International strategic minerals inventory summary report; natural graphite

USGS Publications Warehouse

Krauss, U.H.; Schmidt, H.W.; Taylor, H.A.; Sutphin, D.M.

1989-01-01

Natural graphite is a crystalline mineral of pure carbon which normally occurs in the form of platelet-shaped crystals. It has important properties, such as chemical inertness, low thermal expansion, and lubricity, that make it almost irreplaceable for certain uses such as refractories and steelmaking. Graphite ore types are crystalline (flake and lump} or 'amorphous' (cryptocrystalline}. Refractory applications use the largest total amount of natural graphite, while the most important use of crystalline graphite is in crucibles for handling molten metals. All graphite deposits being mined today are found in the following metamorphic environments: (1) contact metamorphosed coal generally is a source of amorphous graphite; (2)disseminated crystalline flake graphite comes from syngenetic metasediments; and (3) crystalline lump graphite is found in epigenetic veins in high-grade metamorphic regions. Graphite may also occur as a trace mineral in ultrabasic rocks and pegmatites, but these are economically insignificant. The world's identified economically exploitable resources of crystalline graphite in major deposits are estimated to be about 9.7 million metric tons of concentrate. In-place resources of amorphous graphite are about 11.5 million metric tons. Of these, less than 2 percent of the crystalline ore and less than 1 percent of the amorphous ore are in western industrial countries. World mining production of natural graphite rose from 347,000 metric tons in 1973 to 659,000 metric tons in 1986, while the proportion produced by central economy countries increased from about 50 percent for the period from 1973 to 1978 to more than 64 percent in 1979 to 1986. It is estimated that crystalline flake graphite accounts for at least 180,000 metric tons of total annual world mining production of natural graphite, and amorphous graphite makes up the rest.

Electrochemical exfoliation of graphite to stage-III graphite bisulfate flakes in low concentration sulfuric acid solution: A novel synthesis route to completely trilayer graphene suspension

NASA Astrophysics Data System (ADS)

Mir, Afkham; Shukla, Anupam

2018-06-01

Graphene produced from electrochemical exfoliation of graphite show a scatter in the number of layers. This scatter is a serious drawback for sensor and opto-electronic applications since the electronic properties of graphene change with number of layers. The scatter in the layer number of graphene is caused by formation of the intermediate graphite intercalation compounds (GIC) of different stage numbers as well as simultaneous cleaving of the GICs in the dispersion-unsuitable aqueous environment. In this work, we show the synthesis of stage-III graphite bisulfate (GB) enriched flakes by electrochemical exfoliation of graphite in low concentration (0.1 M) sulfuric acid from two different routes. We further show that the intercalated bisulfate planes provide sites for selective cleaving of the GB particles to trilayer graphene in DMF, a solvent favorable for graphene dispersion. Morphological characterizations show that while GB particles from one of the routes give graphene with a small scatter in the layer numbers, the other route provides a completely trilayer graphene dispersion. TEM and optical micrographs show graphene flakes have linear dimensions of several micrometers and a low aspect ratio suitable for use in sensor applications.

Electrolytic exfoliation of graphite in water with multifunctional electrolytes: en route towards high quality, oxide-free graphene flakes.

PubMed

Munuera, J M; Paredes, J I; Villar-Rodil, S; Ayán-Varela, M; Martínez-Alonso, A; Tascón, J M D

2016-02-07

Electrolytic--usually referred to as electrochemical--exfoliation of graphite in water under anodic potential holds enormous promise as a simple, green and high-yield method for the mass production of graphene, but currently suffers from several drawbacks that hinder its widespread adoption, one of the most critical being the oxidation and subsequent structural degradation of the carbon lattice that is usually associated with such a production process. To overcome this and other limitations, we introduce and implement the concept of multifunctional electrolytes. The latter are amphiphilic anions (mostly polyaromatic hydrocarbons appended with sulfonate groups) that play different relevant roles as (1) an intercalating electrolyte to trigger exfoliation of graphite into graphene flakes, (2) a dispersant to afford stable aqueous colloidal suspensions of the flakes suitable for further use, (3) a sacrificial agent to prevent graphene oxidation during exfoliation and (4) a linker to promote nanoparticle anchoring on the graphene flakes, yielding functional hybrids. The implementation of this strategy with some selected amphiphiles even furnishes anodically exfoliated graphenes of a quality similar to that of flakes produced by direct, ultrasound- or shear-induced exfoliation of graphite in the liquid phase (i.e., almost oxide- and defect-free). These high quality materials were used for the preparation of catalytically efficient graphene-Pt nanoparticle hybrids, as demonstrated by model reactions (reduction of nitroarenes). The multifunctional performance of these electrolytes is also discussed and rationalized, and a mechanistic picture of their oxidation-preventing ability is proposed. Overall, the present results open the prospect of anodic exfoliation as a competitive method for the production of very high quality graphene flakes.

How much does size really matter? Exploring the limits of graphene as Li ion battery anode material

NASA Astrophysics Data System (ADS)

Sun, H.; Varzi, A.; Pellegrini, V.; Dinh, D. A.; Raccichini, R.; Del Rio-Castillo, A. E.; Prato, M.; Colombo, M.; Cingolani, R.; Scrosati, B.; Passerini, S.; Bonaccorso, F.

2017-02-01

We unravel the role of flake dimensionality on the lithiation/de-lithiation processes and electrochemical performance of anodes based on few-(FLG) and multi-layer graphene (MLG) flakes prepared by liquid phase exfoliation (LPE) of pristine graphite. The flakes are sorted by lateral size (from 380 to 75 nm) and thickness from 20 (MLG) to 2 nm (FLG) exploiting a sedimentation-based separation in centrifugal field and, finally, deposited onto Cu disks for the realization of four binder-free anodes. The electrochemical results show that decreasing lateral size and thickness leads to an increase of the initial specific capacity from ≈590 to ≈1270mAhg-1. However, an increasing irreversible capacity is also associated to the reduction of flakes' size. We find, in addition, that the preferential Li ions storage by adsorption rather than intercalation in small lateral size (<100 nm) FLG flakes has a detrimental effect on the average de-lithiation voltage, resulting on low voltage efficiency of these anodes. We believe that the results reported in this work, provide the guidelines for the practical exploitation of graphene-based electrodes.

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.

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

Anisotropy in thermal conductivity of graphite flakes–SiC{sub p}/matrix composites: Implications in heat sinking design for thermal management applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Molina, J.M., E-mail: jmmj@ua.es; Departamento de Física Aplicada, Universidad de Alicante, Ap. 99, E-03080 Alicante; Departamento de Química Inorgánica, Universidad de Alicante, Ap. 99, | E-03080 Alicante

2015-11-15

Within the frame of heat dissipation for electronics, a very interesting family of anisotropic composite materials, fabricated by liquid infiltration of a matrix into preforms of oriented graphite flakes and SiC particles, has been recently proposed. Aiming to investigate the implications of the inherent anisotropy of these composites on their thermal conductivity, and hence on their potential applications, materials with matrices of Al–12 wt.% Si alloy and epoxy polymer have been fabricated. Samples have been cut at a variable angle with respect to the flakes plane and thermal conductivity has been measured by means of two standard techniques, namely, steadymore » state technique and laser flash method. Experimental results are presented and discussed in terms of current models, from which important technological implications for heat sinking design can be derived. - Highlights: • Anisotropy in thermal conductivity of graphite flakes-based composites is evaluated. • Samples are cut in a direction forming a variable angle with the oriented flakes. • For angles 0° and 90°, thermal conductivity does not depend on sample geometry. • For intermediate angles, thermal conductivity strongly depends on sample geometry. • “Thin” samples must be thicker than 600 μm, “thick” samples must be encapsulated.« less

Graphene levitation and orientation control using a magnetic field

NASA Astrophysics Data System (ADS)

Niu, Chao; Lin, Feng; Wang, Zhiming M.; Bao, Jiming; Hu, Jonathan

2018-01-01

This paper studies graphene levitation and orientation control using a magnetic field. The torques in all three spatial directions induced by diamagnetic forces are used to predict stable conditions for different shapes of millimeter-sized graphite plates. We find that graphite plates, in regular polygon shapes with an even number of sides, will be levitated in a stable manner above four interleaved permanent magnets. In addition, the orientation of micrometer-sized graphene flakes near a permanent magnet is studied in both air and liquid environments. Using these analyses, we are able to simulate optical transmission and reflection on a writing board and thereby reveal potential applications using this technology for display screens. Understanding the control of graphene flake orientation will lead to the discovery of future applications using graphene flakes.

Stretchable and flexible high-strain sensors made using carbon nanotubes and graphite films on natural rubber.

PubMed

Tadakaluru, Sreenivasulu; Thongsuwan, Wiradej; Singjai, Pisith

2014-01-06

Conventional metallic strain sensors are flexible, but they can sustain maximum strains of only ~5%, so there is a need for sensors that can bear high strains for multifunctional applications. In this study, we report stretchable and flexible high-strain sensors that consist of entangled and randomly distributed multiwall carbon nanotubes or graphite flakes on a natural rubber substrate. Carbon nanotubes/graphite flakes were sandwiched in natural rubber to produce these high-strain sensors. Using field emission scanning electron microscopy, the morphology of the films for both the carbon nanotube and graphite sensors were assessed under different strain conditions (0% and 400% strain). As the strain was increased, the films fractured, resulting in an increase in the electrical resistance of the sensor; this change was reversible. Strains of up to 246% (graphite sensor) and 620% (carbon nanotube sensor) were measured; these values are respectively ~50 and ~120 times greater than those of conventional metallic strain sensors.

Stretchable and Flexible High-Strain Sensors Made Using Carbon Nanotubes and Graphite Films on Natural Rubber

PubMed Central

Tadakaluru, Sreenivasulu; Thongsuwan, Wiradej; Singjai, Pisith

2014-01-01

Conventional metallic strain sensors are flexible, but they can sustain maximum strains of only ∼5%, so there is a need for sensors that can bear high strains for multifunctional applications. In this study, we report stretchable and flexible high-strain sensors that consist of entangled and randomly distributed multiwall carbon nanotubes or graphite flakes on a natural rubber substrate. Carbon nanotubes/graphite flakes were sandwiched in natural rubber to produce these high-strain sensors. Using field emission scanning electron microscopy, the morphology of the films for both the carbon nanotube and graphite sensors were assessed under different strain conditions (0% and 400% strain). As the strain was increased, the films fractured, resulting in an increase in the electrical resistance of the sensor; this change was reversible. Strains of up to 246% (graphite sensor) and 620% (carbon nanotube sensor) were measured; these values are respectively ∼50 and ∼120 times greater than those of conventional metallic strain sensors. PMID:24399158

Effect of milling time on microstructure and mechanical properties of Cu-Ni-graphite composites

NASA Astrophysics Data System (ADS)

Wang, Yiran; Gao, Yimin; Li, Yefei; Zhang, Chao; Huang, Xiaoyu; Zhai, Wenyan

2017-09-01

Cu-Ni-graphite composites are intended for application in switch slide baseplate materials. The microstructure of the composites depends strongly on the ball milling time, and a suitable time can significantly improve the properties of the Cu-Ni-graphite composites. In this study, a two-step milling method was employed. The morphology evolution and microstructural features of the powder was characterized at different milling times. Afterwards, the Cu-Ni-graphite composites were prepared in the process of cold pressing, sintering, re-pressing and re-sintering as a function of the different milling times. Finally, both the microstructure and mechanical properties of the Cu-Ni-graphite composites are discussed. The results show that no new phase was generated during the milling process. The morphology evolution of the mixture of Cu/Ni powder changed from spherical-like to cubic-like, plate-like and flake-like with an increasing milling time. The microstructure of the composites consisted of α-phase and graphite. The boundary area and quantity of pores changed as the milling time increased. The relative density, hardness and flexural strength reached maximum values at 15 h of milling time.

Femtosecond laser induced nanostructuring of graphite for the fabrication of quasi-periodic nanogratings and novel carbon nanostructures

NASA Astrophysics Data System (ADS)

Saikiran, V.; Dar, Mudasir H.; Rao, D. Narayana

2018-01-01

Here we have experimentally studied ultrafast femtosecond laser ablation of graphite in air and water environments for the fabrication of promising nanostructures on the graphite surface and also nanographite flakes, graphene quantum dots in water. After the fs laser irradiation in air quasi-periodic nanogratings were found on the graphite surface and when the irradiation is done in water we observed graphene quantum dots (GQDs) and graphitic flakes dispersed in the solution. The sheets consist of few layers of spongy kind of porous graphene, which form an irregular 3D porous structure. The field emission scanning electron microscopy reveals the formation of fluence dependent quasi-periodic deep-subwavelength nanogratings (Ʌ = 130-230 nm) on the surface. Several characterization methods have confirmed the formation of layered graphene and quantum dots. The studies on the solution confirmed the presence of GQDs with dimensions ranging about 2-4 nm. It is found that the formation of subwavelength structures and GQDs depends on the fs-laser energy and vary with different laser parameters such as fluence, energy, laser polarization.

Study on the Microstructure and Liquid Phase Formation in a Semisolid Gray Cast Iron

NASA Astrophysics Data System (ADS)

Benati, Davi Munhoz; Ito, Kazuhiro; Kohama, Kazuyuki; Yamamoto, Hajime; Zoqui, Eugenio José

2017-10-01

The development of high-quality semisolid raw materials requires an understanding of the phase transformations that occur as the material is heated up to the semisolid state, i.e., its melting behavior. The microstructure of the material plays a very important role during semisolid processing as it determines the flow behavior of the material when it is formed, making a thorough understanding of the microstructural evolution essential. In this study, the phase transformations and microstructural evolution in Fe2.5C1.5Si gray cast iron specially designed for thixoforming processes as it was heated to the semisolid state were observed using in situ high-temperature confocal laser scanning microscopy. At room temperature, the alloy has a matrix of pearlite and ferrite with fine interdendritic type D flake graphite. During heating, the main transformations observed were graphite precipitation inside the grains and at the austenite grain boundaries; graphite flakes and graphite precipitates growing and becoming coarser with the increasing temperature; and the beginning of melting at around 1413 K to 1423 K (1140 °C to 1150 °C). Melting begins with the eutectic phase ( i.e., the carbon-rich phase) and continues with the primary phase (primary austenite), which is consumed as the temperature increases. Melting of the eutectic phase composed by coarsened interdendritic graphite flakes produced a semi-continuous liquid network homogeneously surrounding and wetting the dendrites of the solid phase, causing grains to detach from each other and producing the intended solid globules immersed in liquid.

Fine-Grained Targets for Laser Synthesis of Carbon Nanotubes

NASA Technical Reports Server (NTRS)

Smith, Michael W. (Inventor); Park, Cheol (Inventor)

2017-01-01

A mechanically robust, binder-free, inexpensive target for laser synthesis of carbon nanotubes and a method for making same, comprising the steps of mixing prismatic edge natural flake graphite with a metal powder catalyst and pressing the graphite and metal powder mixture into a mold having a desired target shape.

Fine-Grained Targets for Laser Synthesis of Carbon Nanotubes

NASA Technical Reports Server (NTRS)

Smith, Michael W. (Inventor); Park, Cheol (Inventor)

2015-01-01

A mechanically robust, binder-free, inexpensive target for laser synthesis of carbon nanotubes and a method for making same, comprising the steps of mixing prismatic edge natural flake graphite with a metal powder catalyst and pressing the graphite and metal powder mixture into a mold having a desired target shape.

Graphene oxide liquid crystals: synthesis, phase transition, rheological property, and applications in optoelectronics and display.

PubMed

Lin, Feng; Tong, Xin; Wang, Yanan; Bao, Jiming; Wang, Zhiming M

2015-12-01

Graphene oxide (GO) liquid crystals (LCs) are macroscopically ordered GO flakes dispersed in water or polar organic solvents. Since the first report in 2011, GO LCs have attracted considerable attention for their basic properties and potential device applications. In this review, we summarize recent developments and present a comprehensive understanding of GO LCs via many aspects ranging from the exfoliation of GO flakes from graphite, to phases and phase transitions under various conditions, the orientational responses of GO under external magnetic and electric fields, and finally Kerr effect and display applications. The emphasis is placed on the unique and basic properties of GO and their ordered assembly. We will also discuss challenges and issues that need to be overcome in order to gain a more fundamental understanding and exploit full device potentials of GO LCs.

Superlubric sliding of graphene nanoflakes on graphene.

PubMed

Feng, Xiaofeng; Kwon, Sangku; Park, Jeong Young; Salmeron, Miquel

2013-02-26

The lubricating properties of graphite and graphene have been intensely studied by sliding a frictional force microscope tip against them to understand the origin of the observed low friction. In contrast, the relative motion of free graphene layers remains poorly understood. Here we report a study of the sliding behavior of graphene nanoflakes (GNFs) on a graphene surface. Using scanning tunneling microscopy, we found that the GNFs show facile translational and rotational motions between commensurate initial and final states at temperatures as low as 5 K. The motion is initiated by a tip-induced transition of the flakes from a commensurate to an incommensurate registry with the underlying graphene layer (the superlubric state), followed by rapid sliding until another commensurate position is reached. Counterintuitively, the average sliding distance of the flakes is larger at 5 K than at 77 K, indicating that thermal fluctuations are likely to trigger their transitions from superlubric back to commensurate ground states.

Exfoliated graphite with graphene flakes as potential candidates for TL dosimeters at high gamma doses.

PubMed

Ortiz-Morales, A; López-González, E; Rueda-Morales, G; Ortega-Cervantez, G; Ortiz-Lopez, J

2018-06-06

Graphite powder (GP) subjected to microwave radiation (MWG) results in exfoliation of graphite particles into few-layered graphene flakes (GF) intermixed with partially exfoliated graphite particles (PEG). Characterization of MWG by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Raman spectroscopy reveal few-layer GF with sizes ranging from 0.2 to 5 µm. Raman D, G, and 2D (G') bands characteristic of graphitic structures include evidence of the presence of bilayered graphene. The thermoluminescent (TL) dosimetric properties of MWG are evaluated and can be characterized as a gamma-ray sensitive and dose-resistant material with kinetic parameters (activation energy for the main peak located at 400 and 408 K is 0.69 and 0.72 eV) and threshold dose (~1 kGy and 5 kGy respectively). MWG is a low-Z material (Z eff = 6) with a wide linear range of TL dose-response (0.170-2.5 kGy) tested at doses in the 1-20 kGy range with promising results for applications in gamma-ray dosimetry. Results obtained in gamma irradiated MWG are compared with those obtained in graphite powder samples (GP) without microwave treatment. Copyright © 2018 Elsevier Ltd. All rights reserved.

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.

Screening Level Ecological Risk Assessments of Some Military Munitions and Obscurant-related Compounds for Selected Threatened and Endangered Species

DTIC Science & Technology

2006-10-01

species resulting from dispersion and deposi- tion of vapors and particles found in the fog oils, hexachloroethane smoke, colored smokes, white...dispersion and deposition of vapors and particles found in the fog oils, hexachloroethane smoke, colored smokes, white phosphorus, and obscurants...titanium dioxide colored smoke (red, green, yellow, purple) polyethylene glycol (PEG) brass flakes graphite flakes terephelatic acid For this

A Simple Transmission Electron Microscopy Method for Fast Thickness Characterization of Suspended Graphene and Graphite Flakes.

PubMed

Rubino, Stefano; Akhtar, Sultan; Leifer, Klaus

2016-02-01

We present a simple, fast method for thickness characterization of suspended graphene/graphite flakes that is based on transmission electron microscopy (TEM). We derive an analytical expression for the intensity of the transmitted electron beam I 0(t), as a function of the specimen thickness t (t<λ; where λ is the absorption constant for graphite). We show that in thin graphite crystals the transmitted intensity is a linear function of t. Furthermore, high-resolution (HR) TEM simulations are performed to obtain λ for a 001 zone axis orientation, in a two-beam case and in a low symmetry orientation. Subsequently, HR (used to determine t) and bright-field (to measure I 0(0) and I 0(t)) images were acquired to experimentally determine λ. The experimental value measured in low symmetry orientation matches the calculated value (i.e., λ=225±9 nm). The simulations also show that the linear approximation is valid up to a sample thickness of 3-4 nm regardless of the orientation and up to several ten nanometers for a low symmetry orientation. When compared with standard techniques for thickness determination of graphene/graphite, the method we propose has the advantage of being simple and fast, requiring only the acquisition of bright-field images.

A study on the physicochemical properties of hydroalcoholic solutions to improve the direct exfoliation of natural graphite down to few-layers graphene

NASA Astrophysics Data System (ADS)

Fedi, Filippo; Miglietta, Maria Lucia; Polichetti, Tiziana; Ricciardella, Filiberto; Massera, Ettore; Ninno, Domenico; Di Francia, Girolamo

2015-03-01

Straightforward methods to produce pristine graphene flakes in large quantities are based on the liquid-phase exfoliation processes. These one-step physical transformations of graphite into graphene offer many unique advantages. To date, a large number of liquids have been employed as exfoliation media exploiting their thermodynamic and chemical features as compared to those of graphene. Here, we pursued the goal of realizing water based mixtures to exfoliate graphite and disperse graphene without the aid of surfactants. To this aim, aqueous mixtures with suitable values of surface tension and Hansen solubility parameters (HSPs), were specifically designed and used. The very high water surface tension was decreased by the addition of solvents with lower surface tensions such as alcohols, obtaining, in this way, more favourable HSP distances. The specific role of each of these thermodynamic features was finally investigated. The results showed that the designed hydroalcoholic solutions were effective in both the graphite exfoliation and dispersion without the addition of any surfactants or other stabilizing agents. Stable graphene suspensions were obtained at concentration comparable to those produced with low-boiling solvents and water/surfactants.

Enhancement of the mechanical properties by graphite flake addition

DOEpatents

Bunnell, Sr., Lee R.

1991-01-01

Compositions in accordance with the invention comprise a polymer and flake reinforcing material distributed throughout the polymer in an effective amount to structurally reinforce the polymer. Individual flakes of the flake material (a) are less than or equal to 1,000 Angstroms in thickness, (b) have an aspect ratio greater than or equal to 100, and (c) are preferably significantly randomly oriented throughout the polymer. A novel apparatus for shear grinding a platy solid material into such individual flakes comprises a cylindrical shearing drum and a shear grinder received therein. The shearing drum has a longitudinal axis and an internal surface formed about a first predetermined radius of curvature. The cylindrical drum is supported for rotation about its longitudinal axis. The shear grinder has an external surface formed about a second predetermined radius of curvature. The second radius of curvature is slightly less than the first radius of curvature.

Characterization of airborne and bulk particulate from iron and steel manufacturing facilities.

PubMed

Machemer, Steven D

2004-01-15

Characterization of airborne and bulk particulate material from iron and steel manufacturing facilities, commonly referred to as kish, indicated graphite flakes and graphite flakes associated with spherical iron oxide particles were unique particle characteristics useful in identifying particle emissions from iron and steel manufacturing. Characterization of airborne particulate material collected in receptor areas was consistent with multiple atmospheric release events of kish particles from the local iron and steel facilities into neighboring residential areas. Kish particles deposited in nearby residential areas included an abundance of graphite flakes, tens of micrometers to millimeters in size, and spherical iron oxide particles, submicrometer to tens of micrometers in size. Bulk kish from local iron and steel facilities contained an abundance of similar particles. Approximately 60% of blast furnace kish by volume consisted of spherical iron oxide particles in the respirable size range. Basic oxygen furnace kish contained percent levels of strongly alkaline components such as calcium hydroxide. In addition, concentrations of respirable Mn in airborne particulate in residential areas and at local iron and steel facilities were approximately 1.6 and 53 times the inhalation reference concentration of 0.05 microg/m3 for chronic inhalation exposure of Mn, respectively. Thus, airborne release of kish may pose potential respirable particulate, corrosive, or toxic hazards for human health and/or a corrosive hazard for property and the environment.

Screening of the chemical reactivity of three different graphite sources using the formation of reductively alkylated graphene as a model reaction.

PubMed

Knirsch, Kathrin C; Englert, Jan M; Dotzer, Christoph; Hauke, Frank; Hirsch, Andreas

2013-11-28

Reductive alkylation of three graphite starting materials G(flake), G(powder), and G(spherical) reveals pronounced differences in the obtained covalently functionalized graphene with respect to the degree of functionalization, exfoliation efficiency and product homogeneity, as demonstrated by statistical Raman microscopy (SRM), TGA/MS, IR-spectroscopy and solubility behavior.

Bending fracture in carbon nanotubes.

PubMed

Kuo, Wen-Shyong; Lu, Hsin-Fang

2008-12-10

A novel approach was adopted to incur bending fracture in carbon nanotubes (CNTs). Expanded graphite (EG) was made by intercalating and exfoliating natural graphite flakes. The EG was deposited with nickel particles, from which CNTs were grown by chemical vapor deposition. The CNTs were tip-grown, and their roots were fixed on the EG flakes. The EG flakes were compressed, and many CNTs on the surface were fragmented due to the compression-induced bending. Two major modes of the bending fracture were observed: cone-shaped and shear-cut. High-resolution scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to examine the crack growth within the graphene layers. The bending fracture is characterized by two-region crack growth. An opening crack first appears around the outer-tube due to the bending-induced tensile stress. The crack then branches to grow along an inclined direction toward the inner-tube due to the presence of the shear stress in between graphene layers. An inner-tube pullout with inclined side surface is formed. The onset and development of the crack in these two regions are discussed.

Effect of stray electric fields on cooling of center of mass motion of levitated graphite flakes

NASA Astrophysics Data System (ADS)

Nagornykh, Pavel; Coppock, Joyce; Kane, Bruce

2015-03-01

Levitation of charged multilayer graphene flakes in a quadrupole ion trap provides a unique way to study graphene in isolated conditions. Cooling of a flake in such a setup is necessary for high vacuum measurements of the flake and is achieved by using a parametric feedback scheme. We present data showing the strong dependence of the cooling of the flake's center of mass motion on the stray electric fields. We achieve this by using auxiliary electrodes to shift the position of the trap center in space. Once the point of minimum interaction between the stray fields and the particle is found (leading to cooling of the flake motion to temperatures below 20K at pressure of 10-7 Torr), we can estimate charge and mass of the flake by observing quantized discharge of the particle and measure transient dynamics of the center of mass motion by turning the cooling off and on. As an additional benefit, the behavior of the flake away from the optimum trap position can be used to quantify stray fields' effect on the particle motion by measuring its spinning orientation and frequency dependence on offset from the optimum position.

Graphite

USGS Publications Warehouse

Robinson, Gilpin R.; Hammarstrom, Jane M.; Olson, Donald W.; Schulz, Klaus J.; DeYoung,, John H.; Seal, Robert R.; Bradley, Dwight C.

2017-12-19

Graphite is a form of pure carbon that normally occurs as black crystal flakes and masses. It has important properties, such as chemical inertness, thermal stability, high electrical conductivity, and lubricity (slipperiness) that make it suitable for many industrial applications, including electronics, lubricants, metallurgy, and steelmaking. For some of these uses, no suitable substitutes are available. Steelmaking and refractory applications in metallurgy use the largest amount of produced graphite; however, emerging technology uses in large-scale fuel cell, battery, and lightweight high-strength composite applications could substantially increase world demand for graphite.Graphite ores are classified as “amorphous” (microcrystalline), and “crystalline” (“flake” or “lump or chip”) based on the ore’s crystallinity, grain-size, and morphology. All graphite deposits mined today formed from metamorphism of carbonaceous sedimentary rocks, and the ore type is determined by the geologic setting. Thermally metamorphosed coal is the usual source of amorphous graphite. Disseminated crystalline flake graphite is mined from carbonaceous metamorphic rocks, and lump or chip graphite is mined from veins in high-grade metamorphic regions. Because graphite is chemically inert and nontoxic, the main environmental concerns associated with graphite mining are inhalation of fine-grained dusts, including silicate and sulfide mineral particles, and hydrocarbon vapors produced during the mining and processing of ore. Synthetic graphite is manufactured from hydrocarbon sources using high-temperature heat treatment, and it is more expensive to produce than natural graphite.Production of natural graphite is dominated by China, India, and Brazil, which export graphite worldwide. China provides approximately 67 percent of worldwide output of natural graphite, and, as the dominant exporter, has the ability to set world prices. China has significant graphite reserves, and China’s graphite production is expected to increase, although rising labor costs and some mine production problems are developing. China is expected to continue to be the dominant exporter for the near future. Mexico and Canada export graphite mainly to the United States, which has not had domestic production of natural graphite since the 1950s. Most graphite deposits in the United States are too small, low-grade, or remote to be of commercial value in the near future, and the likelihood of discovering larger, higher-grade, or favorably located domestic deposits is unlikely. The United States is a major producer of synthetic graphite.

Quantitative Analysis of Heavy Metals in Water Based on LIBS with an Automatic Device for Sample Preparation

NASA Astrophysics Data System (ADS)

Hu, Li; Zhao, Nanjing; Liu, Wenqing; Meng, Deshuo; Fang, Li; Wang, Yin; Yu, Yang; Ma, Mingjun

2015-08-01

Heavy metals in water can be deposited on graphite flakes, which can be used as an enrichment method for laser-induced breakdown spectroscopy (LIBS) and is studied in this paper. The graphite samples were prepared with an automatic device, which was composed of a loading and unloading module, a quantitatively adding solution module, a rapid heating and drying module and a precise rotating module. The experimental results showed that the sample preparation methods had no significant effect on sample distribution and the LIBS signal accumulated in 20 pulses was stable and repeatable. With an increasing amount of the sample solution on the graphite flake, the peak intensity at Cu I 324.75 nm accorded with the exponential function with a correlation coefficient of 0.9963 and the background intensity remained unchanged. The limit of detection (LOD) was calculated through linear fitting of the peak intensity versus the concentration. The LOD decreased rapidly with an increasing amount of sample solution until the amount exceeded 20 mL and the correlation coefficient of exponential function fitting was 0.991. The LOD of Pb, Ni, Cd, Cr and Zn after evaporating different amounts of sample solution on the graphite flakes was measured and the variation tendency of their LOD with sample solution amounts was similar to the tendency for Cu. The experimental data and conclusions could provide a reference for automatic sample preparation and heavy metal in situ detection. supported by National Natural Science Foundation of China (No. 60908018), National High Technology Research and Development Program of China (No. 2013AA065502) and Anhui Province Outstanding Youth Science Fund of China (No. 1108085J19)

Room temperature rubbing for few-layer two-dimensional thin flakes directly on flexible polymer substrates

PubMed Central

Yu, Yan; Jiang, Shenglin; Zhou, Wenli; Miao, Xiangshui; Zeng, Yike; Zhang, Guangzu; Liu, Sisi

2013-01-01

The functional layers of few-layer two-dimensional (2-D) thin flakes on flexible polymers for stretchable applications have attracted much interest. However, most fabrication methods are “indirect” processes that require transfer steps. Moreover, previously reported “transfer-free” methods are only suitable for graphene and not for other few-layer 2-D thin flakes. Here, a friction based room temperature rubbing method is proposed for fabricating different types of few-layer 2-D thin flakes (graphene, hexagonal boron nitride (h-BN), molybdenum disulphide (MoS2), and tungsten disulphide (WS2)) on flexible polymer substrates. Commercial 2-D raw materials (graphite, h-BN, MoS2, and WS2) that contain thousands of atom layers were used. After several minutes, different types of few-layer 2-D thin flakes were fabricated directly on the flexible polymer substrates by rubbing procedures at room temperature and without any transfer step. These few-layer 2-D thin flakes strongly adhere to the flexible polymer substrates. This strong adhesion is beneficial for future applications. PMID:24045289

Exfoliation of non-oxidized graphene flakes for scalable conductive film.

PubMed

Park, Kwang Hyun; Kim, Bo Hyun; Song, Sung Ho; Kwon, Jiyoung; Kong, Byung Seon; Kang, Kisuk; Jeon, Seokwoo

2012-06-13

The increasing demand for graphene has required a new route for its mass production without causing extreme damages. Here we demonstrate a simple and cost-effective intercalation based exfoliation method for preparing high quality graphene flakes, which form a stable dispersion in organic solvents without any functionalization and surfactant. Successful intercalation of alkali metal between graphite interlayers through liquid-state diffusion from ternary KCl-NaCl-ZnCl(2) eutectic system is confirmed by X-ray diffraction and X-ray photoelectric spectroscopy. Chemical composition and morphology analyses prove that the graphene flakes preserve their intrinsic properties without any degradation. The graphene flakes remain dispersed in a mixture of pyridine and salts for more than 6 months. We apply these results to produce transparent conducting (∼930 Ω/□ at ∼75% transmission) graphene films using the modified Langmuir-Blodgett method. The overall results suggest that our method can be a scalable (>1 g/batch) and economical route for the synthesis of nonoxidized graphene flakes.

New insight of high temperature oxidation on self-exfoliation capability of graphene oxide.

PubMed

Liu, Yuhang; Zeng, Jie; Han, Di; Wu, Kai; Yu, Bowen; Chai, Songgang; Chen, Feng; Fu, Qiang

2018-05-04

The preparation of graphene oxide (GO) via Hummers method is usually divided into two steps: low temperature oxidation at 35 °C (step I oxidation) and high temperature oxidation at 98 °C (step II oxidation). However, the effects of these two steps on the exfoliation capability and chemical structure of graphite oxide remain unclear. In this study, both the functional group content of graphite oxide and the entire evolution of interlayer spacing were investigated during the two steps. Step I oxidation is a slowly inhomogeneous oxidation step to remove unoxidized graphite flakes. The prepared graphite oxide can be easily self-exfoliated but contains a lot of organic sulfur. During the first 20 min of step II oxidation, the majority of organic sulfur can be efficiently removed and graphite oxide still remains a good exfoliation capability due to sharp increasing of carboxyl groups. However, with a longer oxidation time at step II oxidation, the decrease of organic sulfur content is slowed down apparently but without any carboxyl groups forming, then graphite oxide finally loses self-exfoliation capability. It is concluded that a short time of step II oxidation can produce purer and ultralarge GO sheets via self-exfoliation. The pure GO is possessed with better thermal stability and liquid crystal behavior. Besides, reduced GO films prepared from step II oxidation show better mechanical and electric properties after reducing compared with that obtained only via step I oxidation.

New insight of high temperature oxidation on self-exfoliation capability of graphene oxide

NASA Astrophysics Data System (ADS)

Liu, Yuhang; Zeng, Jie; Han, Di; Wu, Kai; Yu, Bowen; Chai, Songgang; Chen, Feng; Fu, Qiang

2018-05-01

The preparation of graphene oxide (GO) via Hummers method is usually divided into two steps: low temperature oxidation at 35 °C (step I oxidation) and high temperature oxidation at 98 °C (step II oxidation). However, the effects of these two steps on the exfoliation capability and chemical structure of graphite oxide remain unclear. In this study, both the functional group content of graphite oxide and the entire evolution of interlayer spacing were investigated during the two steps. Step I oxidation is a slowly inhomogeneous oxidation step to remove unoxidized graphite flakes. The prepared graphite oxide can be easily self-exfoliated but contains a lot of organic sulfur. During the first 20 min of step II oxidation, the majority of organic sulfur can be efficiently removed and graphite oxide still remains a good exfoliation capability due to sharp increasing of carboxyl groups. However, with a longer oxidation time at step II oxidation, the decrease of organic sulfur content is slowed down apparently but without any carboxyl groups forming, then graphite oxide finally loses self-exfoliation capability. It is concluded that a short time of step II oxidation can produce purer and ultralarge GO sheets via self-exfoliation. The pure GO is possessed with better thermal stability and liquid crystal behavior. Besides, reduced GO films prepared from step II oxidation show better mechanical and electric properties after reducing compared with that obtained only via step I oxidation.

Scalable Production Method for Graphene Oxide Water Vapor Separation Membranes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fifield, Leonard S.; Shin, Yongsoon; Liu, Wei

ABSTRACT Membranes for selective water vapor separation were assembled from graphene oxide suspension using techniques compatible with high volume industrial production. The large-diameter graphene oxide flake suspensions were synthesized from graphite materials via relatively efficient chemical oxidation steps with attention paid to maintaining flake size and achieving high graphene oxide concentrations. Graphene oxide membranes produced using scalable casting methods exhibited water vapor flux and water/nitrogen selectivity performance meeting or exceeding that of membranes produced using vacuum-assisted laboratory techniques. (PNNL-SA-117497)

Hybridized polymer matrix composites

NASA Technical Reports Server (NTRS)

Henshaw, J.

1983-01-01

Methods of improving the fire resistance of graphite epoxy composite laminates were investigated with the objective of reducing the volume of loose graphite fibers disseminated into the airstream as the result of a high intensity aircraft fuel fire. Improvements were sought by modifying the standard graphite epoxy systems without significantly negating their structural effectiveness. The modifications consisted primarily of an addition of a third constituent material such as glass fibers, glass flakes, carbon black in a glassy resin. These additions were designed to encourage coalescense of the graphite fibers and thereby reduce their aerodynamic float characteristics. A total of 38 fire tests were conducted on thin (1.0 mm) and thick (6.0 mm) hybrid panels.

Transferring-free and large-area graphitic carbon film growth by using molecular beam epitaxy at low growth temperature

NASA Astrophysics Data System (ADS)

Lin, Meng-Yu; Wang, Cheng-Hung; Pao, Chun-Wei; Lin, Shih-Yen

2015-09-01

Graphitic carbon films prepared by using molecular beam epitaxy (MBE) on metal templates with different thicknesses deposited on SiO2/Si substrates are investigated in this paper. With thick Cu templates, only graphitic carbon flakes are obtained near the Cu grain boundaries at low growth temperatures on metal/SiO2 interfaces. By replacing the Cu templates with thin Ni templates, complete graphitic carbon films with superior crystalline quality is obtained at 600 °C on SiO2/Si substrates after removing the Ni templates. The enhanced attachment of the graphitic carbon film to the SiO2/Si substrates with reduced Ni thickness makes the approach a promising approach for transferring-free graphene preparation at low temperature by using MBE.

Catalyst-Free Growth of Three-Dimensional Graphene Flakes and Graphene/g-C₃N₄ Composite for Hydrocarbon Oxidation.

PubMed

Chen, Ke; Chai, Zhigang; Li, Cong; Shi, Liurong; Liu, Mengxi; Xie, Qin; Zhang, Yanfeng; Xu, Dongsheng; Manivannan, Ayyakkannu; Liu, Zhongfan

2016-03-22

Mass production of high-quality graphene flakes is important for commercial applications. Graphene microsheets have been produced on an industrial scale by chemical and liquid-phase exfoliation of graphite. However, strong-interaction-induced interlayer aggregation usually leads to the degradation of their intrinsic properties. Moreover, the crystallinity or layer-thickness controllability is not so perfect to fulfill the requirement for advanced technologies. Herein, we report a quartz-powder-derived chemical vapor deposition growth of three-dimensional (3D) high-quality graphene flakes and demonstrate the fabrication and application of graphene/g-C3N4 composites. The graphene flakes obtained after the removal of growth substrates exhibit the 3D curved microstructure, controllable layer thickness, good crystallinity, as well as weak interlayer interactions suitable for preventing the interlayer stacking. Benefiting from this, we achieved the direct synthesis of g-C3N4 on purified graphene flakes to form the uniform graphene/g-C3N4 composite, which provides efficient electron transfer interfaces to boost its catalytic oxidation activity of cycloalkane with relatively high yield, good selectivity, and reliable stability.

Coupling Graphene Sheets with Iron Oxide Nanoparticles for Energy Storage and Microelectronics

DTIC Science & Technology

2015-12-18

obtained from three different synthetic methods: (i) electrochemical exfoliation of highly oriented pyrolytic graphite ( HOPG ) [8], (ii) reduction of ...Fe2O3 -Graphene Sheets Graphene sheets are obtained from electrochemical exfoliation of highly oriented pyrolytic graphite ( HOPG ) flake. Two...fringes of ɤ-Fe2O3 nanoparticles in graphene sheet is shown. Typical X-ray diffraction ( XRD ) patterns of the HOPG , exfoliated graphene, PyDop1-ɤ-Fe2O3

Effect of friction on oxidative graphite intercalation and high-quality graphene formation.

PubMed

Seiler, Steffen; Halbig, Christian E; Grote, Fabian; Rietsch, Philipp; Börrnert, Felix; Kaiser, Ute; Meyer, Bernd; Eigler, Siegfried

2018-02-26

Oxidative wet-chemical delamination of graphene from graphite is expected to become a scalable production method. However, the formation process of the intermediate stage-1 graphite sulfate by sulfuric acid intercalation and its subsequent oxidation are poorly understood and lattice defect formation must be avoided. Here, we demonstrate film formation of micrometer-sized graphene flakes with lattice defects down to 0.02% and visualize the carbon lattice by transmission electron microscopy at atomic resolution. Interestingly, we find that only well-ordered, highly crystalline graphite delaminates into oxo-functionalized graphene, whereas other graphite grades do not form a proper stage-1 intercalate and revert back to graphite upon hydrolysis. Ab initio molecular dynamics simulations show that ideal stacking and electronic oxidation of the graphite layers significantly reduce the friction of the moving sulfuric acid molecules, thereby facilitating intercalation. Furthermore, the evaluation of the stability of oxo-species in graphite sulfate supports an oxidation mechanism that obviates intercalation of the oxidant.

Morphological and optoelectronic characteristics of nanocomposites comprising graphene nanosheets and poly(3-hexylthiophene).

PubMed

Chang, Yo-Wei; Yu, Shiau-Wei; Liu, Cheng-Hao; Tsiang, Raymond Chien-Chao

2010-10-01

P3HT/graphene nanocomposite was prepared via in-situ reduction of exfoliated graphite oxide in the P3HT polymer matrix, where the exfoliated graphite oxide was formed beforehand via the oxidation of graphite via the Hummers method. The oxidation reaction not only imparts functional groups, such as C=O, C-OH, and C-O-C, to graphite but also causes exfoliation of the resulting graphite oxide. The functional groups render graphite oxide an additional, lower thermal degradation temperature (T(d)) and the exfoliation shifts the XRD pattern towards a much smaller angle. The oxidation of graphite into graphite oxide creates a pleated flaking morphology for graphite oxide as opposed to that of graphite. UV/Vis and photoluminescence (PL) spectra of P3HT/graphene nanocomposite indicate that the existence of graphene does not alter the UV/Vis and PL excitation characteristics of P3HT, and the P3HT/graphene composite has higher electron mobility, a smaller band gap and higher conductivity than the pristine P3HT.

Method for uniformly distributing carbon flakes in a positive electrode, the electrode made thereby and compositions

DOEpatents

Mrazek, Franklin C.; Smaga, John A.; Battles, James E.

1983-01-01

A positive electrode for a secondary electrochemical cell wherein an electrically conductive current collector is in electrical contact with a particulate mixture of gray cast iron and an alkali metal sulfide and an electrolyte including alkali metal halides or alkaline earth metal halides. Also present may be a transition metal sulfide and graphite flakes from the conversion of gray cast iron to iron sulfide. Also disclosed is a method of distributing carbon flakes in a cell wherein there is formed an electrochemical cell of a positive electrode structure of the type described and a suitable electrolyte and a second electrode containing a material capable of alloying with alkali metal ions. The cell is connected to a source of electrical potential to electrochemically convert gray cast iron to an iron sulfide and uniformly to distribute carbon flakes formerly in the gray cast iron throughout the positive electrode while forming an alkali metal alloy in the negative electrode. Also disclosed are compositions useful in preparing positive electrodes.

Preparation, quantitative surface analysis, intercalation characteristics and industrial implications of low temperature expandable graphite

NASA Astrophysics Data System (ADS)

Peng, Tiefeng; Liu, Bin; Gao, Xuechao; Luo, Liqun; Sun, Hongjuan

2018-06-01

Expandable graphite is widely used as a new functional carbon material, especially as fire-retardant; however, its practical application is limited due to the high expansion temperature. In this work, preparation process of low temperature and highly expandable graphite was studied, using natural flake graphite as raw material and KMnO4/HClO4/NH4NO3 as oxidative intercalations. The structure, morphology, functional groups and thermal properties were characterized during expanding process by Fourier transform infrared spectroscopy (FTIR), Raman spectra, thermo-gravimetry differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), and scanning electron microscope (SEM). The analysis showed that by oxidation intercalation, some oxygen-containing groups were grafted on the edge and within the graphite layer. The intercalation reagent entered the graphite layer to increase the interlayer spacing. After expansion, the original flaky expandable graphite was completely transformed into worm-like expanded graphite. The order of graphite intercalation compounds (GICs) was proposed and determined to be 3 for the prepared expandable graphite, based on quantitative XRD peak analysis. Meanwhile, the detailed intercalation mechanisms were also proposed. The comprehensive investigation paved a benchmark for the industrial application of such sulfur-free expanded graphite.

Simple room-temperature preparation of high-yield large-area graphene oxide

PubMed Central

Huang, NM; Lim, HN; Chia, CH; Yarmo, MA; Muhamad, MR

2011-01-01

Graphene has attracted much attention from researchers due to its interesting mechanical, electrochemical, and electronic properties. It has many potential applications such as polymer filler, sensor, energy conversion, and energy storage devices. Graphene-based nanocomposites are under an intense spotlight amongst researchers. A large amount of graphene is required for preparation of such samples. Lately, graphene-based materials have been the target for fundamental life science investigations. Despite graphene being a much sought-after raw material, the drawbacks in the preparation of graphene are that it is a challenge amongst researchers to produce this material in a scalable quantity and that there is a concern about its safety. Thus, a simple and efficient method for the preparation of graphene oxide (GO) is greatly desired to address these problems. In this work, one-pot chemical oxidation of graphite was carried out at room temperature for the preparation of large-area GO with ~100% conversion. This high-conversion preparation of large-area GO was achieved using a simplified Hummer’s method from large graphite flakes (an average flake size of 500 μm). It was found that a high degree of oxidation of graphite could be realized by stirring graphite in a mixture of acids and potassium permanganate, resulting in GO with large lateral dimension and area, which could reach up to 120 μm and ~8000 μm2, respectively. The simplified Hummer’s method provides a facile approach for the preparation of large-area GO. PMID:22267928

Nucleation/Growth Mechanisms and Morphological Evolution of Porous MnO₂ Coating Deposited on Graphite for Supercapacitor.

PubMed

Huang, Wenxin; Li, Jun; Xu, Yunhe

2017-10-19

The nucleation and growth mechanisms of porous MnO₂ coating deposited on graphite in MnSO₄ solution were investigated in detail by cyclic voltammetry, chronoamperometry and scanning electron microscopy. The electrochemical properties of honeycomb-like MnO₂ were evaluated by cycle voltammetry and galvanostatic charge-discharge. Results indicated that MnO₂ was synthesized by the following steps: Mn 2+ → Mn 3+ + e⁻, Mn 3+ +2H2O → MnOOH + 3H⁺, and MnOOH → MnO₂ + H⁺+ e⁻. The deposition of MnO₂ was divided into four stages. A short incubation period (approximately 1.5 s) was observed, prior to nucleation. The decreasing trend of the current slowed as time increased due to nucleation and MnO₂ growth in the second stage. A huge number of nuclei were formed by instantaneous nucleation, and these nuclei grew and connected with one another at an exceedingly short time (0.5 s). In the third stage, the gaps in-between initial graphite flakes were filled with MnO₂ until the morphology of the flakes gradually became similar to that of the MnO₂-deposited layer. In the fourth stage, the graphite electrode was covered completely with a thick and dense layer of MnO₂ deposits. All MnO₂ electrodes at different deposition times obtained nearly the same specific capacitance of approximately 186 F/g, thus indicating that the specific capacitance of the electrodes is not related with deposition time.

First-principles determination of the Raman fingerprint of rhombohedral graphite

NASA Astrophysics Data System (ADS)

Torche, Abderrezak; Mauri, Francesco; Charlier, Jean-Christophe; Calandra, Matteo

2017-09-01

Multilayer graphene with rhombohedral stacking is a promising carbon phase possibly displaying correlated states like magnetism or superconductivity due to the occurrence of a flat surface band at the Fermi level. Recently, flakes of thickness up to 17 layers were tentatively attributed to ABC sequences although the Raman fingerprint of rhombohedral multilayer graphene is currently unknown and the 2D resonant Raman spectrum of Bernal graphite is not understood. We provide a first principles description of the 2D Raman peak in three and four layers graphene (all stackings) as well as in Bernal, rhombohedral, and an alternation of Bernal and rhombohedral graphite. We give practical prescriptions to identify long range sequences of ABC multilayer graphene. Our work is a prerequisite to experimental nondestructive identification and synthesis of rhombohedral graphite.

Construction of 3D nanostructure hierarchical porous graphitic carbons by charge-induced self-assembly and nanocrystal-assisted catalytic graphitization for supercapacitors.

PubMed

Ma, Fangwei; Ma, Di; Wu, Guang; Geng, Weidan; Shao, Jinqiu; Song, Shijiao; Wan, Jiafeng; Qiu, Jieshan

2016-05-10

A smart and sustainable strategy based on charge-induced self-assembly and nanocrystal-assisted catalytic graphitization is explored for the efficient construction of 3D nanostructure hierarchical porous graphitic carbons from the pectin biopolymer. The electrostatic interaction between the negatively charged pectin chains and magnesium ions plays a crucial role in the formation of 3D architectures. The 3D HPGCs possess a three-dimensional carbon framework with a hierarchical porous structure, flake-like graphitic carbon walls and high surface area (1320 m(2) g(-1)). The 3D HPGCs show an outstanding specific capacitance of 274 F g(-1) and excellent rate capability with a high capacitance retention of 85% at a high current density of 50 A g(-1) for supercapacitor electrodes. This strategy provided a novel approach to effectively construct 3D porous carbon nanostructures from biopolymers.

Glucose biosensor based on functionalized ZnO nanowire/graphite films dispersed on a Pt electrode

NASA Astrophysics Data System (ADS)

Gallay, P.; Tosi, E.; Madrid, R.; Tirado, M.; Comedi, D.

2016-10-01

We present a glucose biosensor based on ZnO nanowire self-sustained films grown on compacted graphite flakes by the vapor transport method. Nanowire/graphite films were fragmented in water, filtered to form a colloidal suspension, subsequently functionalized with glucose oxidase and finally transferred to a metal electrode (Pt). The obtained devices were evaluated using scanning electron microscopy, energy-dispersive x-ray spectroscopy, cyclic voltammetry and chronoamperometry. The electrochemical responses of the devices were determined in buffer solutions with successive glucose aggregates using a tripolar electrode system. The nanostructured biosensors showed excellent analytical performance, with linear response to glucose concentrations, high sensitivity of up to ≈17 μA cm-2 mM-1 in the 0.03-1.52 mM glucose concentration range, relatively low Michaelis-Menten constant, excellent reproducibility and a fast response. The detection limits are more than an order of magnitude lower than those achievable in commercial biosensors for glucose control, which is promising for the development of glucose monitoring methods that do not require blood extraction from potentially diabetic patients. The strong detection enhancements provided by the functionalized nanostructures are much larger than the electrode surface-area increase and are discussed in terms of the physical and chemical mechanisms involved in the detection and transduction processes.

Colloidal graphite/graphene nanostructures using collagen showing enhanced thermal conductivity.

PubMed

Bhattacharya, Soumya; Dhar, Purbarun; Das, Sarit K; Ganguly, Ranjan; Webster, Thomas J; Nayar, Suprabha

2014-01-01

In the present study, the exfoliation of natural graphite (GR) directly to colloidal GR/graphene (G) nanostructures using collagen (CL) was studied as a safe and scalable process, akin to numerous natural processes and hence can be termed "biomimetic". Although the exfoliation and functionalization takes place in just 1 day, it takes about 7 days for the nano GR/G flakes to stabilize. The predominantly aromatic residues of the triple helical CL forms its own special micro and nanoarchitecture in acetic acid dispersions. This, with the help of hydrophobic and electrostatic forces, interacts with GR and breaks it down to nanostructures, forming a stable colloidal dispersion. Surface enhanced Raman spectroscopy, X-ray diffraction, photoluminescence, fluorescence, and X-ray photoelectron spectroscopy of the colloid show the interaction between GR and CL on day 1 and 7. Differential interference contrast images in the liquid state clearly reveal how the GR flakes are entrapped in the CL fibrils, with a corresponding fluorescence image showing the intercalation of CL within GR. Atomic force microscopy of graphene-collagen coated on glass substrates shows an average flake size of 350 nm, and the hexagonal diffraction pattern and thickness contours of the G flakes from transmission electron microscopy confirm ≤ five layers of G. Thermal conductivity of the colloid shows an approximate 17% enhancement for a volume fraction of less than approximately 0.00005 of G. Thus, through the use of CL, this new material and process may improve the use of G in terms of biocompatibility for numerous medical applications that currently employ G, such as internally controlled drug-delivery assisted thermal ablation of carcinoma cells.

Colloidal graphite/graphene nanostructures using collagen showing enhanced thermal conductivity

PubMed Central

Bhattacharya, Soumya; Dhar, Purbarun; Das, Sarit K; Ganguly, Ranjan; Webster, Thomas J; Nayar, Suprabha

2014-01-01

In the present study, the exfoliation of natural graphite (GR) directly to colloidal GR/graphene (G) nanostructures using collagen (CL) was studied as a safe and scalable process, akin to numerous natural processes and hence can be termed “biomimetic”. Although the exfoliation and functionalization takes place in just 1 day, it takes about 7 days for the nano GR/G flakes to stabilize. The predominantly aromatic residues of the triple helical CL forms its own special micro and nanoarchitecture in acetic acid dispersions. This, with the help of hydrophobic and electrostatic forces, interacts with GR and breaks it down to nanostructures, forming a stable colloidal dispersion. Surface enhanced Raman spectroscopy, X-ray diffraction, photoluminescence, fluorescence, and X-ray photoelectron spectroscopy of the colloid show the interaction between GR and CL on day 1 and 7. Differential interference contrast images in the liquid state clearly reveal how the GR flakes are entrapped in the CL fibrils, with a corresponding fluorescence image showing the intercalation of CL within GR. Atomic force microscopy of graphene-collagen coated on glass substrates shows an average flake size of 350 nm, and the hexagonal diffraction pattern and thickness contours of the G flakes from transmission electron microscopy confirm ≤ five layers of G. Thermal conductivity of the colloid shows an approximate 17% enhancement for a volume fraction of less than approximately 0.00005 of G. Thus, through the use of CL, this new material and process may improve the use of G in terms of biocompatibility for numerous medical applications that currently employ G, such as internally controlled drug-delivery assisted thermal ablation of carcinoma cells. PMID:24648728

The structure of graphene oxide membranes in liquid water, ethanol and water-ethanol mixtures

NASA Astrophysics Data System (ADS)

Talyzin, Alexandr V.; Hausmaninger, Tomas; You, Shujie; Szabó, Tamás

2013-12-01

The structure of graphene oxide (GO) membranes was studied in situ in liquid solvents using synchrotron radiation X-ray diffraction in a broad temperature interval. GO membranes are hydrated by water similarly to precursor graphite oxide powders but intercalation of alcohols is strongly hindered, which explains why the GO membranes are permeated by water and not by ethanol. Insertion of ethanol into the membrane structure is limited to only one monolayer in the whole studied temperature range, in contrast to precursor graphite oxide powders, which are intercalated with up to two ethanol monolayers (Brodie) and four ethanol monolayers (Hummers). As a result, GO membranes demonstrate the absence of ``negative thermal expansion'' and phase transitions connected to insertion/de-insertion of alcohols upon temperature variations reported earlier for graphite oxide powders. Therefore, GO membranes are a distinct type of material with unique solvation properties compared to parent graphite oxides even if they are composed of the same graphene oxide flakes.The structure of graphene oxide (GO) membranes was studied in situ in liquid solvents using synchrotron radiation X-ray diffraction in a broad temperature interval. GO membranes are hydrated by water similarly to precursor graphite oxide powders but intercalation of alcohols is strongly hindered, which explains why the GO membranes are permeated by water and not by ethanol. Insertion of ethanol into the membrane structure is limited to only one monolayer in the whole studied temperature range, in contrast to precursor graphite oxide powders, which are intercalated with up to two ethanol monolayers (Brodie) and four ethanol monolayers (Hummers). As a result, GO membranes demonstrate the absence of ``negative thermal expansion'' and phase transitions connected to insertion/de-insertion of alcohols upon temperature variations reported earlier for graphite oxide powders. Therefore, GO membranes are a distinct type of material with unique solvation properties compared to parent graphite oxides even if they are composed of the same graphene oxide flakes. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr04631a

Erosion and Surface Morphology of Silicon Carbide Under Variable DIII-D Divertor Heat Fluxes

NASA Astrophysics Data System (ADS)

Bringuier, Stefan; Abrams, Tyler; Khalifa, Hesham; Thomas, Dan; Holland, Leo; Rudakov, Dmitry; Briesemeister, Alexis

2017-10-01

A SiC coating of 250 μm, deposited onto a graphite DiMES cap via chemical vapor deposition, was exposed to 80 s of H-mode plasma bombardment in the DIII-D outer divertor with steady-state heat fluxes up to 3 MW m-2 and transient loads due to ELMs typically peaking at 10 MW m-2. In-situ monitoring of Si I and Si II atomic spectral lines revealed the presence of significant neutral Si and Si+ impurity influx, which are used to determine quantitative erosion rates via the S/XB method. No visual macroscopic flaking or delamination of the SiC coating was observed, supporting the notion that SiC is thermal-mechanically robust and compatible with graphite substrates at elevated temperatures. Post-mortem profilometric analysis also indicates no pronounced change in surface roughness after plasma exposure. Finally, we investigate aspects of preferential sputtering and changes to surface composition exposure using scanning electron microscopy and Auger electron spectroscopy. Work supported under USDOE Cooperative Agreement DE-FC02-04ER54698.

Structural and functional polymer-matrix composites for electromagnetic applications

NASA Astrophysics Data System (ADS)

Wu, Junhua

This dissertation addresses the science and technology of functional and structural polymer-matrix composite materials for electromagnetic applications, which include electromagnetic interference (EMI) shielding and low observability (Stealth). The structural composites are continuous carbon fiber epoxy-matrix composites, which are widely used for airframes. The functional composites are composites with discontinuous fillers and in both bulk and coating forms. Through composite structure variation, attractive electromagnetic properties have been achieved. With no degradation of the tensile strength or modulus, the shielding effectiveness of the structural composites has been improved by enhancing multiple reflections through light activation of the carbon fiber. The multiple reflections loss of the electromagnetic wave increases from 1.1 to 10.2 dB at 1.0 GHz due to the activation. Such a large effect of multiple reflections has not been previously reported in any material. The observability of these composites has been lowered by decreasing the electrical conductivity (and hence decreasing the reflection loss) through carbon fiber coating. The incorporation of mumetal, a magnetic alloy particulate filler (28-40 mum size), in a latex paint has been found to be effective for enhancing the shielding only if the electrical resistivity of the resulting composite coating is below 10 O.cm, as rendered by a conductive particulate filler, such as nickel flake (14-20 mum size). This effectiveness (39 dB at 1.0 GHz) is attributed to the absorption of the electromagnetic wave by the mumetal and the nickel flake, with the high conductivity rendered by the presence of the nickel flake resulting in a relatively high reflection loss of 15.5 dB. Without the nickel flake, the mumetal gives only 3 dB of shielding and 1.5 dB of reflection loss at 1.0 GHz. Nickel powder (0.3-0.5 mum size) has been found to be an effective filler for improving the shielding of polyethersulfone (PES) bulk composites. At 13 vol.%, it gives 90 dB of shielding at 1.0 GHz, compared to 46 dB for nickel powder (20-40 mum) and the prior value of 87 dB reported by Shui and Chung for nickel filament (0.4 mum diameter). The minimum filler content for high shielding is 7-13 vol.% for both nickel powders, compared to 3-7 vol.% for nickel filament. Due to the skin effect, a small filler unit size helps the shielding, which is dominated by reflection. Carbon filament (0.1 mum, >100 mum long, >1000 in aspect ratio) is effective for enhancing the shielding effectiveness of a coating made from a water-based colloid that contains graphite particle (0.7-0.8 mum, 22 wt.%) and a starch-type binder. The filament addition increases the shielding from 11 to 20 dB at 1.0 GHz. This increase in shielding is associated with increase in reflectivity and decrease in electrical resistivity. Graphite flake (5 mum) at the same volume proportion is even more effective; its addition increases the shielding from 11 to 28 dB. The combined use of the graphite flake and a low proportion of stainless steel fiber (11 mum diameter, 2 mm long, 180 in aspect ratio) is yet more effective; it increases the shielding from 11 to 34 dB. Alumina particle (5 mum size, 15 vol.%) is effective for increasing the impedance of a coating made from the graphite colloid by 290%, though the shielding effectiveness is reduced from 18 to 11 dB at 1.0 GHz. The high impedance is attractive for MRIcompatible pacemaker leads. The interface between filler and matrix also affects the shielding. Silane treatment of the surface of graphite flake (5 mum) used in the graphite colloid decreases the viscosity (e.g., from 1750 to 1460 CP), but it also decreases the shielding effectiveness (e.g., from 20 to 16 dB at 1 GHz). Ozone treatment gives a similar effect. The decrease of the shielding effectiveness is attributed to the increase in resistivity due to the surface treatment. Measured and calculated values of the reflection loss are comparable, with the measured value lower than the corresponding calculated value, when the resistivity is sufficiently low (e.g., resistivity below 10 O.cm in case of PES-matrix composites) and a strongly magnetic filler such as mumetal is absent. The agreement is better when the skin depth approaches the specimen thickness. The agreement is worse for the latex paint-based composites than the PES-matrix composites, probably due to superior electrical connectivity in the latter.

Theoretical study of nitrogen-doped graphene nanoflakes: Stability and spectroscopy depending on dopant types and flake sizes.

PubMed

Lin, Chih-Kai

2018-03-05

As nitrogen-doped graphene has been widely applied in optoelectronic devices and catalytic reactions, in this work we have investigated where the nitrogen atoms tend to reside in the material and how they affect the electron density and spectroscopic properties from a theoretical point of view. DFT calculations on N-doped hexagonal and rectangular graphene nanoflakes (GNFs) showed that nitrogen atoms locating on zigzag edges are obviously more stable than those on armchair edges or inside flakes, and interestingly, the N-hydrogenated pyridine moiety could be preferable to pure pyridine moiety in large models. The UV-vis absorption spectra of these nitrogen-doped GNFs display strong dependence on flake sizes, where the larger flakes have their major peaks in lower energy ranges. Moreover, the spectra exhibit different connections to various dopant types and positions: the graphitic-type dopant species present large variety in absorption profiles, while the pyridinic-type ones show extraordinary uniform stability and spectra independent of dopant positions/numbers and hence are hardly distinguishable from each other. © 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.

Method for uniformly distributing carbon flakes in a positive electrode, the electrode made thereby and compositions. [Patent application

DOEpatents

Mrazek, F.C.; Smaga, J.A.; Battles, J.E.

1981-01-19

A positive electrode for a secondary electrochemical cell is described wherein an electrically conductive current collector is in electrical contact with a particulate mixture of gray cast iron and an alkali metal sulfide and an electrolyte including alkali metal halides or alkaline earth metal halides. Also present may be a transition metal sulfide and graphite flakes from the conversion of gray cast iron to iron sulfide. Also disclosed is a method of distributing carbon flakes in a cell wherein there is formed an electrochemical cell of a positive electrode structure of the type described and a suitable electrolyte and a second electrode containing a material capable of alloying with alkali metal ions. The cell is connected to a source of electrical potential to electrochemically convert gray cast iron to an iron sulfide and uniformly to distribute carbon flakes formerly in the gray cast iron throughout the positive electrode while forming an alkali metal alloy in the negative electrode. Also disclosed are compositions useful in preparing positive electrodes.

Research on the transformation mechanism of graphite phase and microstructure in the heated region of gray cast iron by laser cladding

NASA Astrophysics Data System (ADS)

Liu, Yancong; Zhan, Xianghua; Yi, Peng; Liu, Tuo; Liu, Benliang; Wu, Qiong

2018-03-01

A double-track lap cladding experiment involving gray cast iron was established to investigate the transformation mechanism of graphite phase and microstructure in a laser cladding heated region. The graphite phase and microstructure in different heated regions were observed under a microscope, and the distribution of elements in various heated regions was analyzed using an electron probe. Results show that no graphite existed in the cladding layer and in the middle and upper parts of the binding region. Only some of the undissolved small graphite were observed at the bottom of the binding region. Except the refined graphite size, the morphological characteristics of substrate graphite and graphite in the heat-affected zone were similar. Some eutectic clusters, which grew along the direction of heat flux, were observed in the heat-affected zone whose microstructure was transformed into a mixture of austenite, needle-like martensite, and flake graphite. Needle-like martensite around graphite was fine, but this martensite became sparse and coarse when it was away from graphite. Some martensite clusters appeared in the local area near the binding region, and the carbon atoms in the substrate did not diffuse into the cladding layer through laser cladding, which only affected the bonding area and the bottom of the cladding layer.

Nucleation/Growth Mechanisms and Morphological Evolution of Porous MnO2 Coating Deposited on Graphite for Supercapacitor

PubMed Central

Huang, Wenxin; Xu, Yunhe

2017-01-01

The nucleation and growth mechanisms of porous MnO2 coating deposited on graphite in MnSO4 solution were investigated in detail by cyclic voltammetry, chronoamperometry and scanning electron microscopy. The electrochemical properties of honeycomb-like MnO2 were evaluated by cycle voltammetry and galvanostatic charge-discharge. Results indicated that MnO2 was synthesized by the following steps: Mn2+→Mn3++e−, Mn3++2H2O→MnOOH+3H+, and MnOOH→MnO2+H++e−. The deposition of MnO2 was divided into four stages. A short incubation period (approximately 1.5 s) was observed, prior to nucleation. The decreasing trend of the current slowed as time increased due to nucleation and MnO2 growth in the second stage. A huge number of nuclei were formed by instantaneous nucleation, and these nuclei grew and connected with one another at an exceedingly short time (0.5 s). In the third stage, the gaps in-between initial graphite flakes were filled with MnO2 until the morphology of the flakes gradually became similar to that of the MnO2-deposited layer. In the fourth stage, the graphite electrode was covered completely with a thick and dense layer of MnO2 deposits. All MnO2 electrodes at different deposition times obtained nearly the same specific capacitance of approximately 186 F/g, thus indicating that the specific capacitance of the electrodes is not related with deposition time. PMID:29048377

Switch on the high thermal conductivity of graphene paper.

