synthetic metal to replace copper. The subject of this paper, intercalated graphite, is such a material. Intercalated graphite is made by heating petroleum or coal to remove the hydrogen and to form more covalent bonds, thus increasing the molecular weight. The coal or petroleum eventually turns to pitch, which can then be drawn into a fiber. With continued heating the pitch-based fiber releases hydrogen and forms a carbon fiber. The carbon fiber, if heated sufficiently, becomes more organized in parallel layers of hexagonally arranged carbon atoms in the form of graphite. A conductor of intercalated graphite is potentially useful for spacecraft or aircraft applications because of its low weight.

  3. Intercalated hybrid graphite fiber composite

    NASA Technical Reports Server (NTRS)

    Gaier, James R. (Inventor)

    1993-01-01

    The invention is directed to a highly conductive lightweight hybrid material and methods of producing the same. The hybrid composite is obtained by weaving strands of a high strength carbon or graphite fiber into a fabric-like structure, depositing a layer of carbon onto the structure, heat treating the structure to graphitize the carbon layer, and intercalating the graphitic carbon layer structure. A laminate composite material useful for protection against lightning strikes comprises at least one layer of the hybrid material over at least one layer of high strength carbon or graphite fibers. The composite material of the present invention is compatible with matrix compounds, has a coefficient of thermal expansion which is the same as underlying fiber layers, and is resistant to galvanic corrosion in addition to being highly conductive. These materials are useful in the aerospace industry, in particular as lightning strike protection for airplanes.

  4. Synthetic Metals from Intercalated Graphite

    DTIC Science & Technology

    1988-05-09

    Studies of the Structure of SbCl 5Graphite Inter- calation Compounds", L.E. McNeil, J. Steinbeck, L. Salamanca- Riba and G. Dresselhaus, Bull. APS 29...Graphite Intercalation Compounds", L.E. McNeil, J. Steinbeck, L. Salamanca- Riba and G. Dresselhaus, Phys. Rev. B31, 2451 (1985). 12. "Non-Ohmic Transport...Boston (1984), p. 149. 16. "High Resolution Electron Microscopy and X-Ray Diffraction Studies on SbCI5 - GIC", G. Roth, L. Salamanca- Riba , A.R. Kortan, G

  5. Superlubricity of Fullerene Intercalated Graphite Composite

    NASA Astrophysics Data System (ADS)

    Miura, Kouji; Tsuda, Daisuke; Itamura, Noriaki; Sasaki, Naruo

    2007-08-01

    A novel superlubric system of fullerene intercalated graphite composite is reported. First, it is clarified that fullerene intercalated graphite films exhibit an ultralow average friction force and an excellent friction coefficient μ <0.001 smaller than μ <0.002 for MoS2 and μ\\cong 0.001 for graphite. Next, it is demonstrated that superlubricity can be controlled by changing the intercalant species. The C60 intercalated graphite film shows much less maximum static friction force than the C70 intercalated graphite film. Finally, we propose one of the simple guidelines on designing a practical superlubric system-reduction in the contact area between the intercalated fullerene and the graphite sheet to the pointlike contact. Our newly developed superlubric system will contribute to solving energy and environmental problems.

  6. Synthetic Metals from Intercalated Graphite.

    DTIC Science & Technology

    1985-09-30

    34, L. Salamanca- Riba and M.S. Dres- selhaus, Carbon, (in press) (1986). 16. "High Resolution Transmission Electron Microscopy on KH.-GICs", L. Salaman...ca- Riba , N.C. Yeh, M.S. Dresselhaus, M. Endo and T. Enoki, J. of Mat. Res. (in press) (1986). 11 04 -.4* 17. "Electron Beam Induced Damage and...Structure of SbCl5 Graphite Intercalation Compounds", L. Salamanca- Riba , G. Roth, J.M. Gibson, A.R. Kortan, G. Dresselhaus and - R.J. Birgeneau, Phys. Rev

  7. Graphite fiber intercalation: Dynamics of the bromine intercalation process

    NASA Technical Reports Server (NTRS)

    Jaworske, D. A.; Zinolabedini, R.

    1985-01-01

    The resistance of pitch-based graphite fibers was monitored, in situ, during a series of bromine intercalation experiments. The threshold pressure for the bromine intercalation of pitch-based fibers was estimated to be 102 torr. When the bromine atmosphere was removed from the reaction chamber, the resistivity of the intercalated graphite fibers increased consistently. This increase was attributed to loss of bromine from the perimeter of the fiber. The loss was confirmed by mapping the bromine concentration across the diameter of single intercalated fibers with either energy dispersive spectroscopy or scanning Auger microscopy. A statistical study comparing fibers intercalated in bromine vapor with fibers intercalated in bromine liquid showed that similar products were obtained with both methods of intercalation.

  8. Superconductivity in graphite intercalation compounds

    DOE PAGES

    Smith, Robert P.; Weller, Thomas E.; Howard, Christopher A.; ...

    2015-02-26

    This study examines the field of superconductivity in the class of materials known as graphite intercalation compounds which has a history dating back to the 1960s. This paper recontextualizes the field in light of the discovery of superconductivity in CaC₆ and YbC₆ in 2005. In what follows, we outline the crystal structure and electronic structure of these and related compounds. We go on to experiments addressing the superconducting energy gap, lattice dynamics, pressure dependence, and how this relates to theoretical studies. The bulk of the evidence strongly supports a BCS superconducting state. However, important questions remain regarding which electronic statesmore » and phonon modes are most important for superconductivity and whether current theoretical techniques can fully describe the dependence of the superconducting transition temperature on pressure and chemical composition.« less

  9. Superconductivity in graphite intercalation compounds

    SciTech Connect

    Smith, Robert P.; Weller, Thomas E.; Howard, Christopher A.; Dean, Mark P. M.; Rahnejat, Kaveh C.; Saxena, Siddharth S.; Ellerby, Mark

    2015-02-26

    This study examines the field of superconductivity in the class of materials known as graphite intercalation compounds which has a history dating back to the 1960s. This paper recontextualizes the field in light of the discovery of superconductivity in CaC₆ and YbC₆ in 2005. In what follows, we outline the crystal structure and electronic structure of these and related compounds. We go on to experiments addressing the superconducting energy gap, lattice dynamics, pressure dependence, and how this relates to theoretical studies. The bulk of the evidence strongly supports a BCS superconducting state. However, important questions remain regarding which electronic states and phonon modes are most important for superconductivity and whether current theoretical techniques can fully describe the dependence of the superconducting transition temperature on pressure and chemical composition.

  10. Stability of Bromine Intercalated Graphite Fibers

    NASA Technical Reports Server (NTRS)

    Gaier, J. R.

    1984-01-01

    Previous evidence suggested that bromine intercalation compounds of crystalline graphite spontaneously deintercalate when the bromine atmosphere is removed. However, results show that bromine intercalated P-100 graphite fibers are stable for long periods of time. They are stable under vacuum conditions, high humidity, and current densities up to 24,000 A/sq cm. They are thermally stable to 200 C, and at temperatures as high as 400 C still retain 80 percent of the conductivity gained by intercalation. At temperatures greater than 300 C, there is significant oxidative degradation of the fibers. The environmental stability shown by the bromine compound makes it a promising candidate for practical applications in aerospace technology.

  11. Graphitized needle cokes and natural graphites for lithium intercalation

    SciTech Connect

    Tran, T.D.; Spellman, L.M.; Pekala, R.W.; Goldberger, W.M.; Kinoshita, K.

    1996-05-10

    This paper examined effects of heat treatment and milling (before or after heat treatment) on the (electrochemical) intercalating ability of needle petroleum coke; natural graphite particles are included for comparison. 1 tab, 4 figs, 7 refs.

  12. Feasibility of intercalated graphite railgun armatures

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Gooden, Clarence E.; Yashan, Doreen; Naud, Steven

    1990-01-01

    Graphite intercalation compounds may provide an excellent material for the fabrication of electro-magnetic railgun armatures. As a pulse of power is fed into the armature the intercalate could be excited into the plasma state around the edges of the armature, while the bulk of the current would be carried through the graphite block. Such an armature would have the desirable characteristics of both diffuse plasma armatures and bulk conduction armatures. In addition, the highly anisotropic nature of these materials could enable the electrical and thermal conductivity to be tailored to meet the specific requirements of electromagnetic railgun armatures. Preliminary investigations were performed in an attempt to determine the feasibility of using graphite intercalation compounds as railgun armatures. Issues of fabrication, resistivity, stability, and electrical current spreading are addressed for the case of highly oriented pyrolytic graphite.

  13. Environmental stability of intercalated graphite fibers

    NASA Technical Reports Server (NTRS)

    Gaier, J. R.; Jaworske, D. A.

    1985-01-01

    Graphite fibers intercalated with bromine, iodine monochloride, ferric chloride, and cupric chloride were subjected to stability tests under four environments which are encountered by engineering materials in the aerospace industry: ambient laboratory conditions, as would be experienced during handling operations and terrestrial applications; high vacuum, as would be experienced in space applications; high humidity, as would be experienced in marine applications; and high temperature, as would be experienced in some processing steps and applications. Monitoring the resistance of the fibers at ambient laboratory conditions revealed that only the ferric chloride intercalated fibers were unstable, due to absorption of water from the air. All four types of intercalated fibers were unstable, due to absorption of water from the air. All four types of intercalated fibers were stable for long periods under high vacuum. Ferric chloride, cupric chloride, and iodine monochloride intercalated fibers were sensitive to high humidity conditions. All intercalated fibers began to degrade above 250 C. The order of their thermal stability, from lowest to highest, was cupric chloride, iodine monochloride, bromine, and ferric chloride. Of the four types of intercalated fibers tested, the bromine intercalated fibers appear to have the most potential for application, based on environmental stability.

  14. EMI Shields made from intercalated graphite composites

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Terry, Jennifer

    1995-01-01

    Electromagnetic interference (EMI) shielding typically makes up about twenty percent of the mass of a spacecraft power system. Graphite fiber/polymer composites have significantly lower densities and higher strengths than aluminum, the present material of choice for EMI shields, but they lack the electrical conductivity that enables acceptable shielding effectiveness. Bromine intercalated pitch-based graphite/epoxy composites have conductivities fifty times higher than conventional structural graphite fibers. Calculations are presented which indicate that EMI shields made from such composites can have sufficient shielding at less than 20% of the mass of conventional aluminum shields. EMI shields provide many functions other than EMI shielding including physical protection, thermal management, and shielding from ionizing radiation. Intercalated graphite composites perform well in these areas also. Mechanically, they have much higher specific strength and modulus than aluminum. They also have shorter half thicknesses for x-rays and gamma radiation than aluminum. Thermally, they distribute infra-red radiation by absorbing and re-radiating it rather than concentrating it by reflection as aluminum does. The prospects for intercalated graphite fiber/polymer composites for EMI shielding are encouraging.

  15. Graphite intercalation compound with iodine as the major intercalate

    NASA Technical Reports Server (NTRS)

    Hung, Ching-Cheh; Kucera, Donald

    1994-01-01

    Halogenated graphite CBr(x)I(y) (I less than y/x less than 10) was made by exposing graphite materials to either pure Br2 or an I2/Br2/HBr mixture to initiate the reaction, and then to iodine vapor containing a small amount of Br2/HBr/IBr to complete the intercalation reaction. Wetting of the graphite materials by the I2/Br2/HBr mixture is needed to start the reaction, and a small amount of Br2/HBr/IBr is needed to complete the charge transfer between iodine and carbon. The interplanar spacings for the graphite materials need to be in the 3.35 to 3.41 A range. The X-ray diffraction data obtained from the halogenated HOPG indicate that the distance between the two carbon layers containing intercalate is 7.25 A. Electrical resistivity of the fiber product is from 3 to 6.5 times the pristine value, The presence of a small amount of isoprene rubber in the reaction significantly increased the iodine-to-bromine ratio in the product. In this reaction, rubber is known to generate HBr and to slowly remove bromine from the vapor. The halogenation generally caused a 22 percent to 25 percent weight increase. The halogens were found uniformly distributed in the product interior. However, although the surface contains very little iodine, it has high concentrations of bromine and oxygen. It is believed that the high concentrations of bromine and oxygen in this surface cause the halogenated fiber to be more resistant to structural damage during subsequent fluorination to fabricate graphite fluoride fibers.

  16. Ferric chloride graphite intercalation compounds prepared from graphite fluoride

    NASA Technical Reports Server (NTRS)

    Hung, Ching-Cheh

    1994-01-01

    The reaction between graphite fluoride and ferric chloride was observed in the temperature range of 300 to 400 C. The graphite fluorides used for this reaction have an sp3 electronic structure and are electrical insulators. They can be made by fluorinating either carbon fibers or powder having various degrees of graphitization. Reaction is fast and spontaneous and can occur in the presence of air. The ferric chloride does not have to be predried. The products have an sp2 electronic structure and are electrical conductors. They contain first stage FeCl3 intercalated graphite. Some of the products contain FeCl2*2H2O, others contain FeF3 in concentrations that depend on the intercalation condition. The graphite intercalated compounds (GIC) deintercalated slowly in air at room temperature, but deintercalated quickly and completely at 370 C. Deintercalation is accompanied by the disappearing of iron halides and the formation of rust (hematite) distributed unevenly on the fiber surface. When heated to 400 C in pure N2 (99.99 vol %), this new GIC deintercalates without losing its molecular structure. However, when the compounds are heated to 800 C in quartz tube, they lost most of its halogen atoms and formed iron oxides (other than hematite), distributed evenly in or on the fiber. This iron-oxide-covered fiber may be useful in making carbon-fiber/ceramic-matrix composites with strong bonding at the fiber-ceramic interface.

  17. Ferrix Chloride-Graphite Intercalation Compounds Prepared From Graphite Flouride

    NASA Technical Reports Server (NTRS)

    Hung, Ching-Cheh

    1995-01-01

    The reaction between graphite fluoride and ferric chloride was observed in the temperature range of 300 to 400 C. The graphite fluorides used for this reaction have an sp(sup 3) electronic structure and are electrical insulators. They can be made by fluorinating either carbon fibers or powder having various degrees of graphitization. Reaction is fast and spontaneous and can occur in the presence of air. The ferric chloride does not have to be predried. The products have an sp(sup 2) electronic structure and are electrical conductors. They contain first-stage FeCl3 intercalated graphite. Some of the products contain FeCl2 (center dot) 2H2O, others contain FeF3, in concentrations that depend on the intercalation condition. The graphite intercalated compounds (GIC) deintercalated slowly in air at room temperature, but deintercalated quickly and completely at 370 C. Deintercalation is accompanied by the disappearance of iron halides and the formation of rust (hematite) distributed unevenly on the fiber surface. When heated to 400 C in pure N2 (99.99 vol%), this new GIC deintercalates without losing its molecular structure. However, when the compounds are exposed to 800 C N2, in a quartz tube, they lost most of their halogen atoms and formed iron oxides (other than hematite), distributed evenly in or on the fiber.

  18. Structure-Property Relationships in Intercalated Graphite.

    DTIC Science & Technology

    1985-07-10

    McNeil, J. Steinbeck, L. Salamanca- Riba and G. Dresselhaus, Bull. APS 29, 253 (1984). 4. "The Effect of Impurities on the Electronic Phase Transition In...12. "Raman Microprobe Observation of Intercalate Contraction In Graphite Inter- calation Compounds", L.E. McNeil, J. Steinbeck, L. Salamanca- Riba and...17. "High Resolution Electron Microscopy and X-Ray Diffraction Studies on SbCl5 - GI0", G. Roth, L. Salamanca- Riba , A.R. Kortan, G. Dresselhaus, R.J

  19. Kinetics of the Formation of Intercalation Compounds in Crystalline Graphite

    NASA Technical Reports Server (NTRS)

    Sharma, P. K.; Hickey, G. S.

    1995-01-01

    Crystalline graphite has a structure that can be best described as an ordered stack of flat aromatic layers. It is known to form intercalation compounds with bromine and nitric acid. Their formation was studied using thermal measurements and analytical techniques. Samples of graphite treated with either bromine or nitric acid were prepared by contacting these reagents with powdered graphite.

  20. Electrochemical intercalation and electrical conductivity of graphite fibers

    NASA Technical Reports Server (NTRS)

    Besenhard, J. O.; Fritz, H. P.; Moehwald, H.; Nickl, J. J.

    1982-01-01

    Lamellar compounds of graphite fibers were prepared by electrochemical intercalation. The dependence of the electrical resistance on the intercalate concentration was determined by a quasi simultaneous method. A factor 30 decrease of the relative fiber resistance was obtained with fluorosulfuric acid.

  1. Obtaining graphene nanoplatelets from various graphite intercalation compounds

    NASA Astrophysics Data System (ADS)

    Melezhyk, A.; Galunin, E.; Memetov, N.

    2015-11-01

    The work compares the exfoliation ability of different graphite materials (expanded graphite intercalation compound, thermally expanded and oxidatively intercalated graphites) and describes the properties of graphene nanoplatelets (GNPs) obtained dependently on intercalation/deintercalation conditions and reagents. Among the studied materials, the graphite intercalated with ammonium persulfate in sulfuric acid and expanded at 40 °C possesses the maximum ability for ultrasonic exfoliation in the presence of a surfactant. The exfoliation efficiency strongly depends on the content of water in sulfuric acid during the intercalation. The highest efficiency was achieved for the expanded graphite intercalation compound (EGIC) prepared in sulfuric acid containing diluted oleum, which may be explained by increased acidity of the medium and, correspondingly, redox potential of the persulfate compound. This is also related to increased amounts of oxygen groups in the GNPs obtained from the EGIC synthesized in 100% sulfuric acid and diluted oleum. Besides, the nature of surface groups on the GNPs strongly depends on the nature of a deintercalating reagent. Thus, the treatment of the EGIC with different nucleophilic molecules (such as water, ammonia, carbamide, hexamethylenetetramine, organic amines, etc.) can yield GNPs with various surface groups. The interaction between the EGIC and nucleophilic molecules does not only include the substitution of sulfate groups, but also redox reactions with participation of graphene layers. Depending on the nature of the nucleophile, those reactions can lead to the formation of different groups attached to the graphene surface. GNPs with almost pure surface were obtained when using ammonia and carbamide.

  2. Homogeneity of pristine and bromine intercalated graphite fibers

    NASA Technical Reports Server (NTRS)

    Gaier, J. R.; Marino, D.

    1985-01-01

    Wide variations in the resistivity of intercalated graphite fibers and to use these materials for electrical applications, their bulk properties must be established. The homogeneity of the diameter, the resistivity, and the mass density of 50 graphite fibers, before and after bromine intercalation was measured. Upon intercalation the diameter was found to expand by about 5%, the resistivity to decrease by a factor of five, and the density to increase by about 6%. Each individual fiber was found to have uniform diameter and resistivity over macroscopic regions for lengths as long as 7 cm. The ratio of pristine to intercalated resistivity increases as the pristine fiber diameter increases at a rate of 0.16 micron, but decreases with the increasing ratio of intercalated diameter to pristine diameter at a rate of 0.08.

  3. The preliminary feasibility of intercalated graphite railgun armatures

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Gooden, Clarence E.; Yashan, Doreen; Naud, Steve

    1991-01-01

    Graphite intercalation compounds may provide an excellent material for the fabrication of electromagnetic railgun armatures. As a pulse of power is fed into the armature the intercalate could be excited into the plasma state around the edges of the armature, while the bulk of the current would be carried through the graphite block. Such an armature would have both diffuse plasma armatures and bulk conduction armatures. In addition, the highly anisotropic nature of these materials could enable the electrical and thermal conductivity to be tailored to meet the specific requirements of electromagnetic railgun armatures. Preliminary investigations have been performed in an attempt to determine the feasibility of using graphite intercalation compounds as railgun armatures. Issues of fabrication, resistivity, stability, and electrical current spreading have been addressed for the case of highly oriented pyrolytic graphite.

  4. Synthesis and insertion mechanism of graphite intercalation compounds

    SciTech Connect

    Leong, K.W.

    1987-01-01

    The formation of graphite intercalation compounds were studied in graphite-oxide and graphite-metal chloride systems. Three types of fibers-type P (Union Carbide), GY-30 and GY-70 (Celanese), and HMS and HT(Hercules)- were oxidized by chemical as well as electrochemical means. The chemically oxidized fibers had an increase in electrical resistivity of over three orders of magnitude compared to the pristine fiber. The interstitial oxidation reduced the tensile strength and elastic modulus of the fiber by no more than 25%. In examining the role played by co-reagents in assisting insertion of AlCl/sub 3/, it was concluded that intercalation was initiated by a charge transfer between the graphite layers and an adsorbed Friedel-Crafts complex. Nitric oxide, hydrogen chloride, and nitrosyl chloride had been identified as new effective coreagents for the intercalation of AlCl/sub 3/. Discovery of these coreagents offered alternative synthetic routes, which are discussed. The kinetic investigation of the intercalation of AlCl/sub 3/-Cl/sub 2/ suggested that charge transfer between graphite and AlCl/sub 3/ is a surface phenomenon, and propagation of electron holes along c-axis is one of the rate-determining steps. To model the non-Fickian diffusion behavior, it was proposed that relaxation of the matrix as driven by elastic interaction of the intercalants contributes to the anomalies. A mathematical expression was derived to correlate the data by superpositioning relaxation terms over the diffusion equation.

  5. Environmentally benign graphite intercalation compound composition for exfoliated graphite, flexible graphite, and nano-scaled graphene platelets

    DOEpatents

    Zhamu, Aruna; Jang, Bor Z.

    2014-06-17

    A carboxylic-intercalated graphite compound composition for the production of exfoliated graphite, flexible graphite, or nano-scaled graphene platelets. The composition comprises a layered graphite with interlayer spaces or interstices and a carboxylic acid residing in at least one of the interstices, wherein the composition is prepared by a chemical oxidation reaction which uses a combination of a carboxylic acid and hydrogen peroxide as an intercalate source. Alternatively, the composition may be prepared by an electrochemical reaction, which uses a carboxylic acid as both an electrolyte and an intercalate source. Exfoliation of the invented composition does not release undesirable chemical contaminants into air or drainage.

  6. Synthesis and Characterization of Highly Intercalated Graphite Bisulfate

    NASA Astrophysics Data System (ADS)

    Salvatore, Marcella; Carotenuto, Gianfranco; De Nicola, Sergio; Camerlingo, Carlo; Ambrogi, Veronica; Carfagna, Cosimo

    2017-03-01

    Different chemical formulations for the synthesis of highly intercalated graphite bisulfate have been tested. In particular, nitric acid, potassium nitrate, potassium dichromate, potassium permanganate, sodium periodate, sodium chlorate, and hydrogen peroxide have been used in this synthesis scheme as the auxiliary reagent (oxidizing agent). In order to evaluate the presence of delamination, and pre-expansion phenomena, and the achieved intercalation degree in the prepared samples, the obtained graphite intercalation compounds have been characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray powder diffraction (XRD), infrared spectroscopy (FT-IR), micro-Raman spectroscopy ( μ-RS), and thermal analysis (TGA). Delamination and pre-expansion phenomena were observed only for nitric acid, sodium chlorate, and hydrogen peroxide, while the presence of strong oxidizers (KMnO4, K2Cr2O7) led to stable graphite intercalation compounds. The largest content of intercalated bisulfate is achieved in the intercalated compounds obtained from NaIO4 and NaClO3.

  7. Durability of Intercalated Graphite Epoxy Composites in Low Earth Orbit

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Davidson, Michelle L.; Shively, Rhonda

    1996-01-01

    The electrical conductivity of graphite epoxy composites can be substantially increased by intercalating (inserting guest atoms or molecules between the graphene planes) the graphite fibers before composite formation. The resulting high strength, low density, electrically conducting composites have been proposed for EMI shielding in spacecraft. Questions have been raised, however, about their durability in the space environment, especially with respect to outgassing of the intercalates, which are corrosive species such as bromine. To answer those concerns, six samples of bromine intercalated graphite epoxy composites were included in the third Evaluation of Oxygen Interaction with Materials (EOIM-3) experiment flown on the Space Shuttle Discovery (STS-46). Changes in electrical conductivity, optical reflectance, surface texture, and mass loss for SiO2 protected and unprotected samples were measured after being exposed to the LEO environment for 42 hours. SiO2 protected samples showed no degradation, verifying conventional protection strategies are applicable to bromine intercalated composites. The unprotected samples showed that bromine intercalation does not alter the degradation of graphite-epoxy composites. No bromine was detected to have been released by the fibers allaying fears that outgassing could be disruptive to the sensitive electronics the EMI shield is meant to protect.

  8. Revisiting the domain model for lithium intercalated graphite

    NASA Astrophysics Data System (ADS)

    Krishnan, Sridevi; Brenet, Gilles; Machado-Charry, Eduardo; Caliste, Damien; Genovese, Luigi; Deutsch, Thierry; Pochet, Pascal

    2013-12-01

    In this Letter, we study the stability of the domain model for lithium intercalated graphite in stages III and II by means of Density Functional Theory and Kinetic Lattice Monte Carlo simulations. We find that the domain model is either thermodynamically or kinetically stable when compared to the standard model in stages III and II. The existence of domains in the intercalation sequence is well supported by recent high resolution transmission electron microscope observations in lithiated graphite. Moreover, we predict that such domain staging sequences leads to a wide range of diffusivity as reported in experiments.

  9. Development of a high conductivity intercalated graphite composite wire

    NASA Astrophysics Data System (ADS)

    Singhal, S. C.

    1982-02-01

    Composite wires previously fabricated by swaging and claimed to possess conductivity equal to or greater than that of copper were analyzed. Intercalation of HOPG crystals with SbF5+HF mixtures was studied to assess the effect of defects in the starting graphite on the final conductivity and also to determine the conductivity as a function of the stage of the compound. Composite wires consisting of copper, aluminum or lead outer sheath and SbF5+HF-or AsF5-intercalated graphite in the core were fabricated by swaging and/or drawing and then analyzed for their electrical conductivity.

  10. Anisotropic Tuning of Graphite Thermal Conductivity by Lithium Intercalation.

    PubMed

    Qian, Xin; Gu, Xiaokun; Dresselhaus, Mildred S; Yang, Ronggui

    2016-11-17

    Understanding thermal transport in lithium intercalated layered materials is not only important for managing heat generation and dissipation in lithium ion batteries but also the understanding potentially provides a novel way to design materials with reversibly tunable thermal conductivity. In this work, the thermal conductivity of lithium-graphite intercalation compounds (LixC6) is calculated using molecular dynamics simulations as a function of the amount of lithium intercalated. We found that intercalation of lithium has an anisotropic effect on tuning the thermal conductivity: the thermal conductivity in the basal plane decreases monotonically from 1232 W/m·K of pristine graphite to 444 W/m·K of the fully lithiated LiC6, while the thermal conductivity along the c-axis decreases first from 6.5 W/m·K for graphite to 1.3 W/m·K for LiC18 and then increases to 5.0 W/m·K for LiC6 as the lithium composition increases. More importantly, we provide the very first atomic-scale insight into the effect of lithium intercalation on the spectral phonon properties of graphite. The intercalated lithium ions are found to suppress the phonon lifetime and to reduce the group velocity of phonons parallel to the basal plane but significantly to increase the phonon group velocity along the c-axis, which anisotropically tunes the thermal conductivity of lithiated graphite compounds. This work could shed some light on the search for tunable thermal conductivity materials and might have strong impacts on the thermal management of lithium ion batteries.

  11. Development of a high conductivity intercalated graphite composite wire

    SciTech Connect

    Singhal, S.C.

    1982-02-01

    Beginning in May 1979, the Department of Energy initiated the present program entitled, Development of a High Conductivity Intercalated Graphite Composite Wire, to develop the scientific base and technology for reproducibly fabricating high conductivity intercalated graphite composite wires. Toward achieving this objective, the following work was carried out in this program: (1) composite wires previously fabricated by swaging at the University of Pennsylvania and claimed to possess conductivity equal to or greater than that of copper were analyzed, (2) intercalation of HOPG crystals with SbF/sub 5/+HF mixtures was studied to assess the effect of defects in the starting graphite on the final conductivity and also to determine the conductivity as a function of the stage of the compound, and (3) composite wires consisting of copper, aluminum or lead outer sheath and SbF/sub 5/+HF- or AsF/sub 5/-intercalated graphite in the core were fabricated by swaging and/or drawing and then analyzed for their electrical conductivity.

  12. Magnetic Properties of CoCl2-Intercalated Graphite,

    DTIC Science & Technology

    1983-04-01

    Dresselhaus, in Intercalated Graphite, edited by M.S. Dresselhaus, G. Dresselhaus, J.E. Fischer and M.J. Moran, ( Elsiever , New York, 1983), vol. 20, p...G. Dresselhau JE. Fischer and M.J. Moran, ( Elsiever , New York, 1983), vol. 20, p. 213. 13. J. Tobochnik and G.V. Chester, Phys. Rev. B20, 3761 (1979

  13. Graphite intercalation compound with iodine as the major intercalant

    NASA Technical Reports Server (NTRS)

    Hung, Ching-Cheh; Kucera, Donald

    1992-01-01

    Halogenated CBr(sub x)I(sub y) (1 less than y/x less than 10) was made by exposing graphite materials with interplanar spacing in the 3.35 to 3.41 A range to either pure Br2 or an I2-Br2 mixture, and then to iodine vapor containing a small amount of Br2. The electrical resistivity of this product is from 3 to 6.5 times the pristine value. The presence of a small amount of isoprene rubber in the reaction significantly increased the iodine to bromine ratio in the product. In this reaction, rubber is known to generate HBr and to slowly remove bromine from the vapor. The halogenation generally caused a 22 to 25 percent weight increase. The halogens were found uniformly distributed in the product interior. However, although the surface contains very little iodine, it has high concentrations of bromine and oxygen. It is believed that the high concentrations of bromine and oxygen in this surface cause the halogenated fiber to be more resistant to fluorine attack during subsequent fluorination to fabricate graphite fluoride fibers.

  14. Reversible Intercalation of Fluoride-Anion Receptor Complexes in Graphite

    NASA Technical Reports Server (NTRS)

    West, William C.; Whitacre, Jay F.; Leifer, Nicole; Greenbaum, Steve; Smart, Marshall; Bugga, Ratnakumar; Blanco, Mario; Narayanan, S. R.

    2007-01-01

    We have demonstrated a route to reversibly intercalate fluoride-anion receptor complexes in graphite via a nonaqueous electrochemical process. This approach may find application for a rechargeable lithium-fluoride dual-ion intercalating battery with high specific energy. The cell chemistry presented here uses graphite cathodes with LiF dissolved in a nonaqueous solvent through the aid of anion receptors. Cells have been demonstrated with reversible cathode specific capacity of approximately 80 mAh/g at discharge plateaus of upward of 4.8 V, with graphite staging of the intercalant observed via in situ synchrotron X-ray diffraction during charging. Electrochemical impedance spectroscopy and B-11 nuclear magnetic resonance studies suggest that cointercalation of the anion receptor with the fluoride occurs during charging, which likely limits the cathode specific capacity. The anion receptor type dictates the extent of graphite fluorination, and must be further optimized to realize high theoretical fluorination levels. To find these optimal anion receptors, we have designed an ab initio calculations-based scheme aimed at identifying receptors with favorable fluoride binding and release properties.

  15. Preparation of graphite oxide by sodium cholate intercalation and sonication from Indonesian natural graphite

    NASA Astrophysics Data System (ADS)

    Panatarani, Camellia; Maulana, Ayu Oktama; Rianto, Anton; Joni, I. Made

    2016-02-01

    Graphite oxide is widely use in renewable energy application such as solar cells, fuel-cells, battery electrodes, catalyst support, etc. This paper reports the preparation of graphite oxide from Indonesian natural graphite by sodium cholate intercalation. The enrichment process of as received graphite with carbon content of 60% was carried out by using acid leaching (HF) method. The enrichment process successfully obtained graphite with carbon content 95.61% with contaminant minerals observed by EDS were magnesium and aluminum. Purified graphite was then intercalated by sodium cholate at various concentration and sonication time. The XRD results shows that preparation with concentration of sodium cholate 2 Wt.% and sonication 10 hours formed a peak characteristic of graphite oxide at 2θ=15°. In addition, the successful oxidation process designated by the C/O ratio of 15.75 observed from EDS and supported by the present of functional C-H and C-O obtained from the FTIR observation. It is concluded that the graphite oxide successfully prepared by intercalation using sodium cholate and sonication.

  16. Graphite intercalation compound with arsenic pentafluoride

    SciTech Connect

    Kozlov, S.P.; Nikonorov, Yu.I.

    1987-04-01

    A decrease in the electrical resistance of the graphite compound with arsenic pentafluoride of the composition C/sub 10.2/AsF/sub 5/ is observed in the 293-510/sup 0/K range. It was hypothesized that this is due to elimination of the weakly conducting fluorides in the compound. When C/sub 10.2/AsF/sub 5/ is treated with water and hydrogen fluoride, it decomposes.

  17. Dry synthesis of lithium intercalated graphite powders and carbon fibers

    SciTech Connect

    Sacci, Robert L; Adamczyk, Leslie A; Veith, Gabriel M; Dudney, Nancy J

    2014-01-01

    Herein we describe the direct synthesis of lithium intercalated graphite by heating under vacuum or ball milling under pressurized Ar(g). Both methods allow for stoichometric control of Li-C ratio in batter-grade graphites and carbon fibers prior formation of a solid electrolyte interphase. The products' surface chemistries, as probed by XPS, suggest that LiC6 are extremely reactive with trace amounts of moisture or oxygen. The open circuit potential and SEM data show that the reactivity of the lithiated battery-grade graphite and the carbon fiber can be related to the density of edge/defect sites on the surfaces. Preliminary results of spontaneous SEI formation on Li-graphite in electrolyte are also given.

  18. Sulfuric acid intercalated graphite oxide for graphene preparation.

    PubMed

    Hong, Yanzhong; Wang, Zhiyong; Jin, Xianbo

    2013-12-06

    Graphene has shown enormous potential for innovation in various research fields. The current chemical approaches based on exfoliation of graphite via graphite oxide (GO) are potential for large-scale synthesis of graphene but suffer from high cost, great operation difficulties, and serious waste discharge. We report a facile preparation of graphene by rapid reduction and expansion exfoliation of sulfuric acid intercalated graphite oxide (SIGO) at temperature just above 100°C in ambient atmosphere, noting that SIGO is easily available as the immediate oxidation descendent of graphite in sulfuric acid. The oxygenic and hydric groups in SIGO are mainly removed through dehydration as catalyzed by the intercalated sulfuric acid (ISA). The resultant consists of mostly single layer graphene sheets with a mean diameter of 1.07 μm after dispersion in DMF. This SIGO process is reductant free, easy operation, low-energy, environmental friendly and generates graphene with low oxygen content, less defect and high conductivity. The provided synthesis route from graphite to graphene via SIGO is compact and readily scalable.

  19. Intercalated graphite fiber composites as EMI shields in aerospace structures

    NASA Technical Reports Server (NTRS)

    Gaier, James R.

    1990-01-01

    The requirements for electromagnetic interference (EMI) shielding in aerospace structures are complicated over that of ground structures by their weight limitations. As a result, the best EMI shielding materials must blend low density, high strength, and high elastic modulus with high shielding ability. In addition, fabrication considerations including penetrations and joints play a major role. The EMI shielding properties are calculated for shields formed from pristine and intercalated graphite fiber/epoxy composites and compared to preliminary experimental results and to shields made from aluminum. Calculations indicate that EMI shields could be fabricated from intercalated graphite composites which would have less than 12 percent of the mass of conventional aluminum shields, based on mechanical properties and shielding properties alone.

  20. Technological hurdles to the application of intercalated graphite fibers

    NASA Technical Reports Server (NTRS)

    Gaier, James R.

    1988-01-01

    Before intercalated graphite fibers can be developed as an effective power material, there are several technological hurdles which must be overcome. These include the environmental stability, homogeneity and bulk properties, connection procedures, and costs. Strides were made within the last several years in stability and homogeneity of intercalated graphite fibers. Bulk properties and connection procedures are areas of active research now. Costs are still prohibitive for all but the most demanding applications. None of these problems, however, appear to be unsolvable, and their solution may result in wide spread GOC application. The development of a relatively simple technology application, such as EMI shielding, would stimulate the solution of scale-up problems. Once this technology is developed, then more demanding applications, such as power bus bars, may be possible.

  1. An enhanced hydrogen adsorption enthalpy for fluoride intercalated graphite compounds.

    PubMed

    Cheng, Hansong; Sha, Xianwei; Chen, Liang; Cooper, Alan C; Foo, Maw-Lin; Lau, Garret C; Bailey, Wade H; Pez, Guido P

    2009-12-16

    We present a combined theoretical and experimental study on H(2) physisorption in partially fluorinated graphite. This material, first predicted computationally using ab initio molecular dynamics simulation and subsequently synthesized and characterized experimentally, represents a novel class of "acceptor type" graphite intercalated compounds that exhibit significantly higher isosteric heat of adsorption for H(2) at near ambient temperatures than previously demonstrated for commonly available porous carbon-based materials. The unusually strong interaction arises from the semi-ionic nature of the C-F bonds. Although a high H(2) storage capacity (>4 wt %) at room temperature is predicted not to be feasible due to the low heat of adsorption, enhanced storage properties can be envisaged by doping the graphitic host with appropriate species to promote higher levels of charge transfer from graphene to F(-) anions.

  2. Atomic intercalation to measure adhesion of graphene on graphite

    DOE PAGES

    Wang, Jun; Sorescu, Dan C.; Jeon, Seokmin; ...

    2016-10-31

    The interest in mechanical properties of layered and 2D materials has reemerged in light of device concepts that take advantage of flexing, adhesion and friction in such systems. Here we provide an effective measurement of the nanoscale elastic adhesion of a graphene sheet atop highly ordered pyrolytic graphite (HOPG) based on the analysis of atomic intercalates in graphite. Atomic intercalation is carried out using conventional ion sputtering, creating blisters in the top-most layer of the HOPG surface. Scanning tunneling microscopy coupled with image analysis and density functional theory are used to reconstruct the atomic positions and the strain map withinmore » the deformed graphene sheet, as well as to demonstrate subsurface diffusion of the ions creating such blisters. To estimate the adhesion energy we invoke an analytical model originally devised for macroscopic deformations of graphene. This model yields a value of 0.221 ± 0.011 J/m-2 for the adhesion energy of graphite, which is in surprisingly good agreement with reported experimental and theoretical values. This implies that macroscopic mechanical properties of graphene scale down to at least a few nanometers length. The simplicity of our method, compared to the macroscale characterization, enables analysis of elastic mechanical properties in two-dimensional layered materials and provides a unique opportunity to investigate the local variability of mechanical properties on the nanoscale.« less

  3. Atomic intercalation to measure adhesion of graphene on graphite

    SciTech Connect

    Wang, Jun; Sorescu, Dan C.; Jeon, Seokmin; Belianinov, Alex; Kalinin, Sergei V.; Baddorf, Arthur P.; Maksymovych, Petro

    2016-10-31

    The interest in mechanical properties of layered and 2D materials has reemerged in light of device concepts that take advantage of flexing, adhesion and friction in such systems. Here we provide an effective measurement of the nanoscale elastic adhesion of a graphene sheet atop highly ordered pyrolytic graphite (HOPG) based on the analysis of atomic intercalates in graphite. Atomic intercalation is carried out using conventional ion sputtering, creating blisters in the top-most layer of the HOPG surface. Scanning tunneling microscopy coupled with image analysis and density functional theory are used to reconstruct the atomic positions and the strain map within the deformed graphene sheet, as well as to demonstrate subsurface diffusion of the ions creating such blisters. To estimate the adhesion energy we invoke an analytical model originally devised for macroscopic deformations of graphene. This model yields a value of 0.221 ± 0.011 J/m-2 for the adhesion energy of graphite, which is in surprisingly good agreement with reported experimental and theoretical values. This implies that macroscopic mechanical properties of graphene scale down to at least a few nanometers length. The simplicity of our method, compared to the macroscale characterization, enables analysis of elastic mechanical properties in two-dimensional layered materials and provides a unique opportunity to investigate the local variability of mechanical properties on the nanoscale.

  4. Superconductivity in the Graphite Intercalation Compound BaC(6).

    PubMed

    Heguri, Satoshi; Kawade, Naoya; Fujisawa, Takumi; Yamaguchi, Akira; Sumiyama, Akihiko; Tanigaki, Katsumi; Kobayashi, Mototada

    2015-06-19

    Among many two-dimensional (2D) high T(C) superconductors, graphite intercalation compounds (GICs) are the most famous intercalation family, which are classified as typical electron-phonon mediated superconductors. We show unambiguous experimental facts that BaC(6), the superconductivity of which has been missing for many years so far among various alkaline earth metal (Ca, Sr, and Ba) intercalted GICs, exhibits superconductivity at T(C)=65  mK. By adding this finding as the additional experimental point, a complete figure displaying the relationship between T(C) and interlayer distance (d) for GICs is now provided, and their possible superconducting mechanisms raised so far are revisited. The present study settles a long-running debate between theories and experiments on the superconductivity in the first stage GICs.

  5. Superconductivity in the Graphite Intercalation Compound BaC 6

    NASA Astrophysics Data System (ADS)

    Heguri, Satoshi; Kawade, Naoya; Fujisawa, Takumi; Yamaguchi, Akira; Sumiyama, Akihiko; Tanigaki, Katsumi; Kobayashi, Mototada

    2015-06-01

    Among many two-dimensional (2D) high TC superconductors, graphite intercalation compounds (GICs) are the most famous intercalation family, which are classified as typical electron-phonon mediated superconductors. We show unambiguous experimental facts that BaC 6 , the superconductivity of which has been missing for many years so far among various alkaline earth metal (Ca, Sr, and Ba) intercalted GICs, exhibits superconductivity at TC=65 mK . By adding this finding as the additional experimental point, a complete figure displaying the relationship between TC and interlayer distance (d ) for GICs is now provided, and their possible superconducting mechanisms raised so far are revisited. The present study settles a long-running debate between theories and experiments on the superconductivity in the first stage GICs.

  6. The 13C nuclear magnetic resonance in graphite intercalation compounds

    NASA Technical Reports Server (NTRS)

    Tsang, T.; Resing, H. A.

    1985-01-01

    The (13)C NMR chemical shifts of graphite intercalation compounds were calculated. For acceptor types, the shifts come mainly from the paramagnetic (Ramsey) intra-atomic terms. They are related to the gross features of the two-dimensional band structures. The calculated anisotropy is about -140 ppm and is independent of the finer details such as charge transfer. For donor types, the carbon 2p pi orbitals are spin-polarized because of mixing with metal conduction electrons, thus there is an additional dipolar contribution which may be correlated with the electronic specific heat. The general agreement with experimental data is satisfactory.

  7. C-13 nuclear magnetic resonance in graphite intercalation compounds

    NASA Technical Reports Server (NTRS)

    Tsang, T.; Resing, H. A.

    1985-01-01

    The C-13 NMR chemical shifts of graphite intercalation compounds have been calculated. For acceptor types, the shifts come mainly from the paramagnetic (Ramsey) intra-atomic terms. They are related to the gross features of the two-dimensional band structures. The calculated anisotropy is about - 140 ppm and is independent of the finer details such as charge transfer. For donor types, the carbon 2p pi orbitals are spin-polarized because of mixing with metal-conduction electrons, thus there is an additional dipolar contribution which may be correlated with the electronic specific heat. The general agreement with experimental data is satisfactory.

  8. Atomic intercalation to measure adhesion of graphene on graphite

    NASA Astrophysics Data System (ADS)

    Wang, Jun; Sorescu, Dan C.; Jeon, Seokmin; Belianinov, Alexei; Kalinin, Sergei V.; Baddorf, Arthur P.; Maksymovych, Petro

    2016-10-01

    The interest in mechanical properties of two-dimensional materials has emerged in light of new device concepts taking advantage of flexing, adhesion and friction. Here we demonstrate an effective method to measure adhesion of graphene atop highly ordered pyrolytic graphite, utilizing atomic-scale `blisters' created in the top layer by neon atom intercalates. Detailed analysis of scanning tunnelling microscopy images is used to reconstruct atomic positions and the strain map within the deformed graphene layer, and demonstrate the tip-induced subsurface translation of neon atoms. We invoke an analytical model, originally devised for graphene macroscopic deformations, to determine the graphite adhesion energy of 0.221+/-0.011 J m-2. This value is in excellent agreement with reported macroscopic values and our atomistic simulations. This implies mechanical properties of graphene scale down to a few-nanometre length. The simplicity of our method provides a unique opportunity to investigate the local variability of nanomechanical properties in layered materials.

  9. Resistivity of pristine and intercalated graphite fiber epoxy composites

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Hambourger, Paul D.; Slabe, Melissa E.

    1991-01-01

    Laminar composites were fabricated from pristine and bromine intercalated Amoco P-55, P-75, and P-100 graphite fibers and Hysol-Grafil EAG101-1 film epoxy. The thickness and r.f. eddy current resistivity of several samples were measured at grid points and averaged point by point to obtain final values. Although the values obtained this way have high precision (less than 3 percent deviation), the resistivity values appear to be 20 to 90 percent higher than resistivities measured on high aspect ratio samples using multi-point techniques, and by those predicted by theory. The temperature dependence of the resistivity indicates that the fibers are neither damaged nor deintercalated by the composite fabrication process. The resistivity of the composites is a function of sample thickness (i.e., resin content). Composite resistivity is dominated by fiber resistivity, so lowering the resistivity of the fibers, either through increased graphitization or intercalation, results in a lower composite resistivity. A modification of the simple rule of mixtures model appears to predict the conductivity of high aspect ratio samples measured along a fiber direction, but a directional dependence appears which is not predicted by the theory. The resistivity of these materials is clearly more complex than that of homogeneous materials.

  10. Resistivity of pristine and intercalated graphite fiber epoxy composites

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Hambourger, Paul D.; Slabe, Melissa E.

    1989-01-01

    Laminar composites were fabricated from pristine and bromine intercalated Amoco P-55, P-75, and P-100 graphite fibers and Hysol-Grafil EAG101-1 film epoxy. The thickness and r.f. eddy current resistivity of several samples were measured at grid points and averaged point by point to obtain final values. Although the values obtained this way have high precision (less than 3 percent deviation), the resistivity values appear to be 20 to 90 percent higher than resistivities measured on high aspect ratio samples using multi-point techniques, and by those predicted by theory. The temperature dependence of the resistivity indicates that the fibers are neither damaged nor deintercalated by the composite fabrication process. The resistivity of the composites is a function of sample thickness (i.e., resin content). Composite resistivity is dominated by fiber resistivity, so lowering the resistivity of the fibers, either through increased graphitization or intercalation, results in a lower composite resistivity. A modification of the simple rule of mixtures model appears to predict the conductivity of high aspect ratio samples measured along a fiber direction, but a directional dependence appears which is not predicted by the theory. The resistivity of these materials is clearly more complex than that of homogeneous materials.

  11. Atomic intercalation to measure adhesion of graphene on graphite

    PubMed Central

    Wang, Jun; Sorescu, Dan C.; Jeon, Seokmin; Belianinov, Alexei; Kalinin, Sergei V.; Baddorf, Arthur P.; Maksymovych, Petro

    2016-01-01

    The interest in mechanical properties of two-dimensional materials has emerged in light of new device concepts taking advantage of flexing, adhesion and friction. Here we demonstrate an effective method to measure adhesion of graphene atop highly ordered pyrolytic graphite, utilizing atomic-scale ‘blisters' created in the top layer by neon atom intercalates. Detailed analysis of scanning tunnelling microscopy images is used to reconstruct atomic positions and the strain map within the deformed graphene layer, and demonstrate the tip-induced subsurface translation of neon atoms. We invoke an analytical model, originally devised for graphene macroscopic deformations, to determine the graphite adhesion energy of 0.221±0.011 J m−2. This value is in excellent agreement with reported macroscopic values and our atomistic simulations. This implies mechanical properties of graphene scale down to a few-nanometre length. The simplicity of our method provides a unique opportunity to investigate the local variability of nanomechanical properties in layered materials. PMID:27796294

  12. Atomic intercalation to measure adhesion of graphene on graphite.

    PubMed

    Wang, Jun; Sorescu, Dan C; Jeon, Seokmin; Belianinov, Alexei; Kalinin, Sergei V; Baddorf, Arthur P; Maksymovych, Petro

    2016-10-31

    The interest in mechanical properties of two-dimensional materials has emerged in light of new device concepts taking advantage of flexing, adhesion and friction. Here we demonstrate an effective method to measure adhesion of graphene atop highly ordered pyrolytic graphite, utilizing atomic-scale 'blisters' created in the top layer by neon atom intercalates. Detailed analysis of scanning tunnelling microscopy images is used to reconstruct atomic positions and the strain map within the deformed graphene layer, and demonstrate the tip-induced subsurface translation of neon atoms. We invoke an analytical model, originally devised for graphene macroscopic deformations, to determine the graphite adhesion energy of 0.221±0.011 J m(-2). This value is in excellent agreement with reported macroscopic values and our atomistic simulations. This implies mechanical properties of graphene scale down to a few-nanometre length. The simplicity of our method provides a unique opportunity to investigate the local variability of nanomechanical properties in layered materials.

  13. Hydrogen Adsorption by Alkali Metal Graphite Intercalation Compounds

    NASA Astrophysics Data System (ADS)

    Purewal, Justin

    Adsorption occurs whenever a solid surface is exposed to a gas or liquid, and is characterized by an increase in fluid density near the interface. Adsorbents have drawn attention in the current effort to engineer materials that store hydrogen at high densities within moderate temperature and pressure regimes. Carbon adsorbents are a logical choice as a storage material due to their low costs and large surface areas. Unfortunately, carbon adsorbents suffer from a low binding enthalpy for H2 (about 5 kJ mol-1), well below the 15 to 18 kJ mol-1) that is considered optimal for hydrogen storage systems. Binding interactions can be increased by the following methods: (1) adjusting the graphite interplanar separation with a pillared structure, and (2) introducing dopant species that interact with H2 molecules by strong electrostatic forces. Graphite intercalation compounds are a class of materials that contain both pillared structures and chemical dopants, making them an excellent model system for studying the fundamentals of hydrogen adsorption in nanostructured carbons. Pressure-composition-temperature diagrams of the MC24(H 2)x graphite intercalation compounds were measured for M = (K, Rb, Cs). Adsorption enthalpies were measured as a function of H2 concentration. Notably, CsC24 had an average adsorption enthalpy of 14.9 kJ mol-1), nearly three times larger than that of pristine graphite. The adsorption enthalpies were found to be positively correlated with the alkali metal size. Adsorption capacities were negatively correlated with the size of the alkali metal. The rate of adsorption is reduced at large H2 compositions, due to the effects of site-blocking and correlation on the H2 diffusion. The strong binding interaction and pronounced molecular-sieving behavior of KC24 is likely to obstruct the translational diffusion of adsorbed H2 molecules. In this work, the diffusion of H2 adsorbed in KC24 was studied by quasielastic neutron scattering measurements and molecular

  14. Micromechanical properties of intercalated compounds of graphite oxide with dodecahydro- closo-dodecaboric acid

    NASA Astrophysics Data System (ADS)

    Karpenko, A. A.; Saldin, V. I.

    2016-08-01

    The micromechanical properties (Young's modulus, deformation, and adhesion) of the intercalated compound of graphite oxide with dodecahydro- closo-dodecaboric acid were studied by atomic force microscopy, transmission electron microscopy, and Raman spectroscopy and compared with the same characteristics of the starting graphite oxide. The significant difference in the micromechanical properties of the materials under study is dictated by differences in the topography and properties of their film surface, which, in turn, can be determined by their chemical composition. The introduction of dodecahydro- closo-dodecaboric acid in the interplanar space of graphite oxide affects the structuring of the latter. A considerable increase in the adhesion of the intercalated compound relative to that of oxide graphite is explained by high adhesive properties of the introduced acid, the Young's modulus of graphite oxide being higher than that of the intercalated compound. This was attributed to the high hydrophilicity of dodecahydro- closo-dodecaboric acid and the difficulty of water removal from the interplanar space; water plasticizes the material, which becomes softer than graphite oxide. The difference in the structure of the coating of the intercalated compounds and the starting graphite oxide was found to be also reflected by their Raman spectra, namely, by the increased intensity of the D line with the preserved position of the G line, which points to the impurity nature of the intercalate and the unchanged hexagonal lattice of graphite.

  15. Ferric chloride-graphite intercalation compounds as anode materials for Li-ion batteries.

    PubMed

    Wang, Lili; Zhu, Yongchun; Guo, Cong; Zhu, Xiaobo; Liang, Jianwen; Qian, Yitai

    2014-01-01

    Ferric chloride-graphite intercalation compounds (FeCl3 -GICs) with stage 1 and stage 2 structures were synthesized by reacting FeCl3 and expanded graphite (EG) in air in a stainless-steel autoclave. As rechargeable Li-ion batteries, these FeCl3 -GICs exhibit high capacity, excellent cycling stability, and superior rate capability, which could be attributed to their unique intercalation features. This work may enable new possibilities for the fabrication of Li-ion batteries.

  16. Optical properties of NbCl5 and ZnMg intercalated graphite compounds

    NASA Astrophysics Data System (ADS)

    Jung, Eilho; Lee, Seokbae; Roh, Seulki; Meng, Xiuqing; Tongay, Sefaattin; Kang, Jihoon; Park, Tuson; Hwang, Jungseek

    2014-12-01

    We studied NbCl5 and ZnMg alloy intercalated graphite compounds using an optical spectroscopy technique. These intercalated metallic graphite samples were quite challenging to obtain optical reflectance spectra since they were not flat and quite thin. By using both a new method and an in situ gold evaporation technique we were able to obtain reliable reflectance spectra of our samples in the far and mid infrared range (80-7000 cm-1). We extracted the optical constants including the optical conductivity and the dielectric function from the measured reflectance spectra using a Kramers-Kronig analysis. We also extracted the dc conductivity and the plasma frequencies from the optical conductivity and dielectric functions. NbCl5 intercalated graphite samples show similar optical conductivity spectra as bare highly oriented pyrolytic graphite even though there are some differences in detail. ZnMg intercalated samples show significantly different optical conductivity spectra from the bare graphite. Optical spectroscopy is one of the most reliable experimental techniques to obtain the electronic band structures of materials. The obtained optical conductivities support the recent theoretically calculated electronic band structures of NbCl5 and ZnMg intercalated graphite compounds. Our results also provide important information of electronic structures and charge carrier properties of these two new intercalated materials for applications.

  17. A micrographic and gravimetric study of intercalation and deintercalation of graphite fibers

    NASA Technical Reports Server (NTRS)

    Hung, C. C.

    1985-01-01

    Intercalation and deintercalation of Union Carbide P-100 graphite fibers with liquid and vaporous bromine was studied gravimetrically and microscopically. The mass of the bromine intercalated fibers was found to be 17 to 20 percent greater than their pristine counterpart. This variation decreased to 17 to 18 percent after heating in air for 3 days at 200 C and to 14.5 to 18 percent after 6 days of 260 C heating. The fiber length did not change throughout the experiment. The fiber diameter increased during intercalation and decreased slightly upon deintercalation but was not affected by heating to 260 C for 3 days in air. Comparing the mass and volume data to those with highly oriented pyrolitic graphite or natural single crystal graphite suggested the possibility that the intercalated P-100 fibers could be mostly stage 4.

  18. Effect of lightning strike on bromine intercalated graphite fiber/epoxy composites

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Slabe, Melissa E.; Brink, Norman O.

    1991-01-01

    Laminar composites were fabricated from pristine and bromine intercalated pitch based graphite fibers. It was found that laminar composites could be fabricated using either pristine or intercalated graphite fibers using standard fabrication techniques. The intercalated graphite fiber composites had electrical properties which were markedly improved over both the corresponding pitch based and polyacrylonitrile (PAN) based composites. Despite composites resistivities more than an order of magnitude lower for pitch based fiber composites, the lightning strike resistance was poorer than that of the Pan based fiber composites. This leads to the conclusion that the mechanical properties of the pitch fibers are more important than electrical or thermal properties in determining the lightning strike resistance. Based on indicated lightning strike tolerance for high elongation to failure materials, the use of vapor grown, rather than pitch based graphite fibers appears promising.

  19. Electronic Properties of Ferric Chloride Intercalated Graphite Compounds

    NASA Astrophysics Data System (ADS)

    Powers, Robert E., Jr.

    This dissertation reports electronic transport measurements on ferric chloride (FeCl_3) graphite intercalation compounds (GIC's). The c-axis conductivity is measured as a function of temperature from 1K to 293K in various stages of FeCl _3 acceptor GIC's and there are marked changes in the behavior of the conductivity as a function of stage. An attempt is made to explain these results on the basis of current theories of c-axis conduction in GIC's, notably the various hopping mechanisms assisted by phonons and impurities in parallel with band conduction. The in-plane resistivity of various stages of FeCl_3 GIC's at temperatures from 1K to 293K is measured and it is found that the absolute conductivity is enhanced from that of highly-oriented pyrolytic graphite and that the temperature behavior is metal-like and stage dependent. The hall effect and magnetoresistance of the samples are measured at low and high applied magnetic fields (up to 20T) and at various fixed point temperatures (1K, 4K, 77K, and 293K). Besides qualitative features obtained from these measurements such as the sign of the predominant carrier and the shape of the fermi surface, the Lorentz -Drude Single Carrier Model is used to obtain the carrier densities and mobilities as a function of stage. Shubnikov-deHaas (SdH) oscillations are observed in the samples at high field and at various temperatures from 1K to about 30K. The data are used to determine the effective carrier masses, relaxation times, and mobilities for some stages. DeHaas-VanAlphen oscillations are also observed in the AC susceptibility in independently measured samples. The frequencies observed are comparable to those observed in the SdH measurements but in the cases of both types of measurements, frequencies which are present in some samples are not found in others. The data is in good agreement with previous preliminary measurements by other investigators. ftn*All degree requirements completed in 1993, but degree will be granted

  20. Dramatic reduction of chemical sputtering of graphite under intercalation of lithium

    NASA Astrophysics Data System (ADS)

    Yagi, H.; Toyoda, H.; Sugai, H.

    2003-03-01

    In previous studies, in situ deposition of a lithium thin layer onto graphite was found to considerably suppress physical sputtering of graphite, owing to rapid diffusion of Li into graphite bulk (so-called intercalation). This paper reports that the Li intercalation dramatically reduces graphite chemical sputtering as well, once the Li-deposited surface is cleaned by hydrogen plasma. This is evidenced in a small-scale plasma experiment on the Li-deposited graphite in hydrogen glow, comparing with an ultra-high-vacuum beam experiment. In the latter experiment, energy-controlled H 2+ beam is irradiated on a Li-deposited graphite sample where methane yield is measured together with in situ surface analysis of graphite by X-ray photoelectron spectroscopy. Both the plasma experiment and the beam experiment showed similar temporal variations of methane yield after the hydrogen exposure of the Li-deposited graphite. Namely, the methane yield gradually decreases down to a negligible level compared with the pure graphite case. The XPS analysis of surface atoms (O, C, Li) suggests that the hydrogen plasma exposure gives rise to removal of Li-containing impurities on the graphite surface. As a consequence, the hydrogen glow conditioning results in an almost complete suppression of chemical erosion of graphite below 500 K.

  1. Biopolymer-modified graphite oxide nanocomposite films based on benzalkonium chloride-heparin intercalated in graphite oxide

    NASA Astrophysics Data System (ADS)

    Meng, Na; Zhang, Shuang-Quan; Zhou, Ning-Lin; Shen, Jian

    2010-05-01

    Heparin is a potent anticoagulant agent that interacts strongly with antithrombin III to prevent the formation of fibrin clots. In the present work, poly(dimethylsiloxane)(PDMS)/graphite oxide-benzalkonium chloride-heparin (PDMS/modified graphite oxide) nanocomposite films were obtained by the solution intercalation technique as a possible drug delivery system. The heparin-benzalkonium chloride (BAC-HEP) was intercalated into graphite oxide (GO) layers to form GO-BAC-HEP (modified graphite oxide). Nanocomposite films were characterized by XRD, SEM, TEM, ATR-FTIR and TGA. The modified graphite oxide was observed to be homogeneously dispersed throughout the PDMS matrix. The effect of modified graphite oxide on the mechanical properties of the nanocomposite film was investigated. When the modified graphite oxide content was lower than 0.2 wt%, the nanocomposites showed excellent mechanical properties. Furthermore, nanocomposite films become delivery systems that release heparin slowly to make the nanocomposite films blood compatible. The in vitro studies included hemocompatibility testing for effects on platelet adhesion, platelet activation, plasma recalcification profiles, and hemolysis. Results from these studies showed that the anticoagulation properties of PDMS/GO-BCA-HEP nanocomposite films were greatly superior to those for no treated PDMS. Cell culture assay indicated that PDMS/GO-BCA-HEP nanocomposite films showed enhanced cell adhesion.

  2. The Study of Band Structure of Graphite Intercalation Compound Containing Sodium Calculated Using Density Functional Theory

    NASA Astrophysics Data System (ADS)

    Nazrul Rosli, Ahmad; Fatimah Wahab, Izzati; Zabidi, Noriza Ahmad; Abu Kassim, Hasan

    2015-06-01

    Sodium intercalation in graphite (GIC-Na) was investigated by the first principle calculation. The structure of GIC-Na was calculated using density functional theory (DFT) with the aid of CASTEP module of Material Studio. The exchange correlation functional has been treat by local density approximation (LDA) and generalized gradient approximation (GGA). It was shown that, unlike potassium GIC and lithium GIC, the band gap of GIC-Na was not induced and has same value of band gap with bulk graphite.

  3. Vacuum-Deposited Porphyrin Protective Films on Graphite: Electrochemical Atomic Force Microscopy Investigation during Anion Intercalation.

    PubMed

    Yivlialin, Rossella; Bussetti, Gianlorenzo; Penconi, Marta; Bossi, Alberto; Ciccacci, Franco; Finazzi, Marco; Duò, Lamberto

    2017-02-01

    The development of graphene products promotes a renewed interest toward the use of graphite in addition to the historical one for its proven viability as battery electrode. However, when exposed to harsh conditions, the graphite surface ages in ways that still need to be fully characterized. In applications to batteries, to optimize the electrode performances in acid solutions, different surface functionalizations have been studied. Among them, aromatic molecules have been recently proposed. In this communication, we report on the protective effect exerted by a physical-vapor-deposited porphyrin layer. Metal-free tetra-phenyl-porphyrins were deposited on a highly oriented pyrolytic graphite crystal to study the modifications that occur during anion intercalation in graphite. The graphite electrode was plunged in an electrolyte solution of 1 M sulfuric acid and subjected to cyclic voltammetry. The results indicate that blister formation, the characteristic swelling of graphite surface induced by anion intercalation, is significantly perturbed by the porphyrin overlayer; the process is inhibited in those areas where the protective porphyrin film is present. We ascribe the inhibition of the anion intercalation to the protective porphyrin wetting layer.

  4. Structural and Kinetic Properties of Graphite Intercalation Compounds

    DTIC Science & Technology

    1982-08-21

    the crystal is heated. the pressure within thC cracks will increase as the intercalate takes on a more gaseous character. Higashida and Kamada...flat crack may open to form a bubble. We propose that the latter fracture mode is responsible for the expansion observed in exfoliation. Higashida and...the crack growth stops rather than propagati:n ca’.astrophical1y to the crystal edge.) Although the analysis of Higashida and Kamada was developed for

  5. Structure and Properties of Intercalated Graphite Fiber-Polymer Composites.

    DTIC Science & Technology

    1983-07-07

    chlorine [7] nor aluminum chloride alone inter- calate graphite strongly suggests the participation of a Friedel - Crafts com- plex. One can then argue [1...reagent that has been alluded to in many of the Friedel - Crafts reactions, for instance, protolysis of alkanes to alkylcar- bonium ions [8]. We recently

  6. Experimental phase diagram of lithium-intercalated graphite

    SciTech Connect

    Woo, K.C.; Mertwoy, H.; Fischer, J.E.; Kamitakahara, W.A.; Robinson, D.S.

    1983-06-15

    First-order transitions to dilute stage 1 from stages 2--4 and from mixed stages are observed in Li-graphite compounds in the range 430--1020 K. The resulting (T,x) phase boundary agrees generally with predictions by Safran and others except for a sharp peak of very stable stage-2 compositions around xapprox.0.4. The commensurability energy does not contribute to this peak since both low-T and high-T phases are disordered.

  7. Structural and Kinetic Properties of Graphite Intercalation Compounds

    DTIC Science & Technology

    1983-04-29

    character. Higashida and Kamada [21J analyzed the stress distribution around pressurized penny-shaped cracks in graphite near a free surface and concluded...observed in exfoliation. Higashida and Kamada found that the internal pressure necessary for fracture by either mode increased as the crack diameter...Although the analysis of Higashida and Kamada was developed for cracks near a surface, it is reasonable to assume that. due to the interaction of stress

  8. The staging mechanism of AlCl4 intercalation in a graphite electrode for an aluminium-ion battery.

    PubMed

    Bhauriyal, Preeti; Mahata, Arup; Pathak, Biswarup

    2017-03-15

    Identifying a suitable electrode material with desirable electrochemical properties remains a primary challenge for rechargeable Al-ion batteries. Recently an ultrafast rechargeable Al-ion battery was reported with high charge/discharge rate, (relatively) high discharge voltage and high capacity that uses a graphite-based cathode. Using calculations from first-principles, we have investigated the staging mechanism of AlCl4 intercalation into bulk graphite and evaluated the stability, specific capacity and voltage profile of AlCl4 intercalated compounds. Ab initio molecular dynamics is performed to investigate the thermal stability of AlCl4 intercalated graphite structures. Our voltage profiles show that the first AlCl4 intercalation step could be a more sluggish step than the successive intercalation steps. However, the diffusion of AlCl4 is very fast in the expanded graphite host layers with a diffusion barrier of ∼0.01 eV, which justifies the ultrafast charging rate of a graphite based Al-ion battery. And such an AlCl4 intercalated battery provides an average voltage of 2.01-2.3 V with a maximum specific capacity of 69.62 mA h g(-1), which is excellent for anion intercalated batteries. Our density of states and Bader charge analysis shows that the AlCl4 intercalation into the bulk graphite is a charging process. Hence, we believe that our present study will be helpful in understanding the staging mechanism of AlCl4 intercalation into graphite-like layered electrodes for Al-ion batteries, thus encouraging further experimental work.

