The Effect of Carbon and Boron on the Friction Behavior of Ti-Implanted 52100 Bearing Steel at Low Sliding Speeds

DTIC Science & Technology

1982-05-01

process, titanium chlorides are produced by passing chlorine gas through a fine titanium powder contained in a graphite chamber. At the high source...CO was used for a carbon source; the boron source was boron trifluoride . The 52100 samples were disks 0.95 cm in diameter and 0.3 cm thick. During...eV modulation amplitude. The ion gun 1w operated in an Ar atmosphere (5 x 10-5 torr) with a rastered beam of 2 keY Ar+ ions at densities ranging from

Experimental research of different plasma cathodes for generation of high-current electron beams

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

Shafir, G.; Kreif, M.; Gleizer, J. Z.

2015-11-21

The results of experimental studies of different types of cathodes—carbon-epoxy rods, carbon-epoxy capillary, edged graphite, and metal-dielectric—under the application of high-voltage pulses with an amplitude of several hundreds of kV and pulse duration of several nanoseconds are presented. The best diode performance was achieved with the edged graphite and carbon-epoxy-based cathodes characterized by uniform and fast (<1 ns) formation of explosive emission plasma spots and quasi-constant diode impedance. This result was achieved for both annular cathodes in a strong magnetic field and planar cathodes of a similar diameter (∼2 cm) with no external magnetic field. The cathodes based on carbon-epoxy rods andmore » carbon-epoxy capillaries operating with an average current density up to 1 kA/cm{sup 2} showed insignificant erosion along 10{sup 6} pulses of the generator and the generated electron beam current showed excellent reproducibility in terms of the amplitude and waveform.« less

Growth and characterization of high-purity SiC single crystals

NASA Astrophysics Data System (ADS)

Augustine, G.; Balakrishna, V.; Brandt, C. D.

2000-04-01

High-purity SiC single crystals with diameter up to 50 mm have been grown by the physical vapor transport method. Finite element analysis was used for thermal modeling of the crystal growth cavity in order to reduce stress in the grown crystal. Crystals are grown in high-purity growth ambient using purified graphite furniture and high-purity SiC sublimation sources. Undoped crystals up to 50 mm in diameter with micropipe density less than 100 cm -2 have been grown using this method. These undoped crystals exhibit resistivities in the 10 3 Ω cm range and are p-type due to the presence of residual acceptor impurities, mainly boron. Semi-insulating SiC material is obtained by doping the crystal with vanadium. Vanadium has a deep donor level located near the middle of the band gap, which compensates the residual acceptor resulting in semi-insulating behavior.

Silicon Ingot Casting - Heat Exchanger Method Multi-wire Slicing - Fixed Abrasive Slicing Technique. Phase 3 Silicon Sheet Growth Development for the Large Area Sheet Task of the Low-cost Solar Array Project

NASA Technical Reports Server (NTRS)

Schmid, F.; Khattak, C. P.

1979-01-01

Several 20 cm diameter silicon ingots, up to 6.3 kg. were cast with good crystallinity. The graphite heat zone can be purified by heating it to high temperatures in vacuum. This is important in reducing costs and purification of large parts. Electroplated wires with 45 um synthetic diamonds and 30 um natural diamonds showed good cutting efficiency and lifetime. During slicing of a 10 cm x 10 cm workpiece, jerky motion occurred in the feed and rocking mechanisms. This problem is corrected and modifications were made to reduce the weight of the bladeheat by 50%.

Tubular graphite cones.

PubMed

Zhang, Guangyu; Jiang, Xin; Wang, Enge

2003-04-18

We report the synthesis of tubular graphite cones using a chemical vapor deposition method. The cones have nanometer-sized tips, micrometer-sized roots, and hollow interiors with a diameter ranging from about 2 to several tens of nanometers. The cones are composed of cylindrical graphite sheets; a continuous shortening of the graphite layers from the interior to the exterior makes them cone-shaped. All of the tubular graphite cones have a faceted morphology. The constituent graphite sheets have identical chiralities of a zigzag type across the entire diameter, imparting structural control to tubular-based carbon structures. The tubular graphite cones have potential for use as tips for scanning probe microscopy, but with greater rigidity and easier mounting than currently used carbon nanotubes.

High heat flux Langmuir probe array for the DIII-D divertor platesa)

NASA Astrophysics Data System (ADS)

Watkins, J. G.; Taussig, D.; Boivin, R. L.; Mahdavi, M. A.; Nygren, R. E.

2008-10-01

Two modular arrays of Langmuir probes designed to handle a heat flux of up to 25 MW/m2 for 10 s exposures have been installed in the lower divertor target plates of the DIII-D tokamak. The 20 pyrolytic graphite probe tips have more than three times higher thermal conductivity and 16 times larger mass than the original DIII-D isotropic graphite probes. The probe tips have a fixed 12.5° surface angle to distribute the heat flux more uniformly than the previous 6 mm diameter domed collectors and a symmetric "rooftop" design to allow operation with reversed toroidal magnetic field. A large spring-loaded contact area improves heat conduction from each probe tip through a ceramic insulator into a cooled graphite divertor floor tile. The probe tips, brazed to molybdenum foil to ensure good electrical contact, are mounted in a ceramic tray for electrical isolation and reliable cable connections. The new probes are located 1.5 cm radially apart in a staggered arrangement near the entrance to the lower divertor pumping baffle and are linearly spaced 3 cm apart on the shelf above the in-vessel cryopump. Typical target plate profiles of Jsat, Te, and Vf with 4 mm spatial resolution are shown.

Thermal stability of lightweight graphite glass sandwich reflectors for far infrared astronomy

NASA Technical Reports Server (NTRS)

Bluege, J. H.; Mayor, R. A.; Hoffman, W. F.

1986-01-01

Graphite fiber-reinforced glass matrix composites are being developed for a variety of structural applications requiring excellent thermomechanical stability. These materials are ideally suited for lightweight, high strength, thermally stable infrared mirrors because of their low density, low thermal expansion, high strength and stiffness, and their ability to be machined, replicated and figured using standard polishing techniques. These properties are particularly promising for applications such as a 3-meter balloon-borne far-infrared and submillimeter telescope mirror which must be both very lightweight and able to retain its figure accuracy when cycled between room temperature and its operating temperature of -50 C. This paper presents the results of a set of low temperature optical tests conducted to determine the figure stability of a 30-cm diameter, frit-bonded graphite/glass mirror in the +20 to -60 C temperature range using a 10.6 micron laser interferometer. The results indicate that the residual change in figure was less than 0.3 microns, rms.

Embedded gage impact study

NASA Technical Reports Server (NTRS)

Schramm, S. W.; Daniel, I. M.

1984-01-01

Impact damage in graphite/epoxy laminates was characterized and transient strain history during impact was correlated. The material investigated was AS-4/3501-6 graphite/epoxy. Eight-ply and sixteen-ply quasi-isotropic laminates of 45/0/-45/90 sub s and 45/0/-45/90 sub 2s layups were fabricated with strain gages embedded between plies during the strain gages and leads from the highly conductive graphite fibers. The specimens were circular plates 12.7 cm (5 in.) in diameter and clamped along their circumference. The specimens were impacted with a 185 gm impactor, dropped from heights of 1.20 m and 1.65 m. An accelerometer was attached to the back surface of the specimen opposite the impact point and was used to trigger the recording instrumentation. The transient strain data were recorded with an eight channel waveform digitizer capable of sampling data at 0.5 microsec intervals. The data were stored, processed, and plotted by means of a microcomputer. Transient strain data were correlated with results from ultrasonic inspection of the specimens.

Analysis of granular flow in a pebble-bed nuclear reactor.

PubMed

Rycroft, Chris H; Grest, Gary S; Landry, James W; Bazant, Martin Z

2006-08-01

Pebble-bed nuclear reactor technology, which is currently being revived around the world, raises fundamental questions about dense granular flow in silos. A typical reactor core is composed of graphite fuel pebbles, which drain very slowly in a continuous refueling process. Pebble flow is poorly understood and not easily accessible to experiments, and yet it has a major impact on reactor physics. To address this problem, we perform full-scale, discrete-element simulations in realistic geometries, with up to 440,000 frictional, viscoelastic 6-cm-diam spheres draining in a cylindrical vessel of diameter 3.5m and height 10 m with bottom funnels angled at 30 degrees or 60 degrees. We also simulate a bidisperse core with a dynamic central column of smaller graphite moderator pebbles and show that little mixing occurs down to a 1:2 diameter ratio. We analyze the mean velocity, diffusion and mixing, local ordering and porosity (from Voronoi volumes), the residence-time distribution, and the effects of wall friction and discuss implications for reactor design and the basic physics of granular flow.

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.

77 FR 33405 - Small Diameter Graphite Electrodes From the People's Republic of China: Affirmative Preliminary...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-06

...The Department of Commerce (``Department'') preliminarily determines that certain small diameter graphite electrodes (``SDGE'') are being exported from the United Kingdom (``U.K.'') to the United States by UK Carbon and Graphite Co., Ltd. (``UKCG'') in circumvention of the antidumping duty order on SDGE from the People's Republic of China (``PRC''),\\1\\ as provided in section 781(b) of the Tariff Act of 1930, as amended (``the Act''). ---------------------------------------------------------------------------

Determination of Graphite-Liquid-Vapor Triple Point by Laser Heating

DTIC Science & Technology

1976-01-30

difficulties in the temperature measure- ments, which were made with an optical pyrometer . He considered that the failure of graphite rod was caused by...temperature measurements were made with a calibrated optical pyrometer . Spherical shiny frozen droplets of graphite, 1 to 3 mm in diameter, indicated...0.8 mm in diameter and 10 mm long in argon until failure by rupture occurred. They measured the tempera- ture with a two-color pyrometer . The

Impact tests on fibrous composite sandwich structures

NASA Technical Reports Server (NTRS)

Rhodes, M. D.

1978-01-01

The effect of low velocity impact on the strength of laminates fabricated from graphite/epoxy and Kevlar 49/epoxy composite materials was studied. The test laminates were loaded statically either in uniaxial tension or compression when impact occurred to evaluate the effect of loading on the initiation of damage and/or failure. Typical aircraft service conditions such as runway debris encountered during landing were simulated by impacting 1.27-cm-diameter projectiles normal to the plane of the test laminates at velocities between 5.2 and 48.8 m/s.

Note: Arc discharge plasma source with plane segmented LaB{sub 6} cathode

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

Akhmetov, T. D., E-mail: t.d.akhmetov@inp.nsk.su; Davydenko, V. I.; Ivanov, A. A.

2016-05-15

A plane cathode composed of close-packed hexagonal LaB{sub 6} (lanthanum hexaboride) segments is described. The 6 cm diameter circular cathode is heated by radiation from a graphite foil flat spiral. The cathode along with a hollow copper anode is used for the arc discharge plasma production in a newly developed linear plasma device. A separately powered coil located around the anode is used to change the magnetic field strength and geometry in the anode region. Different discharge regimes were realized using this coil.

Preparation and characterization of copper-graphite composites by electrical explosion of wire in liquid.

PubMed

Bien, T N; Gul, W H; Bac, L H; Kim, J C

2014-11-01

Copper-graphite nanocomposites containing 5 vol.% graphite were prepared by a powder metallurgy route using an electrical wire explosion (EEW) in liquid method and spark plasma sintering (SPS) process. Graphite rods with a 0.3 mm diameter and copper wire with a 0.2 mm diameter were used as raw materials for EEWin liquid. To compare, a pure copper and copper-graphite mixture was also prepared. The fabricated graphite was in the form of a nanosheet, onto which copper particles were coated. Sintering was performed at 900 degrees C at a heating rate of 30 degrees C/min for 10 min and under a pressure of 70 MPa. The density of the sintered composite samples was measured by the Archimedes method. A wear test was performed by a ball-on-disc tribometer under dry conditions at room temperature in air. The presence of graphite effectively reduced the wear of composites. The copper-graphite nanocomposites prepared by EEW had lower wear rates than pure copper material and simple mixed copper-graphite.

A graphite calorimeter for absolute measurements of absorbed dose to water: application in medium-energy x-ray filtered beams.

PubMed

Pinto, M; Pimpinella, M; Quini, M; D'Arienzo, M; Astefanoaei, I; Loreti, S; Guerra, A S

2016-02-21

The Italian National Institute of Ionizing Radiation Metrology (ENEA-INMRI) has designed and built a graphite calorimeter that, in a water phantom, has allowed the determination of the absorbed dose to water in medium-energy x-rays with generating voltages from 180 to 250 kV. The new standard is a miniaturized three-bodies calorimeter, with a disc-shaped core of 21 mm diameter and 2 mm thickness weighing 1.134 g, sealed in a PMMA waterproof envelope with air-evacuated gaps. The measured absorbed dose to graphite is converted into absorbed dose to water by means of an energy-dependent conversion factor obtained from Monte Carlo simulations. Heat-transfer correction factors were determined by FEM calculations. At a source-to-detector distance of 100 cm, a depth in water of 2 g cm(-2), and at a dose rate of about 0.15 Gy min(-1), results of calorimetric measurements of absorbed dose to water, D(w), were compared to experimental determinations, D wK, obtained via an ionization chamber calibrated in terms of air kerma, according to established dosimetry protocols. The combined standard uncertainty of D(w) and D(wK) were estimated as 1.9% and 1.7%, respectively. The two absorbed dose to water determinations were in agreement within 1%, well below the stated measurement uncertainties. Advancements are in progress to extend the measurement capability of the new in-water-phantom graphite calorimeter to other filtered medium-energy x-ray qualities and to reduce the D(w) uncertainty to around 1%. The new calorimeter represents the first implementation of in-water-phantom graphite calorimetry in the kilovoltage range and, allowing independent determinations of D(w), it will contribute to establish a robust system of absorbed dose to water primary standards for medium-energy x-ray beams.

Genotoxicity of nanomaterials: DNA damage and micronuclei induced by carbon nanotubes and graphite nanofibres in human bronchial epithelial cells in vitro.

PubMed

Lindberg, Hanna K; Falck, Ghita C-M; Suhonen, Satu; Vippola, Minnamari; Vanhala, Esa; Catalán, Julia; Savolainen, Kai; Norppa, Hannu

2009-05-08

Despite the increasing industrial use of different nanomaterials, data on their genotoxicity are scant. In the present study, we examined the potential genotoxic effects of carbon nanotubes (CNTs; >50% single-walled, approximately 40% other CNTs; 1.1 nm x 0.5-100 microm; Sigma-Aldrich) and graphite nanofibres (GNFs; 95%; outer diameter 80-200 nm, inner diameter 30-50 nm, length 5-20 microm; Sigma-Aldrich) in vitro. Genotoxicity was assessed by the single cell gel electrophoresis (comet) assay and the micronucleus assay (cytokinesis-block method) in human bronchial epithelial BEAS 2B cells cultured for 24h, 48h, or 72h with various doses (1-100 microg/cm(2), corresponding to 3.8-380 microg/ml) of the carbon nanomaterials. In the comet assay, CNTs induced a dose-dependent increase in DNA damage at all treatment times, with a statistically significant effect starting at the lowest dose tested. GNFs increased DNA damage at all doses in the 24-h treatment, at two doses (40 and 100 microg/cm(2)) in the 48-h treatment (dose-dependent effect) and at four doses (lowest 10 microg/cm(2)) in the 72-h treatment. In the micronucleus assay, no increase in micronucleated cells was observed with either of the nanomaterials after the 24-h treatment or with CNTs after the 72-h treatment. The 48-h treatment caused a significant increase in micronucleated cells at three doses (lowest 10 microg/cm(2)) of CNTs and at two doses (5 and 10 microg/cm(2)) of GNFs. The 72-h treatment with GNFs increased micronucleated cells at four doses (lowest 10 microg/cm(2)). No dose-dependent effects were seen in the micronucleus assay. The presence of carbon nanomaterial on the microscopic slides disturbed the micronucleus analysis and made it impossible at levels higher than 20 microg/cm(2) of GNFs in the 24-h and 48-h treatments. In conclusion, our results suggest that both CNTs and GNFs are genotoxic in human bronchial epithelial BEAS 2B cells in vitro. This activity may be due to the fibrous nature of these carbon nanomaterials with a possible contribution by catalyst metals present in the materials-Co and Mo in CNTs (<5wt.%) and Fe (<3wt.%) in GNFs.

Carbon nanotube: the inside story.

PubMed

Ando, Yoshinori

2010-06-01

Carbon nanotubes (CNTs) were serendipitously discovered as a byproduct of fullerenes by direct current (DC) arc discharge; and today this is the most-wanted material in the nanotechnology research. In this brief review, I begin with the history of the discovery of CNTs and focus on CNTs produced by arc discharge in hydrogen atmosphere, which is little explored outside my laboratory. DC arc discharge evaporation of pure graphite rod in pure hydrogen gas results in multi-walled carbon nanotubes (MWCNTs) of high crystallinity in the cathode deposit. As-grown MWCNTs have very narrow inner diameter. Raman spectra of these MWCNTs show high-intensity G-band, unusual high-frequency radial breathing mode at 570 cm(-1), and a new characteristic peak near 1850 cm(-1). Exciting carbon nanowires (CNWs), consisting of a linear carbon chain in the center of MWCNTs are also produced. Arc evaporation of graphite rod containing metal catalysts results in single-wall carbon nanotubes (SWCNTs) in the whole chamber like macroscopic webs. Two kinds of arc method have been developed to produce SWCNTs: Arc plasma jet (APJ) and Ferrum-Hydrogen (FH) arc methods. Some new purification methods for as-produced SWCNTs are reviewed. Finally, double-walled carbon nanotubes (DWCNTs) are also described.

The effect of graphitic target density on carbon nanotube synthesis by pulsed laser ablation method

NASA Astrophysics Data System (ADS)

Kazeimzadeh, Fatemeh; Malekfar, Rasoul; Houshiar, Mahboubeh

2018-01-01

Carbon nanotube (CNT) was synthesized by pulsed laser ablation (PLA) of a graphitic target in vacuum chamber filled by argon gas. The effect of different condition of target preparation on the amount and quality of carbon nanotube generation was investigated. The graphite powder with 2 at% micrometer nickel (Ni) powder was mixed and packed in to a mold using a hydraulic press device at a pressure of 1000 kg/cm3. The obtained pellet which contained the mixture powder provided the carbon source for CNTs formation in PLA method. Two pellets with the pressure time of 15 and 200 min was prepared. It has been shown that the time which graphitic target is under pressure is an effective parameter that can increase the amount of produced CNTs. Field emission scanning electron microscopy (FESEM) images show that if the density of graphitic target is increased by raising up the pressure time, CNTs can grow even under the condition in which usually no nanotube can be formed. It can be due to the elimination of the distances between the graphite and catalyst grains that causes the catalysis performance improvement. The experiment was performed for nanometer cobalt ferrite (CoFe2O4) together with Ni catalyst particles too. The diameter of synthesized CNPs was larger in the case of pure nickel that is related to the size of catalysts. Moreover, it was also observed that the production rate of the nanotubes increased for high density targets. This shows that the results are independent of the type of catalyst.

Characteristic of skin formation using zircon- and graphite-coated mold in thin wall ductile iron fabrication

NASA Astrophysics Data System (ADS)

Dhaneswara, Donanta; Suharno, Bambang; Nugroho, Janu Ageng; Ariobimo, Rianti Dewi S.; Sofyan, Nofrijon

2017-03-01

One of the problems in thin wall ductile iron (TWDI) fabrication is skin formation during the casting. The presence of this skin will decrease strength and strain of the TWDI. One of the ways to control this skin formation is to change the cooling rate during the process through a mold coating. In testing the effectiveness of skin prevention, the following variables were used for the mold coating i.e. (i) graphite: (ii) zirconium; and (iii) double layer of graphite-zirconium. After the process, the plates were characterized by non-etching, etching, tensile test, and SEM observation. The results showed that the average skin formation using graphite: 65 µm; zirconium: 13.04 µm; and double layer of graphite-zirconium: 33.25 µm. It seems that zirconium has the most effect on the skin prevention due to sulfur binding and magnesium locked, which then prevented rapid cooling resulting in less skin formation. The results also showed the number of nodules obtained in specimen with graphite: 703 nodules/mm2 with average diameter of 12.57 µm, zirconium: 798 nodules/mm2 with average diameter of 12.15 µm, and double layer of graphite-zirconium: 697 nodules/mm2 with average diameter of 11.9 µm and nodularity percentage of 82.58%, 84.53%, and 84.22%, respectively. Tensile test showed that the strength of the specimen with graphite is 301.1 MPa, with zirconium is 388.8 MPa, and with double layer of graphite-zirconium is 304 MPa. In overall, zirconium give the best performance on the skin formation prevention in TWDI fabrication.

Ancient graphite in the Eoarchean quartz-pyroxene rocks from Akilia in southern West Greenland II: Isotopic and chemical compositions and comparison with Paleoproterozoic banded iron formations

NASA Astrophysics Data System (ADS)

Papineau, Dominic; De Gregorio, Bradley T.; Stroud, Rhonda M.; Steele, Andrew; Pecoits, Ernesto; Konhauser, Kurt; Wang, Jianhua; Fogel, Marilyn L.

2010-10-01

We present detailed petrographic surveys of apatite grains in association with carbonaceous material (CM) in two banded iron formations (BIFs) from the Paleoproterozoic of Uruguay and Michigan for comparison with similar mineral associations in the highly debated Akilia Quartz-pyroxene (Qp) rock. Petrographic and Raman spectroscopic surveys of these Paleoproterozoic BIFs show that apatite grains typically occur in bands parallel to bedding and are more often associated with CM when concentrations of organic matter are high. Carbonaceous material in the Vichadero BIF from Uruguay is generally well-crystallized graphite and occurs in concentrations around 0.01 wt% with an average δ 13C gra value of -28.6 ± 4.4‰ (1 σ). In this BIF, only about 5% of apatite grains are associated with graphite. In comparison, CM in the Bijiki BIF from Michigan is also graphitic, but occurs in concentrations around 2.4 wt% with δ 13C gra values around -24.0 ± 0.3‰ (1 σ). In the Bijiki BIF, more than 78% of apatite grains are associated with CM. Given the geologic context and high levels of CM in the Bijiki BIF, the significantly higher proportion of apatite grains associated with CM in this rock is interpreted to represent diagenetically altered biomass and shows that such diagenetic mineral associations can survive metamorphism up to the amphibolite facies. Isotope compositions of CM in muffled acidified whole-rock powders from the Akilia Qp rock have average δ 13C gra values of -17.5 ± 2.5‰ (1 σ), while δ 13C carb values in whole-rock powders average -4.0 ± 1.0‰ (1 σ). Carbon isotope compositions of graphite associated with apatite and other minerals in the Akilia Qp rock were also measured with the NanoSIMS to have similar ranges of δ 13C gra values averaging -13.8 ± 5.6‰ (1 σ). The NanoSIMS was also used to semi-quantitatively map the distributions of H, N, O, P, and S in graphite from the Akilia Qp rock, and relative abundances were found to be similar for graphite associated with apatite or with hornblende, calcite, and sulfides. These analyses revealed generally lower abundances of trace elements in the Akilia graphite compared to graphite associated with apatite from Paleoproterozoic BIFs. Graphite associated with hornblende, calcite, and sulfides in the Akilia Qp rock was fluid-deposited at high-temperature from carbon-bearing fluids, and since this graphite has similar ranges of δ 13C gra values and of trace elements compared to graphite associated with apatite, we conclude that the Akilia graphite in different mineral associations formed from the same source(s) of CM. Collectively our results do not exclude a biogenic origin of the carbon in the Akilia graphite, but because some observations can not exclude graphitization of abiogenic carbon from CO 2- and CH 4-bearing mantle fluids, there remain ambiguities with respect to the exact origin of carbon in this ancient metasedimentary rock. Accordingly, there may have been several generations of graphite formation along with possibly varying mixtures of CO 2- and CH 4-bearing fluids that may have resulted in large ranges of δ 13C gra values. The possibility of fluid-deposited graphite associated with apatite should be a focus of future investigations as this may prove to be an alternative pathway of graphitization from phosphate-bearing fluids. Correlated micro-analytical approaches tested on terrestrial rocks in this work provide insights into the origin of carbon in ancient graphite and will pave the way for the search for life on other ancient planetary surfaces.

[Raman spectrum of nano-graphite synthesized by explosive detonation].

PubMed

Wen, Chao; Li, Xun; Sun, De-Yu; Guan, Jin-Qing; Liu, Xiao-Xin; Lin, Ying-Rui; Tang, Shi-Ying; Zhou, Gang; Lin, Jun-De; Jin, Zhi-Hao

2005-01-01

The nano-graphite powder synthesized by the detonation of explosives with negative oxygen balance is a new powder material with potential applications. In this work, the preparation of nano-graphite powder in steel chamber by pure TNT (trinitrotoluene) explosives has been introduced. In the synthesis process, the protective gases in the steel chamber are N2, CO2 and Ar, and the pressure is 0.25-2 atm. Raman spectrum of the nano-graphite was measured. The characteristic Raman band assigned to sp2 of graphite has been observed at about 1 585 cm(-1) with half-peak width of 22 cm(-1). The peak shifted to a higher frequency by 5 cm(-1) compared with that of bulk graphite. The authors explain this blue shift phenomenon by size effect. The average size of nanographite from Raman measurement is 2.97-3.97 nm. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to measure the structure and particle size of the nano-graphite. The crystallite size of nano-graphite estimated from XRD andTEM are 2.58 nm (acid untreated) and 1.86 nm (acid treated) respectively, which is in accord with the results of the measurement approximately.

Measurement of leakage neutron spectra from graphite cylinders irradiated with D-T neutrons for validation of evaluated nuclear data.

PubMed

Luo, F; Han, R; Chen, Z; Nie, Y; Shi, F; Zhang, S; Lin, W; Ren, P; Tian, G; Sun, Q; Gou, B; Ruan, X; Ren, J; Ye, M

2016-10-01

A benchmark experiment for validation of graphite data evaluated from nuclear data libraries was conducted for 14MeV neutrons irradiated on graphite cylinder samples. The experiments were performed using the benchmark experimental facility at the China Institute of Atomic Energy (CIAE). The leakage neutron spectra from the surface of graphite (Φ13cm×20cm) at 60° and 120° and graphite (Φ13cm×2cm) at 60° were measured by the time-of-flight (TOF) method. The obtained results were compared with the measurements made by the Monte Carlo neutron transport code MCNP-4C with the ENDF/B-VII.1, CENDL-3.1 and JENDL-4.0 libraries. The results obtained from a 20cm-thick sample revealed that the calculation results with CENDL-3.1 and JENDL-4.0 libraries showed good agreements with the experiments conducted in the whole energy region. However, a large discrepancy of approximately 40% was observed below the 3MeV energy region with the ENDF/B-VII.1 library. For the 2cm-thick sample, the calculated results obtained from the abovementioned three libraries could not reproduce the experimental data in the energy range of 5-7MeV. The graphite data in CENDL-3.1 were verified for the first time and were proved to be reliable. Copyright © 2016 Elsevier Ltd. All rights reserved.

Fast Neutron Spectrum Potassium Worth for Space Power Reactor Design Validation

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

Bess, John D.; Marshall, Margaret A.; Briggs, J. Blair

2015-03-01

A variety of critical experiments were constructed of enriched uranium metal (oralloy ) during the 1960s and 1970s at the Oak Ridge Critical Experiments Facility (ORCEF) in support of criticality safety operations at the Y-12 Plant. The purposes of these experiments included the evaluation of storage, casting, and handling limits for the Y-12 Plant and providing data for verification of calculation methods and cross-sections for nuclear criticality safety applications. These included solid cylinders of various diameters, annuli of various inner and outer diameters, two and three interacting cylinders of various diameters, and graphite and polyethylene reflected cylinders and annuli. Ofmore » the hundreds of delayed critical experiments, one was performed that consisted of uranium metal annuli surrounding a potassium-filled, stainless steel can. The outer diameter of the annuli was approximately 13 inches (33.02 cm) with an inner diameter of 7 inches (17.78 cm). The diameter of the stainless steel can was 7 inches (17.78 cm). The critical height of the configurations was approximately 5.6 inches (14.224 cm). The uranium annulus consisted of multiple stacked rings, each with radial thicknesses of 1 inch (2.54 cm) and varying heights. A companion measurement was performed using empty stainless steel cans; the primary purpose of these experiments was to test the fast neutron cross sections of potassium as it was a candidate for coolant in some early space power reactor designs.The experimental measurements were performed on July 11, 1963, by J. T. Mihalczo and M. S. Wyatt (Ref. 1) with additional information in its corresponding logbook. Unreflected and unmoderated experiments with the same set of highly enriched uranium metal parts were performed at the Oak Ridge Critical Experiments Facility in the 1960s and are evaluated in the International Handbook for Evaluated Criticality Safety Benchmark Experiments (ICSBEP Handbook) with the identifier HEU MET FAST 051. Thin graphite reflected (2 inches or less) experiments also using the same set of highly enriched uranium metal parts are evaluated in HEU MET FAST 071. Polyethylene-reflected configurations are evaluated in HEU-MET-FAST-076. A stack of highly enriched metal discs with a thick beryllium top reflector is evaluated in HEU-MET-FAST-069, and two additional highly enriched uranium annuli with beryllium cores are evaluated in HEU-MET-FAST-059. Both detailed and simplified model specifications are provided in this evaluation. Both of these fast neutron spectra assemblies were determined to be acceptable benchmark experiments. The calculated eigenvalues for both the detailed and the simple benchmark models are within ~0.26 % of the benchmark values for Configuration 1 (calculations performed using MCNP6 with ENDF/B-VII.1 neutron cross section data), but under-calculate the benchmark values by ~7s because the uncertainty in the benchmark is very small: ~0.0004 (1s); for Configuration 2, the under-calculation is ~0.31 % and ~8s. Comparison of detailed and simple model calculations for the potassium worth measurement and potassium mass coefficient yield results approximately 70 – 80 % lower (~6s to 10s) than the benchmark values for the various nuclear data libraries utilized. Both the potassium worth and mass coefficient are also deemed to be acceptable benchmark experiment measurements.« less

Preliminary CFD study of Pebble Size and its Effect on Heat Transfer in a Pebble Bed Reactor

NASA Astrophysics Data System (ADS)

Jones, Andrew; Enriquez, Christian; Spangler, Julian; Yee, Tein; Park, Jungkyu; Farfan, Eduardo

2017-11-01

In pebble bed reactors, the typical pebble diameter used is 6cm, and within each pebble is are thousands of nuclear fuel kernels. However, efficiency of the reactor does not solely depend on the number of kernels of fuel within each graphite sphere, but also depends on the type and motion of the coolant within the voids between the spheres and the reactor itself. In this work a physical analysis of the pebble bed nuclear reactor's fluid dynamics is undertaken using Computational Fluid Dynamics software. The primary goal of this work is to observe the relationship between the different pebble diameters in an idealized alignment and the thermal transport efficiency of the reactor. The model constructed of our idealized argument will consist on stacked 8 pebble columns that fixed at the inlet on the reactor. Two different pebble sizes 4 cm and 6 cm will be studied and helium will be supplied as coolant with a fixed flow rate of 96 kg/s, also a fixed pebble surface temperatures will be used. Comparison will then be made to evaluate the efficiency of coolant to transport heat due to the varying sizes of the pebbles. Assistant Professor for the Department of Civil and Construction Engineering PhD.

Compatibility of the Radio Frequency Mass Gauge with Graphite-Epoxy Composite Tanks

NASA Technical Reports Server (NTRS)

Zimmerli, G. A.; Mueller, C. H.

2015-01-01

The radio frequency mass gauge (RFMG) is a low-gravity propellant quantity gauge being developed at NASA for possible use in long-duration space missions utilizing cryogenic propellants. As part of the RFMG technology development process, we evaluated the compatibility of the RFMG with a graphite-epoxy composite material used to construct propellant tanks. The key material property that can affect compatibility with the RFMG is the electrical conductivity. Using samples of 8552/IM7 graphite-epoxy composite, we characterized the resistivity and reflectivity over a range of frequencies. An RF impedance analyzer was used to characterize the out-of-plane electrical properties (along the sample thickness) in the frequency range 10 to 1800 MHZ. The resistivity value at 500 MHz was 4.8 ohm-cm. Microwave waveguide measurements of samples in the range 1.7 - 2.6 GHz, performed by inserting the samples into a WR-430 waveguide, showed reflectivity values above 98%. Together, these results suggested that a tank constructed from graphite/epoxy composite would produce good quality electromagnetic tank modes, which is needed for the RFMG. This was verified by room-temperature measurements of the electromagnetic modes of a 2.4 m diameter tank constructed by Boeing from similar graphite-epoxy composite material. The quality factor Q of the tank electromagnetic modes, measured via RF reflection measurements from an antenna mounted in the tank, was typically in the range 400 less than Q less than 3000. The good quality modes observed in the tank indicate that the RFMG is compatible with graphite-epoxy tanks, and thus the RFMG could be used as a low-gravity propellant quantity gauge in such tanks filled with cryogenic propellants.

Raman spectra of carbonaceous materials in a fault zone in the Longmenshan thrust belt, China; comparisons with those of sedimentary and metamorphic rocks

NASA Astrophysics Data System (ADS)

Kouketsu, Yui; Shimizu, Ichiko; Wang, Yu; Yao, Lu; Ma, Shengli; Shimamoto, Toshihiko

2017-03-01

We analyzed micro-Raman spectra of carbonaceous materials (CM) in natural and experimentally deformed fault rocks from Longmenshan fault zone that caused the 2008 Wenchuan earthquake, to characterize degree of disordering of CM in a fault zone. Raman spectral parameters for 12 samples from a fault zone in Shenxigou, Sichuan, China, all show low-grade structures with no graphite. Low crystallinity and δ13C values (-24‰ to -25‰) suggest that CM in fault zone originated from host rocks (Late Triassic Xujiahe Formation). Full width at half maximum values of main spectral bands (D1 and D2), and relative intensities of two subbands (D3 and D4) of CM were variable with sample locations. However, Raman parameters of measured fault rocks fall on established trends of graphitization in sedimentary and metamorphic rocks. An empirical geothermometer gives temperatures of 160-230 °C for fault rocks in Shenxigou, and these temperatures were lower for highly sheared gouge than those for less deformed fault breccia at inner parts of the fault zone. The lower temperature and less crystallinity of CM in gouge might have been caused by the mechanical destruction of CM by severe shearing deformation, or may be due to mixing of host rocks on the footwall. CM in gouge deformed in high-velocity experiments exhibits slight changes towards graphitization characterized by reduction of D3 and D4 intensities. Thus low crystallinity of CM in natural gouge cannot be explained by our experimental results. Graphite formation during seismic fault motion is extremely local or did not occur in the study area, and the CM crystallinity from shallow to deep fault zones may be predicted as a first approximation from the graphitization trend in sedimentary and metamorphic rocks. If that case, graphite may lower the friction of shear zones at temperatures above 300 °C, deeper than the lower part of seismogenic zone.

Structural, chemical, and isotopic microanalytical investigations of graphite from supernovae

NASA Astrophysics Data System (ADS)

Croat, T. Kevin; Bernatowicz, Thomas; Amari, Sachiko; Messenger, Scott; Stadermann, Frank J.

2003-12-01

We report the results of coordinated ion microprobe and transmission electron microscope (TEM) studies of presolar graphites from the KE3 separate (1.65-1.72 g/cm 3) of the Murchison CM2 meteorite. Isotopic analysis of individual graphites (1-12 μm) with the ion microprobe shows many to have large 18O excesses combined with large silicon isotopic anomalies, indicative of a supernova (SN) origin. Transmission electron microscopy (TEM) of ultramicrotome slices of these SN graphites revealed a high abundance (25-2400 ppm) of internal titanium carbides (TiCs), with a single graphite in some cases containing hundreds of TiCs. Isotopic compositions of individual TiCs by nanoscale resolution secondary ion mass spectrometry (NanoSIMS) confirmed their presolar origin. In addition to TiCs, composite TiC/Fe grains (TiCs with attached iron-nickel subgrains) and solitary kamacite internal grains were found. In the composite grains, the attached iron phase (kamacite [0-24 at. % Ni] or taenite [up to 60 at. % Ni]) was epitaxially grown onto one or more TiC faces. In contrast to the denser Murchison KFC1 graphites, no Zr-Ti-Mo carbides were observed. The average TiC diameters were quite variable among the SN graphites, from 30 to 232 nm, and were generally independent of the host graphite size. TiC grain morphologies ranged from euhedral to anhedral, with the grain surfaces exhibiting variable degrees of corrosion, and sometimes partially amorphous rims (3 to 15 nm thick). Partially amorphous rims of similar thickness were also observed on some solitary kamacite grains. We speculate that the rims on the internal grains are most plausibly the result of atom bombardment caused by drift of grains with respect to the ambient gas, requiring relative outflow speeds ˜100 km/s (i.e., a few percent of the SN mass outflow speed). Energy dispersive X-ray spectrometry (EDXS) of TiCs revealed significant V in solid solution, with an average V/Ti ratio over all TiCs of ˜83% of the solar value of 0.122. Significant variations about the mean V/Ti ratio were also seen among TiCs in the same graphite, likely indicating chemical equilibration with the surrounding gas over a range of temperatures. In general, the diversity in internal TiC properties suggests that TiCs formed first and had substantially diverse histories before incorporation into the graphite, implying some degree of turbulent mixing in the SN outflows. In most graphites, there is a decrease in the number density of TiCs as a function of increasing radial dis- tance, caused by either preferential depletion of TiCs from the gas or an acceleration of graphite growth with decreasing ambient temperature. In several graphites, TiCs showed a trend of larger V/Ti ratios with increasing distance from the graphite center, an indication of progressive equilibration with the surrounding gas before they were sequestered in the graphites. In all but one graphite, no trend was seen in the TiC size vs. distance from the graphite center, implying that appreciable TiC growth had effectively stopped before the graphites formed, or else that graphite growth was rapid compared to TiC growth. Taken together, the chemical variations among internal grains as well as the presence of partially amorphous rims and epitaxial Fe phases on some TiCs clearly indicate that the phase condensation sequence was TiC, followed by the iron phases (only found in some graphites) and finally graphite. Since graphite typically condenses at a higher temperature than iron at low pressures (<10 -3 bars) in a gas with C > O and otherwise solar composition, the observed condensation sequence implies a relative iron enrichment in the gas or greater supersaturation of graphite relative to iron. The TEM observations allow inferences to be made about the physical conditions in the gas from which the grains condensed. Given the TiC sizes and abundances, the gas was evidently quite dusty. From the observed TiC size range of ˜20 nm to ˜500 nm (assuming ˜1 yr growth time and T ˜ 1800°K), we infer minimum Ti number densities in the gas to be ˜7 × 10 4 to ˜2 × 10 6 atoms/cc, respectively. Although the gas composition is clearly not solar, for scale, these number densities would correspond to a pressure range of ˜0.2 μbar to ˜5.0 μbar in a gas of solar composition. They also correspond to minimum TiC grain number densities of ˜3 × 10 -4 to ˜0.2 grains/cc, assuming complete condensation of Ti in TiC. We estimate the maximum ratio of mean TiC grain separation distance in the gas to grain diameter from the Ti number densities as ˜3 × 10 5 to ˜1 × 10 6.

Accuracy of a dose-area product compared to an absorbed dose to water at a point in a 2 cm diameter field

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

Dufreneix, S.; Ostrowsky, A.; Rapp, B.

Purpose: Graphite calorimeters with a core diameter larger than the beam can be used to establish dosimetric references in small fields. The dose-area product (DAP) measured can theoretically be linked to an absorbed dose at a point by the determination of a profile correction. This study aims at comparing the DAP-based protocol to the usual absorbed dose at a point protocol in a 2 cm diameter field for which both references exist. Methods: Two calorimeters were used, respectively, with a sensitive volume of 0.6 cm (for the absorbed dose at a point measurement) and 3 cm diameter (for the DAPmore » measurement). Profile correction was calculated from a 2D dose mapping using three detectors: a PinPoint chamber, a synthetic diamond, and EBT3 films. A specific protocol to read EBT3 films was implemented and the dose-rate and energy dependences were studied to assure a precise measurement, especially in the penumbra and out-of-field regions. Results: EBT3 films were found independent on dose rates over the range studied but showed a strong under-response (18%) at low energies. Depending on the dosimeter used for calculating the profile correction, a deviation of 0.8% (PinPoint chamber), 0.9% (diamond), or 1.9% (EBT3 films) was observed between the calibration coefficient derived from DAP measurements and the one directly established in terms of absorbed dose to water at a point. Conclusions: The DAP method can currently be linked to the classical dosimetric reference system based in an absorbed dose at a point only with a confidence interval of 95% (k = 2). None of the detectors studied can be used to determine an absorbed dose to water at a point from a DAP measurement with an uncertainty smaller than 1.2%.« less

Effect of resin on impact damage tolerance of graphite/epoxy laminates

NASA Technical Reports Server (NTRS)

Williams, J. G.; Rhodes, M. D.

1982-01-01

Twenty-four different epoxy resin systems were evaluated by a variety of test techniques to identify materials that exhibited improved impact damage tolerance in graphite/epoxy composite laminates. Forty-eight-ply composite panels of five of the material systems were able to sustain 100 m/s impact by a 1.27-cm-diameter aluminum projectile while statically loaded to strains of 0.005. Of the five materials with the highest tolerance to impact, two had elastomeric additives, two had thermoplastic additives, and one had a vinyl modifier; all the five systems used bisphenol A as the base resin. An evaluation of test results shows that the laminate damage tolerance is largely determined by the resin tensile properties, and that improvements in laminate damage tolerance are not necessarily made at the expense of room-temperature mechanical properties. The results also suggest that a resin volume fraction of 40 percent or greater may be required to permit the plastic flow between fibers necessary for improved damage tolerance.

Effect of graphite particle size and content on the formation mechanism of detonation polycrystalline diamond

NASA Astrophysics Data System (ADS)

Tong, Y.; Cao, Y.; Liu, R.; Shang, S. Y.; Huang, F. L.

2018-03-01

The formation mechanism of detonation polycrystalline diamond (DPD) generated from the detonation of a mixed RDX/graphite explosive is investigated. It is found experimentally that the DPD conversion rate decreases with both the content and the particle size of the graphite. Moreover, the particle sizes of the generated DPD powder are analyzed, which shows that, with the decrease in the graphite particle size, the mean number diameter of DPD decreases, but the mean volume diameter increases. In addition, with the help of scanning electron microscopy, it is observed that the in situ phase change occurs in the graphite particles, by which the small particles combine to form numerous large DPD particles. Based on both the experimental data and the classical ZND detonation model, we divide such a DPD synthesis process into two stages: In the first stage, the in situ phase change from graphite to diamond is dominant, supplemented by some coalescence growth at high pressure and temperature, which is affected mainly by the detonation performance of the mixed explosive under consideration. In the second stage, the graphitization of DPD caused by the residual heat is dominant, which is affected mainly by the unloading rate of the particle temperature.

Crushing characteristics of composite tubes with 'near-elliptical' cross sections

NASA Astrophysics Data System (ADS)

Farley, Gary L.; Jones, Robert M.

1992-01-01

An experimental investigation was conducted to determine whether the energy-absorption capability of near-elliptical cross-section composite tubular specimens is a function of included angle. Each half of the near-elliptical cross-section tube is a segment of a circle. The included angle is the angle created by radial lines extending from the center of the circular segment to the ends of the circular segment. Graphite- and Kevlar-reinforced epoxy material was used to fabricate specimens. Tube internal diameters were 2.54, 3.81, and 7.62 cm, and included angles were 180, 160, 135, and 90 degrees. Based upon the test results from these tubes, energy-absorption capability increased between 10 and 30 percent as included angle decreased between 180 and 90 degrees for the materials evaluated. Energy-absorption capability was a decreasing nonlinear function of the ratio of tube internal diameter to wall thickness.

Enhanced ablation of small anodes in a carbon nanotube arc discharge

NASA Astrophysics Data System (ADS)

Raitses, Yevgeny; Fetterman, Abraham; Keidar, Michael

2008-11-01

An atmospheric pressure helium arc discharge is used for carbon nanotube synthesis. The arc discharge operates in an anodic mode with the ablating anode made from a graphite material. For such conditions, models predict the electron-repelling (negative) anode sheath. In the present experiments, the anode ablation rate is investigated as a function of the anode diameter. It is found that anomalously high ablation occurs for small anode diameters (< 0.4 cm). This result is explained by the formation of an electron-attracting (positive) anode sheath leading to increased power losses on small anodes as compared to larger anodes [1]. The suggested mechanism for the positive anode sheath formation is plasma convergence. The increased ablation rate due to this positive sheath could imply a greater yield of carbon nanotube production. [1] A. J. Fetterman, Y. Raitses and M. Keidar, Carbon (2008).

Design and Construction of a Small Vacuum Furnace

NASA Astrophysics Data System (ADS)

Peawbang, P.; Thedsakhulwong, A.

2017-09-01

The purpose of this research is designed and constructed of a small vacuum furnace. A cylindrical graphite was chosen as the material of the furnace, the cylinder aluminium and copper sheets were employed to prevent the heat radiation that transfers from the furnace to the chamber wall. A rotary pump used, the pressure of graphite furnace can be pumped up to 30 mTorr and heated up to 700 °C driving by wire and the temperature of the chamber wall is relatively remained too low. In addition, heat loss obtained from the graphite furnace by conduction, convection, and radiation were analyzed. The dominating heat loss was found to be caused by the blackbody radiation, which can thus be used to estimate the relationship between graphite furnace temperature and the drive power needed. The cylindrical graphite furnace has an inner diameter of 44 mm, the outer diameter of 60 mm and 45 mm in height, the 355.5 W of power is needed to drive the furnace to 700 °C.

An Overview of the Nuclear Electric Xenon Ion System (NEXIS) Activity

NASA Technical Reports Server (NTRS)

Randolph, Thomas M.; Polk, James E., Jr.

2004-01-01

The Nuclear Electric Xenon Ion System (NEXIS) research and development activity within NASA's Project Prometheus, was one of three proposals selected by NASA to develop thruster technologies for long life, high power, high specific impulse nuclear electric propulsion systems that would enable more robust and ambitious science exploration missions to the outer solar system. NEXIS technology represents a dramatic improvement in the state-of-the-art for ion propulsion and is designed to achieve propellant throughput capabilities >= 2000 kg and efficiencies >= 78% while increasing the thruster power to >= 20 kW and specific impulse to >= 6000 s. The NEXIS technology uses erosion resistant carbon-carbon grids, a graphite keeper, a new reservoir hollow cathode, a 65-cm diameter chamber masked to produce a 57-cm diameter ion beam, and a shared neutralizer architecture to achieve these goals. The accomplishments of the NEXIS activity so far include performance testing of a laboratory model thruster, successful completion of a proof of concept reservoir cathode 2000 hour wear test, structural and thermal analysis of a completed development model thruster design, fabrication of most of the development model piece parts, and the nearly complete vacuum facility modifications to allow long duration wear testing of high power ion thrusters.

Characteristics of cold atmospheric plasma source based on low-current pulsed discharge with coaxial electrodes

NASA Astrophysics Data System (ADS)

Bureyev, O. A.; Surkov, Yu S.; Spirina, A. V.

2017-05-01

This work investigates the characteristics of the gas discharge system used to create an atmospheric pressure plasma flow. The plasma jet design with a cylindrical graphite cathode and an anode rod located on the axis of the system allows to realize regularly reproducible spark breakdowns mode with a frequency ∼ 5 kHz and a duration ∼ 40 μs. The device generates a cold atmospheric plasma flame with 1 cm in diameter in the flow of various plasma forming gases including nitrogen and air at about 100 mA average discharge current. In the described construction the cathode spots of individual spark channels randomly move along the inner surface of the graphite electrode creating the secondary plasma stream time-average distributed throughout the whole exit aperture area after the decay of numerous filamentary discharge channels. The results of the spectral diagnostics of plasma in the discharge gap and in the stream coming out of the source are presented. Despite the low temperature of atoms and molecules in plasma stream the cathode spots operation with temperature of ∼ 4000 °C at a graphite electrode inside a discharge system enables to saturate the plasma by CN-radicals and atomic carbon in the case of using nitrogen as the working gas.

Method of fabricating graphite for use as a skeletal prosthesis and product thereof

DOEpatents

Eatherly, Walter P.; Robbins, J. M.; Rosson, Sr., David E.

1978-01-01

A method for producing porous graphite for use as bone replacement with a structure for osteon penetration. Graphite is produced with ordered circular pores of 100 to 1000 microns in diameter covering at least 25% of the exposed surfaces. A cylindrical fiber is coated with a carbon flour-pitch mix and is then wound on a bobbin in a predetermined manner. The product of winding is dried, pressed, carbonized, and then graphitized. The fibers are removed either chemically or by volatilization during carbonization or graphitization.

Analysis of Picosecond Pulsed Laser Melted Graphite

DOE R&D Accomplishments Database

Steinbeck, J.; Braunstein, G.; Speck, J.; Dresselhaus, M. S.; Huang, C. Y.; Malvezzi, A. M.; Bloembergen, N.

1986-12-01

A Raman microprobe and high resolution TEM have been used to analyze the resolidified region of liquid carbon generated by picosecond pulse laser radiation. From the relative intensities of the zone center Raman-allowed mode for graphite at 1582 cm{sup -1} and the disorder-induced mode at 1360 cm{sup -1}, the average graphite crystallite size in the resolidified region is determined as a function of position. By comparison with Rutherford backscattering spectra and Raman spectra from nanosecond pulsed laser melting experiments, the disorder depth for picosecond pulsed laser melted graphite is determined as a function of irradiating energy density. Comparisons of TEM micrographs for nanosecond and picosecond pulsed laser melting experiments show that the structure of the laser disordered regions in graphite are similar and exhibit similar behavior with increasing laser pulse fluence.

Design, fabrication, and test of lightweight shell structure, phase 2

NASA Technical Reports Server (NTRS)

1974-01-01

A cylindrical shell skirt structure 4.57 m (180 in.) in diameter and 3.66 m (144 in.) high was subjected to a design and analysis study using a wide variety of structural materials and concepts. The design loading of 1225.8 N/cm (700 lb/in.) axial compression and 245.2 N/cm (140 lb/in.) torsion is representative of that expected on a typical space tug skirt section. Structural concepts evaluated included honeycomb sandwich, truss, isogrid, and skin/stringer/frame. The materials considered included a wide variety of structural metals as well as glass, graphite, and boron-reinforced composites. The most unique characteristic of the candidate designs is that they involve the use of very thin-gage material. Fabrication and structural test of small panels and components representative of many of the candidate designs served to demonstrate proposed fabrication techniques and to verify design and analysis methods.

Cross-ply laminates with holes in compression - Straight free-edge stresses determined by two- to three-dimensional global/local finite element analysis

NASA Technical Reports Server (NTRS)

Thompson, Danniella Muheim; Griffin, O. Hayden, Jr.; Vidussoni, Marco A.

1990-01-01

A practical example of applying two- to three-dimensional (2- to 3-D) global/local finite element analysis to laminated composites is presented. Cross-ply graphite/epoxy laminates of 0.1-in. (0.254-cm) thickness with central circular holes ranging from 1 to 6 in. (2.54 to 15.2 cm) in diameter, subjected to in-plane compression were analyzed. Guidelines for full three-dimensional finite element analysis and two- to three-dimensional global/local analysis of interlaminar stresses at straight free edges of laminated composites are included. The larger holes were found to reduce substantially the interlaminar stresses at the straight free-edge in proximity to the hole. Three-dimensional stress results were obtained for thin laminates which require prohibitive computer resources for full three-dimensional analyses of comparative accuracy.

Compatibility of the Radio Frequency Mass Gauge with Composite Tanks

NASA Technical Reports Server (NTRS)

Zimmerli, Greg; Mueller, Carl

2015-01-01

The radio frequency mass gauge (RFMG) is a low-gravity propellant quantity gauge being developed at NASA for possible use in long-duration space missions utilizing cryogenic propellants. As part of the RFMG technology development process, we evaluated the compatibility of the RFMG with a graphite-epoxy composite material used to construct propellant tanks. The key material property that can affect compatibility with the RFMG is the electrical conductivity. Using samples of 8552IM7 graphite-epoxy composite, we characterized the resistivity and reflectivity over a range of frequencies. An RF impedance analyzer was used to characterize the out-of-plane electrical properties (along the sample thickness) in the frequency range 10 to 1800 MHZ. The resistivity value at 500 MHz was 4.8 ohm-cm. Microwave waveguide measurements of samples in the range 1.7 2.6 GHz, performed by inserting the samples into a WR-430 waveguide, showed reflectivity values above 98. Together, these results suggested that a tank constructed from graphite-epoxy composite would produce good quality electromagnetic tank modes, which is needed for the RFMG. This was verified by room-temperature measurements of the electromagnetic modes of a 2.4 m diameter tank constructed by Boeing from similar graphite-epoxy composite material. The quality factor Q of the tank electromagnetic modes, measured via RF reflection measurements from an antenna mounted in the tank, was typically in the range 400 Q 3000. The good quality modes observed in the tank indicate that the RFMG is compatible with graphite-epoxy tanks, and thus the RFMG could be used as a low-gravity propellant quantity gauge in such tanks filled with cryogenic propellants.

Mass removal by oxidation and sublimation of porous graphite during fiber laser irradiation

NASA Astrophysics Data System (ADS)

Phillips, Grady T.; Bauer, William A.; Fox, Charles D.; Gonzales, Ashley E.; Herr, Nicholas C.; Gosse, Ryan C.; Perram, Glen P.

2017-01-01

The various effects of laser heating of carbon materials are key to assessing laser weapon effectiveness. Porous graphite plates, cylinders, and cones with densities of 1.55 to 1.82 g/cm3 were irradiated by a 10-kW fiber laser at 0.075 to 3.525 kW/cm2 for 120 s to study mass removal and crater formation. Surface temperatures reached steady state values as high as 3767 K. The total decrease in sample mass ranged from 0.06 to 6.29 g, with crater volumes of 0.52 to 838 mm3, and penetration times for 12.7-mm-thick plates as short as 38 s. Minor contaminants in the graphite samples produced calcium and iron oxide to be redeposited on the graphite surface. Dramatic graphite crystalline structures are also produced at higher laser irradiances. Significantly increased porosity of the sample is observed even outside the laser-irradiated region. Total mass removed increases with deposited laser energy at a rate of 4.83 g/MJ for medium extruded graphite with an apparent threshold of 0.15 MJ. At ˜3.5 kW/cm2, the fractions of the mass removed from the cylindrical samples in the crater, surrounding trench, and outer region of decreased porosity are 38%, 47%, and 15%, respectively. Graphite is particularly resistant to damage by high power lasers. The new understanding of graphite combustion and sublimation during laser irradiation is vital to the more complex behavior of carbon composites.

RECOVERY OF VALUABLE MATERIAL FROM GRAPHITE BODIES

DOEpatents

Fromm, L.W. Jr.

1959-09-01

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

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

Paul Demkowicz; Lance Cole; Scott Ploger

The AGR-1 irradiation experiment ended on November 6, 2009, after 620 effective full power days in the Advanced Test Reactor, achieving a peak burnup of 19.6% FIMA. The test train was shipped to the Materials and Fuels Complex in March 2010 for post-irradiation examination. The first PIE activities included non-destructive examination of the test train, followed by disassembly of the test train and individual capsules and detailed inspection of the capsule contents, including the fuel compacts and the graphite fuel holders. Dimensional measurements of the compacts, graphite holders, and steel capsules shells were performed using a custom vision measurement systemmore » (for outer diameters and lengths) and conventional bore gauges (for inner diameters). Gamma spectrometry of the intact test train gave a preliminary look at the condition of the interior components. No evidence of damage to compacts or graphite components was evident from the isotopic and gross gamma scans. Neutron radiography of the intact Capsule 2 showed a high degree of detail of interior components and confirmed the observation that there was no major damage to the capsule. Disassembly of the capsules was initiated using procedures qualified during out-of-cell mockup testing. Difficulties were encountered during capsule disassembly due to irradiation-induced changes in some of the capsule components’ properties, including embrittled niobium and molybdenum parts that were susceptible to fracture and swelling of the graphite fuel holders that affected their removal from the capsule shells. This required various improvised modifications to the disassembly procedure to avoid damage to the fuel compacts. Ultimately the capsule disassembly was successful and only one compact from Capsule 4 (out of 72 total in the test train) sustained damage during the disassembly process, along with the associated graphite holder. The compacts were generally in very good condition upon removal. Only relatively minor damage or markings were visible using high resolution photographic inspection. Compact dimensional measurements indicated diametrical shrinkage of 0.9 to 1. 4%, and length shrinkage of 0.2 to 1.1%. The shrinkage was somewhat dependent on compact location within each capsule and within the test train. Compacts exhibited a maximum diametrical shrinkage at a fast neutron fluence of approximately 3×1021 n/cm2. A multivariate statistical analysis indicates that fast neutron fluence as well as compact position in the test train influence compact shrinkage.« less

78 FR 22843 - Small Diameter Graphite Electrodes From the People's Republic of China: Affirmative Preliminary...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-17

...The Department of Commerce (``Department'') preliminarily determines that imports from the People's Republic of China (``PRC'') of certain graphite electrodes, produced and/or exported by Sinosteel Jilin Carbon Co., Ltd. and Jilin Carbon Import & Export Company (collectively, ``Jilin Carbon''), with an actual or nominal diameter of 17 inches, and otherwise meeting the description of in-scope merchandise, constitutes merchandise altered in form or appearance in such minor respects that it should be included within the scope of the Order.\\1\\ ---------------------------------------------------------------------------

Surface temperature determination in surface analytic systems by infrared optical pyrometry

NASA Technical Reports Server (NTRS)

Wheeler, Donald R.; Jones, William R., Jr.; Pepper, Stephen V.

1988-01-01

An IR pyrometric technique for measuring the surface temperatures of metal specimens in an ultrahigh-vacuum analytic chamber is described and demonstrated. The experimental setup comprises a commercial IR microscope with a long-working-distance right-angle objective (focal spot diameter 1 mm at 53 cm), a metal-coated glass vacuum chamber with a Ta-mesh-covered quartz viewport, an Mo specimen stub with an internal heating element, and a Ta disk test specimen with a flat side coated with a high-emissivity graphite film. The results of an initial calibration test are presented graphically and briefly characterized. The measurement error at 450 C is found to be less than 10 C.

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.

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

NASA Astrophysics Data System (ADS)

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

2013-08-01

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

Silicon anode materials with ultra-low resistivity from the inside out for lithium ion batteries

NASA Astrophysics Data System (ADS)

Xu, Guojun; Jin, Chenxin; Liu, Liekai; Lan, Yu; Yue, Zhihao; Li, Xiaomin; Sun, Fugen; Huang, Haibin; Zhou, Lang

2017-12-01

Broken silicon (Si) wafers with electrical resistivity of 1 and 0.001 Ω cm were respectively ball-milled to Si particles with median diameters of less than 1 μm. Both these two types of Si particles were deposited with silver (Ag) nanoparticles by self-selective electroless deposition method. 1-Ω cm-Si particles, 0.001-Ω cm-Si particles, Ag-deposited 1-Ω cm-Si particles and Ag-deposited 0.001-Ω cm-Si particles were, respectively, mixed with graphite particles in weight ratio of 1:9 to form four types of Si-C anode materials and then they were assembled into coin cells. The experimental results indicate that the Ag-deposited 0.001-Ω cm-Si sample shows the higher capacity, better rate and cycle performance than other three samples, due to the high conductivity of Ag-deposited 0.001-Ω cm-Si sample from the inside out. At the current density of 750 mA g-1, the discharge capacity gap of Ag-deposited 0.001-Ω cm-Si sample and 0.001-Ω cm-Si sample is as high as 141.7 mA h g-1, which is almost equal to the discharge capacity of the latter. Besides, the discharge capacity retention ratio of Ag-deposited 0.001-Ω cm-Si sample after 50 cycles is 70%, which is 23.5% higher than that of 0.001-Ω cm-Si sample.

Further Development of the Gyrotron- Powered Pellet Accelerator

NASA Astrophysics Data System (ADS)

Perkins, Francis

2007-11-01

The Gyrotron-Powered Pellet Accelerator provides an enabling technology to efficiently fuel ITER with fast pellets launched from the High Field Side (HFS) separatrix. Pellet experiments have repeatedly found that fuel efficiently is high - consistent with 100%. In contrast, Low Field Side (LFS) launch experiments find efficiencies of 50% or less. This report addresses what experimental program and what material choices can be made to retain program momentum. An initial program seeks to establish that our heterogeneous approach to conductivity works, maintaining s 1 mho/m. A demonstration of acceleration can be carried out in a very simple laboratory when the pusher material D2[Be] is replaced by LiH[C] which is a room temperature solid with a graphite particle suspension. No cryogenics or hazard chemicals. The mm-wave mirror will be graphite, the tamper is sapphire, and the payload LiD. The payload has a pellet has diameter = 3mm and a mass M = 4.4x10-4 kg which is 220 joules at V=1000 m/s. A barrel length of 15 cm completes the design specification.

Synthesis of Stacked-Cup Carbon Nanotubes in a Metal Free Low Temperature System

NASA Technical Reports Server (NTRS)

Kimura, Yuki; Nuth, Joseph A.; Johnson, Natasha M.; Farmer, Kevin D.; Roberts, Kenneth P.; Hussaini, Syed R.

2011-01-01

Stacked-cup carbon nanotubes were formed by either Fischer-Tropsch type or Haber Bosch type reactions in a metal free system. Graphite particles were used as the catalyst. The samples were heated at 600 C in a gas mixture of CO 75 Torr, N2 75 Torr and H2 550 Torr for three days. Trans mission electron microscope analysis of the catalyst surface at the completion of the experiment recognized the growth of nanotubes. They were 10-50 nm in diameter and approximately 1 micrometer in length. They had a hollow channel of 5-20 nm in the center. The nanotubes may have grown on graphite surfaces by the CO disproportionation reaction and the surface tension of the carbon nucleus may have determined the diameter. Although, generally, the diameter of a carbon nanotube depends on the size of the cataly1ic particles, the diameter of the nanotubes on graphite particles was independent of the particle size and significantly confined within a narrow range compared with that produced using catalytic amorphous iron-silicate nanoparticles. Therefore, they must have an unknown formation process that is different than the generally accepted mechanism.

Fabrication of graphite/epoxy cases for orbit insertion motors

NASA Technical Reports Server (NTRS)

Schmidt, W. W.

1973-01-01

The fabrication procedures are described for filament-wound rocket motor cases, approximately 26.25 inches long by 25.50 inches diameter, utilizing graphite fibers. The process utilized prepreg tape which consists of Fortafil 4-R fibers in the E-759 epoxy resin matrix. This fabrication effect demonstrated an ability to fabricate high quality graphite/epoxy rocket motor cases in the 26.25 inch by 25.50 inch size range.

Improved Graphite Fiber.

DTIC Science & Technology

1982-10-01

The purpose of the program was to develop a production method for improved graphite fibers. A goal of 750 x 10 to the 3rd power psi tensile strength...at 60-65 x 10 to the 6th power psi modulus was set for the program. Improved 3-4 micron diameter boron strengthened graphite fibers were successfully... graphite fiber. An average tensile strength of 550 x 10 to the 3rd power psi at the 60 x 10 to the 6th power psi modulus level was achieved through a preliminary optimization of the plant processing conditions.

Method for molding threads in graphite panels

DOEpatents

Short, W.W.; Spencer, C.

1994-11-29

A graphite panel with a hole having a damaged thread is repaired by drilling the hole to remove all of the thread and making a new hole of larger diameter. A bolt with a lubricated thread is placed in the new hole and the hole is packed with graphite cement to fill the hole and the thread on the bolt. The graphite cement is cured, and the bolt is unscrewed therefrom to leave a thread in the cement which is at least as strong as that of the original thread. 8 figures.

Fabrication of graphite/polyimide composite structures.

NASA Technical Reports Server (NTRS)

Varlas, M.

1972-01-01

Selection of graphite/polyimide composite as a prime candidate for high-temperature structural applications involving long-duration temperature environments of 400 to 600 F. A variety of complex graphite/polyimide components has been fabricated, using a match-metal die approach developed for making fiber-reinforced resin composites. Parts produced include sections of a missile adapter skin flange, skin frame section, and I-beam and hat-section stringers, as well as unidirectional (0 deg) and plus or minus 45 deg oriented graphite/polyimide tubes in one-, two-, and six-inch diameters.

Study of multi-kilowatt solar arrays for Earth orbit applications

NASA Technical Reports Server (NTRS)

Patterson, R. E.

1983-01-01

A miniaturized Cassegrainian concentrator (MCC) solar array concept is being developed with the objective of significantly reducing the recurring cost of multikilowatt solar arrays. The desired cost reduction is obtained as a result of using very small high efficiency solar cells in conjuction with low cost optics. The MCC single element concept incident slar radiation is reflected rom a primary parabolic reflector to a secondary hyperbolic reflector and finally to a 4 millimeter diameter solar cell. A light catcher cone is used to improve off axis performance. The solar cell is mounted to a heat fin. An element is approximately 13 millimeters thick which permits efficient launch stowage of the concentrator system panels without complex optical component deployments or retractions. The MCC elements are packed in bays within graphite epoxy frames and are electrically connected into appropriate series-parallel circuits. A MCC sngle element with a 21 sq cm entrance aperture and a 20 efficient, 0.25 sq cm gallium arsenide solar cell has the same power output as 30 sq cm of 11-percent efficiency (at 68 C) silicon solar cells.

Cluster formation in laser-induced ablation and evaporation of solids observed by laser ionization time-of-flight mass spectrometry and scanning tunneling microscopy

NASA Astrophysics Data System (ADS)

Tench, R. J.; Balooch, M.; Bernardez, L.; Allen, Mike J.; Siekhaus, W. J.; Olander, D. R.; Wang, W.

1990-04-01

Laser ionization time-of-flight mass analysis (LIMA) used pulses (5ns) of a frequency-quadrupled Nd-YAG laser (266 nm) focused onto spots of 4 to 100 microns diameter to ablate material, and a reflectron time of flight tube to mass-analyze the plume. The observed mass spectra for Si, Pt, SiC, and UO 2 varied in the distribution of ablation products among atoms, molecules and clusters, depending on laser power density and target material. Cleaved surfaces of highly oriented pyrolytic graphite (HOPG) positioned at room temperature either 10 cm away from materials ablated at 10(exp -5) Torr by 1 to 3 excimer laser (308 nm) pulses of 20 ns duration or 1 m away from materials vaporized at 10(exp -8) Torr by 10 Nd-Glass laser pulses of 1 ms duration were analyzed by Scanning Tunneling Microscopy (STM) in air with angstrom resolution. Clusters up to 30 A in diameter were observed.

Cost-effective single-step carbon nanotube synthesis using microwave oven

NASA Astrophysics Data System (ADS)

Algadri, Natheer A.; Ibrahim, K.; Hassan, Z.; Bououdina, M.

2017-08-01

This paper reports the characterization of carbon nanotubes (CNTs) synthesised using a conventional microwave oven method, offering several advantages including fast, simple, low cost, and solvent free growth process. The procedure involves flattening of graphite/ferrocene mixture catalyst inside the microwave oven under ambient conditions for a very short duration of 5 s, which inhibits the loss factor of graphite and ferrocene. The effect of graphite/ferrocene mixture ratio for the synthesis of CNTs is investigated by transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), x-ray diffraction (XRD), Raman spectroscopy and UV-NIR-Vis measurements. The samples produced using the different ratios contain nanotubes with an average diameter in the range 44-79 nm. The highest yield of CNTs is attained with graphite/ferrocene mixture ratio of 70:30. The lowest I D/I G ratio intensity as identified by Raman spectroscopy for 70:30 ratio indicates the improved crystallinity of CNTs. Due to the capillary effect of CNTs, Fe nanoparticles are found to be encapsulated inside the tubes at different positions along the tube length. The obtained results showed that the smaller the diameter of graphite and ferrocene favors the synthesis of graphene oxide upon microwave radiation.

Thermal charging study of compressed expanded natural graphite/phase change material composites

DOE PAGES

Mallow, Anne; Abdelaziz, Omar; Graham, Jr., Samuel

2016-08-12

The thermal charging performance of paraffin wax combined with compressed expanded natural graphite foam was studied for different graphite bulk densities. Constant heat fluxes between 0.39 W/cm 2 and 1.55 W/cm 2 were applied, as well as a constant boundary temperature of 60 °C. Thermal charging experiments indicate that, in the design of thermal batteries, thermal conductivity of the composite alone is an insufficient metric to determine the influence of the graphite foam on the thermal energy storage. By dividing the latent heat of the composite by the time to end of melt for each applied boundary condition, the energymore » storage performance was calculated to show the effects of composite thermal conductivity, graphite bulk density, and latent heat capacity. For the experimental volume, the addition of graphite beyond a graphite bulk density of 100 kg/m 3 showed limited benefit on the energy storage performance due to the decrease in latent heat storage capacity. These experimental results are used to validate a numerical model to predict the time to melt and for future use in the design of heat exchangers with graphite-foam based phase change material composites. As a result, size scale effects are explored parametrically with the validated model.« less

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

Mallow, Anne; Abdelaziz, Omar; Graham, Jr., Samuel

The thermal charging performance of paraffin wax combined with compressed expanded natural graphite foam was studied for different graphite bulk densities. Constant heat fluxes between 0.39 W/cm 2 and 1.55 W/cm 2 were applied, as well as a constant boundary temperature of 60 °C. Thermal charging experiments indicate that, in the design of thermal batteries, thermal conductivity of the composite alone is an insufficient metric to determine the influence of the graphite foam on the thermal energy storage. By dividing the latent heat of the composite by the time to end of melt for each applied boundary condition, the energymore » storage performance was calculated to show the effects of composite thermal conductivity, graphite bulk density, and latent heat capacity. For the experimental volume, the addition of graphite beyond a graphite bulk density of 100 kg/m 3 showed limited benefit on the energy storage performance due to the decrease in latent heat storage capacity. These experimental results are used to validate a numerical model to predict the time to melt and for future use in the design of heat exchangers with graphite-foam based phase change material composites. As a result, size scale effects are explored parametrically with the validated model.« less

Growth of carbon nanotubes in arc plasma treated graphite disc: microstructural characterization and electrical conductivity study

NASA Astrophysics Data System (ADS)

Nayak, B. B.; Sahu, R. K.; Dash, T.; Pradhan, S.