PubMed

Xie, Yangsu; Yuan, Pengyu; Wang, Tianyu; Hashemi, Nastaran; Wang, Xinwei

2016-10-14

This work reports on the discovery of a high thermal conductivity (κ) switch-on phenomenon in high purity graphene paper (GP) when its temperature is reduced from room temperature down to 10 K. The κ after switch-on (1732 to 3013 W m -1 K -1 ) is 4-8 times that before switch-on. The triggering temperature is 245-260 K. The switch-on behavior is attributed to the thermal expansion mismatch between pure graphene flakes and impurity-embedded flakes. This is confirmed by the switch behavior of the temperature coefficient of resistance. Before switch-on, the interactions between pure graphene flakes and surrounding impurity-embedded flakes efficiently suppress phonon transport in GP. After switch-on, the structure separation frees the pure graphene flakes from the impurity-embedded neighbors, leading to a several-fold κ increase. The measured κ before and after switch-on is consistent with the literature reported κ values of supported and suspended graphene. By conducting comparison studies with pyrolytic graphite, graphene oxide paper and partly reduced graphene paper, the whole physical picture is illustrated clearly. The thermal expansion induced switch-on is feasible only for high purity GP materials. This finding points out a novel way to switch on/off the thermal conductivity of graphene paper based on substrate-phonon scattering.

Highly Flexible and Planar Supercapacitors Using Graphite Flakes/Polypyrrole in Polymer Lapping Film.

PubMed

Raj, C Justin; Kim, Byung Chul; Cho, Won-Je; Lee, Won-gil; Jung, Sang-Don; Kim, Yong Hee; Park, Sang Yeop; Yu, Kook Hyun

2015-06-24

Flexible supercapacitor electrodes have been fabricated by simple fabrication technique using graphite nanoflakes on polymer lapping films as flexible substrate. An additional thin layer of conducting polymer polypyrrole over the electrode improved the surface conductivity and exhibited excellent electrochemical performances. Such capacitor films showed better energy density and power density with a maximum capacitance value of 37 mF cm(-2) in a half cell configuration using 1 M H2SO4 electrolyte, 23 mF cm(-2) in full cell, and 6 mF cm(-2) as planar cell configuration using poly(vinyl alcohol) (PVA)/phosphoric acid (H3PO4) solid state electrolyte. Moreover, the graphite nanoflakes/polypyrrole over polymer lapping film demonstrated good flexibility and cyclic stability.

An atomic carbon source for high temperature molecular beam epitaxy of graphene.

PubMed

Albar, J D; Summerfield, A; Cheng, T S; Davies, A; Smith, E F; Khlobystov, A N; Mellor, C J; Taniguchi, T; Watanabe, K; Foxon, C T; Eaves, L; Beton, P H; Novikov, S V

2017-07-26

We report the use of a novel atomic carbon source for the molecular beam epitaxy (MBE) of graphene layers on hBN flakes and on sapphire wafers at substrate growth temperatures of ~1400 °C. The source produces a flux of predominantly atomic carbon, which diffuses through the walls of a Joule-heated tantalum tube filled with graphite powder. We demonstrate deposition of carbon on sapphire with carbon deposition rates up to 12 nm/h. Atomic force microscopy measurements reveal the formation of hexagonal moiré patterns when graphene monolayers are grown on hBN flakes. The Raman spectra of the graphene layers grown on hBN and sapphire with the sublimation carbon source and the atomic carbon source are similar, whilst the nature of the carbon aggregates is different - graphitic with the sublimation carbon source and amorphous with the atomic carbon source. At MBE growth temperatures we observe etching of the sapphire wafer surface by the flux from the atomic carbon source, which we have not observed in the MBE growth of graphene with the sublimation carbon source.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

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 Bmore » 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. Lastly, theoretical calculations are employed to investigate the intercalation behaviour of choloraluminate anions in the graphite electrode.« less

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 Bmore » 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. Lastly, theoretical calculations are employed to investigate the intercalation behaviour of choloraluminate anions in the graphite electrode.« less

Technology Base Enhancement Program. Metal Matrix Composites

DTIC Science & Technology

1993-08-30

efficiency, improved structural reliability, and reduced maintenance when compared to carbon fiber reinforced composites . Aerospace engines (in particular...different materials. The composite consists of a metal matrix reinforced with particulates, flakes, whiskers,3 continuous fibers , filaments, wires, or...graphite and carbon to metals. They come in three general forms: particulates (or particles) with a length to diameter ratio of about 1; chopped fibers or

Graphitized silicon carbide microbeams: wafer-level, self-aligned graphene on silicon wafers

NASA Astrophysics Data System (ADS)

Cunning, Benjamin V.; Ahmed, Mohsin; Mishra, Neeraj; Ranjbar Kermany, Atieh; Wood, Barry; Iacopi, Francesca

2014-08-01

Currently proven methods that are used to obtain devices with high-quality graphene on silicon wafers involve the transfer of graphene flakes from a growth substrate, resulting in fundamental limitations for large-scale device fabrication. Moreover, the complex three-dimensional structures of interest for microelectromechanical and nanoelectromechanical systems are hardly compatible with such transfer processes. Here, we introduce a methodology for obtaining thousands of microbeams, made of graphitized silicon carbide on silicon, through a site-selective and wafer-scale approach. A Ni-Cu alloy catalyst mediates a self-aligned graphitization on prepatterned SiC microstructures at a temperature that is compatible with silicon technologies. The graphene nanocoating leads to a dramatically enhanced electrical conductivity, which elevates this approach to an ideal method for the replacement of conductive metal films in silicon carbide-based MEMS and NEMS devices.

A high-performance ternary Si composite anode material with crystal graphite core and amorphous carbon shell

NASA Astrophysics Data System (ADS)

Sui, Dong; Xie, Yuqing; Zhao, Weimin; Zhang, Hongtao; Zhou, Ying; Qin, Xiting; Ma, Yanfeng; Yang, Yong; Chen, Yongsheng

2018-04-01

Si is a promising anode material for lithium-ion batteries, but suffers from sophisticated engineering structures and complex fabrication processes that pose challenges for commercial application. Herein, a ternary Si/graphite/pyrolytic carbon (SiGC) anode material with a structure of crystal core and amorphous shell using low-cost raw materials is developed. In this ternary SiGC composite, Si component exists as nanoparticles and is spread on the surface of the core graphite flakes while the sucrose-derived pyrolytic carbon further covers the graphite/Si components as the amorphous shell. With this structure, Si together with the graphite contributes to the high specific capacity of this Si ternary material. Also the graphite serves as the supporting and conducting matrix and the amorphous shell carbon could accommodate the volume change effect of Si, reinforces the integrity of the composite architecture, and prevents the graphite and Si from direct exposing to the electrolyte. The optimized ternary SiGC composite displays high reversible specific capacity of 818 mAh g-1 at 0.1 A g-1, initial Coulombic efficiency (CE) over 80%, and excellent cycling stability at 0.5 A g-1 with 83.6% capacity retention (∼610 mAh g-1) after 300 cycles.

Graphene nanosheets preparation using magnetic nanoparticle assisted liquid phase exfoliation of graphite: The coupled effect of ultrasound and wedging nanoparticles.

PubMed

Hadi, Alireza; Zahirifar, Jafar; Karimi-Sabet, Javad; Dastbaz, Abolfazl

2018-06-01

This study aims to investigate a novel technique to improve the yield of liquid phase exfoliation of graphite to graphene sheets. The method is based on the utilization of magnetic Fe 3 O 4 nanoparticles as "particle wedge" to facilitate delamination of graphitic layers. Strong shear forces resulted from the collision of Fe 3 O 4 particles with graphite particles, and intense ultrasonic waves lead to enhanced exfoliation of graphite. High quality of graphene sheets along with the ease of Fe 3 O 4 particle separation from graphene solution which arises from the magnetic nature of Fe 3 O 4 nanoparticles are the unique features of this approach. Initial graphite flakes and produced graphene sheets were characterized by various methods including field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Raman spectroscopy, atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Zeta potential analysis. Moreover, the effect of process factors comprising initial graphite concentration, Fe 3 O 4 nanoparticles concentration, sonication time, and sonication power were investigated. Results revealed that graphene preparation yield and the number of layers could be manipulated by the presence of magnetic nanoparticles. Copyright © 2018 Elsevier B.V. All rights reserved.

Construction variables considered in fabrication of a structural flakeboard

Treesearch

R.L. Geimer; E.W. Price

1978-01-01

Flake geometry, flake quality, flake alignment, average density, density gradients, layer thicknesses, and resin content were factors considered in determining the final construction details on structural flakeboards made from 1) western softwoods and 2) southern hardwood residues. After making compromises between board properties, a three-layer design was recommended...

Dielectric elastomers with novel highly-conducting electrodes

NASA Astrophysics Data System (ADS)

Böse, Holger; Uhl, Detlev

2013-04-01

Beside the characteristics of the elastomer material itself, the performance of dielectric elastomers in actuator, sensor as well as generator applications depends also on the properties of the electrode material. Various electrode materials based on metallic particles dispersed in a silicone matrix were manufactured and investigated. Anisotropic particles such as silver-coated copper flakes and silver-coated glass flakes were used for the preparation of the electrodes. The concentration of the metallic particles and the thickness of the electrode layers were varied. Specific conductivities derived from resistance measurements reached about 100 S/cm and surmount those of the reference materials based on graphite and carbon black by up to three orders of magnitude. The high conductivities of the new electrode materials can be maintained even at very large stretch deformations up to 200 %.

Different techniques for characterizing single-walled carbon nanotube purity

NASA Astrophysics Data System (ADS)

Yuca, Neslihan; Camtakan, Zeyneb; Karatepe, Nilgün

2013-09-01

Transition-metal catalysts, fullerenes, graphitic carbon, amorphous carbon, and graphite flakes are the main impurities in carbon nanotubes. In this study, we demonstrate an easy and optimum method of cleaning SWCNTs and evaluating their purity. The purification method, which employed oxidative heat treatment followed by 6M HNO3, H2SO4, HNO3:H2SO4 and HCl acid reflux for 6h at 120°C and microwave digestion with 1.5M HNO3 for 0.5h at 210°C which was straightforward, inexpensive, and fairly effective. The purified materials were characterized by thermogravimetric analysis and nuclear techniques such as INAA, XRF and XRD.

NSTAR Extended Life Test Discharge Chamber Flake Analysis

NASA Technical Reports Server (NTRS)

deGroh, Kim K.; Banks, Bruce A.; Karniotis, Christina A.

2005-01-01

The Extended Life Test (ELT) of the NASA Solar Electric Propulsion Technology Readiness (NSTAR) ion thruster was concluded after 30,352 hours of operation. The ELT was conducted using the Deep Space 1 (DS1) back-up flight engine, a 30 cm diameter xenon ion thruster. Post-test inspection of the ELT engine revealed numerous contaminant flakes distributed over the bottom of the cylindrical section of the anode within the discharge chamber (DC). Extensive analyses were conducted to determine the source of the particles, which is critical to the understanding of degradation mechanisms of long life ion thruster operation. Analyses included: optical microscopy (OM) and particle length histograms, field emission scanning electron microscopy (FESEM) combined with energy dispersive spectroscopy (EDS), and atomic oxygen plasma exposure tests. Analyses of the particles indicate that the majority of the DC flakes consist of a layered structure, typically with either two or three layers. The flakes comprising two layers were typically found to have a molybdenum-rich (Mo-rich) layer on one side and a carbon-rich (C-rich) layer on the other side. The flakes comprising three layers were found to be sandwich-like structures with Mo-rich exterior layers and a C-rich interior layer. The presence of the C-rich layers indicates that these particles were produced by sputter deposition build-up on a surface external to the discharge chamber from ion sputter erosion of the graphite target in the test chamber. This contaminant layer became thick enough that particles spalled off, and then were electro-statically attracted into the ion thruster interior, where they were coated with Mo from internal sputter erosion of the screen grid and cathode components. Atomic oxygen tests provided evidence that the DC chamber flakes are composed of a significant fraction of carbon. Particle size histograms further indicated that the source of the particles was spalling of carbon flakes from downstream surfaces. Analyses of flakes taken from the downstream surface of the accelerator grid provided additional supportive information. The production of the downstream carbon flakes, and hence the potential problems associated with the flake particles in the ELT ion thruster engine is a facility induced effect and would not occur in the space environment.

Composites of aluminum alloy and magnesium alloy with graphite showing low thermal expansion and high specific thermal conductivity

NASA Astrophysics Data System (ADS)

Oddone, Valerio; Boerner, Benji; Reich, Stephanie

2017-12-01

High thermal conductivity, low thermal expansion and low density are three important features in novel materials for high performance electronics, mobile applications and aerospace. Spark plasma sintering was used to produce light metal-graphite composites with an excellent combination of these three properties. By adding up to 50 vol.% of macroscopic graphite flakes, the thermal expansion coefficient of magnesium and aluminum alloys was tuned down to zero or negative values, while the specific thermal conductivity was over four times higher than in copper. No degradation of the samples was observed after thermal stress tests and thermal cycling. Tensile strength and hardness measurements proved sufficient mechanical stability for most thermal management applications. For the production of the alloys, both prealloyed powders and elemental mixtures were used; the addition of trace elements to cope with the oxidation of the powders was studied.

Composites of aluminum alloy and magnesium alloy with graphite showing low thermal expansion and high specific thermal conductivity

PubMed Central

Oddone, Valerio; Boerner, Benji; Reich, Stephanie

2017-01-01

Abstract High thermal conductivity, low thermal expansion and low density are three important features in novel materials for high performance electronics, mobile applications and aerospace. Spark plasma sintering was used to produce light metal–graphite composites with an excellent combination of these three properties. By adding up to 50 vol.% of macroscopic graphite flakes, the thermal expansion coefficient of magnesium and aluminum alloys was tuned down to zero or negative values, while the specific thermal conductivity was over four times higher than in copper. No degradation of the samples was observed after thermal stress tests and thermal cycling. Tensile strength and hardness measurements proved sufficient mechanical stability for most thermal management applications. For the production of the alloys, both prealloyed powders and elemental mixtures were used; the addition of trace elements to cope with the oxidation of the powders was studied. PMID:28458742

Composites of aluminum alloy and magnesium alloy with graphite showing low thermal expansion and high specific thermal conductivity.

PubMed

Oddone, Valerio; Boerner, Benji; Reich, Stephanie

2017-01-01

High thermal conductivity, low thermal expansion and low density are three important features in novel materials for high performance electronics, mobile applications and aerospace. Spark plasma sintering was used to produce light metal-graphite composites with an excellent combination of these three properties. By adding up to 50 vol.% of macroscopic graphite flakes, the thermal expansion coefficient of magnesium and aluminum alloys was tuned down to zero or negative values, while the specific thermal conductivity was over four times higher than in copper. No degradation of the samples was observed after thermal stress tests and thermal cycling. Tensile strength and hardness measurements proved sufficient mechanical stability for most thermal management applications. For the production of the alloys, both prealloyed powders and elemental mixtures were used; the addition of trace elements to cope with the oxidation of the powders was studied.

Liquid-phase exfoliated graphene self-assembled films: Low-frequency noise and thermal-electric characterization

NASA Astrophysics Data System (ADS)

Tubon Usca, G.; Hernandez-Ambato, J.; Pace, C.; Caputi, L. S.; Tavolaro, A.

2016-09-01

In few years, graphene has become a revolutionary material, leading not only to applications in various fields such as electronics, medicine and environment, but also to the production of new types of 2D materials. In this work, Liquid Phase Exfoliation (LPE) was applied to natural graphite by brief sonication or mixer treatment in suitable solvents, in order to produce Few Layers Graphene (FLG) suspensions. Additionally, zeolite 4A (Z4A) was added during the production of FLG flakes-based inks, with the aim of aiding the exfoliation process. Conductive films were obtained by drop casting three types of suspensions over Al2O3 substrates with interdigitated electrodes, with total channel surface of 1.39 mm2. The morphology characterization resulted in the verification of the presence of thin self-assembled flakes. Raman studies gave evidence of 4 to 10 layers graphene flakes. Electrical measurements were performed to state the Low-Frequency Noise and Thermal-Electric characteristics of the samples. We observe interesting relations between sample preparation procedures and electrical properties.

The graphite deposit at Borrowdale (UK): A catastrophic mineralizing event associated with Ordovician magmatism

NASA Astrophysics Data System (ADS)

Ortega, L.; Millward, D.; Luque, F. J.; Barrenechea, J. F.; Beyssac, O.; Huizenga, J.-M.; Rodas, M.; Clarke, S. M.

2010-04-01

The volcanic-hosted graphite deposit at Borrowdale in Cumbria, UK, was formed through precipitation from C-O-H fluids. The δ 13C data indicate that carbon was incorporated into the mineralizing fluids by assimilation of carbonaceous metapelites of the Skiddaw Group by andesite magmas of the Borrowdale Volcanic Group. The graphite mineralization occurred as the fluids migrated upwards through normal conjugate fractures forming the main subvertical pipe-like bodies. The mineralizing fluids evolved from CO 2-CH 4-H 2O mixtures (XCO 2 = 0.6-0.8) to CH 4-H 2O mixtures. Coevally with graphite deposition, the andesite and dioritic wall rocks adjacent to the veins were intensely hydrothermally altered to a propylitic assemblage. The initial graphite precipitation was probably triggered by the earliest hydration reactions in the volcanic host rocks. During the main mineralization stage, graphite precipitated along the pipe-like bodies due to CO 2 → C + O 2. This agrees with the isotopic data which indicate that the first graphite morphologies crystallizing from the fluid (cryptocrystalline aggregates) are isotopically lighter than those crystallizing later (flakes). Late chlorite-graphite veins were formed from CH 4-enriched fluids following the reaction CH 4 + O 2 → C + 2H 2O, producing the successive precipitation of isotopically lighter graphite morphologies. Thus, as mineralization proceeded, water-generating reactions were involved in graphite precipitation, further favouring the propylitic alteration. The structural features of the pipe-like mineralized bodies as well as the isotopic homogeneity of graphite suggest that the mineralization occurred in a very short period of time.

Comparison on graphite, graphene oxide and reduced graphene oxide: Synthesis and characterization

NASA Astrophysics Data System (ADS)

Hidayah, N. M. S.; Liu, Wei-Wen; Lai, Chin-Wei; Noriman, N. Z.; Khe, Cheng-Seong; Hashim, U.; Lee, H. Cheun

2017-10-01

Graphene oxide (GO) and reduced graphene oxide (RGO) are known to have superior properties for various applications. This work compares the properties of GO and RGO with graphite. GO was prepared by using Improved Hummer's method whereas the produced GO was subjected to chemical reduction with the use of hydrazine hydrate. Graphite, GO and RGO had different morphologies, quality, functionalized groups, UV-Vis absorption peaks and crystallinity. With the removal of oxygen-containing functional group during reduction for RGO, the quality of samples was decreased due to higher intensity of D band than G band was seen in Raman results. In addition, platelet-like surface can be observed on the surface of graphite as compared to GO and RGO where wrinkled and layered flakes, and crumpled thin sheets were observed on GO and RGO surface respectively. Fourier Transform Infra-Red (FTIR) analysis showed the presence of abundant oxygen-containing functional groups in GO as compared to RGO and graphite. The characteristic peaks at 26.62°, 9.03° and 24.10° for graphite, GO and RGO, respectively, can be detected from X-Ray diffraction (XRD). Furthermore, the reduction also caused red shift at 279nm from 238nm, as obtained from ultraviolet visible (UV-Vis) analysis. The results proved that GO was successfully oxidized from graphite whereas RGO was effectively reduced from GO.

Effect of substrate chemical pretreatment on the tribological properties of graphite films

NASA Technical Reports Server (NTRS)

Fusaro, R. L.

1984-01-01

Rubbed films of natural flake Madagascar graphite were applied to ASTM A-355(D) steel with chemical surface pretreatments of zinc phosphate, gas nitride, salt nitride, sulfo-nitride, and with mechanical pretreatment (sandblasting). SAE 1045 steel pins were slid against these films using a pin-on-disk tribometer. The results indicate that two different lubricating mechanisms can occur. In the chemical surface pretreatment, the graphite can mix together to form a surface layer of the two constituents and this plasticity flowing layer provides the lubrication. The longest endurance lives and the lowest pin wear rates were obtained with this mechanism. In the other, surface topography appeared to control the mechanism. A rough surface was necessary to serve as a reservoir to supply the graphite to the flat metallic plateaus where it was sheared in very thin films between the plateaus and the sliding pin surface. For this mechanism, chemical pretreatment seemed to do little more than serve as a means for roughening the surface. Mean friction was not significantly influenced by chemical pretreatment, but surface roughness effects were observed.

Transfer of monolayer TMD WS2 and Raman study of substrate effects

PubMed Central

Mlack, Jerome T.; Masih Das, Paul; Danda, Gopinath; Chou, Yung-Chien; Naylor, Carl H.; Lin, Zhong; López, Néstor Perea; Zhang, Tianyi; Terrones, Mauricio; Johnson, A. T. Charlie; Drndić, Marija

2017-01-01

A facile transfer process for transition metal dichalcogenide WS2 flakes is reported and the effect of the underlying substrate on the flake properties is investigated using Raman spectroscopy. The flakes are transferred from their growth substrate using polymethyl methacrylate (PMMA) and a wet etch to allow the user to transfer the flakes to a final substrate using a microscope and micromanipulator combined with semi-transparent Kapton tape. The substrates used range from insulators such as industry standard high-k dielectric HfO2 and “green polymer” parylene-C, to conducting chemical vapor deposition (CVD) grown graphene. Raman spectroscopy is used first to confirm the material quality of the transferred flakes to the substrates and subsequently to analyze and separate the effects arising from material transfer from those arising from interactions with the substrate. We observe changes in the Raman spectra associated with the interactions between the substrates in the flakes. These interactions affect both in-plane and out-of-plane modes in different ways depending on their sources, for example strain or surface charge. These changes vary with final substrate, with the strongest effects being observed for WS2 transferred onto graphene and HfO2, demonstrating the importance of understanding substrate interaction for fabrication of future devices. PMID:28220852

Large scale production of highly-qualified graphene by ultrasonic exfoliation of expanded graphite under the promotion of (NH4)2CO3 decomposition.

PubMed

Wang, Yunwei; Tong, Xili; Guo, Xiaoning; Wang, Yingyong; Jin, Guoqiang; Guo, Xiangyun

2013-11-29

Highly-qualified graphene was prepared by the ultrasonic exfoliation of commercial expanded graphite (EG) under the promotion of (NH4)2CO3 decomposition. The yield of graphene from the first exfoliation is 7 wt%, and it can be increased to more than 65 wt% by repeated exfoliations. Atomic force microscopy, x-ray photoelectron spectroscopy and Raman analysis show that the as-prepared graphene only has a few defects or oxides, and more than 95% of the graphene flakes have a thickness of ~1 nm. The electrochemical performance of the as-prepared graphene is comparable to reduced graphene oxide in the determination of dopamine (DA) from the mixed solution of ascorbic acid, uric acid and DA. These results show that the decomposition of (NH4)2CO3 molecules in the EG layers under ultrasonication promotes the exfoliation of graphite and provides a low-priced route for large scale production of highly-quality graphene.

Rational and practical exfoliation of graphite using well-defined poly(3-hexylthiophene) for the preparation of conductive polymer/graphene composite.

PubMed

Iguchi, Hiroki; Higashi, Chisato; Funasaki, Yuichi; Fujita, Keisuke; Mori, Atsunori; Nakasuga, Akira; Maruyama, Tatsuo

2017-01-06

Processing and manipulation of highly conductive pristine graphene in large quantities are still major challenges in the practical application of graphene for electric device. In the present study, we report the liquid-phase exfoliation of graphite in toluene using well-defined poly(3-hexylthiophene) (P3HT) to produce a P3HT/graphene composite. We synthesize and use regioregular P3HT with controlled molecular weights as conductive dispersants for graphene. Simple ultrasonication of graphite flakes with the P3HT successfully produces single-layer and few-layer graphene sheets dispersed in toluene. The produced P3HT/graphene composite can be used as conductive graphene ink, indicating that the P3HT/graphene composite has high electrical conductivity owing to the high conductivity of P3HT and graphene. The P3HT/graphene composite also works as an oxidation-resistant and conductive film for a copper substrate, which is due to the high gas-barrier property of graphene.

Large scale production of highly-qualified graphene by ultrasonic exfoliation of expanded graphite under the promotion of (NH4)2CO3 decomposition

NASA Astrophysics Data System (ADS)

Wang, Yunwei; Tong, Xili; Guo, Xiaoning; Wang, Yingyong; Jin, Guoqiang; Guo, Xiangyun

2013-11-01

Highly-qualified graphene was prepared by the ultrasonic exfoliation of commercial expanded graphite (EG) under the promotion of (NH4)2CO3 decomposition. The yield of graphene from the first exfoliation is 7 wt%, and it can be increased to more than 65 wt% by repeated exfoliations. Atomic force microscopy, x-ray photoelectron spectroscopy and Raman analysis show that the as-prepared graphene only has a few defects or oxides, and more than 95% of the graphene flakes have a thickness of ˜1 nm. The electrochemical performance of the as-prepared graphene is comparable to reduced graphene oxide in the determination of dopamine (DA) from the mixed solution of ascorbic acid, uric acid and DA. These results show that the decomposition of (NH4)2CO3 molecules in the EG layers under ultrasonication promotes the exfoliation of graphite and provides a low-priced route for large scale production of highly-quality graphene.

An evaluation of candidate oxidation resistant materials for space applications in LEO

NASA Technical Reports Server (NTRS)

Rutledge, Sharon; Banks, Bruce; Difilippo, Frank; Brady, Joyce; Dever, Therese; Hotes, Deborah

1986-01-01

Ground based testing of materials considered for polyimide (Kapton) solar array blanket protection and graphite-epoxy stroctural member protection was performed in an RF plasma asher. Protective coatings on Kapton from various commercial sources and from NASA Lewis Research Center were exposed to the air plasma; and mass loss per unit area was measured for each sample. All samples evaluated provided some protection to the underlying surface, but metal-oxide-fluoropolymer coatings provided the best protection by exhibiting very little degradation after 47 hr of asher exposure. Mica paint was evaluated as a protective coating for graphite-epoxy structural members. Mica appeared to be resistant to attack by atomic oxygen, but only offered limited protection as a paint. this is believed to be due to the paint vehicle ashing underneath the mica leaving unattached mica flakes lying on the surface. The protective coatings on Kapton evaluated so far are promising but further research on protection of graphite-epoxy support structures is needed.

Rational and practical exfoliation of graphite using well-defined poly(3-hexylthiophene) for the preparation of conductive polymer/graphene composite

NASA Astrophysics Data System (ADS)

Iguchi, Hiroki; Higashi, Chisato; Funasaki, Yuichi; Fujita, Keisuke; Mori, Atsunori; Nakasuga, Akira; Maruyama, Tatsuo

2017-01-01

Processing and manipulation of highly conductive pristine graphene in large quantities are still major challenges in the practical application of graphene for electric device. In the present study, we report the liquid-phase exfoliation of graphite in toluene using well-defined poly(3-hexylthiophene) (P3HT) to produce a P3HT/graphene composite. We synthesize and use regioregular P3HT with controlled molecular weights as conductive dispersants for graphene. Simple ultrasonication of graphite flakes with the P3HT successfully produces single-layer and few-layer graphene sheets dispersed in toluene. The produced P3HT/graphene composite can be used as conductive graphene ink, indicating that the P3HT/graphene composite has high electrical conductivity owing to the high conductivity of P3HT and graphene. The P3HT/graphene composite also works as an oxidation-resistant and conductive film for a copper substrate, which is due to the high gas-barrier property of graphene.

Rational and practical exfoliation of graphite using well-defined poly(3-hexylthiophene) for the preparation of conductive polymer/graphene composite

PubMed Central

Iguchi, Hiroki; Higashi, Chisato; Funasaki, Yuichi; Fujita, Keisuke; Mori, Atsunori; Nakasuga, Akira; Maruyama, Tatsuo

2017-01-01

Processing and manipulation of highly conductive pristine graphene in large quantities are still major challenges in the practical application of graphene for electric device. In the present study, we report the liquid-phase exfoliation of graphite in toluene using well-defined poly(3-hexylthiophene) (P3HT) to produce a P3HT/graphene composite. We synthesize and use regioregular P3HT with controlled molecular weights as conductive dispersants for graphene. Simple ultrasonication of graphite flakes with the P3HT successfully produces single-layer and few-layer graphene sheets dispersed in toluene. The produced P3HT/graphene composite can be used as conductive graphene ink, indicating that the P3HT/graphene composite has high electrical conductivity owing to the high conductivity of P3HT and graphene. The P3HT/graphene composite also works as an oxidation-resistant and conductive film for a copper substrate, which is due to the high gas-barrier property of graphene. PMID:28059127

Environmental and Health Effects Review for Obscurant Graphite Flakes

DTIC Science & Technology

1993-07-01

that failed to resolve during the 3-week or 6-week recovery periods were a mild inflammatory lesion characterized by increased total cells, increased...percentage of neutrophils, and increased protein in lavage fluids, hyperplasia of lung epithelium, and a minor impairment of pulmonary function...J. M. Davis, R. A. Harley, Jr., and R. T. DeTreville. 1973. "Lymphatic Transport of Fibrous Dust from the Lungs." J.L..u LMed. 15(3):186-189. 25 Hanoa

Nano-scaled graphene platelets with a high length-to-width aspect ratio

DOEpatents

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

2010-09-07

This invention provides a nano-scaled graphene platelet (NGP) having a thickness no greater than 100 nm and a length-to-width ratio no less than 3 (preferably greater than 10). The NGP with a high length-to-width ratio can be prepared by using a method comprising (a) intercalating a carbon fiber or graphite fiber with an intercalate to form an intercalated fiber; (b) exfoliating the intercalated fiber to obtain an exfoliated fiber comprising graphene sheets or flakes; and (c) separating the graphene sheets or flakes to obtain nano-scaled graphene platelets. The invention also provides a nanocomposite material comprising an NGP with a high length-to-width ratio. Such a nanocomposite can become electrically conductive with a small weight fraction of NGPs. Conductive composites are particularly useful for shielding of sensitive electronic equipment against electromagnetic interference (EMI) or radio frequency interference (RFI), and for electrostatic charge dissipation.

Alloying of steel and graphite by hydrogen in nuclear reactor

NASA Astrophysics Data System (ADS)

Krasikov, E.

2017-02-01

In traditional power engineering hydrogen may be one of the first primary source of equipment damage. This problem has high actuality for both nuclear and thermonuclear power engineering. Study of radiation-hydrogen embrittlement of the steel raises the question concerning the unknown source of hydrogen in reactors. Later unexpectedly high hydrogen concentrations were detected in irradiated graphite. It is necessary to look for this source of hydrogen especially because hydrogen flakes were detected in reactor vessels of Belgian NPPs. As a possible initial hypothesis about the enigmatical source of hydrogen one can propose protons generation during beta-decay of free neutrons поскольку inasmuch as protons detected by researches at nuclear reactors as witness of beta-decay of free neutrons.

Wear resistance and friction reduction in acrylo nitrile butadiene rubber through hybrid combination of graphite flakes and nano tungsten disulphide

NASA Astrophysics Data System (ADS)

Agrawal, Neha; Pandey, Akanksha; Parihar, A. S.; Mishra, A. K.; Gandhi, M. N.; Bhattacharyya, A. R.; Mukhopadhyay, K.; Prasad, N. E.

2016-05-01

Friction and wear have considerable role in the life span of two interacting parts. Incorporation of nanofillers in polymers/elastomers matrix causes commendable changes in its tribologicalproperties. The main purpose of this work is to reduce the coefficient of friction and wear rate of Acrylo Nitrile Butadiene rubber (NBR). To achieve such objective traditionally well knownlubricants graphite(G), tungsten disulphide (WS2) and there hybrid combination was incorporated in NBR matrix. Effect of applied load (force) and concentration of fillers on tribological properties of NBR had been studied. The filler incorporation enhanced the hardnessby 8%, showed resistance to hydraulic oil and aging effect also got improved significantly. A particular optimized concentration of NBR with hybrid combination of 2% WS2 and 4% Graphite showed minimum coefficient of friction as well as wear rate. A hypothesis could be attributed that similar lamellar structure of WS2 and Graphite along with formation of a stable nanoscale disulfide tribofilmcould result in lowering of friction. These substantially improved properties of nanoreinforced rubber materials would definitely pave promising path for plethora of potential technological applications.

Wear resistance and friction reduction in acrylo nitrile butadiene rubber through hybrid combination of graphite flakes and nano tungsten disulphide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agrawal, Neha, E-mail: neha87bhu@gmail.com; Indian Institute of Technology Bombay, Powai, Mumbai 400076, Maharashtra; Pandey, Akanksha

Friction and wear have considerable role in the life span of two interacting parts. Incorporation of nanofillers in polymers/elastomers matrix causes commendable changes in its tribologicalproperties. The main purpose of this work is to reduce the coefficient of friction and wear rate of Acrylo Nitrile Butadiene rubber (NBR). To achieve such objective traditionally well knownlubricants graphite(G), tungsten disulphide (WS{sub 2}) and there hybrid combination was incorporated in NBR matrix. Effect of applied load (force) and concentration of fillers on tribological properties of NBR had been studied. The filler incorporation enhanced the hardnessby 8%, showed resistance to hydraulic oil and agingmore » effect also got improved significantly. A particular optimized concentration of NBR with hybrid combination of 2% WS{sub 2} and 4% Graphite showed minimum coefficient of friction as well as wear rate. A hypothesis could be attributed that similar lamellar structure of WS{sub 2} and Graphite along with formation of a stable nanoscale disulfide tribofilmcould result in lowering of friction. These substantially improved properties of nanoreinforced rubber materials would definitely pave promising path for plethora of potential technological applications.« less

Studies on the microwave permittivity and electromagnetic wave absorption properties of Fe-based nano-composite flakes in different sizes

NASA Astrophysics Data System (ADS)

Wu, Yanhui; Han, Mangui; Liu, Tao; Deng, Longjiang

2015-07-01

The effective permittivity of composites containing Fe-Cu-Nb-Si-B nanocrystalline micro flakes has been studied within 0.5-10 GHz. Obvious differences in microwave permittivity have been observed for composites consisting of large flakes (size range: 23-111 μm, average thickness: 4.5 μm) and small flakes (size range: 3-21 μm, average thickness: 1.3 μm). Both the real part and imaginary part of permittivity of large flake composite are much larger than these small one in a given frequency. And faster decrease of permittivity with the increasing frequency can be observed for large flake composite than that of small one. These differences in permittivity spectra of different flakes have been explained from the perspective of interfacial polarization and ac conductivity. The assumption that more extensive ohmic contact interface between large flakes and matrix has been validated by the fittings and the calculated percolation threshold. Meanwhile, the permeability spectra of both composites also have been studied by Lorentzian dispersion law. The broadened spectra can be attributed to the distribution of magnetic anisotropy fields of two kinds of ferromagnetic phases in the particles. Finally, the composite containing the small flakes exhibits better electromagnetic wave absorption properties.

Understanding Mechanical Response of Elastomeric Graphene Networks

PubMed Central

Ni, Na; Barg, Suelen; Garcia-Tunon, Esther; Macul Perez, Felipe; Miranda, Miriam; Lu, Cong; Mattevi, Cecilia; Saiz, Eduardo

2015-01-01

Ultra-light porous networks based on nano-carbon materials (such as graphene or carbon nanotubes) have attracted increasing interest owing to their applications in wide fields from bioengineering to electrochemical devices. However, it is often difficult to translate the properties of nanomaterials to bulk three-dimensional networks with a control of their mechanical properties. In this work, we constructed elastomeric graphene porous networks with well-defined structures by freeze casting and thermal reduction, and investigated systematically the effect of key microstructural features. The porous networks made of large reduced graphene oxide flakes (>20 μm) are superelastic and exhibit high energy absorption, showing much enhanced mechanical properties than those with small flakes (<2 μm). A better restoration of the graphitic nature also has a considerable effect. In comparison, microstructural differences, such as the foam architecture or the cell size have smaller or negligible effect on the mechanical response. The recoverability and energy adsorption depend on density with the latter exhibiting a minimum due to the interplay between wall fracture and friction during deformation. These findings suggest that an improvement in the mechanical properties of porous graphene networks significantly depend on the engineering of the graphene flake that controls the property of the cell walls. PMID:26348898

Functional energy nanocomposites surfaces based on mesoscopic microspheres, polymers and graphene flakes

NASA Astrophysics Data System (ADS)

Alekseev, S. A.; Dmitriev, A. S.; Dmitriev, A. A.; Makarov, P. G.; Mikhailova, I. A.

2017-11-01

In recent years, there has been a great interest in the development and creation of new functional energy materials, including for improving the energy efficiency of power equipment and for effectively removing heat from energy devices, microelectronics and optoelectronics (power micro electronics, supercapacitors, cooling of processors, servers and Data centers). In this paper, the technology of obtaining a new nanocomposite based on mesoscopic microspheres, polymers and graphene flakes is considered. The methods of sequential production of functional materials from graphite flakes of different volumetric concentration using polymers based on epoxy resins and polyimide, as well as the addition of a mesoscopic medium in the form of monodisperse microspheres are described. The data of optical and electron microscopy of such nanocomposites are presented, the main problems in the appearance of defects in such materials are described, the possibilities of their elimination by the selection of different concentrations and sizes of the components. Data are given on the measurement of the hysteresis of the contact angle and the evaporation of droplets on similar substrates. The results of studying the mechanical, electrophysical and thermal properties of such nanocomposites are presented. Particular attention is paid to the investigation of the thermal conductivity of these nanocomposites with respect to the creation of thermal interface materials for cooling devices of electronics, optoelectronics and power engineering.

Modified Separator Performing Dual Physical/Chemical Roles to Inhibit Polysulfide Shuttle Resulting in Ultrastable Li-S Batteries.

PubMed

Abbas, Syed Ali; Ding, Jiang; Wu, Sheng Hui; Fang, Jason; Boopathi, Karunakara Moorthy; Mohapatra, Anisha; Lee, Li Wei; Wang, Pen-Cheng; Chang, Chien-Cheng; Chu, Chih Wei

2017-12-26

In this paper we describe a modified (AEG/CH) coated separator for Li-S batteries in which the shuttling phenomenon of the lithium polysulfides is restrained through two types of interactions: activated expanded graphite (AEG) flakes interacted physically with the lithium polysulfides, while chitosan (CH), used to bind the AEG flakes on the separator, interacted chemically through its abundance of amino and hydroxyl functional groups. Moreover, the AEG flakes facilitated ionic and electronic transfer during the redox reaction. Live H-cell discharging experiments revealed that the modified separator was effective at curbing polysulfide shuttling; moreover, X-ray photoelectron spectroscopy analysis of the cycled separator confirmed the presence of lithium polysulfides in the AEG/CH matrix. Using this dual functional interaction approach, the lifetime of the pure sulfur-based cathode was extended to 3000 cycles at 1C-rate (1C = 1670 mA/g), decreasing the decay rate to 0.021% per cycle, a value that is among the best reported to date. A flexible battery based on this modified separator exhibited stable performance and could turn on multiple light-emitting diodes. Such modified membranes with good mechanical strength, high electronic conductivity, and anti-self-discharging shield appear to be a scalable solution for future high-energy battery systems.

Early use of pressure flaking on lithic artifacts at Blombos Cave, South Africa.

PubMed

Mourre, Vincent; Villa, Paola; Henshilwood, Christopher S

2010-10-29

Pressure flaking has been considered to be an Upper Paleolithic innovation dating to ~20,000 years ago (20 ka). Replication experiments show that pressure flaking best explains the morphology of lithic artifacts recovered from the ~75-ka Middle Stone Age levels at Blombos Cave, South Africa. The technique was used during the final shaping of Still Bay bifacial points made on heat-treated silcrete. Application of this innovative technique allowed for a high degree of control during the detachment of individual flakes, resulting in thinner, narrower, and sharper tips on bifacial points. This technology may have been first invented and used sporadically in Africa before its later widespread adoption.

Synthesis of Carboxylated-Graphenes by the Kolbe-Schmitt Process.

PubMed

Eng, Alex Yong Sheng; Sofer, Zdeněk; Sedmidubský, David; Pumera, Martin

2017-02-28

Graphene oxide is an oxidized form of graphene containing a large variety of oxygen groups. Although past models have suggested carboxylic acids to be present in significant amounts, recent evidence has shown otherwise. Toward the production of carboxyl-graphene, a synthetic method is presented herein based on the Kolbe-Schmitt process. A modified procedure of heating graphite oxide in the presence of a KOH/CaO mixture results in up to 11 atom % of carboxylic groups. The graphite oxide starting material and reaction temperature were investigated as two important factors, where a crumpled morphology of graphite oxide flakes and a lower 220 °C temperature preferentially led to greater carboxyl functionalization. Successful carboxylation caused a band gap opening of ∼2.5 eV in the smallest carboxyl-graphene particles, which also demonstrated a yellow fluorescence under UV light unseen in its counterpart produced at 500 °C. These results are in good agreement with theoretical calculations showing band gap opening and spin polarization of impurity states. This demonstrates the current synthetic process as yet another approach toward tuning the physical properties of graphene.

Deposition of hermetic silver shells onto copper flakes.

PubMed

Njagi, John I; Netzband, Christopher M; Goia, Dan V

2017-02-15

Continuous silver shells were deposited on copper flakes using a two-stage precipitation process. A tightly packed layer of silver nanoparticles was first formed on the surface of the base metal by galvanic displacement. The size of the noble metal particles and their distribution on the substrate were controlled using complexing agents and dispersants. A continuous Ag deposit was subsequently grown by reducing slowly [Ag(NH 3 ) 2 ] + ions with glucose. The final shell thickness was controlled by varying the amount of metal deposited in the second step. The electrical properties of resulting silver coated copper flakes are comparable to those measured for silver flakes of similar size and aspect ratio. By preventing the oxidation of copper cores up to 400°C, the hermetic noble metal shell dramatically extends the temperature range in which Ag/Cu flakes can successfully replace pure silver. Copyright © 2016 Elsevier Inc. All rights reserved.

Refractory lining system for high wear area of high temperature reaction vessel

DOEpatents

Hubble, David H.; Ulrich, Klaus H.

1998-01-01

A refractory-lined high temperature reaction vessel comprises a refractory ring lining constructed of refractory brick, a cooler, and a heat transfer medium disposed between the refractory ring lining and the cooler. The refractory brick comprises magnesia (MgO) and graphite. The heat transfer medium contacts the refractory brick and a cooling surface of the cooler, and is composed of a material that accommodates relative movement between the refractory brick and the cooler. The brick is manufactured such that the graphite has an orientation providing a high thermal conductivity in the lengthwise direction through the brick that is higher than the thermal conductivity in directions perpendicular to the lengthwise direction. The graphite preferably is flake graphite, in the range of about 10 to 20 wt %, and has a size distribution selected to provide maximum brick density. The reaction vessel may be used for performing a reaction process including the steps of forming a layer of slag on a melt in the vessel, the slag having a softening point temperature range, and forming a protective frozen layer of slag on the interior-facing surface of the refractory lining in at least a portion of a zone where the surface contacts the layer of slag, the protective frozen layer being maintained at or about the softening point of the slag.

Ultrafast carrier dynamics in bilayer graphene studied by broadband infrared pump-probe spectroscopy

NASA Astrophysics Data System (ADS)

Limmer, Thomas; da Como, Enrico; Niggebaum, Alexander; Feldmann, Jochen

2010-03-01

Recently, bilayer graphene gained a large interest because of its electrically tunable gap appearing in the middle infrared part of the electromagnetic spectrum. This feature is expected to open a number of applications of bilayer graphene in optoelectronics. In this communication we report on the first pump-probe experiment on a single bilayer flake with an unprecedented probe photon energy interval (0.25 -- 1.3 eV). Single flakes were prepared by mechanical exfoliation of graphite and transferred to calcium fluoride substrates. When illuminated with 800 nm (1.5 eV) pump pulses the induced change in transmission shows an ultrafast saturation of the interband transitions from 1.3 to 0.5 eV. In this energy range the saturation recovery occurs within 3 ps and is consistent with an ultrafast relaxation of hot carriers. Interestingly, we report on the observation of a resonance at 0.4 eV characterized by a longer dynamics. The results are discussed considering many-body interactions.

Switchable friction enabled by nanoscale self-assembly on graphene

DOE PAGES

Gallagher, Patrick; Lee, Menyoung; Amet, Francois; ...

2016-02-23

Graphene monolayers are known to display domains of anisotropic friction with twofold symmetry and anisotropy exceeding 200%. This anisotropy has been thought to originate from periodic nanoscale ripples in the graphene sheet, which enhance puckering around a sliding asperity to a degree determined by the sliding direction. Here we demonstrate that these frictional domains derive not from structural features in the graphene but from self-assembly of environmental adsorbates into a highly regular superlattice of stripes with period 4–6 nm. The stripes and resulting frictional domains appear on monolayer and multilayer graphene on a variety of substrates, as well as onmore » exfoliated flakes of hexagonal boron nitride. We show that the stripe-superlattices can be reproducibly and reversibly manipulated with submicrometre precision using a scanning probe microscope, allowing us to create arbitrary arrangements of frictional domains within a single flake. In conclusion, our results suggest a revised understanding of the anisotropic friction observed on graphene and bulk graphite in terms of adsorbates.« less

Coupling Graphene Sheets with Iron Oxide Nanoparticles for Energy Storage and Microelectronics

DTIC Science & Technology

2015-08-13

of highly oriented pyrolytic graphite ( HOPG ) flake. Two electrode system containing platinum as counter electrode and HOPG as working electrode is... XRD ) patterns of the HOPG , exfoliated graphene, PyDop1-ɤ-Fe2O3 and PyDop1-ɤ-Fe2O3-graphene are given in Figure 1e. HOPG show a very sharp diffraction...atoms arranged in hexagonal pattern in honey comb crystal lattice, (c) TEM (d) HRTEM image of graphene- PyDop1-MNP hybrid, (e) XRD pattern of the HOPG

A series of BCN nanosheets with enhanced photoelectrochemical performances

NASA Astrophysics Data System (ADS)

Li, Junqi; Lei, Nan; Hao, Hongjuan; Zhou, Jian

2017-03-01

A series of flake-like BCN compounds were produced by calcination at different reaction temperatures via thermal substitution of C atoms with B atoms of boric acid substructures in graphitic carbon nitrides (g-C3N4). The structural and optical properties of the samples were characterized by XRD, TEM, HRTEM, XPS and UV-vis absorption. The photoelectrochemical (PEC) performance of all samples were characterized through photocurrent and electrochemical impedance spectroscopy (EIS) measurement. The test results demonstrated that BCN nanosheets exhibited higher PEC performance with increasing substituted amount of boron.

The production of concentrated dispersions of few-layer graphene by the direct exfoliation of graphite in organosilanes

PubMed Central

2012-01-01

We report the formation and characterization of graphene dispersions in two organosilanes, 3-glycidoxypropyl trimethoxysilane (GPTMS) and phenyl triethoxysilane (PhTES) as new reactive solvents. The preparation method was mild and easy and does not produce any chemical modification. The dispersions, which exhibit the Tyndall effect, were characterized by TEM and Raman spectroscopy to confirm the presence of few-layer graphene. Concentrations as high as 0.66 and 8.00 mg/ml were found for PhTES and GPTMS, respectively. The latter is one of the highest values reported for a dispersion of graphene obtained by any method. This finding paves the way for the direct synthesis of polymer nanofiller-containing composites consisting of graphene and reactive silanes to be used in sol–gel synthesis, without any need for solvent removal, thus preventing graphene reaggregation to form graphite flakes. PMID:23237423

Wrinkled Few-Layer Graphene as Highly Efficient Load Bearer.

PubMed

Androulidakis, Charalampos; Koukaras, Emmanuel N; Rahova, Jaroslava; Sampathkumar, Krishna; Parthenios, John; Papagelis, Konstantinos; Frank, Otakar; Galiotis, Costas

2017-08-09

Multilayered graphitic materials are not suitable as load-bearers due to their inherent weak interlayer bonding (for example, graphite is a solid lubricant in certain applications). This situation is largely improved when two-dimensional (2D) materials such as a monolayer (SLG) graphene are employed. The downside in these cases is the presence of thermally or mechanically induced wrinkles which are ubiquitous in 2D materials. Here we set out to examine the effect of extensive large wavelength/amplitude wrinkling on the stress transfer capabilities of exfoliated simply supported graphene flakes. Contrary to common belief we present clear evidence that this type of "corrugation" enhances the load-bearing capacity of few-layer graphene as compared to "flat" specimens. This effect is the result of the significant increase of the graphene/polymer interfacial shear stress per increment of applied strain due to wrinkling and paves the way for designing affordable graphene composites with highly improved stress-transfer efficiency.

Simultaneous Graphite Exfoliation and N Doping in Supercritical Ammonia.

PubMed

Sasikala, Suchithra Padmajan; Huang, Kai; Giroire, Baptiste; Prabhakaran, Prem; Henry, Lucile; Penicaud, Alain; Poulin, Philippe; Aymonier, Cyril

2016-11-16

We report the exfoliation of graphite and simultaneous N doping of graphene by two methods: supercritical ammonia treatment and liquid-phase exfoliation with NH 4 OH. While the supercritical ammonia allowed N doping at a level of 6.4 atom % in 2 h, the liquid-phase exfoliation with NH 4 OH allowed N doping at a level of 2.7 atom % in 6 h. The N doped graphene obtained via the supercritical ammonia route had few layers (<5) and showed large lateral flake size (∼8 μm) and low defect density (I D /I G < 0.6) in spite of their high level of N doping. This work is the first demonstration of supercritical ammonia as an exfoliation agent and N doping precursor for graphene. Notably, the N doped graphene showed electrocatalytic activity toward oxygen reduction reaction with high durability and good methanol tolerance compared to those of commercial Pt/C catalyst.

A facile solvothermal method to produce graphene-ZnS composites for superior photoelectric applications

NASA Astrophysics Data System (ADS)

Lei, Yun; Chen, Feifei; Li, Rong; Xu, Jun

2014-07-01

In this experiment, flake graphite (<30 μm) was prepared as raw materials. Graphite oxide is prepared with Hummers method by low temperature, middle temperature and high temperature, and further treated with super-sonic oscillation to get graphene oxide. Graphene-zinc sulfide composites were synthesized through a simple solvothermal method using thiourea or sodium sulfide as sulfur source in the ethylene glycol or ethylenediamine, respectively. The products were characterized by X-ray and SEM, and analyzed by the transient photocurrent response and electrochemical impedance spectra. The results indicate that the properties of graphene-zinc sulfide composites prepared with thiourea in ethylene glycol are superior to those of blank-ZnS and composites prepared with sodium sulfide and ethylenediamine, which is attributed to electron capture and transfer ability of graphene resulting in a more efficient separation of the photoexcited charge carriers from ZnS-graphene composites.

Structural, optical, and electrical characteristics of graphene nanosheets synthesized from microwave-assisted exfoliated graphite

NASA Astrophysics Data System (ADS)

Chamoli, Pankaj; Das, Malay K.; Kar, Kamal K.

2017-11-01

In the present study, low defect density graphene nanosheets (GNs) have been synthesized via chemical reduction of exfoliated graphite (EG) in the presence of a green reducing agent, oxalic acid. EG has been synthesized via chemical intercalation of natural flake graphite followed by exfoliation through microwave irradiation at 800 W for 50 s. 50 mg/mL concentration of oxalic acid helps to extract low defect density GNs from EG. As-synthesized GNs have been characterized by X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, UV-Visible spectroscopy, field emission scanning electron microscopy, and X-ray photon spectroscopy. Raman analysis confirms the removal of oxygen functional groups from EG and achieved an ID/IG ratio of ˜0.10 with low defect density (˜1.12 × 1010 cm-2). Elemental analysis supports the Raman signature of the removal of oxygen functionalities from EG, and a high C/O ratio of ˜15.97 is obtained. Further, transparent conducting films (TCFs) have been fabricated by spray coating. The optical and electrical properties of fabricated TCFs have been measured after thermal graphitization. Thermal graphitization helps to improve the optical and electrical properties of TCFs by tuning the optical bandgap in a controlled way. TCF shows best performance when the film is annealed at 900 °C for 1 h in vacuum. It shows a sheet resistance of ˜1.10 kΩ/◻ and a transmittance of ˜71.56% at 550 nm.

Effect of Synthesis on Quality, Electronic Properties and Environmental Stability of Individual monolayer Ti3C2 MXene Flakes

DOE PAGES

Lipatov, A.; Alhabeb, M.; Lukatskaya, Maria R.; ...

2016-01-01

2D transition metal carbide Ti 3C 2T x (T stands for surface termination), the most widely studied MXene, has shown outstanding electrochemical properties and promise for a number of bulk applications. However, electronic properties of individual MXene flakes, which are important for understanding the potential of these materials, remain largely unexplored. Herein, a modified synthetic method is reported for producing high-quality monolayer Ti 3C 2T x flakes. Field-effect transistors (FETs) based on monolayer Ti 3C 2T x flakes are fabricated and their electronic properties are measured. Individual Ti3C2Tx flakes exhibit a high conductivity of 4600 ± 1100 S cm -1more » and field-effect electron mobility of 2.6 ± 0.7 cm2 V -1 s -1. The resistivity of multilayer Ti 3C 2T x films is only one order of magnitude higher than the resistivity of individual flakes, which indicates a surprisingly good electron transport through the surface terminations of different flakes, unlike in many other 2D materials. Finally, the fabricated FETs are used to investigate the environmental stability and kinetics of oxidation of Ti3C2Tx flakes in humid air. The high-quality Ti 3C 2T x flakes are reasonably stable and remain highly conductive even after their exposure to air for more than 24 h. It is demonstrated that after the initial exponential decay the conductivity of Ti 3C 2T x flakes linearly decreases with time, which is consistent with their edge oxidation.« less

Scale-up of high specific activity 186gRe production using graphite-encased thick 186W targets and demonstration of an efficient target recycling process

DOE PAGES

Balkin, Ethan R.; Gagnon, Katherine; Dorman, Eric; ...

2017-08-18

Production of high specific activity 186gRe is of interest for development of theranostic radiopharmaceuticals. Previous studies have shown that high specific activity 186gRe can be obtained by cyclotron irradiation of enriched 186W via the 186W(d,2n) 186gRe reaction, but most irradiations were conducted at low beam currents and for short durations. In this paper, enriched 186W metal targets were irradiated at high incident deuteron beam currents to demonstrate production rates and contaminants produced when using thick targets. Full-stopping thick targets, as determined using SRIM, were prepared by uniaxial pressing of powdered natural abundance W metal or 96.86% enriched 186W metal encasedmore » between two layers of graphite flakes for target material stabilization. An assessment of structural integrity was made on each target preparation. To assess the performance of graphite-encased thick 186W metal targets, along with the impact of encasing on the separation chemistry, targets were first irradiated using a 22 MeV deuteron beam for 10 min at 10, 20, and 27 μA, with an estimated nominal deuteron energy of 18.7 MeV on the 186W target material (after energy degradation correction from top graphite layer). Gamma-ray spectrometry was performed post EOB on all targets to assess production yields and radionuclidic byproducts. The investigation also evaluated a method to recover and recycle enriched target material from a column isolation procedure. Material composition analyses of target materials, pass-through/wash solutions and recycling process isolates were conducted with SEM, FTIR, XRD, EDS and ICP-MS spectrometry. Finally, to demonstrate scaled-up production, a graphite-encased 186W target made from recycled 186W was irradiated for ~2 h with 18.7 MeV deuterons at a beam current of 27 μA to provide 0.90 GBq (24.3 mCi) of 186gRe, decay-corrected to the end of bombardment. ICP-MS analysis of the isolated 186gRe solution provided data that indicated the specific activity of 186gRe in this scaled-up production run was 2.6±0.5 GBq/μg (70±10 Ci/mg).« less

Scale-up of high specific activity 186gRe production using graphite-encased thick 186W targets and demonstration of an efficient target recycling process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balkin, Ethan R.; Gagnon, Katherine; Dorman, Eric

Production of high specific activity 186gRe is of interest for development of theranostic radiopharmaceuticals. Previous studies have shown that high specific activity 186gRe can be obtained by cyclotron irradiation of enriched 186W via the 186W(d,2n) 186gRe reaction, but most irradiations were conducted at low beam currents and for short durations. In this paper, enriched 186W metal targets were irradiated at high incident deuteron beam currents to demonstrate production rates and contaminants produced when using thick targets. Full-stopping thick targets, as determined using SRIM, were prepared by uniaxial pressing of powdered natural abundance W metal or 96.86% enriched 186W metal encasedmore » between two layers of graphite flakes for target material stabilization. An assessment of structural integrity was made on each target preparation. To assess the performance of graphite-encased thick 186W metal targets, along with the impact of encasing on the separation chemistry, targets were first irradiated using a 22 MeV deuteron beam for 10 min at 10, 20, and 27 μA, with an estimated nominal deuteron energy of 18.7 MeV on the 186W target material (after energy degradation correction from top graphite layer). Gamma-ray spectrometry was performed post EOB on all targets to assess production yields and radionuclidic byproducts. The investigation also evaluated a method to recover and recycle enriched target material from a column isolation procedure. Material composition analyses of target materials, pass-through/wash solutions and recycling process isolates were conducted with SEM, FTIR, XRD, EDS and ICP-MS spectrometry. Finally, to demonstrate scaled-up production, a graphite-encased 186W target made from recycled 186W was irradiated for ~2 h with 18.7 MeV deuterons at a beam current of 27 μA to provide 0.90 GBq (24.3 mCi) of 186gRe, decay-corrected to the end of bombardment. ICP-MS analysis of the isolated 186gRe solution provided data that indicated the specific activity of 186gRe in this scaled-up production run was 2.6±0.5 GBq/μg (70±10 Ci/mg).« less

Experimental high temperature carbon isotope fractionation involving graphite

NASA Astrophysics Data System (ADS)

Kueter, N.; Schmidt, M. W.; Lilley, M. D.; Bernasconi, S. M.

2016-12-01

Graphite/carbonate carbon isotope fractionation was mainly investigated at 400- 800°C and is based on empirical calibrations, theoretical calculations and few experiments [1,2]. Own work on COH-fluid/graphite isotope fractionation shows that in experiments up to 1000oC a fluid phase is always enriched in 13C compared to coexisting graphitic carbon. The eventual kinetic isotope effect in these experiments is best displayed by the graphitic carbon being at least 3 ‰ lighter than methane. Only few experiments done in the graphite/carbonate pair dealt with higher temperatures reaching 1400°C, indicating a fractionation of up to 2 ‰ at temperatures of the Earth's mantle [2-4]. To better understand carbon isotope fractionation in crustal systems and still overcome kinetic effects, we study the graphite/carbonatite pair with piston cylinder experiments in the Na2CO3-CaCO3-CaO-COH system. Tartaric acid (C4H6O6) supplies reduced carbon, time series are performed at 10 kbar, 1300-1800°C. Initial experiments at 1300°C produce well-ordered, micron-sized graphite flakes growing attached to the capsule walls while the Na-Ca-carbonatite-melt quenches to dendritic textures. No gaseous phase was observed. Conditions well above the liquidus of the Na2CO3-CaCO3-binary lead to dissolution of the H2O from tartaric acid decomposition in the melt, any CO2-component is bound by the excess CaO to CaCO3melt while in the relatively oxidizing capsule environment any CH4-component reacts with CO2 to carbon and H2O. The graphite and the carbonatite quench are measured for their δ13C composition using a GasBench II (carbonate-dissolution in phosphoric acid) and TC/EA (residual graphite combusted in oxygen atmosphere) system coupled to a Thermo Fischer IRMS. Our results expand from the graphite-carbonate system to graphite-fluid system when adding available fluid-carbonate fractionation factors, but are also directly applicable to diamond synthesis as graphite is often found as a precursor phase in diamond-growth experiments in carbonatite systems and natural diamonds. [1] Chacko et al. (2001) Rev Min Geochem; Deines & Eggler (2009) GCA; [3] Scheele & Hoefs (1992) CMP; [4] Chacko et al. (1991) GCA

Skin inspired fractal strain sensors using a copper nanowire and graphite microflake hybrid conductive network.

PubMed

Jason, Naveen N; Wang, Stephen J; Bhanushali, Sushrut; Cheng, Wenlong

2016-09-22

This work demonstrates a facile "paint-on" approach to fabricate highly stretchable and highly sensitive strain sensors by combining one-dimensional copper nanowire networks with two-dimensional graphite microflakes. This paint-on approach allows for the fabrication of electronic skin (e-skin) patches which can directly replicate with high fidelity the human skin surface they are on, regardless of the topological complexity. This leads to high accuracy for detecting biometric signals for applications in personalised wearable sensors. The copper nanowires contribute to high stretchability and the graphite flakes offer high sensitivity, and their hybrid coating offers the advantages of both. To understand the topological effects on the sensing performance, we utilized fractal shaped elastomeric substrates and systematically compared their stretchability and sensitivity. We could achieve a high stretchability of up to 600% and a maximum gauge factor of 3000. Our simple yet efficient paint-on approach enabled facile fine-tuning of sensitivity/stretchability simply by adjusting ratios of 1D vs. 2D materials in the hybrid coating, and the topological structural designs. This capability leads to a wide range of biomedical sensors demonstrated here, including pulse sensors, prosthetic hands, and a wireless ankle motion sensor.

Refractory lining system for high wear area of high temperature reaction vessel

DOEpatents

Hubble, D.H.; Ulrich, K.H.

1998-04-21

A refractory-lined high temperature reaction vessel comprises a refractory ring lining constructed of refractory brick, a cooler, and a heat transfer medium disposed between the refractory ring lining and the cooler. The refractory brick comprises magnesia (MgO) and graphite. The heat transfer medium contacts the refractory brick and a cooling surface of the cooler, and is composed of a material that accommodates relative movement between the refractory brick and the cooler. The brick is manufactured such that the graphite has an orientation providing a high thermal conductivity in the lengthwise direction through the brick that is higher than the thermal conductivity in directions perpendicular to the lengthwise direction. The graphite preferably is flake graphite, in the range of about 10 to 20 wt %, and has a size distribution selected to provide maximum brick density. The reaction vessel may be used for performing a reaction process including the steps of forming a layer of slag on a melt in the vessel, the slag having a softening point temperature range, and forming a protective frozen layer of slag on the interior-facing surface of the refractory lining in at least a portion of a zone where the surface contacts the layer of slag, the protective frozen layer being maintained at or about the softening point of the slag. 10 figs.

Refractory lining system for high wear area of high temperature reaction vessel

DOEpatents

Hubble, D.H.; Ulrich, K.H.

1998-09-22

A refractory-lined high temperature reaction vessel comprises a refractory ring lining constructed of refractory brick, a cooler, and a heat transfer medium disposed between the refractory ring lining and the cooler. The refractory brick comprises magnesia (MgO) and graphite. The heat transfer medium contacts the refractory brick and a cooling surface of the cooler, and is composed of a material that accommodates relative movement between the refractory brick and the cooler. The brick is manufactured such that the graphite has an orientation providing a high thermal conductivity in the lengthwise direction through the brick that is higher than the thermal conductivity in directions perpendicular to the lengthwise direction. The graphite preferably is flake graphite, in the range of about 10 to 20 wt %, and has a size distribution selected to provide maximum brick density. The reaction vessel may be used for performing a reaction process including the steps of forming a layer of slag on a melt in the vessel, the slag having a softening point temperature range, and forming a protective frozen layer of slag on the interior-facing surface of the refractory lining in at least a portion of a zone where the surface contacts the layer of slag, the protective frozen layer being maintained at or about the softening point of the slag. 10 figs.

Shaping-lathe headrig will convert small hardwoods into pallet cants plus flakes for structural exterior flakeboard

Treesearch

Peter Koch

1975-01-01

Virtually all nations have an under-utilized resource of small-diameter, low-grade hardwoods of mixed species in a range of densities. The shaping-lathe headrig, now in the final stages of commercialization, is a key to utilizing these hardwoods for pallets, industrial lumber, and-with further development-railroad crossties. Lathe residues in the form of flakes can be...

Roll-to-Roll Continuous Manufacturing Multifunctional Nanocomposites by Electric-Field-Assisted "Z" Direction Alignment of Graphite Flakes in Poly(dimethylsiloxane).

PubMed

Guo, Yuanhao; Chen, Yuwei; Wang, Enmin; Cakmak, Miko

2017-01-11

A roll-to-roll continuous process was developed to manufacture large-scale multifunctional poly(dimethylsiloxane) (PDMS) films embedded with thickness direction ("Z" direction) aligned graphite nanoparticles by application of electric field. The kinetics of particle "Z" alignment and chain formation was studied by tracking the real-time change of optical light transmission through film thickness direction. Benefiting from the anisotropic structure of aligned particle chains, the electrical and thermal properties of the nanocomposites were dramatically enhanced through the thickness direction as compared to those of the nanocomposites containing the same particle loading without electrical field alignment. With 5 vol % graphite loading, 250 times higher electrical conductivity, 43 times higher dielectric permittivity, and 1.5 times higher thermal conductivity was achieved in the film thickness direction after the particles were aligned under electrical field. Moreover, the aligned nanocomposites with merely 2 vol % graphite particles exhibit even higher electric conductivity and dielectric permittivity than those of the nonaligned nanocomposites at random percolation threshold (10 vol % particles), as the "electric-field-directed" percolation threshold concentration is substantially decreased using this process. As the graphite loading increases to 20 vol %, the aligned nanocomposites exhibit thermal conductivity as high as 6.05 W/m·K, which is 35 times the thermal conductivity of pure matrix. This roll-to-roll electric field continuous process provides a simple, low-cost, and commercially viable method to manufacture multifunctional nanocomposites for applications as embedded capacitor, electromagnetic (EM) shielding, and thermal interface materials.

Graphene oxide-silica nanohybrids as fillers for PA6 based nanocomposites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maio, A.; Fucarino, R.; Khatibi, R.

Graphene oxide (GO) was prepared by oxidation of graphite flakes by a mixture of H{sub 2}SO{sub 4}/H{sub 3}PO{sub 4} and KMnO{sub 4} based on Marcano's method. Two different masterbatches containing GO (33.3%) and polyamide-6 (PA6) (66.7%) were prepared both via solvent casting in formic acid and by melt mixing in a mini-extruder (Haake). The two masterbatches were then used to prepare PA6-based nanocomposites with a content of 2% in GO. For comparison, a nanocomposite by direct mixing of PA6 and GO (2%) and PA6/graphite nanocomposites were prepared, too. The oxidation of graphite into GO was assessed by X-ray diffraction (XRD),more » Micro-Raman spectroscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) analyses. All these techniques demonstrated the effectiveness of the graphite modification, since the results put into evidence that, after the acid treatment, interlayer distance, oxygen content and defects increased. SEM micrographs carried out on the nanocomposites, showed GO layers totally surrounded by polyamide-6, this feature is likely due to the strong interaction between the hydrophilic moieties located both on GO and on PA6. On the contrary, no interactions were observed when graphite was used as filler. Mechanical characterization, carried out by tensile and dynamic-mechanical tests, marked an improvement of the mechanical properties observed. Photoluminescence and EPR measurements were carried out onto nanoparticles and nanocomposites to study the nature of the interactions and to assess the possibility to use this class of materials as semiconductors or optical sensors.« less

Graphene oxide-silica nanohybrids as fillers for PA6 based nanocomposites

NASA Astrophysics Data System (ADS)

Maio, A.; Fucarino, R.; Khatibi, R.; Botta, L.; Rosselli, S.; Bruno, M.; Scaffaro, R.