  9. Observation of Landau levels in potassium-intercalated graphite under a zero magnetic field.

    PubMed

    Guo, Donghui; Kondo, Takahiro; Machida, Takahiro; Iwatake, Keigo; Okada, Susumu; Nakamura, Junji

    2012-01-01

    The charge carriers in graphene are massless Dirac fermions and exhibit a relativistic Landau-level quantization in a magnetic field. Recently, it has been reported that, without any external magnetic field, quantized energy levels have been also observed from strained graphene nanobubbles on a platinum surface, which were attributed to the Landau levels of massless Dirac fermions in graphene formed by a strain-induced pseudomagnetic field. Here we show the generation of the Landau levels of massless Dirac fermions on a partially potassium-intercalated graphite surface without applying external magnetic field. Landau levels of massless Dirac fermions indicate the graphene character in partially potassium-intercalated graphite. The generation of the Landau levels is ascribed to a vector potential induced by the perturbation of nearest-neighbour hopping, which may originate from a strain or a gradient of on-site potentials at the perimeters of potassium-free domains.

  10. The effect of length and diameter on the resistivity of bromine intercalated graphite fibers

    NASA Technical Reports Server (NTRS)

    Gaier, James R.

    1989-01-01

    The resistivity of bromine intercalated graphite fibers has been shown to vary with both the diameter and the length of the fibers. This is due to bromine depletion from the fiber surface. Model calculations assuming a 1.0 micron bromine depletion zone for P-100, and 3.0 microns for vapor-grown graphite fibers fit the respective diameter dependence of their resistivities quite well. Length dependence data imply a bromine depletion zone along the length of P-100 fibers which is also a few microns, but that of vapor grown fibers appears to be as large as 300 microns. Despite these values, microfilaments, which are much smaller than the expected depletion zones, do form residual bromine intercalation compounds with resistivities about one-half of their pristine value.

  11. Bidimensional intercalation of Ge between SiC(0001) and a heteroepitaxial graphite top layer

    SciTech Connect

    Kubler, L.; Dentel, D.; Bischoff, J.-L.; Derivaz, M.; Aiet-Mansour, K.; Diani, M.

    2005-09-15

    High temperature annealing of 4H- or 6H-SiC(0001) crystals is well known to desorb Si from the surface and to generate a C-rich (6{radical}3x6{radical}3)R30 deg. (6{radical}3) reconstruction explained as a graphite monolayer in heteroepitaxial registry with the substrate. Ge deposition at room temperature and in the monolayer range on this graphitized reconstruction results in Ge islands. Using a number of surface techniques, we follow subsequent Ge morphology evolutions as a function of isochronal post-annealing treatments at increasing temperatures. In a particular temperature window Ge reacts with the substrate by diffusion under the graphite planes and wets the Si-terminated SiC surface. In spite of this bidimensional insertion of a Ge layer, the epitaxial relationship between the SiC substrate and the graphite is maintained as shown by very clear graphite-(1x1) LEED or RHEED patterns. They denote extended and well-ordered graphite planes at the surface of a graphite/Ge/SiC heterostructure. XPS analyses reveal a complete passivation of the intercalated Ge layer against oxidation by the overlying graphite sheets. Moreover, drastic spectroscopic changes on the bulk-SiC Si 2p and C 1s core levels are observed, depending on whether graphite(6{radical}3)/SiC or graphite(1x1)/Ge/SiC terminations are analyzed. In the latter case, the observed core level splitting of the bulk components is interpreted by a significant upward band bending ({approx}1.2 eV) of the n-doped SiC, making this second interface to act as a Schottky barrier. Above 1300 deg. C, a delayed Ge desorption takes place that allows the graphite sheets to re-form in their initial 6{radical}3 form, i.e., without Ge and with flatter bands.

  12. Low-Voltage Voltammetric Electrowetting of Graphite Surfaces by Ion Intercalation/Deintercalation.

    PubMed

    Zhang, Guohui; Walker, Marc; Unwin, Patrick R

    2016-08-02

    We demonstrate low-voltage electrowetting at the surface of freshly cleaved highly oriented pyrolytic graphite (HOPG). Using cyclic voltammetry (CV), electrowetting of a droplet of a sodium perchlorate solution is observed at moderately positive potentials on high-quality (low step edge coverage) HOPG, leading to significant changes in the contact angle and relative contact diameter that are comparable to the results of the widely studied electrowetting on dielectric (EWOD) system, but over a much lower voltage range. The electrowetting behavior is found to be reasonably fast, reversible, and repeatable for at least 20 cyclic scans (maximum tested). In contrast to classical electrowetting, e.g., EWOD, the electrowetting of the droplet on HOPG occurs with the intercalation/deintercalation of anions between the graphene layers of graphite, driven by the applied potential, observed in the CV response, and detected by X-ray photoelectron spectroscopy. The electrowetting behavior is strongly influenced by those factors that affect the extent of the intercalation/deintercalation of ions on graphite, such as potential range scan rate, potential polarity, quality of the HOPG substrate (step edge density and step height), and type of anion in the solution. In addition to perchlorate, sulfate salts also promote electrowetting, but some other salts do not. Our findings suggest a new mechanism for electrowetting based on ion intercalation, and the results are important to fundamental electrochemistry as well as to diversifying the means by which electrowetting can be controlled and applied.

  13. General observation of lithium intercalation into graphite in ethylene-carbonate-free superconcentrated electrolytes.

    PubMed

    Yamada, Yuki; Usui, Kenji; Chiang, Ching Hua; Kikuchi, Keisuke; Furukawa, Keizo; Yamada, Atsuo

    2014-07-23

    Lithium-ion batteries have exclusively employed an ethylene carbonate (EC)-based electrolyte to ensure the reversibility of the graphite negative electrode reaction. Because of the limitation of electrolyte compositions, there has been no remarkable progress in commercial lithium-ion batteries despite active research on positive electrode materials. Herein, we present a salt-superconcentrating strategy as a simple and effective method of universalizing a graphite negative electrode reaction in various organic solvents. A dilute electrolyte (e.g., 1 mol dm(-3)) of sulfoxide, ether, and sulfone results in solvent cointercalation and/or severe electrolyte decomposition at a graphite electrode, whereas their superconcentrated electrolyte (e.g., >3 mol dm(-3)) allows for highly reversible lithium intercalation into graphite. We have found a unique coordination structure in the superconcentrated solution and an anion-based inorganic SEI film on the cycled graphite electrode, which would be the origin of the reversible graphite negative electrode reaction without EC. Our salt-superconcentrating strategy, expanding the graphite negative electrode reaction in various organic solvents other than EC, will contribute to the development of advanced lithium-ion batteries with high-voltage and fast-charging characters based on new EC-free functional electrolytes.

  14. Synthesis and characterization of graphite-metal fluoride intercalation compounds

    SciTech Connect

    McQuillan, B.W.

    1981-04-01

    The compound C/sub x/AsF/sub 5/ was prepared and characterized by x-ray diffraction and x-ray absorption, which show the presence of As(III) and As(V), and the As-F bond distances are consistent with AsF/sub 3/ and AsF/sup -//sub 6/, C/sup +//sub 8/AsF/sup -//sub 6/ and C/sup +//sub 8/OsF/sup -//sub 6/ were synthesized. The C/sub x/AsF/sub 6/ and numerous standard arsenic-flourine compounds were studied by x-ray absorption. Magnetic susceptibility of C/sup +//sub 8/OsF/sup -//sub 6/ confirms the high degree of oxidation in this compound. X-ray absorption studies were begun to determine the species present within the graphite when BrF/sub 3/ or GeF/sub 4/ + F/sub 2/ are added. In the BrF/sub 3/ case, Br/sub 2/ is evolved and only Br(III) is present in the graphite. The binary phase diagram XeF/sub 2/:Xe/sup +//sub 5/AsF/sup -//sub 6/ was investigated by melting point determination and Raman spectroscopy. This mixture near 1.3:1 forms a kinetically stable glass at room temperature and is molten at 50/sup 0/C. Several new species or phases are observed in the Raman spectra. These species have been assigned tentative structures.

  15. Critical role of intercalated water for electrocatalytically active nitrogen-doped graphitic systems

    DOE PAGES

    Martinez, Ulises; Dumont, Joseph H.; Holby, Edward F.; ...

    2016-03-18

    Graphitic materials are very essential in energy conversion and storage because of their excellent chemical and electrical properties. The strategy for obtaining functional graphitic materials involves graphite oxidation and subsequent dissolution in aqueous media, forming graphene-oxide nanosheets (GNs). Restacked GNs contain substantial intercalated water that can react with heteroatom dopants or the graphene lattice during reduction. We demonstrate that removal of intercalated water using simple solvent treatments causes significant structural reorganization, substantially affecting the oxygen reduction reaction (ORR) activity and stability of nitrogen-doped graphitic systems. Amid contrasting reports describing the ORR activity of GN-based catalysts in alkaline electrolytes, we demonstratemore » superior activity in an acidic electrolyte with an onset potential of ~0.9 V, a half-wave potential (E½) of 0.71 V, and a selectivity for four-electron reduction of >95%. Finally and further, durability testing showed E½ retention >95% in N2- and O2-saturated solutions after 2000 cycles, demonstrating the highest ORR activity and stability reported to date for GN-based electrocatalysts in acidic media.« less

  16. Critical role of intercalated water for electrocatalytically active nitrogen-doped graphitic systems

    SciTech Connect

    Martinez, Ulises; Dumont, Joseph H.; Holby, Edward F.; Artyushkova, Kateryna; Purdy, Geraldine M.; Singh, Akhilesh; Mack, Nathan H.; Atanassov, Plamen; Cullen, David A.; More, Karren L.; Chhowalla, Manish; Zelenay, Piotr; Dattelbaum, Andrew M.; Mohite, Aditya D.; Gupta, Gautam

    2016-03-18

    Graphitic materials are very essential in energy conversion and storage because of their excellent chemical and electrical properties. The strategy for obtaining functional graphitic materials involves graphite oxidation and subsequent dissolution in aqueous media, forming graphene-oxide nanosheets (GNs). Restacked GNs contain substantial intercalated water that can react with heteroatom dopants or the graphene lattice during reduction. We demonstrate that removal of intercalated water using simple solvent treatments causes significant structural reorganization, substantially affecting the oxygen reduction reaction (ORR) activity and stability of nitrogen-doped graphitic systems. Amid contrasting reports describing the ORR activity of GN-based catalysts in alkaline electrolytes, we demonstrate superior activity in an acidic electrolyte with an onset potential of ~0.9 V, a half-wave potential (E½) of 0.71 V, and a selectivity for four-electron reduction of >95%. Finally and further, durability testing showed E½ retention >95% in N2- and O2-saturated solutions after 2000 cycles, demonstrating the highest ORR activity and stability reported to date for GN-based electrocatalysts in acidic media.

  17. Critical role of intercalated water for electrocatalytically active nitrogen-doped graphitic systems

    PubMed Central

    Martinez, Ulises; Dumont, Joseph H.; Holby, Edward F.; Artyushkova, Kateryna; Purdy, Geraldine M.; Singh, Akhilesh; Mack, Nathan H.; Atanassov, Plamen; Cullen, David A.; More, Karren L.; Chhowalla, Manish; Zelenay, Piotr; Dattelbaum, Andrew M.; Mohite, Aditya D.; Gupta, Gautam

    2016-01-01

    Graphitic materials are essential in energy conversion and storage because of their excellent chemical and electrical properties. The strategy for obtaining functional graphitic materials involves graphite oxidation and subsequent dissolution in aqueous media, forming graphene-oxide nanosheets (GNs). Restacked GNs contain substantial intercalated water that can react with heteroatom dopants or the graphene lattice during reduction. We demonstrate that removal of intercalated water using simple solvent treatments causes significant structural reorganization, substantially affecting the oxygen reduction reaction (ORR) activity and stability of nitrogen-doped graphitic systems. Amid contrasting reports describing the ORR activity of GN-based catalysts in alkaline electrolytes, we demonstrate superior activity in an acidic electrolyte with an onset potential of ~0.9 V, a half-wave potential (E½) of 0.71 V, and a selectivity for four-electron reduction of >95%. Further, durability testing showed E½ retention >95% in N2- and O2-saturated solutions after 2000 cycles, demonstrating the highest ORR activity and stability reported to date for GN-based electrocatalysts in acidic media. PMID:27034981

  18. Superconductivity in Li{sub 3}Ca{sub 2}C{sub 6} intercalated graphite

    SciTech Connect

    Emery, Nicolas; Herold, Claire . E-mail: Claire.Herold@lcsm.uhp-nancy.fr; Mareche, Jean-Francois; Bellouard, Christine; Loupias, Genevieve; Lagrange, Philippe

    2006-04-15

    In this paper, we report the discovery of superconductivity in Li{sub 3}Ca{sub 2}C{sub 6}. Several graphite intercalation compounds (GICs) with electron donors, are well known as superconductors [T. Enoki, S. Masatsugu, E. Morinobu, Graphite Intercalation Compounds and Applications, Oxford University Press, Oxford, 2003]. It is probably not astonishing, since it is generally admitted that low dimensionality promotes high superconducting transition temperatures. Superconductivity is lacking in pristine graphite, but after charging the graphene planes by intercalation, its electronic properties change considerably and superconducting behaviour can appear. Li{sub 3}Ca{sub 2}C{sub 6} is a ternary GIC [S. Pruvost, C. Herold, A. Herold, P. Lagrange, Eur. J. Inorg. Chem. 8 (2004) 1661-1667], for which the intercalated sheets are very thick and poly layered (five lithium layers and two calcium ones). It contains a great amount of metal (five metallic atoms for six carbon ones). Its critical temperature of 11.15 K is very close to that of CaC{sub 6} GIC [T.E. Weller, M. Ellerby, S.S. Saxena, R.P. Smith, N.T. Skipper, Nat. Phys. 1 (2005) 39-41; N. Emery, C. Herold, M. d'Astuto, V. Garcia, Ch. Bellin, J.F. Mareche, P. Lagrange, G. Loupias, Phys. Rev. Lett. 95 (2005) 087003] (11.5 K). Both CaC{sub 6} and Li{sub 3}Ca{sub 2}C{sub 6} GICs possess currently the highest transition temperatures among all the GICs.

  19. Novel Ternary Graphite Intercalation Compounds of Alkali Metal Cations and Amines

    NASA Astrophysics Data System (ADS)

    Maluangnont, Tosapol

    Novel ternary graphite intercalation compounds (GICs) of alkali metal cations and a wide variety of amines have been synthesized by one-pot chemical syntheses. Alkali metals studied includes Li, Na and K. The families of amines employed are nalkylamines, branched alkylamines, and different structural isomers of diamines and polyamines. Intragallery structures of the amine co-intercalates residing between the graphene sheets are proposed based on powder X-ray diffraction (PXRD), supplemented by compositional analyses, thermal analyses, and structure optimization when appropriate. A homologous series of M-n-alkylamine-GICs (M = Na, Li) is reported for the first time, with the n-alkylamines of 3-14 carbon atoms (nC3-nC14). The following new GICs with indicated stages and intercalate arrangements are obtained: stage 1, di~ 0.70 nm, monolayer (nC3, nC4); stage 1, di ~ 1.10 nm, bilayer (nC6, nC8); and stage 2, di ~ 1.10 nm, bilayer (nC12, nC14). Here di is the gallery height. Two features new to donor-type GICs found are (i) an intercalate bilayer arrangement with guest alkyl chains parallel to encasing graphene layers, and (ii) the transition from an intercalate bilayer to monolayer arrangement upon evacuation for nC6. GICs containing branched alkylamines co-intercalates are prepared and their intragallery structures compared to those of selected n-alkylamines. A notable difference is observed for amines with 4 carbon atoms. While the linear n-butylamine forms parallel monolayers (di ~ 0.70 nm), the branched analogs (iso-butylamine and sec-butylamine) instead form bilayers with di ~ 1.30 nm. This result contrasts with the general observation that more sterically-hindered intercalates tend to intercalate at lower concentrations. This structural difference is not observed, however, between npropylamine and iso-propylamine (di ~ 0.70 and 0.76 nm respectively). A rare example of a ternary GIC exhibiting cation-directed orientation of the diamine co-intercalate (1

  20. Structural study and crystal chemistry of the first stage calcium graphite intercalation compound

    SciTech Connect

    Emery, Nicolas; Herold, Claire . E-mail: Claire.Herold@lcsm.uhp-nancy.fr; Lagrange, Philippe

    2005-09-15

    A novel and efficient synthesis method concerning the preparation of the first stage calcium graphite intercalation compound is provided. It makes use of a reaction between liquid metallic alloy and pyrolytic graphite. From now on it is especially easy to obtain bulk CaC{sub 6} samples. Thanks to such samples, it was possible to study in detail the crystal structure of this binary intercalation compound. It has been entirely specified, so that we know that CaC{sub 6} crystal is rhombohedral and belongs to the R3-bar m space group with the following parameters: a=517pm and {alpha}=49.55 deg. The elemental unit cell contains one calcium atom and six carbon atoms. In this paper, we show also how the various MC{sub 6} structures evolve according to the size of the intercalated element and to the bond nature that appears in the final compound. CaC{sub 6} is unique, since all the other MC{sub 6} compounds exhibit a hexagonal symmetry.

  1. Approaching the limits of transparency and conductivity in graphitic materials through lithium intercalation

    NASA Astrophysics Data System (ADS)

    Bao, Wenzhong; Wan, Jiayu; Han, Xiaogang; Cai, Xinghan; Zhu, Hongli; Kim, Dohun; Ma, Dakang; Xu, Yunlu; Munday, Jeremy N.; Drew, H. Dennis; Fuhrer, Michael S.; Hu, Liangbing

    2014-07-01

    Various band structure engineering methods have been studied to improve the performance of graphitic transparent conductors; however, none has demonstrated an increase of optical transmittance in the visible range. Here we measure in situ optical transmittance spectra and electrical transport properties of ultrathin graphite (3-60 graphene layers) simultaneously during electrochemical lithiation/delithiation. On intercalation, we observe an increase of both optical transmittance (up to twofold) and electrical conductivity (up to two orders of magnitude), strikingly different from other materials. Transmission as high as 91.7% with a sheet resistance of 3.0 Ω per square is achieved for 19-layer LiC6, which corresponds to a figure of merit σdc/σopt=1,400, significantly higher than any other continuous transparent electrodes. The unconventional modification of ultrathin graphite optoelectronic properties is explained by the suppression of interband optical transitions and a small intraband Drude conductivity near the interband edge. Our techniques enable investigation of other aspects of intercalation in nanostructures.

  2. Indirect measurement of N-14 quadrupolar coupling for NH3 intercalated in potassium graphite

    NASA Technical Reports Server (NTRS)

    Tsang, T.; Fronko, R. M.; Resing, H. A.

    1987-01-01

    A method for indirect measurement of the nuclear quadrupolar coupling was developed and applied to NH3 molecules in the graphite intercalation compound K(NH3)4.3C24, which has a layered structure with alternating carbon and intercalant layers. Three triplets were observed in the H-1 NMR spectra of the compound. The value of the N-14 quadrupolar coupling constant of NH3 (3.7 MHz), determined indirectly from the H-1 NMR spectra, was intermediate between the gas value of 4.1 MHz and the solid-state value of 3.2 MHz. The method was also used to deduce the (H-1)-(H-1) and (N-14)-(H-1) dipolar interactions, the H-1 chemical shifts, and the molecular orientations and motions of NH3.

  3. HTR Fuel Waste Management: TRISO separation and acid-graphite intercalation compounds preparation

    NASA Astrophysics Data System (ADS)

    Guittonneau, Fabrice; Abdelouas, Abdesselam; Grambow, Bernd

    2010-12-01

    Considering the need to reduce waste production and greenhouse emissions and still keeping high energy efficiency, various 4th generation nuclear energy systems have been proposed. As far as graphite-moderated reactors are concerned (future high temperature fast or thermal reactors), one of the key issues is the large volumes of irradiated graphite encountered. With the objective to reduce volume of waste in the HTR concept, it is very important to be able to separate the fuel from low level activity graphite representing a large volume. The separated TRISO particles can then be reprocessed for waste separation or disposed off in geological repository. In addition, preparation of acid-GICs from the separated graphite may constitute a way to recycle this waste. We used HTR-type compact fuel with ZrO 2 TRISO particles to test two separation methods: low (H 2SO 4 + H 2O 2) and high (H 2SO 4 + HNO 3) temperature acid treatments. In both cases the TRISO separation was complete but some TRISO layers oxidized at high temperature. At low temperature, the desegregation of graphite grains is facilitated by intercalation of sulfuric acid between the graphene layers. The acid-GIC obtained consists of pure phases of high quality suggesting their potential industrial recycling.

  4. Surface Layer Evolution on Graphite During Electrochemical Sodium-tetraglyme Co-intercalation.

    PubMed

    Maibach, Julia; Jeschull, Fabian; Brandell, Daniel; Edström, Kristina; Valvo, Mario

    2017-04-12

    One obstacle in sodium ion batteries is the lack of suitable anode materials. As recently shown, the most common anode material of the state of the art lithium ion batteries, graphite, can be used for sodium ion storage as well, if ether-based electrolyte solvents are used. These solvents cointercalate with the sodium ions leading to the highly reversible formation of ternary graphite intercalation compounds (t-GIC). In order for the solvent cointercalation to work efficiently, it is expected that only a very thin surface layer forms during electrochemical cycling. In this article, we therefore present the first dedicated study of the surface layer evolution on t-GICs using soft X-ray photoelectron spectroscopy. This technique with its inherent high surface sensitivity and low probing depth is an ideal tool to study the underlying interfacial reactions during the sodiation and desodiation of graphite. In this report, we apply this approach to graphite composite electrodes cycled in Na half cells with a 1 M sodium bis(fluorosulfonyl)imide/tetraethylene glycol dimethyl ether (NaFSI/TEG-DME) electrolyte. We have found a surface layer on the cycled electrodes, mainly composed of salt decomposition products and hydrocarbons, in line with irreversible capacity losses observed in the electrochemical cycling. Although this surface layer does not seem to block cointercalation completely, it seems to affect its efficiency resulting in a low Coulombic efficiency of the studied battery system.

  5. Stability of bromine, iodine monochloride, copper (II) chloride, and nickel (II) chloride intercalated pitch-based graphite fibers

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Slabe, Melissa E.; Shaffer, Nanette

    1987-01-01

    Four different grades of pitch-based graphite fibers (Amoco P-55, P-75, P-100. and P-120) were intercalated with each of four different intercalates: bromine (Br2), iodine monochloride (ICl), copper (II) chloride (CuCl2), and nickel (II) chloride (NiCl2). The P-55 fibers did not react with Br2 or NiCl2, and the P-75 did not react with NiCl2. The stability of the electrical resistance of the intercalated fibers was monitored over long periods of time in ambient, high humidity (100 percent at 60 C), vacuum (10 to the -6 torr), and high temperature (up to 400 C) conditions. Fibers with lower graphitization form graphite intercalation compounds (GIC's) which are more stable than those with higher graphitization (i.e., P-55 (most stable) greater than P-75 greater than P-100 greater than P-120 (least stable). Br2 formed the most stable GIC's followed in order of decreasing stability by ICl, CuCl2, and NiCl2. While Br2 GIC's had the most stability, ICl had the advantages of forming GIC's with slightly greater reduction in resistance (by about 10%) than Br2, and the ability to intercalate P-55 fiber. Transition metal chlorides are susceptible to water vapor and high temperature. The stability of fibers in composites differs.

  6. Synthesis and characterisation of a novel europium-based graphite intercalation compound

    SciTech Connect

    Emery, Nicolas; Herold, Claire Bellouard, Christine; Delcroix, Pierre; Mareche, Jean-Francois; Lagrange, Philippe

    2008-11-15

    In the lithium-europium-graphite system, a novel ternary compound was synthesised by direct immersion of a pyrolytic graphite platelet in a molten lithium-based alloy with a well chosen Li/Eu ratio at 400 deg. C. The ternary compound exhibits poly-layered intercalated sheets mainly constituted of two europium planes. Its chemical formula can be written Li{sub x}EuC{sub 4}, since the amount of lithium is still not determined. The {sup 151}Eu Moessbauer spectra clearly indicate a +II valence for europium. The magnetic susceptibility and the magnetisation versus temperature reveal a complex behaviour which is qualitatively described thanks to structural hypothesis and analogies with the magnetic properties of the binary EuC{sub 6} compound. A first ferromagnetic transition occurring at 225 K is attributed to interactions between both intercalated europium planes. The lower temperature susceptibility behaviour can be interpreted by antiferromagnetic interactions between in-plane neighbours and ferromagnetic interactions along the c-axis. - Graphical abstract: 1D electronic density profiles along the c-axis of Li{sub x}EuC{sub 4}.

  7. Anisotropic Elliott-Yafet theory and application to KC8 potassium intercalated graphite

    NASA Astrophysics Data System (ADS)

    Márkus, Bence G.; Szolnoki, Lénárd; Iván, Dávid; Dóra, Balázs; Szirmai, Péter; Náfrádi, Bálint; Forró, László; Simon, Ferenc

    2016-12-01

    We report Electron Spin Resonance (ESR) measurements on stage-I potassium intercalated graphite (KC$_8$). Angular dependent measurements show that the spin-lattice relaxation time is longer when the magnetic field is perpendicular to the graphene layer as compared to when the magnetic field is in the plane. This anisotropy is analyzed in the framework of the Elliott-Yafet theory of spin-relaxation in metals. The analysis considers an anisotropic spin-orbit Hamiltonian and the first order perturbative treatment of Elliott is reproduced for this model Hamiltonian. The result provides an experimental input for the first-principles theories of spin-orbit interaction in layered carbon and thus to a better understanding of spin-relaxation phenomena in graphene and in other layered materials as well.

  8. Photoelectron Holographic Atomic Arrangement Imaging of Cleaved Bimetal-intercalated Graphite Superconductor Surface

    NASA Astrophysics Data System (ADS)

    Matsui, Fumihiko; Eguchi, Ritsuko; Nishiyama, Saki; Izumi, Masanari; Uesugi, Eri; Goto, Hidenori; Matsushita, Tomohiro; Sugita, Kenji; Daimon, Hiroshi; Hamamoto, Yuji; Hamada, Ikutaro; Morikawa, Yoshitada; Kubozono, Yoshihiro

    2016-11-01

    From the C 1s and K 2p photoelectron holograms, we directly reconstructed atomic images of the cleaved surface of a bimetal-intercalated graphite superconductor, (Ca, K)C8, which differed substantially from the expected bulk crystal structure based on x-ray diffraction (XRD) measurements. Graphene atomic images were collected in the in-plane cross sections of the layers 3.3 Å and 5.7 Å above the photoelectron emitter C atom and the stacking structures were determined as AB- and AA-type, respectively. The intercalant metal atom layer was found between two AA-stacked graphenes. The K atomic image revealing 2 × 2 periodicity, occupying every second centre site of C hexagonal columns, was reconstructed, and the Ca 2p peak intensity in the photoelectron spectra of (Ca, K)C8 from the cleaved surface was less than a few hundredths of the K 2p peak intensity. These observations indicated that cleavage preferentially occurs at the KC8 layers containing no Ca atoms.

  9. Photoelectron Holographic Atomic Arrangement Imaging of Cleaved Bimetal-intercalated Graphite Superconductor Surface

    PubMed Central

    Matsui, Fumihiko; Eguchi, Ritsuko; Nishiyama, Saki; Izumi, Masanari; Uesugi, Eri; Goto, Hidenori; Matsushita, Tomohiro; Sugita, Kenji; Daimon, Hiroshi; Hamamoto, Yuji; Hamada, Ikutaro; Morikawa, Yoshitada; Kubozono, Yoshihiro

    2016-01-01

    From the C 1s and K 2p photoelectron holograms, we directly reconstructed atomic images of the cleaved surface of a bimetal-intercalated graphite superconductor, (Ca, K)C8, which differed substantially from the expected bulk crystal structure based on x-ray diffraction (XRD) measurements. Graphene atomic images were collected in the in-plane cross sections of the layers 3.3 Å and 5.7 Å above the photoelectron emitter C atom and the stacking structures were determined as AB- and AA-type, respectively. The intercalant metal atom layer was found between two AA-stacked graphenes. The K atomic image revealing 2 × 2 periodicity, occupying every second centre site of C hexagonal columns, was reconstructed, and the Ca 2p peak intensity in the photoelectron spectra of (Ca, K)C8 from the cleaved surface was less than a few hundredths of the K 2p peak intensity. These observations indicated that cleavage preferentially occurs at the KC8 layers containing no Ca atoms. PMID:27811975

  10. Hydrogen diffusion in potassium intercalated graphite studied by quasielastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Purewal, Justin; Keith, J. Brandon; Ahn, Channing C.; Brown, Craig M.; Tyagi, Madhusudan; Fultz, Brent

    2012-12-01

    The graphite intercalation compound KC24 adsorbs hydrogen gas at low temperatures up to a maximum stoichiometry of KC24(H2)2, with a differential enthalpy of adsorption of approximately -9 kJ mol-1. The hydrogen molecules and potassium atoms form a two-dimensional condensed phase between the graphite layers. Steric barriers and strong adsorption potentials are expected to strongly hinder hydrogen diffusion within the host KC24 structure. In this study, self-diffusion in a KC24(H2)0.5 sample is measured experimentally by quasielastic neutron scattering and compared to values from molecular dynamics simulations. Self-diffusion coefficients are determined by fits of the experimental spectra to a honeycomb net diffusion model and found to agree well with the simulated values. The experimental H2 diffusion coefficients in KC24 vary from 3.6 × 10-9 m2 s-1 at 80 K to 8.5 × 10-9 m2 s-1 at 110 K. The measured diffusivities are roughly an order of magnitude lower that those observed on carbon adsorbents, but compare well with the rate of hydrogen self-diffusion in molecular sieve zeolites.

  11. Synthesis and structure of high quality graphene prepared via solvothermal exfoliation of intercalated graphite flakes

    NASA Astrophysics Data System (ADS)

    Al-Hazmi, Farag S.; Al-Harbi, Ghada H.; Beall, Gary W.; Al-Ghamdi, A. A.; Obaid, A. Y.; Mahmoud, Waleed E.

    2015-10-01

    The large-scale production of graphene via a simple approach is the key factor to be introduced into the industrial applications such as energy conversion, storage materials and optical electronics. In this letter, a rapid and facile approach to synthesize high quality graphene layers with large mass production has been developed. The method depends on the intercalation of graphite flakes with tartaric acid. The treated graphite subjected to a thermal shock at 750 °C for 60 s and followed by solvothermal treatment in the presence of isopropanol at 400 °C for 2 h. The produced graphene layers have an average thickness of 0.53 nm which depicted the production of a monolayer graphene. The FT-IR and Raman spectroscopy confirmed that the produced graphene layers have very low surface defects compared to reported approaches. The XPS spectra revealed that the surface of the produced graphene layers contains only 6 at% oxygen, which is better than the reduced graphene by conventional methods. This novel approach will open a new avenue for a scalable production of high quality graphene monolayer.

  12. Prevention of sulfur diffusion using MoS2-intercalated 3D-nanostructured graphite for high-performance lithium-ion batteries.

    PubMed

    Tiwari, Anand P; Yoo, HeeJoun; Lee, JeongTaik; Kim, Doyoung; Park, Jong Hyeok; Lee, Hyoyoung

    2015-07-28

    We report new three-dimensional (3D)-nanostructured MoS2-carbonaceous materials in which MoS2 sheets are intercalated between the graphite layers that possess a multiply repeated graphite/MoS2/graphite structure which prevents the aggregation of MoS2 and diffusion of sulfur from carbonaceous materials, enhancing the cycling stability of Li-ion batteries. We developed an efficient and scalable process applicable to mass production for synthesizing non-aggregated MoS2-intercalated 3D hybrid-nanostructured graphite based on stress induced and microwave irradiation. X-ray diffraction, X-ray photospectroscopy, Raman spectroscopy, field emission scanning electron microscopy, and high-resolution transmission electron microscopy analyses demonstrated that the as-synthesized materials consisted of MoS2-intercalated 3D hybrid-nanostructured graphite platelets that had a multiply repeated graphite/MoS2/graphite structure. The obtained MoS2-graphite powder surpasses MoS2 as an anode material in terms of specific capacity, cyclic stability, and rate performances at high current densities for Li-ion batteries. The electrochemical impedance spectroscopy demonstrated that the graphite sheets not only reduced the contact resistance in the electrode but also facilitated electron transfer in the lithiation/delithiation processes. The superior electrochemical performances especially for the cycling stability of the Li-ion battery originate from prevention of the sulfur diffusion of the MoS2-intercalated 3D-nanostructured graphite.

  13. Staging properties of potassium-ammonia ternary graphite intercalation compounds at high ammonia pressure

    NASA Astrophysics Data System (ADS)

    Qian, X. W.; Solin, S. A.

    1989-04-01

    The pressure dependence of the (00l) x-ray diffraction patterns of the ternary graphite intercalation compound K(NH3)xC24 has been studied in the range 0.5-11 kbar (for which x~4.5) using a diamond anvil cell. A special apparatus for loading the cell with liquid ammonia at room temperature has been constructed and is briefly described. In these experiments, the pressure-transmitting fluid was also an intercalant, namely ammonia. Therefore, the chemical potential of this species was linearly coupled to the applied pressure in contrast to the usual case where the pressure-transmitting fluid is chemically passive. The pressure dependences of the basal spacings and of the relative intensities of key reflections have been measured, as have the compressibilities of the stage-1 and stage-2 components of the two-phase system. Basal-spacing anomalies and anomalies in the relative intensities occur at pressures of ~3.5 and 8.0 kbar and are tentatively attributed to in-plane coordination changes in the potassium-ammonia ratio. Using thermodynamic arguments and Le Chatelier's principle we show quantitatively that a staging phase transition from pure stage-1 phase to an admixture of stage-1 and stage-2 is expected with increased pressure above 10 bar in agreement with experiment. The saturation ammonia compositions (x values) of the admixed stages are found to be 4.5 and 5.4 for the stage-1 and -2 components, respectively. This result is interpreted as evidence that the composition is not sterically limited but is determined by the binding energy of ammonia for potassium and by the perturbation to this energy from the guest-host interaction.

  14. Mechanical and electrical properties of graphite fiber-epoxy composites made from pristine and bromine intercalated fibers

    NASA Technical Reports Server (NTRS)

    Jaworske, Donald A.; Vannucci, Raymond D.; Zinolabedini, Reza

    1987-01-01

    The mechanical and electrical properties of pristine and bromine intercalated graphite fiber-epoxy composites were compared. The two types of composite were similar in terms of tensile modulus, tensile strength, and Poisson's Ratio. However, the interlaminar shear strength of the brominated composite was 18 percent greater than its pristine counterpart. Only slight differences were observed in flexural properties. A five-fold decrease was observed in the electrical resistivity of the brominated composite parallel to the axis of the fibers, resulting in a unidirectional resistivity of about 90 microOmega/cm. Transverse resistivity was unaffected. Both types of composite were subjected to a simulated lightning strike of 10 KJ (at a peak current of 150 kA), and the composite with the intercalated graphite exhibited less damage.

  15. 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.

  16. Effect of sorbed molecules on the resistivity of alkali metal-graphite intercalation compounds

    SciTech Connect

    Akuzawa, Noboru Kunihashi, Yoji; Sato, Yuki; Tsuchiya, Ken-ichi; Matsumoto, Rika

    2007-03-15

    Alkali metal-graphite intercalation compounds with the composition of MC{sub 24} (M=K, Rb, Cs) were prepared by heating a mixture of MC{sub 8} (saturated compound) and graphite sheet (Grafoil) at 350-450 deg. C. The resistivity perpendicular to the layer planes ({rho} {sub c}) of the resulting compounds was determined by the two-terminal method. The anisotropy factor of the resistivity, ({rho} {sub c}/{rho} {sub a}), of KC{sub 24} prepared from Grafoil was {approx}130, being about 1/6-1/10 in magnitude compared with that of KC{sub 24} prepared from highly oriented pyrolytic graphite. The resistivity change during sorption of hydrogen (at 90 K), ethylene (at 194 K) and acetylene (at 194 K) was determined. The resistivity of MC{sub 24} increased with increase of the sorbed amount of H{sub 2}. The magnitude of the increase was in the order KC{sub 24}>RbC{sub 24}>CsC{sub 24}. This resistivity increase was considered to be due to the expansion along c-direction which reduces the charge-transfer interaction between the carbon layers and potassium ions, resulting in the decrease of the density of the conduction electron. The resistivity of MC{sub 24} increased extensively during sorption of C{sub 2}H{sub 4} and C{sub 2}H{sub 2}. It was discussed in connection with the in-plane structural transition and chemical interaction between alkali metal ions and sorbed molecules. - Graphical abstract: The resistivity of MC{sub 24} increased with increase of the sorbed amount of H{sub 2}. The magnitude of the increase was in the order KC{sub 24}>RbC{sub 24}>CsC{sub 24}. This resistivity increase was considered to be due to the expansion along c-direction which reduces the charge-transfer interaction between the carbon layers and potassium ions.

  17. Intercalated graphitic carbon nitride: a fascinating two-dimensional nanomaterial for an ultra-sensitive humidity nanosensor

    NASA Astrophysics Data System (ADS)

    Zhang, Zhenyi; Huang, Jindou; Yuan, Qing; Dong, Bin

    2014-07-01

    We develop a novel humidity nanosensor based on intercalated graphitic carbon nitride (g-C3N4) nanosheets fabricated by a facile thermal polymerization of common urea in the presence of LiCl as the intercalated guest under air and ambient pressure. The response and recovery times of an optimal nanosensor can reach ~0.9 s and ~1.4 s, respectively, which are superior to most of the traditional oxide ceramic-based humidity nanosensors tested under similar conditions. By combining with the theoretical calculations, it is proposed that the ultrafast response-recovery time for this nanosensor is attributed to their unique 2D intercalated nanostructure by which Li species linked with the ``nitrogen pots'' of g-C3N4 can make the protons conduct in the first adsorbed water layer. Meanwhile, the physically adsorbed water on the surface of LiCl-intercalated g-C3N4 nanosheets can be desorbed rapidly at a relative lower RH environment due to their high adsorption energy and the strong diffusion effect of water molecules.We develop a novel humidity nanosensor based on intercalated graphitic carbon nitride (g-C3N4) nanosheets fabricated by a facile thermal polymerization of common urea in the presence of LiCl as the intercalated guest under air and ambient pressure. The response and recovery times of an optimal nanosensor can reach ~0.9 s and ~1.4 s, respectively, which are superior to most of the traditional oxide ceramic-based humidity nanosensors tested under similar conditions. By combining with the theoretical calculations, it is proposed that the ultrafast response-recovery time for this nanosensor is attributed to their unique 2D intercalated nanostructure by which Li species linked with the ``nitrogen pots'' of g-C3N4 can make the protons conduct in the first adsorbed water layer. Meanwhile, the physically adsorbed water on the surface of LiCl-intercalated g-C3N4 nanosheets can be desorbed rapidly at a relative lower RH environment due to their high adsorption energy and

  18. Powder, paper and foam of few-layer graphene prepared in high yield by electrochemical intercalation exfoliation of expanded graphite.

    PubMed

    Wu, Liqiong; Li, Weiwei; Li, Peng; Liao, Shutian; Qiu, Shengqiang; Chen, Mingliang; Guo, Yufen; Li, Qi; Zhu, Chao; Liu, Liwei

    2014-04-09

    A facile and high-yield approach to the preparation of few-layer graphene (FLG) by electrochemical intercalation exfoliation (EIE) of expanded graphite in sulfuric acid electrolyte is reported. Stage-1 H2SO4-graphite intercalation compound is used as a key intermediate in EIE to realize the efficient exfoliation. The yield of the FLG sheets (<7 layers) with large lateral sizes (tens of microns) is more than 75% relative to the total amount of starting expanded graphite. A low degree of oxygen functionalization existing in the prepared FLG flakes enables them to disperse effectively, which contributes to the film-forming characteristics of the FLG flakes. These electrochemically exfoliated FLG flakes are integrated into several kinds of macroscopic graphene structures. Flexible and freestanding graphene papers made of the FLG flakes retain excellent conductivity (≈24,500 S m(-1)). Three-dimensional (3D) graphene foams with light weight are fabricated from the FLG flakes by the use of Ni foams as self-sacrifice templates. Furthermore, 3D graphene/Ni foams without any binders, which are used as supercapacitor electrodes in aqueous electrolyte, provide the specific capacitance of 113.2 F g(-1) at a current density of 0.5 A g(-1), retaining 90% capacitance after 1000 cycles.

  19. Prevention of sulfur diffusion using MoS2-intercalated 3D-nanostructured graphite for high-performance lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Tiwari, Anand P.; Yoo, Heejoun; Lee, Jeongtaik; Kim, Doyoung; Park, Jong Hyeok; Lee, Hyoyoung

    2015-07-01

    We report new three-dimensional (3D)-nanostructured MoS2-carbonaceous materials in which MoS2 sheets are intercalated between the graphite layers that possess a multiply repeated graphite/MoS2/graphite structure which prevents the aggregation of MoS2 and diffusion of sulfur from carbonaceous materials, enhancing the cycling stability of Li-ion batteries. We developed an efficient and scalable process applicable to mass production for synthesizing non-aggregated MoS2-intercalated 3D hybrid-nanostructured graphite based on stress induced and microwave irradiation. X-ray diffraction, X-ray photospectroscopy, Raman spectroscopy, field emission scanning electron microscopy, and high-resolution transmission electron microscopy analyses demonstrated that the as-synthesized materials consisted of MoS2-intercalated 3D hybrid-nanostructured graphite platelets that had a multiply repeated graphite/MoS2/graphite structure. The obtained MoS2-graphite powder surpasses MoS2 as an anode material in terms of specific capacity, cyclic stability, and rate performances at high current densities for Li-ion batteries. The electrochemical impedance spectroscopy demonstrated that the graphite sheets not only reduced the contact resistance in the electrode but also facilitated electron transfer in the lithiation/delithiation processes. The superior electrochemical performances especially for the cycling stability of the Li-ion battery originate from prevention of the sulfur diffusion of the MoS2-intercalated 3D-nanostructured graphite.We report new three-dimensional (3D)-nanostructured MoS2-carbonaceous materials in which MoS2 sheets are intercalated between the graphite layers that possess a multiply repeated graphite/MoS2/graphite structure which prevents the aggregation of MoS2 and diffusion of sulfur from carbonaceous materials, enhancing the cycling stability of Li-ion batteries. We developed an efficient and scalable process applicable to mass production for synthesizing non

  20. Bulk evidence for single-Gap s-wave superconductivity in the intercalated graphite superconductor C6Yb.

    PubMed

    Sutherland, Mike; Doiron-Leyraud, Nicolas; Taillefer, Louis; Weller, Thomas; Ellerby, Mark; Saxena, S S

    2007-02-09

    We report measurements of the in-plane electrical resistivity rho and thermal conductivity kappa of the intercalated graphite superconductor C6Yb down to temperatures as low as Tc/100. When a field is applied along the c axis, the residual electronic linear term kappa0/T evolves in an exponential manner for Hc1

  1. The Use of Pristine and Intercalated Graphite Fiber Composites as Buss Bars in Lead-Acid Batteries

    NASA Technical Reports Server (NTRS)

    Opaluch, Amanda M.

    2004-01-01

    This study was conducted as a part of the Firefly Energy Space Act Agreement project to investigate the possible use of composite materials in lead acid batteries. Specifically, it examined the use of intercalated graphite composites as buss bars. Currently, buss bars of these batteries are made of lead, a material that is problematic for several reasons. Over time, the lead is subject to both corrosion at the positive plate and sulfation at the negative plate, resulting in decreased battery life. In addition, the weight and size of the lead buss bars make for a heavy and cumbersome battery that is undesirable. Functionality and practicality of lead buss bars is adequate at best; consequently, investigation of more efficient composite materials would be advantageous. Practically speaking, graphite composites have a low density that is nearly one fourth that of its lead counterpart. A battery made of less dense materials would be more attractive to the consumer and the producer because it would be light and convenient. More importantly, low weight would be especially beneficial because it would result in greater overall power density of the battery. In addition to power density, use of graphite composite materials can also increase the life of the battery. From a functional standpoint, corrosion and sulfation at the positive and negative plates are major obstacles when considering how to extend battery life. Neither of these reactions are a factor when graphite composites replace lead parts because graphite is chemically non-reactive with the electrolyte within the battery. Without the problem of corrosion or sulfation, battery life expectancy can be almost doubled. The replacement of lead battery parts with composite materials is also more environmentally favorable because of easy disposal of organic materials. For this study, both pristine and bromine intercalated single-ply graphite fiber composites were created. The composites were fabricated in such a way as to

  2. First-principles study of electronic and magnetic properties of FeCl3-based graphite intercalation compounds

    NASA Astrophysics Data System (ADS)

    Li, Yan; Yue, Qu

    2013-09-01

    The structural, electronic and magnetic properties of stage-1 and -2 FeCl3-based graphite intercalation compounds (GICs) are studied in the framework of the GGA+U implementation of density functional theory. The intercalation process extends the c-axis remarkably and modulates the band structure of graphite to p-type doped. A linearly dispersing band structure is observed for stage-1 GIC. The carrier density shows a weak descending tendency from stage-1 GIC to stage-2 GIC. The dependence of the energy level positions of Fe 3d orbitals on parameter U is strong. With the increase of U, the spin-up states move to the deeper energy levels, while the spin-down states move to the shallower energy levels. Stage-1 GIC has antiferromagnetic (AFM) order and stage-2 GICs has ferromagnetic (FM) orders at the ground states, and two combinative effects are proposed to explain the origin of the magnetic transformation from stage-1 GIC to stage-2 GIC.

  3. Topographic Study on Staging Transition in H2SO4-Graphite Intercalation Compound by in situ Raman Scattering Measurements

    NASA Astrophysics Data System (ADS)

    Nishitani, Ryusuke; Sasaki, Yoshiro; Nishina, Yuichiro

    1987-03-01

    The staging kinetics in H2SO4-GIC’s has been investigated experimentally by time-and space-dependent Raman scattering measurements. The stage transition from stage n to n-1 begins at the interface between the intercalant reservoir and the a-face of the graphite crystal. The lower stage-(n-1) domains emerge at the interface and proceed toward the inner region of the crystal. A narrow phase-boundary between different stage domains exists in the localized region and move toward the inner region as the stage transformation progresses. The present results support the model [R. Nishitani, Y. Uno and H. Suematsu: Synth. Met. 7 (1983) 13] that the stage transformation proceeds via propagation of the boundary between well-staged regions. The origin of the stage disorder is also discussed.

  4. Properties of hybrid CVD/PAN graphite fibers and their bromine intercalation compounds

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Lake, Max L.; Moinuddin, Alia; Marabito, Mark

    1992-01-01

    A hybrid fiber with a PAN core surrounded by a vapor grown carbon fiber (VGCF) sheath was fabricated using a proprietary process. The density, ultimate tensile strength, Young's modulus, and resistivity of pristine and bromine intercalated fibers made by this technique having diameters varying from 5 to 50 microns were compared with the values predicted from the rule of mixtures model. For both the pristine and intercalated fibers, the density, ultimate tensile strength, and Young's modulus of the fibers were lower than predicted, but the resistivity was measured to be consistent with predictions. The lower than theoretical mechanical properties may be evidence of a low density disordered interface between the core and the sheath which would lower the density and degrade the mechanical properties, but would leave the resistivity nearly unaffected. Intercalation had little if any effect on the ultimate tensile strength and Young's modulus, but raised the density by about 11 pct., and lowered the resistivity by an order of magnitude. The diameter dependence of the resistivity showed evidence of a depletion layer of the type found in VGCF.

  5. Properties of novel CVD graphite fibers and their bromine intercalation compounds

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Lake, Max L.; Moinuddin, Alia; Marabito, Mark

    1991-01-01

    A hybrid fiber with a PAN core surrounded by a vapor grown carbon fiber (VGCF) sheath was fabricated using a proprietary process. The density, ultimate tensile strength, Young's modulus, and resistivity of pristine and bromine intercalated fibers made by this technique having diameters varying from 5 to 50 microns were compared with the values predicted from the rule of mixtures model. For both the pristine and intercalated fibers, the density, ultimate tensile strength, and Young's modulus of the fibers were lower than predicted, but the resistivity was measured to be consistent with predictions. The lower than theoretical mechanical properties may be evidence of a low density disordered interface between the core and the sheath which would lower the density and degrade the mechanical properties, but would leave the resistivity nearly unaffected. Intercalation had little if any effect on the ultimate tensile strength and Young's modulus, but raised the density by about 11 pct., and lowered the resistivity by an order of magnitude. The diameter dependence of the resistivity showed evidence of a depletion layer of the type found in VGCF.

  6. Effect of length of chopped pristine and intercalated graphite fibers on the resistivity of fiber networks

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Stahl, Mark

    1988-01-01

    Samples of Amoco P-100 fibers were chopped to lengths of 3.14, 2.53, 1.90, 1.27, 0.66 mm, or milled for 2 hours. The two-point resistivity of compacts of these fibers were measured as a function of pressure from 34 kPa to 143 MPa. Samples of each fiber length were intercalated with bromine at room temperature and similarly measured. The low pressure resistivity of the compacts decreased with increasing fiber length. Intercalation lowered the resistivity of each of the chopped length compacts, but raised the resistivity of the milled fiber compacts. Bulk resistivity of all samples decreased with increasing pressure at similar rates. Even though fiber volumes were as low as 5 percent, all measurements exhibited measurable resistivity. A greater change with pressure in the resistance was observed for shorter fibers than for longer, probably an indication of tighter fiber packing. Intercalation appeared to have no effect on the fiber to fiber contact resistance.

  7. Intercalation of Lithium in Pitch-Based Graphitized Carbon Fibers Chemically Modified by Fluorine: Soft Carbon With or Without an Oxide Surface

    NASA Technical Reports Server (NTRS)

    Hung, Ching-Chen; Prisko, Aniko

    1999-01-01

    The effects of carbon structure and surface oxygen on the carbon's performance as the anode in lithium-ion battery were studied. Two carbon materials were used for the electrochemical tests: soft carbon made from defluorination of graphite fluoride, and the carbon precursor from which the graphite fluoride was made. In this research the precursor was graphitized carbon fiber P-100. It was first fluorinated to form CF(0.68), then defluorinated slowly at 350 to 450 C in bromoform, and finally heated in 1000 C nitrogen before exposed to room temperature air, producing disordered soft carbon having basic surface oxides. This process caused very little carbon loss. The electrochemical test involved cycles of lithium intercalation and deintercalation using C/saturated LiI-50/50 (vol %) EC and DMC/Li half cell. The cycling test had four major results. (1) The presence of a basic oxide surface may prevent solvent from entering the carbon structure and therefore prolong the carbon's cycle life for lithium intercalation-deintercalation. (2) The disordered soft carbon can store lithium through two different mechanisms. One of them is lithium intercalation. which gives the disordered carbon an electrochemical behavior similar to its more ordered graphitic precursor. The other is unknown in its chemistry, but is responsible for the high-N,oltage portion (less than 0.3V) of the charge-discharge curve. (3) Under certain conditions, the disordered carbon can store more lithium than its precursor. (4) These sample and its precursor can intercalate at 200 mA/g. and deintercalate at a rate of 2000 mA/g without significant capacity loss.

  8. Properties of Graphite Intercalates and of Aircraft Structural Metals and Alloys. A Comprehensive Data Survey.

    DTIC Science & Technology

    1974-05-01

    Thermal Conductivity of Pure and Alloyed Aluminum . L Solid Aluminum as a Reference Material," From Advances in Thermophysical properties at Extreme...Willey, L.A., Smith, D.W., and Edwards, J.D., "The Properties of High-Purity Aluminum , "Metals and Alloys , 7(8), 189-92, 1938. 4 52254 Irmonn, R...Termal expansion-Specific beat-Beat of fusion-Graphite compound---Composite-Carbides--Aluonun-- Aluminum alloy -Titanium--Titanium alloy -agnesium alloy

  9. Quasi-two-dimensional quantum states of H{sub 2} in stage-2 Rb-intercalated graphite

    SciTech Connect

    Smith, A.P.; Benedek, R.; Trouw, F.R.; Minkoff, M.; Yang, L.H.

    1995-10-30

    Inelastic-incoherent-neutron scattering can be a valuable nanostructural probe of H{sub 2}-doped porous materials, provided the spectral peaks can be interpreted in terms of crystal-field-split hydrogen-molecule energy levels, which represent a signature of the local symmetry. Inelastic-neutron-scattering measurements as well as extensive theoretical analyses have been performed on stage-2 Rb-intercalated graphite (Rb-GIC), with physisorbed H{sub 2}, HD, and D{sub 2}, a layered porous system with abundant spectral peaks, to assess whether the crystal-field-state picture enables a quantitative understanding of the observed structure. Potential-energy surfaces for molecular rotational and translational motion, as well as the intermolecular interactions of hydrogen molecules in Rb-GIC, were calculated within local-density-functional theory (LDFT). Model potentials, parameterized using results of the LDFT calculations, were employed in schematic calculations of rotational and translational excited state spectra of a single physisorbed H{sub 2} molecule in Rb-GIC. Results of the analysis are basically consistent with the assignment by Stead et al. of the lowest-lying peak at 1.4 meV to a rotational-tunneling transition of an isotropic hindered-rotor oriented normal to the planes, but indicate a small azimuthal anisotropy and a lower barrier than for the isotropic case. Based on the experimental isotope shifts and the theoretically predicted states, they conclude that spectral peaks at 11 and 22 meV are most likely related to center of mass excitations.

  10. Spontaneous intercalation of long-chain alkyl ammonium into edge-selectively oxidized graphite to efficiently produce high-quality graphene

    PubMed Central

    Wei, Liangming; Wu, Fei; Shi, Diwen; Hu, Changchen; Li, Xiaolin; Yuan, Weien; Wang, Jian; Zhao, Jiang; Geng, Huijuan; Wei, Hao; Wang, Ying; Hu, Nantao; Zhang, Yafei

    2013-01-01

    Mass production of high-quality graphene nanosheets (GNs) is essential for practical applications. We report that oxidation of graphite by low concentration KMnO4 at relatively high temperature (60°C) leads to edge-selectively oxidized graphite (EOG) which preserves the high crystalline graphitic structure on its basal planes while the edges are functionalized by oxygen-containing groups. Long-chain tetradecyl-ammonium salt (C14N+) could be spontaneously intercalated into EOG to form intercalated EOG-C14N+ compounds. Gentle and short-time sonication of EOG-C14N+ in toluene can full exfoliate EOG into edge-oxidized graphene nanosheets (EOGNs) with concentration of 0.67 mg/ml, monolayer population up to 90% and lateral size from 1 μm to >100 μm. The EOG and EOGN films show excellent electrical conductance, which is far superior to their graphene oxide (GO) counterparts. Our method provides an efficient way to produce high-quality GNs, and the resultant EOG also can be directly used for production of multifunctional materials and devices. PMID:24022463

  11. Enhancement of electrochemical hydrogen storage in NiCl2-FeCl3-PdCl2-graphite intercalation compound effected by chemical exfoliation

    NASA Astrophysics Data System (ADS)

    Skowroński, J. M.; Rozmanowski, T.; Krawczyk, P.

    2013-06-01

    In the present work, a quaternary NiCl2-FeCl3-PdCl2-graphite intercalation compound (NiCl2-FeCl3-PdCl2-GIC) was successfully synthesized by molten salts method. A part of this compound was subsequently subjected to chemical exfoliation to obtain expanded compound (NiCl2-FeCl3-PdCl2-EGIC). The changes created in crystalline structure, morphology and chemical composition of GIC due to exfoliation were examined by XRD, SEM and EDS techniques and then related to electrochemical behaviour of electrodes made of the original and exfoliated compound. The results of electrochemical studies carried out by the cyclic voltammetry (CV) method in 6 M KOH solution showed that current charges of all the cathodic and anodic peaks recorded for NiCl2-FeCl3-PdCl2-EGIC are considerably higher already in the first two cycles as compared to those observed for the original NiCl2-FeCl3-PdCl2-GIC. This improvement is ascribed to chemical exfoliation leading to a tremendous development of surface area of the compound due to the splitting and wrinkling of graphite flakes followed by easier access of hydroxyl ions of the electrolyte to active species of intercalates preserved between the graphene interspaces as well as expelled from the graphite interspacing. A large anodic peak was recorded on CV curves after the potentiostatic polarization of electrodes at the potential of -1.2 V where the reaction of hydrogen sorption/evolution occurs and intercalates highly dispersed in the graphite matrix are reduced to a metal form. This peak mainly corresponding to the recovery of hydrogen stored in the electrode appeared to be over five times higher for electrode made of exfoliated compound. This significant enhancement of the hydrogen storage capacity is attributed to electrochemically active Pd nanoparticles highly dispersed in porous structure of exfoliated compound and likely functioning in synergy with Ni/Fe clusters.

  12. Dual intercalating molten electrolyte batteries

    SciTech Connect

    Carlin, R.T.; Long, H.C. De; Fuller, J.; Lauderdale, W.J.; Naughton, T.; Trulove, P.C.; Bahn, C.S.

    1995-12-31

    Dual Intercalating Molten Electrolyte (DIME) electrodes and cells have been examined using a number of low-melting and room-temperature molten salts. A cell with a chloroaluminate melt achieved a cycling efficiency of 85% with a discharge voltage of 2.92 V. Coke-elastomer composite electrodes underwent cation reductive intercalation without experiencing the exfoliation and degradation seen for graphite rods. Theoretical studies for an imidazolium-graphite intercalate predicted the graphite layer spacing expands between 5.18 and 8.01 {angstrom} upon insertion of the imidazolium molecule into the graphite lattice.

  13. Comparative optical study of the two-dimensional donor-type intercalation compounds graphite-KHx and their binary counterparts C8K and C24K

    NASA Astrophysics Data System (ADS)

    Doll, G. L.; Yang, M. H.; Eklund, P. C.

    1987-06-01

    We report the results of optical reflectivity studies of the stage-1 and -2 graphite-KHx intercalation compounds prepared by direct reaction of highly ordered pyrolytic graphite and KH powder. The stage-1 and -2 binary graphite-K compounds are studied for comparison. The optical data are analyzed in terms of a model involving two-dimensional (2D) graphitic π electrons and three-dimensional (3D) nearly free K(4s) electrons. The model is used to interpret the observed values of the free-carrier unscreened plasma frequencies and the position of the interband absorption threshold to determine experimental values for the Fermi level (EF) in the carbon π band(s) and the fractional occupation of the K(4s) band. For the hydrides, we find quantitative evidence that the hydrogen states lie below EF. Thus, hydrogen is present as H-, acting as an acceptor, thereby compensating the electron donation to the π bands from the K(4s) states. This assumption and the optical data for the stage-1 and -2 hydrides results in a [H]/[K] ratio of 0.8, in excellent agreement with chemical analyses reported by Guérard and co-workers, and leads to very small values for the fractional K(4s) band occupation fK<0.03 electrons per K atom. Within the framework of a superimposed 2D (π) and 3D [K(4s)] rigid-band model, our experimental results support an empty K(4s) band (i.e., fK=0) in stage-2 C24K. In stage-1 C8K, the rigid-band model yields large values for fK (fK>0.5 electrons per K atom), unless the value of the optical mass of the electrons in the K(4s) states is larger than ~2. The C8K results are also discussed in terms of more sophisticated energy-band calculations.

  14. Effect of heat-treatment temperature of vapor-grown graphite fibers. I - Properties of their bromine intercalation compounds

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Hambourger, Paul D.; Slabe, Melissa E.

    1989-01-01

    Vapor-grown graphite fibers were heat treated at 2000, 2200, 2400, 2600, 2800, and 3000 C, brominated at room temperature for two days, and then characterized by X-ray diffraction analysis, differential scanning calorimetry, and resistivity measurements. Fibers greater than 13 microns in diameter had low resistivities (50 microohms or less) irrespective of the heat treatment temperature. An analysis of the results obtained suggests that resistivities below 6 microohms cannot be achieved through a further reduction in defect level unless the amount of bromine is increased.

  15. Structural studies of intercalants

    SciTech Connect

    Hastings, J.B.

    1981-01-01

    The structure of stage 2 potassium intercalated graphite, KC/sub 24/, is discussed in both the ordered and disordered phases. A one-dimensional model is used to illustrate the qualitative features of the KC/sub 24/ diffraction patterns.

  16. Development of Intercalated Wire and Cable.

    DTIC Science & Technology

    1984-02-01

    powder is washed with deionized H20 to remove any unintercalated CuCl 2. To drive off this wash water the powder is heated overnight in a vacuum. Still...Die Design ...... .................. 16 3. Pressure Effects ......... 17 4. CuCl ,-Graphite Experiments ... * 19 5. Conclusions ......... . . . . 19...for most of the intercalated graphite compounds that have been studied to date. Thus, the revelation (9) that CuCl 2 intercalated graphite is entirely

  17. A comparative study on the impact of different glymes and their derivatives as electrolyte solvents for graphite co-intercalation electrodes in lithium-ion and sodium-ion batteries.

    PubMed

    Jache, Birte; Binder, Jan Oliver; Abe, Takeshi; Adelhelm, Philipp

    2016-06-07

    The abundance of sodium has recently sparked considerable interest in sodium-ion batteries (NIBs). Their similarity to conventional lithium-ion technology is obvious; however, the cell chemistry often significantly deviates. Graphite, although being the standard negative electrode in Li-ion batteries, is largely inactive for Na-ion storage in conventional non-aqueous carbonate-based electrolytes, for example. Very recently, it has been demonstrated that graphite can be activated for Na-ion storage in cells with ether-based electrolytes. The storage mechanism is based on co-intercalation of solvent molecules along with the Na-ions, forming ternary graphite intercalation compounds (t-GICs). This process is highly reversible but yet poorly understood. Here, we provide a comprehensive study on the formation and the stability of t-GICs. A series of ether solvents are being discussed: linear glymes with different chain lengths (mono-, di-, tri-, and tetraglyme), several derivatives with side groups as well as tetrahydrofuran (THF) as a cyclic ether and one crown ether. We show that the redox potentials shift depending on the ether chain length and mixing of ethers might enable tailoring of the redox behaviour. The inferior behaviour of triglyme is likely due to the less ideal ion coordination. Complementary experiments with lithium are made and demonstrate the superior behaviour of sodium. We find that the increase in graphene layer spacing during intercalation only slightly depends on the chain length and is in the range of 250%, and still mechanical stability is preserved. We further show the t-GICs possess chemical stability and demonstrate that the kinetically favoured charge transfer is probably due to the absence of a solid electrolyte interphase.

  18. The mechanism of caesium intercalation of graphene.

    PubMed

    Petrović, M; Šrut Rakić, I; Runte, S; Busse, C; Sadowski, J T; Lazić, P; Pletikosić, I; Pan, Z-H; Milun, M; Pervan, P; Atodiresei, N; Brako, R; Šokčević, D; Valla, T; Michely, T; Kralj, M

    2013-01-01

    Properties of many layered materials, including copper- and iron-based superconductors, topological insulators, graphite and epitaxial graphene, can be manipulated by the inclusion of different atomic and molecular species between the layers via a process known as intercalation. For example, intercalation in graphite can lead to superconductivity and is crucial in the working cycle of modern batteries and supercapacitors. Intercalation involves complex diffusion processes along and across the layers; however, the microscopic mechanisms and dynamics of these processes are not well understood. Here we report on a novel mechanism for intercalation and entrapment of alkali atoms under epitaxial graphene. We find that the intercalation is adjusted by the van der Waals interaction, with the dynamics governed by defects anchored to graphene wrinkles. Our findings are relevant for the future design and application of graphene-based nano-structures. Similar mechanisms can also have a role for intercalation of layered materials.

  19. A method to remove intercalates from bromine and iodine intercalated carbon fibers

    NASA Technical Reports Server (NTRS)

    Hung, Ching-Cheh

    1993-01-01

    Upon exposure to room-temperature fluorine, intercalated carbon fibers (containing either bromine alone or iodine and bromine together) become heavier and less stable. For Amoco P-100 graphitized carbon fibers which were intercalated with 18 percent bromine by weight, 1 hr of fluorine exposure results in a large weight increase, but causes only a small decrease in thermal stability. More than l hr of fluorine exposure time results in small additional increases in fiber weight, but significant further decreases in fiber thermal stability. Such phenomena do not occur if the fluorine exposure is at 250 C. These observations suggest the mechanism that at room temperature, fluorine is absorbed quickly by the intercalated fibers and intercalated slowly into the fibers. Most of the original intercalates are replaced by fluorine in the process of fluorine intercalation. Under an inert environment, the bromine intercalated fibers are much more thermally stable. After 800 C vacuum heating for two weeks, the brominated fibers lost about 45 percent of their bromine, and their resistivity increased from 64 omega-cm to a range of 95 to 170 micro omega-cm. This is still much lower than the 300 micro omega-cm value for pristine P-100. For practical purposes, in order to preserve their thermal stability, brominated fibers need to be protected from exposure to fluorine at room temperature, or to any intercalate at a temperature where, upon direct contact to graphite, an intercalation compound can easily be formed.