2018-03-01

Circular graphite discs were treated in arc plasma by varying arcing time. Analysis of the plasma treated discs by field emission scanning electron microscope revealed globular grain morphologies on the surfaces, but when the same were observed at higher magnification and higher resolution under transmission electron microscope, growth of multiwall carbon nanotubes of around 2 nm diameter was clearly seen. In situ growth of carbon nanotube bundles/bunches consisting of around 0.7 nm tube diameter was marked in the case of 6 min treated disc surface. Both the untreated and the plasma treated graphite discs were characterized by X-ray diffraction, energy dispersive spectra of X-ray, X-ray photoelectron spectroscopy, transmission electron microscopy, micro Raman spectroscopy and BET surface area measurement. From Raman spectra, BET surface area and microstructure observed in transmission electron microscope, growth of several layers of graphene was identified. Four-point probe measurements for electrical resistivity/conductivity of the graphite discs treated under different plasma conditions showed significant increase in conductivity values over that of untreated graphite conductivity value and the best result, i.e., around eightfold increase in conductivity, was observed in the case of 6 min plasma treated sample exhibiting carbon nanotube bundles/bunches grown on disc surface. By comparing the microstructures of the untreated and plasma treated graphite discs, the electrical conductivity increase in graphite disc is attributed to carbon nanotubes (including bundles/bunches) growth on disc surface by plasma treatment.

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...

Method for molding threads in graphite panels

DOEpatents

Short, William W.; Spencer, Cecil

1994-01-01

A graphite panel (10) with a hole (11) having a damaged thread (12) is repaired by drilling the hole (11) to remove all of the thread and make a new hole (13) of larger diameter. A bolt (14) with a lubricated thread (17) is placed in the new hole (13) and the hole (13) is packed with graphite cement (16) to fill the hole and the thread on the bolt. The graphite cement (16) is cured, and the bolt is unscrewed therefrom to leave a thread (20) in the cement (16) which is at least as strong as that of the original thread (12).

Fire test methodology for aerospace materials. 1: Thermal and smoke toxicological assessments of graphite/bismaleimide and graphite/epoxy systems

NASA Technical Reports Server (NTRS)

Kanakia, M. D.; Switzer, W. G.; Hartzell, G. E.; Kaplan, H. L.

1980-01-01

Both materials possess a high degree of thermal stability, with total heat release values being essentially identical under piloted ignition conditions over a range of 5 to 10 W/sq cm incident heat flux. The graphite/epoxy material had a tendency to auto-ignite at a lower heat flux (about 7 W/sq cm) and produced about 23 percent higher peak heat release rates, approximately 42 percent more carbon monoxide and considerably more smoke than the graphite/bismaleimide under conditions of piloted ignition. Toxicological potencies of smoke produced from the two composites were equivalent for 30 minute exposures. Potencies were also comparable to many common materials, such as wood. There was no evidence for the formation of an "unusual toxicant" nor for any short term post-exposure toxicological effects.

Modeling and Characterization of a Graphite Nanoplatelet/Epoxy Composite

NASA Technical Reports Server (NTRS)

Odegard, Gregory M.; Chasiotis, I.; Chen, Q.; Gates, T. S.

2004-01-01

A micromechanical modeling procedure is developed to predict the viscoelastic properties of a graphite nanoplatelet/epoxy composite as a function of volume fraction and nanoplatelet diameter. The predicted storage and loss moduli from the model are compared to measured values from the same material using Dynamical Mechanical Analysis, nanoindentation, and tensile tests. In most cases, the model and experiments indicate that for increasing volume fractions of nanoplatelets, both the storage and loss moduli increase. Also, in most cases, the model and experiments indicate that as the nanoplatelet diameter is increased, the storage and loss moduli decrease and increase, respectively.

Formation mechanism of graphite hexagonal pyramids by argon plasma etching of graphite substrates

NASA Astrophysics Data System (ADS)

Glad, X.; de Poucques, L.; Bougdira, J.

2015-12-01

A new graphite crystal morphology has been recently reported, namely the graphite hexagonal pyramids (GHPs). They are hexagonally-shaped crystals with diameters ranging from 50 to 800 nm and a constant apex angle of 40°. These nanostructures are formed from graphite substrates (flexible graphite and highly ordered pyrolytic graphite) in low pressure helicon coupling radiofrequency argon plasma at 25 eV ion energy and, purportedly, due to a physical etching process. In this paper, the occurrence of peculiar crystals is shown, presenting two hexagonal orientations obtained on both types of samples, which confirms such a formation mechanism. Moreover, by applying a pretreatment step with different time durations of inductive coupling radiofrequency argon plasma, for which the incident ion energy decreases at 12 eV, uniform coverage of the surface can be achieved with an influence on the density and size of the GHPs.

76 FR 14910 - Small Diameter Graphite Electrodes From the People's Republic of China: Initiation of Anti...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-18

... correct grade of petroleum coke mix, and have been baked, formed, carbonized, impregnated, and graphitized... required for the production of SDGE (e.g., raw material handling, mixing, forming, baking, impregnating... production process, demonstrating how raw materials are formed, baked, impregnated (if needed), re-baked...

Graphite filament wound pressure vessels

NASA Technical Reports Server (NTRS)

Feldman, A.; Damico, J. J.

1972-01-01

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

The First Discovery of Presolar Graphite Grains from the Highly Reducing Qingzhen (EH3) Meteorite

NASA Astrophysics Data System (ADS)

Xu, Yuchen; Lin, Yangting; Zhang, Jianchao; Hao, Jialong

2016-07-01

Presolar graphite grains have been extensively studied, but are limited in carbonaceous chondrites, particularly in Murchison (CM2) and Orgueil (CI1), which sampled materials from the oxidizing regions in the solar nebula. Here, we report the first discovery of presolar graphite grains from the Qingzhen (EH3) enstatite chondrite which formed under a highly reducing condition. Eighteen presolar graphite grains were identified by C-isotope mapping of the low-density fraction (1.75-1.85 g cm-3) from Qingzhen acid residue. Another 58 graphite spherules were found in different areas of the same sample mount using a scanning electron microscope and were classified into three morphologies, including cauliflower, onion, and cauliflower-onion. The Raman spectra of these spherules vary from ordered, disordered, and glassy to kerogen-like, suggestive of a wide range of thermal metamorphisms. NanoSIMS analysis of the C- and Si-isotopes of these graphite spherules confirmed 23 presolar grains. The other 35 graphite spherules have no significant isotopic anomalies, but they share similar morphologies and Raman spectra with the presolar ones. Another three grains were identified during NanoSIMS analysis. Of all the 44 presolar graphite grains identified, six grains show 28Si-excesses, suggestive of supernovae origins, and four grains are 12C- and 29,30Si-rich, consistent with low-metallicity asymptotic giant branch star origins. Another two graphite spherules have extremely low 12C/13C ratios with marginal solar Si-isotopes. The morphologies, Raman spectra, and C- and Si-isotopic distributions of the presolar graphite grains from the Qingzhen enstatite chondrite are similar to those of the low-density fractions from Murchison carbonaceous chondrites. This study suggests a homogeneous distribution of presolar graphite grains in the solar nebula.

Phase Structures and Magnetic Properties of Graphite Nanosheets and Ni-Graphite Nanocomposite Synthesized by Electrical Explosion of Wire in Liquid

NASA Astrophysics Data System (ADS)

Nguyen, Minh-Thuyet; Kim, Jin-Hyung; Lee, Jung-Goo; Kim, Jin-Chun

2018-03-01

The present work studied on phases and magnetic properties of graphite nanosheets and Ni-graphite nanocomposite synthesized using the electrical explosion of wire (EEW) in ethanol. X-ray diffraction and field emission scanning electron microscope were used to investigate the phases and the morphology of the nanopowders obtained. It was found that graphite nanosheets were absolutely fabricated by EEW with a thickness of 29 nm and 3 μm diameter. The as-synthesized Ni-graphite composite powders had a Ni-coating on the surfaces of graphite sheets. The hysteresis loop of the as-exploded, the hydrogen-treated composite nanopowders and the sintered samples were examined with a vibrating sample magnetometer at room temperature. The Ni-graphite composite exposed the magnetic behaviors which are attributed to Ni component. The magnetic properties of composite had the improvement from 10.2 emu/g for the as-exploded powders to 15.8 emu/g for heat-treated powders and 49.16 emu/g for sintered samples.

Effect of specimen size and grain orientation on the mechanical and physical properties of NBG-18 nuclear graphite

DOE PAGES

Vasudevamurthy, G.; Byun, T. S.; Pappano, Pete; ...

2015-03-13

Here we present a comparison of the measured baseline mechanical and physical properties of with grain (WG) and against grain (AG) non-ASTM size NBG-18 graphite. The objectives of the experiments were twofold: (1) assess the variation in properties with grain orientation; (2) establish a correlation between specimen tensile strength and size. The tensile strength of the smallest sized (4 mm diameter) specimens were about 5% higher than the standard specimens (12 mm diameter) but still within one standard deviation of the ASTM specimen size indicating no significant dependence of strength on specimen size. The thermal expansion coefficient and elastic constantsmore » did not show significant dependence on specimen size. Lastly, experimental data indicated that the variation of thermal expansion coefficient and elastic constants were still within 5% between the different grain orientations, confirming the isotropic nature of NBG-18 graphite in physical properties.« less

Effect of Nd:YAG Laser Irradiation on the Number of Open Dentinal Tubules and Their Diameter with and without Smear of Graphite: An in Vitro Study

PubMed Central

Maleki-pour, Mohammad Reza; Birang, Reza; Khoshayand, Maryam; Naghsh, Narges

2015-01-01

Introduction: Dentin hypersensitivity (DH) is characterized by tooth pain arising from exposure of dental roots. In this study the efficiency of neodymium yttrium-aluminum-garnet (Nd:YAG) laser in association with graphite on dentinal surface changes as the alternative to the treatment of DH was evaluated. Methods: Sixteen noncarious human third molars were collected and sectioned into 5 parts from cementoenamel junction (CEJ) to the furcation area. The prepared samples were randomly assigned into five groups (Gs) of each 16: Control (G1), treated by Nd:YAG laser at 0.5 W (G2), irradiation of Nd:YAG with a 0.25 W output power(G3), smeared with graphite and then using Nd:YAG laser at output powers of 0.5 W (G4) and 0.25 W (G5). For all groups the parameters were 15 Hz, 60 s, at two stages and with a right angle irradiation. The number and diameter of dentinal tubules (DT) were compared and analyzed by SPSS software, One way ANOVA and Post hoc LSD tests. Results:The number of open dentinal tubules varied significantly between all groups except among G1 with G3 and G2 with G5. Multiple comparison tests also exhibited significant differences regarding the diameter of tubules between the groups two by two except among G2 with G5. Conclusion: Nd:YAG laser used at 0.25 W and 0.5 W with application of graphite smear was able to reduce the number and diameter of dentinal tubules. PMID:25699166

Proton irradiated graphite grades for a long baseline neutrino facility experiment

NASA Astrophysics Data System (ADS)

Simos, N.; Nocera, P.; Zhong, Z.; Zwaska, R.; Mokhov, N.; Misek, J.; Ammigan, K.; Hurh, P.; Kotsina, Z.

2017-07-01

In search of a low-Z pion production target for the Long Baseline Neutrino Facility (LBNF) of the Deep Underground Neutrino Experiment (DUNE) four graphite grades were irradiated with protons in the energy range of 140-180 MeV, to peak fluence of ˜6.1 ×1020 p /cm2 and irradiation temperatures between 120 - 200 °C . The test array included POCO ZXF-5Q, Toyo-Tanso IG 430, Carbone-Lorraine 2020 and SGL R7650 grades of graphite. Irradiation was performed at the Brookhaven Linear Isotope Producer. Postirradiation analyses were performed with the objective of (a) comparing their response under the postulated irradiation conditions to guide a graphite grade selection for use as a pion target and (b) understanding changes in physical and mechanical properties as well as microstructure that occurred as a result of the achieved fluence and in particular at this low-temperature regime where pion graphite targets are expected to operate. A further goal of the postirradiation evaluation was to establish a proton-neutron correlation damage on graphite that will allow for the use of a wealth of available neutron-based damage data in proton-based studies and applications. Macroscopic postirradiation analyses as well as energy dispersive x-ray diffraction of 200 KeV x rays at the NSLS synchrotron of Brookhaven National Laboratory were employed. The macroscopic analyses revealed differences in the physical and strength properties of the four grades with behavior however under proton irradiation that qualitatively agrees with that reported for graphite under neutrons for the same low temperature regime and in particular the increase of thermal expansion, strength and Young's modulus. The proton fluence level of ˜1020 cm-2 where strength reaches a maximum before it begins to decrease at higher fluences has been identified and it agrees with neutron-induced changes. X-ray diffraction analyses of the proton irradiated graphite revealed for the first time the similarity in microstructural graphite behavior to that under neutron irradiation and the agreement between the fluence threshold of ˜5 ×1020 cm-2 where the graphite lattice undergoes a dramatic change. The confirmed similarity in behavior and agreement in threshold fluences for proton and neutron irradiation effects on graphite reported for the first time in this study will enable the safe utilization of the wealth of neutron irradiation data on graphite that extends to much higher fluences and different temperature regimes by the proton accelerator community searching for multi-MW graphite targets.

Proton irradiated graphite grades for a long baseline neutrino facility experiment

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

Simos, N.; Nocera, P.; Zhong, Z.

In search of a low-Z pion production target for the Long Baseline Neutrino Facility (LBNF) of the Deep Underground Neutrino Experiment (DUNE) four graphite grades were irradiated with protons in the energy range of 140–180 MeV, to peak fluence of ~6.1×10 20 p/cm 2 and irradiation temperatures between 120–200 °C. The test array included POCO ZXF-5Q, Toyo-Tanso IG 430, Carbone-Lorraine 2020 and SGL R7650 grades of graphite. Irradiation was performed at the Brookhaven Linear Isotope Producer. Postirradiation analyses were performed with the objective of (a) comparing their response under the postulated irradiation conditions to guide a graphite grade selection for use asmore » a pion target and (b) understanding changes in physical and mechanical properties as well as microstructure that occurred as a result of the achieved fluence and in particular at this low-temperature regime where pion graphite targets are expected to operate. A further goal of the postirradiation evaluation was to establish a proton-neutron correlation damage on graphite that will allow for the use of a wealth of available neutron-based damage data in proton-based studies and applications. Macroscopic postirradiation analyses as well as energy dispersive x-ray diffraction of 200 KeV x rays at the NSLS synchrotron of Brookhaven National Laboratory were employed. The macroscopic analyses revealed differences in the physical and strength properties of the four grades with behavior however under proton irradiation that qualitatively agrees with that reported for graphite under neutrons for the same low temperature regime and in particular the increase of thermal expansion, strength and Young’s modulus. The proton fluence level of ~10 20 cm -2 where strength reaches a maximum before it begins to decrease at higher fluences has been identified and it agrees with neutron-induced changes. X-ray diffraction analyses of the proton irradiated graphite revealed for the first time the similarity in microstructural graphite behavior to that under neutron irradiation and the agreement between the fluence threshold of ~5×10 20 cm -2 where the graphite lattice undergoes a dramatic change. The confirmed similarity in behavior and agreement in threshold fluences for proton and neutron irradiation effects on graphite reported for the first time in this study will enable the safe utilization of the wealth of neutron irradiation data on graphite that extends to much higher fluences and different temperature regimes by the proton accelerator community searching for multi-MW graphite targets.« less

Proton irradiated graphite grades for a long baseline neutrino facility experiment

DOE PAGES

Simos, N.; Nocera, P.; Zhong, Z.; ...

2017-07-24

In search of a low-Z pion production target for the Long Baseline Neutrino Facility (LBNF) of the Deep Underground Neutrino Experiment (DUNE) four graphite grades were irradiated with protons in the energy range of 140–180 MeV, to peak fluence of ~6.1×10 20 p/cm 2 and irradiation temperatures between 120–200 °C. The test array included POCO ZXF-5Q, Toyo-Tanso IG 430, Carbone-Lorraine 2020 and SGL R7650 grades of graphite. Irradiation was performed at the Brookhaven Linear Isotope Producer. Postirradiation analyses were performed with the objective of (a) comparing their response under the postulated irradiation conditions to guide a graphite grade selection for use asmore » a pion target and (b) understanding changes in physical and mechanical properties as well as microstructure that occurred as a result of the achieved fluence and in particular at this low-temperature regime where pion graphite targets are expected to operate. A further goal of the postirradiation evaluation was to establish a proton-neutron correlation damage on graphite that will allow for the use of a wealth of available neutron-based damage data in proton-based studies and applications. Macroscopic postirradiation analyses as well as energy dispersive x-ray diffraction of 200 KeV x rays at the NSLS synchrotron of Brookhaven National Laboratory were employed. The macroscopic analyses revealed differences in the physical and strength properties of the four grades with behavior however under proton irradiation that qualitatively agrees with that reported for graphite under neutrons for the same low temperature regime and in particular the increase of thermal expansion, strength and Young’s modulus. The proton fluence level of ~10 20 cm -2 where strength reaches a maximum before it begins to decrease at higher fluences has been identified and it agrees with neutron-induced changes. X-ray diffraction analyses of the proton irradiated graphite revealed for the first time the similarity in microstructural graphite behavior to that under neutron irradiation and the agreement between the fluence threshold of ~5×10 20 cm -2 where the graphite lattice undergoes a dramatic change. The confirmed similarity in behavior and agreement in threshold fluences for proton and neutron irradiation effects on graphite reported for the first time in this study will enable the safe utilization of the wealth of neutron irradiation data on graphite that extends to much higher fluences and different temperature regimes by the proton accelerator community searching for multi-MW graphite targets.« less

Ultrahigh-current-density metal-ion implantation and diamondlike-hydrocarbon films for tribological applications

NASA Astrophysics Data System (ADS)

Wilbur, P. J.

1993-09-01

The metal-ion-implantation system used to implant metals into substrates are described. The metal vapor required for operation is supplied by drawing sufficient electron current from the plasma discharge to an anode-potential crucible so a solid, pure metal placed in the crucible will be heated to the point of vaporization. The ion-producing, plasma discharge is initiated within a graphite-ion-source body, which operates at high temperature, by using an argon flow that is turned off once the metal vapor is present. Extraction of ion beams several cm in diameter at current densities ranging to several hundred micro-A/sq cm on a target 50 cm downstream of the ion source were demonstrated using Mg, Ag, Cr, Cu, Si, Ti, V, B, and Zr. These metals were implanted into over 100 substrates (discs, pins, flats, wires). A model describing thermal stresses induced in materials (e.g. ceramic plates) during high-current-density implantation is presented. Tribological and microstructural characteristics of iron and 304-stainless-steel samples implanted with Ti or B are examined. Diamondlike-hydrocarbon coatings were applied to steel surfaces and found to exhibit good tribological performance.

Effect of graphite target power density on tribological properties of graphite-like carbon films

NASA Astrophysics Data System (ADS)

Dong, Dan; Jiang, Bailing; Li, Hongtao; Du, Yuzhou; Yang, Chao

2018-05-01

In order to improve the tribological performance, a series of graphite-like carbon (GLC) films with different graphite target power densities were prepared by magnetron sputtering. The valence bond and microstructure of films were characterized by AFM, TEM, XPS and Raman spectra. The variation of mechanical and tribological properties with graphite target power density was analyzed. The results showed that with the increase of graphite target power density, the deposition rate and the ratio of sp2 bond increased obviously. The hardness firstly increased and then decreased with the increase of graphite target power density, whilst the friction coefficient and the specific wear rate increased slightly after a decrease with the increasing graphite target power density. The friction coefficient and the specific wear rate were the lowest when the graphite target power density was 23.3 W/cm2.

DSTO Landmine Detection Test Targets

DTIC Science & Technology

2005-06-01

cm diameter, 10 cm high. x x GS 32D50 Galvanised steel, pipe, hollow, 32 cm diameter, 50 cm long, ends capped x x GS 45D50 Galvanised Steel, pipe...hollow, 45 cm diameter, 50 cm long, ends capped x x GS 75D50 Galvanised Steel, pipe, hollow, 75 cm diameter, 50 cm long, ends capped x x

Electrochemical behaviour of vanadium(V)/vanadium(IV) redox couple at graphite electrodes

NASA Astrophysics Data System (ADS)

Zhong, S.; Skyllas-Kazacos, M.

The electrochemical behaviour of the V(V)/V(IV) couple has been studied at a graphite disc electrode in sulfuric acid using both cyclic and rotating-disc voltammetry. The results from the latter technique have revealed that the cathodic and anodic characteristics of this redox couple are quite different. The diffusion coefficient for V(IV), 2.14×10-6 cm2 s-1, is independent of the vanadium concentration. For V(IV) oxidation, the electrode kinetic parameters i0 and α have values of 2.47×10-4 A cm-2 and 0.71, respectively. The exchange current density, i0, for the V(V)/V(IV) reaction has been obtained at both graphite felt and reticulated vitreous carbon electrodes.

The solid film lubrication by carbon ion implantation into α-Al 2O 3

NASA Astrophysics Data System (ADS)

Jun, Tian; Qizu, Wang; Qunji, Xue

1998-10-01

Improvement in tribological performance by C +110 keV implantation can be achieved by having a more graphite-like carbon structure on Al 2O 3. It was shown that fracture toughness and critical peeling load increased for a fluence of 5 × 10 17C +/cm 2 because of residual compression stress and amorphism of surface. The testing in a different implantation dose indicated that the friction and wear mechanism in Optimol fretting wear machine (SRV) was a combination of surface structure and its abrasive wear. Raman shift shows that the amorphous graphite with 5 × 10 17-1 × 10 18 C +/cm 2 implantation dose was formed on Al 2O 3 surface, so that it reduced friction coefficient and wear of Al 2O 3, also it is noticed that the failure of lubrication due to graphite-like film wear is much earlier in the implantation sample with 1 × 10 17C +/cm 2 dose.

THE FIRST DISCOVERY OF PRESOLAR GRAPHITE GRAINS FROM THE HIGHLY REDUCING QINGZHEN (EH3) METEORITE

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

Xu, Yuchen; Lin, Yangting; Zhang, Jianchao

Presolar graphite grains have been extensively studied, but are limited in carbonaceous chondrites, particularly in Murchison (CM2) and Orgueil (CI1), which sampled materials from the oxidizing regions in the solar nebula. Here, we report the first discovery of presolar graphite grains from the Qingzhen (EH3) enstatite chondrite which formed under a highly reducing condition. Eighteen presolar graphite grains were identified by C-isotope mapping of the low-density fraction (1.75–1.85 g cm{sup 3}) from Qingzhen acid residue. Another 58 graphite spherules were found in different areas of the same sample mount using a scanning electron microscope and were classified into three morphologies,more » including cauliflower, onion, and cauliflower–onion. The Raman spectra of these spherules vary from ordered, disordered, and glassy to kerogen-like, suggestive of a wide range of thermal metamorphisms. NanoSIMS analysis of the C- and Si-isotopes of these graphite spherules confirmed 23 presolar grains. The other 35 graphite spherules have no significant isotopic anomalies, but they share similar morphologies and Raman spectra with the presolar ones. Another three grains were identified during NanoSIMS analysis. Of all the 44 presolar graphite grains identified, six grains show {sup 28}Si-excesses, suggestive of supernovae origins, and four grains are {sup 12}C- and {sup 29,30}Si-rich, consistent with low-metallicity asymptotic giant branch star origins. Another two graphite spherules have extremely low {sup 12}C/{sup 13}C ratios with marginal solar Si-isotopes. The morphologies, Raman spectra, and C- and Si-isotopic distributions of the presolar graphite grains from the Qingzhen enstatite chondrite are similar to those of the low-density fractions from Murchison carbonaceous chondrites. This study suggests a homogeneous distribution of presolar graphite grains in the solar nebula.« less

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.

Modifications of Graphite and Multiwall Carbon Nanotubes in the Presence of Urea

NASA Astrophysics Data System (ADS)

Duraia, El-Shazly M.; Fahami, Abbas; Beall, Gary W.

2018-02-01

The effect of high-energy ball milling on two carbon allotropes, graphite and multiwall carbon nanotubes (MWCNT) in the presence of urea has been studied. Samples were investigated using Raman spectroscopy, x-ray diffraction, scanning electron microscope (SEM) and x-ray photoelectron spectroscopy (XPS). Nitrogen-doped graphene has been successfully synthesized via a simple scalable mechanochemistry method using urea and graphite powder precursors. XPS results revealed the existence of the different nitrogen atoms configurations including pyridine, pyrrodic and graphitic N. SEM observations showed that the graphene nanosheets morphology become more wrinkles folded and crumbled as the milling time increased. The ID/IG ratio also increased as the milling time rose. The presence of both D' and G + D bands at 1621 cm-1 and 2940 cm-1, respectively, demonstrated the nitrogen incorporation in the graphene lattice Two factors contribute to the used urea: first it helps to exfoliate graphite into graphene, and second it preserves the graphitic structure from damage during the milling process as well as acting as a solid-state nitrogen source. Based on the phase analysis, the d-spacing of MWCNT samples in the presence of urea decreased due to the mechanical force in the milling process as the milling time increased. On the other hand, in the graphite case, due to its open flat surface, the graphite (002) peak shifts toward lower two theta as the milling time increase. Such findings are important and could be used for large-scale production of N-doped graphene, diminishing the use of either dangerous chemicals or sophisticated equipment.

Carbon doping in molecular beam epitaxy of GaAs from a heated graphite filament

NASA Technical Reports Server (NTRS)

Malik, R. J.; Nottenberg, R. N.; Schubert, E. F.; Walker, J. F.; Ryan, R. W.

1988-01-01

Carbon doping of GaAs grown by molecular beam epitaxy has been obtained for the first time by use of a heated graphite filament. Controlled carbon acceptor concentrations over the range of 10 to the 17th-10 to the 20th/cu cm were achieved by resistively heating a graphite filament with a direct current power supply. Capacitance-voltage, p/n junction and secondary-ion mass spectrometry measurements indicate that there is negligible diffusion of carbon during growth and with postgrowth rapid thermal annealing. Carbon was used for p-type doping in the base of Npn AlGaAs/GaAs heterojunction bipolar transistors. Current gains greater than 100 and near-ideal emitter heterojunctions were obtained in transistors with a carbon base doping of 1 x 10 to the 19th/cu cm. These preliminary results indicate that carbon doping from a solid graphite source may be an attractive substitute for beryllium, which is known to have a relatively high diffusion coefficient in GaAs.

High thermoelectric performance of graphite nanofibers.

PubMed

Tran, Van-Truong; Saint-Martin, Jérôme; Dollfus, Philippe; Volz, Sebastian

2018-02-22

Graphite nanofibers (GNFs) have been demonstrated to be a promising material for hydrogen storage and heat management in electronic devices. Here, by means of first-principles and transport simulations, we show that GNFs can also be an excellent material for thermoelectric applications thanks to the interlayer weak van der Waals interaction that induces low thermal conductance and a step-like shape in the electronic transmission with mini-gaps, which are necessary ingredients to achieve high thermoelectric performance. This study unveils that the platelet form of GNFs in which graphite layers are perpendicular to the fiber axis can exhibit outstanding thermoelectric properties with a figure of merit ZT reaching 3.55 in a 0.5 nm diameter fiber and 1.1 in a 1.1 nm diameter one. Interestingly, by introducing 14 C isotope doping, ZT can even be enhanced up to more than 5, and more than 8 if we include the effect of finite phonon mean free path, which demonstrates the amazing thermoelectric potential of GNFs.

Microstructures of Pd-containing dispersants for admixed dental amalgams.

PubMed

Chern Lin, J H; Greener, E H

1991-10-01

Blended Pd-containing dispersants were developed by the utilization of a Ag-Cu eutectic into which Pd was substituted for Ag or Cu in concentrations of up to 20 wt%. Compositions were melted either in argon-filled sealed vycor tubes or in a graphite-linked carbon crucible of an induction furnace with an argon blanket. Ingots of approximately 1.5 cm in diameter were sectioned to 0.2 cm in thickness and polished through standard metallographic polishing procedures. The possible compounds were identified by XRD. The microstructures of the alloys were examined by SEM/EDS. XRD analysis of the alloys revealed the preferential dissolution of Pd in Cu when the Pd concentration was less than or equal to 10 wt%. When the Pd concentration exceeded 20 wt%, Pd was found to be dissolved in both Ag and Pd. No Cu3Pd x-ray diffraction peaks were found for alloys with Pd concentration of up to 20 wt%. SEM/EDS analysis confirmed XRD results; lamellae of Ag and Cu-Pd were found in alloys with Pd concentration less than or equal to 10 wt%.

Safety evaluation for packaging (onsite) plutonium recycle test reactor graphite cask

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

Romano, T.

This safety evaluation for packaging (SEP) provides the evaluation necessary to demonstrate that the Plutonium Recycle Test Reactor (PRTR) Graphite Cask meets the requirements of WHC-CM-2-14, Hazardous Material Packaging and Shipping, for transfer of Type B, fissile, non-highway route controlled quantities of radioactive material within the 300 Area of the Hanford Site. The scope of this SEP includes risk, shieldling, criticality, and.tiedown analyses to demonstrate that onsite transportation safety requirements are satisfied. This SEP also establishes operational and maintenance guidelines to ensure that transport of the PRTR Graphite Cask is performed safely in accordance with WHC-CM-2-14. This SEP is validmore » until October 1, 1999. After this date, an update or upgrade to this document is required.« less

Impact of support calcination and competitive adsorbate in Fe/Mo-Al2O3 catalyst for synthesis of carbon nanotubes by V-flame

NASA Astrophysics Data System (ADS)

Sun, Ya-Ping; Sun, Bao-Min; Zhai, Gang; Guo, Yong-Hong; Jia, Xiao-Wei; Kang, Zhi-Zhong

2018-05-01

Carbon nanotubes (CNTs) were synthesized via carbon monoxide decomposition with aid of various Fe/Mo-Al2O3 catalysts by V-type flame method. The influences of support calcination and competitive adsorbates on the morphology and properties of CNTs were studied. SEM, HRTEM, TPO and Raman spectroscopy were applied to investigate the morphology and microstructure of CNT products. XRD, H2-TPR were employed to characterize catalysts. The obtained results indicate that calcinated support can increase production and promote the formation of CNTs with small diameter. Utilizing citric acid as a competitive adsorbate is successful in improving the quality of CNTs. Besides, the addition of citric acid and calcinated support in catalyst enhances the catalytic growth activity. The obtained CNTs have a diameter around 4–6 nm within a narrow diameter distribution range. Raman spectrum analysis also illustrates that highly graphitized CNTs are produced on the catalyst with calcinated support and citric acid. These results suggest that support calcination and competitive adsorbate have pronounced effect on the average diameter, diameter distribution, and graphitization of CNTs, which provides a simple and effective way to tune the properties of CNTs.

Graphite fiber intercalation: Basic properties of copper chloride intercalated fibers

NASA Technical Reports Server (NTRS)

Jaworske, D. A.; Miller, J. D.

1986-01-01

In situ resistance measurements were used to follow the intercalation of copper chloride in pitch-based fibers. Subsequent single fiber resistivity measurements reveal a large range of resistivities, from 13 to 160 micro-ohms cm. Additional density measurements reveal a bimodal distribution of mass densities. The dense fibers have lower resistivities and correspond to the stage III compound identified by X-ray diffraction. Neither resistivity nor density correlate with diameter. Both energy dispersive spectroscopy and mass density data suggest that excess chlorine resides in the intercalated fiber, resulting in a stoichiometry of C4.9n CuCl2.5 (where n is the stage number) for the denser fibers. Finally, thermogravimetric analysis shows a 33 percent loss in mass upon heating to 700C. This loss in mass is attributed to loss of both chlorine and carbon.

Experimental development of rod pinch diode radiographic source using modified KALI 1000 pulsed power system

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

Satyanarayana, N.; Basu, Shibaji; Rajawat, R.K., E-mail: satya_3026@yahoo.com

2014-07-01

This paper highlights the development of Rod Pinch (RP) diode for flash X-ray generation as intense radiographic source at BARC, Vizag. The typical RP diode employed used a small diameter (1-2 mm) anode rod extended through a cathode circular aperture (5-6 mm inner diameter). The diode chamber is maintained at 10{sup -5} Torr vacuum by a rotary backed diffusion pump. Experiments performed on a modified Kali 1000 Pulsed Power System (300 kV, 30 kA, 100 ns) were aimed at optimizing the source by maximizing the figure of merit (dose @ 1m in rad/spot diameter{sup 2} in mm{sup 2}) with minimizingmore » of the diode impedance. The typical electron beam parameters used in the experiments are 240-270 kV, 20-25 kA, 100 ns, with a few hundreds of kA/cm{sup 2} current density. The optimization resulted in a configuration with tungsten anode rod having dimensions of a 1.6 mm diameter, tapering extension length 5-25 mm beyond the graphite cathode aperture (Cathode disk ID = 5 mm, thickness = 3mm) to produce a radiation dose of 150-200 milli rad at 1 m distance having an estimated spot-size of 1-2 mm. The radiation emitted from a rod-pinch diode is measured using Thermoluminescence dosimeters (TLDs) at an angular interval of 15° on either side of the rod in horizontal and vertical plane. (author)« less

High-performance field emission device utilizing vertically aligned carbon nanotubes-based pillar architectures

NASA Astrophysics Data System (ADS)

Gupta, Bipin Kumar; Kedawat, Garima; Gangwar, Amit Kumar; Nagpal, Kanika; Kashyap, Pradeep Kumar; Srivastava, Shubhda; Singh, Satbir; Kumar, Pawan; Suryawanshi, Sachin R.; Seo, Deok Min; Tripathi, Prashant; More, Mahendra A.; Srivastava, O. N.; Hahm, Myung Gwan; Late, Dattatray J.

2018-01-01

The vertical aligned carbon nanotubes (CNTs)-based pillar architectures were created on laminated silicon oxide/silicon (SiO2/Si) wafer substrate at 775 °C by using water-assisted chemical vapor deposition under low pressure process condition. The lamination was carried out by aluminum (Al, 10.0 nm thickness) as a barrier layer and iron (Fe, 1.5 nm thickness) as a catalyst precursor layer sequentially on a silicon wafer substrate. Scanning electron microscope (SEM) images show that synthesized CNTs are vertically aligned and uniformly distributed with a high density. The CNTs have approximately 2-30 walls with an inner diameter of 3-8 nm. Raman spectrum analysis shows G-band at 1580 cm-1 and D-band at 1340 cm-1. The G-band is higher than D-band, which indicates that CNTs are highly graphitized. The field emission analysis of the CNTs revealed high field emission current density (4mA/cm2 at 1.2V/μm), low turn-on field (0.6 V/μm) and field enhancement factor (6917) with better stability and longer lifetime. Emitter morphology resulting in improved promising field emission performances, which is a crucial factor for the fabrication of pillared shaped vertical aligned CNTs bundles as practical electron sources.

Method of making a sodium sulfur battery

DOEpatents

Elkins, Perry E.

1981-01-01

A method of making a portion of a sodium sulfur battery is disclosed. The battery portion made is a portion of the container which defines the volume for the cathodic reactant materials which are sulfur and sodium polysulfide materials. The container portion is defined by an outer metal casing with a graphite liner contained therein, the graphite liner having a coating on its internal diameter for sealing off the porosity thereof. The steel outer container and graphite pipe are united by a method which insures that at the operating temperature of the battery, relatively low electrical resistance exists between the two materials because they are in intimate contact with one another.

Graphite to Graphene via Graphene Oxide: An Overview on Synthesis, Properties, and Applications

NASA Astrophysics Data System (ADS)

Hansora, D. P.; Shimpi, N. G.; Mishra, S.

2015-12-01

This work represents a state-of-the-art technique developed for the preparation of graphene from graphite-metal electrodes by the arc-discharge method carried out in a continuous flow of water. Because of continuous arcing of graphite-metal electrodes, the graphene sheets were observed in water with uniformity and little damage. These nanosheets were subjected to various purification steps such as acid treatment, oxidation, water washing, centrifugation, and drying. The pure graphene sheets were analyzed using Raman spectrophotometry, x-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), and tunneling electron microscopy (TEM). Peaks of Raman spectra were recorded at (1300-1400 cm-1) and (1500-1600 cm-1) for weak D-band and strong G-band, respectively. The XRD pattern showed 85.6% crystallinity of pure graphite, whereas pure graphene was 66.4% crystalline. TEM and FE-SEM micrographs revealed that graphene sheets were overlapped to each other and layer-by-layer formation was also observed. Beside this research work, we also reviewed recent developments of graphene and related nanomaterials along with their preparations, properties, functionalizations, and potential applications.

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

Mallow, Anne M; Abdelaziz, Omar; Graham, Samuel

The thermal charging performance of phase change materials, specifically paraffin wax, combined with compressed expanded natural graphite foam is studied under constant heat flux and constant temperature conditions. By varying the heat flux between 0.39 W/cm2 and 1.55 W/cm2 or maintaining a boundary temperature of 60 C for four graphite foam bulk densities, the impact on the rate of thermal energy storage is discussed. Thermal charging experiments indicate that thermal conductivity of the composite is an insufficient metric to compare the influence of graphite foam on the rate of thermal energy storage of the PCM composite. By dividing the latentmore » heat of the composite by the time to melt for various boundary conditions and graphite foam bulk densities, it is determined that bulk density selection is dependent on the applied boundary condition. A greater bulk density is advantageous for samples exposed to a constant temperature near the melting temperature as compared to constant heat flux conditions where a lower bulk density is adequate. Furthermore, the anisotropic nature of graphite foam bulk densities greater than 50 kg/m3 is shown to have an insignificant impact on the rate of thermal charging. These experimental results are used to validate a computational model for future use in the design of thermal batteries for waste heat recovery.« less

State-of-the-Art Technologies for Construction in Space: a Review.

DTIC Science & Technology

1987-09-01

reinforcing fiber or fiber mat. Investigations of bonding, thermal stress, forming tech- niques, specific strengths, specific moduli, and microfracture...diameter and about 15 ft long. The graphite fibers follow the length of the tube and the polymer compound used as the matrix is applied over the graphite...combination of Sthese approaches to obtain the best simulation of the low-Earth orbit environment. Most materials tested to date are polymers such as

Plasma Modification of Graphite Fibers and Its Effect on Composite Properties.

DTIC Science & Technology

1983-08-01

liquids have been difficult to measure with adequate accuracy. As a result, critical surface energy data are not readily available. A flotation method...tension of the fiber surface. However, the fiber density must always exceed the density of the flotation liquid. Although this is a very useful...technioue, it is inanplicable to graphite fiber due to its irregular surface structure, small filament diameter and small difference in density with flotation

Ion sputter textured graphite electrode plates

NASA Technical Reports Server (NTRS)

Curren, A. N.; Forman, R.; Sovey, J. S.; Wintucky, E. G. (Inventor)

1983-01-01

A specially textured surface of pyrolytic graphite exhibits extremely low yields of secondary electrons and reduced numbers of reflected primary electrons after impingement of high energy primary electrons. Electrode plates of this material are used in multistage depressed collectors. An ion flux having an energy between 500 iV and 1000 iV and a current density between 1.0 mA/sq cm and 6.0 mA/sq cm produces surface roughening or texturing which is in the form of needles or spires. Such textured surfaces are especially useful as anode collector plates in high tube devices.

NanoSIMS Determination of Carbon and Oxygen Isotopic Compositions of Presolar Graphites from the Murchison Meteorite

NASA Technical Reports Server (NTRS)

Stadermann, F. J.; Croat, T. K.; Bernatowicz, T.

2004-01-01

Graphite from the Murchison density separate KFC1 (2.15 - 2.20 g/cu cm) has previously been studied by combined SEM/EDX and ion microprobe analysis. These studies found several distinct morphological types of graphites and C isotopic compositions that vary over more than 3 orders of magnitude, clearly establishing their presolar origin. Subsequent TEM measurements of a subset of these particles found abundant embedded crystals of metal (Zr, Mo, Ti, Ru) carbides which were incorporated during the growth of the graphites. A new TEM study of a large set of KFC1 graphites led to the discovery of another type of presolar material, Ru-Fe metal. Here we report results of the C and O isotopic measurements in the same graphite sections, which makes it possible for the first time to directly correlate isotopic and TEM data of KFC1 grains.

EFFECT OF MASSIVE NEUTRON EXPOSURE ON THE DISTORTION OF REACTOR GRAPHITE

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

Helm, J.W.; Davidson, J.M.

1963-05-28

Distortion of reactor-grade graphites was studied at varying neutron exposures ranging up to 14 x 10/sup 21/ neutrons per cm/sup 2/ (nvt)/sup */ at temperatures of irradiation ranging from 425 to 800 deg C. This exposure level corresponds to approximately 100,000 megawatt days per adjacent ton of fuel (Mwd/ At) in a graphite-moderated reactor. A conventionalcoke graphite, CSF, and two needle-coke graphites, NC-7 and NC-8, were studied. At all temperatures of irradiation the contraction rate of the samples cut parallel to the extrusion axis increased with increasing neutron exposure. For parallel samples the needle- coke graphites and the CSF graphitemore » contracted approximately the same amount. In the transverse direction the rate of cortraction at the higher irradiation temperntures appeared to be decreasing. Volume contractions derived from the linear contractions are discussed. (auth)« less

Effect of Graphite Concentration on Shear-Wave Speed in Gelatin-Based Tissue-Mimicking Phantoms

PubMed Central

Anderson, Pamela G.; Rouze, Ned C.; Palmeri, Mark L.

2011-01-01

Elasticity-based imaging modalities are becoming popular diagnostic tools in clinical practice. Gelatin-based, tissue mimicking phantoms that contain graphite as the acoustic scattering material are commonly used in testing and validating elasticity-imaging methods to quantify tissue stiffness. The gelatin bloom strength and concentration are used to control phantom stiffness. While it is known that graphite concentration can be modulated to control acoustic attenuation, the impact of graphite concentrationon phantom elasticity has not been characterized in these gelatin phantoms. This work investigates the impact of graphite concentration on phantom shear stiffness as characterized by shear-wave speed measurements using impulsive acoustic-radiation-force excitations. Phantom shear-wave speed increased by 0.83 (m/s)/(dB/(cm MHz)) when increasing the attenuation coefficient slope of the phantom material through increasing graphite concentration. Therefore, gelatin-phantom stiffness can be affected by the conventional ways that attenuation is modulated through graphite concentration in these phantoms. PMID:21710828

New insight into UO 2F 2 particulate structure by micro-Raman spectroscopy

DOE PAGES

Stefaniak, Elzbieta A.; Darchuk, Larysa; Sapundjiev, Danislav; ...

2013-02-19

Uranyl fluoride particles produced via hydrolysis of uranium hexafluoride have been deposited on different substrates: polished graphite disks, silver foil, stainless steel and gold-coated silicon wafer, and measured with micro-Raman spectroscopy (MRS). All three metallic substrates enhanced the Raman signal delivered by UO 2F 2 in comparison to graphite. The fundamental stretching of the U–O band appeared at 867 cm –1 in case of the graphite substrate, while in case of the others it was shifted to lower frequencies (down to 839 cm –1). All applied metallic substrates showed the expected effect of Raman signal enhancement; however the gold layermore » appeared to be most effective. Lastly, application of new substrates provides more information on the molecular structure of uranyl fluoride precipitation, which is interesting for nuclear safeguards and nuclear environmental analysis.« less

The effect of mechanical stress on electric resistance of nanographite-epoxy composites

NASA Astrophysics Data System (ADS)

Vovchenko, L.; Lazarenko, A.; Matzui, L.; Zhuravkov, A.

2012-03-01

The in-plane electric resistance Ra of composite materials (CMs) thermoexfoliated graphite(TEG)-epoxy resin(ED) under compression along compacting C-axis has been investigated by four-probe method. TEG content was 5-75 wt%. It was shown that specimens prepared by cold pressing are denser and reveal lower values of electric resistivity in comparison with specimens prepared by pouring. It was found that compression of the specimens leads to plastic deformation of specimens (εpl) and essential irreversible decrease of electric resistance during the first cycle of loading (up to 50 MPa), especially for the poured specimens with low density. Within the proposed model the contact resistance Rk between graphite particles in CM has been evaluated and it was shown that it increased with the decrease in TEG content in CM and depends on compacting method of CMs and the dispersity of graphite filler.

Weight and volume equations and tables for six upland hardwoods in southern Illinois.

Treesearch

David J. Polak; Donald Raisanen; Richard C. Schlesinger; Les Stortz

1980-01-01

This paper presents tables of total tree green weight, green weight to a 5 cm and a 10 cm top diameter, dry weight to both 5 cm and 10 cm top diameter, and green volume to a 5 cm and 10 cm top diameter for six upland hardwood species. Both metric and English unit tables are included.

Raman studies of single-walled carbon nanotubes synthesized by pulsed laser ablation at room temperature

NASA Astrophysics Data System (ADS)

Dixit, Saurabh; Shukla, A. K.

2018-06-01

In this article, single-walled carbon nanotubes (SWCNTs) are synthesized at room temperature using pulsed laser ablation of ferrocene mixed graphitic target. Radial breathing mode (RBM) reveals the presence of semiconducting SWCNTs of multiple diameters. Quantum confinement model is developed for Raman line-shape of G - feature. It is invoked here that G-feature is the manifestation of TO phonons in the semiconducting SWCNTs. Disorder in the SWCNTs is studied here as a function of the concentration of ferrocene in the graphitic target using X-ray diffraction analysis, oscillator strength of G - feature and D mode and Raman line-shape model of G - feature. Furthermore, phonon softening of G - feature of semiconducting SWCNTs is observed as a function of the diameter of nanotube.

SU-F-T-461: Dosimetric Evaluation of Indigenous Farmer Type Chamber FAR65- GB for Reference Dosimetry of FFF MV Photon Beam

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

Patwe, P; Mhatre, V; Dandekar, P

Purpose: Indigenous Farmer type chamber FAR 65 GB is a reference class 0.6 cc ion chamber. It can be used for dosimetric evaluation of photon and high energy electron beams. We studied dosimetric characteristics of the chamber for 6MV and 10MV Flattening filter free FFF photon beams available on trueBEAM STx Linac. Methods: The study was carried out on trueBEAM STx Linac having 6 and 10 MV FFF photon beam with maximum dose rate 1400 and 2400 MU per min respectively. The dosimetric device to be evaluated is Rosalina Instruments FAR 65-GB Ion Chamber with active volume 0.65 cc, totalmore » active length 23.1cm, inner diameter of cylinder 6.2mm, wall thickness 0.4mm, inner electrode diameter 1mm. Inner and outer electrodes are made from Aluminium 2.7 gm per cc and graphite 1.82 gm per cc respectively. The ion chamber was placed along central axis of beam at 10cm depth and irradiated for 10cm × 10cm field size at SAD of 100 cm in plastic phantom. We studied Precision, Dose Linearity, Dose Rate dependence, directional dependence, Recombination effect. Recombination effect was determined using standard two-voltage method. Results: 1. Measurements were reproducible std deviation of 0.0105 and type A uncertainty 0.003265 under same set of reference conditions 2. Chamber exhibit dose linearity over a wider dose range. 3. Chamber shows dose rate independence for all available dose rate range. 4. Response of chamber with the angle of incidence of radiation is constant. 5. Recombination correction factors were 1.01848 and 1.02537 for dose rate 1400 and 2400 MU per min resp. Conclusion: Our study reveals that the chamber is prone to saturation effect at dose rate of 2400 MU per min. FAR 65-GB can be used for reference dosimetry of FFF MV photon beam with proper calculation of recombination effect.« less

LSSA large area silicon sheet task continuous Czochralski process development

NASA Technical Reports Server (NTRS)

Rea, S. N.

1978-01-01

A Czochralski crystal growing furnace was converted to a continuous growth facility by installation of a premelter to provide molten silicon flow into the primary crucible. The basic furnace is operational and several trial crystals were grown in the batch mode. Numerous premelter configurations were tested both in laboratory-scale equipment as well as in the actual furnace. The best arrangement tested to date is a vertical, cylindrical graphite heater containing small fused silicon test tube liner in which the incoming silicon is melted and flows into the primary crucible. Economic modeling of the continuous Czochralski process indicates that for 10 cm diameter crystal, 100 kg furnace runs of four or five crystals each are near-optimal. Costs tend to asymptote at the 100 kg level so little additional cost improvement occurs at larger runs. For these conditions, crystal cost in equivalent wafer area of around $20/sq m exclusive of polysilicon and slicing was obtained.

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

NASA Technical Reports Server (NTRS)

Hung, C. C.

1985-01-01

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

A new oxidation based technique for artifact free TEM specimen preparation of nuclear graphite

NASA Astrophysics Data System (ADS)

Johns, Steve; Shin, Wontak; Kane, Joshua J.; Windes, William E.; Ubic, Rick; Karthik, Chinnathambi

2018-07-01

Graphite is a key component in designs of current and future nuclear reactors whose in-service lifetimes are dependent upon the mechanical performance of the graphite. Irradiation damage from fast neutrons creates lattice defects which have a dynamic effect on the microstructure and mechanical properties of graphite. Transmission electron microscopy (TEM) can offer real-time monitoring of the dynamic atomic-level response of graphite subjected to irradiation; however, conventional TEM specimen-preparation techniques, such as argon ion milling itself, damage the graphite specimen and introduce lattice defects. It is impossible to distinguish these defects from the ones created by electron or neutron irradiation. To ensure that TEM specimens are artifact-free, a new oxidation-based technique has been developed. Bulk nuclear grades of graphite (IG-110 and NBG-18) and highly oriented pyrolytic graphite (HOPG) were initially mechanically thinned to ∼60 μm. Discs 3 mm in diameter were then oxidized at temperatures between 575 °C and 625 °C in oxidizing gasses using a new jet-polisher-like set-up in order to achieve optimal oxidation conditions to create self-supporting electron-transparent TEM specimens. The quality of these oxidized specimens were established using optical and electron microscopy. Samples oxidized at 575 °C exhibited large areas of electron transparency and the corresponding lattice imaging showed no apparent damage to the graphite lattice.

A new oxidation based technique for artifact free TEM specimen preparation of nuclear graphite

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

Johns, Steve; Shin, Wontak; Kane, Joshua J.

Graphite is a key component in designs of current and future nuclear reactors whose in-service lifetimes are dependent upon the mechanical performance of the graphite. Irradiation damage from fast neutrons creates lattice defects which have a dynamic effect on the microstructure and mechanical properties of graphite. Transmission electron microscopy (TEM) can offer real-time monitoring of the dynamic atomic-level response of graphite subjected to irradiation; however, conventional TEM specimen-preparation techniques, such as argon ion milling itself, damage the graphite specimen and introduce lattice defects. It is impossible to distinguish these defects from the ones created by electron or neutron irradiation. Thus,tomore » ensure that TEM specimens are artifact-free, a new oxidation-based technique has been developed. Bulk nuclear grades of graphite (IG-110 and NBG-18) and highly oriented pyrolytic graphite (HOPG) were initially mechanically thinned to ~60μm. Discs 3mm in diameter were then oxidized at temperatures between 575°C and 625°C in oxidizing gasses using a new jet-polisher-like set-up in order to achieve optimal oxidation conditions to create self-supporting electron-transparent TEM specimens. The quality of these oxidized specimens were established using optical and electron microscopy. Samples oxidized at 575°C exhibited large areas of electron transparency and the corresponding lattice imaging showed no apparent damage to the graphite lattice.« less

A new oxidation based technique for artifact free TEM specimen preparation of nuclear graphite

DOE PAGES

Johns, Steve; Shin, Wontak; Kane, Joshua J.; ...

2018-04-03

Graphite is a key component in designs of current and future nuclear reactors whose in-service lifetimes are dependent upon the mechanical performance of the graphite. Irradiation damage from fast neutrons creates lattice defects which have a dynamic effect on the microstructure and mechanical properties of graphite. Transmission electron microscopy (TEM) can offer real-time monitoring of the dynamic atomic-level response of graphite subjected to irradiation; however, conventional TEM specimen-preparation techniques, such as argon ion milling itself, damage the graphite specimen and introduce lattice defects. It is impossible to distinguish these defects from the ones created by electron or neutron irradiation. Thus,tomore » ensure that TEM specimens are artifact-free, a new oxidation-based technique has been developed. Bulk nuclear grades of graphite (IG-110 and NBG-18) and highly oriented pyrolytic graphite (HOPG) were initially mechanically thinned to ~60μm. Discs 3mm in diameter were then oxidized at temperatures between 575°C and 625°C in oxidizing gasses using a new jet-polisher-like set-up in order to achieve optimal oxidation conditions to create self-supporting electron-transparent TEM specimens. The quality of these oxidized specimens were established using optical and electron microscopy. Samples oxidized at 575°C exhibited large areas of electron transparency and the corresponding lattice imaging showed no apparent damage to the graphite lattice.« less

Chemical Characterization and Removal of Carbon-14 from Irradiated Graphite II - 13023

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

Dunzik-Gougar, Mary Lou; Cleaver, James; LaBrier, Daniel

2013-07-01

Approximately 250,000 tonnes of irradiated graphite waste exists worldwide and that quantity is expected to increase with decommissioning of Generation II reactors and deployment of Generation IV gas-cooled, graphite moderated reactors. This situation indicates the need for a graphite waste management strategy. Of greatest concern for long-term disposal of irradiated graphite is carbon-14 (C-14), with a half-life of 5730 years. Study of irradiated graphite from some nuclear reactors indicates C-14 is concentrated on the outer 5 mm of the graphite structure. The aim of the research presented last year and updated here is to identify the chemical form of C-14more » in irradiated graphite and develop a practical method by which C-14 can be removed. A nuclear-grade graphite, NBG-18, and a high-surface-area graphite foam, POCOFoam{sup R}, were exposed to liquid nitrogen (to increase the quantity of C-14 precursor) and neutron-irradiated (10{sup 13} neutrons/cm{sup 2}/s). Finer grained NBG-25 was not exposed to liquid nitrogen prior to irradiation at a neutron flux on the order of 10{sup 14} /cm{sup 2}/s. Characterization of pre- and post-irradiation graphite was conducted to determine the chemical environment and quantity of C-14 and its precursors via the use of surface sensitive characterization techniques. Scanning Electron Microscopy (SEM) was used to evaluate the morphological features of graphite samples. The concentration, chemical composition, and bonding characteristics of C-14 and its precursors were determined through X-ray Photoelectron Spectroscopy (XPS), Time-of-Flight Secondary Ion Mass Spectrometry (SIMS), and Energy Dispersive X-ray Analysis Spectroscopy (EDX). Results of post-irradiation characterization of these materials indicate a variety of surface functional groups containing carbon, oxygen, nitrogen and hydrogen. During thermal treatment, irradiated graphite samples are heated in the presence of an inert carrier gas (with or without oxidant gas), which carries off gaseous products released during treatment. Graphite gasification occurs via interaction with adsorbed oxygen complexes. Experiments in argon were performed at 900 deg. C and 1400 deg. C to evaluate the selective removal of C-14. Thermal treatment also was performed with the addition of 3 and 5 volume % oxygen at temperatures 700 deg. C and 1400 deg. C. Thermal treatment experiments were evaluated for the effective selective removal of C-14. Lower temperatures and oxygen levels correlated to more efficient C-14 removal. (authors)« less

Mesocarbon microbead based graphite for spherical fuel element to inhibit the infiltration of liquid fluoride salt in molten salt reactor

NASA Astrophysics Data System (ADS)

Zhong, Yajuan; Zhang, Junpeng; Lin, Jun; Xu, Liujun; Zhang, Feng; Xu, Hongxia; Chen, Yu; Jiang, Haitao; Li, Ziwei; Zhu, Zhiyong; Guo, Quangui

2017-07-01

Mesocarbon microbeads (MCMB) and quasi-isostatic pressing method were used to prepare MCMB based graphite (MG) for spherical fuel element to inhibit the infiltration of liquid fluoride salt in molten salt reactor (MSR). Characteristics of mercury infiltration and molten salt infiltration in MG were investigated and compared with A3-3 (graphite for spherical fuel element in high temperature gas cooled reactor) to identify the infiltration behaviors. The results indicated that MG had a low porosity about 14%, and an average pore diameter of 96 nm. Fluoride salt occupation of A3-3 (average pore diameter was 760 nm) was 10 wt% under 6.5 atm, whereas salt gain did not infiltrate in MG even up to 6.5 atm. It demonstrated that MG could inhibit the infiltration of liquid fluoride salt effectively. Coefficient of thermal expansion (CTE) of MG lies in 6.01 × 10-6 K-1 (α∥) and 6.15 × 10-6 K-1 (α⊥) at the temperature range of 25-700 °C. The anisotropy factor of MG calculated by CTE maintained below 1.02, which could meet the requirement of the spherical fuel element (below 1.30). The constant isotropic property of MG is beneficial for the integrity and safety of the graphite used in the spherical fuel element for a MSR.

A new family of carbon materials with exceptional mechanical properties

NASA Astrophysics Data System (ADS)

Ran, Jiajia; Lin, Kunpeng; Yang, Haotian; Li, Jianlin; Wang, Lianjun; Jiang, Wan

2018-03-01

A new family of carbon materials with ultrahigh-strength and nano-onion grains has been successfully produced from nano-diamond particles by spark plasma sintering. It is believed that the spark plasma and applied pressure help overcome the difficulties in densification. Also diamond has a much greater density than that of graphite, leading to the volume expansion when nano-diamond particles transform to graphite onions during heating, facilitating the consolidation. The as-prepared bulk graphite with a density of 1.84 g/cm3 has ultrahigh bending strength, modulus and microhardness, 150 MPa, 31.3 GPa and 2.6 GPa, respectively, due to the unique microstructure of nano-graphite onions.

Method of making a sodium sulfur battery

DOEpatents

Elkins, P. E.

1981-09-22

A method of making a portion of a sodium sulfur battery is disclosed. The battery portion made is a portion of the container which defines the volume for the cathodic reactant materials which are sulfur and sodium polysulfide materials. The container portion is defined by an outer metal casing with a graphite liner contained therein, the graphite liner having a coating on its internal diameter for sealing off the porosity thereof. The steel outer container and graphite pipe are united by a method which insures that at the operating temperature of the battery, relatively low electrical resistance exists between the two materials because they are in intimate contact with one another. 3 figs.

The Characterization of Grade PCEA Recycle Graphite Pilot Scale Billets

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

Burchell, Timothy D; Pappano, Peter J

2010-10-01

Here we report the physical properties of a series specimens machined from pilot scale (~ 152 mm diameter x ~305 mm length) grade PCEA recycle billets manufactured by GrafTech. The pilot scale billets were processed with increasing amounts of (unirradiated) graphite (from 20% to 100%) introduced to the formulation with the goal of determining if large fractions of recycle graphite have a deleterious effect on properties. The properties determined include Bulk Density, Electrical Resistivity, Elastic (Young s) Modulus, and Coefficient of Thermal Expansion. Although property variations were observed to be correlated with the recycle fraction, the magnitude of the variationsmore » was noted to be small.« less

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

Ganesh, Panchapakesan; Kent, Paul R; Mochalin, Vadym N

We simulate the experimentally observed graphitization of nanodiamonds into multi-shell onion-like carbon nanostructures, also called carbon onions, at different temperatures, using reactive force fields. The simulations include long-range Coulomb and van der Waals interactions. Our results suggest that long-range interactions play a crucial role in the phase-stability and the graphitization process. Graphitization is both enthalpically and entropically driven and can hence be controlled with temperature. The outer layers of the nanodiamond have a lower kinetic barrier toward graphitization irrespective of the size of the nanodiamond and graphitize within a few-hundred picoseconds, with a large volume increase. The inner core ofmore » the nanodiamonds displays a large size-dependent kinetic barrier, and graphitizes much more slowly with abrupt jumps in the internal energy. It eventually graphitizes by releasing pressure and expands once the outer shells have graphitized. The degree of transformation at a particular temperature is thereby determined by a delicate balance between the thermal energy, long-range interactions, and the entropic/enthalpic free energy gained by graphitization. Upon full graphitization, a multi-shell carbon nanostructure appears, with a shell-shell spacing of about {approx}3.4 {angstrom} for all sizes. The shells are highly defective with predominantly five- and seven-membered rings to curve space. Larger nanodiamonds with a diameter of 4 nm can graphitize into spiral structures with a large ({approx}29-atom carbon ring) pore opening on the outermost shell. Such a large one-way channel is most attractive for a controlled insertion of molecules/ions such as Li ions, water, or ionic liquids, for increased electrochemical capacitor or battery electrode applications.« less

Structural transitions in electron beam deposited Co-carbonyl suspended nanowires at high electrical current densities.

PubMed

Gazzadi, Gian Carlo; Frabboni, Stefano

2015-01-01

Suspended nanowires (SNWs) have been deposited from Co-carbonyl precursor (Co2(CO)8) by focused electron beam induced deposition (FEBID). The SNWs dimensions are about 30-50 nm in diameter and 600-850 nm in length. The as-deposited material has a nanogranular structure of mixed face-centered cubic (FCC) and hexagonal close-packed (HCP) Co phases, and a composition of 80 atom % Co, 15 atom % O and 5 atom % C, as revealed by transmission electron microscopy (TEM) analysis and by energy-dispersive X-ray (EDX) spectroscopy, respectively. Current (I)-voltage (V) measurements with current densities up to 10(7) A/cm(2) determine different structural transitions in the SNWs, depending on the I-V history. A single measurement with a sudden current burst leads to a polycrystalline FCC Co structure extended over the whole wire. Repeated measurements at increasing currents produce wires with a split structure: one half is polycrystalline FCC Co and the other half is graphitized C. The breakdown current density is found at 2.1 × 10(7) A/cm(2). The role played by resistive heating and electromigration in these transitions is discussed.

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)

Fuel cell cooler assembly and edge seal means therefor

DOEpatents

Breault, Richard D.; Roethlein, Richard J.; Congdon, Joseph V.

1980-01-01

A cooler assembly for a stack of fuel cells comprises a fibrous, porous coolant tube holder sandwiched between and bonded to at least one of a pair of gas impervious graphite plates. The tubes are disposed in channels which pass through the holder. The channels are as deep as the holder thickness, which is substantially the same as the outer diameter of the tubes. Gas seals along the edges of the holder parallel to the direction of the channels are gas impervious graphite strips.

A comparative study of graphene and graphite-based field effect transistor on flexible substrate

NASA Astrophysics Data System (ADS)

Bhatt, Kapil; Rani, Cheenu; Vaid, Monika; Kapoor, Ankit; Kumar, Pramod; Kumar, Sandeep; Shriwastawa, Shilpi; Sharma, Sandeep; Singh, Randhir; Tripathi, C. C.

2018-06-01

In the present era, there has been a great demand of cost-effective, biodegradable, flexible and wearable electronics which may open the gate to many applications like flexible displays, RFID tags, health monitoring devices, etc. Due to the versatile nature of plastic substrates, they have been extensively used in packaging, printing, etc. However, the fabrication of electronic devices requires specially prepared substrates with high quality surfaces, chemical compositions and solutions to the related fabrication issues along with its non-biodegradable nature. Therefore, in this report, a cost-effective, biodegradable cellulose paper as an alternative dielectric substrate material for the fabrication of flexible field effect transistor (FET) is presented. The graphite and liquid phase exfoliated graphene have been used as the material for the realisation of source, drain and channel on cellulose paper substrate for its comparative analysis. The mobility of fabricated FETs was calculated to be 83 cm2/V s (holes) and 33 cm2/V s (electrons) for graphite FET and 100 cm2/V s (holes) and 52 cm2/V s (electrons) for graphene FET, respectively. The output characteristic of the device demonstrates the linear behaviour and a comprehensive increase in conductance as a function of gate voltages. The fabricated FETs may be used for strain sensing, health care monitoring devices, human motion detection, etc.

Genetic significance of the 867 cm- 1 out-of-plane Raman mode in graphite associated with V-bearing green grossular

NASA Astrophysics Data System (ADS)

Thomas, Rainer; Rericha, Adolf; Pohl, Walter L.; Davidson, Paul

2018-03-01

SE Kenya is the world's largest producer of green vanadium grossular gemstones (tsavorite). Samples from one of the mines near Mwatate, and of occurrences in Tanzania yielded remarkable new insights into the genesis of tsavorite. Graphite is intimately associated with V-grossular and is one of the keys to understanding its origin. In the course of this study we found five different types of graphite. Surprisingly, in one graphite type the "Raman-forbidden" and IR-active 867 cm- 1 band was observed. In this communication, we attempt to find an explanation for this unusual phenomenon. Additionally, our observations also address some of the issues pertaining to the origin of the green grossular-dominated rocks (grossularites), as well as the gem quality tsavorite crystals, since we propose that the anomalous spectroscopic behavior of the graphite is related to the unusual conditions during crystallization of both the grossular and graphite from a near-supercritical volatile- and sulfur-rich silicate melt. The massive green vanadium grossular contains abundant unequivocal crystallized melt inclusions, while the transparent gem quality grossular (tsavorite) displays only fluid inclusions. On the basis of inclusion studies we suggest that anatectic melts originated in the peculiar evaporitic host lithology of the tsavorite deposits. Near peak metamorphic temperatures ( 700 °C) these liquids occurred as a supercritical volatile-rich "fluid/melt phase" characterized by complete miscibility between H2O and silicate liquid. Relatively dry liquid batches precipitated non-transparent green grossular, whereas wet batches segregated fluids that formed transparent tsavorite.

Electrochemical treatment of evaporated residue of soak liquor generated from leather industry.

PubMed

Boopathy, R; Sekaran, G

2013-09-15

The organic and suspended solids present in soak liquor, generated from leather industry, demands treatment. The soak liquor is being segregated and evaporated in solar evaporation pans/multiple effect evaporator due to non availability of viable technology for its treatment. The residue left behind in the pans/evaporator does not carry any reuse value and also faces disposal threat due to the presence of high concentration of sodium chloride, organic and bacterial impurities. In the present investigation, the aqueous evaporated residue of soak liquor (ERSL) was treated by electrochemical oxidation. Graphite/graphite and SS304/graphite systems were used in electrochemical oxidation of organics in ERSL. Among these, graphite/graphite system was found to be effective over SS304/graphite system. Hence, the optimised conditions for the electrochemical oxidation of organics in ERSL using graphite/graphite system was evaluated by response surface methodology (RSM). The mass transport coefficient (km) was calculated based on pseudo-first order rate kinetics for both the electrode systems (graphite/graphite and SS304/graphite). The thermodynamic properties illustrated the electrochemical oxidation was exothermic and non-spontaneous in nature. The calculated specific energy consumption at the optimum current density of 50 mA cm(-2) was 0.41 kWh m(-3) for the removal of COD and 2.57 kWh m(-3) for the removal of TKN. Copyright © 2013 Elsevier B.V. All rights reserved.

KSC-08pd3866

NASA Image and Video Library

2008-11-07

CAPE CANAVERAL, Fla. -- In Building 1555 at Vandenberg Air Force Base in California, ssembly is underway for the Taurus XL rocket that will launch NASA's Orbiting Carbon Observatory, or OCO, spacecraft. Lined up left to right are the Stage 1 and Stage 2 motors, the boattail, the avionics shelf and the Stage 3 motor. The graphite/epoxy boattail structure provides the transition from the smaller diameter of the Stage 2 motor to the larger diameter of the avionics skirt. The avionics skirt, also a graphite/epoxy structure, supports the avionics shelf and carries the primary structural loads from the fairing and payload cone. The aluminum avionics shelf supports the third stage avionics. The OCO is a new Earth-orbiting mission sponsored by NASA's Earth System Science Pathfinder Program. The launch of OCO is targeted for January. Photo credit: NASA/Randy Beaudoin, VAFB

Buckling test of a 3-meter-diameter corrugated graphite-epoxy ring-stiffened cylinder

NASA Technical Reports Server (NTRS)

Davis, R. C.

1982-01-01

A three m diameter by three m long corrugated cylindrical shell with external stiffening rings was tested to failure by buckling. The corrugation geometry for the graphite epoxy composite cylinder wall was optimized to withstand a compressive load producing an ultimate load intensity of 157.6 kN/m without buckling. The test method used to produce the design load intensity was to mount the specimen as a cantilevered cylinder and apply a pure bending moment to the end. A load introduction problem with the specimen was solved by using the BOSOR 4 shell of revolution computer code to analyze the shell and attached loading fixtures. The cylinder test loading achieved was 101 percent of design ultimate, and the resulting mass per unit of shell wall area was 1.96 kg/sq m.

Simulated impact damage in a thick graphite/epoxy laminate using spherical indenters

NASA Technical Reports Server (NTRS)

Poe, C. C., Jr.