2014-05-01

Graphene oxide (GO) was prepared by oxidation of graphite flakes by a mixture of H2SO4/H3PO4 and KMnO4 based on Marcano's method. Two different masterbatches containing GO (33.3%) and polyamide-6 (PA6) (66.7%) were prepared both via solvent casting in formic acid and by melt mixing in a mini-extruder (Haake). The two masterbatches were then used to prepare PA6-based nanocomposites with a content of 2% in GO. For comparison, a nanocomposite by direct mixing of PA6 and GO (2%) and PA6/graphite nanocomposites were prepared, too. The oxidation of graphite into GO was assessed by X-ray diffraction (XRD), Micro-Raman spectroscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) analyses. All these techniques demonstrated the effectiveness of the graphite modification, since the results put into evidence that, after the acid treatment, interlayer distance, oxygen content and defects increased. SEM micrographs carried out on the nanocomposites, showed GO layers totally surrounded by polyamide-6, this feature is likely due to the strong interaction between the hydrophilic moieties located both on GO and on PA6. On the contrary, no interactions were observed when graphite was used as filler. Mechanical characterization, carried out by tensile and dynamic-mechanical tests, marked an improvement of the mechanical properties observed. Photoluminescence and EPR measurements were carried out onto nanoparticles and nanocomposites to study the nature of the interactions and to assess the possibility to use this class of materials as semiconductors or optical sensors.

Spall behavior of cast iron with varying microstructures

NASA Astrophysics Data System (ADS)

Plume, Gifford; Rousseau, Carl-Ernst

2014-07-01

The spall strength of cast iron with varying microstructures has been investigated using plate impact at moderate speed. Stress history measurements were made with manganin stress gauges embedded between the back face of the specimen and a low impedance polycarbonate backing. Five separate cast irons were tested. Four of these consisted of gray cast iron with graphite in flake form, with three classified as Type VII A2 and the fourth containing a bimodal distribution of Types VII A4 and VII D8. The fifth casting consisted of ductile cast iron with graphite in nodular form, classified as Type I, size class 5. The spall strength for the Type VII A2 gray cast irons varied between 40 and 370 MPa, and that of the additional gray cast iron, between 410 and 490 MPa. The spall strength of the ductile cast iron fell within the range of 0.94-1.2 GPa. It is shown that the spall strength is linked to the damage level at the spall plane, where an increased level of tensile stress is required to generate higher levels of damage. Post mortem analysis was performed on the recovered samples, revealing the graphite phase to be the primary factor governing the spall fracture of cast irons, where crack nucleation is directly correlated to the debonding of graphite from the metal matrix. The average length of graphite found within a casting is linked to the material's strength, where strength increases as a function of decreasing length. The morphology and mean free path of graphite precipitates further govern the subsequent coalescence of initiated cracks to form a complete fracture plane. In cases where graphite spacing is large, increased energy level is required to complete the fracture process. A secondary factor governing the spall fracture of cast irons has also been linked to the microstructure of the metal matrix, with pearlite yielding higher spall strengths than free ferrite.

Surface Modification of Self-Assembled Graphene Oxide for Cell Culture Studies

NASA Astrophysics Data System (ADS)

Swain, John E., III

Thin films show great promise for biological applications, from in situ monitoring to pharmaceutical testing. In this study, a graphene oxide (GO) thin film is prepared with the aim to further functionalize the film for pharmaceutical toxicity screening applications. GO was selected due to its capability to be reduced into an optically transparent and electrically conductive thin film. In addition, GO is derived from carbon, a widely abundant element, in contrast to many other thin films that rely on resource-limited precious metals. Special care was taken to select GO and GO film synthesis methods that minimize the amount of organic-based solvents, maintain reactions at atmospheric pressure and moderate temperatures, and are scalable for manufacturing. Chemical oxidation of graphite flakes was carried out via a modified Hummer's Method with a pre-oxidation step. The resulting GO flakes were self-assembled using commercially available 4-sulfocalix[4]arene. Analytical characterizations (e.g., elemental analysis, XRD, FTIR, Raman, SEM, AFM) were performed to evaluate the success of graphite oxidation and formation of the self-assembled thin film. In order to gain a better understanding of the interactions between GO and sulfocalix (SCX), equilibrium conformations of the SCX molecule and truncated GO were calculated using Spartan'16 Parallels. This study demonstrates that the interaction between the GO and the SCX molecule to create a self-assembled thin film is the result of pi-pi stacking, as hypothesized by Sundramoorthy et al. (2015). The self-assembled GO film was successfully deposited on a polyethylene terephthalate (PET) substrate and functionalized with 3-aminopropyl triethoxysilane (APTES), which renders the film capable of further functionalization with proteins for yielding a three-dimensional cell culture or co-culture platform for different applications.

Sheath-Core Graphite/Silk Fiber Made by Dry-Meyer-Rod-Coating for Wearable Strain Sensors.

PubMed

Zhang, Mingchao; Wang, Chunya; Wang, Qi; Jian, Muqiang; Zhang, Yingying

2016-08-17

Recent years have witnessed the explosive development of flexible strain sensors. Nanomaterials have been widely utilized to fabricate flexible strain sensors, because of their high flexibility and electrical conductivity. However, the fabrication processes for nanomaterials and the subsequent strain sensors are generally complicated and are manufactured at high cost. In this work, we developed a facile dry-Meyer-rod-coating process to fabricate sheath-core-structured single-fiber strain sensors using ultrafine graphite flakes as the sheath and silk fibers as the core by virtue of their flexibility, high production, and low cost. The fabricated strain sensor exhibits a high sensitivity with a gauge factor of 14.5 within wide workable strain range up to 15%, and outstanding stability (up to 3000 cycles). The single-fiber-based strain sensors could be attached to a human body to detect joint motions or easily integrated into the multidirectional strain sensor for monitoring multiaxial strain, showing great potential applications as wearable strain sensors.

Three-dimensional strutted graphene grown by substrate-free sugar blowing for high-power-density supercapacitors

PubMed Central

Wang, Xuebin; Zhang, Yuanjian; Zhi, Chunyi; Wang, Xi; Tang, Daiming; Xu, Yibin; Weng, Qunhong; Jiang, Xiangfen; Mitome, Masanori; Golberg, Dmitri; Bando, Yoshio

2013-01-01

Three-dimensional graphene architectures in the macroworld can in principle maintain all the extraordinary nanoscale properties of individual graphene flakes. However, current 3D graphene products suffer from poor electrical conductivity, low surface area and insufficient mechanical strength/elasticity; the interconnected self-supported reproducible 3D graphenes remain unavailable. Here we report a sugar-blowing approach based on a polymeric predecessor to synthesize a 3D graphene bubble network. The bubble network consists of mono- or few-layered graphitic membranes that are tightly glued, rigidly fixed and spatially scaffolded by micrometre-scale graphitic struts. Such a topological configuration provides intimate structural interconnectivities, freeway for electron/phonon transports, huge accessible surface area, as well as robust mechanical properties. The graphene network thus overcomes the drawbacks of presently available 3D graphene products and opens up a wide horizon for diverse practical usages, for example, high-power high-energy electrochemical capacitors, as highlighted in this work. PMID:24336225

Three-dimensional strutted graphene grown by substrate-free sugar blowing for high-power-density supercapacitors

NASA Astrophysics Data System (ADS)

Wang, Xuebin; Zhang, Yuanjian; Zhi, Chunyi; Wang, Xi; Tang, Daiming; Xu, Yibin; Weng, Qunhong; Jiang, Xiangfen; Mitome, Masanori; Golberg, Dmitri; Bando, Yoshio

2013-12-01

Three-dimensional graphene architectures in the macroworld can in principle maintain all the extraordinary nanoscale properties of individual graphene flakes. However, current 3D graphene products suffer from poor electrical conductivity, low surface area and insufficient mechanical strength/elasticity; the interconnected self-supported reproducible 3D graphenes remain unavailable. Here we report a sugar-blowing approach based on a polymeric predecessor to synthesize a 3D graphene bubble network. The bubble network consists of mono- or few-layered graphitic membranes that are tightly glued, rigidly fixed and spatially scaffolded by micrometre-scale graphitic struts. Such a topological configuration provides intimate structural interconnectivities, freeway for electron/phonon transports, huge accessible surface area, as well as robust mechanical properties. The graphene network thus overcomes the drawbacks of presently available 3D graphene products and opens up a wide horizon for diverse practical usages, for example, high-power high-energy electrochemical capacitors, as highlighted in this work.

Structure and properties of a splat cooled 2024 aluminum alloy

NASA Technical Reports Server (NTRS)

Lebo, M.; Grant, N. J.

1974-01-01

In the investigation the alloy was melted, heated to 750 C, and atomized into fine droplets. The droplets were rapidly quenched against a heavy copper disk rotating at 1725 rpm. The resultant splat cooled flakes were screened. Three flake sizes were finally separated. Flakes of each size were separately processed. The characteristics of the splat cooling process and the properties of the obtained products are discussed. Splat cooling against a metallic substrate permits cooling rates up to about 1,000,000 deg C/sec. Increases in yield strength and tensile strength of 14 to 19% are observed for the splat products. Other improvements are connected with increases in fatigue life and stress rupture performance.

Single-crystal and textured polycrystalline Nd2Fe14B flakes with a submicron or nanosize thickness

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cui, BZ; Zheng, LY; Li, WF

2012-02-01

This paper reports on the fabrication, structure and magnetic property optimization of Nd2Fe14B single-crystal and [0 0 1] textured poly-nanocrystalline flakes prepared by surfactant-assisted high-energy ball milling (HEBM). Single-crystal Nd2Fe14B flakes first with micron and then with submicron thicknesses were formed via continuous basal cleavage along the (1 1 0) planes of the irregularly shaped single-crystal microparticles during the early stage of HEBM. With further milling, [0 0 1] textured polycrystalline submicron Nd2Fe14B flakes were formed. Finally, crystallographically anisotropic polycrystalline Nd2Fe14B nanoflakes were formed after milling for 5-6 h. Anisotropic magnetic behavior was found in all of the flake samples.more » Nd2Fe14B flakes prepared with either oleic acid (OA) or oleylamine (OY) as the surfactant exhibited similar morphology, structure and magnetic properties. Both the addition of some low-melting-point eutectic Nd70Cu30 alloy and an appropriate post-annealing can increase the coercivity of the Nd2Fe14B flakes. The coercivity of Nd2Fe14B nanoflakes with an addition of 16.7 wt.% Nd70Cu30 by milling for 5 h in heptane with 20 wt.% OY increased from 3.7 to 6.8 kOe after annealing at 450 degrees C for 0.5 h. The mechanism for formation and coercivity enhancement of Nd2Fe14B single-crystal and textured poly-nanocrystalline flakes with a submicron or nanosize thickness was discussed. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.« less

Optical Band Gap Alteration of Graphene Oxide via Ozone Treatment.

PubMed

Hasan, Md Tanvir; Senger, Brian J; Ryan, Conor; Culp, Marais; Gonzalez-Rodriguez, Roberto; Coffer, Jeffery L; Naumov, Anton V

2017-07-25

Graphene oxide (GO) is a graphene derivative that emits fluorescence, which makes GO an attractive material for optoelectronics and biotechnology. In this work, we utilize ozone treatment to controllably tune the band gap of GO, which can significantly enhance its applications. Ozone treatment in aqueous GO suspensions yields the addition/rearrangement of oxygen-containing functional groups suggested by the increase in vibrational transitions of C-O and C=O moieties. Concomitantly it leads to an initial increase in GO fluorescence intensity and significant (100 nm) blue shifts in emission maxima. Based on the model of GO fluorescence originating from sp 2 graphitic islands confined by oxygenated addends, we propose that ozone-induced functionalization decreases the size of graphitic islands affecting the GO band gap and emission energies. TEM analyses of GO flakes confirm the size decrease of ordered sp 2 domains with ozone treatment, whereas semi-empirical PM3 calculations on model addend-confined graphitic clusters predict the inverse dependence of the band gap energies on sp 2 cluster size. This model explains ozone-induced increase in emission energies yielding fluorescence blue shifts and helps develop an understanding of the origins of GO fluorescence emission. Furthermore, ozone treatment provides a versatile approach to controllably alter GO band gap for optoelectronics and bio-sensing applications.

Synthesis of gold nanoparticles with graphene oxide.

PubMed

Wang, Wenshuo; He, Dawei; Zhang, Xiqing; Duan, Jiahua; Wu, Hongpeng; Xu, Haiteng; Wang, Yongsheng

2014-05-01

Single sheets of functionalized graphene oxide are derived through chemical exfoliation of natural flake graphite. We present an effective synthetic method of graphene-gold nanoparticles hybrid nanocomposites. AFM (Atomic Force Microscope) was used to measure the thickness of the individual GO nanosheet. FTIR (Fourier transform infrared) spectroscopy was used to verify the attachment of oxygen functionalities on the surface of graphene oxide. TEM (Transmission Electron Microscope) data revealed the average diameters of the gold colloids and characterized the composite particles situation. Absorption spectroscopy showed that before and after synthesis the gold particle size did not change. Our studies indicate that the hybrid is potential substrates for catalysts and biosensors.

Growth of nitrogen-doped graphene on copper: Multiscale simulations

NASA Astrophysics Data System (ADS)

Gaillard, P.; Schoenhalz, A. L.; Moskovkin, P.; Lucas, S.; Henrard, L.

2016-02-01

We used multiscale simulations to model the growth of nitrogen-doped graphene on a copper substrate by chemical vapour deposition (CVD). Our simulations are based on ab-initio calculations of energy barriers for surface diffusion, which are complemented by larger scale Kinetic Monte Carlo (KMC) simulations. Our results indicate that the shape of grown doped graphene flakes depends on the temperature and deposition flux they are submitted during the process, but we found no significant effect of nitrogen doping on this shape. However, we show that nitrogen atoms have a preference for pyridine-like sites compared to graphite-like sites, as observed experimentally.

Ferroelectric field-effect transistors based on solution-processed electrochemically exfoliated graphene

NASA Astrophysics Data System (ADS)

Heidler, Jonas; Yang, Sheng; Feng, Xinliang; Müllen, Klaus; Asadi, Kamal

2018-06-01

Memories based on graphene that could be mass produced using low-cost methods have not yet received much attention. Here we demonstrate graphene ferroelectric (dual-gate) field effect transistors. The graphene has been obtained using electrochemical exfoliation of graphite. Field-effect transistors are realized using a monolayer of graphene flakes deposited by the Langmuir-Blodgett protocol. Ferroelectric field effect transistor memories are realized using a random ferroelectric copolymer poly(vinylidenefluoride-co-trifluoroethylene) in a top gated geometry. The memory transistors reveal ambipolar behaviour with both electron and hole accumulation channels. We show that the non-ferroelectric bottom gate can be advantageously used to tune the on/off ratio.

Titanium trisulfide (TiS3): a 2D semiconductor with quasi-1D optical and electronic properties

PubMed Central

Island, Joshua O.; Biele, Robert; Barawi, Mariam; Clamagirand, José M.; Ares, José R.; Sánchez, Carlos; van der Zant, Herre S. J.; Ferrer, Isabel J.; D’Agosta, Roberto; Castellanos-Gomez, Andres

2016-01-01

We present characterizations of few-layer titanium trisulfide (TiS3) flakes which, due to their reduced in-plane structural symmetry, display strong anisotropy in their electrical and optical properties. Exfoliated few-layer flakes show marked anisotropy of their in-plane mobilities reaching ratios as high as 7.6 at low temperatures. Based on the preferential growth axis of TiS3 nanoribbons, we develop a simple method to identify the in-plane crystalline axes of exfoliated few-layer flakes through angle resolved polarization Raman spectroscopy. Optical transmission measurements show that TiS3 flakes display strong linear dichroism with a magnitude (transmission ratios up to 30) much greater than that observed for other anisotropic two-dimensional (2D) materials. Finally, we calculate the absorption and transmittance spectra of TiS3 in the random-phase-approximation (RPA) and find that the calculations are in qualitative agreement with the observed experimental optical transmittance. PMID:26931161

Self-assembly and continuous growth of hexagonal graphene flakes on liquid Cu

NASA Astrophysics Data System (ADS)

Cho, Seong-Yong; Kim, Min-Sik; Kim, Minsu; Kim, Ki-Ju; Kim, Hyun-Mi; Lee, Do-Joong; Lee, Sang-Hoon; Kim, Ki-Bum

2015-07-01

Graphene growth on liquid Cu has received great interest, owing to the self-assembly behavior of hexagonal graphene flakes with aligned orientation and to the possibility of forming a single grain of graphene through a commensurate growth of these graphene flakes. Here, we propose and demonstrate a two-step growth process which allows the formation of self-assembled, completely continuous graphene on liquid Cu. After the formation of full coverage on the liquid Cu, grain boundaries were revealed via selective hydrogen etching and the original grain boundaries were clearly resolved. This result indicates that, while the flakes self-assembled with the same orientation, there still remain structural defects, gaps and voids that were not resolved by optical microscopy or scanning electron microscopy. To overcome this limitation, the two-step growth process was employed, consisting of a sequential process of a normal single-layer graphene growth and self-assembly process with a low carbon flux, followed by the final stage of graphene growth at a high degree of supersaturation with a high carbon flux. Continuity of the flakes was verified via hydrogen etching and a NaCl-assisted oxidation process, as well as by measuring the electrical properties of the graphene grown by the two-step process. Two-step growth can provide a continuous graphene layer, but commensurate stitching should be further studied.Graphene growth on liquid Cu has received great interest, owing to the self-assembly behavior of hexagonal graphene flakes with aligned orientation and to the possibility of forming a single grain of graphene through a commensurate growth of these graphene flakes. Here, we propose and demonstrate a two-step growth process which allows the formation of self-assembled, completely continuous graphene on liquid Cu. After the formation of full coverage on the liquid Cu, grain boundaries were revealed via selective hydrogen etching and the original grain boundaries were clearly resolved. This result indicates that, while the flakes self-assembled with the same orientation, there still remain structural defects, gaps and voids that were not resolved by optical microscopy or scanning electron microscopy. To overcome this limitation, the two-step growth process was employed, consisting of a sequential process of a normal single-layer graphene growth and self-assembly process with a low carbon flux, followed by the final stage of graphene growth at a high degree of supersaturation with a high carbon flux. Continuity of the flakes was verified via hydrogen etching and a NaCl-assisted oxidation process, as well as by measuring the electrical properties of the graphene grown by the two-step process. Two-step growth can provide a continuous graphene layer, but commensurate stitching should be further studied. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03352g

Applying a laser-induced incandescence (LII) diagnostic to monitor nanoparticle synthesis in an atmospheric plasma, in situ

NASA Astrophysics Data System (ADS)

Yatom, Shurik; Mitrani, James; Yeh, Yao-Wen; Shneider, Mikhail; Stratton, Brentley; Raitses, Yevgeny

2016-09-01

A DC arc discharge with a consumed graphite anode is commonly used for synthesis of carbon nanoparticles, including carbon nanotubes (CNTs) and graphene flakes. The graphite electrode is physically vaporized by high currents (20-60 A) in a buffer gas at 100-600 torr, leading to nanoparticle synthesis in a low temperature (>1 eV), plasma. Utilizing arc plasma synthesis technique has resulted in the synthesis of higher quality nanomaterials. However, the formation of nanoparticles in arc discharge plasmas is poorly understood. A particularly interesting question is where in the arc the nanoparticles nucleate and grow. In our current work we show the results of studying the formation of carbon nanotubes in an arc discharge, in situ, using laser-induced incandescence (LII). The results of LII are discussed in combination with ex situ measurements of the synthesized nanoparticles and modeling, to provide an insight into the physics behind nanoparticle synthesis in plasma. This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.

Enhancement of tribofilm formation from water lubricated PEEK composites by copper nanowires

NASA Astrophysics Data System (ADS)

Gao, Chuanping; Fan, Shuguang; Zhang, Shengmao; Zhang, Pingyu; Wang, Qihua

2018-06-01

A high-performance tribofilm is crucial to enhance the tribological performance of tribomaterials. In order to promote tribofilm formation under water lubrication conditions, copper nanowires as a functional nanomaterial were filled into neat polyetheretherketone (PEEK) and PEEK10SCF8Gr (i.e., PEEK filled with 10 vol.% short carbon fibers and 8 vol.% graphite flakes). The results show that the addition of copper nanowires and a greater applied load can enhance materials transfer and tribofilm formation during sliding process. Moreover, copper nanowires can share a part of applied load, and retard the fatigue effect to some extent. In addition, copper nanowires, carbon fibers and graphite can synergistically improve the tribological performance and the tribofilm formation under water lubrication and severe working conditions. In particular, only 0.5 vol.% copper nanowires can form a high-performance tribofilm, which endows superior lubricating property and wear resistance capacity of the PEEK10SCF8Gr. Furthermore, the surface analysis indicates that the tribofilm contains some transferred materials and the products from tribochemical reactions as well.

Electrically conductive nano graphite-filled bacterial cellulose composites.

PubMed

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

2016-01-20

A unique three dimensional (3D) porous structured bacterial cellulose (BC) can act as a supporting material to deposit the nanofillers in order to create advanced BC-based functional nanomaterials for various technological applications. In this study, novel nanocomposites comprised of BC with exfoliated graphite nanoplatelets (xGnP) incorporated into the BC matrix were prepared using a simple particle impregnation strategy to enhance the thermal properties and electrical conductivity of the BC. The flake-shaped xGnP particles were well dispersed and formed a continuous network throughout the BC matrix. The temperature at 10% weight loss, thermal stability and residual ash content of the nanocomposites increased at higher xGnP loadings. The electrical conductivity of the composites increased with increasing xGnP loading (attaining values 0.75 S/cm with the addition of 2 wt.% of xGnP). The enhanced conductive and thermal properties of the BC-xGnP nanocomposites will broaden applications (biosensors, tissue engineering, etc.) of BC and xGnP. Copyright © 2015 Elsevier Ltd. All rights reserved.

Gelatin/graphene systems for low cost energy storage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Landi, Giovanni; Fedi, Filippo; Sorrentino, Andrea

2014-05-15

In this work, we introduce the possibility to use a low cost, biodegradable material for temporary energy storage devices. Here, we report the use of biologically derived organic electrodes composed of gelatin ad graphene. The graphene was obtained by mild sonication in a mixture of volatile solvents of natural graphite flakes and subsequent centrifugation. The presence of exfoliated graphene sheets was detected by atomic force microscopy (AFM) and Raman spectroscopy. The homogeneous dispersion in gelatin demonstrates a good compatibility between the gelatin molecules and the graphene particles. The electrical characterization of the resulting nanocomposites suggests the possible applications as materialsmore » for transient, low cost energy storage device.« less

78 FR 56864 - Small Diameter Graphite Electrodes From the People's Republic of China: Affirmative Final...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-09-16

... DEPARTMENT OF COMMERCE International Trade Administration [A-570-929] Small Diameter Graphite... (Department) determines that imports from the People's Republic of China (PRC) of graphite electrodes... Act of 1930, as amended (the Act).\\1\\ \\1\\ See Antidumping Duty Order: Small Diameter Graphite...

Dust particles in controlled fusion devices: morphology, observations in the plasma and influence on the plasma performance

NASA Astrophysics Data System (ADS)

Rubel, M.; Cecconello, M.; Malmberg, J. A.; Sergienko, G.; Biel, W.; Drake, J. R.; Hedqvist, A.; Huber, A.; Philipps, V.

2001-08-01

The formation and release of particle agglomerates, i.e. debris and dusty objects, from plasma facing components and the impact of such materials on plasma operation in controlled fusion devices has been studied in the Extrap T2 reversed field pinch and the TEXTOR tokamak. Several plasma diagnostic techniques, camera observations and surface analysis methods were applied for in situ and ex situ investigation. The results are discussed in terms of processes that are decisive for dust transfer: localized power deposition connected with wall locked modes causing emission of carbon granules, brittle destruction of graphite and detachment of thick flaking co-deposited layers. The consequences for large next step devices are also addressed.

Application of DFT-Derived Relationships Between Chemical Environment and 29Si Nuclear Magnetic Resonance Spectroscopy to Determine Structure in Silicon Oxycarbide Ceramics

NASA Astrophysics Data System (ADS)

Nimmo, John Paul, II

Silicon oxycarbide (SiCO) is an amorphous ceramic material widely used in industrial applications, for its useful electronic and biologically-compatible properties. SiCO is resistant to crystallization, remaining amorphous even above temperatures at which amorphous SiO2 would crystallize. Though silica (SiO2) and silicon carbide (SiC) are almost immiscible, it is useful to consider the material as a phase composition of these along with carbon, according to the formula below. The first two terms in braces can be considered as being the "SiCO glass" into which a third term representing excess or "free" carbon is incorporated as graphite-like nano-flakes and bands.

Carbon Nanotube Microarrays Grown on Nanoflake Substrates

NASA Technical Reports Server (NTRS)

Schmidt, Howard K.; Hauge, Robert H.; Pint, Cary; Pheasant, Sean

2013-01-01

This innovation consists of a new composition of matter where single-walled carbon nanotubes (SWNTs) are grown in aligned arrays from nanostructured flakes that are coated in Fe catalyst. This method of growth of aligned SWNTs, which can yield well over 400 percent SWNT mass per unit substrate mass, exceeds current yields for entangled SWNT growth. In addition, processing can be performed with minimal wet etching treatments, leaving aligned SWNTs with superior properties over those that exist in entangled mats. The alignment of the nanotubes is similar to that achieved in vertically aligned nanotubes, which are called "carpets. " Because these flakes are grown in a state where they are airborne in a reactor, these flakes, after growing SWNTs, are termed "flying carpets. " These flakes are created in a roll-to-roll evaporator system, where three subsequent evaporations are performed on a 100-ft (approx. =30-m) roll of Mylar. The first layer is composed of a water-soluble "release layer, " which can be a material such as NaCl. After depositing NaCl, the second layer involves 40 nm of supporting layer material . either Al2O3 or MgO. The thickness of the layer can be tuned to synthesize flakes that are larger or smaller than those obtained with a 40-nm deposition. Finally, the third layer consists of a thin Fe catalyst layer with a thickness of 0.5 nm. The thickness of this layer ultimately determines the diameter of SWNT growth, and a layer that is too thick will result in the growth of multiwalled carbon nanotubes instead of single-wall nanotubes. However, between a thickness of 0.5 nm to 1 nm, single-walled carbon nanotubes are known to be the primary constituent. After this three-layer deposition process, the Mylar is rolled through a bath of water, which allows catalyst-coated flakes to detach from the Mylar. The flakes are then collected and dried. The method described here for making such flakes is analogous to that which is used to make birefringent ink that is coated on U.S. currency. After deposition, the growth is carried out in a hot-filament chemical vapor deposition apparatus. A tungsten hot filament placed in the flow of H2 at a temperature greater than 1,600 C creates atomic hydrogen, which serves to reduce the Fe catalyst into a metallic state. The catalyst can now precipitate SWNTs in the presence of growth gases. The gases used for the experiments reported are C2H2, H2O, and H2, at rates of 2, 2, and 400 standard cubic centimeters per minute (sccm), respectively. In order to retain the flakes, a cage is constructed by spot welding stainless steel or copper mesh to form an enclosed area, in which the flakes are placed prior to growth. This allows growth gases and atomic hydrogen to reach the flakes, but does not allow the flakes, which rapidly nucleate SWNTs, to escape from the cage.

A 9700-hour durability test of a five centimeter diameter ion thruster

NASA Technical Reports Server (NTRS)

Nakanishi, S.; Finke, R. C.

1973-01-01

A modified Hughes SIT-5 thruster was life-tested at the Lewis Research Center. The final 2700 hours of the test are described with a charted history of thruster operating parameters and off-normal events. Performance and operating characteristics were nearly constant throughout the test except for neutralizer heater power requirements and accelerator drain current. A post-shutdown inspection revealed sputter erosion of ion chamber components and component flaking of sputtered metal. Several flakes caused beamlet divergence and anomalous grid erosion, causing the test to be terminated. All sputter erosion sources were identified.

Remote catalyzation for direct formation of graphene layers on oxides.

PubMed

Teng, Po-Yuan; Lu, Chun-Chieh; Akiyama-Hasegawa, Kotone; Lin, Yung-Chang; Yeh, Chao-Hui; Suenaga, Kazu; Chiu, Po-Wen

2012-03-14

Direct deposition of high-quality graphene layers on insulating substrates such as SiO(2) paves the way toward the development of graphene-based high-speed electronics. Here, we describe a novel growth technique that enables the direct deposition of graphene layers on SiO(2) with crystalline quality potentially comparable to graphene grown on Cu foils using chemical vapor deposition (CVD). Rather than using Cu foils as substrates, our approach uses them to provide subliming Cu atoms in the CVD process. The prime feature of the proposed technique is remote catalyzation using floating Cu and H atoms for the decomposition of hydrocarbons. This allows for the direct graphitization of carbon radicals on oxide surfaces, forming isolated low-defect graphene layers without the need for postgrowth etching or evaporation of the metal catalyst. The defect density of the resulting graphene layers can be significantly reduced by tuning growth parameters such as the gas ratios, Cu surface areas, and substrate-to-Cu distance. Under optimized conditions, graphene layers with nondiscernible Raman D peaks can be obtained when predeposited graphite flakes are used as seeds for extended growth. © 2012 American Chemical Society

Surface characterization of graphene based materials

NASA Astrophysics Data System (ADS)

Pisarek, M.; Holdynski, M.; Krawczyk, M.; Nowakowski, R.; Roguska, A.; Malolepszy, A.; Stobinski, L.; Jablonski, A.

2016-12-01

In the present study, two kind of samples were used: (i) a monolayer graphene film with a thickness of 0.345 nm deposited by the CVD method on Cu foil, (ii) graphene flakes obtained by modified Hummers method and followed by reduction of graphene oxide. The inelastic mean free path (IMFP), characterizing electron transport in graphene/Cu sample and reduced graphene oxide material, which determines the sampling depth of XPS and AES were evaluated from relative Elastic Peak Electron Spectroscopy (EPES) measurements with the Au standard in the energy range 0.5-2 keV. The measured IMFPs were compared with IMFPs resulting from experimental optical data published in the literature for the graphite sample. The EPES IMFP values at 0.5 and 1.5 keV was practically identical to that calculated from optical data for graphite (less than 4% deviation). For energies 1 and 2 keV, the EPES IMFPs for rGO were deviated up to 14% from IMFPs calculated using the optical data by Tanuma et al. [1]. Before EPES measurements all samples were characterized by various techniques like: FE-SEM, AFM, XPS, AES and REELS to visualize the surface morphology/topography and identify the chemical composition.

Sensor array for the detection of organic and inorganic contaminants in post-consumer recycled plastics for food contact.

PubMed

Davis, Nathan; Danes, Jeffrey E; Vorst, Keith

2017-10-01

Post-consumer recycled (PCR) plastic material is made by collecting used plastic products (e.g., bottles and other plastic packaging materials) and reprocessing them into solid-state pellets or flakes. Plastic recycling has positive environmental benefits, but may also carry potential drawbacks due to unwanted organic and inorganic contaminants. These contaminants can migrate into food packaging made from these recycled plastic materials. The purpose of this research was to identify economically viable real-time monitoring technologies that can be used during the conversion of virgin and recycled resin feedstocks (i.e., various blends of virgin pellets and recycled solid-state pellet or mechanically ground flake) to final articles to ensure the safety, quality and sustainability of packaging feedstocks. Baseline analysis (validation) of real-time technologies was conducted using industry-standard practices for polymer analysis. The data yielded supervised predictive models developed by training sessions completed in a controlled laboratory setting. This technology can be employed to evaluate compliance and aid converters in commodity sourcing of resin without exceeding regulatory thresholds. Furthermore, this technology allowed for real-time decision and diversion strategies during the conversion of resin and flake to final articles or products to minimise the negative impact on human health and environmental exposure.

A 9700-hour durability test of a five centimeter diameter ion thruster

NASA Technical Reports Server (NTRS)

Nakanishi, S.; Finke, R. C.

1973-01-01

A modified Hughes SIT-5 thrustor has been life-tested at the Lewis Research Center. The final 2700 hours of the test are described with a charted history of thrustor operating parameters and off-normal events. Performance and operating characteristics were nearly constant throughout the test except for neutralizer heater power requirements and accelerator drain current. A post-shutdown inspection revealed sputter erosion of ion chamber components and component flaking of sputtered metal. Several flakes caused beamlet divergence and anomalous grid erosion, causing the test to be terminated. All sputter erosion sources have been identified and promising sputter resistant components are currently being evaluated.

Embedded Si/Graphene Composite Fabricated by Magnesium-Thermal Reduction as Anode Material for Lithium-Ion Batteries

NASA Astrophysics Data System (ADS)

Zhu, Jiangliu; Ren, Yurong; Yang, Bo; Chen, Wenkai; Ding, Jianning

2017-12-01

Embedded Si/graphene composite was fabricated by a novel method, which was in situ generated SiO2 particles on graphene sheets followed by magnesium-thermal reduction. The tetraethyl orthosilicate (TEOS) and flake graphite was used as original materials. On the one hand, the unique structure of as-obtained composite accommodated the large volume change to some extent. Simultaneously, it enhanced electronic conductivity during Li-ion insertion/extraction. The MR-Si/G composite is used as the anode material for lithium ion batteries, which shows high reversible capacity and ascendant cycling stability reach to 950 mAh·g-1 at a current density of 50 mA·g-1 after 60 cycles. These may be conducive to the further advancement of Si-based composite anode design.

Study of process variables in supercritical carbon dioxide extraction of soybeans.

PubMed

Wilkinson, Nikolas; Hilton, Ramsey; Hendry, Doug; Venkitasamy, Chandrasekar; Jacoby, William

2014-01-01

Soybean flakes were extracted using supercritical carbon dioxide at 48.3 MPa and 80 °C, which is a higher temperature than previously reported. Several operational parameters were explored to determine their effect on extractions. Flakes, as typically used in this industry, provided the best extraction performance. Particle size distributions were created through grinding. Reducing average particle diameters smaller than 0.069 mm had no appreciable effect on increasing extraction efficiencies. Exploration of flow rate indicated that a residence time of less than 60 s for the supercritical carbon dioxide would be sufficient for complete extractions. A solvent mass to load mass ratio of 10:1 was found to be sufficient for extraction of oils from soybean flakes. Increasing moisture in the soybeans led to decreasing extraction efficiency of oils. Finally, soybean hulls had no effect on extraction efficiency. Thus, the de-hulling procedure can be removed from the extraction process without decreasing extraction efficiency.

Nonlocal Electron Coherence in MoS2 Flakes Correlated through Spatial Self Phase Modulation

NASA Astrophysics Data System (ADS)

Wu, Yanling; Wu, Qiong; Sun, Fei; Tian, Yichao; Zuo, Xu; Meng, Sheng; Zhao, Jimin

2015-03-01

Electron coherence among different flake domains of MoS2 has been generated using ultrafast or continuous wave laser beams. Such electron coherence generates characteristic far-field diffraction patterns through a purely coherent nonlinear optical effect--spatial self-phase modulation (SSPM). A wind-chime model is developed to describe the establishment of the electron coherence through correlating the photo-excited electrons among different flakes using coherent light. Owing to its finite gap band structure, we find different mechanisms, including two-photon processes, might be responsible for the SSPM in MoS2 [with a large nonlinear dielectric susceptibility χ (3) = 1.6 × 10-9 e.s.u. (SI: 2.23 × 10-17 m2/V2) per layer]. Finally, we realized all optical switching based on SSPM, demonstrating that the electron coherence generation we report here is a ubiquitous property of layered quantum materials, by which novel optical applications are accessible. National Natural Science Foundation of China (11274372).

Graphitization of Coke and Its Interaction with Slag in the Hearth of a Blast Furnace

NASA Astrophysics Data System (ADS)

Li, Kejiang; Zhang, Jianliang; Liu, Yanxiang; Barati, Mansoor; Liu, Zhengjian; Zhong, Jianbo; Su, Buxin; Wei, Mengfang; Wang, Guangwei; Yang, Tianjun

2016-04-01

Coke reaction behavior in the blast furnace hearth has yet to be fully understood due to limited access to the high temperature zone. The graphitization of coke and its interaction with slag in the hearth of blast furnace were investigated with samples obtained from the center of the deadman of a blast furnace during its overhaul period. All hearth coke samples from fines to lumps were confirmed to be highly graphitized, and the graphitization of coke in the high temperature zone was convinced to start from the coke surface and lead to the formation of coke fines. It will be essential to perform further comprehensive investigations on graphite formation and its evolution in a coke as well as its multi-effect on blast furnace performance. The porous hearth cokes were found to be filled up with final slag. Further research is required about the capability of coke to fill final slag and the attack of final slag on the hearth bottom refractories since this might be a new degradation mechanism of refractories located in the hearth bottom.

Graphene: powder, flakes, ribbons, and sheets.

PubMed

James, Dustin K; Tour, James M

2013-10-15

Graphene's unique physical and electrical properties (high tensile strength, Young's modulus, electron mobility, and thermal conductivity) have led to its nickname of "super carbon." Graphene research involves the study of several different physical forms of the material: powders, flakes, ribbons, and sheets and others not yet named or imagined. Within those forms, graphene can include a single layer, two layers, or ≤10 sheets of sp² carbon atoms. The chemistry and applications available with graphene depend on both the physical form of the graphene and the number of layers in the material. Therefore the available permutations of graphene are numerous, and we will discuss a subset of this work, covering some of our research on the synthesis and use of many of the different physical and layered forms of graphene. Initially, we worked with commercially available graphite, with which we extended diazonium chemistry developed to functionalize single-walled carbon nanotubes to produce graphitic materials. These structures were soluble in common organic solvents and were better dispersed in composites. We developed an improved synthesis of graphene oxide (GO) and explored how the workup protocol for the synthesis of GO can change the electronic structure and chemical functionality of the GO product. We also developed a method to remove graphene layers one-by-one from flakes. These powders and sheets of GO can serve as fluid loss prevention additives in drilling fluids for the oil industry. Graphene nanoribbons (GNRs) combine small width with long length, producing valuable electronic and physical properties. We developed two complementary syntheses of GNRs from multiwalled carbon nanotubes: one simple oxidative method that produces GNRs with some defects and one reductive method that produces GNRs that are less defective and more electrically conductive. These GNRs can be used in low-loss, high permittivity composites, as conductive reinforcement coatings on Kevlar fibers and in the fabrication of large area transparent electrodes. Using solid carbon sources such as polymers, food, insects, and waste, we can grow monolayer and bilayer graphene directly on metal catalysts, and carbon-sources containing nitrogen can produce nitrogen-doped graphene. The resulting graphene can be transferred to other surfaces, such as metal grids, for potential use in transparent touch screens for applications in personal electronics and large area photovoltaic devices. Because the transfer of graphene from one surface to another can lead to defects, low yields, and higher costs, we have developed methods for growing graphene directly on the substrates of interest. We can also produce patterned graphene to make GNRs or graphane/graphene superlattices within a single sheet. These superlattices could have multiple functions for use in sensors and other devices. This Account only touches upon this burgeoning area of materials chemistry, and the field will continue to expand as researchers imagine new forms and applications of graphene.

Electrically actuatable doped polymer flakes and electrically addressable optical devices using suspensions of doped polymer flakes in a fluid host

DOEpatents

Trajkovska-Petkoska, Anka; Jacobs, Stephen D.; Marshall, Kenneth L.; Kosc, Tanya Z.

2010-05-11

Doped electrically actuatable (electrically addressable or switchable) polymer flakes have enhanced and controllable electric field induced motion by virtue of doping a polymer material that functions as the base flake matrix with either a distribution of insoluble dopant particles or a dopant material that is completely soluble in the base flake matrix. The base flake matrix may be a polymer liquid crystal material, and the dopants generally have higher dielectric permittivity and/or conductivity than the electrically actuatable polymer base flake matrix. The dopant distribution within the base flake matrix may be either homogeneous or non-homogeneous. In the latter case, the non-homogeneous distribution of dopant provides a dielectric permittivity and/or conductivity gradient within the body of the flakes. The dopant can also be a carbon-containing material (either soluble or insoluble in the base flake matrix) that absorbs light so as to reduce the unpolarized scattered light component reflected from the flakes, thereby enhancing the effective intensity of circularly polarized light reflected from the flakes when the flakes are oriented into a light reflecting state. Electro-optic devices contain these doped flakes suspended in a host fluid can be addressed with an applied electric field, thus controlling the orientation of the flakes between a bright reflecting state and a non-reflecting dark state.

Inkjet printing ultra-large graphene oxide flakes

NASA Astrophysics Data System (ADS)

He, Pei; Derby, Brian

2017-06-01

Graphene oxide 2D materials inks with mean flake diameter 36 µm can be inkjet printed, with no significant blockage of the printer or apparent damage to the flakes, despite the mean flake size being  >50% of the printer nozzle diameter and the ink containing individual flakes considerably larger than the nozzle. Printed flakes show a similar level of wrinkle and fold defects as observed in flakes deposited by drop casting. Polarised light imaging of the ink in the printhead prior to printing shows alignment of the flakes in the shear flow and this is believed to allow passage without agglomeration or blocking of the nozzle. The bulk electrical conductivity of these ultra-large flake printed films is 2.48  ×  104 Sm-1 after reduction, which is comparable to that reported with printed pristine graphene. The conductivity of the printed films increases slightly with increasing flake size indicating that there is no increase in damage to electrical properties as the flakes approach and exceed the nozzle diameter.

Adsorption and regeneration of expanded graphite modified by CTAB-KBr/H3PO4 for marine oil pollution.

PubMed

Xu, Congbin; Jiao, Chunlei; Yao, Ruihua; Lin, Aijun; Jiao, Wentao

2018-02-01

The cleaning-up of viscous oil spilled in ocean is a global challenge, especially in Bohai, due to its slow current movement and poor self-purification capacity. Frequent oil-spill accidents not only cause severe and long-term damages to marine ecosystems, but also lead to a great loss of valuable resources. To eliminate the environmental pollution of oil spills, an efficient and environment-friendly oil-recovery approach is necessary. In this study, 1 expanded graphite (EG) modified by CTAB-KBr/H 3 PO 4 was synthesized via composite intercalation agents of CTAB-KBr and natural flake graphite, followed by the activation of phosphoric acid at low temperature. The resultant modified expanded graphite (M-EG) obtained an interconnected and continuous open microstructure with lower polarity surface, more and larger pores, and increased surface hydrophobicity. Due to these characteristics, M-EG exhibited a superior adsorption capacity towards marine oil. The saturated adsorption capacities of M-EG were as large as 7.44  g/g for engine oil, 6.12 g/g for crude oil, 5.34 g/g for diesel oil and 4.10 g/g for gasoline oil in 120min, exceeding the capacity of pristine EG. Furthermore, M-EG maintained good removal efficiency under different adsorption conditions, such as temperature, oil types, and sodium salt concentration. In addition, oils sorbed into M-EG could be recovered either by a simple compression or filtration-drying treatment with a recovery ratio of 58-83%. However, filtration-drying treatment shows better performance in preserving microstructures of M-EG, which ensures the adsorbents can be recycled several times. High removal capability, fast adsorption efficiency, excellent stability and good recycling performance make M-EG an ideal candidate for treating marine oil pollution in practical application. Copyright © 2017 Elsevier Ltd. All rights reserved.

Dual-carbon enhanced silicon-based composite as superior anode material for lithium ion batteries

NASA Astrophysics Data System (ADS)

Wang, Jie; Liu, Dai-Huo; Wang, Ying-Ying; Hou, Bao-Hua; Zhang, Jing-Ping; Wang, Rong-Shun; Wu, Xing-Long

2016-03-01

Dual-carbon enhanced Si-based composite (Si/C/G) has been prepared via employing the widely distributed, low-cost and environmentally friendly Diatomite mineral as silicon raw material. The preparation processes are very simple, non-toxic and easy to scale up. Electrochemical tests as anode material for lithium ion batteries (LIBs) demonstrate that this Si/C/G composite exhibits much improved Li-storage properties in terms of superior high-rate capabilities and excellent cycle stability compared to the pristine Si material as well as both single-carbon modified composites. Specifically for the Si/C/G composite, it can still deliver a high specific capacity of about 470 mAh g-1 at an ultrahigh current density of 5 A g-1, and exhibit a high capacity of 938 mAh g-1 at 0.1 A g-1 with excellent capacity retention in the following 300 cycles. The significantly enhanced Li-storage properties should be attributed to the co-existence of both highly conductive graphite and amorphous carbon in the Si/C/G composite. While the former can enhance the electrical conductivity of the obtained composite, the latter acts as the adhesives to connect the porous Si particulates and conductive graphite flakes to form robust and stable conductive network.

Ionic Liquid-Modified Thermosets and Their Nanocomposites: Dispersion, Exfoliation, Degradation, and Cure

NASA Astrophysics Data System (ADS)

Throckmorton, James A.

This dissertation explores the application of a room temperature ionic liquid (RTIL) to problems in the chemistry, processing, and modification of thermosetting polymers. In particular, the solution properties and reaction chemistry of 1-ethyl-3-methyl imidazolium dicyanamide (EMIM-DCN) are applied to problems of nanoparticle dispersion and processing, graphite exfoliation, cyanate ester (CE) cure, and the environmental degradation of CEs. Nanoparticle Dispersion: Nanocomposite processing can be simplified by using the same compound as both a nanoparticle solvent and an initiator for polymerization. This dual-function molecule can be designed both for solvent potential and reaction chemistry. EMIM-DCN, previously shown by our lab to act as an epoxy initiator, is used in the synthesis of silica and acid expanded graphite composites. These composites are then characterized for particle dispersion and physical properties. Individual particle dispersion of silica nanocomposites is shown, and silica nanocomposites at low loading show individual particle dispersion and improved modulus and fracture toughness. GNP nanocomposites show a 70% increase in modulus along with a 10-order of magnitude increase in electrical conductivity at 6.5 vol%, and an electrical percolation threshold of 1.7 vol%. Direct Graphite Exfoliation By Laminar Shear: This work presents a laminar-shear alternative to chemical processing and chaotic flow-fields for the direct exfoliation of graphite and the single-pot preparation of nanocomposites. Additionally, we develop the theory of laminar flow through a 3-roll mill, and apply that theory to the latest developments in the theory of graphite interlayer shear. The resulting nanocomposite shows low electrical percolation (0.5 vol%) and low thickness (1-3 layer) graphite/graphene flakes. Additionally, the effect of processing conditions by rheometry and comparison with solvent-free conditions reveal the interactions between processing and matrix properties and provide insight into the theory of the chemical and physical exfoliation of graphite crystals and the resulting polymer matrix dispersion. Cyanate Ester Cure: Dicyanamide-containing ionic liquids decrease the cure temperature of bi- and tri-functional CEs. During the cure reaction, the dicyanamide anion completely reacts and is incorporated into the triazine network. The cure effect was found in many dicyanamide-containing ionic liquids with diverse cations. This invention creates a novel, ionic thermoset polymer. The dicyanamide initiator provides an alternative to metal and hydroxyl catalysts (which have been shown to accelerate degradation and possess human and environmental toxicity). Additionally, the ionic character of the new polymer, rare among thermosets, lends itself to future research and novel applications. RTIL initiation also paves the way to new CE technologies, including RTIL-CE nanocomposites, prepared by graphite exfoliation and nanocomposite dispersion techniques developed herin.

Embedded Si/Graphene Composite Fabricated by Magnesium-Thermal Reduction as Anode Material for Lithium-Ion Batteries.

PubMed

Zhu, Jiangliu; Ren, Yurong; Yang, Bo; Chen, Wenkai; Ding, Jianning

2017-12-16

Embedded Si/graphene composite was fabricated by a novel method, which was in situ generated SiO 2 particles on graphene sheets followed by magnesium-thermal reduction. The tetraethyl orthosilicate (TEOS) and flake graphite was used as original materials. On the one hand, the unique structure of as-obtained composite accommodated the large volume change to some extent. Simultaneously, it enhanced electronic conductivity during Li-ion insertion/extraction. The MR-Si/G composite is used as the anode material for lithium ion batteries, which shows high reversible capacity and ascendant cycling stability reach to 950 mAh·g -1 at a current density of 50 mA·g -1 after 60 cycles. These may be conducive to the further advancement of Si-based composite anode design.

Carbon fiber manufacturing via plasma technology

DOEpatents

Paulauskas, Felix L.; Yarborough, Kenneth D.; Meek, Thomas T.

2002-01-01

The disclosed invention introduces a novel method of manufacturing carbon and/or graphite fibers that avoids the high costs associated with conventional carbonization processes. The method of the present invention avoids these costs by utilizing plasma technology in connection with electromagnetic radiation to produce carbon and/or graphite fibers from fully or partially stabilized carbon fiber precursors. In general, the stabilized or partially stabilized carbon fiber precursors are placed under slight tension, in an oxygen-free atmosphere, and carbonized using a plasma and electromagnetic radiation having a power input which is increased as the fibers become more carbonized and progress towards a final carbon or graphite product. In an additional step, the final carbon or graphite product may be surface treated with an oxygen-plasma treatment to enhance adhesion to matrix materials.

Study of Nanoscale Friction Behaviors of Graphene on Gold Substrates Using Molecular Dynamics

NASA Astrophysics Data System (ADS)

Zhu, Pengzhe; Li, Rui

2018-02-01

In this paper, we investigate the friction behaviors of graphene flakes sliding on a gold substrate using molecular dynamics simulations. The effects of flake size, flake shape, relative rotation angle between flake and substrate, and crystal orientation of substrate on the friction process are thoroughly studied. It is found that under the same load, the average friction forces per atom are smaller for a bigger graphene flake, which exhibits an obvious size effect. It is also shown that flake shape is critical in determining the friction in the sliding process. The average friction forces per atom for the square flake are much bigger than those for the triangular and round flakes. Moreover, the average friction forces per atom for the triangular flake are the smallest. We also find that the orientation of graphene flake relative to gold substrate plays a vital role in the friction process. The friction forces for the graphene flake sliding along the armchair direction are much bigger than those for the flakes with rotation. In addition, it is also found that single crystalline gold substrate exhibits a significant anisotropic effect of friction, which is attributed to the anisotropic effect of potential energy corrugation. These understandings not only shed light on the underlying mechanisms of graphene flake sliding on the gold substrates but also may guide the design and fabrication of nanoscale graphene-based devices.

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.

Forming gas treatment of lithium ion battery anode graphite powders

DOEpatents

Contescu, Cristian Ion; Gallego, Nidia C; Howe, Jane Y; Meyer, III, Harry M; Payzant, Edward Andrew; Wood, III, David L; Yoon, Sang Young

2014-09-16

The invention provides a method of making a battery anode in which a quantity of graphite powder is provided. The temperature of the graphite powder is raised from a starting temperature to a first temperature between 1000 and 2000.degree. C. during a first heating period. The graphite powder is then cooled to a final temperature during a cool down period. The graphite powder is contacted with a forming gas during at least one of the first heating period and the cool down period. The forming gas includes H.sub.2 and an inert gas.

Effect of processing techniques on color and active components amount of sweet potato (Ipomoea Batatas l) flakes

NASA Astrophysics Data System (ADS)

Rahmawati, Y.; Mahmudatussa'adah, A.; Yogha, S.

2016-04-01

Sweet potato processing is limited, such as flour, snacks, cystic, or chips. Flakes as pre-cooked meals are made through the stages of making pasta and drying. The purpose of this study was to optimize the production of sweet potato flakes at the stage of making pasta and drying. Making the pasta is done through techniques steamed or baked. Pasta drying using tools a drum dryer or cabinet dryer. As an indicator of optimization is the total of monomeric anthocyanins, β-carotene and color the resulting flakes. The results showed that the amount of anthocyanin monomeric flakes by using steam, and drum dryer (3.83 ± 0.03 mg CYE/g db), flakes by the technique of steam, and cabinet dryer (3.03 ± 0.02 mg CYE/g db), flakes with techniques bake, drum dryer (2.49 ± 0.05 CYE mg/g db), flakes with bake technique, cabinet dryer (1.98 ± 0.03 mg CYE/g db). The Color of purple sweet potato flakes produced through steamed techniques bright purple, while the color purple sweet potato flakes produced through techniques roast give a brownish purple color. The amount of β-carotene yellow flakes sweet potato with stages of cooking steamed, drum dryer (152±0.5 mg/Kg db), grilled drum dryer (136±0.4 mg/Kg db), flakes of yellow sweet potato with stages of roasted and cabinet dryer (140±0.8 mg/Kg db), and grilled stage with cabinet dryer (122±0.3 mg/Kg db). In conclusion sweet potato flakes production techniques through the stages of steam process, and used drum dryers have a number of anthocyanins or β-carotene bigger and brighter colors than the baked flakes techniques and used cabinet dryer.

The cholesterol-lowering effect of coconut flakes in humans with moderately raised serum cholesterol.

PubMed

Trinidad, Trinidad P; Loyola, Anacleta S; Mallillin, Aida C; Valdez, Divinagracia H; Askali, Faridah C; Castillo, Joan C; Resaba, Rosario L; Masa, Dina B

2004-01-01

This study investigated the effect of coconut flakes on serum cholesterol levels of humans with moderately raised serum cholesterol in 21 subjects. The serum total cholesterol of subjects differed and ranged from 259 to 283 mg/dL. The study was conducted in a double-blind randomized crossover design on a 14-week period, consisting of four 2-week experimental periods, with each experimental period separated by a 2-week washout period. The test foods were as follows: corn flakes as the control food, oat bran flakes as the reference food, and corn flakes with 15% and 25% dietary fiber from coconut flakes (made from coconut flour production). Results showed a significant percent reduction in serum total and low-density lipoprotein (LDL) cholesterol (in mg/dL) for all test foods, except for corn flakes, as follows: oat bran flakes, 8.4 +/- 1.4 and 8.8 +/- 6.0, respectively; 15% coconut flakes, 6.9 +/- 1.1 and 11.0 +/- 4.0, respectively; and 25% coconut flakes, 10.8 +/- 1.3 and 9.2 +/- 5.4, respectively. Serum triglycerides were significantly reduced for all test foods: corn flakes, 14.5 +/- 6.3%; oat bran flakes, 22.7 +/- 2.9%; 15% coconut flakes, 19.3 +/- 5.7%; and 25% coconut flakes, 21.8 +/- 6.0%. Only 60% of the subjects were considered for serum triglycerides reduction (serum triglycerides >170 mg/dL). In conclusion, both 15% and 25% coconut flakes reduced serum total and LDL cholesterol and serum triglycerides of humans with moderately raised serum cholesterol levels. Coconut flour is a good source of both soluble and insoluble dietary fiber, and both types of fiber may have significant role in the reduction of the above lipid biomarker. To our knowledge, this is the first study conducted to show a relationship between dietary fiber from a coconut by-product and a lipid biomarker. Results from this study serves as a good basis in the development of coconut flakes/flour as a functional food, justifying the increased production of coconut and coconut by-products.

Preparation and Characterization of Graphite Waste/CeO2 Composites

NASA Astrophysics Data System (ADS)

Kusrini, E.; Utami, C. S.; Nasruddin; Prasetyanto, E. A.; Bawono, Aji A.

2018-03-01

In this research, the chemical modification of graphite waste with CeO2 was developed and characterized. Graphite waste was pretreated with mechanical to obtain the size 200 mesh (75 μm), and thermal methods at 110°C oven for 6 hours. Here, we demonstrate final properties of graphite before modification (GBM), activated graphite (GA) and graphite/CeO2 composite with variation of 0.5, 1 and 2 g of CeO2 (G0.5; G1; G2). The effect of CeO2 concentration was observed. The presence of cerium in modified graphite samples (G0.5; G1; G2) were analyzed using SEM-EDX. The results show that the best surface area was found in G2 is 26.82 m2/g. The presence of CeO2 onto graphite surface does not significantly increase the surface area of composites.

Eddy current effect on the microwave permeability of Fe-based nanocrystalline flakes with different sizes

NASA Astrophysics Data System (ADS)

Wu, Yanhui; Han, Mangui; Tang, Zhongkai; Deng, Longjiang

2014-04-01

The effective permeability values of composites containing Fe-Cu-Nb-Si-B nanocrystalline flakes have been studied within 0.5-10 GHz. Obvious differences in microwave permeability have been observed between large flakes (size range: 23-111 μm, average thickness: 4.5 μm) and small flakes (size range: 3-21 μm, average thickness: 1.3 μm). The initial real part of microwave permeability of large flakes is larger but it is decreasing faster. The larger flakes also show a larger magnetic loss. Taking into account the eddy current effect, the intrinsic microwave permeability values have been extracted based on the modified Maxwell-Garnet law, which have also been verified by the Acher's law. The dependences of skin depth on frequency have been calculated for both kinds of flakes. It is shown that the eddy current effect in the large flakes is significant. However, the eddy current effect can be ignored in the small flakes.

Two-dimensional distribution of carbon nanotubes in copper flake powders.

PubMed

Tan, Zhanqiu; Li, Zhiqiang; Fan, Genlian; Li, Wenhuan; Liu, Qinglei; Zhang, Wang; Zhang, Di

2011-06-03

We report an approach of flake powder metallurgy to the uniform, two-dimensional (2D) distribution of carbon nanotubes (CNTs) in Cu flake powders. It consists of the preparation of Cu flakes by ball milling in an imidazoline derivative (IMD) aqueous solution, surface modification of Cu flakes with polyvinyl alcohol (PVA) hydrosol and adsorption of CNTs from a CNT aqueous suspension. During ball milling, a hydrophobic monolayer of IMD is adsorbed on the surface of the Cu flakes, on top of which a hydrophilic PVA film is adsorbed subsequently. This PVA film could further interact with the carboxyl-group functionalized CNTs and act to lock the CNTs onto the surfaces of the Cu flakes. The CNT volume fraction is controlled easily by adjusting the concentration/volume of CNT aqueous suspension and Cu flake thickness. The as-prepared CNT/Cu composite flakes will serve as suitable building blocks for the self-assembly of CNT/Cu laminated composites that enable the full potential of 2D distributed CNTs to achieve high thermal conductivity.

The response of hardwood flakes and flakeboard to high temperature drying

Treesearch

Walter L. Plagemann; Eddie W. Price; William E. Johns

1982-01-01

This study assesses the effect of high temperature drying on chemical and mechanical properties of flakes and correlates changes in flake quality with board properties. The high temperature drying of flakes was found to have a significant effect on the internal bond (IB) of the resulting panels. The highest IB values were observed in boards produced from flakes dried...

Graphite fiber reinforced thermoplastic resins

NASA Technical Reports Server (NTRS)

Navak, R. C.

1977-01-01

The results of a program designed to optimize the fabrication procedures for graphite thermoplastic composites are described. The properties of the composites as a function of temperature were measured and graphite thermoplastic fan exit guide vanes were fabricated and tested. Three thermoplastics were included in the investigation: polysulfone, polyethersulfone, and polyarylsulfone. Type HMS graphite was used as the reinforcement. Bending fatigue tests of HMS graphite/polyethersulfone demonstrated a gradual shear failure mode which resulted in a loss of stiffness in the specimens. Preliminary curves were generated to show the loss in stiffness as a function of stress and number of cycles. Fan exit guide vanes of HMS graphite polyethersulfone were satisfactorily fabricated in the final phase of the program. These were found to have stiffness and better fatigue behavior than graphite epoxy vanes which were formerly bill of material.

Dissolution Mediated Boron and Carbon Storage during Exhumation of HP Metapelites: Examples from New Hampshire Tourmaline-Graphite Intergrowths

NASA Astrophysics Data System (ADS)

Galvez, M.; Rumble, D.; Cody, G. D.; Sverjensky, D. A.

2013-12-01

The dynamic of light elements (e.g. C,B) in subduction zones is a complex process ultimately governed by variables such as P, T, fH2 and pH. Interface phenomena at scales from the outcrop to intergranular surfaces play key chemical and mechanical roles on this dynamic (e.g. Galvez et al. 2013). We report here a petrological study of hydrated borosilicate tourmaline intergrown with graphite formed at the contact between igneous intrusives and high grade micaschists in New Hampshire graphite deposits (Rumble and Hoering, 1986). Our study includes Raman scattering, SEM, microprobe analysis and thermodynamic modeling, focusing on the Franklin Pierce and Walpole outcrops. Both localities experienced HP-HT metamorphism during the Acadian orogeny as well as complex metasomatic process during exhumation. The tourmaline-graphite intergrowths are structurally localized at and around contacts between an aplite sill and micaschists - biotite-muscovite-garnet-sillimanite-plagioclase-quartz-ilmenite - (Franklin Pierce), or along shear zones (Walpole) in veins. Tourmalines are dravitic in composition (i.e. Na, Mg rich with minor vacancy and Li content 0.2/0.1 a.p.f.u) and contain multiple primary tubular mixed fluid-solid inclusions containing graphite, quartz and gaseous CO2 and CH4. Sharp optical and compositional radial zonations are observed from core to rim in sections along and perpendicular to the c-axis. Blue-green cores are enriched in Mg and Ca (1.5/0.1 a.p.f.u respectively) whereas rims are enriched in Fe, Na and Ti (0.9/0.6/0.1 a.p.f.u respectively). Alternative interpretations in terms of sector zoning or compositional variability of the mineralizing fluid will be discussed. The carbonaceous material (CM) occurs primarily as flakes directly replacing biotite present in wall rocks. The structural ordering of CM, of unambiguous abiotic origin, reveals a material possessing the 3 dimensional structure of hexagonal graphite. Our results are critically compared to measurements done on other metasomatic or biogenic graphite displaying high structural ordering. Other textural habit of graphite are radiating crystals of graphite preferentially growing along crystalline planes of wall rock minerals (e.g. plagioclases) and at the interface between grain edge. We test whether a C and B(OH)3° (×As, Cu) rich acidic vapor unmixing from a salt-rich aqueous fluid exsolved from crystallizing igneous bodies can account for some geochemical and textural greisen-type metasomatic features of these outcrops. Other mechanical and geochemical processes participating in the process will be discussed. This work is direct evidence that respeciation and/or fluid-rock interaction at varying P,T,fH2,pH conditions of fluids during exhumation, as well as interaction between magmatic bodies and metasedimentary units play a key role in the cycling of light elements during exhumation. Rumble, D., III, and Hoering, T.C., 1986, Carbon isotope geochemistry of graphite vein deposits from New Hampshire, U.S.A: Geochimica et Cosmochimica Acta, v. 50, p. 1239-1247. Galvez ME, Beyssac O, Martinez I, Benzerara K, Chaduteau C, Malvoisin B, Malavieille J (2013) Graphite formation by carbonate reduction during subduction. Nature Geoscience 6 (6):473-477

Anomalous Hooke’s law in disordered graphene

NASA Astrophysics Data System (ADS)

Gornyi, I. V.; Kachorovskii, V. Yu; Mirlin, A. D.

2017-03-01

The discovery of graphene, a single monolayer of graphite, has provided an experimental demonstration of stability of 2D crystals. Although thermal fluctuations of such crystals tend to destroy the long-range order in the system, the crystal can be stabilized by strong anharmonicity effects. This competition is the central issue of the crumpling transition, i.e., a transition between flat and crumpled phases. We show that anharmonicity-controlled fluctuations of a graphene membrane around equilibrium flat phase lead to unusual elastic properties. In particular, we demonstrate that stretching ξ of a flake of graphene is a nonlinear function of the applied tension at small tension: ξ \\propto {σ }η /(2-η ) and ξ \\propto {σ }η /(8-η ) for clean and strongly disordered graphene, respectively. Conventional linear Hooke’s law, ξ \\propto σ , is realized at sufficiently large tensions: σ \\gg {σ }* , where {σ }* depends both on temperature and on the disorder strength.

Microscopic insight into the bilateral formation of carbon spirals from a symmetric iron core

PubMed Central

Shiozawa, Hidetsugu; Bachmatiuk, Alicja; Stangl, Andreas; Cox, David C.; Silva, S. Ravi P.; Rümmeli, Mark H.; Pichler, Thomas

2013-01-01

Mirrored carbon-spirals have been produced from pressured ferrocene via the bilateral extrusion of the spiral pairs from an iron core. A parametric plot of the surface geometry displays the fractal growth of the conical helix made with the logarithmic spiral. Electron microscopy studies show the core is a crystalline cementite which grows and transforms its shape from spherical to biconical as it extrudes two spiralling carbon arms. In a cross section along the arms we observe graphitic flakes arranged in a herringbone structure, normal to which defects propagate. Local-wave-pattern analysis reveals nanoscale defect patterns of two-fold symmetry around the core. The data suggest that the bilateral growth originates from a globular cementite crystal with molten surfaces and the nano-defects shape emerging hexagonal carbon into a fractal structure. Understanding and knowledge obtained provide a basis for the controlled production of advanced carbon materials with designed geometries. PMID:23670649

Mechanochemical formation of heterogeneous diamond structures during rapid uniaxial compression in graphite

NASA Astrophysics Data System (ADS)

Kroonblawd, Matthew P.; Goldman, Nir

2018-05-01

We predict mechanochemical formation of heterogeneous diamond structures from rapid uniaxial compression in graphite using quantum molecular dynamics simulations. Ensembles of simulations reveal the formation of different diamondlike products starting from thermal graphite crystal configurations. We identify distinct classes of final products with characteristic probabilities of formation, stress states, and electrical properties and show through simulations of rapid quenching that these products are nominally stable and can be recovered at room temperature and pressure. Some of the diamond products exhibit significant disorder and partial closure of the energy gap between the highest-occupied and lowest-unoccupied molecular orbitals (i.e., the HOMO-LUMO gap). Seeding atomic vacancies in graphite significantly biases toward forming products with small HOMO-LUMO gap. We show that a strong correlation between the HOMO-LUMO gap and disorder in tetrahedral bonding configurations informs which kinds of structural defects are associated with gap closure. The rapid diffusionless transformation of graphite is found to lock vacancy defects into the final diamond structure, resulting in configurations that prevent s p3 bonding and lead to localized HOMO and LUMO states with a small gap.

Coercivity enhancement of Dy-coated Nd-Fe-B flakes by crystallization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fukunaga, H.; Sugimoto, Y.; Nakano, M.