  20. Development of intercalated wire and cable

    NASA Astrophysics Data System (ADS)

    Vogel, F. L.

    1984-02-01

    An extensive study was conducted on the swaging of composite wires consisting of an intercalated graphite core in a copper sheath. The purpose was to develop a method that replicated earlier results wherein high electrical conductivity was encountered. The project was unable to produce those earlier, favorable results. It was determined that analysis of core resistivity cannot be done where the core has a higher resistivity than the sheath. Copper chloride was shown to be an air stable intercalant in graphite with a crystal resistivity in the vicinity of 5 x 10 to the minus 6 ohm cm. The main problem of swaging cored tube samples remains unsolved.

  1. Method for producing thin graphite flakes with large aspect ratios

    DOEpatents

    Bunnell, L. Roy

    1993-01-01

    A method for making graphite flakes of high aspect ratio by the steps of providing a strong concentrated acid and heating the graphite in the presence of the acid for a time and at a temperature effective to intercalate the acid in the graphite; heating the intercalated graphite at a rate and to a temperature effective to exfoliate the graphite in discrete layers; subjecting the graphite layers to ultrasonic energy, mechanical shear forces, or freezing in an amount effective to separate the layes into discrete flakes.

  2. Brazing graphite to graphite

    DOEpatents

    Peterson, George R.

    1976-01-01

    Graphite is joined to graphite by employing both fine molybdenum powder as the brazing material and an annealing step that together produce a virtually metal-free joint exhibiting properties similar to those found in the parent graphite. Molybdenum powder is placed between the faying surfaces of two graphite parts and melted to form molybdenum carbide. The joint area is thereafter subjected to an annealing operation which diffuses the carbide away from the joint and into the graphite parts. Graphite dissolved by the dispersed molybdenum carbide precipitates into the joint area, replacing the molybdenum carbide to provide a joint of virtually graphite.

  3. Effect of graphite surface structure on initial irreversible reaction in graphite anodes

    SciTech Connect

    Suzuki, Kimihito; Hamada, Takeshi; Sugiura, Tsutomu

    1999-03-01

    The initial irreversible reaction that occurs in graphite anodes during the first lithium intercalation in lithium rechargeable batteries was studied in view of graphite surface structure. Graphitized mesophase spheres and pitch-based carbon fibers, which show low irreversible capacity, were shown to have turbostatic surface regions and highly graphitized cores using Ar-ion laser Raman spectroscopy. Burning off these surface regions resulted in remarkable increases of initial irreversible capacity. Those results can be explained by a proposed model that a turbostatic structure of the graphite surface region resists drastic swelling of interlayer spaces arising from cointercalation of solvated ions and depresses the side reaction.

  4. Structural and kinetic characterization of lithium intercalation into carbon anodes for secondary lithium batteries

    SciTech Connect

    Takami, Norio; Satoh, Asako; Hara, Michikazu; Ohsaki, Takahisa

    1995-02-01

    Electrochemical intercalation of lithium into carbons has been studied using mesophase-pitch-based carbon fibers with different heat-treatment temperatures, coke, and graphites as anodes for secondary lithium batteries. The variations in the average layer spacing and the voltage profile for the carbons with intercalating depend on the degree of graphitization. The intercalation into a more disordered carbon fiber heated at 900 C has been characterized as intercalation into the layer structure for 0 < x < 0.5 in Li{sub x}C{sub 6}, but additional lithium insertion into an unorganized carbon loses the layer structure. The polarization resistance (R{sub p}) estimated from the impedance spectrum decreased by increasing degree of graphitization. The variation in R{sub p} with intercalation revealed the intercalation processes in various disordered carbons to be single-phase reactions with different stoichiometries of lithium intercalation. The chemical diffusion coefficient D{sub Li} of lithium ions in carbons decreased by increasing the composition x in Li{sub x}C{sub 6} up to x = 0.5. The chemical diffusion coefficient was considerably affected by the texture and the degree of graphitization of the carbons. The graphitized carbon fiber heated at 3,000 C for 0.1 < x < 0.5 in Li{sub x}C{sub 6} exhibited one order magnitude larger values of D{sub Li} than those of graphites. The rapid diffusion in the graphitized carbon fiber has been attributed to the radial texture in the cross section. It has been found that the activation energy for the diffusion process decreased by increasing the degree of graphitization.

  5. Carbonaceous materials as lithium intercalation anodes

    SciTech Connect

    Tran, T.D.; Feikert, J.H.; Mayer, S.T.; Song, X.; Kinoshita, K.

    1994-10-01

    Commercial and polymer-derived carbonaceous materials were examined as lithium intercalation anodes in propylene carbonate (pyrolysis < 1350C, carbons) and ethylene carbonate/dimethyl carbonate (graphites) electrolytes. The reversible capacity (180--355 mAh/g) and the irreversible capacity loss (15--200 % based on reversible capacity) depend on the type of binder, carbon type, morphology, and phosphorus doping concentration. A carbon-based binder was chosen for electrode fabrication, producing mechanically and chemically stable electrodes and reproducible results. Several types of graphites had capacity approaching LiC{sub 6}. Petroleum fuel green cokes doped with phosphorous gave more than a 20 % increase in capacity compared to undoped samples. Electrochemical characteristics are related to SEM, TEM, XRD and BET measurements.

  6. Graphite on graphite

    NASA Astrophysics Data System (ADS)

    Volovik, G. E.; Pudalov, V. M.

    2016-12-01

    We propose potential geometry for fabrication of the graphite sheets with atomically smooth edges. For such sheets with Bernal stacking, the electron-electron interaction and topology should cause sufficiently high density of states resulting in the high temperature of either spin ordering or superconducting pairing.

  7. The growth of graphite phase on an iridium field electron emitter

    NASA Astrophysics Data System (ADS)

    Bernatskii, D. P.; Pavlov, V. G.

    2016-06-01

    The growth of graphite on the surface of an iridium tip in pyrolysis of benzene to give a ribbed crystal has been found by the methods of field electron and desorption microscopy. The formation of a graphite crystal results in the electric field factor increasing. The adsorption of alkali metals on the surface of graphite is accompanied by the intercalation effect.

  8. On the choice of graphite for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Simon, B.; Flandrois, S.; Guerin, K.; Fevrier-Bouvier, A.; Teulat, I.; Biensan, P.

    Graphites as active materials for negative electrode in lithium batteries are particularly attractive because of their large capacity of lithium intercalation and their low average voltage. In some conditions, they are known to suffer from low reversibility of the initial intercalation process. This phenomenon is shown to be unambiguously related to an exfoliation of graphene layers, that can occur even in EC based electrolytes. Occurrence of a clear correlation between the extent of irreversible behaviour and rhombohedral phase content of graphites is discussed. Milling or thermal treatment of pristine graphites are also shown to influence electrochemical properties.

  9. Thin flexible intercalation anodes

    SciTech Connect

    Levy, S.C.; Cieslak, W.R.; Klassen, S.E.; Lagasse, R.R.

    1994-10-01

    Poly(acrylonitrile) fibers have been pyrolyzed under various conditions to form flexible carbon yarns capable of intercalating lithium ions. These fibers have also been formed into both woven and non woven cloths. Potentiostatic, potentiodynamic and galvanostatic tests have been conducted with these materials in several electrolytes. In some tests, a potential hold was used after each constant current charge and discharge. These tests have shown some of these flexible materials to reversibly intercalate lithium ions to levels that are suitable for use as a practical battery anode.

  10. Room-Temperature Fluorine-Induced Decrease in the Stability of Bromine and Iodine Intercalated Carbon Fibers

    NASA Technical Reports Server (NTRS)

    Hung, Ching-Cheh

    1995-01-01

    Upon exposure to room-temperature fluorine, intercalated carbon fibers (containing either bromine alone or iodine and bromine together) become heavier and less stable. For Amoco P-100 graphitized carbon fibers, which were intercalated with 18 wt percent bromine, 1 hour of fluorine exposure resulted in a large weight increase but caused only a small decrease in thermal stability. An additional 89 hours of fluorine exposure time resulted in small additional increases in fiber weight, but significant further decreases in fiber thermal stability. Such phenomena of weight increase and stability decrease do not occur if the intercalated fibers are exposed to 250 C fluorine. These observations suggest that, at room temperature, fluorine is absorbed quickly by the intercalated fibers and is intercalated slowly into the fibers. Most of the original intercalates are replaced by fluorine in the process of fluorine intercalation. In an inert environment, the bromine intercalated fibers are much more thermally stable. After 800 C vacuum heating for 2 weeks, the brominated fibers lost about 45% of their bromine, and their resistivity increased from 64 mu(Omega)-cm to a range of 95-170 mu(Omega)-cm. This is still much lower than the value of 300 mu(Omega)-cm for pristine P-100. For practical purposes, to preserve their thermal stability, brominated fibers need to be protected from exposure to fluorine at room temperature or to any intercalate at a temperature where, upon direct contact with graphite, an intercalation compound can easily be formed.

  11. Novel graphite salts of high oxidizing potential

    SciTech Connect

    McCarron, E.M. III

    1980-08-01

    The intercalation of graphite by the third-transition-series metal hexafluorides has yielded the graphite salts, C/sub 8//sup +/OsF/sub 6//sup -/, C/sub 8//sup +/IrF/sub 6//sup -/ and C/sub 12//sup 2 +/PtF/sub 6//sup 2 -/. The fluoroplatinate salt represents the highest electron withdrawal from the graphite network yet achieved. Analogues to the Os and Ir salts have been obtained both by fluorination of Group V pentaflouride intercalates, C/sub 8/MF/sub 5/ (M = As, Sb), and by the interaction of the dioxygenyl salts with graphite (8C + O/sub 2/MF/sub 6/ ..-->.. C/sub 8/MF/sub 6/ + O/sub 2/+). Non-intercalating binary fluorides have been observed to intercalate in the presence of a fluorine-rich environment (e.g., 8C + PF/sub 5/ + 1/2 F/sub 2/ ..-->.. C/sub 8/PF/sub 6/). GeF/sub 4/, which also does not spontaneously intercalate graphite, has been observed to interact with graphite in the presence of 2 atmospheres of fluorine overpressure to give the fluoroplatinate salt analogue, C/sub 12//sup 2 +/GeF/sub 6//sup 2 -/. This material is in equilibrium with the pentafluorogermanate at ordinary pressures and temperatures. C/sub 12//sup 2 +/GeF/sub 6//sup 2 -/ ..-->.. C/sub 12//sup +/GeF/sub 5//sup -/ + 1/2 F/sub 2/. C/sub 12/GeF/sub 6/ must have an oxidizing potential close to that of fluorine itself. The graphite fluorometallate salts are both electronic and ionic (F/sup -/) conductors. For the C/sub 8//sup +/MF/sub 6//sup -/ salts, a maximum electronic conductivity an order of magnitude greater than the parent graphite has been observed for stage two. The high oxidizing potential, coupled with the fluoride ion transport capability of the graphite salts, has been exploited in the construction of solid-state galvanic cells. These cells use the graphite fluorometallate salts as electrode materials in combination with a superionic fluoride-ion-conducting solid electrolyte.

  12. 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

  13. GRAPHITE EXTRUSIONS

    DOEpatents

    Benziger, T.M.

    1959-01-20

    A new lubricant for graphite extrusion is described. In the past, graphite extrusion mixtures have bcen composed of coke or carbon black, together with a carbonaceous binder such as coal tar pitch, and a lubricant such as petrolatum or a colloidal suspension of graphite in glycerin or oil. Sinee sueh a lubricant is not soluble in, or compatible with the biiider liquid, such mixtures were difficult to extrude, and thc formed pieees lacked strength. This patent teaches tbe use of fatty acids as graphite extrusion lubricants and definite improvemcnts are realized thereby since the fatty acids are soluble in the binder liquid.

  14. Stacking interactions and DNA intercalation

    SciTech Connect

    Li, Dr. Shen; Cooper, Valentino R; Thonhauser, Prof. Timo; Lundqvist, Prof. Bengt I.; Langreth, David C.

    2009-01-01

    The relationship between stacking interactions and the intercalation of proflavine and ellipticine within DNA is investigated using a nonempirical van der Waals density functional for the correlation energy. Our results, employing a binary stack model, highlight fundamental, qualitative differences between base-pair base-pair interactions and that of the stacked intercalator base pair system. Most notable result is the paucity of torque which so distinctively defines the Twist of DNA. Surprisingly, this model, when combined with a constraint on the twist of the surrounding base-pair steps to match the observed unwinding of the sugar-phosphate backbone, was sufficient for explaining the experimentally observed proflavine intercalator configuration. Our extensive mapping of the potential energy surface of base-pair intercalator interactions can provide valuable information for future nonempirical studies of DNA intercalation dynamics.

  15. Modified natural graphite as anode material for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Wu, Y. P.; Jiang, C.; Wan, C.; Holze, R.

    A concentrated nitric acid solution was used as an oxidant to modify the electrochemical performance of natural graphite as anode material for lithium ion batteries. Results of X-ray photoelectron spectroscopy, electron paramagnetic resonance, thermogravimmetry, differential thermal analysis, high resolution electron microscopy, and measurement of the reversible capacity suggest that the surface structure of natural graphite was changed, a fresh dense layer of oxides was formed. Some structural imperfections were removed, and the stability of the graphite structure increased. These changes impede decomposition of electrolyte solvent molecules, co-intercalation of solvated lithium ions and movement of graphene planes along the a-axis direction. Concomitantly, more micropores were introduced, and thus, lithium intercalation and deintercalation were favored and more sites were provided for lithium storage. Consequently, the reversible capacity and the cycling behavior of the modified natural graphite were much improved by the oxidation. Obviously, the liquid-solid oxidation is advantageous in controlling the uniformity of the products.

  16. Intercalation of WF 6 in the interlayer space of multiwall carbon nanotubes—structural and morphological aspects

    NASA Astrophysics Data System (ADS)

    Claves, D.; Giraudet, J.; Schouler, M. C.; Gadelle, P.; Hamwi, A.

    2004-04-01

    The reactivity of multiwall carbon nanotubes toward WF 6, a strong Lewis acid, has been studied. A material of nominal composition C 36WF 6 has been obtained and characterized by X-ray diffraction. Intercalation between pseudo-graphitic layers has been evidenced, leading to a staging phenomenon at the nanometer scale. A structural model is proposed and the intercalation chemistry of multiwalled carbon nanotubes is discussed.

  17. Superconductivity in intercalated group-IV honeycomb structures

    NASA Astrophysics Data System (ADS)

    Flores-Livas, José A.; Sanna, Antonio

    2015-02-01

    We present a theoretical investigation on the electron-phonon superconductivity of honeycomb M X2 layered structures where X is one element of group IV (C, Si, or Ge) and M is an alkali or an alkaline-earth metal. Among the studied compositions we predict a TC of 7 K in RbGe2, 9 K in RbSi2, and 11 K in SrC2. All these compounds feature a strongly anisotropic superconducting gap. Our results show that despite the different doping levels and structural properties, the three families of materials fall into a similar description of their superconducting behavior. This allows us to estimate an upper critical temperature of about 20 K for the class of intercalated group-IV structures, including intercalated graphite and doped graphene.

  18. Lithium intercalation behavior of surface modified carbonaceous materials

    SciTech Connect

    Tran, T.D.; Murguia, L.X.; Song, X.; Kinoshita, K.

    1997-07-17

    The surface properties of several well-characterized commercial carbon materials were modified by thermal and chemical treatments. The reversible capacities for lithium intercalation of a sponge green coke and a fuel green coke for lithium intercalation increased by as much as 25% after heat treatment in both reducing (5% H{sub 2}/Ar) and oxidizing (CO{sub 2}) environments. The irreversible capacity loss increased significantly with CO{sub 2} treatment at 800{degrees}C. The trend of larger capacity losses with CO{sub 2} treatment is also observed with a synthetic graphite (SFG6) which was produced by heat treatment at about 3000{degrees}C. Carbon fibers that were first impregnated with LiOH solution followed by reaction with CO{sub 2} to form Li{sub 2}CO{sub 3} tended to show lower irreversible capacity losses.

  19. A new way to synthesize superconducting metal-intercalated C60 and FeSe

    PubMed Central

    Takahei, Yuuki; Tomita, Keitaro; Itoh, Yugo; Ashida, Keishi; Lee, Ji-Hyun; Nishimoto, Naoki; Kimura, Takumi; Kudo, Kazutaka; Nohara, Minoru; Kubozono, Yoshihiro; Kambe, Takashi

    2016-01-01

    Doping with the optimum concentration of carriers (electrons or holes) can modify the physical properties of materials. Therefore, improved ways to achieve carrier doping have been pursued extensively for more than 50 years. Metal-intercalation is one of the most important techniques for electron doping of organic / inorganic solids, and has produced superconductors from insulators and metallic solids. The most successful examples are metal-intercalated graphite and C60 superconductors. Metal intercalation has been performed using solid-reaction and liquid solvent techniques. However, precise control of the quantity of intercalants in the target solids can be difficult to achieve using these methods, as that quantity depends largely on the initial conditions. Here we report an electrochemical method for metal-intercalation, and demonstrate the preparation of superconductors using organic and inorganic materials (C60 and FeSe). The metal atoms are effectively intercalated into the spaces in C60 and FeSe solids by supplying an electric current between electrodes in a solvent that includes electrolytes. The recorded superconducting transition temperatures, Tc’s, were the same as those of metal-intercalated C60 and FeSe prepared using solid-reaction or liquid solvent techniques. This technique may open a new avenue in the search for organic / inorganic superconductors. PMID:26732250

  20. Fundamental Electronic Properties of Donor-Type Graphite Intercalated Compounds.

    DTIC Science & Technology

    1984-08-01

    Wiedenmann Laboratoire de Diffraction Neutronique , Department de Recherche Fondamentale, Centre d’Etudes Nucleaires, 85X, F-38 041 Grenoble, France...due to anisotropic *lec- anomalies. tron-phonon interaction. The surprising change to activated behavior below SOK suggests local- lies are... activated process but the 100 A (e along c - 2, ni - 1018/c*3 )1 6 , the results are not well represented by the con- nonlinear Thomas-Fearm calculation

  1. Characterization of Intercalated Graphite Fibers for Microelectromechanical Systems (MEMS) Applications

    DTIC Science & Technology

    2007-03-01

    using the PolyMUMPs pro- cess, were designed with an inset trench that 10 µm diameter carbon fibers could be mounted into for testing, this reduced... Design and Fabrication . . . . . . . . . 48 4.1 PolyMUMPS Process . . . . . . . . . . . . . . . . . . . 48 4.2 PolyMUMPS Material Properties... Designs . . . . . . . . . . . . . 54 4.3.1 Analytical Modeling of Force for Test Structures 55 4.3.2 Coventorware Modeling of Test Structures . . 57 4.4

  2. High van Hove singularity extension and Fermi velocity increase in epitaxial graphene functionalized by intercalated gold clusters

    NASA Astrophysics Data System (ADS)

    Nair, M. N.; Cranney, M.; Vonau, F.; Aubel, D.; Le Fèvre, P.; Tejeda, A.; Bertran, F.; Taleb-Ibrahimi, A.; Simon, L.

    2012-06-01

    Gold intercalation between a buffer layer and a graphene monolayer of epitaxial graphene on SiC(0001) leads to the formation of small aggregates of clusters. Angle-resolved photoemission spectroscopy measurements reveal that these clusters preserve the linear dispersion of the graphene quasiparticles and surprisingly increase their Fermi velocity. They also strongly modify the band structure of graphene around the van Hove singularities by a strong extension without charge transfer. These results give new insight on the role of the intercalant in the renormalization of the bare electronic band structure of graphene usually observed in graphite and graphene intercalation compounds.

  3. Graphite Revisited

    NASA Astrophysics Data System (ADS)

    Draine, B. T.

    2016-11-01

    Laboratory measurements are used to constrain the dielectric tensor for graphite, from microwave to X-ray frequencies. The dielectric tensor is strongly anisotropic even at X-ray energies. The discrete dipole approximation is employed for accurate calculations of absorption and scattering by single-crystal graphite spheres and spheroids. For randomly oriented single-crystal grains, the so-called 1/3{--}2/3 approximation for calculating absorption and scattering cross sections is exact in the limit a/λ \\to 0 and provides better than ∼10% accuracy in the optical and UV even when a/λ is not small, but becomes increasingly inaccurate at infrared wavelengths, with errors as large as ∼40% at λ =10 μ {{m}}. For turbostratic graphite grains, the Bruggeman and Maxwell Garnett treatments yield similar cross sections in the optical and ultraviolet, but diverge in the infrared, with predicted cross sections differing by over an order of magnitude in the far-infrared. It is argued that the Maxwell Garnett estimate is likely to be more realistic, and is recommended. The out-of-plane lattice resonance of graphite near 11.5 μm may be observable in absorption with the MIRI spectrograph on James Webb Space Telescope. Aligned graphite grains, if present in the interstellar medium, could produce polarized X-ray absorption and polarized X-ray scattering near the carbon K edge.

  4. Flexible graphite as battery anode and current collector

    NASA Astrophysics Data System (ADS)

    Yazici, M. S.; Krassowski, D.; Prakash, J.

    In making graphite-based electrodes and current collectors, there is significant simplification if a flexible graphite process is used. The lithium intercalation capacity of Grafoil ® flexible graphite sheet and its powder was evaluated using electrochemical charge-discharge cycling in half-cell configuration (coin cell with Li anode and graphite cathode). The sheet form was used with and without a copper current collector. Excellent electrical conductivity of the monolithic material with very low interface resistance helps as current collector and electrode. The comparatively low capacity of Grafoil ® sheet is thought to be due to diffusion limitation of the structure, especially in the light of the very high capacity of its powder form. The highly irreversible capacity of the powdered material may be due to unfunctionalized graphitic structures or impurities present in the powder. Impedance response for the first intercalation-deintercalation was different than responses taken after several cycles. The presence of a second impedance arc suggests structural modification is taking place in the graphite anode, possibly through formation of a porous structure as a result of graphite expansion. ®GRAFOIL is a registered trademark of Advanced Energy Technology Inc.

  5. NOVEL GRAPHITE SALTS AND THEIR ELECTRICAL CONDUCTIVITIES

    SciTech Connect

    Bartlett, N.; McCarron, E.M.; McQuillan, B.W.; Thompson, T.E.

    1980-02-01

    A set of novel first stage graphite salts of general formula C{sub 8}{sup +}MF{sub 6}{sup -} has been prepared (M = Os, Ir, As). Single crystal X-ray diffraction studies indicate that these salts are hexagonal with a {approx} 4.9 and c {approx} 8.1 {angstrom}. The unit cell volume indicates that the anions are closely packed in the galleries. Platinum hexafluoride, which is the most powerful oxidizer of the third transition series, forms a first stage compound, which analytical, structural, and magnetic studies establish as C{sub 12}{sup 2+}PtF{sub 6}{sup 2-}. In this salt the anions are not close packed, but the electron withdrawal from the graphite planes is greater than for the C{sub 8}{sup +}MF{sub 6}{sup -} series. The variation in the electrical conductivity (in the a-b plane), as a function of composition, has been investigated with the OsF{sub 6}, IrF{sub 6}, PtF{sub 6} and AsF{sub 5} intercalates. For OsF{sub 6} and IrF{sub 6}, the conductance per plane of graphite is found to be a maximum at approximately C{sub 24}MF{sub 6} (second stage); the conductivity being an order of magnitude greater than that of the parent material. Intercalation beyond C{sub 24}MF{sub 6} leads to a marked decrease in conductivity. C{sub 8}MF{sub 6} is comparable in conductivity with the parent graphite. This behavior contrasts with the graphite/AsF{sub 5} system in which a steady increase in conductance per graphite plane with increasing AsF{sub 5} content is observed. For the PtF{sub 6} system, the second as well as the first stage materials are poorly conducting.

  6. Preparation of intercalation compounds of carbon fibers through electrolysis using phosphoric acid electrolyte and their exfoliation

    NASA Astrophysics Data System (ADS)

    Toyoda, Masahiro; Yoshinaga, Aya; Amao, Yutaka; Takagi, Hideyuki; Soneda, Yasushi; Inagaki, Michio

    2006-05-01

    Preparation of intercalation compounds using H3PO4 electrolyte solution in mesophase-pitch-based carbon fibers successfully carried out by electrolysis in less than 10 mol/dm3 of its electrolyte solution. Structural changes with preparation of intercalation compounds of carbon fibers were confirmed by a peak appeared around 2θ=8° observed after electrolysis, which corresponds to an interlayer spacing of about 0.9 nm through XRD pattern (anticathode: Cu Kα). This new peak was reasonably supposed to be due to the intercalation into interspacing of carbon layers. Suitable synthesis condition of the intercalation compounds was determined to be the concentration of electrolyte of 5 mol/dm3 at the electrolysis. It was also confirmed by morphology changes through SEM, that is carbon fibers, which treated low electrolyte concentration synthesized the intercalation compounds easily, and then it revealed markedly morphology changes such as fibrils. It could become exfoliation as well as them treated by other acid treatment through rapid heat-treatment. The formation of graphite oxide was suggested when the kind of intercalate was analyzed with elementary and TPD analysis.

  7. Anode-electrolyte double-layer of Li-ion batteries: Structure and Li-ion intercalation

    NASA Astrophysics Data System (ADS)

    Wipf, David O.; Abou Hamad, Ibrahim; Rikvold, Per Arne; Novotny, Mark A.

    2011-03-01

    The electrochemical double-layer structure plays an important role in Li-ion intercalation during charging of Li-ion batteries with a graphite anode. In our recent Molecular Dynamics studies of a proposed accelerated charging method [I. Abou Hamad~et al., Phys. Chem. Chem. Phys. 12, 2740-2743 (2010)], we notice that ethylene carbonate and propylene carbonate molecules of the electrolyte assemble themselves in a preferred orientation at the electrode-electrolyte interface. On the other hand, they are randomly oriented in the bulk electrolyte. We show that the structure of the double layer is affected by the intercalating Li-ion: while the dipole moments of double-layer molecules far from the intercalating Li-ion point toward the graphite sheets of the anode, they point away from the intercalation site close to the intercalating Li-ion. This observation should contribute to a better understanding of the intercalation process. This work was supported in part by NSF Grant No. DMR-0802288.

  8. Thermally exfoliated graphite oxide

    NASA Technical Reports Server (NTRS)

    Prud'Homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor); Abdala, Ahmed (Inventor)

    2011-01-01

    A modified graphite oxide material contains a thermally exfoliated graphite oxide with a surface area of from about 300 sq m/g to 2600 sq m/g, wherein the thermally exfoliated graphite oxide displays no signature of the original graphite and/or graphite oxide, as determined by X-ray diffraction.

  9. Improvement of electrochemical characteristics of natural graphite negative electrode coated with polyacrylic acid in pure propylene carbonate electrolyte

    NASA Astrophysics Data System (ADS)

    Ui, Koichi; Kikuchi, Shinei; Mikami, Fuminobu; Kadoma, Yoshihiro; Kumagai, Naoaki

    In order to improve the negative electrode characteristics of a graphite electrode in a propylene carbonate (PC)-containing electrolyte, we have prepared a graphite negative electrode coated with a water-soluble anionic polymer as a binder for composite graphite electrodes. The electrochemical characteristics of the coated graphite were evaluated by cyclic voltammetry and charge-discharge cycle tests. The coated graphite negative electrode showed a stable Li + ion intercalation/deintercalation reaction without the exfoliation of the graphene layers caused by the co-intercalation of the PC solvent in the LiClO 4/PC solution. The charge-discharge characteristic of the coated graphite negative electrode in a PC-containing electrolyte was almost the same as that in ethylene carbonate-based electrolyte.

  10. Direct mapping of Li distribution in electrochemically lithiated graphite anodes using scanning Auger electron microscopy

    NASA Astrophysics Data System (ADS)

    Ishida, Nobuyuki; Fukumitsu, Hitoshi; Kimura, Hiroshi; Fujita, Daisuke

    2014-02-01

    The spatial distribution of Li ions in electrochemically lithiated graphite anodes for Li-ion battery is characterized by scanning Auger electron microscopy. We show that direct mapping of Li KVV peak intensity reveal the spatial distribution of intercalated Li and its chemical state in a quantitative manner. Furthermore, we demonstrate that mapping using a C KVV peak also reflects the spatial distribution of Li due to the change in the electronic properties of C atoms induced by the electrode reaction (Li intercalation). Mapping measurements on three samples with different charging states (20%, 50%, and 100%) show that at the early stage of charging Li ions do not intercalate homogenously into all the graphite particles but selectively into some specific ones with higher rates. Our method provides the criteria to evaluate structure-correlated Li intercalation from nanometer- to micrometer-scale, such as conductivity network in the electrodes due to a non-uniform morphology of binder and conductive additives.

  11. Batteries: Beyond intercalation and conversion

    NASA Astrophysics Data System (ADS)

    Grimaud, Alexis

    2017-01-01

    Conventional positive electrode materials for lithium-ion batteries, such as intercalation and conversion compounds, feature a host structure to reversibly insert and conduct lithium ions. Now, electrochemically activated transition metal oxide-lithium fluoride composite materials are shown to be a promising class of positive electrodes.

  12. Simultaneous electrical resistivity and mass uptake measurements in bromine intercalated fibers

    NASA Technical Reports Server (NTRS)

    Jaworske, D. A.

    1986-01-01

    Changes in mass and electrical resistivity of several types of pitch-based and vapor-grown graphite fibers were monitored during reaction with bromine. The observed threshold pressure dependent reaction suggested that the fibers were intercalated. In the fully brominated compound, the mass was increased by 44 percent and the resistivity was improved by a factor of 17. In the residue compound, the mass was increased by 22 percent and the resistivity was improved by a factor of 5. Fibers possessing different degrees of graphitization had surprisingly similar changes in both mass and resistivity.

  13. Synthesis of soluble graphite and graphene.

    PubMed

    Kelly, K F; Billups, W E

    2013-01-15

    resorting to oxidation. Our exfoliation process involves the intercalation of lithium into bulk graphite to yield graphene sheets reduced by the lithium. We can alkylate the resulting graphite salt reductively using solubilizing dodecyl groups. By probe microscopy, we show that these groups are attached covalently only at the graphitic edges.

  14. DFT Calculations of the Electronic Structure and Interlayer Interaction in the Li-INTERCALATED Graphene Bilayer

    NASA Astrophysics Data System (ADS)

    Petrova, N. V.; Yakovkin, I. N.

    The electronic band structure, density of states (DOS) and interlayer interaction in Li-intercalated graphene bilayers are studied by means of density functional theory (DFT) calculations. It has been found that for a pristine bilayer, the relative shift of graphene layers from AB stacking configuration, pertinent to a bulk graphite, to AA configuration results in the opening of the bandgap at Fermi level, so that the bilayer becomes a semiconductor. The Li intercalation of the graphene bilayer significantly increases the density of states at Fermi level, which can be considered as an increased metallicity. The electronic density in the space between graphene layers also substantially increases and leads to related increase of the interlayer interaction. We hope that the obtained results of calculations will be useful for various applications of Li-intercalated graphene layers in nanoelectronics.

  15. Controlling the actuation properties of MXene paper electrodes upon cation intercalation

    SciTech Connect

    Come, Jeremy E.; Black, Jennifer M.; Naguib, Michael; Lukatskaya, Maria R.; Beidaghi, Majid; Wesolowski, David J.; Gogotsi, Yury; Rondinone, Adam J.; Balke, Nina; Kalinin, Sergei V.

    2015-08-05

    Atomic force microscopy was used to monitor the macroscopic deformation in a delaminated Ti₃C₂ paper electrode in-situ, during charge/discharge in a variety of aqueous electrolytes to examine the effect of the cation intercalation on the electrochemical behavior and mechanical response. The results show a strong dependence of the electrode deformation on cation size and charge. The electrode undergoes a large contraction during Li⁺, Na⁺ or Mg²⁺ intercalation, differentiating the Ti₃C₂ paper from conventional electrodes where redox intercalation of ions (e.g. Li⁺) into the bulk phase (e.g. graphite, silicon) results in volumetric expansion. This feature may explain the excellent rate performance and cyclability reported for MXenes. We also demonstrated that the variation of the electromechanical contraction can be easily adjusted by electrolyte exchange, and shows interesting characteristics for the design of actuators based on 2D metal carbides.

  16. Bridged graphite oxide materials

    NASA Technical Reports Server (NTRS)

    Herrera-Alonso, Margarita (Inventor); McAllister, Michael J. (Inventor); Aksay, Ilhan A. (Inventor); Prud'homme, Robert K. (Inventor)

    2010-01-01

    Bridged graphite oxide material comprising graphite sheets bridged by at least one diamine bridging group. The bridged graphite oxide material may be incorporated in polymer composites or used in adsorption media.

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

    SciTech Connect

    Schwarz, Haiqing L.

    2016-01-01

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

  18. Nuclear graphite

    SciTech Connect

    Mercuri, R. A.; Criscione, J. M.

    1985-07-02

    A high strength, high coefficient of thermal expansion fine-grained isotropic graphite article produced from 30% to 70% of attritor milled gilsonite coke or other high CTE carbon filler particles and minor amounts of a binder such a coal tar pitch and petroleum pitch, the article being formed by warm isostatic molding at a temperature of between 50/sup 0/ C. and 70/sup 0/ C. under a pressure between 100 and 1000 psi for a time between 1 and 10 minutes. The particle size of the fillers ranges up to 150 microns.

  19. Ca intercalated bilayer graphene as a thinnest limit of superconducting C6Ca.

    PubMed

    Kanetani, Kohei; Sugawara, Katsuaki; Sato, Takafumi; Shimizu, Ryota; Iwaya, Katsuya; Hitosugi, Taro; Takahashi, Takashi

    2012-11-27

    Success in isolating a 2D graphene sheet from bulky graphite has triggered intensive studies of its physical properties as well as its application in devices. Graphite intercalation compounds (GICs) have provided a platform of exotic quantum phenomena such as superconductivity, but it is unclear whether such intercalation is feasible in the thinnest 2D limit (i.e., bilayer graphene). Here we report a unique experimental realization of 2D GIC, by fabricating calcium-intercalated bilayer graphene C(6)CaC(6) on silicon carbide. We have investigated the structure and electronic states by scanning tunneling microscopy and angle-resolved photoemission spectroscopy. We observed a free-electron-like interlayer band at the Brillouin-zone center, which is thought to be responsible for the superconductivity in 3D GICs, in addition to a large π* Fermi surface at the zone boundary. The present success in fabricating Ca-intercalated bilayer graphene would open a promising route to search for other 2D superconductors as well as to explore its application in devices.

  20. Layer Number Dependence of Li(+) Intercalation on Few-Layer Graphene and Electrochemical Imaging of Its Solid-Electrolyte Interphase Evolution.

    PubMed

    Hui, Jingshu; Burgess, Mark; Zhang, Jiarui; Rodríguez-López, Joaquín

    2016-04-26

    A fundamental question facing electrodes made out of few layers of graphene (FLG) is if they display chemical properties that are different to their bulk graphite counterpart. Here, we show evidence that suggests that lithium ion intercalation on FLG, as measured via stationary voltammetry, shows a strong dependence on the number of layers of graphene that compose the electrode. Despite its extreme thinness and turbostratic structure, Li ion intercalation into FLG still proceeds through a staging process, albeit with different signatures than bulk graphite or multilayer graphene. Single-layer graphene does not show any evidence of ion intercalation, while FLG with four graphene layers displays limited staging peaks, which broaden and increase in number as the layer number increases to six. Despite these mechanistic differences on ion intercalation, the formation of a solid-electrolyte interphase (SEI) was observed on all electrodes. Scanning electrochemical microscopy (SECM) in the feedback mode was used to demonstrate changes in the surface conductivity of FLG during SEI evolution. Observation of ion intercalation on large area FLG was conditioned to the fabrication of "ionic channels" on the electrode. SECM measurements using a recently developed Li-ion sensitive imaging technique evidenced the role of these channels in enabling Li-ion intercalation through localized flux measurements. This work highlights the impact of nanostructure and microstructure on macroscopic electrochemical behavior and provides guidance to the mechanistic control of ion intercalation using graphene, an atomically thin interface where surface and bulk reactivity converge.

  1. Preparation of graphitic articles

    DOEpatents

    Phillips, Jonathan; Nemer, Martin; Weigle, John C.

    2010-05-11

    Graphitic structures have been prepared by exposing templates (metal, metal-coated ceramic, graphite, for example) to a gaseous mixture that includes hydrocarbons and oxygen. When the template is metal, subsequent acid treatment removes the metal to yield monoliths, hollow graphitic structures, and other products. The shapes of the coated and hollow graphitic structures mimic the shapes of the templates.

  2. Water Interaction with Pristine and Nanopatterned Graphite Surfaces

    NASA Astrophysics Data System (ADS)

    Chakarov, Dinko

    2015-03-01

    We used number of surface sensitive techniques to study and compare the interaction of water with pristine surface of highly oriented pyrolytic graphite and model nanostructured surfaces fabricated by hole-mask colloidal lithography and oxygen plasma etching. Surface morphology and concentration of defects play important role and determine the amount of water bound in two- and three-dimensional hydrogen-bonded networks and thus the structure of ice films. Similarly, the amount and concentration of intersheet openings control the rate of water intercalation into graphite structures. The new findings are of particular interest for development of graphene exfoliation methods and for better understanding of graphene functionalization.

  3. The milling of pristine and brominated P-100 graphite fibers

    NASA Technical Reports Server (NTRS)

    Dillehay, M. E.; Gaier, J. R.

    1986-01-01

    Techniques were developed for the ball milling of pristine and brominated P-100 graphite fibers. Because of the lubrication properties of graphite, large ball loads (50 percent by volume) were required. Use of 2-propanol as a milling medium enhanced the efficiency of the process. Milled brominated P-100 fibers had resistivities which were indistinguishable from milled pristine P-100 fibers. Apparent loss of bromine from the brominated fibers suggests that bromine would not be the intercalate of choice in applications where milled fibers of this type are required. Other intercalates which do not degas may be more appropriate for a milled fiber application. These same results, however, do provide evidence that bromine molecules leave the fiber surface when removed from overpressure of bromine. While exploring possible solvent media for milling purposes, it was found that brominated fibers are stable in a wide variety of organic solvents.

  4. Electron oxidation of graphite by fluorospecies

    SciTech Connect

    Rosenthal, G.L.

    1984-09-01

    The fluoride-ion affinity (A/sub F/sup -//) of phosphorus pentafluoride was determined to be 100 kcal/mole from the heats of reaction of the Lewis bases SF/sub 4/ and ClO/sub 2/F with PF/sub 5/ near room temperature. The fluoride-ion affinity of boron trifluoride was determined to be 92 kcal/mole from the heat of reaction of ClO/sub 2/F with BF/sub 3/. The crystal structure of ClO/sub 2/BF/sub 4/ was determined and a precise lattice energy was calculated from this structure and used to determined A/sub F/sup -//. Both PF/sub 5/ and BF/sub 3/ were found to react with graphite in the presence of fluorine gas to yield a variety of non-stoichiometric compounds. The fluoride-ion affinity of silicon tetrafluoride is not known, but it does not react with graphite and F/sub 2/ except at high pressures. These and previous results suggested a threshold in oxidizing power of intercalating species below which the oxidative intercalation reaction would not occur. The reduction of C/sub x/PF/sub 6/ by PF/sub 3/ proved that the reaction is thermodynamically controlled to some extent. The displacement of PF/sub 5/ in C/sub x/PF/sub 6/ by BF/sub 3/ (with a smaller A/sub F/sup -//) suggested that two BF/sub 3/ molecules may have a larger fluoride-ion affinity than one PF/sub 5/ and that B/sub 2/F/sub 7//sup -/ may be a stable anion in graphite. Conductivity studies of PF/sub x/ and BF/sub y/ salts showed that a large drop in conductivity when the reaction reaches first stage is due in the most part to direct fluorination of carbon in graphite.

  5. Magnetic properties of iron-bearing graphite fibers

    NASA Technical Reports Server (NTRS)

    Ferrante, R.; Odeens, D. A.; Walters, P. A.; Hambourger, P. D.; Hung, Ching-Cheh

    1995-01-01

    Carbon fibers containing ferromagnetically-ordered iron or other transition metals could be used in a variety of lightweight magnetic composites. Intercalation of bulk graphite with CoCl2 or FeCl3, followed by reduction with butyl lithium, did indeed produce magnetic samples; however, the observed room temperature permeabilities (mu) were less than 2 G/Oe. Magnetic data are presented on carbon fibers containing large amounts of elemental iron, which were prepared by a new method. In this method Amoco P-75 fibers were intercalated with Br2 and I2 followed by fluorination, forming CF(0.75). This product was then intercalated with FeCl3. Subsequent heat treatments in oxidizing and reducing atmospheres converted most of the iron to the pure alpha phase. Room temperature permeabilities as large as 40 G/Oe are observed.

  6. Electrochemical Ultracapacitors Using Graphitic Nanostacks

    NASA Technical Reports Server (NTRS)

    Marotta, Christopher

    2012-01-01

    Electrochemical ultracapacitors (ECs) have been developed using graphitic nanostacks as the electrode material. The advantages of this technology will be the reduction of device size due to superior power densities and relative powers compared to traditional activated carbon electrodes. External testing showed that these materials display reduced discharge response times compared to state-of-the-art materials. Such applications are advantageous for pulsed power applications such as burst communications (satellites, cell phones), electromechanical actuators, and battery load leveling in electric vehicles. These carbon nanostructures are highly conductive and offer an ordered mesopore network. These attributes will provide more complete electrolyte wetting, and faster release of stored charge compared to activated carbon. Electrochemical capacitor (EC) electrode materials were developed using commercially available nanomaterials and modifying them to exploit their energy storage properties. These materials would be an improvement over current ECs that employ activated carbon as the electrode material. Commercially available graphite nanofibers (GNFs) are used as precursor materials for the synthesis of graphitic nanostacks (GNSs). These materials offer much greater surface area than graphite flakes. Additionally, these materials offer a superior electrical conductivity and a greater average pore size compared to activated carbon electrodes. The state of the art in EC development uses activated carbon (AC) as the electrode material. AC has a high surface area, but its small average pore size inhibits electrolyte ingress/egress. Additionally, AC has a higher resistivity, which generates parasitic heating in high-power applications. This work focuses on fabricating EC from carbon that has a very different structure by increasing the surface area of the GNF by intercalation or exfoliation of the graphitic basal planes. Additionally, various functionalities to the GNS

  7. Synthesis and characterization of anisotropically expanded graphite oxide compounds derived from spherical graphite.

    PubMed

    Zhao, Wenwen; Kido, Gentoku; Harada, Shuji; Unno, Masashi; Noguchi, Hideyuki

    2014-10-01

    Anisotropically expanded graphite oxide (GO) compounds with controlled interlayer distances were synthesized through the intercalation of various quaternary ammonium cations in GO derived from mesocarbon microbeads (MCMB). It was found that the interlayer distance of the as-prepared anisotropically expanded GO varies with the intercalated cations. In tetrabutylammonium (TBA), tetraoctylammonium (TOA) and dioctadecyldimethyl ammonium (DDA) cation intercalated GO compounds (TBA-GO, TOA-GO, TOA-GO) the corresponding interlayer distances were found to be 1.1 nm, 1.9 nm and 2.9 nm, respectively. Moreover, significant morphology changes were observed for TOA-GO and DDA-GO. Our study suggests that it is possible to tailor both the interlayer distance and morphology of GO by choosing proper intercalated cations. It was also found that the expanded GO compounds show lower water content and improved thermal stability than those of pristine GO. The obtained GO compounds were investigated as electrode material for electrochemical capacitors and all of them delivered typical capacitive behavior.

  8. The alkaline earth intercalates of molybdenum disulfide

    NASA Technical Reports Server (NTRS)

    Somoano, R. B.; Hadek, V.; Rembaum, A.; Samson, S.; Woollam, J. A.

    1975-01-01

    Molybdenum disulfide has been intercalated with calcium and strontium by means of the liquid ammonia technique. Chemical, X-ray, and superconductivity data are presented. The X-ray data reveal a lowering of crystal symmetry and increase of complexity of the structure upon intercalation with the alkaline earth metals. The Ca and Sr intercalates start to superconduct at 4 and 5.6 K, respectively, and show considerable anisotropy regarding the critical magnetic field.

  9. Band gap opening in methane intercalated graphene.

    PubMed

    Hargrove, Jasmine; Shashikala, H B Mihiri; Guerrido, Lauren; Ravi, Natarajan; Wang, Xiao-Qian

    2012-08-07

    Recent experimental work has demonstrated production of quasi-free-standing graphene by methane intercalation. The intercalation weakens the coupling of adjacent graphene layers and yields Dirac fermion behaviour of monolayer graphene. We have investigated the electronic characteristics of a methane intercepted graphene bilayer under a perpendicularly applied electric field. Evolution of the band structure of intercalated graphene as a function of the bias is studied by means of density-functional theory including interlayer van der Waals interactions. The implications of controllable band gap opening in methane-intercalated graphene for future device applications are discussed.

  10. Dynamics of DNA/intercalator complexes

    NASA Astrophysics Data System (ADS)

    Schurr, J. M.; Wu, Pengguang; Fujimoto, Bryant S.

    1990-05-01

    Complexes of linear and supercoiled DNAs with different intercalating dyes are studied by time-resolved fluorescence polarization anisotropy using intercalated ethidium as the probe. Existing theory is generalized to take account of excitation transfer between intercalated ethidiums, and Forster theory is shown to be valid in this context. The effects of intercalated ethidium, 9-aminoacridine, and proflavine on the torsional rigidity of linear and supercoiled DNAs are studied up to rather high binding ratios. Evidence is presented that metastable secondary structure persists in dye-relaxed supercoiled DNAs, which contradicts the standard model of supercoiled DNAs.

  11. Industrial Applications of Graphite Fluoride Fibers

    NASA Technical Reports Server (NTRS)

    Hung, Ching-Cheh; Kucera, Donald

    1991-01-01

    Based on fluorination technology developed during 1934 to 1959, and the fiber technology developed during the 1970s, a new process was developed to produce graphite fluoride fibers. In the process, pitch based graphitized carbon fibers are at first intercalated and deintercalated several times by bromine and iodine, followed by several cycles of nitrogen heating and fluorination at 350 to 370 C. Electrical, mechanical, and thermal properties of this fiber depend on the fluorination process and the fluorine content of the graphite fluoride product. However, these properties are between those of graphite and those of PTFE (Teflon). Therefore, it is considered to be a semiplastic. The physical properties suggest that this new material may have many new and unexplored applications. For example, it can be a thermally conductive electrical insulator. Its coefficient of thermal expansion (CTE) can be adjusted to match that of silicon, and therefore, it can be a heat sinking printed circuit board which is CTE compatible with silicon. Using these fibers in printed circuit boards may provide improved electrical performance and reliability of the electronics on the board over existing designs. Also, since it releases fluorine at 300 C or higher, it can be used as a material to store fluorine and to conduct fluorination. This application may simplify the fluorination process and reduce the risk of handling fluorine.

  12. Recent Advances in Preparation, Structure, Properties and Applications of Graphite Oxide.

    PubMed

    Srivastava, Suneel Kumar; Pionteck, Jürgen

    2015-03-01

    Graphite oxide, also referred as graphitic oxide or graphitic acid, is an oxidized bulk product of graphite with a variable composition. However, it did not receive immense attention until it was identified as an important and easily obtainable precursor for the preparation of graphene. This inspired many researchers to explore facts related to graphite oxide in exploiting its fascinating features. The present article culminates up-dated review on different preparative methods, morphology and characterization of physical/chemical properties of graphite oxide by XRD, XPS, FTIR, Raman, NMR, UV-visible, and DRIFT analyses. Finally, recent developments on intercalation and applications of GO in multifaceted areas of catalysis, sensor, supercapacitors, water purification, hydrogen storage and magnetic shielding etc. has also been reviewed.

  13. In situ observation of electrolyte-concentration-dependent solid electrolyte interphase on graphite in dimethyl sulfoxide.

    PubMed

    Liu, Xing-Rui; Wang, Lin; Wan, Li-Jun; Wang, Dong

    2015-05-13

    High lithium salt concentration strategy has been recently reported to be an effective method to enable various organic solvents as electrolyte of Li-ion batteries. Here, we utilize in situ atomic force microscopy (AFM) to investigate the interfacial morphology on the graphite electrode in dimethyl sulfoxide (DMSO)-based electrolyte of various concentrations. The significant differences in interfacial features of the graphite in electrolytes of different concentrations are revealed. In the concentrated electrolyte, stable films form primarily at the step edges and defects on the graphite surface after initial electrochemical cycling. On the other hand, in the dilute electrolyte, DMSO-solvated lithium ions constantly intercalate into graphite layers, and serious decomposition of solvent accompanied by structural deterioration of the graphite surface is observed. The in situ AFM results provide direct evidence for the concentration-dependent interface reactions between graphite electrode and DMSO-based electrolyte.

  14. Anomalous dielectric relaxation of water confined in graphite oxide

    SciTech Connect

    Yu, Ji; Tian, Yuchen; Gu, Min; Tang, Tong B.

    2015-09-28

    Nonmonotonic thermal dependence of dielectric relaxation of water has been observed in hydrated graphite oxide (GO). Graphite oxide prepared via Hummers method then imbued with specific water contents were characterized, with {sup 13}C and {sup 1}H nuclear magnetic resonance spectroscopies, X-ray photoelectron spectroscopy, ambient- and variable-temperature X-ray diffractometries, as well as thermogravimetric analysis. Pressed pellets provided with either conducting or blocking electrodes yielded dielectric loss, which was shown to originate from dielectric relaxation of the confined water. Three relaxation processes were observed in impedance spectroscopy. Our previous work has identified two different types of water in GO, namely, intercalated water and water in inter-grain voids. P{sub 1} expresses the reorientation of water confined inside inter-grain voids, and P{sub 2}, the rotation of intercalated water molecules confined in interlayers. The present work reveals a new process P{sub 3}, which also relates to intercalated water. It slows down with temperature, and this apparent anomaly is explained by the decrease in water content and consequent narrowing of interlayer spacing in graphite oxide, as confirmed by characterization techniques. The present study should contribute to our understanding of surface water dynamics.

  15. Anomalous dielectric relaxation of water confined in graphite oxide

    NASA Astrophysics Data System (ADS)

    Yu, Ji; Tian, Yuchen; Gu, Min; Tang, Tong B.

    2015-09-01

    Nonmonotonic thermal dependence of dielectric relaxation of water has been observed in hydrated graphite oxide (GO). Graphite oxide prepared via Hummers method then imbued with specific water contents were characterized, with 13C and 1H nuclear magnetic resonance spectroscopies, X-ray photoelectron spectroscopy, ambient- and variable-temperature X-ray diffractometries, as well as thermogravimetric analysis. Pressed pellets provided with either conducting or blocking electrodes yielded dielectric loss, which was shown to originate from dielectric relaxation of the confined water. Three relaxation processes were observed in impedance spectroscopy. Our previous work has identified two different types of water in GO, namely, intercalated water and water in inter-grain voids. P1 expresses the reorientation of water confined inside inter-grain voids, and P2, the rotation of intercalated water molecules confined in interlayers. The present work reveals a new process P3, which also relates to intercalated water. It slows down with temperature, and this apparent anomaly is explained by the decrease in water content and consequent narrowing of interlayer spacing in graphite oxide, as confirmed by characterization techniques. The present study should contribute to our understanding of surface water dynamics.

  16. Atomically resolved graphitic surfaces in air by atomic force microscopy.

    PubMed

    Wastl, Daniel S; Weymouth, Alfred J; Giessibl, Franz J

    2014-05-27

    Imaging at the atomic scale using atomic force microscopy in biocompatible environments is an ongoing challenge. We demonstrate atomic resolution of graphite and hydrogen-intercalated graphene on SiC in air. The main challenges arise from the overall surface cleanliness and the water layers which form on almost all surfaces. To further investigate the influence of the water layers, we compare data taken with a hydrophilic bulk-silicon tip to a hydrophobic bulk-sapphire tip. While atomic resolution can be achieved with both tip materials at moderate interaction forces, there are strong differences in force versus distance spectra which relate to the water layers on the tips and samples. Imaging at very low tip-sample interaction forces results in the observation of large terraces of a naturally occurring stripe structure on the hydrogen-intercalated graphene. This structure has been previously reported on graphitic surfaces that are not covered with disordered adsorbates in ambient conditions (i.e., on graphite and bilayer graphene on SiC, but not on monolayer graphene on SiC). Both these observations indicate that hydrogen-intercalated graphene is close to an ideal graphene sample in ambient environments.

  17. Water dynamics in graphite oxide investigated with neutron scattering.

    PubMed

    Buchsteiner, Alexandra; Lerf, Anton; Pieper, Jörg

    2006-11-16

    Graphite oxide is an inorganic multilayer system that preserves the layered structure of graphite but not the conjugated bond structure. In the past few years, detailed studies of the static structure of graphite oxide were carried out. This was mainly done by NMR investigations and led to a new structural model of graphite oxide. The layer distance of graphite oxide increases with increasing humidity level, giving rise to different spacings of the carbon layers in the range from 6 to 12 A. As a consequence, different types of motions of water and functional groups appear. Information about the mobility of the water molecules is not yet complete but is crucial for the understanding of the structure of the carbon layers as well as the intercalation process. In this paper, the hydration- and temperature-dependent dynamic behavior of graphite oxide will be investigated by quasielastic neutron scattering using the time-of-flight spectrometer NEAT at the Hahn-Meitner-Institut Berlin. The character of the embedded water does not change over a wide range of hydration levels. Especially the interlayer water remains tightly bound and does not show any translational motion. In samples with excess water, however, the water is also distributed in noninterlayer voids, leading to the observation of additional motions of bulklike or confined water. The dynamic behavior of hydrated graphite oxide can be described by a consistent model that combines two two-site jump motions for the motions of the water molecules and the motions of OH groups.

  18. Hindered Glymes for Graphite-Compatible Electrolytes.

    PubMed

    Shanmukaraj, Devaraj; Grugeon, Sylvie; Laruelle, Stephane; Armand, Michel

    2015-08-24

    Organic carbonate mixtures are used almost exclusively as lithium battery electrolyte solvents. The linear compounds (dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate) act mainly as thinner for the more viscous and high-melting ethylene carbonate but are the least stable component and have low flash points; these are serious handicaps for lifetime and safety. Polyethers (glymes) are useful co-solvents, but all formerly known representatives solvate Li(+) strongly enough to co-intercalate in the graphite negative electrode and exfoliate it. We have put forward a new electrolyte composition comprising a polyether to which a bulky tert-butyl group is attached ("hindered glyme"), thus completely preventing co-intercalation while maintaining good conductivity. This alkyl-carbonate-free electrolyte shows remarkable cycle efficiency of the graphite electrode, not only at room temperature, but also at 50 and 70 °C in the presence of lithium bis(fluorosulfonimide). The two-ethylene-bridge hindered glyme has a high boiling point and a flash point of 80 °C, a considerable advantage for safety.

  19. Chapter 20: Graphite

    SciTech Connect

    Burchell, Timothy D

    2012-01-01

    Graphite is truly a unique material. Its structure, from the nano- to the millimeter scale give it remarkable properties that lead to numerous and diverse applications. Graphite bond anisotropy, with strong in-plane covalent bonds and weak van der Waals type bonding between the planes, gives graphite its unique combination of properties. Easy shear of the crystal, facilitated by weak interplaner bonds allows graphite to be used as a dry lubricant, and is responsible for the substances name! The word graphite is derived from the Greek to write because of graphites ability to mark writing surfaces. Moreover, synthetic graphite contains within its structure, porosity spanning many orders of magnitude in size. The thermal closure of these pores profoundly affects the properties for example, graphite strength increases with temperature to temperatures in excess of 2200 C. Consequently, graphite is utilized in many high temperature applications. The basic physical properties of graphite are reviewed here. Graphite applications include metallurgical; (aluminum and steel production), single crystal silicon production, and metal casting; electrical (motor brushes and commutators); mechanical (seals, bearings and bushings); and nuclear applications, (see Chapter 91, Nuclear Graphite). Here we discuss the structure, manufacture, properties, and applications of Graphite.

  20. Intercalation chemistry of zirconium 4-sulfophenylphosphonate

    SciTech Connect

    Svoboda, Jan; Zima, Vítězslav; Melánová, Klára; Beneš, Ludvík; Trchová, Miroslava

    2013-12-15

    Zirconium 4-sulfophenylphosphonate is a layered material which can be employed as a host for the intercalation reactions with basic molecules. A wide range of organic compounds were chosen to represent intercalation ability of zirconium 4-sulfophenylphosphonate. These were a series of alkylamines from methylamine to dodecylamine, 1,4-phenylenediamine, p-toluidine, 1,8-diaminonaphthalene, 1-aminopyrene, imidazole, pyridine, 4,4′-bipyridine, poly(ethylene imine), and a series of amino acids from glycine to 6-aminocaproic acid. The prepared compounds were characterized by powder X-ray diffraction, thermogravimetry analysis and IR spectroscopy and probable arrangement of the guest molecules in the interlayer space of the host is proposed based on the interlayer distance of the prepared intercalates and amount of the intercalated guest molecules. - Graphical abstract: Nitrogen-containing organic compounds can be intercalated into the interlayer space of zirconium 4-sulfophenylphosphonate. - Highlights: • Zirconium 4-sulfophenylphosphonate was examined as a host material in intercalation chemistry. • A wide range of nitrogen-containing organic compounds were intercalated. • Possible arrangement of the intercalated species is described.

  1. Graphite Technology Development Plan

    SciTech Connect

    W. Windes; T. Burchell; M.Carroll

    2010-10-01

    The Next Generation Nuclear Plant (NGNP) will be a helium-cooled High Temperature Gas Reactor (HTGR) with a large graphite core. Graphite physically contains the fuel and comprises the majority of the core volume. Graphite has been used effectively as a structural and moderator material in both research and commercial high-temperature gas-cooled reactors. This development has resulted in graphite being established as a viable structural material for HTGRs. While the general characteristics necessary for producing nuclear grade graphite are understood, historical “nuclear” grades no longer exist. New grades must be fabricated, characterized, and irradiated to demonstrate that current grades of graphite exhibit acceptable non-irradiated and irradiated properties upon which the thermomechanical design of the structural graphite in NGNP is based. This Technology Development Plan outlines the research and development (R&D) activities and associated rationale necessary to qualify nuclear grade graphite for use within the NGNP reactor.

  2. Rheological and electrical properties of hybrid nanocomposites of epoxy resins filled with graphite nanoplatelets and carbon black.

    PubMed

    Truong, Quang-Trung; Lee, Seon-Suk; Lee, Dai-Soo

    2011-02-01

    Graphite nanoplatelets (GNP) were prepared by microwave irradiation of natural graphites intercalated with ferric chloride in nitromethane (GIC). Intercalated structure of GIC was confirmed by X-ray diffraction patterns. SEM images of GIC after microwave irradiation showed the exfoliation of GIC, the formation of GNPs. Hybrid nanocomposites of bisphenol-A type epoxy resins filled with GNP and a conductive carbon black (CB) were prepared and rheological and electrical properties of the nanocomposites were investigated. Viscosity and electrical surface resistivity of the nanocomposites showed minima at certain mixtures of GNP and CB in the epoxy resins.

  3. Effects of milling brominated P-100 graphite fibers

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Dillehay, Michael E.; Hambourger, Paul D.

    1987-01-01

    Preliminary procedures have been developed for the ball milling of pristine and brominated P-100 graphite fibers. Because of the lubricative properties of graphite, large ball loads (50 percent by volume) are required. Use of 2-propanol as a milling medium enhances the efficiency of the process. The fibers, when allowed to settle from the milling medium, tend to be preferentially aligned with rather few fibers standing up. Milled, brominated P-100 fibers have resistivities that are indistinguishable from their pristine counterparts, apparently because of loss of bromine. This suggests that bromine would not be the intercalate of choice in applications where milled fibers of this type are required. It was found that brominated graphite fibers are stable in a wide variety of organic solvents.

  4. Atomic intercalation - a practical method to determine the nanoscale adhesion energy of graphene on HOPG

    NASA Astrophysics Data System (ADS)

    Wang, Jun; Sorescu, Dan; Jeon, Seokmin; Belianinov, Alexei; Kalinin, Sergei; Baddorf, Arthur; Maksymovych, Petro

    A detailed analysis of atomic intercalates in graphite provides a direct estimate of the nanoscale elastic adhesion of a graphene sheet atop highly ordered pyrolytic graphite (HOPG). Atomic intercalation is carried out using conventional ion sputtering, creating ``blisters'' in the top-most layer of the HOPG surface. Scanning tunneling microscopy coupled with image analysis and density functional theory is used to reconstruct the atomic positions and the strain map within the deformed graphene sheet. To estimate the adhesion energy we invoke an analytical model originally devised for macroscopic deformations of graphene. This model yields a value of is 0.221 +/- 0.011 J/m2 for the adhesion energy of graphite, which is in surprisingly good agreement with reported experimental and theoretical values. This implies that mechanical properties of graphene scale at least to lengths of a few nanometers. The simplicity of our method enables analysis of elastic mechanical properties in many two-dimensional layered materials and provides a unique opportunity to investigate the local variability of mechanical properties on the nanoscale. Acknowledgements: Experiments were conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility.

  5. Advanced rechargeable aluminium ion battery with a high-quality natural graphite cathode

    DOE PAGES

    Wang, Di-Yan; Wei, Chuan-Yu; Lin, Meng-Chang; ...

    2017-02-13

    There has been some interest in aluminium ion batteries with aluminium anodes, graphite cathodes and ionic liquid electrolytes has increased; however, much remains to be done to increase the cathode capacity and to understand details of the anion–graphite intercalation mechanism. An aluminium ion battery cell made using pristine natural graphite flakes achieves a specific capacity of B110 mAhg-1 with Coulombic efficiency B98%, at a current density of 99mAg-1 (0.9 C) with clear discharge voltage plateaus (2.25–2.0 V and 1.9–1.5 V). The cell has a capacity of 60mAhg-1 at 6 C, over 6,000 cycles with Coulombic efficiency B 99%. Raman spectroscopymore » shows two different intercalation processes involving chloroaluminate anions at the two discharging plateaus, while C–Cl bonding on the surface, or edges of natural graphite, is found using X-ray absorption spectroscopy. Lastly, theoretical calculations are employed to investigate the intercalation behaviour of choloraluminate anions in the graphite electrode.« less

  6. Advanced rechargeable aluminium ion battery with a high-quality natural graphite cathode

    PubMed Central

    Wang, Di-Yan; Wei, Chuan-Yu; Lin, Meng-Chang; Pan, Chun-Jern; Chou, Hung-Lung; Chen, Hsin-An; Gong, Ming; Wu, Yingpeng; Yuan, Chunze; Angell, Michael; Hsieh, Yu-Ju; Chen, Yu-Hsun; Wen, Cheng-Yen; Chen, Chun-Wei; Hwang, Bing-Joe; Chen, Chia-Chun; Dai, Hongjie

    2017-01-01

    Recently, interest in aluminium ion batteries with aluminium anodes, graphite cathodes and ionic liquid electrolytes has increased; however, much remains to be done to increase the cathode capacity and to understand details of the anion–graphite intercalation mechanism. Here, an aluminium ion battery cell made using pristine natural graphite flakes achieves a specific capacity of ∼110 mAh g−1 with Coulombic efficiency ∼98%, at a current density of 99 mA g−1 (0.9 C) with clear discharge voltage plateaus (2.25–2.0 V and 1.9–1.5 V). The cell has a capacity of 60 mAh g−1 at 6 C, over 6,000 cycles with Coulombic efficiency ∼ 99%. Raman spectroscopy shows two different intercalation processes involving chloroaluminate anions at the two discharging plateaus, while C–Cl bonding on the surface, or edges of natural graphite, is found using X-ray absorption spectroscopy. Finally, theoretical calculations are employed to investigate the intercalation behaviour of choloraluminate anions in the graphite electrode. PMID:28194027

  7. Advanced rechargeable aluminium ion battery with a high-quality natural graphite cathode

    NASA Astrophysics Data System (ADS)

    Wang, Di-Yan; Wei, Chuan-Yu; Lin, Meng-Chang; Pan, Chun-Jern; Chou, Hung-Lung; Chen, Hsin-An; Gong, Ming; Wu, Yingpeng; Yuan, Chunze; Angell, Michael; Hsieh, Yu-Ju; Chen, Yu-Hsun; Wen, Cheng-Yen; Chen, Chun-Wei; Hwang, Bing-Joe; Chen, Chia-Chun; Dai, Hongjie

    2017-02-01

    Recently, interest in aluminium ion batteries with aluminium anodes, graphite cathodes and ionic liquid electrolytes has increased; however, much remains to be done to increase the cathode capacity and to understand details of the anion-graphite intercalation mechanism. Here, an aluminium ion battery cell made using pristine natural graphite flakes achieves a specific capacity of ~110 mAh g-1 with Coulombic efficiency ~98%, at a current density of 99 mA g-1 (0.9 C) with clear discharge voltage plateaus (2.25-2.0 V and 1.9-1.5 V). The cell has a capacity of 60 mAh g-1 at 6 C, over 6,000 cycles with Coulombic efficiency ~ 99%. Raman spectroscopy shows two different intercalation processes involving chloroaluminate anions at the two discharging plateaus, while C-Cl bonding on the surface, or edges of natural graphite, is found using X-ray absorption spectroscopy. Finally, theoretical calculations are employed to investigate the intercalation behaviour of choloraluminate anions in the graphite electrode.