1988-01-01

A study was made to determine the extent of fiber damage caused by low-velocity impact of spherical impactors to a very thick graphite/epoxy laminate. The laminate was cut from a filament wound case being developed for the Space Shuttle solid rocket motors. The case was wound using a wet process with AS4W graphite fiber and HBRF-55A epoxy. Impacts were simulated under quasi-static conditions by pressing hemispherically shaped indenters against the laminate at different locations. The contact force and indenter diameter were varied from location to location. The forces were chosen for each indenter diameter to produce contact pressures below and above that required to initiate damage. After the forces were applied, the laminate was cut into smaller pieces so that each piece contained a test site. The pieces were then deplied and the individual plies examined to determine the extent of fiber damage. Broken fibers were found in the outer layers directly beneath the contact site. The locus of broken fibers in each layer resembled a crack normal to the direction of the fibers. The maximum length and depth of the cracks increased with increasing contact pressure and indenter diameter. The internal stresses in the laminate were calculated using Hertz's law and Love's solution for pressure applied on part of the boundary of a semi-infinite body. The maximum length and depth of the cracks were predicted using a maximum shear stress criterion. Predictions and measurements were in good agreement.

Ultrahigh Surface Area Three-Dimensional Porous Graphitic Carbon from Conjugated Polymeric Molecular Framework

DOE PAGES

To, John W. F.; Chen, Zheng; Yao, Hongbin; ...

2015-05-18

Porous graphitic carbon is essential for many applications such as energy storage devices, catalysts, and sorbents. However, current graphitic carbons are limited by low conductivity, low surface area, and ineffective pore structure. Here we report a scalable synthesis of porous graphitic carbons using a conjugated polymeric molecular framework as precursor. The multivalent cross-linker and rigid conjugated framework help to maintain micro- and mesoporous structures, while promoting graphitization during carbonization and chemical activation. The above unique design results in a class of highly graphitic carbons at temperature as low as 800 °C with record-high surface area (4073 m 2 g –1),more » large pore volume (2.26 cm –3), and hierarchical pore architecture. Such carbons simultaneously exhibit electrical conductivity >3 times more than activated carbons, very high electrochemical activity at high mass loading, and high stability, as demonstrated by supercapacitors and lithium–sulfur batteries with excellent performance. Moreover, the synthesis can be readily tuned to make a broad range of graphitic carbons with desired structures and compositions for many applications.« less

Performance of 10-kW class xenon ion thrusters

NASA Technical Reports Server (NTRS)

Patterson, Michael J.; Rawlin, Vincent K.

1988-01-01

Presented are performance data for laboratory and engineering model 30 cm-diameter ion thrusters operated with xenon propellant over a range of input power levels from approximately 2 to 20 kW. Also presented are preliminary performance results obtained from laboratory model 50 cm-diameter cusp- and divergent-field ion thrusters operating with both 30 cm- amd 50 cm-diameter ion optics up to a 20 kW input power. These data include values of discharge chamber propellant and power efficiencies, as well as values of specific impulse, thruster efficiency, thrust and power. The operation of the 30 cm- and 50 cm-diameter ion optics are also discussed.

Relevance of impacter shape to nonvisible damage and residual tensile strength of a thick graphite/epoxy laminate

NASA Technical Reports Server (NTRS)

Poe, Clarence C., Jr.

1991-01-01

A study was made to determine the relevance of impacter shape to nonvisible damage and tensile residual strength of a 36 mm thick graphite/epoxy motor case. The shapes of the impacters were as follows: 12.7 mm and 25.4 mm diameter hemispheres, a sharp corner, and a 6.3 mm diameter bolt-like rod. The investigation revealed that damage initiated when the contact pressure exceeded a critical level. However, the damage was not visible on the surface until an even higher pressure was exceeded. The impact energy to initiate damage or cause visible damage on the surface increased approximately with impacter diameter to the third power. The reduction in strength for nonvisible damage increased with increasing diameter, 9 and 30 percent for the 12.7 mm and 25.4 mm diameter hemispheres, respectively. The corner impacter made visible damage on the surface for even the smallest impact energy. The rod impacter acted like a punch and sliced through the composite. Even so, the critical level of pressure to initiate damage was the same for the rod and hemispherical impacters. Factors of safety for nonvisible damage increased with increasing kinetic energy of impact. The effects of impacter shape on impact force, damage size, damage visibility, and residual tensile strength were predicted quite well assuming Hertzian contact and using maximum stress criteria and a surface crack analysis.

Tension strength of a thick graphite/epoxy laminate after impact by a 1/2-in. radius impactor

NASA Technical Reports Server (NTRS)

Poe, C. C., Jr.; Illg, W.; Garber, D. P.

1986-01-01

NASA is developing graphite/epoxy filament-wound cases for solid rocket motors of the space shuttle. They are wet-wound with AS4W graphite fiber and HBRF-55A epoxy. The membrane region is about 1.4 inches thick. Two 30-inch-diameter by 12-inch-long cylinders were impacted every two inches of circumference with 1/2-inch radius impactors that were dropped from various heights. One cylinder was empty and the other was filled with inert propellant. Two-inch-wide test specimens were cut from the cylinders. Each was centered on an impact site. The specimens were x-rayed and loaded to failure in uniaxial tension. Rigid body mechanics and the Hertz law were used to predict impact force, local deformations, contact diameters, and contact pressures. The depth of impact damage was predicted using Love's solution for pressure applied on part of the boundary of a semi-infinite body. The predictions were reasonably good. The strengths of the impacted specimens were reduced by as much as 37 percent without visible surface damage. Even the radiographs did not reveal the nonvisible damage.

Effect of Temperature and Graphite Immersion Method on Carbothermic Reduction of Fayalite Slag

NASA Astrophysics Data System (ADS)

Mitrašinović, Aleksandar

2017-09-01

In this work, graphite flakes were used to reduce fayalite slag originated from the pyrometallurgical copper extraction process. Experiments were conducted with a significantly different contact area between graphite and slag at two temperatures, 1300°C and 1400°C. The process was continuously monitored via the concentration change of CO and CO2 in off-gas. Reduction rate values in experiments where 150-micron-diameter graphite flakes were submerged into the slag and left to float slowly to the top are about four times higher compared with when graphite flakes were dispersed at the top surface of liquid slag. The activation energy for instigating reduction was 302.61 kJ mol-1 and 306.67 kJ mol-1 in the case where graphite flakes were submerged into the slag and dispersed at the surface, respectively. The reduction process is characterized by two distinctive periods: an initial steep increase in the concentration of CO and CO2 controlled by the Boudouard reaction and a subsequent slow decrease of CO and CO2 concentrations in the off-gas controlled by mass transfer of reducible oxides from bulk to the gas-slag interface.

Auger Electrons as Probes for Composite Micro- and Nano- structured Materials: Application to Solid Electrolyte Interphases in Graphite and Silicon-Graphite Electrodes

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

Kalaga, Kaushik; Shkrob, Ilya A.; Haasch, Richard T.

In this study, Auger electron spectroscopy (AES) combined with ion sputtering profilometry, Xray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) have been used in a complementary fashion to examine chemical and microstructural changes in graphite (Gr) and silicon/graphite (Si/Gr) blends contained in the negative electrodes of lithium-ion cells. We demonstrate how AES can be used to characterize morphology of the solid-electrolyte interphase (SEI) deposits in such heterogeneous media, complementing well-established methods, such as XPS and SEM. In this way we demonstrate that the SEI does not consist of uniformly thick layers on the graphite and silicon; the thickness ofmore » the SEI layers in cycle-life aged electrodes follows an exponential distribution with a mean of ca. 13 nm for the graphite and ca. 20-25 nm for the silicon nanoparticles (with a crystalline core of 50-70 nm in diameter). Furthermore, a “sticky-sphere” model, in which Si nanoparticles are covered with a layer of polymer binder (that is replaced by the SEI during cycling) of variable thickness is introduced to account for the features observed.« less

Auger Electrons as Probes for Composite Micro- and Nano- structured Materials: Application to Solid Electrolyte Interphases in Graphite and Silicon-Graphite Electrodes

DOE PAGES

Kalaga, Kaushik; Shkrob, Ilya A.; Haasch, Richard T.; ...

2017-10-05

In this study, Auger electron spectroscopy (AES) combined with ion sputtering profilometry, Xray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) have been used in a complementary fashion to examine chemical and microstructural changes in graphite (Gr) and silicon/graphite (Si/Gr) blends contained in the negative electrodes of lithium-ion cells. We demonstrate how AES can be used to characterize morphology of the solid-electrolyte interphase (SEI) deposits in such heterogeneous media, complementing well-established methods, such as XPS and SEM. In this way we demonstrate that the SEI does not consist of uniformly thick layers on the graphite and silicon; the thickness ofmore » the SEI layers in cycle-life aged electrodes follows an exponential distribution with a mean of ca. 13 nm for the graphite and ca. 20-25 nm for the silicon nanoparticles (with a crystalline core of 50-70 nm in diameter). Furthermore, a “sticky-sphere” model, in which Si nanoparticles are covered with a layer of polymer binder (that is replaced by the SEI during cycling) of variable thickness is introduced to account for the features observed.« less

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

NASA Astrophysics Data System (ADS)

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

2015-09-01

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

Advanced Solar Panel Designs

NASA Technical Reports Server (NTRS)

Ralph, E. L.; Linder, E. B.

1995-01-01

Solar panel designs that utilize new high-efficiency solar cells and lightweight rigid panel technologies are described. The resulting designs increase the specific power (W/kg) achievable in the near-term and are well suited to meet the demands of higher performance small satellites (smallsats). Advanced solar panel designs have been developed and demonstrated on two NASA SBIR contracts at Applied Solar. The first used 19% efficient, large area (5.5 cm x 6.5 cm) GaAs/Ge solar cells with a lightweight rigid graphite epoxy isogrid substrate configuration. A 1,445 sq cm coupon was fabricated and tested to demonstrate 60 W/kg with a high potential of achieving 80 W/kg. The second panel design used new 22% efficiency, dual-junction GaInP2/GaAs/Ge solar cells combined with a lightweight aluminum core/graphite fiber mesh facesheet substrate. A 1,445 sq cm coupon was fabricated and tested to demonstrate 105 W/kg with the potential of achieving 115 W/kg.

Formation, characterization, and dynamics of onion-like carbon structures for electrical energy storage from nanodiamonds using reactive force fields

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

Ganesh, P.; Kent, P. R. C.; Mochalin, V.

We simulate the experimentally observed graphitization of nanodiamonds into multi-shell onion-like carbonnanostructures, also called carbon onions, at different temperatures, using reactive force fields. The simulations include long-range Coulomb and van der Waals interactions. Our results suggest that long-range interactions play a crucial role in the phase-stability and the graphitization process. Graphitization is both enthalpically and entropically driven and can hence be controlled with temperature. The outer layers of the nanodiamond have a lower kinetic barrier toward graphitization irrespective of the size of the nanodiamond and graphitize within a few-hundred picoseconds, with a large volume increase. The inner core of themore » nanodiamonds displays a large size-dependent kinetic barrier, and graphitizes much more slowly with abrupt jumps in the internal energy. It eventually graphitizes by releasing pressure and expands once the outer shells have graphitized. The degree of transformation at a particular temperature is thereby determined by a delicate balance between the thermal energy, long-range interactions, and the entropic/enthalpic free energy gained by graphitization. Upon full graphitization, a multi-shell carbonnanostructure appears, with a shell-shell spacing of about ~3.4 Å for all sizes. The shells are highly defective with predominantly five- and seven-membered rings to curve space. Larger nanodiamonds with a diameter of 4 nm can graphitize into spiral structures with a large (~29-atom carbon ring) pore opening on the outermost shell. Such a large one-way channel is most attractive for a controlled insertion of molecules/ions such as Li ions, water, or ionic liquids, for increased electrochemical capacitor or battery electrode applications.« less

Formation, characterization and dynamics of onion like carbon structures from nanodiamonds using reactive force-fields for electrical energy storage

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

Kent, Paul R

We simulate the experimentally observed graphitization of nanodiamonds into multi-shell onion-like carbon nanostructures, also called carbon onions, at different temperatures, using reactive force fields. The simulations include long-range Coulomb and van der Waals interactions. Our results suggest that long-range interactions play a crucial role in the phase-stability and the graphitization process. Graphitization is both enthalpically and entropically driven and can hence be controlled with temperature. The outer layers of the nanodiamond have a lower kinetic barrier toward graphitization irrespective of the size of the nanodiamond and graphitize within a few-hundred picoseconds, with a large volume increase. The inner core ofmore » the nanodiamonds displays a large size-dependent kinetic barrier, and graphitizes much more slowly with abrupt jumps in the internal energy. It eventually graphitizes by releasing pressure and expands once the outer shells have graphitized. The degree of transformation at a particular temperature is thereby determined by a delicate balance between the thermal energy, long-range interactions, and the entropic/enthalpic free energy gained by graphitization. Upon full graphitization, a multi-shell carbon nanostructure appears, with a shell-shell spacing of about {approx}3.4 {angstrom} for all sizes. The shells are highly defective with predominantly five- and seven-membered rings to curve space. Larger nanodiamonds with a diameter of 4 nm can graphitize into spiral structures with a large ({approx}29-atom carbon ring) pore opening on the outermost shell. Such a large one-way channel is most attractive for a controlled insertion of molecules/ions such as Li ions, water, or ionic liquids, for increased electrochemical capacitor or battery electrode applications.« less

Graphite fiber intercalation: Dynamics of the bromine intercalation process

NASA Technical Reports Server (NTRS)

Jaworske, D. A.; Zinolabedini, R.

1985-01-01

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

Pulse laser-induced particle separation from polymethyl methacrylate: a mechanistic study

NASA Astrophysics Data System (ADS)

Arif, S.; Armbruster, O.; Kautek, W.

2013-04-01

The separation mechanism of opaque and transparent model micro-particles, graphite and polystyrene copolymer spheres, respectively, from polymethyl methacrylate (PMMA) substrates were investigated employing a ns-pulse laser radiating at 532 nm. The particles transparent in the visible wavelength range could be removed from PMMA efficiently in a very narrow fluence range between 1 and 2 J/cm2 according to a simple 1D thermal expansion model. Above this fluence region, with single pulses, the transparent microspheres caused local ablation of the PMMA substrate in the optical microlens nearfield. This process led to removal of the particles themselves due to the expansion of the ablation plasma. The irregularly shaped graphite particles shaded the underlying substrate from the incoming radiation so that no optical nearfield damage mechanism could be observed. Therefore, a substantial cleaning window between 0.5 and more than 16 J/cm2 was provided. The graphite data suggest an ablation mechanism of the particulates themselves due to a high optical absorption coefficient.

Hierarchically Porous Graphitic Carbon with Simultaneously High Surface Area and Colossal Pore Volume Engineered via Ice Templating

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

Estevez, Luis; Prabhakaran, Venkateshkumar; Garcia, Adam L.

Developing hierarchical porous carbon (HPC) materials with competing textural characteristics such as surface area and pore volume in one material is difficult to accomplish—particulalry for an atomically ordered (graphitic) carbon. Herein we describe a synthesis strategy to engineer tunable hierarchically porous carbon (HPC) materials across micro- meso- and macroporous length scales, allowing the fabrication of a graphitic HPC with both very high surface area (> 2500 m2/g) and pore volume (>10 cm3/g), the combination of which has not been seen previously. The mesopore volume alone for these materials is up to 7.91 cm3/g, the highest ever reported. The unique materialmore » was explored for use as a supercapaictor electrode and for oil adsorption; two applications that require textural properties that are typicaly exclusive to one another. This design scheme for HPCs can be utilized in broad applications, including electrochemical systems such as batteries and supercapacitors, sorbents, and catalyst supports.« less

Honeycomblike large area LaB6 plasma source for Multi-Purpose Plasma facility

NASA Astrophysics Data System (ADS)

Woo, Hyun-Jong; Chung, Kyu-Sun; You, Hyun-Jong; Lee, Myoung-Jae; Lho, Taihyeop; Choh, Kwon Kook; Yoon, Jung-Sik; Jung, Yong Ho; Lee, Bongju; Yoo, Suk Jae; Kwon, Myeon

2007-10-01

A Multi-Purpose Plasma (MP2) facility has been renovated from Hanbit mirror device [Kwon et al., Nucl. Fusion 43, 686 (2003)] by adopting the same philosophy of diversified plasma simulator (DiPS) [Chung et al., Contrib. Plasma Phys. 46, 354 (2006)] by installing two plasma sources: LaB6 (dc) and helicon (rf) plasma sources; and making three distinct simulators: divertor plasma simulator, space propulsion simulator, and astrophysics simulator. During the first renovation stage, a honeycomblike large area LaB6 (HLA-LaB6) cathode was developed for the divertor plasma simulator to improve the resistance against the thermal shock fragility for large and high density plasma generation. A HLA-LaB6 cathode is composed of the one inner cathode with 4in. diameter and the six outer cathodes with 2in. diameter along with separate graphite heaters. The first plasma is generated with Ar gas and its properties are measured by the electric probes with various discharge currents and magnetic field configurations. Plasma density at the middle of central cell reaches up to 2.6×1012 cm-3, while the electron temperature remains around 3-3.5eV at the low discharge current of less than 45A, and the magnetic field intensity of 870G. Unique features of electric property of heaters, plasma density profiles, is explained comparing with those of single LaB6 cathode with 4in. diameter in DiPS.

Honeycomblike large area LaB6 plasma source for Multi-Purpose Plasma facility.

PubMed

Woo, Hyun-Jong; Chung, Kyu-Sun; You, Hyun-Jong; Lee, Myoung-Jae; Lho, Taihyeop; Choh, Kwon Kook; Yoon, Jung-Sik; Jung, Yong Ho; Lee, Bongju; Yoo, Suk Jae; Kwon, Myeon

2007-10-01

A Multi-Purpose Plasma (MP(2)) facility has been renovated from Hanbit mirror device [Kwon et al., Nucl. Fusion 43, 686 (2003)] by adopting the same philosophy of diversified plasma simulator (DiPS) [Chung et al., Contrib. Plasma Phys. 46, 354 (2006)] by installing two plasma sources: LaB(6) (dc) and helicon (rf) plasma sources; and making three distinct simulators: divertor plasma simulator, space propulsion simulator, and astrophysics simulator. During the first renovation stage, a honeycomblike large area LaB(6) (HLA-LaB(6)) cathode was developed for the divertor plasma simulator to improve the resistance against the thermal shock fragility for large and high density plasma generation. A HLA-LaB(6) cathode is composed of the one inner cathode with 4 in. diameter and the six outer cathodes with 2 in. diameter along with separate graphite heaters. The first plasma is generated with Ar gas and its properties are measured by the electric probes with various discharge currents and magnetic field configurations. Plasma density at the middle of central cell reaches up to 2.6 x 10(12) cm(-3), while the electron temperature remains around 3-3.5 eV at the low discharge current of less than 45 A, and the magnetic field intensity of 870 G. Unique features of electric property of heaters, plasma density profiles, is explained comparing with those of single LaB(6) cathode with 4 in. diameter in DiPS.

Graphite-fiber-reinforced polyimide liners of various compositions in plain spherical bearings

NASA Technical Reports Server (NTRS)

Sliney, H. E.; Jacobson, T. P.

1978-01-01

A plain spherical bearing design with a ball diameter of 28.6 mm, a race length of 12.7 mm, and a 1.7-mm-thick, molded composite liner was evaluated. The liner material is a self-lubricating composite of graphite-fiber-reinforced polyimide resin (GFRPI). The liner is prepared by transfer molding a mixture of one part chopped graphite fiber and one part partially polymerized resin into the space between the bearing ball and the outer race and then completing the polymerization under heat and pressure. Several liner compositions were evaluated: two types of polyimide, condensation and addition; two types of graphite fiber, low and high modulus; and four powder additives - cadmium oxide, cadmium iodide, graphite fluoride, and molybdenum disulfide. The bearings were oscillated + or - 15 deg at 1 Hz for 20 kilocycles under a radial unit load of 29 MN sq m (4200 psi) in dry air at 25, 200, or 315 C. Both types of fiber and polyimide gave low friction and wear. A simple equation was developed to fit the wear-time data and adequately predicted wear to 100 kilocycles.

Radial Breathing Modes in Cosmochemistry and Meteoritics

NASA Technical Reports Server (NTRS)

Wilson, T.L.; Wilson, K.B.

2009-01-01

One area of continuing interest in cosmochemistry and meteoritics (C&M) is the identification of the nature of Q-phase, although some researchers in C&M are not reporting relevant portions of Raman spectral data. Q is the unidentified carrier of noble gases in carbonaceous chondrites (CCs). Being carbonaceous, the focus has been on any number of Q-candidates arising from the sp2 hybridization of carbon (C). These all derive from various forms of graphene, a monolayer of C atoms packed into a two-dimensional (2D) hexagonal honeycomb lattice that is the basic building block for graphitic materials of all other dimensions for sp2 allotropes of C. As a basic lattice, 2D graphene can be curled into fullerenes (0D), wrapped into carbon nanotubes or CNTs (1D), and stacked into graphite (3D). These take such additional forms as scroll-like carbon whiskers, carbon fibers, carbon onions, GPCs (graphite polyhedral crystals) [6], and GICs (graphite intercalation compounds). Although all of these have been observed in meteoritics, the issue is which can explain the Q-abundances. In brief, one or more of the 0D-3D sp2 hybridization forms of C is Q. For some Q-candidates, the radial breathing modes (RBMs) are the most important Raman active vibrational modes that exist, and bear a direct relevance to solving this puzzle. Typically in C&M they are ignored when present. Their importance is addressed here as smoking-gun signatures for certain Q-candidates and are very relevant to the ultimate identification of Q.

Highly Conducting Graphite Epoxy Composite Demonstrated

NASA Technical Reports Server (NTRS)

Gaier, James R.

1999-01-01

Weight savings as high as 80 percent could be achieved if graphite polymer composites could replace aluminum in structures such as electromagnetic interference shielding covers and grounding planes. This could result in significant cost savings, especially for the mobile electronics found in spacecraft, aircraft, automobiles, and hand-held consumer electronics. However, such composites had not yet been fabricated with conductivity sufficient to enable these applications. To address this lack, a partnership of the NASA Lewis Research Center, Manchester College, and Applied Sciences, Inc., fabricated nonmetallic composites with unprecedented electrical conductivity. For these composites, heat-treated, vapor-grown graphite fibers were selected which have a resistivity of about 80 mW-cm, more than 20 times more conductive than typical carbon fibers. These fibers were then intercalated with iodine bromide (IBr). Intercalation is the insertion of guest atoms or molecules between the carbon planes of the graphite fibers. Since the carbon planes are not highly distorted in the process, intercalation has little effect on mechanical and thermal properties. Intercalation does, however, lower the carbon fiber resistivity to less than 10 mW-cm, which is comparable to that of metal fibers. Scaleup of the reaction was required since the initial intercalation experiments would be carried out on 20-mg quantities of fibers, and tens of grams of intercalated fibers would be needed to fabricate even small demonstration composites. The reaction was first optimized through a time and temperature study that yielded fibers with a resistivity of 8.7 2 mW-cm when exposed to IBr vapor at 114 C for 24 hours. Stability studies indicated that the intercalated fibers rapidly lost their conductivity when exposed to temperatures as low as 40 C in air. They were not, however, susceptible to degradation by water vapor in the manner of most graphite intercalation compounds. The 1000-fold scaleup experiments concluded that 114 C was near the optimum temperature, but that the intercalation time needed to be lengthened by a factor of 3.

KSC-08pd3867

NASA Image and Video Library

2008-11-07

CAPE CANAVERAL, Fla. -- In Building 1555 at Vandenberg Air Force Base in California, assembly is underway for the Taurus XL rocket that will launch NASA's Orbiting Carbon Observatory, or OCO, spacecraft. In the foreground at left is the boattail; behind it is the Stage 0 Castor 120 motor. At right near the wall (from left) are the Stage 1 and Stage 2 motors, the avionics shelf and the Stage 3 motor. The graphite/epoxy boattail structure provides the transition from the smaller diameter of the Stage 2 motor to the larger diameter of the avionics skirt. The avionics skirt, also a graphite/epoxy structure, supports the avionics shelf and carries the primary structural loads from the fairing and payload cone. The aluminum avionics shelf supports the third stage avionics. The OCO is a new Earth-orbiting mission sponsored by NASA's Earth System Science Pathfinder Program. The launch of OCO is targeted for January. Photo credit: NASA/Randy Beaudoin, VAFB

Evaluation of graphite composite materials for bearingless helicopter rotor application

NASA Technical Reports Server (NTRS)

Ulitchny, M. G.; Lucas, J. J.

1974-01-01

Small scale combined load fatigue tests were conducted on twelve unidirectional graphite-glass scrim-epoxy composite specimens. The specimens were 1 in. (2.54 cm) wide by 0.1 in. (.25 cm) thick by 5 in. (12.70 cm) long. The fatigue data was developed for the preliminary design of the spar for a bearingless helicopter main rotor. Three loading conditions were tested. Combinations of steady axial, vibratory torsion, and vibratory bending stresses were chosen to simulate the calculated stresses which exist at the root and at the outboard end of the pitch change section of the spar. Calculated loads for 150 knots (77.1 m/sec) level flight were chosen as the baseline condition. Test stresses were varied up to 4.4 times the baseline stress levels. Damage resulted in reduced stiffness; however, in no case was complete fracture of the specimen experienced.

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

Pseudocapacitive performance of electrodeposited porous Co3O4 film on electrophoretically modified graphite electrodes with carbon nanotubes

NASA Astrophysics Data System (ADS)

Kazazi, Mahdi; Sedighi, Ali Reza; Mokhtari, Mohammad Amin

2018-05-01

A facile and efficient two-step procedure was developed for the fabrication of a high-performance and binder-free cobalt oxide-carbon nanotubes (CO/CNT) pseudocapacitive electrode. First, CNTs were deposited on the surface of a chemically activated graphite sheet by cathodic electrophoretic deposition technique from their ethanolic suspension. In the next step, a thin film of cobalt oxide was electrodeposited on the CNTs coated graphite substrate by a galvanostatic method, followed by a thermal treatment in air. The structure and morphology of the prepared cobaltite electrode with and without CNT interlayer were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and nitrogen adsorption-desorption measurement. The results indicated that Co3O4 nanoparticles were uniformly attached on the surface of CNTs, to form a porous-structured CO/CNT composite electrode with a high specific surface area of 144.9 m2 g-1. Owing to the superior electrical conductivity of CNTs, high surface area and open porous structure, and improved integrity of the electrode structure, the composite electrode delivered a high areal capacitance of 4.96F cm-2 at a current density of 2 mA cm-2, a superior rate performance (64.7% capacitance retention from 2 mA cm-2 to 50 mA cm-2), as well as excellent cycling stability (91.8% capacitance retention after 2000 cycles), which are higher than those of the pure cobaltite electrode.

Getter pump for hydrogen and hydrocarbon gases

DOEpatents

Hsu, Wen L.

1989-01-01

A gettering device for hydrogen isotopes and gaseous hydrocarbons based on the interaction of a plasma and graphite used as cathodic material. The plasma is maintained at a current density within the range of about 1 to about 1000 mA/cm.sup.2. The graphite may be heated to a temperature greater than 1000.degree. C. The new device offers high capacity, low noise, and gas species selectivity.

Getter pump for hydrogen and hydrocarbon gases

DOEpatents

Hsu, Wen Ling

1987-10-14

A gettering device for hydrogen isotopes and gaseous hydrocarbons based on the interaction of a plasma and graphite used as cathodic material. The plasma is maintained at a current density within the range of about 1 to about 1000 mA/cm/sup 2/. The graphite may be heated to a temperature greater than 1000/degree/C. The new device offers high capacity, low noise, and gas species selectivity. 2 figs.

Modeling irradiation creep of graphite using rate theory

DOE PAGES

Sarkar, Apu; Eapen, Jacob; Raj, Anant; ...

2016-02-20

In this work we examined irradiation induced creep of graphite in the framework of transition state rate theory. Experimental data for two grades of nuclear graphite (H-337 and AGOT) were analyzed to determine the stress exponent (n) and activation energy (Q) for plastic flow under irradiation. Here we show that the mean activation energy lies between 0.14 and 0.32 eV with a mean stress-exponent of 1.0 ± 0.2. A stress exponent of unity and the unusually low activation energies strongly indicate a diffusive defect transport mechanism for neutron doses in the range of 3-4 x 10 22 n/cm 2.

Organic-Inorganic Graphite and Transition Metal Dichalcogenide Based Composites for 3D Printing

NASA Astrophysics Data System (ADS)

Catalan Gonzalez, Jorge Alfredo

This project was multipronged to help fuse together topics of additive manufacturing and two-dimensional (2D) layered materials, and studying the mechanical and electrical properties of the composites produced. The composites are made from the thermoplastic polymer acting as a matrix and the graphite and 2D transition metal dichalcogenides (TMDs) serving as the filler or reinforcement. Different concentrations of TMD's were added to the matrix to study the effect of composition on the mechanical and electrical properties. To shed insights into the mechanical properties, test coupons were produced as "dog bone" structures for tensile testing using the ASTM D638 type 5 standard, which were printed with the aid of a Lulzbot TAZ 6 3D printer. In the same way, two-terminal resistor-like structures were printed to test the electrical properties inherent to the composites. From the measurements conducted, polyethylene terephthalate glycol (PETG)--graphite composites had a yield strength (YS) ≈ 50 MPa, an ultimate tensile strength (UTS) ≈ 30 MPa and had a better ductility (strain to rupture ≈ 8%) compared to theacrylonitrile butadiene styrene (ABS) composite counterparts. Also, molybdenum disulfide (MoS2) had a more positive effect than tungsten disulfide (WS2), since the strength was retained while the ductility was increased at low loadings of the material. Strain levels were measured to be 30%-120% when adding 1 wt% of MoS2 and WS2. On the other hand, with high additions of MoS2 and WS2 (15 and 20 wt%) ductility was completely lost since no plastic deformation occurred during the testing. Moreover, PETG - graphite resistor-like structures were 3-dimensional (3D) printed and tested with the help of a semiconductor parameter analyzer. All samples were tested at different radius of curvatures (0 cm-1, 0.072 cm-1, 0.087 cm-1, 0.112 cm-1, 0.157 cm-1, and 0.262 cm -1) which showed a composite that was strain insensitive. The obtained average conductivity and resistivity were ≈ 5.27 Siemens-m-1 and 0.250 Ohm-m, respectively. In the process of forming the composites, some pretreatment of the 2D material may also be necessary. We studied one aspect of this pretreatment by looking at particle size measured using dynamic light scattering. The fragmentation rate (FR) of 2D MoS2, WS2, and graphite in N-methyl-pyrrolidinone (NMP) was computed in chemical exfoliants, where FR is a measure of the particle size reduction as a function of ultrasonication time. For the 2D layered materials, the highest FR generally occurred for sonication times tsonic = 30 min., after which point FR varied less sensitively with tsonic. The highest FR occurred for graphite, where FRGraphite was -1176.4 microm-hr -1, while FRWS2 and FRMoS2 was measured to be -32.4 microm-hr-1 and -3.8 microm-hr-1, respectively. This pretreatment maybe an important step to further tune the properties of the hybrid organic-inorganic composites of 2D materials with polymeric systems for a number of application platforms.

Spontaneous modification of graphite anode by anthraquinone-2-sulfonic acid for microbial fuel cells.

PubMed

Tang, Xinhua; Li, Haoran; Du, Zhuwei; Ng, How Yong

2014-07-01

In this study, anthraquinone-2-sulfonic acid (AQS), an electron transfer mediator, was immobilized onto graphite felt surface via spontaneous reduction of the in situ generated AQS diazonium cations. Cyclic voltammetry (CV) and energy dispersive spectrometry (EDS) characterizations of AQS modified graphite demonstrated that AQS was covalently grafted onto the graphite surface. The modified graphite, with a surface AQS concentration of 5.37 ± 1.15 × 10(-9)mol/cm(2), exhibited good electrochemical activity and high stability. The midpoint potential of the modified graphite was about -0.248 V (vs. normal hydrogen electrode, NHE), indicating that electrons could be easily transferred from NADH in bacteria to the electrode. AQS modified anode in MFCs increased the maximum power density from 967 ± 33 mW/m(2) to 1872 ± 42 mW/m(2). These results demonstrated that covalently modified AQS functioned as an electron transfer mediator to facilitate extracellular electron transfer from bacteria to electrode and significantly enhanced the power production in MFCs. Copyright © 2014 Elsevier Ltd. All rights reserved.

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

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

Kumaran, R.; Alagar, M.; Dinesh Kumar, S.

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

Sulfur-Doping Templated Synthesis of Nanoporous Graphitic Nanocages and Its Supported Catalysts for Efficient Methanol Oxidation.

PubMed

Sheng, Zhao Min; Hong, Cheng Yang; Dai, Xian You; Chang, Cheng Kang; Chen, Jian Bin; Liu, Yan

2015-04-01

We demonstrate a new sulfur (S)-doping templated approach to fabricate highly nanoporous graphitic nanocages (GNCs) by air-oxidizing the templates in the graphitic shells to create nanopores. Sulfur can be introduced, when Fe@C core-shell nanoparticles are prepared and then S-doped GNCs can be obtained by removing their ferrous cores. Due to removing S-template, both the specific surface area (from 540 to 850 m2 g(-1)) and the mesopore volume (from 0.44 to 0.9 cm3 g(-1)) of the graphitic nanocages have sharply risen. Its high specific surface area improves catalyst loading to provide more reaction electro-active sites while its high mesopore volume pro- motes molecule diffusion across the nanocages, making it an excellent material to support Pt/Ru catalysts for direct methanol fuel cells.

Pitch-based carbon foam and composites and uses thereof

DOEpatents

Klett, James W.; Burchell, Timothy D.; Choudhury, Ashok

2004-01-06

A thermally conductive carbon foam is provided, normally having a thermal conductivity of at least 40 W/m.multidot.K. The carbon foam usually has a specific thermal conductivity, defined as the thermal conductivity divided by the density, of at least about 75 W.multidot.cm.sup.3 /m.multidot..degree.K.multidot.gm. The foam also has a high specific surface area, typically at least about 6,000 m.sup.2 /m.sup.3. The foam is characterized by an x-ray diffraction pattern having "doublet" 100 and 101 peaks characterized by a relative peak split factor no greater than about 0.470. The foam is graphitic and exhibits substantially isotropic thermal conductivity. The foam comprises substantially ellipsoidal pores and the mean pore diameter of such pores is preferably no greater than about 340 microns. Other materials, such as phase change materials, can be impregnated in the pores in order to impart beneficial thermal properties to the foam. Heat exchange devices and evaporatively cooled heat sinks utilizing the foams are also disclosed.

Addition of acetate improves stability of power generation using microbial fuel cells treating domestic wastewater.

PubMed

Stager, Jennifer L; Zhang, Xiaoyuan; Logan, Bruce E

2017-12-01

Power generation using microbial fuel cells (MFCs) must provide stable, continuous conversion of organic matter in wastewaters into electricity. However, when relatively small diameter (0.8cm) graphite fiber brush anodes were placed close to the cathodes in MFCs, power generation was unstable during treatment of low strength domestic wastewater. One reactor produced 149mW/m 2 before power generation failed, while the other reactor produced 257mW/m 2 , with both reactors exhibiting severe power overshoot in polarization tests. Using separators or activated carbon cathodes did not result in stable operation as the reactors continued to exhibit power overshoot based on polarization tests. However, adding acetate (1g/L) to the wastewater produced stable performance during fed batch and continuous flow operation, and there was no power overshoot in polarization tests. These results highlight the importance of wastewater strength and brush anode size for producing stable and continuous power in compact MFCs. Copyright © 2017 Elsevier B.V. All rights reserved.

Constraints on the Compositions of Phobos and Deimos from Mineral Absorptions

NASA Technical Reports Server (NTRS)

Fraeman, A. A.; Murchie, S. L.; Arvidson, R. E.; Rivkin, A. S.; Morris, R. V.

2013-01-01

The compositions of Phobos and Deimos have remained controversial despite multiple Earth- and space-based observations acquired during the last 40 years. Phobos is composed of at least two spectral units that are both dark yet distinct at visible to near infrared wavelenghts; a spectrally red-sloped "red" unit covers most of the moon and a less red-sloped "blue" unit is present in the ejecta of the approximately 9-km diameter impact crater Stickney [1,2]. Deimos is similar spectrally to Phobos' "red" unit [2]. Here we report results from mapping mineral absorptions on Phobos and Deimos using visible/near infrared observations from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). We find evidence for an absorption feature at 0.65 m in the Phobos red unit and Deimos that is reproducible in observations from other instruments. The phase responsible is uncertain but may be a Fe-bearing phyllosilicate and/or graphite, consistent with the notion that Phobos and Deimos have compositions similar to CM carbonaceous chondrites [3].

Characteristics of Pool Boiling on Graphite-Copper Composite Surfaces

NASA Technical Reports Server (NTRS)

Zhang, Nengli; Chao, David F.; Yang, Wen-Jei

2002-01-01

Nucleate pool boiling performance of different liquids on graphite-copper composite (Gr-Cu) surfaces has been experimentally studied and modeled. Both highly wetting fluids, such as freon-113 and pentane, and a moderately wetting fluid (water) were tested on the Gr-Cu surfaces with different graphite-fiber volume fractions to reveal the enhancement effects of the composite surfaces on the nucleate pool boiling. Results of the experiments show that the graphite-fiber volume fraction has an optimum value. The Gr-Cu composite surface with 25 percent graphite-fiber volume (f=0.25) has a maximum enhancement effect on the nucleate boiling heat transfer comparing to the pure copper surface. For the highly wetting fluid, the nucleate boiling heat transfer is generally enhanced on the Gr- Cu composite surfaces by 3 to 6 times shown. In the low heat flux region, the enhancement is over 6 times, but in the high heat flux region, the enhancement is reduced to about 40%. For the moderately wetting fluid (water), stronger enhancement of nucleate boiling heat transfer is achieved on the composite surface. It shown the experimental results in which one observes the nucleate boiling heat transfer enhancement of 5 to 10 times in the low heat flux region and an enhancement of 3 to 5 times in the high heat flux region. Photographs of bubble departure during the initial stage of nucleate boiling indicate that the bubbles detached from the composite surface are much smaller in diameter than those detached from the pure copper surface. Typical photographs are presented.It shows that the bubbles departed from the composite surface have diameters of only O(0.1) mm, while those departed from the pure copper surface have diameters of O(1) mm. It is also found that the bubbles depart from the composite surface at a much higher frequency, thus forming vapor columns. These two phenomena combined with high thermal conductivity of the graphite fiber are considered the mechanisms for such a significant augmentation in nucleate boiling heat transfer on the composite surfaces. A physical model is developed to describe the phenomenon of bubble departure from the composite surface: The preferred site of bubble nucleation is the fiber tip because of higher tip temperature than the surrounding copper base and poor wettability of the graphite tip compared with that of the base material (copper). The high evaporation rate near the contact line produces the vapor cutback due to the vapor recoil pushing the three-phase line outwards from the fiber tip, and so a neck of the bubble is formed near the bubble bottom. Evaporation and surface tension accelerate the necking process and finally result in the bubble departure while a new small bubble is formed at the tip when the surface tension pushes the three-phase line back to the tip. The process is schematically shown. The proposed model is based on and confirmed by experimental results.

A feasibility study of the Tehran research reactor as a neutron source for BNCT.

PubMed

Kasesaz, Yaser; Khalafi, Hossein; Rahmani, Faezeh; Ezati, Arsalan; Keyvani, Mehdi; Hossnirokh, Ashkan; Shamami, Mehrdad Azizi; Monshizadeh, Mahdi

2014-08-01

Investigation on the use of the Tehran Research Reactor (TRR) as a neutron source for Boron Neutron Capture Therapy (BNCT) has been performed by calculating and measuring energy spectrum and the spatial distribution of neutrons in all external irradiation facilities, including six beam tubes, thermal column, and the medical room. Activation methods with multiple foils and a copper wire have been used for the mentioned measurements. The results show that (1) the small diameter and long length beam tubes cannot provide sufficient neutron flux for BNCT; (2) in order to use the medical room, the TRR core should be placed in the open pool position, in this situation the distance between the core and patient position is about 400 cm, so neutron flux cannot be sufficient for BNCT; and (3) the best facility which can be adapted for BNCT application is the thermal column, if all graphite blocks can be removed. The epithermal and fast neutron flux at the beginning of this empty column are 4.12×10(9) and 1.21×10(9) n/cm(2)/s, respectively, which can provide an appropriate neutron beam for BNCT by designing and constructing a proper Beam Shaping Assembly (BSA) structure. Copyright © 2014 Elsevier Ltd. All rights reserved.

Self-Supporting GaN Nanowires/Graphite Paper: Novel High-Performance Flexible Supercapacitor Electrodes.

PubMed

Wang, Shouzhi; Sun, Changlong; Shao, Yongliang; Wu, Yongzhong; Zhang, Lei; Hao, Xiaopeng

2017-02-01

Flexible supercapacitors have attracted great interest as energy storage devices because of their promise in applications such as wearable and smart electronic devices. Herein, a novel flexible supercapacitor electrode based on gallium nitride nanowire (GaN NW)/graphite paper (GP) nanocomposites is reported. The outstanding electrical conductivities of the GaN NW (6.36 × 10 2 S m -1 ) and GP (7.5 × 10 4 S m -1 ) deliver a synergistically enhanced electrochemical performance that cannot be achieved by either of the components alone. The composite electrode exhibits excellent specific capacitance (237 mF cm -2 at 0.1 mA cm -2 ) and outstanding cycling performance (98% capacitance retention after 10 000 cycles). The flexible symmetric supercapacitor also manifests high energy and power densities (0.30 mW h cm -3 and 1000 mW cm -3 ). These findings demonstrate that the GaN/GP composite electrode has significant potential as a candidate for the flexible energy storage devices. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Comparison of absorbed-dose-to-water units for Co-60 and high-energy x-rays between PTB and LNE-LNHB

NASA Astrophysics Data System (ADS)

Delaunay, F.; Kapsch, R.-P.; Gouriou, J.; Illemann, J.; Krauss, A.; Le Roy, M.; Ostrowsky, A.; Sommier, L.; Vermesse, D.

2012-10-01

During the Euramet project JRP7 ‘External Beam Cancer Therapy’, PTB and LNE-LNHB used primary standards to determine the absorbed dose to water under IMRT conditions (in small fields). PTB used a water calorimeter to determine the absorbed-dose-to-water references in 6 MV and 10 MV beams for field sizes of 10 cm × 10 cm and 3 cm × 3 cm while LNE-LNHB used graphite calorimeters in 6 MV and 12 MV beams for field sizes of 10 cm × 10 cm, 4 cm × 4 cm and 2 cm × 2 cm. The purpose of this study is to compare PTB and LNE-LNHB new absorbed-dose-to-water references. LNE-LNHB sent an Exradin A1SL ionization chamber traceable to its primary standard to the PTB for calibration in 60Co and in linac beams and PTB sent a PTW 31010 ionization chamber traceable to its primary standard to LNE-LNHB for calibration in 60Co and in linac beams. Calculated Sw,air will be used as beam quality specifier for the ionization chamber comparison at different field sizes. The standard uncertainties (k = 1) of PTB and LNE-LNHB calibration coefficients lie respectively between 0.25% (60Co) and 0.40% (linac) and between 0.29% and 0.46%. PTB and LNE-LNHB absorbed-dose-to-water references developed for this project, based respectively on water calorimetry and on graphite calorimetry, agree within 1.5 standard deviations for field size of 10 cm × 10 cm down to 2 cm × 2 cm and for beams of 6 MV to 10 MV.

Performance of large area xenon ion thrusters for orbit transfer missions

NASA Technical Reports Server (NTRS)

Rawlin, Vincent K.

1989-01-01

Studies have indicated that xenon ion propulsion systems can enable the use of smaller Earth-launch vehicles for satellite placement which results in significant cost savings. These analyses have assumed the availability of advanced, high power ion thrusters operating at about 10 kW or higher. A program was initiated to explore the viability of operating 50 cm diameter ion thrusters at this power level. Operation with several discharge chamber and ion extraction grid set combinations has been demonstrated and data were obtained at power levels to 16 kW. Fifty cm diameter thrusters using state of the art 30 cm diameter grids or advanced technology 50 cm diameter grids allow discharge power and beam current densities commensurate with long life at power levels up to 10 kW. In addition, 50 cm diameter thrusters are shown to have the potential for growth in thrust and power levels beyond 10 KW.

Hydrothermal flake graphite mineralisation in Paleoproterozoic rocks of south-east Greenland

NASA Astrophysics Data System (ADS)

Rosing-Schow, Nanna; Bagas, Leon; Kolb, Jochen; Balić-Žunić, Tonči; Korte, Christoph; Fiorentini, Marco L.

2017-06-01

Flake graphite mineralisation is hosted in the Kuummiut Terrane of the Paleoproterozoic Nagssugtoqidian Orogen, south-east Greenland. Eclogite-facies peak-metamorphic assemblages record temperatures of 640-830 °C and pressures of 22-25 kbar, and are retrogressed in the high-pressure amphibolite-facies during ca. 1870-1820 Ma. Graphite occurs as lenses along cleavage planes in breccia and as garnet-quartz-graphite veins in various metamorphic host rocks in the Tasiilaq area at Auppaluttoq, Kangikajik, and Nuuk-Ilinnera. Graphite contents reach >30 vol% in 0.2-4 × 20 m wide semi-massive mineralisation (Auppaluttoq, Kangikajik). Supergene alteration formed 1- to 2-m-thick and up to a 2.5 × 2.5 km wide loose limonitic gravel containing graphite flakes in places. The flake size ranges from 1 to 6 mm in diameter with an average of 3 mm. Liberation efficiency is at minimum 60%. Hydrothermal fluids at 600 °C, transporting carbon as CO2 and CH4, formed the mineralisation commonly hosted by shear zones, which acted as pathways for the mineralising fluids. The hydrothermal alteration assemblage is quartz-biotite-grunerite-edenite-pargasite-K-feldspar-titanite. The δ13C values of graphite, varying from -30 to -18‰ PDB, indicate that the carbon was derived from organic matter most likely from metasedimentary sources. Devolatilisation of marble may have contributed a minor amount of carbon by fluid mixing. Precipitation of graphite involved retrograde hydration reactions, depleting the fluid in H2O and causing graphite saturation. Although the high-grade mineralisation is small, it represents an excellent example of hydrothermal mineralisation in an eclogite-facies terrane during retrograde exhumation.

Contributions a la caracterisation et a l'amelioration de l'usinabilite de pieces d'acier elaborees par metallurgie des poudres

NASA Astrophysics Data System (ADS)

Boilard, Patrick

Even though powder metallurgy (P/M) is a near net shape process, a large number of parts still require one or more machining operations during the course of their elaboration and/or their finishing. The main objectives of the work presented in this thesis are centered on the elaboration of blends with enhanced machinability, as well as helping with the definition and in the characterization of the machinability of P/M parts. Enhancing machinability can be done in various ways, through the use of machinability additives and by decreasing the amount of porosity of the parts. These different ways of enhancing machinability have been investigated thoroughly, by systematically planning and preparing series of samples in order to obtain valid and repeatable results leading to meaningful conclusions relevant to the P/M domain. Results obtained during the course of the work are divided into three main chapters: (1) the effect of machining parameters on machinability, (2) the effect of additives on machinability, and (3) the development and the characterization of high density parts obtained by liquid phase sintering. Regarding the effect of machining parameters on machinability, studies were performed on parameters such as rotating speed, feed, tool position and diameter of the tool. Optimal cutting parameters are found for drilling operations performed on a standard FC-0208 blend, for different machinability criteria. Moreover, study of material removal rates shows the sensitivity of the machinability criteria for different machining parameters and indicates that thrust force is more regular than tool wear and slope of the drillability curve in the characterization of machinability. The chapter discussing the effect of various additives on machinability reveals many interesting results. First, work carried out on MoS2 additions reveals the dissociation of this additive and the creation of metallic sulphides (namely CuxS sulphides) when copper is present. Results also show that it is possible to reduce the amount of MoS2 in the blend so as to lower the dimensional change and the cost (blend Mo8A), while enhancing machinability and keeping hardness values within the same range (70 HRB). Second, adding enstatite (MgO·SiO2) permits the observation of the mechanisms occurring with the use of this additive. It is found that the stability of enstatite limits the diffusion of graphite during sintering, leading to the presence of free graphite in the pores, thus enhancing machinability. Furthermore, a lower amount of graphite in the matrix leads to a lower hardness, which is also beneficial to machinability. It is also found that the presence of copper enhances the diffusion of graphite, through the formation of a liquid phase during sintering. With the objective of improving machinability by reaching higher densities, blends were developed for densification through liquid phase sintering. High density samples are obtained (>7.5 g/cm3) for blends prepared with Fe-C-P constituents, namely with 0.5%P and 2.4%C. By systematically studying the effect of different parameters, the importance of the chemical composition (mainly the carbon content) and the importance of the sintering cycle (particularly the cooling rate) are demonstrated. Moreover, various heat treatments studied illustrate the different microstructures achievable for this system, showing various amounts of cementite, pearlite and free graphite. Although the machinability is limited for samples containing large amounts of cementite, it can be greatly improved with very slow cooling, leading to graphitization of the carbon in presence of phosphorus. Adequate control of the sintering cycle on samples made from FGS1625 powder leads to the obtention of high density (≥7.0 g/cm 3) microstructures containing various amounts of pearlite, ferrite and free graphite. Obtaining ferritic microstructures with free graphite designed for very high machinability (tool wear <1.0%) or fine pearlitic microstructures with excellent mechanical properties (transverse rupture strength >1600 MPa) is therefore possible. These results show that improvement of machinability through higher densities is limited by microstructure. Indeed, for the studied samples, microstructure is dominant in the determination of machinability, far more important than density, judging by the influence of cementite or of the volume fraction of free graphite on machinability for example. (Abstract shortened by UMI.)

Thermodynamic, Transport and Chemical Properties of Reference JP-8

DTIC Science & Technology

2006-06-01

external diameter, 0.18 cm internal diameter) that are sealed on one end with a stainless steel plug welded by a clean tungsten-inert-gas ( TIG ) 15...tubing with an internal diameter of 0.02 cm, also TIG welded to the cell. Each cell and valve is capable of withstanding a pressure in excess of 105... process . Each cell is connected to a high-pressure high-temperature valve at the other end with a short length of 0.16 cm diameter 316 stainless steel

Constraints on Grain Formation around Carbon Stars from Laboratory Studies of Presolar Graphite

NASA Astrophysics Data System (ADS)

Bernatowicz, Thomas J.; Akande, Onaolapo Wali; Croat, Thomas K.; Cowsik, Ramanath

2005-10-01

We report the results of an investigation into the physical conditions in the mass outflows of asymptotic giant branch (AGB) carbon stars that are required for the formation of micron-sized presolar graphite grains, with and without previously formed internal crystals of titanium carbide (TiC). A lower mass limit of 1.1 Msolar for stars capable of contributing grains to the solar nebula is derived. This mass limit, in conjunction with a mass-luminosity relation for carbon stars, identifies the region of the H-R diagram relevant to the production of presolar graphite. Detailed dynamical models of AGB outflows, along with constraints provided by kinetics and equilibrium thermodynamics, indicate that grain formation occurs at radii from 2.3 to 3.7 AU for AGB carbon stars in the 1.1-5 Msolar range. This analysis also yields time intervals available for graphite growth that are on the order of a few years. By considering the luminosity variations of carbon stars, we show that grains formed during minima in the luminosity are likely to be evaporated subsequently, while those formed at luminosity maxima will survive. We calculate strict upper limits on grain sizes for graphite and TiC in spherically symmetric AGB outflows. Graphite grains can reach diameters in the observed micron size range (1-2 μm) only under ideal growth conditions (perfect sticking efficiency, no evaporation, no depletion of gas species contributing to grain growth), and then only in outflows from carbon stars with masses <~2.5 Msolar. The same is true for TiC grains that are found within presolar graphite, which have mean diameters of 24+/-14 nm. In general, the mass-loss rates that would be required to produce the observed grain sizes in spherically symmetric outflows are at least an order of magnitude larger than the maximum observed AGB carbon star mass-loss rates. These results, as well as pressure constraints derived from equilibrium thermodynamics, force us to conclude that presolar graphite and TiC must form in regions of enhanced density (clumps, jets) in AGB outflows having small angular scales. As shown in the companion paper by Croat et al., the enrichment of 12C in many AGB graphites, and the overabundances of the s-process elements Mo, Zr, and Ru in the carbides found within them, often greatly exceed the values observed astronomically in AGB outflows. These observations not only lend further support to the idea that the outflows are clumpy, but also imply that the outflowing matter is not well mixed in the circumstellar envelope out to the radii where grain condensation takes place.

A Fluorinated Ether Electrolyte Enabled High Performance Prelithiated Graphite/Sulfur Batteries

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

Chen, Shuru; Yu, Zhaoxin; Gordin, Mikhail L.

Lithium/sulfur (Li/S) batteries have attracted great attention as a promising energy storage technology, but so far their practical applications are greatly hindered by issues of polysulfide shuttling and unstable lithium/electrolyte interface. To address these issues, a feasible strategy is to construct a rechargeable prelithiated graphite/sulfur batteries. In this study, a fluorinated ether of bis(2,2,2-trifluoroethyl) ether (BTFE) was reported to blend with 1,3-dioxolane (DOL) for making a multifunctional electrolyte of 1.0 M LiTFSI DOL/BTFE (1:1, v/v) to enable high performance prelithiated graphite/S batteries. First, the electrolyte significantly reduces polysulfide solubility to suppress the deleterious polysulfide shuttling and thus improves capacity retentionmore » of sulfur cathodes. Second, thanks to the low viscosity and good wettability, the fluorinated electrolyte dramatically enhances the reaction kinetics and sulfur utilization of high-areal-loading sulfur cathodes. More importantly, this electrolyte forms a stable solid-electrolyte interphase (SEI) layer on graphite surface and thus enables remarkable cyclability of graphite anodes. Lastly, by coupling prelithiated graphite anodes with sulfur cathodes with high areal capacity of ~3 mAh cm -2, we demonstrate prelithiated graphite/sulfur batteries that show high sulfur-specific capacity of ~1000 mAh g -1 and an excellent capacity retention of >65% after 450 cycles at C/10.« less

A Fluorinated Ether Electrolyte Enabled High Performance Prelithiated Graphite/Sulfur Batteries

DOE PAGES

Chen, Shuru; Yu, Zhaoxin; Gordin, Mikhail L.; ...

2017-02-03

Lithium/sulfur (Li/S) batteries have attracted great attention as a promising energy storage technology, but so far their practical applications are greatly hindered by issues of polysulfide shuttling and unstable lithium/electrolyte interface. To address these issues, a feasible strategy is to construct a rechargeable prelithiated graphite/sulfur batteries. In this study, a fluorinated ether of bis(2,2,2-trifluoroethyl) ether (BTFE) was reported to blend with 1,3-dioxolane (DOL) for making a multifunctional electrolyte of 1.0 M LiTFSI DOL/BTFE (1:1, v/v) to enable high performance prelithiated graphite/S batteries. First, the electrolyte significantly reduces polysulfide solubility to suppress the deleterious polysulfide shuttling and thus improves capacity retentionmore » of sulfur cathodes. Second, thanks to the low viscosity and good wettability, the fluorinated electrolyte dramatically enhances the reaction kinetics and sulfur utilization of high-areal-loading sulfur cathodes. More importantly, this electrolyte forms a stable solid-electrolyte interphase (SEI) layer on graphite surface and thus enables remarkable cyclability of graphite anodes. Lastly, by coupling prelithiated graphite anodes with sulfur cathodes with high areal capacity of ~3 mAh cm -2, we demonstrate prelithiated graphite/sulfur batteries that show high sulfur-specific capacity of ~1000 mAh g -1 and an excellent capacity retention of >65% after 450 cycles at C/10.« less

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...

Photocurrent generation by direct electron transfer using photosynthetic reaction centres

NASA Astrophysics Data System (ADS)

Mahmoudzadeh, A.; Saer, R.; Jun, D.; Mirvakili, S. M.; Takshi, A.; Iranpour, B.; Ouellet, E.; Lagally, E. T.; Madden, J. D. W.; Beatty, J. T.

2011-09-01

Photosynthetic reaction centres (RCs) convert light into separated charges with nearly perfect quantum efficiency, and have been used to generate photocurrent. Previous work has shown that electron tunnelling rates between redox centres in proteins depend exponentially on the tunnelling distance. In this work the RC from Rhodobacter sphaeroides was genetically modified with the aim of achieving the shortest tunnelling distances yet demonstrated between the RC's electron-accepting P site and underlying graphite and gold electrodes, and between the electron donor Q site and graphite electrodes. Opposite charges are carried to counter electrodes using mobile mediators, as in dye-sensitised solar cells. Native RCs are bound to graphite surfaces through N-(1-pyrene)iodoacetamide. Although the linker's length is only 4 Å, the electron transfer pathway between the Q electron donor site on the RC and the electrode surface is still too large for current to be significant. A mutant version with the electron acceptor P side close to the graphite surface produced currents of 15 nA cm-2 upon illumination. Direct binding of RCs to a gold surface is shown, resulting in currents of 5 nA cm-2. In both cases the current was unaffected by mediator concentration but increased with illumination, suggesting that direct electron transfer was achieved. The engineering of an RC to achieve direct electron transfer will help with long term efforts to demonstrate RC-based photovoltaic devices.

Highly active, bi-functional and metal-free B4C-nanoparticle-modified graphite felt electrodes for vanadium redox flow batteries

NASA Astrophysics Data System (ADS)

Jiang, H. R.; Shyy, W.; Wu, M. C.; Wei, L.; Zhao, T. S.

2017-10-01

The potential of B4C as a metal-free catalyst for vanadium redox reactions is investigated by first-principles calculations. Results show that the central carbon atom of B4C can act as a highly active reaction site for redox reactions, due primarily to the abundant unpaired electrons around it. The catalytic effect is then verified experimentally by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests, both of which demonstrate that B4C nanoparticles can enhance the kinetics for both V2+/V3+ and VO2+/VO2+ redox reactions, indicating a bi-functional effect. The B4C-nanoparticle-modified graphite felt electrodes are finally prepared and tested in vanadium redox flow batteries (VRFBs). It is shown that the batteries with the prepared electrodes exhibit energy efficiencies of 88.9% and 80.0% at the current densities of 80 and 160 mA cm-2, which are 16.6% and 18.8% higher than those with the original graphite felt electrodes. With a further increase in current densities to 240 and 320 mA cm-2, the batteries can still maintain energy efficiencies of 72.0% and 63.8%, respectively. All these results show that the B4C-nanoparticle-modified graphite felt electrode outperforms existing metal-free catalyst modified electrodes, and thus can be promising electrodes for VRFBs.

HF/H2O2 treated graphite felt as the positive electrode for vanadium redox flow battery

NASA Astrophysics Data System (ADS)

He, Zhangxing; Jiang, Yingqiao; Meng, Wei; Jiang, Fengyun; Zhou, Huizhu; Li, Yuehua; Zhu, Jing; Wang, Ling; Dai, Lei

2017-11-01

In order to improve the electrochemical performance of the positive graphite felt electrode in vanadium flow redox battery, a novel method is developed to effectively modify the graphite felt by combination of etching of HF and oxidation of H2O2. After the etching of HF for the graphite felt at ambient temperature, abundant oxygen-containing functional groups were further introduced on the surface of graphite felt by hydrothermal treatment using H2O2 as oxidant. Benefiting from the surface etching and introduction of functional groups, mass transfer and electrode process can be improved significantly on the surface of graphite felt. VO2+/VO2+ redox reaction on the graphite felt modified by HF and H2O2 jointly (denote: GF-HF/H2O2) exhibits superior electrochemical kinetics in comparison with the graphite felt modified by single HF or H2O2 treatment. The cell using GF-HF/H2O2 as the positive electrode was assembled and its electrochemical properties were evaluated. The increase of energy efficiency of 4.1% for GF-HF/H2O2 at a current density of 50 mA cm-2 was obtained compared with the pristine graphite felt. The cell using GF-HF/H2O2 also demonstrated higher discharge capacity. Our study revealed that HF/H2O2 treatment is an efficient method to enhance the electrochemical performance of graphite felt, further improving the comprehensive energy storage performance of the vanadium flow redox battery.

Common iliac artery aneurysms in patients with abdominal aortic aneurysms.

PubMed

Armon, M P; Wenham, P W; Whitaker, S C; Gregson, R H; Hopkinson, B R

1998-03-01

To determine the incidence of common iliac artery (CIA) aneurysms in patients with abdominal aortic aneurysms (AAA) and to evaluate the relationship between AAA and CIA diameter. Spiral CT angiography was used to measure the maximum diameters of the abdominal aorta and the common iliac arteries of 215 patients with AAA. The median CIA diameter was 1.7 cm--significantly greater than the published mean of 1.25 (2 S.D. = 0.85-1.65) cm of an age-matched, non-vascular population. Thirty-four patients (16%) had unilateral and 26 patients (12%) bilateral CIA aneurysms > or = 2.4 cm diameter. Eight-six vessels (20%) were affected. Right CIA diameters were wider than left CIA diameters (p < 0.0001, Wilcoxon matched-pairs signed rank test). The correlation between AAA size and CIA diameter was weak. The AAA population has abnormally dilated common iliac arteries. In this population, common iliac artery aneurysms should be defined as those greater than 2.4 cm diameter. 20% of CIAs in patients with AAA are aneurysmal according to this definition.

Porous carbon derived from disposable shaddock peel as an excellent catalyst toward VO2+/VO2+ couple for vanadium redox battery

NASA Astrophysics Data System (ADS)

Liu, J.; Wang, Z. A.; Wu, X. W.; Yuan, X. H.; Hu, J. P.; Zhou, Q. M.; Liu, Z. H.; Wu, Y. P.

2015-12-01

Functional porous carbon (PC) derived from bio-friendly shaddock peel has been firstly explored as catalyst for vanadium redox flow battery (VRB). The prepared PC is micro-mesoporous with high BET surface area of 882.7 m2 g-1, has some surface oxygen-containing functional groups, and is doped with N and P heteroatoms. These three factors greatly favor the electrochemical reactions of VO2+/VO2+ on the PC modified glass carbon (PC-GC). Compared with the naked GC and graphite modified GC, the PC-GC presents a lower peak separation (66 mV), higher anodic current density (17.1 mA cm-2) and cathodic current density (15.0 mA cm-2). The VRB using PC modified graphite felt (GF) as positive electrode demonstrates an enhanced voltage efficiency of 82.7% at the current density of 60 mA cm-2, and a better rate performance than that from the virginal GF.

Structural and High-Temperature Tensile Properties of Special Pitch-Coke Graphites

NASA Technical Reports Server (NTRS)

Kotlensky, W. V.; Martens, H. E.

1961-01-01

The room-temperature structural properties and the tensile properties up to 5000 F (275O C) were determined for ten grades of specially prepared petroleum-coke coal-tar-pitch graphites which were graphitized at 5430 F (3000 C). One impregnation with coal-tar pitch increased the bulk density from 1.41 to 1.57 g/cm3 and the maximum strength at 4500 F (2500 C) from 4000 to 5700 psi. None of the processing parameters studied had a marked effect on the closed porosity or the X-ray structure or the per cent graphitization. The coarse-particle filler resulted in the lowest coefficient of thermal expansion and the fine-particle filler in the highest coefficient. A marked improvement in uniformity of tensile strength was observed. A standard-deviation analysis gave a one-sigma value of approximately 150 psi for one of these special grades and values of 340-420 psi for three commercial grades.

The electrophoretic deposition of ZnO on highly oriented pyrolytic graphite

NASA Astrophysics Data System (ADS)

Ghalamboran, Milad; Jahangiri, Mojtaba; Yousefiazari, Ehsan

2017-12-01

Intensive research has been conducted on ZnO thin and thick films in recent years. Such layers, used in different electronic devices, are deposited utilizing various methods, but electrophoretic deposition (EPD) has been chosen because of the advantages like low energy consumption, economical superiority, ecofriendliness, controllability, and high deposition rate. Here, we report electrophoretically depositing ZnO layers onto highly oriented pyrolytic graphite. Well-dispersed and stable ZnO suspensions are used for the deposition of continuous and even layers of ZnO on the substrate. ZnO powder is dispersed in acetone. The electric field applied is in the 250 V/cm to 2000 V/cm range. The morphology of the deposits are studied by SEM at the different stages of the deposition process.

In-situ observation of the chemical erosion of graphite in the scrape-off-layer of TEXTOR

NASA Astrophysics Data System (ADS)

Philipps, V.; Vietzke, E.; Erdweg, M.

1989-04-01

A sniffer probe system has been used to investigate the chemical erosion during interaction of the TEXTOR scrape-off plasma with a pyrolytic graphite plate at temperatures up to 1400 °C. Floating potential conditions as well as 200 V bias has been applied at plasma ion fluxes of about 10 18ions/cm 2 sec.Methane formation was found to be 8 × 10 -3 CH 4/H and 1.5 × 10 -2 CD 4/D + for room temperature graphite and floating potential increasing by a factor of two at temperature around 500 °C. Biasing the graphite decreases the methane yield at room temperature and increase it in the maximum temperature range. CO formation due to chemical interaction of oxygen ions with the graphite reaches ratios between 3 and 6 × 10 -2 CO/D(H) near the limiter edge under normal TEXTOR scrape-off conditions and exceeds the chemical hydro-(deu-tero-carbon formation significantly. The results are discussed in view of the present status of hydro-(deutero-)carbon formation on graphite and carbon impurity observations made in fusion experiments.

A contrastive study of three graphite anodes in the piperidinium based electrolytes for lithium ion batteries

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

Jiang, Xiao-Tao; Wang, Chen-Yi; Gao, Kun, E-mail: gaokun0451@163.com

Graphical abstract: The fitting results of R{sub sei} and R{sub ct} of three graphite/Li cells. Besides three graphite/Li cells show the similar R{sub sei}, the NG198/Li cell demonstrates a higher R{sub ct} value in all test temperatures. Especially, the R{sub ct} at 333 K is even up to 355.8 Ω cm{sup 2}. Obviously, the narrow distribution of edge plane for NG198 caused this result, and then greatly restricts its cell capacity. By contrast, CMB with bigger specific surface area and more Li{sup +} insertion points shows lower resistance at room temperature, which should help to improve its capacity. - Highlights:more » • SEI film is closely related to graphite structures and formation temperature. • The graphite with bigger surface area and more Li{sup +} insertion points behaves better. • The graphite with narrow edge plane is uncompetitive for ionic liquid electrolyte. - Abstract: The electrochemical behaviors of natural graphite (NG198), artificial graphite (AG360) and carbon microbeads (CMB) in an ionic liquid based electrolyte are investigated by cyclic voltammetry (CV). The surface and structure of three graphite materials are characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD) before and after cycling. It is found that solid electrolyte interface (SEI) is closely related to graphite structure. Benefiting from larger specific surface area and more dispersed Li{sup +} insertion points, CMB shows a better Li{sup +} insertion/de-insertion behavior than NG198 and AG360. Furthermore, electrochemical impedance spectra (EIS) prove that the SEI of different graphite electrodes has different intrinsic resistance and Li{sup +} penetrability. By comparison, CMB behaves better cell performances than AG360, while the narrow edge plane makes NG198 uncompetitive as a potential anode for the ionic liquids (ILs)-type Li-ion battery.« less

The prevalence of cervical myelopathy among subjects with narrow cervical spinal canal in a population-based magnetic resonance imaging study: the Wakayama Spine Study.

PubMed

Nagata, Keiji; Yoshimura, Noriko; Hashizume, Hiroshi; Muraki, Shigeyuki; Ishimoto, Yuyu; Yamada, Hiroshi; Takiguchi, Noboru; Nakagawa, Yukihiro; Minamide, Akihito; Oka, Hiroyuki; Kawaguchi, Hiroshi; Nakamura, Kozo; Akune, Toru; Yoshida, Munehito

2014-12-01

A narrow cervical spinal canal (CSC) is a well-known risk factor for cervical myelopathy (CM). However, no epidemiologic data of the CSC based on a population-based cohort are available. The purpose of the study was to investigate the age-related differences in CSC diameters on plain radiographs and to examine the associated magnetic resonance imaging (MRI) abnormalities including cervical cord compression and increased signal intensity (ISI) as well as the clinical CM with the narrow CSC. This was a cross-sectional study. Data were obtained from the baseline survey of the Wakayama Spine Study that was performed from 2008 to 2010 in a western part of Japan. Finally, a total of 959 subjects (319 men and 640 women; mean age, 66.4 years) were included. The outcome measures included in the study were the CSC diameter at C5 level on plain radiographs, cervical cord compression and ISI on sagittal T2-weighted MRI, and physical signs related to CM (eg, the Hoffmann reflex, hyperreflexia of the patellar tendon, the Babinski reflex, sensory and motor function, and bowel/bladder symptoms). The age-related differences of CSC diameters in men and women were investigated by descriptive statistics. The prevalence of MRI abnormalities and clinical CM was compared among the groups divided by the CSC diameter (less than 13, 13-15, and 15 mm or more). In addition, a logistic regression analysis was performed to determine the association of the CSC diameter with cervical cord compression/clinical CM after overall adjustment for age, sex, and body mass index. The CSC diameter was narrower with increasing age in both men and women. The prevalence of cervical cord compression, ISI, and the clinical CM was significantly higher in the narrower CSC group. The prevalence of cervical cord compression, ISI, and CM among subjects with CSC diameter less than 13 mm was 38.0%, 5.4%, and 10.1%, respectively. In the logistic model, the CSC diameter was a significant predictive factor for the clinical CM (p<.0001). This study firstly confirmed the age-related differences in CSC diameters and the significant association of the narrow CSC diameter with CM in a population-based cohort. Copyright © 2014 Elsevier Inc. All rights reserved.