2011-04-01

The coercivity of isotropic Dy-coated Nd-Fe-B flakes was enhanced by crystallization and simultaneous diffusion of Dy from their surfaces. Amorphous Dy-coated Nd-Fe-B flakes were crystallized by heating them to 923 K 2over a 2 min period followed by rapid cooling. During crystallization, the Dy on the surface diffused into the flakes. This low-temperature rapid annealing produced flakes with fine grains and the Dy diffusion enhanced their coercivity. The coercivity after crystallization increased with increasing Dy layer thickness, although the remanence decreased when the layer thickness exceeded 3 {mu}m. Thick coatings of over 6 {mu}m resulted in the formation of DyFe{submore » 2}, which degraded the magnetic properties of the crystallized flakes. Flakes with a 3-{mu}m-thick coating exhibited excellent magnetic properties after annealing: They had a coercivity of 1880 kA/m and a remanence of 78 emu/g. This coercivity is approximately 500 kA/m higher than that of uncoated flakes, whereas the remanence is comparable to that of uncoated flakes.« less

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 surface will be added that can exhibit pseudocapacitance. This pseudocapacitance exhibits faradaic (charge transfer) properties that can further increase the overall relative and volumetric capacitance of the material. A process is also proposed to use GNF as a precursor material to fabricate GNS that will be used as EC electrodes. This results in much better electrical conductivity than activated carbon. This is advantageous for high-pulsed-power applications to reduce parasitic heating. Larger average pore size allows more complete electrolyte wetting (faster charge transfer kinetics). These properties contribute to a lowered equivalent series resistance (ESR), increased specific power, shorter charging times, and decreased parasitic heating. The high density of basal plane edges provides nucleation sites for activation (addition of hydrophilic functional groups) that facilitate electrolyte wetting, and will contribute to pseudocapacitance.

Effect of slurry ice on the functional properties of proteins related to quality loss during skipjack tuna (Katsuwonus pelamis) chilled storage.

PubMed

Zhang, Bin; Deng, Shang-gui; Gao, Meng; Chen, Jing

2015-04-01

The effect of slurry ice on the quality of Skipjack tuna (Katsuwonus pelamis) during chilling storage was investigated and compared to flake ice. Slurry ice-treated samples showed significantly higher springiness and chewiness variables than the blank and flake ice-treated samples (P < 0.05). The growth of microorganisms in tuna muscle treated with slurry ice was also down significantly (P < 0.05), and the total aerobic counts didn't reach higher scores than 5.0 log CFU/g during the whole chilling storage. Additionally, the myofibrillar protein, Ca(2+)-ATPase activity, and total sulfydryl (SH) content in muscle treated with slurry ice were all significantly higher than the blank and flake-iced samples (P < 0.05). This was probably due to the faster cooling, subzero final-temperature, and larger heat exchange derived from slurry ice. Standard error of mean and sodium dodecyl sulfate-polyacrylamide gel electrophoresis results also confirmed that slurry ice treatment could effectively retard the degradation of myofibrillar proteins and showed a positive effect on the stability of tissue structures. © 2015 Institute of Food Technologists®

BioGraphene: Direct Exfoliation of Graphite in a Kitchen Blender for Enzymology Applications.

PubMed

Kumar, C V; Pattammattel, A

2016-01-01

A high yielding method for the aqueous exfoliation of graphite crystals to produce high quality graphene nanosheets in a kitchen blender is described here. Bovine serum albumin (BSA), β-lactoglobulin, ovalbumin, lysozyme, and hemoglobin as well as calf serum were used for the exfoliation of graphene. Among these, BSA gave the maximum exfoliation efficiency, exceeding 4mgmL(-1)h(-1) of graphene. Quality of graphene produced was examined by Raman spectroscopy, which indicated 3-5 layer graphene of very high quality and very low levels of defects. Transmission electron microscopy indicated an average size of ~0.5μm flakes. The graphene/BSA dispersions were stable over pH 3.0-11, and at 5°C or 50°C, for more than 2 months. Current approach gave higher rates of BSA/graphene (BioGraphene) in better yields than other methods. Calf serum, when used in place of BSA, also gave high yields of good quality BioGraphene and these preparations may be of direct use for cell culture studies. A simple example of BioGraphene preparation is described that can be adapted in most laboratories, and graphene-adsorbed glucose oxidase is nearly as active as the free enzyme. Current approach may facilitate large-scale production of graphene in most laboratories around the world and it may open new opportunities for biological applications of graphene. © 2016 Elsevier Inc. All rights reserved.

Facile preparation of efficient electrocatalysts for oxygen reduction reaction: One-dimensional meso/macroporous cobalt and nitrogen Co-doped carbon nanofibers

NASA Astrophysics Data System (ADS)

Yoon, Ki Ro; Choi, Jinho; Cho, Su-Ho; Jung, Ji-Won; Kim, Chanhoon; Cheong, Jun Young; Kim, Il-Doo

2018-03-01

Efficient electrocatalyst for oxygen reduction reaction (ORR) is an essential component for stable operation of various sustainable energy conversion and storage systems such as fuel cells and metal-air batteries. Herein, we report a facile preparation of meso/macroporous Co and N co-doped carbon nanofibers (Co-Nx@CNFs) as a high performance and cost-effective electrocatalyst toward ORR. Co-Nx@CNFs are simply obtained from electrospinning of Co precursor and bicomponent polymers (PVP/PAN) followed by temperature controlled carbonization and further activation step. The prepared Co-Nx@CNF catalyst carbonized at 700 °C (Co-Nx@CNF700) shows outstanding ORR performance, i.e., a low onset potential (0.941 V) and half wave potential (0.814 V) with almost four-electron transfer pathways (n= 3.9). In addition, Co-Nx@CNF700 exhibits a superior methanol tolerance and higher stability (>70 h) in Zn-air battery in comparison with Pt/C catalyst (∼30 h). The outstanding performance of Co-Nx@CNF700 catalysts is attributed to i) enlarged surface area with bimodal porosity achieved by leaching of inactive species, ii) increase of exposed ORR active Co-Nx moieties and graphitic edge sites, and iii) enhanced electrical conductivity and corrosion resistance due to the existence of numerous graphitic flakes in carbon matrix.

UV absorption investigation of ferromagnetically filled ultra-thick carbon onions, carriers of the 217.5 nm Interstellar Absorption Feature

NASA Astrophysics Data System (ADS)

Boi, Filippo S.; Zhang, Xiaotian; Ivaturi, Sameera; Liu, Qianyang; Wen, Jiqiu; Wang, Shanling

2017-12-01

Carbon nano-onions (CNOs) are fullerene-like structures which consist of quasi-spherical closed carbon shells. These structures have become a subject of great interest thanks to their characteristic absorption feature of interstellar origin (at 217.5 nm, 4.6 μm-1). An additional extinction peak at 3.8 μm-1 has also been reported and attributed to absorption by graphitic residues between the as-grown CNOs. Here, we report the ultraviolet absorption properties of ultra-thick CNOs filled with FePt3 crystals, which also exhibit two main absorption peaks—features located at 4.58 μm-1 and 3.44 μm-1. The presence of this additional feature is surprising and is attributed to nonmagnetic graphite flakes produced as a by-product in the pyrolysis experiment (as confirmed by magnetic separation methods). Instead, the feature at 4.58 μm-1 is associated with the π-plasmonic resonance of the CNOs structures. The FePt3 filled CNOs were fabricated in situ by an advanced one-step fast process consisting in the direct sublimation and pyrolysis of two molecular precursors, namely, ferrocene and dichloro-cyclooctadiene-platinum in a chemical vapour deposition system. The morphological, structural, and magnetic properties of the as-grown filled CNOs were characterized by a means of scanning and transmission electron microscopy, X-ray diffraction, and magnetometry.

GUM Analysis for TIMS and SIMS Isotopic Ratios in Graphite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heasler, Patrick G.; Gerlach, David C.; Cliff, John B.

2007-04-01

This report describes GUM calculations for TIMS and SIMS isotopic ratio measurements of reactor graphite samples. These isotopic ratios are used to estimate reactor burn-up, and currently consist of various ratios of U, Pu, and Boron impurities in the graphite samples. The GUM calculation is a propagation of error methodology that assigns uncertainties (in the form of standard error and confidence bound) to the final estimates.

Motion of Doped-Polymer-Cholesteric Liquid Crystal Flakes in a Direct-Current Electric Field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trajkovska Petkoska, A.; Kosc, T.Z.; Marshall, K.L.

The behavior of polymer cholesteric liquid crystal (PCLC) flakes suspended in silicone oil host fluids has been explored in the presence of a direct-current electric field. In addition to “neat” (undoped) flakes, the PCLC material was doped with either conductive, carbon-based particles or highly dielectric inorganic particles to modify the dielectric properties of the resulting PCLC flakes. Doping with conductive particles produced flakes with a net charge, and they exhibited either translational or rotational motion depending on both the distribution of dopant within the flake and the dielectric characteristics of the host fluid. Flakes doped with titania (TiO2) particles reorientedmore » 90º when suspended in a host fluid with a differing dielectric permittivity« less

Cooling and stabilization of graphene nanoplatelets in high vacuum

NASA Astrophysics Data System (ADS)

Nagornykh, Pavel

The study of 2D materials is a rapidly growing area of research, where the ability to isolate and probe an individual single-layer specimen is of high importance. The levitation approach serves as a natural solution for this problem and can be used in ways complementary to the standard techniques. Experiments, including study of properties at high or close to melting temperatures, stretching, folding, vibration and functionalization, can be conducted on levitated 2D materials. As a first step towards realization of all these ideas, one needs to develop and test a system allowing for control over the thermal state and orientation of mono-layer flakes. In this thesis, I present the results of implementation of the parametric feedback cooling scheme in a quadrupole ion trap for stabilization and cooling of graphene nanopletelets. I have tested and showed that the feedback allows to stabilize levitated graphene nanoplatelets in high vacuum conditions (<1 microTorr) to have trapped life times longer than a week. Cooling of the center of mass motion to temperatures below 20 K for all translational degrees of freedom was observed. I have also studied the coupling of DC patch potentials, which were found to be present in the high vacuum chamber. Their effect on cooling was studied and the protocol for minimizing the noise coupling created by the DC fields was designed. We have shown that by varying DC voltages on a set of auxiliary DC electrodes, placed near the trap, one can balance out the DC fields and achieve the lowest cooling temperature. The settings corresponding to this temperature were measured to have a slow drift in time. Ability to tune the settings to balance this drift without breaking the vacuum was studied and found to be a viable solution for the drift cancellation. In addition, our effort in characterization of the flakes is presented. It was shown that the flake discharge quantization observed during the initial pumping down of the high vacuum chamber allows to extract absolute values of flake mass and charge. I also mention the issues experienced with estimation of the shape of the flake, as well as its temperature based on an equipartition theorem. Finally, I discuss the preliminary data on the precession and reorientation of the flakes in the presence of circularly polarized light (CPL) and DC stray fields. The dependence of flake orientation on the offset from the nulling settings is observed and is explained in terms of basic model of a solid charged disk in the presence of two torques created by CPL and DC stray fields.

PROCESS OF PREPARING URANIUM-IMPREGNATED GRAPHITE BODY

DOEpatents

Kanter, M.A.

1958-05-20

A method for the fabrication of graphite bodies containing uniformly distributed uranium is described. It consists of impregnating a body of graphite having uniform porosity and low density with an aqueous solution of uranyl nitrate hexahydrate preferably by a vacuum technique, thereafter removing excess aqueous solution from the surface of the graphite, then removing the solvent water from the body under substantially normal atmospheric conditions of temperature and pressure in the presence of a stream of dry inert gas, and finally heating the dry impregnated graphite body in the presence of inert gas at a temperature between 800 and 1400 d C to convert the uranyl nitrate hexahydrate to an oxide of uranium.

Motion of polymer cholesteric liquid crystal flakes in an electric field

NASA Astrophysics Data System (ADS)

Kosc, Tanya Zoriana

Polymer cholesteric liquid crystal (PCLC) flakes suspended in a host fluid can be manipulated with an electric field. Controlling a flake's orientation provides the opportunity to change and control the amount of selective reflection from the flake surface. Flake motion results from charge accumulation and an induced dipole moment established due to Maxwell-Wagner polarization. The type of flake behavior, whether random motion or uniform reorientation, depends upon the dielectric properties of the host fluid, which in turn dictate whether a DC or an AC electric field must be applied. PCLC flakes suspended in highly dielectric silicone oil host fluids tend to move randomly in the presence of a DC electric field, and no motion is seen in AC fields. Flakes suspended in a moderately conductive host fluid reorient 90° in the presence of an AC field within a specific frequency range. The flake shape and size are also important parameters that need to be controlled in order to produce uniform motion. Several methods for patterning flakes were investigated and identical square flakes were produced. Square PCLC flakes (80 mum sides) suspended in propylene carbonate reorient in 400 ms when a 40mVrms/mum field at 70 Hz is applied to the test device. Theoretical modeling supported experimental observations well, particularly in identifying the inverse quadratic dependence on the applied electric field and the electric field frequency dependence that is governed by the host fluid conductivity. Future goals and suggested experiments are provided, as well as an explanation and comparison of possible commercial applications for PCLC flakes. This research has resulted in one patent application and a series of invention disclosures that could place this research group and any industrial collaborators in a strong position to pursue commercial applications, particularly in the area of displays, and more specifically, electronic paper.

Total phenolics, flavonoids, antioxidant activity, crude fibre and digestibility in non-traditional wheat flakes and muesli.

PubMed

Sumczynski, Daniela; Bubelova, Zuzana; Sneyd, Jan; Erb-Weber, Susanne; Mlcek, Jiri

2015-05-01

The five different types of muesli composed of non-traditional wheat flakes were prepared and analysed. Dickkopf wheat, red wheat, kamut and spelt were compared with commercial wheat flakes. Wheat flakes and muesli were assessed for basic analyses (dry matter, ash, protein, starch and fat content), total phenolic and flavonoid content, antioxidant activity (ABTS and DPPH assays), crude fibre content and in vitro digestibility. Furthermore, sensory evaluation of muesli involving scale and ranking preference tests was provided. Flakes and muesli made from Dickkopf wheat and red wheat showed the highest total phenolic and flavonoid content and, consequently, the highest antioxidant activity. Moreover, these cereals were high in crude fibre and thus were less digestible. On the other hand, the lowest total phenolic and flavonoid contents and antioxidant activity were determined in commercial flakes and muesli produced from these flakes. The flakes made from non-traditional wheat were sensorially comparable to commercial products. Copyright © 2014 Elsevier Ltd. All rights reserved.

New insights into canted spiro carbon interstitial in graphite

NASA Astrophysics Data System (ADS)

EL-Barbary, A. A.

2017-12-01

The self-interstitial carbon is the key to radiation damage in graphite moderator nuclear reactor, so an understanding of its behavior is essential for plant safety and maximized reactor lifetime. The density functional theory is applied on four different graphite unit cells, starting from of 64 carbon atoms up to 256 carbon atoms, using AIMPRO code to obtain the energetic, athermal and mechanical properties of carbon interstitial in graphite. This study presents first principles calculations of the energy of formation that prove its high barrier to athermal diffusion (1.1 eV) and the consequent large critical shear stress (39 eV-50 eV) necessary to shear graphite planes in its presence. Also, for the first time, the gamma surface of graphite in two dimensions is calculated and found to yield the critical shear stress for perfect graphite. Finally, in contrast to the extensive literature describing the interstitial of carbon in graphite as spiro interstitial, in this work the ground state of interstitial carbon is found to be canted spiro interstitial.

THE FUEL ELEMENT GRAPHITE. Project DRAGON.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Graham, L.W.; Price, M.S.T.

1963-01-15

The main requirements of a fuel element graphite for reactors based on the Dragon concept are low transmission coefficient for fission products, dimensional stability under service conditions, high strength, high thermal conductivity, high purity, and high resistance to oxidation. Since conclusions reached in early 1960, a considerable amount of information has accumulated concerning the likely behaviour of graphites in high temperature reactor systems, particularly data on dimensional stability under irradiation. The influence of this new knowledge on the development of fuel element graphite with the Dragon Project is discussed in detail in the final section of this paper.

GUM Analysis for SIMS Isotopic Ratios in BEP0 Graphite Qualification Samples, Round 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gerlach, David C.; Heasler, Patrick G.; Reid, Bruce D.

2009-01-01

This report describes GUM calculations for TIMS and SIMS isotopic ratio measurements of reactor graphite samples. These isotopic ratios are used to estimate reactor burn-up, and currently consist of various ratios of U, Pu, and Boron impurities in the graphite samples. The GUM calculation is a propagation of error methodology that assigns uncertainties (in the form of standard error and confidence bound) to the final estimates.

A scanning tunneling microscope capable of imaging specified micron-scale small samples.

PubMed

Tao, Wei; Cao, Yufei; Wang, Huafeng; Wang, Kaiyou; Lu, Qingyou

2012-12-01

We present a home-built scanning tunneling microscope (STM) which allows us to precisely position the tip on any specified small sample or sample feature of micron scale. The core structure is a stand-alone soft junction mechanical loop (SJML), in which a small piezoelectric tube scanner is mounted on a sliding piece and a "U"-like soft spring strip has its one end fixed to the sliding piece and its opposite end holding the tip pointing to the sample on the scanner. Here, the tip can be precisely aligned to a specified small sample of micron scale by adjusting the position of the spring-clamped sample on the scanner in the field of view of an optical microscope. The aligned SJML can be transferred to a piezoelectric inertial motor for coarse approach, during which the U-spring is pushed towards the sample, causing the tip to approach the pre-aligned small sample. We have successfully approached a hand cut tip that was made from 0.1 mm thin Pt∕Ir wire to an isolated individual 32.5 × 32.5 μm(2) graphite flake. Good atomic resolution images and high quality tunneling current spectra for that specified tiny flake are obtained in ambient conditions with high repeatability within one month showing high and long term stability of the new STM structure. In addition, frequency spectra of the tunneling current signals do not show outstanding tip mount related resonant frequency (low frequency), which further confirms the stability of the STM structure.

Wetting of water on graphene nanopowders of different thicknesses

NASA Astrophysics Data System (ADS)

Bera, Bijoyendra; Shahidzadeh, Noushine; Mishra, Himanshu; Belyaeva, Liubov A.; Schneider, Grégory F.; Bonn, Daniel

2018-04-01

We study the wetting of graphene nanopowders by measuring the water adsorption in nanopowder flakes of different flake thicknesses. Chemical analysis shows that the graphene flakes, especially the thin ones, might exist in the partially oxidized state. We observe that the thinnest graphene nanopowder flakes do not adsorb water at all, independent of the relative humidity. Thicker flakes, on the other hand, do adsorb an increasing amount of water with increasing humidity. This allows us to assess their wetting behavior which is actually the result of the competition between the adhesive interactions of water and graphene and the cohesive interactions of water. Explicit calculation of these contributions from the van der Waals interactions confirms that the adhesive interactions between very thin flakes of graphene oxide and water are extremely weak, which makes the flakes superhydrophobic. "Liquid marble" tests with graphene nanopowder flakes confirm the superhydrophobicity. This shows that the origin of the much debated "wetting transparency" of graphene is due to the fact that a single graphene or graphene oxide layer does not contribute significantly to the adhesion between a wetting phase and the substrate.

Graphite distortion ``C`` Reactor. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wood, N.H.

1962-02-08

This report covers the efforts of the Laboratory in an investigation of the graphite distortion in the ``C`` reactor at Hanford. The particular aspects of the problem to be covered by the Laboratory were possible ``fixes`` to the control rod sticking problem caused by VSR channel distortion.

Fabrication of hybrid molecular devices using multi-layer graphene break junctions.

PubMed

Island, J O; Holovchenko, A; Koole, M; Alkemade, P F A; Menelaou, M; Aliaga-Alcalde, N; Burzurí, E; van der Zant, H S J

2014-11-26

We report on the fabrication of hybrid molecular devices employing multi-layer graphene (MLG) flakes which are patterned with a constriction using a helium ion microscope or an oxygen plasma etch. The patterning step allows for the localization of a few-nanometer gap, created by electroburning, that can host single molecules or molecular ensembles. By controlling the width of the sculpted constriction, we regulate the critical power at which the electroburning process begins. We estimate the flake temperature given the critical power and find that at low powers it is possible to electroburn MLG with superconducting contacts in close proximity. Finally, we demonstrate the fabrication of hybrid devices with superconducting contacts and anthracene-functionalized copper curcuminoid molecules. This method is extendable to spintronic devices with ferromagnetic contacts and a first step towards molecular integrated circuits.

Fabrication of hybrid molecular devices using multi-layer graphene break junctions

NASA Astrophysics Data System (ADS)

Island, J. O.; Holovchenko, A.; Koole, M.; Alkemade, P. F. A.; Menelaou, M.; Aliaga-Alcalde, N.; Burzurí, E.; van der Zant, H. S. J.

2014-11-01

We report on the fabrication of hybrid molecular devices employing multi-layer graphene (MLG) flakes which are patterned with a constriction using a helium ion microscope or an oxygen plasma etch. The patterning step allows for the localization of a few-nanometer gap, created by electroburning, that can host single molecules or molecular ensembles. By controlling the width of the sculpted constriction, we regulate the critical power at which the electroburning process begins. We estimate the flake temperature given the critical power and find that at low powers it is possible to electroburn MLG with superconducting contacts in close proximity. Finally, we demonstrate the fabrication of hybrid devices with superconducting contacts and anthracene-functionalized copper curcuminoid molecules. This method is extendable to spintronic devices with ferromagnetic contacts and a first step towards molecular integrated circuits.

Development of a low loss magnetic composite utilizing amorphous metal flake. Second semi-annual progress report, March 19-September 18, 1979

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1979-10-01

Composite specimens of amorphous metal flakes have been made using several different binders and several different compaction parameters. The binders have included epoxies, anaerobic adhesives, polyimides, polyamideimides, polyeherimides, and polyesterimides. Compaction variables included the time, temperature and pressure of compaction; flake size, and flake alignment. The best results were achieved using a polyetherimide and aligned flake. Packing factors of 87% were achieved in specimens which also exhibited high mechanical integrity and the ability to withstand a high temperature anneal.

High temperature gas-cooled reactor (HTGR) graphite pebble fuel: Review of technologies for reprocessing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mcwilliams, A. J.

2015-09-08

This report reviews literature on reprocessing high temperature gas-cooled reactor graphite fuel components. A basic review of the various fuel components used in the pebble bed type reactors is provided along with a survey of synthesis methods for the fabrication of the fuel components. Several disposal options are considered for the graphite pebble fuel elements including the storage of intact pebbles, volume reduction by separating the graphite from fuel kernels, and complete processing of the pebbles for waste storage. Existing methods for graphite removal are presented and generally consist of mechanical separation techniques such as crushing and grinding chemical techniquesmore » through the use of acid digestion and oxidation. Potential methods for reprocessing the graphite pebbles include improvements to existing methods and novel technologies that have not previously been investigated for nuclear graphite waste applications. The best overall method will be dependent on the desired final waste form and needs to factor in the technical efficiency, political concerns, cost, and implementation.« less

Documenting Differences between Early Stone Age Flake Production Systems: An Experimental Model and Archaeological Verification.

PubMed

Presnyakova, Darya; Archer, Will; Braun, David R; Flear, Wesley

2015-01-01

This study investigates morphological differences between flakes produced via "core and flake" technologies and those resulting from bifacial shaping strategies. We investigate systematic variation between two technological groups of flakes using experimentally produced assemblages, and then apply the experimental model to the Cutting 10 Mid -Pleistocene archaeological collection from Elandsfontein, South Africa. We argue that a specific set of independent variables--and their interactions--including external platform angle, platform depth, measures of thickness variance and flake curvature should distinguish between these two technological groups. The role of these variables in technological group separation was further investigated using the Generalized Linear Model as well as Linear Discriminant Analysis. The Discriminant model was used to classify archaeological flakes from the Cutting 10 locality in terms of their probability of association, within either experimentally developed technological group. The results indicate that the selected independent variables play a central role in separating core and flake from bifacial technologies. Thickness evenness and curvature had the greatest effect sizes in both the Generalized Linear and Discriminant models. Interestingly the interaction between thickness evenness and platform depth was significant and played an important role in influencing technological group membership. The identified interaction emphasizes the complexity in attempting to distinguish flake production strategies based on flake morphological attributes. The results of the discriminant function analysis demonstrate that the majority of flakes at the Cutting 10 locality were not associated with the production of the numerous Large Cutting Tools found at the site, which corresponds with previous suggestions regarding technological behaviors reflected in this assemblage.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Inam, A., E-mail: aqil.ceet@pu.edu.pk; Brydson, R., E-mail: mtlrmdb@leeds.ac.uk; Edmonds, D.V., E-mail: d.v.edmonds@leeds.ac.uk

The potential for using graphite particles as an internal lubricant during machining is considered. Graphite particles were found to form during graphitisation of experimental medium-carbon steel alloyed with Si and Al. The graphite nucleation sites were strongly influenced by the starting microstructure, whether ferrite–pearlite, bainite or martensite, as revealed by light and electron microscopy. Favourable nucleation sites in the ferrite–pearlite starting microstructure were, not unexpectedly, found to be located within pearlite colonies, no doubt due to the presence of abundant cementite as a source of carbon. In consequence, the final distribution of graphite nodules in ferrite–pearlite microstructures was less uniformmore » than for the bainite microstructure studied. In the case of martensite, this study found a predominance of nucleation at grain boundaries, again leading to less uniform graphite dispersions. - Highlights: • Metallography of formation of graphite particles in experimental carbon steel. • Potential for using graphite in steel as an internal lubricant during machining. • Microstructure features expected to influence improved machinability studied. • Influence of pre-anneal starting microstructure on graphite nucleation sites. • Influence of pre-anneal starting microstructure on graphite distribution. • Potential benefit is new free-cutting steel compositions without e.g. Pb alloying.« less

Effect of Silver Flakes in Silver Paste on the Joining Process and Properties of Sandwich Power Modules (IGBTs Chip/Silver Paste/Bare Cu)

NASA Astrophysics Data System (ADS)

Zhao, Su-Yan; Li, Xin; Mei, Yun-Hui; Lu, Guo-Quan

2016-11-01

In this study, a silver paste has been introduced for attaching chips onto bare Cu substrates (without coating) without applying pressure. Small nano-thickness Ag flakes, measuring 1 μm-5 μm length, were embedded uniformly in Ag nanoparticles for improving the density of the material. The presence of silver flakes in the silver paste affected the joining process and its microstructure. Microstructure characterization revealed that densification of the silver layer was affected by the presence of silver flakes as the flakes coarsened and formed reactive in situ nanoparticles, which facilitated the sintering between the flakes and the incorporated nanoparticles. Coarsening of silver flakes depended on the sintering temperature, time, and the atmosphere, which affected the decomposition and burning out of organics presented on the surface of the flakes. A high-density silver layer was obtained due to the presence of compact silver flakes. With an increase in the microstructure density, a higher bonding strength and a lower thermal impedance of the sintered joints were achieved. On performing pressureless sintering at 270°C for 30 min under 99.99% N2 or 4% H2/N2, the bonding strength and thermal impedance for 11 × 11 mm2 chips were excellent, measuring approximately 21.9 MPa and 0.077°C/W, respectively.

Fire effects on flaked stone, ground stone, and other stone artifacts [Chapter 4

Treesearch

Krista Deal

2012-01-01

Lithic artifacts can be divided into two broad classes, flaked stone and ground stone, that overlap depending on the defining criteria. For this discussion, flaked stone is used to describe objects that cut, scrape, pierce, saw, hack, etch, drill, or perforate, and the debris (debitage) created when these items are manufactured. Objects made of flaked stone include...

Large-area synthesis of high-quality monolayer 1T’-WTe2 flakes

NASA Astrophysics Data System (ADS)

Naylor, Carl H.; Parkin, William M.; Gao, Zhaoli; Kang, Hojin; Noyan, Mehmet; Wexler, Robert B.; Tan, Liang Z.; Kim, Youngkuk; Kehayias, Christopher E.; Streller, Frank; Zhou, Yu Ren; Carpick, Robert; Luo, Zhengtang; Park, Yung Woo; Rappe, Andrew M.; Drndić, Marija; Kikkawa, James M.; Johnson, A. T. Charlie

2017-06-01

Large-area growth of monolayer films of the transition metal dichalcogenides is of the utmost importance in this rapidly advancing research area. The mechanical exfoliation method offers high quality monolayer material but it is a problematic approach when applied to materials that are not air stable. One important example is 1T’-WTe2, which in multilayer form is reported to possess a large non saturating magnetoresistance, pressure induced superconductivity, and a weak antilocalization effect, but electrical data for the monolayer is yet to be reported due to its rapid degradation in air. Here we report a reliable and reproducible large-area growth process for obtaining many monolayer 1T’-WTe2 flakes. We confirmed the composition and structure of monolayer 1T’-WTe2 flakes using x-ray photoelectron spectroscopy, energy-dispersive x-ray spectroscopy, atomic force microscopy, Raman spectroscopy and aberration corrected transmission electron microscopy. We studied the time dependent degradation of monolayer 1T’-WTe2 under ambient conditions, and we used first-principles calculations to identify reaction with oxygen as the degradation mechanism. Finally we investigated the electrical properties of monolayer 1T’-WTe2 and found metallic conduction at low temperature along with a weak antilocalization effect that is evidence for strong spin-orbit coupling.

Life history of a large flake biface

NASA Astrophysics Data System (ADS)

Baena Preysler, Javier; Torres Navas, Concepción; Sharon, Gonen

2018-06-01

Bifaces, primarily handaxes and cleavers, are the hallmark of the Acheulian techno-complex lithic industry. They spread across Africa and Eurasia during the Early to Middle Pleistocene. While many attempts have been made to define and describe the typology and technology of these tools, most focus on a single stage in their manufacture and usage, from quarry to discard. These attempts are fragmented, primarily due to the fact that at no single site are all stages of biface manufacture and use represented. An additional factor that appears to impede attempts to present the full "life cycle" of bifaces is the view of all Acheulian assemblages as belonging to a single cultural entity. While all assemblages belong to the same techno-complex, distinct stages and phases should be recognized, each different in typology, technology, and probably also in chronology. This research focuses on the large flake stage of the Acheulian. Data accumulated over many years of research from different regions are analyzed together in an attempt to present a holistic view of the life cycle of a biface. The study of particular Acheulian sites from the Levant and Western Europe enables us to reconstruct all stages of the biface, from raw material exploitation to final discard. The result is a model more comprehensive and precise than those suggested previously for understanding the Large Flake Acheulian.

Research on metal-plated cellulose nitrate flakes and their infrared / millimeter wave characteristics

NASA Astrophysics Data System (ADS)

Ye, Shu-qin; Zhu, Chen-guang; Wang, Li-hong; Ou'yang, De-hua; Pan, Gong-pei

2016-10-01

Copper-plated and silver-plated cellulose nitrate flakes, which were prepared by using chemical plating technology, were used to jam infrared detector and millimeter-wave radar. It was tested for the conductivity and infrared jamming performance of plating and also the RCS (Radar Cross Section) performance of millimeter-wave radar. Test results showed that the prepared metal-plated cellulose nitrate flakes have obvious conductivity, and infrared total radiation energy of silver plating and copper plating had approximately increased 32% and 21% respectively. Through determination, the millimeter-wave reflecting property and RCS of silver-plated cellulose nitrate flakes were higher than that of copper-plated cellulose nitrate flakes. Therefore, silver-plated cellulose nitrate flakes can be used as an effective infrared / millimeter wave composite jamming material.

76 FR 56397 - Small Diameter Graphite Electrodes from the People's Republic of China: Final Results of the...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-13

... value (``SV'') information: SGL Carbon LLC and Superior Graphite Co. (``Petitioners''); Fushun Jinly Petrochemical Carbon Co., Ltd. (``Fushun Jinly''); and Beijing Fangda Carbon Tech Co., Ltd. (``Beijing Fangda''), Chengdu Rongguang Carbon Co., Ltd. (``Rongguang''), Fangda Carbon New Material Co., Ltd. (``Fangda Carbon...

Tip-induced local strain on Mo S 2 / graphite detected by inelastic electron tunneling spectroscopy

DOE PAGES

Ko, Wonhee; Hus, Saban M.; Li, Xufan; ...

2018-03-02

We report the detection of tip-induced local strain applied to the monolayer MoS 2 grown on a graphite substrate by scanning tunneling microscope. Monolayer MoS 2 behaves as both mechanical and tunneling barriers that prevent the tip from contacting the graphite while maintaining the tunneling current. Inelastic tunneling electron spectroscopy (IETS) is utilized to probe the phonon modes in graphite. As the tip pushes the sample, IETS reveals a continuous phonon softening in graphite, corroborated by a downward shift of the phonon energy as calculated by density-functional theory. Finally, our results demonstrate a way to apply local mechanical strain andmore » simultaneously detect the induced change in phonon modes by unitizing IETS with two-dimensional materials as a tunneling barrier.« less

Tip-induced local strain on Mo S 2 / graphite detected by inelastic electron tunneling spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ko, Wonhee; Hus, Saban M.; Li, Xufan

We report the detection of tip-induced local strain applied to the monolayer MoS 2 grown on a graphite substrate by scanning tunneling microscope. Monolayer MoS 2 behaves as both mechanical and tunneling barriers that prevent the tip from contacting the graphite while maintaining the tunneling current. Inelastic tunneling electron spectroscopy (IETS) is utilized to probe the phonon modes in graphite. As the tip pushes the sample, IETS reveals a continuous phonon softening in graphite, corroborated by a downward shift of the phonon energy as calculated by density-functional theory. Finally, our results demonstrate a way to apply local mechanical strain andmore » simultaneously detect the induced change in phonon modes by unitizing IETS with two-dimensional materials as a tunneling barrier.« less

Electrically Addressable Optical Devices Using A System Of Composite Layered Flakes Suspended In A Fluid Host To Obtain Angularly Depende

DOEpatents

Kosc, Tanya Z.; Marshall, Kenneth L.; Jacobs, Stephen D.

2004-12-07

Composite or layered flakes having a plurality of layers of different materials, which may be dielectric materials, conductive materials, or liquid crystalline materials suspended in a fluid host and subjected to an electric field, provide optical effects dependent upon the angle or orientation of the flakes in the applied electric field. The optical effects depend upon the composition and thickness of the layers, producing reflectance, interference, additive and/or subtractive color effects. The composition of layered flakes may also be selected to enhance and/or alter the dielectric properties of flakes, whereby flake motion in an electric field is also enhanced and/or altered. The devices are useful as active electro-optical displays, polarizers, filters, light modulators, and wherever controllable polarizing, reflecting and transmissive optical properties are desired.

Invited review: summary of steam-flaking corn or sorghum grain for lactating dairy cows.

PubMed

Theurer, C B; Huber, J T; Delgado-Elorduy, A; Wanderley, R

1999-09-01

Nineteen lactation trials (43 grain processing comparisons) are summarized, in addition to digestibility and postabsorptive metabolism studies. The net energy for lactation (NEL) of steam-flaked corn or sorghum grain is about 20% greater than the NEL for dry-rolled corn or sorghum. Based on lactational performance, steam-flaked sorghum grain is of equal value to steam-flaked corn, and steam-flaked corn is superior to steam-rolled corn. Steam-flaking of corn or sorghum compared to steam-rolling of corn or dry-rolling of corn or sorghum consistently improves milk production and milk protein yield. This result is because of a much greater proportion of dietary starch fermented in the rumen, enhanced digestibility of the smaller fraction of dietary starch reaching the small intestine, and increased total starch digestion. Steam-flaking increases cycling of urea to the gut, microbial protein flow to the small intestine, and estimated mammary uptake of amino acids. Steam-rolling compared to dry-rolling of barley or wheat did not alter total starch digestibilities in two trials, one with each grain source. Lactation studies with these processing comparisons have not been reported. Most cited studies have been with total mixed rations (TMR) and alfalfa hay as the principal forage. Additional studies are needed with lactating cows fed steam-flaked corn or sorghum in TMR containing alfalfa or corn silage. Optimal flake density of steam-processed corn or sorghum grain appears to be about 360 g/L (approximately 28 lb/bu).

Determining tensile properties of sweetgum veneer flakes

Treesearch

E.W. Price

1976-01-01

Rotary-cut 8weetgum veneer flakes measuring 3 inchee along the grain, 3/8 inch wide, and 0.015 inch thick, were stressed in tension parallel to the grain at gage lengths from 0.00 to 1.25 inchee for unpressed control and at 0.75 inch gage length for flakes pressed in a flakeboard mat. The control flakes had an average tensile strength of 9,400 psi for the smaller age...

Plasmonic-enhanced graphene flake counter electrodes for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Kim, Hyun-Young; Lee, Myung Woo; Song, Da Hyun; Yoon, Hyeok Jin; Suh, Jung Sang

2017-06-01

A plasmonic-enhanced graphene flake counter electrode for dye-sensitized solar cells (DSSCs) was fabricated by immobilization of gold nanoparticles (NPs) on fluorine-doped tin oxide (FTO) glass and the deposition of a thin layer of graphene flakes. The graphene flakes, fabricated using a thermal plasma jet system, were very thin and pure and had good crystallinity. Even though their average size is larger than 100 nm, they had great dispersibility in common solvents. Their relatively large size and good crystallinity resulted in good conductivity, and their good dispersibility allowed us to fabricate relatively uniform films. The efficiency of the DSSC with a graphene flake/Au NP/FTO counter electrode was as much as 9.78%, which is higher than that with a conventional Pt/FTO (9.08%) or graphene flake/FTO (8.98%) counter electrode. Using cyclic voltammograms and electrochemical impedance spectroscopy and by measuring the incident photo-conversion efficiency, we proved that by the localized surface plasmon resonance effect of the Au NPs included between the graphene flakes and FTO, the charge-transfer resistance at the electrode/electrolyte interface was decreased. Consequently, the catalytic rate for I- regeneration improved, and the energy conversion efficiency of the DSSC with a graphene flake/Au NP/FTO counter electrode improved.

N-Doped graphene/PEDOT composite films as counter electrodes in DSSCs: Unveiling the mechanism of electrocatalytic activity enhancement

NASA Astrophysics Data System (ADS)

Paterakis, Georgios; Raptis, Dimitrios; Ploumistos, Alexandros; Belekoukia, Meltiani; Sygellou, Lamprini; Ramasamy, Madeshwaran Sekkarapatti; Lianos, Panagiotis; Tasis, Dimitrios

2017-11-01

A composite film was obtained by layer deposition of N-doped graphene and poly(3,4-ethylenedioxythiophene) (PEDOT) and was used as Pt-free counter electrode for dye-sensitized solar cells. N-doping of graphene was achieved by annealing mixtures of graphene oxide with urea. Various parameters concerning the treatment of graphene oxide-urea mixtures were monitored in order to optimize the electrocatalytic activity in the final solar cell device. These include the mass ratio of components, the annealing temperature, the starting concentration of the mixture in aqueous solution and the spinning rate for film formation. PEDOT was applied by electrodeposition. The homogeneity of PEDOT coverage onto either untreated or thermally annealed graphene oxide-urea film was assessed by imaging (AFM/SEM) and surface techniques (XPS). It was found that PEDOT was deposited in the form of island structures onto untreated graphene oxide-urea film. On the contrary, the annealed film was homogeneously covered by the polymer, acquiring morphology of decreased roughness. An apparent chemical interaction between PEDOT and N-doped graphene flakes was revealed by XPS data, involving potential grafting of PEDOT chains onto graphitic lattice through Csbnd C bonding. In addition, diffusion of nitrogen-containing fragments within the PEDOT layer was found to take place during electrodeposition process, resulting in enhanced interfacial interactions between components. The solar cell with the optimized N-doped graphene/PEDOT composite counter electrode exhibited a power conversion efficiency (η) of 7.1%, comparable within experimental error to that obtained by using a reference Pt counter electrode, which showed a value of 7.0%.

75 FR 76026 - United States v. Graftech International Ltd., Et al.; Proposed Final Judgment and Competitive...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-12-07

... and other inputs to form cylinders that are shot through with electricity and baked to produce... electricity into the furnace, heating the furnace and melting scrap steel. 11. Graphite electrodes oxidize and... consumption of graphite electrodes. 12. Petroleum needle coke, relative to other varieties of coke, is...

Microwave limb sounder, graphite epoxy support structure

NASA Technical Reports Server (NTRS)

Pynchon, G.

1980-01-01

The manufacturing and processing procedures which were used to fabricate a precision graphite/epoxy support structure for a spherical microwave reflecting surface are described. The structure was made fromm GY-70/930 ultra high modulus graphite prepreg, laminated to achieve an isotropic in plane thermal expansion of less than + or - 0.1 PPM/F. The structure was hand assembled to match the interface of the reflective surface, which was an array of 18 flexure supported, aluminum, spherically contoured tiles. Structural adhesives were used in the final assembly to bond the elements into their final configuration. A eutectic metal coating was applied to the composite surface to reduce dimensional instabilities arising from changes in the composite epoxy moisture content due to environmental effects. Basic materials properties data are reported and the results of a finite element structural analysis are referenced.

Exterior structural composite panels with southern pine veneer faces and cores of southern hardwood flakes

Treesearch

C. -Y. Hse

1976-01-01

One-half-inch-thick, 8tructural exterior composite panels of various constructions were made in a one-step process, with faces of eouthern pine veneer and corea of mixed southern hardwood flakes. The flakes were precisely machined to be 3/8-inch wide, 3 inches long and 0.015 inch thick. Two veneer, cross-laminated on each face over an oriented flake core, yielded the...

Enhancement of mechanical properties of polymers by thin flake addition and apparatus for producing such thin flakes

DOEpatents

Bunnell, Sr., Lee R.

1991-01-01

Compositions in accordance with the invention comprise a polymer and flake reinforcing material distributed throughout the polymer in an effective amount to structurally reinforce the polymer. Individual flakes of the flake material (a) are less than or equal to 1,000 Angstroms in thickness, (b) have an aspect ratio greater than or equal to 100, and (c) are preferably significantly randomly oriented throughout the polymer. A novel apparatus for shear grinding a platy solid material into such individual flakes comprises a cylindrical shearing drum and a shear grinder received therein. The shearing drum has a longitudinal axis and an internal surface formed about a first predetermined radius of curvature. The cylindrical drum is supported for rotation about its longitudinal axis. The shear grinder has an external surface formed about a second predetermined radius of curvature. The second radius of curvature is slightly less than the first radius of curvature.

Role of impurities on the optical properties of rectangular graphene flakes

NASA Astrophysics Data System (ADS)

Sadeq, Z. S.; Muniz, Rodrigo A.; Sipe, J. E.

2018-01-01

We study rectangular graphene flakes using mean field states as the basis for a configuration interaction calculation, which allows us to analyze the low lying electronic excited states including electron correlations beyond the mean field level. We find that the lowest energy transition is polarized along the long axis of the flake, but the charge distributions involved in these transitions are invariably localized on the zigzag edges. We also investigate the impact of both short and long range impurity potentials on the optical properties of these systems. We predict that even a weak impurity localized at a zigzag edge of the flake can have a significant—and often dramatic—effect on its optical properties. This is in contrast to impurities localized at armchair edges or central regions of the flake, for which we predict almost no change to the optical properties of the flake even with strong impurity potentials.

Synthesis of porous graphene powder through improved Hummers' method

NASA Astrophysics Data System (ADS)

Gupta, Siddhant; Bonageri, Shrilakshmi; Achar, Siddarth Krishnaraja; Menon, Atul; Basavaraja R., J.

2018-05-01

Graphene due to its high specific surface area is considered to be a potential adsorbent for air and water purification systems. In this study, graphene was synthesized using the recently developed Improved Hummers' method to achieve a high oxidation rate and thermal treatment of the synthesized graphene was done to increase its pore size and make it more capable for applications in purification systems. Graphite flakes were oxidized to obtain graphene oxide which was then reduced to obtain graphene. The synthesized graphene was then thermally treated at 200 °C for two hours in a muffle furnace to improve its surface properties. The characterization results of graphene oxide and graphene show the presence of many impurities which is inferred to be the result of contaminated water used in the experimentation. The analysis of the characterization results also shows that the thermally treated graphene has more spacing and voids when compared to graphene which makes it a better suit for adsorption of gases such as carbon dioxide.

Graphene growth from reduced graphene oxide by chemical vapour deposition: seeded growth accompanied by restoration

NASA Astrophysics Data System (ADS)

Chang, Sung-Jin; Hyun, Moon Seop; Myung, Sung; Kang, Min-A.; Yoo, Jung Ho; Lee, Kyoung G.; Choi, Bong Gill; Cho, Youngji; Lee, Gaehang; Park, Tae Jung

2016-03-01

Understanding the underlying mechanisms involved in graphene growth via chemical vapour deposition (CVD) is critical for precise control of the characteristics of graphene. Despite much effort, the actual processes behind graphene synthesis still remain to be elucidated in a large number of aspects. Herein, we report the evolution of graphene properties during in-plane growth of graphene from reduced graphene oxide (RGO) on copper (Cu) via methane CVD. While graphene is laterally grown from RGO flakes on Cu foils up to a few hundred nanometres during CVD process, it shows appreciable improvement in structural quality. The monotonous enhancement of the structural quality of the graphene with increasing length of the graphene growth from RGO suggests that seeded CVD growth of graphene from RGO on Cu surface is accompanied by the restoration of graphitic structure. The finding provides insight into graphene growth and defect reconstruction useful for the production of tailored carbon nanostructures with required properties.

Graphene growth from reduced graphene oxide by chemical vapour deposition: seeded growth accompanied by restoration.

PubMed

Chang, Sung-Jin; Hyun, Moon Seop; Myung, Sung; Kang, Min-A; Yoo, Jung Ho; Lee, Kyoung G; Choi, Bong Gill; Cho, Youngji; Lee, Gaehang; Park, Tae Jung

2016-03-10

Understanding the underlying mechanisms involved in graphene growth via chemical vapour deposition (CVD) is critical for precise control of the characteristics of graphene. Despite much effort, the actual processes behind graphene synthesis still remain to be elucidated in a large number of aspects. Herein, we report the evolution of graphene properties during in-plane growth of graphene from reduced graphene oxide (RGO) on copper (Cu) via methane CVD. While graphene is laterally grown from RGO flakes on Cu foils up to a few hundred nanometres during CVD process, it shows appreciable improvement in structural quality. The monotonous enhancement of the structural quality of the graphene with increasing length of the graphene growth from RGO suggests that seeded CVD growth of graphene from RGO on Cu surface is accompanied by the restoration of graphitic structure. The finding provides insight into graphene growth and defect reconstruction useful for the production of tailored carbon nanostructures with required properties.

Graphene growth from reduced graphene oxide by chemical vapour deposition: seeded growth accompanied by restoration

PubMed Central

Chang, Sung-Jin; Hyun, Moon Seop; Myung, Sung; Kang, Min-A; Yoo, Jung Ho; Lee, Kyoung G.; Choi, Bong Gill; Cho, Youngji; Lee, Gaehang; Park, Tae Jung

2016-01-01

Understanding the underlying mechanisms involved in graphene growth via chemical vapour deposition (CVD) is critical for precise control of the characteristics of graphene. Despite much effort, the actual processes behind graphene synthesis still remain to be elucidated in a large number of aspects. Herein, we report the evolution of graphene properties during in-plane growth of graphene from reduced graphene oxide (RGO) on copper (Cu) via methane CVD. While graphene is laterally grown from RGO flakes on Cu foils up to a few hundred nanometres during CVD process, it shows appreciable improvement in structural quality. The monotonous enhancement of the structural quality of the graphene with increasing length of the graphene growth from RGO suggests that seeded CVD growth of graphene from RGO on Cu surface is accompanied by the restoration of graphitic structure. The finding provides insight into graphene growth and defect reconstruction useful for the production of tailored carbon nanostructures with required properties. PMID:26961409

Graphene nanocomposites as thermal interface materials for cooling energy devices

NASA Astrophysics Data System (ADS)

Dmitriev, A. S.; Valeev, A. R.

2017-11-01

The paper describes the technology of creating samples of graphene nanocomposites based on graphene flakes obtained by splitting graphite with ultrasound of high power. Graphene nanocomposites in the form of samples are made by the technology of weak sintering at high pressure (200-300 bar) and temperature up to 150 0 C, and also in the form of compositions with polymer matrices. The reflection spectra in the visible range and the near infrared range for the surface of nanocomposite samples are studied, the data of optical and electronic spectroscopy of such samples are givenIn addition, data on the electrophysical and thermal properties of the nanocomposites obtained are presented. Some analytical models of wetting and spreading over graphene nanocomposite surfaces have been constructed and calculated, and their effective thermal conductivity has been calculated and compared with the available experimental data. Possible applications of graphene nanocomposites for use as thermal interface materials for heat removal and cooling for power equipment, as well as microelectronics and optoelectronics devices are described.

Preparation of polyvinyl alcohol graphene oxide phosphonate film and research of thermal stability and mechanical properties.

PubMed

Li, Jihui; Song, Yunna; Ma, Zheng; Li, Ning; Niu, Shuai; Li, Yongshen

2018-05-01

In this article, flake graphite, nitric acid, peroxyacetic acid and phosphoric acid are used to prepare graphene oxide phosphonic and phosphinic acids (GOPAs), and GOPAs and polyvinyl alcohol (PVA) are used to synthesize polyvinyl alcohol graphene oxide phosphonate and phosphinate (PVAGOPs) in the case of faint acidity and ultrasound irradiation, and PVAGOPs are used to fabricate PVAGOPs film, and the structure and morphology of GOPAs, PVAGOPs and PVAGOPs film are characterized, and the thermal stability and mechanical properties of PVAGOPs film are investigated. Based on these, it has been proved that GOPAs consist of graphene oxide phosphonic acid and graphene oxide phosphinic acid, and there are CP covalent bonds between them, and PVAGOPs are composed of GOPAs and PVA, and there are six-member lactone rings between GOPAs and PVA, and the thermal stability and mechanical properties of PVAGOPs film are improved effectively. Copyright © 2018 Elsevier B.V. All rights reserved.

Effect of Heating Time on Hardness Properties of Laser Clad Gray Cast Iron Surface

NASA Astrophysics Data System (ADS)

Norhafzan, B.; Aqida, S. N.; Mifthal, F.; Zulhishamuddin, A. R.; Ismail, I.

2018-03-01

This paper presents effect of heating time on cladded gray cast iron. In this study, the effect of heating time on cladded gray cast iron and melted gray cast iron were analysed. The gray cast iron sample were added with mixed Mo-Cr powder using laser cladding technique. The mixed Mo and Cr powder was pre-placed on gray cast iron surface. Modified layer were sectioned using diamond blade cutter and polish using SiC abrasive paper before heated. Sample was heated in furnace for 15, 30 and 45 minutes at 650 °C and cool down in room temperature. Metallographic study was conduct using inverted microscope while surface hardness properties were tested using Wilson hardness test with Vickers scale. Results for metallographic study showed graphite flakes within matrix of pearlite. The surface hardness for modified layer decreased when increased heating time process. These findings are significant to structure stability of laser cladded gray cast iron with different heating times.

Pulsed laser vaporization synthesis of boron loaded few layered graphene (Conference Presentation)

NASA Astrophysics Data System (ADS)

Tennyson, Wesley D.; Tian, Mengkun; More, Karren L.; Geohegan, David B.; Puretzky, Alexander A.; Papandrew, Alexander B.; Rouleau, Christopher M.; Yoon, Mina

2017-02-01

The bulk production of loose graphene flakes and its doped variants are important for energy applications including batteries, fuel cells, and supercapacitors as well as optoelectronic and thermal applications. While laser-based methods have been reported for large-scale synthesis of single-wall carbon nanohorns (SWNHs), similar large-scale production of graphene has not been reported. Here we explored the synthesis of doped few layered graphene by pulsed laser vaporization (PLV) with the goal of producing an oxidation resistant electrode support for solid acid fuel cells. PLV of graphite with various amounts of boron was carried out in mixtures in either Ar or Ar/H2 at 0.1 MPa at elevated temperatures under conditions typically used for synthesis of SWNHs. Both the addition of hydrogen to the background argon, or the addition of boron to the carbon target, was found to shift the formation of carbon nanohorns to two-dimensional flakes of a new form of few-layer graphene material, with sizes up to microns in dimension as confirmed by XRD and TEM. However, the materials made with boron exhibited superior resistance to carbon corrosion in the solid acid fuel cell and thermal oxidation resistance in air compared to similar product made without boron. Mechanisms for the synthesis and oxidation resistance of these materials will be discussed based upon detailed characterization and modeling. •Synthesis science was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences (BES), Materials Sciences and Engineering Division. Material processing and characterization science supported by ARPA-E under Cooperative Agreement Number DE-AR0000499 and as a user project at the Center for Nanophase Materials Sciences, a Department of Energy Office of Science User Facility.

Documenting Differences between Early Stone Age Flake Production Systems: An Experimental Model and Archaeological Verification

PubMed Central

Presnyakova, Darya; Archer, Will; Braun, David R.; Flear, Wesley

2015-01-01

This study investigates morphological differences between flakes produced via “core and flake” technologies and those resulting from bifacial shaping strategies. We investigate systematic variation between two technological groups of flakes using experimentally produced assemblages, and then apply the experimental model to the Cutting 10 Mid -Pleistocene archaeological collection from Elandsfontein, South Africa. We argue that a specific set of independent variables—and their interactions—including external platform angle, platform depth, measures of thickness variance and flake curvature should distinguish between these two technological groups. The role of these variables in technological group separation was further investigated using the Generalized Linear Model as well as Linear Discriminant Analysis. The Discriminant model was used to classify archaeological flakes from the Cutting 10 locality in terms of their probability of association, within either experimentally developed technological group. The results indicate that the selected independent variables play a central role in separating core and flake from bifacial technologies. Thickness evenness and curvature had the greatest effect sizes in both the Generalized Linear and Discriminant models. Interestingly the interaction between thickness evenness and platform depth was significant and played an important role in influencing technological group membership. The identified interaction emphasizes the complexity in attempting to distinguish flake production strategies based on flake morphological attributes. The results of the discriminant function analysis demonstrate that the majority of flakes at the Cutting 10 locality were not associated with the production of the numerous Large Cutting Tools found at the site, which corresponds with previous suggestions regarding technological behaviors reflected in this assemblage. PMID:26111251

Change of properties after oxidation of IG-11 graphite by air and CO 2 gas

NASA Astrophysics Data System (ADS)

Lim, Yun-Soo; Chi, Se-Hwan; Cho, Kwang-Yun

2008-02-01

Artificial graphite is typically manufactured by carbonization of a shaped body of a kneaded mixture using granular cokes as a filler and pitch as a binder. It undergoes a pitch impregnation process if necessary and finally applying graphitization heat treatment. The effect of thermal oxidation in air or a CO 2 atmosphere on IG-11 graphite samples is investigated in this study. The results show a localized oxidation process that progressively reveals the large coke particles with increasing level of overall weight loss in air. The surface of the graphite was peeled off and no change was found in the specific gravity after air oxidation. However, the specific gravity of graphite was continuously decreased by CO 2 oxidation. The decrease in the specific gravity by CO 2 oxidation was due to CO 2 gas that progressed from the surface to the interior. The pore shape after CO 2 oxidation differed from that under air oxidation.

Development of graphite/copper composites utilizing engineered interfaces. M.S. Thesis Final Report

NASA Technical Reports Server (NTRS)

Devincent, Sandra M.

1991-01-01

In situ measurements of graphite/copper alloy contact angles were made using the sessile drop method. The interfacial energy values obtained from these measurements were then applied to a model for the fiber matrix interfacial debonding phenomenon found in graphite/copper composites. The formation obtained from the sessile drop tests led to the development of a copper alloy that suitably wets graphite. Characterization of graphite/copper alloy interfaces subjected to elevated temperatures was conducted using Scanning Electron Microscopy, Energy Dispersive Spectroscopy, Auger Electron Spectroscopy, and X Ray Diffraction analyses. These analyses indicated that during sessile drop tests conducted at 1130 C for 1 hour, copper alloys containing greater than 0.98 at pct chromium form continuous reaction layers of approx. 10 microns in thickness. The reaction layers are adherent to the graphite surface. The copper wets the reaction layer to form a contact angle of 60 deg or less. X ray diffraction results indicate that the reaction layer is Cr3C2.

Ti-doped isotropic graphite: A promising armour material for plasma-facing components

NASA Astrophysics Data System (ADS)

García-Rosales, C.; López-Galilea, I.; Ordás, N.; Adelhelm, C.; Balden, M.; Pintsuk, G.; Grattarola, M.; Gualco, C.

2009-04-01

Finely dispersed Ti-doped isotropic graphites with 4 at.% Ti have been manufactured using synthetic mesophase pitch 'AR' as raw material. These new materials show a thermal conductivity at room temperature of ˜200 W/mK and flexural strength close to 100 MPa. Measurement of the total erosion yield by deuterium bombardment at ion energies and sample temperatures for which pure carbon shows maximum values, resulted in a reduction of at least a factor of 4, mainly due to dopant enrichment at the surface caused by preferential erosion of carbon. In addition, ITER relevant thermal shock loads were applied with an energetic electron beam at the JUDITH facility. The results demonstrated a significantly improved performance of Ti-doped graphite compared to pure graphite. Finally, Ti-doped graphite was successfully brazed to a CuCrZr block using a Mo interlayer. These results let assume that Ti-doped graphite can be a promising armour material for divertor plasma-facing components.

Roll-to-Roll Laser-Printed Graphene-Graphitic Carbon Electrodes for High-Performance Supercapacitors.

PubMed

Kang, Sangmin; Lim, Kyungmi; Park, Hyeokjun; Park, Jong Bo; Park, Seong Chae; Cho, Sung-Pyo; Kang, Kisuk; Hong, Byung Hee

2018-01-10

Carbon electrodes including graphene and thin graphite films have been utilized for various energy and sensor applications, where the patterning of electrodes is essentially included. Laser scribing in a DVD writer and inkjet printing were used to pattern the graphene-like materials, but the size and speed of fabrication has been limited for practical applications. In this work, we devise a simple strategy to use conventional laser-printer toner materials as precursors for graphitic carbon electrodes. The toner was laser-printed on metal foils, followed by thermal annealing in hydrogen environment, finally resulting in the patterned thin graphitic carbon or graphene electrodes for supercapacitors. The electrochemical cells made of the graphene-graphitic carbon electrodes show remarkably higher energy and power performance compared to conventional supercapacitors. Furthermore, considering the simplicity and scalability of roll-to-roll (R2R) electrode patterning processes, the proposed method would enable cheaper and larger-scale synthesis and patterning of graphene-graphitic carbon electrodes for various energy applications in the future.

Use of Kelvin probe force microscopy for identification of CVD grown graphene flakes on copper foil

NASA Astrophysics Data System (ADS)

Kumar, Rakesh; Mehta, B. R.; Kanjilal, D.

2017-05-01

Graphene flakes have been grown by chemical vapour deposition (CVD) method on Cu foils. The obtained graphene flakes have been characterized by optical microscopy, field emission scanning electron microscopy, Kelvin probe force microscopy (KPFM) and Raman spectroscopy. The graphene flakes grown on Cu foil comprise mainly single layer graphene and confirm that the nucleation for graphene growth starts very quickly. Moreover, KPFM has been found to be a valuable technique to differentiate between covered and uncovered portion of Cu foil by graphene flakes deposited for shorter duration. The results show that KPFM can be a very useful technique in understanding the mechanism of graphene growth.

Fracture mechanisms in multilayer phosphorene assemblies: from brittle to ductile.

PubMed

Liu, Ning; Hong, Jiawang; Zeng, Xiaowei; Pidaparti, Ramana; Wang, Xianqiao

2017-05-24

The outstanding mechanical performance of nacre has stimulated numerous studies on the design of artificial nacres. Phosphorene, a new two-dimensional (2D) material, has a crystalline in-plane structure and non-bonded interaction between adjacent flakes. Therefore, multi-layer phosphorene assemblies (MLPs), in which phosphorene flakes are piled up in a staggered manner, may exhibit outstanding mechanical performance, especially exceptional toughness. Therefore, molecular dynamics simulations are performed to study the dependence of the mechanical properties on the overlap distance between adjacent phosphorene layers and the number of phosphorene flakes per layer. The results indicate that when the flake number is equal to 1, a transition of fracture patterns is observed by increasing the overlap distance, from a ductile failure controlled by interfacial friction to a brittle failure dominated by the breakage of covalent bonds inside phosphorene flakes. Moreover, the failure pattern can be tuned by changing the number of flakes in each phosphorene layer. The results imply that the ultimate strength follows a power law with the exponent -0.5 in terms of the flake number, which is in good agreement with our analytical model. Furthermore, the flake number in each phosphorene layer is optimized as 2 when the temperature is 1 K in order to potentially achieve both high toughness and strength. Moreover, our results regarding the relations between mechanical performance and overlap distance can be explained well using a shear-lag model. However, it should be pointed out that increasing the temperature of MLPs could cause the transition of fracture patterns from ductile to brittle. Therefore, the optimal flake number depends heavily on temperature to achieve both its outstanding strength and toughness. Overall, our findings unveil the fundamental mechanism at the nanoscale for MLPs as well as provide a method to design phosphorene-based structures with targeted properties via tunable overlap distance and flake number in phosphorene layers.

Computational investigation of spin-polarization in cobalt/graphite superlattices

NASA Astrophysics Data System (ADS)

Goto, Kim F.; Hill, Nicola A.; Sanvito, Stefano

2003-03-01

We present results of a computational investigation of the magnetic properties of cobalt/ graphite superlattices. This work was motivated by experimental data showing spin injection into carbon nanotubes via cobalt contacts [1] as well as the discovery of a magnetic meteorite made from graphite and magnetic particles, in which part of the magnetization is on the carbon atoms [2]. Using density functional theory within the local spin-density approximation (the SIESTA implementation), we show that cobalt induces both n-doping and a magnetic moment in the graphite layers adjacent to the cobalt-carbon interface. We also show that the magnetic properties are strongly affected by the orientation of the graphite. Finally, implications for spin injection and spin-polarized transport are discussed. [1] K. Tsukagoshi, B.W. Alphenaar, and H. Ago, Nature (London) 401, 572 (1999) [2] J.M.D. Coey, M. Venkatesan, C.B. Fitzgerald, A.P. Douvalis and I.S. Sanders, Nature (London) 420, 156 (2002)

Shape and edge dependent electronic and magnetic properties of silicene nano-flakes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohan, Brij, E-mail: brijmohanhpu@yahoo.com; Pooja,; Ahluwalia, P. K.

2015-06-24

We performed first-principle study of the geometric, electronic and magnetic properties of arm-chair and zigzag edge silicene nano-flakes of triangular and hexagonal shapes. Electronic properties of silicene nano-flakes show strong dependence on their edge structure and shape. The considered nanostructures shows energy gap ranging ∼ 0.4 – 1.0 eV. Zigzag edged triangular nano-flake is magnetic and semiconducting in nature with 4.0 µ{sub B} magnetic moment and ∼ 0.4 eV energy gap.

Wild monkeys flake stone tools.

PubMed

Proffitt, Tomos; Luncz, Lydia V; Falótico, Tiago; Ottoni, Eduardo B; de la Torre, Ignacio; Haslam, Michael

2016-11-03

Our understanding of the emergence of technology shapes how we view the origins of humanity. Sharp-edged stone flakes, struck from larger cores, are the primary evidence for the earliest stone technology. Here we show that wild bearded capuchin monkeys (Sapajus libidinosus) in Brazil deliberately break stones, unintentionally producing recurrent, conchoidally fractured, sharp-edged flakes and cores that have the characteristics and morphology of intentionally produced hominin tools. The production of archaeologically visible cores and flakes is therefore no longer unique to the human lineage, providing a comparative perspective on the emergence of lithic technology. This discovery adds an additional dimension to interpretations of the human Palaeolithic record, the possible function of early stone tools, and the cognitive requirements for the emergence of stone flaking.

Significantly enhanced high-frequency permeability for composites with amorphous-membrane-fillers prepared using an infiltration method

NASA Astrophysics Data System (ADS)

Li, Z. W.; Yang, Z. H.

2016-03-01

Amorphous-membrane-filler composites have been fabricated using an infiltration method. The composites are able to significantly increase the permeability by 200%, as compared to general amorphous flake composites. SEM and magnetic measurement show that the amorphous flakes in membrane are in-plane arrangement. A model, which considers the effect of flake arrangement on demagnetizing factor Nd and permeability, is proposed. The effect of the arrangement of flakes is equivalent to an effective Nd, which is equal to 1/3 and zero for random and complete in-plane arrangements, respectively. Due to in-plane arrangement of amorphous flakes, the decreased Nd leads to significantly enhanced permeability for the amorphous-membrane-filler composites, based on the Maxwell-Garret mixing law.

Effects of eddy current and dispersion of magnetic anisotropy on the high-frequency permeability of Fe-based nanocomposites

NASA Astrophysics Data System (ADS)

Han, M.; Rozanov, K. N.; Zezyulina, P. A.; Wu, Yan-Hui

2015-06-01

Fe-Cu-Nb-Si-B microflakes have been prepared by ball milling. The structural, magnetostatic and microwave permeability of the flakes and flake-filled composites have been studied. Two ferromagnetic phases, nanograins and amorphous matrix, are found in the flakes. The Mössbauer study shows that the nanograins are α-Fe3(Si) with D03 superlattice structure. High resolution transmission electron microscopy shows that the nanograins are well dispersed in the matrix. The microwave permeability of composites containing the flakes has been measured. The comparison of the intrinsic permeability of the flakes obtained from the permeability measurements and from the anisotropy field distribution reveals a disagreement in the magnetic loss peak location. It is concluded that the low-frequency loss in the composites is not due to the effect of eddy currents. The low-frequency loss may be attributed to other sources, such as domain wall motion or peculiarities of the magnetic structure of the flakes in the composite.

Physicochemical properties of flakes made from three varieties of banana

NASA Astrophysics Data System (ADS)

Ratnawati, Lia; Afifah, Nok

2017-11-01

Ripe and unripe banana flour from three varieties of banana (Kepok, Raja and Ambon) were used to make a flake. This study aims to determine the physicochemical properties of flakes made from three types of banana varieties. The moisture, ash, protein, fat and carbohydrate content of flakes ranged from 1.01 to 4.40%, 2.40 to 2.99%, 7.38 to 9.19%, 4.71 to 8.32 % and 77.78 to 82.65%, respectively. WAI, WSI and TDF values of flakes ranged from 1.81 to 2.11 g/g, 34.54 to 52.64% and 8.64 to 10.04%, respectively. Values of hardness and fracturability were ranging from 346.65 to 563.50 g and 15.16 to 17.62 mm. The colour parameter values are lightness (L*), redness (a*) and yellowness (b*) of flakes ranged from 42.56 to 55.82, 3.34 to 6.60 and 3.99 to 13.09, respectively.

Selective colors reflection from stratified aragonite calcium carbonate plates of mollusk shells.