  8. Solvent-driven electron trapping and mass transport in reduced graphites to access perfect graphene

    PubMed Central

    Vecera, Philipp; Holzwarth, Johannes; Edelthalhammer, Konstantin F.; Mundloch, Udo; Peterlik, Herwig; Hauke, Frank; Hirsch, Andreas

    2016-01-01

    Herein, we report on a significant discovery, namely, the quantitative discharging of reduced graphite forms, such as graphite intercalation compounds, graphenide dispersions and graphenides deposited on surfaces with the simple solvent benzonitrile. Because of its comparatively low reduction potential, benzonitrile is reduced during this process to the radical anion, which exhibits a red colour and serves as a reporter molecule for the quantitative determination of negative charges on the carbon sheets. Moreover, this discovery reveals a very fundamental physical–chemical phenomenon, namely a quantitative solvent reduction induced and electrostatically driven mass transport of K+ ions from the graphite intercalation compounds into the liquid. The simple treatment of dispersed graphenides suspended on silica substrates with benzonitrile leads to the clean conversion to graphene. This unprecedented procedure represents a rather mild, scalable and inexpensive method for graphene production surpassing previous wet-chemical approaches. PMID:27506380

  9. Solvent-driven electron trapping and mass transport in reduced graphites to access perfect graphene

    NASA Astrophysics Data System (ADS)

    Vecera, Philipp; Holzwarth, Johannes; Edelthalhammer, Konstantin F.; Mundloch, Udo; Peterlik, Herwig; Hauke, Frank; Hirsch, Andreas

    2016-08-01

    Herein, we report on a significant discovery, namely, the quantitative discharging of reduced graphite forms, such as graphite intercalation compounds, graphenide dispersions and graphenides deposited on surfaces with the simple solvent benzonitrile. Because of its comparatively low reduction potential, benzonitrile is reduced during this process to the radical anion, which exhibits a red colour and serves as a reporter molecule for the quantitative determination of negative charges on the carbon sheets. Moreover, this discovery reveals a very fundamental physical-chemical phenomenon, namely a quantitative solvent reduction induced and electrostatically driven mass transport of K+ ions from the graphite intercalation compounds into the liquid. The simple treatment of dispersed graphenides suspended on silica substrates with benzonitrile leads to the clean conversion to graphene. This unprecedented procedure represents a rather mild, scalable and inexpensive method for graphene production surpassing previous wet-chemical approaches.

  10. Intercalation of Europium (III) species into bentonite

    SciTech Connect

    Sanchez, A.; Echeverria, Y.; Torres, C.M. Sotomayor; Gonzalez, G.; Benavente, E. . E-mail: ebenaven@uchile.cl

    2006-06-15

    It is shown that the intercalation of [Europium(bipyridine){sub 2}]{sup 3+} into bentonite results in a new nanocomposite which preserves the emission properties of Europium (III). The exchange of sodium by europium in bentonite is correlated with the cation exchange capacity and molecular size. The intercalated complex exhibits luminescence where both the 2,2-bipyridine 'antenna' effect and the intensity maxima are comparable to the free complex suggesting that clay intercalated with rare earths may results in novel optical materials.

  11. Effect of expanded graphite lattice in exfoliated graphite nanofibers on hydrogen storage.

    PubMed

    Lueking, Angela D; Pan, Ling; Narayanan, Deepa L; Clifford, Caroline E B

    2005-07-07

    A graphite exfoliation technique, using intercalation of a concentrated sulfuric/nitric acid mixture followed by a thermal shock, has successfully exfoliated a herringbone graphite nanofiber (GNF). The exfoliated GNF retains the overall nanosized dimensions of the original GNF, with the exfoliation temperature determining the degree of induced defects, lattice expansion, and resulting microstructure. High-resolution transmission electron microscopy indicated that the fibers treated at an intermediate temperature of 700 degrees C for 2 min had dislocations in the graphitic structure and a 4% increase in graphitic lattice spacing to 3.5 A. The fibers treated at 1000 degrees C for 36 h were expanded along the fiber axis, with regular intervals of graphitic and amorphous regions ranging from 0.5 to >50 nm in width. The surface area of the starting material was increased from 47 m(2)/g to 67 m(2)/g for the 700- degrees C treatment and to 555 m(2)/g for the 1000- degrees C treatment. Hydrogen uptake measurements at 20 bar indicate that the overall hydrogen uptake and operative adsorption temperature are sensitive to the structural variations and graphitic spacing. The increased surface area after the 1000- degrees C treatment led to a 1.2% hydrogen uptake at 77 K and 20 bar, a 3-fold increase in hydrogen physisorption of the starting material. The uptake of the 700- degrees C-treated material had a 0.29% uptake at 300 K and 20 bar; although low, this was a 14-fold uptake over the starting material and higher than other commonly used pretreatment methods that were tested in parallel. These results suggest that selective exfoliation of a nanofiber is a means by which to control the relative binding energy of the hydrogen interaction with the carbon structure and thus vary the operative adsorption temperature.

  12. High energy density sodium-ion capacitors through co-intercalation mechanism in diglyme-based electrolyte system

    NASA Astrophysics Data System (ADS)

    Han, Pengxian; Han, Xiaoqi; Yao, Jianhua; Zhang, Lixue; Cao, Xiaoyan; Huang, Changshui; Cui, Gunglei

    2015-11-01

    A novel sodium-ion capacitor (NIC) was assembled using graphitic mesocarbon microbead anode and activated carbon cathode in diglyme-based electrolyte. Charge/discharge tests indicate that sodium ions can reversibly co-intercalated with diglyme solvent into graphite anode and show good rate performance. The energy densities of the NICs are as high as 93.5 and 86.5 Wh kg-1 at 573 and 2832 W kg-1 (equal to 4 C and 50 C) in the voltage window at 1-4 V, respectively. By optimizing the voltage ranges, the capacity retention of the NIC at 20 C is 98.3% even after 3000 cycles. Such superior electrochemical performance should be attributed to the reversible intercalated/deintercalated reaction of sodium ions and the formation of ternary graphite intercalation compounds in diglyme-based electrolyte. The present work pioneers new realms of hybrid energy storage system with high energy density, high power density and long cycle life.

  13. Producing graphite with desired properties

    NASA Technical Reports Server (NTRS)

    Dickinson, J. M.; Imprescia, R. J.; Reiswig, R. D.; Smith, M. C.

    1971-01-01

    Isotropic or anisotropic graphite is synthesized with precise control of particle size, distribution, and shape. The isotropic graphites are nearly perfectly isotropic, with thermal expansion coefficients two or three times those of ordinary graphites. The anisotropic graphites approach the anisotropy of pyrolytic graphite.

  14. Graphite for nuclear reactors

    SciTech Connect

    Virgiliev, Yu.S.; Kalyagina, I.P.

    1993-12-31

    Relative dimensional changes and physical properties of structural graphites - {Gamma}p-280 (nuclear graphite) and {Gamma}p{Pi}-2 (modificated variety of nuclear graphite for the rings of elastic contact) irradiated at temperatures ranging from 320 to 1900K with a fluence of about 2.5.10{sup 22}nvt (E {ge} 0.18 MeV) are represented. In order to ensure a long-time serviceability of the VGM - reactor blocks the high-strength graphite of {Gamma}p-1 grade are developed. The properties and its irradiation changes of {Gamma}p-1 graphite are represented. A secondary swelling of the graphite develops similar to the swelling of metals, alloys and high-melting compounds.

  15. Radiation Effects in Graphite

    SciTech Connect

    Burchell, Timothy D

    2012-01-01

    The requirements for a solid moderator are reviewed and the reasons that graphite has become the solid moderator of choice discussed. The manufacture and properties of some currently available near-isotropic and isotropic grades are described. The major features of a graphite moderated reactors are briefly outlined. Displacement damage and the induced structural and dimensional changes in graphite are described. Recent characterization work on nano-carbons and oriented pyrolytic graphites that have shed new light on graphite defect structures are reviewed, and the effect of irradiation temperature on the defect structures is highlighted. Changes in the physical properties of nuclear graphite caused by neutron irradiation are reported. Finally, the importance of irradiation induced creep is presented, along with current models and their deficiencies.

  16. Interaction of boron with graphite: A van der Waals density functional study

    NASA Astrophysics Data System (ADS)

    Liu, Juan; Wang, Chen; Liang, Tongxiang; Lai, Wensheng

    2016-08-01

    Boron doping has been widely investigated to improve oxidation resistance of graphite. In this work the interaction of boron with graphite is investigated by a van der Waals density-functional approach (vdW-DF). The traditional density-functional theory (DFT) is well accounted for the binding in boron-substituted graphite. However, to investigate the boron atom on graphite surface and the interstitial impurities require use of a description of graphite interlayer binding. Traditional DFT cannot describe the vdW physics, for instance, GGA calculations show no relevant binding between graphite sheets. LDA shows some binding, but they fail to provide an accurate account of vdW forces. In this paper, we compare the calculation results of graphite lattice constant and cohesive energy by several functionals, it shows that vdW-DF such as two optimized functionals optB88-vdW and optB86b-vdW give much improved results than traditional DFT. The vdW-DF approach is then applied to study the interaction of boron with graphite. Boron adsorption, substitution, and intercalation are discussed in terms of structural parameters and electronic structures. When adsorbing on graphite surface, boron behaves as π electron acceptor. The π electron approaches boron atom because of more electropositive of boron than carbon. For substitution situation, the hole introduced by boron mainly concentrates on boron and the nearest three carbon atoms. The B-doped graphite system with the hole has less ability to offer electrons to oxygen, ultimately resulted in the inhibition of carbon oxidation. For interstitial doping, vdW-DFs show more accurate formation energy than LDA. PBE functional cannot describe the interstitial boron in graphite reasonably because of the ignoring binding of graphite sheets. The investigation of electron structures of boron doped graphite will play an important role in understanding the oxidation mechanism in further study.

  17. Oxidation Resistant Graphite Studies

    SciTech Connect

    W. Windes; R. Smith

    2014-07-01

    The Very High Temperature Reactor (VHTR) Graphite Research and Development Program is investigating doped nuclear graphite grades exhibiting oxidation resistance. During a oxygen ingress accident the oxidation rates of the high temperature graphite core region would be extremely high resulting in significant structural damage to the core. Reducing the oxidation rate of the graphite core material would reduce the structural effects and keep the core integrity intact during any air-ingress accident. Oxidation testing of graphite doped with oxidation resistant material is being conducted to determine the extent of oxidation rate reduction. Nuclear grade graphite doped with varying levels of Boron-Carbide (B4C) was oxidized in air at nominal 740°C at 10/90% (air/He) and 100% air. The oxidation rates of the boronated and unboronated graphite grade were compared. With increasing boron-carbide content (up to 6 vol%) the oxidation rate was observed to have a 20 fold reduction from unboronated graphite. Visual inspection and uniformity of oxidation across the surface of the specimens were conducted. Future work to determine the remaining mechanical strength as well as graphite grades with SiC doped material are discussed.

  18. Physicochemical Characterization, and Relaxometry Studies of Micro-Graphite Oxide, Graphene Nanoplatelets, and Nanoribbons

    PubMed Central

    Paratala, Bhavna S.; Jacobson, Barry D.; Kanakia, Shruti; Francis, Leonard Deepak; Sitharaman, Balaji

    2012-01-01

    The chemistry of high-performance magnetic resonance imaging contrast agents remains an active area of research. In this work, we demonstrate that the potassium permanganate-based oxidative chemical procedures used to synthesize graphite oxide or graphene nanoparticles leads to the confinement (intercalation) of trace amounts of Mn2+ ions between the graphene sheets, and that these manganese intercalated graphitic and graphene structures show disparate structural, chemical and magnetic properties, and high relaxivity (up to 2 order) and distinctly different nuclear magnetic resonance dispersion profiles compared to paramagnetic chelate compounds. The results taken together with other published reports on confinement of paramagnetic metal ions within single-walled carbon nanotubes (a rolled up graphene sheet) show that confinement (encapsulation or intercalation) of paramagnetic metal ions within graphene sheets, and not the size, shape or architecture of the graphitic carbon particles is the key determinant for increasing relaxivity, and thus, identifies nano confinement of paramagnetic ions as novel general strategy to develop paramagnetic metal-ion graphitic-carbon complexes as high relaxivity MRI contrast agents. PMID:22685555

  19. Physicochemical characterization, and relaxometry studies of micro-graphite oxide, graphene nanoplatelets, and nanoribbons.

    PubMed

    Paratala, Bhavna S; Jacobson, Barry D; Kanakia, Shruti; Francis, Leonard Deepak; Sitharaman, Balaji

    2012-01-01

    The chemistry of high-performance magnetic resonance imaging contrast agents remains an active area of research. In this work, we demonstrate that the potassium permanganate-based oxidative chemical procedures used to synthesize graphite oxide or graphene nanoparticles leads to the confinement (intercalation) of trace amounts of Mn(2+) ions between the graphene sheets, and that these manganese intercalated graphitic and graphene structures show disparate structural, chemical and magnetic properties, and high relaxivity (up to 2 order) and distinctly different nuclear magnetic resonance dispersion profiles compared to paramagnetic chelate compounds. The results taken together with other published reports on confinement of paramagnetic metal ions within single-walled carbon nanotubes (a rolled up graphene sheet) show that confinement (encapsulation or intercalation) of paramagnetic metal ions within graphene sheets, and not the size, shape or architecture of the graphitic carbon particles is the key determinant for increasing relaxivity, and thus, identifies nano confinement of paramagnetic ions as novel general strategy to develop paramagnetic metal-ion graphitic-carbon complexes as high relaxivity MRI contrast agents.

  20. Method for producing dustless graphite spheres from waste graphite fines

    DOEpatents

    Pappano, Peter J [Oak Ridge, TN; Rogers, Michael R [Clinton, TN

    2012-05-08

    A method for producing graphite spheres from graphite fines by charging a quantity of spherical media into a rotatable cylindrical overcoater, charging a quantity of graphite fines into the overcoater thereby forming a first mixture of spherical media and graphite fines, rotating the overcoater at a speed such that the first mixture climbs the wall of the overcoater before rolling back down to the bottom thereby forming a second mixture of spherical media, graphite fines, and graphite spheres, removing the second mixture from the overcoater, sieving the second mixture to separate graphite spheres, charging the first mixture back into the overcoater, charging an additional quantity of graphite fines into the overcoater, adjusting processing parameters like overcoater dimensions, graphite fines charge, overcoater rotation speed, overcoater angle of rotation, and overcoater time of rotation, before repeating the steps until graphite fines are converted to graphite spheres.

  1. Hydrogen intercalation under graphene on Ir(111)

    NASA Astrophysics Data System (ADS)

    Grånäs, Elin; Gerber, Timm; Schröder, Ulrike A.; Schulte, Karina; Andersen, Jesper N.; Michely, Thomas; Knudsen, Jan

    2016-09-01

    Using high resolution X-ray photoelectron spectroscopy and scanning tunneling microscopy we study the intercalation of hydrogen under graphene/Ir(111). The hydrogen intercalated graphene is characterized by a component in C 1s that is shifted -0.10 to -0.18 eV with respect to pristine graphene and a component in Ir 4f at 60.54 eV. The position of this Ir 4f component is identical to that of the Ir(111) surface layer with hydrogen atoms adsorbed, indicating that the atomic hydrogen adsorption site on bare Ir(111) and beneath graphene is the same. Based on co-existence of fully- and non-intercalated graphene, and the inability to intercalate a closed graphene film covering the entire Ir(111) surface, we conclude that hydrogen dissociatively adsorbs at bare Ir(111) patches, and subsequently diffuses rapidly under graphene. A likely entry point for the intercalating hydrogen atoms is identified to be where graphene crosses an underlying Ir(111) step.

  2. Collecting Duct Intercalated Cell Function and Regulation

    PubMed Central

    Roy, Ankita; Al-bataineh, Mohammad M.

    2015-01-01

    Intercalated cells are kidney tubule epithelial cells with important roles in the regulation of acid-base homeostasis. However, in recent years the understanding of the function of the intercalated cell has become greatly enhanced and has shaped a new model for how the distal segments of the kidney tubule integrate salt and water reabsorption, potassium homeostasis, and acid-base status. These cells appear in the late distal convoluted tubule or in the connecting segment, depending on the species. They are most abundant in the collecting duct, where they can be detected all the way from the cortex to the initial part of the inner medulla. Intercalated cells are interspersed among the more numerous segment-specific principal cells. There are three types of intercalated cells, each having distinct structures and expressing different ensembles of transport proteins that translate into very different functions in the processing of the urine. This review includes recent findings on how intercalated cells regulate their intracellular milieu and contribute to acid-base regulation and sodium, chloride, and potassium homeostasis, thus highlighting their potential role as targets for the treatment of hypertension. Their novel regulation by paracrine signals in the collecting duct is also discussed. Finally, this article addresses their role as part of the innate immune system of the kidney tubule. PMID:25632105

  3. Organic intercalation of structure modified vermiculite.

    PubMed

    Wu, Nian; Wu, Limei; Liao, Libing; Lv, Guocheng

    2015-11-01

    The experiment used cationic surfactants of different chain lengths to intercalate structure modified vermiculites. The influences of structure modification, chain length and dosage of surfactants on the intercalation behavior of vermiculites were studied, and intercalation mechanism and features of interlayer chemical reactions were discussed. Results indicate that structure modified vermiculites with different layer charge have different intercalation behavior. The basal spacing of the organic intercalated modified vermiculite is the largest when acid concentration used in structure modification is 0.003 mol/L, and increases with increasing the chain length and dosage of the organics. Molecular dynamics simulation verifies that interlayer organics align almost parallel to structure layer of vermiculite, with alkyl chain stretching to the middle of interlayer space. -N(+) groups of the three surfactants locate above the leached [SiO4], which has stronger interaction with interlayer organic cations. Electrostatic force is the main interaction force between interlayer organics and structure layer of vermiculite, and then is Van der Waals force, no chemical bond formed.

  4. Coating method for graphite

    DOEpatents

    Banker, John G.; Holcombe, Jr., Cressie E.

    1977-01-01

    A method of limiting carbon contamination from graphite ware used in induction melting of uranium alloys is provided comprising coating the graphite surface with a suspension of Y.sub.2 O.sub.3 particles in water containing about 1.5 to 4% by weight sodium carboxymethylcellulose.

  5. Coating method for graphite

    DOEpatents

    Banker, J.G.; Holcombe, C.E. Jr.

    1975-11-06

    A method of limiting carbon contamination from graphite ware used in induction melting of uranium alloys is provided. The graphite surface is coated with a suspension of Y/sub 2/O/sub 3/ particles in water containing about 1.5 to 4 percent by weight sodium carboxymethylcellulose.

  6. Intercalation of Aldehydes into Vanadyl Phosphate

    NASA Astrophysics Data System (ADS)

    Melánová, Klára; Beneš, Ludvík.; Zima, Vítězslav; Votinský, Jiří

    2001-02-01

    Intercalates of VOPO4 with several aliphatic aldehydes, benzaldehyde, and 4-methylbenzaldehyde were prepared and characterized by thermogravimetric analysis, X-ray diffractometry, and IR and UV-vis spectroscopies. Aliphatic aldehyde intercalates are unstable and the guests undergo aldol condensation and oxidation. The arrangement of the guest molecules in the interlayer space of the host is discussed. A part of aliphatic aldehydes is anchored to the host layers by coordination of their carbonyl oxygen to the vanadium atom; the rest is probably bonded by weak van der Waals forces. In the benzaldehyde and 4-methylbenzaldehyde intercalates, all guest molecules are coordinated to the vanadium atoms with their benzene rings perpendicular to the sheets of the host.

  7. Controlling the actuation properties of MXene paper electrodes upon cation intercalation

    DOE PAGES

    Come, Jeremy E.; Black, Jennifer M.; Naguib, Michael; ...

    2015-08-05

    Atomic force microscopy was used to monitor the macroscopic deformation in a delaminated Ti₃C₂ paper electrode in-situ, during charge/discharge in a variety of aqueous electrolytes to examine the effect of the cation intercalation on the electrochemical behavior and mechanical response. The results show a strong dependence of the electrode deformation on cation size and charge. The electrode undergoes a large contraction during Li⁺, Na⁺ or Mg²⁺ intercalation, differentiating the Ti₃C₂ paper from conventional electrodes where redox intercalation of ions (e.g. Li⁺) into the bulk phase (e.g. graphite, silicon) results in volumetric expansion. This feature may explain the excellent rate performancemore » and cyclability reported for MXenes. We also demonstrated that the variation of the electromechanical contraction can be easily adjusted by electrolyte exchange, and shows interesting characteristics for the design of actuators based on 2D metal carbides.« less

  8. Synthesis, electrical and thermal conductivities, and potential applications of graphite fluoride fibers

    NASA Technical Reports Server (NTRS)

    Hung, Ching-Cheh; Long, Martin; Stahl, Mark

    1988-01-01

    Graphite fluoride fibers can be produced by fluorinating pristine or intercalated graphite fibers. The higher the degree of graphitization of the fibers, the higher the temperature needed to reach the same degree of fluorination. Structural damage during high temperature fluorination can be reduced or eliminated by pretreating the fibers with bromine and/or fluorine. The electrical resistivity of the fibers was in the 0.01 to 10 to the 11th ohm-cm range. The thermal conductivity of these fibers ranged from 5 to 75 W/m-K, which is much larger than the thermal conductivity of glass (1.1 W/m-K), the commonly used fiber in epoxy composites. A composite made from graphite fluoride fibers and epoxy or PTFE may be highly thermally conducting and electrically insulating or semiconducting. The electrically insulating product may be used as heat sinks for electrical or electronic instruments.

  9. A stable graphite negative electrode for the lithium-sulfur battery.

    PubMed

    Jeschull, Fabian; Brandell, Daniel; Edström, Kristina; Lacey, Matthew J

    2015-12-14

    Efficient, reversible lithium intercalation into graphite in ether-based electrolytes is enabled through a protective electrode binder, polyacrylic acid sodium salt (PAA-Na). In turn, this enables the creation of a stable "lithium-ion-sulfur" cell, using a lithiated graphite negative electrode with a sulfur positive electrode, using the common DME:DOL solvent system suited to the electrochemistry of the lithium-sulfur battery. Graphite-sulfur lithium-ion cells show average coulombic efficiencies of ∼99.5%, compared with <95% for lithium-sulfur cells, and significantly better capacity retention, taking into account cell balancing considerations. The high efficiency derives from the considerably better interfacial stability of the graphite electrode, which suppresses the polysulfide redox shuttle and self-discharge.

  10. Large-scale preparation of graphene by high temperature insertion of hydrogen into graphite.

    PubMed

    Kamali, Ali Reza; Fray, Derek J

    2015-07-14

    Experimental evidence for high temperature diffusion of hydrogen into the interlayer space of graphite is provided. This process is discussed as a possible method for the rapid production of high-quality, inexpensive graphene in large quantities, which could lead to the widespread application of graphene. It was found that hydrogen cations, dissolved in molten LiCl, can be discharged on cathodically polarized graphite rods, which then intercalate into the graphite structure, leading to the peeling of graphite to produce graphene. The graphene nanosheets produced displayed a single-crystalline structure with a lateral size of several hundred nanometers and a high degree of crystallinity and thermal stability. The method introduced could be scaled up to produce industrial quantities of high-quality graphene.

  11. Role of Peroxide Ions in Formation of Graphene Nanosheets by Electrochemical Exfoliation of Graphite

    PubMed Central

    Rao, Kodepelly Sanjeeva; Senthilnathan, Jaganathan; Liu, Yung-Fang; Yoshimura, Masahiro

    2014-01-01

    This study demonstrates a facile, mild and environmentally-friendly sustainable (soft processing) approach for the efficient electrochemical exfoliation of graphite using a sodium hydroxide/hydrogen peroxide/water (NaOH/H2O2/H2O) system that can produce high-quality, anodic few-layer graphene nanosheets in 95% yield at ambient reaction conditions. The control experiment conducted using NaOH/H2O revealed the crucial role of H2O2 in the exfoliation of graphite. A possible exfoliation mechanism is proposed. The reaction of H2O2 with hydroxyl ions (HO−) leads to the formation of highly nucleophilic peroxide ions (O22−), which play a crucial role in the exfoliation of graphite via electrochemical-potential-assisted intercalation and strong expansion of graphite sheets. PMID:24577336

  12. Role of Peroxide Ions in Formation of Graphene Nanosheets by Electrochemical Exfoliation of Graphite

    NASA Astrophysics Data System (ADS)

    Rao, Kodepelly Sanjeeva; Senthilnathan, Jaganathan; Liu, Yung-Fang; Yoshimura, Masahiro

    2014-02-01

    This study demonstrates a facile, mild and environmentally-friendly sustainable (soft processing) approach for the efficient electrochemical exfoliation of graphite using a sodium hydroxide/hydrogen peroxide/water (NaOH/H2O2/H2O) system that can produce high-quality, anodic few-layer graphene nanosheets in 95% yield at ambient reaction conditions. The control experiment conducted using NaOH/H2O revealed the crucial role of H2O2 in the exfoliation of graphite. A possible exfoliation mechanism is proposed. The reaction of H2O2 with hydroxyl ions (HO-) leads to the formation of highly nucleophilic peroxide ions (O22-), which play a crucial role in the exfoliation of graphite via electrochemical-potential-assisted intercalation and strong expansion of graphite sheets.

  13. A new facile route for synthesizing of graphene oxide using mixture of sulfuric-nitric-phosphoric acids as intercalating agent

    NASA Astrophysics Data System (ADS)

    Panwar, Vinay; Chattree, Ananya; Pal, Kaushik

    2015-09-01

    In this work, graphene oxide (GO) has been prepared through three different processes namely, eco-friendly Hummers method, modification in improved Hummers method and a new approach. This new approach has been designed by changing some processing parameters and intercalating agent for significant reduction in processing time and to improve the quantity of GO in comparison to the other two methods. This has been achieved through better oxidization of graphite using nitric-sulfuric acid (HNO3-H2SO4) as intercalating agent. X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, Atomic Force Microscopy (AFM), X-ray photoelectron spectroscopy (XPS), UV-visible spectroscopy, and Thermogravimetric analysis (TGA) are used to characterize the GO prepared through different processes. These characterizations have confirmed an improved exfoliation of graphite, using addition of HNO3 in intercalating agent, in a short processing time and bring on higher yield of GO via this new process.

  14. NEW METHOD OF GRAPHITE PREPARATION

    DOEpatents

    Stoddard, S.D.; Harper, W.T.

    1961-08-29

    BS>A method is described for producing graphite objects comprising mixing coal tar pitch, carbon black, and a material selected from the class comprising raw coke, calcined coke, and graphite flour. The mixture is placed in a graphite mold, pressurized to at least 1200 psi, and baked and graphitized by heating to about 2500 deg C while maintaining such pressure. (AEC)

  15. Graphite for fusion energy applications

    SciTech Connect

    Eatherly, W.P.; Clausing, R.E.; Strehlow, R.A.; Kennedy, C.R.; Mioduszewski, P.K.

    1987-03-01

    Graphite is in widespread and beneficial use in present fusion energy devices. This report reflects the view of graphite materials scientists on using graphite in fusion devices. Graphite properties are discussed with emphasis on application to fusion reactors. This report is intended to be introductory and descriptive and is not intended to serve as a definitive information source. (JDH)

  16. Superlubricity of graphite.

    PubMed

    Dienwiebel, Martin; Verhoeven, Gertjan S; Pradeep, Namboodiri; Frenken, Joost W M; Heimberg, Jennifer A; Zandbergen, Henny W

    2004-03-26

    Using a home-built frictional force microscope that is able to detect forces in three dimensions with a lateral force resolution down to 15 pN, we have studied the energy dissipation between a tungsten tip sliding over a graphite surface in dry contact. By measuring atomic-scale friction as a function of the rotational angle between two contacting bodies, we show that the origin of the ultralow friction of graphite lies in the incommensurability between rotated graphite layers, an effect proposed under the name of "superlubricity" [Phys. Rev. B 41, 11 837 (1990)

  17. Commercial cokes and graphites as anode materials for lithium - ion cells

    SciTech Connect

    Derwin, D J; Kinoshita, K; Tran, T D; Zaleski, P

    2000-10-26

    Several types of carbonaceous materials from Superior Graphite Co. were investigated for lithium ion intercalation. These commercially available cokes, graphitized cokes and graphites have a wide range of physical and chemical properties. The coke materials were investigated in propylene carbonate based electrolytes and the graphitic materials were studied in ethylene carbonate/dimethyl solutions to prevent exfoliation. The reversible capacities of disordered cokes are below 230 mAh/g and those for many highly ordered synthetic (artificial) and natural graphites approached 372 mAh/g (LiC{sub 6}). The irreversible capacity losses vary between 15 to as much as 200% of reversible capacities for various types of carbon. Heat treated cokes with the average particle size of 10 microns showed marked improvements in reversible capacity for lithium intercalation. The electrochemical characteristics are correlated with data obtained from scanning electron microscopy (SEM), high resolution transmission electron microscopy (TEM), X-ray diffraction (XRD) and BET surface area analysis. The electrochemical performance, availability, cost and manufacturability of these commercial carbons will be discussed.

  18. A comparison of the bromination dynamics of various carbon and graphite fibers

    NASA Technical Reports Server (NTRS)

    Gaier, James R.

    1987-01-01

    The electrical resistance of four grades of pitch-based graphite fibers and three experimental organic vapor-derived fibers was determined in situ during bromination and subsequent exposure to ambient laboratory air. The results show that the least graphitic pitch-based fiber does not brominate significantly, and that bromination and debrominaton reactions proceed much slower for vapor-derived fibers than for pitch-based ones. It is suggested that this decreased reacton rate is primarily due to the differences in graphene plane orientation between the fiber types. The results also imply that the vapor-derived and pitch-based fibers produce true intercalation compounds.

  19. A Topological Model of Bilingual Intercalation Behavior.

    ERIC Educational Resources Information Center

    Attinasi, John; And Others

    This paper reviews issues and analyses in bilingual switching, or intercalation, and offers a topological model to represent the activity of code switching, sometimes under the same environmental conditions and with the same interlocutors. The topological notion of catastrophe is proposed as a means to model the various factors that influence code…

  20. Silicon on graphite cloth

    SciTech Connect

    Rand, J.A.; Cotter, J.E.; Thomas, C.J.; Ingram, A.E.; Bai, Y.B.; Ruffins, T.R.; Barnett, A.M.

    1994-12-31

    A new polycrystalline silicon solar cell has been developed that utilizes commercially available graphite cloth as a substrate. This solar cell has achieved an energy conversion efficiency of 13.4% (AM1.5G). It is believed that this is a record efficiency for a silicon solar cell formed on a graphite substrate. The silicon-on-fabric structure is comprised of a thin layer of polycrystalline silicon grown directly on the graphite fabric substrate. The structure is fabricated by a low-cost ribbon process that avoids the expense and waste of wafering. The fabric substrate gives structural support to the thin device. Critical to the achievement of device quality silicon layers is control over impurities in the graphite fabric. The silicon-on-fabric technology has the potential to supply lightweight, low-cost solar cells to weight-sensitive markets at a fraction of the cost of conventionally thinned wafers.

  1. Graphite Technology Development Plan

    SciTech Connect

    W. Windes; T. Burchell; R. Bratton

    2007-09-01

    This technology development plan is designed to provide a clear understanding of the research and development direction necessary for the qualification of nuclear grade graphite for use within the Next Generation Nuclear Plant (NGNP) reactor. The NGNP will be a helium gas cooled Very High Temperature Reactor (VHTR) with a large graphite core. Graphite physically contains the fuel and comprises the majority of the core volume. Considerable effort will be required to ensure that the graphite performance is not compromised during operation. Based upon the perceived requirements the major data needs are outlined and justified from the perspective of reactor design, reatcor performance, or the reactor safety case. The path forward for technology development can then be easily determined for each data need. How the data will be obtained and the inter-relationships between the experimental and modeling activities will define the technology development for graphite R&D. Finally, the variables affecting this R&D program are discussed from a general perspective. Factors that can significantly affect the R&D program such as funding, schedules, available resources, multiple reactor designs, and graphite acquisition are analyzed.

  2. Carbon-14 Graphitization Chemistry

    NASA Astrophysics Data System (ADS)

    Miller, James; Collon, Philippe; Laverne, Jay

    2014-09-01

    Accelerator Mass Spectrometry (AMS) is a process that allows for the analysis of mass of certain materials. It is a powerful process because it results in the ability to separate rare isotopes with very low abundances from a large background, which was previously impossible. Another advantage of AMS is that it only requires very small amounts of material for measurements. An important application of this process is radiocarbon dating because the rare 14C isotopes can be separated from the stable 14N background that is 10 to 13 orders of magnitude larger, and only small amounts of the old and fragile organic samples are necessary for measurement. Our group focuses on this radiocarbon dating through AMS. When performing AMS, the sample needs to be loaded into a cathode at the back of an ion source in order to produce a beam from the material to be analyzed. For carbon samples, the material must first be converted into graphite in order to be loaded into the cathode. My role in the group is to convert the organic substances into graphite. In order to graphitize the samples, a sample is first combusted to form carbon dioxide gas and then purified and reduced into the graphite form. After a couple weeks of research and with the help of various Physics professors, I developed a plan and began to construct the setup necessary to perform the graphitization. Once the apparatus is fully completed, the carbon samples will be graphitized and loaded into the AMS machine for analysis.

  3. Polytypic phase transitions in metal intercalated Bi2Se3

    NASA Astrophysics Data System (ADS)

    Wang, Mengjing; Koski, Kristie J.

    2016-12-01

    The temperature and concentration dependent phase diagrams of zero-valent copper, cobalt, and iron intercalated bismuth selenide are investigated using in situ transmission electron microscopy. Polytypic phase transitions associated with superlattice formation along with order-disorder transitions of the guest intercalant are determined. Dual-element intercalants of CuCo, CuFe, and CoFe-Bi2Se3 are also investigated. Hexagonal and striped domain formation consistent with two-dimensional ordering of the intercalant and Pokrovksy-Talapov theory is identified as a function of concentration. These studies provide a complete picture of the structural behavior of zero-valent metal intercalated Bi2Se3.

  4. Onset of superconductivity in sodium and potassium intercalated molybdenum disulphide

    NASA Technical Reports Server (NTRS)

    Somoano, R. B.; Rembaum, A.

    1971-01-01

    Molybdenum disulfide in the form of natural crystals or powder has been intercalated at -65 to -70 C with sodium and potassium using the liquid ammonia technique. All intercalated samples were found to show a superconducting transition. A plot of the percent of diamagnetic throw versus temperature indicates the possible existence of two phases in the potassium intercalated molybdenum disulfide. The onset of superconductivity in potassium and sodium intercalated molybdenite powder was found to be approximately 6.2 and approximately 4.5 K, respectively. The observed superconductivity is believed to be due to an increase in electron density as a result of intercalation.

  5. Graphite-incorporated MoS2 nanotubes: a new coaxial binary system.

    PubMed

    Reza-San German, C; Santiago, P; Ascencio, J A; Pal, U; Pérez-Alvarez, M; Rendón, L; Mendoza, D

    2005-09-22

    Graphite-filled MoS2 nanotubes were synthesized by pyrolizing propylene inside MoS2 nanotubes prepared by a template-assisted technique. The large coaxial nanotubes were constituted of graphite sheets inserted between the MoS2 layers, forming the outer part, and coaxial multiwall carbon nanotubes intercalated with MoS2 inside. High-resolution electron microscopy (HREM) and electron energy loss spectroscopy techniques along with molecular dynamics simulation and quantum mechanical calculations were used to characterize the samples. The one-dimensional structures exhibit diverse morphologies such as long straight and twisted nanotubes with several structural irregularities. The interplanar spacing between the MoS2 layers was found to increase from 6.3 to 7.4 A due to intercalation with carbon. Simulated HREM images revealed the presence of mechanical strains in the carbon-intercalated MoS2 layers as the reason for obtaining these twisted nanostructures. The mechanism of formation of carbon-intercalated MoS2 tubular structures and their stability and electronic properties are discussed. Our results open up the possibility of using MoS2 nanotubes as templates for the synthesis of new one-dimensional binary-phase systems.

  6. Analysis on Thermal Conductivity of Graphite/Al Composite by Experimental and Modeling Study

    NASA Astrophysics Data System (ADS)

    Xue, C.; Bai, H.; Tao, P. F.; Jiang, N.; Wang, S. L.

    2017-01-01

    Graphite/Al composites were fabricated by vacuum hot pressing technology in this study. The main factors affecting the thermal conductivity (TC) of graphite/Al composites were deeply investigated by experimental and modeling study. The results showed that the TC of graphite/Al composite can be improved via designing the preferred orientation of graphite flakes, selecting graphite flakes with large diameter, increasing the content of graphite flakes in graphite/Al composite and solving the poor wettability between Al and graphite. The modified model can well predict the heat transfer behavior of graphite/Al composite.

  7. Comparison of reduction products from graphite oxide and graphene oxide for anode applications in lithium-ion batteries and sodium-ion batteries.

    PubMed

    Sun, Yige; Tang, Jie; Zhang, Kun; Yuan, Jinshi; Li, Jing; Zhu, Da-Ming; Ozawa, Kiyoshi; Qin, Lu-Chang

    2017-02-16

    Hydrazine-reduced graphite oxide and graphene oxide were synthesized to compare their performances as anode materials in lithium-ion batteries and sodium-ion batteries. Reduced graphite oxide inherits the layer structure of graphite, with an average spacing between neighboring layers (d-spacing) of 0.374 nm; this exceeds the d-spacing of graphite (0.335 nm). The larger d-spacing provides wider channels for transporting lithium ions and sodium ions in the material. We showed that reduced graphite oxide as an anode in lithium-ion batteries can reach a specific capacity of 917 mA h g(-1), which is about three times of 372 mA h g(-1), the value expected for the LiC6 structures on the electrode. This increase is consistent with the wider d-spacing, which enhances lithium intercalation and de-intercalation on the electrodes. The electrochemical performance of the lithium-ion batteries and sodium-ion batteries with reduced graphite oxide anodes show a noticeable improvement compared to those with reduced graphene oxide anodes. This improvement indicates that reduced graphite oxide, with larger interlayer spacing, has fewer defects and is thus more stable. In summary, we found that reduced graphite oxide may be a more favorable form of graphene for the fabrication of electrodes for lithium-ion and sodium-ion batteries and other energy storage devices.

  8. Coexistence of covalent and metallic bonding in the boron intercalation superconductor MgB2

    NASA Astrophysics Data System (ADS)

    Belashchenko, K. D.; Schilfgaarde, M. Van; Antropov, V. P.

    2001-09-01

    Chemical bonding and electronic structure of MgB2, a boron-based newly discovered superconductor, is studied using self-consistent band-structure techniques. Analysis of the transformation of the band structure for the hypothetical series of graphite-primitive graphite-primitive graphitelike boron-intercalated boron, shows that the band structure of MgB2 is graphitelike, with π bands falling deeper than in ordinary graphite. These bands possess a typically delocalized and metallic, as opposed to covalent, character. The in-plane σ bands retain their two-dimensional (2D) covalent character, but exhibit a metallic hole-type conductivity. The coexistence of 2D covalent in-plane and three-dimensional (3D) metallic-type interlayer conducting bands is a peculiar feature of MgB2. We analyze the 2D and 3D features of the band structure of MgB2 and related compounds, and their contributions to conductivity.

  9. Purification process of natural graphite as anode for Li-ion batteries: chemical versus thermal

    NASA Astrophysics Data System (ADS)

    Zaghib, K.; Song, X.; Guerfi, A.; Rioux, R.; Kinoshita, K.

    The intercalation of Li ions in natural graphite that was purified by chemical and thermal processes was investigated. A new chemical process was developed that involved a mixed aqueous solution containing 30% H 2SO 4 and 30% NH xF y heated to 90 °C. The results of this process are compared to those obtained by heating the natural graphite from 1500 to 2400 °C in an inert environment (thermal process). The first-cycle coulombic efficiency of the purified natural graphite obtained by the chemical process is 91 and 84% after the thermal process at 2400 °C. Grinding the natural graphite before or after purification had no significant effect on electrochemical performance at low currents. However, grinding to a very small particle size before purification permitted optimization of the size distribution of the particles, which gives rise to a more homogenous electrode. The impurities in the graphite play a role as microabrasion agents during grinding which enhances its hardness and improves its mechanical properties. Grinding also modifies the particle morphology from a 2- to a 3-D structure (similar in shape to a potato). This potato-shaped natural graphite shows high reversible capacity at high current densities (about 90% at 1 C rate). Our analysis suggests that thermal processing is considerably more expensive than the chemical process to obtain purified natural graphite.

  10. Phosphate-stabilized Lithium intercalation compounds

    SciTech Connect

    Richardson, Thomas J.

    2002-07-22

    Four manganese and iron phosphates with alluaudite or fillowite structures have been prepared by solid state reactions: Na2FeMn2(PO4)3, LiNaFeMn2(PO4)3, NaFe3(PO4)3, and Na2Mn3(PO4)3. LixNa2-xFeMn2(PO4)3 with x close to 2 was prepared from Na2FeMn2(PO4)3 by molten salt ion exchange. These materials are similar in stoichiometry to the phospho-olivines LiFe(Mn)PO4, but have a more complex structure that can accommodate mixed transition metal oxidation states. They are of interest as candidates for lithium battery cathodes because of their somewhat higher electronic conductivity, high intercalant ion mobility, and ease of preparation. Their performance as intercalation electrodes in non-aqueous lithium cells was, however, poor.

  11. Recompressed exfoliated graphite articles

    DOEpatents

    Zhamu, Aruna; Shi, Jinjun; Guo, Jiusheng; Jang, Bor Z

    2013-08-06

    This invention provides an electrically conductive, less anisotropic, recompressed exfoliated graphite article comprising a mixture of (a) expanded or exfoliated graphite flakes; and (b) particles of non-expandable graphite or carbon, wherein the non-expandable graphite or carbon particles are in the amount of between about 3% and about 70% by weight based on the total weight of the particles and the expanded graphite flakes combined; wherein the mixture is compressed to form the article having an apparent bulk density of from about 0.1 g/cm.sup.3 to about 2.0 g/cm.sup.3. The article exhibits a thickness-direction conductivity typically greater than 50 S/cm, more typically greater than 100 S/cm, and most typically greater than 200 S/cm. The article, when used in a thin foil or sheet form, can be a useful component in a sheet molding compound plate used as a fuel cell separator or flow field plate. The article may also be used as a current collector for a battery, supercapacitor, or any other electrochemical cell.

  12. Graphite Gamma Scan Results

    SciTech Connect

    Mark W. Drigert

    2014-04-01

    This report documents the measurement and data analysis of the radio isotopic content for a series of graphite specimens irradiated in the first Advanced Graphite Creep (AGC) experiment, AGC-1. This is the first of a series of six capsules planned as part of the AGC experiment to fully characterize the neutron irradiation effects and radiation creep behavior of current nuclear graphites. The AGC-1 capsule was irradiated in the Advanced Test Reactor (ATR) at INL at approximately 700 degrees C and to a peak dose of 7 dpa (displacements per atom). Details of the irradiation conditions and other characterization measurements performed on specimens in the AGC-1 capsule can be found in “AGC-1 Specimen Post Irradiation Data Report” ORNL/TM 2013/242. Two specimens from six different graphite types are analyzed here. Each specimen is 12.7 mm in diameter by 25.4 mm long. The isotope with the highest activity was 60Co. Graphite type NBG-18 had the highest content of 60Co with an activity of 142.89 µCi at a measurement distance of 47 cm.

  13. Monte Carlo simulation of intercalated carbon nanotubes.

    PubMed

    Mykhailenko, Oleksiy; Matsui, Denis; Prylutskyy, Yuriy; Le Normand, Francois; Eklund, Peter; Scharff, Peter

    2007-01-01

    Monte Carlo simulations of the single- and double-walled carbon nanotubes (CNT) intercalated with different metals have been carried out. The interrelation between the length of a CNT, the number and type of metal atoms has also been established. This research is aimed at studying intercalated systems based on CNTs and d-metals such as Fe and Co. Factors influencing the stability of these composites have been determined theoretically by the Monte Carlo method with the Tersoff potential. The modeling of CNTs intercalated with metals by the Monte Carlo method has proved that there is a correlation between the length of a CNT and the number of endo-atoms of specific type. Thus, in the case of a metallic CNT (9,0) with length 17 bands (3.60 nm), in contrast to Co atoms, Fe atoms are extruded out of the CNT if the number of atoms in the CNT is not less than eight. Thus, this paper shows that a CNT of a certain size can be intercalated with no more than eight Fe atoms. The systems investigated are stabilized by coordination of 3d-atoms close to the CNT wall with a radius-vector of (0.18-0.20) nm. Another characteristic feature is that, within the temperature range of (400-700) K, small systems exhibit ground-state stabilization which is not characteristic of the higher ones. The behavior of Fe and Co endo-atoms between the walls of a double-walled carbon nanotube (DW CNT) is explained by a dominating van der Waals interaction between the Co atoms themselves, which is not true for the Fe atoms.

  14. Arrhythmogenic cardiomyopathy: a disease of intercalated discs.

    PubMed

    Calore, Martina; Lorenzon, Alessandra; De Bortoli, Marzia; Poloni, Giulia; Rampazzo, Alessandra

    2015-06-01

    Arrhythmogenic cardiomyopathy (ACM) is an acquired progressive disease having an age-related penetrance and showing clinical manifestations usually during adolescence and young adulthood. It is characterized clinically by a high incidence of severe ventricular tachyarrhythmias and sudden cardiac death and pathologically by degeneration of ventricular cardiomyocytes with replacement by fibro-fatty tissue. Whereas, in the past, the disease was considered to involve only the right ventricle, more recent clinical studies have established that the left ventricle is frequently involved. ACM is an inherited disease in up to 50% of cases, with predominantly an autosomal dominant pattern of transmission, although recessive inheritance has also been described. Since most of the pathogenic mutations have been identified in genes encoding desmosomal proteins, ACM is currently defined as a disease of desmosomes. However, on the basis of the most recent description of the intercalated disc organization and of the identification of a novel ACM gene encoding for an area composita protein, ACM can be considered as a disease of the intercalated disc, rather than only as a desmosomal disease. Despite increasing knowledge of the genetic basis of ACM, we are just beginning to understand early molecular events leading to cardiomyocyte degeneration, fibrosis and fibro-fatty substitution. This review summarizes recent advances in our comprehension of the link between the molecular genetics and pathogenesis of ACM and of the novel role of cardiac intercalated discs.

  15. Core level shifts of intercalated graphene

    NASA Astrophysics Data System (ADS)

    Schröder, Ulrike A.; Petrović, Marin; Gerber, Timm; Martínez-Galera, Antonio J.; Grånäs, Elin; Arman, Mohammad A.; Herbig, Charlotte; Schnadt, Joachim; Kralj, Marko; Knudsen, Jan; Michely, Thomas

    2017-03-01

    Through intercalation of metals and gases the Dirac cone of graphene on Ir(111) can be shifted with respect to the Fermi level without becoming destroyed by strong hybridization. Here, we use x-ray photoelectron spectroscopy to measure the C 1s core level shift (CLS) of graphene in contact with a number of structurally well-defined intercalation layers (O, H, Eu, and Cs). By analysis of our own and additional literature data for decoupled graphene, the C 1s CLS is found to be a non-monotonic function of the doping level. For small doping levels the shifts are well described by a rigid band model. However, at larger doping levels, a second effect comes into play which is proportional to the transferred charge and counteracts the rigid band shift. Moreover, not only the position, but also the C 1s peak shape displays a unique evolution as a function of doping level. Our conclusions are supported by intercalation experiments with Li, with which, due to the absence of phase separation, the doping level of graphene can be continuously tuned.

  16. Cesium diffusion in graphite

    SciTech Connect

    Evans, R.B. III; Davis, W. Jr.; Sutton, A.L. Jr.

    1980-05-01

    Experiments on diffusion of /sup 137/Cs in five types of graphite were performed. The document provides a completion of the report that was started and includes a presentation of all of the diffusion data, previously unpublished. Except for data on mass transfer of /sup 137/Cs in the Hawker-Siddeley graphite, analyses of experimental results were initiated but not completed. The mass transfer process of cesium in HS-1-1 graphite at 600 to 1000/sup 0/C in a helium atmosphere is essentially pure diffusion wherein values of (E/epsilon) and ..delta..E of the equation D/epsilon = (D/epsilon)/sub 0/ exp (-..delta..E/RT) are about 4 x 10/sup -2/ cm/sup 2//s and 30 kcal/mole, respectively.

  17. Irradiation Creep in Graphite

    SciTech Connect

    Ubic, Rick; Butt, Darryl; Windes, William

    2014-03-13

    An understanding of the underlying mechanisms of irradiation creep in graphite material is required to correctly interpret experimental data, explain micromechanical modeling results, and predict whole-core behavior. This project will focus on experimental microscopic data to demonstrate the mechanism of irradiation creep. High-resolution transmission electron microscopy should be able to image both the dislocations in graphite and the irradiation-induced interstitial clusters that pin those dislocations. The team will first prepare and characterize nanoscale samples of virgin nuclear graphite in a transmission electron microscope. Additional samples will be irradiated to varying degrees at the Advanced Test Reactor (ATR) facility and similarly characterized. Researchers will record microstructures and crystal defects and suggest a mechanism for irradiation creep based on the results. In addition, the purchase of a tensile holder for a transmission electron microscope will allow, for the first time, in situ observation of creep behavior on the microstructure and crystallographic defects.

  18. Coatings for graphite fibers

    NASA Technical Reports Server (NTRS)

    Galasso, F. S.; Scola, D. A.; Veltri, R. D.

    1980-01-01

    Graphite fibers released from composites during burning or an explosion caused shorting of electrical and electronic equipment. Silicon carbide, silica, silicon nitride and boron nitride were coated on graphite fibers to increase their electrical resistances. Resistances as high as three orders of magnitude higher than uncoated fiber were attained without any significant degradation of the substrate fiber. An organo-silicone approach to produce coated fibers with high electrical resistance was also used. Celion 6000 graphite fibers were coated with an organo-silicone compound, followed by hydrolysis and pyrolysis of the coating to a silica-like material. The shear and flexural strengths of composites made from high electrically resistant fibers were considerably lower than the shear and flexural strengths of composites made from the lower electrically resistant fibers. The lower shear strengths of the composites indicated that the coatings on these fibers were weaker than the coating on the fibers which were pyrolyzed at higher temperature.

  19. Superlubricity of Graphite

    NASA Astrophysics Data System (ADS)

    Dienwiebel, Martin; Verhoeven, Gertjan S.; Pradeep, Namboodiri; Frenken, Joost W.; Heimberg, Jennifer A.; Zandbergen, Henny W.

    2004-03-01

    Using a home-built frictional force microscope that is able to detect forces in three dimensions with a lateral force resolution down to 15 pN, we have studied the energy dissipation between a tungsten tip sliding over a graphite surface in dry contact. By measuring atomic-scale friction as a function of the rotational angle between two contacting bodies, we show that the origin of the ultralow friction of graphite lies in the incommensurability between rotated graphite layers, an effect proposed under the name of “superlubricity” [

    M. Hirano and K. Shinjo, Phys. Rev. BPRBMDO0163-1829 41, 11 837 (1990)10.1103/PhysRevB.41.11837
    ].

  20. Intercalation compounds and electrodes for batteries

    DOEpatents

    Chiang, Yet-Ming; Sadoway, Donald R.; Jang, Young-Il; Huang, Biyan

    2004-09-07

    This invention concerns intercalation compounds and in particular lithium intercalation compounds which have improved properties for use in batteries. Compositions of the invention include particulate metal oxide material having particles of multicomponent metal oxide, each including an oxide core of at least first and second metals in a first ratio, and each including a surface coating of metal oxide or hydroxide that does not include the first and second metals in the first ratio formed by segregation of at least one of the first and second metals from the core. The core may preferably comprise Li.sub.x M.sub.y N.sub.z O.sub.2 wherein M and N are metal atom or main group elements, x, y and z are numbers from about 0 to about 1 and y and z are such that a formal charge on M.sub.y N.sub.z portion of the compound is (4-x), and having a charging voltage of at least about 2.5V. The invention may also be characterized as a multicomponent oxide microstructure usable as a lithium intercalation material including a multiphase oxide core and a surface layer of one material, which is a component of the multiphase oxide core, that protects the underlying intercalation material from chemical dissolution or reaction. In a particular preferred example the multicomponent oxide may be an aluminum-doped lithium manganese oxide composition. Such aluminum-doped lithium manganese oxide compositions, having an orthorhombic structure, also form a part of the invention. In addition, the invention includes articles, particularly electrodes, for batteries formed from the compositions of the invention, and batteries including such electrodes. The invention further relates to a composite intercalation material comprising at least two compounds in which at least one compound has an orthorhombic structure Li.sub.x Al.sub.y Mn.sub.1-y O.sub.2, where y is nonzero, or a mixture of orthorhombic and monoclinic Li.sub.x Al.sub.y Mn.sub.1-y O.sub.2.

  1. Pristine and intercalated transition metal dichalcogenide superconductors

    NASA Astrophysics Data System (ADS)

    Klemm, Richard A.

    2015-07-01

    Transition metal dichalcogenides (TMDs) are quasi-two-dimensional layered compounds that exhibit strongly competing effects of charge-density wave (CDW) formation and superconductivity (SC). The weak van der Waals interlayer bonding between hexagonal layers of octahedral or trigonal prismatic TMD building blocks allows many polytypes to form. In the single layer 1 T polytype materials, one or more CDW states can form, but the pristine TMDs are not superconducting. The 2 H polytypes have two or more Fermi surfaces and saddle bands, allowing for dual orderings, which can be coexisting CDW and SC orderings, two SC gaps as in MgB2, two CDW gaps, and possibly even pseudogaps above the onset TCDW s of CDW orderings. Higher order polytypes allow for multiple CDW gaps and at least one superconducting gap. The CDW transitions TCDW s usually greatly exceed the superconducting transitions at their low Tc values, their orbital order parameters (OPs) are generally highly anisotropic and can even contain nodes, and the SC OPs can be greatly affected by their simultaneous presence. The properties of the CDWs ubiquitously seen in TMDs are remarkably similar to those of the pseudogaps seen in the high-Tc cuprates. In 2H-NbSe2, for example, the CDW renders its general s-wave SC OP orbital symmetry to be highly anisotropic and strongly reduces its Josephson coupling strength (IcRn) with the conventional SC, Pb. Hence, the pristine TMDs are highly "unconventional" in comparison with Pb, but are much more "conventional" than are the ferromagnetic superconductors such as URhGe. Applied pressure and intercalation generally suppress the TMD CDWs, allowing for enhanced SC formation, even in the 1 T polytype materials. The misfit intercalation compound (LaSe)1.14(NbSe2) and many 2 H -TMDs intercalated with organic Lewis base molecules, such as TaS2(pyridine)1/2, have completely incoherent c-axis transport, dimensional-crossover effects, and behave as stacks of intrinsic Josephson junctions

  2. Improved graphite furnace atomizer

    DOEpatents

    Siemer, D.D.

    1983-05-18

    A graphite furnace atomizer for use in graphite furnace atomic absorption spectroscopy is described wherein the heating elements are affixed near the optical path and away from the point of sample deposition, so that when the sample is volatilized the spectroscopic temperature at the optical path is at least that of the volatilization temperature, whereby analyteconcomitant complex formation is advantageously reduced. The atomizer may be elongated along its axis to increase the distance between the optical path and the sample deposition point. Also, the atomizer may be elongated along the axis of the optical path, whereby its analytical sensitivity is greatly increased.

  3. Ag induced electromagnetic interference shielding of Ag-graphite/PVDF flexible nanocomposites thinfilms

    SciTech Connect

    Kumaran, R.; Alagar, M.; Dinesh Kumar, S.; Subramanian, V.; Dinakaran, K.

    2015-09-14

    We report Ag nanoparticle induced Electromagnetic Interference (EMI) shielding in a flexible composite films of Ag nanoparticles incorporated graphite/poly-vinylidene difluoride (PVDF). PVDF nanocomposite thin-films were synthesized by intercalating Ag in Graphite (GIC) followed by dispersing GIC in PVDF. The X-ray diffraction analysis and the high-resolution transmission electron microscope clearly dictate the microstructure of silver nanoparticles in graphite intercalated composite of PVDF matrix. The conductivity values of nanocomposites are increased upto 2.5 times when compared to neat PVDF having a value of 2.70 S/cm at 1 MHz. The presence of Ag broadly enhanced the dielectric constant and lowers the dielectric loss of PVDF matrix proportional to Ag content. The EMI shielding effectiveness of the composites is 29.1 dB at 12.4 GHz for the sample having 5 wt. % Ag and 10 wt. % graphite in PVDF.

  4. Graphite-based photovoltaic cells

    DOEpatents

    Lagally, Max; Liu, Feng

    2010-12-28

    The present invention uses lithographically patterned graphite stacks as the basic building elements of an efficient and economical photovoltaic cell. The basic design of the graphite-based photovoltaic cells includes a plurality of spatially separated graphite stacks, each comprising a plurality of vertically stacked, semiconducting graphene sheets (carbon nanoribbons) bridging electrically conductive contacts.

  5. The intercalation chemistry of layered iron chalcogenide superconductors

    NASA Astrophysics Data System (ADS)

    Vivanco, Hector K.; Rodriguez, Efrain E.

    2016-10-01

    The iron chalcogenides FeSe and FeS are superconductors composed of two-dimensional sheets held together by van der Waals interactions, which makes them prime candidates for the intercalation of various guest species. We review the intercalation chemistry of FeSe and FeS superconductors and discuss their synthesis, structure, and physical properties. Before we review the latest work in this area, we provide a brief background on the intercalation chemistry of other inorganic materials that exhibit enhanced superconducting properties upon intercalation, which include the transition metal dichalcogenides, fullerenes, and layered cobalt oxides. From past studies of these intercalated superconductors, we discuss the role of the intercalates in terms of charge doping, structural distortions, and Fermi surface reconstruction. We also briefly review the physical and chemical properties of the host materials-mackinawite-type FeS and β-FeSe. The three types of intercalates for the iron chalcogenides can be placed in three categories: 1.) alkali and alkaline earth cations intercalated through the liquid ammonia technique; 2.) cations intercalated with organic amines such as ethylenediamine; and 3.) layered hydroxides intercalated during hydrothermal conditions. A recurring theme in these studies is the role of the intercalated guest in electron doping the chalcogenide host and in enhancing the two-dimensionality of the electronic structure by spacing the FeSe layers apart. We end this review discussing possible new avenues in the intercalation chemistry of transition metal monochalcogenides, and the promise of these materials as a unique set of new inorganic two-dimensional systems.

  6. (Irradiation creep of graphite)

    SciTech Connect

    Kennedy, C.R.

    1990-12-21

    The traveler attended the Conference, International Symposium on Carbon, to present an invited paper, Irradiation Creep of Graphite,'' and chair one of the technical sessions. There were many papers of particular interest to ORNL and HTGR technology presented by the Japanese since they do not have a particular technology embargo and are quite open in describing their work and results. In particular, a paper describing the failure of Minor's law to predict the fatigue life of graphite was presented. Although the conference had an international flavor, it was dominated by the Japanese. This was primarily a result of geography; however, the work presented by the Japanese illustrated an internal program that is very comprehensive. This conference, a result of this program, was better than all other carbon conferences attended by the traveler. This conference emphasizes the need for US participation in international conferences in order to stay abreast of the rapidly expanding HTGR and graphite technology throughout the world. The United States is no longer a leader in some emerging technologies. The traveler was surprised by the Japanese position in their HTGR development. Their reactor is licensed and the major problem in their graphite program is how to eliminate it with the least perturbation now that most of the work has been done.

  7. GRAPHITE BONDING METHOD

    DOEpatents

    King, L.D.P.

    1964-02-25

    A process for bonding or joining graphite members together in which a thin platinum foil is placed between the members, heated in an inert atmosphere to a temperature of 1800 deg C, and then cooled to room temperature is described. (AEC)

  8. Structural graphitic carbon foams

    SciTech Connect

    Kearns, K.M.; Anderson, H.J.

    1998-12-31

    Graphitic carbon foams are a unique material form with very high structural and thermal properties at a light weight. A process has been developed to produce microcellular, open-celled graphitic foams. The process includes heating a mesophase pitch preform above the pitch melting temperature in a pressurized reactor. At the appropriate time, the pressure is released, the gas nucleates bubbles, and these bubbles grow forming the pitch into the foam structure. The resultant foamed pitch is then stabilized in an oxygen environment. At this point a rigid structure exists with some mechanical integrity. The foam is then carbonized to 800 C followed by a graphitization to 2700 C. The shear action from the growing bubbles aligns the graphitic planes along the foam struts to provide the ideal structure for good mechanical properties. Some of these properties have been characterized for some of the foam materials. It is known that variations of the blowing temperature, blowing pressure and saturation time result in foams of variously sized with mostly open pores; however, the mechanism of bubble nucleation is not known. Therefore foams were blown with various gases to begin to determine the nucleation method. These gases are comprised of a variety of molecular weights as well as a range of various solubility levels. By examining the resultant structures of the foam, differences were noted to develop an explanation of the foaming mechanism.

  9. Coatings for Graphite Fibers

    NASA Technical Reports Server (NTRS)

    Galasso, F. S.; Scola, D. A.; Veltri, R. D.

    1980-01-01

    Several approaches for applying high resistance coatings continuously to graphite yarn were investigated. Two of the most promising approaches involved (1) chemically vapor depositing (CVD) SiC coatings on the surface of the fiber followed by oxidation, and (2) drawing the graphite yarn through an organo-silicone solution followed by heat treatments. In both methods, coated fibers were obtained which exhibited increased electrical resistances over untreated fibers and which were not degraded. This work was conducted in a previous program. In this program, the continuous CVD SiC coating process used on HTS fiber was extended to the coating of HMS, Celion 6000, Celion 12000 and T-300 graphite fiber. Electrical resistances three order of magnitude greater than the uncoated fiber were measured with no significant degradation of the fiber strength. Graphite fibers coated with CVD Si3N4 and BN had resistances greater than 10(exp 6) ohm/cm. Lower pyrolysis temperatures were used in preparing the silica-like coatings also resulting in resistances as high as three orders of magnitude higher than the uncoated fiber. The epoxy matrix composites prepared using these coated fibers had low shear strengths indicating that the coatings were weak.

  10. Magnetic frustration of graphite oxide

    NASA Astrophysics Data System (ADS)

    Lee, Dongwook; Seo, Jiwon

    2017-03-01

    Delocalized π electrons in aromatic ring structures generally induce diamagnetism. In graphite oxide, however, π electrons develop ferromagnetism due to the unique structure of the material. The π electrons are only mobile in the graphitic regions of graphite oxide, which are dispersed and surrounded by sp3-hybridized carbon atoms. The spin-glass behavior of graphite oxide is corroborated by the frequency dependence of its AC susceptibility. The magnetic susceptibility data exhibit a negative Curie temperature, field irreversibility, and slow relaxation. The overall results indicate that magnetic moments in graphite oxide slowly interact and develop magnetic frustration.

  11. Magnetic frustration of graphite oxide

    PubMed Central

    Lee, Dongwook; Seo, Jiwon

    2017-01-01

    Delocalized π electrons in aromatic ring structures generally induce diamagnetism. In graphite oxide, however, π electrons develop ferromagnetism due to the unique structure of the material. The π electrons are only mobile in the graphitic regions of graphite oxide, which are dispersed and surrounded by sp3-hybridized carbon atoms. The spin-glass behavior of graphite oxide is corroborated by the frequency dependence of its AC susceptibility. The magnetic susceptibility data exhibit a negative Curie temperature, field irreversibility, and slow relaxation. The overall results indicate that magnetic moments in graphite oxide slowly interact and develop magnetic frustration. PMID:28327606

  12. Rechargeable lithium-ion cells using graphitized mesophase-pitch-based carbon fiber anodes

    SciTech Connect

    Takami, Norio; Satoh, Asako; Hara, Michikazu; Ohsaki, Takahisa

    1995-08-01

    The electrochemistry of lithium intercalation into a graphitized mesophase-pitch-based carbon fiber with a radial-like texture used as the anode material in rechargeable lithium-ion cells was characterized. The radial-like texture in the cross section of the carbon fiber contributed to the rapid diffusion of lithium ions, resulting in the high rate capability. The anode performance of the graphitized carbon fiber was superior to that of the graphite. Experimental flat-plate C/LiCoO{sub 2} lithium-ion cells using the graphitized carbon fiber anode exhibited a high mid-discharge voltage of 3.7 V, a high rate capability, and a long cycle life of more than 400 cycles at 2 mA/cm{sup 2} mA/cm{sup 2} during charge-discharge cycling between 4.2 and 2.7 V. The long cycle life obtained for the cell was due to no significant change in resistance associated with the passivating films on the graphitized carbon fiber with extended cycles. It was also demonstrated that A size C/LiCoO{sub 2} cells using the graphitized carbon fiber anode have excellent rate performance at discharge currents between 0.25 and 3 A, a large discharge capacity of 0.95 Ah, and a high energy density of 310 Wh/dm{sup 3} and 120 Wh/kg.