Assembly, growth, and catalytic activity of gold nanoparticles in hollow carbon nanofibers.

PubMed

La Torre, Alessandro; Giménez-López, Maria del Carmen; Fay, Michael W; Rance, Graham A; Solomonsz, William A; Chamberlain, Thomas W; Brown, Paul D; Khlobystov, Andrei N

2012-03-27

Graphitized carbon nanofibers (GNFs) act as efficient templates for the growth of gold nanoparticles (AuNPs) adsorbed on the interior (and exterior) of the tubular nanostructures. Encapsulated AuNPs are stabilized by interactions with the step-edges of the individual graphitic nanocones, of which GNFs are composed, and their size is limited to approximately 6 nm, while AuNPs adsorbed on the atomically flat graphitic surfaces of the GNF exterior continue their growth to 13 nm and beyond under the same heat treatment conditions. The corrugated structure of the GNF interior imposes a significant barrier for the migration of AuNPs, so that their growth mechanism is restricted to Ostwald ripening. Conversely, nanoparticles adsorbed on smooth GNF exterior surfaces are more likely to migrate and coalesce into larger nanoparticles, as revealed by in situ transmission electron microscopy imaging. The presence of alkyl thiol surfactant within the GNF channels changes the dynamics of the AuNP transformations, as surfactant molecules adsorbed on the surface of the AuNPs diminished the stabilization effect of the step-edges, thus allowing nanoparticles to grow until their diameters reach the internal diameter of the host nanofiber. Nanoparticles thermally evolved within the GNF channel exhibit alignment, perpendicular to the GNF axis due to interactions with the step-edges and parallel to the axis because of graphitic facets of the nanocones. Despite their small size, AuNPs in GNF possess high stability and remain unchanged at temperatures up to 300 °C in ambient atmosphere. Nanoparticles immobilized at the step-edges within GNF are shown to act as effective catalysts promoting the transformation of dimethylphenylsilane to bis(dimethylphenyl)disiloxane with a greater than 10-fold enhancement of selectivity as compared to free-standing or surface-adsorbed nanoparticles. © 2012 American Chemical Society

High performance Li-ion sulfur batteries enabled by intercalation chemistry.

PubMed

Lv, Dongping; Yan, Pengfei; Shao, Yuyan; Li, Qiuyan; Ferrara, Seth; Pan, Huilin; Graff, Gordon L; Polzin, Bryant; Wang, Chongmin; Zhang, Ji-Guang; Liu, Jun; Xiao, Jie

2015-09-11

The unstable interface of lithium metal in high energy density Li sulfur (Li-S) batteries raises concerns of poor cycling, low efficiency and safety issues, which may be addressed by using intercalation types of anode. Herein, a new prototype of Li-ion sulfur battery with high performance has been demonstrated by coupling a graphite anode with a sulfur cathode (2 mA h cm(-2)) after successfully addressing the interface issue of graphite in an ether based electrolyte.

Digital terrestrial photogrammetric methods for tree stem analysis

Treesearch

Neil A. Clark; Randolph H. Wynne; Daniel L. Schmoldt; Matt Winn

2000-01-01

A digital camera was used to measure diameters at various heights along the stem on 20 red oak trees. Diameter at breast height ranged from 16 to over 60 cm, and height to a 10-cm top ranged from 12 to 20 m. The chi-square maximum anticipated error of geometric mean diameter estimates at the 95 percent confidence level was within ±4 cm for all heights when...

Quantifying the Hierarchical Order in Self-Aligned Carbon Nanotubes from Atomic to Micrometer Scale.

PubMed

Meshot, Eric R; Zwissler, Darwin W; Bui, Ngoc; Kuykendall, Tevye R; Wang, Cheng; Hexemer, Alexander; Wu, Kuang Jen J; Fornasiero, Francesco

2017-06-27

Fundamental understanding of structure-property relationships in hierarchically organized nanostructures is crucial for the development of new functionality, yet quantifying structure across multiple length scales is challenging. In this work, we used nondestructive X-ray scattering to quantitatively map the multiscale structure of hierarchically self-organized carbon nanotube (CNT) "forests" across 4 orders of magnitude in length scale, from 2.0 Å to 1.5 μm. Fully resolved structural features include the graphitic honeycomb lattice and interlayer walls (atomic), CNT diameter (nano), as well as the greater CNT ensemble (meso) and large corrugations (micro). Correlating orientational order across hierarchical levels revealed a cascading decrease as we probed finer structural feature sizes with enhanced sensitivity to small-scale disorder. Furthermore, we established qualitative relationships for single-, few-, and multiwall CNT forest characteristics, showing that multiscale orientational order is directly correlated with number density spanning 10 9 -10 12 cm -2 , yet order is inversely proportional to CNT diameter, number of walls, and atomic defects. Lastly, we captured and quantified ultralow-q meridional scattering features and built a phenomenological model of the large-scale CNT forest morphology, which predicted and confirmed that these features arise due to microscale corrugations along the vertical forest direction. Providing detailed structural information at multiple length scales is important for design and synthesis of CNT materials as well as other hierarchically organized nanostructures.

Electrochemical fabrication of interconnected tungsten bronze nanosheets for high performance supercapacitor

NASA Astrophysics Data System (ADS)

Yang, Gan; Liu, Xiao-Xia

2018-04-01

Interconnected H0.12WO3ṡH2O nanosheets with high electrochemical performances are fabricated on partial exfoliated graphite substrate (Ex-GF) by potential-limited pulse galvanostatic method (PLPG). The dead volume problem of bulk pesudocapacitive materials is addressed by the novel interconnected nanosheets structure, enabling a large specific capacitance of 5.95 F cm-2 (495.8 F g-1) at 2 mA cm-2. Merited from the fluent electrolyte penetration channels established by the plenty voids among nanosheets, as well as fast electron transportation in the electronic conductive tungsten bronze which is directly grown from graphite substrate, the obtained WO3/Ex-GF demonstrates excellent rate capability. The material can maintain 60.0% of its capacitance when the discharge current density increases from 2 to 100 mA cm-2. Moreover, WO3/Ex-GF doesn't show capacitance decay after 5000 galvanostatic charge-discharge cycles, displaying its super stability. Furthermore, a high performance asymmetric supercapacitor assembled by using WO3/Ex-GF and electrochemical fabricated MnO2/Ex-GF as negative and positive electrodes, respectively displays a high energy density of 2.88 mWh cm-3 at the power density of 11.1 mW cm-3, demonstrating its potential application for energy storage.

Graphite-Conjugated Rhenium Catalysts for Carbon Dioxide Reduction

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

Oh, Seokjoon; Gallagher, James R.; Miller, Jeffrey T.

2016-02-17

Condensation of fac-Re(5,6-diamino-1,10-phenanthroline)(CO)(3)Cl to o-quinone edge defects on graphitic carbon surfaces generates graphite-conjugated rhenium (GCC-Re) catalysts that are highly active for CO2 reduction to CO in acetonitrile electrolyte. X-ray photo-electron and X-ray absorption spectroscopies establish the formation of surface-bound Re centers with well-defined coordination environments. GCC-Re species on glassy carbon surfaces display catalytic currents greater than 50 mA cm(-2) with 96 +/- 3% Faradaic efficiency for CO production. Normalized for the number of Re active sites, GCC-Re catalysts exhibit higher turnover frequencies than that of a soluble molecular analogue, fac-Re(1,10-phenanthroline)(CO)(3)Cl, and turnover numbers greater than 12,000. In contrast to themore » molecular analogue, GCC-Re surfaces display a Tafel slope of 150 mV/decade, indicative of a catalytic mechanism involving rate-limiting one-electron transfer. This work establishes graphite conjugation as a powerful strategy for generating well-defined, tunable, heterogeneous electrocatalysts on ubiquitous graphitic carbon surfaces.« less

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...

Graphite fluoride fibers and their applications in the space industry

NASA Technical Reports Server (NTRS)

Hung, Ching-Chen; Long, Martin; Dever, Therese

1990-01-01

Characterization and potential space applications of graphite fluoride fibers from commercially available graphitized carbon fibers are presented. Graphite fluoride fibers with fluorine to carbon ratios of 0.65 and 0.68 were found to have electrical resistivity values of 10(exp 4) and 10(exp 11) Ohms-cm, respectively, and thermal conductivity values of 24 and 5 W/m-K, respectively. At this fluorine content range, the fibers have tensile strength of 0.25 + or - 0.10 GPa (36 + or - 14 ksi), Young's modulus of 170 + or - 30 GPa (25 + or - 5 Msi). The coefficient of thermal expansion value of a sample with fluorine to carbon ratio of 0.61 was found to be 7 ppm/C. These properties change and approach the graphite value as the fluorine content approach 0. Electrically insulative graphite fluoride fiber is at least five times more thermally conductive than fiberglass. Therefore, it can be used as a heat sinking printed circuit board material for low temperature, long life power electronics in spacecraft. Also, partially fluorinated fiber with tailor-made physical properties to meet the requirements of certain engineering design can be produced. For example, a partially fluorinated fiber could have a predetermined CTE value in -1.5 to 7 ppm/C range and would be suitable for use in solar concentrators in solar dynamic power systems. It could also have a predetermined electrical resistivity value suitable for use as a low observable material. Experimental data indicate that slightly fluorinated graphite fibers are more durable in the atomic oxygen environment than pristine graphite. Therefore, fluorination of graphite used in the construction of spacecraft that would be exposed to the low Earth orbit atomic oxygen may protect defect sites in atomic oxygen protective coatings and therefore decrease the rate of degradation of graphite.

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

PubMed

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

2016-06-29

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

Enhancement mechanism of field electron emission properties in hybrid carbon nanotubes with tree- and wing-like features

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

Yang, G.M.; School of Materials Science and Engineering, The University of New South Wales, NSW 2052; Yang, C.C., E-mail: ccyang@unsw.edu.a

2009-12-15

In this work, the tree-like carbon nanotubes (CNTs) with branches of different diameters and the wing-like CNTs with graphitic-sheets of different densities were synthesized by using plasma enhanced chemical vapor deposition. The nanostructures of the as-prepared hybrid carbon materials were characterized by scanning electron microscopy and transmission electron microscopy. The structural dependence of field electron emission (FEE) property was also investigated. It is found that both of the tree- and wing-like CNTs exhibit a lower turn-on field and higher emission current density than the pristine CNTs, which can be ascribed to the effects of branch size, crystal orientation, and graphitic-sheetmore » density. - Graphical abstract: Tree-like carbon nanotubes (CNTs) with branches and the wing-like CNTs with graphitic-sheets were synthesized by using plasma enhanced chemical vapor deposition. The structural dependence of field electron emission property was also investigated.« less

Development of IR Contrast Data Analysis Application for Characterizing Delaminations in Graphite-Epoxy Structures

NASA Technical Reports Server (NTRS)

Havican, Marie

2012-01-01

Objective: Develop infrared (IR) flash thermography application based on use of a calibration standard for inspecting graphite-epoxy laminated/honeycomb structures. Background: Graphite/Epoxy composites (laminated and honeycomb) are widely used on NASA programs. Composite materials are susceptible for impact damage that is not readily detected by visual inspection. IR inspection can provide required sensitivity to detect surface damage in composites during manufacturing and during service. IR contrast analysis can provide characterization of depth, size and gap thickness of impact damage. Benefits/Payoffs: The research provides an empirical method of calibrating the flash thermography response in nondestructive evaluation. A physical calibration standard with artificial flaws such as flat bottom holes with desired diameter and depth values in a desired material is used in calibration. The research devises several probability of detection (POD) analysis approaches to enable cost effective POD study to meet program requirements.

Synthesis and characterization of MOF-aminated graphite oxide composites for CO2 capture

NASA Astrophysics Data System (ADS)

Zhao, Yunxia; Ding, Huiling; Zhong, Qin

2013-11-01

A kind of metal-organic frameworks (MOF-5) and aminated graphite oxide (AGO) composites were prepared for CO2 capture to mitigate global warming. MOF-5, MOF-5/GO (composite of MOF-5 and graphite oxide) and MOF-5/AGO samples were characterized by X-ray powder diffraction (XRD), infrared spectroscopy (IR), scanning electron microscope (SEM), nitrogen adsorption as well as thermogravimetric analysis to figure out their chemistry and structure information. Three types of samples with suitable specific surface area and pore diameter were chosen to test CO2 adsorption performance and stability under humidity conditions. The results indicate that high surface area and pore volume, pore similar in size to the size of gas adsorbate, and extra reactive sites modified in the composites contributes to the high CO2 capacity. Besides, the composites involved by GO or AGO show better anti-moisture performance than the parent MOF.

Postbuckling behavior of axially compressed graphite-epoxy cylindrical panels with circular holes

NASA Technical Reports Server (NTRS)

Knight, N. F., Jr.; Starnes, J. H., Jr.

1984-01-01

The results of an experimental and analytical study of the effects of circular holes on the postbuckling behavior of graphite-epoxy cylindrical panels loaded in axial compression are presented. The STAGSC-1 general shell analysis computer code is used to determine the buckling and postbuckling response of the panels. The loaded, curved ends of the specimens were clamped by fixtures and the unloaded, straight edges were simply supported by knife-edge restraints. The panels are loaded by uniform end shortening to several times the end shortening at buckling. The unstable equilibrium path of the postbuckling response is obtained analytically by using a method based on controlling an equilibrium-path-arc-length parameter instead of the traditional load parameter. The effects of hole diameter, panel radius, and panel thickness on postbuckling response are considered in the study. Experimental results are compared with the analytical results and the failure characteristics of the graphite-epoxy panels are described.

Radiation damage and thermal shock response of carbon-fiber-reinforced materials to intense high-energy proton beams

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

Simos, N.; Zhong, Z.; Ghose, S.

Here, a comprehensive study on the effects of energetic protons on carbon-fiber composites and compounds under consideration for use as low-Z pion production targets in future high-power accelerators and low-impedance collimating elements for intercepting TeV-level protons at the Large Hadron Collider has been undertaken addressing two key areas, namely, thermal shock absorption and resistance to irradiation damage. Carbon-fiber composites of various fiber weaves have been widely used in aerospace industries due to their unique combination of high temperature stability, low density, and high strength. The performance of carbon-carbon composites and compounds under intense proton beams and long-term irradiation have beenmore » studied in a series of experiments and compared with the performance of graphite. The 24-GeV proton beam experiments confirmed the inherent ability of a 3D C/C fiber composite to withstand a thermal shock. A series of irradiation damage campaigns explored the response of different C/C structures as a function of the proton fluence and irradiating environment. Radiolytic oxidation resulting from the interaction of oxygen molecules, the result of beam-induced radiolysis encountered during some of the irradiation campaigns, with carbon atoms during irradiation with the presence of a water coolant emerged as a dominant contributor to the observed structural integrity loss at proton fluences ≥5×10 20 p/cm 2. The carbon-fiber composites were shown to exhibit significant anisotropy in their dimensional stability driven by the fiber weave and the microstructural behavior of the fiber and carbon matrix accompanied by the presence of manufacturing porosity and defects. Carbon-fiber-reinforced molybdenum-graphite compounds (MoGRCF) selected for their impedance properties in the Large Hadron Collider beam collimation exhibited significant decrease in postirradiation load-displacement behavior even after low dose levels (~5×10 18 p cm -2). In addition, the studied MoGRCF compound grade suffered a high degree of structural degradation while being irradiated in a vacuum after a fluence ~5×10 20 p cm -2. Finally, x-ray diffraction studies on irradiated C/C composites and a carbon-fiber-reinforced Mo-graphite compound revealed (a) low graphitization in the “as-received” 3D C/C and high graphitization in the MoGRCF compound, (b) irradiation-induced graphitization of the least crystallized phases in the carbon fibers of the 2D and 3D C/C composites, (c) increased interplanar distances along the c axis of the graphite crystal with increasing fluence, and (d) coalescence of interstitial clusters after irradiation forming new crystalline planes between basal planes and excellent agreement with fast neutron irradiation effects.« less

Radiation damage and thermal shock response of carbon-fiber-reinforced materials to intense high-energy proton beams

DOE PAGES

Simos, N.; Zhong, Z.; Ghose, S.; ...

2016-11-16

Here, a comprehensive study on the effects of energetic protons on carbon-fiber composites and compounds under consideration for use as low-Z pion production targets in future high-power accelerators and low-impedance collimating elements for intercepting TeV-level protons at the Large Hadron Collider has been undertaken addressing two key areas, namely, thermal shock absorption and resistance to irradiation damage. Carbon-fiber composites of various fiber weaves have been widely used in aerospace industries due to their unique combination of high temperature stability, low density, and high strength. The performance of carbon-carbon composites and compounds under intense proton beams and long-term irradiation have beenmore » studied in a series of experiments and compared with the performance of graphite. The 24-GeV proton beam experiments confirmed the inherent ability of a 3D C/C fiber composite to withstand a thermal shock. A series of irradiation damage campaigns explored the response of different C/C structures as a function of the proton fluence and irradiating environment. Radiolytic oxidation resulting from the interaction of oxygen molecules, the result of beam-induced radiolysis encountered during some of the irradiation campaigns, with carbon atoms during irradiation with the presence of a water coolant emerged as a dominant contributor to the observed structural integrity loss at proton fluences ≥5×10 20 p/cm 2. The carbon-fiber composites were shown to exhibit significant anisotropy in their dimensional stability driven by the fiber weave and the microstructural behavior of the fiber and carbon matrix accompanied by the presence of manufacturing porosity and defects. Carbon-fiber-reinforced molybdenum-graphite compounds (MoGRCF) selected for their impedance properties in the Large Hadron Collider beam collimation exhibited significant decrease in postirradiation load-displacement behavior even after low dose levels (~5×10 18 p cm -2). In addition, the studied MoGRCF compound grade suffered a high degree of structural degradation while being irradiated in a vacuum after a fluence ~5×10 20 p cm -2. Finally, x-ray diffraction studies on irradiated C/C composites and a carbon-fiber-reinforced Mo-graphite compound revealed (a) low graphitization in the “as-received” 3D C/C and high graphitization in the MoGRCF compound, (b) irradiation-induced graphitization of the least crystallized phases in the carbon fibers of the 2D and 3D C/C composites, (c) increased interplanar distances along the c axis of the graphite crystal with increasing fluence, and (d) coalescence of interstitial clusters after irradiation forming new crystalline planes between basal planes and excellent agreement with fast neutron irradiation effects.« less

Radiation damage and thermal shock response of carbon-fiber-reinforced materials to intense high-energy proton beams

NASA Astrophysics Data System (ADS)

Simos, N.; Zhong, Z.; Ghose, S.; Kirk, H. G.; Trung, L.-P.; McDonald, K. T.; Kotsina, Z.; Nocera, P.; Assmann, R.; Redaelli, S.; Bertarelli, A.; Quaranta, E.; Rossi, A.; Zwaska, R.; Ammigan, K.; Hurh, P.; Mokhov, N.

2016-11-01

A comprehensive study on the effects of energetic protons on carbon-fiber composites and compounds under consideration for use as low-Z pion production targets in future high-power accelerators and low-impedance collimating elements for intercepting TeV-level protons at the Large Hadron Collider has been undertaken addressing two key areas, namely, thermal shock absorption and resistance to irradiation damage. Carbon-fiber composites of various fiber weaves have been widely used in aerospace industries due to their unique combination of high temperature stability, low density, and high strength. The performance of carbon-carbon composites and compounds under intense proton beams and long-term irradiation have been studied in a series of experiments and compared with the performance of graphite. The 24-GeV proton beam experiments confirmed the inherent ability of a 3D C/C fiber composite to withstand a thermal shock. A series of irradiation damage campaigns explored the response of different C/C structures as a function of the proton fluence and irradiating environment. Radiolytic oxidation resulting from the interaction of oxygen molecules, the result of beam-induced radiolysis encountered during some of the irradiation campaigns, with carbon atoms during irradiation with the presence of a water coolant emerged as a dominant contributor to the observed structural integrity loss at proton fluences ≥5 ×1020 p /cm2 . The carbon-fiber composites were shown to exhibit significant anisotropy in their dimensional stability driven by the fiber weave and the microstructural behavior of the fiber and carbon matrix accompanied by the presence of manufacturing porosity and defects. Carbon-fiber-reinforced molybdenum-graphite compounds (MoGRCF) selected for their impedance properties in the Large Hadron Collider beam collimation exhibited significant decrease in postirradiation load-displacement behavior even after low dose levels (˜5 ×1018 p cm-2 ). In addition, the studied MoGRCF compound grade suffered a high degree of structural degradation while being irradiated in a vacuum after a fluence ˜5 ×1020 p cm-2 . Finally, x-ray diffraction studies on irradiated C/C composites and a carbon-fiber-reinforced Mo-graphite compound revealed (a) low graphitization in the "as-received" 3D C/C and high graphitization in the MoGRCF compound, (b) irradiation-induced graphitization of the least crystallized phases in the carbon fibers of the 2D and 3D C/C composites, (c) increased interplanar distances along the c axis of the graphite crystal with increasing fluence, and (d) coalescence of interstitial clusters after irradiation forming new crystalline planes between basal planes and excellent agreement with fast neutron irradiation effects.

A continuous silicon-coating facility

NASA Technical Reports Server (NTRS)

Butter, C.; Heaps, J. D.

1979-01-01

Automatic continuous silicon-coating facility is used to process 100 by 10 cm graphite-coated ceramic substrates for silicon solar cells. Process reduces contamination associated with conventional dip-coating processes, improving material service life.

Fabrication and Vibration Results of 30-cm Pyrolytic Graphite Ion Optics

NASA Technical Reports Server (NTRS)

DePano, Michael K.; Hart, Stephen L.; Hanna, Andrew A.; Schneider, Analyn C.

2004-01-01

Boeing Electron Dynamic Devices, Inc. is currently developing pyrolytic graphite (PG) grids designed to operate on 30-cm NSTAR-type thrusters for the Carbon Based Ion Optics (CBIO) program. The PG technology effort of the CBIO program aims to research PG as a flightworthy material for use in dished ion optics by designing, fabricating, and performance testing 30-cm PG grids. As such, PG grid fabrication results will be discussed as will PG design considerations and how they must differ from the NSTAR molybdenum grid design. Surface characteristics and surface processing of PG will be explored relative to effects on voltage breakdown. Part of the CBIO program objectives is to understand the erosion of PG due to Xenon ion bombardment. Discussion of PG and CC sputter yields will be presented relative to molybdenum. These sputter yields will be utilized in the life modeling of carbon-based grids. Finally, vibration results of 30-cm PG grids will be presented and compared to a first-order model generated at Boeing EDD. Performance testing results of the PG grids will not be discussed in this paper as it has yet to be completed.

Anatomic characteristics of ruptured abdominal aortic aneurysm on conventional CT scans: Implications for rupture risk.

PubMed

Fillinger, Mark F; Racusin, Jessica; Baker, Robert K; Cronenwett, Jack L; Teutelink, Arno; Schermerhorn, Marc L; Zwolak, Robert M; Powell, Richard J; Walsh, Daniel B; Rzucidlo, Eva M

2004-06-01

The purpose of this study was to analyze anatomic characteristics of patients with ruptured abdominal aortic aneurysms (AAAs), with conventional two-dimensional computed tomography (CT), including comparison with control subjects matched for age, gender, and size. Records were reviewed to identify all CT scans obtained at Dartmouth-Hitchcock Medical Center or referring hospitals before emergency AAA repair performed because of rupture or acute severe pain (RUP group). CT scans obtained before elective AAA repair (ELEC group) were reviewed for age and gender match with patients in the RUP group. More than 40 variables were measured on each CT scan. Aneurysm diameter matching was achieved by consecutively deleting the largest RUP scan and the smallest ELEC scan to prevent bias. CT scans were analyzed for 259 patients with AAAs: 122 RUP and 137 ELEC. Patients were well matched for age, gender, and other demographic variables or risk factors. Maximum AAA diameter was significantly different in comparisons of all patients (RUP, 6.5 +/- 2 cm vs ELEC, 5.6 +/- 1 cm; P <.0001), and mean diameter of ruptured AAAs was 5 mm smaller in female patients (6.1 +/- 2 cm vs 6.6 +/- 2 cm; P =.007). Two hundred patients were matched for diameter, gender, and age (100 from each group; maximum AAA diameter, 6.0 +/- 1 cm vs 6.0 +/- 1 cm). Analysis of diameter-matched AAAs indicated that most variables were statistically similar in the two groups, including infrarenal neck length (17 +/- 1 mm vs 19 +/- 1 mm; P =.3), maximum thrombus thickness (25 +/- 1 mm vs 23 +/- 1 mm, P =.4), and indices of body habitus, such as [(maximum AAA diameter)/(normal suprarenal aorta diameter)] or [(maximum AAA diameter)/(L3 transverse diameter)]. Multivariate analysis controlling for gender indicated that the most significant variables for rupture were aortic tortuosity (odds ratio [OR] 3.3, indicating greater risk with no or mild tortuosity), diameter asymmetry (OR, 3.2 for a 1-cm difference in major-minor axis), and current smoking (OR, 2.7, with the greater risk in current smokers). When matched for age, gender, and diameter, ruptured AAAs tend to be less tortuous, yet have greater cross-sectional diameter asymmetry. On conventional two-dimensional CT axial sections, it appears that when diameter asymmetry is associated with low aortic tortuosity, the larger diameter on axial sections more accurately reflects rupture risk, and when diameter asymmetry is associated with moderate or severe aortic tortuosity, the smaller diameter on axial sections more accurately reflects rupture risk. Current smoking is significantly associated with rupture, even when controlling for gender and AAA anatomy.

Comparison of the oxidation rate and degree of graphitization of selected IG and NBG nuclear graphite grades

NASA Astrophysics Data System (ADS)

Chi, Se-Hwan; Kim, Gen-Chan

2008-10-01

The oxidation rate and degree of graphitization (DOG) were determined for some selected nuclear graphite grades (i.e., IG-110, IG-430, NBG-18, NBG-25) and compared in view of their filler coke type (i.e., pitch or petroleum coke) and the physical property of the grades. Oxidation rates were determined at six temperatures between 600 and 960 °C in air by using a three-zone vertical tube furnace at a 10 l/min air flow rate. The specimens were a cylinder with a 25.4 mm diameter and a 25.4 mm length. The DOG was determined based on the lattice parameter c determined from an X-ray diffraction (XRD). Results showed that, even though the four examined nuclear graphite grades showed a highly temperature-sensitive oxidation behavior through out the test temperature range of 600-950 °C, the differences between the grades were not significant. The oxidation rates determined for a 5-10% weight loss at the six temperatures were nearly the same except for 702 and 808 °C, where the pitch coke graphites showed an apparent decrease in their oxidation rate, more so than the petroleum coke graphites. These effects of the coke type reduced or nearly disappeared with an increasing temperature. The average activation energy determined for 608-808 °C was 161.5 ± 7.3 kJ/mol, showing that the dominant oxidation reaction occurred by a chemical control. A relationship between the oxidation rate and DOG was not observed.

Pore diameter effects on phase behavior of a gas condensate in graphitic one-and two-dimensional nanopores.

PubMed

Welch, William R W; Piri, Mohammad

2016-01-01

Molecular dynamics (MD) simulations were performed on a hydrocarbon mixture representing a typical gas condensate composed mostly of methane and other small molecules with small fractions of heavier hydrocarbons, representative of mixtures found in tight shale reservoirs. The fluid was examined both in bulk and confined to graphitic nano-scale slits and pores. Numerous widths and diameters of slits and pores respectively were examined under variable pressures at 300 K in order to find conditions in which the fluid at the center of the apertures would not be affected by capillary condensation due to the oil-wet walls. For the bulk fluid, retrograde phase behavior was verified by liquid volumes obtained from Voronoi tessellations. In cases of both one and two-dimensional confinement, for the smallest apertures, heavy molecules aggregated inside the pore space and compression of the gas outside the solid structure lead to decreases in density of the confined fluid. Normal density/pressure relationships were observed for slits having gaps of above 3 nm and pores having diameters above 6 nm. At 70 bar, the minimum gap width at which the fluid could pass through the center of slits without condensation effects was predicted to be 6 nm and the corresponding diameter in pores was predicted to be 8 nm. The models suggest that in nanoscale networks involving pores smaller than these limiting dimensions, capillary condensation should significantly impede transmission of natural gases with similar composition.

A novel carbon black graphite hybrid air-cathode for efficient hydrogen peroxide production in bioelectrochemical systems

NASA Astrophysics Data System (ADS)

Li, Nan; An, Jingkun; Zhou, Lean; Li, Tian; Li, Junhui; Feng, Cuijuan; Wang, Xin

2016-02-01

Carbon black and graphite hybrid air-cathode is proved to be effective for H2O2 production in bioelectrochemical systems. The optimal mass ratio of carbon black to graphite is 1:5 with the highest H2O2 yield of 11.9 mg L-1 h-1 cm-2 (12.3 mA cm-2). Continuous flow is found to improve the current efficiency due to the avoidance of H2O2 accumulation. In the biological system, the highest H2O2 yield reaches 3.29 mg L-1h-1 (0.079 kg m-3day-1) with a current efficiency of 72%, which is higher than the abiotic system at the same current density. H2O2 produced in this system is mainly from the oxygen diffused through this air-cathode (>66%), especially when a more negative cathode potential is applied (94% at -1.0 V). This hybrid air-cathode has advantages of high H2O2 yield, high current density and no need of aeration, which make the synthesis of H2O2 more efficient and economical.

Poco Graphite Inc. SuperSiC 0.25m Mirror Cryogenic Test Result

NASA Technical Reports Server (NTRS)

Eng, Ron; Stahl, Phil; Hogue, Bill; Hadaway, James

2004-01-01

SuperSiC, a low areal density material, developed by POCO Graphite, have been used as mirror substrate for high energy lasers, laser radar systems, surveillance, telescopes, scan mirrors and satellites. SuperSiC has excellent thermal properties and cryogenic stability. It exhibits exceptional polishability for reflective optics with high strength, stiffness, and excellent thermal conductivity. A lightweighted 0.2-diameter polished SuperSic mirror was tested at cryogenic temperature at NASMSFC. Optical test results showed 6nm cry0 deformation from ambient to 30 degrees Kelvin and little to no change in its surface figure due to cry0 cycling.

Hypervelocity impacts into graphite

NASA Astrophysics Data System (ADS)

Latunde-Dada, S.; Cheesman, C.; Day, D.; Harrison, W.; Price, S.

2011-03-01

Studies have been conducted into the characterisation of the behaviour of commercial graphite (brittle) when subjected to hypervelocity impacts by a range of projectiles. The experiments were conducted with a two-stage gas gun capable of launching projectiles of differing density and strength to speeds of about 6kms-1 at right angles into target plates. The damage caused is quantified by measurements of the crater depth and diameters. From the experimental data collected, scaling laws were derived which correlate the crater dimensions to the velocity and the density of the projectile. It was found that for moderate projectile densities the crater dimensions obey the '2/3 power law' which applies to ductile materials.

Carbothermal transformation of a graphitic carbon nanofiber/silica aerogel composite to a SiC/silica nanocomposite.

PubMed

Lu, Weijie; Steigerwalt, Eve S; Moore, Joshua T; Sullivan, Lisa M; Collins, W Eugene; Lukehart, C M

2004-09-01

Carbon nanofiber/silica aerogel composites are prepared by sol-gel processing of surface-enhanced herringbone graphitic carbon nanofibers (GCNF) and Si(OMe)4, followed by supercritical CO2 drying. Heating the resulting GCNF/silica aerogel composites to 1650 degrees C under a partial pressure of Ar gas initiates carbothermal reaction between the silica aerogel matrix and the carbon nanofiber component to form SiC/silica nanocomposites. The SiC phase is present as nearly spherical nanoparticles, having an average diameter of ca. 8 nm. Formation of SiC is confirmed by powder XRD and by Raman spectroscopy.

Electrocatalytic activity of cobalt phosphide-modified graphite felt toward VO2+/VO2+ redox reaction

NASA Astrophysics Data System (ADS)

Ge, Zhijun; Wang, Ling; He, Zhangxing; Li, Yuehua; Jiang, Yingqiao; Meng, Wei; Dai, Lei

2018-04-01

A novel strategy for improving the electro-catalytic properties of graphite felt (GF) electrode in vanadium redox flow battery (VRFB) is designed by depositing cobalt phosphide (CoP) onto GF surface. The CoP powder is synthesized by direct carbonization of Co-based zeolitic imidazolate framework (ZIF-67) followed by phosphidation. Cyclic voltammetry results confirm that the CoP-modified graphite felt (GF-CoP) electrode has excellent reversibility and electro-catalytic activity to the VO2+/VO2+ cathodic reaction compared with the pristine GF electrode. The cell using GF-CoP electrode shows apparently higher discharge capacity over that based on GF electrode. The cell using GF-CoP electrode has the capacity of 67.2 mA h at 100 mA cm-2, 32.7 mA h larger than that using GF electrode. Compared with cell using GF electrode, the voltage efficiency of the cell based on GF-CoP electrode increases by 5.9% and energy efficiency by 5.4% at a current density of 100 mA cm-2. The cell using GF-CoP electrode can reach 94.31% capacity retention after 50 cycles at a current density of 30 mA cm-2. The results show that the CoP can effectively promote the VO2+/VO2+ redox reaction, implying that metal phosphides are a new kind of potential catalytic materials for VRFB.

Growth characteristics of mangrove seedling in silvofishery pond – the allometric relationship of height, diameter and leaf abundance

NASA Astrophysics Data System (ADS)

Dwi Hastuti, Endah; Budi Hastuti, Rini

2018-03-01

Dynamic environment condition of the silvofishery pond should provide an effect on the growth of mangrove seedling. This research aimed to observe the morphometric growth rate of mangrove seedling of Avicennia marina and Rhizophora mucronata planted in the silvofishery pond and to analyze the morphometric growth relationship of height, diameter and leaf number development of mangrove seedling. The research was conducted through field experiment involving mangrove species of A. marina and R. mucronata for 18 months during March 2015 to September 2016, both single structured and mixed structure. The observation was conducted every 13 weeks including seedling height, diameter and number of leaves. Data analysis was conducted by regression to provide the statistical relation between the growth of diameter – height, diameter – number of leaves and height – number of leaves. The result showed that the growth rate of A. marina in single structured pond was ranged from 0.38 – 3.00 cm.wk-1, 0.0015 – 0.0969 cm.wk‑1 and 0.1 – 13.7 leaves.wk‑1 respectively for height, diameter and number of leaves, while in mixed structure was 0.23 – 1.69 cm.wk‑1, 0.0169 – 0.0731 cm.wk‑1 and 0.5 – 14.0 leaves.wk-. The growth of R. mucronata respectively in single and mixed structure were 0.08 – 2.00 cm.wk‑1 and 0.15 – 2.62 cm.wk‑1, 0.0031 – 0.1369 cm.wk‑1 and 0.0008 – 0.0831 cm.wk‑1 and 0.0 – 1.9 leaves.wk‑1 and 0.0 – 1.6 leaves.wk-1respectively for height, diameter and number of leaves. Data analysis showed that the growth of seedling height of Avicennia in the mixed structure was significantly affected by its diameter growth and the number of leaves of Avicennia in single structured was significantly affected by its diameter. While the height, diameter and number of leaves of R. mucronata both in mixed and single structured silvofishery ponds were independent to each other. This research concluded that mangrove seedling growth is varied among species and growth environment.

Manufacturing High-Quality Carbon Nanotubes at Lower Cost

NASA Technical Reports Server (NTRS)

Benavides, Jeanette M.; Lidecker, Henning

2004-01-01

A modified electric-arc welding process has been developed for manufacturing high-quality batches of carbon nanotubes at relatively low cost. Unlike in some other processes for making carbon nanotubes, metal catalysts are not used and, consequently, it is not necessary to perform extensive cleaning and purification. Also, unlike some other processes, this process is carried out at atmospheric pressure under a hood instead of in a closed, pressurized chamber; as a result, the present process can be implemented more easily. Although the present welding-based process includes an electric arc, it differs from a prior electric-arc nanotube-production process. The welding equipment used in this process includes an AC/DC welding power source with an integral helium-gas delivery system and circulating water for cooling an assembly that holds one of the welding electrodes (in this case, the anode). The cathode is a hollow carbon (optionally, graphite) rod having an outside diameter of 2 in. (approximately equal to 5.1 cm) and an inside diameter of 5/8 in. (approximately equal to 1.6 cm). The cathode is partly immersed in a water bath, such that it protrudes about 2 in. (about 5.1 cm) above the surface of the water. The bottom end of the cathode is held underwater by a clamp, to which is connected the grounding cable of the welding power source. The anode is a carbon rod 1/8 in. (approximately equal to 0.3 cm) in diameter. The assembly that holds the anode includes a thumbknob- driven mechanism for controlling the height of the anode. A small hood is placed over the anode to direct a flow of helium downward from the anode to the cathode during the welding process. A bell-shaped exhaust hood collects the helium and other gases from the process. During the process, as the anode is consumed, the height of the anode is adjusted to maintain an anode-to-cathode gap of 1 mm. The arc-welding process is continued until the upper end of the anode has been lowered to a specified height above the surface of the water bath. The process causes carbon nanotubes to form in the lowest 2.5 cm of the anode. It also causes a deposit reminiscent of a sandcastle to form on the cathode. The nanotube-containing material is harvested. The cathode and anode can then be cleaned (or the anode is replaced, if necessary) and the process repeated to produce more nanotubes. Tests have shown that the process results in approximately equal to 50-percent yield of carbon nanotubes (mostly of the single-wall type) of various sizes. Whereas the unit cost of purified single-wall carbon nanotubes produced by other process is about $1,000/g in the year 2000, it has been estimated that for the present process, the corresponding cost would be about $10/g.

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

NASA Technical Reports Server (NTRS)

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

1987-01-01

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

Relevance of impacter shape to nonvisible damage and residual tensile strength of a thick graphite/epoxy laminate

NASA Technical Reports Server (NTRS)

Poe, C. C., Jr.

1990-01-01

A study was made to determine the relevance of impacter shape to nonvisible damage and tensile residual strength of a 36 mm (1.4 in.) thick graphite/epoxy motor case. The shapes of the impacters were as follows: 12.7 mm (0.5 in.) and 25.4 mm (1.0 in.) diameter hemispheres, a sharp corner, and a 6.3 mm (0.25 in.) diameter bolt-like rod. The investigation revealed that damage initiated when the contact pressure exceeded a critical level. However, the damage was not visible on the surface until an even higher pressure was exceeded. The damage on the surface consisted of a crater shaped like the impacter, and the damage below the surface consisted of broken fibers. The impact energy to initiate damage or cause visible damage on the surface increased approximately with impacter diameter to the third power. The reduction in strength for nonvisible damage increased with increasing diameter, 9 and 30 percent for the 12.7 mm (0.5 in.) and 25.4 mm (1.0 in.) diameter hemispheres, respectively. The corner impacter made visible damage on the surface for even the smallest impact energy. The rod impacter acted like a punch and sliced through the composite. Even so, the critical level of pressure to initiate damage was the same for the rod and hemispherical impacters. Factors of safety for nonvisible damage increased with increasing kinetic energy of impact. The effects of impacter shape on impact force, damage size, damage visibility, and residual tensile strength were predicted quite well assuming Hertzian contact and using maximum stress criteria and a surface crack analysis.

Economics of ingot slicing with an internal diameter saw for low-cost solar cells

NASA Technical Reports Server (NTRS)

Daud, T.; Liu, J. K.; Fiegl, G.

1981-01-01

Slicing of silicon ingots using diamond impregnated internal diameter blade saws has been a standard technology of the semiconductor industry. This paper describes work on improvements to this technology for 10 cm diameter ingot slicing. Ingot rotation, dynamic blade edge control with feedback, mechanized blade dressing and development of thinner blades are the approaches tried. A comparison of the results for wafering with and without ingot rotation is also made. A sensitivity analysis of the major cost elements in wafering is performed for 10 cm diameter ingot and extended to the 15 cm diameter ingot case. Various parameter values such as machine cost, feed rate and consumable materials cost are identified both for single and multiple ingot slicing.

Effect of Initial Conditions on Gas-Puff Z-Pinch Dynamics.

NASA Astrophysics Data System (ADS)

Peterson, Gus Gordon

This dissertation concerns the effects initial conditions have on the dynamics of an imploded, annular gas-puff z-pinch. The influence of axial magnetic fields, nozzle size and composition, different gases, pre-ionization, and electrode design on pinch quality and x-ray yield is investigated. The experiment uses a 5-kJ capacitor bank to deliver 0.35 MA to the pinch load in 1.4 mu rm s. This research establishes parameters important to increasing the x-ray yield of dense z-pinches. The initial stage of the implosion is diagnosed with a framing camera that photographs visible light emitted from z-pinch gas breakdown. Data from subsequent stages of the pinch is recorded with a B-dot probe, filtered x-ray diodes, an x-ray filtered pinhole camera, and a nitrogen laser interferometer. Applied axial magnetic fields of ~100 gauss increase average x-ray yield by more than 20%. A substantial increase of K-shell x -ray yield of more than 200% was obtained by increasing the energy delivered to the plasma by enlarging the nozzle diameter from 4 to 5 cm. The use of a Teflon outer-mantle for the nozzle resulted in less uniform gas breakdown as compared to graphite and copper outer-mantles, but x-ray yield and final state uniformity were not reduced. Lower Z gases showed poorer breakdown uniformity. Pre-ionization improved the uniformity of helium and neon breakdown but did not appear to affect subsequent dynamics. X-ray yield was significantly higher using a knife-edge annular anode, as opposed to a flat stainless steel honeycomb anode. Annular anodes with diameters more than a few millimeters different than the nozzle diameter produced low quality pinches with substantially lower x-ray yield.

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.

Study on structural recovery of graphite irradiated with swift heavy ions at high temperature

NASA Astrophysics Data System (ADS)

Pellemoine, F.; Avilov, M.; Bender, M.; Ewing, R. C.; Fernandes, S.; Lang, M.; Li, W. X.; Mittig, W.; Schein, M.; Severin, D.; Tomut, M.; Trautmann, C.; Zhang, F. X.

2015-12-01

Thin graphite foils bombarded with an intense high-energy (8.6 MeV/u) gold beam reaching fluences up to 1 × 1015 ions/cm2 lead to swelling and electrical resistivity changes. As shown earlier, these effects are diminished with increasing irradiation temperature. The work reported here extends the investigation of beam induced changes of these samples by structural analysis using synchrotron X-ray diffraction and transmission electron microscope. A nearly complete recovery from swelling at irradiation temperatures above about 1500 °C is identified.

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.

Tetracyanoethylene oxide-functionalized graphene and graphite characterized by Raman and Auger spectroscopy

DOE PAGES

Frolova, Liliya V.; Magedov, Igor V.; Harper, Aaron; ...

2014-09-28

The tetracyanoethylene oxide (TCNEO) functionalization of chemical vapor deposition grown large area graphene and graphite was performed using reaction of TCNEO with carbon surface in chlorobenzene. The successful functionalization has been confirmed by Raman and Auger spectroscopy, and by numerical modeling of the structure and vibrational modes of TCNEO-functionalized graphene. Raman spectra of TCNEO-functionalized graphene and graphite show several groups of lines corresponding to vibrations of attached carbonyl ylide. Lastly, one of key signatures of TCNEO attachment is the high intensity Raman band at ~1450 cm ₋1, which represents the C-C=C in plane vibrations in functionalization-distorted graphene. We find Ramanmore » spectra indicate the existence of central (pristine) attachment of TCNEO to graphene surface.« less

Modeling to study the role of catalyst in the formation of graphitic shells during carbon nanofiber growth subjected to reactive plasma

NASA Astrophysics Data System (ADS)

Gupta, Ravi; Gupta, Neha; Sharma, Suresh C.

2018-04-01

An analytical model to study the role of a metal catalyst nanofilm in the nucleation, growth, and resulting structure of carbon nanofibers (CNFs) in low-temperature hydrogen diluted acetylene plasma has been developed. The model incorporates the nanostructuring of thin catalyst films, growth of CNF, restructuring of catalyst nanoparticles during growth, and its repercussion on the resulting structure (alignment of rolled graphene sheets around catalyst nanoparticles) by taking into account the plasma sheath formalization, kinetics of neutrals and positively charged species in the reactive plasma, flux of plasma species onto the catalyst front surface, and numerous surface reactions for carbon generation. In order to examine the influence of the catalyst film on the growth of CNFs, the numerical solutions of the model equations have been obtained for experimentally determined initial conditions and glow discharge plasma parameters. From the solutions obtained, we found that nanostructuring of thin films leads to the formation of small nanoparticles with high surface number density. The CNF nucleates over these small-sized nanoparticles grow faster and attain early saturation because of the quick poisoning of small-sized catalyst particles, and contain only a few graphitic shells. However, thick nanofilms result in shorter CNFs with large diameters composed of many graphitic shells. Moreover, we found that the inclination of graphitic shells also depends on the extent up to which the catalyst can reconstruct itself during the growth. The small nanoparticles show much greater elongation along the growth axis and also show a very small difference between their tip and base diameter during the growth due to which graphitic shells align at very small angles as compared to the larger nanoparticles. The present study is useful to synthesize the thin and more extended CNFs/CNTs having a smaller opening angle (inclination angle of graphene layers) as the opening angle has a significant influence on their field emission properties. The comparisons of these theoretical findings to the experimental observations confirm the adequacy of the proposed model.

CT dose equilibration and energy absorption in polyethylene cylinders with diameters from 6 to 55 cm

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

Li, Xinhua; Zhang, Da; Liu, Bob, E-mail: bliu7@mgh.harvard.edu

2015-06-15

Purpose: ICRU Report No. 87 Committee and AAPM Task Group 200 designed a three-sectional polyethylene phantom of 30 cm in diameter and 60 cm in length for evaluating the midpoint dose D{sub L}(0) and its rise-to-the-equilibrium curve H(L) = D{sub L}(0)/D{sub eq} from computed tomography (CT) scanning, where D{sub eq} is the equilibrium dose. To aid the use of the phantom in radiation dose assessment and to gain an understanding of dose equilibration and energy absorption in polyethylene, the authors evaluated the short (20 cm) to long (60 cm) phantom dose ratio with a polyethylene diameter of 30 cm, assessedmore » H(L) in polyethylene cylinders of 6–55 cm in diameters, and examined energy absorption in these cylinders. Methods: A GEANT4-based Monte Carlo program was used to simulate the single axial scans of polyethylene cylinders (diameters 6–55 cm and length 90 cm, as well as diameter 30 cm and lengths 20 and 60 cm) on a clinical CT scanner (Somatom Definition dual source CT, Siemens Healthcare). Axial dose distributions were computed on the phantom central and peripheral axes. An average dose over the central 23 or 100 mm region was evaluated for modeling dose measurement using a 0.6 cm{sup 3} thimble chamber or a 10 cm long pencil ion chamber, respectively. The short (20 cm) to long (90 cm) phantom dose ratios were calculated for the 30 cm diameter polyethylene phantoms scanned at four tube voltages (80–140 kV) and a range of beam apertures (1–25 cm). H(L) was evaluated using the dose integrals computed with the 90 cm long phantoms. The resultant H(L) data were subsequently used to compute the fraction of the total energy absorbed inside or outside the scan range (E{sub in}/E or E{sub out}/E) on the phantom central and peripheral axes, where E = LD{sub eq} was the total energy absorbed along the z axis. Results: The midpoint dose in the 60 cm long polyethylene phantom was equal to that in the 90 cm long polyethylene phantom. The short-to-long phantom dose ratios changed with beam aperture and phantom axis but were insensitive to tube voltage. H(L) was insensitive to tube voltage and CT scanner model. As phantom diameter increased from 6 to 55 cm, E{sub in}/E generally decreased but asymptotically approached constant levels on the peripheral axes of large phantoms. The curve of E{sub in}/E versus scan length was almost identical to that of H(L). Similarly, E{sub out}/E increased with scan length and asymptotically approached the equilibrium for large scan lengths. E{sub out}/D{sub eq} was much less than the equilibrium length L{sub eq} where H(L) = 0.98, even with scan lengths much larger than L{sub eq}. Conclusions: The polyethylene phantom designed by ICRU Report No. 87 Committee and AAPM Task Group 200 is adequately long for assessing the midpoint dose and its equilibration in CT scanning. The short-to-long phantom dose ratios and the H(L) data provided in this paper allow easy evaluations of the midpoint dose, longitudinal dose distribution, and energy absorption in polyethylene phantoms. The results of dose equilibration and energy absorption presented herein may be insightful for the clinical CT scans with various subject sizes and scan lengths.« less

Advanced solar panel designs

NASA Technical Reports Server (NTRS)

Ralph, E. L.; Linder, E.

1995-01-01

This paper describes solar cell panel designs that utilize new hgih efficiency solar cells along with lightweight rigid panel technology. The resulting designs push the W/kg and W/sq m parameters to new high levels. These new designs are well suited to meet the demand for higher performance small satellites. This paper reports on progress made on two SBIR Phase 1 contracts. One panel design involved the use of large area (5.5 cm x 6.5 cm) GaAs/Ge solar cells of 19% efficiency combined with a lightweight rigid graphite fiber epoxy isogrid substrate configuration. A coupon (38 cm x 38 cm) was fabricated and tested which demonstrated an array specific power level of 60 W/kg with a potential of reaching 80 W/kg. The second panel design involved the use of newly developed high efficiency (22%) dual junction GaInP2/GaAs/Ge solar cells combined with an advanced lightweight rigid substrate using aluminum honeycomb core with high strength graphite fiber mesh facesheets. A coupon (38 cm x 38 cm) was fabricated and tested which demonstrated an array specific power of 105 W/kg and 230 W/sq m. This paper will address the construction details of the panels and an a analysis of the component weights. A strawman array design suitable for a typical small-sat mission is described for each of the two panel design technologies being studied. Benefits in respect to weight reduction, area reduction, and system cost reduction are analyzed and compared to conventional arrays.

High-performance wearable supercapacitors fabricated with surface activated continuous filament graphite fibers

NASA Astrophysics Data System (ADS)

Jia, Dedong; Yu, Xin; Chen, Tinghan; Wang, Shu; Tan, Hua; Liu, Hong; Wang, Zhong Lin; Li, Linlin

2017-08-01

Generally, carbon or graphite fibers (GFs) are used as the supporting materials for the preparation of flexible supercapacitors (SCs) by assembling various electrochemically active nanomaterials on them. A facile and rapid electrochemical oxidation method with a voltage of 3 V in a mixed H2SO4-HNO3 solution for 2-15 min is proposed to active continuous filament GFs. Detailed structural characterization, SEM, TEM, XRD, Raman and XPS demonstrate that the GFs-8 (oxidized for 8 min) possessing high specific surface area which provided numerous electrochemical sites and a large number of oxygen-containing functional groups producing pseudocapacitance. Cyclic voltammetric (CV), galvanostatic charge-discharge measurements and electrochemical impedance spectroscopy (EIS) are conducted to test the capacitive of GFs and activated GFs. The capacitance of GFs-8 reaches as high as 570 mF cm-1 at the current density of 1 mA cm-1 in LiCl electrolyte, a 1965-fold enhancement with respect to the pristine GFs (0.29 mF cm-1). The fabricated fiber solid-state supercapacitors (SSCs) provide high energy density of 0.68 mWh cm-3 at the power density 3.3 W cm-3 and have excellent durability with 90% capacitance retention after 10000 cycles. In addition, such fiber SSCs features flexibility and mechanical stability, which may have wide applications in wearable electronic devices.

Mesoporous graphene-like nanobowls as Pt electrocatalyst support for highly active and stable methanol oxidation

NASA Astrophysics Data System (ADS)

Yan, Zaoxue; He, Guoqiang; Jiang, Zhifeng; Wei, Wei; Gao, Lina; Xie, Jimin

2015-06-01

Mesoporous graphene-like nanobowls (GLBs) with high surface area of 1091 m2 g-1, high pore volume of 2.7 cm3 g-1 and average pore diameter of 9.8 nm are synthesized through template method. The GLBs with inherent excellent electrical conductivity and chemical inertia show the properties of well mass transfer, poison resistance and stable loading of smaller Pt particles. Therefore, the Pt/GLB catalyst shows much higher activity and stability than that of commercial Pt/C (TKK) for methanol oxidation reaction (MOR). Therein, the peak current density on Pt/GLB (2075 mA mgPt-1) for MOR is 2.87 times that of commercial Pt/C (723 mA mgPt-1); and the onset potential for the MOR on the former is negatively shifted about 160 mV compared with that on the latter. The catalytic performances of the Pt/GLB are also better than those of the Pt loading on mesoporous amorphous carbon nanobowls (Pt/BLC), indicating promotion effect of graphite on Pt catalytic performance.

Sulfur Isotropic Studies of Archean Slate and Graywacke from Northern Minnesota: Evidence for the Existence of Sulfate Reducing Bacteria

NASA Technical Reports Server (NTRS)

Ripley, E. M.; Nicol, D. L.

1979-01-01

Sulfur isotopic studies of pyrite from metasediments in the 2.6 b.y. old Deer Lake greenstone sequence, Minnesota, were conducted in order to evaluate the possible importance of sulfate reducing bacteria in sulfide formation. Pyrite occurs as ovules up to 2 cm in diameter within graphitic slates, and as fine disseminations in metagraywacke units. SEM studies indicate the pyrite is framboidal in morphology. Delta notation values of pyrite from the Deer Lake sediments range from -2.3 to 11.1 0/00, with a peak at approximately +2 o/oo. Isotopic data is consistent with either high temperature inorganic reduction of circulating seawater sulfate, or low temperature bacterial reduction. However, the lack of sulfide bands or massive occurrences in the sediments, the restriction of pyrite mineralization to the sediments, and the absence of evidence for hot spring activity suggest that a diagenetic origin of pyrite is more feasible. Sulfide in such an environment would be produced principally by the action of sulfate reducing bacteria.

NASA Tech Briefs, December 2006

NASA Technical Reports Server (NTRS)

2006-01-01

Topic include: Inferring Gear Damage from Oil-Debris and Vibration Data; Forecasting of Storm-Surge Floods Using ADCIRC and Optimized DEMs; User Interactive Software for Analysis of Human Physiological Data; Representation of Serendipitous Scientific Data; Automatic Locking of Laser Frequency to an Absorption Peak; Self-Passivating Lithium/Solid Electrolyte/Iodine Cells; Four-Quadrant Analog Multipliers Using G4-FETs; Noise Source for Calibrating a Microwave Polarimeter; Hybrid Deployable Foam Antennas and Reflectors; Coating MCPs with AlN and GaN; Domed, 40-cm-Diameter Ion Optics for an Ion Thruster; Gesture-Controlled Interfaces for Self-Service Machines; Dynamically Alterable Arrays of Polymorphic Data Types; Identifying Trends in Deep Space Network Monitor Data; Predicting Lifetime of a Thermomechanically Loaded Component; Partial Automation of Requirements Tracing; Automated Synthesis of Architecture of Avionic Systems; SSRL Emergency Response Shore Tool; Wholly Aromatic Ether-Imides as n-Type Semiconductors; Carbon-Nanotube-Carpet Heat-Transfer Pads; Pulse-Flow Microencapsulation System; Automated Low-Gravitation Facility Would Make Optical Fibers; Alignment Cube with One Diffractive Face; Graphite Composite Booms with Integral Hinges; Tool for Sampling Permafrost on a Remote Planet; and Special Semaphore Scheme for UHF Spacecraft Communications.

Transport of energy by ultraintense laser-generated electrons in nail-wire targets

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

Ma, T.; Lawrence Livermore National Laboratory, Livermore, California 94550; Key, M. H.

2009-11-15

Nail-wire targets (20 {mu}m diameter copper wires with 80 {mu}m hemispherical head) were used to investigate energy transport by relativistic fast electrons generated in intense laser-plasma interactions. The targets were irradiated using the 300 J, 1 ps, and 2x10{sup 20} W{center_dot}cm{sup -2} Vulcan laser at the Rutherford Appleton Laboratory. A spherically bent crystal imager, a highly ordered pyrolytic graphite spectrometer, and single photon counting charge-coupled device gave absolute Cu K{alpha} measurements. Results show a concentration of energy deposition in the head and an approximately exponential fall-off along the wire with about 60 {mu}m 1/e decay length due to resistive inhibition.more » The coupling efficiency to the wire was 3.3{+-}1.7% with an average hot electron temperature of 620{+-}125 keV. Extreme ultraviolet images (68 and 256 eV) indicate additional heating of a thin surface layer of the wire. Modeling using the hybrid E-PLAS code has been compared with the experimental data, showing evidence of resistive heating, magnetic trapping, and surface transport.« less

Structure, temperature and frequency dependent electrical conductivity of oxidized and reduced electrochemically exfoliated graphite

NASA Astrophysics Data System (ADS)

Radoń, Adrian; Włodarczyk, Patryk; Łukowiec, Dariusz

2018-05-01

The article presents the influence of reduction by hydrogen in statu nascendi and modification by hydrogen peroxide on the structure and electrical conductivity of electrochemically exfoliated graphite. It was confirmed that the electrochemical exfoliation can be used to produce oxidized nanographite with an average number of 25 graphene layers. The modified electrochemical exfoliated graphite and reduced electrochemical exfoliated graphite were characterized by high thermal stability, what was associated with removing of labile oxygen-containing groups. The presence of oxygen-containing groups was confirmed using Fourier-transform infrared spectroscopy. Influence of chemical modification by hydrogen and hydrogen peroxide on the electrical conductivity was determined in wide frequency (0.1 Hz-10 kHz) and temperature range (-50 °C-100 °C). Material modified by hydrogen peroxide (0.29 mS/cm at 0 °C) had the lowest electrical conductivity. This can be associated with oxidation of unstable functional groups and was also confirmed by analysis of Raman spectra. The removal of oxygen-containing functional groups by hydrogen in statu nascendi resulted in a 1000-fold increase in the electrical conductivity compared to the electrochemical exfoliated graphite.

Coatings for Graphite Fibers

NASA Technical Reports Server (NTRS)

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

1980-01-01

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

Biodistribution of a High Dose of Diamond, Graphite, and Graphene Oxide Nanoparticles After Multiple Intraperitoneal Injections in Rats.

PubMed

Kurantowicz, Natalia; Strojny, Barbara; Sawosz, Ewa; Jaworski, Sławomir; Kutwin, Marta; Grodzik, Marta; Wierzbicki, Mateusz; Lipińska, Ludwika; Mitura, Katarzyna; Chwalibog, André

2015-12-01

Carbon nanoparticles have recently drawn intense attention in biomedical applications. Hence, there is a need for further in vivo investigations of their biocompatibility and biodistribution via various exposure routes. We hypothesized that intraperitoneally injected diamond, graphite, and graphene oxide nanoparticles may have different biodistribution and exert different effects on the intact organism. Forty Wistar rats were divided into four groups: the control and treated with nanoparticles by intraperitoneal injection (4 mg of nanoparticles/kg body weight) eight times during the 4-week period. Blood was collected for evaluation of blood morphology and biochemistry parameters. Photographs of the general appearance of each rat's interior were taken immediately after sacrifice. The organs were excised and their macroscopic structure was visualized using a stereomicroscope. The nanoparticles were retained in the body, mostly as agglomerates. The largest agglomerates (up to 10 mm in diameter) were seen in the proximity of the injection place in the stomach serous membrane, between the connective tissues of the abdominal skin, muscles, and peritoneum. Numerous smaller, spherical-shaped aggregates (diameter around 2 mm) were lodged among the mesentery. Moreover, in the connective and lipid tissue in the proximity of the liver and spleen serosa, small aggregates of graphite and graphene oxide nanoparticles were observed. However, all tested nanoparticles did not affect health and growth of rats. The nanoparticles had no toxic effects on blood parameters and growth of rats, suggesting their potential applicability as remedies or in drug delivery systems.

Preliminary Results of IS Plasma Focus as a Breeder of Short-Lived Radioisotopes 12C(d,n)13N

NASA Astrophysics Data System (ADS)

Sadat Kiai, S. M.; Elahi, M.; Adlparvar, S.; Shahhoseini, E.; Sheibani, S.; Ranjber akivaj, H.; Alhooie, S.; Safarien, A.; Farhangi, S.; Aghaei, N.; Amini, S.; Khalaj, M. M.; Zirak, A. R.; Dabirzadeh, A. A.; Soleimani, J.; Torkzadeh, F.; Mousazadeh, M. M.; Moradi, K.; Abdollahzadeh, M.; Talaei, A.; Zaeem, A. A.; Moslehi, A.; Kashani, A.; Babazadeh, A. R.; Bagiyan, F.; Ardestani, M.; Roozbahani, A.; Pourbeigi, H.; Tajik Ahmadi, H.; Ahmadifaghih, M. A.; Mahlooji, M. S.; Mortazavi, B. N.; Zahedi, F.

2011-04-01

Modified IS (Iranian Sun) plasma focus (10 kJ,15 kV, 94 μF, 0.1 Hz) has been used to produce the short-lived radioisotope 13N (half-life of 9.97 min) through 12C(d,n)13N nuclear reaction. The filling gas was 1.5-3 torr of hydrogen (60%) deuterium (40%) mixture. The target was solid nuclear grade graphite with 5 mm thick, 9 cm width and 13 in length. The activations of the exogenous target on average of 20 shots (only one-third acceptable) through 10-13 kV produced the 511 keV gamma rays. Another peak found at the 570 keV gamma of which both was measured by a NaI portable gamma spectrometer calibrated by a 137Cs 0.25 μCi sealed reference source with its single line at 661.65 keV and 22Na 0.1 μCi at 511 keV. To measure the gamma rays, the graphite target converts to three different phases; solid graphite, powder graphite, and powder graphite in water solution. The later phase approximately has a doubled activity with respect to the solid graphite target up to 0.5 μCi of 511 keV and 1.1 μCi of 570 keV gamma lines were produced. This increment in activity was perhaps due to structural transformation of graphite powder to nano-particles characteristic in liquid water.

Effect of filler content on the properties of expanded- graphite-based composite bipolar plates for application in polymer electrolyte membrane fuel cells

NASA Astrophysics Data System (ADS)

Masand, Aakash; Borah, Munu; Pathak, Abhishek K.; Dhakate, Sanjay R.

2017-09-01

Minimization of the weight and volume of a hydrogen-based PEM fuel cell stack is an essential area of research for the development and commercialization of PEMFCs for various applications. Graphite-based composite bipolar plates have significant advantages over conventional metallic bipolar plates due to their corrosion resistivity and low cost. On the other hand, expanded graphite is seen to be a potential candidate for facilitating the required electrical, thermal and mechanical properties of bipolar plates with a low density. Therefore, in the present study, the focus is on minimization of the high loading of graphite and optimizes its composition to meet the target properties of bipolar plates as per the USDOE target. Three types of expanded graphite (EG)-phenolic-resin-based composite bipolar plates were developed by partially replacing the expanded graphite content with natural graphite (NG) and carbon black as an additional filler. The three types of composite plate with the reinforcing constituent ratio EG:NG:R (25:25:50) give a bending strength of 49 MPa, a modulus of ~6 GPa, electrical conductivity  >100 S cm-1, a shore hardness of 55 and a bulk density of 1.55 g/cc. The 50 wt% loading of resin is sufficient to wet the 50 wt% filler content in the composite plate. This study gives an insight into using hybrid reinforcements in order to achieve the desired properties of bipolar plates.

77 FR 40854 - Small Diameter Graphite Electrodes From the People's Republic of China: Final Results of the...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-07-11

...). The administrative review covers Fushun Jinly Petrochemical Carbon Co., Ltd. (Fushun Jinly), Xinghe County Muzi Carbon Co., Ltd. (Muzi Carbon), Sichuan Guanghan Shida Carbon Co., Ltd. (Shida Carbon), Jilin Carbon Import and Export Company (Jilin Carbon), the Fangda Group (comprised of five collapsed companies...

77 FR 15042 - Small Diameter Graphite Electrodes From the People's Republic of China: Amended Final Results of...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-14

..., Department of Commerce. DATES: Effective Date: March 14, 2012. SUMMARY: On September 13, 2011, the Department... Jinly Petrochemical Carbon Co., Ltd. (``Fushun Jinly''); Beijing Fangda Carbon Tech Co., Ltd. (``Beijing Fangda''), Fangda Carbon New Material Co., Ltd. (``Fangda Carbon''), Fushun Carbon Co., Ltd. (```Fushun...

Residual strength assessment of low velocity impact damage of graphite-epoxy laminates

NASA Technical Reports Server (NTRS)

Lal, K. M.

1983-01-01

This report contains the study of Low Velocity Transverse Impact Damage of graphite-epoxy T300/5208 composite laminates. The specimen, 100 mm diameter clamped plates, were impact damaged by a cantilever-type instrumented 1-inch diameter steel ball. Study was limited to impact velocity 6 m/sec. Rectangular strips, 50 mm x 125 mm, were cut from the impact-damage specimens so that the impact damage zone was in the center of the strips. These strips were tested in tension to obtain their residual strength. An energy dissipation model was developed to predict the residual strength from fracture mechanics concepts. Net energy absorbed I(a) was evaluated from coefficient of restitution concepts based on shear dominated theory of fiber-reinforced materials, with the modification that during loading and unloading the shear deformation are respectively elastic-plastic and elastic. Delamination energy I(d) was predicted by assuming that the stiffness of the laminate dropped due to debonding. Fiber-breakage energy, assumed to be equal to the difference of I(a) and I(d), was used to determine the residual strength. Predictions were compared with test results.

Chlorine effect on the formation of carbon nanofibers.

PubMed

Lin, Wang-Hua; Takahashi, Yusuke; Li, Yuan-Yao; Sakoda, Akiyoshi

2012-12-01

Platelet graphite nanofibers (GNFs) and turbostratic carbon nanofibers (CNFs) are synthesized by the thermal evaporation and decomposition of a polymer-based mixture at 700 degrees C using Ni as a catalyst. The mixture consists of poly(ethylene glycol) (PEG), serving as the carbon source, and hydrochloric acid solution (HCl(aq)), serving as the promoter/additive for the growth of CNFs. High-purity zigzag-shaped platelet GNFs form with 10 wt% HCl(aq) as an additive in the PEG. The diameters of the platelet GNFs are in the range of 40-60 nm, with lengths of a few micrometers. High-resolution transmission electron microscopy images indicate a high degree of graphitization and well ordered graphene layers along the fiber axis. In contrast, high-purity turbostratic CNFs form with 20 wt% HCl(aq) in the PEG. The diameter and length of the turbostratic CNFs are 20-40 nm and a few micrometers, respectively. The participation of HCl in the thermal process leads to the formation of Ni-Cl compounds. The amount of chlorine affects the shape of the Ni catalyst, which determines the type of CNF formed.

Low temperature synthesis of coiled carbon nanotubes and their magnetic properties

NASA Astrophysics Data System (ADS)

Krishna, Vemula Mohana; Somanathan, T.; Manikandan, E.

2018-04-01

In this paper, coiled like structure of carbon nanotubes (c-CNTs) have been effectively grown on bi-metal substituted α-alumina nanoparticles catalyst by chemical vapor deposition (CVD) system. Highly graphitized and dense bundles of carbon product were attained at a low temperature of 550 °C. The coiled carbon nanostructures in very longer lengths were noticed by field emission scanning electron microscope (FESEM) observation. Furthermore, high purity material was achieved, which correlates the energy dispersive x-ray spectroscopy (EDX) analysis. High resolution transmission electron microscope (HRTEM) revealed the diameter and graphitization of coiled structures. The superparamagnetic like behavior was observed at room temperature for the as-synthesized product, which was found by VSM investigation.

Noncovalently functionalized graphitic mesoporous carbon as a stable support of Pt nanoparticles for oxygen reduction

NASA Astrophysics Data System (ADS)

Shao, Yuyan; Zhang, Sheng; Kou, Rong; Wang, Xiqing; Wang, Chongmin; Dai, Sheng; Viswanathan, Vilayanur; Liu, Jun; Wang, Yong; Lin, Yuehe

We report a durable electrocatalyst support, highly graphitized mesoporous carbon (GMPC), for oxygen reduction in polymer electrolyte membrane (PEM) fuel cells. GMPC is prepared through graphitizing the self-assembled soft-template mesoporous carbon (MPC) under high temperature. Heat-treatment at 2800 °C greatly improves the degree of graphitization while most of the mesoporous structures and the specific surface area of MPC are retained. GMPC is then noncovalently functionalized with poly(diallyldimethylammonium chloride) (PDDA) and loaded with Pt nanoparticles by reducing Pt precursor (H 2PtCl 6) in ethylene glycol. Pt nanoparticles of ∼3.0 nm in diameter are uniformly dispersed on GMPC. Compared to Pt supported on Vulcan XC-72 carbon black (Pt/XC-72), Pt/GMPC exhibits a higher mass activity towards oxygen reduction reaction (ORR) and the mass activity retention (in percentage) is improved by a factor of ∼2 after 44 h accelerated degradation test under the potential step (1.4-0.85 V) electrochemical stressing condition which focuses on support corrosion. The enhanced activity and durability of Pt/GMPC are attributed to the graphitic structure of GMPC which is more resistant to corrosion. These findings demonstrate that GMPC is a promising oxygen reduction electrocatalyst support for PEM fuel cells. The approach reported in this work provides a facile, eco-friendly promising strategy for synthesizing stable metal nanoparticles on hydrophobic support materials.

Summary of a study to determine low-velocity impact damage and residual tension strength for a thick graphite/epoxy motor case

NASA Technical Reports Server (NTRS)

Poe, C. C., Jr.