PubMed

Lertvachirapaiboon, Chutiparn; Parnklang, Tewarak; Pienpinijtham, Prompong; Wongravee, Kanet; Thammacharoen, Chuchaat; Ekgasit, Sanong

2015-08-01

An interaction between the incident light and the structural architecture within the shell of Asian green mussel (Perna viridis) induces observable pearlescent colors. In this paper, we investigate the influence of the structural architecture on the expressed colors. After a removal of the organic binder, small flakes from crushed shells show vivid rainbow reflection under an optical microscope. An individual flake expresses vivid color under a bright-field illumination while become transparent under a dark-field illumination. The expressed colors of the aragonite flakes are directly associated with its structural architecture. The flakes with aragonite thickness of 256, 310, and 353 nm, respectively, appear blue, green, and red under an optical microscope. The spectral simulation corroborates the experimentally observed optical effects as the flakes with thicker aragonite layers selectively reflected color with longer wavelengths. Flakes with multiple aragonite thicknesses expressed multi-color as the upper aragonite layers allow reflected colors from the lower layers to be observed. Copyright © 2015 Elsevier Inc. All rights reserved.

Adhesive force between graphene nanoscale flakes and living biological cells.

PubMed

Al Faouri, Radwan; Henry, Ralph; Biris, Alexandru S; Sleezer, Rob; Salamo, Gregory J

2017-11-01

We report on a measurement technique that quantifies the adhesive force between multi-layers of graphene flakes and the cell wall of live Escherichia coli cells using atomic force microscopy (AFM) in-fluid Peak Force- Quantitative Nanomechanical Mapping mode. To measure the adhesive force, we made use of the negative charge of E. coli cells to allow them to stick to positively charged surfaces, such as glass or silicon, that were covered by poly-L-Lysine. With this approach, cells were held in place for AFM characterization. Both pristine graphene (PG) flakes and functionalized graphene (FG) flakes were put on the E. coli cells and measurements of lateral size, flake thickness, and adhesion were made. Using this approach, the measured values of the adhesive force between multi-layers of graphene flakes (total thickness of 50 nm) and E. coli was determined to be equal or greater than 431 ± 65pN for (PG) and 694 ± 98pN for the (FG). More interestingly, the adhesive force of a graphene flake (thickness 1.3 nm) with the cell is determined to be equal or greater than 38.2 ± 16.4pN for the (PG) and 34.8 ± 15.3pN for the (FG). These interaction values can play an important role in determining and understanding the possible toxicity of graphene flakes. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Textured Nd2Fe14B flakes with enhanced coercivity

NASA Astrophysics Data System (ADS)

Cui, B. Z.; Zheng, L. Y.; Marinescu, M.; Liu, J. F.; Hadjipanayis, G. C.

2012-04-01

Morphology, structure, and magnetic properties of the [001] textured Nd2Fe14B nanocrystalline flakes prepared by surfactant-assisted high energy ball milling (HEBM) and subsequent annealing were studied. These flakes have a thickness of 80-200 nm, a length of 0.5-10 μm, and an average grain size of 10-14 nm. The addition of some amount of Dy, Nd70Cu30 alloy, and an appropriate post annealing increased the coercivity iHc of the Nd2Fe14B flakes. iHc was 3.7, 4.3, and 5.7 kOe for the Nd15.5Fe78.5B6, Nd14Dy1.5Fe78.5B6 and 83.3 wt.% Nd14Dy1.5Fe78.5B6 + 16.7 wt.% Nd70Cu30 flakes prepared by HEBM for 5 h in heptane with 20 wt.% oleylamine, respectively. After annealing at 450 °C for 0.5 h, their iHc increased to 5.1, 6.2, and 7.0 kOe, respectively. Anisotropic magnetic behavior was found in all of the as-milled and annealed flakes. Both, the thickening of Nd-rich phase at grain boundaries via diffusion of Nd70Cu30 and the surface modification of the Nd2Fe14B flake could be the main reasons for the coercivity enhancement in the as-milled and annealed Nd70Cu30-added Nd2Fe14B flakes.

Iron deposition as acidic groundwater encounters carbonates in the alluvium of Pinal Creek, Arizona, U.S.A.

USGS Publications Warehouse

Lind, Carol J.; Oscarson, R.L.

1997-01-01

In a column experiment, acidic groundwater from Pinal Creek Arizona, a Cu mining area, was eluted through a composited alluvial sample obtained from a core that had been removed from a well downgradient of the acidic groundwater. The minerals present in typical grains and flakes in the alluvium before and after the elution were determined by X-ray diffraction (XRD), scanning electron microscopy, and energy dispersive multichannel analyses (EDX). The concentrations of Fe, Ti, Mn, Si, Al, Na, Ca, K, Mg and S in these grains and flakes and in their microcrystalline surface coatings were measured by EDX. In addition to magnetite, hematite, and Fe-Ti oxides, Fe was most concentrated in micas (especially biotite-like flakes) and in the microcrystalline coatings. The measured elements in these microcrystalline coatings were primarily K, Fe, Al, and Si. The microcrystalline coatings on the mica flakes also contained Mg. The approximate 1:3 Mg:Si atomic ratios (ARs) of the biotite-like flakes both before and after the elution would suggest that the Fe deposited during the elution had not substituted for Mg in these flakes. As a result of the elution, assuming no loss of Si, the averaged recorded Fe:Si AR of the microcrystalline coatings increased from (0,46 to 0.58):3.00. Iron deposition on the typical grains and flakes may relate to the presence of Fe in the particle on which it is deposited or to the presence of Fe in the microcrystalline surface coatings before elution. The data here are not sufficient for a statistical evaluation, but elution caused the following trends: (1) The Fe:Si A R increased in the (K,Fe,Al,Si)-microcrystalline surface coatings; (2) For the mica flakes, there was more than a 2-fold increase in the Fe:Si AR for the microcrystalline surface coatings of the Fe-rich biotite-like flakes but no measurable increase of the Fe:Si AR for the microcrystalline surface coatings of the muscovite-like flakes that contained 3-5 times less Fe; (3) Also for the biotite-like flakes, the increase in Fe:Si AR was greater in the flakes that had a higher Fe:Si AR; (4) The Fe deposition on the Fe-rich microcrystalline surface coatings of the feldspar was much greater than on the Fe-poor, beige quartz and feldspar grains that, prior to elution, had only CaSO4 microcrystalline coatings; and (5) No Fe was deposited on Fe-poor grains with no microcrystalline surface coating.

40 CFR 417.60 - Applicability; description of the manufacture of soap flakes and powders subcategory.

Code of Federal Regulations, 2014 CFR

2014-07-01

... manufacture of soap flakes and powders subcategory. 417.60 Section 417.60 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS SOAP AND DETERGENT MANUFACTURING POINT SOURCE CATEGORY Manufacture of Soap Flakes and Powders Subcategory § 417.60 Applicability...

40 CFR 417.60 - Applicability; description of the manufacture of soap flakes and powders subcategory.

Code of Federal Regulations, 2012 CFR

2012-07-01

... manufacture of soap flakes and powders subcategory. 417.60 Section 417.60 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS SOAP AND DETERGENT MANUFACTURING POINT SOURCE CATEGORY Manufacture of Soap Flakes and Powders Subcategory § 417.60 Applicability...

40 CFR 417.60 - Applicability; description of the manufacture of soap flakes and powders subcategory.

Code of Federal Regulations, 2013 CFR

2013-07-01

... manufacture of soap flakes and powders subcategory. 417.60 Section 417.60 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS SOAP AND DETERGENT MANUFACTURING POINT SOURCE CATEGORY Manufacture of Soap Flakes and Powders Subcategory § 417.60 Applicability...

Inclusion of various amounts of steam-flaked soybeans in lactating dairy cattle diets

USDA-ARS?s Scientific Manuscript database

While most soybean feedstuffs have been extensively investigated for use in ruminant diets, there is a lack of information regarding steam-flaked soybeans. This research evaluated various inclusion rates of steam-flaked soybeans (SFSB) in lactating dairy cattle diets. Twelve multiparous Holstein cow...

Method for making precisely configured flakes useful in optical devices

DOEpatents

Trajkovska-Petkoska, Anka [Rochester, NY; Jacobs, Stephen D [Pittsford, NY; Kosc, Tanya Z [Rochester, NY; Marshall, Kenneth L [Rochester, NY

2007-07-03

Precisely configured, especially of geometric shape, flakes of liquid crystal material are made using a mechanically flexible polymer mold with wells having shapes which are precisely configured by making the mold with a photolithographically manufactured or laser printed master. The polymer liquid crystal is poured into the wells in the flexible mold. When the liquid crystal material has solidified, the flexible mold is bent and the flakes are released and collected for use in making an electrooptical cell utilizing the liquid crystal flakes as the active element therein.

Two-step fabrication of single-layer rectangular SnSe flakes

NASA Astrophysics Data System (ADS)

Jiang, Jizhou; Wong, Calvin Pei Yu; Zou, Jing; Li, Shisheng; Wang, Qixing; Chen, Jianyi; Qi, Dianyu; Wang, Hongyu; Eda, Goki; Chua, Daniel H. C.; Shi, Yumeng; Zhang, Wenjing; Thye Shen Wee, Andrew

2017-06-01

Recent findings about ultrahigh thermoelectric performances in SnSe single crystals have stimulated research on this binary semiconductor material. Furthermore, single-layer SnSe is an interesting analogue of phosphorene, with potential applications in two-dimensional (2D) nanoelectronics. Although significant advances in the synthesis of SnSe nanocrystals have been made, fabrication of well-defined large-sized single-layer SnSe flakes in a facile way still remains a challenge. The growth of single-layer rectangular SnSe flakes with a thickness of ~6.8 Å and lateral dimensions of about 30 µm  ×  50 µm is demonstrated by a two-step synthesis method, where bulk rectangular SnSe flakes were synthesized first by a vapor transport deposition method followed by a nitrogen etching technique to fabricate single-layer rectangular SnSe flakes in an atmospheric pressure system. The as-obtained rectangular SnSe flakes exhibited a pure crystalline phase oriented along the a-axis direction. Field-effect transistor devices fabricated on individual single-layer rectangular SnSe flakes using gold electrodes exhibited p-doped ambipolar behavior and a hole mobility of about 0.16 cm2 V-1 s-1. This two-step fabrication method can be helpful for growing other similar 2D large-sized single-layer materials.

The shaping-lathe headrig-- key to utilization of hardwoods growing on southern pine sites

Treesearch

P. Koch

1974-01-01

For every cubic foot of pine on southern pine sites, there is about 0.8 cubic foot of hardwood. The shaping-lathe headrig, now in the final stages of commercialization, is a key to utilizing these small mixed hardwoods for pallets and industrial lumber. Lathe residues in the form of flakes can be the raw material for a new major industry manufacturing exterior...

Ultrafast transformation of graphite to diamond: an ab initio study of graphite under shock compression.

PubMed

Mundy, Christopher J; Curioni, Alessandro; Goldman, Nir; Will Kuo, I-F; Reed, Evan J; Fried, Laurence E; Ianuzzi, Marcella

2008-05-14

We report herein ab initio molecular dynamics simulations of graphite under shock compression in conjunction with the multiscale shock technique. Our simulations reveal that a novel short-lived layered diamond intermediate is formed within a few hundred of femtoseconds upon shock loading at a shock velocity of 12 kms (longitudinal stress>130 GPa), followed by formation of cubic diamond. The layered diamond state differs from the experimentally observed hexagonal diamond intermediate found at lower pressures and previous hydrostatic calculations in that a rapid buckling of the graphitic planes produces a mixture of hexagonal and cubic diamond (layered diamond). Direct calculation of the x-ray absorption spectra in our simulations reveals that the electronic structure of the final state closely resembles that of compressed cubic diamond.

Conductive polymer binder for nano-silicon/graphite composite electrode in lithium-ion batteries towards a practical application

DOE PAGES

Zhao, Hui; Du, Allen; Ling, Min; ...

2016-05-10

The state-of-the-art graphite anode containing a small portion of silicon represents a promising way of applying high-capacity alloy anode in the next generation high energy density lithium-ion batteries. The conductive polymeric binders developed for Si anodes proved to be an effective binder for this graphite/nanoSi composite electrode. Without any acetylene black conductive additives in the electrode, a high areal capacity of above 2.5 mAh/cm 2 is achieved during long-term cycling over 100 cycles. Finally, this conductive polymer-enabled graphite/nanoSi composite electrode exhibits high specific capacity and high 1 st cycle efficiency, which is a significant progress toward commercial application of Simore » anodes.« less

Textured Nd2Fe14B flakes with enhanced coercivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cui, BZ; Zheng, LY; Marinescu, M

2012-04-01

Morphology, structure, and magnetic properties of the [001] textured Nd2Fe14B nanocrystalline flakes prepared by surfactant-assisted high energy ball milling (HEBM) and subsequent annealing were studied. These flakes have a thickness of 80-200 nm, a length of 0.5-10 mu m, and an average grain size of 10-14nm. The addition of some amount of Dy, Nd70Cu30 alloy, and an appropriate post annealing increased the coercivity H-i(c) of the Nd2Fe14B flakes. iHc was 3.7, 4.3, and 5.7 kOe for the Nd15.5Fe78.5B6, Nd14Dy1.5Fe78.5B6 and 83.3wt.% Nd14Dy1.5Fe78.5B6+16.7 wt.% Nd70Cu30 flakes prepared by HEBM for 5 h in heptane with 20 wt.% oleylamine, respectively. After annealingmore » at 450 degrees C for 0.5h, their iHc increased to 5.1, 6.2, and 7.0 kOe, respectively. Anisotropic magnetic behavior was found in all of the as-milled and annealed flakes. Both, the thickening of Nd-rich phase at grain boundaries via diffusion of Nd70Cu30 and the surface modification of the Nd2Fe14B flake could be the main reasons for the coercivity enhancement in the as-milled and annealed Nd70Cu30-added Nd2Fe14B flakes. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3679425]« less

Optical devices having flakes suspended in a host fluid to provide a flake/fluid system providing flakes with angularly dependent optical properties in response to an alternating current electric field due to the dielectric properties of the system

DOEpatents

Kosc, Tanya Z [Rochester, NY; Marshall, Kenneth L [Rochester, NY; Jacobs, Stephen D [Pittsford, NY

2006-05-09

Optical devices utilizing flakes (also called platelets) suspended in a host fluid have optical characteristics, such as reflective properties, which are angular dependent in response to an AC field. The reflectivity may be Bragg-like, and the characteristics are obtained through the use of flakes of liquid crystal material, such as polymer liquid crystal (PLC) materials including polymer cholesteric liquid crystal (PCLC) and polymer nematic liquid crystal (PNLC) material or birefringent polymers (BP). The host fluid may be propylene carbonate, poly(ethylene glycol) or other fluids or fluid mixtures having fluid conductivity to support conductivity in the flake/host system. AC field dependent rotation of 90.degree. can be obtained at rates and field intensities dependent upon the frequency and magnitude of the AC field. The devices are useful in providing displays, polarizers, filters, spatial light modulators and wherever switchable polarizing, reflecting, and transmission properties are desired.

Effects of processing parameters on the inactivation of Bacillus cereus spores on red pepper (Capsicum annum L.) flakes by microwave-combined cold plasma treatment.

PubMed

Kim, Jung Eun; Choi, Hyeon-Son; Lee, Dong-Un; Min, Sea C

2017-12-18

The efficacy of microwave-combined cold plasma treatment (MCPT) for inactivating Bacillus cereus spores contaminating red pepper (Capsicum annum L.) flakes was investigated. The effects of red pepper drying method, particle size, and water activity (a w ) were also evaluated at two levels of microwave power (1700 and 2500W/cm 2 ). The inactivation effect of MCPT was higher at higher microwave power. Spore reduction was more effective with vacuum-dried red pepper than far-infrared-dried flakes. A significantly higher level of spore reduction was observed with the red pepper sample with a smaller surface to volume ratio when one surface (exterior surface) was inoculated (p<0.05). Spore reduction by MCPT at high microwave power increased from 1.7 to 2.6logspores/cm 2 when the a w of flake increased from 0.4 to 0.9 (p<0.05). MCPT did not change the color of red pepper flakes. MCPT demonstrated potential as a microbial decontaminating technology for red pepper flakes. Copyright © 2017 Elsevier B.V. All rights reserved.

Molecularly Imprinted Polymers Chitosan-Glutaraldehyde for Monosodium Glutamate

NASA Astrophysics Data System (ADS)

Mulyasuryani, Ani; Haryanto, Edi; Sulistyarti, Hermin; Rumhayati, Barlah

2018-01-01

Chitosan has been used as a functional monomer in the synthesis of molecularly imprinted polymers (MIP) for monosodium glutamate (MSG). MIP is made from a mixture of 5 g chitosan, 50 mg glutaraldehyde and 2 g MSG, MIP is formed as flakes and beads. MIPs are identified by the FTIR spectrum, SEM image and their adsorption capabilities. MIP flakes and beads have no structural differences if they are based on FTIR or SEM spectra, but MIP adsorption capacity of beads higher than flakes. Adsorption capacity of MIP flakes is 548 mg/g and MIP beads 627 mg/g.

Temperature Dependence of Wavelength Selectable Zero-Phonon Emission from Single Defects in Hexagonal Boron Nitride.

PubMed

Jungwirth, Nicholas R; Calderon, Brian; Ji, Yanxin; Spencer, Michael G; Flatté, Michael E; Fuchs, Gregory D

2016-10-12

We investigate the distribution and temperature-dependent optical properties of sharp, zero-phonon emission from defect-based single photon sources in multilayer hexagonal boron nitride (h-BN) flakes. We observe sharp emission lines from optically active defects distributed across an energy range that exceeds 500 meV. Spectrally resolved photon-correlation measurements verify single photon emission, even when multiple emission lines are simultaneously excited within the same h-BN flake. We also present a detailed study of the temperature-dependent line width, spectral energy shift, and intensity for two different zero-phonon lines centered at 575 and 682 nm, which reveals a nearly identical temperature dependence despite a large difference in transition energy. Our temperature-dependent results are well described by a lattice vibration model that considers piezoelectric coupling to in-plane phonons. Finally, polarization spectroscopy measurements suggest that whereas the 575 nm emission line is directly excited by 532 nm excitation, the 682 nm line is excited indirectly.

First-principles study of a MXene terahertz detector.

PubMed

Jhon, Y I; Seo, M; Jhon, Y M

2017-12-21

2D transition metal carbides, nitrides, and carbonitrides called MXenes have attracted increasing attention due to their outstanding properties in many fields. By performing systematic density functional theory calculations, here we show that MXenes can serve as excellent terahertz detecting materials. Giant optical absorption and extinction coefficients are observed in the terahertz range in the most popular MXene, namely, Ti 3 C 2 , which is regardless of the stacking degree. Various other optical properties have been investigated as well in the terahertz range for in-depth understanding of its optical response. We find that the thermoelectric figure of merit (ZT) of stacked Ti 3 C 2 flakes is comparable to that of carbon nanotube films. Based on excellent terahertz absorption and decent thermoelectric efficiency in MXenes, we finally suggest the promise of MXenes in terahertz detection applications, which includes terahertz bolometers and photothermoelectric detectors. Possible ZT improvements are discussed in large-scale MXene flake films and/or MXene-polymer composite films.

Defect-selective dry etching for quick and easy probing of hexagonal boron nitride domains.

PubMed

Wu, Qinke; Lee, Joohyun; Park, Sangwoo; Woo, Hwi Je; Lee, Sungjoo; Song, Young Jae

2018-03-23

In this study, we demonstrate a new method to selectively etch the point defects or the boundaries of as-grown hexagonal boron nitride (hBN) films and flakes in situ on copper substrates using hydrogen and argon gases. The initial quality of the chemical vapor deposition-grown hBN films and flakes was confirmed by UV-vis absorption spectroscopy, atomic force microscopy, and transmission electron microscopy. Different gas flow ratios of Ar/H 2 were then employed to etch the same quality of samples and it was found that etching with hydrogen starts from the point defects and grows epitaxially, which helps in confirming crystalline orientations. However, etching with argon is sensitive to line defects (boundaries) and helps in visualizing the domain size. Finally, based on this defect-selective dry etching technique, it could be visualized that the domains of a polycrystalline hBN monolayer merged together with many parts, even with those that grew from a single nucleation seed.

Defect-selective dry etching for quick and easy probing of hexagonal boron nitride domains

NASA Astrophysics Data System (ADS)

Wu, Qinke; Lee, Joohyun; Park, Sangwoo; Woo, Hwi Je; Lee, Sungjoo; Song, Young Jae

2018-03-01

In this study, we demonstrate a new method to selectively etch the point defects or the boundaries of as-grown hexagonal boron nitride (hBN) films and flakes in situ on copper substrates using hydrogen and argon gases. The initial quality of the chemical vapor deposition-grown hBN films and flakes was confirmed by UV-vis absorption spectroscopy, atomic force microscopy, and transmission electron microscopy. Different gas flow ratios of Ar/H2 were then employed to etch the same quality of samples and it was found that etching with hydrogen starts from the point defects and grows epitaxially, which helps in confirming crystalline orientations. However, etching with argon is sensitive to line defects (boundaries) and helps in visualizing the domain size. Finally, based on this defect-selective dry etching technique, it could be visualized that the domains of a polycrystalline hBN monolayer merged together with many parts, even with those that grew from a single nucleation seed.

Quality of Graphite Target for Biological/Biomedical/Environmental Applications of 14C-Accelerator Mass Spectrometry

PubMed Central

2010-01-01

Catalytic graphitization for 14C-accelerator mass spectrometry (14C-AMS) produced various forms of elemental carbon. Our high-throughput Zn reduction method (C/Fe = 1:5, 500 °C, 3 h) produced the AMS target of graphite-coated iron powder (GCIP), a mix of nongraphitic carbon and Fe3C. Crystallinity of the AMS targets of GCIP (nongraphitic carbon) was increased to turbostratic carbon by raising the C/Fe ratio from 1:5 to 1:1 and the graphitization temperature from 500 to 585 °C. The AMS target of GCIP containing turbostratic carbon had a large isotopic fractionation and a low AMS ion current. The AMS target of GCIP containing turbostratic carbon also yielded less accurate/precise 14C-AMS measurements because of the lower graphitization yield and lower thermal conductivity that were caused by the higher C/Fe ratio of 1:1. On the other hand, the AMS target of GCIP containing nongraphitic carbon had higher graphitization yield and better thermal conductivity over the AMS target of GCIP containing turbostratic carbon due to optimal surface area provided by the iron powder. Finally, graphitization yield and thermal conductivity were stronger determinants (over graphite crystallinity) for accurate/precise/high-throughput biological, biomedical, and environmental14C-AMS applications such as absorption, distribution, metabolism, elimination (ADME), and physiologically based pharmacokinetics (PBPK) of nutrients, drugs, phytochemicals, and environmental chemicals. PMID:20163100

Adsorption of charged albumin subdomains on a graphite surface.

PubMed

Raffaini, Giuseppina; Ganazzoli, Fabio

2006-03-01

We report some new molecular dynamics simulation results about the adsorption on a hydrophobic graphite surface of two albumin subdomains, each formed by three different alpha-helices, considering the correctly charged side groups at pH = 7 instead of the neutral ones as done in our previous exploratory paper (Raffaini and Ganazzoli, Langmuir 2003;19:3403-3412). We find that the presence of charges affects somewhat the initial adsorption stage on the electrostatically neutral surface, but not the final one. Thus, we recover the result that a monolayer of aminoacids is eventually formed, with a rough parallelism of distant strands to optimize both the intramolecular and the surface interactions. This feature is consistent with the adsorption on the hydrophobic surface being driven by dispersion forces only, and with the "soft" nature of albumin. Additional optimizations of the final monolayer carried out at pH = 3 and 11 do not modify appreciably this picture, suggesting that adsorption on graphite is basically independent of pH. The enhanced hydration of the final adsorption state due to the (delocalized) charges of the side groups is also discussed in comparison with similar results of the neutralized subdomains. (c) 2005 Wiley Periodicals, Inc.

Flake storage effects on properties of laboratory-made flakeboards

Treesearch

C. G. Carll

1998-01-01

Aspen (Populus gradidentata) and loblolly pine (Pinus taeda) flakes were prepared with tangential-grain and radial-grain faces on a laboratory disk flaker. These were gently dried in a steam-heated rotary drum dryer. Approximately 1 week after drying, surface wettability was measured on a large sample of flakes using an aqueous dye solution. Three replicate boards of...

Flake Orientation Effects On Physical and Mechanical Properties of Sweetgum Flakeboard

Treesearch

T.F. Shupe; Chung-Yun Hse; E.W. Price

2001-01-01

Research was initiated to determine the effect of flake orientation on the physical and mechanical properties offlakeboard. The panel fabrication techniques investigated were single-layer panels with random and oriented flake distribution, three-layer, five-layer, and seven-layer panels. Single-layer oriented panels had panel directional property ratios of 11.8 and 12....

BSM Delta Qualification 2, volume 3, book 2

NASA Technical Reports Server (NTRS)

1994-01-01

This report, presented in three volumes, provides the results of a two-motor Delta Qualification 2 program conducted in 1993 to certify the following enhancements for incorporation into booster separation motor (BSM0 flight hardware: vulcanized-in-place nozzle aft closure insulation; new iso-static ATJ bulk graphite throat insert material, adhesive EA9394 for bonding the nozzle throat, igniter grain rod/centering insert/igniter case; deletion of the igniter adapter insulator ring; deletion of the igniter adapter/igniter case interface RTV; and deletion of loctite from igniter retainer plate threads. The enhancements above directly resulted from (1) the BSM total quality management (TQM) team initiatives to enhance the BSM producibility, and (2) the necessity to qualify new throat insert and adhesive systems to replace existing materials that will not be available. Testing was completed at both the component and motor levels. Component testing was accomplished to screen candidate materials (e.g., throat materials, adhesive systems) and to optimize processes (e.g., aft closure insulator vulcanization approach) prior to their incorporation into the test motors. Motor testing--consisting of two motors, randomly selected by USBI's on-site quality personnel from production lot AAY, which were modified to accept the enhancements -- was completed to provide the final qualification of the enhancements for incorporation into flight hardware. Volume 3, Book 2 provides various supporting documentation to the previous volumes with regards to the testing of the two Delta qualification units: data acceptance records, thermal conditioning analysis, igniter adapter thermal flake analysis, laboratory adhesive (EA-9394) qualification report, throat insert thermal/structural analysis, Delta Qualification Nonconformance Reports (NCR's), O-ring seating tests, and interim test report for vulcanization process qualification.

Experimental Insights into the Cognitive Significance of Early Stone Tools

PubMed Central

Perston, Yinika

2016-01-01

Stone-flaking technology is the most enduring evidence for the evolving cognitive abilities of our early ancestors. Flake-making was mastered by African hominins ~3.3 ma, followed by the appearance of handaxes ~1.75 ma and complex stone reduction strategies by ~1.6 ma. Handaxes are stones flaked on two opposed faces (‘bifacially’), creating a robust, sharp-edged tool, and complex reduction strategies are reflected in strategic prior flaking to prepare or ‘predetermine’ the nature of a later flake removal that served as a tool blank. These technologies are interpreted as major milestones in hominin evolution that reflect the development of higher-order cognitive abilities, and the presence and nature of these technologies are used to track movements of early hominin species or ‘cultures’ in the archaeological record. However, the warranting argument that certain variations in stone tool morphologies are caused by differences in cognitive abilities relies on analogy with technical replications by skilled modern stoneworkers, and this raises the possibility that researchers are projecting modern approaches to technical problems onto our non-modern hominin ancestors. Here we present the results of novel experiments that randomise flake removal and disrupt the modern stoneworker’s inclination to use higher-order reasoning to guide the stone reduction process. Although our protocols prevented goal-directed replication of stone tool types, the experimental assemblage is morphologically standardised and includes handaxe-like ‘protobifaces’ and cores with apparently ‘predetermined’ flake removals. This shows that the geometrical constraints of fracture mechanics can give rise to what appear to be highly-designed stoneworking products and techniques when multiple flakes are removed randomly from a stone core. PMID:27392022

Factors affecting emulsion stability and quality of oil recovered from enzyme-assisted aqueous extraction of soybeans.

PubMed

Jung, S; Maurer, D; Johnson, L A

2009-11-01

The objectives of the present study were to assess how the stability of the emulsion recovered from aqueous extraction processing of soybeans was affected by characteristics of the starting material and extraction and demulsification conditions. Adding endopeptidase Protex 6L during enzyme-assisted aqueous extraction processing (EAEP) of extruded soybean flakes was vital to obtaining emulsions that were easily demulsified with enzymes. Adding salt (up to 1.5 mM NaCl or MgCl(2)) during extraction and storing extruded flakes before extraction at 4 and 30 degrees C for up to 3 months did not affect the stabilities of emulsions recovered from EAEP of soy flour, flakes and extruded flakes. After demulsification, highest free oil yield was obtained with EAEP of extruded flakes, followed by flour and then flakes. The same protease used for the extraction step was used to demulsify the EAEP cream emulsion from extruded full-fat soy flakes at concentrations ranging from 0.03% to 2.50% w/w, incubation times ranging from 2 to 90 min, and temperatures of 25, 50 or 65 degrees C. Highest free oil recoveries were achieved at high enzyme concentrations, mild temperatures, and short incubation times. Both the nature of enzyme (i.e., protease and phospholipase), added alone or as a cocktail, concentration of enzymes (0.5% vs. 2.5%) and incubation time (1 vs. 3 h), use during the extraction step, and nature of enzyme added for demulsifying affected free oil yield. The free oil recovered from EAEP of extruded flakes contained less phosphorus compared with conventional hexane-extracted oil. The present study identified conditions rendering the emulsion less stable, which is critical to increasing free oil yield recovered during EAEP of soybeans, an environmentally friendly alternative processing method to hexane extraction.

[Study of enzymes of xenobiotic metabolism in the evaluation of quality of protein-containing wheat germ flakes and wallpaper flour].

PubMed

Martinchuk, A N; E En Gyn; Safronova, A M; Peskova, E V

1991-01-01

Intake of wheat upholstery meal by growing rats was attended by a sharp decrease in the content and activity of xenobiotic metabolism enzymes in the hepatic microsomes, that was caused by the low biological value of the meal proteins. Hepatic microsomes of the rats that were fed with wheat germ flakes showed increased specific content of cytochromes P-450 and b5, but the total blood protein content per 100 g of body mass was lower than during casein consumption. No significant changes were detected in hydroxylation rate of benz(a)pyrene, aniline and ethylmorphine. During consumption of wheat germ flakes induction of UDP-glucuronide-transferase was detected in hepatic microsomes. Wheat germ flakes induced a 5-fold increase of Se-dependent glutathione peroxidase activity. Wheat germ flakes produced no significant effect on glutathione-S-aryltransferase and glutathione reductase activity.

Apparatus for producing thin flakes

DOEpatents

Bunnell, Sr., Lee R.

1991-01-01

Compositions in accordance with the invention comprise a polymer and flake reinforcing material distributed throughout the polymer in an effective amount to structurally reinforce the polymer. Individual flakes of the flake material a) are less than or equal to 1,000 Angstroms in thickness, b) have an aspect ratio greater than or equal to 100, and c) are preferably significantly randomly oriented throughout the polymer. A novel apparatus for shear grinding a platy solid material into such individual flakes comprises a cylindrical shearing drum and a shear grinder received therein. The shearing drum has a longitudinal axis and an internal surface formed about a first predetermined radius of curvature. The cylindrical drum is supported for rotation about its longitudinal axis. The shear grinder has an external surface formed about a second predetermined radius of curvature. The second radius of curvature is slightly less than the first radius of curvature.

Improvements in nanoscale zero-valent iron production by milling through the addition of alumina

NASA Astrophysics Data System (ADS)

Ribas, D.; Cernik, M.; Martí, V.; Benito, J. A.

2016-07-01

A new milling procedure for a cost-effective production of nanoscale zero-valent iron for environmental remediation is presented. Conventional ball milling of iron in an organic solvent as Mono Ethylene Glycol produces flattened iron particles that are unlikely to break even after very long milling times. With the aim of breaking down these iron flakes, in this new procedure, further milling is carried out by adding an amount of fine alumina powder to the previously milled solution. As the amount of added alumina increases from 9 to 54 g l-1, a progressive decrease of the presence of flakes is observed. In the latter case, the appearance of the particles formed by fragments of former flakes is rather homogeneous, with most of the final nanoparticles having an equivalent diameter well below 1 µm and with an average particle size in solution of around 400 nm. An additional increase of alumina content results in a highly viscous solution showing worse particle size distribution. Milled particles, in the case of alumina concentrations of 54 g l-1, have a fairly large specific surface area and high Fe(0) content. These new particles show a very good Cr(VI) removal efficiency compared with other commercial products available. This good reactivity is related to the absence of an oxide layer, the large amount of superficial irregularities generated by the repetitive fracture process during milling and the presence of a fine nanostructure within the iron nanoparticles.

Transformation of graphite by tectonic and hydrothermal processes in an active plate boundary fault zone, Alpine Fault, New Zealand

NASA Astrophysics Data System (ADS)

Kirilova, Matina; Toy, Virginia; Timms, Nicholas; Halfpenny, Angela; Menzies, Catriona; Craw, Dave; Rooney, Jeremy; Giorgetti, Carolina

2017-04-01

Graphite is a material with one of the lowest frictional strengths, with coefficient of friction of 0.1 and thus in natural fault zones it may act as a natural solid lubricant. Graphitization, or the transformation of organic matter (carbonaceous material, or CM) into crystalline graphite, is induced by compositional and structural changes during diagenesis and metamorphism. The supposed irreversible nature of this process has allowed the degree of graphite crystallinity to be calibrated as an indicator of the peak temperatures reached during progressive metamorphism. We examine processes of graphite emplacement and deformation in the Alpine Fault Zone, New Zealand's active continental tectonic plate boundary. Raman spectrometry indicates that graphite in the distal, amphibolite-facies Alpine Schist, which experienced peak metamorphic temperatures up to 640 ◦C, is highly crystalline and occurs mainly along grain boundaries within quartzo-feldspathic domains. The subsequent mylonitisation in the Alpine Fault Zone resulted in progressive reworking of CM under lower temperature conditions (500◦C-600◦C) in a structurally controlled environment, resulting in spatial clustering in lower-strain protomylonites, and further foliation-alignment in higher-strain mylonites. Subsequent brittle deformation of the mylonitised schists resulted in cataclasites that contain over three-fold increase in the abundance of graphite than mylonites. Furthermore, cataclasites contain graphite with two different habits: highly-crystalline, foliated forms that are inherited mylonitic graphite; and lower-crystallinity, less mature patches of finer-grained graphite. The observed graphite enrichment and the occurrence of poorly-organised graphite in the Alpine Fault cataclasites could result from: i) hydrothermal precipitation from carbon-supersaturated fluids; and/or ii) mechanical degradation by structural disordering of mylonitic graphite combined with strain-induced graphite localisation. The lack of published systematic studies of mechanical modification of the structure of graphite inhibits further conclusion to be drawn. Thus, we performed laboratory deformation experiments during which we sheared highly crystalline graphite powder at room temperature, normal stresses of 5 MPa and 25 MPa and sliding velocities of 1 µm/s, 10 µm/s and 100 µm/s. The degree of graphite crystallinity, both in the starting and resulting materials, was analysed by Raman microspectroscopy. Our results demonstrate consistent decrease of graphite crystallinity with increasing shear strain. We conclude that: i) graphite 'thermometers' are unreliable in brittely deformed rocks; ii) a shear strain calibration of graphite 'thermometers' is needed; iii) fault creep is very likely responsible for the observed structural and textural characteristics of graphite in the Alpine Fault cataclasites. Finally, to investigate the possibility of hydrothermal origin for at least some of the graphite in the Alpine Fault cataclasites we will also present synchrotron FTIR and carbon isotope analysis of the Alpine fault rocks.

Room-temperature solution-processed and metal oxide-free nano-composite for the flexible transparent bottom electrode of perovskite solar cells

NASA Astrophysics Data System (ADS)

Lu, Haifei; Sun, Jingsong; Zhang, Hong; Lu, Shunmian; Choy, Wallace C. H.

2016-03-01

The exploration of low-temperature and solution-processed charge transporting and collecting layers can promote the development of low-cost and large-scale perovskite solar cells (PVSCs) through an all solution process. Here, we propose a room-temperature solution-processed and metal oxide-free nano-composite composed of a silver nano-network and graphene oxide (GO) flawless film for the transparent bottom electrode of a PVSC. Our experimental results show that the amount of GO flakes play a critical role in forming the flawless anti-corrosive barrier in the silver nano-network through a self-assembly approach under ambient atmosphere, which can effectively prevent the penetration of liquid or gaseous halides and their corrosion against the silver nano-network underneath. Importantly, we simultaneously achieve good work function alignment and surface wetting properties for a practical bottom electrode by controlling the degree of reduction of GO flakes. Finally, flexible PVSC adopting the room-temperature and solution-processed nano-composite as the flexible transparent bottom electrode has been demonstrated on a polyethylene terephthalate (PET) substrate. As a consequence, the demonstration of our room-temperature solution-processed and metal oxide-free flexible transparent bottom electrode will contribute to the emerging large-area flexible PVSC technologies.The exploration of low-temperature and solution-processed charge transporting and collecting layers can promote the development of low-cost and large-scale perovskite solar cells (PVSCs) through an all solution process. Here, we propose a room-temperature solution-processed and metal oxide-free nano-composite composed of a silver nano-network and graphene oxide (GO) flawless film for the transparent bottom electrode of a PVSC. Our experimental results show that the amount of GO flakes play a critical role in forming the flawless anti-corrosive barrier in the silver nano-network through a self-assembly approach under ambient atmosphere, which can effectively prevent the penetration of liquid or gaseous halides and their corrosion against the silver nano-network underneath. Importantly, we simultaneously achieve good work function alignment and surface wetting properties for a practical bottom electrode by controlling the degree of reduction of GO flakes. Finally, flexible PVSC adopting the room-temperature and solution-processed nano-composite as the flexible transparent bottom electrode has been demonstrated on a polyethylene terephthalate (PET) substrate. As a consequence, the demonstration of our room-temperature solution-processed and metal oxide-free flexible transparent bottom electrode will contribute to the emerging large-area flexible PVSC technologies. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00011h

Area-wide application of verbenone-releasing flakes reduces mortality of whitebark pine Pinus albicaulis caused by the mountain pine beetle Dendroctonus ponderosae

Treesearch

Nancy E. Gillette; E. Matthew Hansen; Constance J. Mehmel; Sylvia R. Mori; Jeffrey N. Webster; Nadir Erbilgin; David L. Wood

2012-01-01

DISRUPT Micro-Flake Verbenone Bark Beetle Anti-Aggregant flakes (Hercon Environmental, Inc., Emigsville, Pennsylvania) were applied in two large-scale tests to assess their efficacy for protecting whitebark pine Pinus albicaulis Engelm. from attack by mountain pine beetle Dendroctonus ponderosae Hopkins (Coleoptera: Scolytinae) (MPB). At two locations, five...

Flakeboard properties as affected by flake cutting techniques

Treesearch

E.W. Price; Lehmann W.F.

1979-01-01

Flakeboards were prepared from flakes obtained from disk, drum, and ring flakers, and a shaping-lathe headrig. Species used were lodgepole pine,loblolly pine, sweetgum, southern red oak, and mockernut hickory at 1.25 compression ratio and two resin contents (5% and 8%). The three-layer panels had 25 percent of the largest flakes on each surface; all other material...

Verbenone-releasing flakes protect individual Pinus contorta trees from attack by Dendroctonus ponderosae and Dendroctonus valens (Coleoptera: Curculionidae, Scolytinae)

Treesearch

Nancy E. Gillette; John D. Stein; Donald R. Owen; Jeffrey N. Webster; Gary O. Fiddler; Sylvia R. Mori; David L. Wood

2006-01-01

In a study site in interior northern California, twenty individual lodgepole pines Pinus contorta were sprayed with a suspension of DISRUPT Micro-Flake ® Verbenone (4,6,6-trimethylbicyclo(3.1)hept-3-en-2-one) Bark Beetle Anti-Aggregant flakes (Hercon Environmental, Emigsville, Pennsylvania) in water, with sticker and...

A facile way to control phase of tin selenide flakes by chemical vapor deposition

NASA Astrophysics Data System (ADS)

Wang, Zhigang; Pang, Fei

2018-06-01

Although two-dimensional (2D) tin selenides are attracting intense attentions, studies on its phase transition are still relatively few. Here we report a facile way to control the phase growth of tin selenide flakes on mica and SiO2/Si by only adjusting nominal Sn:Se ratio, which refers to the amount of loaded SnO2 and Se precursors. High normal Sn:Se ratio induced SnSe flakes, conversely SnSe2 flakes formed. It could be used as a practical guide to selectively synthesize pure phase of single crystalline 2D layered chalcogenide materials similar to tin selenides.

Sputtering ultra-small Pt on nanographitic flakes deposited by electrophoresis for ethanol electro oxidation

NASA Astrophysics Data System (ADS)

Daryakenari, Ahmad Ahmadi; Daryakenari, Mohammad Ahmadi; Omidvar, Hamid

2018-01-01

To acquire highly efficient and cost-effective fuel cells, numerous research works have been carried out to the development low cost and excellent performance of electrocatalysts. In this paper, a solution-based electrophoretic deposition (EPD) technique for fabrication of Pt-based catalyst layers is studied. Nanographitic flake coatings used as catalyst support for sputtered platinium (Pt) were fabricated via the electrophoretic deposition (EPD) of dispersed nanographitic flakes in isopropyl alcohol. Magnesium nitrate hexahydrate (MNH) was used as an additive binder in the EPD process. Subsequently, the platinium particles were deposited by a direct sputtering on the fabricated nanographitic flake coatings.

RESEARCH AND DEVELOPMENT ON ADVANCED GRAPHITE MATERIALS. Final Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

1962-04-01

A review is given of activities over the period October 15, 1960 to October 15, 1961 on a three year program for the research and development of materials, experimental techniques, and equipment for development of premium quality, reproducible graphite-base materials suitable for missile and astronautic applications. Progress is reported on research and development in the study areas of raw materials, fabrication, and material characterization and evaluation. (auth)

Formation mechanism of the graphite-rich protective layer in blast furnace hearths

NASA Astrophysics Data System (ADS)

Jiao, Ke-xin; Zhang, Jian-liang; Liu, Zheng-jian; Liu, Feng; Liang, Li-sheng

2016-01-01

A long campaign life of blast furnaces is heavily linked to the existence of a protective layer in their hearths. In this work, we conducted dissection studies and investigated damage in blast furnace hearths to estimate the formation mechanism of the protective layer. The results illustrate that a significant amount of graphite phase was trapped within the hearth protective layer. Furthermore, on the basis of the thermodynamic and kinetic calculations of the graphite precipitation process, a precipitation potential index related to the formation of the graphite-rich protective layer was proposed to characterize the formation ability of this layer. We determined that, under normal operating conditions, the precipitation of graphite phase from hot metal was thermodynamically possible. Among elements that exist in hot metal, C, Si, and P favor graphite precipitation, whereas Mn and Cr inhibit this process. Moreover, at the same hot-face temperature, an increase of carbon concentration in hot metal can shorten the precipitation time. Finally, the results suggest that measures such as reducing the hot-face temperature and increasing the degree of carbon saturation in hot metal are critically important to improve the precipitation potential index.

Graphite Recycling from Spent Lithium-Ion Batteries.

PubMed

Rothermel, Sergej; Evertz, Marco; Kasnatscheew, Johannes; Qi, Xin; Grützke, Martin; Winter, Martin; Nowak, Sascha

2016-12-20

The present work reports on challenges in utilization of spent lithium-ion batteries (LIBs)-an increasingly important aspect associated with a significantly rising demand for electric vehicles (EVs). In this context, the feasibility of anode recycling in combination with three different electrolyte extraction concepts is investigated. The first method is based on a thermal treatment of graphite without electrolyte recovery. The second method additionally utilizes a subcritical carbon-dioxide (subcritical CO 2 )-assisted electrolyte extraction prior to thermal treatment. And the final investigated approach uses supercritical carbon dioxide (scCO 2 ) as extractant, subsequently followed by the thermal treatment. It is demonstrated that the best performance of recycled graphite anodes can be achieved when electrolyte extraction is performed using subcritical CO 2 . Comparative studies reveal that, in the best case, the electrochemical performance of recycled graphite exceeds the benchmark consisting of a newly synthesized graphite anode. As essential efforts towards electrolyte extraction and cathode recycling have been made in the past, the electrochemical behavior of recycled graphite, demonstrating the best performance, is investigated in combination with a recycled LiNi 1/3 Co 1/3 Mn 1/3 O 2 cathode. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of the RGO/Al2O3 core-shell nanocomposite flakes and characterization of their unique electrostatic properties using zeta potential measurements

NASA Astrophysics Data System (ADS)

Jastrzębska, A. M.; Karcz, J.; Letmanowski, R.; Zabost, D.; Ciecierska, E.; Zdunek, J.; Karwowska, E.; Siekierski, M.; Olszyna, A.; Kunicki, A.

2016-01-01

The aim of this study was to describe the influence of the modification of electrostatic properties of RGO/Al2O3 core-shell nanocomposite flakes. The amount of crystalline form of aluminum oxide was very small. It existed mostly in amorphous phase in the form of covalently bonded to GO surface. The morphological, structural and physicochemical investigations results showed that spherical Al2O3 nanoparticles (ca. 41 nm) in gamma phase completely covered the surface of curly-shaped RGO flakes and acted as a spreader between individual flakes. The high BET specific surface area of the analyzed composite (119.71 m2/g) together with very low open porosity (0.479 cm3/g) indicated that RGO/Al2O3 nanocomposite flakes showed low tendency to agglomeration. The zeta potential curves obtained for RGO/Al2O3 core-shell nanocomposite flakes were differing from curves obtained for GO and Al2O3 suspensions in distilled water and neutral environment. The specific electrostatic properties of the core-shell system of RGO/Al2O3 flakes had an influence on its surface charge (zeta potential) which was measured by applying an external electric field. The FTIR and Raman investigations results also confirmed that the Cdbnd O species were not taking part in the surface amphoteric reactions resulting in the formation of electrostatic surface charge.

Catalytically-etched hexagonal boron nitride flakes and their surface activity

NASA Astrophysics Data System (ADS)

Kim, Do-Hyun; Lee, Minwoo; Ye, Bora; Jang, Ho-Kyun; Kim, Gyu Tae; Lee, Dong-Jin; Kim, Eok-Soo; Kim, Hong Dae

2017-04-01

Hexagonal boron nitride (h-BN) is a ceramic compound which is thermally stable up to 1000 °C in air. Due to this, it is a very challenging task to etch h-BN under air atmosphere at low temperature. In this study, we report that h-BN flakes can be easily etched by oxidation at 350 °C under air atmosphere in the presence of transition metal (TM) oxide. After selecting Co, Cu, and Zn elements as TM precursors, we simply oxidized h-BN sheets impregnated with the TM precursors at 350 °C in air. As a result, microscopic analysis revealed that an etched structure was created on the surface of h-BN flakes regardless of catalyst type. And, X-ray diffraction patterns indicated that the air oxidation led to the formation of Co3O4, CuO, and ZnO from each precursor. Thermogravimetric analysis showed a gradual weight loss in the temperature range where the weight of h-BN flakes increased by air oxidation. As a result of etching, pore volume and pore area of h-BN flakes were increased after catalytic oxidation in all cases. In addition, the surface of h-BN flakes became highly active when the h-BN samples were etched by Co3O4 and CuO catalysts. Based on these results, we report that h-BN flakes can be easily oxidized in the presence of a catalyst, resulting in an etched structure in the layered structure.

Effect of the corn breaking method on oil distribution between stillage phases of dry-grind corn ethanol production.

PubMed

Wang, H; Wang, T; Johnson, L A; Pometto, A L

2008-11-12

The majority of fuel ethanol in the United States is produced by using the dry-grind corn ethanol process. The corn oil that is contained in the coproduct, distillers' dried grains with solubles (DDGS), can be recovered for use as a biodiesel feedstock. Oil removal will also improve the feed quality of DDGS. The most economical way to remove oil is considered to be at the centrifugation step for separating thin stillage (liquid) from coarse solids after distilling the ethanol. The more oil there is in the liquid, the more it can be recovered by centrifugation. Therefore, we studied the effects of corn preparation and grinding methods on oil distribution between liquid and solid phases. Grinding the corn to three different particle sizes, flaking, flaking and grinding, and flaking and extruding were used to break up the corn kernel before fermentation, and their effects on oil distribution between the liquid and solid phases were examined by simulating an industrial decanter centrifuge. Total oil contents were measured in the liquid and solids after centrifugation. Dry matter yield and oil partitioning in the thin stillage were highly positively correlated. Flaking slightly reduced bound fat. The flaked and then extruded corn meal released the highest amount of free oil, about 25% compared to 7% for the average of the other treatments. The freed oil from flaking, however, became nonextractable after the flaked corn was ground. Fine grinding alone had little effect on oil partitioning.

Covering surface nanobubbles with a NaCl nanoblanket.

PubMed

Berkelaar, Robin P; Zandvliet, Harold J W; Lohse, Detlef

2013-09-10

By letting a NaCl aqueous solution of low (0.01 M) concentration evaporate on a highly oriented pyrolytic graphite (HOPG) surface, it is possible to form a thin film of salt. However, pre-existing surface nanobubbles prevent the homogeneous coverage of the surface with the salt, keeping the footprint areas on the substrate pristine. Comparing the surface nanobubbles in the salt solution with their associated footprint after drying, provides information on the shrinkage of nanobubbles during the hours-long process of drying the liquid film. At a slightly higher NaCl concentration and thus salt layer thickness, the nanobubbles are covered with a thin blanket of salt. Once the liquid film has evaporated until a water film remains that is smaller than the height of the nanobubbles, the blanket of salt cracks and unfolds into a flower-like pattern of salt flakes that is located at the rim of the nanobubble footprint. The formation of a blanket of salt covering the nanobubbles is likely to considerably or even completely block the gas out-flux from the nanobubble, partially stabilizing the nanobubbles against dissolution.

Facile synthesis and electrochemical performances of hollow graphene spheres as anode material for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Yao, Ran-Ran; Zhao, Dong-Lin; Bai, Li-Zhong; Yao, Ning-Na; Xu, Li

2014-07-01

The hollow graphene oxide spheres have been successfully fabricated from graphene oxide nanosheets utilizing a water-in-oil emulsion technique, which were prepared from natural flake graphite by oxidation and ultrasonic treatment. The hollow graphene oxide spheres were reduced to hollow graphene spheres at 500°C for 3 h under an atmosphere of Ar(95%)/H2(5%). The first reversible specific capacity of the hollow graphene spheres was as high as 903 mAh g-1 at a current density of 50 mAh g-1. Even at a high current density of 500 mAh g-1, the reversible specific capacity remained at 502 mAh g-1. After 60 cycles, the reversible capacity was still kept at 652 mAh g-1 at the current density of 50 mAh g-1. These results indicate that the prepared hollow graphene spheres possess excellent electrochemical performances for lithium storage. The high rate performance of hollow graphene spheres thanks to the hollow structure, thin and porous shells consisting of graphene sheets.

Graphene-like carbon synthesized from popcorn flakes

NASA Astrophysics Data System (ADS)

Mendoza, D.; Flores, C. B.; Berrú, R. Y. Sato

2015-01-01

The synthesis of graphene-like carbon using popcorn kernels as a renewable resource is presented. In a first step popcorn kernels were heated to produce popcorn flakes with a spongy appearance consisting of a polygonal cellular structure. In a second step, the flakes were treated at high temperature in an inert atmosphere to produce carbonization. Raman spectroscopy shows graphene-like structure with a high degree of disorder.

Prototype flaking head smooths surfaces left by headrig or edger chipping heads

Treesearch

Peter Koch

1976-01-01

Flaking heads arranged to follow headrig and edger chipper cheads could smooth machined surfaces and produce high-value flakes of near optimum dimsneions for structural flakeboard. In the proposed concept, eight knives are closely grouped in a 45-degree helix on a cutterhead tipped at 45-degree angle to the direction of workpiece feed. Each knife is set out in cutting...

Prototype flaking head smooths surfaces left by headrig or edger chipping heads

Treesearch

P. Koch

1976-01-01

Flaking heads arranged to follow headrig and edger chipper heads would smooth machined surfaces and produce high-value flakes of near optimum dimensions for structural flakeboard. In the proposed concept, eight knives are closely grouped in a 45-degree helix on a cutterhead tipped at 45-degree angle to the direction of workpiece feed. Each knife is set out in cutting...

Use of Geologic Mapping of the Medicine Lake Volcano in NE California to Constrain Interpretation of Cultural Uses of Rhyolite Obsidian

NASA Astrophysics Data System (ADS)

de la Fuente, J. A.; Johnson, L.; Cassidy, J.; Stevens, M.

2012-12-01

Recently published geologic mapping of Medicine Lake volcano in N. California (Donnelly-Nolan, 2010) provides a context for evaluating cultural use of Pleistocene rhyolitic obsidian at the volcano. The mapping identified an area of gravel that forms a small alluvial fan. The alluvial deposit includes abundant obsidian, some as water-worn cobbles, and some as flakes of obsidian. The alluvial fan is located about 3 km south of the nearest outcrop of obsidian, which is mapped as "rhyolite of Grasshopper Flat." This rhyolite unit has been identified over a distance of 30 km on the west side of Medicine Lake volcano as distributed chemically identical outcrops along a north-northeast trend. The aphyric obsidian provided excellent raw material for cultural use by Native Americans, and projectile point styles at nearby sites suggest up to 10,000 years of utilization. Obsidian in the fan deposit includes cobbles and flakes, some of which show definite signs of water transport, to a depth of >0.6 m. In addition to the definite anthropogenic flakes in the deposit, there are also unmodified obsidian pieces. The range of variation in the amount of water wear and other weathering on the obsidian makes it difficult to tell whether some of the flakes are anthropogenic or if they were broken by natural processes. It is also difficult to determine whether some of the definite anthropogenic flakes were created on site, or if all flakes in the deposit were created at a quarry upstream and transported with the other stream material. Lastly, some of the flakes display secondary flaking, perhaps related to recent logging activities or natural processes. The presence of anthropogenic flakes in the alluvium would indicate water transport during Holocene time, since there is little evidence of human occupation prior to the Holocene. Local scatters of clearly anthropogenic flakes are also present outside the stream deposit, indicating that at least some tool-making activity occurred in the vicinity. Glacial ice was present over the top of the volcano in latest Pleistocene time, but there is no evidence of ice in Holocene time, indicating that water capable of transporting the obsidian likely resulted from intense thunderstorm activity, or rapid melting of a thick snow pack upstream. High-resolution LiDAR will become available in the near future, allowing geologists and archaeologists an opportunity to identify additional deposits of water-transported obsidian, and possibly provide access to material for C-14 dating of the deposits. Establishing absolute dates for the flakes via C-14 analysis would assist in the interpretation of their origin.

Germanium Nanowires-in-Graphite Tubes via Self-Catalyzed Synergetic Confined Growth and Shell-Splitting Enhanced Li-Storage Performance.

PubMed

Sun, Yong; Jin, Shuaixing; Yang, Guowei; Wang, Jing; Wang, Chengxin

2015-04-28

Despite the high theoretical capacity, pure Ge has various difficulties such as significant volume expansion and electron and Li(+) transfer problems, when applied as anode materials in lithium ion battery (LIB), for which the solution would finally rely on rational design like advanced structures and available hybrid. Here in this work, we report a one-step synthesis of Ge nanowires-in-graphite tubes (GNIGTs) with the liquid Ge/C synergetic confined growth method. The structure exhibits impressing LIB behavior in terms of both cyclic stability and rate performance. We found the semiclosed graphite shell with thickness of ∼50 layers experience an interesting splitting process that was driven by electrolyte diffusion, which occurs before the Ge-Li alloying plateau begins. Two types of different splitting mechanism addressed as "inside-out"/zipper effect and "outside-in" dominate this process, which are resulted from the SEI layer growing longitudinally along the Ge-graphite interface and the lateral diffusion of Li(+) across the shell, respectively. The former mechanism is the predominant way driving the initial shell to split, which behaves like a zipper with SEI layer as invisible puller. After repeated Li(+) insertion/exaction, the GNIGTs configuration is finally reconstructed by forming Ge nanowires-thin graphite strip hybrid, both of which are in close contact, resulting in enormous enchantment to the electrons/Li(+) transport. These features make the structures perform well as anode material in LIB. We believe both the progress in 1D assembly and the structure evolution of this Ge-C composite would contribute to the design of advanced LIB anode materials.

Electrohydrodynamic printing for scalable MoS2 flake coating: application to gas sensing device

NASA Astrophysics Data System (ADS)

Lim, Sooman; Cho, Byungjin; Bae, Jaehyun; Kim, Ah Ra; Lee, Kyu Hwan; Kim, Se Hyun; Hahm, Myung Gwan; Nam, Jaewook

2016-10-01

Scalable sub-micrometer molybdenum disulfide ({{MoS}}2) flake films with highly uniform coverage were created using a systematic approach. An electrohydrodynamic (EHD) printing process realized a remarkably uniform distribution of exfoliated {{MoS}}2 flakes on desired substrates. In combination with a fast evaporating dispersion medium and an optimal choice of operating parameters, the EHD printing can produce a film rapidly on a substrate without excessive agglomeration or cluster formation, which can be problems in previously reported liquid-based continuous film methods. The printing of exfoliated {{MoS}}2 flakes enabled the fabrication of a gas sensor with high performance and reproducibility for {{NO}}2 and {{NH}}3.

Electronic screening in stacked graphene flakes revealed by scanning tunneling microscopy

NASA Astrophysics Data System (ADS)

Feng, Xiaofeng; Salmeron, Miquel

2013-02-01

Electronic doping and screening effects in stacked graphene flakes on Ru and Cu substrates have been observed using scanning tunneling microscopy (STM). The screening affects the apparent STM height of each flake in successive layers reflecting the density of states near the Fermi level and thus the doping level. It is revealed in this way that the strong doping of the first graphene layer on Ru(0001) is attenuated in the second one, and almost eliminated in the third and fourth layers. Similar effect is also observed in graphene flakes on Cu(111). In contrast, the strong doping effect is suppressed immediately by a water layer intercalated between the graphene and Ru.

Salt-assisted direct exfoliation of graphite into high-quality, large-size, few-layer graphene sheets.

PubMed

Niu, Liyong; Li, Mingjian; Tao, Xiaoming; Xie, Zhuang; Zhou, Xuechang; Raju, Arun P A; Young, Robert J; Zheng, Zijian

2013-08-21

We report a facile and low-cost method to directly exfoliate graphite powders into large-size, high-quality, and solution-dispersible few-layer graphene sheets. In this method, aqueous mixtures of graphite and inorganic salts such as NaCl and CuCl2 are stirred, and subsequently dried by evaporation. Finally, the mixture powders are dispersed into an orthogonal organic solvent solution of the salt by low-power and short-time ultrasonication, which exfoliates graphite into few-layer graphene sheets. We find that the as-made graphene sheets contain little oxygen, and 86% of them are 1-5 layers with lateral sizes as large as 210 μm(2). Importantly, the as-made graphene can be readily dispersed into aqueous solution in the presence of surfactant and thus is compatible with various solution-processing techniques towards graphene-based thin film devices.

The modeling and synthesis of nanodiamonds by laser ablation of graphite and diamond-like carbon in liquid-confined ambient

NASA Astrophysics Data System (ADS)

Basso, L.; Gorrini, F.; Bazzanella, N.; Cazzanelli, M.; Dorigoni, C.; Bifone, A.; Miotello, A.

2018-01-01

Nanodiamonds have attracted considerable interest for their potential applications in quantum computation, sensing, and bioimaging. However, synthesis of nanodiamonds typically requires high pressures and temperatures, and is still a challenge. Here, we demonstrate production of nanodiamonds by pulsed laser ablation of graphite and diamond-like carbon in water. Importantly, this technique enables production of nanocrystalline diamonds at room temperature and standard pressure conditions. Moreover, we propose a method for the purification of nanodiamonds from graphitic and amorphous carbon phases that do not require strong acids and harsh chemical conditions. Finally, we present a thermodynamic model that describes the formation of nanodiamonds during pulsed laser ablation. We show that synthesis of the crystalline phase is driven by a graphite-liquid-diamond transition process that occurs at the extreme thermodynamic conditions reached inside the ablation plume.

Final Report: Novel ALD-Coated Nanoparticle Anodes for Enhanced Performance Lithium-Ion Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Groner, Markus

2009-04-16

The Phase I effort is described in detail in the Phase I report given below. The key accomplishments of the Phase I project were (1) the demonstration of high stability LiCoO2 cathodes using ALD-coated LiCoO2 particles, as well as on ALD-coated LiCoO2 electrodes and (2) the demonstration of high stability of graphite anodes using ALD-coated graphite electrodes.

Ultra-high aspect ratio titania nanoflakes for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Lee, Yang-Yao; El-Shall, Hassan

2017-12-01

Micron sized titania flakes with thickness about 40 nm were used in the titania pastes to assemble dye-sensitized solar cells (DSSCs). Using the same deposition method, better particle dispersion of titania flakes resulted in well bonded and integral films comparing to cracking of Degussa P25 nanoparticle films during the evaporation and sintering processes. There are two features of titania flakes which leads to improved conversion efficiency of DSSC: (1) Higher and stronger adsorption of N-719 dyes due to high specific surface area (2) Stronger light scattering of visible light spectrum because of micron scale wide in two dimensions of the flakes. The thickness of the conducting TiO2 was critical to the IV characteristics of DSSC such as the short-circuit current density (Isc) and open-circuit voltage (Voc). Under the same thickness basis, calcined titania flakes provided 5 times higher efficiency than the photoelectrodes consisted of Degussa P25 nanoparticles (7.4% vs. 1.2%).

The different adsorption mechanism of methane molecule onto a boron nitride and a graphene flakes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seyed-Talebi, Seyedeh Mozhgan; Neek-Amal, M., E-mail: neekamal@srttu.edu

2014-10-21

Graphene and single layer hexagonal boron-nitride are two newly discovered 2D materials with wonderful physical properties. Using density functional theory, we study the adsorption mechanism of a methane molecule over a hexagonal flake of single layer hexagonal boron-nitride (h-BN) and compare the results with those of graphene. We found that independent of the used functional in our ab-initio calculations, the adsorption energy in the h-BN flake is larger than that for graphene. Despite of the adsorption energy profile of methane over a graphene flake, we show that there is a long range behavior beyond minimum energy in the adsorption energymore » of methane over h-BN flake. This result reveals the higher sensitivity of h-BN sheet to the adsorption of a typical closed shell molecule with respect to graphene. The latter gives insight in the recent experiments of graphene over hexagonal boron nitride.« less

Basic properties of full-size st ructural flakeboards fabricated with flakes on a shaping lathe

Treesearch

Eddie W. Prie

1977-01-01

Structural exterior flakeboards manufactured in 4 by 8 ft (1.22 by 2.44 m ) size with phenolic resin and flakes produced on a shaping-lathe headrig were evaluated for plate shear modulus, internal bond, bending properties, and 24-hour water soak stability. Both mixed and single species flakeboards were produced. Panels with mixed flakes had 20% by weight of hickory,...

Determining tensile properties of sweetgum veneer flakes

Treesearch

Eddie W. Price

1976-01-01

Rotary-cut sweetgum veneer flakes measuring 3 inches along the grain, 3/8 inch wide, and 0.015 inch thick, were stressed in tension parallel to the grain at gage lengths from 0.50 to 1.25 inches for unpressed control and at 0.75 inch gage length for flakes pressed in a flakeboard mat. The control fkaes had an average tensile strength of 9,400 psi for the smaller gage...

Reliable Exfoliation of Large-Area High-Quality Flakes of Graphene and Other Two-Dimensional Materials.

PubMed

Huang, Yuan; Sutter, Eli; Shi, Norman N; Zheng, Jiabao; Yang, Tianzhong; Englund, Dirk; Gao, Hong-Jun; Sutter, Peter

2015-11-24

Mechanical exfoliation has been a key enabler of the exploration of the properties of two-dimensional materials, such as graphene, by providing routine access to high-quality material. The original exfoliation method, which remained largely unchanged during the past decade, provides relatively small flakes with moderate yield. Here, we report a modified approach for exfoliating thin monolayer and few-layer flakes from layered crystals. Our method introduces two process steps that enhance and homogenize the adhesion force between the outermost sheet in contact with a substrate: Prior to exfoliation, ambient adsorbates are effectively removed from the substrate by oxygen plasma cleaning, and an additional heat treatment maximizes the uniform contact area at the interface between the source crystal and the substrate. For graphene exfoliation, these simple process steps increased the yield and the area of the transferred flakes by more than 50 times compared to the established exfoliation methods. Raman and AFM characterization shows that the graphene flakes are of similar high quality as those obtained in previous reports. Graphene field-effect devices were fabricated and measured with back-gating and solution top-gating, yielding mobilities of ∼4000 and 12,000 cm(2)/(V s), respectively, and thus demonstrating excellent electrical properties. Experiments with other layered crystals, e.g., a bismuth strontium calcium copper oxide (BSCCO) superconductor, show enhancements in exfoliation yield and flake area similar to those for graphene, suggesting that our modified exfoliation method provides an effective way for producing large area, high-quality flakes of a wide range of 2D materials.

Decellularization of Human Nasal Septal Cartilage for the Novel Filler Material of Vocal Fold Augmentation.

PubMed

Kang, Dae-Woon; Shin, Sung-Chan; Jang, Jeon-Yeob; Park, Hee-Young; Lee, Jin-Choon; Wang, Soo-Geun; Lee, Byung-Joo

2017-01-01

The clinical application of allogenic and/or xenogenic cartilage for vocal fold augmentation requires to remove the antigenic cellular component. The objective of this study was to assess the effect of cartilage decellularization and determine the change in immunogenicity after detergent treatment in human nasal septal cartilage flakes made by the freezing and grinding method. Human nasal septal cartilages were obtained from surgical cases. The harvested cartilages were treated by the freezing and grinding technique. The obtained cartilage flakes were treated with 1% Triton X-100 or 2% sodium dodecyl sulfate (SDS) for decellularization of the cartilage flakes. Hematoxylin and eosin stain (H&E stain), surface electric microscopy, immunohistochemical stain for major histocompatibility complex I and II, and ELISA for DNA contents were performed to assess the effect of cartilage decellularization after detergent treatment. A total of 10 nasal septal cartilages were obtained from surgical cases. After detergent treatment, the average size of the cartilage flakes was significantly decreased. With H&E staining, the cell nuclei of decellularized cartilage flakes were not observed. The expression of major histocompatibility complex (MHC)-I and II antigens was not identified in the decellularized cartilage flakes after treatment with detergent. DNA content was removed almost entirely from the decellularized cartilage flakes. Treatment with 2% SDS or 1% Triton X-100 for 1 hour appears to be a promising method for decellularization of human nasal septal cartilage for vocal fold augmentation. Copyright © 2017 The Voice Foundation. Published by Elsevier Inc. All rights reserved.