  13. Intercalation of water into lithium. beta. -alumina

    SciTech Connect

    Dudney, N J; Bates, J B; Wang, J C; Brown, G M; Larson, B C; Engstrom, H

    1981-01-01

    Infrared absorption, neutron diffraction and weight loss techniques have been used to investigate the hydration of single crystals of Li ..beta..-alumina. The hydration is a reversible intercalation reaction. Up to approximately two water molecules per formula unit can penetrate the conduction plane. Other protonated species are formed from the dissociation of the molecular water. The rate of hydration is controlled by the diffusion of water in the conduction plane. A likely diffusion mechanism requires dissociation of the water and an interstitialcy motion of the oxygen.

  14. A Nanoporous Carbon/Exfoliated Graphite Composite For Supercapacitor Electrodes

    NASA Astrophysics Data System (ADS)

    Rosi, Memoria; Ekaputra, Muhamad P.; Iskandar, Ferry; Abdullah, Mikrajuddin; Khairurrijal

    2010-12-01

    Nanoporous carbon was prepared from coconut shells using a simple heating method. The nanoporous carbon is subjected to different treatments: without activation, activation with polyethylene glycol (PEG), and activation with sodium hydroxide (NaOH)-PEG. The exfoliated graphite was synthesized from graphite powder oxidized with zinc acetate (ZnAc) and intercalated with polyvinyl alcohol (PVA) and NaOH. A composite was made by mixing the nanoporous carbon with NaOH-PEG activation, the exfoliated graphite and a binder of PVA solution, grinding the mixture, and annealing it using ultrasonic bath for 1 hour. All of as-synthesized materials were characterized by employing a scanning electron microscope (SEM), a MATLAB's image processing toolbox, and an x-ray diffractometer (XRD). It was confirmed that the composite is crystalline with (002) and (004) orientations. In addition, it was also found that the composite has a high surface area, a high distribution of pore sizes less than 40 nm, and a high porosity (67%). Noting that the pore sizes less than 20 nm are significant for ionic species storage and those in the range of 20 to 40 nm are very accessible for ionic clusters mobility across the pores, the composite is a promising material for the application as supercapacitor electrodes.

  15. One-pot synthesis of fluorescent carbon nanoribbons, nanoparticles, and graphene by the exfoliation of graphite in ionic liquids.

    PubMed

    Lu, Jiong; Yang, Jia-xiang; Wang, Junzhong; Lim, Ailian; Wang, Shuai; Loh, Kian Ping

    2009-08-25

    In this work we demonstrate a facile means to generate fluorescent carbon nanoribbons, nanoparticles, and graphene from graphite electrode using ionic liquid-assisted electrochemical exfoliation. A time-dependence study of products exfoliated from the graphite anode allows the reconstruction of the exfoliation mechanism based on the interplay of anodic oxidation and anion intercalation. We have developed strategies to control the distribution of the exfoliated products. In addition, the fluorescence of these carbon nanomaterials can be tuned from the visible to ultraviolet region by controlling the water content in the ionic liquid electrolyte.

  16. Piezo-Electrochemical Transducer Effect (PECT) Intercalated Graphite Micro-Electromechanical Actuators

    DTIC Science & Technology

    2007-11-01

    Nobel Laureate Richard Feynman predicted the rise of small scale machinery and “a hundred tiny hands” as the method to reduce the size of...1985 when a Stanford University graduate student, Tom Newman, successfully reduced a paragraph of “A Tale of Two Cities” by 1/25,000 [35]. Feynman ...revolutionize miniature mechanical devices [37] and a year later, in 1983, Dr. Feynman predicted the genesis of MEMS saying “I believe that with today’s

  17. Li(V0.5Ti0.5)S2 as a 1 V lithium intercalation electrode

    NASA Astrophysics Data System (ADS)

    Clark, Steve J.; Wang, Da; Armstrong, A. Robert; Bruce, Peter G.

    2016-03-01

    Graphite, the dominant anode in rechargeable lithium batteries, operates at ~0.1 V versus Li+/Li and can result in lithium plating on the graphite surface, raising safety concerns. Titanates, for example, Li4Ti5O12, intercalate lithium at~1.6 V versus Li+/Li, avoiding problematic lithium plating at the expense of reduced cell voltage. There is interest in 1 V anodes, as this voltage is sufficiently high to avoid lithium plating while not significantly reducing cell potential. The sulfides, LiVS2 and LiTiS2, have been investigated as possible 1 V intercalation electrodes but suffer from capacity fading, large 1st cycle irreversible capacity or polarization. Here we report that the 50/50 solid solution, Li1+x(V0.5Ti0.5)S2, delivers a reversible capacity to store charge of 220 mAhg-1 (at 0.9 V), 99% of theoretical, at a rate of C/2, retaining 205 mAhg-1 at C-rate (92% of theoretical). Rate capability is excellent with 200 mAhg-1 at 3C. C-rate is discharge in 1 h. Polarization is low, 100 mV at C/2. To the best of our knowledge, the properties/performances of Li(V0.5Ti0.5)S2 exceed all previous 1 V electrodes.

  18. Intercalation processes of copper complexes in DNA.

    PubMed

    Galindo-Murillo, Rodrigo; García-Ramos, Juan Carlos; Ruiz-Azuara, Lena; Cheatham, Thomas E; Cortés-Guzmán, Fernando

    2015-06-23

    The family of anticancer complexes that include the transition metal copper known as Casiopeínas® shows promising results. Two of these complexes are currently in clinical trials. The interaction of these compounds with DNA has been observed experimentally and several hypotheses regarding the mechanism of action have been developed, and these include the generation of reactive oxygen species, phosphate hydrolysis and/or base-pair intercalation. To advance in the understanding on how these ligands interact with DNA, we present a molecular dynamics study of 21 Casiopeínas with a DNA dodecamer using 10 μs of simulation time for each compound. All the complexes were manually inserted into the minor groove as the starting point of the simulations. The binding energy of each complex and the observed representative type of interaction between the ligand and the DNA is reported. With this extended sampling time, we found that four of the compounds spontaneously flipped open a base pair and moved inside the resulting cavity and four compounds formed stacking interactions with the terminal base pairs. The complexes that formed the intercalation pocket led to more stable interactions.

  19. The dynamics of copper intercalated molybdenum ditelluride

    NASA Astrophysics Data System (ADS)

    Onofrio, Nicolas; Guzman, David; Strachan, Alejandro

    2016-11-01

    Layered transition metal dichalcogenides are emerging as key materials in nanoelectronics and energy applications. Predictive models to understand their growth, thermomechanical properties, and interaction with metals are needed in order to accelerate their incorporation into commercial products. Interatomic potentials enable large-scale atomistic simulations connecting first principle methods and devices. We present a ReaxFF reactive force field to describe molybdenum ditelluride and its interactions with copper. We optimized the force field parameters to describe the energetics, atomic charges, and mechanical properties of (i) layered MoTe2, Mo, and Cu in various phases, (ii) the intercalation of Cu atoms and small clusters within the van der Waals gap of MoTe2, and (iii) bond dissociation curves. The training set consists of an extensive set of first principles calculations computed using density functional theory (DFT). We validate the force field via the prediction of the adhesion of a single layer MoTe2 on a Cu(111) surface and find good agreement with DFT results not used in the training set. We characterized the mobility of the Cu ions intercalated into MoTe2 under the presence of an external electric field via finite temperature molecular dynamics simulations. The results show a significant increase in drift velocity for electric fields of approximately 0.4 V/Å and that mobility increases with Cu ion concentration.

  20. Superconductivity in alkali metal intercalated iron selenides

    NASA Astrophysics Data System (ADS)

    Krzton-Maziopa, A.; Svitlyk, V.; Pomjakushina, E.; Puzniak, R.; Conder, K.

    2016-07-01

    Alkali metal intercalated iron selenide superconductors A x Fe2-y Se2 (where A  =  K, Rb, Cs, Tl/K, and Tl/Rb) are characterized by several unique properties, which were not revealed in other superconducting materials. The compounds crystallize in overall simple layered structure with FeSe layers intercalated with alkali metal. The structure turned out to be pretty complex as the existing Fe-vacancies order below ~550 K, which further leads to an antiferromagnetic ordering with Néel temperature fairly above room temperature. At even lower temperatures a phase separation is observed. While one of these phases stays magnetic down to the lowest temperatures the second is becoming superconducting below ~30 K. All these effects give rise to complex relationships between the structure, magnetism and superconductivity. In particular the iron vacancy ordering, linked with a long-range magnetic order and a mesoscopic phase separation, is assumed to be an intrinsic property of the system. Since the discovery of superconductivity in those compounds in 2010 they were investigated very extensively. Results of the studies conducted using a variety of experimental techniques and performed during the last five years were published in hundreds of reports. The present paper reviews scientific work concerning methods of synthesis and crystal growth, structural and superconducting properties as well as pressure investigations.

  1. Intercalation processes of copper complexes in DNA

    PubMed Central

    Galindo-Murillo, Rodrigo; García-Ramos, Juan Carlos; Ruiz-Azuara, Lena; Cheatham, Thomas E.; Cortés-Guzmán, Fernando

    2015-01-01

    The family of anticancer complexes that include the transition metal copper known as Casiopeínas® shows promising results. Two of these complexes are currently in clinical trials. The interaction of these compounds with DNA has been observed experimentally and several hypotheses regarding the mechanism of action have been developed, and these include the generation of reactive oxygen species, phosphate hydrolysis and/or base-pair intercalation. To advance in the understanding on how these ligands interact with DNA, we present a molecular dynamics study of 21 Casiopeínas with a DNA dodecamer using 10 μs of simulation time for each compound. All the complexes were manually inserted into the minor groove as the starting point of the simulations. The binding energy of each complex and the observed representative type of interaction between the ligand and the DNA is reported. With this extended sampling time, we found that four of the compounds spontaneously flipped open a base pair and moved inside the resulting cavity and four compounds formed stacking interactions with the terminal base pairs. The complexes that formed the intercalation pocket led to more stable interactions. PMID:25958394

  2. Intercalation and delamination of layered carbides and carbonitrides.

    PubMed

    Mashtalir, Olha; Naguib, Michael; Mochalin, Vadym N; Dall'Agnese, Yohan; Heon, Min; Barsoum, Michel W; Gogotsi, Yury

    2013-01-01

    Intercalation and delamination of two-dimensional solids in many cases is a requisite step for exploiting their unique properties. Herein we report on the intercalation of two-dimensional Ti3C2, Ti3CN and TiNbC-so called MXenes. Intercalation of hydrazine, and its co-intercalation with N,N-dimethylformamide, resulted in increases of the c-lattice parameters of surface functionalized f-Ti3C2, from 19.5 to 25.48 and 26.8 Å, respectively. Urea is also intercalated into f-Ti3C2. Molecular dynamics simulations suggest that a hydrazine monolayer intercalates between f-Ti3C2 layers. Hydrazine is also intercalated into f-Ti3CN and f-TiNbC. When dimethyl sulphoxide is intercalated into f-Ti3C2, followed by sonication in water, the f-Ti3C2 is delaminated forming a stable colloidal solution that is in turn filtered to produce MXene 'paper'. The latter shows excellent Li-ion capacity at extremely high charging rates.

  3. Plasmon characteristics in stage-1 graphene intercalation compounds

    NASA Astrophysics Data System (ADS)

    Acharya, Sidharth; Sharma, Raman

    2015-05-01

    We report the Plasmon characteristics in stage-1 graphene intercalation compounds (GIC's), using the massless Dirac fermion (MDF) gas approximation. With the discussion of the weak and the strong c-axis coupling at graphene-intercalant hetrojunction plasmon characteristics of GIC's are predicted. We have found a reasonable agreement between our results and the experimental results of Ritsko and Rice.

  4. Solution structure and thermodynamics of 2',5' RNA intercalation.

    PubMed

    Horowitz, Eric D; Lilavivat, Seth; Holladay, Benjamin W; Germann, Markus W; Hud, Nicholas V

    2009-04-29

    As a means to explore the influence of the nucleic acid backbone on the intercalative binding of ligands to DNA and RNA, we have determined the solution structure of a proflavine-bound 2',5'-linked octamer duplex with the sequence GCCGCGGC. This structure represents the first NMR structure of an intercalated RNA duplex, of either backbone structural isomer. By comparison with X-ray crystal structures, we have identified similarities and differences between intercalated 3',5' and 2',5'-linked RNA duplexes. First, the two forms of RNA have different sugar pucker geometries at the intercalated nucleotide steps, yet have the same interphosphate distances. Second, as in intercalated 3',5' RNA, the phosphate backbone angle zeta at the 2',5' RNA intercalation site prefers to be in the trans conformation, whereas unintercalated 2',5' and 3',5' RNA prefer the -gauche conformation. These observations provide new insights regarding the transitions required for intercalation of a phosphodiester-ribose backbone and suggest a possible contribution of the backbone to the origin of the nearest-neighbor exclusion principle. Thermodynamic studies presented for intercalation of both structural RNA isomers also reveal a surprising sensitivity of intercalator binding enthalpy and entropy to the details of RNA backbone structure.

  5. Improved Graphite Fiber Adhesion.

    DTIC Science & Technology

    1981-09-01

    determined from a variety of surface analysis techniques , the oxygen-containing functional groups on commercial AS-i graphite fiber are predominantly...heterogenity within the fiber itself or experimental errors within the technique . In the limited time devoted to this work we did not devise a procedure...samples. Drzal optically measured the diameter of each fiber tested. Figure 6 shows the linear regression analysis plot used to determine the polar and

  6. Microcracks in nuclear graphite and highly oriented pyrolytic graphite (HOPG)

    NASA Astrophysics Data System (ADS)

    Wen, Keyun; Marrow, James; Marsden, Barry

    2008-10-01

    Microcracks with varied length and width are observed in nuclear grade graphite and highly oriented pyrolytic graphite (HOPG) by transmission electron microscopy. In situ observations show that these cracks tend to close up on heating the sample. The crystal dimensional change from in situ electron-irradiation also causes the closure of the cracks. Although some of the cracks may be identifiable as accommodation porosity (i.e. Mrozowski cracks), others appear to have already formed prior to carbonization and graphitization.

  7. Superconductivity in the alkali metal intercalates of molybdenum disulphide

    NASA Technical Reports Server (NTRS)

    Somoano, R. B.; Hadek, V.; Rembaum, A.

    1972-01-01

    The complete series of alkali metals, lithium through cesium, have been intercalated into molybdenum disulphide, using both the liquid ammonia and vapor techniques. All the intercalates with the exception of lithium yielded full superconducting transitions with onset temperatures of 6 K for AxMoS2(Ax=K,Rb,Cs) and 4 K for BxMoS2(Bx=Li,Na). The superconducting transition for lithium was incomplete down to 1.5 K. Stoichiometries and unit cell parameters have been determined for the intercalation compounds. Both rhombohedral and hexagonal polymorphs of MoS2 have been intercalated and found to exhibit the same superconductivity behavior. The nature of the extraneous superconducting transition of some intercalated samples on exposure to air was elucidated.

  8. Quasi-freestanding graphene on Ni(111) by Cs intercalation

    NASA Astrophysics Data System (ADS)

    Alattas, M.; Schwingenschlögl, U.

    2016-05-01

    A possible approach to achieve quasi-freestanding graphene on a substrate for technological purpose is the intercalation of alkali metal atoms. Cs intercalation between graphene and Ni(111) therefore is investigated using density functional theory, incorporating van der Waals corrections. It is known that direct contact between graphene and Ni(111) perturbs the Dirac states. We find that Cs intercalation restores the linear dispersion characteristic of Dirac fermions, which agrees with experiments, but the Dirac cone is shifted to lower energy, i.e., the graphene sheet is n-doped. Cs intercalation therefore decouples the graphene sheet from the substrate except for a charge transfer. On the other hand, the spin polarization of Ni(111) does not extend through the intercalated atoms to the graphene sheet, for which we find virtually spin-degeneracy.

  9. Metal intercalation-induced selective adatom mass transport on graphene

    DOE PAGES

    Liu, Xiaojie; Wang, Cai -Zhuang; Hupalo, Myron; ...

    2016-03-29

    Recent experiments indicate that metal intercalation is a very effective method to manipulate the graphene-adatom interaction and control metal nanostructure formation on graphene. A key question is mass transport, i.e., how atoms deposited uniformly on graphene populate different areas depending on the local intercalation. Using first-principles calculations, we show that partially intercalated graphene, with a mixture of intercalated and pristine areas, can induce an alternating electric field because of the spatial variations in electron doping, and thus, an oscillatory electrostatic potential. As a result, this alternating field can change normal stochastic adatom diffusion to biased diffusion, leading to selective massmore » transport and consequent nucleation, on either the intercalated or pristine areas, depending on the charge state of the adatoms.« less

  10. Metal intercalation-induced selective adatom mass transport on graphene

    SciTech Connect

    Liu, Xiaojie; Wang, Cai -Zhuang; Hupalo, Myron; Lin, Hai -Qing; Ho, Kai -Ming; Thiel, Patricia A.; Tringides, Michael C.

    2016-03-29

    Recent experiments indicate that metal intercalation is a very effective method to manipulate the graphene-adatom interaction and control metal nanostructure formation on graphene. A key question is mass transport, i.e., how atoms deposited uniformly on graphene populate different areas depending on the local intercalation. Using first-principles calculations, we show that partially intercalated graphene, with a mixture of intercalated and pristine areas, can induce an alternating electric field because of the spatial variations in electron doping, and thus, an oscillatory electrostatic potential. As a result, this alternating field can change normal stochastic adatom diffusion to biased diffusion, leading to selective mass transport and consequent nucleation, on either the intercalated or pristine areas, depending on the charge state of the adatoms.

  11. METHOD OF FABRICATING A GRAPHITE MODERATED REACTOR

    DOEpatents

    Kratz, H.R.

    1963-05-01

    S>A nuclear reactor formed of spaced bodies of uranium and graphite blocks is improved by diffusing helium through the graphite blocks in order to replace the air in the pores of the graphite with helium. The helium-impregnated graphite conducts heat better, and absorbs neutrons less, than the original air- impregnated graphite. (AEC)

  12. CMB-13 research on carbon and graphite

    NASA Technical Reports Server (NTRS)

    Smith, M. C.

    1972-01-01

    Preliminary results of the research on carbon and graphite accomplished during this report period are presented. Included are: particle characteristics of Santa Maria fillers, compositions and density data for hot-molded Santa Maria graphites, properties of hot-molded Santa Maria graphites, and properties of hot-molded anisotropic graphites. Ablation-resistant graphites are also discussed.

  13. Intercalated layered clay composites and their applications

    NASA Astrophysics Data System (ADS)

    Phukan, Anjali

    Supported inorganic reagents are rapidly emerging as new and environmentally acceptable reagents and catalysts. The smectite group of layered clay minerals, such as, Montmorillonite, provides promising character for adsorption, catalytic activity, supports etc. for their large surface area, swelling behavior and ion exchange properties. Aromatic compounds intercalated in layered clays are useful in optical molecular devices. Clay is a unique material for adsorption of heavy metals and various toxic substances. Clay surfaces are known to be catalytically active due to their surface acidity. Acid activated clays possess much improved surface areas and acidities and have higher pore volumes so that can absorb large molecules in the pores. The exchangeable cations in clay minerals play a key role in controlling surface acidity and catalytic activity. Recently, optically active metal-complex-Montmorillonite composites are reported to be active in antiracemization purposes. In view of the above, a research work, relating to the preparation of different modified clay composites and their catalytic applications were carried out. The different aspects and results of the present work have been reported in four major chapters. Chapter I: This is an introductory chapter, which contains a review of the literature regarding clay-based materials. Clay minerals are phyllosilicates with layer structure. Montmorillonite, a member of smectite group of clay, is 2:1 phyllosilicate, where a layer is composed of an octahedral sheet sandwiched by two tetrahedral sheets. Such clay shows cation exchange capacity (CEC) and is expressed in milli-equivalents per 100 gm of dry clay. Clays can be modified by interaction with metal ion, metal complexes, metal cluster and organic cations for various applications. Clays are also modified by treating with acid followed by impregnation with metal salts or ions. Montmorillonite can intercalate suitable metal complexes in excess of CEC to form double

  14. Heat exchanger using graphite foam

    DOEpatents

    Campagna, Michael Joseph; Callas, James John

    2012-09-25

    A heat exchanger is disclosed. The heat exchanger may have an inlet configured to receive a first fluid and an outlet configured to discharge the first fluid. The heat exchanger may further have at least one passageway configured to conduct the first fluid from the inlet to the outlet. The at least one passageway may be composed of a graphite foam and a layer of graphite material on the exterior of the graphite foam. The layer of graphite material may form at least a partial barrier between the first fluid and a second fluid external to the at least one passageway.

  15. Intercalation and controlled release properties of vitamin C intercalated layered double hydroxide

    NASA Astrophysics Data System (ADS)

    Gao, Xiaorui; Lei, Lixu; O'Hare, Dermot; Xie, Juan; Gao, Pengran; Chang, Tao

    2013-07-01

    Two drug-inorganic composites involving vitamin C (VC) intercalated in Mg-Al and Mg-Fe layered double hydroxides (LDHs) have been synthesized by the calcination-rehydration (reconstruction) method. Powder X-ray diffraction (XRD), Fourier transform infrared (FTIR), and UV-vis absorption spectroscopy indicate a successful intercalation of VC into the interlayer galleries of the LDH host. Studies of VC release from the LDHs in deionised water and in aqueous CO32- solutions imply that Mg3Al-VC LDH is a better controlled release system than Mg3Fe-VC LDH. Analysis of the release profiles using a number of kinetic models suggests a solution-dependent release mechanism, and a diffusion-controlled deintercalation mechanism in deionised water, but an ion exchange process in CO32- solution.

  16. Fabrication of Iron-Containing Carbon Materials From Graphite Fluoride

    NASA Technical Reports Server (NTRS)

    Hung, Ching-cheh

    1996-01-01

    Carbon materials containing iron alloy, iron metal, iron oxide or iron halide were fabricated. Typical samples of these metals were estimated to contain 1 iron atom per 3.5 to 5 carbon atoms. Those carbon materials containing iron alloy, iron metal, and/or Fe3O4 were magnetic. The kinetics of the fabrication process were studied by exposing graphite fluoride (CF(0.68)) to FeCl3 over a 280 to 420 C temperature range. Between 280 and 295 C, FeCl3 quickly entered the structure of CF(0.68), broke the carbon-fluorine bonds, and within 10 to 30 min, completely converted it to carbon made up of graphite planes between which particles of crystalline FeF3 and noncrystalline FeCl3 were located. Longer reaction times (e.g., 28 hr) or higher reaction temperatures (e.g., 420 C) produced materials containing graphite, a FeCl3-graphite intercalation compound, FeCl2(center dot)4H2O, and FeCl2(center dot)2H2O. These products were further heat treated to produce iron-containing carbon materials. When the heating temperature was kept in the 750 to 850 C range, and the oxygen supply was kept at the optimum level, the iron halides in the carbon structure were converted to iron oxides. Raising the heat to temperatures higher than 900 C reduced such iron oxides to iron metal. The kinetics of these reactions were used to suggest processes for fabricating carbon materials containing iron alloy. Such processes were then tested experimentally. In one of the successful trial runs, commercially purchased CF(0.7) powder was used as the reactant, and NiO was added during the final heating to 1200 C as a source of both nickel and oxygen. The product thus obtained was magnetic and was confirmed to be a nickel-iron alloy in carbon.

  17. Intercalation and controlled release properties of vitamin C intercalated layered double hydroxide

    SciTech Connect

    Gao, Xiaorui; Lei, Lixu; O'Hare, Dermot; Xie, Juan; Gao, Pengran; Chang, Tao

    2013-07-15

    Two drug-inorganic composites involving vitamin C (VC) intercalated in Mg–Al and Mg–Fe layered double hydroxides (LDHs) have been synthesized by the calcination–rehydration (reconstruction) method. Powder X-ray diffraction (XRD), Fourier transform infrared (FTIR), and UV–vis absorption spectroscopy indicate a successful intercalation of VC into the interlayer galleries of the LDH host. Studies of VC release from the LDHs in deionised water and in aqueous CO{sub 3}{sup 2−} solutions imply that Mg{sub 3}Al–VC LDH is a better controlled release system than Mg{sub 3}Fe–VC LDH. Analysis of the release profiles using a number of kinetic models suggests a solution-dependent release mechanism, and a diffusion-controlled deintercalation mechanism in deionised water, but an ion exchange process in CO{sub 3}{sup 2−} solution. - Graphical abstract: Vitamin C anions have been intercalated in the interlayer space of layered double hydroxide and released in CO{sub 3}{sup 2−} solution and deionised water. - Highlights: • Vitamin C intercalated Mg–Al and Mg–Fe layered double hydroxides were prepared. • Release property of vitamin C in aqueous CO{sub 3}{sup 2−} solution is better. • Avrami-Erofe’ev and first-order models provide better fit for release results. • Diffusion-controlled and ion exchange processes occur in deionised water. • An ion exchange process occurs in CO{sub 3}{sup 2−} solution.

  18. Graphitic packing removal tool

    DOEpatents

    Meyers, Kurt Edward; Kolsun, George J.

    1997-01-01

    Graphitic packing removal tools for removal of the seal rings in one piece. he packing removal tool has a cylindrical base ring the same size as the packing ring with a surface finish, perforations, knurling or threads for adhesion to the seal ring. Elongated leg shanks are mounted axially along the circumferential center. A slit or slits permit insertion around shafts. A removal tool follower stabilizes the upper portion of the legs to allow a spanner wrench to be used for insertion and removal.

  19. Graphitic packing removal tool

    DOEpatents

    Meyers, K.E.; Kolsun, G.J.

    1997-11-11

    Graphitic packing removal tools for removal of the seal rings in one piece are disclosed. The packing removal tool has a cylindrical base ring the same size as the packing ring with a surface finish, perforations, knurling or threads for adhesion to the seal ring. Elongated leg shanks are mounted axially along the circumferential center. A slit or slits permit insertion around shafts. A removal tool follower stabilizes the upper portion of the legs to allow a spanner wrench to be used for insertion and removal. 5 figs.

  20. Graphitic packing removal tool

    SciTech Connect

    Meyers, K.E.; Kolsun, G.J.

    1996-12-31

    Graphitic packing removal tools are described for removal of the seal rings in one piece from valves and pumps. The packing removal tool has a cylindrical base ring the same size as the packing ring with a surface finish, perforations, knurling or threads for adhesion to the seal ring. Elongated leg shanks are mounted axially along the circumferential center. A slit or slits permit insertion around shafts. A removal tool follower stabilizes the upper portion of the legs to allow a spanner wrench to be used for insertion and removal.

  1. Intercalation studies of zinc hydroxide chloride: Ammonia and amino acids

    SciTech Connect

    Arizaga, Gregorio Guadalupe Carbajal

    2012-01-15

    Zinc hydroxide chloride (ZHC) is a layered hydroxide salt with formula Zn{sub 5}(OH){sub 8}Cl{sub 2}{center_dot}2H{sub 2}O. It was tested as intercalation matrix for the first time and results were compared with intercalation products of the well-known zinc hydroxide nitrate and a Zn/Al layered double hydroxide. Ammonia was intercalated into ZHC, while no significant intercalation occurred in ZHN. Aspartic acid intercalation was only achieved by co-precipitation at pH=10 with ZHC and pH=8 with zinc hydroxide nitrate. Higher pH resistance in ZHC favored total deprotonation of both carboxylic groups of the Asp molecule. ZHC conferred more thermal protection against Asp combustion presenting exothermic peaks even at 452 Degree-Sign C while the exothermic event in ZHN was 366 Degree-Sign C and in the LDH at 276 Degree-Sign C. - Graphical abstract: The zinc hydroxide chloride (ZHC) with formula Zn{sub 5}(OH){sub 8}Cl{sub 2}{center_dot}2H{sub 2}O was tested as intercalation matrix. In comparison with the well-known zinc hydroxide nitrate (ZHN) and layered double hydroxides (LDH), ZHC was the best matrix for thermal protection of Asp combustion, presenting exothermic peaks even at 452 Degree-Sign C, while the highest exothermic event in ZHN was at 366 Degree-Sign C, and in the LDH it was at 276 Degree-Sign C. Highlights: Black-Right-Pointing-Pointer Zinc hydroxide chloride (ZHC) was tested as intercalation matrix for the first time. Black-Right-Pointing-Pointer ZHC has higher chemical and thermal stability than zinc hydroxide nitrate and LDH. Black-Right-Pointing-Pointer NH{sub 3} molecules can be intercalated into ZHC. Black-Right-Pointing-Pointer The amino group of amino acids limits the intercalation by ion-exchange.

  2. Stable aqueous dispersions of functionalized multi-layer graphene by pulsed underwater plasma exfoliation of graphite

    NASA Astrophysics Data System (ADS)

    Meyer-Plath, Asmus; Beckert, Fabian; Tölle, Folke J.; Sturm, Heinz; Mülhaupt, Rolf

    2016-02-01

    A process was developed for graphite particle exfoliation in water to stably dispersed multi-layer graphene. It uses electrohydraulic shockwaves and the functionalizing effect of solution plasma discharges in water. The discharges were excited by 100 ns high voltage pulsing of graphite particle chains that bridge an electrode gap. The underwater discharges allow simultaneous exfoliation and chemical functionalization of graphite particles to partially oxidized multi-layer graphene. Exfoliation is caused by shockwaves that result from rapid evaporation of carbon and water to plasma-excited gas species. Depending on discharge energy and locus of ignition, the shockwaves cause stirring, erosion, exfoliation and/or expansion of graphite flakes. The process was optimized to produce long-term stable aqueous dispersions of multi-layer graphene from graphite in a single process step without requiring addition of intercalants, surfactants, binders or special solvents. A setup was developed that allows continuous production of aqueous dispersions of flake size-selected multi-layer graphenes. Due to the well-preserved sp2-carbon structure, thin films made from the dispersed graphene exhibited high electrical conductivity. Underwater plasma discharge processing exhibits high innovation potential for morphological and chemical modifications of carbonaceous materials and surfaces, especially for the generation of stable dispersions of two-dimensional, layered materials.

  3. Synthesis, physical and chemical properties, and potential applications of graphite fluoride fibers

    NASA Technical Reports Server (NTRS)

    Hung, Ching-Cheh; Long, Martin; Stahl, Mark

    1987-01-01

    Graphite fluoride fibers can be produced by fluorinating pristine or intercalated graphite fibers. The higher the degree of graphitization of the fibers, the higher the temperature needed to reach the same degree of fluorination. Pitched based fibers were fluorinated to flourine-to-carbon atom rations between 0 and 1. The graphite fluoride fibers with a fluorine-to-carbon atom ration near 1 have extensive visible structural damage. On the other hand, fluorination of fibers pretreated with bromine or fluorine and bromine result in fibers with a fluorine-to-carbon atom ratio nearly equal to 0.5 with no visible structural damage. The electrical resistivity of the fibers is dependent upon the fluorine to carbon atom ratio and ranged from .01 to 10 to the 11th ohm/cm. The thermal conductivity of these fibers ranged from 5 to 73 W/m-k, which is much larger than the thermal conductivity of glass, which is the regular filler in epoxy composites. If graphite fluoride fibers are used as a filler in epoxy or PTFE, the resulting composite may be a high thermal conductivity material with an electrical resistivity in either the insulator or semiconductor range. The electrically insulating product may provide heat transfer with lower temperature gradients than many current electrical insulators. Potential applications are presented.

  4. Amine-intercalated α-zirconium phosphates as lubricant additives

    NASA Astrophysics Data System (ADS)

    Xiao, Huaping; Dai, Wei; Kan, Yuwei; Clearfield, Abraham; Liang, Hong

    2015-02-01

    In this study, three types of amines intercalated α-zirconium phosphate nanosheets with different interspaces were synthesized and examined as lubricant additives to a mineral oil. Results from tribological experiments illustrated that these additives improved lubricating performance. Results of rheological experiments showed that the viscosity of the mineral oil was effectively reduced with the addition of α-zirconium phosphate nanosheets. The two-dimensional structure, with larger interspaces, resulting from amine intercalation, exhibited improved effectiveness in reducing viscosity. This study demonstrates that the nanosheet structure of α-zirconium phosphates is effective in friction reduction. The manufacture of lubricants with tailored viscosity is possible by using different intercalators.

  5. REFRACTORY COATING FOR GRAPHITE MOLDS

    DOEpatents

    Stoddard, S.D.

    1958-06-24

    Refractory coating for graphite molds used in the casting of uranium is described. The coating is an alumino-silicate refractory composition which may be used as a mold surface in solid form or as a coating applied to the graphite mold. The composition consists of a mixture of ball clay, kaolin, alumina cement, alumina, water, sodium silicate, and sodium carbonate.

  6. Cryotribology of diamond and graphite

    SciTech Connect

    Iwasa, Yukikazu; Ashaboglu, A.F.; Rabinowicz, E.R.

    1996-12-31

    An experimental study was carried out on the tribological behavior of materials of interest in cryogenic applications, focusing on diamond and graphite. Both natural diamond (referred in the text as diamond) and chemical-vapor-deposition (CVD) diamond (CVD-diamond) were used. The experiment was carried out using a pin-on-disk tribometer capable of operating at cryogenic temperatures, from 4.2 to 293 K. Two basic scenarios of testing were used: (1) frictional coefficient ({mu}) vs velocity (v) characteristics at constant temperatures; (2) {mu} vs temperature (T) behavior at fixed sliding speeds. For diamond/CVD-diamond, graphite/CVD-diamond, stainless steel/CVD-diamond pairs, {mu}`s are virtually velocity independent. For each of diamond/graphite, alumina/graphite, and graphite/graphite pairs, the {partial_derivative}{mu}/{partial_derivative}v characteristic is favorable, i.e., positive. For diamond/CVD-diamond and graphite/CVD-diamond pairs, {mu}`s are nearly temperature independent between in the range 77 - 293 K. Each {mu} vs T plot for pin materials sliding on graphite disks has a peak at a temperature in the range 100 - 200 K.

  7. Baseline Graphite Characterization: First Billet

    SciTech Connect

    Mark C. Carroll; Joe Lords; David Rohrbaugh

    2010-09-01

    The Next Generation Nuclear Plant Project Graphite Research and Development program is currently establishing the safe operating envelope of graphite core components for a very high temperature reactor design. To meet this goal, the program is generating the extensive amount of quantitative data necessary for predicting the behavior and operating performance of the available nuclear graphite grades. In order determine the in-service behavior of the graphite for the latest proposed designs, two main programs are underway. The first, the Advanced Graphite Creep (AGC) program, is a set of experiments that are designed to evaluate the irradiated properties and behavior of nuclear grade graphite over a large spectrum of temperatures, neutron fluences, and compressive loads. Despite the aggressive experimental matrix that comprises the set of AGC test runs, a limited amount of data can be generated based upon the availability of space within the Advanced Test Reactor and the geometric constraints placed on the AGC specimens that will be inserted. In order to supplement the AGC data set, the Baseline Graphite Characterization program will endeavor to provide supplemental data that will characterize the inherent property variability in nuclear-grade graphite without the testing constraints of the AGC program. This variability in properties is a natural artifact of graphite due to the geologic raw materials that are utilized in its production. This variability will be quantified not only within a single billet of as-produced graphite, but also from billets within a single lot, billets from different lots of the same grade, and across different billets of the numerous grades of nuclear graphite that are presently available. The thorough understanding of this variability will provide added detail to the irradiated property data, and provide a more thorough understanding of the behavior of graphite that will be used in reactor design and licensing. This report covers the

  8. Pristine graphite oxide.

    PubMed

    Dimiev, Ayrat; Kosynkin, Dmitry V; Alemany, Lawrence B; Chaguine, Pavel; Tour, James M

    2012-02-08

    Graphite oxide (GO) is a lamellar substance with an ambiguous structure due to material complexity. Recently published GO-related studies employ only one out of several existing models to interpret the experimental data. Because the models are different, this leads to confusion in understanding the nature of the observed phenomena. Lessening the structural ambiguity would lead to further developments in functionalization and use of GO. Here, we show that the structure and properties of GO depend significantly on the quenching and purification procedures, rather than, as is commonly thought, on the type of graphite used or oxidation protocol. We introduce a new purification protocol that produces a product that we refer to as pristine GO (pGO) in contrast to the commonly known material that we will refer to as conventional GO (cGO). We explain the differences between pGO and cGO by transformations caused by reaction with water. We produce ultraviolet-visible spectroscopic, Fourier transform infrared spectroscopic, solid-state nuclear magnetic resonance spectroscopic, thermogravimetric, and scanning electron microscopic analytical evidence for the structure of pGO. This work provides a new explanation for the acidity of GO solutions and allows us to add critical details to existing GO models.

  9. Intercalated samarium as an agent enabling the intercalation of oxygen under a monolayer graphene film on iridium

    NASA Astrophysics Data System (ADS)

    Afanas'eva, E. Yu.; Rut'kov, E. V.; Gall', N. R.

    2016-06-01

    Using thermal desorption time-of-flight mass spectrometry and thermionic methods, it is shown that oxygen does not intercalate under a graphene monolayer grown correctly on iridium, at least at temperatures of T = 300-400 K and exposures below 12000 L. However, if the graphene film on iridium is preliminary intercalated with samarium atoms (up to coverage of θSm = 0.2-0.45), the penetration of oxygen atoms under the graphene film is observed. The oxygen atoms in the intercalated state are chemically bonded to samarium atoms and remain under graphene up to high temperatures (~2150 K).

  10. Effect of a pyrrolidinium zwitterion on charge/discharge cycle properties of Li/LiCoO2 and graphite/Li cells containing an ionic liquid electrolyte

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Seitaro; Yoshizawa-Fujita, Masahiro; Takeoka, Yuko; Rikukawa, Masahiro

    2016-11-01

    Ionic liquids (ILs) containing zwitterions have been studied as electrolytes for lithium-ion batteries (LIBs). The effects of addition of a pyrrolidinium zwitterion in an IL electrolyte on the thermal and electrochemical stability and charge/discharge properties of Li/LiCoO2 and graphite/Li cells were investigated. The thermal decomposition temperature of the IL electrolyte composed of N-methyl-N-propylpyrrolidinium bis(fluorosulfonyl)amide ([P13][FSA])/lithium bis(trifluoromethylsulfonyl)amide (LiTFSA) with 3-(1-butylpyrrolidinium)propane-1-sulfonate (Bpyps) as the zwitterionic additive, the thermal decomposition temperature was about 300 °C. The electrochemical window of [P13][FSA]/LiTFSA/Bpyps was 0-+5.4 V vs. Li/Li+, which was almost identical to that of [P13][FSA]/LiTFSA. Li|electrolyte|LiCoO2 cells containing the IL/Bpyps electrolyte system exhibited high capacities in the cut-off voltage range of 3.0-4.6 V, even after 50 cycles. The increase in the interfacial resistance between the electrolyte and cathode with cycling was suppressed. In the cyclic voltammograms of cells employing a graphite electrode, the intercalation/deintercalation of lithium ions were observed in the range of 0 and + 0.4 V vs. Li/Li+. Further, graphite|electrolyte|Li cells containing [P13][FSA]/LiTFSA/Bpyps exhibited stable charge/discharge cycle behaviour over 50 cycles.

  11. Method for intercalating alkali metal ions into carbon electrodes

    DOEpatents

    Doeff, M.M.; Ma, Y.; Visco, S.J.; DeJonghe, L.

    1995-08-22

    A low cost, relatively flexible, carbon electrode for use in a secondary battery is described. A method is provided for producing same, including intercalating alkali metal salts such as sodium and lithium into carbon.

  12. Method for intercalating alkali metal ions into carbon electrodes

    DOEpatents

    Doeff, Marca M.; Ma, Yanping; Visco, Steven J.; DeJonghe, Lutgard

    1995-01-01

    A low cost, relatively flexible, carbon electrode for use in a secondary battery is described. A method is provided for producing same, including intercalating alkali metal salts such as sodium and lithium into carbon.

  13. Removal of cesium ions from clays by cationic surfactant intercalation.

    PubMed

    Park, Chan Woo; Kim, Bo Hyun; Yang, Hee-Man; Seo, Bum-Kyoung; Moon, Jei-Kwon; Lee, Kune-Woo

    2017-02-01

    We propose a new approach to remediate cesium-contaminated clays based on intercalation of the cationic surfactant dodecyltrimethylammonium bromide (DTAB) into clay interlayers. Intercalation of DTAB was found to occur very rapidly and involved exchanging interlayer cations. The reaction yielded efficient cesium desorption (∼97%), including of a large amount of otherwise non-desorbable cesium ions by cation exchange with ammonium ions. In addition, the intercalation of DTAB afforded an expansion of the interlayers, and an enhanced desorption of Cs by cation exchange with ammonium ions even at low concentrations of DTAB. Finally, the residual intercalated surfactants were easily removed by a decomposition reaction with hydrogen peroxide in the presence of Cu(2+)/Fe(2+) catalysts.

  14. Formation and chemical reactivity of carbon fibers prepared by defluorination of graphite fluoride

    NASA Technical Reports Server (NTRS)

    Hung, Ching-Cheh

    1994-01-01

    Defluorination of graphite fluoride (CFX) by heating to temperatures of 250 to 450 C in chemically reactive environments was studied. This is a new and possibly inexpensive process to produce new carbon-based materials. For example, CF 0.68 fibers, made from P-100 carbon fibers, can be defluorinated in BrH2C-CH = CH-CH2Br (1,4-dibromo-2butene) heated to 370 C, and graphitized to produce fibers with an unusually high modulus and a graphite layer structure that is healed and cross-linked. Conversely, a sulfur-doped, visibly soft carbon fiber was produced by defluorinating CF 0.9 fibers, made from P-25, in sulfur (S) vapor at 370 C and then heating to 660 C in nitrogen (N2). Furthermore, defluorination of the CF 0.68 fibers in bromine (Br2) produced fragile, structurally damaged carbon fibers. Heating these fragile fibers to 1100 C in N2 caused further structural damage, whereas heating to 150 C in bromoform (CHBr3) and then to 1100 C in N2 healed the structural defects. The defluorination product of CFX, tentatively called activated graphite, has the composition and molecular structure of graphite, but is chemically more reactive. Activated graphite is a scavenger of manganese (Mn), and can be intercalated with magnesium (Mg). Also, it can easily collect large amounts of an alloy made from copper (Cu) and type 304 stainless steel to form a composite. Finally, there are indications that activated graphite can wet metals or ceramics, thereby forming stronger composites with them than the pristine carbon fibers can form.

  15. Comparison of the electrochemical properties of several commercial graphites with a templated disordered carbon

    SciTech Connect

    GUIDOTTI,RONALD A.; REINHARDT,FREDERICK W.; SANDI,GISELLE

    2000-03-22

    A templated carbon was prepared by the pyrolysis of pyrene impregnated into pillared clay (PILC). The electrochemical performance of this was evaluated with the goal of using this material as an anode in Li-ion cells. The reversible capacity was measured as a function of C rate and the cycling characteristics were determined for various intercalation protocols. The performance of this material was compared to that of several commercial graphites tested under the same conditions. The PILC carbon shows great promise as a Li-ion anode if the fade and first-cycle losses can be controlled.

  16. Comparison of the electrochemical properties of several commercial graphites with a templated disordered carbon

    SciTech Connect

    Guidotti, R. A.; Reinhardt, F. W.; Sandi, G.

    2000-04-11

    A templated carbon was prepared by the pyrolysis of pyrene impregnated into pillared clay (PILC). The electrochemical performance of this was evaluated with the goal of using this material as an anode in Li-ion cells. The reversible capacity was measured as a function of C rate and the cycling characteristics were determined for various intercalation protocols. The performance of this material was compared to that of several commercial graphites tested under the same conditions. The PILC carbon shows great promise as a Li-ion anode if the fade and first-cycle losses can be controlled.

  17. Electronic properties of carbon fibers intercalated with copper chloride

    NASA Technical Reports Server (NTRS)

    Oshima, H.; Natarajan, V.; Woollam, J. A.; Yavrouian, A.; Haugland, E. J.; Tsuzuku, T.

    1984-01-01

    Copper chloride intercalated pitch-based carbon fibers are found to have electrical resistivities as low as 12.9 micro-ohm-cm, and are air- and thermally-stable at and above room temperature. This is therefore a good candidate system for conductor application. In addition, Shubnikov-deHaas quantum oscillatory effects were found, and electronic properties of the intercalated fiber are studied using magnetic fields to 20 tesla.

  18. Intercalation-driven reversible control of magnetism in bulk ferromagnets.

    PubMed

    Dasgupta, Subho; Das, Bijoy; Knapp, Michael; Brand, Richard A; Ehrenberg, Helmut; Kruk, Robert; Hahn, Horst

    2014-07-16

    An extension in magnetoelectric effects is proposed to include reversible chemistry-controlled magnetization variations. This ion-intercalation-driven magnetic control can be fully reversible and pertinent to bulk material volumes. The concept is demonstrated for ferromagnetic iron oxide where the intercalated lithium ions cause valence change and partial redistribution of Fe(3+) cations yielding a large and fully reversible change in magnetization at room temperature.

  19. Should an intercalated degree be compulsory for undergraduate medical students?

    PubMed

    Philip, Aaron B; Prasad, Sunila J; Patel, Ankur

    2015-01-01

    Undertaking an intercalated year whilst at medical school involves taking time out of the medicine undergraduate programme in order to pursue a separate but related degree. It is widely seen as a challenging but rewarding experience, with much to be gained from the independent project or research component of most additional degrees. However, whilst intercalating is encouraged at many universities and is incorporated into some undergraduate curricula, it is by no means compulsory for all students. The literature would suggest that those who have intercalated tend to do better academically, both for the remainder of medical school and after graduating. Despite this, the issue of making intercalation mandatory is one of considerable debate, with counter-arguments ranging from the detrimental effect time taken out of the course can have to the lack of options available to cater for all students. Nonetheless, the research skills developed during an intercalated year are invaluable and help students prepare for taking a critical evidence-based approach to medicine. If intercalated degrees were made compulsory for undergraduates, it would be a step in the right direction. It would mean the doctors of tomorrow would be better equipped to practise medicine in disciplines that are constantly evolving.

  20. Cellulose nanocrystals: A layered host candidate for fabricating intercalated nanocomposites.

    PubMed

    Guo, Juan; Du, Wenbo; Wang, Siqun; Yin, Yafang; Gao, Yong

    2017-02-10

    The stacking of cellulose chains along planes and weak intersheet interactions make cellulose nanocrystals (CNCs) promising as a layered host candidate for fabricating intercalated nanocomposites. As a proof-of-concept, we demonstrate the intercalation of alkyls into CNCs through the in situ intercalative chemical reaction between terminal groups of N-octadecyl isocyanates and hydroxyl groups on the (200) planes in CNCs. Results showed that CNCs could intercalate alkyls in a high degree of substitution to form dense brushes on their (200) planes. After intercalation, a significant enlargement of interlayer spacing was observed. Moreover, alkyls were fully extended in all-trans configuration and crystallized in a co-existing organization of αH, βH and βO crystalline forms. This meant that the molecular arrangement in CNCs/alkyl intercalated nanocomposites would involve a bilayer model in which alkyls were in the ordered packing and titled to (200) plane. Furthermore, CNCs/alkyl intercalated nanocomposites possessed increased thermal properties and decreased char residue.

  1. Stochastic Terminal Dynamics in Epithelial Cell Intercalation

    NASA Astrophysics Data System (ADS)

    Eule, Stephan; Metzger, Jakob; Reichl, Lars; Kong, Deqing; Zhang, Yujun; Grosshans, Joerg; Wolf, Fred

    2015-03-01

    We found that the constriction of epithelial cell contacts during intercalation in germ band extension in Drosophila embryos follows intriguingly simple quantitative laws. The mean contact length < L > follows < L > (t) ~(T - t) α , where T is the finite collapse time; the time dependent variance of contact length is proportional to the square of the mean; finally the time dependent probability density of the contact lengths remains close to Gaussian during the entire process. These observations suggest that the dynamics of contact collapse can be captured by a stochastic differential equation analytically tractable in small noise approximation. Here, we present such a model, providing an effective description of the non-equilibrium statistical mechanics of contact collapse. All model parameters are fixed by measurements of time dependent mean and variance of contact lengths. The model predicts the contact length covariance function that we obtain in closed form. The contact length covariance function closely matches experimental observations suggesting that the model well captures the dynamics of contact collapse.

  2. Photoemission studies of fluorine functionalized porous graphitic carbon

    SciTech Connect

    Ganegoda, Hasitha; Olive, Daniel; Cheng, Lidens; Segre, Carlo U.; Terry, Jeff; Jensen, David S.; Linford, Matthew R.

    2012-03-01

    Porous graphitic carbon (PGC) has unique properties desirable for liquid chromatography applications when used as a stationary phase. The polar retention effect on graphite (PREG) allows efficient separation of polar and non-polar solutes. Perfluorinated hydrocarbons however lack polarizabilty and display strong lipo- and hydrophobicity, hence common lipophilic and hydrophilic analytes have low partition coefficiency in fluorinated stationary phases. Attractive interaction between fluorinated stationary phase and fluorinated analytes results in strong retention compared to non-fluorinated analytes. In order to change the selectivities of PGC, it is necessary to develop a bonded PGC stationary phase. In this study, we have synthesized perfluorinated, PGC using hepatadecafluoro-1-iodooctane, under different temperature conditions. Surface functionalization of the raw material was studied using photoelectron spectroscopy (PES). Results indicate the existence of fluorine containing functional groups, -CF, -CF{sub 2} along with an intercalated electron donor species. Multiple oxygen functional groups were also observed, likely due to the presence of oxygen in the starting material. These oxygen species may be responsible for significant modifications to planer and tetrahedral carbon ratios.

  3. Shear Assisted Electrochemical Exfoliation of Graphite to Graphene.

    PubMed

    Shinde, Dhanraj B; Brenker, Jason; Easton, Christopher D; Tabor, Rico F; Neild, Adrian; Majumder, Mainak

    2016-04-12

    The exfoliation characteristics of graphite as a function of applied anodic potential (1-10 V) in combination with shear field (400-74 400 s(-1)) have been studied in a custom-designed microfluidic reactor. Systematic investigation by atomic force microscopy (AFM) indicates that at higher potentials thicker and more fragmented graphene sheets are obtained, while at potentials as low as 1 V, pronounced exfoliation is triggered by the influence of shear. The shear-assisted electrochemical exfoliation process yields large (∼10 μm) graphene flakes with a high proportion of single, bilayer, and trilayer graphene and small ID/IG ratio (0.21-0.32) with only a small contribution from carbon-oxygen species as demonstrated by X-ray photoelectron spectroscopy measurements. This method comprises intercalation of sulfate ions followed by exfoliation using shear induced by a flowing electrolyte. Our findings on the crucial role of hydrodynamics in accentuating the exfoliation efficiency suggest a safer, greener, and more automated method for production of high quality graphene from graphite.

  4. Bionanocomposites containing magnetic graphite as potential systems for drug delivery.

    PubMed

    Ribeiro, Lígia N M; Alcântara, Ana C S; Darder, Margarita; Aranda, Pilar; Herrmann, Paulo S P; Araújo-Moreira, Fernando M; García-Hernández, Mar; Ruiz-Hitzky, Eduardo

    2014-12-30

    New magnetic bio-hybrid matrices for potential application in drug delivery are developed from the assembly of the biopolymer alginate and magnetic graphite nanoparticles. Ibuprofen (IBU) intercalated in a Mg-Al layered double hydroxide (LDH) was chosen as a model drug delivery system (DDS) to be incorporated as third component of the magnetic bionanocomposite DDS. For comparative purposes DDS based on the incorporation of pure IBU in the magnetic bio-hybrid matrices were also studied. All the resulting magnetic bionanocomposites were processed as beads and films and characterized by different techniques with the aim to elucidate the role of the magnetic graphite on the systems, as well as that of the inorganic brucite-like layers in the drug-loaded LDH. In this way, the influence of both inorganic components on the mechanical properties, the water uptake ability, and the kinetics of the drug release from these magnetic systems were determined. In addition, the possibility of modulating the levels of IBU release by stimulating the bionanocomposites with an external magnetic field was also evaluated in in vitro assays.

  5. METHOD OF OBTAINING UNIFORM COATINGS ON GRAPHITE

    DOEpatents

    Campbell, I.E.

    1961-04-01

    A method is given for obtaining uniform carbide coatings on graphite bodies. According to the invention a metallic halide in vapor form is passed over the graphite body under such conditions of temperature and pressure that the halide reacts with the graphite to form a coating of the metal carbide on the surface of the graphite.

  6. Method of Obtaining Uniform Coatings on Graphite

    DOEpatents

    Campbell, I. E.

    1961-04-01

    A method is given for obtaining uniform carbide coatings on graphite bodies. According to the invention a metallic halide in vapor form is passed over the graphite body under such conditions of temperature and pressure that the halide reacts with the graphite to form a coating of the metal carbide on the surface of the graphite.

  7. Mineral resource of the month: graphite

    USGS Publications Warehouse

    ,

    2008-01-01

    The article presents facts about graphite ideal for industrial applications. Among the characteristics of graphite are its metallic luster, softness, perfect basal cleavage and electrical conductivity. Batteries, brake linings and powdered metals are some of the products that make use of graphite. It attributes the potential applications for graphite in high-technology fields to innovations in thermal technology and acid-leaching techniques.

  8. Spent graphite fuel element processing

    SciTech Connect

    Holder, N.D.; Olsen, C.W.

    1981-07-01

    The Department of Energy currently sponsors two programs to demonstrate the processing of spent graphite fuel elements. General Atomic in San Diego operates a cold pilot plant to demonstrate the processing of both US and German high-temperature reactor fuel. Exxon Nuclear Idaho Company is demonstrating the processing of spent graphite fuel elements from Rover reactors operated for the Nuclear Rocket Propulsion Program. This work is done at Idaho National Engineering Laboratory, where a hot facility is being constructed to complete processing of the Rover fuel. This paper focuses on the graphite combustion process common to both programs.

  9. Microstructural characterisation of nuclear grade graphite

    NASA Astrophysics Data System (ADS)

    Jones, A. N.; Hall, G. N.; Joyce, M.; Hodgkins, A.; Wen, K.; Marrow, T. J.; Marsden, B. J.

    2008-10-01

    Field emission and transmission electron microscopy are used to characterise the microstructure and morphology of baked carbon block and graphitized grades (from the same carbon block stock) of nuclear graphite. Quantitative analysis using Raman and energy dispersive spectroscopy (EDS) were used to investigate the decrease of crystallinity with graphitization and sample purity. Both baked carbon and graphitized nuclear graphites show no sensitivity of the Raman band shift to strain, consistent with strain accommodation by the porous structure.

  10. CALANDRIA TYPE SODIUM GRAPHITE REACTOR

    DOEpatents

    Peterson, R.M.; Mahlmeister, J.E.; Vaughn, N.E.; Sanders, W.J.; Williams, A.C.

    1964-02-11

    A sodium graphite power reactor in which the unclad graphite moderator and fuel elements are contained within a core tank is described. The core tank is submersed in sodium within the reactor vessel. Extending longitudinally through the core thnk are process tubes with fuel elements positioned therein. A bellows sealing means allows axial expansion and construction of the tubes. Within the core tank, a leakage plenum is located below the graphite, and above the graphite is a gas space. A vent line regulates the gas pressure in the space, and another line removes sodium from the plenum. The sodium coolant flows from the lower reactor vessel through the annular space between the fuel elements and process tubes and out into the reactor vessel space above the core tank. From there, the heated coolant is drawn off through an outlet line and sent to the heat exchange. (AEC)

  11. Graphite-reinforced bone cement

    NASA Technical Reports Server (NTRS)

    Knoell, A. C.

    1976-01-01

    Chopped graphite fibers added to surgical bone cement form bonding agent with mechanical properties closely matched to those of bone. Curing reaction produces less heat, resulting in reduced traumatization of body tissues. Stiffness is increased without affecting flexural strength.

  12. Graphite for the nuclear industry

    SciTech Connect

    Burchell, T.D.; Fuller, E.L.; Romanoski, G.R.; Strizak, J.P.

    1991-01-01

    Graphite finds applications in both fission and fusion reactors. Fission reactors harness the energy liberated when heavy elements, such as uranium or plutonium, fragment or fission''. Reactors of this type have existed for nearly 50 years. The first nuclear fission reactor, Chicago Pile No. 1, was constructed of graphite under a football stand at Stagg Field, University of Chicago. Fusion energy devices will produce power by utilizing the energy produced when isotopes of the element hydrogen are fused together to form helium, the same reaction that powers our sun. The role of graphite is very different in these two reactor systems. Here we summarize the function of the graphite in fission and fusion reactors, detailing the reasons for their selection and discussing some of the challenges associated with their application in nuclear fission and fusion reactors. 10 refs., 15 figs., 1 tab.

  13. Ammonia intercalated flower-like MoS2 nanosheet film as electrocatalyst for high efficient and stable hydrogen evolution

    PubMed Central

    Wang, F. Z.; Zheng, M. J.; Zhang, B.; Zhu, C. Q.; Li, Q.; Ma, L.; Shen, W. Z.

    2016-01-01

    Ammonia intercalated flower-like MoS2 electrocatalyst film assembled by vertical orientated ultrathin nanosheet on graphite sheethas been successfully synthesized using one-step hydrothermal method. In this strategy, ammonia can effectively insert into the parallel plane of the MoS2 nanosheets, leading to the expansion of lattice and phase transfer from 2H to 1T, generating more active unsaturated sulfur atoms. The flower-like ammoniated MoS2 electrocatalysts with more active sites and large surface area exhibited excellent HER activity with a small Tafel slope and low onset overpotential, resulting a great enhancement in hydrogen evolution. The high efficient activity and recyclable utilization, as well as large-scale, indicate that it is a very promising electrocatalyst to replace Pt in industry application. PMID:27538812

  14. Resonating Valence Bonds and Mean-Field d-Wave Superconductivity in Graphite

    SciTech Connect

    Black-Schaffer, Annica M.

    2010-04-27

    We investigate the possibility of inducing superconductivity in a graphite layer by electronic correlation effects. We use a phenomenological microscopic Hamiltonian which includes nearest neighbor hopping and an interaction term which explicitly favors nearest neighbor spin-singlets through the well-known resonance valence bond (RVB) character of planar organic molecules. Treating this Hamiltonian in mean-field theory, allowing for bond-dependent variation of the RVB order parameter, we show that both s- and d-wave superconducting states are possible. The d-wave solution belongs to a two-dimensional representation and breaks time reversal symmetry. At zero doping there exists a quantum critical point at the dimensionless coupling J/t = 1.91 and the s- and d-wave solutions are degenerate for low temperatures. At finite doping the d-wave solution has a significantly higher T{sub c} than the s-wave solution. By using density functional theory we show that the doping induced from sulfur absorption on a graphite layer is enough to cause an electronically driven d-wave superconductivity at graphite-sulfur interfaces. We also discuss applying our results to the case of the intercalated graphites as well as the validity of a mean-field approach.

  15. Effects of temperature on internal friction of Graphit-iC graphite-like carbon coatings

    NASA Astrophysics Data System (ADS)

    Zhu, Zhi-yong; Shi, Wen; Wan, Zi; Yuan, Jun-feng; Li, Xiao

    2013-12-01

    Graphit-iC graphite-like carbon coatings were deposited on SDC90 cold work die steel by using an unbalanced magnetron sputtering technology. Effects of the temperature on microstructure and internal friction of the carbon coatings were characterized by Raman spectroscopy (Raman) and a low-frequency mechanical analyzer (LMA-1) testing system. The results indicate that the internal friction of the two-side deposited carbon coatings is small (2.17×10-4), being higher than one of the substrate (1.63×10-4), and increases with temperature. However, there is an internal friction peak at 250°C accompanied with partial sp3 transferred to sp2 and increasing the intensity ratio ID/IG. There is gradual graphitization tendency of the carbon coatings as temperatures increase from 25°C to 350 °C. This would be progressive transformation from amorphous to crystalline.

  16. DNA intercalation optimized by two-step molecular lock mechanism

    PubMed Central

    Almaqwashi, Ali A.; Andersson, Johanna; Lincoln, Per; Rouzina, Ioulia; Westerlund, Fredrik; Williams, Mark C.

    2016-01-01

    The diverse properties of DNA intercalators, varying in affinity and kinetics over several orders of magnitude, provide a wide range of applications for DNA-ligand assemblies. Unconventional intercalation mechanisms may exhibit high affinity and slow kinetics, properties desired for potential therapeutics. We used single-molecule force spectroscopy to probe the free energy landscape for an unconventional intercalator that binds DNA through a novel two-step mechanism in which the intermediate and final states bind DNA through the same mono-intercalating moiety. During this process, DNA undergoes significant structural rearrangements, first lengthening before relaxing to a shorter DNA-ligand complex in the intermediate state to form a molecular lock. To reach the final bound state, the molecular length must increase again as the ligand threads between disrupted DNA base pairs. This unusual binding mechanism results in an unprecedented optimized combination of high DNA binding affinity and slow kinetics, suggesting a new paradigm for rational design of DNA intercalators. PMID:27917863

  17. Graphene/SiC(0001) interface structures induced by Si intercalation and their influence on electronic properties of graphene

    NASA Astrophysics Data System (ADS)

    Visikovskiy, Anton; Kimoto, Shin-ichi; Kajiwara, Takashi; Yoshimura, Masamichi; Iimori, Takushi; Komori, Fumio; Tanaka, Satoru

    2016-12-01

    Epitaxial graphene growth on SiC surfaces is considered advantageous in terms of device application. However, the first graphitic layer on SiC transforms to a buffer layer because of strong coupling with the substrate. The properties of several subsequent layers are also significantly degraded. One method to decouple graphene from the substrate is Si intercalation. In the present work, we report observation and analysis of interface structures formed by Si intercalation in between the graphene layer and the SiC(0001) surface depending on Si coverage and influence of these interfaces on graphene electronic structure by means of low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), angle-resolved photoemission spectroscopy (ARPES), and theoretical first-principles calculations. The STM appearance of observed periodic interface structures strongly resembles previously known Si-rich phases on the SiC(0001) surface. Based on the observed range of interface structures we discuss the mechanism of graphene layer decoupling and differences in stability of the Si-rich phases on clean SiC(0001) and in the graphene/SiC(0001) interface region. We also discuss a possibility to tune graphene electronic properties by interface engineering.

  18. Promising Cell Configuration for Next-Generation Energy Storage: Li2S/Graphite Battery Enabled by a Solvate Ionic Liquid Electrolyte.

    PubMed

    Li, Zhe; Zhang, Shiguo; Terada, Shoshi; Ma, Xiaofeng; Ikeda, Kohei; Kamei, Yutaro; Zhang, Ce; Dokko, Kaoru; Watanabe, Masayoshi

    2016-06-29

    Lithium-ion sulfur batteries with a [graphite|solvate ionic liquid electrolyte|lithium sulfide (Li2S)] structure are developed to realize high performance batteries without the issue of lithium anode. Li2S has recently emerged as a promising cathode material, due to its high theoretical specific capacity of 1166 mAh/g and its great potential in the development of lithium-ion sulfur batteries with a lithium-free anode such as graphite. Unfortunately, the electrochemical Li(+) intercalation/deintercalation in graphite is highly electrolyte-selective: whereas the process works well in the carbonate electrolytes inherited from Li-ion batteries, it cannot take place in the ether electrolytes commonly used for Li-S batteries, because the cointercalation of the solvent destroys the crystalline structure of graphite. Thus, only very few studies have focused on graphite-based Li-S full cells. In this work, simple graphite-based Li-S full cells were fabricated employing electrolytes beyond the conventional carbonates, in combination with highly loaded Li2S/graphene composite cathodes (Li2S loading: 2.2 mg/cm(2)). In particular, solvate ionic liquids can act as a single-phase electrolyte simultaneously compatible with both the Li2S cathode and the graphite anode and can further improve the battery performance by suppressing the shuttle effect. Consequently, these lithium-ion sulfur batteries show a stable and reversible charge-discharge behavior, along with a very high Coulombic efficiency.

  19. Tunable thermal expansion in framework materials through redox intercalation

    NASA Astrophysics Data System (ADS)

    Chen, Jun; Gao, Qilong; Sanson, Andrea; Jiang, Xingxing; Huang, Qingzhen; Carnera, Alberto; Rodriguez, Clara Guglieri; Olivi, Luca; Wang, Lei; Hu, Lei; Lin, Kun; Ren, Yang; Lin, Zheshuai; Wang, Cong; Gu, Lin; Deng, Jinxia; Attfield, J. Paul; Xing, Xianran

    2017-02-01

    Thermal expansion properties of solids are of fundamental interest and control of thermal expansion is important for practical applications but can be difficult to achieve. Many framework-type materials show negative thermal expansion when internal cages are empty but positive thermal expansion when additional atoms or molecules fill internal voids present. Here we show that redox intercalation offers an effective method to control thermal expansion from positive to zero to negative by insertion of Li ions into the simple negative thermal expansion framework material ScF3, doped with 10% Fe to enable reduction. The small concentration of intercalated Li ions has a strong influence through steric hindrance of transverse fluoride ion vibrations, which directly controls the thermal expansion. Redox intercalation of guest ions is thus likely to be a general and effective method for controlling thermal expansion in the many known framework materials with phonon-driven negative thermal expansion.