1990-01-01

Impacters of various shapes and masses were dropped from various heights onto 36 mm (1.4 in.) thick graphite/epoxy cylinders, which represented filament wound cases (FWC) for the booster motors of the Space Shuttle. Insert solid propellant was cast into some of the cylinders. The cylinders were impacted numerous times around the circumference and then cut into 51 mm (2.0 in.) wide tension specimens, each containing an impact site. Four indenters were used: a sharp corner, two hemispheres, and a bolt-like rod. The diameters of the hemispheres were 12.7 mm (0.5 in.) and 25.4 mm (1.0 in.), and the diameter of the rod was 6.3 mm (0.25 in.). Impacts with the rod were simulated by pressing the rod against the face of specimens. For the hemispheres, the damage initiated beneath the surface at a critical contact pressure and was not visible on the surface until an even larger pressure was exceeded. The damage consisted of matrix cracking and broken fiber. The rod and corner made visible surface damage in all tests. For the hemispheres, the tension strength was reduced considerably before the damage was visible on the surface, 30 percent for the 25.4 mm (1.0 in.) diameter hemisphere and 10 percent for the 12.7 mm (0.5 in.) diameter hemisphere. Analytical methods were used to predict the damage and residual tension strength. A factor of safety to account for nonvisible damage was determined.

Summary of a study to determine low-velocity impact damage and residual tension strength for a thick graphite/epoxy motor case

NASA Technical Reports Server (NTRS)

Poe, C. C., Jr.

1990-01-01

Impacters of various shapes and masses were dropped from various heights onto 36 mm (1.4 in.) thick graphite/epoxy cylinders, which represented filament wound cases (FWC) for the booster motors of the Space Shuttle. Insert solid propellant was cast into some of the cylinders. The cylinders were impacted numerous times around the circumference and then cut into 51 mm (2.0 in.) wide tension specimens, each containing an impact site. Four indenters were used: a sharp corner, two hemispheres, and a bolt-like rod. The diameters of the hemispheres were 12.7 mm mm (0.5 in.) and 25.4 mm (1.0 in.), and the diameter of the rod was 6.3 mm (0.25 in.). Impacts with the rod were simulated by pressing the rod against the face of specimens. For the hemispheres, the damage initiated beneath the surface at a critical contact pressure and was not visible on the surface until an even larger pressure was exceeded. The damage consisted of matrix cracking and broken fiber. The rod an corner made visible surface damage in all tests. For the hemispheres, the tension strength was reduced considerably before the damage was visible on the surface, 30 percent for the 25.4 mm (1.0 in.) diameter hemisphere and 10 percent for the 12.7 mm (0.5 in.) diameter hemisphere. Analytical methods were used to predict the damage and residual tension strength. A factor of safety to account for nonvisible damage was determined.

Synthesis of carbon nanoparticles from commercially available liquified petroleum gas

NASA Astrophysics Data System (ADS)

Nandiyanto, A. B. D.; Fadhlulloh, M. A.; Rahman, T.; Mudzakir, A.

2016-04-01

The aim of this study was to synthesize carbon nanoparticles (CNPs) from commercially available liquefied petroleum gas (LPG). In the research procedure, LPG was reacted with air to construct CNPs. To confirm the successful synthesis of CNPs, we conducted several sample analyses: Gas Chromatography-Mass Spectrometry (GC-MS), Transmission Electron Microscope (TEM), X-ray Diffraction (XRD), and Infrared Spectra (FTIR). We also varied LPG and oxygen mole ratios at 0.8; 2.4; 4.8; and 7.2. The GC-MS results indicated the composition of LPG was propane (58.90%), isobutane (18.35%), butane (22.26%), and butane, 2-methyl (0.48%). The TEM results showed that the particles were spheres with sizes of between 25 and 35 nm. The sizes of particles were controllable, depending on the mole ratio. The XRD results showed mole ratios of LPG and oxygen of 0.80 and 2.40 were natural graphite, whereas the mole ratios of 4.80 and 7.20 were hexagonal graphite. FT-IR results showed CNPs have absorption peaks at wave number (i) 752 (C-H bend sp2); (ii) 835 (C=C); (iii) 1274 (C-O-C vibration); (iv) 1400 and 1600 (C-C stretch aromatic); (v) 2800 (C-H sp2); (vi) 2900 (CH sp3); (vii) 3100 (C-H aromatic); and (viii) 3400 cm-1 (O-H). From the FTIR analysis results, the sample contained allotrope graphite due to detection of peaks at 1400 and 1600 cm-1 (C-C stretch aromatic) and 3100 cm-1 (C-H aromatic).

Physical vapor deposition of one-dimensional nanoparticle arrays on graphite: seeding the electrodeposition of gold nanowires.

PubMed

Cross, C E; Hemminger, J C; Penner, R M

2007-09-25

One-dimensional (1D) ensembles of 2-15 nm diameter gold nanoparticles were prepared using physical vapor deposition (PVD) on highly oriented pyrolytic graphite (HOPG) basal plane surfaces. These 1D Au nanoparticle ensembles (NPEs) were prepared by depositing gold (0.2-0.6 nm/s) at an equivalent thickness of 3-4 nm onto HOPG surfaces at 670-690 K. Under these conditions, vapor-deposited gold nucleated selectively at the linear step edge defects present on these HOPG surfaces with virtually no nucleation of gold particles on terraces. The number density of 2-15 nm diameter gold particles at step edges was 30-40 microm-1. These 1D NPEs were up to a millimeter in length and organized into parallel arrays on the HOPG surface, following the organization of step edges. Surprisingly, the deposition of more gold by PVD did not lead to the formation of continuous gold nanowires at step edges under the range of sample temperature or deposition flux we have investigated. Instead, these 1D Au NPEs were used as nucleation templates for the preparation by electrodeposition of gold nanowires. The electrodeposition of gold occurred selectively on PVD gold nanoparticles over the potential range from 700-640 mV vs SCE, and after optimization of the electrodeposition parameters continuous gold nanowires as small as 80-90 nm in diameter and several micrometers in length were obtained.

Rationally designed graphene-nanotube 3D architectures with a seamless nodal junction for efficient energy conversion and storage

PubMed Central

Xue, Yuhua; Ding, Yong; Niu, Jianbing; Xia, Zhenhai; Roy, Ajit; Chen, Hao; Qu, Jia; Wang, Zhong Lin; Dai, Liming

2015-01-01

One-dimensional (1D) carbon nanotubes (CNTs) and 2D single-atomic layer graphene have superior thermal, electrical, and mechanical properties. However, these nanomaterials exhibit poor out-of-plane properties due to the weak van der Waals interaction in the transverse direction between graphitic layers. Recent theoretical studies indicate that rationally designed 3D architectures could have desirable out-of-plane properties while maintaining in-plane properties by growing CNTs and graphene into 3D architectures with a seamless nodal junction. However, the experimental realization of seamlessly-bonded architectures remains a challenge. We developed a strategy of creating 3D graphene-CNT hollow fibers with radially aligned CNTs (RACNTs) seamlessly sheathed by a cylindrical graphene layer through a one-step chemical vapor deposition using an anodized aluminum wire template. By controlling the aluminum wire diameter and anodization time, the length of the RACNTs and diameter of the graphene hollow fiber can be tuned, enabling efficient energy conversion and storage. These fibers, with a controllable surface area, meso-/micropores, and superior electrical properties, are excellent electrode materials for all-solid-state wire-shaped supercapacitors with poly(vinyl alcohol)/H2SO4 as the electrolyte and binder, exhibiting a surface-specific capacitance of 89.4 mF/cm2 and length-specific capacitance up to 23.9 mF/cm, — one to four times the corresponding record-high capacities reported for other fiber-like supercapacitors. Dye-sensitized solar cells, fabricated using the fiber as a counter electrode, showed a power conversion efficiency of 6.8% and outperformed their counterparts with an expensive Pt wire counter electrode by a factor of 2.5. These novel fiber-shaped graphene-RACNT energy conversion and storage devices are so flexible they can be woven into fabrics as power sources. PMID:26601246

Rationally designed graphene-nanotube 3D architectures with a seamless nodal junction for efficient energy conversion and storage.

PubMed

Xue, Yuhua; Ding, Yong; Niu, Jianbing; Xia, Zhenhai; Roy, Ajit; Chen, Hao; Qu, Jia; Wang, Zhong Lin; Dai, Liming

2015-09-01

One-dimensional (1D) carbon nanotubes (CNTs) and 2D single-atomic layer graphene have superior thermal, electrical, and mechanical properties. However, these nanomaterials exhibit poor out-of-plane properties due to the weak van der Waals interaction in the transverse direction between graphitic layers. Recent theoretical studies indicate that rationally designed 3D architectures could have desirable out-of-plane properties while maintaining in-plane properties by growing CNTs and graphene into 3D architectures with a seamless nodal junction. However, the experimental realization of seamlessly-bonded architectures remains a challenge. We developed a strategy of creating 3D graphene-CNT hollow fibers with radially aligned CNTs (RACNTs) seamlessly sheathed by a cylindrical graphene layer through a one-step chemical vapor deposition using an anodized aluminum wire template. By controlling the aluminum wire diameter and anodization time, the length of the RACNTs and diameter of the graphene hollow fiber can be tuned, enabling efficient energy conversion and storage. These fibers, with a controllable surface area, meso-/micropores, and superior electrical properties, are excellent electrode materials for all-solid-state wire-shaped supercapacitors with poly(vinyl alcohol)/H2SO4 as the electrolyte and binder, exhibiting a surface-specific capacitance of 89.4 mF/cm(2) and length-specific capacitance up to 23.9 mF/cm, - one to four times the corresponding record-high capacities reported for other fiber-like supercapacitors. Dye-sensitized solar cells, fabricated using the fiber as a counter electrode, showed a power conversion efficiency of 6.8% and outperformed their counterparts with an expensive Pt wire counter electrode by a factor of 2.5. These novel fiber-shaped graphene-RACNT energy conversion and storage devices are so flexible they can be woven into fabrics as power sources.

New Raman-peak at 1850 cm(-1) observed in multiwalled carbon nanotubes produced by hydrogen arc discharge.

PubMed

Chen, B; Kadowaki, Y; Inoue, S; Ohkohchi, M; Zhao, X; Ando, Y

2010-06-01

The new peak (near 1850 cm(-1)) assigned to carbon linear chain included in the centre of very thin innermost multiwalled carbon nanotubes (MWNTs) has been verified by Raman spectroscopy. These MWNTs were produced by dc arc discharge of pure graphite rods in pure hydrogen gas and existed in the cathode deposit. In this paper, we clarified that the new Raman-peaks could also be observed in the cathode deposit including MWNTs produced by hydrogen dc arc discharge using graphite electrode with added Y or La. By changing the quantity of addition (Y or La), dc arc current and pressure of ambient hydrogen gas, the optimum condition to get maximum intensity of the new Raman-peaks was obtained. For the case of 1 wt% La, dc 50 A, H2 pressure of 50 Torr was found to be optimum, and the intensity of new Raman-peak was even higher than the G-band peak. For the case of 1 wt% Y, dc 50 A, H2 pressure of 50 Torr was optimum, but the intensity of new Raman-peak was weaker than the G-band peak. Transmission electron microscopy observation revealed that the crystallinity of MWNTs produced with pure graphite rod was better than those produced with added Y or La.

Development of fuel cell bipolar plates from graphite filled wet-lay thermoplastic composite materials

NASA Astrophysics Data System (ADS)

Huang, Jianhua; Baird, Donald G.; McGrath, James E.

A method with the potential to produce economical bipolar plates with high electrical conductivity and mechanical properties is described. Thermoplastic composite materials consisting of graphite particles, thermoplastic fibers and glass or carbon fibers are generated by means of a wet-lay (paper-making) process to yield highly formable sheets. The sheets are then stacked and compression molded to form bipolar plates with gas flow channels. Poly(phenylene sulfide) (PPS) based wet-lay composite plates have in-plane conductivity of 200-300 S cm -1, tensile strength of 57 MPa, flexural strength of 96 MPa and impact strength (unnotched) of 81 J m -1 (1.5 ft-lb in. -1). These values well exceed industrial as well as Department of Energy requirements or targets and have never been reached before for composite bipolar plates. The use of wet-lay sheets also makes it possible to choose different components including polymer, graphite particle and reinforcement for the core and outer layers of the plate, respectively, to optimize the properties and/or reduce the cost of the plate. The through-plane conductivity (around 20 S cm -1) and half-cell resistance of the bipolar plate indicate that the through-plane conductivity of the material needs some improvement.

Electrochemical and impedance investigation of the effect of lithium malonate on the performance of natural graphite electrodes in lithium-ion batteries

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

Sun, Xiao-Guang; Dai, Sheng

2010-01-01

Lithium malonate (LM) was coated on the surface of a natural graphite (NG) electrode, which was then tested as the negative electrode in the electrolytes of 0.9 M LiPF6/EC-PC-DMC (1/1/3, by weight) and 1.0 M LiBF4/EC-PC-DMC (1/1/3, by weight) under a current density of 0.075 mA cm-2. LM was also used as an additive to the electrolyte of 1.0 M LiPF6/EC-DMC-DEC (1/1/1, by volume) and tested on a bare graphite electrode. It was found that both the surface coating and the additive approach were effective in improving first charge discharge capacity and coulomb efficiency. Electrochemical impedance spectra showed that themore » decreased interfacial impedance was coupled with improved coulomb efficiency of the cells using coated graphite electrodes. Cyclic voltammograms (CVs) on fresh bare and coated natural graphite electrodes confirmed that all the improvement in the half-cell performance was due to the suppression of the solvent decomposition through the surface modification with LM. The CV data also showed that the carbonate electrolyte with LM as the additive was not stable against oxidation, which resulted in lower capacity of the full cell with commercial graphite and LiCoO2 electrodes.« less

Comparison on exfoliated graphene nano-sheets and triturated graphite nano-particles for mode-locking the Erbium-doped fibre lasers

NASA Astrophysics Data System (ADS)

Yang, Chun-Yu; Lin, Yung-Hsiang; Wu, Chung-Lun; Cheng, Chih-Hsien; Tsai, Din-Ping; Lin, Gong-Ru

2018-06-01

Comparisons on exfoliated graphene nano-sheets and triturated graphite nano-particles for mode-locking the Erbium-doped fiber lasers (EDFLs) are performed. As opposed to the graphite nano-particles obtained by physically triturating the graphite foil, the tri-layer graphene nano-sheets is obtained by electrochemically exfoliating the graphite foil. To precisely control the size dispersion and the layer number of the exfoliated graphene nano-sheet, both the bias of electrochemical exfoliation and the speed of centrifugation are optimized. Under a threshold exfoliation bias of 3 volts and a centrifugation at 1000 rpm, graphene nano-sheets with an average diameter of 100  ±  40 nm can be obtained. The graphene nano-sheets with an area density of 15 #/µm2 are directly imprinted onto the end-face of a single-mode fiber made patchcord connector inside the EDFL cavity. Such electrochemically exfoliated graphene nano-sheets show comparable saturable absorption with standard single-graphene and perform the self-amplitude modulation better than physically triturated graphite nano-particles. The linear transmittance and modulation depth of the inserted graphene nano-sheets are 92.5% and 53%, respectively. Under the operation with a power gain of 21.5 dB, the EDFL can be passively mode-locked to deliver a pulsewidth of 454.5 fs with a spectral linewidth of 5.6 nm. The time-bandwidth product of 0.31 is close to the transform limit. The Kelly sideband frequency spacing of 1.34 THz is used to calculate the chirp coefficient as  ‑0.0015.

Review of Kaufman thruster development at the Lewis Research Center - 1973

NASA Technical Reports Server (NTRS)

Kerslake, W. R.

1973-01-01

Work on Kaufman thruster development completed during the years 1971 and 1972 is reviewed. Thrusters tested have ranged in size from 2.5-cm to 150-cm diameters, in thrust from 0.4 to 4300 mN, and in power from 0.03 to 203 kW. A 2.5-cm thruster was briefly tested and found to have surprisingly high thruster efficiency. Emphasis is placed on thruster system reliability and lifetime as previous work has increased thruster efficiency to a high level. Work also proceeds on definition of thruster-spacecraft interactions. Major R&D efforts are directed at present into two areas of thruster size: a 5-cm to 8-cm diameter thruster to be used for station keeping and attitude control of geosynchronous spacecraft; and a 30-cm diameter thruster to be used for primary propulsion in a 3- to 7-thruster array for solar electric propulsion of interplanetary spacecraft.

Spectral Characteristics of Laser-Induced Graphite Plasma in Ambient Air

NASA Astrophysics Data System (ADS)

Wang, Jinmei; Zheng, Peichao; Liu, Hongdi; Fang, Liang

2016-11-01

An experimental setup of laser-induced graphite plasma was built and the spectral characteristics and properties of graphite plasma were studied. From the temporal behavior of graphite plasma, the duration of CN partials (B2 Σ+ → X2 Σ+) emission was two times longer than that of atomic carbon, and all intensities reached the maximum during the early stage from 0.2 μs to 0.8 μs. The electron temperature decreased from 11807 K to 8755 K, the vibration temperature decreased from 8973 K to 6472 K, and the rotational temperature decreased from 7288 K to 4491 K with the delay time, respectively. The effect of the laser energy was also studied, and it was found that the thresholds and spectral characteristics of CN molecular and C atomic spectroscopy presented great differences. At lower laser energies, the electron excited temperature, the electron density, the vibrational temperature and rotational temperature of CN partials increased rapidly. At higher laser energies, the increasing of electron excited temperature and electron density slow down, and the vibrational temperature and rotational temperature even trend to saturation due to plasma shielding and dissociation of CN molecules. The relationship among the three kinds of temperatures was Telec>Tvib>Trot at the same time. The electron density of the graphite plasma was in the order of 1017 cm-3 and 1018 cm-3. supported by National Natural Science Foundation of China (No. 61205149), Scientific Research Foundation for the Returned Overseas Chinese Scholars of State Education Ministry, Science Research Funds of Chongqing Municipal Education Commission (KJ1500436), Scientific and Technological Talents Training Project of Chongqing (CSTC2013kjrc-qnrc40002), Key Project of Foundation and Advanced Technology Research Project of Chongqing (CSTC2015jcyjB0358), Visiting Scholarship of State Key Laboratory of Power Transmission Equipment & System Security and New Technology (2007DA10512714409)

Synthesis of core-shell iron nanoparticles via a new (novel) approach

NASA Astrophysics Data System (ADS)

Chaudhary, Rakesh P.; Koymen, Ali R.

2014-03-01

Carbon-encapsulated iron (Fe) nanoparticles were synthesized by a newly developed method in toluene. Transmission Electron Microscopy (TEM) and High Resolution Transmission Electron Microscopy (HRTEM) of the as prepared sample reveal that core-shell nanostructures have been formed with Fe as core and graphitic carbon as shell. Fe nanoparticles with diameter 11nm to 102 nm are encapsulated by 6-8 nm thick graphitic carbon layers. There was no iron carbide formation observed between the Fe core and the graphitic shell. The Fe nanoparticles have body centered cubic (bcc) crystal structure. The magnetic hysteresis loop of the as synthesized powder at room temperature showed a saturation magnetization of 9 Am2 kg-1. After thermal treatment crystalline order of the samples improved and hence saturation magnetization increased to 24 Am2kg-1. We foresee that the carbon-encapsulated Fe nanoparticles are biologically friendly and could have potential applications in Magnetic Resonance Imaging (MRI) and Photothermal cancer therapy.

Hierarchically Macroporous Graphitic Nanowebs Exhibiting Ultra-fast and Stable Charge Storage Performance

NASA Astrophysics Data System (ADS)

Yun, Young Soo

2018-02-01

The macro/microstructures of carbon-based electrode materials for supercapacitor applications play a key role in their electrochemical performance. In this study, hierarchically macroporous graphitic nanowebs (HM-GNWs) were prepared from bacterial cellulose by high-temperature heating at 2400 °C. The HM-GNWs were composed of well-developed graphitic nanobuilding blocks with a high aspect ratio, which was entangled as a nanoweb structure. The morphological and microstructural characteristics of the HM-GNWs resulted in remarkable charge storage performance. In particular, the HM-GNWs exhibited very fast charge storage behaviors at scan rates ranging from 5 to 100 V s-1, in which area capacitances ranging from 8.9 to 3.8 mF cm-2 were achieved. In addition, 97% capacitance retention was observed after long-term cycling for more than 1,000,000 cycles.

Performance evaluation of tubular fuel cells fuelled by pulverized graphite

NASA Astrophysics Data System (ADS)

Kim, Jong-Pil; Lim, Ho; Jeon, Chung-Hwan; Chang, Young-June; Koh, Kwang-Nak; Choi, Soon-Mok; Song, Ju-Hun

A fuel cell fuelled by carbonaceous graphite is proposed. The tubular fuel cell, with the carbon in a fixed-bed form on the anode side, is employed to convert directly the chemical energy of carbon into electricity. Surface platinum electrodes are coated on the cell electrolyte, which is a yttria-stabilized zirconia (YSZ) tube of 1.5 mm thickness. The effect of using different sizes of graphite powder (in the range 0-180 μm) as fuel is analyzed. Power density and actual open-circuit voltage (OCV) values are measured as the temperature is varied from 0 to 950 °C. The cell provides a maximum power density of 16.8 mW cm -2 and an OCV of 1.115 V at the highest temperature condition (950 °C) tested in this study.

Unzipping of multi-wall carbon nanotubes with different diameter distributions: Effect on few-layer graphene oxide obtention

NASA Astrophysics Data System (ADS)

Torres, D.; Pinilla, J. L.; Suelves, I.

2017-12-01

Few-layer graphene oxide (FLGO) was obtained by chemical unzipping of multi-wall carbon nanotubes (MWCNT) of different diameter distributions. MWCNT were synthesized by catalytic decomposition of methane using Fe-Mo/MgO catalysts. The variation in the Fe/Mo ratio (1, 2 and 5) was very influential in MWCNT diameter distribution and type of MWCNT obtained, including textural, chemical, structural and morphological characteristics. MWCNT diameter distribution and surface defects content had a profound impact on the characteristics of the resulting FLGO. Thus, MWCNT obtained with the catalyst with a Fe/Mo: 5 and presenting a narrow diameter distribution centered at 8.6 ± 3.3 nm led to FLGO maintaining non-oxidized graphite stacking (according to XRD analysis), lower specific surface area and higher thermostability as compared to FLGO obtained from MWCNT showing wider diameter distributions. The presence of more oxygen-containing functionalities and structural defects in large diameter nanotubes promotes the intercalation of species towards the inner layers of the nanotube, resulting in an enhanced MWCNT oxidation and opening into FLGO, what improves both micro- and mesoporosity.

Charging and discharging Teflon

NASA Technical Reports Server (NTRS)

Passenheim, B. C.; Vanlint, V. A. J.

1981-01-01

The charging and discharging characteristics of several common satellite materials exposed to 0-30KV electrons are measured. Teflon is discussed because the charging characteristics are radically altered immediately after a spontaneous discharge. The exterior geometry of the test structure is shown. In all cases dielectric samples were 82 cm in diameter mounted on the front of a 120 cm diameter cylinder supported on an 85 cm, 0.95 cm thick plexiglass disc. Dielectric materials investigated were: back surface aluminized Kapton, back surface silvered Teflon, silicon alkyd white thermal control paint, and 50 cm by 50 cm array of 0.030 cm thick MgF2 coated fused silica solar cell cover slips.

Method of making a current collector for a sodium/sulfur battery

DOEpatents

Tischer, R.P.; Winterbottom, W.L.; Wroblowa, H.S.

1987-03-10

This specification is directed to a method of making a current collector for a sodium/sulfur battery. The current collector so-made is electronically conductive and resistant to corrosive attack by sulfur/polysulfide melts. The method includes the step of forming the current collector for the sodium/sulfur battery from a composite material formed of aluminum filled with electronically conductive fibers selected from the group of fibers consisting essentially of graphite fibers having a diameter up to 10 microns and silicon carbide fibers having a diameter in a range of 500--1,000 angstroms. 2 figs.

Method of making a current collector for a sodium/sulfur battery

DOEpatents

Tischer, Ragnar P.; Winterbottom, Walter L.; Wroblowa, Halina S.

1987-01-01

This specification is directed to a method of making a current collector (14) for a sodium/sulfur battery (10). The current collector so-made is electronically conductive and resistant to corrosive attack by sulfur/polysulfide melts. The method includes the step of forming the current collector for the sodium/sulfur battery from a composite material (16) formed of aluminum filled with electronically conductive fibers selected from the group of fibers consisting essentially of graphite fibers having a diameter up to 10 microns and silicon carbide fibers having a diameter in a range of 500-1000 angstroms.

77 FR 13284 - Small Diameter Graphite Electrodes From the People's Republic of China: Preliminary Results and...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-06

... with 19 CFR 351.213(b) from Fushun Jinly Petrochemical Carbon Co., Ltd. (Fushun Jinly), Xinghe County Muzi Carbon Co., Ltd. (Muzi Carbon), Sichuan Guanghan Shida Carbon Co., Ltd. (Shida Carbon), and Beijing Fangda Carbon Tech Co., Ltd., Chengdu Rongguang Carbon Co., Ltd., Fangda Carbon New Material Co...

78 FR 14964 - Small Diameter Graphite Electrodes From the People's Republic of China: Preliminary Results of...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-03-08

... segment. 1. Brilliant Charter Limited, 2. Dalian Thrive Metallurgy Imp. & Exp. Co., Ltd. 3. GES (China) Co... Carbon (China) Co., Limited 4. Anssen Metallurgy Group Co., Ltd. 5. AMGL 6. Apex Maritime (Dalian) Co.... Dalian Horton International Trading Co., Ltd. 21. Dalian LST Metallurgy Co., Ltd. 22. Dalian Shuangji Co...

77 FR 37873 - Small Diameter Graphite Electrodes From the People's Republic of China: Initiation of...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-25

..., the use of the merchandise, the channels of marketing and the cost of any modification relative to the... characteristics; (2) expectations of ultimate users; (3) use of merchandise; (4) channels of marketing; and (5... 10-11 and Exhibit 1. D. Channels of Marketing The petitioners assert that both alleged SDGEs and in...

76 FR 12325 - Small Diameter Graphite Electrodes From the People's Republic of China: Preliminary Results of...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-07

... Group). 26 Haimen Shuguang Carbon Industry Co., Ltd. 27 Handan Hanbo Material Co., Ltd. 28 Hebei Long Great Wall Electrode Co., Ltd. (aka Chang Cheng Chang Electrode Co., Ltd. and Laishui Long Great Wall... Inner Mongolia Xinghe County Hongyuan Electrical Carbon Factory. 35 Jiang Long Carbon. 36 Jiangsu Yafei...

Theoretical Modeling of the Interior Ballistics of the Electrothermal Gun

DTIC Science & Technology

1993-07-01

latter one 19 Table 2.1 Parameters Used for Nominal Data Base (after Oberle [2]). Chamber Volume 97.108 cm 3 Projectile Travel 145 cm Bore Diameter 14...at the time when the plasma supply is completed. When this occurs in the case of instantaneous mixing one has the projectile travel reduced by... Travel 400.0 cm Bore Diameter 4.0 cm Projectile Hass 160 g Plasma Energy 2000000 J Plasma Mass 0.0 g Working Fluid 420 g of H20 Density I g/cm. Bulk

Grid-translation beam deflection systems for 5-cm and 30-cm diameter Kaufman thrusters.

NASA Technical Reports Server (NTRS)

Lathem, W. C.

1972-01-01

A 5-cm grid translation mechanism has been developed capable of 10-deg beam deflection. A 2026-hour endurance test was run at a preset 10-deg deflection angle, and an extrapolated lifetime of better than 10,000 hours was obtained. Response time data for grid translation are presented. Preliminary results for a 30-cm diameter system are given, and results of a theoretical analysis of a dished grid system are discussed.

Grid-translation beam deflection systems for 5-cm and 30-cm diameter Kaufman thrusters

NASA Technical Reports Server (NTRS)

Lathem, W. C.

1972-01-01

A 5-cm grid translation mechanism has been developed capable of 10 deg beam deflection. A 2026-hour endurance test was run at a preset 10 deg deflection angle and an extrapolated lifetime of better than 10,000 hours obtained. Response time data for grid translation are presented. Preliminary results for a 30-cm diameter system are given and results of a theoretical analysis of a dished grid system are discussed.

Brown rot in inner heartwood: why large logs support characteristics saproxylic beetle assemblages of conservation concern

Treesearch

Marie Yee; Simon J. Grove; Alastair M.M. Richardson; Caroline L. Mohammed

2006-01-01

It is not clear why large diameter logs generally host saproxylic beetle assemblages that are different from those of small diameter logs. In a study in Tasmanian wet eucalypt forest, two size-classes of Eucalyptus obliqua logs (>100cm and 30-60cm diameter) were destructively sampled to assess their beetle fauna and the associations of this fauna...

A comparison of pine height models for the Crossett Experimental Forest

Treesearch

D. Bragg

2008-01-01

Many models to predict tree height from diameter have been developed, but not all are equally useful. This study compared a set of height diameter models for loblolly (Pinus taeda) and shortleaf (Pinus echinata) pines from Ashley County, Arkansas. Almost 560 trees ranging in diameter at breast height (DBH) from 0.3 cm (both species) to 91.9 cm (for shortleaf) or 108.2...

Fabrication of TiO2/Carbon Photocatalyst using Submerged DC Arc Discharged in Ethanol/Acetic Acid Medium

NASA Astrophysics Data System (ADS)

Saraswati, T. E.; Nandika, A. O.; Andhika, I. F.; Patiha; Purnawan, C.; Wahyuningsih, S.; Rahardjo, S. B.

2017-05-01

This study aimed to fabricate a modified photocatalyst of TiO2/C to enhance its performance. The fabrication was achieved using the submerged direct current (DC) arc-discharge method employing two graphite electrodes, one of which was filled with a mixture of carbon powder, TiO2, and binder, in ethanol with acetic acid added in various concentrations. The arc-discharge method was conducted by flowing a current of 10-20 A (~20 V). X-ray diffraction (XRD) patterns showed significant placements of the main peak characteristics of TiO2, C graphite, and titanium carbide. The surface analysis using Fourier transform infrared spectroscopy (FTIR) revealed that fabricated TiO2/C nanoparticles had stretching vibrations of Ti-O, C-H, C═O, C-O, O-H and C═C in the regions of 450-550 cm-1, 2900-2880 cm-1, 1690-1760 cm-1, 1050-1300 cm-1, 3400-3700 cm-1 and ~1600 cm-1, respectively. In addition, the study investigated the photocatalysts of unmodified and modified TiO2/C for photodegradation of methylene blue (MB) dye solution under mercury lamp irradiation. The effectiveness of the degradation was defined by the decrease in 60-minute absorbance under a UV-Vis spectrophotometer. Modified TiO2/C proved to be significantly more efficient in reducing dye concentrations, reaching ~70%. It indicated that the oxygen-containing functional groups have been successfully attached to the surface of the nanoparticles and played a role in enhancing photocatalytic activity.

Synthesis and characterization of lithium ion nanobatteries and lithium battery nanoelectrode arrays

NASA Astrophysics Data System (ADS)

Vullum, Fride

2005-07-01

Arrays of individual nanobatteries were constructed by confining V 2O5 ambigel and a PEO wax electrolyte containing lithium triflate in the porous structure of an alumina membrane. The pores had an average diameter of 200 nm. Cyclic voltammetry data indicated that this configuration could be described by a nanoelectrode array model. A.C. impedance data of the macro cell coupled with a lithium anode showed that there was little or no unstable passivation behavior of the lithium anode in contact with the PEO wax electrolyte. This was attributed to a self-assembled hydrocarbon layer that formed at the surface of the wax preventing the lithium metal from chemically reacting with oxygen atoms in the PEO backbone. Individual nanobatteries were characterized by charge/discharge analysis. Electrical contact with individual nanocathodes was achieved using the cantilever tip of an atomic force microscope. Of the three different anode materials that were investigated SnO2 seemed to perform better than either graphite or lithium metal. This was attributed to SnO2 being able to accept more lithium ions into its structure than graphite. The favorable capacity values compared to the lithium anode batteries were attributed to better contact between the electrolyte and the anode. Average volumetric capacities for the SnO2 system were found to be around 45 muAh/cm2mum, which compare favorably to similar systems reported in literature. These nanobatteries also exhibited capacitor-like behavior, having capacitances around 300-400 F/g, which is in the range of what is expected for a supercapacitor. An electrochemical cell combining battery-like and capacitor-like behavior is a very promising power supply for applications such as electric vehicle propulsion systems.

Selectable-Tip Corrosion-Testing Electrochemical Cell

NASA Technical Reports Server (NTRS)

Lomness, Janice; Hintze, Paul

2008-01-01

The figure depicts aspects of an electrochemical cell for pitting- corrosion tests of material specimens. The cell is designed to generate a region of corrosion having a pit diameter determined by the diameter of a selectable tip. The average depth of corrosion is controlled by controlling the total electric charge passing through the cell in a test. The cell is also designed to produce minimal artifacts associated with crevice corrosion. There are three selectable tips, having diameters of 0.1 in. (0.254 cm), 0.3 in. (0.762 cm), and 0.6 in. (1.524 cm), respectively.

Pyrolytic Carbon Nanosheets for Ultrafast and Ultrastable Sodium-Ion Storage.

PubMed

Cho, Se Youn; Kang, Minjee; Choi, Jaewon; Lee, Min Eui; Yoon, Hyeon Ji; Kim, Hae Jin; Leal, Cecilia; Lee, Sungho; Jin, Hyoung-Joon; Yun, Young Soo

2018-04-01

Na-ion cointercalation in the graphite host structure in a glyme-based electrolyte represents a new possibility for using carbon-based materials (CMs) as anodes for Na-ion storage. However, local microstructures and nanoscale morphological features in CMs affect their electrochemical performances; they require intensive studies to achieve high levels of Na-ion storage performances. Here, pyrolytic carbon nanosheets (PCNs) composed of multitudinous graphitic nanocrystals are prepared from renewable bioresources by heating. In particular, PCN-2800 prepared by heating at 2800 °C has a distinctive sp 2 carbon bonding nature, crystalline domain size of ≈44.2 Å, and high electrical conductivity of ≈320 S cm -1 , presenting significantly high rate capability at 600 C (60 A g -1 ) and stable cycling behaviors over 40 000 cycles as an anode for Na-ion storage. The results of this study show the unusual graphitization behaviors of a char-type carbon precursor and exceptionally high rate and cycling performances of the resulting graphitic material, PCN-2800, even surpassing those of supercapacitors. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Swift heavy ion-induced radiation damage in isotropic graphite studied by micro-indentation and in-situ electrical resistivity

NASA Astrophysics Data System (ADS)

Hubert, Christian; Voss, Kay Obbe; Bender, Markus; Kupka, Katharina; Romanenko, Anton; Severin, Daniel; Trautmann, Christina; Tomut, Marilena

2015-12-01

Due to its excellent thermo-physical properties and radiation hardness, isotropic graphite is presently the most promising material candidate for new high-power ion accelerators which will provide highest beam intensities and energies. Under these extreme conditions, specific accelerator components including production targets and beam protection modules are facing the risk of degradation due to radiation damage. Ion-beam induced damage effects were tested by irradiating polycrystalline, isotropic graphite samples at the UNILAC (GSI, Darmstadt) with 4.8 MeV per nucleon 132Xe, 150Sm, 197Au, and 238U ions applying fluences between 1 × 1011 and 1 × 1014 ions/cm2. The overall damage accumulation and its dependence on energy loss of the ions were studied by in situ 4-point resistivity measurements. With increasing fluence, the electric resistivity increases due to disordering of the graphitic structure. Irradiated samples were also analyzed off-line by means of micro-indentation in order to characterize mesoscale effects such as beam-induced hardening and stress fields within the specimen. With increasing fluence and energy loss, hardening becomes more pronounced.

Experimental Results for an Acoustic Driver for MTF

NASA Astrophysics Data System (ADS)

Laberge, Michel

2009-06-01

General Fusion is planning to form an FRC or spheromak of 1017 cm-3, 100 eV, 40 cm diameter by merging two spheromaks with reverse or co-helicity. This target will be further compressed in a 3 m diameter tank filled with liquid PbLi with the plasma in the center. The tank is surrounded with pneumatically powered impact pistons that will send a convergent shock wave in the liquid to compress the plasma to 1020 cm-3, 10 keV, 4 cm diameter for 7 μs. General Fusion has built a 500 kJ, 80 μs, 6 GW pneumatic impact piston capable of developing 2 GPa (300 kpsi). In this paper we will present the performances achieved to date.

Automated estimation of abdominal effective diameter for body size normalization of CT dose.

PubMed

Cheng, Phillip M

2013-06-01

Most CT dose data aggregation methods do not currently adjust dose values for patient size. This work proposes a simple heuristic for reliably computing an effective diameter of a patient from an abdominal CT image. Evaluation of this method on 106 patients scanned on Philips Brilliance 64 and Brilliance Big Bore scanners demonstrates close correspondence between computed and manually measured patient effective diameters, with a mean absolute error of 1.0 cm (error range +2.2 to -0.4 cm). This level of correspondence was also demonstrated for 60 patients on Siemens, General Electric, and Toshiba scanners. A calculated effective diameter in the middle slice of an abdominal CT study was found to be a close approximation of the mean calculated effective diameter for the study, with a mean absolute error of approximately 1.0 cm (error range +3.5 to -2.2 cm). Furthermore, the mean absolute error for an adjusted mean volume computed tomography dose index (CTDIvol) using a mid-study calculated effective diameter, versus a mean per-slice adjusted CTDIvol based on the calculated effective diameter of each slice, was 0.59 mGy (error range 1.64 to -3.12 mGy). These results are used to calculate approximate normalized dose length product values in an abdominal CT dose database of 12,506 studies.

Rapid reduction of MORB glass in piston cylinder experiments with graphite capsule - a XANES study

NASA Astrophysics Data System (ADS)

Ni, P.; Zhang, Y.; Fiege, A.; Newville, M.; Lanzirotti, A.

2017-12-01

Graphite capsules have been widely used in high-pressure, high-temperature experiments to prevent iron loss from iron-bearing samples. One common uncertainty with this experimental setup is the oxygen fugacity (fO2) inside the capsule imposed by the presence of graphite. As Holloway et al. (1992) pointed out, the use of graphite capsule places an upper limit on the fO2 in the experiment to be below CCO (graphite-CO-CO2 buffer). More recently, Medard et al. (2015) estimated the fO2 for their experiments using Pt-graphite or graphite-only capsules to be CCO-0.8. Despite the improved understanding on the fO2 using graphite capsule, the mechanism and kinetics of fO2 control in graphite capsule is still poorly understood. Such knowledge is especially important to understand whether equilibrium fO2 is reached in the sample when short experiment durations are needed (e.g. for kinetic experiments). In this study, MORB glasses after olivine dissolution (Chen and Zhang 2008) and plagioclase dissolution (Yu et al. 2016) experiments at 0.5 GPa and 1300 ºC with durations ranging from 10 s to 30 min are analyzed by XANES to obtain Fe3+/Fetotal profiles from their contact with the graphite capsule. The results show rapid Fe reduction away from the graphite-melt interface, causing a decrease of Fe3+/Fetotal from 12% to 3%. In a duration of 30 min, the 1200-µm-thick and 2000-µm-diameter basaltic glass reached near equilibrium in its iron oxidation state, with Fe3+/Fetotal ranging from 3% to 4% throughout the run product. The equilibrium Fe3+/Fetotal ratio corresponds to an fO2 of CCO-1.4, which is within error compared to the result in Medard et al. (2015). Even in the shortest experiment with an effective duration of only 10 s, a 60 µm long reduction profile was detected. Such a rapid fO2 change can be explained by rapid H2 diffusion in melt and its reaction with ferric iron: H2+Fe2O3=2FeO+H2O, which is also supported by the H2O concentration profiles measured along the reduction profile. Our results indicate rapid fO2 equilibration in MORB-glass-composition samples during nominally anhydrous graphite capsule experiments at 1300°C, and can be used to guide experimental designs.

Evaluation of Cadmium Ratio and Foil Activation Measurements for a Beryllium-Reflected Assembly of U(93.15)O 2 Fuel Rods (1.506-cm Triangular Pitch)

DOE PAGES

Marshall, Margaret A.

2014-11-04

A series of small, compact critical assembly (SCCA) experiments were completed from 1962 to 1965 at Oak Ridge National Laboratory’s Critical Experiments Facility (ORCEF) in support of the Medium-Power Reactor Experiments (MPRE) program. Initial experiments, performed in November and December of 1962, consisted of a core of un-moderated stainless-steel tubes, each containing 26 UOIdaho National Laboratory (INL), Idaho Falls, ID (United States) fuel pellets, surrounded by a graphite reflector. Measurements were performed to determine critical reflector arrangements, fission-rate distributions, and cadmium ratio distributions. The graphite reflectors were then changed to beryllium reflectors. For the beryllium reflected assemblies, the fuel wasmore » in 1.506-cm-triangular and 7-tube clusters leading to two critical configurations. Once the critical configurations had been achieved, various measurements of reactivity, relative axial and radial activation rates of 235U, and cadmium ratios were performed. The cadmium ratio, reactivity, and activation rate measurements, performed on the 1.506-cm-array critical configuration, have been evaluated and are described in this paper.« less

Potential of porous Co3O4 nanorods as cathode catalyst for oxygen reduction reaction in microbial fuel cells.

PubMed

Kumar, Ravinder; Singh, Lakhveer; Zularisam, A W; Hai, Faisal I

2016-11-01

This study aims to investigate the potential of porous Co3O4 nanorods as the cathode catalyst for oxygen reduction reaction (ORR) in aqueous air cathode microbial fuel cells (MFCs). The porous Co3O4 nanorods were synthesized by a facile and cost-effective hydrothermal method. Three different concentrations (0.5mg/cm(2), 1mg/cm(2), and 2mg/cm(2)) of Co3O4 nanorods coated on graphite electrodes were used to test its performance in MFCs. The results showed that the addition of porous Co3O4 nanorods enhanced the electrocatalytic activity and ORR kinetics significantly and the overall resistance of the system was greatly reduced. Moreover, the MFC with a higher concentration of the catalyst achieved a maximum power density of 503±16mW/m(2), which was approximately five times higher than the bare graphite electrode. The improved catalytic activity of the cathodes could be due to the porous properties of Co3O4 nanorods that provided the higher number of active sites for oxygen. Copyright © 2016 Elsevier Ltd. All rights reserved.

Optical properties of sputtered aluminum on graphite/epoxy composite material

NASA Technical Reports Server (NTRS)

Witte, William G., Jr.; Teichman, Louis A.

1989-01-01

Solar absorptance, emittance, and coating thickness were measured for a range of coating thicknesses from about 400 A to 2500 A. The coatings were sputtered from an aluminum target onto 1-inch-diameter substrates of T300/5209 graphite/epoxy composite material with two different surface textures. Solar absorptance and emittance values for the specimens with the smooth surface finish were lower than those for the specimens with the rough surface finish. The ratio of solar absorptance to emittance was higher for the smooth specimens, increasing from 2 to 4 over the coating thickness range, than for the rough ones, which had a constant ratio of about 1. The solar absorptance and emittance values were dependent on the thickness of the sputtered coating.

Comparison of epidermal/dermal damage between the long-pulsed 1064 nm Nd:YAG and 755 nm alexandrite lasers under relatively high fluence conditions: quantitative and histological assessments.

PubMed

Lee, Ju Hwan; Park, So Ra; Jo, Jeong Ho; Park, Sung Yun; Seo, Young Kwon; Kim, Sung Min

2014-07-01

The purpose of this study was to compare degrees of epidermal/dermal tissue damage quantitatively and histologically after laser irradiation, to find ideal treatment conditions with relatively high fluence for skin rejuvenation. A number of recent studies have evaluated the clinical efficacy and safety of therapeutic lasers under relatively low fluence conditions. We transmitted the long-pulsed 1064 nm Nd:YAG and 755 nm Alexandrite lasers into pig skin according to different fluences and spot diameters, and estimated epidermal/dermal temperatures. Pig skin specimens were stained with hematoxylin and eosin for histological assessments. The fluence conditions comprised 26, 30, and 36 J/cm2, and the spot diameter conditions were 5, 8, and 10 mm. Pulse duration was 30 ms for all experiments. Both lasers produced reliable thermal damage on the dermis without any serious epidermal injuries, under relatively high fluence conditions. The 1064 nm laser provided more active fibrous formations than the 755 nm laser, while higher risks for tissue damages simultaneously occurred. The ideal treatment conditions for skin rejuvenation were 8 mm diameter with 30 J/cm2 and 10 mm diameter with 26 J/cm2 for the 1064 nm laser, and 8 mm diameter with 36 J/cm2 and 10 mm diameter with 26 J/cm2 for the 755 nm laser.

Pilot study: safety and effectiveness of simple ultrasound-guided high-intensity focused ultrasound ablating uterine leiomyoma with a diameter greater than 10 cm.

PubMed

Hou, Ruijie; Wang, Liwei; Li, Shaoping; Rong, Fengmin; Wang, Yuanyuan; Qin, Xuena; Wang, Shijin

2018-02-01

The study aimed to prospectively investigate whether uterine leiomyoma greater than 10 cm in diameter could be treated with simple ultrasound-guided high-intensity focused ultrasound (USgHIFU) in one-time treatment. A total of 36 patients with 36 symptomatic uterine leiomyoma greater than 10 cm in diameter who underwent simple USgHIFU treatment alone were analysed. Enhanced MRI was performed before and after HIFU treatment, and all patients had follow-up for 6 months after treatment. Symptom severity scores, treatment time, treatment speed, ablation rate, energy effect ratio, uterine leiomyoma regression rate, adverse events, liver and kidney functions, coagulation function and routine blood count were included in the study endpoints. The mean diameter of uterine leiomyoma was 11.2 ± 1.3 cm (10.0-14.3 cm). The median treatment time and treatment speed were 104.0 min (90.0-140.0 min) and 118.8 cm 3  h -1  (86.2-247.1 cm 3  h -1 ), respectively. The ablation rate of uterine leiomyoma was 71.9 ± 20.4% (32.1-100.0%), and the regression rate of uterine leiomyoma was 40.8 ± 7.5% (25.6-59.9%) at 6 months after treatment. The mean symptom severity scores decreased by an average of approximately 8.6 ± 2.3 (5-14) points. There were no significant changes in haemogram and blood chemical indexes of patients, except for the transient elevation of aspartate aminotransferase, total bilirubin and white blood cells after treatment. No serious adverse reactions occurred. According to our preliminary results, simple USgHIFU is a safe and effective single-treatment method of treating uterine leiomyoma greater than 10 cm in diameter and is an almost innocuous alternative therapeutic strategy. Advances in knowledge: The conclusions indicate simple USgHIFU is safe and effective as one-time treatment of uterine leiomyoma greater than 10 cm in diameter, it could be a promising therapeutic strategy.

Er:YLF-laser microperforation of the nail plate for drug delivery

NASA Astrophysics Data System (ADS)

Belikov, Andrey V.; Skrypnik, Alexei V.; Sergeev, Andrey N.; Smirnov, Sergey N.; Tavalinskaya, Anastasia D.

2018-04-01

Laser microperforation of a human nail plate is an effective method to increase the speed of local drugs delivery in the treatment of nail diseases. In this paper we present the study results of the influence of spatial parameters of Er:YLFlaser- produced microhole array in human nail plate (the diameter of microholes and their packing density) on the rate (vsp) of 0.25 % water-alcohol solution of methylene blue penetration through a single microhole and on the time (Tmp) required for uniform distribution of this drug under the nail plate. In experiments, the diameter of microholes was 220 +/- 10 μm, 300 +/- 10 μm or 350 +/- 10 μm. The packing density for microholes of each of these diameters was 100 μholes/cm2, 400 μholes/cm2 and 950 μholes/cm2. It is shown that vsp is mainly determined by the microhole diameter, and the packing density does not have a significant influence on it. It was experimentally established that the rate vsp is maximal for microholes with 350 μm diameter at packing density of 950 μholes/cm2 and reaches a value of 6.3 μm/s, and the time Tmp is minimal and equal to 180 +/- 10 s at the same values of microhole diameter and packing density.

Further development of chemical vapor deposition process for production of large diameter carbon-base monofilaments

NASA Technical Reports Server (NTRS)

Hough, R. L.; Richmond, R. D.

1974-01-01

The development of large diameter carbon-base monofilament in the 50 micron to 250 micron diameter range using the chemical vapor deposition process is described. The object of this program was to determine the critical process variables which control monofilament strength, monofilament modulus, and monofilament diameter. It was confirmed that wide scatter in the carbon substrate strength is primarily responsible for the scatter in the monofilament strength. It was also shown through etching experiments that defective substrate surface conditions which can induce low strength modular growth in the monofilament layers are best controlled by processing improvements during the synthesis of the substrate. Modulus was found to be linearily proportional to monofilament boron content. Filament modulus was increased to above 27.8MN/sq cm but only by a considerable increase in monofilament boron content to 60 wt. % or more. Monofilament diameter depended upon dwell time in the synthesis apparatus. A monofilament was prepared using these findings which had the combined properties of a mean U.T.S. of 398,000 N/sq cm, a modulus of 18.9 MN/sq cm (24,000,000 psi), and a diameter of 145 microns. Highest measured strength for this fiber was 451,000 N/sq cm (645,000 psi).

Portal vein aneurysm associated with Budd-Chiari syndrome treated with transjugular intrahepatic portosystemic shunt: a case report.

PubMed

Tsauo, Jiaywei; Li, Xiao

2015-03-07

A 65-year-old woman with Budd-Chiari syndrome (BCS) presented with right upper quadrant pain. A computed tomography (CT) scan showed a saccular aneurysm located at the extrahepatic portal vein main branch measuring 3.2 cm in height and 2.5 cm × 2.4 cm in diameter. The aneurysm was thought to be associated with BCS as there was no preceding history of trauma and it had not been present on Doppler ultrasound examination performed 3 years previously. Because of increasing pain and concern for complications due to aneurysm size, the decision was made to relieve the hepatic venous outflow obstruction. Transjugular intrahepatic portosystemic shunt (TIPS) was created without complications. She had complete resolution of her abdominal pain within 2 d and remained asymptomatic after 1 year of follow-up. CT scans obtained after TIPS showed that the aneurysm had decreased in size to 2.4 cm in height and 2.0 cm × 1.9 cm in diameter at 3 mo, and had further decreased to 1.9 cm in height and 1.6 cm × 1.5 cm in diameter at 1 year.

Nanodiamond preparation and surface characterization for biological applications

NASA Astrophysics Data System (ADS)

Woodhams, Ben J.; Knowles, Helena S.; Kara, Dhiren M.; Atatüre, Mete; Bohndiek, Sarah E.

2017-02-01

Nanodiamonds contain stable fluorescent emitters and hence can be used for molecular fluorescence imaging and precision sensing of electromagnetic fields. The physical properties of these emitters together with their low reported cytotoxicity make them attractive for biological imaging applications. The controlled application of nanodiamonds for cellular imaging requires detailed understanding of surface chemistry, size ranges and aggregation, as these can all influence cellular interactions. We compared these characteristics for graphitic and oxidized nanodiamonds. Oxidation is generally used for surface functionalization, and was optimized by Thermogravimetric Analysis, achieved by 445+/-5°C heating in air for 5 hours, then confirmed via Raman and Infrared spectroscopies. Size ranges and aggregation were assessed using Atomic Force Microscopy and Dynamic Light Scattering. Biocompatibility in breast cancer cell lines was measured using a proliferation assay. Heating at 445+/-5°C reduced the Raman signal of graphitic carbon (1575 cm-1) as compared to that of diamond (1332 cm-1) from 0.31+/-0.07 Raman intensity units to 0.07+/-0.04. This temperature was substantially below the onset of major mass loss (observed at 535+/-1°C) and therefore achieved cost efficiency, convenience and high yield. Graphitic and oxidized nanodiamonds formed aggregates in water, with a mean particle size of 192+/-4nm and 166+/-2nm at a concentration of 66μg/mL. We then applied the graphitic and oxidized nanodiamonds to cells in culture at 1μg/mL and found no significant change in the proliferation rate (-5+/-2% and -1+/-3% respectively). Nanodiamonds may therefore be suitable for development as a novel transformative tool in the life sciences.

Characterization of Mechanical Properties of Nuclear Graphite Using Subsize Specimens and Reusing Tested Specimens

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

Ji Hyun, Yoon; Byun, Thak Sang; Strizak, Joe P

2011-01-01

The mechanical properties of NBG-18 nuclear grade graphite have been characterized using small specimen test techniques and statistical treatment on the test results. New fracture strength and toughness test techniques were developed to use subsize cylindrical specimens with glued heads and to reuse their broken halves. Three sets of subsize cylindrical specimens with the different diameters of 4 mm, 8 mm, and 12 mm were tested to obtain tensile fracture strength. The longer piece of the broken halves was cracked from side surfaces and tested under three-point bend loading to obtain fracture toughness. Both the strength and fracture toughness datamore » were analyzed using Weibull distribution models focusing on size effect. The mean fracture strength decreased from 22.9 MPa to 21.5 MPa as the diameter increased from 4 mm to 12 mm, and the mean strength of 15.9 mm diameter standard specimen, 20.9 MPa, was on the extended trend line. These fracture strength data indicate that in the given diameter range the size effect is not significant and much smaller than that predicted by the Weibull statistics-based model. Further, no noticeable size effect existed in the fracture toughness data, whose mean values were in a narrow range of 1.21 1.26 MPa. The Weibull moduli measured for fracture strength and fracture toughness datasets were around 10. It is therefore believed that the small or negligible size effect enables to use the subsize specimens and that the new fracture toughness test method to reuse the broken specimens to help minimize irradiation space and radioactive waste.« less

Laser microprobe and resonant laser ablation for depth profile measurements of hydrogen isotope atoms contained in graphite.

PubMed

Yorozu, M; Yanagida, T; Nakajyo, T; Okada, Y; Endo, A

2001-04-20

We measured the depth profile of hydrogen atoms in graphite by laser microprobing combined with resonant laser ablation. Deuterium-implanted graphite was employed for the measurements. The sample was ablated by a tunable laser with a wavelength corresponding to the resonant wavelength of 1S-2S of deuterium with two-photon excitation. The ablated deuterium was ionized by a 2 + 1 resonant ionization process. The ions were analyzed by a time-of-flight mass spectrometer. The deuterium ions were detected clearly with the resonant ablation. The detection limit was estimated to be less than 10(16) atoms/cm(3) in our experiments. We determined the depth profile by considering the etching profile and the etching rate. The depth profile agreed well with Monte Carlo simulations to within a precision of 23 mum for the center position and 4-mum precision for distributions for three different implantation depths.

In-situ measurement of smoke particles in the wintertime polar mesosphere between 80 and 85 km altitude

NASA Astrophysics Data System (ADS)

Amyx, K.; Sternovsky, Z.; Knappmiller, S.; Robertson, S.; Horanyi, M.; Gumbel, J.

2008-01-01

The MAGIC sounding rocket, launched in January 2005 into the polar mesosphere, carried two detectors for charged aerosol particles. The detectors are graphite patch collectors mounted flush with the skin of the payload and are connected to sensitive electrometers. The measured signal is the net current deposited on the detectors by heavy aerosol particles. The collection of electrons and ions is prevented by magnetic shielding and a small positive bias, respectively. Both instruments detected a layer of heavy aerosol particles between 80 and 85 km with a number density approximately 103 cm-3. Aerodynamic flow simulations imply that the collected particles are larger than ˜1 nm in radius. The particles are detected as a net positive charge deposited on the graphite collectors. It is suggested that the measured positive polarity is due to the electrification of the smoke particles upon impact on the graphite collectors.

Progress in developing ultrathin solar cell blanket technology

NASA Technical Reports Server (NTRS)

Patterson, R. E.; Mesch, H. G.; Scott-Monck, J.

1984-01-01

A program was conducted to develop technologies for welding interconnects to three types of 50-micron-thick, 2 by 2-cm solar cells. Parallel-gap resistance welding was used for interconnect attachment. Weld schedules were independently developed for each of the three cell types and were coincidentally identical. Six 48-cell modules were assembled with 50-micron (nominal) thick cells, frosted fused-silica covers, silver-plated Invar interconnectors, and four different substrate designs. Three modules (one for each cell type) have single-layer Kapton (50-micron-thick) substrates. The other three modules each have a different substrate (Kapton-Kevlar-Kapton, Kapton-graphite-Kapton, and Kapton-graphite-aluminum honeycomb-graphite). All six modules were subjected to 4112 thermal cycles from -175 to 65 C (corresponding to over 40 years of simulated geosynchronous orbit thermal cycling) and experienced only negligible electrical degradation (1.1 percent average of six 48-cell modules).

Square lattice honeycomb tri-carbide fuels for 50 to 250 KN variable thrust NTP design

NASA Astrophysics Data System (ADS)

Anghaie, Samim; Knight, Travis; Gouw, Reza; Furman, Eric

2001-02-01

Ultrahigh temperature solid solution of tri-carbide fuels are used to design an ultracompact nuclear thermal rocket generating 950 seconds of specific impulse with scalable thrust level in range of 50 to 250 kilo Newtons. Solid solutions of tri-carbide nuclear fuels such as uranium-zirconium-niobium carbide. UZrNbC, are processed to contain certain mixing ratio between uranium carbide and two stabilizing carbides. Zirconium or niobium in the tri-carbide could be replaced by tantalum or hafnium to provide higher chemical stability in hot hydrogen environment or to provide different nuclear design characteristics. Recent studies have demonstrated the chemical compatibility of tri-carbide fuels with hydrogen propellant for a few to tens of hours of operation at temperatures ranging from 2800 K to 3300 K, respectively. Fuel elements are fabricated from thin tri-carbide wafers that are grooved and locked into a square-lattice honeycomb (SLHC) shape. The hockey puck shaped SLHC fuel elements are stacked up in a grooved graphite tube to form a SLHC fuel assembly. A total of 18 fuel assemblies are arranged circumferentially to form two concentric rings of fuel assemblies with zirconium hydride filling the space between assemblies. For 50 to 250 kilo Newtons thrust operations, the reactor diameter and length including reflectors are 57 cm and 60 cm, respectively. Results of the nuclear design and thermal fluid analyses of the SLHC nuclear thermal propulsion system are presented. .

Effect of Powder-Suspended Dielectric on the EDM Characteristics of Inconel 625

NASA Astrophysics Data System (ADS)

Talla, Gangadharudu; Gangopadhyay, S.; Biswas, C. K.

2016-02-01

The current work attempts to establish the criteria for powder material selection by investigating the influence of various powder-suspended dielectrics and machining parameters on various EDM characteristics of Inconel 625 (a nickel-based super alloy) which is nowadays regularly used in aerospace, chemical, and marine industries. The powders include aluminum (Al), graphite, and silicon (Si) that have significant variation in their thermo-physical characteristics. Results showed that powder properties like electrical conductivity, thermal conductivity, density, and hardness play a significant role in changing the machining performance and the quality of the machined surface. Among the three powders, highest material removal rate was observed for graphite powder due to its high electrical and thermal conductivities. Best surface finish and least radial overcut (ROC) were attained using Si powder. Maximum microhardness was found for Si due to its low thermal conductivity and high hardness. It is followed by graphite and aluminum powders. Addition of powder to the dielectric has increased the crater diameter due to expansion of plasma channel. Powder-mixed EDM (PMEDM) was also effective in lowering the density of surface cracks with least number of cracks obtained with graphite powder. X-ray diffraction analysis indicated possible formation of metal carbides along with grain growth phenomenon of Inconel 625 after PMEDM.

Dimensional analysis of human saphenous vein grafts: Implications for external mesh support.

PubMed

Human, Paul; Franz, Thomas; Scherman, Jacques; Moodley, Lovendran; Zilla, Peter

2009-05-01

Constrictive external mesh support of vein grafts was shown to mitigate intimal hyperplasia in animal experiments. To determine the degree of constriction required for the elimination of dimensional irregularities in clinically used vein grafts, a detailed anatomic study of human saphenous veins was conducted. In 200 consecutive patients having coronary artery bypass grafting, harvested saphenous veins (length 34.4 +/- 10.8 cm) were analyzed regarding diameter irregularities, side branch distribution, and microstructure. The mean outer diameter of surgically distended saphenous veins was 4.2 +/- 0.6 mm (men, 4.3 +/- 0.6 mm vs women, 3.9 +/- 0.5 mm; P < .0001). Although the outer diameter significantly decreased over the initial 18 cm (-7.6%; P < .0001), the overall increase between malleolus and thigh was not significant (+11.2%). Smaller-diameter veins (<3.5 mm) had more pronounced diameter fluctuations than larger veins (31.8% +/- 11.0% vs 21.2% +/- 8.8%; P < .0001), with more than 71% of all veins showing caliber changes of more than 20%. There was 1 side branch every 5.4 +/- 4.3 cm, with a significantly higher incidence between 20 and 32 cm from the malleolus (P < .0001 to distal, P < .0004 to proximal). Generally, women had more side branches than men (0.30 +/- 0.15 cm(-1) vs 0.25 +/- 0.12 cm(-1); P = .0190). Thick-walled veins (565.7 +/- 138.4 mum) had a significantly higher number of large side branches (P < .0001), and thin-walled veins (398.7 +/- 123.2 mum) had significantly more small side branches (P < .0001). Pronounced intimal thickening ("cushions") was found in 28% of vessels (119.8 +/- 28.0 mum vs 40.1 +/- 18.2 mum; P < .0001). Although the preferential location of side branches may be addressed by the deliberate discarding of infragenicular vein segments, a diameter constriction of 27% on average would eliminate diameter irregularities in 98% of vein grafts.

Advanced solar panel designs

NASA Technical Reports Server (NTRS)

Ralph, E. L.; Linder, E. B.

1996-01-01

Solar panel designs that utilize new high-efficiency solar cells and lightweight rigid panel technologies are described. The resulting designs increase the specific power (W/kg) achievable in the near-term and are well suited to meet the demands of higher performance small satellites (smallsats). Advanced solar panel designs have been developed and demonstrated on two NASA SBIR contracts at Applied Solar. The first used 19% efficient, large area (5.5 cm x 6.5 cm) GaAs/Ge solar cells with a lightweight rigid graphite epoxy isogrid substrate configuration. A 1,445 cm(exp 2) coupon was fabricated and tested to demonstrate 60 W/kg with a high potential of achieving 80 W/kg. The second panel design used new 22% efficiency, dual junction GaInP2/GaAs/Ge solar cells combined with a lightweight aluminum core/graphite fiber mesh facesheet substrate. A 1,445 cm(exp 2) coupon was fabricated and tested to demonstrate 105 W/kg with the potential of achieving 115 W/kg. This paper will address the construction details for the GaAs/isogrid and dual-junction GaAs/carbon mesh panel configurations. These are ultimately sized to provide 75 Watts and 119 Watts respectively for smallsats or may be used as modular building blocks for larger systems. GaAs/isogrid and dual-junction GaAs/carbon mesh coupons have been fabricated and tested to successfully demonstrate critical performance parameters and results are also provided here.

Multilayer core-shell structured composite paper electrode consisting of copper, cuprous oxide and graphite assembled on cellulose fibers for asymmetric supercapacitors

NASA Astrophysics Data System (ADS)

Wan, Caichao; Jiao, Yue; Li, Jian

2017-09-01

An easily-operated and inexpensive strategy (pencil-drawing-electrodeposition-electro-oxidation) is proposed to synthesize a novel class of multilayer core-shell structured composite paper electrode, which consists of copper, cuprous oxide and graphite assembled on cellulose fibers. This interesting electrode structure plays a pivotal role in providing more active sites for electrochemical reactions, facilitating ion and electron transport and shorting their diffusion pathways. This electrode demonstrates excellent electrochemical properties with a high specific capacitance of 601 F g-1 at 2 A g-1 and retains 83% of this capacitance when operated at an ultrahigh current density of 100 A g-1. In addition, a high energy density of 13.4 W h kg-1 at the power density of 0.40 kW kg-1 and a favorable cycling stability (95.3%, 8000 cycles) were achieved for this electrode. When this electrode was assembled into an asymmetric supercapacitor with carbon paper as negative electrode, the device displays remarkable electrochemical performances with a large areal capacitances (122 mF cm-2 at 1 mA cm-2), high areal energy density (10.8 μW h cm-2 at 402.5 μW cm-2) and outstanding cycling stability (91.5%, 5000 cycles). These results unveil the potential of this composite electrode as a high-performance electrode material for supercapacitors.

Ecological Importance of Small-Diameter Trees to the Structure, Diversity and Biomass of a Tropical Evergreen Forest at Rabi, Gabon.

PubMed

Memiaghe, Hervé R; Lutz, James A; Korte, Lisa; Alonso, Alfonso; Kenfack, David

2016-01-01

Tropical forests have long been recognized for their biodiversity and ecosystem services. Despite their importance, tropical forests, and particularly those of central Africa, remain understudied. Until recently, most forest inventories in Central Africa have focused on trees ≥10 cm in diameter, even though several studies have shown that small-diameter tree population may be important to demographic rates and nutrient cycling. To determine the ecological importance of small-diameter trees in central African forests, we used data from a 25-ha permanent plot that we established in the rainforest of Gabon to study the diversity and dynamics of these forests. Within the plot, we censused 175,830 trees ≥1 cm dbh from 54 families, 192 genera, and 345 species. Average tree density was 7,026 trees/ha, basal area 31.64 m2/ha, and above-ground biomass 369.40 Mg/ha. Fabaceae, Ebenaceae and Euphorbiaceae were the most important families by basal area, density and above-ground biomass. Small-diameter trees (1 cm ≥ dbh <10 cm) comprised 93.7% of the total tree population, 16.5% of basal area, and 4.8% of the above-ground biomass. They also had diversity 18% higher at family level, 34% higher at genus level, and 42% higher at species level than trees ≥10 cm dbh. Although the relative contribution of small-diameter trees to biomass was comparable to other forests globally, their contribution to forest density, and diversity was disproportionately higher. The high levels of diversity within small-diameter classes may give these forests high levels of structural resilience to anthropogenic/natural disturbance and a changing climate.

Ecological Importance of Small-Diameter Trees to the Structure, Diversity and Biomass of a Tropical Evergreen Forest at Rabi, Gabon

PubMed Central

Memiaghe, Hervé R.; Lutz, James A.; Korte, Lisa; Alonso, Alfonso; Kenfack, David

2016-01-01

Tropical forests have long been recognized for their biodiversity and ecosystem services. Despite their importance, tropical forests, and particularly those of central Africa, remain understudied. Until recently, most forest inventories in Central Africa have focused on trees ≥10 cm in diameter, even though several studies have shown that small-diameter tree population may be important to demographic rates and nutrient cycling. To determine the ecological importance of small-diameter trees in central African forests, we used data from a 25-ha permanent plot that we established in the rainforest of Gabon to study the diversity and dynamics of these forests. Within the plot, we censused 175,830 trees ≥1 cm dbh from 54 families, 192 genera, and 345 species. Average tree density was 7,026 trees/ha, basal area 31.64 m2/ha, and above-ground biomass 369.40 Mg/ha. Fabaceae, Ebenaceae and Euphorbiaceae were the most important families by basal area, density and above-ground biomass. Small-diameter trees (1 cm ≥ dbh <10 cm) comprised 93.7% of the total tree population, 16.5% of basal area, and 4.8% of the above-ground biomass. They also had diversity 18% higher at family level, 34% higher at genus level, and 42% higher at species level than trees ≥10 cm dbh. Although the relative contribution of small-diameter trees to biomass was comparable to other forests globally, their contribution to forest density, and diversity was disproportionately higher. The high levels of diversity within small-diameter classes may give these forests high levels of structural resilience to anthropogenic/natural disturbance and a changing climate. PMID:27186658

CO2 content of andesitic melts at graphite-saturated upper mantle conditions with implications for redox state of oceanic basalt source regions and remobilization of reduced carbon from subducted eclogite

NASA Astrophysics Data System (ADS)

Eguchi, James; Dasgupta, Rajdeep

2017-03-01

We have performed experiments to determine the effects of pressure, temperature and oxygen fugacity on the CO2 contents in nominally anhydrous andesitic melts at graphite saturation. The andesite composition was specifically chosen to match a low-degree partial melt composition that is generated from MORB-like eclogite in the convective, oceanic upper mantle. Experiments were performed at 1-3 GPa, 1375-1550 °C, and fO2 of FMQ -3.2 to FMQ -2.3 and the resulting experimental glasses were analyzed for CO2 and H2O contents using FTIR and SIMS. Experimental results were used to develop a thermodynamic model to predict CO2 content of nominally anhydrous andesitic melts at graphite saturation. Fitting of experimental data returned thermodynamic parameters for dissolution of CO2 as molecular CO2: ln( K 0) = -21.79 ± 0.04, Δ V 0 = 32.91 ± 0.65 cm3mol-1, Δ H 0 = 107 ± 21 kJ mol-1, and dissolution of CO2 as CO3 2-: ln (K 0 ) = -21.38 ± 0.08, Δ V 0 = 30.66 ± 1.33 cm3 mol-1, Δ H 0 = 42 ± 37 kJ mol-1, where K 0 is the equilibrium constant at some reference pressure and temperature, Δ V 0 is the volume change of reaction, and Δ H 0 is the enthalpy change of reaction. The thermodynamic model was used along with trace element partition coefficients to calculate the CO2 contents and CO2/Nb ratios resulting from the mixing of a depleted MORB and the partial melt of a graphite-saturated eclogite. Comparison with natural MORB and OIB data suggests that the CO2 contents and CO2/Nb ratios of CO2-enriched oceanic basalts cannot be produced by mixing with partial melts of graphite-saturated eclogite. Instead, they must be produced by melting of a source containing carbonate. This result places a lower bound on the oxygen fugacity for the source region of these CO2-enriched basalts, and suggests that fO2 measurements made on cratonic xenoliths may not be applicable to the convecting upper mantle. CO2-depleted basalts, on the other hand, are consistent with mixing between depleted MORB and partial melts of a graphite-saturated eclogite. Furthermore, calculations suggest that eclogite can remain saturated in graphite in the convecting upper mantle, acting as a reservoir for C.