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 (E ½) of 0.71 V, and a selectivity for four-electron reduction of >95%. Finally and further, durability testing showed E ½ retention >95% in N 2- and O 2-saturated solutions after 2000 cycles, demonstrating the highest ORR activity and stability reported to date for GN-based electrocatalysts in acidic media.« less

A Comparison of the Irradiation Creep Behavior of Several Graphites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burchell, Timothy D; Windes, Will

2016-01-01

Graphite creep strain data from the irradiation creep capsule Advanced Graphite Creep-1 (AGC-1) are reported. This capsule was the first (prototype) of a series of five or six capsules planned as part of the AGC experiment, which was designed to fully characterize the effects of neutron irradiation and the radiation creep behavior of current nuclear graphite. The creep strain data and analysis are reported for the six graphite grades incorporated in the capsule. The AGC-1 capsule was irradiated in the Advanced Test Reactor at Idaho National Laboratory (INL) at approximately 700 C and to a peak dose of 7 dpamore » (displacements per atom). The specimen s final dose, temperature, and stress conditions have been reported by INL and were used during this analysis. The derived creep coefficients (K) were calculated for each grade and were found to compare well to literature data for the creep coefficient, even under the wide range of AGC-1 specimen temperatures. Comparisons were made between AGC-1 data and historical grade data for creep coefficients.« less

Study on Flake Formation Behavior and Its Influence Factors in Cr5 Steel

PubMed Central

Chen, Huitao; Zhao, Wu; Yan, Liang

2018-01-01

A flake is a crack that is induced by trapped hydrogen within steel. To study its formation mechanism, previous studies mostly focused on the formation process and magnitude of hydrogen pressure in hydrogen traps such as cavities and cracks. However, according to recent studies, the hydrogen leads to the decline of the mechanical properties of steel, which is known as hydrogen embrittlement, is another reason for flake formation. In addition, the phenomenon of stress induced hydrogen uphill diffusion should not be neglected. All of the three behaviors are at work simultaneously. In order to further explore the formation mechanism of flakes in steel, the process of flake initiation and growth were studied with the following three coupling factors: trap hydrogen pressure, hydrogen embrittlement, and stress induced hydrogen re-distribution. The analysis model was established using the finite element method, and a crack whose radius is 0.5 mm was set in its center. The cohesive method and Bilinear Traction Separate Law (BTSL) were used to address the coupling effect. The results show that trap hydrogen pressure is the main driving force for flake formation. After the high hydrogen pressure was generated around the trap, a stress field formed. In addition, the trap is the center of stress concentration. Then, hydrogen is concentrated in a distribution around this trap, and most of the steel mechanical properties are reduced. The trap size is a key factor for defining the critical hydrogen content for flake formation and propagation. However, when the trap size exceeds the specified value, the critical hydrogen content does not change any more. As for the crack whose radius is 0.5 mm, the critical hydrogen content of Cr5VMo steel is 2.2 ppm, which is much closer to the maximum safe hydrogen concentration of 2.0 ppm used in China. The work presented in this article increases our understanding of flake formation and propagation mechanisms in steel. PMID:29702610

Evaluating COSMO's lake module (FLake) for an East-African lake using a comprehensive set of lake temperature profiles

NASA Astrophysics Data System (ADS)

Thiery, W.; Martynov, A.; Darchambeau, F.; Demuzere, M.; van Lipzig, N.

2012-04-01

The African great lakes are of utmost importance for the local economy (fishing), as well as being essential to the survival of the local people. During last decades, these lakes have been changing rapidly and their evolution is a major concern. Hence, it is important to correctly represent them in regional climate models for simulations over tropical Africa. However, so far lake models have been developed and tested primarily for boreal conditions. In this study, for the first time the freshwater lake model FLake is evaluated over East-Africa, more specifically over lake Kivu. Meteorological observations from January 2003 to December 2008 from an automatic weather station in Bukavu, DRC, are used to drive the standalone version of FLake. For the evaluation, a unique dataset is used which contains over 200 temperature profiles recorded since 2002. Results show that FLake in its default configuration is very successful at reproducing both the timing and magnitude of the seasonal cycle at 5 m depth. Flake captures that this seasonality is regulated by the water vapour pressure, which constrains evaporation except during summer (JJA). A positive bias of ~1 K is attributed to the driving data, which are collected in the city and are therefore expected to mirror higher temperatures and lower wind speeds compared to the lake surface. The evaluation also showed that driving FLake with Era-Interim from the nearest pixel does only slightly deteriorate the model performance. Using forcing fields from the Canadian Regional Climate Model, version 5 (CRCM5) simulation output gives similar performance as Era-Interim. Furthermore, a drawback of FLake is that it does not account for salinity and its effect upon lake stratification, and therefore requires artificial initial conditions for both lake depth and bottom temperature in order to reproduce the correct mixing regime in lake Kivu. Further research will therefore aim at improving FLake's representation of tropical lakes.

Ways to Improve the Quality of Die Steel 5KhNM

NASA Astrophysics Data System (ADS)

Efimov, S. V.; Malykhina, O. Yu; Pavlova, A. G.; Milyuts, V. G.; Tsukanov, V. V.; Vikharev, V. V.

2017-12-01

There was performed an analysis of influence of the deoxidation technology, hydrogen content and high concentration of titanium in steel 5KhNM (Rus. “5XHM”) on quality of die blanks, evaluated based on the results of the ultrasonic test. The fractographic examinations of fractures and the X-ray microprobe analysis of chemical composition of non-metallic inclusions were conducted, the evaluation of macro- and micro-structure of a die blank with high titanium content was performed. It is demonstrated that defects of dies from steel 5KhNM (Rus. “5XHM”) are cracks from merged flakes and micro-flakes; in most cases large concentrations of sulphides appeared to be hydrogen collectors for formation of flakes and micro-flakes.

Synthesis of sub-micro-flakes CrSe2 on glass and (110) Si substrates by solvothermal method

NASA Astrophysics Data System (ADS)

Tang, Qingkai; Liu, Changyou; Zhang, Binbin; Jie, Wanqi

2018-06-01

Layered structure MX2 (M = transition metal, X = S, Se and Te) chalcogenides have rich physic properties and potential applications. While it is still a challenge to prepare the chalcogenides by solvothermal method. In this work, we reported a new solution method to prepare CrSe2 sub-micro-flakes on different substrates. The surface morphologies, structures and compositions of the precursor CrSe2(en)1/2 and CrSe2 were investigated by SEM, XRD, thermogravimetric, IR and Raman spectra. The CrSe2 flakes with the sizes of 5-15 μm were obtained on both glass and (110) Si crystalline substrates. The formation mechanism of CrSe2 sub-micro-flakes is suggested.

Nanoscale current spreading analysis in solution-processed graphene oxide/silver nanowire transparent electrodes via conductive atomic force microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shaw, Joseph E.; Perumal, Ajay; Bradley, Donal D. C.

2016-05-21

We use conductive atomic force microscopy (CAFM) to study the origin of long-range conductivity in model transparent conductive electrodes composed of networks of reduced graphene oxide (rGO{sub X}) and silver nanowires (AgNWs), with nanoscale spatial resolution. Pristine networks of rGO{sub X} (1–3 monolayers-thick) and AgNWs exhibit sheet resistances of ∼100–1000 kΩ/□ and 100–900 Ω/□, respectively. When the materials are deposited sequentially to form bilayer rGO{sub X}/AgNW electrodes and thermally annealed at 200 °C, the sheet resistance reduces by up to 36% as compared to pristine AgNW networks. CAFM was used to analyze the current spreading in both systems in order to identify themore » nanoscale phenomena responsible for this effect. For rGO{sub X} networks, the low intra-flake conductivity and the inter-flake contact resistance is found to dominate the macroscopic sheet resistance, while for AgNW networks the latter is determined by the density of the inter-AgNW junctions and their associated resistance. In the case of the bilayer rGO{sub X}/AgNWs' networks, rGO{sub X} flakes are found to form conductive “bridges” between AgNWs. We show that these additional nanoscopic electrical connections are responsible for the enhanced macroscopic conductivity of the bilayer rGO{sub X}/AgNW electrodes. Finally, the critical role of thermal annealing on the formation of these nanoscopic connections is discussed.« less

Effective size selection of MoS2 nanosheets by a novel liquid cascade centrifugation: Influences of the flakes dimensions on electrochemical and photoelectrochemical applications.

PubMed

Kajbafvala, Marzieh; Farbod, Mansoor

2018-05-14

Although liquid phase exfoliation is a powerful method to produce MoS 2 nanosheets in large scale, but its effectiveness is limited by the diversity of produced nanosheets sizes. Here a novel approach for separation of MoS 2 flakes having various lateral sizes and thicknesses based on the cascaded centrifugation has been introduced. This method involves a pre-separation step which is performed through low-speed centrifugation to avoid the deposition of large area single and few-layers by the heavier particles. The bulk MoS 2 powders were dispersed in an aqueous solution of sodium cholate (SC) and sonicated for 12 h. The main separation step was performed using different speed centrifugation intervals of 10-11, 8-10, 6-8, 4-6, 2-4 and 0.5-2 krpm by which nanosheets containing 2, 4, 7, 8, 14, 18 and 29 layers were obtained respectively. The samples were characterized using XRD, FESEM, AFM, TEM, DLS and also UV-vis, Raman and PL spectroscopy measurements. Dynamic light scattering (DLS) measurements have confirmed the existence of a larger number of single or few-layers MoS 2 nanosheets compared to when the pre-separation step was not used. Finally, Photocurrent and cyclic voltammetry of different samples were measured and found that the flakes with bigger surface area had larger CV loop area. Our results provide a method for the preparation of a MoS 2 monolayer enriched suspension which can be used for different applications. Copyright © 2018 Elsevier Inc. All rights reserved.

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.

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.

77 FR 47596 - Small Diameter Graphite Electrodes From the People's Republic of China: Affirmative Final...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-09

...., Anticircumvention Inquiry of the Antidumping and Countervailing Duty Orders on Certain Pasta From Italy: Affirmative... 6, 2003) (``Pasta Circumvention Prelim''), unchanged in Anticircumvention Inquiry of the Antidumping and Countervailing Duty Orders on Certain Pasta from Italy: Affirmative Final Determinations of...

Estimation of Sorption Behavior of Europium(III) Using Biotite Flakes - 13272

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sasaki, Go; Niibori, Yuichi; Mimura, Hitoshi

2013-07-01

The interaction of biotite and Eu(III) (europium (III)) was examined by using secondary ion-microprobe mass spectrometer (SIMS), fluorescence emission spectrum and decay behavior of fluorescence emission spectrum in addition to the time-changes of Eu(III) and potassium ions concentrations in a solution, using the flake form samples. The results of SIMS showed that the intensity of Eu was gradually decreasing with depth, while the intensity of Eu in the case shaken for 30 days exceeded that in the case for 1 day. Furthermore, the spatial distribution of Eu(III) and potassium ions in the flake of biotite suggested that Eu ions diffusemore » mainly from the edges of biotite flake, while Eu ions can slightly diffuse through some small cracks existing on the flake surface far from the edges. Besides, the elution amount of potassium from the biotite flakes into a solution was proportional to the sorption amount of Eu(III). The changes nearly revealed ion exchange between these ions, while muscovite flake sample did not show such ion exchange reaction. In addition, from the time-change of Eu(III) concentration, an apparent diffusion coefficient was estimated to be 8.0x10{sup -12} m{sup 2}/s, by using two-dimensional diffusion model coupled with a film between the solid phase and the liquid phase. Furthermore, the fluorescent intensity decreased with the shaking (contacting) time. This means that Eu(III) gradually diffuses into the inside of biotite edges of the biotite flakes, after the sorption of Eu(III) in the edges. This tendency was observed also in the powder samples. The observed fluorescence decay (at 592 nm in wave length) showed almost similar curve in any samples, indicating a certain sorption form of Eu(III) onto the edges of the biotite flakes. These results mentioned above suggest that the diffusion processes through internal layer in biotite mainly control the sorption behavior of multivalent ions. Such diffusion processes affect the retardation-effects on fracture surfaces in the rock matrix, depending on the fluid flow velocity of groundwater. That is, a more reliable model considering the mass transfer in the internal layer of biotite may be required to estimate the sorption behavior of RNs with biotite which controls the whole sorption behavior of granite. (authors)« less

Fluorescence Intermittency and Nanodot Evolution in Graphene Oxide

NASA Astrophysics Data System (ADS)

Ruth, Anthony; Michitoshi, Hayashi; McDonald, Matthew; Si, Jixin; Morozov, Yuri; Zapol, Peter; Kuno, Masaru; Janko, Boldizsar

In recent experiments, micron-sized reduced graphene oxide (rGO) flakes were observed to exhibit strong photoluminescence intensity fluctuations, or blinking. Although blinking has been observed in a wide variety of nanoscale emitters, and striking universalities exist across these very different systems, rGO is the first quasi-two dimensional emitter that shows blinking. Despite the widespread presence of blinking at nanoscale, a microscopic mechanism behind this phenomenon remains elusive. Here we provide density functional theory results, analytical calculations, and Monte Carlo simulations to connect the fluorescence trajectories observed in the experiment to microscopic processes. Through Monte Carlo simulations of chemical processes occurring on the graphene oxide surface, we observe the formation and destruction of carbon nanodots. Finally, we use emission characteristics of carbon nanodots from Ab Initio methods to reconstruct the photoluminescence of the macroscopic flake. In particular, we are investigating whether fluorescence intermittency in reduced graphene oxide is an intrinsic optoelectronic property of the nanodot constituents or the result of reversible chemical processes capable of changing the size and number of graphene nanodots. This work was supported by a NASA Space Technology Research Fellowship.

Low-cost and facile synthesis of Ni(OH)2/ZnO nanostructures for high-sensitivity glucose detection

NASA Astrophysics Data System (ADS)

Strano, V.; Mirabella, S.

2018-01-01

An efficient electrode for non-enzymatic glucose detection is produced with low-cost techniques on a Cu wire. ZnO nanorods (NRs) were grown on a Cu wire by chemical bath deposition and were used as the substrate for pulsed electrodeposition of nanostructured Ni(OH)2 flakes. The effect of the electrodeposition potential on the final morphology and electrochemical behavior of the Ni(OH)2/ZnO/Cu structures is reported. ZnO NRs resulted to be well dressed by Ni(OH)2 flakes and were tested as glucose sensing electrodes in 0.1 M NaOH solution, showing high sensitivities (up to 3 mA mM-1 cm-2) and long-term stability. The presence of ZnO NRs was shown to improve the performance of the glucose sensor in terms of electrochemical stability over the time and sensitivity compared to Ni(OH)2/Cu sample. The reported data demonstrate a simple, versatile and low-cost fabrication approach for effective glucose sensing system within a urban mines framework.

Powder and particulate production of metallic alloys

NASA Technical Reports Server (NTRS)

Grant, N. J.

1982-01-01

Developments of particulate metallurgy of alloyed materials where the final products is a fully dense body are discussed. Particulates are defined as powders, flakes, foils, silvers, ribbons and strip. Because rapid solidification is an important factor in particulate metallurgy, all of the particulates must have at least one dimension which is very fine, sometimes as fine as 10 to 50 microns, but move typically up to several hundred microns, provided that the dimension permits a minimum solidification rate of at least 100 K/s.

Similkameen River Multipurpose Project Feasibility Study, Cultural Resource Reconnaissance

DTIC Science & Technology

1987-04-01

fill below the vicinity of Nighthawk. Soil survey data and well drilling logs suggest that a large block of ice occupied the western half of Palmer Lake...granodiorite on the south side of the river opposite the staging gauge at R.M. 15.3 (Rinehart and Fox 1972); the north side of the river does not...Utilized 7 Penetration Drilling Drill 1 Projectile Impact Projectile Point 10 Percussion Chopping Chopper 2 Flaking Complete Flake 84 Broken Flake 40

Folding and stacking defects of graphene flakes probed by electron nanobeam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Persichetti, L.; Fanfoni, M.; Sgarlata, A.

2011-07-25

Combining nanoscale imaging with local electron spectroscopy and diffraction has provided direct information on folding and stacking defects of graphene flakes produced by unrolled multi-walled carbon nanotubes. Structural data obtained by nanoarea electron diffraction complemented with systematic electron energy loss spectroscopy measurements of the surface plasmon losses of single flakes show the presence of flat bilayer regions coexisting with folded areas where the topology of buckled graphene resembles that of warped carbon nanostructures.

Characterization and quality assessment of recycled post-consumption poly(ethylene terephthalate) (PET).

PubMed

Masmoudi, Fatma; Fenouillot, Françoise; Mehri, Afef; Jaziri, Mohamed; Ammar, Emna

2018-06-05

In the present study, the recycled post-consumption polyethylene terephthalate (PET) flakes were investigated as possible raw materials for the production of food packaging. After heating at 220 °C for 1 h, a steaming stage was conducted as a control test to assess the quality of the product. Different samples were characterized by 1 H-NMR, FT-IR, DSC/TGA analysis, viscosity index (VI), and trace metals analysis. The results showed that the recycled post-consumed PET flakes' properties were generally conform to the standard norms of PET except the color of some flakes turned to yellow. Subsequently, a complementary study was undertaken to assess whether the material could be possibly reused for food packaging. For this purpose, rheological, thermal, and mechanical characterizations were performed. The results of the comparative study between the virgin and the recycled PET flakes concluded that the PET recycling affected the rheological properties but did not have any significant effect on their thermal and mechanical characteristics. Hence, it was deduced that the post-consumed PET flakes could be reused as a packaging material except food products.

Rhenium in ores of the Mikheevskoe porphyry Cu-Mo deposit, South Urals

NASA Astrophysics Data System (ADS)

Plotinskaya, O. Yu.; Grabezhev, A. I.; Seltmann, R.

2015-03-01

The distribution of Re in ores of the Mikheevskoe Mo-Cu deposit in the South Urals is studied. It is established that the grade of Re in the ores usually does not exceed 0.5 g/t. A positive correlation between concentrations of Re and Mo (correlation coefficient 0.94), and Re and Cu (correlation coefficient 0.52) is found. EMPA of individual flakes of molybdenite showed that a Re content higher than the detection limit has been measured in most flakes studied, as a rule as high as 0.4-0.5 wt %, but occasionally reaching 1.34 wt %. Re within flakes of molybdenite is irregularly distributed. Patchy, linear, and concentric-zoned patterns of zones with elevated Re content (usually 0.5-1 wt % Re, sometimes higher) are found against the lower content (up to 0.2 wt % Re) that is regularly distributed within the flake. Later hydrothermal processes and mechanical deformation of flakes result in epigenetic Re redistribution in molybdenite that leads to homogenization of molybdenite composition and smoothing of primary pattern, or removal of Re from molybdenite.

Rice flakes produced from commercial wild rice: Chemical compositions, vitamin B compounds, mineral and trace element contents and their dietary intake evaluation.

PubMed

Sumczynski, Daniela; Koubová, Eva; Šenkárová, Lenka; Orsavová, Jana

2018-10-30

Non-traditional wild rice flakes were analysed for chemical composition, vitamin B compounds, α-tocopherol, mineral and trace elements. Dietary intakes of vitamins, minerals and trace elements were evaluated using FAO/WHO and Institute of Medicine regulations. Wild rice flakes proved to be significant contributors of pyridoxine, pantothenic and folic acids, niacin, thiamine, chromium, magnesium, manganese, phosphorus, zinc, copper, molybdenum and iron to essential dietary intakes values. Toxic dietary intake values for aluminium, cadmium, tin and mercury were less than 33%, which complies the limits for adults set by FAO/WHO for toxic elements intake related to the body weight of 65 kg for females and 80 kg for males taking 100 g of flakes as a portion. However, concentrations of Hg reaching between 3.67 and 12.20 µg/100 g in flakes exceeded the average Hg value of 0.27-1.90 μg/100 g in cereals consumed in the EU. It has to be respected in the future. Copyright © 2018 Elsevier Ltd. All rights reserved.

Manufacture and characterization of a yogurt-like beverage made with oat flakes fermented by selected lactic acid bacteria.

PubMed

Luana, Nionelli; Rossana, Coda; Curiel, José Antonio; Kaisa, Poutanen; Marco, Gobbetti; Rizzello, Carlo Giuseppe

2014-08-18

This study aimed at investigating the suitability of oat flakes for making functional beverages. Different technological options were assayed, including the amount of flakes, the inoculum of the starter and the addition of enzyme preparations. The beverage containing 25% (wt/wt) of oat flakes and fermented with L. plantarum LP09 was considered optimal on the basis of sensory and technological properties. The enzyme addition favored the growth of the starter, shortened the time needed to reach pH4.2 to ca. 8h, and favored a decrease of the quotient of fermentation. Fermentation increased the polyphenols availability and the antioxidant activity (25 and 70% higher, respectively) and decreased the hydrolysis index in vitro. Sensory analyses showed that fermented oat flakes beverage had the typical features of a yogurt-like beverage, enhancing the overall intensity of odor and flavor compared to the non-fermented control. Selection of proper processing and fermentation condition allowed the obtainment of a beverage with better nutritional and sensory properties. Copyright © 2014 Elsevier B.V. All rights reserved.

Non-destructive analysis of flake properties in automotive paints with full-field optical coherence tomography and 3D segmentation.

PubMed

Zhang, Jinke; Williams, Bryan M; Lawman, Samuel; Atkinson, David; Zhang, Zijian; Shen, Yaochun; Zheng, Yalin

2017-08-07

Automotive coating systems are designed to protect vehicle bodies from corrosion and enhance their aesthetic value. The number, size and orientation of small metallic flakes in the base coat of the paint has a significant effect on the appearance of automotive bodies. It is important for quality assurance (QA) to be able to measure the properties of these small flakes, which are approximately 10μm in radius, yet current QA techniques are limited to measuring layer thickness. We design and develop a time-domain (TD) full-field (FF) optical coherence tomography (OCT) system to scan automotive panels volumetrically, non-destructively and without contact. We develop and integrate a segmentation method to automatically distinguish flakes and allow measurement of their properties. We test our integrated system on nine sections of five panels and demonstrate that this integrated approach can characterise small flakes in automotive coating systems in 3D, calculating the number, size and orientation accurately and consistently. This has the potential to significantly impact QA testing in the automotive industry.

Electrically switchable polymer liquid crystal and polymer birefringent flake in fluid host systems and optical devices utilizing same

DOEpatents

Marshall, Kenneth L.; Kosc, Tanya Z.; Jacobs, Stephen D.; Faris, Sadeg M.; Li, Le

2003-12-16

Flakes or platelets of polymer liquid crystals (PLC) or other birefringent polymers (BP) suspended in a fluid host medium constitute a system that can function as the active element in an electrically switchable optical device when the suspension is either contained between a pair of rigid substrates bearing transparent conductive coatings or dispersed as microcapsules within the body of a flexible host polymer. Optical properties of these flake materials include large effective optical path length, different polarization states and high angular sensitivity in their selective reflection or birefringence. The flakes or platelets of these devices need only a 3-20.degree. rotation about the normal to the cell surface to achieve switching characteristics obtainable with prior devices using particle rotation or translation.

Graphene interfaced perovskite solar cells: Role of graphene flake size

NASA Astrophysics Data System (ADS)

Sakorikar, Tushar; Kavitha, M. K.; Tong, Shi Wun; Vayalamkuzhi, Pramitha; Loh, Kian Ping; Jaiswal, Manu

2018-04-01

Graphene interfaced inverted planar heterojunction perovskite solar cells are fabricated by facile solution method and studied its potential as hole conducting layer. Reduced graphene oxide (rGO) with small and large flake size and Polyethylenedioxythiophene:polystyrene sulfonate (PEDOT:PSS) are utilized as hole conducting layers in different devices. For the solar cell employing PEDOT:PSS as hole conducting layer, 3.8 % photoconversion efficiency is achieved. In case of solar cells fabricated with rGO as hole conducting layer, the efficiency of the device is strongly dependent on flake size. With all other fabrication conditions kept constant, the efficiency of graphene-interfaced solar cell improves by a factor of 6, by changing the flake size of graphene oxide. We attribute this effect to uniform coverage of graphene layer and improved electrical percolation network.

Motion Driven by Strain Gradient Fields

PubMed Central

Wang, Chao; Chen, Shaohua

2015-01-01

A new driving mechanism for direction-controlled motion of nano-scale objects is proposed, based on a model of stretching a graphene strip linked to a rigid base with linear springs of identical stiffness. We find that the potential energy difference induced by the strain gradient field in the graphene strip substrate can generate sufficient force to overcome the static and kinetic friction forces between the nano-flake and the strip substrate, resulting in the nanoscale flake motion in the direction of gradient reduction. The dynamics of the nano-flake can be manipulated by tuning the stiffness of linear springs, stretching velocity and the flake size. This fundamental law of directional motion induced by strain gradient could be very useful for promising designs of nanoscale manipulation, transportation and smart surfaces. PMID:26323603

Coercivity enhancement in Mn-Al-Cu flakes produced by surfactant-assisted milling

NASA Astrophysics Data System (ADS)

Saravanan, P.; Hsu, Jen-Hwa; Vinod, V. T. P.; Černík, Miroslav; Kamat, S. V.

2015-11-01

We herein report the achievement of exceptionally high coercivity (Hc) values: 9.92 and 5.86 kOe at 5 and 300 K, respectively, for Mn55Al43Cu2 flakes produced by surfactant-assisted milling process without employing any heat-treatment. The use of surfactants such as oleic acid and oleylamine during milling yielded high-aspect ratio flakes for the Mn-Al-Cu alloy. Structural studies confirmed the presence of τ- and β-phases as the major constituents in the Mn-Al-Cu flakes. The observed Hc enhancement is due to the increase in anisotropy field and structural defects, which is hypothesized to originate from the domain-wall pinning as a consequence of precipitation of fine Cu-particles present at the grain boundaries.

NO2 sensing at room temperature using vertically aligned MoS2 flakes network

NASA Astrophysics Data System (ADS)

Kumar, Rahul; Goel, Neeraj; Kumar, Mahesh

2018-04-01

To exploit the role of alignment of MoS2 flake in chemical sensing, here, we have synthesized the horizontally and vertically aligned MoS2 flake network using conventional chemical vapor deposition technique. The morphology and number of layers were confirmed by SEM and Raman spectroscopy, respectively. The sensing performance of horizontally aligned and vertically aligned flake network was investigated to NO2 at room temperature. Vertically aligned MoS2 based sensor showed higher sensitivity 51.54 % and 63.2 % compared to horizontally aligned MoS2 sensor' sensitivity of 35.32 % and 45.2 % to 50 ppm and 100 ppm NO2, respectively. This high sensitivity attributed to the high aspect ratio and high adsorption energy on the edge site of vertically aligned MoS2.

Evaluation of co-cokes from bituminous coal with vacuum resid or decant oil, and evaluation of anthracites, as precursors to graphite

NASA Astrophysics Data System (ADS)

Nyathi, Mhlwazi S.

2011-12-01

Graphite is utilized as a neutron moderator and structural component in some nuclear reactor designs. During the reactor operaction the structure of graphite is damaged by collision with fast neutrons. Graphite's resistance to this damage determines its lifetime in the reactor. On neutron irradiation, isotropic or near-isotropic graphite experiences less structural damage than anisotropic graphite. The degree of anisotropy in a graphite artifact is dependent on the structure of its precursor coke. Currently, there exist concerns over a short supply of traditional precursor coke, primarily due to a steadily increasing price of petroleum. The main goal of this study was to study the anisotropic and isotropic properties of graphitized co-cokes and anthracites as a way of investigating the possibility of synthesizing isotropic or near-isotropic graphite from co-cokes and anthracites. Demonstrating the ability to form isotropic or near-isotropic graphite would mean that co-cokes and anthracites have a potential use as filler material in the synthesis of nuclear graphite. The approach used to control the co-coke structure was to vary the reaction conditions. Co-cokes were produced by coking 4:1 blends of vacuum resid/coal and decant oil/coal at temperatures of 465 and 500 °C for reaction times of 12 and 18 hours under autogenous pressure. Co-cokes obtained were calcined at 1420 °C and graphitized at 3000 °C for 24 hours. Optical microscopy, X-ray diffraction, temperature-programmed oxidation and Raman spectroscopy were used to characterize the products. It was found that higher reaction temperature (500 °C) or shorter reaction time (12 hours) leads to an increase in co-coke structural disorder and an increase in the amount of mosaic carbon at the expense of textural components that are necessary for the formation of anisotropic structure, namely, domains and flow domains. Characterization of graphitized co-cokes showed that the quality, as expressed by the degree of graphitization and crystallite dimensions, of the final product is dependent on the nature of the precursor co-coke. The methodology for studying anthracites was to select two anthracites on basis of rank, PSOC1515 being semi-anthracite and DECS21 anthracite. The selected anthracites were graphitized, in both native and demineralized states, under the same conditions as co-cokes. Products obtained from DECS21 showed higher degrees of graphitization and larger crystallite dimensions than products obtained from PSOC1515. Demineralization of anthracites served to increase the degree of graphitization, indicating that the minerals contained in these anthracites have no graphitization-enhancing ability. A larger crystallite length for products obtained from native versions, compared to demineralized versions, was attributed to a formation and decomposition of a silicon carbide during graphitization of native versions. In order to examine the anisotropic and isotropic properties, nuclear-grade graphite samples obtained from Oak Ridge National Laboratory (ORNL) and commercial graphite purchased from Fluka were characterized under similar conditions as graphitized co-cokes and anthracites. These samples served as representatives of "two extremes", with ORNL samples being the isotropic end and commercial graphite being the anisotropic end. Through evaluating relationships between structural parameters, it was observed that graphitized co-cokes are situated, structurally, somewhere between the "two extremes", whereas graphitized anthracites are closer to the anisotropic end. Basically, co-cokes have a better potential than anthracites to transform to isotropic or near-isotropic graphite upon graphitization. By co-coking vacuum resid/coal instead of decant oil/coal or using 500 °C instead of 465 °C, a shift away from commercial graphite towards ORNL samples was attained. Graphitizing a semi-anthracite or demineralizing anthracites before graphitization also caused a shift towards ORNL samples.

"Bricks and mortar" self-assembly approach to graphitic mesoporous carbon nanocomposites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fulvio, P. F.; Mayes, R.; Wang, X. Q.

2011-04-20

Mesoporous carbon materials do not have sufficient ordering at the atomic scale to exhibit good electronic conductivity. To date, mesoporous carbons having uniform mesopores and high surface areas have been prepared from partially-graphitizable precursors in the presence of templates. High temperature thermal treatments above 2000 °C, which are usually required to increase conductivity, result in a partial or total collapse of the mesoporous structures and reduced surface areas induced by growth of graphitic domains, limiting their applications in electric double layer capacitors and lithium-ion batteries. In this work, we successfully implemented a “brick-and-mortar” approach to obtain ordered graphitic mesoporous carbonmore » nanocomposites with tunable mesopore sizes below 850 °C without using graphitization catalysts or high temperature thermal treatments. Phenolic resin-based mesoporous carbons act as mortar to highly conductive carbon blacks and carbon onions (bricks). The capacitance and resistivity of final materials can be tailored by changing the mortar to brick ratios.« less

Brick-and-Mortar Self-Assembly Approach to Graphitic Mesoporous Carbon Nanocomposites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dai, Sheng; Fulvio, Pasquale F; Mayes, Richard T

2011-01-01

Mesoporous carbon materials do not have sufficient ordering at the atomic scale to exhibit good electronic conductivity. To date, mesoporous carbons having uniform mesopores and high surface areas have been prepared from partially-graphitizable precursors in the presence of templates. High temperature thermal treatments above 2000 C, which are usually required to increase conductivity, result in a partial or total collapse of the mesoporous structures and reduced surface areas induced by growth of graphitic domains, limiting their applications in electric double layer capacitors and lithium-ion batteries. In this work, we successfully implemented a 'brick-and-mortar' approach to obtain ordered graphitic mesoporous carbonmore » nanocomposites with tunable mesopore sizes below 850 C without using graphitization catalysts or high temperature thermal treatments. Phenolic resin-based mesoporous carbons act as mortar to highly conductive carbon blacks and carbon onions (bricks). The capacitance and resistivity of final materials can be tailored by changing the mortar to brick ratios.« less

Forgery at the Snite Museum of Art? Improving AMS Radiocarbon Dating at the University of Notre Dame

NASA Astrophysics Data System (ADS)

Troyer, Laura; Bagwell, Connor; Anderson, Tyler; Clark, Adam; Nelson, Austin; Skulski, Michael; Collon, Philippe

2017-09-01

The Snite Museum of Art recently obtained several donations of artifacts. Five of the pieces lack sufficient background information to prove authenticity and require further analysis to positively determine the artwork's age. One method to determine the artwork's age is radiocarbon dating via Accelerator Mass Spectrometry (AMS) performed at the University of Notre Dame's Nuclear Science Laboratory. Samples are prepared by combustion of a small amount of material and subsequent reduction to carbon into an iron powder matrix (graphitization). The graphitization procedure affects the maximum measurement rate, and a poor graphitization can be detrimental to the AMS measurement of the sample. Previous graphitization procedures resulted in a particle current too low or inconsistent to optimize AMS measurements. Thus, there was a desire to design and refine the graphitization system. The finalized process yielded physically darker samples and increased sample currents by two orders of magnitude. Additionally, the first testing of the samples was successful, yet analysis of the dates proved inconclusive. AMS measurements will be performed again to obtain better sampling statistics in the hopes of narrowing the reported date ranges. NSF and JINA-CEE.

A superhard, quenchable carbon polymorph formed by the room-temperature compression of graphite (Invited)

NASA Astrophysics Data System (ADS)

Wang, Y.; Kiefer, B.; Lee, K. K.

2010-12-01

As one of the revolutionary inventions of the 20th century, synthetic diamond has had a large impact on industry and on scientific research. However, the necessities of high pressures, high temperatures and a metal catalyst during the manufacturing of synthetic diamond make it energy consuming thus limits its availability and use. Here, we report on the synthesis of a superhard non-diamond material resulting from the compression of graphite above ~20 GPa at room temperature without the utilization of metal catalysts. The final product includes a nano-sized phase of carbon that is recoverable at ambient conditions. Furthermore, the ring cracks left on the diamond anvils suggest that the hardness of this post-graphite phase is at least comparable to that of diamond. We use high-resolution synchrotron x-ray diffraction and micro-Raman spectroscopy to monitor the structural transformation in graphite under high pressure and room temperature and find the transition to be sluggish. The possible crystal structure of the new, quenchable phase will be discussed and the time-dependent formation of this superhard post-graphite carbon will be addressed and compared to first-principle predictions.

Stereoscopy for visual simulation of materials of complex appearance

NASA Astrophysics Data System (ADS)

da Graça, Fernando; Paljic, Alexis; Lafon-Pham, Dominique; Callet, Patrick

2014-03-01

The present work studies the role of stereoscopy on perceived surface aspect of computer generated complex materials. The objective is to investigate if, and how, the additional information conveyed by the binocular vision affects the observer judgment on the evaluation of flake density in an effect paint simulation. We have set up a heuristic flake model with a Voronoi: modelization of flakes. The model was implemented in our rendering engine using global illumination, ray tracing, with an off axis-frustum method for the calculation of stereo images. We conducted a user study based on a flake density discrimination task to determine perception thresholds (JNDs). Results show that stereoscopy slightly improves density perception. We propose an analysis methodology based on granulometry. This allows for a discussion of the results on the basis of scales of observation.

Tuning Magnetic Soliton Phase via Dimensional Confinement in Exfoliated 2D Cr 1/3 NbS 2 Thin Flakes

DOE PAGES

Tang, Siwei; Fishman, Randy S.; Okamoto, Satoshi; ...

2018-05-02

Thin flakes of Cr 1/3NbS 2 are fabricated successfully via microexfoliation techniques. Temperature-dependent and field-dependent magnetizations of thin flakes with various thicknesses are investigated. When the thickness of the flake is around several hundred nanometers, the softening and eventual disappearance of the bulk soliton peak is accompanied by the appearance of other magnetic peaks at lower magnetic fields. The emergence and annihilation of the soliton peaks are explained and simulated theoretically by the change in spin spiral number inside the soliton lattice due to dimensional confinement. Compared to the conventional magnetic states in nanoscale materials, the stability and thickness tunabilitymore » of quantified spin spirals make Cr 1/3NbS 2 a potential candidate for spintronics nanodevices beyond Moore’s law.« less

Tuning Magnetic Soliton Phase via Dimensional Confinement in Exfoliated 2D Cr 1/3 NbS 2 Thin Flakes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Siwei; Fishman, Randy S.; Okamoto, Satoshi

Thin flakes of Cr 1/3NbS 2 are fabricated successfully via microexfoliation techniques. Temperature-dependent and field-dependent magnetizations of thin flakes with various thicknesses are investigated. When the thickness of the flake is around several hundred nanometers, the softening and eventual disappearance of the bulk soliton peak is accompanied by the appearance of other magnetic peaks at lower magnetic fields. The emergence and annihilation of the soliton peaks are explained and simulated theoretically by the change in spin spiral number inside the soliton lattice due to dimensional confinement. Compared to the conventional magnetic states in nanoscale materials, the stability and thickness tunabilitymore » of quantified spin spirals make Cr 1/3NbS 2 a potential candidate for spintronics nanodevices beyond Moore’s law.« less

Shape-dependent electronic properties of blue phosphorene nano-flakes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhatia, Pradeep; Swaroop, Ram; Kumar, Ashok, E-mail: ashok@cup.ac.in

In recent year’s considerable attention has been given to the first principles method for modifying and controlling electronic properties of nano-materials. We performed DFT-based calculations on the electronic properties of zigzag-edged nano-flakes of blue phosphorene with three possible shapes namely rectangular, triangular and hexagonal. We observed that HOMO-LUMO gap of zigzag phosphorene nano-flakes with different shapes is ∼2.9 eV with H-passivations and ∼0.7 – 1.2 eV in pristine cases. Electronic properties of blue phosphorene nano-flakes show the strong dependence on their shape. We observed that distributions of molecular orbitals were strongly affected by the different shapes. Zigzag edged considered nanostructuresmore » are non-magnetic and semiconducting in nature. The shape dependent electronic properties may find applications in tunable nano-electronics.« less

Graphene/semicrystalline-carbon derived from amylose films for supercapacitor application

NASA Astrophysics Data System (ADS)

Deraman, M.; Sazali, N. E. S.; Hanappi, M. F. Y. M.; Tajuddin, N. S. M.; Hamdan, E.; Suleman, M.; Othman, M. A. R.; Omar, R.; Hashim, M. A.; Basri, N. H.; Nor, N. S. M.; Dolah, B. N. M.; Noor, A. M.; Jasni, M. R. M.

2016-08-01

Graphene/semicrystalline-carbon in the form of carbon flakes is produced by carbonization up to 600, 700, 800, 900 and 1000°C, respectively, of the amylose films prepared by a casting method on copper foil substrate. The carbon flakes are characterized by X-ray diffraction (XRD) method to determine their microcrystallite interlayer spacing, width and stack-height; and Raman spectroscopy (RS) method to obtain structural information from the D-, D2- and G-bands peak-intensities. The XRD results show that increase in carbonization temperature lead to ~(1-3%), ~85% and ~30%increase in the microcrystallites interlayer spacing, width and stack-height, respectively, indicating that a larger growth of microcrytallite of carbon flakes occurs in the direction parallel to (001) plane or film planar surface. The specific surface area of carbon flakes estimated from the XRD results in decreases from ~4400 to ~3400 m2/g, corresponding to the specific capacitance between ~500 to ~400 F/g, which are well within the range of specific capacitance for typical electrodes carbon for supercapacitor application. The RS results show that the multilayer graphene co-exist with semicrystalline- carbon within the carbon flakes, with the multilayer graphene relative quantities increase with increasing carbonization temperature.

Compositional Analysis of Whole Grains, Processed Grains, Grain Co-Products, and Other Carbohydrate Sources with Applicability to Pet Animal Nutrition

PubMed Central

Beloshapka, Alison N.; Buff, Preston R.; Fahey, George C.; Swanson, Kelly S.

2016-01-01

Our objective was to measure the proximate, starch, amino acid, and mineral compositions of grains, grain co-products, and other carbohydrate sources with potential use in pet foods. Thirty-two samples from barley (barley flake, cut barley, ground pearled barley, malted barley, whole pearled barley, pearled barley flakes, and steamed rolled barley); oats (groats, ground oatmeal, ground steamed groats, instant oats, oat bran, oat fiber, oat flour, quick oats, regular rolled oats, steamed rolled oat groats, and steel cut groats); rice (brown rice, polished rice, defatted rice bran, and rice flour); and miscellaneous carbohydrate sources (canary grass seed, hulled millet, whole millet, quinoa, organic spelt hull pellets, potato flake, sorghum, whole wheat, and whole yellow corn) were analyzed. Crude protein, amino acid, fat, dietary fiber, resistant starch, and mineral concentrations were highly variable among the respective fractions (i.e., barley flake vs. malted barley vs. steamed rolled barley) as well as among the various grains (i.e., barley flake vs. brown rice vs. canary grass seed). These ingredients not only provide a readily available energy source, but also a source of dietary fiber, resistant starch, essential amino acids, and macrominerals for pet diets. PMID:28231117

Picosecond laser ablation of polyamide electrospun nanofibers

NASA Astrophysics Data System (ADS)

Götze, Marco; Krimig, Olaf; Kürbitz, Tobias; Henning, Sven; Heilmann, Andreas; Hillrichs, Georg

2017-02-01

Electrospun nanofibers mats have a great potential in tissue engineering and regenerative medicine. Their high porosity and enormous volume to surface ratio stimulate the growth and adhesion of mammalian cells and serve as a stable support structure. These suitable properties can be further optimized by structuring of the nanofibers. Ultrashort pulsed lasers can be used for modifying of the electrospun nanofibers without significant heat exposure. It seems also possible to generate very fine cuts from the fiber mats. In this study, polyamide electrospun nanofibers samples were processed with picosecond UV-laser irradiation (λ = 355 nm, τ = 15 ps). The samples were processed in dry, wet and immersed condition. To optimize cutting and structuring of nanofiber tissue flakes, the influence of different laser parameters on line widths, edge quality, heat-affected zone (HAZ) and the contamination of the fibers by ablated particles (debris) were examined. One additional aim was the minimization of the flake size. It was possible to generate nanofiber flakes in the sub-millimeter range. The quality of the nanofiber flakes could be improved by ablation near the ablation threshold of the material. For cutting under wet conditions shrinking of the flakes has to be taken into account.

Head lice

MedlinePlus

Pediculosis capitis - head lice ... Head lice infect hair on the head. Tiny eggs on the hair look like flakes of dandruff . However, ... flaking off the scalp, they stay in place. Head lice can live up to 30 days on a ...

Optimization and Domestic Sourcing of Lithium Ion Battery Anode Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wood, III, D. L.; Yoon, S.

2012-10-25

The purpose of this Cooperative Research and Development Agreement (CRADA) between ORNL and A123Systems, Inc. was to develop a low-temperature heat treatment process for natural graphite based anode materials for high-capacity and long-cycle-life lithium ion batteries. Three major problems currently plague state-of-the-art lithium ion battery anode materials. The first is the cost of the artificial graphite, which is heat-treated well in excess of 2000°C. Because of this high-temperature heat treatment, the anode active material significantly contributes to the cost of a lithium ion battery. The second problem is the limited specific capacity of state-of-the-art anodes based on artificial graphites, whichmore » is only about 200-350 mAh/g. This value needs to be increased to achieve high energy density when used with the low cell-voltage nanoparticle LiFePO4 cathode. Thirdly, the rate capability under cycling conditions of natural graphite based materials must be improved to match that of the nanoparticle LiFePO4. Natural graphite materials contain inherent crystallinity and lithium intercalation activity. They hold particular appeal, as they offer huge potential for industrial energy savings with the energy costs essentially subsidized by geological processes. Natural graphites have been heat-treated to a substantially lower temperature (as low as 1000-1500°C) and used as anode active materials to address the problems described above. Finally, corresponding graphitization and post-treatment processes were developed that are amenable to scaling to automotive quantities.« less

Molecular modeling of the microstructure evolution during carbon fiber processing

NASA Astrophysics Data System (ADS)

Desai, Saaketh; Li, Chunyu; Shen, Tongtong; Strachan, Alejandro

2017-12-01

The rational design of carbon fibers with desired properties requires quantitative relationships between the processing conditions, microstructure, and resulting properties. We developed a molecular model that combines kinetic Monte Carlo and molecular dynamics techniques to predict the microstructure evolution during the processes of carbonization and graphitization of polyacrylonitrile (PAN)-based carbon fibers. The model accurately predicts the cross-sectional microstructure of the fibers with the molecular structure of the stabilized PAN fibers and physics-based chemical reaction rates as the only inputs. The resulting structures exhibit key features observed in electron microcopy studies such as curved graphitic sheets and hairpin structures. In addition, computed X-ray diffraction patterns are in good agreement with experiments. We predict the transverse moduli of the resulting fibers between 1 GPa and 5 GPa, in good agreement with experimental results for high modulus fibers and slightly lower than those of high-strength fibers. The transverse modulus is governed by sliding between graphitic sheets, and the relatively low value for the predicted microstructures can be attributed to their perfect longitudinal texture. Finally, the simulations provide insight into the relationships between chemical kinetics and the final microstructure; we observe that high reaction rates result in porous structures with lower moduli.

Laser-induced incandescence (LII) diagnostic for in situ monitoring of nanoparticle synthesis in a high-pressure arc discharge

NASA Astrophysics Data System (ADS)

Yatom, Shurik; Vekselman, Vladislav; Mitrani, James; Stratton, Brentley; Raitses, Yevgeny; LaboratoryPlasma Nanosynthesis Team

2016-10-01

A DC arc discharge is commonly used for synthesis of carbon nanoparticles, including buckyballs, carbon nanotubes, and graphene flakes. In this work we show the first results of nanoparticles monitored during the arc discharge. The graphite electrode is vaporized by high current (60 A) in a buffer Helium gas leading to nanoparticle synthesis in a low temperature plasma. The arc was shown to oscillate, which can possibly influence the nano-synthesis. To visualize the nanoparticles in-situ we employ the LII technique. The nanoparticles with radii >50 nm, emerging from the arc area are heated with a short laser pulse and incandesce. The resulting radiation is captured with an ICCD camera, showing the location of the generated nanoparticles. The images of incandescence are studied together with temporally synchronized fast-framing imaging of C2 emission, to connect the dynamics of arc instabilities, C2 molecules concentration and nanoparticles. The time-resolved incandescence signal is analyzed with combination of ex-situ measurements of the synthesized nanoparticles and LII modeling, to provide the size distribution of produced nanoparticles. This work was supported by US Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.

Characterisation of thin films of graphene–surfactant composites produced through a novel semi-automated method

PubMed Central

Nabok, Alexei; Davis, Frank; Higson, Séamus P J

2016-01-01

Summary In this paper we detail a novel semi-automated method for the production of graphene by sonochemical exfoliation of graphite in the presence of ionic surfactants, e.g., sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB). The formation of individual graphene flakes was confirmed by Raman spectroscopy, while the interaction of graphene with surfactants was proven by NMR spectroscopy. The resulting graphene–surfactant composite material formed a stable suspension in water and some organic solvents, such as chloroform. Graphene thin films were then produced using Langmuir–Blodgett (LB) or electrostatic layer-by-layer (LbL) deposition techniques. The composition and morphology of the films produced was studied with SEM/EDX and AFM. The best results in terms of adhesion and surface coverage were achieved using LbL deposition of graphene(−)SDS alternated with polyethyleneimine (PEI). The optical study of graphene thin films deposited on different substrates was carried out using UV–vis absorption spectroscopy and spectroscopic ellipsometry. A particular focus was on studying graphene layers deposited on gold-coated glass using a method of total internal reflection ellipsometry (TIRE) which revealed the enhancement of the surface plasmon resonance in thin gold films by depositing graphene layers. PMID:26977378

Large-Scale Production of Nanographite by Tube-Shear Exfoliation in Water

PubMed Central

Engström, Ann-Christine; Hummelgård, Magnus; Andres, Britta; Forsberg, Sven; Olin, Håkan

2016-01-01

The number of applications based on graphene, few-layer graphene, and nanographite is rapidly increasing. A large-scale process for production of these materials is critically needed to achieve cost-effective commercial products. Here, we present a novel process to mechanically exfoliate industrial quantities of nanographite from graphite in an aqueous environment with low energy consumption and at controlled shear conditions. This process, based on hydrodynamic tube shearing, produced nanometer-thick and micrometer-wide flakes of nanographite with a production rate exceeding 500 gh-1 with an energy consumption about 10 Whg-1. In addition, to facilitate large-area coating, we show that the nanographite can be mixed with nanofibrillated cellulose in the process to form highly conductive, robust and environmentally friendly composites. This composite has a sheet resistance below 1.75 Ω/sq and an electrical resistivity of 1.39×10-4 Ωm and may find use in several applications, from supercapacitors and batteries to printed electronics and solar cells. A batch of 100 liter was processed in less than 4 hours. The design of the process allow scaling to even larger volumes and the low energy consumption indicates a low-cost process. PMID:27128841

Temperature Dependence of Raman-Active In-Plane E2g Phonons in Layered Graphene and h-BN Flakes

NASA Astrophysics Data System (ADS)

Li, Xiaoli; Liu, Jian; Ding, Kai; Zhao, Xiaohui; Li, Shuai; Zhou, Wenguang; Liang, Baolai

2018-01-01

Thermal properties of sp2 systems such as graphene and hexagonal boron nitride (h-BN) have attracted significant attention because of both systems being excellent thermal conductors. This research reports micro-Raman measurements on the in-plane E2g optical phonon peaks ( 1580 cm-1 in graphene layers and 1362 cm-1 in h-BN layers) as a function of temperature from - 194 to 200 °C. The h-BN flakes show higher sensitivity to temperature-dependent frequency shifts and broadenings than graphene flakes. Moreover, the thermal effect in the c direction on phonon frequency in h-BN layers is more sensitive than that in graphene layers but on phonon broadening in h-BN layers is similar as that in graphene layers. These results are very useful to understand the thermal properties and related physical mechanisms in h-BN and graphene flakes for applications of thermal devices.

Investigation of surface potentials in reduced graphene oxide flake by Kelvin probe force microscopy

NASA Astrophysics Data System (ADS)

Negishi, Ryota; Takashima, Kai; Kobayashi, Yoshihiro

2018-06-01

The surface potential (SP) of reduced graphene oxide (rGO) flakes prepared by thermal treatments of GO under several conditions was analyzed by Kelvin probe force microscopy. The low-crystalline rGO flakes in which a significant amount of oxygen functional groups and structural defects remain have a much lower SP than mechanically exfoliated graphene free from oxygen and defects. On the other hand, the highly crystalline rGO flake after a thermal treatment for the efficient removal of oxygen functional groups and healing of structural defects except for domain boundary shows SP equivalent to that of the mechanically exfoliated graphene. These results indicate that the work function of rGO is sensitively modulated by oxygen functional groups and structural defects remaining after the thermal reduction process, but is not affected significantly by the domain boundary remaining after the healing of structural defects through the thermal treatment at high temperature.

Morphology and magnetic properties of CeCo5 submicron flakes prepared by surfactant-assisted high-energy ball milling

NASA Astrophysics Data System (ADS)

Zhang, J. J.; Gao, H. M.; Yan, Y.; Bai, X.; Su, F.; Wang, W. Q.; Du, X. B.

2012-10-01

CeCo5 permanent magnetic alloy has been processed by surfactant assisted high energy ball milling. Heptane and oleic acid were used as the solvent and surfactant, respectively. The amount of surfactant used was 50% by weight of the starting powder. The produced particles were deposited on a piece of copper (4 mm in length and width) under a magnetic field of 27 kOe applied along the copper surface and immobilized by ethyl α-cyanoacrylate. Scanning electron microscope pictures show that the particles are flakes, several μm in length and width and tens of nm in thickness. X-ray diffraction patterns and magnetic measurements prove that the flakes are crystalline with c-axes magnetic anisotropy. The easy magnetization axis is oriented perpendicular to the surface of the flake. A maximum coercivity of 3.3 kOe was obtained for the sample milled for 40 min.

Failure Processes in Embedded Monolayer Graphene under Axial Compression

PubMed Central

Androulidakis, Charalampos; Koukaras, Emmanuel N.; Frank, Otakar; Tsoukleri, Georgia; Sfyris, Dimitris; Parthenios, John; Pugno, Nicola; Papagelis, Konstantinos; Novoselov, Kostya S.; Galiotis, Costas

2014-01-01

Exfoliated monolayer graphene flakes were embedded in a polymer matrix and loaded under axial compression. By monitoring the shifts of the 2D Raman phonons of rectangular flakes of various sizes under load, the critical strain to failure was determined. Prior to loading care was taken for the examined area of the flake to be free of residual stresses. The critical strain values for first failure were found to be independent of flake size at a mean value of –0.60% corresponding to a yield stress up to -6 GPa. By combining Euler mechanics with a Winkler approach, we show that unlike buckling in air, the presence of the polymer constraint results in graphene buckling at a fixed value of strain with an estimated wrinkle wavelength of the order of 1–2 nm. These results were compared with DFT computations performed on analogue coronene/PMMA oligomers and a reasonable agreement was obtained. PMID:24920340

Slime mold solves maze in one pass, assisted by gradient of chemo-attractants.

PubMed

Adamatzky, Andrew

2012-06-01

Plasmodium of Physarum polycephalum is a large cell, visible by unaided eye, which exhibits sophisticated patterns of foraging behaviour. The plasmodium's behaviour is well interpreted in terms of computation, where data are spatially extended configurations of nutrients and obstacles, and results of computation are networks of protoplasmic tubes formed by the plasmodium. In laboratory experiments and numerical simulation we show that if plasmodium of P. polycephalum is inoculated in a maze's peripheral channel and an oat flake (source of attractants) in a the maze's central chamber then the plasmodium grows toward target oat flake and connects the flake with the site of original inoculation with a pronounced protoplasmic tube. The protoplasmic tube represents a path in the maze. The plasmodium solves maze in one pass because it is assisted by a gradient of chemo-attractants propagating from the target oat flake.

Atomistic simulation of Al-graphene thin film growth on polycrystalline Al substrate

NASA Astrophysics Data System (ADS)

Zhang, Lan; Zhu, Yongchao; Li, Na; Rong, Yan; Xia, Huimin; Ma, Huizhong

2018-03-01

The growth of Al-Graphene composite coatings on polycrystalline Al substrate was investigated by using classical molecular dynamics (MD) simulations. Unlike the diffusion behaviors on single crystal surface, most of adatoms were easily bound by the steps on polycrystalline Al surface, owing to the local accelerated energy. Both Ehrlich-Schwoebel (ES) barriers and the steering effect backed up the volmer-weber growth mode, which was consistent with the dynamic growth process observed in the deposit. The morphology of composite coatings was significantly affected by graphene flakes. Enrichment of graphene flakes gave rise to an increase of the local thickness, and graphene flakes only existed in Al grain boundaries. The size of Al grains in the composite coating visibly decreased when compared with that in the pure Al coating. This grain refinement and the mechanical property can be reinforced by the increase of graphene flakes.

Scalable Synthesis of Graphene Based Heterostructures and Their Use in Energy Sensing, Conversion and Storage

NASA Astrophysics Data System (ADS)

Bhimanapati, Ganesh Rahul

2D materials are a unique class of materials system which has spread across the entire spectrum of materials including semi-metallic graphene to insulating boron nitride. Since graphene there has been many other 2D material systems (such as boron nitride (hBN), transition metal dichalcogenides (TMDs)) that provide a wider array of unique chemistries and properties to explore for applications specifically in optoelectronics, mechanical and energy applications. Specifically tailored heterostructures can be made which can retain the character of single-atom thick sheets while having an entirely different optical and mechanical properties compared to the parent materials. In the current work, heterostructures based on graphene, hBN and TMDs have been made, which were used to study the fundamental process-property relations and their use in energy conversion and storage have been studied. The first part of this dissertation focuses on scalable approach for liquid phase exfoliation of graphene oxide (GO) and hBN (Chapter 2). The current work successfully shows an exfoliation efficiency of 25% monolayer material for hBN, which was not previously achieved. These exfoliated materials were further mixed in the liquid environment to form a new heterostructure BCON (Chapter 3). This newly formed heterostructure was studied in detail for its process-property relations. At pH 4-8, BCON was highly stable and can be dried to form paper or ribbon like material. New bonds were observed in BCON which could be linked to the GO linkage at the nitrogen sites of the hBN. This free standing BCON was tested under various radiation sources like x-rays, alpha, beta, gamma sources and heavy ion like Ar particles and was found that it is very robust to radiation (Chapter 5). By understanding the chemistry, stability and properties of these materials, this could lay a foundation in using these materials for integration in conductive and insulating ink development, polymer composite development to improve the thermal and mechanical properties. Another major focus of this dissertation work is combining TMDs and graphene for energy applications specifically hydrogen evolution reactions (HERs) and Lithium ion batteries (LiBs). TMD's specifically MoS2 and WSe2 were grown on graphite paper using powder vaporization and metal organic chemical vapor deposition (MOCVD) (Chapter 4). Control over the architecture of the MoS2 and WSe2 was achieved by varying the precursor concentration and pressure, which was observed by using scanning electron microscopy. These samples were further characterized using cross-sectional transmission electron microscopy, x-ray photoelectron spectroscopy and Raman microscopy confirming the high quality of the material that was grown. The MoS2/graphite flowers were tested for hydrogen evolution reactions and were found that they are highly active for catalysis and by modifying the surface using simple UV-Ozone treatments, this activity can be increased by 4x (reducing the Tafel slope from 185 to 54 mV/Dec). Similar performance was observed for WSe2/Graphite heterostructure where the tiny 100 nm vertical flakes on graphite paper showed one of the lowest reported Tafel slope of 64 mV/Dec (Chapter 6). MoS2/Graphite was further tested for lithium ion batteries and was found that it had a higher cyclic capacity of 750 mV/Dec. This enhanced stability and performance for energy applications was achieved because of the direct growth technique on graphite. Hence this technique could be used as a scalable alternative to make anodes for lithium ion batteries.

Process Optimization for Solid Extraction, Flavor Improvement and Fat Removal in the Production of Soymilk From Full Fat Soy Flakes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prawiradjaja, Stanley

Traditionally soymilk has been made with whole soybeans; however, there are other alternative raw ingredients for making soymilk, such as soy flour or full-fat soy flakes. US markets prefer soymilk with little or no beany flavor. modifying the process or using lipoxygenase-free soybeans can be used to achieve this. Unlike the dairy industry, fat reduction in soymilk has been done through formula modification instead of by conventional fat removal (skimming). This project reports the process optimization for solids and protein extraction, flavor improvement and fat removal in the production of 5, 8 and 12 °Brix soymilk from full fat soymore » flakes and whole soybeans using the Takai soymilk machine. Proximate analyses, and color measurement were conducted in 5, 8 and 12 °Brix soymilk. Descriptive analyses with trained panelists (n = 9) were conducted using 8 and 12 °Brix lipoxygenase-free and high protein blend soy flake soymilks. Rehydration of soy flakes is necessary to prevent agglomeration during processing and increase extractability. As the rehydration temperature increases from 15 to 50 to 85 C, the hexanal concentration was reduced. Enzyme inactivation in soy flakes milk production (measured by hexanal levels) is similar to previous reports with whole soybeans milk production; however, shorter rehydration times can be achieved with soy flakes (5 to 10 minutes) compared to whole beans (8 to 12 hours). Optimum rehydration conditions for a 5, 8 and 12 °Brix soymilk are 50 C for 5 minutes, 85 C for 5 minutes and 85 C for 10 minutes, respectively. In the flavor improvement study of soymilk, the hexanal date showed differences between undeodorized HPSF in contrast to triple null soymilk and no differences between deodorized HPSF in contrast to deodorized triple null. The panelists could not differentiate between the beany, cereal, and painty flavors. However, the panelists responded that the overall aroma of deodorized 8 °Brix triple null and HPSF soymilk are lower than the undeodorized triple null and HPSF soymilk. The triple null soymilk was perceived to be more bitter than the HPSF soymilk by the sensory panel due to oxidation on the triple null soy flakes. This oxidation may produce other aroma that was not analyzed using the GC but noticed by the panelists. The sensory evaluation results did show that the deodorizer was able to reduce the soymilk aroma in HPSF soymilk so it would be similar to triple null soymilk at 8 °Brix level. Regardless of skimming method and solids levels, the fat from the whole soybean milk was removed less efficiently than soy flake milk (7 to 30% fat extraction in contrast to 50 to 80% fat extraction respectively). In soy flake milk, less fat was removed as the % solid increases regardless of the processing method. In whole soybean milk, the fat was removed less efficiently at lower solids level milk using the commercial dairy skimmer and more efficient at lower solids level using the centrifuge-decant method. Based on the Hunter L, a, b measurement, the color of the reduced fat soy flake milk yielded a darker, greener and less yellow colored milk than whole soymilk (α < 0.05), whereas no differences were noticed in reduced fat soybean milk (α < 0.05). Color comparison of whole and skim cow's milk showed the same the same trend as in the soymilk.« less

Oxidation resistance of selected mechanical carbons at 650 deg C in dry flowing air

NASA Technical Reports Server (NTRS)

Allen, G. P.; Wisander, D. W.

1973-01-01

Oxidation experiments were conducted with several experimental mechanical carbons at 650 C in air flowing at 28 cu cm/sec (STP). Experiments indicate that boron carbide addition and zinc phosphate treatment definitely improved oxidation resistance. Impregnation with coal tar pitch before final graphitization had some beneficial effect on oxidation resistance and it markedly improved flexure strength and hardness. Graphitization temperature alone did not affect oxidation resistance, but with enough added boron carbide the oxidation resistance was increased although the hardness greatly decreased.

Alteration of biomacromolecule in corn by steam flaking in relation to biodegradation kinetics in ruminant, revealed with vibrational molecular spectroscopy

NASA Astrophysics Data System (ADS)

Xu, Ningning; Liu, Jianxin; Yu, Peiqiang

2018-02-01

Large scale of steam flaked corn has been used in dairy ration to maintain high milk production level. This study aimed to determine effects of steam flaking on processing-induced intrinsic molecular structure changes that were associated with rumen degradation kinetics and nutrients supply. The advanced vibrational molecular spectroscopy was applied to reveal the processing-induced intrinsic structure changes on a molecular basis. The rumen degradation kinetics and nutrient supply were determined using in situ approach in ruminant livestock system. Raw corn grain (RC) and steam flaked corn grain (SFC) were obtained from two different processing plants. The results showed that (1) Compared to RC, SFC had greater truly digestible non-fiber carbohydrate [tdNFC: 86.8 versus 78.0% dry matter (DM)], but lower truly digestible crude protein [tdCP: 7.7 versus 9.0% DM]. (2) The steam flaking increased (P < 0.01) rumen degradable DM (RDDM) and starch (RDSt), but decreased (P < 0.01) rumen degradable protein (RDP). (3) Molecular absorbance intensities of most carbohydrate biopolymers were greater in SFC (P < 0.01), but protein amides associated molecular spectral intensities were lower (P < 0.01) in SFC. (4). The molecular structure and nutrient interactive study showed that carbohydrate spectral intensities were positively (P < 0.10) associated with RDDM and RDSt and protein amide spectral intensities were positively (P < 0.10) associated with RDP. This results indicated that the steam flaking induced molecular structure changes had an interactive relationship with rumen degradation kinetics.

[Compressive and bend strength of experimental admixed high copper alloys].

PubMed

Sourai, P; Paximada, H; Lagouvardos, P; Douvitsas, G

1988-01-01

Mixed alloys for dental amalgams have been used mainly in the form of admixed alloys, where eutectic spheres are blend with conventional flakes. In the present study the compressive strength, bend strength and microstructure of two high-copper alloys (Tytin, Ana-2000) is compared with three experimental alloys prepared of the two high copper by mixing them in proportions of 3:1, 1:1 and 1:3 by weight. The results revealed that experimental alloys inherited high early and final strength values without any significant change in their microstructure.

Effect of Cooling Rate on Morphology of TiAl3 Particles in Al-4Ti Master Alloy.

PubMed

Zhao, Jianhua; Wang, Tao; Chen, Jing; Fu, Lu; He, Jiansheng

2017-02-27

The Al-4Ti master alloy was fabricated by aluminum (Al) and sponge titanium particle in a resistance furnace at different cooling rates. This work aims to investigate the relationship between the cooling rate and morphology of TiAl3. The microstructure and composition of master alloys at different cooling rates were characterized and analyzed by optical microscopy (OM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and SEM with energy dispersive spectroscopy (EDS). The results showed that various morphologies of TiAl3 particles in the Al-4Ti master alloy could be acquired at different cooling rates. Petal-like, blocky, and flake-like TiAl3 particles in the Al-4Ti master alloy were respectively acquired at the cooling rates of 3.36 K/s, 2.57 K/s, and 0.31 K/s. It was also found that the morphology of TiAl3 particles in the prepared master alloy changed from petal-like to blocky, then finally to flake-like, with the decrease of cooling rate. In addition, the morphology of the TiAl3 particles has no effect on the phase inversion temperature of Al-4Ti master alloy.

Effect of Cooling Rate on Morphology of TiAl3 Particles in Al–4Ti Master Alloy

PubMed Central

Zhao, Jianhua; Wang, Tao; Chen, Jing; Fu, Lu; He, Jiansheng

2017-01-01

The Al–4Ti master alloy was fabricated by aluminum (Al) and sponge titanium particle in a resistance furnace at different cooling rates. This work aims to investigate the relationship between the cooling rate and morphology of TiAl3. The microstructure and composition of master alloys at different cooling rates were characterized and analyzed by optical microscopy (OM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and SEM with energy dispersive spectroscopy (EDS). The results showed that various morphologies of TiAl3 particles in the Al–4Ti master alloy could be acquired at different cooling rates. Petal-like, blocky, and flake-like TiAl3 particles in the Al–4Ti master alloy were respectively acquired at the cooling rates of 3.36 K/s, 2.57 K/s, and 0.31 K/s. It was also found that the morphology of TiAl3 particles in the prepared master alloy changed from petal-like to blocky, then finally to flake-like, with the decrease of cooling rate. In addition, the morphology of the TiAl3 particles has no effect on the phase inversion temperature of Al–4Ti master alloy. PMID:28772598

Experimental studies illuminate the cultural transmission of percussive technologies in Homo and Pan

PubMed Central

Whiten, Andrew

2015-01-01

The complexity of Stone Age tool-making is assumed to have relied upon cultural transmission, but direct evidence is lacking. This paper reviews evidence bearing on this question provided through five related empirical perspectives. Controlled experimental studies offer special power in identifying and dissecting social learning into its diverse component forms, such as imitation and emulation. The first approach focuses on experimental studies that have discriminated social learning processes in nut-cracking by chimpanzees. Second come experiments that have identified and dissected the processes of cultural transmission involved in a variety of other force-based forms of chimpanzee tool use. A third perspective is provided by field studies that have revealed a range of forms of forceful, targeted tool use by chimpanzees, that set percussion in its broader cognitive context. Fourth are experimental studies of the development of flint knapping to make functional sharp flakes by bonobos, implicating and defining the social learning and innovation involved. Finally, new and substantial experiments compare what different social learning processes, from observational learning to teaching, afford good quality human flake and biface manufacture. Together these complementary approaches begin to delineate the social learning processes necessary to percussive technologies within the Pan–Homo clade. PMID:26483537

Onion-like nanoscale structures and fullerene-type cages formed by electron irradiation on turbostratic B{sub x}C{sub 1{minus}x} (x<0.2)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Golberg, D.; Bando, Y.; Kurashima, K.