  20. Tunable thermal expansion in framework materials through redox intercalation

    PubMed Central

    Chen, Jun; Gao, Qilong; Sanson, Andrea; Jiang, Xingxing; Huang, Qingzhen; Carnera, Alberto; Rodriguez, Clara Guglieri; Olivi, Luca; Wang, Lei; Hu, Lei; Lin, Kun; Ren, Yang; Lin, Zheshuai; Wang, Cong; Gu, Lin; Deng, Jinxia; Attfield, J. Paul; Xing, Xianran

    2017-01-01

    Thermal expansion properties of solids are of fundamental interest and control of thermal expansion is important for practical applications but can be difficult to achieve. Many framework-type materials show negative thermal expansion when internal cages are empty but positive thermal expansion when additional atoms or molecules fill internal voids present. Here we show that redox intercalation offers an effective method to control thermal expansion from positive to zero to negative by insertion of Li ions into the simple negative thermal expansion framework material ScF3, doped with 10% Fe to enable reduction. The small concentration of intercalated Li ions has a strong influence through steric hindrance of transverse fluoride ion vibrations, which directly controls the thermal expansion. Redox intercalation of guest ions is thus likely to be a general and effective method for controlling thermal expansion in the many known framework materials with phonon-driven negative thermal expansion. PMID:28181576

  1. Drug-DNA intercalation: from discovery to the molecular mechanism.

    PubMed

    Mukherjee, Arnab; Sasikala, Wilbee D

    2013-01-01

    The ability of small molecules to perturb the natural structure and dynamics of nucleic acids is intriguing and has potential applications in cancer therapeutics. Intercalation is a special binding mode where the planar aromatic moiety of a small molecule is inserted between a pair of base pairs, causing structural changes in the DNA and leading to its functional arrest. Enormous progress has been made to understand the nature of the intercalation process since its idealistic conception five decades ago. However, the biological functions were detected even earlier. In this review, we focus mainly on the acridine and anthracycline types of drugs and provide a brief overview of the development in the field through various experimental methods that led to our present understanding of the subject. Subsequently, we discuss the molecular mechanism of the intercalation process, free-energy landscapes, and kinetics that was revealed recently through detailed and rigorous computational studies.

  2. Electrochemical synthesis of alkali-intercalated iron selenide superconductors

    NASA Astrophysics Data System (ADS)

    Shen, Shi-Jie; Ying, Tian-Ping; Wang, Gang; Jin, Shi-Feng; Zhang, Han; Lin, Zhi-Ping; Chen, Xiao-Long

    2015-11-01

    Electrochemical method has been used to insert K/Na into FeSe lattice to prepare alkali-intercalated iron selenides at room temperature. Magnetization measurement reveals that KxFe2Se2 and NaxFe2Se2 are superconductive at 31 K and 46 K, respectively. This is the first successful report of obtaining metal-intercalated FeSe-based high-temperature superconductors using electrochemical method. It provides an effective route to synthesize metal-intercalated layered compounds for new superconductor exploration. Project supported by the National Natural Science Foundation of China (Grant Nos. 51322211and 91422303), the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (Grant No. XDB07020100), Beijing Nova Program of China (Grant No. 2011096), and K. C. Wong Education Foundation, Hong Kong, China.

  3. Tunable thermal expansion in framework materials through redox intercalation.

    PubMed

    Chen, Jun; Gao, Qilong; Sanson, Andrea; Jiang, Xingxing; Huang, Qingzhen; Carnera, Alberto; Rodriguez, Clara Guglieri; Olivi, Luca; Wang, Lei; Hu, Lei; Lin, Kun; Ren, Yang; Lin, Zheshuai; Wang, Cong; Gu, Lin; Deng, Jinxia; Attfield, J Paul; Xing, Xianran

    2017-02-09

    Thermal expansion properties of solids are of fundamental interest and control of thermal expansion is important for practical applications but can be difficult to achieve. Many framework-type materials show negative thermal expansion when internal cages are empty but positive thermal expansion when additional atoms or molecules fill internal voids present. Here we show that redox intercalation offers an effective method to control thermal expansion from positive to zero to negative by insertion of Li ions into the simple negative thermal expansion framework material ScF3, doped with 10% Fe to enable reduction. The small concentration of intercalated Li ions has a strong influence through steric hindrance of transverse fluoride ion vibrations, which directly controls the thermal expansion. Redox intercalation of guest ions is thus likely to be a general and effective method for controlling thermal expansion in the many known framework materials with phonon-driven negative thermal expansion.

  4. Progressive specification rather than intercalation of segments during limb regeneration.

    PubMed

    Roensch, Kathleen; Tazaki, Akira; Chara, Osvaldo; Tanaka, Elly M

    2013-12-13

    An amputated salamander limb regenerates the correct number of segments. Models explaining limb regeneration were largely distinct from those for limb development, despite the presence of common patterning molecules. Intercalation has been an important concept to explain salamander limb regeneration, but clear evidence supporting or refuting this model was lacking. In the intercalation model, the first blastema cells acquire fingertip identity, creating a gap in positional identity that triggers regeneration of the intervening region from the stump. We used HOXA protein analysis and transplantation assays to show that axolotl limb blastema cells acquire positional identity in a proximal-to-distal sequence. Therefore, intercalation is not the primary mechanism for segment formation during limb regeneration in this animal. Patterning in development and regeneration uses similar mechanisms.

  5. Real-time electrochemical LAMP: a rational comparative study of different DNA intercalating and non-intercalating redox probes.

    PubMed

    Martin, Alexandra; Bouffier, Laurent; Grant, Kathryn B; Limoges, Benoît; Marchal, Damien

    2016-06-20

    We present a comparative study of ten redox-active probes for use in real-time electrochemical loop-mediated isothermal amplification (LAMP). Our main objectives were to establish the criteria that need to be fulfilled for minimizing some of the current limitations of the technique and to provide future guidelines in the search for ideal redox reporters. To ensure a reliable comparative study, each redox probe was tested under similar conditions using the same LAMP reaction and the same entirely automatized custom-made real-time electrochemical device (designed for electrochemically monitoring in real-time and in parallel up to 48 LAMP samples). Electrochemical melt curve analyses were recorded immediately at the end of each LAMP reaction. Our results show that there are a number of intercalating and non-intercalating redox compounds suitable for real-time electrochemical LAMP and that the best candidates are those able to intercalate strongly into ds-DNA but not too much to avoid inhibition of the LAMP reaction. The strongest intercalating redox probes were finally shown to provide higher LAMP sensitivity, speed, greater signal amplitude, and cleaner-cut DNA melting curves than the non-intercalating molecules.

  6. Dielectric relaxation of alkyl chains in graphite oxide and n-alkylammonium halides

    NASA Astrophysics Data System (ADS)

    Ai, Xiaoqian; Tian, Yuchen; Gu, Min; Yu, Ji; Tang, Tong B.

    2016-05-01

    The dynamic of n-alkylammonium halides and n-alkylammonium cations (n = 12, 14, 16, 18) intercalated in graphite oxide (GO) have been investigated with complex impedance spectroscopy. X-ray diffraction, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, elemental analysis and thermogravimetry served to characterize the materials. The intercalated alkylammonium cations distributes as monolayers (when n = 12, 14 or 16) or bilayers (when n = 18), with their long axis parallel to GO layers, and with cations of headgroups bonded ionically to C-O- groups of GO; backbones of the confined molecules remain free. All halides and intercalation compounds suffer dielectric loss at low temperature. Arrhenius plots of the thermal dependence of the loss peaks, which are asymmetric, produce apparent activation energies that rise with increasing n. Ngai's correlated-state model helps to correct for effects of dipole-dipole interaction, leading to virtually identical values for actual activation energy of 110 meV ± 5%; the values are also almost the same as the barrier energy for internal rotation in the alkyl macromolecule. We conclude that the relaxation of the alkylammonium cations arises not from C3 reorientation of the CH3 at its headgroup, but from small-angle wobbling around its major axis, an intrinsic motion.

  7. A facile liquid phase exfoliation method to prepare graphene sheets with different sizes expandable graphite

    SciTech Connect

    Zhou, Keqing; Shi, Yongqian; Jiang, Saihua; Song, Lei; Hu, Yuan; Gui, Zhou

    2013-09-01

    Graphical abstract: - Highlights: • This study presented a novel method for the production of high-quality graphene sheets through the exfoliation of Li-intercalated EG with sonication. • The quality of the graphene sheets produced from different sizes EG was compared for the first time and the formation mechanism was discussed. • The graphene sheets obtained from the small size EG have less layers than the large size EG. - Abstract: In this work, graphene sheets suspension were synthesized directly from expandable graphite (EG) via an intercalation and exfoliation pathway using n-butyl lithium as the intercalating agent, water and N,N-dimethylformamide (DMF) as the exfoliating agent. The quality of the graphene sheets produced from different sizes EG was compared and the formation mechanism was discussed. The formation of the graphene sheets and its formation mechanism were confirmed by transmission electron microscopy (TEM), high-resolution TEM (HRTEM), selected area electron diffraction (SAED), Raman spectroscopy measurement, inductively coupled plasma atomic emission spectrometry (ICP-AES) and thermogravimetric analysis (TGA). The graphene sheets obtained from the small size EG have less layers than the large size EG.

  8. Hierarchical Porous and Intercalation-Type V2O3 for High-Performance Anode Materials of Li-Ion Batteries.

    PubMed

    Liu, Pengcheng; Zhu, Kongjun; Xu, Yuan; Bian, Kan; Wang, Jing; Tai, Guoan; Gao, Yanfeng; Luo, Hongjie; Lu, Li; Liu, Jinsong

    2017-03-28

    As intercalation-type anode materials for Li-ion batteries (LIBs), the commercially-used graphite and Li4Ti5O12 can exhibit good cycling and rate properties, but their theoretical specific capacities are too low to meet the ever-growing demands of high-energy applications (such as electrical vehicles). So, it becomes a very attractive and interesting issue if the new intercalation-type anode materials with larger capacity can be found and developed. Herein, we design and synthesize the novel 3D hierarchical porous V2O3@C micro/nano-structures, consisting of crumpled nanosheets, by self-reducing under annealing from the similar structural VO2 (B)@C precursors without adding any other reducing reagent and gas. Excitingly, it is found for the first time by the ex situ XRD technology that V2O3 is a new promising intercalation-type anode material for LIBs with a high capacity. V2O3@C micro/nano-structures can deliver a large capacity of 732 mAh/g without capacity loss at 100 mA/g even after 136 cycles. Moreover, they also exhibit the excellent cycling and rate performance. Furthermore, we also elaborate the application of V2O3 for Na-ion batteries (NIBs) for the first time, and excitingly find that V2O3@C micro/nano-structures are also one new and promising anode material for NIBs.

  9. Intercalation of paracetamol into the hydrotalcite-like host

    SciTech Connect

    Kovanda, Frantisek; Maryskova, Zuzana; Kovar, Petr

    2011-12-15

    Hydrotalcite-like compounds are often used as host structures for intercalation of various anionic species. The product intercalated with the nonionic, water-soluble pharmaceuticals paracetamol, N-(4-hydroxyphenyl)acetamide, was prepared by rehydration of the Mg-Al mixed oxide obtained by calcination of hydrotalcite-like precursor at 500 Degree-Sign C. The successful intercalation of paracetamol molecules into the interlayer space was confirmed by powder X-ray diffraction and infrared spectroscopy measurements. Molecular simulations showed that the phenolic hydroxyl groups of paracetamol interact with hydroxide sheets of the host via the hydroxyl groups of the positively charged sites of Al-containing octahedra; the interlayer water molecules are located mostly near the hydroxide sheets. The arrangement of paracetamol molecules in the interlayer is rather disordered and interactions between neighboring molecules cause their tilting towards the hydroxide sheets. Dissolution tests in various media showed slower release of paracetamol intercalated in the hydrotalcite-like host in comparison with tablets containing the powdered pharmaceuticals. - Graphical abstract: Molecular simulations showed disordered arrangement of paracetamol molecules in the interlayer; most of the interlayer water molecules are located near the hydroxide sheets. Black-Small-Square Highlights: Black-Right-Pointing-Pointer Paracetamol was intercalated in Mg-Al hydrotalcite-like host by rehydration/reconstruction procedure. Black-Right-Pointing-Pointer Paracetamol phenolic groups interact with positively charged sites in hydroxide sheets. Black-Right-Pointing-Pointer Molecular simulations showed disordered arrangement of guest molecules in the interlayer. Black-Right-Pointing-Pointer Slower release of paracetamol intercalated in the hydrotalcite-like host was observed.

  10. Graphite Formation in Cast Iron

    NASA Technical Reports Server (NTRS)

    Stefanescu, D. M.

    1985-01-01

    In the first phase of the project it was proven that by changing the ratio between the thermal gradient and the growth rate for commercial cast iron samples solidifying in a Bridgman type furnace, it is possible to produce all types of graphite structures, from flake to spheroidal, and all types of matrices, from ferritic to white at a certain given level of cerium. KC-135 flight experiments have shown that in a low-gravity environment, no flotation occurs even in spheroidal graphite cast irons with carbon equivalent as high as 5%, while extensive graphite flotation occurred in both flake and spheroidal graphite cast irons, in high carbon samples solidified in a high gravity environment. This opens the way for production of iron-carbon composite materials, with high carbon content (e.g., 10%) in a low gravity environment. By using KC-135 flights, the influence of some basic elements on the solidification of cast iron will be studied. The mechanism of flake to spheroidal graphite transition will be studied, by using quenching experiments at both low and one gravity for different G/R ratios.

  11. NGNP Graphite Testing and Qualification Specimen Selection Strategy

    SciTech Connect

    Robert Bratton

    2005-05-01

    The available grades of graphite for the NGNP are reviewed. A selection matrix is presented outlining the available grades for the NGNP graphite irradiation program based upon input from potential NGNP vendors, graphite manufactures, and graphite experts.

  12. Another morphogenetic movement on the map: Charting dorsal intercalation in C. elegans.

    PubMed

    Walck-Shannon, Elise; Hardin, Jeff

    2016-01-01

    Dorsal intercalation is a coordinated cell migration event that rearranges hypodermal cells during C. elegans embryogenesis, and that resembles cell intercalation in many systems from flies to mice. Despite its conservation, the molecular mechanisms that govern dorsal intercalation in worms have remained elusive. Here, we comment on our recent publication, Walck-Shannon et al.,(1) which begins to spatially map the molecular requirements for intercalation. First, we provide a historical perspective on the factors that have previously hampered the study of dorsal intercalation. Next, we provide a summary of the molecular pathways identified in Walck-Shannon et al.,(1) pointing out surprises along the way. Finally, we consider the potential conservation of the molecular pathway we described and discuss future questions surrounding dorsal intercalation. Despite the challenges, dorsal intercalation is a process poised to advance our understanding of cell intercalation during morphogenesis throughout the animal kingdom.

  13. Thermal Pyrolytic Graphite Enhanced Components

    NASA Technical Reports Server (NTRS)

    Hardesty, Robert E. (Inventor)

    2015-01-01

    A thermally conductive composite material, a thermal transfer device made of the material, and a method for making the material are disclosed. Apertures or depressions are formed in aluminum or aluminum alloy. Plugs are formed of thermal pyrolytic graphite. An amount of silicon sufficient for liquid interface diffusion bonding is applied, for example by vapor deposition or use of aluminum silicon alloy foil. The plugs are inserted in the apertures or depressions. Bonding energy is applied, for example by applying pressure and heat using a hot isostatic press. The thermal pyrolytic graphite, aluminum or aluminum alloy and silicon form a eutectic alloy. As a result, the plugs are bonded into the apertures or depressions. The composite material can be machined to produce finished devices such as the thermal transfer device. Thermally conductive planes of the thermal pyrolytic graphite plugs may be aligned in parallel to present a thermal conduction path.

  14. Systems and methods for forming defects on graphitic materials and curing radiation-damaged graphitic materials

    DOEpatents

    Ryu, Sunmin; Brus, Louis E.; Steigerwald, Michael L.; Liu, Haitao

    2012-09-25

    Systems and methods are disclosed herein for forming defects on graphitic materials. The methods for forming defects include applying a radiation reactive material on a graphitic material, irradiating the applied radiation reactive material to produce a reactive species, and permitting the reactive species to react with the graphitic material to form defects. Additionally, disclosed are methods for removing defects on graphitic materials.

  15. Method of Joining Graphite Fibers to a Substrate

    NASA Technical Reports Server (NTRS)

    Beringer, Durwood M. (Inventor); Caron, Mark E. (Inventor); Taddey, Edmund P. (Inventor); Gleason, Brian P. (Inventor)

    2014-01-01

    A method of assembling a metallic-graphite structure includes forming a wetted graphite subassembly by arranging one or more layers of graphite fiber material including a plurality of graphite fibers and applying a layer of metallization material to ends of the plurality of graphite fibers. At least one metallic substrate is secured to the wetted graphite subassembly via the layer of metallization material.

  16. Graphite filament wound pressure vessels

    NASA Technical Reports Server (NTRS)

    Feldman, A.; Damico, J. J.

    1972-01-01

    Filament wound NOL rings, 4-inch and 8-inch diameter closed-end vessels involving three epoxy resin systems and three graphite fibers were tested to develop property data and fabrication technology for filament wound graphite/epoxy pressure vessels. Vessels were subjected to single-cycle burst tests at room temperature. Manufacturing parameters were established for tooling, winding, and curing that resulted in the development of a pressure/vessel performance factor (pressure x volume/weight) or more than 900,000 in. for an oblate spheroid specimen.

  17. Graphite fiber reinforced thermoplastic resins

    NASA Technical Reports Server (NTRS)

    Novak, R. C.

    1975-01-01

    Mechanical properties of neat resin samples and graphite fiber reinforced samples of thermoplastic resins were characterized with particular emphasis directed to the effects of environmental exposure (humidity, temperature and ultraviolet radiation). Tensile, flexural, interlaminar shear, creep and impact strengths were measured for polysulfone, polyarylsulfone and a state-of-the-art epoxy resin samples. In general, the thermoplastic resins exhibited environmental degradation resistance equal to or superior to the reference epoxy resin. Demonstration of the utility and quality of a graphite/thermoplastic resin system was accomplished by successfully thermoforming a simulated compressor blade and a fan exit guide vane.

  18. Pyrolytic graphite collector development program

    NASA Technical Reports Server (NTRS)

    Wilkins, W. J.

    1982-01-01

    Pyrolytic graphite promises to have significant advantages as a material for multistage depressed collector electrodes. Among these advantages are lighter weight, improved mechanical stiffness under shock and vibration, reduced secondary electron back-streaming for higher efficiency, and reduced outgassing at higher operating temperatures. The essential properties of pyrolytic graphite and the necessary design criteria are discussed. This includes the study of suitable electrode geometries and methods of attachment to other metal and ceramic collector components consistent with typical electrical, thermal, and mechanical requirements.

  19. Layered Compounds and Intercalation Chemistry: An Example of Chemistry and Diffusion in Solids.

    ERIC Educational Resources Information Center

    Whittingham, M. Stanley; Chianelli, Russell R.

    1980-01-01

    Considers a few areas of oxide/sulfide and intercalation-type chemistry. Discusses synthesis of the disulfides of the metals of group IVB, VB, and VIB; the intercalation reaction between lithium and titanium disulfide; other intercalates; and sulfide catalysts. (CS)

  20. Intercalated Compounds: A New Class of Materials as Advanced Solid Lubricants.

    DTIC Science & Technology

    1982-01-25

    CLASSIFICATION OF THIS PAGE (Whin DaE~I’ _______________ RED fI3TRUCTIOMSREPORT DOCUMENTATION PAGE Ston COMPLEIM7VG FORm I.RPR NUM an GVT ACCESO NO L...contain multiple layers of intercalant between adjacent carbon planes 41. As a consequence of intercalation, the interplanar distance between intercalated

  1. RECOVERY OF VALUABLE MATERIAL FROM GRAPHITE BODIES

    DOEpatents

    Fromm, L.W. Jr.

    1959-09-01

    An electrolytic process for recovering uranium from a graphite fuel element is described. The uraniumcontaining graphite body is disposed as the anode of a cell containing a nitric acid electrolyte and a 5 amp/cm/sup 2/ current passed to induce a progressive disintegration of the graphite body. The dissolved uranium is quickly and easily separated from the resulting graphite particles by simple mechanical means, such as centrifugation, filtration, and decontamination.

  2. Raman characterization of bulk ferromagnetic nanostructured graphite

    NASA Astrophysics Data System (ADS)

    Pardo, Helena; Divine Khan, Ngwashi; Faccio, Ricardo; Araújo-Moreira, F. M.; Fernández-Werner, Luciana; Makarova, Tatiana; Mombrú, Álvaro W.

    2012-08-01

    Raman spectroscopy was used to characterize bulk ferromagnetic graphite samples prepared by controlled oxidation of commercial pristine graphite powder. The G:D band intensity ratio, the shape and position of the 2D band and the presence of a band around 2950 cm-1 showed a high degree of disorder in the modified graphite sample, with a significant presence of exposed edges of graphitic planes as well as a high degree of attached hydrogen atoms.

  3. Composition and method for brazing graphite to graphite

    DOEpatents

    Taylor, Albert J.; Dykes, Norman L.

    1984-01-01

    The present invention is directed to a brazing material for joining graphite structures that can be used at temperatures up to about 2800.degree. C. The brazing material formed of a paste-like composition of hafnium carbide and uranium oxide with a thermosetting resin. The uranium oxide is converted to uranium dicarbide during the brazing operation and then the hafnium carbide and uranium dicarbide form a liquid phase at a temperature about 2600.degree. C. with the uranium diffusing and vaporizing from the joint area as the temperature is increased to about 2800.degree. C. so as to provide a brazed joint consisting essentially of hafnium carbide. This brazing temperature for hafnium carbide is considerably less than the eutectic temperature of hafnium carbide of about 3150.degree. C. The brazing composition also incorporates the thermosetting resin so that during the brazing operation the graphite structures may be temporarily bonded together by thermosetting the resin so that machining of the structures to final dimensions may be completed prior to the completion of the brazing operation. The resulting brazed joint is chemically and thermally compatible with the graphite structures joined thereby and also provides a joint of sufficient integrity so as to at least correspond with the strength and other properties of the graphite.

  4. Facile synthesis of mesophase pitch/exfoliated graphite nanoplatelets nanocomposite and its application as anode materials for lithium-ion batteries

    SciTech Connect

    Yang Yishuang; Wang Chengyang; Chen Mingming; Shi Zhiqiang; Zheng Jiaming

    2010-09-15

    Mesophase pitch (MP)/exfoliated graphite nanoplatelets (GNPs) nanocomposite has been prepared by an efficient method with an initiation of graphite intercalation compounds (GIC). X-ray diffraction, optical microscopy, high-resolution transmission electron microscopy and scanning electron microscopy analysis techniques are used to characterize the samples. It is observed that GIC has exfoliated completely into GNPs during the formation of MP/GNPs nanocomposite and the GNPs are distributed uniformly in MP matrix, which represent a conductive path for a movement of electrons throughout the composites. Electrochemical tests demonstrate that the carbonized MP/GNPs nanocomposite displays higher capacity and better cycle performance in comparison with the pure carbonized MP. It is concluded that such a large improvement of electrochemical performance within the nanocomposite may in general be related to the enhanced electronic conductivity, which is achieved by good dispersion of GNPs within MP matrix and formation of a 3D network of GNPs. - Graphical abstract: Uniform mesophase pitch/exfoliated graphite nanoplatelets nanocomposite has been efficiently fabricated with an initiation of graphite intercalation compounds. The as-prepared composite electrode exhibited high electrochemical performance for Li-ion batteries.

  5. Exfoliation of Hexagonal Boron Nitride via Ferric Chloride Intercalation

    NASA Technical Reports Server (NTRS)

    Hung, Ching-cheh; Hurst, Janet; Santiago, Diana; Rogers, Richard B.

    2014-01-01

    Sodium fluoride (NaF) was used as an activation agent to successfully intercalate ferric chloride (FeCl3) into hexagonal boron nitride (hBN). This reaction caused the hBN mass to increase by approx.100 percent, the lattice parameter c to decrease from 6.6585 to between 6.6565 and 6.6569 ?, the x-ray diffraction (XRD) (002) peak to widen from 0.01deg to 0.05deg of the full width half maximum value, the Fourier transform infrared (FTIR) spectrum's broad band (1277/cm peak) to change shape, and new FTIR bands to emerge at 3700 to 2700 and 1600/cm. This indicates hBN's structural and chemical properties are significantly changed. The intercalated product was hygroscopic and interacted with moisture in the air to cause further structural and chemical changes (from XRD and FTIR). During a 24-h hold at room temperature in air with 100 percent relative humidity, the mass increased another 141 percent. The intercalated product, hydrated or not, can be heated to 750 C in air to cause exfoliation. Exfoliation becomes significant after two intercalation-air heating cycles, when 20-nm nanosheets are commonly found. Structural and chemical changes indicated by XRD and FTIR data were nearly reversed after the product was placed in hydrochloric acid (HCl), resulting in purified, exfoliated, thin hBN products.

  6. Intercalation of paracetamol into the hydrotalcite-like host

    NASA Astrophysics Data System (ADS)

    Kovanda, František; Maryšková, Zuzana; Kovář, Petr

    2011-12-01

    Hydrotalcite-like compounds are often used as host structures for intercalation of various anionic species. The product intercalated with the nonionic, water-soluble pharmaceuticals paracetamol, N-(4-hydroxyphenyl)acetamide, was prepared by rehydration of the Mg-Al mixed oxide obtained by calcination of hydrotalcite-like precursor at 500 °C. The successful intercalation of paracetamol molecules into the interlayer space was confirmed by powder X-ray diffraction and infrared spectroscopy measurements. Molecular simulations showed that the phenolic hydroxyl groups of paracetamol interact with hydroxide sheets of the host via the hydroxyl groups of the positively charged sites of Al-containing octahedra; the interlayer water molecules are located mostly near the hydroxide sheets. The arrangement of paracetamol molecules in the interlayer is rather disordered and interactions between neighboring molecules cause their tilting towards the hydroxide sheets. Dissolution tests in various media showed slower release of paracetamol intercalated in the hydrotalcite-like host in comparison with tablets containing the powdered pharmaceuticals.

  7. [Raman and infrared spectrograms of organic borate intercalated hydrotalcite].

    PubMed

    Zhang, Jing-Yu; Bai, Zhi-Min; Zhao, Dong

    2013-03-01

    The pattern of X-ray diffraction, the Raman and infrared spectra of organic borate intercalated hydrotalcite were discussed. The well crystallized zinc-aluminum layered double hydroxides (Zn-Al LDHs) intercalated by carbonate ions and borate ions were respectively prepared by co-precipitation method. Patterns of X-ray diffraction showed that the (003) reflection of borate-LDHs was sharp and symmetric and shifted to lower angle than that of carbonate-LDHs. The gallery height of borate-LDHs increased from 0. 28 nm to 0.42 nm after intercalation, indicating that interlayered carbonate ions were substituted by borate anions. The Raman and IR spectra showed that specific bands of carbonate ions in the borate-LDHs disappeared, but with the presence of B3O3(OH)4- X B4O5(OH)4(2-) and B(OH)4- in the interlayer galleries. The hydroxide interlayer anions had a significant influence on the band positions in Raman and infrared spectra of modes related to the hydroxyl group. Our results indicate that single phase and pure borate-pillared LDHs can be obtained using tributyl orthoborate as intercalating agents, and the change in the structure and nature of hydrotalcite can be detected precisely by Raman spectroscopy.

  8. Intercalation of papain enzyme into hydrotalcite type layered double hydroxide

    NASA Astrophysics Data System (ADS)

    Zou, N.; Plank, J.

    2012-09-01

    Intercalation of proteolytic enzyme papain into hydrotalcite type LDH structure was achieved by controlled co-precipitation at pH=9.0 in the presence of papain. Characterization of the MgAl-papain-LDH phase was carried out using X-ray powder diffraction (XRD), elemental analysis, infrared spectroscopy (IR) and thermogravimetry (TG). According to XRD, papain was successfully intercalated. The d-value for the basal spacing of MgAl-papain-LDH was found at ˜5.3 nm. Consequently, original papain (hydrodynamic diameter ˜7.2 nm) attains a compressed conformation during intercalation.Formation of MgAl-papain-LDH was confirmed by elemental analysis and transmission electron microscopy (TEM). Under SEM, MgAl-papain-LDH phases appear as nanothin platelets which are intergrown to flower-like aggregates. Steric size and activity of the enzyme was retained after deintercalation from MgAl-LDH framework, as was evidenced by light scattering and UV/vis measurements. Thus, papain is not denatured during intercalation, and LDH is a suitable host structure which can provide a time-controlled release of the biomolecule.

  9. High speed hydrogen/graphite interaction

    NASA Technical Reports Server (NTRS)

    Kelly, A. J.; Hamman, R.; Sharma, O. P.; Harrje, D. T.

    1974-01-01

    Various aspects of a research program on high speed hydrogen/graphite interaction are presented. Major areas discussed are: (1) theoretical predictions of hydrogen/graphite erosion rates; (2) high temperature, nonequilibrium hydrogen flow in a nozzle; and (3) molecular beam studies of hydrogen/graphite erosion.

  10. Separation medium containing thermally exfoliated graphite oxide

    NASA Technical Reports Server (NTRS)

    Prud'homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor); Herrera-Alonso, Margarita (Inventor)

    2012-01-01

    A separation medium, such as a chromatography filling or packing, containing a modified graphite oxide material, which is a thermally exfoliated graphite oxide with a surface area of from about 300 m.sup.2/g to 2600 m.sup.2/g, wherein the thermally exfoliated graphite oxide has a surface that has been at least partially functionalized.

  11. CMB-13 research on carbon and graphite

    NASA Technical Reports Server (NTRS)

    Smith, M. C.

    1972-01-01

    The research on graphite and carbon for this period is reported. Topics discussed include: effects of grinding on the Santa Marie graphites, properties and purities of coal-tar, resin-bonded graphite, carbonization of resin components, and glass-like carbon filler.

  12. Graphitization behaviour of chemically derived graphene sheets.

    PubMed

    Long, Donghui; Li, Wei; Qiao, Wenming; Miyawaki, Jin; Yoon, Seong-Ho; Mochida, Isao; Ling, Licheng

    2011-09-01

    Graphene sheets were prepared via chemical reduction of graphite oxides and then graphitized at 2800 °C. The structure changes from pristine graphite to graphitized graphene sheets were monitored using X-ray diffraction and Raman spectroscopy. It was found that the graphitized graphene sheets exhibited relatively low degree of graphitization and high level of structural defects. XPS spectra revealed that oxygen functionalities could be completely eliminated after graphitization. Morphology observations indicated that graphitization could induce the coalescence and connection of the crumpled graphene agglomerations into compressed grains. The connections included the joint of graphitic sheets along the c-axis with van der Waals force between graphitic sheets and the joint of sheets in the in-plane with covalent bond between carbon atoms. New structures such as the formation of loop at the tip of graphene sheets and the formation of 3D concentric graphene nanoparticles occurred in the graphitized graphene sheets, as a result of self-organization to achieve their lowest potential energy. Our findings should provide some experimental implications for understanding of graphitization behaviour and thermal stability of strictly 2D graphene monolayers.

  13. First principles investigation of copper and silver intercalated molybdenum disulfide

    NASA Astrophysics Data System (ADS)

    Guzman, D. M.; Onofrio, N.; Strachan, A.

    2017-02-01

    We characterize the energetics and atomic structures involved in the intercalation of copper and silver into the van der Waals gap of molybdenum disulfide as well as the resulting ionic and electronic transport properties using first-principles density functional theory. The intercalation energy of systems with formula (Cu,Ag)xMoS2 decreases with ion concentration and ranges from 1.2 to 0.8 eV for Cu; Ag exhibits a stronger concentration dependence from 2.2 eV for x = 0.014 to 0.75 eV for x = 1 (using the fcc metal as a reference). Partial atomic charge analysis indicates that approximately half an electron is transferred per metallic ion in the case of Cu at low concentrations and the ionicity decreases only slightly with concentration. In contrast, while Ag is only slightly less ionic than Cu for low concentrations, charge transfer reduces significantly to approximately 0.1 e for x = 1. This difference in ionicity between Cu and Ag correlates with their intercalation energies. Importantly, the predicted values indicate the possibility of electrochemical intercalation of both Cu and Ag into MoS2 and the calculated activation energies associated with ionic transport within the gaps, 0.32 eV for Cu and 0.38 eV for Ag, indicate these materials to be good ionic conductors. Analysis of the electronic structure shows that charge transfer leads to a shift of the Fermi energy into the conduction band resulting in a semiconductor-to-metal transition. Electron transport calculations based on non-equilibrium Green's function show that the low-bias conductance increases with metal concentration and is comparable in the horizontal and vertical transport directions. These properties make metal intercalated transition metal di-chalcogenides potential candidates for several applications including electrochemical metallization cells and contacts in electronics based on 2D materials.

  14. Technical Report-Final-Electrochemistry of Nanostructured Intercalation Hosts

    SciTech Connect

    Professor William H. Smyrl, Principal Investigator

    2009-03-09

    We have shown that: (1) Li+ ions are inserted reversibly, without diffusion control, up to the level of at least 4 moles Li+ ions per mole for V2O5, in the aerogel (ARG) form (500 m2/g specific surface area) and aerogel-like (ARG-L) form (200 m2/g specific surface area)(6,7,1,2); (2) polyvalent cations (Al+3, Mg+2, Zn+2) may be intercalated reversibly into V2O5 (ARG) with high capacity (approaching 4 equivalents/mole V2O5 (ARG)) for each (5); (3) dopant cations such as Ag+ and Cu+2 increase the conductivity of V2O5 (XRG) up to three orders of magnitude(3), they are electrochemically active – showing reduction to the metallic-state in parallel to intercalation of Li+ ions – but are not released to the electrolyte upon oxidation and Li+ ion release (Cu+2 ions are reduced to Cu metal and reoxidized to Cu+2 in Li+ ion insertion/release cycles, but the copper ions are not released to the electrolyte over more than 400 cycles of the XRG form); (4) we have shown that Cu+2 ion (dopant) and Zn+2 ions (chemical insertion and dopant) occupy the same intercalation site inV2O5 xerogel and aerogel(4); (5) the reversible intercalation of Zn+2, Mg+2, and Al+3 in the ARG(11) indicates that these cations are “mobile”, but that Cu+2 ions and Ag+ ions are “immobile” in the xerogel, i.e., the latter ions are not exchanged with the electrolyte in Li+ ion intercalation cycling(3).

  15. Fabrication of Reticulated Graphitic Foam.

    DTIC Science & Technology

    2007-11-02

    mesophase pitch (MP). Mesophase pitch is...goes through several heat treatments to stabilize the mesophase pitch , burn out the polyurethane, carbonize and finally graphitize the foam, all the while maintaining the same morphology as the initial polyurethane foam....struts gives some initial molecular orientation. The dipped foam is dried, leaving behind a the polyurethane foam coated with the pitch . The foam

  16. Graphite oral tattoo: case report.

    PubMed

    Moraes, Renata Mendonça; Gouvêa Lima, Gabriela de Morais; Guilhermino, Marinaldo; Vieira, Mayana Soares; Carvalho, Yasmin Rodarte; Anbinder, Ana Lia

    2015-10-16

    Pigmented oral lesions compose a large number of pathological entities, including exogenous pigmentat oral tattoos, such as amalgam and graphite tattoos. We report a rare case of a graphite tattoo on the palate of a 62-year-old patient with a history of pencil injury, compare it with amalgam tattoos, and determine the prevalence of oral tattoos in our Oral Pathology Service. We also compare the clinical and histological findings of grafite and amalgam tattoos. Oral tattoos affect women more frequently in the region of the alveolar ridge. Graphite tattoos occur in younger patients when compared with the amalgam type. Histologically, amalgam lesions represent impregnation of the reticular fibers of vessels and nerves with silver, whereas in cases of graphite tattoos, this impregnation is not observed, but it is common to observe a granulomatous inflammatory response, less evident in cases of amalgam tattoos. Both types of lesions require no treatment, but in some cases a biopsy may be done to rule out melanocytic lesions.

  17. Igneous Graphite in Enstatite Chondrites

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.

    1997-01-01

    Igneous graphite. a rare constituent in terrestrial mafic and ultramafic rocks. occurs in three EH and one EL enstatite chondrite impact-melt breccias as 2-150 Ilm long euhedrallaths. some with pyramidal terminations. In contrast. graphite in most enstatite chondrites exsolved from metallic Fe-Ni as polygonal. rounded or irregular aggregates. Literature data for five EH chondrites on C combusting at high temperatures show that Abee contains the most homogeneous C isotopes (i.e. delta(sup 13)C = -8.1+/-2.1%); in addition. Abee's mean delta(sup l3)C value is the same as the average high-temperature C value for the set of five EH chondrites. This suggests that Abee scavenged C from a plurality of sources on its parent body and homogenized the C during a large-scale melting event. Whereas igneous graphite in terrestrial rocks typically forms at relatively high pressure and only moderately low oxygen fugacity (e.g., approx. 5 kbar. logfO2, approx. -10 at 1200 C ). igneous graphite in asteroidal meteorites formed at much lower pressures and oxygen fugacities.

  18. 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

  19. Modelling the graphite fracture mechanisms

    SciTech Connect

    Jacquemoud, C.; Marie, S.; Nedelec, M.

    2012-07-01

    In order to define a design criterion for graphite components, it is important to identify the physical phenomena responsible for the graphite fracture, to include them in a more effective modelling. In a first step, a large panel of experiments have been realised in order to build up an important database; results of tensile tests, 3 and 4 point bending tests on smooth and notched specimens have been analysed and have demonstrated an important geometry related effects on the behavior up to fracture. Then, first simulations with an elastic or an elastoplastic bilinear constitutive law have not made it possible to simulate the experimental fracture stress variations with the specimen geometry, the fracture mechanisms of the graphite being at the microstructural scale. That is the reason why a specific F.E. model of the graphite structure has been developed in which every graphite grain has been meshed independently, the crack initiation along the basal plane of the particles as well as the crack propagation and coalescence have been modelled too. This specific model has been used to test two different approaches for fracture initiation: a critical stress criterion and two criteria of fracture mechanic type. They are all based on crystallographic considerations as a global critical stress criterion gave unsatisfactory results. The criteria of fracture mechanic type being extremely unstable and unable to represent the graphite global behaviour up to the final collapse, the critical stress criterion has been preferred to predict the results of the large range of available experiments, on both smooth and notched specimens. In so doing, the experimental observations have been correctly simulated: the geometry related effects on the experimental fracture stress dispersion, the specimen volume effects on the macroscopic fracture stress and the crack propagation at a constant stress intensity factor. In addition, the parameters of the criterion have been related to

  20. Graphite nanoreinforcements in polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Fukushima, Hiroyuki

    Nanocomposites composed of polymer matrices with clay reinforcements of less than 100 nm in size, are being considered for applications such as interior and exterior accessories for automobiles, structural components for portable electronic devices, and films for food packaging. While most nanocomposite research has focused on exfoliated clay platelets, the same nanoreinforcement concept can be applied to another layered material, graphite, to produce nanoplatelets and nanocomposites. Graphite is the stiffest material found in nature (Young's Modulus = 1060 GPa), having a modulus several times that of clay, but also with excellent electrical and thermal conductivity. The key to utilizing graphite as a platelet nanoreinforcement is in the ability to exfoliate this material. Also, if the appropriate surface treatment can be found for graphite, its exfoliation and dispersion in a polymer matrix will result in a composite with not only excellent mechanical properties but electrical properties as well, opening up many new structural applications as well as non-structural ones where electromagnetic shielding and high thermal conductivity are requirements. In this research, a new process to fabricate exfoliated nano-scale graphite platelets was established (Patent pending). The size of the resulted graphite platelets was less than 1 um in diameter and 10 nm in thickness, and the surface area of the material was around 100 m2/g. The reduction of size showed positive effect on mechanical properties of composites because of the increased edge area and more functional groups attached with it. Also various surface treatment techniques were applied to the graphite nanoplatelets to improve the surface condition. As a result, acrylamide grafting treatment was found to enhance the dispersion and adhesion of graphite flakes in epoxy matrices. The resulted composites showed better mechanical properties than those with commercially available carbon fibers, vapor grown carbon fibers

  1. Catalytic properties of lamellar compounds of graphite

    NASA Astrophysics Data System (ADS)

    Novikov, Yu. N.; Vol'pin, M. E.

    1981-05-01

    In heterogenous catalysis, the supports derived from graphite and carbon-graphite materials constitute a unique and exceptionally attractive group. The lamellar compounds of graphite with various kinds of electron acceptors and donors show catalytic activities on the following reactions: the oxidation of organic compounds with molecular oxygen, many sorts of polymerization, alcohol and formic acid dehydrogenation, hydrogenation and isomerization of olefins and acetylenes, ammonia synthesis from nitrogen and hydrogen, and also CO hydrogenation. Furthermore, the transition metal lamellar compounds of graphite are highly active catalysts in the process of the graphite-to-diamond conversion.

  2. Research on graphite reinforced glass matrix composites

    NASA Technical Reports Server (NTRS)

    Bacon, J. F.; Prewo, K. M.

    1977-01-01

    The results of research for the origination of graphite-fiber reinforced glass matrix composites are presented. The method selected to form the composites consisted of pulling the graphite fiber through a slurry containing powdered glass, winding up the graphite fiber and the glass it picks up on a drum, drying, cutting into segments, loading the tape segment into a graphite die, and hot pressing. During the course of the work, composites were made with a variety of graphite fibers in a glass matrix.

  3. On the superconductivity of graphite interfaces

    NASA Astrophysics Data System (ADS)

    Esquinazi, P.; Heikkilä, T. T.; Lysogorskiy, Y. V.; Tayurskii, D. A.; Volovik, G. E.

    2014-11-01

    We propose an explanation for the appearance of superconductivity at the interfaces of graphite with Bernal stacking order. A network of line defects with flat bands appears at the interfaces between two slightly twisted graphite structures. Due to the flat band the probability to find high temperature superconductivity at these quasi one-dimensional corridors is strongly enhanced. When the network of superconducting lines is dense it becomes effectively two-dimensional. The model provides an explanation for several reports on the observation of superconductivity up to room temperature in different oriented graphite samples, graphite powders as well as graphite-composite samples published in the past.

  4. Optimized Conditioning of Activated Reactor Graphite

    SciTech Connect

    Tress, G.; Doehring, L.; Pauli, H.; Beer, H.-F.

    2002-02-25

    The research reactor DIORIT at the Paul Scherrer Institute was decommissioned in 1993 and is now being dismantled. One of the materials to be conditioned is activated reactor graphite, approximately 45 tons. A cost effective conditioning method has been developed. The graphite is crushed to less than 6 mm and added to concrete and grout. This graphite concrete is used as matrix for embedding dismantling waste in containers. The waste containers that would have been needed for separate conditioning and disposal of activated reactor graphite are thus saved. Applying the new method, the cost can be reduced from about 55 SFr/kg to about 17 SFr/kg graphite.

  5. Effects of Propylene Carbonate Content in CsPF6-Containing Electrolytes on the Enhanced Performances of Graphite Electrode for Lithium-Ion Batteries

    SciTech Connect

    Zheng, Jianming; Yan, Pengfei; Cao, Ruiguo; Xiang, Hongfa; Engelhard, Mark H.; Polzin, Bryant; Wang, Chong M.; Zhang, Jiguang; Xu, Wu

    2016-02-10

    Cesium salt has been demonstrated as an efficient electrolyte additive in suppressing the lithium (Li) dendrite formation and directing the formation of an ultrathin and stable solid electrolyte interphase (SEI) even in propylene carbonate (PC)-ethylene carbonate (EC)-based electrolytes. Here, we further investigate the effect of PC content in the presence of CsPF6 additive (0.05 M) on the performances of graphite electrode in Li||graphite half cells and in graphite||LiNi0.80Co0.15Al0.05O2 (NCA) full cells. It is found that the performance of graphite electrode is also affected by PC content even though CsPF6 additive is present in the electrolytes. An optimal PC content of 20% by weight in the solvent mixtures is identified. The enhanced electrochemical performance of graphite electrode is attributed to the synergistic effects of the Cs+ additive and the PC solvent. The formation of a robust, ultrathin and compact SEI layer containing lithium-enriched species on the graphite electrode, directed by Cs+, effectively suppresses the PC co-intercalation and thus prevents the graphite exfoliation. This SEI layer is only permeable for de-solvated Li+ ions and allows fast Li+ ion transport through it, which therefore largely alleviates the Li dendrite formation on graphite electrode during lithiation even at high current densities. The presence of low-melting-point PC solvent also enables the sustainable operation of the graphite||NCA full cells under a wide spectrum of temperatures. The fundamental findings of this work shed light on the importance of manipulating/maintaining the electrode/electrolyte interphasial stability in a variety of energy storage devices.

  6. AGC-2 Graphite Preirradiation Data Package

    SciTech Connect

    David Swank; Joseph Lord; David Rohrbaugh; William Windes

    2012-10-01

    The NGNP Graphite R&D program is currently establishing the safe operating envelope of graphite core components for a Very High Temperature Reactor (VHTR) design. The program is generating quantitative data necessary for predicting the behavior and operating performance of the new nuclear graphite grades. To determine the in-service behavior of the graphite for pebble bed and prismatic designs, the Advanced Graphite Creep (AGC) experiment is underway. This experiment is examining the properties and behavior of nuclear grade graphite over a large spectrum of temperatures, neutron fluences and compressive loads. Each experiment consists of over 400 graphite specimens that are characterized prior to irradiation and following irradiation. Six experiments are planned with the first, AGC-1, currently being irradiated in the Advanced Test Reactor (ATR) and pre-irradiation characterization of the second, AGC-2, completed. This data package establishes the readiness of 512 specimens for assembly into the AGC-2 capsule.

  7. Solvothermal-assisted liquid-phase exfoliation of graphite in a mixed solvent of toluene and oleylamine.

    PubMed

    Dang, Dinh Khoi; Kim, Eui Jung

    2015-12-01

    We report an effective method for producing graphene sheets using solvothermal-assisted exfoliation of graphite in a mixed solvent of toluene and oleylamine. The mixed solvent of toluene and oleylamine produces higher yield of graphene than its constituents, oleylamine and toluene. The oleylamine molecules with its long chain enwrap the graphene sheets efficiently, while toluene helps the oleylamine molecules become more flexible and easily intercalate into the edge of graphite. The prepared graphene sheets have a high quality, and the concentration of graphene in the dispersion is as high as 0.128 mg mL(-1). The high-quality graphene sheets obtained in this work make them suitable for application in many fields such as energy-storage materials and polymer composites.

  8. A unique perylene-based DNA intercalator: localization in cell nuclei and inhibition of cancer cells and tumors.

    PubMed

    Xu, Zejun; Guo, Kunru; Yu, Jieshi; Sun, Haili; Tang, Jun; Shen, Jie; Müllen, Klaus; Yang, Wantai; Yin, Meizhen

    2014-10-29

    To date, perylene derivatives have not been explored as DNA intercalator to inhibit cancer cells by intercalating into the base pairs of DNA. Herein, a water-soluble perylene bisimide (PBDI) that efficiently intercalates into the base pairs of DNA is synthesized. Excitingly, PBDI is superior to the commercial DNA intercalator, amonafide, for specific nuclear accumulation and effective suppression of cancer cells and tumors.

  9. Composition and method for brazing graphite to graphite

    DOEpatents

    Taylor, A.J.; Dykes, N.L.

    1982-08-10

    A brazing material is described for joining graphite structures that can be used up to 2800/sup 0/C. The brazing material is formed of a paste-like composition of hafnium carbide and uranium oxide with a thermosetting resin. The uranium oxide is converted to uranium dicarbide during the brazing operation and then the hafnium carbide and uranium dicarbide form a liquid phase at a temperature about 2600/sup 0/C with the uranium diffusing and vaporizing from the joint area as the temperature is increased to about 2800/sup 0/C so as to provide a brazed joint consisting essentially of hafnium carbide. The resulting brazed joint is chemically and thermally compatible with the graphite structures.

  10. Evidence of graphitic AB stacking order of graphite oxides.

    PubMed

    Jeong, Hae-Kyung; Lee, Yun Pyo; Lahaye, Rob J W E; Park, Min-Ho; An, Kay Hyeok; Kim, Ick Jun; Yang, Cheol-Woong; Park, Chong Yun; Ruoff, Rodney S; Lee, Young Hee

    2008-01-30

    Graphite oxide (GO) samples were prepared by a simplified Brodie method. Hydroxyl, epoxide, carboxyl, and some alkyl functional groups are present in the GO, as identified by solid-state 13C NMR, Fourier-transform infrared spectroscopy, and X-ray photoemission spectroscopy. Starting with pyrolytic graphite (interlayer separation 3.36 A), the average interlayer distance after 1 h of reaction, as determined by X-ray diffraction, increased to 5.62 A and then increased with further oxidation to 7.37 A after 24 h. A smaller signal in 13C CPMAS NMR compared to that in 13C NMR suggests that carboxyl and alkyl groups are at the edges of the flakes of graphite oxide. Other aspects of the chemical bonding were assessed from the NMR and XPS data and are discussed. AB stacking of the layers in the GO was inferred from an electron diffraction study. The elemental composition of GO prepared using this simplified Brodie method is further discussed.

  11. Controlling the photoconductivity: Graphene oxide and polyaniline self assembled intercalation

    SciTech Connect

    Vempati, Sesha; Ozcan, Sefika; Uyar, Tamer

    2015-02-02

    We report on controlling the optoelectronic properties of self-assembled intercalating compound of graphene oxide (GO) and HCl doped polyaniline (PANI). Optical emission and X-ray diffraction studies revealed a secondary doping phenomenon of PANI with –OH and –COOH groups of GO, which essentially arbitrate the intercalation. A control on the polarity and the magnitude of the photoresponse (PR) is harnessed by manipulating the weight ratios of PANI to GO (viz., 1:1.5 and 1:2.2 are abbreviated as PG1.5 and PG2.2, respectively), where ±PR = 100(R{sub Dark} – R{sub UV-Vis})/R{sub Dark} and R corresponds to the resistance of the device in dark or UV-Vis illumination. To be precise, the PR from GO, PANI, PG1.5, and PG2.2 are +34%, −111%, −51%, and +58%, respectively.

  12. DNA Intercalated Psoralen Undergoes Efficient Photoinduced Electron Transfer.

    PubMed

    Fröbel, Sascha; Reiffers, Anna; Torres Ziegenbein, Christian; Gilch, Peter

    2015-04-02

    The interaction of psoralens with DNA has been used for therapeutic and research purposes for decades. Still the photoinduced behavior of psoralens in DNA has never been observed directly. Femtosecond transient absorption spectroscopy is used here to gain direct insight into the photophysics of a DNA-intercalated psoralen (4'-aminomethyl-4,5',8-trimethyl-psoralen (AMT)). Intercalation reduces the excited singlet lifetime of AMT to 4 ps compared with 1400 ps for AMT in water. This singlet quenching prohibits the population of the triplet state that is accessed in free AMT. Instead, a DNA to AMT electron transfer takes place. The resulting radical pair decays primarily via charge recombination with a time constant of 30 ps. The efficient electron transfer observed here reveals a completely new aspect of the psoralen-DNA interaction.

  13. Intercalation Pseudocapacitance of Exfoliated Molybdenum Disulfide for Ultrafast Energy Storage

    DOE PAGES

    Yoo, Hyun Deog; Li, Yifei; Liang, Yanliang; ...

    2016-05-23

    In this study, we report intercalation pseudocapacitance of 250 F g-1 for exfoliated molybdenum disulfide (MoS2) in non-aqueous electrolytes that contain lithium ions. The exfoliated MoS2 shows surface-limited reaction kinetics with high rate capability up to 3 min of charge or discharge. The intercalation pseudocapacitance originates from the extremely fast kinetics due to the enhanced ionic and electronic transport enabled by the slightly expanded layer structure as well as the metallic 1T-phase. The exfoliated MoS2 could be also used in a Li-Mg-ion hybrid capacitor, which shows full cell specific capacitance of 240 F g-1.

  14. Intercalation Pseudocapacitance of Exfoliated Molybdenum Disulfide for Ultrafast Energy Storage

    SciTech Connect

    Yoo, Hyun Deog; Li, Yifei; Liang, Yanliang; Lan, Yucheng; Wang, Feng; Yao, Yan

    2016-05-23

    In this study, we report intercalation pseudocapacitance of 250 F g-1 for exfoliated molybdenum disulfide (MoS2) in non-aqueous electrolytes that contain lithium ions. The exfoliated MoS2 shows surface-limited reaction kinetics with high rate capability up to 3 min of charge or discharge. The intercalation pseudocapacitance originates from the extremely fast kinetics due to the enhanced ionic and electronic transport enabled by the slightly expanded layer structure as well as the metallic 1T-phase. The exfoliated MoS2 could be also used in a Li-Mg-ion hybrid capacitor, which shows full cell specific capacitance of 240 F g-1.

  15. Tissue tectonics: morphogenetic strain rates, cell shape change and intercalation.

    PubMed

    Blanchard, Guy B; Kabla, Alexandre J; Schultz, Nora L; Butler, Lucy C; Sanson, Benedicte; Gorfinkiel, Nicole; Mahadevan, L; Adams, Richard J

    2009-06-01

    The dynamic reshaping of tissues during morphogenesis results from a combination of individual cell behaviors and collective cell rearrangements. However, a comprehensive framework to unambiguously measure and link cell behavior to tissue morphogenesis is lacking. Here we introduce such a kinematic framework, bridging cell and tissue behaviors at an intermediate, mesoscopic, level of cell clusters or domains. By measuring domain deformation in terms of the relative motion of cell positions and the evolution of their shapes, we characterized the basic invariant quantities that measure fundamental classes of cell behavior, namely tensorial rates of cell shape change and cell intercalation. In doing so we introduce an explicit definition of cell intercalation as a continuous process. We mapped strain rates spatiotemporally in three models of tissue morphogenesis, gaining insight into morphogenetic mechanisms. Our quantitative approach has broad relevance for the precise characterization and comparison of morphogenetic phenotypes.

  16. Amphiphilic properties of poly(oxyalkylene)amine-intercalated smectite aluminosilicates.

    PubMed

    Lin, Jiang-Jen; Chen, Yu-Min

    2004-05-11

    Layered aluminosilicates, including synthetic fluorine mica and natural montmorillonite (MMT), were intercalated with poly(oxypropylene)-polyamine quaternary salts with a 230-5000 molecular weight range. The X-ray basal spacing of these silicates had been expanded from 13.5 to 83.7 A for the synthetic mica and to 92.0 A for MMT. The relative silicate dimensions (300-1000 nm for synthetic mica and 80-100 nm for MMT) were ascertained by direct TEM observations in the case of the co-intercalated synthetic mica and MMT mixtures with Mw = 2000 quaternary ammonium salts. The tailored organic incorporation of synthetic mica and MMT clays could alter these hydrophilic clays, making them amphiphilic, and enable the lowering of toluene/water interfacial tension to 2.0 mN/m at the critical concentration of 0.1 wt %.

  17. Rational design of a triple helix-specific intercalating ligand.

    PubMed

    Escudé, C; Nguyen, C H; Kukreti, S; Janin, Y; Sun, J S; Bisagni, E; Garestier, T; Hélène, C

    1998-03-31

    DNA triple helices offer new perspectives toward oligonucleotide-directed gene regulation. However, the poor stability of some of these structures might limit their use under physiological conditions. Specific ligands can intercalate into DNA triple helices and stabilize them. Molecular modeling and thermal denaturation experiments suggest that benzo[f]pyrido[3, 4-b]quinoxaline derivatives intercalate into triple helices by stacking preferentially with the Hoogsteen-paired bases. Based on this model, it was predicted that a benzo[f]quino[3,4-b]quinoxaline derivative, which possesses an additional aromatic ring, could engage additional stacking interactions with the pyrimidine strand of the Watson-Crick double helix upon binding of this pentacyclic ligand to a triplex structure. This compound was synthesized. Thermal denaturation experiments and inhibition of restriction enzyme cleavage show that this new compound can indeed stabilize triple helices with great efficiency and specificity and/or induce triple helix formation under physiological conditions.

  18. Electrochemical Doping of Halide Perovskites with Ion Intercalation.

    PubMed

    Jiang, Qinglong; Chen, Mingming; Li, Junqiang; Wang, Mingchao; Zeng, Xiaoqiao; Besara, Tiglet; Lu, Jun; Xin, Yan; Shan, Xin; Pan, Bicai; Wang, Changchun; Lin, Shangchao; Siegrist, Theo; Xiao, Qiangfeng; Yu, Zhibin

    2017-01-24

    Halide perovskites have recently been investigated for various solution-processed optoelectronic devices. The majority of studies have focused on using intrinsic halide perovskites, and the intentional incoporation of dopants has not been well explored. In this work, we discovered that small alkali ions, including lithium and sodium ions, could be electrochemically intercalated into a variety of halide and pseudohalide perovskites. The ion intercalation caused a lattice expansion of the perovskite crystals and resulted in an n-type doping of the perovskites. Such electrochemical doping improved the conductivity and changed the color of the perovskites, leading to an electrochromism with more than 40% reduction of transmittance in the 450-850 nm wavelength range. The doped perovskites exhibited improved electron injection efficiency into the pristine perovskite crystals, resulting in bright light-emitting diodes with a low turn-on voltage.

  19. Intercalation of Trichloroethene by Sediment-Associated Clay Minerals

    SciTech Connect

    Matthieu, Donald E.; Brusseau, Mark; Johnson, G. R.; Artiola, J. L.; Bowden, Mark E.; Curry, J. E.

    2013-01-01

    The objective of this research was to examine the potential for intercalation of trichloroethene (TCE) by clay minerals associated with aquifer sediments. Sediment samples were collected from a field site inTucson, AZ. Two widely used Montmorillonite specimen clays were employed as controls. X-ray diffraction, conducted with a controlled-environment chamber, was used to characterize smectite interlayer dspacing for three treatments (bulk air-dry sample, sample mixed with synthetic groundwater, sample mixed with TCE-saturated synthetic groundwater). The results show that the d-spacing measured for the samples treated with TCE-saturated synthetic groundwater are larger (*26%) than those of the untreated samples for all field samples as well as the specimen clays. These results indicate that TCE was intercalated by the clay minerals, which may have contributed to the extensive elution tailing observed in prior miscible-displacement experiments conducted with this sediment.

  20. Abl suppresses cell extrusion and intercalation during epithelium folding.

    PubMed

    Jodoin, Jeanne N; Martin, Adam C

    2016-09-15

    Tissue morphogenesis requires control over cell shape changes and rearrangements. In the Drosophila mesoderm, linked epithelial cells apically constrict, without cell extrusion or intercalation, to fold the epithelium into a tube that will then undergo epithelial-to-mesenchymal transition (EMT). Apical constriction drives tissue folding or cell extrusion in different contexts, but the mechanisms that dictate the specific outcomes are poorly understood. Using live imaging, we found that Abelson (Abl) tyrosine kinase depletion causes apically constricting cells to undergo aberrant basal cell extrusion and cell intercalation. abl depletion disrupted apical-basal polarity and adherens junction organization in mesoderm cells, suggesting that extruding cells undergo premature EMT. The polarity loss was associated with abnormal basolateral contractile actomyosin and Enabled (Ena) accumulation. Depletion of the Abl effector Enabled (Ena) in abl-depleted embryos suppressed the abl phenotype, consistent with cell extrusion resulting from misregulated ena Our work provides new insight into how Abl loss and Ena misregulation promote cell extrusion and EMT.

  1. 3He on preplated graphite

    NASA Astrophysics Data System (ADS)

    Gordillo, M. C.; Boronat, J.

    2016-10-01

    By using the diffusion Monte Carlo method, we obtained the full phase diagram of 3He on top of graphite preplated with a solid layer of 4He. All the 4He atoms of the substrate were explicitly considered and allowed to move during the simulation. We found that the ground state is a liquid of density 0.007 ±0.001 Å-2, in good agreement with available experimental data. This is significantly different from the case of 3He on clean graphite, in which both theory and experiment agree on the existence of a gas-liquid transition at low densities. Upon an increase in 3He density, we predict a first-order phase transition between a dense liquid and a registered 7/12 phase, the 4/7 phase being found metastable in our calculations. At larger second-layer densities, a final transition is produced to an incommensurate triangular phase.

  2. Graphite moderated (252)Cf source.

    PubMed

    Sajo-Bohus, Laszlo; Barros, Haydn; Greaves, Eduardo D; Vega-Carrillo, Hector Rene

    2015-06-01

    The Thorium molten-salt reactor is an attractive and affordable nuclear power option for developing countries with insufficient infrastructure and limited technological capability. In the aim of personnel training and experience gathering at the Universidad Simon Bolivar there is in progress a project of developing a subcritical thorium liquid-fuel reactor. The neutron source to run this subcritical reactor is a (252)Cf source and the reactor will use high-purity graphite as moderator. Using the MCNP5 code the neutron spectra of the (252)Cf in the center of the graphite moderator has been estimated along the channel where the liquid thorium salt will be inserted; also the ambient dose equivalent due to the source has been determined around the moderator.

  3. Fission Product Sorptivity in Graphite

    SciTech Connect

    Tompson, Jr., Robert V.; Loyalka, Sudarshan; Ghosh, Tushar; Viswanath, Dabir; Walton, Kyle; Haffner, Robert

    2015-04-01

    Both adsorption and absorption (sorption) of fission product (FP) gases on/into graphite are issues of interest in very high temperature reactors (VHTRs). In the original proposal, we proposed to use packed beds of graphite particles to measure sorption at a variety of temperatures and to use an electrodynamic balance (EDB) to measure sorption onto single graphite particles (a few μm in diameter) at room temperature. The use of packed beds at elevated temperature is not an issue. However, the TPOC requested revision of this initial proposal to included single particle measurements at elevated temperatures up to 1100 °C. To accommodate the desire of NEUP to extend the single particle EDB measurements to elevated temperatures it was necessary to significantly revise the plan and the budget. These revisions were approved. In the EDB method, we levitate a single graphite particle (the size, surface characteristics, morphology, purity, and composition of the particle can be varied) or agglomerate in the balance and measure the sorption of species by observing the changes in mass. This process involves the use of an electron stepping technique to measure the total charge on a particle which, in conjunction with the measured suspension voltages for the particle, allows for determinations of mass and, hence, of mass changes which then correspond to measurements of sorption. Accommodating elevated temperatures with this type of system required a significant system redesign and required additional time that ultimately was not available. These constraints also meant that the grant had to focus on fewer species as a result. Overall, the extension of the original proposed single particle work to elevated temperatures added greatly to the complexity of the proposed project and added greatly to the time that would eventually be required as well. This means that the bulk of the experimental progress was made using the packed bed sorption systems. Only being able to recruit one

  4. Dispersive interactions in graphitic nanostructures

    NASA Astrophysics Data System (ADS)

    Woods, L. M.; Popescu, A.; Drosdoff, D.; Bondarev, I. V.

    2013-02-01

    The Casimir interaction between graphitic nanostructures, such as carbon nanotubes and graphene sheets, is investigated at the quantum mechanical limit (T = 0 K) using a quantum electrodynamical approach for absorbing and dispersive media. It is found that the nanotube/nanotube interaction in a double wall carbon nanotube configuration is profoundly affected by the collective low frequency excitations of individual nanotubes. It is shown that pronounced, low frequency peaks in the nanotube electron energy loss spectra are a main factor contributing to the strength of the intertube attraction. The graphene/graphene force is also investigated. It is obtained that the graphene optical transparency is the main reason for the reduced attraction as compared to the one for perfect metals. This study presents a unified approach for electromagnetic interactions in graphitic nanostructures, which is able to account for their unique electronic and response properties and geometry configurations.

  5. 3D-graphite structure

    SciTech Connect

    Belenkov, E. A. Ali-Pasha, V. A.

    2011-01-15

    The structure of clusters of some new carbon 3D-graphite phases have been calculated using the molecular-mechanics methods. It is established that 3D-graphite polytypes {alpha}{sub 1,1}, {alpha}{sub 1,3}, {alpha}{sub 1,5}, {alpha}{sub 2,1}, {alpha}{sub 2,3}, {alpha}{sub 3,1}, {beta}{sub 1,2}, {beta}{sub 1,4}, {beta}{sub 1,6}, {beta}{sub 2,1}, and {beta}{sub 3,2} consist of sp{sup 2}-hybridized atoms, have hexagonal unit cells, and differ in regards to the structure of layers and order of their alternation. A possible way to experimentally synthesize new carbon phases is proposed: the polymerization and carbonization of hydrocarbon molecules.