BROACHING AND TUBE-INSTALLING APPARATUS

DOEpatents

Frantz, C.E.; Cawley, W.E.

1961-05-16

An apparatus is given for sizing long holes in graphite bodies. The apparatus comprises a shaft having 3 spiral broach cutting elements and a straight broach cutting element rotatably mounted thereon. The broach cutting elements are keyed to each other in end to end relationship with the straight broach cutting element at one end of the shaft. The spiral broach cutting elements when considered toward the straight broach cutting element increase in diameter and the cutting teeth thereon increase in lead angle. The straight broach cutting element, when considered in the same direction, increases in diameter from the minimum to maximum diameters of the spiral broach cutting elements. No longitudinal movement of the broach cutting elements is permitted on the shsft snd means are provided for the removal of chips from the apparatus.

Influence of multiple brain metastases’ size and number on the quality of SRS - VMAT dose delivery

NASA Astrophysics Data System (ADS)

Prentou, G.; Koutsouveli, E.; Pantelis, E.; Papagiannis, P.; Georgiou, E.; Karaiskos, P.

2017-11-01

Stereotactic radiosurgery with volumetric modulated arc therapy (SRS-VMAT) has recently been introduced for treatment of multiple brain metastases with a single isocenter. The technique’s high efficiency is nevertheless dependent of metastatic tumors’ characteristics such as size and number. In this work the impact of the metastases’ size and number on the plan quality indices clinically used for plan evaluation and acceptance is investigated. Fifteen targets with a diameter of 1 cm and average volume of 0.7 cm3 and ten targets with a diameter of 2 cm and average volume of 6.5 cm3 were contoured on an anonymized patient CT dataset, in Monaco (Elekta) treatment planning system. VMAT plans for different target volumes (1 and 2 cm in diameter) and various target numbers (1-15) were generated using four non-coplanar arcs and the Agility (Elekta) linear accelerator (5 mm MLC width) using a Monte Carlo dose calculation algorithm and 1mm dose calculation grid resolution. Conformity index (CI), gradient index (GI) and heterogeneity index (HI) were determined for each target. High quality plans were created for both 1 cm and 2 cm in diameter targets for limited (<6) number of targets per plan. For increased number of irradiated targets (>6) both CI and GI, clinically used for plan evaluation and acceptance, were found to deteriorate.

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

Experimental evaluation of foil-supported resilient-pad gas-lubricated thrust bearing

NASA Technical Reports Server (NTRS)

Nemeth, Z. N.

1977-01-01

A new type of resilient-pad gas thrust bearing was tested to determine the feasibility of the design. The bearing consists of carbon graphite pads mounted asymmetrically on foil beams. Two bearing configurations were tested at thrust loads from 27 to 80 newtons at speeds to 9000 rpm. The outside diameter of the bearing was 8.9 centimeters.

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

Effect of lung and target density on small-field dose coverage and PTV definition

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

Higgins, Patrick D., E-mail: higgi010@umn.edu; Ehler, Eric D.; Cho, Lawrence C.

We have studied the effect of target and lung density on block margin for small stereotactic body radiotherapy (SBRT) targets. A phantom (50 × 50 × 50 cm{sup 3}) was created in the Pinnacle (V9.2) planning system with a 23-cm diameter lung region of interest insert. Diameter targets of 1.6, 2.0, 3.0, and 4.0 cm were placed in the lung region of interest and centered at a physical depth of 15 cm. Target densities evaluated were 0.1 to 1.0 g/cm{sup 3}, whereas the surrounding lung density was varied between 0.05 and 0.6 g/cm{sup 3}. A dose of 100 cGy wasmore » delivered to the isocenter via a single 6-MV field, and the ratio of the average dose to points defining the lateral edges of the target to the isocenter dose was recorded for each combination. Field margins were varied from none to 1.5 cm in 0.25-cm steps. Data obtained in the phantom study were used to predict planning treatment volume (PTV) margins that would match the clinical PTV and isodose prescription for a clinical set of 39 SBRT cases. The average internal target volume (ITV) density was 0.73 ± 0.17, average local lung density was 0.33 ± 0.16, and average ITV diameter was 2.16 ± 0.8 cm. The phantom results initially underpredicted PTV margins by 0.35 cm. With this offset included in the model, the ratio of predicted-to-clinical PTVs was 1.05 ± 0.32. For a given target and lung density, it was found that treatment margin was insensitive to target diameter, except for the smallest (1.6-cm diameter) target, for which the treatment margin was more sensitive to density changes than the larger targets. We have developed a graphical relationship for block margin as a function of target and lung density, which should save time in the planning phase by shortening the design of PTV margins that can satisfy Radiation Therapy Oncology Group mandated treatment volume ratios.« less

High-powered microwave ablation with a small-gauge, gas-cooled antenna: initial ex vivo and in vivo results.

PubMed

Lubner, Meghan G; Hinshaw, J Louis; Andreano, Anita; Sampson, Lisa; Lee, Fred T; Brace, Christopher L

2012-03-01

To evaluate the performance of a gas-cooled, high-powered microwave system. Investigators performed 54 ablations in ex vivo bovine livers using three devices-a single 17-gauge cooled radiofrequency(RF) electrode; a cluster RF electrode; and a single 17-gauge, gas-cooled microwave (MW) antenna-at three time points (n = 6 at 4 minutes, 12 minutes, and 16 minutes). RF power was applied using impedance-based pulsing with maximum 200 W generator output. MW power of 135 W at 2.45 GHz was delivered continuously. An approved in vivo study was performed using 13 domestic pigs. Hepatic ablations were performed using single applicators and the above-mentioned MW and RF generator systems at treatment times of 2 minutes (n = 7 MW, n = 6 RF), 5 minutes (n = 23 MW, n = 8 RF), 7 minutes (n = 11 MW, n = 6 RF), and 10 minutes (n = 7 MW, n = 9 RF). Mean transverse diameter and length of the ablation zones were compared using analysis of variance (ANOVA) with post-hoc t tests and Wilcoxon rank-sum tests. Single ex vivo MW ablations were larger than single RF ablations at all time points (MW mean diameter range 3.5-4.8 cm 4-16 minutes; RF mean diameter range 2.6-3.1 cm 4-16 minutes) (P < .05). There was no difference in mean diameter between cluster RF and MW ablations (RF 3.3-4.4 cm 4-16 minutes; P = .4-.9). In vivo lesion diameters for MW (and RF) were as follows: 2.6 cm ± 0.72 (RF 1.5 cm ± 0.14), 3.6 cm ± 0.89 (RF 2.0 cm ± 0.4), 3.4 cm ± 0.87 (RF 1.8 cm ± 0.23), and 3.8 cm ± 0.74 (RF 2.1 cm ± 0.3) at 2 minutes, 5 minutes, 7 minutes, and 10 minutes (P < .05 all time points). Gas-cooled, high-powered MW ablation allows the generation of large ablation zones in short times. Copyright © 2012 SIR. Published by Elsevier Inc. All rights reserved.

Ceramic backup ring prevents undesirable weld-metal buildup

NASA Technical Reports Server (NTRS)

Leonard, G. E.

1971-01-01

Removable ceramic backup material butted against weld zone back prevents weld metal buildup at that site. Method is successful with manual tungsten-inert gas /TIG/ welding of 316 corrosion resistant steel /CRES/ pieces with 0.76 cm throat diameter and 1.57 cm pipe internal diameter.

Direct printing and reduction of graphite oxide for flexible supercapacitors

NASA Astrophysics Data System (ADS)

Jung, Hanyung; Ve Cheah, Chang; Jeong, Namjo; Lee, Junghoon

2014-08-01

We report direct printing and photo-thermal reduction of graphite oxide (GO) to obtain a highly porous pattern of interdigitated electrodes, leading to a supercapacitor on a flexible substrate. Key parameters optimized include the amount of GO delivered, the suitable photo-thermal energy level for effective flash reduction, and the substrate properties for appropriate adhesion after reduction. Tests with supercapacitors based on the printed-reduced GO showed performance comparable with commercial supercapacitors: the energy densities were 1.06 and 0.87 mWh/cm3 in ionic and organic electrolytes, respectively. The versatility in the architecture and choice of substrate makes this material promising for smart power applications.

Synthesis of graphene nanoribbons from amyloid templates by gallium vapor-assisted solid-phase graphitization

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

Murakami, Katsuhisa, E-mail: k.murakami@bk.tsukuba.ac.jp; Dong, Tianchen; Kajiwara, Yuya

2014-06-16

Single- and double-layer graphene nanoribbons (GNRs) with widths of around 10 nm were synthesized directly onto an insulating substrate by solid-phase graphitization using a gallium vapor catalyst and carbon templates made of amyloid fibrils. Subsequent investigation revealed that the crystallinity, conductivity, and carrier mobility were all improved by increasing the temperature of synthesis. The carrier mobility of the GNR synthesized at 1050 °C was 0.83 cm{sup 2}/V s, which is lower than that of mechanically exfoliated graphene. This is considered to be most likely due to electron scattering by the defects and edges of the GNRs.

Verification of statistical method CORN for modeling of microfuel in the case of high grain concentration

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

Chukbar, B. K., E-mail: bchukbar@mail.ru

Two methods of modeling a double-heterogeneity fuel are studied: the deterministic positioning and the statistical method CORN of the MCU software package. The effect of distribution of microfuel in a pebble bed on the calculation results is studied. The results of verification of the statistical method CORN for the cases of the microfuel concentration up to 170 cm{sup –3} in a pebble bed are presented. The admissibility of homogenization of the microfuel coating with the graphite matrix is studied. The dependence of the reactivity on the relative location of fuel and graphite spheres in a pebble bed is found.

Comparison of Epidermal/Dermal Damage Between the Long-Pulsed 1064 nm Nd:YAG and 755 nm Alexandrite Lasers Under Relatively High Fluence Conditions: Quantitative and Histological Assessments

PubMed Central

Lee, Ju Hwan; Park, So Ra; Jo, Jeong Ho; Park, Sung Yun; Seo, Young Kwon

2014-01-01

Abstract Objective: The purpose of this study was to compare degrees of epidermal/dermal tissue damage quantitatively and histologically after laser irradiation, to find ideal treatment conditions with relatively high fluence for skin rejuvenation. Background data: A number of recent studies have evaluated the clinical efficacy and safety of therapeutic lasers under relatively low fluence conditions. Methods: We transmitted the long-pulsed 1064 nm Nd:YAG and 755 nm Alexandrite lasers into pig skin according to different fluences and spot diameters, and estimated epidermal/dermal temperatures. Pig skin specimens were stained with hematoxylin and eosin for histological assessments. The fluence conditions comprised 26, 30, and 36 J/cm2, and the spot diameter conditions were 5, 8, and 10 mm. Pulse duration was 30 ms for all experiments. Results: Both lasers produced reliable thermal damage on the dermis without any serious epidermal injuries, under relatively high fluence conditions. The 1064 nm laser provided more active fibrous formations than the 755 nm laser, while higher risks for tissue damages simultaneously occurred. Conclusions: The ideal treatment conditions for skin rejuvenation were 8 mm diameter with 30 J/cm2 and 10 mm diameter with 26 J/cm2 for the 1064 nm laser, and 8 mm diameter with 36 J/cm2 and 10 mm diameter with 26 J/cm2 for the 755 nm laser. PMID:24992273

Long-term diameter growth for trees in the Cinnamon Bay Watershed

Treesearch

Peter L. Weaver

2009-01-01

From 1983 to 2008, the mean annual diameter growth (MAI) for 1,402 surviving stems of 62 species in the Cinnamon Bay watershed was 0.08¡À0.002 cm yr-1. Long-term MAI ranged from 0.02 cm yr-1 for Randia aculeata to 0.23 cm yr-1 for Inga laurina. Of the 30 species with ¡Ý8 surviving stems, eight averaged ¡Ý0.10 cm yr-1. Hurricane Hugo in 1989, Hurricane Marilyn in 1995,...

Failure mechanisms of uni-ply composite plates with a circular hole under static compressive loading

NASA Technical Reports Server (NTRS)

Khamseh, A. R.; Waas, A. M.

1992-01-01

The objective of the study was to identify and study the failure mechanisms associated with compressive-loaded uniply graphite/epoxy square plates with a central circular hole. It is found that the type of compressive failure depends on the hole size. For large holes with the diameter/width ratio exceeding 0.062, fiber buckling/kinking initiated at the hole is found to be the dominant failure mechanism. In plates with smaller hole sizes, failure initiates away from the hole edge or complete global failure occurs. Critical buckle wavelengths at failure are presented as a function of the normalized hole diameter.

Stripping the Sheath From Stranded Cables

NASA Technical Reports Server (NTRS)

Prisk, A. L.; Rotta, J. W.

1985-01-01

Device similar to tubing cutter removes tough plastic cover. Insulation stripper is 3 in. (7.6 cm) long and 1.5 (3.8 cm) in diameter. Two rollers are small-diameter bearings. Cutter blade journaled for rotation between pair of similar bearings. Bearings either pin or ball types of suitable dimensions.

Nano-graphite functionalized mesocellular carbon foam with enhanced intra-penetrating electrical percolation networks for high performance electrochemical energy storage electrode materials.

PubMed

Jo, Changshin; An, Sunhyung; Kim, Younghoon; Shim, Jongmin; Yoon, Songhun; Lee, Jinwoo

2012-04-28

Mesocellular carbon foam (MSU-F-C) is functionalized with hollow nanographite by a simple solution-phase method to enhance the intrapenetrating electrical percolation network. The electrical conductivity of the resulting material, denoted as MSU-F-C-G, is increased by a factor of 20.5 compared with the pristine MSU-F-C. Hollow graphite nanoparticles are well-dispersed in mesocellular carbon foam, as confirmed by transmission electron microscopy (TEM), and the d spacing of the (002) planes is 0.343 nm, which is only slightly larger than that of pure graphite (0.335 nm), suggesting a random combination of graphitic and turbostratic stacking. After nanographitic functionalization, the BET surface area and total pore volume decreased from 928 m(2) g(-1) and 1.5 cm(3) g(-1) to 394 m(2) g(-1) and 0.7 cm(3) g(-1), respectively. Thermogravimetric analysis in air shows that the thermal stability of MSU-F-C-G is improved relative to that of MSU-F-C, and the one-step weight loss indicates that the nanographite is homogeneously functionalized on the MSU-F-C particles. When the resulting mesocellular carbon materials are used as electrode materials for an electric double layer capacitor (EDLC), the specific capacitances (C(sp)) of the MSU-F-C and MSU-F-C-G electrodes at 4 mV s(-1) are 109 F g(-1) and 93 F g(-1), respectively. The MSU-F-C-G electrode exhibited a very high area capacitance (C(area), 23.5 μF cm(-2)) compared with that of the MSU-F-C electrode (11.7 μF cm(-2)), which is attributed to the enhanced intraparticle conductivity by the nanographitic functionalization. MSU-F-C-G exhibited high capacity retention (52%) at a very high scan rate of 512 mV s(-1), while only a 23% capacity retention at 512 mV s(-1) was observed in the case of the MSU-F-C electrode. When applied as an anode in a lithium ion battery, a significant increase in the initial efficiency (44%), high reversible discharge capacity (580 mA h g(-1)) in the lower voltage region, and a higher rate capability were observed. The high rate capability of the MSU-F-C-G electrode as charge storage was due to the low resistance derived from the nanographitic functionalization. This journal is © the Owner Societies 2012

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 ).

Bolted joints in graphite-epoxy composites

NASA Technical Reports Server (NTRS)

Hart-Smith, L. J.

1976-01-01

All-graphite/epoxy laminates and hybrid graphite-glass/epoxy laminates were tested. The tests encompassed a range of geometries for each laminate pattern to cover the three basic failure modes - net section tension failure through the bolt hole, bearing and shearout. Static tensile and compressive loads were applied. A constant bolt diameter of 6.35 mm (0.25 in.) was used in the tests. The interaction of stress concentrations associated with multi-row bolted joints was investigated by testing single- and double-row bolted joints and open-hole specimens in tension. For tension loading, linear interaction was found to exist between the bearing stress reacted at a given bolt hole and the remaining tension stress running by that hole to be reacted elsewhere. The interaction under compressive loading was found to be non-linear. Comparative tests were run using single-lap bolted joints and double-lap joints with pin connection. Both of these joint types exhibited lower strengths than were demonstrated by the corresponding double-lap joints. The analysis methods developed here for single bolt joints are shown to be capable of predicting the behavior of multi-row joints.

Guided waves and defect scattering in metal matrix composite plates

NASA Technical Reports Server (NTRS)

Datta, Subhendu K.; Bratton, Robert L.; Shah, Arvind H.

1989-01-01

Guided Rayleigh-Lamb waves in a continuous graphite fiber reinforced magnesium plate has been studied. The interest in this material arises from its high thermal stability and because it provides high strength-to-weight ratio. Previous studies have shown that for wavelengths much larger than the fiber diameters and spacing, the material can be characterized as transversely isotropic with the symmetry axis aligned with the fiber direction. Because of the high longitudinal stiffness of the graphite fibers, the material shows strong anisotropy, with very high modulus in the fiber direction. For this reason, dispersion of guided waves is strongly influenced by the deviation of the direction of propagation from the symmetry axis. Results are given for propagation in different directions and for scattering of antiplane shear waves by surface-breaking cracks and delaminations.

A Neural Network/Acoustic Emission Analysis of Impact Damaged Graphite/Epoxy Pressure Vessels

NASA Technical Reports Server (NTRS)

Walker, James L.; Hill, Erik v. K.; Workman, Gary L.; Russell, Samuel S.

1995-01-01

Acoustic emission (AE) signal analysis has been used to measure the effects of impact damage on burst pressure in 5.75 inch diameter, inert propellant filled, filament wound pressure vessels. The AE data were collected from fifteen graphite/epoxy pressure vessels featuring five damage states and three resin systems. A burst pressure prediction model was developed by correlating the AE amplitude (frequency) distribution, generated during the first pressure ramp to 800 psig (approximately 25% of the average expected burst pressure for an undamaged vessel) to known burst pressures using a four layered back propagation neural network. The neural network, trained on three vessels from each resin system, was able to predict burst pressures with a worst case error of 5.7% for the entire fifteen bottle set.

Fabrication and Testing of Carbon Fiber, Graphite-Epoxy Panels for Submillimeter Telescope Use

NASA Astrophysics Data System (ADS)

Rieger, H.; Helwig, G.; Parks, R. E.; Ulich, B. L.

1983-12-01

An experimental carbon-fiber, graphite-epoxy, aluminum Flexcore sandwich panel roughly 1-m square was made by Dornier System, Friedrichshafen, West Germany. The panel was a pre-prototype of the panels to be used in the dish of the 10-m diameter Sub-Millimeter Telescope, a joint project of the Max-Planck-Institute fur Radioastronomie, Bonn, West Germany, and Steward Observatory, the University of Arizona in Tucson. This paper outlines the fabrication process for the panel and indicates the surface accuracy of the panel replication process. To predict the behavior of the panel under various environmental loads, the panel was modeled structurally using anisotropic elements for the core material. Results of this analysis along with experimental verification of these predictions are also given.

Determination of Pd, Pt and Rh in vehicles escape fumes by GF-AAS and ICP-OES.

PubMed

Goncalves, Antonio; Domínguez, José R; Alvarado, José

2008-04-15

Automotive exhaust gases from vehicles using catalytic converters were filtered through cellulose filter papers to collect suspended particles expulsed along with the engine's escape fumes. A specially designed sample collector was used for supporting the filter papers during collection. The collector was manufactured from a new car's exhaust pipe. A cellulose circular paper filter, 11 cm diameter, was attached to one end of the pipe and kept centered by pressing it against the borders of the pipe by means of a perforated aluminum cap, slightly wider than the pipe, used to cover this end of the collector. Filter papers loaded with the solid particles were acid-digested using a modified domestic microwave oven to bring the solid material into solution. The resulting solutions were analyzed for Pt by graphite furnace atomic absorption spectrometry (GF-AAS) and for Pd and Rh by inductively coupled plasma (ICP-OES). Results indicate that concentration of these analytes in the particulate is higher for new vehicles, having new catalytic converters, than for old ones. Maximum Pd, Pt and Rh in the samples analyzed were found to be 5.36, 12.60 and 1.03 microg g(-1), respectively.

Ablation and deceleration of mass-driver launched projectiles for space disposal of nuclear wastes

NASA Astrophysics Data System (ADS)

Park, C.; Bowen, S. W.

1981-01-01

The energy cost of launching a projectile containing nuclear waste is two orders of magnitude lower with a mass driver than with a typical rocket system. A mass driver scheme will be feasible, however, only if ablation and deceleration are within certain tolerable limits. It is shown that if a hemisphere-cylinder-shaped projectile protected thermally with a graphite nose is launched vertically to attain a velocity of 17 km/sec at an altitude of 40 km, the mass loss from ablation during atmospheric flight will be less than 0.1 ton, provided the radius of the projectile is under 20 cm and the projectile's mass is of the order of 1 ton. The velocity loss from drag will vary from 0.4 to 30 km/sec, depending on the mass and radius of the projectile, the smaller velocity loss corresponding to large mass and small radius. Ablation is always within a tolerable range for schemes using a mass driver launcher to dispose of nuclear wastes outside the solar system. Deceleration can also be held in the tolerable range if the mass and diameter of the projectile are properly chosen.

Performance evaluation and characterization of metallic bipolar plates in a proton exchange membrane (PEM) fuel cell

NASA Astrophysics Data System (ADS)

Hung, Yue

Bipolar plate and membrane electrode assembly (MEA) are the two most repeated components of a proton exchange membrane (PEM) fuel cell stack. Bipolar plates comprise more than 60% of the weight and account for 30% of the total cost of a fuel cell stack. The bipolar plates perform as current conductors between cells, provide conduits for reactant gases, facilitate water and thermal management through the cell, and constitute the backbone of a power stack. In addition, bipolar plates must have excellent corrosion resistance to withstand the highly corrosive environment inside the fuel cell, and they must maintain low interfacial contact resistance throughout the operation to achieve optimum power density output. Currently, commercial bipolar plates are made of graphite composites because of their relatively low interfacial contact resistance (ICR) and high corrosion resistance. However, graphite composite's manufacturability, permeability, and durability for shock and vibration are unfavorable in comparison to metals. Therefore, metals have been considered as a replacement material for graphite composite bipolar plates. Since bipolar plates must possess the combined advantages of both metals and graphite composites in the fuel cell technology, various methods and techniques are being developed to combat metallic corrosion and eliminate the passive layer formed on the metal surface that causes unacceptable power reduction and possible fouling of the catalyst and the electrolyte. The main objective of this study was to explore the possibility of producing efficient, cost-effective and durable metallic bipolar plates that were capable of functioning in the highly corrosive fuel cell environment. Bulk materials such as Poco graphite, graphite composite, SS310, SS316, incoloy 800, titanium carbide and zirconium carbide were investigated as potential bipolar plate materials. In this work, different alloys and compositions of chromium carbide coatings on aluminum and SS316 substrates were also tested for suitability in performing as PEM fuel cell bipolar plates. Interfacial contact resistance and accelerated corrosion resistance tests were carried out for various bulk materials and chromium carbide coatings. Results of the study showed that chromium carbide protective coatings had relatively low interfacial contact resistance and moderate corrosion resistance in comparison to other metals. Single fuel cells with 6.45cm2 and 50cm2 active areas were fabricated and tested for performance and lifetime durability using chromium carbide coated aluminum bipolar plates and graphite composite bipolar plates as a control reference. Polarization curves and power curves were recorded from these single cells under various load conditions. The results showed that coated aluminum bipolar plates had an advantage of anchoring the terminals directly into the plates resulting in higher power density of the fuel cell. This was due to the elimination of additional ICR to the power stack caused by the need for extra terminal plates. However, this study also revealed that direct terminal anchoring was efficient and useable only with metallic bipolar plates but was inapplicable to graphite composite plates due to the poor mechanical strength and brittleness of the graphite composite material. In addition, the 1000 hour lifetime testing of coated aluminum single cells conducted at 70°C cell temperature under cyclic loading condition showed minimal power degradation (<5%) due to metal corrosion. Surface characterization was also conducted on the bipolar plates and MEAs to identify possible chemical change to their surfaces during the fuel cell operation and the electrochemical reaction. The single cell performance evaluation was complemented by an extended study on the fuel cell stack level. For the latter, a ten-cell graphite composite stack with a 40 cm2 active area was fabricated and evaluated for the effect of humidity and operating temperature on the stack performance. Graphite plates were selected for this study to eliminate any possible metal corrosion. A finite element analysis (FEA) model of a bipolar plate was developed to evaluate the effect of air cooling system design parameters and different bipolar plate materials on maintaining the PEM power stack at a safe operating temperature of 80°C or less. In the final stage of this work, a three-cell metallic stack with a 50 cm2 active area and coated aluminum bipolar plates was fabricated based on the positive results that were obtained from earlier studies. The three-cell stack was successfully operated and tested for 750 hours at different temperatures and power densities. This laboratory testing coupled with characterization studies showed that small amounts of aluminum oxide were observed on the coating surface due to localized imperfections in the coating and a lack of protection in the uncoated areas, such as internal manifolds and mounting plates. However, the scanning electron microscopy (SEM) and the energy dispersive x-ray spectroscopy (EDX) showed that coating thickness, chemistry, and surface morphology remained consistent after 750 hours of operation.

Performance and safety of holmium: YAG laser optical fibers.

PubMed

Knudsen, Bodo E; Glickman, Randolph D; Stallman, Kenneth J; Maswadi, Saher; Chew, Ben H; Beiko, Darren T; Denstedt, John D; Teichman, Joel M H

2005-11-01

Lower-pole ureteronephroscopy requires transmission of holmium:YAG energy along a deflected fiber. Current ureteroscopes are capable of high degrees of deflection, which may stress laser fibers beyond safe limits during lower-pole use. We hypothesized that optical fiber and safety measures differ among manufacturers. Small (200-273-microm) and medium-diameter (300-400-microm) Ho:YAG fibers were tested in a straight and 180 degrees bent configuration. Energy transmission was measured by an energy detector. Fiber durability was assessed by firing the laser in sequentially tighter bending diameters. The fibers were bent to 180 degrees with a diameter of 6 cm and run at 200- to 4000-mJ pulse energy to determine the minimum energy required to fracture the fiber. The bending diameter was decreased by 1-cm increments and testing repeated until a bending diameter of 1 cm was reached. The maximum deflection of the ACMI DUR-8E ureteroscope with each fiber in the working channel was recorded. The flow rate through the working channel of the DUR-8E was measured for each fiber. The mean energy transmission differed among fibers (P < 0.001). The Lumenis SL 200 and the InnovaQuartz 400 were the best small and medium-diameter fibers, respectively, in resisting thermal breakdown (P < 0.01). The Dornier Lightguide Super 200 fractured repeatedly at a bend diameter of 2 cm and with the lowest energy (200 mJ). The other small fibers fractured only at a bend diameter of 1 cm. The Sharplan 200 and InnovaQuartz Sureflex 273T were the most flexible fibers, the Lumenis SL 365 the least. The flow rate was inversely proportional to four times the power of the diameter of the fiber. Optical performance and safety differ among fibers. Fibers transmit various amounts of energy to their cladding when bent. During lower-pole nephroscopy with the fiber deflected, there is a risk of fiber fracture from thermal breakdown and laser-energy transmission to the endoscope. Some available laser fibers carry a risk of ureteroscope damage.

Discrimination between neoplastic and non-neoplastic lesions in cirrhotic liver using contrast-enhanced ultrasound

PubMed Central

Xu, H-X; Lu, M-D; Liu, L-N; Zhang, Y-F; Guo, L-H; Xu, J-M; Liu, C

2012-01-01

Objectives To assess the value of contrast-enhanced ultrasound (CEUS) in differentiating hepatocellular carcinoma (HCC) from non-neoplastic lesion in cirrhotic liver in comparison with baseline ultrasound. Methods A total of 147 nodules (diameter ≤5.0 cm) in 133 cirrhotic patients (mean age±standard deviation: 52±13 years, range 20–82 years; gender: 111 males and 22 females) were examined with CEUS. There were 116 HCCs, 26 macroregenerative nodules and 5 high-grade dysplastic nodules. CEUS was performed with a real-time contrast-specific mode and a sulphur hexafluoride-filled microbubble contrast agent. Results Hypervascularity was observed in 94.8% (110/116) HCCs, 3.8% (1/26) macroregenerative nodules and 60.0% (3/5) high-grade dysplastic nodules during arterial phase on CEUS. Detection rates of typical vascular pattern (i.e. hypervascularity during arterial phase and subsequent washout) in HCCs with a diameter of ≤2.0 cm, 2.1–3.0 cm and 3.1–5.0 cm were 69.2% (27/39), 97.1% (33/34) and 100.0% (43/43), respectively. CEUS significantly improved the sensitivity [88.8% (103/116) vs 37.1% (43/116), p<0.001], negative predictive value [70.5% (31/44) vs 31.5% (29/92), p<0.001], and accuracy [91.2% (134/147) vs 49.0% (72/147), p<0.001] in differentiating HCCs from non-neoplastic lesions when compared with baseline ultrasound. However, the sensitivity and accuracy of CEUS for HCCs ≤2.0 cm in diameter were significantly lower than those for HCCs of 2.1–3.0 cm and 3.1–5.0 cm in diameter. Conclusions CEUS improves diagnostic performance in differentiating HCCs from non-neoplastic nodules in cirrhotic patients compared with baseline ultrasound. Diagnosis of HCCs ≤2.0 cm diameter by CEUS is still a clinical concern, and thus needs further investigation. PMID:22553290

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

A 20000-hour endurance test of a structurally and thermally integrated 5-cm diameter ion thruster main cathode

NASA Technical Reports Server (NTRS)

Wintucky, E. G.

1975-01-01

A 5-cm diameter mercury ion thruster main cathode has completed over 20,000 hours of operation in an ongoing lifetime endurance test. The cathode operating parameters remained at acceptable performance levels throughout the test, the first 9175 hours of which were part of a thruster endurance test. After 20,000 hours, the cathode discharge was easily restarted, the tip orifice indicated negligible erosion and the tip heater showed no degradation. The cathode-isolator- vaporizer assembly, a major thruster subsystem, has thus successfully demonstrated an operational lifetime capability of 20,000 hours, which is the lifetime goal of the 8-cm diameter auxiliary propulsion ion thruster.

Ion optics for high power 50-cm-diam ion thrusters

NASA Technical Reports Server (NTRS)

Rawlin, Vincent K.; Millis, Marc G.

1989-01-01

The process used at the NASA-Lewis to fabricate 30 and 50-cm-diameter ion optics is described. The ion extraction capabilities of the 30 and 50-cm diameter ion optics were evaluated on divergent field and ring-cusp discharge chambers and compared. Perveance was found to be sensitive to the effects of the type and power of the discharge chamber and to the accelerator electrode hole diameter. Levels of up to 0.64 N and 20 kW for thrust and input power, respectively, were demonstrated with the divergent-field discharge chamber. Thruster efficiencies and specific impulse values up to 79 percent and 5000 sec., respectively, were achieved with the ring-cusp discharge chamber.

Electron reflection and secondary emission characteristics of sputter-textured pyrolytic graphite surfaces

NASA Technical Reports Server (NTRS)

Wintucky, E. G.; Curren, A. N.; Sovey, J. S.

1981-01-01

Measurements are presented of secondary electron emission and reflected primary electron characteristics of sputter-textured pyrolitic graphite surfaces with microstructures of various sizes and densities, made with an Auger cylindrical mirror analyzer in a high-vacuum chamber at pressures below 1.33 x 10 to the -7th N/sq m (10 to the -9th torr). A dense, tall, thin, spire-like microstructure, obtained at ion energies of 1000 eV and ion current densities of 5 mA/sq cm, is the most effective. The secondary electron emission from such a surface is lower than that of soot, whose secondary emission is among the lowest of any material. At a primary electron energy of 1000 eV, the secondary electron emission yield of smooth CU is about 350% greater than the lowest value obtained for sputter-textured pyrolitic graphite. The reflected primary electron index of smooth Cu is a factor of 80 greater. If the secondary electron emission yield is reduced to 0.3, which is possible with sputter-textured pyrolitic graphite, the traveling wave tube collector efficiency could be improved by as much as 4% over that for smooth copper.

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

PubMed Central

2014-01-01

In this study, Co/Cu-decorated carbon nanofibers are introduced as novel electrocatalyst for methanol oxidation. The introduced nanofibers have been prepared based on graphitization of poly(vinyl alcohol) which has high carbon content compared to many polymer precursors for carbon nanofiber synthesis. Typically, calcination in argon atmosphere of electrospun nanofibers composed of cobalt acetate tetrahydrate, copper acetate monohydrate, and poly(vinyl alcohol) leads to form carbon nanofibers decorated by CoCu nanoparticles. The graphitization of the poly(vinyl alcohol) has been enhanced due to presence of cobalt which acts as effective catalyst. The physicochemical characterization affirmed that the metallic nanoparticles are sheathed by thin crystalline graphite layer. Investigation of the electrocatalytic activity of the introduced nanofibers toward methanol oxidation indicates good performance, as the corresponding onset potential was small compared to many reported materials; 310 mV (vs. Ag/AgCl electrode) and a current density of 12 mA/cm2 was obtained. Moreover, due to the graphite shield, good stability was observed. Overall, the introduced study opens new avenue for cheap and stable transition metals-based nanostructures as non-precious catalysts for fuel cell applications. PMID:24387682

Thirty-Eight Years of Autogenic, Woody Understory Dynamics in a Mature, Temperate Pine-Oak Forest

Treesearch

Michael D. Cain; Michael G. Shelton

1997-01-01

In 1935, 32 ha of a pine-hardwood forest were set aside from future timber management in southern Arkansas, U.S.A. Old-growth timber had been cut to a 36-cm stump diameter before 1915. Between 1952 and 1993, four inventories were made of the overstory and midstory components (number of live trees 29 cm in diameter breast height (DBH) taken at 1.37 m, by 2.54-cm DBH...

Volumetric Growth of the Liver in the Human Fetus: An Anatomical, Hydrostatic, and Statistical Study.

PubMed

Szpinda, Michał; Paruszewska-Achtel, Monika; Woźniak, Alina; Mila-Kierzenkowska, Celestyna; Elminowska-Wenda, Gabriela; Dombek, Małgorzata; Szpinda, Anna; Badura, Mateusz

2015-01-01

Using anatomical, hydrostatic, and statistical methods, liver volumes were assessed in 69 human fetuses of both sexes aged 18-30 weeks. No sex differences were found. The median of liver volume achieved by hydrostatic measurements increased from 6.57 cm(3) at 18-21 weeks through 14.36 cm(3) at 22-25 weeks to 20.77 cm(3) at 26-30 weeks, according to the following regression: y = -26.95 + 1.74 × age ± Z × (-3.15 + 0.27 × age). The median of liver volume calculated indirectly according to the formula liver volume = 0.55 × liver length × liver transverse diameter × liver sagittal diameter increased from 12.41 cm(3) at 18-21 weeks through 28.21 cm(3) at 22-25 weeks to 49.69 cm(3) at 26-30 weeks. There was a strong relationship (r = 0.91, p < 0.001) between the liver volumes achieved by hydrostatic (x) and indirect (y) methods, expressed by y = -0.05 + 2.16x ± 7.26. The liver volume should be calculated as follows liver volume = 0.26 × liver length × liver transverse diameter × liver sagittal diameter. The age-specific liver volumes are of great relevance in the evaluation of the normal hepatic growth and the early diagnosis of fetal micro- and macrosomias.

Use of disposable graduated biopsy forceps improves accuracy of polyp size measurements during endoscopy.

PubMed

Jin, Hei-Ying; Leng, Qiang

2015-01-14

To determine the accuracy of endoscopic polyp size measurements using disposable graduated biopsy forceps (DGBF). Gradations accurate to 1 mm were assessed with the wire of disposable graduated biopsy forceps. When a polyp was noted, endoscopists determined the width of the polyp; then, the graduated biopsy forceps was inserted and the largest diameter of the tumor was measured. After excision, during surgery or endoscopy, the polyp was measured using the vernier caliper. One hundred and thirty-three colorectal polyps from 119 patients were studied. The mean diameter, by post-polypectomy measurement, was 0.92 ± 0.69 cm; 83 were < 1 cm, 36 were between 1 and 2 cm, and 14 were > 2 cm. The mean diameter, by visual estimation, was 1.15 ± 0.88 cm; compared to the actual size measured using vernier calipers, the difference was statistically significant. The mean diameter measured using the DGBF was 0.93 ± 0.68 cm; compared to the actual size measured using vernier calipers, this difference was not statistically significant. The ratio between the mean size estimated by visual estimation and the actual size was significantly different from that between the mean size estimated using the DGBF and the actual size (1.26 ± 0.30 vs 1.02 ± 0.11). The accuracy of polyp size estimation was low by visual assessment; however, it improved when the DGBF was used.

Methods for detecting the mobility of trace elements during medium-temperature pyrolysis

USGS Publications Warehouse

Shiley, R.H.; Konopka, K.L.; Cahill, R.A.; Hinckley, C.C.; Smith, Gerard V.; Twardowska, H.; Saporoschenko, Mykola

1983-01-01

The mobility (volatility) of trace elements in coal during pyrolysis has been studied for distances of up to 40 cm between the coal and the trace element collector, which was graphite or a baffled solvent trap. Nineteen elements not previously recorded as mobile were detected. ?? 1983.

USE OF CARBON STABLE ISOTOPE TO INVESTIGATE CHLOROMETHANE FORMATION IN THE ELECTROLYTIC DECHLORINATION OF TRICHLOROETHYLENE

EPA Science Inventory

Carbon stable isotope trichloroethylene (¹³C TCE) was used to investigate the formation of chloromethane (CM) during the electrolytic dechlorination of trichloroethylene (TCE) at a granular-graphite packed cathode. A method was developed to use a conventional GC/MS to ...

Sodium chloride-catalyzed oxidation of multiwalled carbon nanotubes for environmental benefit.

PubMed

Endo, Morinobu; Takeuchi, Kenji; Tajiri, Takeyuki; Park, Ki Chul; Wang, Feng; Kim, Yoong-Ahm; Hayashi, Takuya; Terrones, Mauricio; Dresselhaus, Mildred S

2006-06-22

A sodium chloride (NaCl) catalyst (0.1 w/w %) lowers the oxidation temperature of graphitized multiwalled carbon nanotubes: MWCNT-20 (diameter: 20-70 nm) and MWCNT-80 (diameter: 80-150 nm). The analysis of the reaction kinetics indicates that the oxidation of MWCNT-20 and MWCNT-80 mixed with no NaCl exhibits single reaction processes with activation energies of E(a) = 159 and 152 kJ mol(-1), respectively. The oxidation reaction in the presence of NaCl is shown to consist of two different reaction processes, that is, a first reaction and a second reaction process. The first reaction process is dominant at a low temperature of around 600 degrees C, while the second reaction process becomes more dominant than the first one in a higher temperature region. The activation energies of the first reaction processes (MWCNT-20: E(a1) = 35.7 kJ mol(-1); MWCNT-80: E(a1) = 43.5 kJ mol(-1)) are much smaller than those of the second reaction processes (MWCNT-20: E(a2) = 170 kJ mol(-1); MWCNT-80: E(a2) = 171 kJ mol(-1)). The comparison of the kinetic parameters and the results of the spectroscopic and microscopic analyses imply that the lowering of the oxidation temperature in the presence of NaCl results from the introduction of disorder into the graphitized MWCNTs (during the first reaction process), thus increasing the facility of the oxidation reaction of the disorder-induced nanotubes (in the second reaction process). It is found that the larger nanopits and cracks on the outer graphitic layers are caused by the catalytic effect of NaCl. Therefore, the NaCl-mixed samples showed more rapid and stronger oxidation compared with that of the nonmixed samples at the same residual quantity.

The compression and expansion waves of the forward and backward flows: an in-vitro arterial model.

PubMed

Feng, J; Khir, A W

2008-05-01

Although the propagation of arterial waves of forward flows has been studied before, that of backward flows has not been thoroughly investigated. The aim of this research is to investigate the propagation of the compression and expansion waves of backward flows in terms of wave speed and dissipation, in flexible tubes. The aim is also to compare the propagation of these waves with those of forward flows. A piston pump generated a flow waveform in the shape of approximately half-sinusoid, in flexible tubes (12 mm and 16 mm diameter). The pump produced flow in either the forward or the backward direction by moving the piston forward, in a 'pushing action' or backward, in a 'pulling action', using a graphite brushes d.c. motor. Pressure and flow were measured at intervals of 5 cm along each tube and wave speed was determined using the PU-loop method. The simultaneous measurements of diameter were also taken at the same position of the pressure and flow in the 16 mm tube. Wave intensity analysis was used to determine the magnitude of the pressure and velocity waveforms and wave intensity in the forward and backward directions. Under the same initial experimental conditions, wave speed was higher during the pulling action (backward flow) than during the pushing action (forward flow). The amplitudes of pressure and velocity in the pulling action were significantly higher than those in the pushing action. The tube diameter was approximately 20 per cent smaller in the pulling action than in the pushing action in the 16 mm tube. The compression and expansion waves resulting from the pushing and pulling actions dissipated exponentially along the travelling distance, and their dissipation was greater in the smaller than in the larger tubes. Local wave speed in flexible tubes is flow direction- and wave nature-dependent and is greater with expansion than with compression waves. Wave dissipation has an inverse relationship with the vessel diameter, and dissipation of the expansion wave of the pulling action was greater than that of the pushing action.

Eight-cm mercury ion thruster system technology

NASA Technical Reports Server (NTRS)

1974-01-01

The technology status of 8 cm diameter electron bombardment ion thrusters is presented. Much of the technology resulting from the 5 cm diameter thruster has been adapted and improved upon to increase the reliability, durability, and efficiency of the 8 cm thruster. Technology discussed includes: dependence of neutralizer tip erosion upon neutralizer flow rate; impregnated and rolled-foil insert cathode performance and life testing; neutralizer position studies; thruster ion beam profile measurements; high voltage pulse ignition; high utilization ion machined accelerator grids; deposition internal and external to the thruster; thruster vectoring systems; thruster cycling life testing and thruster system weights for typical mission applications.

Dosimetric effects of saline- versus water-filled balloon applicators for IORT using the model S700 electronic brachytherapy source.

PubMed

Redler, Gage; Templeton, Alistair; Zhen, Heming; Turian, Julius; Bernard, Damian; Chu, James C H; Griem, Katherine L; Liao, Yixiang

The Xoft Axxent Electronic Brachytherapy System (Xoft, Inc., San Jose, CA) is a viable option for intraoperative radiation therapy (IORT) treatment of early-stage breast cancer. The low-energy (50-kVp) X-ray source simplifies shielding and increases relative biological effectiveness but increases dose distribution sensitivity to medium composition. Treatment planning systems typically assume homogenous water for brachytherapy dose calculations, including precalculated atlas plans for Xoft IORT. However, Xoft recommends saline for balloon applicator filling. This study investigates dosimetric differences due to increased effective atomic number (Z eff ) for saline (Z eff  = 7.56) versus water (Z eff  = 7.42). Balloon applicator diameters range from 3 to 6 cm. Monte Carlo N-Particle software is used to calculate dose at the surface (D s ) of and 1 cm away (D 1cm ) from the water-/saline-filled balloon applicator using a single dwell at the applicator center as a simple estimation of the dosimetry and multiple dwells simulating the clinical dose distributions for the atlas plans. Single-dwell plans show a 4.4-6.1% decrease in D s for the 3- to 6-cm diameter applicators due to the saline. Multidwell plans show similar results: 4.9% and 6.4% D s decrease, for 4-cm and 6-cm diameter applicators, respectively. For the single-dwell plans, D 1cm decreases 3.6-5.2% for the 3- to 6-cm diameter applicators. For the multidwell plans, D 1cm decreases 3.3% and 5.3% for the 4-cm and 6-cm applicators, respectively. The dosimetric effect introduced by saline versus water filling for Xoft balloon applicator-based IORT treatments is ∼5%. Users should be aware of this in the context of both treatment planning and patient outcome studies. Copyright © 2017 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

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.

Sodium-22 In Supernovae

NASA Astrophysics Data System (ADS)

Amari, Sachiko

2008-05-01

There are several isotopically distinct noble gas components in meteorites. Of them, Ne-E(L), heavily enriched in 22Ne, is carried by graphite with a range of density (1.6 - 2.2 g/cm3). Bulk (=aggregates) noble gas analysis of graphite separates from the Murchison meteorite indicate that a dominant source of 22Ne is 22Na (T1/2 = 2.6 a) with varying proportions of 22Ne via 14N(α,γ)18F(e+ν)18O(α,γ)22Ne with density. Low-density graphite grains, from their isotopic signatures, are believed to have formed in supernovae. Examinations of both bulk and single-grain analyses of low-density graphite grains (Amari et al., 1995; Nichols et al., 1994) indicate that all 22Ne in low-density graphite grains is from the decay of 22Na that was produced in the O/Ne zone in supernovae. One may argue why implanted 20,22Ne was not observed in the grains, considering the fact that the mass fraction of 20Ne is 5 orders of magnitude larger than that of 22Na. Croat et al. (2003) observed TiC subgrains inside low-density graphite grains have amorphous rims with the thickness of 3 to 15 nm, indicating atom bombardment from the surrounding gas. Assuming the gas is He, they estimated the velocity is 50 km/s or less. If the relative velocities between the Ne and the graphite grains are in that range, the penetration depth into the graphite grains is 2nm. Such shallow surface layers would be sputtered once the grains hit the reverse shock and keep traveling into the hot H-rich region (Nozawa et al, 2007). It remains to be seen whether or not 22Na in higher-density graphite is from supernovae or novae, or both. Amari, S. et al. 1995, Geochim. Cosmochim. Acta, 59, 1411 Croat, T.K. et al. 2003, Geochim. Cosmochim. Acta, 67, 4705 Nichols R.H. et al. 1994, Meteoritics, 29, 510 Nozawa, T. et al. 2007 ApJ, 666, 955

Behavior of graphite under heat load and in contact with a hydrogen plasma

NASA Astrophysics Data System (ADS)

Bohdansky, J.; Croessmann, C. D.; Linke, J.; McDonald, J. M.; Morse, D. H.; Pontau, A. E.; Watson, R. D.; Whitley, J. B.; Goebel, D. M.; Hirooka, Y.; Leung, K.; Conn, R. W.; Roth, J.; Ottenberger, W.; Kotzlowski, H. E.

1987-05-01

Graphite is extensively used in large tokamaks today. In these machines the material is exposed to vacuum, to intense heat loads, and to the edge plasma. The use of graphite in such machines, therefore, depends on the outgassing behavior, the heat shock resistance, and thermochemical properties in a hydrogen plasma. Investigations of these properties made at different laboratories are described here. Experiments conducted at Sandia National Laboratories (SNL), Livermore, and the Max-Planck-Institut für Plasmaphysik (IPP) in Garching showed that the outgassing behavior of fine-grain reactor-grade graphite and carbon fiber composites depends on the pretreatment (manufacturing and/or storage). However, after proper outgassing the samples tested behave similarly in the case of fine-grain graphite, but the outgassing remains high for the carbon fiber composites. Heat shock tests have been made with the Electron Beam Test System (EBTS) at SNL, Albuquerque. Directly cooled graphite samples (FE 159 graphite brazed onto Mo tubes) showed no failure at a heat load of 700 W/cm 2, 20 s; or 10 kW, 1 s. Thermal erosion due to sublimination and particle emission from the graphite surface was observed. This effect is related to the surface temperature and becomes significant at temperatures above 2500°K. Fourteen different types of graphite were tested; the main differences among these samples were the different surface temperatures obtained under the same heating conditions. Cracking due to heat shocks was observed in some of the samples, but none of the carbon fiber composites failed. Thermochemical properties have been tested in the PISCES plasma generator at UCLA for ion energies of around 100 eV. The formation of C-H compounds was observed spectroscopically at sample temperatures of around 600°C. However, this chemical reaction did not lead to erosion as observed in beam experiments but to a drastic change of the surface structure due to redeposition. Carbon-hydrogen lines were still observed at sample temperatures of around 100°C. Under these conditions the erosion yield is high and in agreement with those measured in beam experiments.

Carbon Nanotubes Growth by CVD on Graphite Fibers

NASA Technical Reports Server (NTRS)

Zhu, Shen; Su, Ching-Hua; Cochrane, J. C.; Lehoczky, S. L.; Muntele, I.; Ila, D.; Curreri, Peter A. (Technical Monitor)

2002-01-01

Due to the superior electrical and mechanical properties of carbon nanotubes (CNT), synthesizing CNT on various substances for electronics devices and reinforced composites have been engaged in many efforts for applications. This presentation will illustrate CNT synthesized on graphite fibers by thermal CVD. On the fiber surface, iron nanoparticles as catalysts for CNT growth are coated. The growth temperature ranges from 600 to 1000 C and the pressure ranges from 100 Torr to one atmosphere. Methane and hydrogen gases with methane content of 10% to 100% are used for the CNT synthesis. At high growth temperatures (greater than or equal to 900 C), the rapid inter-diffusion of the transition metal iron on the graphite surface results in the rough fiber surface without any CNT grown on it. When the growth temperature is relative low (650-800 C), CNT with catalytic particles on the nanotube top ends are fabricated on the graphite surface. (Methane and hydrogen gases with methane content of 10% to 100% are used for the CNT synthesis.) (By measuring the samples) Using micro Raman spectroscopy in the breath mode region, single-walled or multi-walled CNT (MWCNT), depending on growth concentrations, are found. Morphology, length and diameter of these MWCNT are determined by scanning electron microscopy and Raman spectroscopy. The detailed results of syntheses and characterizations will be discussed in the presentation.

Abundances of presolar graphite and SiC from supernovae and AGB stars in the Murchison meteorite

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

Amari, Sachiko; Zinner, Ernst; Gallino, Roberto

2014-05-02

Pesolar graphite grains exhibit a range of densities (1.65 – 2.20 g/cm{sup 3}). We investigated abundances of presolar graphite grains formed in supernovae and in asymptotic giant branch (AGB) stars in the four density fractions KE3, KFA1, KFB1 and KFC1 extracted from the Murchison meteorite to probe dust productions in these stellar sources. Seventy-six and 50% of the grains in the low-density fractions KE3 and KFA1, respectively, are supernova grains, while only 7.2% and 0.9% of the grains in the high-density fractions KFB1 and KFC1 have a supernova origin. Grains of AGB star origin are concentrated in the high-density fractionsmore » KFB1 and KFC1. From the C isotopic distributions of these fractions and the presence of s-process Kr with {sup 86}Kr/{sup 82}Kr = 4.43±0.46 in KFC1, we estimate that 76% and 80% of the grains in KFB1 and KFC1, respectively, formed in AGB stars. From the abundance of graphite grains in the Murchison meteorite, 0.88 ppm, the abundances of graphite from supernovae and AGB stars are 0.24 ppm and 0.44 ppm, respectively: the abundances of graphite in supernovae and AGB stars are comparable. In contrast, it has been known that 1% of SiC grains formed in supernovae and 95% formed in AGB stars in meteorites. Since the abundance of SiC grains is 5.85 ppm in the Murchison meteorite, the abundances of SiC from supernovae and AGB stars are 0.063 ppm and 5.6 ppm, respectively: the dominant source of SiC grains is AGB stars. Since SiC grains are harder and likely to survive better in space than graphite grains, the abundance of supernova graphite grains, which is higher than that of supernova SiC grains, indicates that supernovae proficiently produce graphite grains. Graphite grains from AGB stars are, in contrast, less abundant that SiC grains from AGB stars (0.44 ppm vs. 5.6 ppm). It is difficult to derive firm conclusions for graphite and SiC formation in AGB stars due to the difference in susceptibility to grain destruction. Metallicity of the parent AGB stars of graphite grains is much lower than that of SiC grains and the difference in metallicity might also have affected to the difference in the abundances in the Murchison meteorite.« less

Nesting biology of Trypoxylon (Trypargilum) lactitarse Saussure (Hymenoptera, Crabronidae) in trap-nests in Southern Brazil.

PubMed

Buschini, M L T; Niesing, F; Wolff, L L

2006-08-01

This study was carried in the Parque Municipal das Araucárias in the municipality of Guarapuava, state of Paraná, Southern Brazil. Three hundred and sixty five nests of T. lactitarse were obtained using trap-nests of 0.7, 1.0, and 1.3 cm in diameter. All of them had similar architecture, regardless of the diameter of the trap-nest. Completed nests consisted of a linear series of brood cells whose average number per nest was of 3.3, 4.0 and 3.6 for the nests with 0.7 cm, 1.0 cm and 1.3 cm in diameter, respectively. They were constructed more often during the summer. T. lactitarse had two types of life cycles: direct development (without diapause), and delayed development (with diapause during winter). Natural enemies included Chrysididae, Sarcophagidae, Dolichopodidae and Ichneumonidae. Out of 1,353 identified spider prey, 1,313 belonged to the Araneidae family.

Heat dissipation sensors of variable length for the measurement of sap flow in trees with deep sapwood.

PubMed

James, Shelley A; Clearwater, Michael J; Meinzer, Frederick C; Goldstein, Guillermo

2002-03-01

Robust thermal dissipation sensors of variable length (3 to 30 cm) were developed to overcome limitations to the measurement of radial profiles of sap flow in large-diameter tropical trees with deep sapwood. The effective measuring length of the custom-made sensors was reduced to 1 cm at the tip of a thermally nonconducting shaft, thereby minimizing the influence of nonuniform sap flux density profiles across the sapwood. Sap flow was measured at different depths and circumferential positions in the trunks of four trees at the Parque Natural Metropolitano canopy crane site, Panama City, Republic of Panama. Sap flow was detected to a depth of 24 cm in the trunks of a 1-m-diameter Anacardium excelsum (Bertero & Balb. ex Kunth) Skeels tree and a 0.65-m-diameter Ficus insipida Willd. tree, and to depths of 7 cm in a 0.34-m-diameter Cordia alliodora (Ruiz & Pav.) Cham. trunk, and 17 cm in a 0.47-m-diameter Schefflera morototoni (Aubl.) Maguire, Steyerm. & Frodin trunk. Sap flux density was maximal in the outermost 4 cm of sapwood and declined with increasing sapwood depth. Considerable variation in sap flux density profiles was observed both within and among the trees. In S. morototoni, radial variation in sap flux density was associated with radial variation in wood properties, particularly vessel lumen area and distribution. High variability in radial and circumferential sap flux density resulted in large errors when measurements of sap flow at a single depth, or a single radial profile, were used to estimate whole-plant water use. Diurnal water use ranged from 750 kg H2O day-1 for A. excelsum to 37 kg H2O day-1 for C. alliodora.

Technical note: estimating absorbed doses to the thyroid in CT.

PubMed

Huda, Walter; Magill, Dennise; Spampinato, Maria V

2011-06-01

To describe a method for estimating absorbed doses to the thyroid in patients undergoing neck CT examinations. Thyroid doses in anthropomorphic phantoms were obtained for all 23 scanner dosimetry data sets in the ImPACT CT patient dosimetry calculator. Values of relative thyroid dose [R(thy)(L)], defined as the thyroid dose for a given scan length (L) divided by the corresponding thyroid dose for a whole body scan, were determined for neck CT scans. Ratios of the maximum thyroid dose to the corresponding CTDI(vol) and [D'(thy)], were obtained for two phantom diameters. The mass-equivalent water cylinder of any patient can be derived from the neck cross-sectional area and the corresponding average Hounsfield Unit, and compared to the 16.5-cm diameter water cylinder that models the ImPACT anthropomorphic phantom neck. Published values of relative doses in water cylinders of varying diameter were used to adjust thyroid doses in the anthropomorphic phantom to those of any sized patient. Relative thyroid doses R(thy)(L) increase to unity with increasing scan length and with very small difference between scanners. A 10-cm scan centered on the thyroid would result in a dose that is, nearly 90% of the thyroid dose from a whole body scan when performed using the constant radiographic techniques. At 120 kV, the average value of D'(thy) for the 16-cm diameter was 1.17 +/- 0.05 and was independent of CT vendor and year of CT scanner, and choice of x-ray tube voltage. The corresponding average value of D'(thy) in the 32-cm diameter phantom was 2.28 +/- 0.22 and showed marked variations depending on vendor, year of introduction into clinical practice as well as x-ray tube voltage. At 120 kV, a neck equivalent to a 10-cm diameter cylinder of water would have thyroid doses 36% higher than those in the ImPACT phantom, whereas a neck equivalent to a 25-cm cylinder diameter would have thyroid doses 35% lower. Patient thyroid doses can be estimated by taking into account the amount of radiation used to perform the CT examination (CTDI(vol)) and accounting for scan length and patient anatomy (i.e., neck diameter) at the thyroid location.

Verde plant bug (Hemiptera: Miridae) feeding injury to cotton bolls characterized by boll age, size, and damage ratings.

PubMed

Armstrong, J Scott; Brewer, Michael J; Parker, Roy D; Adamczyk, J J

2013-02-01

The verde plant bug, Creontiades signatus (Distant), has been present in south Texas for several years but has more recently been documented as an economic threat to cultivated cotton, (Gossypium hirsutum L. Our studies over 2 yr (2009 and 2010) and two locations (Weslaco and Corpus Christi, TX) investigated feeding-injury of the verde plant bug to a range of cotton boll age classes defined by boll diameter and accumulated degree-days (anthesis to the time of infesting) for first-position cotton bolls infested with the plant bugs. The most detrimental damage to younger cotton holls from verde plant bug feeding was boll abscission. Cotton bolls <04 accumulating daily degree-days (ACDD), or a boll diameter of 1.3 cm were subject to 60-70% higher boll abscission when compared with the noninfested controls. Significantly higher boll abscission occurred from verde plant bug injured bolls compared with the controls up to 162 ACDD or a mean boll diameter 2.0 cm. Cotton seed weights were significantly reduced up to 179 ACDD or a boll diameter of 2.0 cm at Weslaco in 2009, and up to 317 ACDD or boll diameter 2.6 cm for Weslaco in 2010 when compared with the noninfested controls. Lint weight per cotton boll for infested and noninfested bolls was significantly reduced up to 262 ACDD or boll diameter 2.5 for Corpus Christi in 2010 and up to 288 ACCD or boll diameter 2.6 cm for Weslaco, TX, in 2010. Damage ratings (dependant variable) regressed against infested and noninfested seed-cotton weights showed that in every instance, the infested cotton bolls had a strong and significant relationship with damage ratings for all age classes of bolls. Damage ratings for the infested cotton bolls that did not abscise by harvest showed visual signs of verde plant bug feeding injury and the subsequent development ofboll rot; however, these two forms of injury causing lint and seed mass loss are hard to differentiate from open or boll-locked cotton bolls. Based on the results of both lint and seed loss over 2 yr and four studies cotton bolls should be protected up to approximately 300 ACDD or a boll diameter of 2.5 cm. This equilibrates to bolls that are 12-14 d of age dependent upon daily maximum and minimum temperatures.

Fine woody fuel particle diameters for improved planar intersect fuel loading estimates in Southern Rocky Mountain ponderosa pine forests

Treesearch

Emma Vakili; Chad M. Hoffman; Robert E. Keane

2016-01-01

Fuel loading estimates from planar intersect sampling protocols for fine dead down woody surface fuels require an approximation of the mean squared diameter (d2) of 1-h (0-0.63 cm), 10-h (0.63-2.54 cm), and 100-h (2.54-7.62 cm) timelag size classes. The objective of this study is to determine d2 in ponderosa pine (Pinus ponderosa) forests of New Mexico and Colorado,...

Direct printing and reduction of graphite oxide for flexible supercapacitors

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

Jung, Hanyung; Ve Cheah, Chang; Jeong, Namjo

2014-08-04

We report direct printing and photo-thermal reduction of graphite oxide (GO) to obtain a highly porous pattern of interdigitated electrodes, leading to a supercapacitor on a flexible substrate. Key parameters optimized include the amount of GO delivered, the suitable photo-thermal energy level for effective flash reduction, and the substrate properties for appropriate adhesion after reduction. Tests with supercapacitors based on the printed-reduced GO showed performance comparable with commercial supercapacitors: the energy densities were 1.06 and 0.87 mWh/cm{sup 3} in ionic and organic electrolytes, respectively. The versatility in the architecture and choice of substrate makes this material promising for smart powermore » applications.« less

Antarctic meteorite descriptions, 1980

NASA Technical Reports Server (NTRS)

Score, R.; Schwarz, C. M.; Mason, B.; Bogard, D. D.

1982-01-01

Specimens found in the Alan Hills area include 361 ordinary chondrites, 4 carbonaceous chondrites, 6 achondrites, and 2 irons. Thirteen specimens measured over 11 cm in diameter and 69 between 5 to 10 cm in diameter are reported. The remainder of the finds were small, and many were paired. One of the irons was estimated to weigh about 20 kilograms.

Proof of the Feasibility of Coherent and Incoherent Schemes for Pumping a Gamma-ray Laser

DTIC Science & Technology

1992-12-31

the Texas-X was investigated by using metallic indium disks 1.0 cm in diameter and 0.127 mm thick as well as plastic planchettes 5.0 cm in diameter and...Spectral Distribution The spectral distribution was examined by irradiating the full set of the calibration nuclides listed in Table 1. Planchettes

High purity low dislocation GaAs single crystals

NASA Technical Reports Server (NTRS)

Chen, R. T.; Holmes, D. E.; Kirkpatrick, C. G.

1982-01-01

Recent advances in GaAs bulk crystal growth using the LEC (liquid encapsulated Czochralski) technique are described. The dependence of the background impurity concentration and the dislocation density distribution on the materials synthesis and growth conditions were investigated. Background impurity concentrations as low as 4 x 10 to the 15th power were observed in undoped LEC GaAs. The dislocation density in selected regions of individual ingots was very low, below the 3000 cm .3000/sq cm threshold. The average dislocation density over a large annular ring on the wafers fell below the 10000/sq cm level for 3 inch diameter ingots. The diameter control during the program advanced to a diameter variation along a 3 inch ingot less than 2 mm.

Highly catalytic and stabilized titanium nitride nanowire array-decorated graphite felt electrodes for all vanadium redox flow batteries

NASA Astrophysics Data System (ADS)

Wei, L.; Zhao, T. S.; Zeng, L.; Zeng, Y. K.; Jiang, H. R.

2017-02-01

In this work, we prepare a highly catalytic and stabilized titanium nitride (TiN) nanowire array-decorated graphite felt electrode for all vanadium redox flow batteries (VRFBs). Free-standing TiN nanowires are synthesized by a two-step process, in which TiO2 nanowires are first grown onto the surface of graphite felt via a seed-assisted hydrothermal method and then converted to TiN through nitridation reaction. When applied to VRFBs, the prepared electrode enables the electrolyte utilization and energy efficiency to be 73.9% and 77.4% at a high current density of 300 mA cm-2, which are correspondingly 43.3% and 15.4% higher than that of battery assembled with a pristine electrode. More impressively, the present battery exhibits good stability and high capacity retention during the cycle test. The superior performance is ascribed to the significant improvement in the electrochemical kinetics and enlarged active sites toward V3+/V2+ redox reaction.

Quantitative, nondestructive estimates of coarse root biomass in a temperate pine forest using 3-D ground-penetrating radar (GPR)

NASA Astrophysics Data System (ADS)

Molon, Michelle; Boyce, Joseph I.; Arain, M. Altaf

2017-01-01

Coarse root biomass was estimated in a temperate pine forest using high-resolution (1 GHz) 3-D ground-penetrating radar (GPR). GPR survey grids were acquired across a 400 m2 area with varying line spacing (12.5 and 25 cm). Root volume and biomass were estimated directly from the 3-D radar volume by using isometric surfaces calculated with the marching cubes algorithm. Empirical relations between GPR reflection amplitude and root diameter were determined for 14 root segments (0.1-10 cm diameter) reburied in a 6 m2 experimental test plot and surveyed at 5-25 cm line spacing under dry and wet soil conditions. Reburied roots >1.4 cm diameter were detectable as continuous root structures with 5 cm line separation. Reflection amplitudes were strongly controlled by soil moisture and decreased by 40% with a twofold increase in soil moisture. GPR line intervals of 12.5 and 25 cm produced discontinuous mapping of roots, and GPR coarse root biomass estimates (0.92 kgC m-2) were lower than those obtained previously with a site-specific allometric equation due to nondetection of vertical roots and roots <1.5 cm diameter. The results show that coarse root volume and biomass can be estimated directly from interpolated 3-D GPR volumes by using a marching cubes approach, but mapping of roots as continuous structures requires high inline sampling and line density (<5 cm). The results demonstrate that 3-D GPR is viable approach for estimating belowground carbon and for mapping tree root architecture. This methodology can be applied more broadly in other disciplines (e.g., archaeology and civil engineering) for imaging buried structures.

Physical Properties of Venous Stents: An Experimental Comparison.

PubMed

Dabir, Darius; Feisst, Andreas; Thomas, Daniel; Luetkens, Julian A; Meyer, Carsten; Kardulovic, Ana; Menne, Matthias; Steinseifer, Ulrich; Schild, Hans H; Kuetting, Daniel L R

2018-06-01

Iliocaval obstruction is a substantial contributor to chronic venous insufficiency and is increasingly being treated endovascularly with angioplasty and stent placement. Utilization of an appropriate stent for treatment is pivotal; however, until today, mechanical properties of venous stents remain unknown. We analyzed the radial resistive force, the chronic outward force, as well as the crush resistance of seven stent models [Zilver Vena (Cook, Bjaeverskov, Denmark), Sinus Venous, Sinus Obliquus and Sinus XL Flex (Optimed, Ettlingen, Germany), Vici (Veniti; St. Louis, USA), Wallstent (Boston Scientific, Marlborough, USA), and Venovo (Bard, Tempe, USA)] in vitro using a radial force testing machine (RX-650, Machine Solutions Inc., Flagstaff, AZ, USA) and a hardness testing machine (zwickiLine, Zwick Roell, Ulm, Germany). The Sinus Obliquus revealed the highest radial resistive force (19.41 N/cm) and the highest chronic outward force at 50 and 30% nominal diameter (7.93 N/cm at 50%, 16.97 N/cm at 30%) while the Venovo revealed the highest chronic outward force at 90 and 80% nominal diameter (4.83 N/cm at 90%, 5.37 N/cm at 80%). The radial resistive force and the chronic outward force of the Wallstent greatly depended on whether the stent ends were fixated. The Wallstent revealed the highest crush resistance at nominal diameters of 90% (0.46 N/cm) to 60% (1.16 N/cm). The Sinus Obliquus revealed the highest crush resistance at a nominal diameter of 50% (1.41 N/cm). Venous stents greatly differ regarding their mechanical properties. These results should be considered when choosing an appropriate stent for the treatment of venous obstruction.

Hydrogen cyanide production due to mid-size impacts in a redox-neutral N2-rich atmosphere.

PubMed

Kurosawa, Kosuke; Sugita, Seiji; Ishibashi, Ko; Hasegawa, Sunao; Sekine, Yasuhito; Ogawa, Nanako O; Kadono, Toshihiko; Ohno, Sohsuke; Ohkouchi, Naohiko; Nagaoka, Yoichi; Matsui, Takafumi

2013-06-01

Cyanide compounds are amongst the most important molecules of the origin of life. Here, we demonstrate the importance of mid-size (0.1-1 km in diameter) hence frequent meteoritic impacts to the cyanide inventory on the early Earth. Subsequent aerodynamic ablation and chemical reactions with the ambient atmosphere after oblique impacts were investigated by both impact and laser experiments. A polycarbonate projectile and graphite were used as laboratory analogs of meteoritic organic matter. Spectroscopic observations of impact-generated ablation vapors show that laser irradiation to graphite within an N2-rich gas can produce a thermodynamic environment similar to that produced by oblique impacts. Thus, laser ablation was used to investigate the final chemical products after this aerodynamic process. We found that a significant fraction (>0.1 mol%) of the vaporized carbon is converted to HCN and cyanide condensates, even when the ambient gas contains as much as a few hundred mbar of CO2. As such, the column density of cyanides after carbon-rich meteoritic impacts with diameters of 600 m would reach ~10 mol/m(2) over ~10(2) km(2) under early Earth conditions. Such a temporally and spatially concentrated supply of cyanides may have played an important role in the origin of life.