Flakes of CVD grown B{sub x}C{sub 1{minus}x} (x<0.2) films were exposed to intense electron irradiation (flux density up to {approximately}100 A/cm{sup 2}) in a 300 kV high resolution electron microscope equipped with a field emission gun. The starting flakes revealed a turbostratic B{sub x}C{sub 1{minus}x} structure. The composition of the starting materials and irradiated products was determined by using electron energy loss spectroscopy (EELS). Depending on the electron dose applied, irradiation of the turbostratic material led to formation of soap-bubble-like irregularly-shaped objects (linear dimensions of {approximately}2--5 nm), onion- and semi-onion-like structures (d{approximately}10nm), nested fullerenes (3--14 shells) and elementary fullerene-type cagesmore » (d{approximately}0.7 nm). It is thought that these curled and closed nanostructures arise from a continuous bending of the hexagonal B{sub x}C{sub 1{minus}x} sheets under electron irradiation. Finally, some possible structural models of B{sub x}C{sub 1{minus}x} fullerenes are considered.« less

Comparison of Conventional and Microwave Assisted Heating on Carbohydrate Content, Antioxidant Capacity and Postprandial Glycemic Response in Oat Meals

PubMed Central

Olędzki, Remigiusz

2018-01-01

Minimally processed cereal breakfast products from whole grain entered the market due to consumer demand of more nutritional food with more controlled sugar release. However, the subsequent processing of such products with different cooking methods in the consumer’s kitchen may lead to significant differentiation of their nutritional value. Therefore, the evaluation of the impact of frequently used cooking methods on a final quality of breakfast cereals meal is needed. The present study investigates how the two different methods of heating, conventional and microwave (MW) assisted, affect the carbohydrate content, profile and resulting glycemic index of so prepared food as well as the antioxidant activity of meals. Two products available on the market—oat bran and flakes—were used. The highest starch content in fluid phase of oatmeal was detected in samples heated for 3 min with microwaves, regardless the type. The lowest starch content was obtained for 5 min MW heated flakes sample. The total content of glucose was about 1.5 times lower in bran vs. flakes oatmeal. The highest β-glucan content in fluid fraction was also observed for bran meal but its release was independent of applied conditions. PMID:29443904

In Situ Exfoliation of Graphene in Epoxy Resins: A Facile Strategy to Efficient and Large Scale Graphene Nanocomposites.

PubMed

Li, Yan; Zhang, Han; Crespo, Maria; Porwal, Harshit; Picot, Olivier; Santagiuliana, Giovanni; Huang, Zhaohui; Barbieri, Ettore; Pugno, Nicola M; Peijs, Ton; Bilotti, Emiliano

2016-09-14

Any industrial application aiming at exploiting the exceptional properties of graphene in composites or coatings is currently limited by finding viable production methods for large volumes of good quality and high aspect ratio graphene, few layer graphene (FLG) or graphite nanoplatelets (GNP). Final properties of the resulting composites are inherently related to those of the initial graphitic nanoparticles, which typically depend on time-consuming, resource-demanding and/or low yield liquid exfoliation processes. In addition, efficient dispersion of these nanofillers in polymer matrices, and their interaction, is of paramount importance. Here we show that it is possible to produce graphene/epoxy nanocomposites in situ and with high conversion of graphite to FLG/GNP through the process of three-roll milling (TRM), without the need of any additives, solvents, compatibilisers or chemical treatments. This readily scalable production method allows for more than 5 wt % of natural graphite (NG) to be directly exfoliated into FLG/GNP and dispersed in an epoxy resin. The in situ exfoliated graphitic nanoplatelets, with average aspect ratios of 300-1000 and thicknesses of 5-17 nm, were demonstrated to conferee exceptional enhancements in mechanical and electrical properties to the epoxy resin. The above conclusions are discussed and interpreted in terms of simple analytical models.

Fischer-Tropsch-Type Production of Organic Materials in the Solar Nebula: Studies Using Graphite Catalysts and Measuring the Trapping of Noble Gases

NASA Technical Reports Server (NTRS)

Nuth, Joseph A., III; Ferguson, Frank T.; Lucas, Christopher; Kimura, Yuki; Hohenberg, Charles

2009-01-01

The formation of abundant carbonaceous material in meteorites is a long standing problem and an important factor in the debate on the potential for the origin of life in other stellar systems. The Fischer-Tropsch-type (FTT) catalytic reduction of CO by hydrogen was once the preferred model for production of organic materials in the primitive solar nebula. We have demonstrated that many grain surfaces can catalyze both FTT and HB-type reactions, including amorphous iron and magnesium silicates, pure silica smokes as well as several minerals. Graphite is not a particularly good FTT catalyst, especially compared to iron powder or to amorphous iron silicate. However, like other silicates that we have studied, it gets better with exposure to CO. N2 and H2 over time: e.g., after formation of a macromolecular carbonaceous layer on the surfaces of the underlying gains. While amorphous iron silicates required only 1 or 2 experimental runs to achieve steady state reaction rates, graphite only achieved steady state after 6 or more experiments. We will present results showing the catalytic action of graphite grains increasing with increasing number of experiments and will also discuss the nature of the final "graphite" grains aster completion of our experiments.

New method for binder and carbon black detection at nanometer scale in carbon electrodes for lithium ion batteries

NASA Astrophysics Data System (ADS)

Pfaffmann, Lukas; Jaiser, Stefan; Müller, Marcus; Scharfer, Philip; Schabel, Wilhelm; Bauer, Werner; Scheiba, Frieder; Ehrenberg, Helmut

2017-09-01

In the current work, graphite electrodes comprising PVDF binder and carbon black are subjected to characterization. An energy selective backscatter detector is used to localize carbon black and fluorine of PVDF. Therefore, it is necessary to distinguish between graphite, amorphous carbon and fluorine rich regions. Typically, an angular selective backscatter detector is employed to obtain an image providing the material contrast of the sample. Suitable materials for that detector are e.g. alloys to observe intermetallic phases, semiconductor for ;channeling contrast;, or imaging SiO2 and Au nanoparticles in biological cells. However, this detector cannot be used to distinguish between light elements with low atomic numbers, such as C to P. In addition, the contrast of fluorine rich regions and graphite is poor in normal in-lens images due to the low difference of the atomic mass between C and F. The aim of this study is to enhance the contrast of fluorine rich regions to graphite to carbon black. Therefore, the energy selective backscatter detector is used and its advantages and setup is described. Finally this technique is applied to investigate 400 μm thick cross-sections of graphite electrodes dried at different temperatures and obtain the carbon black distribution.

New Occurrence of Shocked Graphite Aggregates at Barringer Crater

NASA Astrophysics Data System (ADS)

Miura, Y.; Noma, Y.; Iancu, O. G.

1993-07-01

High-pressure carbon minera]s are considered to be formed by solid-solid transformation under static or impact high-pressure condition, but shocked quartz aggregates of impact craters are considered to be formed by quenched accretion of various aggregates by dynamic impact process [1-3]. The main purpose of this study is to elucidate new findings and occurrences of shocked graphite (SG) aggregates [2,3] at the Barringer meteorite crater. The graphite nodule block of Barringer Crater used in this study is collected near the rim. The sample is compared with standard graphite samples of Korea, Madagascar, and artificial impact graphites. There are four different mineral aggregates of the Barringer graphite nodule sample: (1) shocked graphite-1, (2) shocked graphite-2 and hexagonal diamond in the vein, (3) shocked quartz-1 (with kamacite) in the rim, and (4) calcite in the rim (Table 1). X-ray diffraction peaks of shocked graphite reveal low X-ray intensity, high Bragg-angle shift of X-ray diffraction peak, and multiple splitting of X-ray diffraction peaks. X-ray calculated density (rho) has been determined by X-ray diffractometer by the equation of density deviation Delta rho (%) = 100 x {(rho-rho(sub)0)/rho(sub)0}, where standard density rho(sub)0 is 2.255 g/cm^3 in Korean graphite [2,3]. The high-density value of shocked graphite grain obtained in Barringer is Delta rho = +0.6 +/- 0.1%. Shocked hexagonal diamonds (chaoite) show a high value of Delta rho = +0.6 +/- 0.9%. Analytical electron microscopy data reveal three different aggregates in the graphite nodule samples (Table 1): (1) shocked graphite-1 in the matrix, which contains uniformly Fe and Ca elements formed under gas state; (2) shocked graphite-2 in the vein, where crystallized shocked graphites and hexagonal diamonds are surrounded by kamacite-rich metals formed under gas-melt states of mixed compositions from iron meteorite and target rocks; and (3) shocked quartz-1 and kamacite in the rim, where coexisted elements are supplied from kamacite, sandstone, and limestone. The shocked quartz-1 grains with high density contain Fe and Ca elements that are different from the shocked quartz-2 of pure silica [1] formed at the final stage from the Coconino sandstone. (4) Limestone in the rim is attached from Kaibab limestone. The present shocked graphites with high density are the same as artificial fine-grained shocked graphites (Delta rho = +0.7%). Table 1, which appears here in the hard copy, shows formation stages with two shocked graphites in the Barringer Crater. Formation of shocked aggregates with chemical contamination indicate dynamic accretion processes of quenching and depression at impact. The existence of two shocked graphites indicates the two formation stages of the first gas-state and the second gas-melt states with quenching processes. The origin of carbon in the shocked graphites is considered in this study to be from Kaibab limestone. References: [1] Miura Y. (1991) Shock Waves, 1, 35-41. [2] Miura Y. (1992) Proc. Shock Waves (Japan), 2, 54-57. [3] Miura Y. et al. (1993) Symp. NIPR Antarctic Meteorite (Tokyo), in press. [4] Foote A. E. (1891) Am. J. Sci., 42, 413-417. [5] Hannemann R. E. et al. (1967) Science, 155, 995-997.

Large-size porous ZnO flakes with superior gas-sensing performance

NASA Astrophysics Data System (ADS)

Wen, Wei; Wu, Jin-Ming; Wang, Yu-De

2012-06-01

A simple top-down route is developed to fabricate large size porous ZnO flakes via solution combustion synthesis followed by a subsequent calcination in air, which is template-free and can be easily enlarged to an industrial scale. The achieved porous ZnO flakes, which are tens to hundreds of micrometers in flat and tens of nanometers in thickness, exhibit high response for detecting acetone and ethanol, because the unique two-dimensional architecture shortens effectively the gas diffusion distance and provides highly accessible open channels and active surfaces for the target gas.

Simple approach to detection and estimation of photoactivity of silver particles on graphene oxide in aqueous-organic dispersion

NASA Astrophysics Data System (ADS)

Vlasov, D. V.; Vlasova, T. D.; Apresyan, L. A.; Krasovskiy, V. I.; Feofanov, I. N.; Kazaryan, M. A.

2015-12-01

The effect of sediment flotation was observed in dispersion of graphene oxide flakes with Ag-particles deposited thereon in the aqueous-organic (containing dimethylformamide) under the visible light action, with subsequent stabilization of the dispersion, which does not occur in the absence of Ag-particles. The main reason for this laser light induced movement of sediment graphene oxide flakes may be associated with the appearance of small bubbles. The further development of this approach seem to be able to estimate the of graphene flakes photoactivity with different activating particles.

Ultrafast Optical Microscopy of Single Monolayer Molybdenum Disulfide Flakes

DOE PAGES

Seo, Minah; Yamaguchi, Hisato; Mohite, Aditya D.; ...

2016-02-15

We performed ultrafast optical microscopy on single flakes of atomically thin CVD-grown molybdenum disulfide, using non-degenerate femtosecond pump-probe spectroscopy to excite and probe carriers above and below the indirect and direct band gaps. These measurements reveal the influence of layer thickness on carrier dynamics when probing near the band gap. Furthermore, fluence-dependent measurements indicate that carrier relaxation is primarily influenced by surface-related defect and trap states after above-bandgap photoexcitation. Furthermore, the ability to probe femtosecond carrier dynamics in individual flakes can thus give much insight into light-matter interactions in these two-dimensional nanosystems.

[Development of a milk beverage based on pumpkin flakes].

PubMed

Fernandez, Z F; Guerra, N B; Diniz, N M; Salgado, S; Guerra, T M; Lopes, A C; Neta, J C; Padilha, M R

1998-06-01

Vitamin A deficiency is one of the majors public health problems in Brazilian Northeast, and among other causes may be concerned to precocious weaning. Aiming at reducing this problem, a dehydrated product based on powdered milk and pumpkin flakes was developed to act as a carotene source at weaning period. Pumpkin flakes were obtained by drum drying at a 6 atm steam pressure, 0.75 m2 contact surface and 1 rpm, and had their content of carotenoids, beta carotene, centesimal composition molds and yeast and faecal coliforms evaluated. The flakes were added to sugar and whole powdered milk according to FAO/WHO nutritional recommendation to 6-12 months old children and submitted to acceptability test by a 6 judges' panel. The results showed that the drying process had a 7% efficiency score and the flakes composition presented 4.84% moisture; 4.0% protein; 5.5% ash; 1.30% fat; 6.22% fiber; 78.14% carbohydrates; 115.08 micrograms/g total carotenois and 80.64 micrograms/g beta-carotene content. No coliforms were detected and molds and yeast content was 4.0 x 10(2) CFU/g. The powdered formulation properly diluted in water supports 45% of the RDA for children (calories, protein, carbohydrates and lipids) and 100% vitamin A and protein considering a 400 ml/day ingestion.

Raman Enhancement Effect on Thin GaSe Flake and Its Thickness Dependence

NASA Astrophysics Data System (ADS)

Quan, Lin; Song, Yuqing; Zhang, Guanghui; Wu, Yukun; Jin, Ke; Ding, Huaiyi; Pan, Nan; Luo, Yi; Wang, Xiaoping

Chemical enhancement is one of the important mechanisms in surface-enhanced Raman spectroscopy, however, its origin is still under debate. Two dimensional (2D) layered material is thought to be a strong candidate to investigate the chemical mechanism of Raman enhancement because it has flat surface, well defined structure and without the interference of electromagnetic enhancement. Herein we report the systematic studies of Raman enhancement effect on the gallium selenide (GaSe) flake by using copper phthalocyanine (CuPc) molecule as a probe. It is found that the Raman signal of CuPc on the monolayer GaSe can be significantly increased by one order of magnitude than that on the SiO2/Si substrate. Meanwhile, the enhancement effect is found to decrease with increasing the thickness of GaSe flake. The origin of the Raman enhancement is attributed to the chemical mechanism resulted from the charge transfer between the GaSe flake and the detected molecules. The supposition is further verified by the investigation of Raman enhancement effect of CuPc with different thicknesses on the GaSe flake. Our work will shed more light on the understanding of the chemical mechanism for Raman enhancement and expand more practical applications of GaSe.

Erosion and Soil Contamination Control Using Coconut Flakes And Plantation Of Centella Asiatica And Chrysopogon Zizanioides

NASA Astrophysics Data System (ADS)

Roslan, Rasyikin; Che Omar, Rohayu; Nor Zuliana Baharuddin, Intan; Zulkarnain, M. S.; Hanafiah, M. I. M.

2016-11-01

Land degradation in Malaysia due to water erosion and water logging cause of loss of organic matter, biodiversity and slope instability but also land are contaminated with heavy metals. Various alternative such as physical remediation are use but it not showing the sustainability in term of environmental sustainable. Due to that, erosion and soil contamination control using coconut flakes and plantation of Centella asiatica and Chrysopogon zizanioides are use as alternative approach for aid of sophisticated green technology known as phytoremediation and mycoremediation. Soil from cabonaceous phyllite located near to Equine Park, Sri Kembangan are use for monitoring the effect of phytoremediation and mycoremediation in reducing soil contamination and biotechnology for erosion control. Five laboratory scale prototypes were designed to monitor the effect of different proportion of coconut flakes i.e. 10%, 25%, 50% & 100% and plantation of Centella asiatica and Chrysopogon zizanioides to reduce the top soil from eroding and reduce the soil contamination. Prototype have been observe started from first week and ends after 12 weeks. Centella asiatica planted on 10% coconut flakes with 90% soil and Chrysopogon zizanioides planted on 25% coconut flakes with 75% soil are selected proportion to be used as phytoremediation and mycoremediation in reducing soil contamination and biotechnology for erosion control.

Nutritional and sensory characteristics of gluten-free quinoa (Chenopodium quinoa Willd)-based cookies development using an experimental mixture design.

PubMed

Brito, Isabelle L; de Souza, Evandro Leite; Felex, Suênia Samara Santos; Madruga, Marta Suely; Yamashita, Fábio; Magnani, Marciane

2015-09-01

The aim of this study was to develop a gluten-free formulation of quinoa (Chenopodium quinoa Willd.)-based cookies using experimental design of mixture to optimize a ternary mixture of quinoa flour, quinoa flakes and corn starch for parameters of colour, specific volume and hardness. Nutritional and sensory aspects of the optimized formulation were also assessed. Corn starch had a positive effect on the lightness of the cookies, but increased amounts of quinoa flour and quinoa flakes in the mixture resulted in darker product. Quinoa flour showed a negative effect on the specific volume, producing less bulky cookies, and quinoa flour and quinoa flakes had a positive synergistic effect on the hardness of the cookies. According the results and considering the desirability profile for colour, hardness and specific volume in gluten-free cookies, the optimized formulation contains 30 % quinoa flour, 25 % quinoa flakes and 45 % corn starch. The quinoa-based cookie obtained was characterized as a product rich in dietary fibre, a good source of essential amino acids, linolenic acid and minerals, with good sensory acceptability. These findings reports for the first time the application of quinoa processed as flour and flakes in mixture with corn starch as an alternative ingredient for formulations of gluten-free cookies-type biscuits.

Techniques for tritium recovery from carbon flakes and dust at the JET active gas handling system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gruenhagen, S.; Perevezentsev, A.; Brennan, P. D.

2008-07-15

Detritiation of highly tritium contaminated carbon and metal material used as first wall armour is a key issue for fusion machines like JET and ITER. Re-deposited carbon and hydrogen in the form of flakes and dust can lead to a build-up of the tritium inventory and therefore this material must be removed and processed. The high tritium concentration of the flake and dust material collected from the JET vacuum vessel makes it unsuitable for direct waste disposal without detritiation. A dedicated facility to process the tritiated carbon flake material and recover the tritium has been designed and built. In severalmore » test runs active material was successfully processed and de-tritiated in the new facility. Samples containing only carbon and hydrogen isotopes have been completely oxidized without any residue. Samples containing metallic impurities, e.g. beryllium, require longer processing times, adjusted processing parameters and yield an oxide residue. The detritiation factor was 2x10{sup 4}. In order to simulate in-vessel and ex-vessel detritiation techniques, the detritiation of a carbon flake sample by isotopic exchange in a hydrogen atmosphere was investigated. 2.8% of tritium was recovered by this means. (authors)« less

Orbital Debris Shape and Orientation Effects on Impact Damage to Shuttle Tiles

NASA Technical Reports Server (NTRS)

Evans, Steven W.; Williamsen, Joel

2006-01-01

Taking the damage results from a previous paper as a guide, and using a tile model created for the STS-107 accident investigation, we used the SPHC hydrodynamic code to evaluate the probable worst-case impact effects of flat, rectangular, "flake-shaped," orbital debris particles on Space Shuttle thermal tiles. We compared the damage from flakes with that produced by spheres. The flakes and spheres were sized according to a "characteristic length" (Lc) derived from radar cross-section measurements, and embodied in the NASA Standard Breakup Model (SBM). Impacts were simulated at near-normal obliquity, at 12 km/sec. We modeled the worst-case flake orientation: a corner-on impact, an orientation we term a "Face A-B" impact. Results of our simulations indicate that flake impactors are less damaging than spheres of the same Lc. Since spherical impactors have been assumed in analyses of shuttle orbital debris impact risk, we find that these risks may have been overestimated. This work represents a preliminary second step, i.e., a follow-on to [1], in developing a sensitivity analysis for the expected range of effects on damage considering spherical vs. non-spherical impactors, as recommended by the Institute for Defense Analyses (IDA) report to the Columbia Accident Investigation Board.

Compression failure mechanisms of composite structures

NASA Technical Reports Server (NTRS)

Hahn, H. T.; Sohi, M.; Moon, S.

1986-01-01

An experimental and analytical study was conducted to delineate the compression failure mechanisms of composite structures. The present report summarizes further results on kink band formation in unidirectional composites. In order to assess the compressive strengths and failure modes of fibers them selves, a fiber bundle was embedded in epoxy casting and tested in compression. A total of six different fibers were used together with two resins of different stiffnesses. The failure of highly anisotropic fibers such as Kevlar 49 and P-75 graphite was due to kinking of fibrils. However, the remaining fibers--T300 and T700 graphite, E-glass, and alumina--failed by localized microbuckling. Compressive strengths of the latter group of fibers were not fully utilized in their respective composite. In addition, acoustic emission monitoring revealed that fiber-matrix debonding did not occur gradually but suddenly at final failure. The kink band formation in unidirectional composites under compression was studied analytically and through microscopy. The material combinations selected include seven graphite/epoxy composites, two graphite/thermoplastic resin composites, one Kevlar 49/epoxy composite and one S-glass/epoxy composite.

A New Method to Measure Crack Extension in Nuclear Graphite Based on Digital Image Correlation

DOE PAGES

Lai, Shigang; Shi, Li; Fok, Alex; ...

2017-01-01

Graphite components, used as moderators, reflectors, and core-support structures in a High-Temperature Gas-Cooled Reactor, play an important role in the safety of the reactor. Specifically, they provide channels for the fuel elements, control rods, and coolant flow. Fracture is the main failure mode for graphite, and breaching of the above channels by crack extension will seriously threaten the safety of a reactor. In this paper, a new method based on digital image correlation (DIC) is introduced for measuring crack extension in brittle materials. Cross-correlation of the displacements measured by DIC with a step function was employed to identify the advancingmore » crack tip in a graphite beam specimen under three-point bending. The load-crack extension curve, which is required for analyzing the R-curve and tension softening behaviors, was obtained for this material. Furthermore, a sensitivity analysis of the threshold value employed for the cross-correlation parameter in the crack identification process was conducted. Finally, the results were verified using the finite element method.« less

A New Method to Measure Crack Extension in Nuclear Graphite Based on Digital Image Correlation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lai, Shigang; Shi, Li; Fok, Alex

Graphite components, used as moderators, reflectors, and core-support structures in a High-Temperature Gas-Cooled Reactor, play an important role in the safety of the reactor. Specifically, they provide channels for the fuel elements, control rods, and coolant flow. Fracture is the main failure mode for graphite, and breaching of the above channels by crack extension will seriously threaten the safety of a reactor. In this paper, a new method based on digital image correlation (DIC) is introduced for measuring crack extension in brittle materials. Cross-correlation of the displacements measured by DIC with a step function was employed to identify the advancingmore » crack tip in a graphite beam specimen under three-point bending. The load-crack extension curve, which is required for analyzing the R-curve and tension softening behaviors, was obtained for this material. Furthermore, a sensitivity analysis of the threshold value employed for the cross-correlation parameter in the crack identification process was conducted. Finally, the results were verified using the finite element method.« less

What makes lithium substituted polyacrylic acid a better binder than polyacrylic acid for silicon-graphite composite anodes?

DOE PAGES

Hays, Kevin A.; Ruther, Rose E.; Kukay, Alexander J.; ...

2018-03-04

Lithium substituted polyacrylic acid (LiPAA) has previously been demonstrated as a superior binder over polyacrylic acid (PAA) for Si anodes, but from where does this enhanced performance arise? In this paper, full cells are assembled with PAA and LiPAA based Si-graphite composite anodes that dried at temperatures from 100 °C to 200 °C. The performance of full cells containing PAA based Si-graphite anodes largely depend on the secondary drying temperature, as decomposition of the binder is correlated to increased electrode moisture and a rise in cell impedance. Full cells containing LiPAA based Si-graphite composite electrodes display better Coulombic efficiency thanmore » those with PAA, because of the electrochemical reduction of the PAA binder. This is identified by attenuated total reflectance Fourier transform infrared spectrometry and observed gassing during the electrochemical reaction. Finally, Coulombic losses from the PAA and Si SEI, along with depletion of the Si capacity in the anode results in progressive underutilization of the cathode and full cell capacity loss.« less

What makes lithium substituted polyacrylic acid a better binder than polyacrylic acid for silicon-graphite composite anodes?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hays, Kevin A.; Ruther, Rose E.; Kukay, Alexander J.

Lithium substituted polyacrylic acid (LiPAA) has previously been demonstrated as a superior binder over polyacrylic acid (PAA) for Si anodes, but from where does this enhanced performance arise? In this paper, full cells are assembled with PAA and LiPAA based Si-graphite composite anodes that dried at temperatures from 100 °C to 200 °C. The performance of full cells containing PAA based Si-graphite anodes largely depend on the secondary drying temperature, as decomposition of the binder is correlated to increased electrode moisture and a rise in cell impedance. Full cells containing LiPAA based Si-graphite composite electrodes display better Coulombic efficiency thanmore » those with PAA, because of the electrochemical reduction of the PAA binder. This is identified by attenuated total reflectance Fourier transform infrared spectrometry and observed gassing during the electrochemical reaction. Finally, Coulombic losses from the PAA and Si SEI, along with depletion of the Si capacity in the anode results in progressive underutilization of the cathode and full cell capacity loss.« less

Graphite fiber textile preform/copper matrix composites

NASA Technical Reports Server (NTRS)

Gilatovs, G. J.; Lee, Bruce; Bass, Lowell

1995-01-01

Graphite fiber reinforced/copper matrix composites have sufficiently high thermal conduction to make them candidate materials for critical heat transmitting and rejection components. The term textile composites arises because the preform is braided from fiber tows, conferring three-dimensional reinforcement and near net shape. The principal issues investigated in the past two years have centered on developing methods to characterize the preform and fabricated composite and on braidability. It is necessary to have an analytic structural description for both processing and final property modeling. The structure of the true 3-D braids used is complex and has required considerable effort to model. A structural mapping has been developed as a foundation for analytic models for thermal conduction and mechanical properties. The conductivity has contributions both from the copper and the reinforcement. The latter is accomplished by graphitization of the fibers, the higher the amount of graphitization the greater the conduction. This is accompanied by an increase in the fiber modulus, which is desirable from a stiffness point of view but decreases the braidability; the highest conductivity fibers are simply too brittle to be braided. Considerable effort has been expended on determining the optimal braidability--conductivity region. While a number of preforms have been fabricated, one other complication intervenes; graphite and copper are immiscible, resulting in a poor mechanical bond and difficulties in infiltration by molten copper. The approach taken is to utilize a proprietary fiber coating process developed by TRA, of Salt Lake City, Utah, which forms an itermediary bond. A number of preforms have been fabricated from a variety of fiber types and two sets of these have been infiltrated with OFHC copper, one with the TRA coating and one without. Mechanical tests have been performed using a small-scale specimen method and show the coated specimens to have superior mechanical properties. Final batches of preforms, including a finned, near net shape tube, are being fabricated and will be infiltrated before summer.

Graphite Microstructural Characterization Using Time-Domain and Correlation-Based Ultrasonics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spicer, James

Among techniques that have been used to determine elastic modulus in nuclear graphites, ultrasonic methods have enjoyed wide use and standards using contacting piezoelectric tranducers have been developed to ensure repeatability of these types of measurements. However, the use of couplants and the pressures used to effectively couple transducers to samples can bias measurements and produce results that are not wholly related to the properties of the graphite itself. In this work, we have investigated the use of laser ultrasonic methods for making elastic modulus measurements in nuclear graphites. These methods use laser-based transmitters and receivers to gather data andmore » do not require use of ultrasonic couplants or mechanical contact with the sample. As a result, information directly related to the elastic responses of graphite can be gathered even if the graphite is porous, brittle and compliant. In particular, we have demonstrated the use of laser ultrasonics for the determination of both Young’s modulus and shear modulus in a range of nuclear graphites including those that are being considered for use in future nuclear reactors. These results have been analyzed to assess the contributions of porosity and microcracking to the elastic responses of these graphites. Laser-based methods have also been used to assess the moduli of NBG-18 and IG-110 where samples of each grade were oxidized to produce specific changes in porosity. These data were used to develop new models for the elastic responses of nuclear graphites and these models have been used to infer specific changes in graphite microstructure that occur during oxidation that affect elastic modulus. Specifically, we show how ultrasonic measurements in oxidized graphites are consistent with nano/microscale oxidation processes where basal plane edges react more readily than basal plane surfaces. We have also shown the use of laser-based methods to perform shear-wave birefringence measurements and have shown how these measurements can be used to assess elastic anisotropy in nuclear graphites. Using models developed in this program, ultrasonic data were interpreted to extract orientation distribution coefficients that could be used to represent anisotropy in these materials. This demonstration showed the use of ultrasonic methods to quantify anisotropy and how these methods provide more detailed information than do measurements of thermal expansion – a technique commonly used for assessing anisotropy in nuclear graphites. Finally, we have employed laser-based, ultrasonic-correlation techniques in attempts to quantify aspects of graphite microstructure such as pore size and distribution. Results of these measurements indicate that additional work must be performed to make this ultrasonic approach viable for quantitative microstructural characterization.« less

METAL RECOVERY/REMOVAL USING NON-ELECTROLYTIC METAL RECOVERY

EPA Science Inventory

Radiator repair shops most commonly use hot caustic solutions to clean radiator sections prior to resoldering. he hot caustic, or "boil-out" solutions as they are cabled in the trade, become contaminated with dirt, rust flakes, paint flakes and miscellaneous particulate debris. n...

Design and evaluation of noise suppression sheet for GHz band utilizing magneto-elastic effect

NASA Astrophysics Data System (ADS)

Igarashi, Toshiyuki; Kondo, Koichi; Yoshida, Shigeyoshi

2017-12-01

Feasibility of realizing a noise suppression sheet (NSS) coping with the low SHF band such as the 5 GHz band was investigated, which was composed of soft magnetic metal flakes dispersed in a polymer. For suppressing noises, the higher frequency one of the bimodal frequency dispersion (lower frequency one: Dispersion DII, higher frequency one: Dispersion DIII) seen in the imaginary permeability (μ″; magnetic loss component) spectrum of the NSS was aimed to utilize. Referring to the previous finding that Dispersion DIII is originated from a magneto-elastic effect, several magnetic composite sheets were prepared using various alloy flakes with different saturation magnetostriction (λs), and their frequency (fr(DIII)) and magnitude (μ″(DIII)) of Dispersion DIII were investigated. It was found that the NSS containing flakes with higher λs exhibited higher fr(DIII) and higher μ″(DIII)/μ″(DII), which was ratio of μ″(DIII) to the magnitude of Dispersion DII (μ″(DII)). The fr(DIII) for the NSS having the highest λs containing Fe-Co alloy flake reached 7.45 GHz and μ″ in the 5 GHz band was approximately twice as high as the conventional NSS containing Fe-Si-Al alloy flake. For transmission attenuation power ratio (Rtp) when an NSS was placed on a microstrip line with characteristic impedance of 50 Ω, NSS with larger fr(DIII)2 · μ″(DIII) ∝ Ms2 (Ms: saturation magnetization), which theoretically gave the frequency limit of imaginary permeability for a thin film, exhibited larger Rtp in the low SHF band. These results suggested that an NSS containing a magnetic flake material with both large λs and Ms was suitable for suppressing low SHF band noises.

The archaeology, chronology and stratigraphy of Madjedbebe (Malakunanja II): A site in northern Australia with early occupation.

PubMed

Clarkson, Chris; Smith, Mike; Marwick, Ben; Fullagar, Richard; Wallis, Lynley A; Faulkner, Patrick; Manne, Tiina; Hayes, Elspeth; Roberts, Richard G; Jacobs, Zenobia; Carah, Xavier; Lowe, Kelsey M; Matthews, Jacqueline; Florin, S Anna

2015-06-01

Published ages of >50 ka for occupation at Madjedbebe (Malakunanja II) in Australia's north have kept the site prominent in discussions about the colonisation of Sahul. The site also contains one of the largest stone artefact assemblages in Sahul for this early period. However, the stone artefacts and other important archaeological components of the site have never been described in detail, leading to persistent doubts about its stratigraphic integrity. We report on our analysis of the stone artefacts and faunal and other materials recovered during the 1989 excavations, as well as the stratigraphy and depositional history recorded by the original excavators. We demonstrate that the technology and raw materials of the early assemblage are distinctive from those in the overlying layers. Silcrete and quartzite artefacts are common in the early assemblage, which also includes edge-ground axe fragments and ground haematite. The lower flaked stone assemblage is distinctive, comprising a mix of long convergent flakes, some radial flakes with faceted platforms, and many small thin silcrete flakes that we interpret as thinning flakes. Residue and use-wear analysis indicate occasional grinding of haematite and woodworking, as well as frequent abrading of platform edges on thinning flakes. We conclude that previous claims of extensive displacement of artefacts and post-depositional disturbance may have been overstated. The stone artefacts and stratigraphic details support previous claims for human occupation 50-60 ka and show that human occupation during this time differed from later periods. We discuss the implications of these new data for understanding the first human colonisation of Sahul. Copyright © 2015 Elsevier Ltd. All rights reserved.

Well-defined flake-like polypyrrole grafted graphene nanosheets composites as electrode materials for supercapacitors with enhanced cycling stability

NASA Astrophysics Data System (ADS)

Wang, Xue; Wang, Tingmei; Yang, Chao; Li, Haidong; Liu, Peng

2013-12-01

Well-defined flake-like polypyrrole grafted graphene nanosheets composites (PPy-g-GNS) were fabricated by the in-situ chemical oxidative grafting polymerization of pyrrole in the presence of the 4-aminophenyl modified graphene nanosheets (AP-GNS), which were prepared via the coupling reaction of the graphene nanosheets (GNS) with diazonium salt. The flake-like PPy-g-GNS composite showed the high conductivity at room temperature. A maximum discharge capacitance of 191.2 F/g at the scan rate of 10 mV/s could be achieved in the three-electrode cell electrochemical testing in 1.0 mol/L NaNO3 electrolyte solution. It is higher than those of the AP-GNS, pure PPy, and the GNS/PPy composite prepared with the unmodified graphene nanosheets (GNS). The flake-like PPy-g-GNS composites also exhibited the excellent electrochemical stability even after 1000 cycles. It revealed the synergistic effect between the conducting polymer and the carbon-based support.

Mesoporous MnCo2O4 with a flake-like structure as advanced electrode materials for lithium-ion batteries and supercapacitors.

PubMed

Mondal, Anjon Kumar; Su, Dawei; Chen, Shuangqiang; Ung, Alison; Kim, Hyun-Soo; Wang, Guoxiu

2015-01-19

A mesoporous flake-like manganese-cobalt composite oxide (MnCo2O4) is synthesized successfully through the hydrothermal method. The crystalline phase and morphology of the materials are characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and Brunauer-Emmett-Teller methods. The flake-like MnCo2O4 is evaluated as the anode material for lithium-ion batteries. Owing to its mesoporous nature, it exhibits a high reversible capacity of 1066 mA h g(-1), good rate capability, and superior cycling stability. As an electrode material for supercapacitors, the flake-like MnCo2O4 also demonstrates a high supercapacitance of 1487 F g(-1) at a current density of 1 A g(-1), and an exceptional cycling performance over 2000 charge/discharge cycles. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Experimental Demonstration of Printed Graphene Nano-flakes Enabled Flexible and Conformable Wideband Radar Absorbers.

PubMed

Huang, Xianjun; Pan, Kewen; Hu, Zhirun

2016-12-07

In this work, we have designed, fabricated and experimentally characterized a printed graphene nano-flakes enabled flexible and conformable wideband radar absorber. The absorber covers both X (8-12 GHz) and Ku (12-18 GHz) bands and is printed on flexible substrate using graphene nano-flakes conductive ink through stencil printing method. The measured results show that an effective absorption (above 90%) bandwidth spans from 10.4 GHz to 19.7 GHz, namely a 62% fraction bandwidth, with only 2 mm thickness. The flexibility of the printed graphene nano-flakes enables the absorber conformably bending and attaching to a metal cylinder. The radar cross section (RCS) of the cylinder with and without absorber attachment has been compared and excellent absorption has been obtained. Only 3.6% bandwidth reduction has been observed comparing to that of un-bended absorber. This work has demonstrated unambiguously that printed graphene can provide flexible and conformable wideband radar absorption, which extends the graphene's application to practical RCS reductions.

PCLC flake-based apparatus and method

DOEpatents

Cox, Gerald P; Fromen, Cathy A; Marshall, Kenneth L; Jacobs, Stephen D

2012-10-23

A PCLC flake/fluid host suspension that enables dual-frequency, reverse drive reorientation and relaxation of the PCLC flakes is composed of a fluid host that is a mixture of: 94 to 99.5 wt % of a non-aqueous fluid medium having a dielectric constant value .di-elect cons., where 1<.di-elect cons.<7, a conductivity value .sigma., where 10.sup.-9>.sigma.>10.sup.-7 Siemens per meter (S/m), and a resistivity r, where 10.sup.7>r>10.sup.10 ohm-meters (.OMEGA.-m), and which is optically transparent in a selected wavelength range .DELTA..lamda.; 0.0025 to 0.25 wt % of an inorganic chloride salt; 0.0475 to 4.75 wt % water; and 0.25 to 2 wt % of an anionic surfactant; and 1 to 5 wt % of PCLC flakes suspended in the fluid host mixture. Various encapsulation forms and methods are disclosed including a Basic test cell, a Microwell, a Microcube, Direct encapsulation (I), Direct encapsulation (II), and Coacervation encapsulation. Applications to display devices are disclosed.

Helium trapping in aluminium near the critical dose on blister formation

NASA Astrophysics Data System (ADS)

Fukahori, T.; Kanda, Y.; Mori, K.; Tobimatsu, H.

1985-08-01

Blistering and flaking caused by energetic He ions emitted from the plasma in fusion reactors possibly contribute to first-wall erosion. In order to study their characteristics, the numbers of He atoms trapped in He-ion-irradiated Al samples have been measured by a He atom measurement system and every sample has been observed by a scanning electron microscope. The samples have been prepared from a polycrystalline plate and irradiated with 20 keV He ions at room temperature. The saw-tooth like variation of the trapped He atoms with the dose has three edges corresponding to the blistering, flaking and double flaking, respectively. The critical doses for the three events are found to be 4 × 10 21, 7 × 10 21, 12 × 10 21 He atoms m -2, respectively. The average number of He atoms included in an event is 5.4 × 10 10 He atoms in the case of the blistering and 2.1 × 10 11 He atoms in the case of flaking.

Atomic defects in monolayer titanium carbide (Ti 3C 2T x) MXene

DOE PAGES

Sang, Xiahan; Xie, Yu; Lin, Ming -Wei; ...

2016-09-06

Here, the 2D transition metal carbides or nitrides, or MXenes, are emerging as a group of materials showing great promise in lithium ion batteries and supercapacitors. Until now, characterization and properties of single-layer MXenes have been scarcely reported. Here, using scanning transmission electron microscopy, we determined the atomic structure of freestanding monolayer Ti 3C 2T x flakes prepared via the minimally intensive layer delamination method and characterized different point defects that are prevalent in the monolayer flakes. We determine that the Ti vacancy concentration can be controlled by the etchant concentration during preparation. Density function theory-based calculations confirm the defectmore » structures and predict that the defects can influence the surface morphology and termination groups, but do not strongly influence the metallic conductivity. Using devices fabricated from single- and few-layer Ti 3C 2T x MXene flakes, the effect of the number of layers in the flake on conductivity has been demonstrated.« less

Oxidative cleavage and hydrolytic boosting of cellulose in soybean spent flakes by Trichoderma reesei Cel61A lytic polysaccharide monooxygenase.

PubMed

Pierce, Brian C; Agger, Jane Wittrup; Wichmann, Jesper; Meyer, Anne S

2017-03-01

The auxiliary activity family 9 (AA9) copper-dependent lytic polysaccharide monooxygenase (LPMO) from Trichoderma reesei (EG4; TrCel61A) was investigated for its ability to oxidize the complex polysaccharides from soybean. The substrate specificity of the enzyme was assessed against a variety of substrates, including both soy spent flake, a by-product of the soy food industry, and soy spent flake pretreated with sodium hydroxide. Products from enzymatic treatments were analyzed using mass spectrometry and high performance anion exchange chromatography. We demonstrate that TrCel61A is capable of oxidizing cellulose from both pretreated soy spent flake and phosphoric acid swollen cellulose, oxidizing at both the C1 and C4 positions. In addition, we show that the oxidative activity of TrCel61A displays a synergistic effect capable of boosting endoglucanase activity, and thereby substrate depolymerization of soy cellulose, by 27%. Copyright © 2016 Elsevier Inc. All rights reserved.

Observation of phonon-polaritons in thin flakes of hexagonal boron nitride on gold

NASA Astrophysics Data System (ADS)

Ciano, C.; Giliberti, V.; Ortolani, M.; Baldassarre, L.

2018-04-01

Hexagonal Boron Nitride (hBN) is a layered van der Waals material able to sustain hyperbolic phonon-polaritons within its mid-infrared reststrahlen bands. We study the effect of a metallic substrate adjacent to hBN flakes on the polariton dispersion and on the standing wave patterns in nanostructures by means of mid-infrared nanospectroscopy and nanoimaging. We exploit the gold-coated tip apex for atomic force microscopy to launch polaritons in thin hBN flakes. The photo-thermal induced mechanical resonance is used to detect the amplitude profile of polariton standing waves with a lateral resolution of 30 nm. We observe the polariton excitation spectra on hBN flakes as thin as 4 nm, thanks to the infrared field enhancement in the nanogap between the gold-coated tip apex and an ultraflat gold substrate. The data indicate no major effect of remote screening of the free electrons in gold on the phonon-polariton excitation that appears robust also against geometrical imperfections.

Enhanced photoactivity of BiPO4/(001) facet-dominated square BiOBr flakes by combining heterojunctions with facet engineering effects

NASA Astrophysics Data System (ADS)

Shi, Jingzhi; Meng, Xiangying; Hao, Mengjian; Cao, Zhenzhu; He, Weiyan; Gao, Yanfang; Liu, Jinrong

2018-02-01

In this study, BiPO4/highly (001) facet exposed square BiOBr flake heterojunction photocatalysts with different molar ratios were fabricated via a two-step method. The synergetic effect of the heterojunction and facet engineering was systematically investigated. The physicochemical properties of the BiPO4/square BiOBr flake composites were characterized based on X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, Brunauer-Emmett-Teller method, X-ray photoelectron spectroscopy, ultraviolet-visible diffuse reflectance spectra, photoluminescence, electrochemical impedance spectroscopy, and the photocurrent response. The BiPO4/square BiOBr flake heterojunction photocatalyst exhibited much higher photocatalytic performance compared with the individual BiPO4 and BiOBr. In particular, the BiPO4/BiOBr composite where P/Br = 1/3 exhibited the highest photocatalytic activity. The intensified separation of photoinduced charges at the p-n heterojunction between the BiPO4 nanoparticle and (001) facet of BiOBr was mainly responsible for the enhanced photoactivity.

Low-loss flake-graphene saturable absorber mirror for laser mode-locking at sub-200-fs pulse duration

NASA Astrophysics Data System (ADS)

Cunning, B. V.; Brown, C. L.; Kielpinski, D.

2011-12-01

Saturable absorbers are a key component for mode-locking femtosecond lasers. Polymer films containing graphene flakes have recently been used in transmission as laser mode-lockers but suffer from high nonsaturable loss, limiting their application in low-gain lasers. Here, we present a saturable absorber mirror based on a film of pure graphene flakes. The device is used to mode lock an erbium-doped fiber laser, generating pulses with state-of-the-art, sub-200-fs duration. The laser characteristic indicates that the film exhibits low nonsaturable loss (13% per pass) and large absorption modulation depth (45% of low-power absorption).

Archaeology in the Mississippi River Floodplain at Sand Run Slough, Iowa,

DTIC Science & Technology

1987-06-01

28 Contracting 36/. 40 51/.45 87/.43 Parallel 36/. 40 23/.20 59/.29 N=87 N=115 N=202 End Flake 75/.86 85/.74 160/.79 Side Flake 12/.14 30 /.26 42/.21...13 12/.09 TECHNOLOGY AND MORPHOLOGY .* Platform Types N=39 N=10 N=44 N=89 Bifacial Tool Edge Unfaceted 18/.51 3/. 30 19/.43 40 /.45 Faceted 2/.06 2/.20 7...25/.45 10/.53 26/. 40 61/.44 " Bifacial Wear 30 /.54 9/.47 37/.57 76/.54 Table 4. 10. Chert types and unhafted flake tool types from Stratum I, 13LA38

Electrochemical behavior of monolayer and bilayer graphene.

PubMed

Valota, Anna T; Kinloch, Ian A; Novoselov, Kostya S; Casiraghi, Cinzia; Eckmann, Axel; Hill, Ernie W; Dryfe, Robert A W

2011-11-22

Results of a study on the electrochemical properties of exfoliated single and multilayer graphene flakes are presented. Graphene flakes were deposited on silicon/silicon oxide wafers to enable fast and accurate characterization by optical microscopy and Raman spectroscopy. Conductive silver paint and silver wires were used to fabricate contacts; epoxy resin was employed as a masking coating in order to expose a stable, well-defined area of graphene. Both multilayer and monolayer graphene microelectrodes showed quasi-reversible behavior during voltammetric measurements in potassium ferricyanide. However, the standard heterogeneous charge transfer rate constant, k°, was estimated to be higher for monolayer graphene flakes. © 2011 American Chemical Society

Graphite fiber textile preform/copper matrix composites

NASA Technical Reports Server (NTRS)

Filatovs, G. J.

1993-01-01

This project has the objective of exploring the use of graphite fiber textile preform/copper matrix composites in spacecraft heat transmitting and radiating components. The preforms are to be fabricated by braiding of tows and when infiltrated with copper will result in a 3-D reinforced, near net shape composite with improved specific properties such as lower density and higher stiffness. It is anticipated that the use of textile technology will result in a more robust preform and consequently better final composite; it is hard to anticipate what performance tradeoffs will result, and these will be explored through testing and characterization.

Carbide Coatings for Nickel Alloys, Graphite and Carbon/Carbon Composites to be used in Fluoride Salt Valves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nagle, Denis; Zhang, Dajie

2015-10-22

The focus of this research was concerned with developing materials technology that supports the evolution of Generation IV Advanced High Temperature Reactor (AHTR) concepts. Specifically, we investigate refractory carbide coatings for 1) nickel alloys, and 2) commercial carbon-carbon composites (CCCs). Numerous compelling reasons have driven us to focus on carbon and carbide materials. First, unlike metals, the strength and modulus of CCCs increase with rising temperature. Secondly, graphite and carbon composites have been proven effective for resisting highly corrosive fluoride melts such as molten cryolite [Na₃AlF₆] at ~1000°C in aluminum reduction cells. Thirdly, graphite and carbide materials exhibit extraordinary radiationmore » damage tolerance and stability up to 2000°C. Finally, carbides are thermodynamically more stable in liquid fluoride salt than the corresponding metals (i.e. Cr and Zr) found in nickel based alloys.« less

Effects of Rapid Solidification on Phase Formation and Microstructure Evolution of AgSbTe₂-Based Thermoelectric Compounds.

PubMed

Castellero, Alberto; Fiore, Gianluca; Evenstein, Eliran; Baricco, Marcello; Amouyal, Yaron

2017-03-01

We report on rapid solidification of an Ag(16.7)Sb(30.0)Te(53.3) compound using planar flow casting to stabilize the δ-AgSbTe₂ single phase and avoid precipitation of the interconnected Sb₂Te₃ phase, which leads to deterioration of thermoelectric properties. Rapidly solidified samples are in form of flakes with different thickness (60–400 μm). Precipitation of Sb2Te₃ phase is fully inhibited in thin flakes (thickness below 100 μm), which consist of an homogeneous δ-AgSbTe₂ matrix, whereas isolated Sb₂Te₃ precipitates, dispersed throughout the δ-AgSbTe₂ matrix, were found in thick flakes (thickness above 100 μm). The lattice parameter of the δ-AgSbTe₂ phase progressively increases with the cooling rate, indicating progressive supersaturation of the matrix for high degree of supercooling. Bulk specimens were prepared by hot pressing of the rapidly solidified flakes to evaluate thermoelectric properties. After sintering of the rapidly solidified flakes, the differential scanning calorimetry (DSC) traces indicates partial decomposition of the non equilibrium δ-AgSbTe₂ into the stable phases. Measurements of the thermoelectric transport properties indicate the positive effects of rapid solidification on thermal conductivity and Seebeck coefficient and its negative effect on electrical conductivity, suggesting an operative way to improve thermoelectric performance.

Tuning the thickness of exfoliated quasi-two-dimensional β-Ga2O3 flakes by plasma etching

NASA Astrophysics Data System (ADS)

Kwon, Yongbeom; Lee, Geonyeop; Oh, Sooyeoun; Kim, Jihyun; Pearton, Stephen J.; Ren, Fan

2017-03-01

We demonstrated the thinning of exfoliated quasi-two-dimensional β-Ga2O3 flakes by using a reactive ion etching technique. Mechanical exfoliation of the bulk β-Ga2O3 by using an adhesive tape was followed by plasma etching to tune its thickness. Since β-Ga2O3 is not a van der Waals material, it is challenging to obtain ultra-thin flakes below a thickness of 100 nm. In this study, an etch rate of approximately 16 nm/min was achieved at a power of 200 W with a flow of 50 sccm of SF6, and under these conditions, thinning of β-Ga2O3 flakes from 300 nm down to ˜60 nm was achieved with smooth morphology. We believe that the reaction between SF6 and Ga2O3 results in oxygen and volatile oxygen fluoride compounds, and non-volatile compounds such as GaFX that can be removed by ion bombardment. The opto-electrical properties were also characterized by fabricating solar-blind photodetectors using the plasma-thinned β-Ga2O3 flakes; these detectors showed fast response and decay with excellent responsivity and selectivity. Our results pave the way for tuning the thickness of two-dimensional materials by using this scalable, industry-compatible dry etching technique.

Diamondlike flakes

NASA Technical Reports Server (NTRS)

Banks, B. A. (Inventor)

1985-01-01

A carbon coating was vacuum arc deposited on a smooth surface of a target which was simultaneously ion beam sputtered. The bombarding ions have sufficient energy to create diamond bonds. Spalling occurs as the carbon deposit thickens. The resulting diamond like carbon flakes improve thermal, electrical, mechanical, and tribological properties when used in aerospace structures and components.

Verbenone flakes may help slow mountain pine beetle's spread

Treesearch

Nancy (featured scientist) Gillette

2009-01-01

According to "Aerially Applied Verbenone-Releasing Laminated Flakes Protect Pinus contorta Stands from Attack by Dendroctonus ponderosae (mountain pine beetle) in California and Idaho," a US Forest Service–funded study appearing in the February issue of Forest Ecology and Management, not only has the "current...

Post-extraction algal residue in steam-flaked corn-based diets for beef cattle

USDA-ARS?s Scientific Manuscript database

The effects of post-extraction algal residue (PEAR) as N source 23 in steam-flaked corn-based (SFC) beef cattle finishing diets on intake, duodenal flow, digestion, ruminal microbial efficiency, ruminal parameters, and blood constituents were evaluated. Ruminally and duodenally cannulated steers (BW...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Woltornist, Steven J.; Carrillo, Jan-Michael Y.; Xu, Thomas O.

The unique electrical, thermal, and mechanical properties of graphene make it a perfect candidate for applications in graphene/graphite based polymer composites, yet challenges due to the lack of solubility of pristine graphene/graphite in water and common organic solvents have limited its practical utilization. In this paper, we report a scalable and environmentally friendly technique to form water-in-oil type emulsions stabilized by overlapping pristine graphene sheets, enabling the synthesis of open cell foams containing a continuous graphitic network. Our approach utilizes the insolubility of graphene/graphite in both water and organic solvents and so does not require oxidation, reduction, surfactants, high boilingmore » solvents, chemical functionalization, or the input of large amounts of mechanical energy or heat. At the heart of our technique is the strong attraction of graphene to high-energy oil and water interfaces. This allows for the creation of stable water-in-oil emulsions with controlled droplet size and overlapping graphene sheets playing the role of surfactant by covering the droplet surface and stabilizing the interfaces with a thin graphitic skin. Finally, these emulsions are used as templates for the synthesis of open cell foams with densities below 0.35 g/cm 3 that exhibit remarkable mechanical and electrical properties including compressive moduli up to ~100 MPa, compressive strengths of over 8.3 MPa (1200 psi), and bulk conductivities approaching 7 S/m.« less

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

DOE PAGES

Woltornist, Steven J.; Carrillo, Jan-Michael Y.; Xu, Thomas O.; ...

2015-01-21

The unique electrical, thermal, and mechanical properties of graphene make it a perfect candidate for applications in graphene/graphite based polymer composites, yet challenges due to the lack of solubility of pristine graphene/graphite in water and common organic solvents have limited its practical utilization. In this paper, we report a scalable and environmentally friendly technique to form water-in-oil type emulsions stabilized by overlapping pristine graphene sheets, enabling the synthesis of open cell foams containing a continuous graphitic network. Our approach utilizes the insolubility of graphene/graphite in both water and organic solvents and so does not require oxidation, reduction, surfactants, high boilingmore » solvents, chemical functionalization, or the input of large amounts of mechanical energy or heat. At the heart of our technique is the strong attraction of graphene to high-energy oil and water interfaces. This allows for the creation of stable water-in-oil emulsions with controlled droplet size and overlapping graphene sheets playing the role of surfactant by covering the droplet surface and stabilizing the interfaces with a thin graphitic skin. Finally, these emulsions are used as templates for the synthesis of open cell foams with densities below 0.35 g/cm 3 that exhibit remarkable mechanical and electrical properties including compressive moduli up to ~100 MPa, compressive strengths of over 8.3 MPa (1200 psi), and bulk conductivities approaching 7 S/m.« less

Facile and Scalable Synthesis Method for High-Quality Few-Layer Graphene through Solution-Based Exfoliation of Graphite.

PubMed

Wee, Boon-Hong; Wu, Tong-Fei; Hong, Jong-Dal

2017-02-08

Here we describe a facile and scalable method for preparing defect-free graphene sheets exfoliated from graphite using the positively charged polyelectrolyte precursor poly(p-phenylenevinylene) (PPV-pre) as a stabilizer in an aqueous solution. The graphene exfoliated by PPV-pre was apparently stabilized in the solution as a form of graphene/PPV-pre (denoted to GPPV-pre), which remains in a homogeneous dispersion over a year. The thickness values of 300 selected 76% GPPV-pre flakes ranged from 1 to 10 nm, corresponding to between one and a few layers of graphene in the lateral dimensions of 1 to 2 μm. Furthermore, this approach was expected to yield a marked decrease in the density of defects in the electronic conjugation of graphene compared to that of graphene oxide (GO) obtained by Hummers' method. The positively charged GPPV-pre was employed to fabricate a poly(ethylene terephthalate) (PET) electrode layer-by-layer with negatively charged GO, yielding (GPPV-pre/GO) n film electrode. The PPV-pre and GO in the (GPPV-pre/GO) n films were simultaneously converted using hydroiodic acid vapor to fully conjugated PPV and reduced graphene oxide (RGO), respectively. The electrical conductivity of (GPPV/RGO) 23 multilayer films was 483 S/cm, about three times greater than that of the (PPV/RGO) 23 multilayer films (166 S/cm) comprising RGO (prepared by Hummers method). Furthermore, the superior electrical properties of GPPV were made evident, when comparing the capacitive performances of two supercapacitor systems; (polyaniline PANi/RGO) 30 /(GPPV/RGO) 23 /PET (volumetric capacitance = 216 F/cm 3 ; energy density = 19 mWh/cm 3 ; maximum power density = 498 W/cm 3 ) and (PANi/RGO) 30 /(PPV/RGO) 23 /PET (152 F/cm 3 ; 9 mWh/cm 3 ; 80 W/cm 3 ).

Modifying optical properties of reduced/graphene oxide with controlled ozone and thermal treatment in aqueous suspensions.

PubMed

Hasan, Md Tanvir; Senger, Brian J; Mulford, Price; Ryan, Conor; Doan, Hung; Gryczynski, Zygmunt; Naumov, Anton V

2017-02-10

Graphene possesses a number of advantageous properties, however, does not exhibit optical emission, which limits its use in optoelectronics. Unlike graphene, its functional derivative, graphene oxide (GO) exhibits fluorescence emission throughout the visible. Here, we focus on controlled methods for tuning the optical properties of GO. We introduce ozone treatment of reduced graphene oxide (RGO) in order to controllably transform it from non-emissive graphene-like material into GO with a specific fluorescence emission response. Solution-based treatment of RGO for 5-45 min with ∼1.2 g l -1 ozone/oxygen gas mixture yields a drastic color change, bleaching of the absorption in the visible and the stepwise increase in fluorescence intensity and lifetime. This is attributed to the introduction of oxygen-containing functional groups to RGO graphitic platform as detected by the infrared spectroscopy. A reverse process: controllable quenching of this fluorescence is achieved by the thermal treatment of GO in aqueous suspension up to 90 °C. This methodology allows for the wide range alteration of GO optical properties starting from the dark-colored non-emissive RGO material up to nearly transparent highly ozone-oxidized GO showing substantial fluorescence emission. The size of the GO flakes is concomitantly altered by oxidation-induced scission. Semi-empirical PM3 theoretical calculations on HyperChem models are utilized to explore the origins of optical response from GO. Two models are considered, attributing the induced emission either to the localized states produced by oxygen-containing addends or the islands of graphitic carbon enclosed by such addends. Band gap values calculated from the models are in the agreement with experimentally observed transition peak maxima. The controllable variation of GO optical properties in aqueous suspension by ozone and thermal treatments shown in this work provides a route to tune its optical response for particular optoelectronics or biomedical applications.

Modifying optical properties of reduced/graphene oxide with controlled ozone and thermal treatment in aqueous suspensions

NASA Astrophysics Data System (ADS)

Tanvir Hasan, Md; Senger, Brian J.; Mulford, Price; Ryan, Conor; Doan, Hung; Gryczynski, Zygmunt; Naumov, Anton V.

2017-02-01

Graphene possesses a number of advantageous properties, however, does not exhibit optical emission, which limits its use in optoelectronics. Unlike graphene, its functional derivative, graphene oxide (GO) exhibits fluorescence emission throughout the visible. Here, we focus on controlled methods for tuning the optical properties of GO. We introduce ozone treatment of reduced graphene oxide (RGO) in order to controllably transform it from non-emissive graphene-like material into GO with a specific fluorescence emission response. Solution-based treatment of RGO for 5-45 min with ˜1.2 g l-1 ozone/oxygen gas mixture yields a drastic color change, bleaching of the absorption in the visible and the stepwise increase in fluorescence intensity and lifetime. This is attributed to the introduction of oxygen-containing functional groups to RGO graphitic platform as detected by the infrared spectroscopy. A reverse process: controllable quenching of this fluorescence is achieved by the thermal treatment of GO in aqueous suspension up to 90 °C. This methodology allows for the wide range alteration of GO optical properties starting from the dark-colored non-emissive RGO material up to nearly transparent highly ozone-oxidized GO showing substantial fluorescence emission. The size of the GO flakes is concomitantly altered by oxidation-induced scission. Semi-empirical PM3 theoretical calculations on HyperChem models are utilized to explore the origins of optical response from GO. Two models are considered, attributing the induced emission either to the localized states produced by oxygen-containing addends or the islands of graphitic carbon enclosed by such addends. Band gap values calculated from the models are in the agreement with experimentally observed transition peak maxima. The controllable variation of GO optical properties in aqueous suspension by ozone and thermal treatments shown in this work provides a route to tune its optical response for particular optoelectronics or biomedical applications.

Strategies to improve the electrochemical performance of electrodes for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Yang, Ming-Che

Lithium-ion batteries are widely used in consumer market because of their lightweight and rechargeable property. However, for the application as power sources of hybrid electric vehicles (HEVs), which need excellent cycling performance, high energy density, high power density, capacity, and low cost, new materials still need to be developed to meet the demands. In this dissertation work, three different strategies were developed to improve the properties of the electrode of lithium batteries. First, the voltage profile and lithium diffusion battier of LiM1/2Mn 3/2O4 (M=Ti, V, Cr, Fe, Co, Ni and Cu) were predicted by first principles theory. The computation results suggest that doping with Co or Cu can potentially lower Li diffusion barrier compared with Ni doping. Our experimental research has focused on LiNixCuyMn 2-x-yO4 (0

Charge carrier transfer in tungsten disulfide—black phosphorus heterostructures

NASA Astrophysics Data System (ADS)

Zhao, Siqi; He, Dawei; Wang, Yongsheng; Zhang, Xinwu; He, Jiaqi

2017-11-01

Photocarrier dynamics in tungsten disulfide—black phosphorus (BP) heterostructures were studied by time-resolved differential reflection measurements. The heterostructures were fabricated by stacking together monolayer WS2 and BP flakes that are both fabricated by mechanical exfoliation. Efficient and ultrafast transfer of photocarriers from WS2 to BP flakes was observed. This confirms the type-I band alignment of WS2/BP heterostructures that was predicted by theory. Accompanied with the photocarrier interlayer transfer process from WS2 to BP flakes, the change of the absorption of WS2 persists for several nanoseconds. These results promote the consciousness about the carrier dynamics of interlayer transfer process in van der Waals heterostructures and its application in optoelectronic devices.

Vertically aligned cobalt hydroxide nano-flake coated electro-etched carbon fiber cloth electrodes for supercapacitors

NASA Astrophysics Data System (ADS)

Cheng, Qian; Tang, Jie; Zhang, Han; Qin, Lu-Chang

2014-11-01

We describe preparation and characterization of nanostructured electrodes using Co(OH)2 nano-flakes and carbon fiber cloth for supercapacitors. Nanostructured Co(OH)2 flakes are produced by electrodeposition and they are coated onto the electro-etched carbon fiber cloth. A highest specific capacitance of 3404.8 F g-1 and an area-normalized specific capacitance of 3.3 F cm-2 have been obtained from such electrodes. Morphology and structure of the nanostructured electrodes have been characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical properties have been studied by cyclic voltammetry (CV), constant-current charge and discharge, electrochemical impedance spectroscopy (EIS), and long-time cycling.

Structural, optical and compositional stability of MoS2 multi-layer flakes under high dose electron beam irradiation

NASA Astrophysics Data System (ADS)

Rotunno, E.; Fabbri, F.; Cinquanta, E.; Kaplan, D.; Longo, M.; Lazzarini, L.; Molle, A.; Swaminathan, V.; Salviati, G.

2016-06-01

MoS2 multi-layer flakes, exfoliated from geological molybdenite, have been exposed to high dose electron irradiation showing clear evidence of crystal lattice and stoichiometry modifications. A massive surface sulfur depletion is induced together with the consequent formation of molybdenum nanoislands. It is found that a nanometric amorphous carbon layer, unwillingly deposited during the transmission electron microscope experiments, prevents the formation of the nanoislands. In the absence of the carbon layer, the formation of molybdenum grains proceeds both on the top and bottom surfaces of the flake. If carbon is present on both the surfaces then the formation of Mo grains is completely prevented.

Recent Progress in Graphite Intercalation Compounds for Rechargeable Metal (Li, Na, K, Al)-Ion Batteries.

PubMed

Xu, Jiantie; Dou, Yuhai; Wei, Zengxi; Ma, Jianmin; Deng, Yonghong; Li, Yutao; Liu, Huakun; Dou, Shixue

2017-10-01

Lithium-ion batteries (LIBs) with higher energy density are very necessary to meet the increasing demand for devices with better performance. With the commercial success of lithiated graphite, other graphite intercalation compounds (GICs) have also been intensively reported, not only for LIBs, but also for other metal (Na, K, Al) ion batteries. In this Progress Report, we briefly review the application of GICs as anodes and cathodes in metal (Li, Na, K, Al) ion batteries. After a brief introduction on the development history of GICs, the electrochemistry of cationic GICs and anionic GICs is summarized. We further briefly summarize the use of cationic GICs and anionic GICs in alkali ion batteries and the use of anionic GICs in aluminium-ion batteries. Finally, we reach some conclusions on the drawbacks, major progress, emerging challenges, and some perspectives on the development of GICs for metal (Li, Na, K, Al) ion batteries. Further development of GICs for metal (Li, Na, K, Al) ion batteries is not only a strong supplement to the commercialized success of lithiated-graphite for LIBs, but also an effective strategy to develop diverse high-energy batteries for stationary energy storage in the future.

Recent Progress in Graphite Intercalation Compounds for Rechargeable Metal (Li, Na, K, Al)‐Ion Batteries

PubMed Central

Xu, Jiantie; Dou, Yuhai; Wei, Zengxi; Li, Yutao; Liu, Huakun; Dou, Shixue

2017-01-01

Abstract Lithium‐ion batteries (LIBs) with higher energy density are very necessary to meet the increasing demand for devices with better performance. With the commercial success of lithiated graphite, other graphite intercalation compounds (GICs) have also been intensively reported, not only for LIBs, but also for other metal (Na, K, Al) ion batteries. In this Progress Report, we briefly review the application of GICs as anodes and cathodes in metal (Li, Na, K, Al) ion batteries. After a brief introduction on the development history of GICs, the electrochemistry of cationic GICs and anionic GICs is summarized. We further briefly summarize the use of cationic GICs and anionic GICs in alkali ion batteries and the use of anionic GICs in aluminium‐ion batteries. Finally, we reach some conclusions on the drawbacks, major progress, emerging challenges, and some perspectives on the development of GICs for metal (Li, Na, K, Al) ion batteries. Further development of GICs for metal (Li, Na, K, Al) ion batteries is not only a strong supplement to the commercialized success of lithiated‐graphite for LIBs, but also an effective strategy to develop diverse high‐energy batteries for stationary energy storage in the future. PMID:29051856

Infrared Extinction Coefficients of Aerosolized Conductive Flake Powders and Flake Suspensions having a Zero-Truncated Poisson Size Distribution

DTIC Science & Technology

2012-11-01

report may not be cited for purposes of advertisement . This report has been approved for public release. Acknowledgments The authors would...visible wavelengths, the eye perceives an image as a result of color contrasts that consist of differences in luminance and chromaticity (hue and

Data basic to the engineering of reconstituted flakeboard

Treesearch

Robert L. Geimer

1979-01-01

Flakeboards made with uniform densities throughout their thickness and different degrees of flake alignment were used to establish relationships between bending, tension, and compression values of modulus of elasticity or modulus of rupture (or stress to maximum load) and the variables of specific gravity and flake alignment. An equation using sonic velocity as an...