  6. AGC-3 Graphite Preirradiation Data Analysis Report

    SciTech Connect

    William Windes; David Swank; David Rohrbaugh; Joseph Lord

    2013-09-01

    This report describes the specimen loading order and documents all pre-irradiation examination material property measurement data for the graphite specimens contained within the third Advanced Graphite Capsule (AGC-3) irradiation capsule. The AGC-3 capsule is third in six planned irradiation capsules comprising the Advanced Graphite Creep (AGC) test series. The AGC test series is used to irradiate graphite specimens allowing quantitative data necessary for predicting the irradiation behavior and operating performance of new nuclear graphite grades to be generated which will ascertain the in-service behavior of the graphite for pebble bed and prismatic Very High Temperature Reactor (VHTR) designs. The general design of AGC-3 test capsule is similar to the AGC-2 test capsule, material property tests were conducted on graphite specimens prior to loading into the AGC-3 irradiation assembly. However the 6 major nuclear graphite grades in AGC-2 were modified; two previous graphite grades (IG-430 and H-451) were eliminated and one was added (Mersen’s 2114 was added). Specimen testing from three graphite grades (PCEA, 2114, and NBG-17) was conducted at Idaho National Laboratory (INL) and specimen testing for two grades (IG-110 and NBG-18) were conducted at Oak Ridge National Laboratory (ORNL) from May 2011 to July 2013. This report also details the specimen loading methodology for the graphite specimens inside the AGC-3 irradiation capsule. The AGC-3 capsule design requires "matched pair" creep specimens that have similar dose levels above and below the neutron flux profile mid-plane to provide similar specimens with and without an applied load. This document utilized the neutron flux profile calculated for the AGC-3 capsule design, the capsule dimensions, and the size (length) of the selected graphite and silicon carbide samples to create a stacking order that can produce "matched pairs" of graphite samples above and below the AGC-3 capsule elevation mid-point to

  7. Exfoliation and intercalation of montmorillonite by small peptides.

    PubMed

    Block, Karin A; Trusiak, Adrianna; Katz, Al; Alimova, Alexandra; Wei, Hui; Gottlieb, Paul; Steiner, Jeffrey C

    2015-04-01

    Understanding structural changes in clay minerals induced by complexation with organic matter is relevant to soil science and agricultural applications. In this study, the effect of peptide storage in montmorillonite and the thermal stability of peptide-clay complexes was examined through characterization by X-ray diffraction (XRD), electron microscopy, UV absorption, and thermogravimetric analysis (TGA). XRD analysis of small peptide-montmorillonite clay complexes produced profiles consisting of reflections associated with the smectite 001 reflection and related peaks similar to that produced by a mixed layer clay mineral structure. Shifts in higher order diffraction maxima were attributed to disorder caused by the intercalation with the peptides. Increasing peptide concentrations resulted in greater shifts towards smaller 2θ from 6.37° (1.39 nm) to 5.45° (1.62 nm) as the interlayer space expanded. The expansion was accompanied by broadening of the 001 reflection (FWHM increases from 0.51 to 1.22° 2θ). The XRD line broadening was interpreted as caused by poorer crystallinity resulting from intercalation and tactoid exfoliation. SEM images revealed montmorillonite platelets with upwardly rolled edges that tend toward cylindrical structures with the production of tubules. High-resolution TEM images revealed bending of montmorillonite platelets, confirming exfoliation. The distribution of basal spacings in the micrographs was determined from the spatial frequencies obtained by Fourier analysis of density profiles. The distribution indicated the presence of discrete coherent crystallite domains. XRD and TGA results indicated that higher peptide concentrations resulted in a greater fraction of intercalated peptides and that surface adsorption of peptides mediated intercalation. Therefore, higher peptide concentration led to more stable organoclay complexes. However, UV absorption and TGA found that peptide adsorption onto montmorillonite had a finite limit at

  8. Exfoliation and intercalation of montmorillonite by small peptides

    PubMed Central

    Block, Karin A.; Trusiak, Adrianna; Katz, Al; Alimova, Alexandra; Wei, Hui; Gottlieb, Paul; Steiner, Jeffrey C.

    2015-01-01

    Understanding structural changes in clay minerals induced by complexation with organic matter is relevant to soil science and agricultural applications. In this study, the effect of peptide storage in montmorillonite and the thermal stability of peptide-clay complexes was examined through characterization by X-ray diffraction (XRD), electron microscopy, UV absorption, and thermogravimetric analysis (TGA). XRD analysis of small peptide-montmorillonite clay complexes produced profiles consisting of reflections associated with the smectite 001 reflection and related peaks similar to that produced by a mixed layer clay mineral structure. Shifts in higher order diffraction maxima were attributed to disorder caused by the intercalation with the peptides. Increasing peptide concentrations resulted in greater shifts towards smaller 2θ from 6.37° (1.39 nm) to 5.45° (1.62 nm) as the interlayer space expanded. The expansion was accompanied by broadening of the 001 reflection (FWHM increases from 0.51 to 1.22° 2θ). The XRD line broadening was interpreted as caused by poorer crystallinity resulting from intercalation and tactoid exfoliation. SEM images revealed montmorillonite platelets with upwardly rolled edges that tend toward cylindrical structures with the production of tubules. High-resolution TEM images revealed bending of montmorillonite platelets, confirming exfoliation. The distribution of basal spacings in the micrographs was determined from the spatial frequencies obtained by Fourier analysis of density profiles. The distribution indicated the presence of discrete coherent crystallite domains. XRD and TGA results indicated that higher peptide concentrations resulted in a greater fraction of intercalated peptides and that surface adsorption of peptides mediated intercalation. Therefore, higher peptide concentration led to more stable organoclay complexes. However, UV absorption and TGA found that peptide adsorption onto montmorillonite had a finite limit at

  9. Graphite/Thermoplastic-Pultrusion Die

    NASA Technical Reports Server (NTRS)

    Wilson, Maywood L.; Frye, Mark W.; Johnson, Gary S.; Stanfield, Clarence E.

    1990-01-01

    Attachment to extruder produces thermoplastic-impregnated graphite tape. Consists of profile die, fiber/resin collimator, and crosshead die body. Die designed to be attached to commercially available extrusion machine capable of extruding high-performance thermoplastics. Simple attachment to commercial extruder enables developers of composites to begin experimenting with large numbers of proprietary resins, fibers, and hybrid composite structures. With device, almost any possible fiber/resin combination fabricated.

  10. Poco Graphite Mirror Metrology Report

    NASA Technical Reports Server (NTRS)

    Kester, Thomas J.

    2005-01-01

    Recently a lightweight mirror technology was tested at Marshall Space Flight Center's Space Optic Manufacturing Technology Center (MSFC, SOMTC). The mirror is a Poco Graphite CVD Si clad SiC substrate. It was tested for cryogenic (cryo) survivability to 20deg Kelvin in SOMTC's X-ray Calibration and Cryogenic Test Facility. The surface figure of the mirror was measured before and after cry0 cycling. The test technique and results are discussed.

  11. Manipulate the Doping of Graphene at Nanoscale with Intercalated Oxygen

    NASA Astrophysics Data System (ADS)

    Zhang, Xin; Luo, Hong; Liu, Lei; Gu, Gong; Stradi, Daniele; Brandbyge, Mads

    2015-03-01

    We have created nanoscale p- and n-doped graphene regions side by side, by partially removing the oxygen between the graphene and the Cu foil growth substrate intercalated upon elongated air exposure. The Cu foil surface is almost exclusively (100) oriented, and the removal of intercalated oxygen is by thermal annealing. Scanning tunneling microscopy (STM) reveals a 0.72 × 0.72 nm square superlattice in the single layer (1L) graphene/O/Cu(100) structure, assigned to be Cu(2√{ 2} × 2√{ 2})R45°-O, which has not been reported so far. Graphene with intercalated oxygen underneath it is p-doped while the surrounding graphene areas, directly in contact with the copper surface, are n-doped. Comparing the scanning tunneling spectra (STS) of the two types of regions, we show a charge transfer-induced shift of the electronic structure. Such a shift is also observed between p- and n-doped twisted bilayer (2L) graphene regions, where the van Hove singularity (vHS) peaks are used as markers to precisely determine the energy shift. Across the boundaries between the p- and n-doped regions, the shift of the electronic structure is spatially resolved, showing the vanishing and reappearance of the vHS peaks. The experimental observations are consistent with first-principles calculations.

  12. Electrochemical Intercalation of Lithium Ions into Carbon Nanotube Bundles

    NASA Astrophysics Data System (ADS)

    Allen, J. L.; Sumanasekera, G. U.; Rao, A. M.; Fang, S.; Eklund, P. C.

    1998-03-01

    We have investigated the electrochemical intercalation of lithium ions into ropes of single-walled carbon nanotubes (SWNTs) in a standard three electrode cell. The SWNT mat pressed onto a Pt plate was the working electrode. Lithium was used at both the counter and reference electrodes, and 1M LiAsF6 in ethylene carbonate:diethyl carbonate (1:1 by volume) served as the electrolyte. Raman spectra of the SWNTs were recorded in situ as a function of electrochemical charge using 514.5 nm excitation. During galvanostatic intercalation, we observed a relatively steep decrease in voltage until a plateau at around 1.2 V is reached. We attribute this initial decrease to the intercalation of lithium into SWNT and a concurrent electron doping of the SWNT π band. In the Raman spectrum, as the voltage reaches 1.2 V, the tangential mode frequency down shifted from 1593 cm-1 to 1591 cm-1 consistent with electron addition to the π^* band. We speculate that surface reactions of the lithium doped SWNT and the electrolyte are occuring during the plateau. During the evolution of the plateau, the Raman signal of the tangential mode gradually diminishes without further downshift of the its frequency and eventually disappears completely. Cyclic voltammograms show a minimum at around 1.2 V and peaks at around 0.7 V and 1.7 V. The origin of this structure is not presently understood.

  13. Incommensurate Graphene Foam as a High Capacity Lithium Intercalation Anode

    NASA Astrophysics Data System (ADS)

    Paronyan, Tereza M.; Thapa, Arjun Kumar; Sherehiy, Andriy; Jasinski, Jacek B.; Jangam, John Samuel Dilip

    2017-01-01

    Graphite’s capacity of intercalating lithium in rechargeable batteries is limited (theoretically, 372 mAh g‑1) due to low diffusion within commensurately-stacked graphene layers. Graphene foam with highly enriched incommensurately-stacked layers was grown and applied as an active electrode in rechargeable batteries. A 93% incommensurate graphene foam demonstrated a reversible specific capacity of 1,540 mAh g‑1 with a 75% coulombic efficiency, and an 86% incommensurate sample achieves above 99% coulombic efficiency exhibiting 930 mAh g‑1 specific capacity. The structural and binding analysis of graphene show that lithium atoms highly intercalate within weakly interacting incommensurately-stacked graphene network, followed by a further flexible rearrangement of layers for a long-term stable cycling. We consider lithium intercalation model for multilayer graphene where capacity varies with N number of layers resulting LiN+1C2N stoichiometry. The effective capacity of commonly used carbon-based rechargeable batteries can be significantly improved using incommensurate graphene as an anode material.

  14. Incommensurate Graphene Foam as a High Capacity Lithium Intercalation Anode

    PubMed Central

    Paronyan, Tereza M.; Thapa, Arjun Kumar; Sherehiy, Andriy; Jasinski, Jacek B.; Jangam, John Samuel Dilip

    2017-01-01

    Graphite’s capacity of intercalating lithium in rechargeable batteries is limited (theoretically, 372 mAh g−1) due to low diffusion within commensurately-stacked graphene layers. Graphene foam with highly enriched incommensurately-stacked layers was grown and applied as an active electrode in rechargeable batteries. A 93% incommensurate graphene foam demonstrated a reversible specific capacity of 1,540 mAh g−1 with a 75% coulombic efficiency, and an 86% incommensurate sample achieves above 99% coulombic efficiency exhibiting 930 mAh g−1 specific capacity. The structural and binding analysis of graphene show that lithium atoms highly intercalate within weakly interacting incommensurately-stacked graphene network, followed by a further flexible rearrangement of layers for a long-term stable cycling. We consider lithium intercalation model for multilayer graphene where capacity varies with N number of layers resulting LiN+1C2N stoichiometry. The effective capacity of commonly used carbon-based rechargeable batteries can be significantly improved using incommensurate graphene as an anode material. PMID:28059110

  15. Selective and low temperature transition metal intercalation in layered tellurides

    PubMed Central

    Yajima, Takeshi; Koshiko, Masaki; Zhang, Yaoqing; Oguchi, Tamio; Yu, Wen; Kato, Daichi; Kobayashi, Yoji; Orikasa, Yuki; Yamamoto, Takafumi; Uchimoto, Yoshiharu; Green, Mark A.; Kageyama, Hiroshi

    2016-01-01

    Layered materials embrace rich intercalation reactions to accommodate high concentrations of foreign species within their structures, and find many applications spanning from energy storage, ion exchange to secondary batteries. Light alkali metals are generally most easily intercalated due to their light mass, high charge/volume ratio and in many cases strong reducing properties. An evolving area of materials chemistry, however, is to capture metals selectively, which is of technological and environmental significance but rather unexplored. Here we show that the layered telluride T2PTe2 (T=Ti, Zr) displays exclusive insertion of transition metals (for example, Cd, Zn) as opposed to alkali cations, with tetrahedral coordination preference to tellurium. Interestingly, the intercalation reactions proceed in solid state and at surprisingly low temperatures (for example, 80 °C for cadmium in Ti2PTe2). The current method of controlling selectivity provides opportunities in the search for new materials for various applications that used to be possible only in a liquid. PMID:27966540

  16. Selective and low temperature transition metal intercalation in layered tellurides

    NASA Astrophysics Data System (ADS)

    Yajima, Takeshi; Koshiko, Masaki; Zhang, Yaoqing; Oguchi, Tamio; Yu, Wen; Kato, Daichi; Kobayashi, Yoji; Orikasa, Yuki; Yamamoto, Takafumi; Uchimoto, Yoshiharu; Green, Mark A.; Kageyama, Hiroshi

    2016-12-01

    Layered materials embrace rich intercalation reactions to accommodate high concentrations of foreign species within their structures, and find many applications spanning from energy storage, ion exchange to secondary batteries. Light alkali metals are generally most easily intercalated due to their light mass, high charge/volume ratio and in many cases strong reducing properties. An evolving area of materials chemistry, however, is to capture metals selectively, which is of technological and environmental significance but rather unexplored. Here we show that the layered telluride T2PTe2 (T=Ti, Zr) displays exclusive insertion of transition metals (for example, Cd, Zn) as opposed to alkali cations, with tetrahedral coordination preference to tellurium. Interestingly, the intercalation reactions proceed in solid state and at surprisingly low temperatures (for example, 80 °C for cadmium in Ti2PTe2). The current method of controlling selectivity provides opportunities in the search for new materials for various applications that used to be possible only in a liquid.

  17. Towards efficient solar hydrogen production by intercalated carbon nitride photocatalyst.

    PubMed

    Gao, Honglin; Yan, Shicheng; Wang, Jiajia; Huang, Yu An; Wang, Peng; Li, Zhaosheng; Zou, Zhigang

    2013-11-07

    The development of efficient photocatalytic material for converting solar energy to hydrogen energy as viable alternatives to fossil-fuel technologies is expected to revolutionize energy shortage and environment issues. However, to date, the low quantum yield for solar hydrogen production over photocatalysts has hindered advances in the practical applications of photocatalysis. Here, we show that a carbon nitride intercalation compound (CNIC) synthesized by a simple molten salt route is an efficient polymer photocatalyst with a high quantum yield. We found that coordinating the alkali metals into the C-N plane of carbon nitride will induce the un-uniform spatial charge distribution. The electrons are confined in the intercalated region while the holes are in the far intercalated region, which promoted efficient separation of photogenerated carriers. The donor-type alkali metal ions coordinating into the nitrogen pots of carbon nitrides increase the free carrier concentration and lead to the formation of novel nonradiative paths. This should favor improved transport of the photogenerated electron and hole and decrease the electron-hole recombination rate. As a result, the CNIC exhibits a quantum yield as high as 21.2% under 420 nm light irradiation for solar hydrogen production. Such high quantum yield opens up new opportunities for using cheap semiconducting polymers as energy transducers.

  18. Graphite Nanoreinforcements for Aerospace Nanocomposites

    NASA Technical Reports Server (NTRS)

    Drzal, Lawrence T.

    2005-01-01

    New advances in the reinforcement of polymer matrix composite materials are critical for advancement of the aerospace industry. Reinforcements are required to have good mechanical and thermal properties, large aspect ratio, excellent adhesion to the matrix, and cost effectiveness. To fulfill the requirements, nanocomposites in which the matrix is filled with nanoscopic reinforcing phases having dimensions typically in the range of 1nm to 100 nm show considerably higher strength and modulus with far lower reinforcement content than their conventional counterparts. Graphite is a layered material whose layers have dimensions in the nanometer range and are held together by weak Van der Waals forces. Once these layers are exfoliated and dispersed in a polymer matrix as nano platelets, they have large aspect ratios. Graphite has an elastic modulus that is equal to the stiffest carbon fiber and 10-15 times that of other inorganic reinforcements, and it is also electrically and thermally conductive. If the appropriate surface treatment can be found for graphite, its exfoliation and dispersion in a polymer matrix will result in a composite with excellent mechanical properties, superior thermal stability, and very good electrical and thermal properties at very low reinforcement loadings.

  19. Development of polyphenylquinoxaline graphite composites

    NASA Technical Reports Server (NTRS)

    Hoggatt, J. T.; Hergenrother, P. M.; Shdo, J. G.

    1973-01-01

    The potential of polyphenylquinoxaline (PPQ)/graphite composites to serve as structural material at 316 C (600 F)has been demonstrated using a block copolymer, BlCo(13), PPQ derivative. Initially, thirteen polyphenylquinoxalines were evaluated. From this work, four candidate polymers were selected for preliminary evaluation as matrices for HMS graphite fiber reinforced composites. The preliminary composite evaluation enabled selection of one of the four polymers for advanced composite preparation and testing. Using an experimentally established cure schedule for each of the four polymers, preliminary laminates of 50% resin volume content, prepared without postcure, were tested for flexure strength and modulus, interlaminar shear strength (short beam), and tensile strength and modulus at ambient temperature. A block copolymer (Bl Co 13) derived from one mole p-bis (phenylglyoxalyl) benzene, one fourth mole 3,3'-diaminobenzidine and three-fourths mole 3,3', 4,4'-tetraminobenzophenone was selected for extensive study. Tensile, flexural, and interlaminar shear values were obtained after aging and testing postcured BlCo(13) laminates at 316 C (600 F). The potential of PPQ/graphite laminates to serve as short term structural materials at temperatures up to 371 C (700 F) was demonstrated through weight loss experiments.

  20. Electrochemical and in-situ scanning tunneling microscopy studies of bis(fluorosulfonyl)imide and bis(trifluoromethanesulfonyl)imide based ionic liquids on graphite and gold electrodes and lithium salt influence

    NASA Astrophysics Data System (ADS)

    Hu, Xiaoyan; Chen, Chunlei; Yan, Jiawei; Mao, Bingwei

    2015-10-01

    We report electrochemical and in-situ scanning tunneling microscopy (STM) studies of surface processes on graphite and Au(111) electrodes in N-methyl-N-propylpyrrolidinium bis(fluorosulfonyl)imide (Py13FSI) and N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide (Py13TFSI) ionic liquids in the absence and presence of LiTFSI salt. In both of neat ionic liquids, the intercalation of cations and exfoliation of HOPG layers occur during cathodic excursion. However, the surface decomposition of FSI anions can form an effective protection film on the surface, which suppresses the intercalation and exfoliation processes, while the surface decomposition of TFSI anions mainly causes etching of the surface, which makes the intercalation and exfoliation easier to proceed. The addition of Li salt can promote the formation of the protective film, especially in Py13FSI, and thus significantly suppress the intercalation and exfoliation processes. The discrepancies between these two ionic liquids are caused by the different anion interactions with graphite. Additionally, comparisons of the behaviors on HOPG and on Au(111) confirm that the surface processes are crucially dependent on the nature of the electrode. Trace amounts of oxygen and water can cause the formation of a film-like structure on Au(111), but show no apparent influence on HOPG.

  1. Pyrolytic graphite gauge for measuring heat flux

    NASA Technical Reports Server (NTRS)

    Bunker, Robert C. (Inventor); Ewing, Mark E. (Inventor); Shipley, John L. (Inventor)

    2002-01-01

    A gauge for measuring heat flux, especially heat flux encountered in a high temperature environment, is provided. The gauge includes at least one thermocouple and an anisotropic pyrolytic graphite body that covers at least part of, and optionally encases the thermocouple. Heat flux is incident on the anisotropic pyrolytic graphite body by arranging the gauge so that the gauge surface on which convective and radiative fluxes are incident is perpendicular to the basal planes of the pyrolytic graphite. The conductivity of the pyrolytic graphite permits energy, transferred into the pyrolytic graphite body in the form of heat flux on the incident (or facing) surface, to be quickly distributed through the entire pyrolytic graphite body, resulting in small substantially instantaneous temperature gradients. Temperature changes to the body can thereby be measured by the thermocouple, and reduced to quantify the heat flux incident to the body.

  2. Uranium Oxide Aerosol Transport in Porous Graphite

    SciTech Connect

    Blanchard, Jeremy; Gerlach, David C.; Scheele, Randall D.; Stewart, Mark L.; Reid, Bruce D.; Gauglitz, Phillip A.; Bagaasen, Larry M.; Brown, Charles C.; Iovin, Cristian; Delegard, Calvin H.; Zelenyuk, Alla; Buck, Edgar C.; Riley, Brian J.; Burns, Carolyn A.

    2012-01-23

    The objective of this paper is to investigate the transport of uranium oxide particles that may be present in carbon dioxide (CO2) gas coolant, into the graphite blocks of gas-cooled, graphite moderated reactors. The transport of uranium oxide in the coolant system, and subsequent deposition of this material in the graphite, of such reactors is of interest because it has the potential to influence the application of the Graphite Isotope Ratio Method (GIRM). The GIRM is a technology that has been developed to validate the declared operation of graphite moderated reactors. GIRM exploits isotopic ratio changes that occur in the impurity elements present in the graphite to infer cumulative exposure and hence the reactor’s lifetime cumulative plutonium production. Reference Gesh, et. al., for a more complete discussion on the GIRM technology.

  3. METHOD FOR COATING GRAPHITE WITH METALLIC CARBIDES

    DOEpatents

    Steinberg, M.A.

    1960-03-22

    A method for producing refractory coatings of metallic carbides on graphite was developed. In particular, the graphite piece to be coated is immersed in a molten solution of 4 to 5% by weight of zirconium, titanium, or niobium dissolved in tin. The solution is heated in an argon atmosphere to above 1400 deg C, whereby the refractory metal reacts with the surface of the graphite to form a layer of metalic carbide. The molten solution is cooled to 300 to 400 deg C, and the graphite piece is removed. Excess tin is wiped from the graphite, which is then heated in vacuum to above 2300 deg C. The tin vaporizes from the graphite surface, leaving the surface coated with a tenacious layer of refractory metallic carbide.

  4. Removal of carbon-14 from irradiated graphite

    NASA Astrophysics Data System (ADS)

    Dunzik-Gougar, Mary Lou; Smith, Tara E.

    2014-08-01

    Approximately 250,000 tonnes of irradiated graphite waste exists worldwide and that quantity is expected to increase with decommissioning of Generation II reactors and deployment of Generation IV gas-cooled, graphite moderated reactors. This situation indicates the need for a graphite waste management strategy. On of the isotopes of great concern for long-term disposal of irradiated graphite is carbon-14 (14C), with a half-life of 5730 years. Study of irradiated graphite from some nuclear reactors indicates 14C is concentrated on the outer 5 mm of the graphite structure. The aim of the research presented here is to develop a practical method by which 14C can be removed. In parallel with these efforts, the same irradiated graphite material is being characterized to identify the chemical form of 14C in irradiated graphite. A nuclear-grade graphite, NBG-18, and a high-surface-area graphite foam, POCOFoam®, were exposed to liquid nitrogen (to increase the quantity of 14C precursor) and neutron-irradiated (1013 neutrons/cm2/s). During post-irradiation thermal treatment, graphite samples were heated in the presence of an inert carrier gas (with or without the addition of an oxidant gas), which carries off gaseous products released during treatment. Graphite gasification occurs via interaction with adsorbed oxygen complexes. Experiments in argon only were performed at 900 °C and 1400 °C to evaluate the selective removal of 14C. Thermal treatment also was performed with the addition of 3 and 5 vol% oxygen at temperatures 700 °C and 1400 °C. Thermal treatment experiments were evaluated for the effective selective removal of 14C. Lower temperatures and oxygen levels correlated to more efficient 14C removal.

  5. METHOD FOR COATING GRAPHITE WITH NIOBIUM CARBIDE

    DOEpatents

    Kane, J.S.; Carpenter, J.H.; Krikorian, O.H.

    1962-01-16

    A method is given for coating graphite with a hard, tenacious layer of niobium carbide up to 30 mils or more thick. The method makes use of the discovery that niobium metal, if degassed and heated rapidly below the carburization temperature in contact with graphite, spreads, wets, and penetrates the graphite without carburization. The method includes the obvious steps of physically contacting niobium powders or other physical forms of niobium with graphite, degassing the assembly below the niobium melting point, e.g., 1400 deg C, heating to about 2200 to 2400 deg C within about 15 minutes while outgassing at a high volume throughput, and thereafter carburizing the niobium. (AEC)

  6. NGNP Graphite Selection and Acquisition Strategy

    SciTech Connect

    Burchell, T.; Bratton, R.; Windes, W.

    2007-09-30

    The nuclear graphite (H-451) previously used in the United States for High-Temperature Reactors (HTRs) is no longer available. New graphites have been developed and are considered suitable candidates for the Next-Generation Nuclear Plant (NGNP). A complete properties database for these new, available, candidate grades of graphite must be developed to support the design and licensing of NGNP core components. Data are required for the physical, mechanical (including radiation-induced creep), and oxidation properties of graphites. Moreover, the data must be statistically sound and take account of in-billet, between billets, and lot-to-lot variations of properties. These data are needed to support the ongoing development1 of the risk-derived American Society of Mechanical Engineers (ASME) graphite design code (a consensus code being prepared under the jurisdiction of the ASME by gas-cooled reactor and NGNP stakeholders including the vendors). The earlier Fort St. Vrain design of High-Temperature Reactor (HTRs) used deterministic performance models for H-451, while the NGNP will use new graphite grades and risk-derived (probabilistic) performance models and design codes, such as that being developed by the ASME. A radiation effects database must be developed for the currently available graphite materials, and this requires a substantial graphite irradiation program. The graphite Technology Development Plan (TDP)2 describes the data needed and the experiments planned to acquire these data in a timely fashion to support NGNP design, construction, and licensing. The strategy for the selection of appropriate grades of graphite for the NGNP is discussed here. The final selection of graphite grades depends upon the chosen reactor type and vendor because the reactor type (pebble bed or prismatic block) has a major influence on the graphite chosen by the designer. However, the time required to obtain the needed irradiation data for the selected NGNP graphite is sufficiently

  7. Nickel coated graphite fiber conductive composites

    SciTech Connect

    Evans, R.E.; Hall, D.E.; Luxon, B.A.

    1986-07-01

    Nickel coated graphite (NCG) fiber, consisting of a thin continuous plating of high purity nickel over an aerospace-grade graphite core, offers performance added features by combining the lightweight and high structural reinforcement of graphite fiber with the thermal and electrical conductivity of nickel. These NCG filaments, which are composite constructions in their own right, can be processed and impregnated with thermosetting or thermoplastic resins in the same manner that graphite fiber tows are processed and impregnated to produce roving, tape or fabric prepreg. Therefore, NCG fibers can be readily integrated into structural laminate assemblies using established composites-manufacturing practices.

  8. Nanostructured carbon films with oriented graphitic planes

    SciTech Connect

    Teo, E. H. T.; Kalish, R.; Kulik, J.; Kauffmann, Y.; Lifshitz, Y.

    2011-03-21

    Nanostructured carbon films with oriented graphitic planes can be deposited by applying energetic carbon bombardment. The present work shows the possibility of structuring graphitic planes perpendicular to the substrate in following two distinct ways: (i) applying sufficiently large carbon energies for deposition at room temperature (E>10 keV), (ii) utilizing much lower energies for deposition at elevated substrate temperatures (T>200 deg. C). High resolution transmission electron microscopy is used to probe the graphitic planes. The alignment achieved at elevated temperatures does not depend on the deposition angle. The data provides insight into the mechanisms leading to the growth of oriented graphitic planes under different conditions.

  9. DNA intercalators in cancer therapy: organic and inorganic drugs and their spectroscopic tools of analysis.

    PubMed

    Wheate, Nial J; Brodie, Craig R; Collins, J Grant; Kemp, Sharon; Aldrich-Wright, Janice R

    2007-06-01

    Since the discovery of the DNA intercalation process by Lerman in 1961 thousands of organic, inorganic octahedral (particularly ruthenium(II) and rhodium(III)) and square-planar (particularly platinum(II)) compounds have been developed as potential anticancer agents and diagnostic agents. The design and synthesis of new drugs is focused on bis-intercalators which have two intercalating groups linked via a variety of ligands, and synergistic drugs, which combine the anticancer properties of intercalation with other functionalities, such as covalent binding or boron-cages (for radiation therapy). Advances in spectroscopic techniques mean that the process of DNA intercalation can be examined in far greater detail than ever before, yielding important information on structure-activity relationships. In this review we examine the history and development of DNA intercalators as anticancer agents and advances in the analysis of DNA-drug interactions.

  10. Anticorrelation of Shubnikov-deHaas amplitudes and negative magnetoresistance magnitudes in intercalated pitch based graphite fibers

    NASA Technical Reports Server (NTRS)

    Woollam, John A.; Natarajan, V.; Brandt, Bruce

    1986-01-01

    In pitch based carbon fibers at low temperatures, simultaneous presence of a negative magnetoresistance and the Shubnikov-deHaas effect are found. The strengths of these effects correlate inversely. These results can be understood in terms of the amount of order vs disorder in the fiber, as described by Guigon and Oberlin from structural studies.

  11. Magnetic field effects on superconductivity in alkali metal intercalates of MoS2

    NASA Technical Reports Server (NTRS)

    Woollam, J. A.; Flood, D. J.; Wagoner, D. E.; Somoano, R. B.; Rembaum, A.

    1972-01-01

    The effects of a magnetic field on the superconducting transition in MoS2 intercalated with potassium and sodium were studied. It was found that the potassium intercalated MoS2 has better properties in a magnetic field. In zero magnetic field the transition to superconductivity begins near 6.4 K. Diagrams of the basic circuitry for superconducting transition studies, and charts showing critical magnetic field versus critical temperature for the intercalated MoS2 are included.

  12. High field superconductivity in alkali metal intercalates of MoS2

    NASA Technical Reports Server (NTRS)

    Woollam, J. A.; Flood, D. J.; Wagoner, D. E.; Somoano, R. B.; Rembaum, A.

    1973-01-01

    In the search for better high temperature, high critical field superconductors, a class of materials was found which have layered structures and can be intercalated with various elements and compounds. Since a large number of compounds can be formed, intercalation provides a method of control of superconducting properties. They also provide the possible medium for excitonic superconductivity. Results of magnetic field studies are presented on alkali metal (Na, K, Rb, and Cs) intercalated MoS2 (2H polymorph).

  13. Synthesis of ACECLOFENAC/HYDROXYPROPYL-β-CYCLODEXTRIN Intercalated Layered Double Hydroxides and Controlled Release Properties

    NASA Astrophysics Data System (ADS)

    Li, Shifeng; Shen, Yanming; Liu, Dongbin; Fan, Lihui; Wu, Keke; Xiao, Min

    2013-04-01

    Aceclofenac (AC)/hydroxypropyl-β-cyclodextrin (HP-β-CD) complex intercalated layered double hydroxides (LDHs) have been synthesized by reconstruction method. X-ray diffraction, Fourier transform infrared and thermal gravimetric analyses indicated a successful intercalation of AC/HP-β-CD complex into the LDHs gallery. The AC release properties were also studied in different pH values buffer solution. The results indicate that the AC/HP-β-CD intercalated LDH has a potential application in drug delivery agent.

  14. Graphitized-carbon fiber/carbon char fuel

    SciTech Connect

    Cooper, John F.

    2007-08-28

    A method for recovery of intact graphitic fibers from fiber/polymer composites is described. The method comprises first pyrolyzing the graphite fiber/polymer composite mixture and then separating the graphite fibers by molten salt electrochemical oxidation.

  15. Proceedings of the conference on electrochemistry of carbon allotropes: Graphite, fullerenes and diamond

    SciTech Connect

    Kinoshita, K.; Scherson, D.

    1998-02-01

    This conference provided an opportunity for electrochemists, physicists, materials scientists and engineers to meet and exchange information on different carbon allotropes. The presentations and discussion among the participants provided a forum to develop recommendations on research and development which are relevant to the electrochemistry of carbon allotropes. The following topics which are relevant to the electrochemistry of carbon allotropes were addressed: Graphitized and disordered carbons, as Li-ion intercalation anodes for high-energy-density, high-power-density Li-based secondary batteries; Carbons as substrate materials for catalysis and electrocatalysis; Boron-doped diamond film electrodes; and Electrochemical characterization and electrosynthesis of fullerenes and fullerene-type materials. Abstracts of the presentations are presented.

  16. The correlation between the surface chemistry and the performance of Li-carbon intercalation anodes for rechargeable rocking-chair type batteries

    SciTech Connect

    Aurbach, D.; Ein-Eli, Y.; Chusid, O. . Dept. of Chemistry); Carmeli, Y.; Babai, M.; Yamin, H. . Battery Div.)

    1994-03-01

    The correlation between the electrochemical properties of Li carbon intercalation electrodes and their surface chemistry in solutions was investigated. The carbons investigated were primarily graphite and petroleum coke, and the solvent systems included methyl formate (MF), propylene and ethylene carbonates, ethers and their mixtures. The surface chemistry of the electrodes was studied using mainly diffuse reflectance Fourier transform infrared spectroscopy. The following aspects were studied: (1) the effect of temperature on the buildup of the surface films; (2) the effect of additives (e.g., CO[sub 2], crown ethers), (3) the behavior when the passive layer is built in one solution followed by cycling in another; and (4) the effect of cosolvent in MF solutions. The results obtained further prove that the electrochemical behavior of these systems is surface film controlled. An understanding of the surface chemistry of these electrodes enables judicious optimization of carbon-solution systems for use in rechargeable Li batteries.

  17. Structure and physical properties of gallium selenide laser-intercalated with nickel

    NASA Astrophysics Data System (ADS)

    Pokladok, N. T.; Grygorchak, I. I.; Lukiyanets, B. A.; Popovich, D. I.

    2007-04-01

    Intercalated crystals of indium and gallium selenide are prepared. It is shown that laser intercalation of nickel into GaSe samples leads to a giant magnetoresistive effect whose magnitude and sign depend on the concentration of the guest component. The giant magnetoresistive effect in the InSe intercalation compounds is considerably weaker and does not exceed 5%. The experimental data obtained are explained in terms of magnetic delocalization (localization) of charge carriers with the participation of states of intercalated magnetically active atoms in the vicinity of the Fermi level.

  18. Tuning the properties of polymer bulk heterojunction solar cells by adjusting fullerene size to control intercalation.

    PubMed

    Cates, Nichole C; Gysel, Roman; Beiley, Zach; Miller, Chad E; Toney, Michael F; Heeney, Martin; McCulloch, Iain; McGehee, Michael D

    2009-12-01

    We demonstrate that intercalation of fullerene derivatives between the side chains of conjugated polymers can be controlled by adjusting the fullerene size and compare the properties of intercalated and nonintercalated poly(2,5-bis(3-hexadecylthiophen-2-yl)thieno[3,2-b]thiophene (pBTTT):fullerene blends. The intercalated blends, which exhibit optimal solar-cell performance at 1:4 polymer:fullerene by weight, have better photoluminescence quenching and lower absorption than the nonintercalated blends, which optimize at 1:1. Understanding how intercalation affects performance will enable more effective design of polymer:fullerene solar cells.

  19. Structure and thermal decomposition of sulfated β-cyclodextrin intercalated in a layered double hydroxide

    NASA Astrophysics Data System (ADS)

    Wang, Ji; Wei, Min; Rao, Guoying; Evans, David G.; Duan, Xue

    2004-01-01

    The sodium salt of hexasulfated β-cyclodextrin has been synthesized and intercalated into a magnesium-aluminum layered double hydroxide by ion exchange. The structure, composition and thermal decomposition behavior of the intercalated material have been studied by variable temperature X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), inductively coupled plasma emission spectroscopy (ICP), and thermal analysis (TG-DTA) and a model for the structure has been proposed. The thermal stability of the intercalated sulfated β-cyclodextrin is significantly enhanced compared with the pure form before intercalation.

  20. The action of macrosounds on graphite ore and derived products

    NASA Technical Reports Server (NTRS)

    Bradeteanu, C.; Dragan, O.

    1974-01-01

    A suspension of graphite ore, floated graphite, and the gangue left over from flotation were subjected to the action of macrosounds under determinant conditions. The following was found: (1) The graphite ore undergoes an efficient settling action. (2) The floated graphite is strongly crushed down to the dimensions of colloidal graphite. (3) The gangue left over from flotation can be further processed to recuperate graphite from its nuclei.

  1. Resin/graphite fiber composites

    NASA Technical Reports Server (NTRS)

    Cavano, P. J.; Jones, R. J.; Vaughan, R. W.

    1972-01-01

    High temperature resin matrices suitable for use in advanced graphite fiber composites for jet engine applications were evaluated. A series of planned, sequential screening experiments with resin systems in composite form were performed to reduce the number of candidates to a single A-type polyimide resin that repetitively produced void-free, high strength and modulus composites acceptable for use in the 550 F range for 1000 hours. An optimized processing procedure was established for this system. Extensive mechanical property studies characterized this single system, at room temperature, 500 F, 550 F and 600 F, for various exposure times.

  2. Intercalation and de-intercalation pathway of proflavine through the minor and major grooves of DNA: roles of water and entropy.

    PubMed

    Sasikala, Wilbee D; Mukherjee, Arnab

    2013-05-07

    DNA intercalation is a clinically relevant biophysical process due to its potential to inhibit the growth and survival of tumor cells and microbes through the arrest of the transcription and replication processes. Extensive kinetic and thermodynamic studies have followed since the discovery of the intercalative binding mode. However, the molecular mechanism and the origin of the thermodynamic and kinetic profile of the process are still not clear. Here we have constructed the free energy landscape of intercalation, de-intercalation and dissociation from both the major and minor grooves of DNA using extensive all-atom metadynamics simulations, capturing both the free energy barriers and stability in close agreement with fluorescence kinetic experiments. In the intercalated state, an alternate orientation of proflavine is found with an almost equal stability compared to the crystal orientation, however, separated by a 5.0 kcal mol(-1) barrier that decreases as the drug approaches the groove edges. This study provides a comprehensive picture in comparison with experiments, which indicates that the intercalation and de-intercalation of proflavine happen through the major groove side, although the effective intercalation barrier increases because the path of intercalation goes through the stable (abortive) minor groove bound state, making the process a millisecond long one in excellent agreement with the experiments. The molecular origin of the higher barrier for the intercalation from the minor groove side is attributed to the desolvation energy of DNA and the loss of entropy, while the barrier from the major groove, in the absence of desolvation energy, is primarily entropic.

  3. Analysis of Wigner energy release process in graphite stack of shut-down uranium-graphite reactor

    NASA Astrophysics Data System (ADS)

    Bespala, E. V.; Pavliuk, A. O.; Kotlyarevskiy, S. G.

    2015-10-01

    Data, which finding during thermal differential analysis of sampled irradiated graphite are presented. Results of computational modeling of Winger energy release process from irradiated graphite staking are demonstrated. It's shown, that spontaneous combustion of graphite possible only in adiabatic case.

  4. Li(V0.5Ti0.5)S2 as a 1 V lithium intercalation electrode

    PubMed Central

    Clark, Steve J.; Wang, Da; Armstrong, A. Robert; Bruce, Peter G.

    2016-01-01

    Graphite, the dominant anode in rechargeable lithium batteries, operates at ∼0.1 V versus Li+/Li and can result in lithium plating on the graphite surface, raising safety concerns. Titanates, for example, Li4Ti5O12, intercalate lithium at∼1.6 V versus Li+/Li, avoiding problematic lithium plating at the expense of reduced cell voltage. There is interest in 1 V anodes, as this voltage is sufficiently high to avoid lithium plating while not significantly reducing cell potential. The sulfides, LiVS2 and LiTiS2, have been investigated as possible 1 V intercalation electrodes but suffer from capacity fading, large 1st cycle irreversible capacity or polarization. Here we report that the 50/50 solid solution, Li1+x(V0.5Ti0.5)S2, delivers a reversible capacity to store charge of 220 mAhg−1 (at 0.9 V), 99% of theoretical, at a rate of C/2, retaining 205 mAhg−1 at C-rate (92% of theoretical). Rate capability is excellent with 200 mAhg−1 at 3C. C-rate is discharge in 1 h. Polarization is low, 100 mV at C/2. To the best of our knowledge, the properties/performances of Li(V0.5Ti0.5)S2 exceed all previous 1 V electrodes. PMID:26996753

  5. Fluorinated graphite fibers as a new engineering material: Promises and challenges

    NASA Technical Reports Server (NTRS)

    Hung, Ching-Cheh; Long, Martin

    1989-01-01

    Pitch based graphitized carbon fibers with electrical resistivity of 300 micro-Ohm/cm were brominated and partially debrominated to 18 percent bromine at room temperature, and then fluorinated at 300 to 450 C, either continuously or intermittently for several cycles. In addition, on fluorine and titanium fluoride intercalated fiber sample was fluorinated at 270 C from the same fiber source. The mass and conductivity of the brominated-debrominated then fluorinated fibers (with fluorine-to-carbon atom ratio of 0.54 or higher) stabilized at room temperature air in a few days. However, at 200 C, these values decreased rapidly and then more slowly, throughout a 2-week test period. The electrically insulative or semiconductive fibers were found to be compatible with epoxy and have the fluorine-to-carbon atom ratio of 0.65 to 0.68, thermal conductivity of 5 to 24 W/m-K, electrical resistivity of 10(exp 4) to 10(exp 11) Ohm/cm, tensile strength of 70 to 150 ksi, Young's modulus of 20 to 30 msi, and CTE (coefficient of thermal expansion) values of 7 ppm/deg C. Data of these physical property values are preliminary. However, it is concluded that these physical properties can be tailor-made. They depend largely on the fluorine content of the final products and the intercalant in the fibers before fluorination, and, to a smaller extent, on the fluorination temperature histogram.

  6. Surface structure of lithiated graphite by X-ray photoelectron diffraction

    NASA Astrophysics Data System (ADS)

    Lee, Choong Man; Yang, S.-H.; Mun, B.-J.; Ross, Philip N.

    2001-04-01

    The surface composition and structure of a stage-one lithium intercalation compound (Li-GIC) was studied by X-ray photoelectron diffraction (XPD) from Li 1s and C 1s core levels. The Li-GIC was prepared in situ by vapor phase intercalation of lithium into highly oriented pyrolitic graphite (HOPG) in an ultra-high vacuum system. Stage-one Li-GIC, LiC 6, having a characteristic golden color, was obtained using Li evaporation onto a HOPG substrate at 400 K, while a metallic lithium overlayer was observed at depositions below room temperature. XPD patterns of Li 1s and C 1s intensities as a function of the polar emission angle were obtained at a fixed photon energy of 1253.6 eV. The experimental XPD patterns on the HOPG and the stage-one Li-GIC were both in quite good agreement with calculated XPD patterns based on Rehr-Albers separable representation for scattering of the emitted photoelectrons. The structural model for the surface of the Li-GIC producing the best fit to the experimental data has the bulk LiC 6 lattice with surface termination in the graphene plane.

  7. Copper-Intercalated Birnessite as a Water Oxidation Catalyst.

    PubMed

    Thenuwara, Akila C; Shumlas, Samantha L; Attanayake, Nuwan H; Cerkez, Elizabeth B; McKendry, Ian G; Frazer, Laszlo; Borguet, Eric; Kang, Qing; Zdilla, Michael J; Sun, Jianwei; Strongin, Daniel R

    2015-11-24

    We report a synthetic method to increase the catalytic activity of birnessite toward water oxidation by intercalating copper in the interlayer region of the layered manganese oxide. Intercalation of copper, verified by XRD, XPS, ICP, and Raman spectroscopy, was accomplished by exposing a suspension of birnessite to a Cu(+)-bearing precursor molecule that underwent disproportionation in solution to yield Cu(0) and Cu(2+). Electrocatalytic studies showed that the Cu-modified birnessite exhibited an overpotential for water oxidation of ∼490 mV (at 10 mA/cm(2)) and a Tafel slope of 126 mV/decade compared to ∼700 mV (at 10 mA/cm(2)) and 240 mV/decade, respectively, for birnessite without copper. Impedance spectroscopy results suggested that the charge transfer resistivity of the Cu-modified sample was significantly lower than Cu-free birnessite, suggesting that Cu in the interlayer increased the conductivity of birnessite leading to an enhancement of water oxidation kinetics. Density functional theory calculations show that the intercalation of Cu(0) into a layered MnO2 model structure led to a change of the electronic properties of the material from a semiconductor to a metallic-like structure. This conclusion from computation is in general agreement with the aforementioned impedance spectroscopy results. X-ray photoelectron spectroscopy (XPS) showed that Cu(0) coexisted with Cu(2+) in the prepared Cu-modified birnessite. Control experiments using birnessite that was decorated with only Cu(2+) showed a reduction in water oxidation kinetics, further emphasizing the importance of Cu(0) for the increased activity of birnessite. The introduction of Cu(0) into the birnessite structure also increased the stability of the electrocatalyst. At a working current of 2 mA, the Cu-modified birnessite took ∼3 times longer for the overpotential for water oxdiation to increase by 100 mV compared to when Cu was not present in the birnessite.

  8. Inhibition of Oxidation in Nuclear Graphite

    SciTech Connect

    Phil Winston; James W. Sterbentz; William E. Windes

    2013-10-01

    Graphite is a fundamental material of high temperature gas cooled nuclear reactors, providing both structure and neutron moderation. Its high thermal conductivity, chemical inertness, thermal heat capacity, and high thermal structural stability under normal and off normal conditions contribute to the inherent safety of these reactor designs. One of the primary safety issues for a high temperature graphite reactor core is the possibility of rapid oxidation of the carbon structure during an off normal design basis event where an oxidizing atmosphere (air ingress) can be introduced to the hot core. Although the current Generation IV high temperature reactor designs attempt to mitigate any damage caused by a postualed air ingress event, the use of graphite components that inhibit oxidation is a logical step to increase the safety of these reactors. Recent experimental studies of graphite containing between 5.5 and 7 wt% boron carbide (B4C) indicate that oxidation is dramatically reduced even at prolonged exposures at temperatures up to 900°C. The proposed addition of B4C to graphite components in the nuclear core would necessarily be enriched in B-11 isotope in order to minimize B-10 neutron absorption and graphite swelling. The enriched boron can be added to the graphite during billet fabrication. Experimental oxidation rate results and potential applications for borated graphite in nuclear reactor components will be discussed.

  9. Mineral Resource of the Month: Graphite

    USGS Publications Warehouse

    Olson, Donald W.

    2008-01-01

    Graphite, a grayish black opaque mineral with a metallic luster, is one of four forms of pure crystalline carbon (the others are carbon nanotubes, diamonds and fullerenes). It is one of the softest minerals and it exhibits perfect basal (one-plane) cleavage. Graphite is the most electrically and thermally conductive of the nonmetals, and it is chemically inert.

  10. Tire containing thermally exfoliated graphite oxide

    NASA Technical Reports Server (NTRS)

    Prud'homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor)

    2011-01-01

    A tire, tire lining or inner tube, containing a polymer composite, made of at least one rubber and/or at least one elastomer and a modified graphite oxide material, which is a thermally exfoliated graphite oxide with a surface area of from about 300 sq m/g to 2600 sq m/g.

  11. Lithium intercalation reaction into the Keggin type polyoxomolybdates

    NASA Astrophysics Data System (ADS)

    Sonoyama, Noriyuki; Suganuma, Yoshiaki; Kume, Tomohiro; Quan, Zhen

    The electrochemical property of Keggin type hetero polyoxomolybdate K 3[PMo 12O 40] (KPM) as the cathode electrode material for lithium battery was examined. KPM showed charge-discharge performance in the potential region from 4.2 V to 1.5 V with capacity of over 200 mAh g -1. From the result of the ex situ XRD measurement, it is presumed that the electrochemical reaction of KPM proceeds via the lithium (de-)intercalation. The cycle performance of KPM is largely dependent on the charge-discharge potential range. The capacity fade caused by deep discharging seems to be concerned to the < to ® isomerization of KPM.

  12. Intercalation of small hydrophobic molecules in lipid bilayers containing cholesterol

    SciTech Connect

    Worcester, D.L.; Hamacher, K.; Kaiser, H.; Kulasekere, R.; Torbet, J.

    1994-12-31

    Partitioning of small hydrophobic molecules into lipid bilayers containing cholesterol has been studied using the 2XC diffractometer at the University of Missouri Research Reactor. Locations of the compounds were determined by Fourier difference methods with data from both deuterated and undeuterated compounds introduced into the bilayers from the vapor phase. Data fitting procedures were developed for determining how well the compounds were localized. The compounds were found to be localized in a narrow region at the center of the hydrophobic layer, between the two halves of the bilayer. The structures are therefore intercalated structures with the long axis of the molecules in the plane of the bilayer.

  13. Hydrogen storage in graphite nanofibers

    SciTech Connect

    Park, C.; Tan, C.D.; Hidalgo, R.; Baker, R.T.K.; Rodriguez, N.M.

    1998-08-01

    Graphite nanofibers (GNF) are a type of material that is produced by the decomposition of carbon containing gases over metal catalyst particles at temperatures around 600 C. These molecularly engineered structures consist of graphene sheets perfectly arranged in a parallel, perpendicular or at angle orientation with respect to the fiber axis. The most important feature of the material is that only edges are exposed. Such an arrangement imparts the material with unique properties for gas adsorption because the evenly separated layers constitute the most ordered set of nanopores that can accommodate an adsorbate in the most efficient manner. In addition, the non-rigid pore walls can also expand so as to accommodate hydrogen in a multilayer conformation. Of the many varieties of structures that can be produced the authors have discovered that when gram quantities of a selected number of GNF are exposed to hydrogen at pressures of {approximately} 2,000 psi, they are capable of adsorbing and storing up to 40 wt% of hydrogen. It is believed that a strong interaction is established between hydrogen and the delocalized p-electrons present in the graphite layers and therefore a new type of chemistry is occurring within these confined structures.

  14. SIMPLIFIED SODIUM GRAPHITE REACTOR SYSTEM

    DOEpatents

    Dickinson, R.W.

    1963-03-01

    This patent relates to a nuclear power reactor comprising a reactor vessel, shielding means positioned at the top of said vessel, means sealing said reactor vessel to said shielding means, said vessel containing a quantity of sodium, a core tank, unclad graphite moderator disposed in said tank, means including a plurality of process tubes traversing said tank for isolating said graphite from said sodium, fuel elements positioned in said process tubes, said core tank being supported in spaced relation to the walls and bottom of said reactor vessel and below the level of said sodium, neutron shielding means positioned adjacent said core tank between said core tank and the walls of said vessel, said neutron shielding means defining an annuiar volume adjacent the inside wall of said reactor vessel, inlet plenum means below said core tank for providing a passage between said annular volume and said process tubes, heat exchanger means removably supported from the first-named shielding means and positioned in said annular volume, and means for circulating said sodium over said neutron shielding means down through said heat exchanger, across said inlet plenum and upward through said process tubes, said last-named means including electromagnetic pumps located outside said vessel and supported on said vessel wall between said heat exchanger means and said inlet plenum means. (AEC)

  15. Status of Graphite Oxidation Work

    SciTech Connect

    Rebecca Smith

    2010-05-01

    Data were developed to compare the extent of structural damage associated with high temperature exposure to an air leak. Two materials, NBG-18 graphite and unpurified PCEA graphite have been tested as of this report. The scope was limited to isothermal oxidation at a single temperature, 750°C. Ambient post-oxidation compression strength testing was performed for three levels of burn off (1%, 5%, and 10% mass loss) for two leak scenarios: 100% air and 10% air in helium. Temperature, gas flow, and dynamic mass loss oxidation conditions were monitored and recorded for each sample. The oxidation period was controlled with flow of inert gas during the thermal ramp and upon cool down with a constant 10 liter per minute flow maintained throughout furnace operation. Compressive strengths of parallel un-oxidized samples were tested to assess the relative mass loss effects. In addition to baseline samples matching the un-oxidized dimensions of the oxidized samples, two sets of mechanically reduced samples were prepared. One set was trimmed to achieve the desired mass loss by removing an effectively uniform depth from the geometric surface of the sample. The other set was cored to produce a full penetration axial hole down the center of each sample.

  16. Development of polyphenylquinoxaline graphite composites

    NASA Technical Reports Server (NTRS)

    Hoggatt, J. T.; Hill, S. G.; Shdo, J. G.

    1974-01-01

    This exploratory program was divided into four basic tasks. The initial phase was devoted toward investigating processing variables associated with previously developed PPO resins. These polymers were derived from p-bis(phenyl glyoxalyl)benzene reacted with 3,3'-diamino benzidine and/or 3,3',4,4'-tetramino benzophenone. Four new phenyl quinoxaline polymers were synthesized and characterized in Tasks 2 and 3. These consisted of a hydroxyl group containing PPQ synthesized from 3,3'-diamino benzidine (DAB), m-bis(phenyl glyoxal)benzene and m-bis(p'-hydroxy phenyl glyoxalyl) benzene; a cyano group containing PPQ from the reaction of DAB and p-bis(p'-cyano phenoxy phenyl glyoxalyl)benzene; an end-capped block copolymer; and a polymer from the reaction of 3,3',4,4'-tetraamino benzo phenone and m-bis(phenyl glyoxalyl)benzene. The latter two polymers were chosen for composite studies in the latter two tasks of the program. Mechanical properties of the graphite reinforced PPQ composites were determined over the temperature range of +21 C to 316 C. Flexural strengths of the HMS graphite fiber composites were in excess of 8.97 X 10 to the 8th power N/sq m (130,000 psi) at +21 C (70 F) with over 50% strength retention at +316 C.

  17. Microstructural Characterization of Next Generation Nuclear Graphites

    SciTech Connect

    Karthik Chinnathambi; Joshua Kane; Darryl P. Butt; William E. Windes; Rick Ubic

    2012-04-01

    This article reports the microstructural characteristics of various petroleum and pitch based nuclear graphites (IG-110, NBG-18, and PCEA) that are of interest to the next generation nuclear plant program. Bright-field transmission electron microscopy imaging was used to identify and understand the different features constituting the microstructure of nuclear graphite such as the filler particles, microcracks, binder phase, rosette-shaped quinoline insoluble (QI) particles, chaotic structures, and turbostratic graphite phase. The dimensions of microcracks were found to vary from a few nanometers to tens of microns. Furthermore, the microcracks were found to be filled with amorphous carbon of unknown origin. The pitch coke based graphite (NBG-18) was found to contain higher concentration of binder phase constituting QI particles as well as chaotic structures. The turbostratic graphite, present in all of the grades, was identified through their elliptical diffraction patterns. The difference in the microstructure has been analyzed in view of their processing conditions.

  18. Fiber release characteristics of graphite hybrid composites

    NASA Technical Reports Server (NTRS)

    Henshaw, J.

    1980-01-01

    The paper considers different material concepts that can be fabricated of hybridized composites which demonstrate improved graphite fiber retention capability in a severe fire without significant reduction to the composite properties. More than 30 panels were fabricated for mechanical and fire tests, the details and results of which are presented. Methods of composite hybridization investigated included the addition of oxidation resistant fillers to the resin, mechanically interlocking the graphite fibers by the use of woven fabrics, and the addition of glass fibers and glass additives designed to melt and fuse the graphite fibers together. It is concluded that a woven fabric with a serving of glass around each graphite tow is by far the superior of those evaluated: not only is there a coalescing effect in each graphite layer, but there is also a definite adhesion of each layer to its neighbor.

  19. Research on graphite reinforced glass matrix composites

    NASA Technical Reports Server (NTRS)

    Bacon, J. F.; Prewo, K. M.; Thompson, E. R.

    1978-01-01

    A composite that can be used at temperatures up to 875 K with mechanical properties equal or superior to graphite fiber reinforced epoxy composites is presented. The composite system consist of graphite fiber, uniaxially or biaxially, reinforced borosilicate glass. The mechanical and thermal properties of such a graphite fiber reinforced glass composite are described, and the system is shown to offer promise as a high performance structural material. Specific properties that were measured were: a modified borosilicate glass uniaxially reinforced by Hercules HMS graphite fiber has a three-point flexural strength of 1030 MPa, a four-point flexural strength of 964 MPa, an elastic modulus of 199 GPa and a failure strain of 0.0052. The preparation and properties of similar composites with Hercules HTS, Celanese DG-102, Thornel 300 and Thornel Pitch graphite fibers are also described.

  20. Structure of different grades of nuclear graphite

    NASA Astrophysics Data System (ADS)

    Mironov, B. E.; Westwood, A. V. K.; Scott, A. J.; Brydson, R.; Jones, A. N.

    2012-07-01

    Owing to its low neutron absorption cross-section, large scattering cross section and thermal and chemical stability, graphite is a key component of operational nuclear reactors where it is used as a moderator, reflector and as major structural component for 90% of current UK nuclear plants. It is also of interest for use in developing the future high temperature gas-cooled reactors. The properties of the nuclear graphite are influenced by its structural characteristics, which change as a function of neutron irradiation, temperature and oxidation. The principal structural changes during neutron irradiation that affect the integrity and dimensions of nuclear graphite components, thereby affecting service lifetime, are that the a-axis contracts and the c-axis expands in the crystallites. Characterization of virgin graphite structure and of the damage evolution after irradiation of nuclear graphite has an important role to play in the understanding and development of materials used in current and future nuclear reactors, respectively.

  1. Microstructural characterization of next generation nuclear graphites.

    PubMed

    Karthik, Chinnathambi; Kane, Joshua; Butt, Darryl P; Windes, William E; Ubic, Rick

    2012-04-01

    This article reports the microstructural characteristics of various petroleum and pitch based nuclear graphites (IG-110, NBG-18, and PCEA) that are of interest to the next generation nuclear plant program. Bright-field transmission electron microscopy imaging was used to identify and understand the different features constituting the microstructure of nuclear graphite such as the filler particles, microcracks, binder phase, rosette-shaped quinoline insoluble (QI) particles, chaotic structures, and turbostratic graphite phase. The dimensions of microcracks were found to vary from a few nanometers to tens of microns. Furthermore, the microcracks were found to be filled with amorphous carbon of unknown origin. The pitch coke based graphite (NBG-18) was found to contain higher concentration of binder phase constituting QI particles as well as chaotic structures. The turbostratic graphite, present in all of the grades, was identified through their elliptical diffraction patterns. The difference in the microstructure has been analyzed in view of their processing conditions.

  2. Model experiments of superlubricity of graphite

    NASA Astrophysics Data System (ADS)

    Dienwiebel, Martin; Pradeep, Namboodiri; Verhoeven, Gertjan S.; Zandbergen, Henny W.; Frenken, Joost W. M.

    2005-02-01

    Graphite is known to be a good solid lubricant. The low-friction behavior is traditionally ascribed to the low resistance to shear. We have recently observed that the ultra-low friction found in friction force microscopy experiments on graphite is due to a effect called superlubricity [M. Dienwiebel, G. S. Verhoeven, N. Pradeep, J.W.M. Frenken, J.A. Heimberg, H.W. Zandbergen, Phys. Rev. Lett. 92 (2004) 126101]. Here, we provide additional experimental evidence that superlubricity has been taken place between a small graphite flake attached to the scanning tip and the graphite surface. Finally, we speculate about the significance of this for the lubricating properties of graphite.

  3. Graphene-based materials via benzidine-assisted exfoliation and reduction of graphite oxide and their electrochemical properties

    NASA Astrophysics Data System (ADS)

    Vermisoglou, E. C.; Giannakopoulou, T.; Romanos, G.; Boukos, N.; Psycharis, V.; Lei, C.; Lekakou, C.; Petridis, D.; Trapalis, C.

    2017-01-01

    Benzidine, a compound bearing aromatic rings and terminal amino groups, was employed for the intercalation and simultaneous reduction of graphite oxide (GO). The aromatic diamine can be intercalated into GO as follows: (1) by grafting with the epoxy groups of GO, (2) by hydrogen bonding with the oxygen containing groups of GO. Stacking between benzidine aromatic rings and unoxidized domains of GO may occur through π-π interaction. The role of benzidine is influenced by pH conditions and the weight ratio GO/benzidine. Two weight ratios were tested i.e. 1:2 and 1:3. Under strong alkaline conditions through K2CO3 addition (pH ∼10.4-10.6) both intercalation and reduction of GO via amino groups occur, while under strong acidic conditions through HCl addition (pH ∼1.4-2.2) π-π stacking is preferred. When no base or acid is added (pH ∼5.2) and the weight ratio is 1:2, there are indications that reduction and π-π stacking occur, while at a GO/benzidine weight ratio 1:3 intercalation via amino groups and reduction seem to dominate. The aforementioned remarks render benzidine a multifunctional tool towards production of reduced graphene oxide. The effect of pH conditions and the GO/benzidine weight ratio on the quality and the electrochemical properties of the produced graphene-based materials were investigated. Cyclic voltammetry measurements using three-electrode cell and KCl aqueous solution as an electrolyte gave specific capacitance values up to ∼178 F/g. When electric double-layer capacitors (EDLC) were fabricated from these materials, the maximum capacitance in organic electrolyte i.e., tetraethyl ammonium tetrafluoroborate (TEABF4) in polycarbonate (PC) was ∼29 F/g.

  4. AGC-2 Graphite Preirradiation Data Analysis Report

    SciTech Connect

    William Windes; W. David Swank; David Rohrbaugh; Joseph Lord

    2013-08-01

    This report described the specimen loading order and documents all pre-irradiation examination material property measurement data for the graphite specimens contained within the second Advanced Graphite Capsule (AGC-2) irradiation capsule. The AGC-2 capsule is the second in six planned irradiation capsules comprising the Advanced Graphite Creep (AGC) test series. The AGC test series is used to irradiate graphite specimens allowing quantitative data necessary for predicting the irradiation behavior and operating performance of new nuclear graphite grades to be generated which will ascertain the in-service behavior of the graphite for pebble bed and prismatic Very High Temperature Reactor (VHTR) designs. Similar to the AGC-1 specimen pre-irradiation examination report, material property tests were conducted on specimens from 18 nuclear graphite types but on an increased number of specimens (512) prior to loading into the AGC-2 irradiation assembly. All AGC-2 specimen testing was conducted at Idaho National Laboratory (INL) from October 2009 to August 2010. This report also details the specimen loading methodology for the graphite specimens inside the AGC-2 irradiation capsule. The AGC-2 capsule design requires “matched pair” creep specimens that have similar dose levels above and below the neutron flux profile mid-plane to provide similar specimens with and without an applied load. This document utilized the neutron flux profile calculated for the AGC-2 capsule design, the capsule dimensions, and the size (length) of the selected graphite and silicon carbide samples to create a stacking order that can produce “matched pairs” of graphite samples above and below the AGC-2 capsule elevation mid-point to provide specimens with similar neutron dose levels.

  5. Modeling Fission Product Sorption in Graphite Structures

    SciTech Connect

    Szlufarska, Izabela; Morgan, Dane; Allen, Todd

    2013-04-08

    The goal of this project is to determine changes in adsorption and desorption of fission products to/from nuclear-grade graphite in response to a changing chemical environment. First, the project team will employ principle calculations and thermodynamic analysis to predict stability of fission products on graphite in the presence of structural defects commonly observed in very high- temperature reactor (VHTR) graphites. Desorption rates will be determined as a function of partial pressure of oxygen and iodine, relative humidity, and temperature. They will then carry out experimental characterization to determine the statistical distribution of structural features. This structural information will yield distributions of binding sites to be used as an input for a sorption model. Sorption isotherms calculated under this project will contribute to understanding of the physical bases of the source terms that are used in higher-level codes that model fission product transport and retention in graphite. The project will include the following tasks: Perform structural characterization of the VHTR graphite to determine crystallographic phases, defect structures and their distribution, volume fraction of coke, and amount of sp2 versus sp3 bonding. This information will be used as guidance for ab initio modeling and as input for sorptivity models; Perform ab initio calculations of binding energies to determine stability of fission products on the different sorption sites present in nuclear graphite microstructures. The project will use density functional theory (DFT) methods to calculate binding energies in vacuum and in oxidizing environments. The team will also calculate stability of iodine complexes with fission products on graphite sorption sites; Model graphite sorption isotherms to quantify concentration of fission products in graphite. The binding energies will be combined with a Langmuir isotherm statistical model to predict the sorbed concentration of fission

  6. Modelleing the Multiaxial Strength of Nuclear Graphite

    SciTech Connect

    Burchell, Timothy D; Yahr, Terry; Battiste, Rick

    2006-01-01

    The core of a prismatic High Temperature Reactor (HTR) is constructed from an array of nuclear graphite components including replaceable fuel blocks, replaceable and permanent moderator blocks, and core support posts. Similarly, the core of a Pebble Bed Reactor is confined by large graphite blocks which define the (annular) core geometry. In both HTR designs (prismatic and pebble bed) the large graphite components act as neutron moderator and reflector as well as providing mechanical support to the active core. During reactor operation the graphite components of the core are subjected to complex stress states arising from structural loads, thermal gradients, neutron irradiation damage, and seismic events. Structural design of HTR cores requires that the designer have a suitable theory of failure. Both deterministic (e.g. maximum principal stress theory) and probabilistic (e.g., Weibull failure theory) have been considered as candidates. To test candidate theories a multiaxial testing program was conducted at Oak Ridge National Laboratory on grade H-451 graphite, the fuel element and moderator graphite used in the Fort St. Vrain high temperature reactor in the USA. Large test specimens ({approx}27 cm length) were subjected to combined axial stress (both tension and compression) and internal pressure. A total of 59 specimens were tested at 9 stress ratios in the first and fourth stress quadrants. In a parallel effort a physically based fracture model of graphite was developed. The model used a fracture mechanics based failure criteria and has been shown to predict the tensile failure probability of several graphites of widely ranging texture. Here we report the basis and performance of the fracture model and multiaxial strength data for grade H-451 graphite. Moreover, we report the successful extension of the model to predict the failure envelope for H-451 graphite in the first and fourth multiaxial quadrants. The model's predictions are compared to experimental

  7. Scaling Relations for Intercalation Induced Damage in Electrodes

    SciTech Connect

    Chen, Chien-Fan; Barai, Pallab; Smith, Kandler; Mukherjee, Partha P.