Progress in HTS trapped field magnets: J(sub c), area, and applications

NASA Technical Reports Server (NTRS)

Weinstein, Roy; Ren, Yanru; Liu, Jianxiong; Sawh, Ravi; Parks, Drew; Foster, Charles; Obot, Victor; Arndt, G. Dickey; Crapo, Alan

1995-01-01

Progress in trapped field magnets is reported. Single YBCO grains with diameters of 2 cm are made in production quantities, while 3 cm, 4 1/2 cm and 6 cm diameters are being explored. For single grain tiles: J(sub c) is approximately 10,000 A/cm(exp 2) for melt textured grains; J(sub c) is approximately 40,000 A/cm2 for light ion irradiation; and J(sub c) is approximately 85,000 A/cm(exp 2) for heavy ion irradiation. Using 2 cm diameter tiles bombarded by light ions, we have fabricated a mini-magnet which trapped 2.25 Tesla at 77K, and 5.3 Tesla at 65K. A previous generation of tiles, 1 cm x 1 cm, was used to trap 7.0 Tesla at 55K. Unirradiated 2.0 cm tiles were used to provide 8 magnets for an axial gap generator, in a collaborative experiment with Emerson Electric Co. This generator delivered 100 Watts to a resistive load, at 2265 rpm. In this experiment activation of the TFMs was accomplished by a current pulse of 15 ms duration. Tiles have also been studied for application as a bumper-tether system for the soft docking of spacecraft. A method for optimizing tether forces, and mechanisms of energy dissipation are discussed. A bus bar was constructed by welding three crystals while melt-texturing, such that their a,b planes were parallel and interleaved. The bus bar, an area of approximately 2 cm(exp 2), carried a transport current of 1000 amps, the limit of the testing equipment available.

FOD impact testing of composite fan blades

NASA Technical Reports Server (NTRS)

Johns, R. H.

1974-01-01

The results of impact tests on large, fiber composite fan blades for aircraft turbofan engine applications are discussed. Solid composite blades of two different sizes and designs were tested. Both graphite/epoxy and boron/epoxy were evaluated. In addition, a spar-shell blade design was tested that had a boron/epoxy shell bonded to a titanium spar. All blades were tested one at a time in a rotating arm rig to simulate engine operating conditions. Impacting media included small gravel, two inch diameter ice balls, gelatin and RTV foam-simulated birds, as well as starlings and pigeons. The results showed little difference in performance between the graphite and boron/epoxy blades. The results also indicate that composite blades may be able to tolerate ice ball and small bird impacts but need improvement to tolerate birds in the small duck and larger category.

FOD impact testing of composite fan blades

NASA Technical Reports Server (NTRS)

Johns, R. H.

1974-01-01

The results of impact tests on large, fiber composite fan blades for aircraft turbofan engine applications are discussed. Solid composite blades of two different sizes and designs were tested. Both graphite/epoxy and boron/epoxy were evaluated. In addition, a spar-shell blade design was tested that had a boron/epoxy shell bonded to a titanium spar. All blades were tested one at a time in a rotating arm rig to simulate engine operating conditions. Impacting media included small gravel, two inch diameter ice balls, gelatin, and RTV foam-simulated birds, as well as starlings and pigeons. The results showed little difference in performance between the graphite and boron/epoxy blades. The results also indicate that composite blades may be able to tolerate ice ball and small bird impacts but need improvement to tolerate birds in the small duck and larger category.

Impact testing on composite fan blades

NASA Technical Reports Server (NTRS)

Johns, R. H.

1974-01-01

The results of impact tests on large, fiber composite fan blades for aircraft turbofan engine applications are discussed. Solid composite blades of two different sizes and designs were tested. Both graphite/epoxy and boron/epoxy were evaluated. In addition, a spar-shell blade design was tested that had a boron/epoxy shell bonded to a titanium spar. All blades were tested one at a time in a rotating arm rig to simulate engine operating conditions. Impacting media included small gravel, two inch diameter ice balls, gelatin and RTV foam-simulated birds, as well as starlings and pigeons. The results showed little difference in performance between the graphite and boron/epoxy blades. The results also indicate that composite blades may be able to tolerate ice ball and small bird impacts but need improvement to tolerate birds in the small duck and larger category.

Modeling and Testing of the Viscoelastic Properties of a Graphite Nanoplatelet/Epoxy Composite

NASA Technical Reports Server (NTRS)

Odegard, Gregory M.; Gates, Thomas S.

2005-01-01

In order to facilitate the interpretation of experimental data, a micromechanical modeling procedure is developed to predict the viscoelastic properties of a graphite nanoplatelet/epoxy composite as a function of volume fraction and nanoplatelet diameter. The predicted storage and loss moduli for the composite are compared to measured values from the same material using three test methods; Dynamical Mechanical Analysis, nanoindentation, and quasi-static tensile tests. In most cases, the model and experiments indicate that for increasing volume fractions of nanoplatelets, both the storage and loss moduli increase. Also, the results indicate that for nanoplatelet sizes above 15 microns, nanoindentation is capable of measuring properties of individual constituents of a composite system. Comparison of the predicted values to the measured data helps illustrate the relative similarities and differences between the bulk and local measurement techniques.

Study of CO2 adsorption capacity of mesoporous carbon and activated carbon modified by triethylenetetramine (TETA)

NASA Astrophysics Data System (ADS)

Sulistianti, I.; Krisnandi, Y. K.; Moenandar, I.

2017-04-01

Mesoporous carbon was synthesized by soft template method using phloroglucinol and formaldehyde as a carbon source; and Pluronic F-127 as a mesoporous template. The synthesized mesoporous carbon and commercial activated carbon were modified with triethylenetetramine (TETA) to increase CO2 adsorption capacity. Based on FTIR characterization, the synthesized mesoporous carbon and the activated carbon without modification process has similarity pattern. After the modification, both of them showed absorption peaks in the area around 1580 to 1650 cm-1 which is known as N-H bending vibration and absorption peaks in the area around 3150 to 3380 cm-1 which is known as N-H stretching vibration. The XRD results showed two peaks at 2θ = 24.21° and 2θ = 43.85°, according to JCPDS index No. 75-1621 those peak are the typical peaks for hexagonal graphite carbon. In BET analysis, the synthesized mesoporous carbon and activated carbon modified TETA have surface area, pore volume and pore diameter lower than without modification process. In carbon dioxide adsorption testing, the synthesized mesoporous carbon showed better performance than the commercial activated carbon for CO2 adsorption both without modification and by modification. The synthesized mesoporous carbon obtained CO2 adsorption of 9.916 mmol/g and the activated carbon of 3.84 mmol/g for on 3.5 hours of adsorption. It is three times better than activated carbon for adsorption of carbon dioxide. The modified mesoporous carbon has the best performance for adsorption of gas CO2 if compared by unmodified.

Use of disposable graduated biopsy forceps improves accuracy of polyp size measurements during endoscopy

PubMed Central

Jin, Hei-Ying; Leng, Qiang

2015-01-01

AIM: To determine the accuracy of endoscopic polyp size measurements using disposable graduated biopsy forceps (DGBF). METHODS: Gradations accurate to 1 mm were assessed with the wire of disposable graduated biopsy forceps. When a polyp was noted, endoscopists determined the width of the polyp; then, the graduated biopsy forceps was inserted and the largest diameter of the tumor was measured. After excision, during surgery or endoscopy, the polyp was measured using the vernier caliper. RESULTS: One hundred and thirty-three colorectal polyps from 119 patients were studied. The mean diameter, by post-polypectomy measurement, was 0.92 ± 0.69 cm; 83 were < 1 cm, 36 were between 1 and 2 cm, and 14 were > 2 cm. The mean diameter, by visual estimation, was 1.15 ± 0.88 cm; compared to the actual size measured using vernier calipers, the difference was statistically significant. The mean diameter measured using the DGBF was 0.93 ± 0.68 cm; compared to the actual size measured using vernier calipers, this difference was not statistically significant. The ratio between the mean size estimated by visual estimation and the actual size was significantly different from that between the mean size estimated using the DGBF and the actual size (1.26 ± 0.30 vs 1.02 ± 0.11). CONCLUSION: The accuracy of polyp size estimation was low by visual assessment; however, it improved when the DGBF was used. PMID:25605986

Volumetric Growth of the Liver in the Human Fetus: An Anatomical, Hydrostatic, and Statistical Study

PubMed Central

Szpinda, Michał; Paruszewska-Achtel, Monika; Mila-Kierzenkowska, Celestyna; Elminowska-Wenda, Gabriela; Dombek, Małgorzata; Szpinda, Anna; Badura, Mateusz

2015-01-01

Using anatomical, hydrostatic, and statistical methods, liver volumes were assessed in 69 human fetuses of both sexes aged 18–30 weeks. No sex differences were found. The median of liver volume achieved by hydrostatic measurements increased from 6.57 cm3 at 18–21 weeks through 14.36 cm3 at 22–25 weeks to 20.77 cm3 at 26–30 weeks, according to the following regression: y = −26.95 + 1.74 × age ± Z  × (−3.15 + 0.27 × age). The median of liver volume calculated indirectly according to the formula liver volume = 0.55 × liver length × liver transverse diameter × liver sagittal diameter increased from 12.41 cm3 at 18–21 weeks through 28.21 cm3 at 22–25 weeks to 49.69 cm3 at 26–30 weeks. There was a strong relationship (r = 0.91, p < 0.001) between the liver volumes achieved by hydrostatic (x) and indirect (y) methods, expressed by y = −0.05 + 2.16x  ± 7.26. The liver volume should be calculated as follows liver volume = 0.26 × liver length × liver transverse diameter × liver sagittal diameter. The age-specific liver volumes are of great relevance in the evaluation of the normal hepatic growth and the early diagnosis of fetal micro- and macrosomias. PMID:26413551

Experimental Observations of Microwave Emission from a 35 GHz Cyclotron Autoresonant Maser

DTIC Science & Technology

1990-07-27

available graphite products) with a density of p =1.84 gm/cm 3 . The electron beam in the diode is generated through the process of explosive field emission...introduction to the physics of intense charge particle beams. Plenum Press, 1982. [331 D. Prosnitz %... .. T. Scharlemann. Beam quality definitions

Effect of load, area of contact, and contact stress on the tribological properties of polyimide bonded graphite fluoride films

NASA Technical Reports Server (NTRS)

Fusaro, R. L.

1981-01-01

A pin-on-disk type of friction and wear apparatus was used to study the effect of load, contact stress and rider area of contact on the friction and wear properties of polyimide-bonded graphite fluoride films. Different rider area contacts were obtained by initially generating flats (with areas of 0.0035, 0.0071, 0.0145, and 0.0240 cm) on 0.476-cm radius hemispherically-tipped riders. Different projected contact stresses were obtained by applying loads of 2.5-to 58.8-N to the flats. Two film wear mechanisms were observed. The first was found to be a linear function of contact stress and was independent of rider area of contact. The second was found to increase exponentially as the stress increased. The second also appeared to be a function of rider contact area. Wear equations for each mechanism were empirically derived from the experimental data. In general, friction coefficients increased with increasing rider contact area and with sliding duration. This was related to the build-up of thick rider transfer films.

Synergistic Effects between Doped Nitrogen and Phosphorus in Metal-Free Cathode for Zinc-Air Battery from Covalent Organic Frameworks Coated CNT.

PubMed

Li, Zhongtao; Zhao, Weinan; Yin, Changzhi; Wei, Liangqin; Wu, Wenting; Hu, Zhenpeng; Wu, Mingbo

2017-12-27

A covalent organic framework that is composed of hexachlorocyclotriphosphazene and dicyanamide has been coated on CNT to prepare metal-free oxygen reduction reaction catalyst through thermal polymerization of the Zn-air battery cathode. The N,P-codoped nanohybrids have highly porous structure and active synergistic effect between graphitic-N and -P, which promoted the electrocatalytic performance. The electrocatalysts exhibits remarkable half-wave potential (-0.162 V), high current density (6.1 mA/cm -2 ), good stability (83%), and excellent methanol tolerance for ORR in alkaline solution. Furthermore, the N,P-codoped nanohybrids were used as an air electrode for fabrication of a high performance Zn-air battery. The battery achieves a high open-circuit potential (1.53 V) and peak power density (0.255 W cm -2 ). Moreover, the effect of N,P codoping on the conjugate carbon system and the synergistic effect between graphitic-N and P have been calculated through density functional theory calculations, which are essentially in agreement with experimental data.

SPOUTED BED DESIGN CONSIDERATIONS FOR COATED NUCLEAR FUEL PARTICLES

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

Marshall, Douglas W.

High Temperature Gas Cooled Reactors (HTGRs) are fueled with tristructural isotropic (TRISO) coated nuclear fuel particles embedded in a carbon-graphite fuel body. TRISO coatings consist of four layers of pyrolytic carbon and silicon carbide that are deposited on uranium ceramic fuel kernels (350µm – 500µm diameters) in a concatenated series of batch depositions. Each layer has dedicated functions such that the finished fuel particle has its own integral containment to minimize and control the release of fission products into the fuel body and reactor core. The TRISO coatings are the primary containment structure in the HTGR reactor and must havemore » very high uniformity and integrity. To ensure high quality TRISO coatings, the four layers are deposited by chemical vapor deposition (CVD) using high purity precursors and are applied in a concatenated succession of batch operations before the finished product is unloaded from the coating furnace. These depositions take place at temperatures ranging from 1230°C to 1550°C and use three different gas compositions, while the fuel particle diameters double, their density drops from 11.1 g/cm3 to 3.0 g/cm3, and the bed volume increases more than 8-fold. All this is accomplished without the aid of sight ports or internal instrumentation that could cause chemical contamination within the layers or mechanical damage to thin layers in the early stages of each layer deposition. The converging section of the furnace retort was specifically designed to prevent bed stagnation that would lead to unacceptably high defect fractions and facilitate bed circulation to avoid large variability in coating layer dimensions and properties. The gas injection nozzle was designed to protect precursor gases from becoming overheated prior to injection, to induce bed spouting and preclude bed stagnation in the bottom of the retort. Furthermore, the retort and injection nozzle designs minimize buildup of pyrocarbon and silicon carbide on the retort wall and manage nozzle orifice accretions. The equipment and operating methods have yielded very good reproducibility in the TRISO coated particles batches.« less

Error rate of automated calculation for wound surface area using a digital photography.

PubMed

Yang, S; Park, J; Lee, H; Lee, J B; Lee, B U; Oh, B H

2018-02-01

Although measuring would size using digital photography is a quick and simple method to evaluate the skin wound, the possible compatibility of it has not been fully validated. To investigate the error rate of our newly developed wound surface area calculation using digital photography. Using a smartphone and a digital single lens reflex (DSLR) camera, four photographs of various sized wounds (diameter: 0.5-3.5 cm) were taken from the facial skin model in company with color patches. The quantitative values of wound areas were automatically calculated. The relative error (RE) of this method with regard to wound sizes and types of camera was analyzed. RE of individual calculated area was from 0.0329% (DSLR, diameter 1.0 cm) to 23.7166% (smartphone, diameter 2.0 cm). In spite of the correction of lens curvature, smartphone has significantly higher error rate than DSLR camera (3.9431±2.9772 vs 8.1303±4.8236). However, in cases of wound diameter below than 3 cm, REs of average values of four photographs were below than 5%. In addition, there was no difference in the average value of wound area taken by smartphone and DSLR camera in those cases. For the follow-up of small skin defect (diameter: <3 cm), our newly developed automated wound area calculation method is able to be applied to the plenty of photographs, and the average values of them are a relatively useful index of wound healing with acceptable error rate. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Ultrafast plasmon-enhanced hot electron process in model heterojunctions: Ag/TiO2 and Ag/graphite

NASA Astrophysics Data System (ADS)

Petek, Hrvoje

We study the plasmonically enhanced nonlinear photoemission from Ag nanocluster-decorated graphite and TiO2(110) surfaces by time-resolved two-photon photoemission spectroscopy (TR-2PP). Evaporating Ag atoms on graphite and TiO2 surfaces forms pancake-like Ag clusters with 5 nm diameter and 1-1.5 nm height through self-limiting growth mode. The Ag nanoparticles enhance the two-photon photoemission (2PP) signal by approximately two-orders of magnitude as compared with the bare surfaces for p-polarized excitation. In the case of s-polarization there is essentially no enhancement for graphite, and only about an order-of-magnitude enhancement for TiO2. Wavelength dependent measurements of the enhancement reveal that for Ag/graphite there is a single plasmonic resonance due to the ⊥-plasmon mode at 3.6 eV. By contrast, for Ag/TiO2 there are ⊥ and ||-plasmon modes with resonant energies of 3.8 and 3.1 eV, respectively. Apparently the dielectric properties of the substrate have strong influence on the type and frequency of Ag plasmonic modes that can exist on the surfaces. 2PP spectra of the Ag/graphite and Ag/TiO2 surfaces reveal two distinct components that are common to both. The high energy component consists of a coherent 2PP process from an occupied interface state, which only exists in the presence of Ag. We identify this state, as an interface state formed by charge donation from the Ag-5s band to the unoccupied states of the substrates. The low energy component consists of a hot electron signal that is created by plasmon dephasing. TR-2PP measurements are performed on the plasmon-induced electron dynamics to assess their relevance for plasmonically enhanced femtochemistry. This research was supported by NSF Grant CHE-1414466.

Maximal aortic diameter affects outcome after endovascular repair of abdominal aortic aneurysms.

PubMed

Huang, Ying; Gloviczki, Peter; Duncan, Audra A; Kalra, Manju; Oderich, Gustavo S; Fleming, Mark D; Harmsen, William S; Bower, Thomas C

2017-05-01

The purpose of this study was to evaluate whether maximal aortic diameter affects outcome after endovascular aneurysm repair (EVAR) of abdominal aortic aneurysm (AAA). Clinical data of patients undergoing EVAR between 1997 and 2011 for nonruptured asymptomatic AAAs in a tertiary center were reviewed. Patients were classified according to diameter of AAA: group 1, <5.0 cm; group 2, 5.0 to 5.4 cm; group 3, 5.5 to 5.9 cm; and group 4, ≥6.0 cm. The primary end point was all-cause mortality; secondary end points were complications, reinterventions, and ruptures. There were 874 patients studied (female, 108 [12%]; group 1, 119; group 2, 246; group 3, 243; group 4, 266); mean age was 76 ± 7.2 years. The 30-day mortality rate was 1.0%, not significantly different between groups (P = .22); complication and reintervention rates were 13% and 4.1%, respectively, similar between groups (P < .05). Five-year survival was 68%; freedom from complications and reinterventions was 65% and 74%, respectively; rupture rate was 0.5%. Multivariate analysis revealed that factors associated with all-cause mortality included maximal aortic diameter, age, gender, surgical risk, cancer history, and endograft type (P < .05). Group 4 had increased risks of mortality (hazard ratio [HR], 2.0; 95% confidence interval [CI], 1.38-2.85; P = .002) and complications (HR, 1.6; 95% CI, 1.2-2.7; P = .009) relative to group 1. Reinterventions were more frequent for aneurysms ≥6.0 cm (HR, 2.0; 95% CI, 1.2-3.3; P = .01). Late rupture rate after EVAR was not different between groups. Maximal aortic diameter is associated with long-term outcomes after elective EVAR. Patients with large AAAs (≥6.0 cm) have higher all-cause mortality, complication, and reintervention rates after EVAR than those with smaller aneurysms. We continue to recommend that AAAs be repaired when they reach 5.5 cm as recommended by the guidelines of the Society for Vascular Surgery. On the basis of our data, EVAR should be considered even in high-risk patients with a maximal aortic diameter between 5.5 and 6.0 cm because surgical risk with aneurysm size above 6.0 cm will increase significantly. Copyright © 2016 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.

Chirality correlation in double-wall carbon nanotubes as studied by electron diffraction

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

Hirahara, Kaori; Bandow, Shunji; Kociak, Mathieu

2006-05-15

Structural correlation between two adjacent graphitic layers in double-wall carbon nanotubes (DWNTs) was systematically examined by using electron diffraction. Chiral angles and tube diameters were carefully measured, and the chiral indices of individual DWNTs were accurately determined. As a result, it was found that the interlayer distances of DWNTs were widely distributed in the range between 0.34 and 0.38 nm. Chiralities of the inner and outer tubes tended to be distributed at higher chiral angles, approaching 30 deg., for the tubes with diameter D<{approx}3 nm. On the other hand, for the tubes with D>{approx}3 nm, the chiral angles were widelymore » distributed, covering the chiral map entirely. Therefore, we consider that tubes with small diameters have a tendency to form armchair type. Correlation of chiralities between the inner and outer tubes was found to be random.« less

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.

Fluence correction factor for graphite calorimetry in a clinical high-energy carbon-ion beam.

PubMed

Lourenço, A; Thomas, R; Homer, M; Bouchard, H; Rossomme, S; Renaud, J; Kanai, T; Royle, G; Palmans, H

2017-04-07

The aim of this work is to develop and adapt a formalism to determine absorbed dose to water from graphite calorimetry measurements in carbon-ion beams. Fluence correction factors, [Formula: see text], needed when using a graphite calorimeter to derive dose to water, were determined in a clinical high-energy carbon-ion beam. Measurements were performed in a 290 MeV/n carbon-ion beam with a field size of 11  ×  11 cm 2 , without modulation. In order to sample the beam, a plane-parallel Roos ionization chamber was chosen for its small collecting volume in comparison with the field size. Experimental information on fluence corrections was obtained from depth-dose measurements in water. This procedure was repeated with graphite plates in front of the water phantom. Fluence corrections were also obtained with Monte Carlo simulations through the implementation of three methods based on (i) the fluence distributions differential in energy, (ii) a ratio of calculated doses in water and graphite at equivalent depths and (iii) simulations of the experimental setup. The [Formula: see text] term increased in depth from 1.00 at the entrance toward 1.02 at a depth near the Bragg peak, and the average difference between experimental and numerical simulations was about 0.13%. Compared to proton beams, there was no reduction of the [Formula: see text] due to alpha particles because the secondary particle spectrum is dominated by projectile fragmentation. By developing a practical dose conversion technique, this work contributes to improving the determination of absolute dose to water from graphite calorimetry in carbon-ion beams.

Probe for Sampling of Interstitial Fluid From Bone

NASA Technical Reports Server (NTRS)

Janle, Elsa M.

2004-01-01

An apparatus characterized as both a membrane probe and a bone ultrafiltration probe has been developed to enable in vivo sampling of interstitial fluid in bone. The probe makes it possible to measure the concentration of calcium and other constituents of the fluid that may be relevant to bone physiology. The probe could be especially helpful in experimental studies of microgravitational bone loss and of terrestrial bone-loss disease states, including osteoporosis. The probe can be implanted in the bone tissue of a living animal and can be used to extract samples of the interstitial bone fluid from time to time during a long-term study. The probe includes three 12-cm-long polyacrylonitrile fibers configured in a loop form and attached to polyurethane tubing [inside diameter 0.025 in. (0.64 mm), outside diameter 0.040 in. (1 mm)]; the attachment is made by use of a 1-cm-long connecting piece of polyurethane tubing [inside diameter 0.035 0.003 in. (0.89 0.08 mm), outside diameter 0.060 0.003 in. (1.52 0.08 mm)]. At the distal end, a 2-cm-long piece of polyurethane tubing of the same inner and outer diameters serves as a connector to a hub. A 1-cm long piece of expanded poly (tetrafluoroethylene) tubing over the joint between the fibers and the connecting tubing serves as a tissue-in-growth site.

Nonlinear Vibration of a Magnetic Spring

ERIC Educational Resources Information Center

Zhong, Juhua; Cheng, Zhongqi; Ge, Ziming; Zhang, Yuelan; Lu, Wenqiang; Song, Feng; Li, Chuanyong

2012-01-01

To demonstrate the different vibration characteristics of a magnetic spring compared with those of a metal one, a magnetic spring apparatus was constructed from a pair of circular magnets of the same size with an inside diameter of 2.07 cm and an outside diameter of 4.50 cm. To keep the upper magnet in a suspension state, the two magnets were…

Large Mode Area Yb-Doped Photonic Bandgap Fiber Lasers

DTIC Science & Technology

2015-02-08

was estimated to be 1 dB/m at a pump wavelength of 976 nm. Approximately 11 m of this fiber was mounted on a cold spool possessing a diameter of 53 cm...Approximately 11 m of this fiber was mounted on a cold spool possessing a diameter of 53 cm. The PBGF was pumped in a counter-propagating configuration

Angular and radial dependence of the energy response factor for LIF-TLD micro-rods in 125L permanent implant source.

PubMed

Mobit, Paul; Badragan, Iulian

2006-01-01

EGSnrc Monte Carlo simulations were used to calculate the angular and radial dependence of the energy response factor for LiF-thermoluminescence dosemeters (TLDs) irradiated with a commercially available (125)I permanent brachytherapy source. The LiF-TLDs were modelled as cylindrical micro-rods of length 6 mm and with diameters of 1 mm and 5 mm. The results show that for a LiF-TLD micro-rod of 1 mm diameter, the energy response relative to (60)Co gamma rays is 1.406 +/- 0.3% for a polar angle of 90 degrees and radial distance of 1.0 cm. When the diameter of the micro-rod is increased from 1 to 5 mm, the energy response decreases to 1.32 +/- 0.3% at the same point. The variation with position of the energy response factor is not >5% in a 6 cm x 6 cm x 6 cm calculation grid for the 5 mm diameter micro-rod. The results show that there is a change in the photon spectrum with angle and radial distance, which causes the variation of the energy response.

Composite propulsion feedlines for cryogenic space vehicles, volume 1

NASA Technical Reports Server (NTRS)

Hall, C. A.; Laintz, D. J.; Phillips, J. M.

1973-01-01

Thin metallic liners that provide leak-free service in cryogenic propulsion systems are overwrapped with a glass-fiber composite that provides strength and protection from handling damage. The resultant tube is lightweight, strong and has a very low thermal flux. Several styles of tubing ranging from 5 to 38 cm in diameter and up to 305 cm long were fabricated and tested at operating temperatures from 294 to 21 K and operating pressures up to 259 N/sq cm. The primary objective for the smaller sizes was thermal performance optimization of the propulsion system while the primary objective of the larger sizes was weight optimization and to prove fabricability. All major program objectives were met resulting in a design concept that is adaptable to a wide range of aerospace vehicle requirements. Major items of development included: bonding large diameter aluminum end fittings to the thin Inconel liner; fabrication of a 38 cm diameter tube from 0.008 cm thick Inconel; and evaluation of tubing which provides essentially zero quality propellant in a very short period of time resulting in a lower mass of propellant expended in chilldown.

Extraction and speciation of arsenic in lacustrine sediments

USGS Publications Warehouse

Ficklin, W.H.

1990-01-01

Arsenic was partially extracted with 4.OM hydrochloric acid, from samples collected at 25-cm intervals in a 350-cm column of sediment at Milltown Reservoir, Montana and from a 60-cm core of sediment collected at the Cheyenne River Embayment of Lake Oahe, South Dakota. The sediment in both reservoirs is highly contaminated with arsenic. The extracted arsenic was separated into As(III) and As(V) on acetate form Dowex 1-X8 ion-exchange resin with 0.12M HCl eluent. Residual arsenic was sequentially extracted with KClO3 and HCl. Arsenic was determined by graphite-furnace atomic-absorption spectrometry. The analytical results define oxidized and reduced zones in the sediment columns. ?? 1990.

Correction factors for the ISO rod phantom, a cylinder phantom, and the ICRU sphere for reference beta radiation fields of the BSS 2

NASA Astrophysics Data System (ADS)

Behrens, R.

2015-03-01

The International Organization for Standardization (ISO) requires in its standard ISO 6980 that beta reference radiation fields for radiation protection be calibrated in terms of absorbed dose to tissue at a depth of 0.07 mm in a slab phantom (30 cm x 30 cm x 15 cm). However, many beta dosemeters are ring dosemeters and are, therefore, irradiated on a rod phantom (1.9 cm in diameter and 30 cm long), or they are eye dosemeters possibly irradiated on a cylinder phantom (20 cm in diameter and 20 cm high), or area dosemeters irradiated free in air with the conventional quantity value (true value) being defined in a sphere (30 cm in diameter, made of ICRU tissue (International Commission on Radiation Units and Measurements)). Therefore, the correction factors for the conventional quantity value in the rod, the cylinder, and the sphere instead of the slab (all made of ICRU tissue) were calculated for the radiation fields of 147Pm, 85Kr, 90Sr/90Y, and, 106Ru/106Rh sources of the beta secondary standard BSS 2 developed at PTB. All correction factors were calculated for 0° up to 75° (in steps of 15°) radiation incidence. The results are ready for implementation in ISO 6980-3 and have recently been (partly) implemented in the software of the BSS 2.

Progress in HTS Trapped Field Magnets: J(sub c), Area, and Applications

NASA Technical Reports Server (NTRS)

Weinstein, Roy; Ren, Yanru; Liu, Jian-Xiong; Sawh, Ravi; Parks, Drew; Foster, Charles; Obot, Victor; Arndt, G. Dickey; Crapo, Alan

1995-01-01

Progress in trapped field magnets is reported. Single YBCO grains with diameters of 2 cm are made in production quantities, while 3 cm, 4 1/2 cm and 6 cm diameters are being explored. For single grain tiles: J(sub c) - 10,000 A/sq cm for melt textured grains; J(sub c) - 40,000 A/sq cm for light ion irradiation; and J(sub c) - 85,000 A/J(sub c) for heavy ion irradiation. Using 2 cm diameter tiles bombarded by light ions, we have fabricated a mini-magnet which trapped 2.25 Tesla at 77K, and 5.3 Tesla at 65K. A previous generation of tiles, 1 cm x 1 cm, was used to trap 7.0 Tesla at 55K. Unirradiated 2.0 cm tiles were used to provide 8 magnets for an axial gap generator, in a collaborative experiment with Emerson Electric Co. This generator delivered 100 Watts to a resistive load, at 2265 rpm. In this experiment, activation of the TFMs was accomplished by a current pulse of 15 ms duration. Tiles have also been studied for application as a bumper-tether system for the soft docking of spacecraft. A method for optimizing tether forces, and mechanisms of energy dissipation are discussed. A bus bar was constructed by welding three crystals while melt-texturing, such that their a,b planes were parallel and interleaved. The bus bar, of area approx. 2 sq cm, carried a transport current of 1000 amps, the limit of the testing equipment available.

Percutaneous Renal Cryoablation: Short-Axis Ice-Ball Margin as a Predictor of Outcome.

PubMed

Ge, Benjamin H; Guzzo, Thomas J; Nadolski, Gregory J; Soulen, Michael C; Clark, Timothy W I; Malkowicz, Stanley B; Wein, Alan J; Hunt, Stephen J; Stavropoulos, S William

2016-03-01

To determine if CT characteristics of intraprocedural ice balls correlate with outcomes after cryoablation. A retrospective review was performed on 63 consecutive patients treated with renal cryoablation. Preprocedural and intraprocedural images were used to identify the size and location of renal tumors and ice balls as well as the tumor coverage and ice-ball margins. Review of follow-up imaging (1 mo and then 3-6-mo intervals) distinguished successful ablations from cases of residual tumor. Patients who underwent successful ablation (n = 50; 79%) had a mean tumor diameter of 2.5 cm (range, 0.9-4.3 cm) and mean ice-ball margin of 0.4 cm (range, 0.2-1.2 cm). Patients with residual tumor (n = 13; 21%) had a mean tumor diameter of 3.8 cm (range, 1.8-4.5 cm) and mean ice-ball margin of -0.4 cm (range, -0.9 to 0.4 cm). Residual and undertreated tumors were larger and had smaller ice-ball margins than successfully treated tumors (P < .01). Ice-ball diameters were significantly smaller after image reformatting (P < .01). Ice-ball margins of 0.15 cm had 90% sensitivity, 92% specificity, and 98% positive predictive value for successful ablation. Success was independent of tumor location or number of cryoprobes. Ice-ball margin and real-time intraprocedural reformatting could be helpful in predicting renal cryoablation outcomes. Although a 0.5-cm margin is preferred, a well-centered ice ball with a short-axis margin greater than 0.15 cm strongly correlated with successful ablation. Copyright © 2016 SIR. Published by Elsevier Inc. All rights reserved.

Status, technology and development of silicon solar cells at INER

NASA Astrophysics Data System (ADS)

Jao, S. S.; Tseng, H. H.; Cheng, C.; Tzeng, Y. C.; Chang, H. H.; Hwang, H. L.

Test runs using 200 5-cm-diameter silicon wafers are carried out, yielding 87% with an AM1 conversion efficiency greater than 11.5%. The highest efficiency is 12.7%. Concentrator solar cells of 2 x 2 sq cm are made with an AM1 efficiency of 14%. Solar cells with a diameter of 7.5 cm have attained AM1 efficiencies of more than 11.3%, and texturized solar cells of the same diameter fabricated from rejected wafers show AM1 efficiencies of 9.5-10.5%. It is noted that solar panels comprising 68 cells with a maximum output power of 13.5 W have been manufactured. The results of a 6-month test of a photovoltaic charge station for electric motorcycles are reported.

Proceedings of the International Conference on Electrorheological Fluids (4th) Held in Feldkirch (Austria) on 20-23 July 1993

DTIC Science & Technology

1994-01-01

which predicts that cylinder diameter or spacing has any influence on the dielctric spectra once the concer~tration of cylinders is fixed, and thus...differences in column girth and spacing . Furthermore, in applying the Sillars’ model to the present situation no precise meaning is attached to his end...cm). The test cell comprises two duralumin electrodes 9 cm in diameter spaced by 1.4 cm. Thu planar section of the upper half sphere, solid with a

Blast Wave Experiments at Z

DTIC Science & Technology

2007-06-01

radiation flows upward, it passes though a 1.7-mm high, tapered, 25-μm thick gold wall cone that is filled 20 ± 3 mg/cm3 silica aerogel (SiO2). Above...this cone is a 20 ± 3 mg/cm3 silica aerogel filled, 1-mm high, 2.4-mm inner diameter, 25-μm thick gold wall cylinder. On the cylinder rests a 4-mm...diameter gold platform that supports a higher density (40-60 mg/cm3) silica aerogel . This aerogel is the region where the blast wave forms after

Focal Hydrothermal Ablation: Preliminary Investigation of a New Concept

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

Roy, Sumit, E-mail: sumit.roy@online.no

2013-08-01

PurposeTo determine whether focal tissue ablation is possible with interstitial instillation of steam.MethodsFresh swine livers were used. Through a 20 gauge needle, steam was instilled every 5 s, 3 (n = 5), 6 (n = 5), 9 (n = 5), or 12 (n = 5 + 5) times in a liver lobe. The ablated zones were sectioned parallel (n = 20) or perpendicular (n = 5) to the needle track. The longitudinal long and short axis diameters, or transverse long and short axis diameters of areas with discoloration on macroscopic examination, were measured. The experiment was repeated in vivo onmore » a pig. Steam instillation was performed once every 5 s for 5 min in the liver (n = 3) and in muscle (n = 4), and temperature changes at three neighboring sites were monitored. Long and short axis diameters of the discolored areas were measured.ResultsA well-defined area of discoloration was invariably present at the site of steam instillation. The median longitudinal long axis diameter were 2.0, 2.5, 2.5, and 3.5 cm for 3, 6, 9, and 12 steam instillations in vitro, while median short axis diameters were 1.0, 1.5, 1.5, and 1.5 cm, respectively. Six attempts at ablation in vivo could be successfully completed. The long axis diameters of the ablated zones in the liver were 7.0 and 8.0 cm, while in muscle it ranged from 5.5 to 7.0 cm.ConclusionInstillation of steam in the liver in vitro and in vivo, and in muscle in vivo rapidly leads to circumscribed zones of coagulation necrosis.« less

Wavelet-based algorithm to the evaluation of contrasted hepatocellular carcinoma in CT-images after transarterial chemoembolization.

PubMed

Alvarez, Matheus; de Pina, Diana Rodrigues; Romeiro, Fernando Gomes; Duarte, Sérgio Barbosa; Miranda, José Ricardo de Arruda

2014-07-26

Hepatocellular carcinoma is a primary tumor of the liver and involves different treatment modalities according to the tumor stage. After local therapies, the tumor evaluation is based on the mRECIST criteria, which involves the measurement of the maximum diameter of the viable lesion. This paper describes a computed methodology to measure through the contrasted area of the lesions the maximum diameter of the tumor by a computational algorithm. 63 computed tomography (CT) slices from 23 patients were assessed. Non-contrasted liver and HCC typical nodules were evaluated, and a virtual phantom was developed for this purpose. Optimization of the algorithm detection and quantification was made using the virtual phantom. After that, we compared the algorithm findings of maximum diameter of the target lesions against radiologist measures. Computed results of the maximum diameter are in good agreement with the results obtained by radiologist evaluation, indicating that the algorithm was able to detect properly the tumor limits. A comparison of the estimated maximum diameter by radiologist versus the algorithm revealed differences on the order of 0.25 cm for large-sized tumors (diameter > 5 cm), whereas agreement lesser than 1.0 cm was found for small-sized tumors. Differences between algorithm and radiologist measures were accurate for small-sized tumors with a trend to a small decrease for tumors greater than 5 cm. Therefore, traditional methods for measuring lesion diameter should be complemented non-subjective measurement methods, which would allow a more correct evaluation of the contrast-enhanced areas of HCC according to the mRECIST criteria.

Drag reduction in silica nanochannels induced by graphitic wall coatings

NASA Astrophysics Data System (ADS)

Wagemann, Enrique; Walther, J. H.; Zambrano, Harvey A.

2017-11-01

Transport of water in hydrophilic nanopores is of significant technological and scientific interest. Water flow through hydrophilic nanochannels is known to experience enormous hydraulic resistance. Therefore, drag reduction is essential for the development of highly efficient nanofluidic devices. In this work, we propose the use of graphitic materials as wall coatings in hydrophilic silica nanopores. Specifically, by conducting atomistic simulations, we investigate the flow inside slit and cylindrical silica channels with walls coated with graphene (GE) layers and carbon nanotubes (CNTs), respectively. We develop realistic force fields to simulate the systems of interest and systematically, compare flow rates in coated and uncoated nanochannels under different pressure gradients. Moreover, we assess the effect that GE and CNT translucencies to wettability have on water hydrodynamics in the nanochannels. The influence of channel size is investigated by systematically varying channel heights and nanopore diameters. In particular, we present the computed water density and velocity profiles, volumetric flow rates, slip lengths and flow enhancements, to clearly demonstrate the drag reduction capabilities of graphitic wall coatings. We wish to thank partial funding from CRHIAM Conicyt/ Fondap Project 15130015 and computational support from DTU and NLHPC (Chile).

Synthesis of carbon nanotubes by arc discharge in open air.

PubMed

Paladugu, Mohan Chand; Maneesh, K; Nair, P Kesavan; Haridoss, Prathap

2005-05-01

In this work Carbon nanotubes have been synthesized by arc discharge in open air. A TIG welding ac/dc inverter was used as the power source for arc discharge. During each run of the arc discharge based synthesis, the anode was a low purity (approximately 85% C by weight) graphite rod. The effect of varying the atmosphere on the yield of soot of the carbon nanotube containing carbon soot has been studied. Various soots were produced, purified by oxidation and characterized to confirm formation of carbon nanotubes and their relative quality, using transmission electron microscopy, Raman spectroscopy, and XRD. It was found that the yield of soot formed on the cathode is higher when synthesis is carried out in open air than when carried out in a flowing argon atmosphere. When synthesized in open air, using a 7.2-mm-diameter graphite rod as anode, the yield of soot was around 50% by weight of the graphite consumed. Current and voltage for arcing were at identical starting values in all the experiments. This modified method does not require a controlled atmosphere as in the case of a conventional arc discharge method of synthesis and hence the cost of production may be reduced.

The influence of buoyant forces and volume fraction of particles on the particle pushing/entrapment transition during directional solidification of Al/SiC and Al/graphite composites

NASA Technical Reports Server (NTRS)

Stefanescu, Doru M.; Moitra, Avijit; Kacar, A. Sedat; Dhindaw, Brij K.

1990-01-01

Directional solidification experiments in a Bridgman-type furnace were used to study particle behavior at the liquid/solid interface in aluminum metal matrix composites. Graphite or silicon-carbide particles were first dispersed in aluminum-base alloys via a mechanically stirred vortex. Then, 100-mm-diameter and 120-mm-long samples were cast in steel dies and used for directional solidification. The processing variables controlled were the direction and velocity of solidification and the temperature gradient at the interface. The material variables monitored were the interface energy, the liquid/particle density difference, the particle/liquid thermal conductivity ratio, and the volume fraction of particles. These properties were changed by selecting combinations of particles (graphite or silicon carbide) and alloys (Al-Cu, Al-Mg, Al-Ni). A model which consideres process thermodynamics, process kinetics (including the role of buoyant forces), and thermophysical properties was developed. Based on solidification direction and velocity, and on materials properties, four types of behavior were predicted. Sessile drop experiments were also used to determine some of the interface energies required in calculation with the proposed model. Experimental results compared favorably with model predictions.

The influence of buoyant forces and volume fraction of particles on the particle pushing/entrapment transition during directional solidification of Al/SiC and Al/graphite composites

NASA Astrophysics Data System (ADS)

Stefanescu, Doru M.; Moitra, Avijit; Kacar, A. Sedat; Dhindaw, Brij K.

1990-01-01

Directional solidification experiments in a Bridgman-type furnace were used to study particle behavior at the liquid/solid interface in aluminum metal matrix composites. Graphite or siliconcarbide particles were first dispersed in aluminum-base alloys via a mechanically stirred vortex. Then, 100-mm-diameter and 120-mm-long samples were cast in steel dies and used for directional solidification. The processing variables controlled were the direction and velocity of solidification and the temperature gradient at the interface. The material variables monitored were the interface energy, the liquid/particle density difference, the particle/liquid thermal conductivity ratio, and the volume fraction of particles. These properties were changed by selecting combinations of particles (graphite or silicon carbide) and alloys (Al-Cu, Al-Mg, Al-Ni). A model which considers process thermodynamics, process kinetics (including the role of buoyant forces), and thermophysical properties was developed. Based on solidification direction and velocity, and on materials properties, four types of behavior were predicted. Sessile drop experiments were also used to determine some of the interface energies required in calculation with the proposed model. Experimental results compared favorably with model predictions.

The optimization of CMC concentration as graphite binder on the anode of LiFePO4 battery

NASA Astrophysics Data System (ADS)

Hidayat, S.; Cahyono, T.; Mindara, J. Y.; Riveli, N.; Alamsyah, W.; Rahayu, I.

2017-05-01

Recently, the most dominating power supply on the mobile electronics market are rechargeable Lithium-ion batteries. This is because of a higher energy density and a longer lifetime compared to similar rechargeable battery systems. Graphite is commonly used as anode material in the Lithium-ion batteries, because of its excellent electrochemical characteristics and low cost fabrication. In this paper, we reported the optimization of the concentration of the CMC (carboxymethyl cellulose), that acts as the binder for graphite anode. Based on our experimental results, the best composition of graphite : C : CMC is 90 : 8 : 2 in weight %. Anode with such composition has, based on SEM measurement, a relatively good surface morphology, while it also has relatively high conductivity, about 2.68 S/cm. The result of cyclic voltammogram with a scan rate of 10 mV/s in the voltage range of 0 to 1 Volt, shows the peak of reduction voltage at 0.85 Volts and the peak voltage of oxidation is at -1.5 Volt. The performance of the battery system with LiFePO4 set as the cathode, shows that the working voltage is about 2.67 Volts at 1 mA current-loading, with the efficiency around 47%.

Lithium-ion capacitors using carbide-derived carbon as the positive electrode - A comparison of cells with graphite and Li4Ti5O12 as the negative electrode

NASA Astrophysics Data System (ADS)

Rauhala, Taina; Leis, Jaan; Kallio, Tanja; Vuorilehto, Kai

2016-11-01

The use of carbide-derived carbon (CDC) as the positive electrode material for lithium-ion capacitors (LICs) is investigated. CDC based LIC cells are studied utilizing two different negative electrode materials: graphite and lithium titanate Li4Ti5O12 (LTO). The graphite electrodes are prelithiated before assembling the LICs, and LTO containing cells are studied with and without prelithiation. The rate capability and cycle life stability during 1000 cycles are evaluated by galvanostatic cycling at current densities of 0.4-4 mA cm-2. The CDC shows a specific capacitance of 120 F g-1 in the organic lithium-containing electrolyte, and the LICs demonstrate a good stability over 1000 charge-discharge cycles. The choice of the negative electrode is found to have an effect on the utilization of the CDC positive electrode during cycling and on the specific energy of the device. The graphite/CDC cell delivers a maximum specific discharge energy of 90 Wh kg-1 based on the total mass of active material in the cell. Both the prelithiated and non-prelithiated LTO/CDC cells show a specific energy of around 30 Wh kg-1.

Technology development for phosphoric acid fuel cell powerplant, phase 2

NASA Technical Reports Server (NTRS)

Christner, L.

1981-01-01

The development of materials, cell components, and reformers for on site integrated energy systems is described. Progress includes: (1) heat-treatment of 25 sq cm, 350 sq cm and 1200 sq cm cell test hardware was accomplished. Performance of fuel cells is improved by using this material; (2) electrochemical and chemical corrosion rates of heat-treated and as-molded graphite/phenolic resin composites in phosphoric acid were determined; (3) three cell, 5 in. x 15 in. stacks operated for up to 10,000 hours and 12 in. x 17 in. five cell stacks were tested for 5,000 hours; (4) a three cell 5 in. x 15 in. stack with 0.12 mg Pt/sq cm anodes and 0.25 mg Pt/sq cm cathodes was operated for 4,500 hours; and (5) an ERC proprietary high bubble pressure matrix, MAT-1, was tested for up to 10,000 hours.

High conductivity a-C:N thin films prepared by electron gun evaporation

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

Rebollo-Plata, B.; Lozada-Morales, R.; Palomino-Merino, R.

2007-08-15

By employing electron beam evaporation, amorphous carbon nitride (a-C:N) thin films, with a low nitrogen content ({approx} 1%), were prepared on Si(110) and glass substrates at about 150 deg. C. The source was a graphite target and an ambient of N{sub 2} was introduced into the growing chamber. The source-substrate distance (SSD) was the main parameter that was intentionally varied. Electron dispersion spectroscopy measurements indicate the nitrogen concentration in the layer as {approx} 1%. The dark electrical conductivity ({sigma}) of layers was very sensitive to SSD variation, changing up to six orders of magnitude when this parameter was varied frommore » 10.5 to 23.5 cm. A maximum value of {sigma} = 1 x 10{sup 3} {omega}{sup -1} cm{sup -1} at room temperature was obtained when the SSD was equal to 15.5 cm. We have deduced that, in accordance with the Ferrari-Robertson model (FRM), our samples are localized in the second stage of the amorphization trajectory of FRM. When the SSD increases the C atoms have more probability to collide with N{sub 2} molecules, and the content of nitrogen in the a-C film increases. The amorphization trajectory followed by the films with an SSD increase is from nanocrystalline graphite to amorphous carbon. The changes in the amorphization are due to the nitrogen content in the layers.« less

Fabrication and electrodynamic properties of all-carbon terahertz planar metamaterials by laser direct-write

NASA Astrophysics Data System (ADS)

Komlenok, M. S.; Lebedev, S. P.; Komandin, G. A.; Piqué, A.; Konov, V. I.

2018-03-01

A new approach to THz metamaterial structures is proposed and experimentally realized. It is based on metal-less conductive subwavelength structures on diamond surfaces generated by laser direct-write. 200 nm thick graphitized layers with DC conductivity of 730 Ω-1 cm-1 are formed on a chemical vapour deposited polycrystalline diamond surface after irradiation with an excimer KrF laser (τ l  =  20 ns, λ  =  248 nm). The optical properties of such layers are determined and simulated according to the Drude model. A polarizer with a graphitized subwavelength grating is fabricated and tested in the THz range (0.9-1.2 THz), and shows different transmission losses for orthogonal polarizations.

Heat exchanger-ingot casting/slicing process, phase 1: Silicon sheet growth development for the large area silicon sheet task of the low cost silicon solar array project

NASA Technical Reports Server (NTRS)

Schmid, F.; Khattak, C. P.

1977-01-01

A controlled growth, heat-flow and cool-down process is described that yielded silicon with a high degree of single crystallinity. Even when the seed melted out, very large grains formed. Solar cell samples made from cast material yielded conversion efficiency of over 9%. Representative characterizations of grown silicon demonstrated a dislocation density of less than 100/sq cm and a minority carrier diffusion length of 31 micron. The source of silicon carbide in silicon ingots was identified to be from graphite retainers in contact with silica crucibles. Higher growth rates were achieved with the use of a graphite plug at the bottom of the silica crucible.

Ground-layer plant community responses to even-age and uneven-age silvicultural treatments in Wisconsin northern hardwood forests

Treesearch

Cristel C. Kern; Brian J. Palik; Terry F. Strong

2006-01-01

We evaluated ground-layer plant diversity and community composition in northern hardwood forests among uncut controls and stands managed with even-age or uneven-age silvicultural systems. Even-age treatments included diameter-limit cuttings (20-cm diameter at 30-cm stem height) in 1952 and shelterwood removals in 1964. Uneven-age treatments included three intensities...

Evaluation of right ventricular function in early period following transcatheter closure of atrial septal defect.

PubMed

Ağaç, Mustafa Tarık; Akyüz, Ali Rıza; Acar, Zeydin; Akdemir, Ramazan; Korkmaz, Levent; Kırış, Abdülkadir; Erkuş, Emre; Erkan, Hakan; Celik, Sükrü

2012-03-01

There is limited data on alterations in novel right ventricular (RV) function indices like tricuspid annular plane systolic excursion (TAPSE) and tricuspid annular systolic velocity (TASV) after transcatheter atrial septal defect (ASD) closure. We aimed to evaluate RV function by echocardiography (ECG) with these novel indices in early period in patients with secundum-type ASD that was closed percutaneously. Patients were enrolled to study if they had secundum-type ASD that was suitable for percutaneous closure. Patient population consisted of 4 men and 16 women. Echocardiography was performed before and 1 month after closure. Mean age was 37 ± 16. Mean diameter of ASD and total atrial septum length measured by ECG were 19 ± 6 mm and 49 ± 7 mm, respectively. Mean diameter of defect in transesophageal echocardiography was 20 ± 6 mm. Stretched mean diameter in catheterization was 23 ± 6 mm. One month after closure, there were statistically significant decreases in RV end-diastolic diameters (43.3 ± 10.7 mm vs. 34.9 ± 5.5 mm; P < 0.001), RV/left ventricular (LV) end-diastolic diameter ratio (1.1 ± 0.3 vs. 0.87 ± 0.1; P < 0.001), TASV (16.9 ± 3.2 cm/sec vs. 14.3 ± 3.3 cm/sec; P < 0.05), early diastolic tricuspid annular velocity (15.3 ± 3.1 cm/sec vs. 13.4 ± 2.4 cm/sec P <0.05), late diastolic tricuspid annular velocity (16.2 ± 5.4 cm/sec vs. 14.3 ± 6.3 cm/sec; P < 0.05), and TAPSE (29.9 ± 6.2 mm vs. 22.4 ± 7.4 mm; P < 0.001). LV end-diastolic diameter (38.0 ± 6.9 mm and 40.0 ± 4.5 P < 0.05) was increased, whereas there was no change in LV ejection fraction. Closure of ASD by using Amplatzer devices led to decrease in right heart chamber size, tissue Doppler-derived tricuspid annular velocities and TAPSE in early period. © 2011, Wiley Periodicals, Inc.

The effects of space radiation on a chemically modified graphite-epoxy composite material

NASA Technical Reports Server (NTRS)

Reed, S. M.; Herakovich, C. T.; Sykes, G. F.

1986-01-01

The effects of the space environment on the engineering properties and chemistry of a chemically modified T300/934 graphite-epoxy composite system are characterized. The material was subjected to 1.0 x 10 to the 10th power rads of 1.0 MeV electron irradiation under vacuum to simulate 30 years in geosynchronous earth orbit. Monotonic tension tests were performed at room temperature (75 F/24 C) and elevated temperature (250 F/121 C) on 4-ply unidirectional laminates. From these tests, inplane engineering and strength properties (E sub 1, E sub 2, Nu sub 12, G sub 12, X sub T, Y sub T) were determined. Cyclic tests were also performed to characterize energy dissipation changes due to irradiation and elevated temperature. Large diameter graphite fibers were tested to determine the effects of radiation on their stiffness and strength. No significant changes were observed. Dynamic-mechanical analysis demonstrated that the glass transition temperature was reduced by 50 F(28 C) after irradiation. Thermomechanical analysis showed the occurrence of volatile products generated upon heating of the irradiated material. The chemical modification of the epoxy did not aid in producing a material which was more radiation resistant than the standard T300/934 graphite-epoxy system. Irradiation was found to cause crosslinking and chain scission in the polymer. The latter produced low molecular weight products which plasticize the material at elevated temperatures and cause apparent material stiffening at low stresses at room temperature.

High-density sodium and lithium ion battery anodes from banana peels.

PubMed

Lotfabad, Elmira Memarzadeh; Ding, Jia; Cui, Kai; Kohandehghan, Alireza; Kalisvaart, W Peter; Hazelton, Michael; Mitlin, David

2014-07-22

Banana peel pseudographite (BPPG) offers superb dual functionality for sodium ion battery (NIB) and lithium ion battery (LIB) anodes. The materials possess low surface areas (19-217 m(2) g(-1)) and a relatively high electrode packing density (0.75 g cm(-3) vs ∼1 g cm(-3) for graphite). Tested against Na, BPPG delivers a gravimetric (and volumetric) capacity of 355 mAh g(-1) (by active material ∼700 mAh cm(-3), by electrode volume ∼270 mAh cm(-3)) after 10 cycles at 50 mA g(-1). A nearly flat ∼200 mAh g(-1) plateau that is below 0.1 V and a minimal charge/discharge voltage hysteresis make BPPG a direct electrochemical analogue to graphite but with Na. A charge capacity of 221 mAh g(-1) at 500 mA g(-1) is degraded by 7% after 600 cycles, while a capacity of 336 mAh g(-1) at 100 mAg(-1) is degraded by 11% after 300 cycles, in both cases with ∼100% cycling Coulombic efficiency. For LIB applications BPPG offers a gravimetric (volumetric) capacity of 1090 mAh g(-1) (by material ∼2200 mAh cm(-3), by electrode ∼900 mAh cm(-3)) at 50 mA g(-1). The reason that BPPG works so well for both NIBs and LIBs is that it uniquely contains three essential features: (a) dilated intergraphene spacing for Na intercalation at low voltages; (b) highly accessible near-surface nanopores for Li metal filling at low voltages; and (c) substantial defect content in the graphene planes for Li adsorption at higher voltages. The <0.1 V charge storage mechanism is fundamentally different for Na versus for Li. A combination of XRD and XPS demonstrates highly reversible Na intercalation rather than metal underpotential deposition. By contrast, the same analysis proves the presence of metallic Li in the pores, with intercalation being much less pronounced.

[Study on accuracy of endoscopic polyp size measurement by disposable graduated biopsy forceps].

PubMed

Liu, Ping; Zhang, Xiu; Lin, Hui-ping; Jin, Hei-jing; Leng, Qiang; Zhang, Jin-hao; Zhang, Yang; Yao, Hang; Wu, Kun-lan

2013-12-01

To study the accuracy of endoscopic polyp size measurement by disposable graduated biopsy forceps (DGBF). Accurate gradation of 1 mm was made in the wire of disposable graduated biopsy forceps, which was used to measure the size of tumors under endoscopy. Fifty-eight polyps from 43 patients underwent endoscopy in our department from May to June 2013 were enrolled. Size of polyp was measured and compared among DGBF, routine estimation and direct measurement after resection. The accuracy of polyp size measurement was investigated by four colonoscopists who had finished at least 2000 procedures of colonoscopy. The mean diameter of post-polypectomy measurement was (1.02±0.84) cm. Diameter was less than 1 cm in 36 polyps, 1 to 2 cm in 15, and over 2 cm in 7. The mean diameter of visual estimation was (1.29±1.07) cm, and the difference was significant as compared with actual size (P=0.000). The mean diameter measured by DGBF was (1.02±0.82) cm, and the difference was not significant as compared with actual size (P=0.775). The ratio of visual estimation to actual size was 1.29±0.31, and DGBF estimation to actual size was 1.02±0.11 with significant difference (P=0.000). The accurate rate of DGBF in estimating polyp size was 77.6% (45/58), which was obviously higher as compared to visual estimation [19.0% (11/58), P=0.000]. The accuracy of DGBF as a scale in the estimation of poly size increases as compared to visual estimation.

Mastitis outcomes on pre-ovulatory follicle diameter, estradiol concentrations, subsequent luteal profiles and conception rate in Buffaloes.

PubMed

Mansour, Mohamed Mohsen; Zeitoun, Moustafa M; Hussein, Fekry M

2017-06-01

The objectives of this study was to investigate the outcome of mastitis, in its clinical or subclinical forms, on the mean diameter of pre-ovulatory follicle (POF), plasma estradiol concentration on the day of estrus, subsequent luteal profile and subsequent conception rate in buffaloes. Sixty dairy buffalo (Bubalus bubalus) conducted in this study were divided into three groups {healthy (H), n=20; subclinical mastitis (SCM), n=18; and clinical mastitis (CM), n=22}. Ultrasonography of ovaries revealed that mean diameter of POF was larger (P<0.05) in H buffalo (14.35mm) compared to SCM (12.40mm) and CM (10.25mm). Also, plasma estradiol concentration on the day of estrus was higher (P<0.05) in H buffalo compared to SCM and CM counterparts; 34.95 vs. 32.87 and 27.50pg/ml, respectively. Besides, positive correlation was observed between the POF diameter with plasma estradiol concentration in H, SCM and CM buffaloes (r=0.64, 0.74, 0.72 respectively, P<0.05). Moreover, positive correlations (P<0.01) were found on days 9, 12, 16, and 21 post-ovulation between POF diameter and luteal profile. Thus, the conception rate in H buffalo was higher (P<0.05) compared with SCM and CM counterparts; 55% vs. 38.89 and 18.18%, respectively. In conclusion, mastitis in its clinical or subclinical forms disrupts the functioning of the pre-ovulatory follicle on the day of estrus, associated with low follicular estradiol production, resulting in suppression to subsequent luteal profile leading to substantial decrease in pregnancy consequence of buffaloes. Copyright © 2017 Elsevier B.V. All rights reserved.

Potential of Cerbera odollam as a bio-fungicide for post-harvest pathogen Penicilium digitatum

NASA Astrophysics Data System (ADS)

Singh, Harbant; Yin-Chu, Sue; Al-Samarrai, Ghassan; Syarhabil, Muhammad

2015-05-01

Postharvest diseases due to fungal infection contribute to economic losses in agriculture industry during storage, transportation or in the market. Penicillium digitatum is one of the common pathogen responsible for the postharvest rot in fruits. This disease is currently being controlled by synthetic fungicides such as Guazatine and Imazalil. However, heavy use of fungicides has resulted in environmental pollution, such as residue in fruit that expose a significant risk to human health. Therefore, there is a strong need to develop alternatives to synthetic fungicide to raise customer confidence. In the current research, different concentrations (500 to 3000 ppm) of ethanol extract of Cerbera odollam or commonly known as Pong-pong were compared with Neem and the controls (Positive control/Guazatine; Negative control/DMSO) for the anti-fungicide activity in PDA media contained in 10 cm diameter Petri dishes, using a modification of Ruch and Worf's method. The toxicity (Lc50) of the C.odollam extract was determined by Brine-shrimp test (BST). The results of the research indicated that crude extraction from C.odollam showed the highest inhibition rate (93%) and smallest colony diameter (0.63 cm) at 3000 ppm in vitro compared with Neem (inhibition rate: 88%; colony diameter: 1.33 cm) and control (Positive control/Guazatine inhibition rate: 79%, colony diameter: 1.9 cm; Negative control/DMSO inhibition rate: 0%, colony diameter: 9.2 cm). C.odollam recorded Lc50 value of 5 µg/ml which is safe but to be used with caution (unsafe level: below 2 µg/ml). The above anti-microbial activity and toxicity value results indicate that C.odollam has a potential of being a future bio-fungicide that could be employed as an alternative to synthetic fungicide.

[Indication for limited surgery on small lung cancer tumors measuring 1cm or less in diameter on preoperative computed tomography and long-term results].

PubMed

Togashi, K; Koike, T; Emura, I; Usuda, H

2008-07-01

Non-invasive lung cancers showed a good prognosis after limited surgery. But it is still uncertain about invasive lung cancers. We investigated the indications for limited surgery for small lung cancer tumors measuring 1 cm or less in diameter on preoperative computed tomography (CT). This study retrospectively analyzed of 1,245 patients who underwent complete resection of lung cancer between 1989 and 2004 in our hospital. Sixty-two patients (5%) had tumors measuring 1 cm or less in diameter. The probability of survival was calculated using the Kaplan-Meier method. All diseases were detected by medical checkup, 52 % of the patients were not definitively diagnosed with lung cancer before surgery. Adenocarcinoma was histologically diagnosed in 49 patients (79%). Other histologic types included squamous cell carcinoma (8), large cell carcinoma (1), small cell carcinoma (1), carcinoid (2), and adenosquamous cell carcinoma (1). Fifty-seven patients (92%) showed pathologic stage IA. The other stages were IB (2), IIA (1), and IIIB (2). There were 14 bronchioloalveolar carcinomas (25% of IA diseases). The 5-year survival rates of IA patients were 90%. The 5-year survival rate of patients with tumors measuring 1cm or less diameter was 91% after lobectomy or pneumonectomy, and 90% after wedge resection or segmentectomy. There were 3 deaths from cancer recurrence, while there were no deaths in 14 patients with bronchioloalveolar carcinoma After limited surgery, non-invasive cancer showed good long-term results, while invasive cancer showed a recurrence rate of 2.3% to 79% even though the tumor measured 1 cm or less in diameter on preoperative CT.

Influence of porewidening duration on the template assisted growth of graphitic carbon nitride nanostructures

NASA Astrophysics Data System (ADS)

Suchitra, S. M.; Udayashankar, N. K.

2018-01-01

Porous anodic aluminium oxide (AAO) membranes with a highly ordered pore arrangement are typically used as ideal templates for the synthesis of numerous nanostructured materials. Highly ordered templates gained significant attraction due to the fact that they are readily fabricated through self-organised simple anodization process. In this paper, the effect of different pore-widening treatments on the quality of the pores of the AAO templates prepared with different electrolytes were inspected. Results confirmed that, without altering the interpore distance different pore dimensions and diameters of the AAO templates can be easily achieved by chemical pore widening process at room temperature. Also, graphitic carbon nitride nanorods of different dimension have been fabricated from AAO template after porewidening process. These nanostructures are widely used in case of metal free visible light driven photo catalysis, photo degradation of organic pollutants, photo electric conversion and water splitting applications.

Fluorescent carbon and graphene oxide nanoparticles synthesized by the laser ablation in liquid

NASA Astrophysics Data System (ADS)

Małolepszy, A.; Błonski, S.; Chrzanowska-Giżyńska, J.; Wojasiński, M.; Płocinski, T.; Stobinski, L.; Szymanski, Z.

2018-04-01

The results of synthesis of the fluorescent carbon dots (CDots) from graphite target and reduced graphene oxide (rGO) nanoparticles performed by the nanosecond laser ablation in polyethylene glycol 200 (PEG200) are shown. Two-step laser irradiation (first graphite target, next achieved suspension) revealed a very effective production of CDots. However, the ablation in PEG appeared to be effective with 1064 nm laser pulse in contrast to the ablation with 355 nm laser pulse. In the case of rGO nanoparticles similar laser irradiation procedure was less efficient. In both cases, received nanoparticles exhibited strong, broadband photoluminescence with a maximum dependent on the excitation wavelength. The size distribution for obtained CDots was evaluated using the DLS technique and HRTEM images. The results from both methods show quite good agreement in nanoparticle size estimation although the DLS method slightly overestimates nanoparticle's diameter.

Electron cyclotron resonance plasma reactor for production of carbon stripper foil

NASA Astrophysics Data System (ADS)

Faith Romero, Camille; Kanamori, Keita; Kinsho, Michikazu; Yoshimoto, Masahiro; Wada, Motoi

2018-01-01

A graphite antenna for the production of carbon-containing hydrogen plasmas is being developed to prepare impurity-free charge exchange foils for high-energy synchrotrons. Microwave power at 2.45 GHz frequency drives a coaxial structure antenna with a 12-mm-diameter central graphite cylinder and a tapered surrounding cylinder serving as the ground electrode. The antenna was placed in a linear magnetic field to investigate how it performs under an electron cyclotron resonance (ECR) condition. A clear resonance phenomenon was observed in plasma luminosity, microwave power absorption, and microwave power reflection when the induction current used to produce a linear magnetic field was changed. The antenna realized the best microwave coupling to the plasma with the ECR zone formed 5 mm from the end of the center electrode. The antenna realized stable operation for more than 5 h with 100 W input microwave power and with operating hydrogen pressure from 0.5 to 50 Pa.

Remarkable cycle-activated capacity increasing in onion-like carbon nanospheres as lithium battery anode material

NASA Astrophysics Data System (ADS)

Dong, Jiajun; Zhang, Tong; Zhang, Dong; Zhang, Weiwei; Zhang, Huafang; Liu, Ran; Yao, Mingguang; Liu, Bingbing

2017-01-01

Onion-like carbon nanospheres (OCNSs) with an average diameter of 43 nm were produced on a large scale via a combustion method and examined as an anode material for lithium ion batteries. The OCNSs exhibit a remarkable electrochemical cycling behavior and a capacity much higher than that of graphite. The capacity increases significantly with increasing charge-discharge cycles and reaches a value of 178% of the initial value (from 586 mA h g-1to 1045 mA h g-1) after 200 cycles. Further investigation provides unambiguous experimental evidence that such a remarkable capacity increase is related to the stable onion-like structure of the OCNSs and to the existence of large numbers of disordered/short graphitic fragments, which gradually provide more active sites for Li ion storage. The unique electrochemical performance of OCNSs provides a new way to design a high-performance anode material for rechargeable batteries.

Lightning discharge protection rod

NASA Technical Reports Server (NTRS)

Bryan, Charles F., Jr. (Inventor)

1987-01-01

A system for protecting an in-air vehicle from damage due to a lighning strike is disclosed. It is an extremely simple device consisting of a sacrificial graphite composite rod, approximately the diameter of a pencil with a length of about five inches. The sacrificial rod is constructed with the graphite fibers running axially within the rod in a manner that best provides a path of conduction axially from the trailing edge of an aircraft to the trailing end of the rod. The sacrificial rod is inserted into an attachment hole machined into trailing edges of aircraft flight surfaces, such as a vertical fin cap and attached with adhesive in a manner not prohibiting the conduction path between the rod and the aircraft. The trailing end of the rod may be tapered for aerodynamic and esthetic requirements. This rod is sacrificial but has the capability to sustain several lightning strikes and still provide protection.

Benchmarking of HEU Mental Annuli Critical Assemblies with Internally Reflected Graphite Cylinder

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

Xiaobo, Liu; Bess, John D.; Marshall, Margaret A.

Three experimental configurations of critical assemblies, performed in 1963 at the Oak Ridge Critical Experiment Facility, which are assembled using three different diameter HEU annuli (15-9 inches, 15-7 inches and 13-7 inches) metal annuli with internally reflected graphite cylinder are evaluated and benchmarked. The experimental uncertainties which are 0.00055, 0.00055 and 0.00055 respectively, and biases to the detailed benchmark models which are -0.00179, -0.00189 and -0.00114 respectively, were determined, and the experimental benchmark keff results were obtained for both detailed and simplified model. The calculation results for both detailed and simplified models using MCNP6-1.0 and ENDF VII.1 agree well tomore » the benchmark experimental results with a difference of less than 0.2%. These are acceptable benchmark experiments for inclusion in the ICSBEP Handbook.« less

A new technique for augmentation phalloplasty: albugineal surgery with bilateral saphenous grafts--three years of experience.

PubMed

Austoni, E; Guarneri, A; Cazzaniga, A

2002-09-01

Penile augmentation surgery is a highly controversial issue due to the low level of standardisation of surgical techniques. The aim of the study is to illustrate a new technique to solve the problem of enlarging the penis by means of additive surgery on the albuginea of the corpora cavernosa, guaranteeing a real increase in size of the erect penis. Between 1995 and 1997, 39 patients who requested an increase in the diameter of their penises underwent augmentation phalloplasty with bilateral saphena grafts. The patients considered eligible for surgery were patients with either hypoplasia of the penis or functional penile dysmorphophobia. All the patients included in our study presented normal erection at screening. The average penis diameter in a flaccid state and during erection was found to be 2.1cm (1.6-2.7 cm) and 2.9 cm (2.2-3.7 cm), respectively. Before surgery the patients were informed of the experimental nature of the surgical procedure. The increase in volume of the corpora cavernosa was achieved by applying saphena grafts to longitudinal openings made bilaterally in the albuginea along the whole length of the penis. No major complications and specifically no losses of sensitivity of the penis or erection deficiencies occurred during the post-operative follow-up period. All the patients resumed their sexual activity in 4 months. A measurement of the penile dimensions was carried out 9 months after surgery. No clinical meaningful increases in the diameter of the flaccid penis were documented. The average penis diameter during erection was found to be 4.2 cm (3.4-4.9) with post-surgery increases in diameter varying from 1.1 to 2.1cm (p<0.01). The penile enlargement phalloplasty technique with albuginea surgery suggested by the authors definitely is indicated for increasing the volume of the corpora cavernosa during erection. Albuginea surgery with saphena grafts has been found to be free from aesthetic and functional complications with excellent patient satisfaction.

Effect of facility variation on the acoustic characteristics of three single stream nozzles

NASA Technical Reports Server (NTRS)

Gutierrez, O. A.