Experimental Demonstration of Printed Graphene Nano-flakes Enabled Flexible and Conformable Wideband Radar Absorbers

PubMed Central

Huang, Xianjun; Pan, Kewen; Hu, Zhirun

2016-01-01

In this work, we have designed, fabricated and experimentally characterized a printed graphene nano-flakes enabled flexible and conformable wideband radar absorber. The absorber covers both X (8–12 GHz) and Ku (12–18 GHz) bands and is printed on flexible substrate using graphene nano-flakes conductive ink through stencil printing method. The measured results show that an effective absorption (above 90%) bandwidth spans from 10.4 GHz to 19.7 GHz, namely a 62% fraction bandwidth, with only 2 mm thickness. The flexibility of the printed graphene nano-flakes enables the absorber conformably bending and attaching to a metal cylinder. The radar cross section (RCS) of the cylinder with and without absorber attachment has been compared and excellent absorption has been obtained. Only 3.6% bandwidth reduction has been observed comparing to that of un-bended absorber. This work has demonstrated unambiguously that printed graphene can provide flexible and conformable wideband radar absorption, which extends the graphene’s application to practical RCS reductions. PMID:27924823

An Einzel lens apparatus for deposition of levitated graphene on a substrate in UHV

NASA Astrophysics Data System (ADS)

Coppock, Joyce; Nagornykh, Pavel; McAdams, Ian; Kane, Bruce

The goal of our research is to levitate a charged micron-scale graphene flake in an electrical AC quadrupole trap in ultra-high vacuum (UHV) in order to study its properties and dynamics while decoupled from any substrate. As a complement to the optical measurements that can be performed on the levitated flake, we are developing a method of depositing the same flake on a substrate, which can be removed from the system for further study using such probes as atomic force microscopy (AFM) and scanning tunneling microscopy (STM). As the flake is released from the trap and propelled toward the substrate, its trajectory will be controlled by an Einzel (electrostatic) lens to achieve accurate positioning on the substrate. This talk will discuss the design of the lens as well as particle tracing simulations to determine the proper lens voltage to focus the particle's trajectory. In the future, deposited graphene may be used to passivate H-terminated silicon. The method is expected to be generalizable to achieve deposition of 2D materials on surfaces in a clean UHV environment.

Chemically exfoliating large sheets of phosphorene via choline chloride urea viscosity-tuning

NASA Astrophysics Data System (ADS)

Ng, A.; Sutto, T. E.; Matis, B. R.; Deng, Y.; Ye, P. D.; Stroud, R. M.; Brintlinger, T. H.; Bassim, N. D.

2017-04-01

Exfoliation of two-dimensional phosphorene from bulk black phosphorous through chemical means is demonstrated where the solvent system of choice (choline chloride urea diluted with ethanol) has the ability to successfully exfoliate large-area multi-layer phosphorene sheets and further protect the flakes from ambient degradation. The intercalant solvent molecules, aided by low-powered sonication, diffuse between the layers of the bulk black phosphorus, allowing for the exfoliation of the multi-layer phosphorene through breaking of the interlayer van der Waals bonds. Through viscosity tuning, the optimal parameters (1:1 ratio between the intercalant and the diluting solvent) at which the exfoliation takes place is determined. Our exfoliation technique is shown to produce multi-layer phosphorene flakes with surface areas greater than 3 μm2 (a factor of three larger than what has previously been reported for a similar exfoliation method) while limiting exposure to the ambient environment, thereby protecting the flakes from degradation. Characterization techniques such as optical microscopy, Raman spectroscopy, ultraviolet-visible spectroscopy, and (scanning) transmission electron microscopy are used to investigate the quality, quantity, and thickness of the exfoliated flakes.

Continuities in stone flaking technology at Liang Bua, Flores, Indonesia.

PubMed

Moore, M W; Sutikna, T; Jatmiko; Morwood, M J; Brumm, A

2009-11-01

This study examines trends in stone tool reduction technology at Liang Bua, Flores, Indonesia, where excavations have revealed a stratified artifact sequence spanning 95k.yr. The reduction sequence practiced throughout the Pleistocene was straightforward and unchanging. Large flakes were produced off-site and carried into the cave where they were reduced centripetally and bifacially by four techniques: freehand, burination, truncation, and bipolar. The locus of technological complexity at Liang Bua was not in knapping products, but in the way techniques were integrated. This reduction sequence persisted across the Pleistocene/Holocene boundary with a minor shift favoring unifacial flaking after 11ka. Other stone-related changes occurred at the same time, including the first appearance of edge-glossed flakes, a change in raw material selection, and more frequent fire-induced damage to stone artifacts. Later in the Holocene, technological complexity was generated by "adding-on" rectangular-sectioned stone adzes to the reduction sequence. The Pleistocene pattern is directly associated with Homo floresiensis skeletal remains and the Holocene changes correlate with the appearance of Homo sapiens. The one reduction sequence continues across this hominin replacement.

How similar are nut-cracking and stone-flaking? A functional approach to percussive technology

PubMed Central

Bril, Blandine; Parry, Ross; Dietrich, Gilles

2015-01-01

Various authors have suggested similarities between tool use in early hominins and chimpanzees. This has been particularly evident in studies of nut-cracking which is considered to be the most complex skill exhibited by wild apes, and has also been interpreted as a precursor of more complex stone-flaking abilities. It has been argued that there is no major qualitative difference between what the chimpanzee does when he cracks a nut and what early hominins did when they detached a flake from a core. In this paper, similarities and differences between skills involved in stone-flaking and nut-cracking are explored through an experimental protocol with human subjects performing both tasks. We suggest that a ‘functional’ approach to percussive action, based on the distinction between functional parameters that characterize each task and parameters that characterize the agent's actions and movements, is a fruitful method for understanding those constraints which need to be mastered to perform each task successfully, and subsequently, the nature of skill involved in both tasks. PMID:26483533

High-quality graphene flakes exfoliated on a flat hydrophobic polymer

NASA Astrophysics Data System (ADS)

Pedrinazzi, Paolo; Caridad, José M.; Mackenzie, David M. A.; Pizzocchero, Filippo; Gammelgaard, Lene; Jessen, Bjarke S.; Sordan, Roman; Booth, Timothy J.; Bøggild, Peter

2018-01-01

We show that graphene supported on a hydrophobic and flat polymer surface results in flakes with extremely low doping and strain as assessed by their Raman spectroscopic characteristics. We exemplify this technique by micromechanical exfoliation of graphene on flat poly(methylmethacrylate) layers and demonstrate Raman peak intensity ratios I(2D)/I(G) approaching 10, similar to pristine freestanding graphene. We verify that these features are not an artifact of optical interference effects occurring at the substrate: they are similarly observed when varying the substrate thickness and are maintained when the environment of the graphene flake is completely changed, by encapsulating preselected flakes between hexagonal boron nitride layers. The exfoliation of clean, pristine graphene layers directly on flat polymer substrates enables high performance, supported, and non-encapsulated graphene devices for flexible and transparent optoelectronic studies. We additionally show that the access to a clean and supported graphene source leads to high-quality van der Waals heterostructures and devices with reproducible carrier mobilities exceeding 50 000 cm2 V-1 s-1 at room temperature.

FEM analysis of magnetic flake composites

NASA Astrophysics Data System (ADS)

Claassen, J. H.

2009-07-01

A composite comprised of layered flake-like magnetic particles embedded in an insulating medium has been proposed as a low permeability, low loss core material. This would be an alternative to "distributed air gap" compressed powder cores that are widely used for inductors in power applications. Since the lowest loss metallic materials are manufactured in the form of very thin sheets, the particles after pulverizing would be in the form of flakes. The effective permeability and average core loss have been computed for model systems of flake composites in a two-dimensional approximation. The core loss is modeled by eddy current dissipation in the low-frequency limit, where the conductor thickness is much less than the skin depth. It is found that useful values of permeability should be obtained for a modest filling fraction of magnetic material, in contrast to the powder cores which require a value close to unity. The core loss will scale as the inverse of filling fraction, with a small additional enhancement due to perpendicular field components. It is thus expected that useful core materials may be attainable without the necessity of large compaction forces.

Stress transfer mechanisms at the submicron level for graphene/polymer systems.

PubMed

Anagnostopoulos, George; Androulidakis, Charalampos; Koukaras, Emmanuel N; Tsoukleri, Georgia; Polyzos, Ioannis; Parthenios, John; Papagelis, Konstantinos; Galiotis, Costas

2015-02-25

The stress transfer mechanism from a polymer substrate to a nanoinclusion, such as a graphene flake, is of extreme interest for the production of effective nanocomposites. Previous work conducted mainly at the micron scale has shown that the intrinsic mechanism of stress transfer is shear at the interface. However, since the interfacial shear takes its maximum value at the very edge of the nanoinclusion it is of extreme interest to assess the effect of edge integrity upon axial stress transfer at the submicron scale. Here, we conduct a detailed Raman line mapping near the edges of a monolayer graphene flake that is simply supported onto an epoxy-based photoresist (SU8)/poly(methyl methacrylate) matrix at steps as small as 100 nm. We show for the first time that the distribution of axial strain (stress) along the flake deviates somewhat from the classical shear-lag prediction for a region of ∼ 2 μm from the edge. This behavior is mainly attributed to the presence of residual stresses, unintentional doping, and/or edge effects (deviation from the equilibrium values of bond lengths and angles, as well as different edge chiralities). By considering a simple balance of shear-to-normal stresses at the interface we are able to directly convert the strain (stress) gradient to values of interfacial shear stress for all the applied tensile levels without assuming classical shear-lag behavior. For large flakes a maximum value of interfacial shear stress of 0.4 MPa is obtained prior to flake slipping.

Effects of storage in ozonised slurry ice on the sensory and microbial quality of sardine (Sardina pilchardus).

PubMed

Campos, Carmen A; Rodríguez, Oscar; Losada, Vanesa; Aubourg, Santiago P; Barros-Velázquez, Jorge

2005-08-25

The use of slurry ice, both alone and in combination with ozone, as compared with traditional flake ice was investigated as a new refrigeration system for the storage of sardine (Sardina pilchardus). Microbiological, chemical and sensory analyses were carried out throughout a storage period of 22 days. According to sensory analyses, sardine specimens stored in ozonised slurry ice had a shelf life of 19 days, while counterpart batches stored in slurry ice or flake ice had shelf lives of 15 and 8 days, respectively. Storage in ozonised slurry ice led to significantly lower counts of aerobic mesophiles, psychrotrophic bacteria, anaerobes, coliforms, and both lipolytic and proteolytic microorganisms in sardine muscle, and of surface counts of mesophiles and psychrotrophic bacteria in sardine skin as compared with the slurry ice and the flake ice batches. In all cases, the slurry ice batch also exhibited significantly lower microbial counts, both in muscle and skin, than the flake ice batch. Chemical parameters revealed that the use of slurry ice slowed down the formation of TVB-N and TMA-N to a significant extent in comparison with storage in flake ice. A combination of slurry ice with ozone also allowed a better control of pH and TMA-N formation as compared with slurry ice alone. This work demonstrates that the combined use of slurry ice and ozone for the storage of sardine can be recommended to improve the quality and extend the shelf life of this fish species.

Back-gated Nb-doped MoS2 junctionless field-effect-transistors

NASA Astrophysics Data System (ADS)

Mirabelli, Gioele; Schmidt, Michael; Sheehan, Brendan; Cherkaoui, Karim; Monaghan, Scott; Povey, Ian; McCarthy, Melissa; Bell, Alan P.; Nagle, Roger; Crupi, Felice; Hurley, Paul K.; Duffy, Ray

2016-02-01

Electrical measurements were carried out to measure the performance and evaluate the characteristics of MoS2 flakes doped with Niobium (Nb). The flakes were obtained by mechanical exfoliation and transferred onto 85 nm thick SiO2 oxide and a highly doped Si handle wafer. Ti/Au (5/45 nm) deposited on top of the flake allowed the realization of a back-gate structure, which was analyzed structurally through Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). To best of our knowledge this is the first cross-sectional TEM study of exfoliated Nb-doped MoS2 flakes. In fact to date TEM of transition-metal-dichalcogenide flakes is extremely rare in the literature, considering the recent body of work. The devices were then electrically characterized by temperature dependent Ids versus Vds and Ids versus Vbg curves. The temperature dependency of the device shows a semiconductor behavior and, the doping effect by Nb atoms introduces acceptors in the structure, with a p-type concentration 4.3 × 1019 cm-3 measured by Hall effect. The p-type doping is confirmed by all the electrical measurements, making the structure a junctionless transistor. In addition, other parameters regarding the contact resistance between the top metal and MoS2 are extracted thanks to a simple Transfer Length Method (TLM) structure, showing a promising contact resistivity of 1.05 × 10-7 Ω/cm2 and a sheet resistance of 2.36 × 102 Ω/sq.

Applications of optical coherence tomography in the non-contact assessment of automotive paints

NASA Astrophysics Data System (ADS)

Lawman, Samuel; Zhang, Jinke; Williams, Bryan M.; Zheng, Yalin; Shen, Yao-Chun

2017-06-01

The multiple layer paint systems on modern cars serve two end purposes, they firstly protect against corrosion and secondly give the desired visual appearance. To ensure consistent corrosion protection and appearance, suitable Quality Assurance (QA) measures on the final product are required. Various (layer thickness and consistency, layer composition, flake statistics, surface profile and layer dryness) parameters are of importance, each with specific techniques that can measure one or some of them but no technique that can measure all or most of them. Optical Coherence Tomography (OCT) is a 3D imaging technique with micrometre resolution. Since 2016, OCT measurements of layer thickness and consistency, layer composition fingerprint and flake statistics have been reported. In this paper we demonstrate two more novel applications of OCT to automotive paints. Firstly, we use OCT to quantify unwanted surface texture, which leads to an "orange peel" visual defect. This was done by measuring the surface profiles of automotive paints, with an unoptimised precision of 37 nm over lateral range of 7 mm, to quantify texture of less than 500 nm. Secondly, we demonstrate that OCT can measure how dry a coating layer is by measuring how fast it is still shrinking quasiinstantaneously, using Fourier phase sensitivity.

Effect of Carbon in the Dielectric Fluid and Workpieces on the Characteristics of Recast Layers Machined by Electrical Discharge Machining

NASA Astrophysics Data System (ADS)

Muttamara, Apiwat; Kanchanomai, Chaosuan

2016-06-01

Electrical discharge machining (EDM) is a popular non-traditional machining technique that is usually performed in kerosene. Carbon from the kerosene is mixed into the recast layer during EDM, increasing its hardness. EDM can be performed in deionized water, which causes decarburization. We studied the effects of carbon in the dielectric fluid and workpiece on the characteristics of recast layers. Experiments were conducted using gray cast iron and mild steel workpieces in deionized water or kerosene under identical operating conditions. Scanning electron microscopy revealed that the recast layer formed on gray iron was rougher than that produced on mild steel. Moreover, the dispersion of graphite flakes in the gray iron seemed to cause subsurface cracks, even when EDM was performed in deionized water. Dendritic structures and iron carbides were found in the recast layer of gray iron treated in deionized water. Kerosene caused more microcracks to form and increased surface roughness compared with deionized water. The microcrack length per unit area of mild steel treated in deionized water was greater than that treated in kerosene, but the cracks formed in kerosene were wider. The effect of the diffusion of carbon during cooling on the characteristics of the recast layer was discussed.

Graphene Inks with Cellulosic Dispersants: Development and Applications for Printed Electronics

NASA Astrophysics Data System (ADS)

Secor, Ethan Benjamin

Graphene offers promising opportunities for applications in printed and flexible electronic devices due to its high electrical and thermal conductivity, mechanical flexibility and strength, and chemical and environmental stability. However, scalable production and processing of graphene presents a critical technological challenge preventing the application of graphene for flexible electronic interconnects, electrochemical energy storage, and chemically robust electrical contacts. In this thesis, a promising and versatile platform for the production, patterning, and application of graphene inks is presented based on cellulosic dispersants. Graphene is produced from flake graphite using scalable liquid-phase exfoliation methods, using the polymers ethyl cellulose and nitrocellulose as multifunctional dispersing agents. These cellulose derivatives offer high colloidal stability and broadly tunable rheology for graphene dispersions, providing an effective and tunable platform for graphene ink development. Thermal or photonic annealing decomposes the polymer dispersant to yield high conductivity, flexible graphene patterns for various electronics applications. In particular, the chemical stability of graphene enables robust electrical contacts for ceramic, metallic, organic and electrolytic materials, validating the diverse applicability of graphene in printed electronics. Overall, the strategy for graphene ink design presented here offers a simple, efficient, and versatile method for integrating graphene in a wide range of printed devices and systems, providing both fundamental insight for nanomaterial ink development and realistic opportunities for practical applications.

Microstructure Evolution of TiC Particles In Situ, Synthesized by Laser Cladding

PubMed Central

Liu, Yanhui; Ding, Jieqiong; Qu, Weicheng; Su, Yu; Yu, Zhishui

2017-01-01

In this paper, a TiC reinforcement metal matrix composite coating is produced using nickel and graphite mixing powder on the surface ofTi-6Al-4V alloy by laser radiation. The microstructure of the coatings is investigated by XRD, SEM and EDS. Results show that most of the TiC phase is granular, with a size of several micrometers, and a few of the TiC phases are petals or flakes. At the cross-section of the coatings, a few special TiC patterns are found and these TiC patterns do not always occur at the observed cross-section. The even distribution of the TiC phase in the coatings confirms that the convection of the laser-melted pool leads to the homogenization of titanium atoms from the molten substrate, and carbon atoms from the preplace powder layer, by the mass transfer. The characteristics of the TiC pattern confirm that the morphology and distribution of the primary TiC phase could be influenced by convection. Two main reasons for this are that the density of the TiC phase is lower than the liquid melt, and that the primary TiC phase precipitates from the pool with a high convection speed at high temperature. PMID:28772641

Microstructure Evolution of TiC Particles In Situ, Synthesized by Laser Cladding.

PubMed

Liu, Yanhui; Ding, Jieqiong; Qu, Weicheng; Su, Yu; Yu, Zhishui

2017-03-11

In this paper, a TiC reinforcement metal matrix composite coating is produced using nickel and graphite mixing powder on the surface ofTi-6Al-4V alloy by laser radiation. The microstructure of the coatings is investigated by XRD, SEM and EDS. Results show that most of the TiC phase is granular, with a size of several micrometers, and a few of the TiC phases are petals or flakes. At the cross-section of the coatings, a few special TiC patterns are found and these TiC patterns do not always occur at the observed cross-section. The even distribution of the TiC phase in the coatings confirms that the convection of the laser-melted pool leads to the homogenization of titanium atoms from the molten substrate, and carbon atoms from the preplace powder layer, by the mass transfer. The characteristics of the TiC pattern confirm that the morphology and distribution of the primary TiC phase could be influenced by convection. Two main reasons for this are that the density of the TiC phase is lower than the liquid melt, and that the primary TiC phase precipitates from the pool with a high convection speed at high temperature.

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

NASA Technical Reports Server (NTRS)

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

2007-01-01

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

Conductive Adhesive Based on Mussel-Inspired Graphene Decoration with Silver Nanoparticles.

PubMed

Casa, Marcello; Sarno, Maria; Liguori, Rosalba; Cirillo, Claudia; Rubino, Alfredo; Bezzeccheri, Emanuele; Liu, Johan; Ciambelli, Paolo

2018-02-01

Decoration with silver nanoparticles was obtained by coating graphene with a polydopamine layer, able to induce spontaneous metallic nanoparticles formation without any specific chemical interfacial modifier, neither using complex instrumentation. The choice of dopamine was inspired by the composition of adhesive proteins in mussels, related to their robust attach to solid surfaces. The synthesis procedure started from graphite and involved eco-friendly compounds, such as Vitamin C and glucose as reducing agent and water as reaction medium. Silver decorated graphene was inserted as secondary nanofiller in the formulation of a reference conductive adhesive based on epoxy resin and silver flakes. A wide characterization of the intermediate materials obtained along the step procedure for the adhesive preparation was carried out by several techniques. We have found that the presence of nanofiller yields, in addition to an improvement of the thermal conductivity (up to 7.6 W/m · K), a dramatic enhancement of the electrical conductivity of the adhesive. In particular, starting from 3 · 102 S/cm of the reference adhesive, we obtained a value of 4 · 104 S/cm at a nanofiller concentration of 11.5 wt%. The combined double filler conductivity was evaluated by Zallen's model. The effect of the temperature on the resistivity of the adhesive has been also studied.

The Investigation and Development of Low Cost Hardware Components for Proton-Exchange Membrane Fuel Cells - Final Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

George A. Marchetti

1999-12-15

Proton exchange membrane (PEM) fuel cell components, which would have a low-cost structure in mass production, were fabricated and tested. A fuel cell electrode structure, comprising a thin layer of graphite (50 microns) and a front-loaded platinum catalyst layer (600 angstroms), was shown to produce significant power densities. In addition, a PEM bipolar plate, comprising flexible graphite, carbon cloth flow-fields and an integrated polymer gasket, was fabricated. Power densities of a two-cell unit using this inexpensive bipolar plate architecture were shown to be comparable to state-of-the-art bipolar plates.

TUNGSTEN BASE ALLOYS

DOEpatents

Schell, D.H.; Sheinberg, H.

1959-12-15

A high-density quaternary tungsten-base alloy having high mechanical strength and good machinability composed of about 2 wt.% Ni, 3 wt.% Cu, 5 wt.% Pb, and 90wt.% W is described. This alloy can be formed by the powder metallurgy technique of hot pressing in a graphite die without causing a reaction between charge and the die and without formation of a carbide case on the final compact, thereby enabling re-use of the graphite die. The alloy is formable at hot- pressing temperatures of from about 1200 to about 1350 deg C. In addition, there is little component shrinkage, thereby eliminating the necessity of subsequent extensive surface machining.

IMPREGNATION OF GRAPHITE SPECIMENS USING THE FURFURYL ALCOHOL IMPREGNATION PROCESS. Project DRAGON

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martina, R.A.; Vohler, O.J.

1964-11-15

This report gives the results of the furfuryl alcohol impregnation treatment of graphite fuel rods and end plugs done by Sigri Kohlefabrikate GmbH, Meitingen, from May 1962 till April 1964. By impregnating the components two and three times, resp. the permeability was decreased, starting from a coefficient of about 5 x 10{sup -2}cm{sup 2}sec{sup -1}, to a value of 10{sup -6} - 10{sup -7}cm{sup 2}sec{sup -1}. The rejects as occured with the first batches were finally diminished to a negligible amount by studying the single steps of treatment. (auth)

Highly efficient computer algorithm for identifying layer thickness of atomically thin 2D materials

NASA Astrophysics Data System (ADS)

Lee, Jekwan; Cho, Seungwan; Park, Soohyun; Bae, Hyemin; Noh, Minji; Kim, Beom; In, Chihun; Yang, Seunghoon; Lee, Sooun; Seo, Seung Young; Kim, Jehyun; Lee, Chul-Ho; Shim, Woo-Young; Jo, Moon-Ho; Kim, Dohun; Choi, Hyunyong

2018-03-01

The fields of layered material research, such as transition-metal dichalcogenides (TMDs), have demonstrated that the optical, electrical and mechanical properties strongly depend on the layer number N. Thus, efficient and accurate determination of N is the most crucial step before the associated device fabrication. An existing experimental technique using an optical microscope is the most widely used one to identify N. However, a critical drawback of this approach is that it relies on extensive laboratory experiences to estimate N; it requires a very time-consuming image-searching task assisted by human eyes and secondary measurements such as atomic force microscopy and Raman spectroscopy, which are necessary to ensure N. In this work, we introduce a computer algorithm based on the image analysis of a quantized optical contrast. We show that our algorithm can apply to a wide variety of layered materials, including graphene, MoS2, and WS2 regardless of substrates. The algorithm largely consists of two parts. First, it sets up an appropriate boundary between target flakes and substrate. Second, to compute N, it automatically calculates the optical contrast using an adaptive RGB estimation process between each target, which results in a matrix with different integer Ns and returns a matrix map of Ns onto the target flake position. Using a conventional desktop computational power, the time taken to display the final N matrix was 1.8 s on average for the image size of 1280 pixels by 960 pixels and obtained a high accuracy of 90% (six estimation errors among 62 samples) when compared to the other methods. To show the effectiveness of our algorithm, we also apply it to TMD flakes transferred on optically transparent c-axis sapphire substrates and obtain a similar result of the accuracy of 94% (two estimation errors among 34 samples).

Making High-Tensile-Strength Amalgam Components

NASA Technical Reports Server (NTRS)

Grugel, Richard

2008-01-01

Structural components made of amalgams can be made to have tensile strengths much greater than previously known to be possible. Amalgams, perhaps best known for their use in dental fillings, have several useful attributes, including room-temperature fabrication, corrosion resistance, dimensional stability, and high compressive strength. However, the range of applications of amalgams has been limited by their very small tensile strengths. Now, it has been discovered that the tensile strength of an amalgam depends critically on the sizes and shapes of the particles from which it is made and, consequently, the tensile strength can be greatly increased through suitable choice of the particles. Heretofore, the powder particles used to make amalgams have been, variously, in the form of micron-sized spheroids or flakes. The tensile reinforcement contributed by the spheroids and flakes is minimal because fracture paths simply go around these particles. However, if spheroids or flakes are replaced by strands having greater lengths, then tensile reinforcement can be increased significantly. The feasibility of this concept was shown in an experiment in which electrical copper wires, serving as demonstration substitutes for copper powder particles, were triturated with gallium by use of a mortar and pestle and the resulting amalgam was compressed into a mold. The tensile strength of the amalgam specimen was then measured and found to be greater than 10(exp 4) psi (greater than about 69 MPa). Much remains to be done to optimize the properties of amalgams for various applications through suitable choice of starting constituents and modification of the trituration and molding processes. The choice of wire size and composition are expected to be especially important. Perusal of phase diagrams of metal mixtures could give insight that would enable choices of solid and liquid metal constituents. Finally, whereas heretofore, only binary alloys have been considered for amalgams, ternary additions to liquid or solid components should be considered as means to impart desired properties to amalgams.

Automated eddy current analysis of materials

NASA Technical Reports Server (NTRS)

Workman, Gary L.

1991-01-01

The use of eddy current techniques for characterizing flaws in graphite-based filament-wound cylindrical structures is described. A major emphasis was also placed upon incorporating artificial intelligence techniques into the signal analysis portion of the inspection process. Developing an eddy current scanning system using a commercial robot for inspecting graphite structures (and others) was a goal in the overall concept and is essential for the final implementation for the expert systems interpretation. Manual scans, as performed in the preliminary work here, do not provide sufficiently reproducible eddy current signatures to be easily built into a real time expert system. The expert systems approach to eddy current signal analysis requires that a suitable knowledge base exist in which correct decisions as to the nature of a flaw can be performed. A robotic workcell using eddy current transducers for the inspection of carbon filament materials with improved sensitivity was developed. Improved coupling efficiencies achieved with the E-probes and horseshoe probes are exceptional for graphite fibers. The eddy current supervisory system and expert system was partially developed on a MacIvory system. Continued utilization of finite element models for predetermining eddy current signals was shown to be useful in this work, both for understanding how electromagnetic fields interact with graphite fibers, and also for use in determining how to develop the knowledge base. Sufficient data was taken to indicate that the E-probe and the horseshoe probe can be useful eddy current transducers for inspecting graphite fiber components. The lacking component at this time is a large enough probe to have sensitivity in both the far and near field of a thick graphite epoxy component.

Production of Fatty Acid Methyl Esters via the In Situ Transesterification of Soybean Oil in Carbon Dioxide-Expanded Methanol

USDA-ARS?s Scientific Manuscript database

The production of fatty acid methyl esters (FAME) by direct alkali- and acid-catalyzed in situ transesterification of soybean flakes in CO2-expanded methanol was examined at various temperatures and pressures. Attempts to synthesize FAME from soy flakes via alkaline catalysis, using sodium methoxid...

76 FR 14055 - Notice of Inventory Completion: California State Department of Transportation (Caltrans...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-15

... silicate core, 2 lots of debitage, 490 faunal bones, 2 flake tools, 61 tule mat impressions, 20 modified bones, 1 modified shell, 2 modified stones, 20 pieces of ochre, 14 ornaments, 3 pestles, 20 projectile..., 5 faunal bones, 1 flake tool, 1 modified bone, 1 quartz rock, 1 steatite ring, and 5 bone whistles...

Dimensional stability of flakeboards as affected by board specific gravity and flake alignment

Treesearch

Robert L. Geimer

1982-01-01

The objective was to determine the relationship between the variables specific gravity (SG) and flake alignment and the dimensional stability properties of flakeboard. Boards manufactured without a density gradient were exposed to various levels of relative humidity and a vacuum-pressure soak (VPS) treatment. Changes in moisture content (MC), thickness swelling, and...

Mechanical performance of cellulose nanofibril film-wood flake laminate

Treesearch

Jen-Chieh Liu; Robert J. Moon; Alan Rudie; Jeffrey P. Youngblood

2014-01-01

Homogeneous and transparent CNF films, fabricated from the (2,2,6,6- tetramethylpiperidin-1-yl) oxyl (TEMPO)-modified CNF suspension, were laminated onto wood flakes (WF) based on phenol-formaldehyde (PF) resin and the reinforcement potential of the material has been investigated. The focus was on the influence of CNF film lamination, relative humidity (RH), heat...

Reel wheels : an application of material science

Treesearch

Robert L. Geimer

1979-01-01

Circular plates of reconstituted wood were fabricated and destructively tested to appraise the potential of such material for cable reel flanges. The reconstituted wood consisted of flakeboard from quality-cut flakes and also from factory residue. The high quality flakeboard used 0.020- by 1/2-by 2-inch southern pine flakes cut on a disk flaker, whereas the flakeboard...

Aerially applied methylcyclohexenone-releasing flakes protect Psuedotsuga menziesii stands from attack by Dendroctonus pseudotsugae

Treesearch

N. E. Gillette; C. J. Mehmel; J. N. Webster; S. R. Mori; N. Erbilgin; D. L. Wood; J. D. Stein

2009-01-01

We tested methylcyclohexenone (MCH), an anti-aggregation pheromone for the Douglas-fir beetle (Dendroctonus pseudotsugae), for protection of Douglas-fir (Pseudotsuga menziesii) stands by applying MCH-releasing polymer flakes by helicopter twice during summer 2006 to five 4.05-ha plots in the State of Washington, USA. Five similar plots served as...

40 CFR 417.60 - Applicability; description of the manufacture of soap flakes and powders subcategory.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 29 2011-07-01 2009-07-01 true Applicability; description of the manufacture of soap flakes and powders subcategory. 417.60 Section 417.60 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS SOAP AND DETERGENT MANUFACTURING POINT SOURCE CATEGORY Manufacture of Soap...

40 CFR 417.60 - Applicability; description of the manufacture of soap flakes and powders subcategory.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 28 2010-07-01 2010-07-01 true Applicability; description of the manufacture of soap flakes and powders subcategory. 417.60 Section 417.60 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS SOAP AND DETERGENT MANUFACTURING POINT SOURCE CATEGORY Manufacture of Soap...

The Role of Expertise in Tool Use: Skill Differences in Functional Action Adaptations to Task Constraints

ERIC Educational Resources Information Center

Bril, Blandine; Rein, Robert; Nonaka, Tetsushi; Wenban-Smith, Francis; Dietrich, Gilles

2010-01-01

Tool use can be considered a particularly useful model to understand the nature of functional actions. In 3 experiments, tool-use actions typified by stone knapping were investigated. Participants had to detach stone flakes from a flint core through a conchoidal fracture. Successful flake detachment requires controlling various functional…

Metamaterial composition comprising frequency-selective-surface resonant element disposed on/in a dielectric flake, methods, and applications

DOEpatents

Shelton, David; Boreman, Glenn; D'Archangel, Jeffrey

2015-11-10

Infrared metamaterial arrays containing Au elements immersed in a medium of benzocyclobutene (BCB) were fabricated and selectively etched to produce small square flakes with edge dimensions of approximately 20 .mu.m. Two unit-cell designs were fabricated: one employed crossed-dipole elements while the other utilized square-loop elements.

Raman enhancement by graphene-Ga2O3 2D bilayer film.

PubMed

Zhu, Yun; Yu, Qing-Kai; Ding, Gu-Qiao; Xu, Xu-Guang; Wu, Tian-Ru; Gong, Qian; Yuan, Ning-Yi; Ding, Jian-Ning; Wang, Shu-Min; Xie, Xiao-Ming; Jiang, Mian-Heng

2014-01-28

2D β-Ga2O3 flakes on a continuous 2D graphene film were prepared by a one-step chemical vapor deposition on liquid gallium surface. The composite was characterized by optical microscopy, scanning electron microscopy, Raman spectroscopy, energy dispersive spectroscopy, and X-ray photoelectron spectroscopy (XPS). The experimental results indicate that Ga2O3 flakes grew on the surface of graphene film during the cooling process. In particular, tenfold enhancement of graphene Raman scattering signal was detected on Ga2O3 flakes, and XPS indicates the C-O bonding between graphene and Ga2O3. The mechanism of Raman enhancement was discussed. The 2D Ga2O3-2D graphene structure may possess potential applications.

Two-dimensional MoTe2 materials: From synthesis, identification, and charge transport to electronics applications

NASA Astrophysics Data System (ADS)

Chang, Yuan-Ming; Lin, Che-Yi; Lin, Yen-Fu; Tsukagoshi, Kazuhito

2016-11-01

We present a review of recent developments in the synthesis, thickness identification, electronic properties, and possible applications of layered MoTe2 flakes. Special emphasis is made on two-dimensional (2D) MoTe2 semiconductors and the extensive research in recent years on their applications in electronics. Layered MoTe2 flakes have been the focus of substantial interest in the research community because of their fascinating characteristics, including an appropriate band gap and a simple fabrication method (exfoliation) to form layered nanomaterials. Our aim is to provide the readers an overview of layered MoTe2 flakes and to understand their properties, which may lead to their applications in micro- and nanoelectronics.

78 FR 55680 - Small Diameter Graphite Electrodes From the People's Republic of China: Final Results of...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-09-11

.... Acclcarbon Co., Ltd. 3. Allied Carbon (China) Co., Limited 4. Anssen Metallurgy Group Co., Ltd. 5. AMGL 6... International Trade Co., Ltd. 20. Dalian Horton International Trading Co., Ltd. 21. Dalian LST Metallurgy Co...

A phase-field approach to model multi-axial and microstructure dependent fracture in nuclear grade graphite

DOE PAGES

Chakraborty, Pritam; Sabharwall, Piyush; Carroll, Mark C.

2016-04-07

The fracture behavior of nuclear grade graphites is strongly influenced by underlying microstructural features such as the character of filler particles, and the distribution of pores and voids. These microstructural features influence the crack nucleation and propagation behavior, resulting in quasi-brittle fracture with a tortuous crack path and significant scatter in measured bulk strength. This paper uses a phase-field method to model the microstructural and multi-axial fracture in H-451, a historic variant of nuclear graphite that provides the basis for an idealized study on a legacy grade. The representative volume elements are constructed from randomly located pores with random sizemore » obtained from experimentally determined log-normal distribution. The representative volume elements are then subjected to simulated multi-axial loading, and a reasonable agreement of the resulting fracture stress with experiments is obtained. Finally, quasi-brittle stress-strain evolution with a tortuous crack path is also observed from the simulations and is consistent with experimental results.« less

Effects of pore formers on microstructure and performance of cathode membranes for solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Nie, Lifang; Liu, Juncheng; Zhang, Yujun; Liu, Meilin

La 0.6Sr 0.4Co 0.2Fe 0.8O 3- δ (LSCF) is the most widely used cathode material for intermediate temperature solid oxide fuel cells. In the present communication, porous LSCF cathodes are fabricated by tape casting, a low-cost and reproducible fabrication process. The effects of four different pore formers, namely, graphite, carbon black, rice starch, and corn starch, on the microstructure and electrochemical performance of the LSCF cathode are investigated. Examination of the microstructures reveals that the shape of the pores, the pore size, and the pore distribution in the final ceramic are related to the type of pore formers. Impedance analysis and cell testing show that the best performance is obtained from the cathode using graphite as the pore former. The microstructure indicates that graphite results in a porous LSCF cathode with a large surface area and high porosity, which can offer a considerably long triple phase boundary for catalytic reactions as well as channels for gas phase transport.

Stress Transfer Mechanisms at the Submicron Level for Graphene/Polymer Systems

PubMed Central

2015-01-01

The stress transfer mechanism from a polymer substrate to a nanoinclusion, such as a graphene flake, is of extreme interest for the production of effective nanocomposites. Previous work conducted mainly at the micron scale has shown that the intrinsic mechanism of stress transfer is shear at the interface. However, since the interfacial shear takes its maximum value at the very edge of the nanoinclusion it is of extreme interest to assess the effect of edge integrity upon axial stress transfer at the submicron scale. Here, we conduct a detailed Raman line mapping near the edges of a monolayer graphene flake that is simply supported onto an epoxy-based photoresist (SU8)/poly(methyl methacrylate) matrix at steps as small as 100 nm. We show for the first time that the distribution of axial strain (stress) along the flake deviates somewhat from the classical shear-lag prediction for a region of ∼2 μm from the edge. This behavior is mainly attributed to the presence of residual stresses, unintentional doping, and/or edge effects (deviation from the equilibrium values of bond lengths and angles, as well as different edge chiralities). By considering a simple balance of shear-to-normal stresses at the interface we are able to directly convert the strain (stress) gradient to values of interfacial shear stress for all the applied tensile levels without assuming classical shear-lag behavior. For large flakes a maximum value of interfacial shear stress of 0.4 MPa is obtained prior to flake slipping. PMID:25644121

Effect of resin variables on the creep behavior of high density hardwood composite panels

Treesearch

R.C. Tang; Jianhua Pu; C.Y Hse

1993-01-01

The flexural creep behavior of oriented strandboards (OSB) fabricated with mixed high, density hardwood flakes was investigated. Three types of adhesives, liquid phenolic-formaldehyde (LPF), melamine modified urea-formaldehyde (MUF), and LPF (face)/MUF (core) were chosen in this investigation. The resin contents (RC) used were 3.5 percent and 5.0 percent. The flakes...

Properties of flakeboards from hardwoods growing on southern pine sites

Treesearch

C. -Y. Hse

1975-01-01

Boards 0.5 inch thick were made from 3-inch-long flakes of 9 species of southern hardwoods commonly found on pine sites. The main effects of species were due to variation in wood density; low-density species compacted readily when pressed, and the resulting good flake contact improved bonding and gave boards of high strength. With species having specific gravities...

77 FR 59969 - Notice of Inventory Completion: San Francisco State University, Department of Anthropology, San...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-10-01

..., 5 chert flaked stone tools, 27 pieces of chert debitage, 15 ground stone tools, 75 bone tools, 1 basalt flake, 1 granite tool, 1 schist tool, 2 steatite ear plugs, 1 ceramic fragment, 1 bone bead, 1... individuals were identified. The 247 associated funerary objects are 128 bone tools, 78 obsidian tools, 18...

Properties of flakeboards from hardwoods growing on southern pine sites

Treesearch

Chung-Yun Hse

1975-01-01

Boards 0.5 inch thick were made from 3-inch-long flakes of 9 species of southern hardwoods commonly found on pine sites. The main effects of species were doe to variation in wood density; low-density species compacted readily when pressed, and the resulting good flake contact improved bonding and gave boards of high strength. With species having specific gravities...

Effects of A New Caul System on Strength and Stability of Structural Flakeboard

Treesearch

Cheng Piao; Todd F. Shupe; Chung Y. Hse

2004-01-01

Pressing flakes or fibers at high moisture content (MC) may generate substantial benefits for the manufacture of wood composites. Such technology could reduce furnish drying costs and the risk of fire hazard, improve panel mechanicaland moisture soaking properties, and reduce emission of volatile organic compounds (VOCs) at drying of flakes and at hot pressing. However...

Effects of sorghum wet distillers grains plus solubles in steam-flaked corn-based finishing diets on steer performance, carcass characteristics, and digestibility characteristics

USDA-ARS?s Scientific Manuscript database

Two studies were conducted to evaluate the effects of sorghum wet distillers grains (SWDGS) in finishing diets on steer performance, carcass characteristics, and nutrient digestibility. In Exp. 1, 240 steers (initial BW = 379 +/-1 kg) were fed steam-flaked corn (SFC)-based diets with or without 25%...

Synthesis of α-MoO3 nano-flakes by dry oxidation of RF sputtered Mo thin films and their application in gas sensing

NASA Astrophysics Data System (ADS)

Dwivedi, Priyanka; Dhanekar, Saakshi; Das, Samaresh

2016-11-01

Synthesis of orthorhombic (α) MoO3 nano-flakes by dry oxidation of RF sputtered Mo thin film is presented. The influence of Mo thickness variation, oxidation temperature and time on the crystallographic structure, surface morphology and roughness of MoO3 thin films was studied using SEM, AFM, XRD and Raman spectroscopy. A structural study shows that MoO3 is polycrystalline in nature with an α phase. It was noticed that oxidation temperature plays an important role in the formation of nano-flakes. The synthesis technique proposed is simple and suitable for large scale productions. The synthesis parameters were optimized for the fabrication of sensors. Chrome gold-based IDE (interdigitated electrodes) structures were patterned for the electrical detection of organic vapors. Sensors were exposed to wide range 5-100 ppm of organic vapors like ethanol, acetone, IPA (isopropanol alcohol) and water vapors. α-MoO3 nano-flakes have demonstrated selective sensing to acetone in the range of 10-100 ppm at 150 °C. The morphology of such nanostructures has potential in applications such as sensor devices due to their high surface area and thermal stability.

Structural evaluation of reduced graphene oxide in graphene oxide during ion irradiation: X-ray absorption spectroscopy and in-situ sheet resistance studies

NASA Astrophysics Data System (ADS)

Saravanan, K.; Jayalakshmi, G.; Suresh, K.; Sundaravel, B.; Panigrahi, B. K.; Phase, D. M.

2018-03-01

We report the structural evolution of reduced graphene oxide (rGO) in graphene oxide (GO) flakes during 1 MeV Si+ ion irradiation. In-situ electrical resistivity measurements facilitate monitoring the sheet resistance with the increase in the fluence. The electrical sheet resistance of the GO flake shows the exponential decay behaviour with the increasing ion fluence. Raman spectra of the GO flake reveal the increase in the ID/IG ratio, indicating restoration of the sp2 network upon irradiation. The C/O ratio estimated from resonant Rutherford backscattering spectrometry analysis directly evidenced the reduction of oxygen moieties upon irradiation. C K-edge X-ray absorption near edge structure spectra reveal the restoration of C=C sp2-hybridized carbon atoms and the removal of oxygen-containing functional groups in the GO flake. STM data reveal the higher conductance in the rGO regime in comparison with the regime, where the oxygen functional groups are present. The experimental investigation demonstrates that the ion irradiation can be employed for efficient reduction of GO with tunable electrical and structural properties.

A comparative study on the activity of fungal lytic polysaccharide monooxygenases for the depolymerization of cellulose in soybean spent flakes.

PubMed

Pierce, Brian C; Agger, Jane Wittrup; Zhang, Zhenghong; Wichmann, Jesper; Meyer, Anne S

2017-09-08

Lytic polysaccharide monooxygenases (LPMOs) are copper-dependent enzymes capable of the oxidative breakdown of polysaccharides. They are of industrial interest due to their ability to enhance the enzymatic depolymerization of recalcitrant substrates by glycoside hydrolases. In this paper, twenty-four lytic polysaccharide monooxygenases (LPMOs) expressed in Trichoderma reesei were evaluated for their ability to oxidize the complex polysaccharides in soybean spent flakes, an abundant and industrially relevant substrate. TrCel61A, a soy-polysaccharide-active AA9 LPMO from T. reesei, was used as a benchmark in this evaluation. In total, seven LPMOs demonstrated activity on pretreated soy spent flakes, with the products from enzymatic treatments evaluated using mass spectrometry and high performance anion exchange chromatography. The hydrolytic boosting effect of the top-performing enzymes was evaluated in combination with endoglucanase and beta-glucosidase. Two enzymes (TrCel61A and Aspte6) showed the ability to release more than 36% of the pretreated soy spent flake glucose - a greater than 75% increase over the same treatment without LPMO addition. Copyright © 2017 Elsevier Ltd. All rights reserved.

Recycling disposable cups into paper plastic composites.

PubMed

Mitchell, Jonathan; Vandeperre, Luc; Dvorak, Rob; Kosior, Ed; Tarverdi, Karnik; Cheeseman, Christopher

2014-11-01

The majority of disposable cups are made from paper plastic laminates (PPL) which consist of high quality cellulose fibre with a thin internal polyethylene coating. There are limited recycling options for PPLs and this has contributed to disposable cups becoming a high profile, problematic waste. In this work disposable cups have been shredded to form PPL flakes and these have been used to reinforce polypropylene to form novel paper plastic composites (PPCs). The PPL flakes and polypropylene were mixed, extruded, pelletised and injection moulded at low temperatures to prevent degradation of the cellulose fibres. The level of PPL flake addition and the use of a maleated polyolefin coupling agent to enhance interfacial adhesion have been investigated. Samples have been characterised using tensile testing, dynamic mechanical analysis (DMA) and thermogravimetric analysis. Use of a coupling agent allows composites containing 40 wt.% of PPL flakes to increase tensile strength of PP by 50% to 30 MPa. The Young modulus also increases from 1 to 2.5 GPa and the work to fracture increases by a factor of 5. The work demonstrates that PPL disposable cups have potential to be beneficially reused as reinforcement in novel polypropylene composites. Copyright © 2014 Elsevier Ltd. All rights reserved.

Technique for the polymerization of monomers for PPQ/graphite fiber composites

NASA Technical Reports Server (NTRS)

Serafini, T. T.; Delvigs, P.; Vannucci, R. D.

1973-01-01

Impregnation of fiber prior to appreciable polymerization completely eliminates impregnation problems encountered with use of high viscosity high molecular weight polyphenylquinoxalines (PPQ) solutions. Major part of polymerization of reactant mixture is conducted on fiber during solvent removal and final curing stages.

Selectivity in the inelastic rotational scattering of D2 and HD molecules from graphite: Similarities and differences respect to the H2 case

NASA Astrophysics Data System (ADS)

Rutigliano, Maria; Pirani, Fernando

2018-03-01

The inelastic scattering of D2 and HD molecules impinging on a graphite surface in well-defined initial roto-vibrational states has been studied by using the computational setup recently developed to characterize important selectivities in the molecular dynamics occurring at the gas-surface interface. In order to make an immediate comparison of determined elastic and inelastic scattering probabilities, we considered for D2 and HD molecules the same initial states, as well as the same collision energy range, previously selected for the investigation of H2 behaviour. The analysis of the back-scattered molecules shows that, while low-lying initial vibrational states are preserved, the medium-high initial ones give rise to final states covering the complete ladder of vibrational levels, although with different probability for the various cases investigated. Moreover, propensities in the formation of the final rotational states are found to depend strongly on the initial ones, on the collision energy, and on the isotopologue species.

Shape Modification and Size Classification of Microcrystalline Graphite Powder as Anode Material for Lithium-Ion Batteries

NASA Astrophysics Data System (ADS)

Wang, Cong; Gai, Guosheng; Yang, Yufen

2018-03-01

Natural microcrystalline graphite (MCG) composed of many crystallites is a promising new anode material for lithium-ion batteries (LiBs) and has received considerable attention from researchers. MCG with narrow particle size distribution and high sphericity exhibits excellent electrochemical performance. A nonaddition process to prepare natural MCG as a high-performance LiB anode material is described. First, raw MCG was broken into smaller particles using a pulverization system. Then, the particles were modified into near-spherical shape using a particle shape modification system. Finally, the particle size distribution was narrowed using a centrifugal rotor classification system. The products with uniform hemispherical shape and narrow size distribution had mean particle size of approximately 9 μm, 10 μm, 15 μm, and 20 μm. Additionally, the innovative pilot experimental process increased the product yield of the raw material. Finally, the electrochemical performance of the prepared MCG was tested, revealing high reversible capacity and good cyclability.

Insights into early lithic technologies from ethnography

PubMed Central

Hayden, Brian

2015-01-01

Oldowan lithic assemblages are often portrayed as a product of the need to obtain sharp flakes for cutting into animal carcases. However, ethnographic and experimental research indicates that the optimal way to produce flakes for such butchering purposes is via bipolar reduction of small cryptocrystalline pebbles rather than from larger crystalline cores resembling choppers. Ethnographic observations of stone tool-using hunter-gatherers in environments comparable with early hominins indicate that most stone tools (particularly chopper forms and flake tools) were used for making simple shaft tools including spears, digging sticks and throwing sticks. These tools bear strong resemblances to Oldowan stone tools. Bipolar reduction for butchering probably preceded chopper-like core reduction and provides a key link between primate nut-cracking technologies and the emergence of more sophisticated lithic technologies leading to the Oldowan. PMID:26483534

Influence of various surface pretreatments on adherence of sputtered molybdenum disulfide to silver, gold, copper, and bronze

NASA Technical Reports Server (NTRS)

Spalvins, T.

1973-01-01

Solid film lubricants of radio frequency sputtered molybdenum disulfide (MoS2) were applied to silver, gold, copper, and bronze surfaces that had various pretreatments (mechanical polishing, sputter etching, oxidation, and sulfurization). Optical and electron transmission micrographs and electron diffraction patterns were used to interpret the film formation characteristics and to evaluate the sputtering conditions in regard to the film and substrate compatibility. Sputtered MoS2 films flaked and peeled on silver, copper, and bronze surfaces except when the surfaces had been specially oxidized. The flaking and peeling was a result of sulfide compound formation and the corresponding grain growth of the sulfide film. Sputtered MoS2 films showed no peeling and flaking on gold surfaces regardless of surface pretreatment.

Raman enhancement by graphene-Ga2O3 2D bilayer film

PubMed Central

2014-01-01

2D β-Ga2O3 flakes on a continuous 2D graphene film were prepared by a one-step chemical vapor deposition on liquid gallium surface. The composite was characterized by optical microscopy, scanning electron microscopy, Raman spectroscopy, energy dispersive spectroscopy, and X-ray photoelectron spectroscopy (XPS). The experimental results indicate that Ga2O3 flakes grew on the surface of graphene film during the cooling process. In particular, tenfold enhancement of graphene Raman scattering signal was detected on Ga2O3 flakes, and XPS indicates the C-O bonding between graphene and Ga2O3. The mechanism of Raman enhancement was discussed. The 2D Ga2O3-2D graphene structure may possess potential applications. PMID:24472433

Wettability of graphitic-carbon and silicon surfaces: MD modeling and theoretical analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramos-Alvarado, Bladimir; Kumar, Satish; Peterson, G. P.

2015-07-28

The wettability of graphitic carbon and silicon surfaces was numerically and theoretically investigated. A multi-response method has been developed for the analysis of conventional molecular dynamics (MD) simulations of droplets wettability. The contact angle and indicators of the quality of the computations are tracked as a function of the data sets analyzed over time. This method of analysis allows accurate calculations of the contact angle obtained from the MD simulations. Analytical models were also developed for the calculation of the work of adhesion using the mean-field theory, accounting for the interfacial entropy changes. A calibration method is proposed to providemore » better predictions of the respective contact angles under different solid-liquid interaction potentials. Estimations of the binding energy between a water monomer and graphite match those previously reported. In addition, a breakdown in the relationship between the binding energy and the contact angle was observed. The macroscopic contact angles obtained from the MD simulations were found to match those predicted by the mean-field model for graphite under different wettability conditions, as well as the contact angles of Si(100) and Si(111) surfaces. Finally, an assessment of the effect of the Lennard-Jones cutoff radius was conducted to provide guidelines for future comparisons between numerical simulations and analytical models of wettability.« less

Lightweight Ceramic Insulation

NASA Technical Reports Server (NTRS)

Wheeler, W. H.; Creedon, J. F.

1986-01-01

Fiber burnout process yields low densities. Low density attained by process of sacrificial burnout. Graphite or carbon fibers mixed into slurry of silica, alumina, and boron-compound fibers in amounts ranging from 25 to 75 percent of total fiber content by weight. Mixture formed into blocks and dried. Blocks placed in kiln and heated to 1,600 degrees F(870 degrees C) for several hours. Graphite or carbon fibers slowly oxidize away, leaving voids and reducing block density. Finally, blocks heated to 2,350 degrees F (1,290 degrees C) for 90 minutes to bond remaining ceramic fibers together. Developed for use on Space Shuttle and other spacecraft, rigid insulation machined to requisite shape and bonded in place.

Microrobot with passive diamagnetic levitation for microparticle manipulations

NASA Astrophysics Data System (ADS)

Feng, Lin; Zhang, Shengyuan; Jiang, Yonggang; Zhang, Deyuan; Arai, Fumihito

2017-12-01

In this paper, an innovative microrobot with passive diamagnetic levitation is presented. Based on theoretical analysis, finite element method simulation, and experiments, the shape of pyrolytic graphite is redesigned, which improves the stability of passive diamagnetic levitation significantly. Therefore, passive diamagnetic levitation is able to be applied for 3-D control of the microrobot. Compared with the traditional microrobots driven by permanent magnets in a microfluidic chip, the microrobot made of pyrolytic graphite and driven by magnetic force has two advantages, no friction and 3-D control, which is able to expand the scope of the microrobot applications. Finally, the microrobot with passive diamagnetic levitation was demonstrated by being encapsulated in a microfluidic chip for microparticle manipulations.

Shaping-lathe headrig yields solid and molded-flake hardwood products.

Treesearch

P. Koch; R.A. Caughey

1978-01-01

A shaping-lathe headrig, operated one shift daily, can be used to manufacture hardwood cants to be resawed into pallet shook, one-piece and dowel-laminated crossties, posts and rail, and other solid wood products in lengths from 6 to 9 feet. Residual flakes machined by the headrig supply a three-shift operation in which molded pallets and 4- by 8-foot sheets of...

shaping-lathe headrig yields solid and molded-flake hardwood products

Treesearch

Peter Koch; R.A. Caughey

1978-01-01

A shaping-lathe headrig, operated one shift daily, can be used to manufacture hardwood cants to be resawed into pallet shook, one-piece and dowel-laminated crossties, posts and rails, and other solid wood products in lengths from 6 to 9 feet. Residual flakes machined by the headrig supply a three-shift operation in which molded pallets and 4- by 8-foot sheets of...

Manufacture and performance of full size structural flakeboards from Douglas-fir forest residues

Treesearch

J. Dobbin McNatt

1978-01-01

The Forest Products Laboratory manufactured and assessed the performance of 4- by 8-foot structural flakeboard panels from Douglas-fir forest residues after target performance goals were developed. The 42 pcf, three- layer boards were 1/2 inch thick with high quality disk cut flakes for the faces and lower quality flakes processed through a ring flaker in the core....

78 FR 19303 - Notice of Inventory Completion for Native American Human Remains and Associated Funerary Objects...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-03-29

... are 22 shell beads, 24 pieces of a single Baytown Plain ceramic jar, and 13 ceramic sherds. The Boyd site is located in Madison County, MS, and consists of a village area and six mounds. On the basis of... faunal elements, 2 flakes, 1 piece of shatter, 4 points, 1 flake tool, 1 piece of charcoal, 1 discoidal...

Lathe creates hardwood flakes for manufacture of "super strong" flakeboard

Treesearch

P. Koch

1973-01-01

Most industry members got their first look at a prototype of the Koch lathe at this year's Southern Forest Products Assn. Machinery Exhibition held in Atlanta. With the residue from this machine, Dr. Peter Koch, project leader at the Southern Forest Experiment Station in Pineville, LA thinks it will be possible to create a flake that can be used for making a...

Flake-shell capsules: adjustable inorganic structures.

PubMed

Ji, Qingmin; Guo, Chunyan; Yu, Xiaoyan; Ochs, Christopher J; Hill, Jonathan P; Caruso, Frank; Nakazawa, Hiromoto; Ariga, Katsuhiko

2012-08-06

Structure-adjustable capsules are fabricated from inorganic components by using a self-template dissolution-regrowth mechanism to give flake-shell silica microcapsules. The capsules shrink under thermal stimulus and their structures can be adjusted by treatment at different pH values. Tuning of shell pore diameters leads to tailored drug release over prolonged periods. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Diamondlike flake composites

NASA Technical Reports Server (NTRS)

Banks, B. A. (Inventor)

1984-01-01

A carbon coating is vacuum arc deposited on a smooth surface of a target which is simultaneously ion beam sputtered. The bombarding ions have sufficient energy to create diamond bonds. Spalling occurs as the carbon deposit thickens. The resulting diamond-like carbon flakes are mixed with a binder or matrix material to form a composite material having improved thermal, electrical, mechanical, and tribological properties when used in aerospace structures and components.

Effects of glycerin concentration in steam-flaked corn-based diets with supplemental yellow grease on performance and carcass characteristics of finishing beef steers

USDA-ARS?s Scientific Manuscript database

Forty-eight individually fed crossbred steers (initial BW = 381 ± 7.61 kg) were used to determine the effects of glycerin (GLY) concentration in steam-flaked corn (SFC)-based diets with added yellow grease on animal performance and carcass characteristics. Glycerin was included at 0, 2.5, 5, and 10...

The Acheulian and Early Middle Paleolithic in Latium (Italy): Stability and Innovation.

PubMed

Villa, Paola; Soriano, Sylvain; Grün, Rainer; Marra, Fabrizio; Nomade, Sebastien; Pereira, Alison; Boschian, Giovanni; Pollarolo, Luca; Fang, Fang; Bahain, Jean-Jacques

2016-01-01

We present here the results of a technological and typological analysis of the Acheulian and early Middle Paleolithic assemblages from Torre in Pietra (Latium, Italy) together with comparisons with the Acheulian small tools of Castel di Guido. The assemblages were never chronometrically dated before. We have now 40Ar/39Ar dates and ESR-U-series dates, within a geomorphological framework, which support correlations to marine isotope stages. The Acheulian (previously correlated to MIS 9) is now dated to MIS 10 while the Middle Paleolithic is dated to MIS 7. Lithic analyses are preceded by taphonomic evaluations. The Levallois method of the Middle Paleolithic assemblage is an innovation characterized by the production of thin flake blanks without cortex. In contrast, the small tool blanks of the Acheulian were either pebbles or thick flakes with some cortex. They provided a relatively easy manual prehension. The choice of Levallois thin flake blanks in the Middle Paleolithic assemblage suggest that the new technology is most likely related to the emergence of hafting. Accordingly, the oldest direct evidence of hafting technology is from the site of Campitello Quarry in Tuscany (Central Italy) where birch-bark tar, found on the proximal part of two flint flakes, is dated to the end of MIS 7. Nevertheless, a peculiar feature of the Middle Paleolithic at Torre in Pietra is the continuous presence of small tool blanks on pebbles and cores and on thick flake albeit at a much lower frequency than in the older Acheulian industries. The adoption of the new technology is thus characterized by innovation combined with a degree of stability. The persistence of these habits in spite of the introduction of an innovative technique underlies the importance of cultural transmission and conformity in the behavior of Neandertals.

Using vibrational molecular spectroscopy to reveal association of steam-flaking induced carbohydrates molecular structural changes with grain fractionation, biodigestion and biodegradation

NASA Astrophysics Data System (ADS)

Xu, Ningning; Liu, Jianxin; Yu, Peiqiang

2018-04-01

Advanced vibrational molecular spectroscopy has been developed as a rapid and non-destructive tool to reveal intrinsic molecular structure conformation of biological tissues. However, this technique has not been used to systematically study flaking induced structure changes at a molecular level. The objective of this study was to use vibrational molecular spectroscopy to reveal association between steam flaking induced CHO molecular structural changes in relation to grain CHO fractionation, predicted CHO biodegradation and biodigestion in ruminant system. The Attenuate Total Reflectance Fourier-transform Vibrational Molecular Spectroscopy (ATR-Ft/VMS) at SRP Key Lab of Molecular Structure and Molecular Nutrition, Ministry of Agriculture Strategic Research Chair Program (SRP, University of Saskatchewan) was applied in this study. The fractionation, predicted biodegradation and biodigestion were evaluated using the Cornell Net Carbohydrate Protein System. The results show that: (1) The steam flaking induced significant changes in CHO subfractions, CHO biodegradation and biodigestion in ruminant system. There were significant differences between non-processed (raw) and steam flaked grain corn (P < .01); (2) The ATR-Ft/VMS molecular technique was able to detect the processing induced CHO molecular structure changes; (3) Induced CHO molecular structure spectral features are significantly correlated (P < .05) to CHO subfractions, CHO biodegradation and biodigestion and could be applied to potentially predict CHO biodegradation (R2 = 0.87, RSD = 0.74, P < .01) and intestinal digestible undegraded CHO (R2 = 0.87, RSD = 0.24, P < .01). In summary, the processing induced molecular CHO structure changes in grain corn could be revealed by the ATR-Ft/VMS vibrational molecular spectroscopy. These molecular structure changes in grain were potentially associated with CHO biodegradation and biodigestion.

Mycotoxin co-occurrence in rice, oat flakes and wheat noodles used as staple foods in Ecuador.

PubMed

Ortiz, Johana; Van Camp, John; Mestdagh, Frédéric; Donoso, Silvana; De Meulenaer, Bruno

2013-01-01

The co-occurrence of aflatoxin B₁ (AFB₁), B₂ (AFB₂), G₁ (AFG₁) and G₂ (AFG₂), ochratoxin A (OTA), deoxynivalenol (DON), fumonisin B₁ (FB₁), zearalenone (ZEN), and HT-2 and T-2 toxins in the main Ecuadorian staple cereals (rice, oat flakes, and yellow and white wheat noodles) was evaluated. A ultra high performance liquid chromatography/time-of-flight mass spectrometry (UHPLC/TOFMS) method was developed and validated to screen for the presence of these mycotoxins in those cereal matrices. Matrix-matched calibration curves were used to compensate for ion suppression and extraction losses and the recovery values were in agreement with the minimum requirements of Regulation 401/2006/EC (70-110%). For most mycotoxins, the LODs obtained allowed detection in compliance with the maximum permitted levels set in Regulation EC/2006/1881, with the exception of OTA in all cereals and AFB1 in yellow noodles. Extra target analysis of OTA in oat flakes and wheat noodles was performed by HPLC with fluorescence detection. High rates of contamination were observed in paddy rice (23% DON, 23% FB₁, 7% AFB₁, 2% AFG₁ and 2% AFG₂), white wheat noodles (33% DON and 5% OTA) and oat flakes (17% DON, 2% OTA and 2% AFB₁), whereas the rates of contamination were lower in polished rice (2% AFG₁ and 4% HT-2 toxin) and yellow noodles (5% DON). Low rates of co-occurrence of several mycotoxins were observed only for white wheat noodles (5%) and paddy rice (7%). White noodles were contaminated with DON and/or OTA, while combinations of AFG₁, AFB₁, DON and FB₁ were found in paddy rice. Yellow noodles were contaminated with DON only; oat flakes contained DON, OTA or AFB₁, and polished rice was contaminated with AFG₁ and HT-2 toxin.

The Acheulian and Early Middle Paleolithic in Latium (Italy): Stability and Innovation

PubMed Central

Soriano, Sylvain; Grün, Rainer; Marra, Fabrizio; Nomade, Sebastien; Pereira, Alison; Boschian, Giovanni; Pollarolo, Luca; Fang, Fang; Bahain, Jean-Jacques

2016-01-01

We present here the results of a technological and typological analysis of the Acheulian and early Middle Paleolithic assemblages from Torre in Pietra (Latium, Italy) together with comparisons with the Acheulian small tools of Castel di Guido. The assemblages were never chronometrically dated before. We have now 40Ar/39Ar dates and ESR-U-series dates, within a geomorphological framework, which support correlations to marine isotope stages. The Acheulian (previously correlated to MIS 9) is now dated to MIS 10 while the Middle Paleolithic is dated to MIS 7. Lithic analyses are preceded by taphonomic evaluations. The Levallois method of the Middle Paleolithic assemblage is an innovation characterized by the production of thin flake blanks without cortex. In contrast, the small tool blanks of the Acheulian were either pebbles or thick flakes with some cortex. They provided a relatively easy manual prehension. The choice of Levallois thin flake blanks in the Middle Paleolithic assemblage suggest that the new technology is most likely related to the emergence of hafting. Accordingly, the oldest direct evidence of hafting technology is from the site of Campitello Quarry in Tuscany (Central Italy) where birch-bark tar, found on the proximal part of two flint flakes, is dated to the end of MIS 7. Nevertheless, a peculiar feature of the Middle Paleolithic at Torre in Pietra is the continuous presence of small tool blanks on pebbles and cores and on thick flake albeit at a much lower frequency than in the older Acheulian industries. The adoption of the new technology is thus characterized by innovation combined with a degree of stability. The persistence of these habits in spite of the introduction of an innovative technique underlies the importance of cultural transmission and conformity in the behavior of Neandertals. PMID:27525705

Fast detection and low power hydrogen sensor using edge-oriented vertically aligned 3-D network of MoS2 flakes at room temperature

NASA Astrophysics Data System (ADS)

Agrawal, A. V.; Kumar, R.; Venkatesan, S.; Zakhidov, A.; Zhu, Z.; Bao, Jiming; Kumar, Mahesh; Kumar, Mukesh

2017-08-01

The increased usage of hydrogen as a next generation clean fuel strongly demands the parallel development of room temperature and low power hydrogen sensors for their safety operation. In this work, we report strong evidence for preferential hydrogen adsorption at edge-sites in an edge oriented vertically aligned 3-D network of MoS2 flakes at room temperature. The vertically aligned edge-oriented MoS2 flakes were synthesised by a modified CVD process on a SiO2/Si substrate and confirmed by Scanning Electron Microscopy. Raman spectroscopy and PL spectroscopy reveal the signature of few-layer MoS2 flakes in the sample. The sensor's performance was tested from room temperature to 150 °C for 1% hydrogen concentration. The device shows a fast response of 14.3 s even at room temperature. The sensitivity of the device strongly depends on temperature and increases from ˜1% to ˜11% as temperature increases. A detail hydrogen sensing mechanism was proposed based on the preferential hydrogen adsorption at MoS2 edge sites. The proposed gas sensing mechanism was verified by depositing ˜2-3 nm of ZnO on top of the MoS2 flakes that partially passivated the edge sites. We found a decrease in the relative response of MoS2-ZnO hybrid structures. This study provides a strong experimental evidence for the role of MoS2 edge-sites in the fast hydrogen sensing and a step closer towards room temperature, low power (0.3 mW), hydrogen sensor development.