    2016-04-02

    Mechanical degradation, owing to intercalation induced stress and microcrack formation, is a key contributor to the electrode performance decay in lithium-ion batteries (LIBs). The stress generation and formation of microcracks are caused by the solid state diffusion of lithium in the active particles. Here in this work, scaling relations are constructed for diffusion induced damage in intercalation electrodes based on an extensive set of numerical experiments with a particle-level description of microcrack formation under disparate operating and cycling conditions, such as temperature, particle size, C-rate, and drive cycle. The microcrack formation and evolution in active particles is simulated based on a stochastic methodology. A reduced order scaling law is constructed based on an extensive set of data from the numerical experiments. The scaling relations include combinatorial constructs of concentration gradient, cumulative strain energy, and microcrack formation. Lastly, the reduced order relations are further employed to study the influence of mechanical degradation on cell performance and validated against the high order model for the case of damage evolution during variable current vehicle drive cycle profiles.

  8. Scaling Relations for Intercalation Induced Damage in Electrodes

    SciTech Connect

    Chen, Chien-Fan; Barai, Pallab; Smith, Kandler; Mukherjee, Partha P.

    2016-06-01

    Mechanical degradation, owing to intercalation induced stress and microcrack formation, is a key contributor to the electrode performance decay in lithium-ion batteries (LIBs). The stress generation and formation of microcracks are caused by the solid state diffusion of lithium in the active particles. In this work, scaling relations are constructed for diffusion induced damage in intercalation electrodes based on an extensive set of numerical experiments with a particle-level description of microcrack formation under disparate operating and cycling conditions, such as temperature, particle size, C-rate, and drive cycle. The microcrack formation and evolution in active particles is simulated based on a stochastic methodology. A reduced order scaling law is constructed based on an extensive set of data from the numerical experiments. The scaling relations include combinatorial constructs of concentration gradient, cumulative strain energy, and microcrack formation. The reduced order relations are further employed to study the influence of mechanical degradation on cell performance and validated against the high order model for the case of damage evolution during variable current vehicle drive cycle profiles.

  9. An intercalation-locked parallel-stranded DNA tetraplex

    PubMed Central

    Tripathi, Shailesh; Zhang, Daoning; Paukstelis, Paul J.

    2015-01-01

    DNA has proved to be an excellent material for nanoscale construction because complementary DNA duplexes are programmable and structurally predictable. However, in the absence of Watson–Crick pairings, DNA can be structurally more diverse. Here, we describe the crystal structures of d(ACTCGGATGAT) and the brominated derivative, d(ACBrUCGGABrUGAT). These oligonucleotides form parallel-stranded duplexes with a crystallographically equivalent strand, resulting in the first examples of DNA crystal structures that contains four different symmetric homo base pairs. Two of the parallel-stranded duplexes are coaxially stacked in opposite directions and locked together to form a tetraplex through intercalation of the 5′-most A–A base pairs between adjacent G–G pairs in the partner duplex. The intercalation region is a new type of DNA tertiary structural motif with similarities to the i-motif. 1H–1H nuclear magnetic resonance and native gel electrophoresis confirmed the formation of a parallel-stranded duplex in solution. Finally, we modified specific nucleotide positions and added d(GAY) motifs to oligonucleotides and were readily able to obtain similar crystals. This suggests that this parallel-stranded DNA structure may be useful in the rational design of DNA crystals and nanostructures. PMID:25628357

  10. Abl suppresses cell extrusion and intercalation during epithelium folding

    PubMed Central

    Jodoin, Jeanne N.; Martin, Adam C.

    2016-01-01

    Tissue morphogenesis requires control over cell shape changes and rearrangements. In the Drosophila mesoderm, linked epithelial cells apically constrict, without cell extrusion or intercalation, to fold the epithelium into a tube that will then undergo epithelial-to-mesenchymal transition (EMT). Apical constriction drives tissue folding or cell extrusion in different contexts, but the mechanisms that dictate the specific outcomes are poorly understood. Using live imaging, we found that Abelson (Abl) tyrosine kinase depletion causes apically constricting cells to undergo aberrant basal cell extrusion and cell intercalation. abl depletion disrupted apical–basal polarity and adherens junction organization in mesoderm cells, suggesting that extruding cells undergo premature EMT. The polarity loss was associated with abnormal basolateral contractile actomyosin and Enabled (Ena) accumulation. Depletion of the Abl effector Enabled (Ena) in abl-depleted embryos suppressed the abl phenotype, consistent with cell extrusion resulting from misregulated ena. Our work provides new insight into how Abl loss and Ena misregulation promote cell extrusion and EMT. PMID:27440923

  11. Anion-Intercalating Cathodes for High-Energy-Density Cells

    NASA Technical Reports Server (NTRS)

    West, William

    2006-01-01

    A report discusses physicochemical issues affecting a fluoride-intercalating cathode that operates in conjunction with a lithium ion-intercalating anode in a rechargeable electrochemical cell described in a cited prior report. The instant report also discusses corresponding innovations made in solvent and electrolyte compositions since the prior report. The advantages of this cell, relative to other lithium-ion-based cells, are said to be greater potential (5 V vs. 4 V), and greater theoretical cathode specific capacity (0.9 to 2.2 A-h/g vs. about 0.18 A-h/g). The discussion addresses a need for the solvent to be unreactive toward the lithium anode and to resist anodic oxidation at potentials greater than about 4.5 V vs. lithium; the pertinent innovation is the selection of propylene carbonate (PC) as a solvent having significantly more stability, relative to other solvents that have been tried. The discussion also addresses the need for an electrolyte additive, denoted an anion receptor, to complex the fluoride ion; the pertinent innovation is the selection of tris(hexafluoroisopropyl) borate as a superior alternative to the prior anion receptor, which was tris(pentafluorophenyl) borate.

  12. Stochastics of diffusion induced damage in intercalation materials

    NASA Astrophysics Data System (ADS)

    Barai, Pallab; Mukherjee, Partha P.

    2016-10-01

    Fundamental understanding of the underlying diffusion-mechanics interplay in the intercalation electrode materials is critical toward improved life and performance of lithium-ion batteries for electric vehicles. Especially, diffusion induced microcrack formation in brittle, intercalation active materials, with emphasis on the grain/grain-boundary (GB) level implications, has been fundamentally investigated based on a stochastic modeling approach. Quasistatic damage evolution has been analyzed under lithium concentration gradient induced stress. Scaling of total amount of microcrack formation shows a power law variation with respect to the system size. Difference between the global and local roughness exponent indicates the existence of anomalous scaling. The deterioration of stiffness with respect to microcrack density displays two distinct regions of damage propagation; namely, diffused damage evolution and stress concentration driven localized crack propagation. Polycrystalline material microstructures with different grain sizes have been considered to study the diffusion-induced fracture in grain and GB regions. Intergranular crack paths are observed within microstructures containing softer GB region, whereas, transgranular crack paths have been observed in microstructures with relatively strong GB region. Increased tortuosity of the spanning crack has been attributed as the reason behind attaining increased fracture strength in polycrystalline materials with smaller grain sizes.

  13. Electron Beam Irradiated Intercalated CNT Yarns For Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Waters, Deborah L.; Gaier, James R.; Williams, Tiffany S.; Lopez Calero, Johnny E.; Ramirez, Christopher; Meador, Michael A.

    2015-01-01

    Multi-walled CNT yarns have been experimentally and commercially created to yield lightweight, high conductivity fibers with good tensile properties for application as electrical wiring and multifunctional tendons. Multifunctional tendons are needed as the cable structures in tensegrity robots for use in planetary exploration. These lightweight robust tendons can provide mechanical strength for movement of the robot in addition to power distribution and data transmission. In aerospace vehicles, such as Orion, electrical wiring and harnessing mass can approach half of the avionics mass. Use of CNT yarns as electrical power and data cables could reduce mass of the wiring by thirty to seventy percent. These fibers have been intercalated with mixed halogens to increase their specific electrical conductivity to that near copper. This conductivity, combined with the superior strength and fatigue resistance makes it an attractive alternative to copper for wiring and multifunctional tendon applications. Electron beam irradiation has been shown to increase mechanical strength in pristine CNT fibers through increased cross-linking. Both pristine and intercalated CNT yarns have been irradiated using a 5-megavolt electron beam for various durations and the conductivities and tensile properties will be discussed. Structural information obtained using a field emission scanning electron microscope, energy dispersive X-ray spectroscopy (EDS), and Raman spectroscopy will correlate microstructural details with bulk properties.

  14. Modeling of alkyl quaternary ammonium cations intercalated into montmorillonite lattice

    SciTech Connect

    Daoudi, El Mehdi; Boughaleb, Yahia; El Gaini, Layla; Meghea, Irina; Bakasse, Mina

    2013-05-15

    Highlights: ► The modification of montmorillonites by three surfactants increases the basal spacing. ► The model proposed show a bilayer conformation for the surfactant ODTMA. ► The DODMA and TOMA surfactants adopt a paraffin type arrangement. ► Behavior of surfactants in interlayer space was confirmed by TGA and ATR analysis. - Abstract: The objective of this work was to study the conformation of the quaternary ammonium cations viz., octadecyl trimethyl ammonium (ODTMA), dioctadecyl dimethyl ammonium (DMDOA) and trioctadecyl methyl ammonium (TOMA) intercalated within montmorillonite. The modified montmorillonite was characterized by X-ray diffraction in small angle (SAXS), thermal analysis (TGA) and infrared spectroscopy of attenuated total reflection (ATR). The modification of organophilic montmorillonites by the three surfactants ODTMA, DMDOA and TOMA increases the basal spacing from their respective intercalated distances of 1.9 nm, 2.6 nm and 3.4 nm respectively. The increase in the spacing due to the basic organic modification was confirmed by the results of thermal analysis (TGA) and infrared spectroscopy (ATR), and also supported by theoretical calculations of longitudinal and transversal chain sizes of these alkyl quaternary ammonium cations.

  15. Intercalation of alkylamines into an organic polymer crystal

    NASA Astrophysics Data System (ADS)

    Matsumoto, Akikazu; Odani, Toru; Sada, Kazuki; Miyata, Mikiji; Tashiro, Kohji

    2000-05-01

    Organic solid-state synthesis allows formation of products that are difficult or impossible to produce by conventional methods. This feature, and the high degree of reaction selectivity that can be achieved, is a direct result of the control over the relative orientation of the reactants afforded by the solid state. But as the successful development of `topochemical reactions' requires the careful design of suitable reactant crystals, the range of both reactions and products amenable to this approach has been limited. However, recent advances in organic crystal engineering, particularly the rational design of complex solid architectures through supramolecular preorganization, have renewed interest in topochemical reactions. Previously, we have orientated muconate monomers-diene moieties with a carboxylate group on each end-using long-chain n-alkylammonium ions, such that the topochemical photopolymerization of the solid-state reactants produces layered crystals of stereoregular and high-molecular-mass polymers. Here we show that these polymer crystals are capable of repeated, reversible intercalation by conversion to the analogous poly(carboxylic acid), followed by transformation into a number of poly(alkylammonium muconate)s upon addition of the appropriate amine. Introduction of functional groups into these crystals may allow the design of organic solids for applications such as molecular recognition, separation and catalysis, thereby extending the range and practical utility of current intercalation compounds.

  16. Intercalation of alkylamines into an organic polymer crystal

    PubMed

    Matsumoto; Odani; Sada; Miyata; Tashiro

    2000-05-18

    Organic solid-state synthesis allows formation of products that are difficult or impossible to produce by conventional methods. This feature, and the high degree of reaction selectivity that can be achieved, is a direct result of the control over the relative orientation of the reactants afforded by the solid state. But as the successful development of 'topochemical reactions' requires the careful design of suitable reactant crystals, the range of both reactions and products amenable to this approach has been limited. However, recent advances in organic crystal engineering, particularly the rational design of complex solid architectures through supramolecular preorganization, have renewed interest in topochemical reactions. Previously, we have orientated muconate monomers--diene moieties with a carboxylate group on each end--using long-chain n-alkylammonium ions, such that the topochemical photopolymerization of the solid-state reactants produces layered crystals of stereoregular and high-molecular-mass polymers. Here we show that these polymer crystals are capable of repeated, reversible intercalation by conversion to the analogous poly(carboxylic acid), followed by transformation into a number of poly(alkylammonium muconate)s upon addition of the appropriate amine. Introduction of functional groups into these crystals may allow the design of organic solids for applications such as molecular recognition, separation and catalysis, thereby extending the range and practical utility of current intercalation compounds.

  17. Duplex-Selective Ruthenium-based DNA Intercalators

    PubMed Central

    Shade, Chad M.; Kennedy, Robert D.; Rouge, Jessica L.; Rosen, Mari S.; Wang, Mary X.; Seo, Soyoung E.; Clingerman, Daniel J.

    2016-01-01

    We report the design and synthesis of small molecules that exhibit enhanced luminescence in the presence of duplex rather than single-stranded DNA. The local environment presented by a well-known [Ru(dipyrido[2,3-a:3',2'-c]phenazine)L2]2+-based DNA intercalator was modified by functionalizing the bipyridine ligands with esters and carboxylic acids. By systematically varying the number and charge of the pendant groups, it was determined that decreasing the electrostatic interaction between the intercalator and the anionic DNA backbone reduced single-strand interactions and translated to better duplex specificity. In studying this class of complexes, a single RuII complex emerged that selectively luminesces in the presence of duplex DNA with little to no background from interacting with single stranded DNA. This complex shows promise as a new dye capable of selectively staining double versus single-stranded DNA in gel electrophoresis, which cannot be done with conventional SYBR dyes. PMID:26119581

  18. Lithium intercalation properties in manganese-iron Prussian blue analogues

    NASA Astrophysics Data System (ADS)

    Matsuda, T.; Kurihara, Y.; Moritomo, Y.

    2013-04-01

    We investigated the electronic states and structural properties of LixMn[Fe(CN)6]0.83·3.5H2O, and LixMn[Fe(CN)6]0.87·2.6H2O, which have different amount of [Fe(CN)6] vacancies. X-ray absorption spectra near the Fe and Mn K-edges revealed that the Li intercalation/deintercalation process is two-electron reaction, i.e. MnII—NC—FeII, MnII—NC—FeIII, and MnIII—NC—FeIII. The crystal structure of LixMn[Fe(CN)6]0.83·3.5H2O remains cubic and single phase throughout the Li intercalation/deintercalation process. The crystal structure of LixMn[Fe(CN)6]0.87·2.6H2O is also cubic, while phase separation of Li+-rich phase and Li+-poor phase was observed during the MnII/MnIII reduction/oxidation process.

  19. Scaling Relations for Intercalation Induced Damage in Electrodes

    DOE PAGES

    Chen, Chien-Fan; Barai, Pallab; Smith, Kandler; ...

    2016-04-02

    Mechanical degradation, owing to intercalation induced stress and microcrack formation, is a key contributor to the electrode performance decay in lithium-ion batteries (LIBs). The stress generation and formation of microcracks are caused by the solid state diffusion of lithium in the active particles. Here in this work, scaling relations are constructed for diffusion induced damage in intercalation electrodes based on an extensive set of numerical experiments with a particle-level description of microcrack formation under disparate operating and cycling conditions, such as temperature, particle size, C-rate, and drive cycle. The microcrack formation and evolution in active particles is simulated based onmore » a stochastic methodology. A reduced order scaling law is constructed based on an extensive set of data from the numerical experiments. The scaling relations include combinatorial constructs of concentration gradient, cumulative strain energy, and microcrack formation. Lastly, the reduced order relations are further employed to study the influence of mechanical degradation on cell performance and validated against the high order model for the case of damage evolution during variable current vehicle drive cycle profiles.« less

  20. Intercalation of cellulase enzyme into a hydrotalcite layer structure

    NASA Astrophysics Data System (ADS)

    Zou, N.; Plank, J.

    2015-01-01

    A new inorganic-organic hybrid material whereby cellulase enzyme is incorporated into a hydrotalcite type layered double hydroxide (LDH) structure is reported. The Mg2Al-cellulase-LDH was synthesized via co-precipitation from Mg/Al nitrate at pH=9.6. Characterization was performed using X-ray powder diffraction (XRD), small angle X-ray scattering (SAXS), elemental analysis, infrared spectroscopy (IR) and thermogravimetry (TG). From XRD and SAXS measurements, a d-value of ~5.0 nm was identified for the basal spacing of the Mg2Al-cellulase-LDH. Consequently, the cellulase enzyme (hydrodynamic diameter ~6.6 nm) attains a slightly compressed conformation when intercalated. Formation of the LDH hybrid was also confirmed via scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Mg2Al-cellulase-LDH phases appear as ~20 nm thin foils which are intergrown to flower-like aggregates. Activity of the enzyme was retained after deintercalation from the Mg2Al-LDH framework using anion exchange. Accordingly, cellulase is not denatured during the intercalation process, and LDH presents a suitable host structure for time-controlled release of the biomolecule.

  1. An intercalation-locked parallel-stranded DNA tetraplex

    DOE PAGES

    Tripathi, S.; Zhang, D.; Paukstelis, P. J.

    2015-01-27

    DNA has proved to be an excellent material for nanoscale construction because complementary DNA duplexes are programmable and structurally predictable. However, in the absence of Watson–Crick pairings, DNA can be structurally more diverse. Here, we describe the crystal structures of d(ACTCGGATGAT) and the brominated derivative, d(ACBrUCGGABrUGAT). These oligonucleotides form parallel-stranded duplexes with a crystallographically equivalent strand, resulting in the first examples of DNA crystal structures that contains four different symmetric homo base pairs. Two of the parallel-stranded duplexes are coaxially stacked in opposite directions and locked together to form a tetraplex through intercalation of the 5'-most A–A base pairs betweenmore » adjacent G–G pairs in the partner duplex. The intercalation region is a new type of DNA tertiary structural motif with similarities to the i-motif. 1H–1H nuclear magnetic resonance and native gel electrophoresis confirmed the formation of a parallel-stranded duplex in solution. Finally, we modified specific nucleotide positions and added d(GAY) motifs to oligonucleotides and were readily able to obtain similar crystals. This suggests that this parallel-stranded DNA structure may be useful in the rational design of DNA crystals and nanostructures.« less

  2. Methotrexate intercalated ZnAl-layered double hydroxide

    NASA Astrophysics Data System (ADS)

    Chakraborty, Manjusha; Dasgupta, Sudip; Soundrapandian, Chidambaram; Chakraborty, Jui; Ghosh, Swapankumar; Mitra, Manoj K.; Basu, Debabrata

    2011-09-01

    The anticancerous drug methotrexate (MTX) has been intercalated into an ZnAl-layered double hydroxide (LDH) using an anion exchange technique to produce LDH-MTX hybrids having particle sizes in the range of 100-300 nm. X-ray diffraction studies revealed increases in the basal spacings of ZnAl-LDH-MTX hybrid on MTX intercalation. This was corroborated by the transmission electron micrographs, which showed an increase in average interlayer spacing from 8.9 Å in pristine LDH to 21.3 Å in LDH-MTX hybrid. Thermogravimetric analyses showed an increase in the decomposition temperature for the MTX molecule in the LDH-MTX hybrid indicating enhanced thermal stability of the drug molecule in the LDH nanovehicle. The cumulative release profile of MTX from ZnAl-LDH-MTX hybrids in phosphate buffer saline (PBS) at pH 7.4 was successfully sustained for 48 h following Rigter-Peppas model release kinetics via diffusion.

  3. Role of the intercalated disc in cardiac propagation and arrhythmogenesis.

    PubMed

    Kleber, Andre G; Saffitz, Jeffrey E

    2014-01-01

    This review article discusses mechanisms underlying impulse propagation in cardiac muscle with specific emphasis on the role of the cardiac cell-to-cell junction, called the "intercalated disc."The first part of this review deals with the role of gap junction channels, formed by connexin proteins, as a determinant of impulse propagation. It is shown that, depending on the underlying structure of the cellular network, decreasing the conductance of gap junction channels (so-called "electrical uncoupling") may either only slow, or additionally stabilize propagation and reverse unidirectional propagation block to bidirectional propagation. This is because the safety factor for propagation increases with decreasing intercellular electrical conductance. The role of heterogeneous connexin expression, which may be present in disease states, is also discussed. The hypothesis that so-called ephaptic impulse transmission plays a role in heart and can substitute for electrical coupling has been revived recently. Whereas ephaptic transmission can be demonstrated in theoretical simulations, direct experimental evidence has not yet been presented. The second part of this review deals with the interaction of three protein complexes at the intercalated disc: (1) desmosomal and adherens junction proteins, (2) ion channel proteins, and (3) gap junction channels consisting of connexins. Recent work has revealed multiple interactions between these three protein complexes which occur, at least in part, at the level of protein trafficking. Such interactions are likely to play an important role in the pathogenesis of arrhythmogenic cardiomyopathy, and may reveal new therapeutic concepts and targets.

  4. An intercalation-locked parallel-stranded DNA tetraplex

    SciTech Connect

    Tripathi, S.; Zhang, D.; Paukstelis, P. J.

    2015-01-27

    DNA has proved to be an excellent material for nanoscale construction because complementary DNA duplexes are programmable and structurally predictable. However, in the absence of Watson–Crick pairings, DNA can be structurally more diverse. Here, we describe the crystal structures of d(ACTCGGATGAT) and the brominated derivative, d(ACBrUCGGABrUGAT). These oligonucleotides form parallel-stranded duplexes with a crystallographically equivalent strand, resulting in the first examples of DNA crystal structures that contains four different symmetric homo base pairs. Two of the parallel-stranded duplexes are coaxially stacked in opposite directions and locked together to form a tetraplex through intercalation of the 5'-most A–A base pairs between adjacent G–G pairs in the partner duplex. The intercalation region is a new type of DNA tertiary structural motif with similarities to the i-motif. 1H–1H nuclear magnetic resonance and native gel electrophoresis confirmed the formation of a parallel-stranded duplex in solution. Finally, we modified specific nucleotide positions and added d(GAY) motifs to oligonucleotides and were readily able to obtain similar crystals. This suggests that this parallel-stranded DNA structure may be useful in the rational design of DNA crystals and nanostructures.

  5. Transition Metal Intercalators as Anticancer Agents—Recent Advances

    PubMed Central

    Deo, Krishant M.; Pages, Benjamin J.; Ang, Dale L.; Gordon, Christopher P.; Aldrich-Wright, Janice R.

    2016-01-01

    The diverse anticancer utility of cisplatin has stimulated significant interest in the development of additional platinum-based therapies, resulting in several analogues receiving clinical approval worldwide. However, due to structural and mechanistic similarities, the effectiveness of platinum-based therapies is countered by severe side-effects, narrow spectrum of activity and the development of resistance. Nonetheless, metal complexes offer unique characteristics and exceptional versatility, with the ability to alter their pharmacology through facile modifications of geometry and coordination number. This has prompted the search for metal-based complexes with distinctly different structural motifs and non-covalent modes of binding with a primary aim of circumventing current clinical limitations. This review discusses recent advances in platinum and other transition metal-based complexes with mechanisms of action involving intercalation. This mode of DNA binding is distinct from cisplatin and its derivatives. The metals focused on in this review include Pt, Ru and Cu along with examples of Au, Ni, Zn and Fe complexes; these complexes are capable of DNA intercalation and are highly biologically active. PMID:27809241

  6. Baseline Graphite Initial Mechanical Test Report

    SciTech Connect

    Mark Carroll; Randy Lloyd

    2009-09-01

    The Next Generation Nuclear Plant (NGNP) Project is tasked with selecting a high temperature gas reactor technology that will be capable of generating electricity and supplying large amounts of process heat. The NGNP is presently being designed as a helium-cooled high temperature gas reactor (HTGR) with a large graphite core. The graphite baseline characterization project is conducting the research and development (R&D) activities deemed necessary to fully qualify nuclear-grade graphite for use in the NGNP reactor. One of the major fundamental objectives of the project is establishing nonirradiated thermomechanical and thermophysical properties by characterizing lot-to-lot and billet-to-billet variations (for probabilistic baseline data needs) through extensive data collection and statistical analysis. The reactor core will be made up of stacks of graphite moderator blocks. In order to gain a more comprehensive understanding of the varying characteristics in a wide range of suitable graphites, any of which can be classified as “nuclear grade,” an experimental program has been initiated to develop an extensive database of the baseline characteristics of numerous candidate graphites. Various factors known to affect the properties of graphite will be investigated, including specimen size, spatial location within a graphite billet, specimen orientation within a billet (either parallel to [P] or transverse to [T] the long axis of the as-produced billet), and billet-to-billet variations within a lot or across different production lots. Because each data point is based on a certain position within a given billet of graphite, particular attention must be paid to the traceability of each specimen and its spatial location and orientation within each billet. The evaluation of these properties is discussed in the Graphite Technology Development Plan (Windes et. al 2007). One of the key components in the evaluation of these graphite types will be mechanical testing of

  7. Investigation of the electrochemically active surface area and lithium diffusion in graphite anodes by a novel OsO4 staining method

    NASA Astrophysics Data System (ADS)

    Pfaffmann, Lukas; Birkenmaier, Claudia; Müller, Marcus; Bauer, Werner; Mitsch, Tim; Feinauer, Julian; Krämer, Yvonne; Scheiba, Frieder; Hintennach, Andreas; Schleid, Thomas; Schmidt, Volker; Ehrenberg, Helmut

    2016-03-01

    Negative electrodes of lithium-ion batteries generally consist of graphite-based active materials. In order to realize batteries with a high current density and therefore accelerated charging processes, the intercalation of lithium and the diffusion processes of these carbonaceous materials must be understood. In this paper, we visualized the electrochemical active surface area for three different anode materials using a novel OsO4 staining method in combination with scanning electron microscopy techniques. The diffusion behavior of these three anode materials is investigated by potentiostatic intermittent titration technique measurements. From those we determine the diffusion coefficient with and without consideration of the electrochemical active surface area.

  8. Click modification of diazido acridine intercalators: a versatile route towards decorated DNA nanostructures.

    PubMed

    Moradpour Hafshejani, Shahrbanou; Watson, Scott M D; Tuite, Eimer M; Pike, Andrew R

    2015-09-01

    Diazido derivatives of 3,6-diamino acridine (proflavine) intercalate into DNA and undergo functionalization through click chemistry to form 1D nanostructures with redox active, conductive nanowire, and fluorescent properties. This two-step approach, intercalation followed by click modification allows for the controlled decoration of DNA nanostructures.

  9. Intercalating Arabidopsis leaf cells: a jigsaw puzzle of lobes, necks, ROPs, and RICs.

    PubMed

    Settleman, Jeffrey

    2005-03-11

    Intercalation of cells is an evolutionarily conserved strategy used for a variety of developmental processes in animals. In this issue of Cell, Fu et al. have uncovered an elaborate Rho GTPase-mediated mechanism by which cytoskeletal-dependent intercalation of Arabidopsis leaf cells is achieved, suggesting that conserved Rho GTPase signaling pathways may similarly regulate tissue morphogenesis in animals and plants.

  10. A technique for brazing graphite/graphite and stainless steel/high-carbon steel joints

    SciTech Connect

    Ohmura, H.; Kawashiri, K. . Dept. of Metals and Inorganic Materials); Yoshida, T. . Vehicle Machine Engineering Dept.); Yoshimoto, O. . Quality Control Dept.)

    1994-10-01

    A new brazing technique for joining graphite to itself or to metals such as Mo, W, or Cu, with conventional brazing filler metals has been developed. Essentially, it is impossible to braze graphite with Cu filler metal because no wetting occurs. However, when a graphite base material is combined with an Fe base metal in Cu brazing, the Fe base metal dissolves in molten Cu. Simultaneously, the dissolved Fe grows as part of a columnar Fe-9 [approximately] 6Cu-1.6C alloy phase at the graphite interface at a constant brazing temperature, that is, the dissolution and deposit of base metal takes place. By placing an Fe foil insert between both graphite base materials, therefore, the columnar phase is formed at both graphite faces and grows toward the Fe foil during heating. As a result, both graphite base materials are united by the columnar phase through the Fe foil. In the same way, a graphite/Mo or /W joint can be produced. Moreover, when using BAu-1, which has a lower melting point than that of BCu-1, it is also possible to braze graphite to Cu. The shear strength of a graphite/graphite joint with a 0.12-mm thick Fe foil at room temperature was about 32 MPa. Further, the bending strength of the graphite/graphite and /Cu joints at 873 K (1,112 F), as measured using the four-point bending test, was 35 and 11 MPa, respectively. In addition, the technique can be applied to the brazing of AISI 304 stainless steel to high-C steel with BCu-1 where, normally, Cr[sub 23]C[sub 6] and Cr[sub 7]C[sub 3] layers are formed at the high-C steel braze interface; these carbide layers result in the loss of mechanical properties of the joint.

  11. Role of Cooperative Interactions in the Intercalation of Heteroatoms between Graphene and a Metal Substrate.

    PubMed

    Li, Geng; Zhou, Haitao; Pan, Lida; Zhang, Yi; Huang, Li; Xu, Wenyan; Du, Shixuan; Ouyang, Min; Ferrari, Andrea C; Gao, Hong-Jun

    2015-06-10

    The intercalation of heteroatoms between graphene and a metal substrate has been studied intensively over the past few years, due to its effect on the graphene properties, and as a method to create vertical heterostructures. Various intercalation processes have been reported with different combinations of heteroatoms and substrates. Here we study Si intercalation between graphene and Ru(0001). We elucidate the role of cooperative interactions between hetero-atoms, graphene, and substrate. By combining scanning tunneling microscopy with density functional theory, the intercalation process is confirmed to consist of four key steps, involving creation of defects, migration of heteroatoms, self-repairing of graphene, and growth of an intercalated monolayer. Both theory and experiments indicate that this mechanism applies also to other combinations of hetero-atoms and substrates.

  12. Graphite-metal brazing for thermal applications

    SciTech Connect

    Hosking, F.M.; Koski, J.A.

    1991-01-01

    Various plasma facing components are being designed and fabricated to support Magnetic Fusion Energy experiments. They typically consist of graphite tiles mechanically or metallurgically attached to metallic cooling substrates. This paper will discuss the active brazing of isotropic and pyrolytic graphite to oxygen free, high conductivity (OFHC) Cu and an alumina-dispersion strengthened Cu with a Ag-Cu-Ti active filler metal. The Ti constituent promotes direct wetting of graphite with the formation of a thin TiC reaction layer. Joint design and materials selection are critical factors since graphite and Cu have large thermal expansion differences that affect residual stresses after brazing and subsequent component thermal performance. Low thermal expansion Mo and compliant Cu interlayers were introduced to lower the residual stresses and extend the thermal life of prototype graphite-Cu braze joints. Although the interlayers showed evidence of reducing the incidence of graphite cracking and spalling under thermal loading when brazed to the dispersion-stengthened Cu, the best graphite braze joints were produced with the more ductile OFHC Cu substrates and no interlayer. These latter joints survived simulated tokamak surface high heat fluxes of 30 MW{center dot}m{sup {minus}2} or greater, while comparable dispersion strengthened Cu samples failed at 10 MW{center dot}m{sup {minus}2}. 23 refs., 14 figs., 2 tabs.

  13. Graphite-metal brazing for thermal applications

    NASA Astrophysics Data System (ADS)

    Hosking, F. M.; Koski, J. A.

    Various plasma facing components are being designed and fabricated to support Magnetic Fusion Energy experiments. They typically consist of graphite tiles mechanically or metallurgically attached to metallic cooling substrates. This paper will discuss the active brazing of isotropic and pyrolytic graphite to oxygen free, high conductivity (OFHC) Cu and an alumina-dispersion strengthened Cu with a Ag-Cu-Ti active filler metal. The Ti constituent promotes direct wetting of graphite with the formation of a thin TiC reaction layer. Joint design and materials selection are critical factors since graphite and Cu have large thermal expansion differences that affect residual stresses after brazing and subsequent component thermal performance. Low thermal expansion Mo and compliant Cu interlayers were introduced to lower the residual stresses and extend the thermal life of prototype graphite-Cu braze joints. Although the interlayers showed evidence of reducing the incidence of graphite cracking and spalling under thermal loading when brazed to the dispersion stengthened Cu, the best graphite braze joints were produced with the more ductile OFHC Cu substrates and no interlayer. These latter joints survived simulated tokamak surface high heat fluxes of 30 MW x m(exp -2) or greater, while comparable dispersion strengthened Cu samples failed at 10 MW x m(exp -2)

  14. THE NEXT GENERATION NUCLEAR PLANT GRAPHITE PROGRAM

    SciTech Connect

    William E. Windes; Timothy D. Burchell; Robert L. Bratton

    2008-09-01

    Developing new nuclear grades of graphite used in the core of a High Temperature Gas-cooled Reactor (HTGR) is one of the critical development activities being pursued within the Next Generation Nuclear Plant (NGNP) program. Graphite’s thermal stability (in an inert gas environment), high compressive strength, fabricability, and cost effective price make it an ideal core structural material for the HTGR reactor design. While the general characteristics necessary for producing nuclear grade graphite are understood, historical “nuclear” grades no longer exist. New grades must be fabricated, characterized, and irradiated to demonstrate that current grades of graphite exhibit acceptable non-irradiated and irradiated properties upon which the thermo-mechanical design of the structural graphite in NGNP is based. The NGNP graphite R&D program has selected a handful of commercially available types for research and development activities necessary to qualify this nuclear grade graphite for use within the NGNP reactor. These activities fall within five primary areas; 1) material property characterization, 2) irradiated material property characterization, 3) modeling, and 4) ASTM test development, and 5) ASME code development efforts. Individual research and development activities within each area are being pursued with the ultimate goal of obtaining a commercial operating license for the nuclear graphite from the US NRC.

  15. Resin/graphite fiber composites

    NASA Technical Reports Server (NTRS)

    Cavano, P. J.

    1974-01-01

    Processing techniques were developed for the fabrication of both polyphenylquinoxaline and polyimide composites by the in situ polymerization of monomeric reactants directly on the graphite reinforcing fibers, rather than using previously prepared prepolymer varnishes. Void-free polyphenylquinoxaline composites were fabricated and evaluated for room and elevated flexure and shear properties. The technology of the polyimide system was advanced to the point where the material is ready for commercial exploitation. A reproducible processing cycle free of operator judgment factors was developed for fabrication of void-free composites exhibiting excellent mechanical properties and a long time isothermal life in the range of 288 C to 316 C. The effects of monomer reactant stoichiometry and process modification on resin flow were investigated. Demonstration of the utility and quality of this polyimide system was provided through the successful fabrication and evaluation of four complex high tip speed fan blades.

  16. Development of polyphenylquinoxaline graphite composites

    NASA Technical Reports Server (NTRS)

    Shdo, J. D.

    1976-01-01

    Six polyphenylquinoxalines (PPQ) containing pendant cyano (CN) groups were synthesized. The polymers were characterized in terms of inherent viscosity, glass transition temperature, softening temperature and weight loss due to aging in air at 316 C (600 F). The potential for crosslinking PPQs by trimerization of pendant CN groups was investigated. A polymer derived from 1 mole 3,3,4,4 -tetraaminobenzophenone, .2 mole p-bis(p -cyanophenoxyphenylglyoxalyl)benzene and .8 mole p-bis(phenylglyoxalyl)benzene was selected for more extensive characterization in HM-S graphite fiber-reinforced composites. Mechanical properties were determined using composites made from HM-S fiber and polymer and composites made from HM-S fiber, polymer and a potential CN group trimerization catalyst. Composite mechanical properties, inter-laminar shear strength and flexure properties, were determined over the temperature range of +21 C to 316 C.

  17. The characterization of fluorinated graphite

    SciTech Connect

    Hagaman, E.W.; Gakh, A.A.; Annis, B.K.

    1995-12-31

    The characterization of solid fossil fuels by chemical and spectroscopic methods requires extensive modelling in less complex systems for chemical proof of principle and technique development. In previous work coal was fluorinated with dilute, elemental fluorine under conditions that were expected to lead to materials that contain only fluoromethine moieties. The solid state, cross polarization/magic angle spinning (CP/MAS) {sup 13}C NMR spectra of the fluorinated coal are complex, indicating more chemical modification than originally anticipated. Our goal in the coal derivatization was to sequentially increase the severity of the fluorination and observe by {sup 19}F and {sup 13}C NMR the type and concentration of fluorine functional groups created in the coal milieu. This requires the ability to discriminate between C, CF, CF{sub 2}, and CF, moieties in the coal matrix. The task can be accomplished by implementing the spectral editing technique of Wu and Zilm which distinguishes different kinds of carbon resonances, especially CH and CH{sub 2} resonances. These experiments utilize cross polarization (CP) and polarization inversion (PI) to effect the discrimination. Our version of this experiment is a triple resonance experiment that incorporates {sup 19}F-{sup 13}C CP, PI, and simultaneous {sup 1}H and {sup 19}F dipolar decoupling. In order to evaluate the elemental fluorine chemistry in a matrix simpler than coal, fluorinated graphite was prepared. X-ray photoelectron spectroscopy (XPS) was used to characterize the surface species, i.e., count CF, CF{sub 2} and CF{sub 3} species. These well-characterized samples are the models we will use to test the NIVIR editing experiments. The XPS and atomic force microscopy (AFM) data on the first fluorinated graphites we have prepared are reported in this paper.

  18. Self-Printing on Graphitic Nanosheets with Metal Borohydride Nanodots for Hydrogen Storage

    NASA Astrophysics Data System (ADS)

    Li, Yongtao; Ding, Xiaoli; Zhang, Qingan

    2016-08-01

    Although the synthesis of borohydride nanostructures is sufficiently established for advancement of hydrogen storage, obtaining ultrasmall (sub-10 nm) metal borohydride nanocrystals with excellent dispersibility is extremely challenging because of their high surface energy, exceedingly strong reducibility/hydrophilicity and complicated composition. Here, we demonstrate a mechanical-force-driven self-printing process that enables monodispersed (~6 nm) NaBH4 nanodots to uniformly anchor onto freshly-exfoliated graphitic nanosheets (GNs). Both mechanical-forces and borohydride interaction with GNs stimulate NaBH4 clusters intercalation/absorption into the graphite interlayers acting as a ‘pen’ for writing, which is accomplished by exfoliating GNs with the ‘printed’ borohydrides. These nano-NaBH4@GNs exhibit favorable thermodynamics (decrease in ∆H of ~45%), rapid kinetics (a greater than six-fold increase) and stable de-/re-hydrogenation that retains a high capacity (up to ~5 wt% for NaBH4) compared with those of micro-NaBH4. Our results are helpful in the scalable fabrication of zero-dimensional complex hydrides on two-dimensional supports with enhanced hydrogen storage for potential applications.

  19. In situ detection of lithium metal plating on graphite in experimental cells

    NASA Astrophysics Data System (ADS)

    Uhlmann, C.; Illig, J.; Ender, M.; Schuster, R.; Ivers-Tiffée, E.

    2015-04-01

    Lithium plating is a common problem for charging in high-rate and low-temperature Li-ion battery applications. The current "standard anode" material graphite is especially susceptible to the formation of lithium metal on its surface instead of intercalation. In order to improve the understanding of this phenomenon, this investigation was conducted using pulse-relaxation experiments, scanning electron microscopy (SEM) and optical in-situ microscopy. For that purpose, current pulses up to 10 C were applied on graphite half-cells to induce plating on the anode's surface. The resulting characteristics (e.g., cell voltage and changes in surface morphology) were analyzed during pulses and subsequent relaxation. Several characteristic attributes could be detected whenever lithium plating occurred: i) a prominent kink of the voltage transient during charging, ii) a distinctive plateau in the subsequent relaxation of the cell voltage, iii) a gray deposit covering the anode surface which under high magnification shows iv) a net-like structure covering the carbon particles. These attributes may provide useful detection tools for Li plating. The observed characteristics for Li plating were explained regarding the involved microscopic processes. This model was used to understand dissolution of plated lithium on the particle surface after the charging pulse and could thus be confirmed by SEM investigations.

  20. Self-Printing on Graphitic Nanosheets with Metal Borohydride Nanodots for Hydrogen Storage

    PubMed Central

    Li, Yongtao; Ding, Xiaoli; Zhang, Qingan

    2016-01-01

    Although the synthesis of borohydride nanostructures is sufficiently established for advancement of hydrogen storage, obtaining ultrasmall (sub-10 nm) metal borohydride nanocrystals with excellent dispersibility is extremely challenging because of their high surface energy, exceedingly strong reducibility/hydrophilicity and complicated composition. Here, we demonstrate a mechanical-force-driven self-printing process that enables monodispersed (~6 nm) NaBH4 nanodots to uniformly anchor onto freshly-exfoliated graphitic nanosheets (GNs). Both mechanical-forces and borohydride interaction with GNs stimulate NaBH4 clusters intercalation/absorption into the graphite interlayers acting as a ‘pen’ for writing, which is accomplished by exfoliating GNs with the ‘printed’ borohydrides. These nano-NaBH4@GNs exhibit favorable thermodynamics (decrease in ∆H of ~45%), rapid kinetics (a greater than six-fold increase) and stable de-/re-hydrogenation that retains a high capacity (up to ~5 wt% for NaBH4) compared with those of micro-NaBH4. Our results are helpful in the scalable fabrication of zero-dimensional complex hydrides on two-dimensional supports with enhanced hydrogen storage for potential applications. PMID:27484735

  1. In Situ Raman Microscopy of a Single Graphite Microflake Electrode in a Li(+)-containing Electrolyte

    NASA Technical Reports Server (NTRS)

    Shi, Qing-Fang; Dokko, Kaoru; Scherson, Daniel A.

    2003-01-01

    Highly detailed Raman spectra from a single KS-44 graphite microflake electrode as a function of the applied potential have been collected in situ using a Raman microscope and a sealed spectroelectrochemical cell isolated from the laboratory environment. Correlations were found between the Raman spectral features and the various Li(+) intercalation stages while recording in real time Raman spectra during a linear potential scan from 0.7 down ca. 0.0V vs Li/Li(+) at a rate of 0.1 mV/s in a 1M LiClO4 solution in a 1:l (by volume) ethylene carbonate (EC):diethyl carbonate (DEC) mixture. In particular, clearly defined isosbestic points were observed for data collected in the potential range where the transition between dilute phase 1 and phase 4 of lithiated graphite is known to occur, i.e. 0.157 < E < 0.215 vs Li/Li(+). Statistical analysis of the spectroscopic data within this region made it possible to determine independently the fraction of each of the two phases present as a function of potential without relying on coulometric information and then predict, based on the proposed stoichiometry for the transition, a spectrally-derived voltammetric feature.

  2. Self-Printing on Graphitic Nanosheets with Metal Borohydride Nanodots for Hydrogen Storage.

    PubMed

    Li, Yongtao; Ding, Xiaoli; Zhang, Qingan

    2016-08-03

    Although the synthesis of borohydride nanostructures is sufficiently established for advancement of hydrogen storage, obtaining ultrasmall (sub-10 nm) metal borohydride nanocrystals with excellent dispersibility is extremely challenging because of their high surface energy, exceedingly strong reducibility/hydrophilicity and complicated composition. Here, we demonstrate a mechanical-force-driven self-printing process that enables monodispersed (~6 nm) NaBH4 nanodots to uniformly anchor onto freshly-exfoliated graphitic nanosheets (GNs). Both mechanical-forces and borohydride interaction with GNs stimulate NaBH4 clusters intercalation/absorption into the graphite interlayers acting as a 'pen' for writing, which is accomplished by exfoliating GNs with the 'printed' borohydrides. These nano-NaBH4@GNs exhibit favorable thermodynamics (decrease in ∆H of ~45%), rapid kinetics (a greater than six-fold increase) and stable de-/re-hydrogenation that retains a high capacity (up to ~5 wt% for NaBH4) compared with those of micro-NaBH4. Our results are helpful in the scalable fabrication of zero-dimensional complex hydrides on two-dimensional supports with enhanced hydrogen storage for potential applications.

  3. Method for molding threads in graphite panels

    DOEpatents

    Short, W.W.; Spencer, C.

    1994-11-29

    A graphite panel with a hole having a damaged thread is repaired by drilling the hole to remove all of the thread and making a new hole of larger diameter. A bolt with a lubricated thread is placed in the new hole and the hole is packed with graphite cement to fill the hole and the thread on the bolt. The graphite cement is cured, and the bolt is unscrewed therefrom to leave a thread in the cement which is at least as strong as that of the original thread. 8 figures.

  4. Method for molding threads in graphite panels

    DOEpatents

    Short, William W.; Spencer, Cecil

    1994-01-01

    A graphite panel (10) with a hole (11) having a damaged thread (12) is repaired by drilling the hole (11) to remove all of the thread and make a new hole (13) of larger diameter. A bolt (14) with a lubricated thread (17) is placed in the new hole (13) and the hole (13) is packed with graphite cement (16) to fill the hole and the thread on the bolt. The graphite cement (16) is cured, and the bolt is unscrewed therefrom to leave a thread (20) in the cement (16) which is at least as strong as that of the original thread (12).

  5. Graphite Fluoride Fiber Composites For Heat Sinking

    NASA Technical Reports Server (NTRS)

    Hung, Ching-Cheh; Long, Martin; Stahl, Mark

    1989-01-01

    Graphite fluoride fiber/polymer composite materials consist of graphite fluoride fibers in epoxy, polytetrafluoroethylene, or polyimide resin. Combines high electrical resistivity with high thermal conductivity and solves heat-transfer problems of many electrical systems. Commercially available in powder form, for use as dry lubricant or cathode material in lithium batteries. Produced by direct fluorination of graphite powder at temperature of 400 to 650 degree C. Applications include printed-circuit boards for high-density power electronics, insulators for magnetic-field cores like those found in alternators and transformers, substrates for thin-film resistors, and electrical-protection layers in aircraft de-icers.

  6. Status of Chronic Oxidation Studies of Graphite

    SciTech Connect

    Contescu, Cristian I.; Mee, Robert W.

    2016-05-01

    Graphite will undergo extremely slow, but continuous oxidation by traces of moisture that will be present, albeit at very low levels, in the helium coolant of HTGR. This chronic oxidation may cause degradation of mechanical strength and thermal properties of graphite components if a porous oxidation layer penetrates deep enough in the bulk of graphite components during the lifetime of the reactor. The current research on graphite chronic oxidation is motivated by the acute need to understand the behavior of each graphite grade during prolonged exposure to high temperature chemical attack by moisture. The goal is to provide the elements needed to develop predictive models for long-time oxidation behavior of graphite components in the cooling helium of HTGR. The tasks derived from this goal are: (1) Oxidation rate measurements in order to determine and validate a comprehensive kinetic model suitable for prediction of intrinsic oxidation rates as a function of temperature and oxidant gas composition; (2) Characterization of effective diffusivity of water vapor in the graphite pore system in order to account for the in-pore transport of moisture; and (3) Development and validation of a predictive model for the penetration depth of the oxidized layer, in order to assess the risk of oxidation caused damage of particular graphite grades after prolonged exposure to the environment of helium coolant in HTGR. The most important and most time consuming of these tasks is the measurement of oxidation rates in accelerated oxidation tests (but still under kinetic control) and the development of a reliable kinetic model. This report summarizes the status of chronic oxidation studies on graphite, and then focuses on model development activities, progress of kinetic measurements, validation of results, and improvement of the kinetic models. Analysis of current and past results obtained with three grades of showed that the classical Langmuir-Hinshelwood model cannot reproduce all

  7. Adsorption of lead over graphite oxide.

    PubMed

    Olanipekun, Opeyemi; Oyefusi, Adebola; Neelgund, Gururaj M; Oki, Aderemi

    2014-01-24

    The adsorption efficiency and kinetics of removal of lead in presence of graphite oxide (GO) was determined using the Atomic Absorption Spectrophotometer (AAS). The GO was prepared by the chemical oxidation of graphite and characterized using FTIR, SEM, TGA and XRD. The adsorption efficiency of GO for the solution containing 50, 100 and 150 ppm of Pb(2+) was found to be 98%, 91% and 71% respectively. The adsorption ability of GO was found to be higher than graphite. Therefore, the oxidation of activated carbon in removal of heavy metals may be a viable option to reduce pollution in portable water.

  8. High electrical resistivity carbon/graphite fibers

    NASA Technical Reports Server (NTRS)

    Vogel, F. L.; Forsman, W. C.

    1980-01-01

    Carbon/graphite fibers were chemically oxidized in the liquid phase to fibers of graphite oxide. Resistivity increases as high as 10,000 times were obtained, the oxidized fiber decomposed on exposure to atmosphere. A factor of 1,000 remained as a stable increment. The largest change observed was 1,000,000 times. Best results were obtained on the most highly graphitized fibers. Electrochemical oxidation yielded a lower increase--about 10 times, but provided a controllable method of synthesis and insight to the mechanism of reaction. Tensile tests indicated that the strength of the fiber on oxidation was decreased by no more than 25 percent.

  9. Self-Retracting Motion of Graphite Microflakes

    NASA Astrophysics Data System (ADS)

    Zheng, Quanshui; Jiang, Bo; Liu, Shoupeng; Weng, Yuxiang; Lu, Li; Xue, Qikun; Zhu, Jing; Jiang, Qing; Wang, Sheng; Peng, Lianmao

    2008-02-01

    We report the observation of a novel phenomenon, the self-retracting motion of graphite, in which tiny flakes of graphite, after being displaced to various suspended positions from islands of highly orientated pyrolytic graphite, retract back onto the islands under no external influences. Reports of this phenomenon have not been found in the literature for single crystals of any kind. Models that include the van der Waals force, electrostatic force, and shear strengths were considered to explain the observed phenomenon. These findings may conduce to create nanoelectromechanical systems with a wide range of mechanical frequency from megahertz to gigahertz.

  10. Fabrication of graphite/polyimide composite structures.

    NASA Technical Reports Server (NTRS)

    Varlas, M.

    1972-01-01

    Selection of graphite/polyimide composite as a prime candidate for high-temperature structural applications involving long-duration temperature environments of 400 to 600 F. A variety of complex graphite/polyimide components has been fabricated, using a match-metal die approach developed for making fiber-reinforced resin composites. Parts produced include sections of a missile adapter skin flange, skin frame section, and I-beam and hat-section stringers, as well as unidirectional (0 deg) and plus or minus 45 deg oriented graphite/polyimide tubes in one-, two-, and six-inch diameters.

  11. Monolithic porous graphitic carbons obtained through catalytic graphitization of carbon xerogels

    NASA Astrophysics Data System (ADS)

    Kiciński, Wojciech; Norek, Małgorzata; Bystrzejewski, Michał

    2013-01-01

    Pyrolysis of organic xerogels accompanied by catalytic graphitization and followed by selective-combustion purification was used to produce porous graphitic carbons. Organic gels impregnated with iron(III) chloride or nickel(II) acetate were obtained through polymerization of resorcinol and furfural. During the pyrolysis stage graphitization of the gel matrix occurs, which in turn develops mesoporosity of the obtained carbons. The evolution of the carbon into graphitic structures is strongly dependent on the concentrations of the transition metal. Pyrolysis leads to monoliths of carbon xerogel characterized by substantially enhanced mesoporosity resulting in specific surface areas up to 400 m2/g. Removal of the amorphous carbon by selective-combustion purification reduces the xerogels' mesoporosity, occasionally causing loss of their mechanical strength. The graphitized carbon xerogels were investigated by means of SEM, XRD, Raman scattering, TG-DTA and N2 physisorption. Through this procedure well graphitized carbonaceous materials can be obtained as bulk pieces.

  12. Facile synthesis of mesophase pitch/exfoliated graphite nanoplatelets nanocomposite and its application as anode materials for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Yang, Yi-Shuang; Wang, Cheng-Yang; Chen, Ming-Ming; Shi, Zhi-Qiang; Zheng, Jia-Ming

    2010-09-01

    Mesophase pitch (MP)/exfoliated graphite nanoplatelets (GNPs) nanocomposite has been prepared by an efficient method with an initiation of graphite intercalation compounds (GIC). X-ray diffraction, optical microscopy, high-resolution transmission electron microscopy and scanning electron microscopy analysis techniques are used to characterize the samples. It is observed that GIC has exfoliated completely into GNPs during the formation of MP/GNPs nanocomposite and the GNPs are distributed uniformly in MP matrix, which represent a conductive path for a movement of electrons throughout the composites. Electrochemical tests demonstrate that the carbonized MP/GNPs nanocomposite displays higher capacity and better cycle performance in comparison with the pure carbonized MP. It is concluded that such a large improvement of electrochemical performance within the nanocomposite may in general be related to the enhanced electronic conductivity, which is achieved by good dispersion of GNPs within MP matrix and formation of a 3D network of GNPs.

  13. Stable dispersions of polymer-coated graphitic nanoplatelets

    NASA Technical Reports Server (NTRS)

    Stankovich, Sasha (Inventor); Nguyen, Sonbinh T. (Inventor); Ruoff, Rodney S. (Inventor)

    2011-01-01

    A method of making a dispersion of reduced graphite oxide nanoplatelets involves providing a dispersion of graphite oxide nanoplatelets and reducing the graphite oxide nanoplatelets in the dispersion in the presence of a reducing agent and a polymer. The reduced graphite oxide nanoplatelets are reduced to an extent to provide a higher C/O ratio than graphite oxide. A stable dispersion having polymer-treated reduced graphite oxide nanoplatelets dispersed in a dispersing medium, such as water or organic liquid is provided. The polymer-treated, reduced graphite oxide nanoplatelets can be distributed in a polymer matrix to provide a composite material.

  14. Electrochemical Techniques for Intercalation Electrode Materials in Rechargeable Batteries.

    PubMed

    Zhu, Yujie; Gao, Tao; Fan, Xiulin; Han, Fudong; Wang, Chunsheng

    2017-03-16

    Understanding of the thermodynamic and kinetic properties of electrode materials is of great importance to develop new materials for high performance rechargeable batteries. Compared with computational understanding of physical and chemical properties of electrode materials, experimental methods provide direct and convenient evaluation of these properties. Often, the information gained from experimental work can not only offer feedback for the computational methods but also provide useful insights for improving the performance of materials. However, accurate experimental quantification of some properties can still be challenging. Among them, chemical diffusion coefficient is one representative example. It is one of the most crucial parameters determining the kinetics of intercalation compounds, which are by far the dominant electrode type used in rechargeable batteries. Therefore, it is of significance to quantitatively evaluate this parameter. For this purpose, various electrochemical techniques have been invented, for example, galvanostatic intermittent titration technique (GITT), potentiostatic intermittent titration technique (PITT), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). One salient advantage of these electrochemical techniques over other characterization techniques is that some implicit thermodynamic and kinetic quantities can be linked with the readily measurable electrical signals, current, and voltage, with very high precision. Nevertheless, proper application of these techniques requires not just an understanding of the structure and chemistry of the studied materials but sufficient knowledge of the physical model for ion transport within solid host materials and the analysis method to solve for chemical diffusion coefficient. Our group has been focusing on using various electrochemical techniques to investigate battery materials, as well as developing models for studying some emerging materials. In this Account, the

  15. The Role of Cesium Cation in Controlling Interphasial Chemistry on Graphite Anode in Propylene Carbonate-Rich Electrolytes

    SciTech Connect

    Xiang, Hongfa; Mei, Donghai; Yan, Pengfei; Bhattacharya, Priyanka; Burton, Sarah D.; Cresce, Arthur V.; Cao, Ruiguo; Engelhard, Mark H.; Bowden, Mark E.; Zhu, Zihua; Polzin, Bryant; Wang, Chong M.; Xu, Kang; Zhang, Jiguang; Xu, Wu

    2015-09-10

    Propylene carbonate (PC) is seldom used in lithium-ion batteries (LIBs) due to its sustained co-intercalation into graphene structure and the eventual graphite exfoliation, despite potential advantages it brings, such as wider liquid range and lower cost. Here we discover that cesium cation (Cs+), originally used to suppress dendrite growth of Li metal anode, directs the formation of solid electrolyte interphase (SEI) on graphitic anode in PC-rich electrolytes through preferential solvation. Effective suppression of PC-decomposition and graphite-exfoliation was achieved when the ratio of ethylene carbonate (EC)/PC in electrolytes was so adjusted that the reductive decomposition of Cs+-(EC)m (1≤m≤2) complex precedes that of Li+-(PC)n (3≤n≤5). The interphase directed by Cs+ is stable, ultrathin and compact, leading to significant improvements in LIB performances. In a broader context, the accurate tailoring of SEI chemical composition by introducing a new solvation center represents a fundamental breakthrough in manipulating interfacial reactions processes that once were elusive.

  16. Theoretical and experimental determination of the electronic structure of V(2)O(5), reduced V(2)O(5-x) and sodium intercalated NaV(2)O(5).

    PubMed

    Laubach, Stefan; Schmidt, Peter C; Thissen, Andreas; Fernandez-Madrigal, Francisco Javier; Wu, Qi-Hui; Jaegermann, Wolfram; Klemm, Matthias; Horn, Siegfried

    2007-05-28

    In this work the electronic structure of V(2)O(5), reduced V(2)O(5-x) (V(16)O(39)) and sodium intercalated NaV(2)O(5) has been studied by both theoretical and experimental methods. Theoretical band structure calculations have been performed using density functional methods (DFT). We have investigated the electron density distribution of the valence states, the total density of states (total DOS) and the partial valence band density of states (PVBDOS). Experimentally, amorphous V(2)O(5) thin films have been prepared by physical vapour deposition (PVD) on freshly cleaved highly oriented pyrolytic graphite (HOPG) substrates at room temperature with an initial oxygen understoichiometry of about 4%, resulting in a net stoichiometry of V(2)O(4.8). These films have been intercalated by sodium using vacuum deposition with subsequent spontaneous intercalation (NaV(2)O(5)) at room temperature. Resonant V3p-V3d photoelectron spectroscopy (ResPES) experiments have been performed to determine the PVBDOS focusing on the calculation of occupation numbers and the determination of effective oxidation state, reflecting ionicity and covalency of the V-O bonds. Using X-ray absorption near edge spectra (XANES) an attempt is made to visualize the changes in the unoccupied DOS due to sodium intercalation. For comparison measurements on nearly stoichiometric V(2)O(5) single crystals have been performed. The experimental data for the freshly cleaved and only marginally reduced V(2)O(5) single crystals and the NaV(2)O(5) results are in good agreement with the calculated values. The ResPES results for V(2)O(4.8) agree in principle with the calculations, but the trends in the change of the ionicity differ between experiment and theory. Experimentally we find partly occupied V 3d states above the oxygen 2p-like states and a band gap between these and the unoccupied states. In theory one finds this occupation scheme assuming oxygen vacancies in V(2)O(5) and by performing a spin

  17. Superhydrophilic graphite surfaces and water-dispersible graphite colloids by electrochemical exfoliation

    SciTech Connect

    Li, Yueh-Feng; Chen, Shih-Ming; Lai, Wei-Hao; Sheng, Yu-Jane; Tsao, Heng-Kwong

    2013-08-14

    Superhydrophilic graphite surfaces and water-dispersible graphite colloids are obtained by electrochemical exfoliation with hydrophobic graphite electrodes. Such counterintuitive characteristics are caused by partial oxidation and investigated by examining both graphite electrodes and exfoliated particles after electrolysis. The extent of surface oxidation can be explored through contact angle measurement, scanning electron microscope, electrical sheet resistance, x-ray photoelectron spectroscopy, zeta-potential analyzer, thermogravimetric analysis, UV-visible, and Raman spectroscopy. The degree of wettability of the graphite anode can be altered by the electrolytic current and time. The water contact angle declines generally with increasing the electrolytic current or time. After a sufficient time, the graphite anode becomes superhydrophilic and its hydrophobicity can be recovered by peeling with adhesive tape. This consequence reveals that the anodic graphite is oxidized by oxygen bubbles but the oxidation just occurs at the outer layers of the graphite sheet. Moreover, the characteristics of oxidation revealed by UV peak shift, peak ratio between D and G bands, and negative zeta-potential indicate the presence of graphite oxide on the outer shell of the exfoliated colloids. However, thermogravimetric analysis for the extent of decomposition of oxygen functional groups verifies that the amount of oxygen groups is significantly less than that of graphite oxide prepared via Hummer method. The structure of this partially oxidized graphite may consist of a graphite core covered with an oxidized shell. The properties of the exfoliated colloids are also influenced by pH of the electrolytic solution. As pH is increased, the extent of oxidation descends and the thickness of oxidized shell decreases. Those results reveal that the degree of oxidation of exfoliated nanoparticles can be manipulated simply by controlling pH.

  18. FennoFlakes: a project for identifying flake graphite ores in the Fennoscandian shield and utilizing graphite in different applications

    NASA Astrophysics Data System (ADS)

    Palosaari, Jenny; Eklund, O.; Raunio, S.; Lindfors, T.; Latonen, R.-M.; Peltonen, J.; Smått, J.-H.; Kauppila, J.; Lund, S.; Sjöberg-Eerola, P.; Blomqvist, R.; Marmo, J.

    2016-04-01

    Natural graphite is a strategic mineral, since the European Commission stated (Report on critical raw materials for the EU (2014)) that graphite is one of the 20 most critical materials for the European Union. The EU consumed 13% of all flake graphite in the world but produced only 3%, which stresses the demand of the material. Flake graphite, which is a flaky version of graphite, forms under high metamorphic conditions. Flake graphite is important in different applications like batteries, carbon brushes, heat sinks etc. Graphene (a single layer of graphite) can be produced from graphite and is commonly used in many nanotechnological applications, e.g. in electronics and sensors. The steps to obtain pure graphene from graphite ore include fragmentation, flotation and exfoliation, which can be cumbersome and resulting in damaging the graphene layers. We have started a project named FennoFlakes, which is a co-operation between geologists and chemists to fill the whole value chain from graphite to graphene: 1. Exploration of graphite ores (geological and geophysical methods). 2. Petrological and geochemical analyses on the ores. 3. Development of fragmentation methods for graphite ores. 4. Chemical exfoliation of the enriched flake graphite to separate flake graphite into single and multilayer graphene. 5. Test the quality of the produced material in several high-end applications with totally environmental friendly and disposable material combinations. Preliminary results show that flake graphite in high metamorphic areas has better qualities compared to synthetic graphite produced in laboratories.

  19. Morphology and Structure of Amino-fatty Acid Intercalated Montmorillonite

    NASA Astrophysics Data System (ADS)

    Reyes, Larry; Sumera, Florentino

    2015-04-01

    Natural clays and its modified forms have been studied for their wide range of applications, including polymer-layered silicate, catalysts and adsorbents. For nanocomposite production, montmorillonite (MMT) clays are often modified with organic surfactants to favor its intermixing with the polymer matrix. In the present study, Na+-montmorillonite (Na+-MMT) was subjected to organo-modification with a protonated 12-aminolauric acid (12-ALA). The amount of amino fatty acid surfactants loaded was 25, 50, 100 and 200% the cation exchange capacity (CEC) of Na+-MMT (25CEC-AMMT, 50CEC-AMMT, 100CEC-AMMT and 200CEC-AMMT). Fatty acid-derived surfactants are an attractive resource of intercalating agents for clays due to their renewability and abundance. X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) were performed to determine the occurrence of intercalation of 12-ALA and their molecular structure in the clay's silicates. XRD analysis revealed that the interlayer spacing between the alumino-silicate layers increased from 1.25 nm to 1.82 nm with increasing ALA content. The amino fatty acid chains were considered to be in a flat monolayer structure at low surfactant loading, and a bilayered to a pseudotrilayered structure at high surfactant loading. On the other hand, FTIR revealed that the alkyl chains adopt a gauche conformation, indicating their disordered state based on their CH2symmetric and asymmetric vibrations. Thermogravimetric analyses (TGA) allows the determination of the moisture and organic content in clays. Here, TGA revealed that the surfactant in the clay was thermally stable, with Td ranging from 353° C to 417° C. The difference in the melting behavior of the pristine amino fatty acids and confined fatty acids in the interlayer galleries of the clay were evaluated by Differential Scanning Calorimerty (DSC). The melting temperatures (Tm) of the amino fatty acid in the clay were initially found to be higher than those of the free

  20. Tuning thermal conductivity in molybdenum disulfide by electrochemical intercalation

    PubMed Central

    Zhu, Gaohua; Liu, Jun; Zheng, Qiye; Zhang, Ruigang; Li, Dongyao; Banerjee, Debasish; Cahill, David G.

    2016-01-01

    Thermal conductivity of two-dimensional (2D) materials is of interest for energy storage, nanoelectronics and optoelectronics. Here, we report that the thermal conductivity of molybdenum disulfide can be modified by electrochemical intercalation. We observe distinct behaviour for thin films with vertically aligned basal planes and natural bulk crystals with basal planes aligned parallel to the surface. The thermal conductivity is measured as a function of the degree of lithiation, using time-domain thermoreflectance. The change of thermal conductivity correlates with the lithiation-induced structural and compositional disorder. We further show that the ratio of the in-plane to through-plane thermal conductivity of bulk crystal is enhanced by the disorder. These results suggest that stacking disorder and mixture of phases is an effective mechanism to modify the anisotropic thermal conductivity of 2D materials. PMID:27767030