1980-01-01

The characteristics of the jet noise produced by three single stream nozzles were investigated statistically at the NASA-Lewis Research Center outdoor jet acoustic facility. The nozzles consisted of a 7.6 cm diameter convergent conical, a 10.2 cm diameter convergent conical and an 8-lobe daisy nozzle with 7.6 cm equivalent diameter flow area. The same nozzles were tested previously at cold flow conditions in other facilities such as the Royal Aircraft Establishment (RAE) 7.3 m acoustic wind tunnel. The acoustic experiments at NASA covered pressure ratios from 1.4 to 2.5 at total temperatures of 811 K and ambient. The data obtained with four different microphone arrays are compared. The results are also compared with data taken at the RAE facility and with a NASA prediction procedure.

Optimization of Acetalated Dextran-Based Nanocomposite Microparticles for Deep Lung Delivery of Therapeutics via Spray-Drying.

PubMed

Wang, Zimeng; Meenach, Samantha A

2017-12-01

Nanocomposite microparticle (nCmP) systems exhibit promising potential in the application of therapeutics for pulmonary drug delivery. This work aimed at identifying the optimal spray-drying condition(s) to prepare nCmP with specific drug delivery properties including small aerodynamic diameter, effective nanoparticle (NP) redispersion upon nCmP exposure to an aqueous solution, high drug loading, and low water content. Acetalated dextran (Ac-Dex) was used to form NPs, curcumin was used as a model drug, and mannitol was the excipient in the nCmP formulation. Box-Behnken design was applied using Design-Expert software for nCmP parameter optimization. NP ratio (NP%) and feed concentration (Fc) are significant parameters that affect the aerodynamic diameters of nCmP systems. NP% is also a significant parameter that affects the drug loading. Fc is the only parameter that influenced the water content of the particles significantly. All nCmP systems could be completely redispersed into the parent NPs, indicating that none of the factors have an influence on this property within the design range. The optimal spray-drying condition to prepare nCmP with a small aerodynamic diameter, redispersion of the NPs, low water content, and high drug loading is 80% NP%, 0.5% Fc, and an inlet temperature lower than 130°C. Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Morphological control of three-dimensional carbon nanotube anode for high-capacity lithium-ion battery

NASA Astrophysics Data System (ADS)

Kang, Chiwon; Lee, Hoo-Jeong

2018-05-01

In this paper, we report the results of modulating the processing conditions (mainly, temperature) of a two-step method consisting of sputtering deposition of a Ni catalytic layer and chemical vapor deposition (CVD) of carbon nanotubes (CNTs) on a three-dimensional (3D)-structured Cu mesh to control the morphology of CNTs for advanced Li-ion battery (LIB) applications. We disclosed that CNT growth at a low temperature (700 °C) produced small-diameter CNTs (CNT_S) with an average diameter of ∼20 nm, while that at a high temperature (750 °C) produced large-diameter CNTs (CNT_L) with an average diameter of 200–300 nm. The high-resolution transmission electron microscopy (HR-TEM) and Raman analyses manifested poorly crystalline CNTs for both samples. CNTS showed a specific capacity of 476 mAh g‑1, which is ∼176% superior to that of CNTL (271 mAh g‑1) and ∼128% higher than the theoretical capacity of the state-of-the-art graphites and recently reported nanostructured carbon-based anode materials.

Design study of imaging techniques for the Starprobe mission

NASA Technical Reports Server (NTRS)

Bottema, M.

1981-01-01

A 10 cm aperture, off-axis aplanatic gregorian telescope is investigated as a candidate instrument for imaging from Starprobe in the 115 nm to 900 nm wavelength range. Focal lengths of 300 cm (f/30) and 150 cm (f/15) are compared in terms of optical performance, compatibility with the Starprobe spacecraft and response to the thermal environment in a 20-hour time interval, centered on perihelion. Ultraviolet/visible imaging from Starprobe concluded should be technically feasible. A 10 cm aperture telescope with focal length close to 300 cm is recommended for further study. This instrument should be capable of a detector-limited angular resoluton of about 2 arc sec. The estimated overall dimensions should not exceed 105 cm by 40 cm by 25 cm and its mass be less than 28 kg. The recommended concept assumes solid blank ULE mirrors, a graphite-epoxy optical bench, and an aluminum thermal enclosure, covered with multilayer insulation. These materials must be carefully selected to minimize the risk of UV photopolymerization of contaminants at the mirror surfaces during observtions.

The Effect of Stone Composition on the Efficacy of Retrograde Intrarenal Surgery: Kidney Stones 1 - 3 cm in Diameter.

PubMed

Xue, Yuquan; Zhang, Peng; Yang, Xiaojie; Chong, Tie

2015-05-01

The goal of this study was to analyze the effect of stone composition on the efficacy of retrograde intrarenal surgery (RIRS) with kidney stones of 1-3 cm, 1-2 cm, and 2-3 cm in diameter. We undertook a retrospective analysis of 74 patients with kidney stones who underwent RIRS. The patients were divided into two groups based on stone composition: Group I (n=47) (calcium oxalate monohydrate and calcium phosphate) was the hard to fragment stone group and group II (n=27) (calcium oxalate dihydrate, magnesium ammonium phosphate, and uric acid) was the easy to fragment stone group. Forty-six patients with kidney stones 1 to 2 cm in diameter were divided into group A (n=30) (smaller than 20 mm, hard to fragment stones) and group B (n=16) (smaller than 20 mm, easy to fragment stones). Twenty-eight patients with stones 2 to 3 cm in diameter were divided into group C (n=17) (larger than 20 mm, hard to fragment stones) and group D (n=11) (larger than 20 mm, easy-to-crush stones). The stone clearance rates of group I and group II were 66.0% and 88.9%, respectively (P<0.05). The stone clearance rates of group A and group B were 73.3% and 100% (P<0.05). The stone clearance rates of group C and group D were 52.9% and 72.7%, respectively. Stone composition has a significant impact on the efficacy of RIRS in the management of 1 to 3 cm kidney stones. For 2-3 cm calcium oxalate dihydrate stones, uric acid stones, and magnesium ammonium phosphate stones, the outcome of RIRS treatment was relatively good, and RIRS is recommended.

77 FR 15798 - Notice of Intent To Repatriate Cultural Items: San Francisco State University, San Francisco, CA

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-16

... height and 10.5 cm in diameter and is made of deer grass, sedge, redbud and bracken fern root. There are... deer grass, saw grass, redbud and bracken fern root. A tag attached to the basket was labeled... height with a maximum diameter of 18 cm and is made of deer grass, sedge, redbud and bracken fern root. A...

Flow rate of some pharmaceutical diluents through die-orifices relevant to mini-tableting.

PubMed

Kachrimanis, K; Petrides, M; Malamataris, S

2005-10-13

The effects of cylindrical orifice length and diameter on the flow rate of three commonly used pharmaceutical direct compression diluents (lactose, dibasic calcium phosphate dihydrate and pregelatinised starch) were investigated, besides the powder particle characteristics (particle size, aspect ratio, roundness and convexity) and the packing properties (true, bulk and tapped density). Flow rate was determined for three different sieve fractions through a series of miniature tableting dies of different orifice diameter (0.4, 0.3 and 0.2 cm) and thickness (1.5, 1.0 and 0.5 cm). It was found that flow rate decreased with the increase of the orifice length for the small diameter (0.2 cm) but for the large diameter (0.4 cm) was increased with the orifice length (die thickness). Flow rate changes with the orifice length are attributed to the flow regime (transitional arch formation) and possible alterations in the position of the free flowing zone caused by pressure gradients arising from the flow of self-entrained air, both above the entrance in the die orifice and across it. Modelling by the conventional Jones-Pilpel non-linear equation and by two machine learning algorithms (lazy learning, LL, and feed-forward back-propagation, FBP) was applied and predictive performance of the fitted models was compared. It was found that both FBP and LL algorithms have significantly higher predictive performance than the Jones-Pilpel non-linear equation, because they account both dimensions of the cylindrical die opening (diameter and length). The automatic relevance determination for FBP revealed that orifice length is the third most influential variable after the orifice diameter and particle size, followed by the bulk density, the difference between bulk and tapped densities and the particle convexity.

From tissue iron retention to low systemic haemoglobin levels, new pathophysiological biomarkers of human abdominal aortic aneurysm.

PubMed

Martinez-Pinna, R; Lindholt, J S; Madrigal-Matute, J; Blanco-Colio, L M; Esteban-Salan, M; Torres-Fonseca, M M; Lefebvre, T; Delbosc, S; Laustsen, J; Driss, F; Vega de Ceniga, M; Gouya, L; Weiss, G; Egido, J; Meilhac, O; Michel, J-B; Martin-Ventura, J

2014-07-03

Iron deposits are observed in tissue of abdominal aortic aneurysm (AAA) patients, although the underlying mechanisms are not completely elucidated. Therefore we explored circulating markers of iron metabolism in AAA patients, and tested if they could serve as biomarkers of AAA. Increased red blood cell (RBC)-borne iron retention and transferrin, transferrin receptor and ferritin expression was observed in AAA tissue compared to control aorta (immunohistochemistry and western blot). In contrast, decreased circulating iron, transferrin, mean corpuscular haemoglobin concentration (MCHC) and haemoglobin concentration, along with circulating RBC count, were observed in AAA patients (aortic diameter >3 cm, n=114) compared to controls (aortic diameter <3 cm, n=88) (ELISA), whereas hepcidin concentrations were increased in AAA subjects (MS/MS assay). Moreover, iron, transferrin and haemoglobin levels were negatively, and hepcidin positively, correlated with aortic diameter in AAA patients. The association of low haemoglobin with AAA presence or aortic diameter was independent of specific risk factors. Moreover, MCHC negatively correlated with thrombus area in another cohort of AAA patients (aortic diameter 3-5 cm, n=357). We found that anaemia was significantly more prevalent in AAA patients (aortic diameter >5 cm, n=8,912) compared to those in patients with atherosclerotic aorto-iliac occlusive disease (n=17,737) [adjusted odds ratio=1.77 (95% confidence interval: 1.61;1.93)]. Finally, the mortality risk among AAA patients with anaemia was increased by almost 30% [adjusted hazard ratio: 1.29 (95% confidence interval: 1.16;1.44)] as compared to AAA subjects without anaemia. In conclusion, local iron retention and altered iron recycling associated to high hepcidin and low transferrin systemic concentrations could lead to reduced circulating haemoglobin levels in AAA patients. Low haemoglobin levels are independently associated to AAA presence and clinical outcome.

Nanofluid optical property characterization: towards efficient direct absorption solar collectors.

PubMed

Taylor, Robert A; Phelan, Patrick E; Otanicar, Todd P; Adrian, Ronald; Prasher, Ravi

2011-03-15

Suspensions of nanoparticles (i.e., particles with diameters < 100 nm) in liquids, termed nanofluids, show remarkable thermal and optical property changes from the base liquid at low particle loadings. Recent studies also indicate that selected nanofluids may improve the efficiency of direct absorption solar thermal collectors. To determine the effectiveness of nanofluids in solar applications, their ability to convert light energy to thermal energy must be known. That is, their absorption of the solar spectrum must be established. Accordingly, this study compares model predictions to spectroscopic measurements of extinction coefficients over wavelengths that are important for solar energy (0.25 to 2.5 μm). A simple addition of the base fluid and nanoparticle extinction coefficients is applied as an approximation of the effective nanofluid extinction coefficient. Comparisons with measured extinction coefficients reveal that the approximation works well with water-based nanofluids containing graphite nanoparticles but less well with metallic nanoparticles and/or oil-based fluids. For the materials used in this study, over 95% of incoming sunlight can be absorbed (in a nanofluid thickness ≥10 cm) with extremely low nanoparticle volume fractions - less than 1 × 10-5, or 10 parts per million. Thus, nanofluids could be used to absorb sunlight with a negligible amount of viscosity and/or density (read: pumping power) increase.

Nanofluid optical property characterization: towards efficient direct absorption solar collectors

PubMed Central

2011-01-01

Suspensions of nanoparticles (i.e., particles with diameters < 100 nm) in liquids, termed nanofluids, show remarkable thermal and optical property changes from the base liquid at low particle loadings. Recent studies also indicate that selected nanofluids may improve the efficiency of direct absorption solar thermal collectors. To determine the effectiveness of nanofluids in solar applications, their ability to convert light energy to thermal energy must be known. That is, their absorption of the solar spectrum must be established. Accordingly, this study compares model predictions to spectroscopic measurements of extinction coefficients over wavelengths that are important for solar energy (0.25 to 2.5 μm). A simple addition of the base fluid and nanoparticle extinction coefficients is applied as an approximation of the effective nanofluid extinction coefficient. Comparisons with measured extinction coefficients reveal that the approximation works well with water-based nanofluids containing graphite nanoparticles but less well with metallic nanoparticles and/or oil-based fluids. For the materials used in this study, over 95% of incoming sunlight can be absorbed (in a nanofluid thickness ≥10 cm) with extremely low nanoparticle volume fractions - less than 1 × 10-5, or 10 parts per million. Thus, nanofluids could be used to absorb sunlight with a negligible amount of viscosity and/or density (read: pumping power) increase. PMID:21711750

Ultrasonography of umbilical structures in clinically normal foals.

PubMed

Reef, V B; Collatos, C

1988-12-01

The umbilical arteries, urachus, and umbilical vein were scanned ultrasonographically in 13 clinically normal foals that ranged in age from 6 hours to 4 weeks. Sonograms were obtained using a 7.5-MHz sector scanner transducer placed across the midline of the ventral portion of the foal's abdominal wall. The umbilical vein was scanned from the umbilical stalk to its entrance into the hepatic parenchyma. The mean (+/- SD) diameter of the umbilical vein was 0.61 +/- 0.20 cm immediately cranial to the umbilical stalk, 0.52 +/- 0.19 cm midway between the umbilicus and liver, and 0.6 +/- 0.19 cm at the liver. The urachus and umbilical arteries were scanned from the umbilical stalk to the apex of the urinary bladder and had a mean total diameter of 1.75 +/- 0.37 cm at the bladder apex. The umbilical arteries also were scanned along either side of the bladder and had a mean diameter of 0.85 +/- 0.21 cm. These measurements and the ultrasonographic appearance of the internal umbilical structures from clinically normal foals can be used as references to diagnose abnormalities of the umbilical structures in neonatal foals.

Microwave plasma chemical synthesis of nanocrystalline carbon film structures and study their properties

NASA Astrophysics Data System (ADS)

Bushuev, N.; Yafarov, R.; Timoshenkov, V.; Orlov, S.; Starykh, D.

2015-08-01

The self-organization effect of diamond nanocrystals in polymer-graphite and carbon films is detected. The carbon materials deposition was carried from ethanol vapors out at low pressure using a highly non-equilibrium microwave plasma. Deposition processes of carbon film structures (diamond, graphite, graphene) is defined. Deposition processes of nanocrystalline structures containing diamond and graphite phases in different volume ratios is identified. The solid film was obtained under different conditions of microwave plasma chemical synthesis. We investigated the electrical properties of the nanocrystalline carbon films and identified it's from various factors. Influence of diamond-graphite film deposition mode in non-equilibrium microwave plasma at low pressure on emission characteristics was established. This effect is justified using the cluster model of the structure of amorphous carbon. It was shown that the reduction of bound hydrogen in carbon structures leads to a decrease in the threshold electric field of emission from 20-30 V/m to 5 V/m. Reducing the operating voltage field emission can improve mechanical stability of the synthesized film diamond-graphite emitters. Current density emission at least 20 A/cm2 was obtained. Nanocrystalline carbon film materials can be used to create a variety of functional elements in micro- and nanoelectronics and photonics such as cold electron source for emission in vacuum devices, photonic devices, cathodoluminescent flat display, highly efficient white light sources. The obtained graphene carbon net structure (with a net size about 6 μm) may be used for the manufacture of large-area transparent electrode for solar cells and cathodoluminescent light sources

Nanodiamond Formation at the Lithogenesis and Low-Stages of Regional Metamorphism

NASA Astrophysics Data System (ADS)

Simakov, S. K.; Melnik, N. N.; Vyalov, V. I.

2018-02-01

Samples of gilsonite from Adzharia, anthraxolite and graphite of coal from Taimyr, shungite from Karelia, and anthracite from Donbass are studied using Raman spectroscopy. Peaks at 1600 cm-1, indicating the presence of nanographite, are recorded in all samples. The anthracite sample from Donbass, 1330 cm-1, corresponds to the sp 3-line of carbon hybridization conforming to a nanodiamond. It is concluded that in nature diamonds can be formed at late stages of lithogenesis (catagensis, metagenesis), and for coals, it can occur at the zeolite stage of regional metamorphism of rocks, before the green schist stage.

Image mottle in abdominal CT.

PubMed

Ende, J F; Huda, W; Ros, P R; Litwiller, A L

1999-04-01

To investigate image mottle in conventional CT images of the abdomen as a function of radiographic technique factors and patient size. Water-filled phantoms simulating the abdomens of adult (32 cm in diameter) and pediatric (16 cm in diameter) patients were used to investigate image mottle in CT as a function of x-ray tube potential and mAs. CT images from 39 consecutive patients with noncontrast liver scans and 49 patients with iodine contrast scans were analyzed retrospectively. Measurements were made of the mean liver parenchyma Hounsfield unit value and the corresponding image mottle. For a given water phantom and x-ray tube potential, image mottle was proportional to the mAs-0.5. Increasing the phantom diameter from 16 cm (pediatric) to 32 cm increased the mottle by a factor of 2.4, and increasing the x-ray tube potential from 80 kVp to 140 kVp reduced the mottle by a factor of 2.5. All patients were scanned at 120 kVp, with no correlation between patient size and the x-ray tube mAs. The mean mottle level was 7.8 +/- 2.2 and 10.0 +/- 2.5 for the noncontrast and contrast studies, respectively. An increase in patient diameter of 3 cm would require approximately 65% more mAs to maintain the same level of image mottle. The mottle in abdominal CT images may be controlled by adjusting radiographic technique factors, which should be adjusted to take into account the size of the patient undergoing the examination.

Outstanding electrochemical performance of a graphene-modified graphite felt for vanadium redox flow battery application

NASA Astrophysics Data System (ADS)

González, Zoraida; Flox, Cristina; Blanco, Clara; Granda, Marcos; Morante, Juan R.; Menéndez, Rosa; Santamaría, Ricardo

2017-01-01

The development of more efficient electrode materials is essential to obtain vanadium redox flow batteries (VRFBs) with enhanced energy densities and to make these electrochemical energy storage devices more competitive. A graphene-modified graphite felt synthesized from a raw graphite felt and a graphene oxide water suspension by means of electrophoretic deposition (EPD) is investigated as a suitable electrode material in the positive side of a VRFB cell by means of cyclic voltammetry, impedance spectroscopy and charge/discharge experiments. The remarkably enhanced performance of the resultant hybrid material, in terms of electrochemical activity and kinetic reversibility towards the VO2+/VO2+, and mainly the markedly high energy efficiency of the VRFB cell (c.a. 95.8% at 25 mA cm-2) can be ascribed to the exceptional morphological and chemical characteristics of this tailored material. The 3D-architecture consisting of fibers interconnected by graphene-like sheets positively contributes to the proper development of the vanadium redox reactions and so represents a significant advance in the design of effective electrode materials.

Flower-like Copper Cobaltite Nanosheets on Graphite Paper as High-Performance Supercapacitor Electrodes and Enzymeless Glucose Sensors.

PubMed

Liu, Shude; Hui, K S; Hui, K N

2016-02-10

Flower-like copper cobaltite (CuCo2O4) nanosheets anchored on graphite paper have been synthesized using a facile hydrothermal method followed by a postannealing treatment. Supercapacitor electrodes employing CuCo2O4 nanosheets exhibit an enhanced capacitance of 1131 F g(-1) at a current density of 1 A g(-1) compared with previously reported supercapacitor electrodes. The CuCo2O4 electrode delivers a specific capacitance of up to 409 F g(-1) at a current density of as high as 50 A g(-1), and a good long-term cycling stability, with 79.7% of its specific capacitance retained after 5000 cycles at 10 A g(-1). Furthermore, the as-prepared CuCo2O4 nanosheets on graphite paper can be fabricated as electrodes and used as enzymeless glucose sensors, which exhibit good sensitivity (3.625 μA μM(-1) cm(-2)) and an extraordinary linear response ranging up to 320 μM with a low detection limit (5 μM).

Graphitic biochar as a cathode electrocatalyst support for microbial fuel cells.

PubMed

Huggins, Tyler M; Pietron, Jeremy J; Wang, Heming; Ren, Zhiyong Jason; Biffinger, Justin C

2015-11-01

Graphitic biochar (BC) was generated using high temperature gasification and alkaline post-treatment (BCw) of wood-based biomass. The BCw was evaluated as a manganese oxide electrocatalytic support (MnO/BCw) and microbial fuel cell (MFC) air cathode. Nano-structured MnO2 crystals were successfully immobilized on biomass-based graphitic sheets and characterized using physical, chemical, and electrochemical analyses. Cyclic voltammetry of MnO/BCw/Nafion inks showed electrochemical features typical of β-MnO2 with a current density of 0.9 mA cm(-2). BC showed satisfactory maximum power densities of 146.7 mW m(-2) (BCw) and 187.8 W m(-2) (MnO/BCw), compared with Vulcan Carbon (VC) (156.8 mW m(-2)) and manganese oxide VC composites (MnO/VC) (606.1 mW m(-2)). These materials were also tested as oxygen reduction reaction (ORR) catalysts for single chamber MFCs inoculated with anaerobic sludge. Our results demonstrate that BC can serve as an effective, low cost, and scalable material for MFC application. Published by Elsevier Ltd.

Purpura

MedlinePlus

Blood spots; Skin hemorrhages ... and 10 mm (millimeters) in diameter. When purpura spots are less than 4 mm in diameter, they are called petechiae . Purpura spots larger than 1 cm (centimeter) are called ecchymoses. ...

Large area Czochralski silicon

NASA Technical Reports Server (NTRS)

Rea, S. N.; Gleim, P. S.

1977-01-01

The overall cost effectiveness of the Czochralski process for producing large-area silicon was determined. The feasibility of growing several 12 cm diameter crystals sequentially at 12 cm/h during a furnace run and the subsequent slicing of the ingot using a multiblade slurry saw were investigated. The goal of the wafering process was a slice thickness of 0.25 mm with minimal kerf. A slice + kerf of 0.56 mm was achieved on 12 cm crystal using both 400 grit B4C and SiC abrasive slurries. Crystal growth experiments were performed at 12 cm diameter in a commercially available puller with both 10 and 12 kg melts. Several modifications to the puller hoz zone were required to achieve stable crystal growth over the entire crystal length and to prevent crystallinity loss a few centimeters down the crystal. The maximum practical growth rate for 12 cm crystal in this puller design was 10 cm/h, with 12 to 14 cm/h being the absolute maximum range at which melt freeze occurred.

Scaling law in free walking of mice in circular open fields of various diameters.

PubMed

Shoji, Hiroto

2016-03-01

Open-field tests are routinely used to study locomotor activity in rodents. I studied the effects of apparatus size on rodent locomotor activity, specifically with respect to how resting and walking periods are interwoven. I explored the open-field behavior of mice utilizing circular open fields of various diameters. When the diameter of the test apparatus was greater than 75 cm, the durations of the resting and moving periods of free walking behavior obeyed bounded power-law distribution functions. I found that the properties of the scaling exponents and model selection became similar for test apparatus diameters greater than 75 cm. These results can provide a guide for the selection of the size of the test apparatus for use in the study of the open-field behavior of rodents.

The development of an 85-kW (thermal) steam Rankine solar receiver

NASA Technical Reports Server (NTRS)

Wright, C. C.; Bank, H.

1981-01-01

The receiver is a once-through monotube boiler designed for steam/electric and process steam applications at pressures up to 17.24 MPa (2500 psia) and temperatures up to 704 C (1300 F). The unit is 76.2 cm (30.0 in.) in diameter and 95.8 cm (37.7 in.) in length; it weighs 220 kg (485 lb). Its heat transfer surface, which is 45.7 cm (18 in.) in diameter by 57 cm (22.4 in.) long, is an Inconel 625, cylindrical, tube-coil assembly composed of primary and reheat sections. A test unit was successfully operated at up to 6.9 MPa (1000 psia) and 704 C (1300 F) with solar input from a 11-m-dia parabolic dish concentrator.

Multipolar radiofrequency ablation with internally cooled electrodes: experimental study in ex vivo bovine liver with mathematic modeling.

PubMed

Clasen, Stephan; Schmidt, Diethard; Boss, Andreas; Dietz, Klaus; Kröber, Stefan M; Claussen, Claus D; Pereira, Philippe L

2006-03-01

To evaluate the size and geometry of thermally induced coagulation by using multipolar radiofrequency (RF) ablation and to determine a mathematic model to predict coagulation volume. Multipolar RF ablations (n = 80) were performed in ex vivo bovine livers by using three internally cooled bipolar applicators with two electrodes on the same shaft. Applicators were placed in a triangular array (spacing, 2-5 cm) and were activated in multipolar mode (power output, 75-225 W). The size and geometry of the coagulation zone, together with ablation time, were assessed. Mathematic functions were fitted, and the goodness of fit was assessed by using r(2). Coagulation volume, short-axis diameter, and ablation time were dependent on power output and applicator distance. The maximum zone of coagulation (volume, 324 cm(3); short-axis diameter, 8.4 cm; ablation time, 193 min) was induced with a power output of 75 W at an applicator distance of 5 cm. Coagulation volume and ablation time decreased as power output increased. Power outputs of 100-125 W at applicator distances of 2-4 cm led to a reasonable compromise between coagulation volume and ablation time. At 2 cm (100 W), coagulation volume, short-axis diameter, and ablation time were 66 cm(3), 4.5 cm, and 19 min, respectively; at 3 cm (100 W), 90 cm(3), 5.2 cm, and 22 min, respectively; at 4 cm (100 W), 132 cm(3), 6.1 cm, and 27 min, respectively; at 2 cm (125 W), 56 cm(3), 4.2 cm, and 9 min, respectively; at 3 cm (125 W), 73 cm(3), 4.9 cm, and 12 min, respectively; and at 4 cm (125 W), 103 cm(3), 5.5 cm, and 16 min, respectively. At applicator distances of 4 cm (>125 W) and 5 cm (>100 W), the zones of coagulation were not confluent. Coagulation volume (r(2) = 0.80) and RF ablation time (r(2) = 0.93) were determined by using the mathematic model. Multipolar RF ablation with three bipolar applicators may produce large volumes of confluent coagulation ex vivo. A compromise is necessary between prolonged RF ablations at lower power outputs, which produce larger volumes of coagulation, and faster RF ablations at higher power outputs, which produce smaller volumes of coagulation. Copyright RSNA, 2006.

Triamcinolone Acetonide Selectively Inhibits Angiogenesis in Small Blood Vessels and Decreases Vessel Diameter within the Vascular Tree

NASA Technical Reports Server (NTRS)

McKay, Terri L.; Gredeon, Dan J.; Vickerman, Mary B.; Hylton, alan G.; Ribita, Daniela; Olar, Harry H.; Kaiser, Peter K.; Parsons-Wingerter, Patricia

2007-01-01

The steroid triamcinolone acetonide (TA) is a potent anti-angiogenesis drug used to treat retinal vascular diseases that include diabetic retinopathy, vascular occlusions and choroidal neovascularization. To quantify the effects of TA on branching morphology within the angiogenic microvascular tree of the chorioallantoic membrane (CAM) of quail embryos. Increasing concentrations of TA (0-16 ng/ml) were applied topically on embryonic day 7 (E7) to the chorioallantoic membrane (CAM) of quail embryos cultured in Petri dishes, and incubated for an additional 24 or 48 hours until fixation. Binary (black/white) microscopic images of arterial end points were quantified by VESGEN software (for Generational Analysis of Vessel Branching) to obtain major vascular parameters that include vessel diameter (Dv), fractal dimension (Df), tortuosity (Tv) and densities of vessel area, length, number and branch point (Av, Lv, Nv and Brv). For assessment of specific changes in vascular morphology induced by TA, the VESGEN software automatically segmented the vascular tree into branching generations (G1...G10) according to changes in vessel diameter and branching. Vessel density decreased significantly up to 34% as the function of increasing concentration of TA according to Av, Lv, Brv, Nv and Df. TA selectively inhibited the growth of new, small vessels, because Lv decreased from 13.14plus or minus 0.61 cm/cm2 for controls to 8.012 plus or minus 0.82 cm/cm2 at 16 ng TA/ml in smaller branching generations (G7-G10), and for Nv from 473.83 plus or minus 29.85 cm(-)2 to 302.32 plus or minus 33.09 cm-()2. In contrast, vessel diameter (Dv) decreased throughout the vascular tree (G1-G10).

[The sural medial perforator flap: Anatomical bases, surgical technique and indications in head and neck reconstruction].

PubMed

Struk, S; Schaff, J-B; Qassemyar, Q

2018-04-01

The medial sural artery perforator (MSAP) flap is defined as a thin cutaneo-adipose perforator flap harvested on the medial aspect of the leg. The aims of this study were to describe the anatomical basis as well as the surgical technique and discuss the indications in head and neck reconstructive surgery. We harvested 10 MSAP flap on 5 fresh cadavers. For each case, the number and the location of the perforators were recorded. For each flap, the length of pedicle, the diameter of source vessels and the thickness of the flap were studied. Finally, we performed a clinical application of a MSAP flap. A total of 23 perforators with a diameter superior than 1mm were dissected on 10 legs. The medial sural artery provided between 1 and 4 musculocutaneous perforators. Perforators were located in average at 10.3cm±2cm from the popliteal fossa and at 3.6cm±1cm from the median line of the calf. The mean pedicle length was 12.1cm±2.5cm. At its origin, the source artery diameter was 1.8mm±0.25mm and source veins diameters were 2.45mm±0.9mm in average. There was no complication in our clinical application. This study confirms the reliability of previous anatomical descriptions of the medial sural artery perforator flap. This flap was reported as thin and particularly adapted for oral cavity reconstruction and for facial or limb resurfacing. Sequelae might be reduced as compared to those of the radial forearm flap with comparable results. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Graphene Oxide from Carbon Rod Waste

NASA Astrophysics Data System (ADS)

Rahmawati, F.; Prasasti, B. L. W.; Mudjijono, M.

2018-03-01

Carbon rods extracted from Zn-C primary battery waste was used as raw material for graphene oxide (GO) synthesis. The synthesis used a modified Hummers method by providing potassium permanganate-sulfuric acid as the oxidizing agent. XRD analysis confirms a significant change between the graphite waste pattern and the produced graphene oxide pattern. A major peak at 2θ 27 ° which present in the graphite waste pattern is disappeared after it converts to the product, as well as a broad peak under 25 ° referring the presence of amorphous carbon. A broad peak at low angle of 12.02 ° dominantly present in the prepared GO pattern as a characteristic peak of GO. Meanwhile, some small peaks at 2θ of 17.76 °, 28.58 °, and 37.28 ° confirming the presence of manganese oxide which was used as oxidizing agent. A sharp peak at 1700 – 1500 cm-1 in the FT-IR spectrum indicates the presence of –C=O group, and at 1600 cm-1 refers to –C=C group. It confirms that this research has produced the targeted GO. Even though, the purity is need to be enhanced by removing the rest of oxidizing agent that still exist in the material.

Experimental investigation of graphite/polyimide sandwich panels in edgewise compression

NASA Technical Reports Server (NTRS)

Camarda, C. J.

1980-01-01

The local and general buckling behavior of graphite/polyimide sandwich panels simply supported along all four edges and loaded in uniaxial edgewise compression was investigated. Material properties of adhesive and facings were determined from flatwise tension and sandwich beam flexure tests. Tensile and compressive material properties of the facings were determined at 116, R.T., and 589 K (-250, R.T., and 600 F) using the sandwich beam flexure test method. Results indicate that Gr/PI is a usable structural material for short term use at temperatures as high as 589 K (600 F). Buckling specimens were 30.5 X 33.0 cm (12 x 13 in.), had quasi-isotropic symmetric facings and a glass/polyimide honeycomb core. Core thicknesses varied and three panels of each thickness were tested in edgewise compression at room temperature to investigate failure modes and corresponding buckling formulas. Specimens 0.635 cm (0.25 in.) thick failed by overall buckling at loads close to the analytically predicted buckling load; all other panels failed by face wrinkling. Results of the winkling tests indicate that several buckling formulas were unconservative and therefore not suitable for design purposes; recommended wrinkling equations are presented.

Catalytic behavior of a palladium doped binder free paper based cobalt electrode in electroreduction of hydrogen peroxide

NASA Astrophysics Data System (ADS)

Zhang, Dongming; Ye, Ke; Cao, Dianxue; Yin, Jinling; Cheng, Kui; Wang, Bin; Xu, Yang; Wang, Guiling

2015-01-01

A piece of flexible and conductive A4 paper is prepared by coating a layer of graphite with a normal 8B pencil. Then, Co nano-plates and Pd are assembled by a simple electrodeposition and chemical-reduction methods on the surface of the electrified paper, respectively. The as-prepared paper substrate/graphite-Co film-Pd (PG-CoPd) electrode is characterized by scanning electron microscopy equipped with energy dispersive X-ray spectrometer, transmission electron microscope and X-ray diffractometer. The catalytic activity of the PG-CoPd electrode for H2O2 electroreduction is investigated by means of cyclic voltammetry and chronoamperometry. The preparation process of the PG-CoPd electrode does not use any binder and it exhibits a three dimensional (3D) nano structure, high stability and good electric conductivity. The mass of the Pd in PG-CoPd is about 0.0535 mg cm-2 and the reduction current density reaches to -4.30 A cm-2 mg-1 in 1 mol dm-3 NaOH and 1.4 mol dm-3 H2O2 at -0.5 V, which is higher than our previous reports of Au/Pd modified Co electrode.

An assessment of the utility of a non-metric digital camera for measuring standing trees

Treesearch

Neil Clark; Randolph H. Wynne; Daniel L. Schmoldt; Matthew F. Winn

2000-01-01

Images acquired with a commercially available digital camera were used to make measurements on 20 red oak (Quercus spp.) stems. The ranges of diameter at breast height (DBH) and height to a 10 cm upper-stem diameter were 16-66 cm and 12-20 m, respectively. Camera stations located 3, 6, 9, 12, and 15 m from the stem were studied to determine the best distance to be...

A mechanical property and stress corrosion evaluation of 431 stainless steel alloy

NASA Technical Reports Server (NTRS)

Montano, J. W.

1973-01-01

The mechanical properties of type 431 stainless steel in two conditions: annealed bar and hardened and tempered bar are presented. Test specimens, manufactured from approximately 1.0 inch (2.54 cm) diameter bar stock, were tested at temperatures of 80 F (+26.7 C), 0 F (-17.8 C), -100 F (-73 C), and -200 F (-129 C). The test data indicated excellent tensile strength, notched/unnotched tensile ratio, ductility, shear, and impact properties at all testing temperatures. Results of the alternate immersion stress corrosion tests on stressed and unstressed longitudinal tensile specimens 0.1250 inch (0.3175 cm) diameter and transverse C-ring specimens, machined from 1.0 inch (2.54 cm) diameter bar stock, indicated that the material is not susceptible to stress corrosion cracking when tested in a 3.5 percent NaCl solution for 180 days.

IR femtochemistry on the surface of wide-gap ionic crystals

NASA Astrophysics Data System (ADS)

Laptev, V. B.; Chekalin, S. V.; Dorofeyev, I. A.; Kompanets, V. O.; Pigulsky, S. V.; Ryabov, E. A.

2018-02-01

We have found and studied a phenomenon of the growth of films resulting from decomposition of some organic and silicon-containing molecules adsorbed on the surface of ionic crystals under the action of IR (1.4-5.4 µm) femtosecond radiation of a moderate intensity, ~1011 W cm-2. In the gas phase, these molecules do not decompose. Microstructured films consisting of amorphous carbon, graphite oxide, and silicon dioxide have been obtained. The formation of carbon films was accompanied by the appearance of different hydrocarbons in the gas phase. The extensive films of graphite oxide have been obtained. The decomposition of molecules on the surface is apparently caused by non-resonant ionization and subsequent deep fragmentation. The mechanisms of ionization at relatively low intensities of the femtosecond IR radiation have been discussed.

Multiferroic BiFeO3 thin films and nanodots grown on highly oriented pyrolytic graphite substrates

NASA Astrophysics Data System (ADS)

Shin, Hyun Wook; Son, Jong Yeog

2017-12-01

Multiferroic BiFeO3 (BFO) thin films and nanodots are deposited on highly oriented pyrolytic graphite (HOPG) substrates via a pulsed laser deposition technique, where the HOPG surface has a honeycomb lattice structure made of carbon atoms, similar to graphene. A graphene/BFO/HOPG capacitor exhibited multiferroic properties, namely ferroelectricity (a residual polarization of 26.8 μC/cm2) and ferromagnetism (a residual magnetization of 1.1 × 10-5 emu). The BFO thin film had high domain wall energies and demonstrated switching time of approximately 82 ns. An 8-nm BFO nanodot showed a typical piezoelectric hysteresis loop with an effective residual piezoelectric constant of approximately 110 pm/V and exhibited two clearly separated current curves depending on the ferroelectric polarization direction.

Automated assembly of Gallium Arsenide and 50-micron thick silicon solar cell modules

NASA Technical Reports Server (NTRS)

Mesch, H. G.

1984-01-01

The TRW automated solar array assembly equipment was used for the module assembly of 300 GaAs solar cells and 300 50 micron thick silicon solar cells (2 x 4 cm in size). These cells were interconnected with silver plated Invar tabs by means of welding. The GaAs cells were bonded to Kapton graphite aluminum honeycomb graphite substrates and the thin silicon cells were bonded to 0.002 inch thick single layer Kapton substrates. The GaAs solar cell module assembly resulted in a yield of 86% and the thin cell assembly produced a yield of 46% due to intermittent sticking of weld electrodes during the front cell contact welding operation. (Previously assembled thin cell solar modules produced an overall assembly yield of greater than 80%).

The Importance of Large-Diameter Trees to Forest Structural Heterogeneity

PubMed Central

Lutz, James A.; Larson, Andrew J.; Freund, James A.; Swanson, Mark E.; Bible, Kenneth J.

2013-01-01

Large-diameter trees dominate the structure, dynamics and function of many temperate and tropical forests. However, their attendant contributions to forest heterogeneity are rarely addressed. We established the Wind River Forest Dynamics Plot, a 25.6 ha permanent plot within which we tagged and mapped all 30,973 woody stems ≥1 cm dbh, all 1,966 snags ≥10 cm dbh, and all shrub patches ≥2 m2. Basal area of the 26 woody species was 62.18 m2/ha, of which 61.60 m2/ha was trees and 0.58 m2/ha was tall shrubs. Large-diameter trees (≥100 cm dbh) comprised 1.5% of stems, 31.8% of basal area, and 17.6% of the heterogeneity of basal area, with basal area dominated by Tsuga heterophylla and Pseudotsuga menziesii. Small-diameter subpopulations of Pseudotsuga menziesii, Tsuga heterophylla and Thuja plicata, as well as all tree species combined, exhibited significant aggregation relative to the null model of complete spatial randomness (CSR) up to 9 m (P≤0.001). Patterns of large-diameter trees were either not different from CSR (Tsuga heterophylla), or exhibited slight aggregation (Pseudotsuga menziesii and Thuja plicata). Significant spatial repulsion between large-diameter and small-diameter Tsuga heterophylla suggests that large-diameter Tsuga heterophylla function as organizers of tree demography over decadal timescales through competitive interactions. Comparison among two forest dynamics plots suggests that forest structural diversity responds to intermediate-scale environmental heterogeneity and disturbances, similar to hypotheses about patterns of species richness, and richness- ecosystem function. Large mapped plots with detailed within-plot environmental spatial covariates will be required to test these hypotheses. PMID:24376579

The importance of large-diameter trees to forest structural heterogeneity.

PubMed

Lutz, James A; Larson, Andrew J; Freund, James A; Swanson, Mark E; Bible, Kenneth J

2013-01-01

Large-diameter trees dominate the structure, dynamics and function of many temperate and tropical forests. However, their attendant contributions to forest heterogeneity are rarely addressed. We established the Wind River Forest Dynamics Plot, a 25.6 ha permanent plot within which we tagged and mapped all 30,973 woody stems ≥ 1 cm dbh, all 1,966 snags ≥ 10 cm dbh, and all shrub patches ≥ 2 m(2). Basal area of the 26 woody species was 62.18 m(2)/ha, of which 61.60 m(2)/ha was trees and 0.58 m(2)/ha was tall shrubs. Large-diameter trees (≥ 100 cm dbh) comprised 1.5% of stems, 31.8% of basal area, and 17.6% of the heterogeneity of basal area, with basal area dominated by Tsuga heterophylla and Pseudotsuga menziesii. Small-diameter subpopulations of Pseudotsuga menziesii, Tsuga heterophylla and Thuja plicata, as well as all tree species combined, exhibited significant aggregation relative to the null model of complete spatial randomness (CSR) up to 9 m (P ≤ 0.001). Patterns of large-diameter trees were either not different from CSR (Tsuga heterophylla), or exhibited slight aggregation (Pseudotsuga menziesii and Thuja plicata). Significant spatial repulsion between large-diameter and small-diameter Tsuga heterophylla suggests that large-diameter Tsuga heterophylla function as organizers of tree demography over decadal timescales through competitive interactions. Comparison among two forest dynamics plots suggests that forest structural diversity responds to intermediate-scale environmental heterogeneity and disturbances, similar to hypotheses about patterns of species richness, and richness- ecosystem function. Large mapped plots with detailed within-plot environmental spatial covariates will be required to test these hypotheses.

Development of high-density helicon plasma sources and their applications

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

Shinohara, Shunjiro; Hada, Tohru; Motomura, Taisei

2009-05-15

We report on the development of unique, high-density helicon plasma sources and describe their applications. Characterization of one of the largest helicon plasma sources yet constructed is made. Scalings of the particle production efficiency are derived from various plasma production devices in open literature and our own data from long and short cylinder devices, i.e., high and low values of the aspect ratio A (the ratio of the axial length to the diameter), considering the power balance in the framework of a simple diffusion model. A high plasma production efficiency is demonstrated, and we clarify the structures of the excitedmore » waves in the low A region down to 0.075 (the large device diameter of 73.8 cm with the axial length as short as 5.5 cm). We describe the application to plasma propulsion using a new concept that employs no electrodes. A very small diameter (2.5 cm) helicon plasma with 10{sup 13} cm{sup -3} density is produced, and the preliminary results of electromagnetic plasma acceleration are briefly described.« less

Preoperative tumor size at MRI predicts deep myometrial invasion, lymph node metastases, and patient outcome in endometrial carcinomas.

PubMed

Ytre-Hauge, Sigmund; Husby, Jenny A; Magnussen, Inger J; Werner, Henrica M J; Salvesen, Øyvind O; Bjørge, Line; Trovik, Jone; Stefansson, Ingunn M; Salvesen, Helga B; Haldorsen, Ingfrid S

2015-03-01

The aim of this study was to explore the relation between preoperative tumor size based on magnetic resonance imaging (MRI) and the surgical pathologic staging parameters (deep myometrial invasion, cervical stroma invasion, and metastatic lymph nodes) and to assess the prognostic impact of tumor size in endometrial carcinomas. Interobserver variability for the different tumor size measurements was also assessed. Preoperative pelvic MRI of 212 patients with histologically confirmed endometrial carcinomas was read independently by 3 radiologists. Maximum tumor diameters were measured in 3 orthogonal planes (anteroposterior, transverse, and craniocaudal planes [CC]), and tumor volumes were estimated. Tumor size was analyzed in relation to surgical staging results and patient survival. The multivariate analyses were adjusted for preoperative risk status based on endometrial biopsy. Intraclass correlation coefficients and receiver operating characteristics curves for the different tumor measurements were also calculated. Anteroposterior tumor diameter independently predicted deep myometrial invasion (P < 0.001), whereas CC tumor diameter tended to independently predict lymph node metastases (P = 0.06). Based on receiver operating characteristic curves, the following tumor size cutoff values were identified: anteroposterior diameter greater than 2 cm predicted deep myometrial invasion (unadjusted odds ratio [OR], 12.4; P < 0.001; adjusted OR, 6.7; P < 0.001) and CC diameter greater than 4 cm predicted lymph node metastases (unadjusted OR, 6.2; P < 0.001; adjusted OR, 4.9; P = 0.009). Large tumor size was associated with reduced progression/recurrence-free survival (P ≤ 0.005 for all size parameters), and CC diameter had an independent impact on survival (adjusted hazards ratio, 1.04; P = 0.009). The interobserver variability for the different size measurements was very low (intraclass correlation coefficient, 0.78-0.85). Anteroposterior tumor diameter greater than 2 cm predicts deep myometrial invasion, and CC tumor diameter greater than 4 cm predicts lymph node metastases. Tumor size is a strong prognostic factor in endometrial carcinomas. Preoperative tumor measurements based on MRI may potentially improve preoperative risk stratification models and thus enable better tailored surgical treatment in endometrial cancer.

Laser inertial fusion-based energy: Neutronic design aspects of a hybrid fusion-fission nuclear energy system

NASA Astrophysics Data System (ADS)

Kramer, Kevin James

This study investigates the neutronics design aspects of a hybrid fusion-fission energy system called the Laser Fusion-Fission Hybrid (LFFH). A LFFH combines current Laser Inertial Confinement fusion technology with that of advanced fission reactor technology to produce a system that eliminates many of the negative aspects of pure fusion or pure fission systems. When examining the LFFH energy mission, a significant portion of the United States and world energy production could be supplied by LFFH plants. The LFFH engine described utilizes a central fusion chamber surrounded by multiple layers of multiplying and moderating media. These layers, or blankets, include coolant plenums, a beryllium (Be) multiplier layer, a fertile fission blanket and a graphite-pebble reflector. Each layer is separated by perforated oxide dispersion strengthened (ODS) ferritic steel walls. The central fusion chamber is surrounded by an ODS ferritic steel first wall. The first wall is coated with 250-500 mum of tungsten to mitigate x-ray damage. The first wall is cooled by Li17Pb83 eutectic, chosen for its neutron multiplication and good heat transfer properties. The Li17Pb 83 flows in a jacket around the first wall to an extraction plenum. The main coolant injection plenum is immediately behind the Li17Pb83, separated from the Li17Pb83 by a solid ODS wall. This main system coolant is the molten salt flibe (2LiF-BeF2), chosen for beneficial neutronics and heat transfer properties. The use of flibe enables both fusion fuel production (tritium) and neutron moderation and multiplication for the fission blanket. A Be pebble (1 cm diameter) multiplier layer surrounds the coolant injection plenum and the coolant flows radially through perforated walls across the bed. Outside the Be layer, a fission fuel layer comprised of depleted uranium contained in Tristructural-isotropic (TRISO) fuel particles having a packing fraction of 20% in 2 cm diameter fuel pebbles. The fission blanket is cooled by the same radial flibe flow that travels through perforated ODS walls to the reflector blanket. This reflector blanket is 75 cm thick comprised of 2 cm diameter graphite pebbles cooled by flibe. The flibe extraction plenum surrounds the reflector bed. Detailed neutronics designs studies are performed to arrive at the described design. The LFFH engine thermal power is controlled using a technique of adjusting the 6Li/7Li enrichment in the primary and secondary coolants. The enrichment adjusts system thermal power in the design by increasing tritium production while reducing fission. To perform the simulations and design of the LFFH engine, a new software program named LFFH Nuclear Control (LNC) was developed in C++ to extend the functionality of existing neutron transport and depletion software programs. Neutron transport calculations are performed with MCNP5. Depletion calculations are performed using Monteburns 2.0, which utilizes ORIGEN 2.0 and MCNP5 to perform a burnup calculation. LNC supports many design parameters and is capable of performing a full 3D system simulation from initial startup to full burnup. It is able to iteratively search for coolant 6Li enrichments and resulting material compositions that meet user defined performance criteria. LNC is utilized throughout this study for time dependent simulation of the LFFH engine. Two additional methods were developed to improve the computation efficiency of LNC calculations. These methods, termed adaptive time stepping and adaptive mesh refinement were incorporated into a separate stand alone C++ library name the Adaptive Burnup Library (ABL). The ABL allows for other client codes to call and utilize its functionality. Adaptive time stepping is useful for automatically maximizing the size of the depletion time step while maintaining a desired level of accuracy. Adaptive meshing allows for analysis of fixed fuel configurations that would normally require a computationally burdensome number of depletion zones. Alternatively, Adaptive Mesh Refinement (AMR) adjusts the depletion zone size according to the variation in flux across the zone or fractional contribution to total absorption or fission. A parametric analysis on a fully mixed fuel core was performed using the LNC and ABL code suites. The resulting system parameters are found to optimize performance metrics using a 20 MT DU fuel load with a 20% TRISO packing and a 300 im kernel diameter operated with a fusion input power of 500 MW and a fission blanket gain of 4.0. LFFH potentially offers a proliferation resistant technology relative to other nuclear energy systems primarily because of no need for fuel enrichment or reprocessing. A figure of merit of the material attractiveness is examined and it is found that the fuel is effectively contaminated to an unattractive level shortly after the system is started due to fission product and minor actinide build up.

Membraneless glucose/oxygen enzymatic fuel cells using redox hydrogel films containing carbon nanotubes.

PubMed

MacAodha, Domhnall; Ó Conghaile, Peter; Egan, Brenda; Kavanagh, Paul; Leech, Dónal

2013-07-22

Co-immobilisation of three separate multiple blue copper oxygenases, a Myceliophthora thermophila laccase, a Streptomyces coelicolor laccase and a Myrothecium verrucaria bilirubin oxidase, with an [Os(2,2'-bipyridine)2 (polyvinylimidazole)10Cl](+/2+) redox polymer in the presence of multi-walled carbon nanotubes (MWCNTs) on graphite electrodes results in enzyme electrodes that produce current densities above 0.5 mA cm(-2) for oxygen reduction at an applied potential of 0 V versus Ag/AgCl. Fully enzymatic membraneless fuel cells are assembled with the oxygen-reducing enzyme electrodes connected to glucose-oxidising anodes based on co-immobilisation of glucose oxidase or a flavin adenine dinucleotide-dependent glucose dehydrogenase with an [Os(4,4'-dimethyl-2,2'-bipyridine)2(polyvinylimidazole)10Cl](+/2+) redox polymer in the presence of MWCNTs on graphite electrodes. These fuel cells can produce power densities of up to 145 μW cm(-2) on operation in pH 7.4 phosphate buffer solution at 37 °C containing 150 mM NaCl, 5 mM glucose and 0.12 mM O2. The fuel cells based on Myceliophthora thermophila laccase enzyme electrodes produce the highest power density if combined with glucose oxidase-based anodes. Although the maximum power density of a fuel cell of glucose dehydrogenase and Myceliophthora thermophila laccase enzyme electrodes decreases from 110 μW cm(-2) in buffer to 60 μW cm(-2) on testing in artificial plasma, it provides the highest power output reported to date for a fully enzymatic glucose-oxidising, oxygen-reducing fuel cell in artificial plasma. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The outcome of laparoscopic Heller myotomy for achalasia is not influenced by the degree of esophageal dilatation.

PubMed

Sweet, Matthew P; Nipomnick, Ian; Gasper, Warren J; Bagatelos, Karen; Ostroff, James W; Fisichella, Piero M; Way, Lawrence W; Patti, Marco G

2008-01-01

In the past, a Heller myotomy was considered to be ineffective in patients with achalasia and a markedly dilated or sigmoid-shaped esophagus. Esophagectomy was the standard treatment. The aims of this study were (a) to evaluate the results of laparoscopic Heller myotomy and Dor fundoplication in patients with achalasia and various degrees of esophageal dilatation; and (b) to assess the role of endoscopic dilatation in patients with postoperative dysphagia. One hundred and thirteen patients with esophageal achalasia were separated into four groups based on the maximal diameter of the esophageal lumen and the shape of the esophagus: group A, diameter<4.0 cm, 46 patients; group B, esophageal diameter 4.0-6.0 cm, 32 patients; group C, diameter>6.0 cm and straight axis, 23 patients; and group D, diameter>6.0 cm and sigmoid-shaped esophagus, 12 patients. All had a laparoscopic Heller myotomy and Dor fundoplication. The median length of follow-up was 45 months (range 7 months to 12.5 years). The postoperative recovery was similar among the four groups. Twenty-three patients (20%) had postoperative dilatations for dysphagia, and five patients (4%) required a second myotomy. Excellent or good results were obtained in 89% of group A and 91% of groups B, C, and D. None required an esophagectomy to maintain clinically adequate swallowing. These data show that (a) a laparoscopic Heller myotomy relieved dysphagia in most patients with achalasia, even when the esophagus was dilated; (b) about 20% of patients required additional treatment; (c) in the end, swallowing was good in 90%.

The prevalence of incidental simple ovarian cysts >or= 3 cm detected by transvaginal sonography in early pregnancy.

PubMed

Glanc, Phyllis; Brofman, Nicole; Salem, Shia; Kornecki, Anat; Abrams, Jason; Farine, Dan

2007-06-01

To determine the prevalence of simple ovarian cysts of >or= 3 cm diameter detected by transvaginal sonography (TVS) in a population of asymptomatic women in early pregnancy. We conducted a retrospective review of 10,830 consecutive women presenting prior to 14 weeks' gestational age (GA) for early dating TVS. The records of all women with simple cysts >or= 3 cm in diameter were included. The study population was divided into five groups by GA: >or= 6 weeks; 6.1-8 weeks; 8.1-10 weeks; 10.1-12 weeks; and 12.1-14 weeks. A simple cyst >or= 3 cm in diameter was present in 4.9% of women at >or= 6 weeks' gestation, in 5.1% between 6.1 and 8 weeks, in 5.3% between 8.1 and 10 weeks, in 3.2% between 10.1. and 12 weeks, and in 1.5% between 12 and 14 weeks. Overall, a simple cyst >or= 3 cm was present in 516 women (4.8%). Prior to 10 weeks, 5.1% had simple cysts >or= 3 cm, dropping to 2.7% after 10 weeks, a statistically significant decrease (P<0.0001). Between 10.1 weeks and 12 weeks, the prevalence dropped to 3.2%, and then to 1.5% in the 12.1-14 week group. This investigation provides reference data on the prevalence of detecting simple ovarian cysts >or= 3 cm by TVS in an asymptomatic early pregnancy population. A progressive decline in the frequency of detecting simple ovarian cysts >or= 3 cm begins after 10 weeks' gestational age.

Vertically aligned GaAs nanowires on graphite and few-layer graphene: generic model and epitaxial growth.

PubMed

Munshi, A Mazid; Dheeraj, Dasa L; Fauske, Vidar T; Kim, Dong-Chul; van Helvoort, Antonius T J; Fimland, Bjørn-Ove; Weman, Helge

2012-09-12

By utilizing the reduced contact area of nanowires, we show that epitaxial growth of a broad range of semiconductors on graphene can in principle be achieved. A generic atomic model is presented which describes the epitaxial growth configurations applicable to all conventional semiconductor materials. The model is experimentally verified by demonstrating the growth of vertically aligned GaAs nanowires on graphite and few-layer graphene by the self-catalyzed vapor-liquid-solid technique using molecular beam epitaxy. A two-temperature growth strategy was used to increase the nanowire density. Due to the self-catalyzed growth technique used, the nanowires were found to have a regular hexagonal cross-sectional shape, and are uniform in length and diameter. Electron microscopy studies reveal an epitaxial relationship of the grown nanowires with the underlying graphitic substrates. Two relative orientations of the nanowire side-facets were observed, which is well explained by the proposed atomic model. A prototype of a single GaAs nanowire photodetector demonstrates a high-quality material. With GaAs being a model system, as well as a very useful material for various optoelectronic applications, we anticipate this particular GaAs nanowire/graphene hybrid to be promising for flexible and low-cost solar cells.

Epitaxial Growth of Aligned and Continuous Carbon Nanofibers from Carbon Nanotubes.

PubMed

Lin, Xiaoyang; Zhao, Wei; Zhou, Wenbin; Liu, Peng; Luo, Shu; Wei, Haoming; Yang, Guangzhi; Yang, Junhe; Cui, Jie; Yu, Richeng; Zhang, Lina; Wang, Jiaping; Li, Qunqing; Zhou, Weiya; Zhao, Weisheng; Fan, Shoushan; Jiang, Kaili

2017-02-28

Exploiting the superior properties of nanomaterials at macroscopic scale is a key issue of nanoscience. Different from the integration strategy, "additive synthesis" of macroscopic structures from nanomaterial templates may be a promising choice. In this paper, we report the epitaxial growth of aligned, continuous, and catalyst-free carbon nanofiber thin films from carbon nanotube films. The fabrication process includes thickening of continuous carbon nanotube films by gas-phase pyrolytic carbon deposition and further graphitization of the carbon layer by high-temperature treatment. As-fabricated nanofibers in the film have an "annual ring" cross-section, with a carbon nanotube core and a graphitic periphery, indicating the templated growth mechanism. The absence of a distinct interface between the carbon nanotube template and the graphitic periphery further implies the epitaxial growth mechanism of the fiber. The mechanically robust thin film with tunable fiber diameters from tens of nanometers to several micrometers possesses low density, high electrical conductivity, and high thermal conductivity. Further extension of this fabrication method to enhance carbon nanotube yarns is also demonstrated, resulting in yarns with ∼4-fold increased tensile strength and ∼10-fold increased Young's modulus. The aligned and continuous features of the films together with their outstanding physical and chemical properties would certainly promote the large-scale applications of carbon nanofibers.

[Value of asymmetry criterion in MRI for the diagnosis of small pelvic lymphadenopathies (inferior or equal to 1 cm)].

PubMed

Roy, C; Le Bras, Y; Mangold, L; Tuchmann, C; Vasilescu, C; Saussine, C; Jacqmin, D

1996-12-01

The purpose of this study was to determine if lymph node asymmetry in small (< 1.0 cm) pelvic nodes was a significant prognostic feature in determining metastatic disease. 216 patients who presented pelvic carcinoma underwent MR imaging. They were correlated to pathological findings obtained by surgery. We considered on the axial plan the maximum diameter (MAD) of both round or oval-shaped suspicious masses. Two different cut-off values were determined: node diameter superior to 1.0 cm (criterion 1) and node diameter superior to 0.5 cm with asymmetry relative to the opposite side for nodes ranging from 0.5 cm to 1.0 cm (criterion 2). With criterion 1 MR Imaging had an accuracy of 88%, a sensitivity of 65%, a specificity of 96%, a PPV of 88% and a NPV of 88% in detection of pelvic node metastasis. By considering criterion 2, MR Imaging had an accuracy of 85%, a sensitivity of 75%, a specificity of 89%, a PPV of 71% and a NPV of 91%. Normal small asymmetric lymph nodes were present in 5.6% of cases. Asymmetry of normal or inflammatory pelvic nodes is not uncommon. It cannot be relied on to diagnose metastatic involvement in cases of small suspicious lymph nodes, especially because of its low specificity and positive predictive value.

Removal of Pb, Cd, and Cr in a water purification system using modified mineral waste materials and activated carbon derived from waste materials

NASA Astrophysics Data System (ADS)

Lu, H. R.; Su, L. C.; Ruan, H. D.

2016-08-01

This study attempts to find out and optimize the removal efficiency of heavy metals in a water purification unit using a low-cost waste material and modified mineral waste materials (MMWM) accompanied with activated carbon (AC) derived from waste materials. The factors of the inner diameter of the purification unit (2.6-5cm), the height of the packing materials (5-20cm), the size of AC (200-20mesh), the size of MMWM (1-0.045mm), and the ratio between AC and MMWM in the packing materials (1:0 - 0:1) were examined based on a L18 (5) 3 orthogonal array design. In order to achieve an optimally maximum removal efficiency, the factors of the inner diameter of the purification unit (2.6-7.5cm), the height of the packing materials (10-30cm), and the ratio between AC and MMWM in the packing materials (1:4-4:1) were examined based on a L16 (4) 3 orthogonal array design. A height of 25cm, inner diameter of 5cm, ratio between AC and MMWM of 3:2 with size of 60-40mesh and 0.075-0.045mm, respectively, were the best conditions determined by the ICP-OES analysis to perform the adsorption of heavy metals in this study.

Surgical outcomes of lung cancer measuring less than 1 cm in diameter.

PubMed

Hamatake, Daisuke; Yoshida, Yasuhiro; Miyahara, So; Yamashita, Shin-ichi; Shiraishi, Takeshi; Iwasaki, Akinori

2012-11-01

The increased use of computed tomography has led to an increasing proportion of lung cancers that are identified when still less than 1 cm in diameter. However, there is no defined treatment strategy for such cases. The aim of this study was to investigate the surgical outcomes of small lung cancers. A total of 143 patients were retrospectively evaluated, who had undergone a complete surgical resection for lung cancer less than 1 cm in diameter between January 1995 and December 2011. The 143 study subjects included 62 male and 81 female patients. The mean age was 64.0 years (43-82 years). The mean tumour size was 0.8 cm (0.3-1.0 cm). Seventy-seven patients (53.8%) underwent lobectomy. Thirty-two patients (22.4%) underwent segmentectomy and 34 patients (23.8%) underwent wedge resection. The 3-, 5- and 10-year survival rates were 95.7, 92.2 and 85.7%, respectively, after resection for sub-centimetre lung cancer. There were no significant differences between sub-lobar resection and lobectomy. However, two patients (1.4%) had recurrent cancer and seven (4.9%) had lymph node metastasis. The selection of the surgical procedure is important and a long-term follow-up is mandatory, because lung cancer of only 1 cm or less can be associated with lymph node metastasis and distant metastatic recurrence.

Inducing microstructural changes in Nafion by incorporating graphitic carbon nitride to enhance the vanadium-blocking effect.

PubMed

Wu, Chunxiao; Lu, Shanfu; Zhang, Jin; Xiang, Yan

2018-03-14

Two-dimensional graphitic carbon nitride (g-C 3 N 4 ) nanosheets are introduced into a Nafion matrix to prepare a 'vanadium-blocking' recast Nafion membrane for vanadium redox flow battery (VRFB) applications. After 0.2 wt% g-C 3 N 4 nanosheets are incorporated, the vanadium ion permeability of the composite membrane decreases from 3.3 × 10 -7 cm 2 min -1 to 3.8 × 10 -9 cm 2 min -1 , which is a reduction of two orders of magnitude in comparison to the pristine recast Nafion membrane. This satisfactory result contributes to the physical blocking effect as well as the Donnan effect from the 2D morphology and functional amino groups of g-C 3 N 4 nanosheets. Notably, this work reveals that the g-C 3 N 4 nanosheets can help reinforce the vanadium-blocking effect by changing the microstructure of Nafion in addition to the well-known effects mentioned above. The g-C 3 N 4 nanosheets induce shrinkage in the original spherical structure of the ion cluster and generate a new lamellar structure. Correspondingly, the amorphous phase of Nafion is interrupted, and the membrane crystallinity is reduced. The VRFB with an optimized composite membrane achieves a high coulombic efficiency of 97% and an energy efficiency of 83% at a current density of 160 mA cm -2 . Meanwhile, the battery exhibited excellent lifetime stability during a 100 charge-discharge cycling test.

Electrochemical investigations of ionic liquids with vinylene carbonate for applications in rechargeable lithium ion batteries

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

Sun, Xiao-Guang; Dai, Sheng

2010-01-01

Ionic liquids based on methylpropylpyrrolidinium (MPPY) and methylpropylpiperidinium (MPPI) cations and bis(trifluoromethanesulfionyl)imide (TFSI) anion have been synthesized and characterized by thermal analysis, cyclic voltammetry, impedance spectroscopy as well as gavanostatic charge/discharge tests. 10 wt% of vinylene carbonate (VC) was added to the electrolytes of 0.5 M LiTFSI/MPPY.TFSI and 0.5 M LiTFSI/MPPI.TFSI, which were evaluated in Li || natural graphite (NG) half cells at 25 oC and 50 oC under different current densities. At 25 oC, due to their intrinsic high viscosities, the charge/discharge capacities under the current density of 80 A cm-2 were much lower than those under the currentmore » density of 40 A cm-2. At 50 oC, with reduced viscosities, the charge/discharge capacities under both current densities were almost indistinguishable, which were also close to the typical values obtained using conventional carbonate electrolytes. In addition, the discharge capacities of the half cells were very stable with cycling, due to the effective formation of solid electrolyte interphase (SEI) on the graphite electrode. On the contrary, the charge/discharge capacities of the Li || LiCoO2 cells using both ionic liquid electrolytes under the current density of 40 A cm-2 decreased continually with cycling, which were primarily due to the low oxidative stability of VC on the surface of LiCoO2.« less

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

NASA Technical Reports Server (NTRS)

Hung, Ching-Cheh

1993-01-01

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

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

NASA Technical Reports Server (NTRS)

Hung, Ching-Cheh

1995-01-01

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

Preliminary Results of Field Emission Cathode Tests

NASA Technical Reports Server (NTRS)

Sovey, James S.; Kovaleski, Scott D.

2001-01-01

Preliminary screening tests of field emission cathodes such as chemical vapor deposited (CVD) diamond, textured pyrolytic graphite, and textured copper were conducted at background pressures typical of electric thruster test facilities to assess cathode performance and stability. Very low power electric thrusters which provide tens to hundreds micronewtons of thrust may need field emission neutralizers that have a capability of tens to hundreds of microamperes. From current voltage characteristics, it was found that the CVD diamond and textured metals cathodes clearly satisfied the Fowler-Nordheim emission relation. The CVD diamond and a textured copper cathode had average current densities of 270 and 380 mA/sq cm, respectively, at the beginning-of-life. After a few hours of operation the cathode emission currents degraded by 40 to 75% at background pressures in the 10(exp -5) Pa to 10(exp -4) Pa range. The textured pyrolytic graphite had a modest current density at beginning-of-life of 84 mA/sq cm, but this cathode was the most stable of all. Extended testing of the most promising cathodes is warranted to determine if current degradation is a burn-in effect or whether it is a long-term degradation process. Preliminary experiments with ferroelectric emission cathodes, which are ceramics with spontaneous electric polarization, were conducted. Peak current densities of 30 to 120 mA/sq cm were obtained for pulse durations of about 500 ns in the 10(exp -4) Pa pressure range.

Measurements of stem diameter: implications for individual- and stand-level errors.

PubMed

Paul, Keryn I; Larmour, John S; Roxburgh, Stephen H; England, Jacqueline R; Davies, Micah J; Luck, Hamish D

2017-08-01

Stem diameter is one of the most common measurements made to assess the growth of woody vegetation, and the commercial and environmental benefits that it provides (e.g. wood or biomass products, carbon sequestration, landscape remediation). Yet inconsistency in its measurement is a continuing source of error in estimates of stand-scale measures such as basal area, biomass, and volume. Here we assessed errors in stem diameter measurement through repeated measurements of individual trees and shrubs of varying size and form (i.e. single- and multi-stemmed) across a range of contrasting stands, from complex mixed-species plantings to commercial single-species plantations. We compared a standard diameter tape with a Stepped Diameter Gauge (SDG) for time efficiency and measurement error. Measurement errors in diameter were slightly (but significantly) influenced by size and form of the tree or shrub, and stem height at which the measurement was made. Compared to standard tape measurement, the mean systematic error with SDG measurement was only -0.17 cm, but varied between -0.10 and -0.52 cm. Similarly, random error was relatively large, with standard deviations (and percentage coefficients of variation) averaging only 0.36 cm (and 3.8%), but varying between 0.14 and 0.61 cm (and 1.9 and 7.1%). However, at the stand scale, sampling errors (i.e. how well individual trees or shrubs selected for measurement of diameter represented the true stand population in terms of the average and distribution of diameter) generally had at least a tenfold greater influence on random errors in basal area estimates than errors in diameter measurements. This supports the use of diameter measurement tools that have high efficiency, such as the SDG. Use of the SDG almost halved the time required for measurements compared to the diameter tape. Based on these findings, recommendations include the following: (i) use of a tape to maximise accuracy when developing allometric models, or when monitoring relatively small changes in permanent sample plots (e.g. National Forest Inventories), noting that care is required in irregular-shaped, large-single-stemmed individuals, and (ii) use of a SDG to maximise efficiency when using inventory methods to assess basal area, and hence biomass or wood volume, at the stand scale (i.e. in studies of impacts of management or site quality) where there are budgetary constraints, noting the importance of sufficient sample sizes to ensure that the population sampled represents the true population.

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

Mullins, JP; Deufel, CL

Purpose: Bile duct cancer affects 2–3 thousand people annually in the United States. Radiation therapy has been shown to double median survival, with combined external beam and intraluminal high dose-rate (HDR) brachytherapy being most effective. Endoscopic retrograde cholangiopancreatography (ERCP) biliary HDR, a less-invasive alternative to trans-hepatic brachytherapy, is delivered through a catheter that travels a tortuous path from nose to bile duct, requiring wire drive force and dexterity beyond typical afterloader performance specifications. Thus, specific afterloader quality assurance(QA) is recommended for this procedure. Our aim was to create a device and process for Varisource afterloader clearance QA with objectives thatmore » it be quantitative and can monitor afterloader performance over time, compare performance between two distinct afterloaders and potentially Result in a predictive nomogram for patient-specific clearance. Methods: Based on retrospective reconstruction of 20 ERCP patient anatomies, we designed a phantom to test afterloader ability to drive the source wire along an intended treatment path. The ability of the afterloader to fully extend the intended treatment path is a function of number and diameters of turns. We have determined experimentally that relative position of the turns does not impact performance. Results: Both patient and QA paths involve three common turns/loops: a large turn representing the stomach(10.8cm±2.0cm), an elliptical loop representing the duodenum(7.3cm±1.5cmx4.8cm±0.7cm), and a final turn at the end of the bile duct that may be tight for some patient-specific anatomies and absent in others(3.7cm±0.7cm, where present). Our phantom design uses anatomical average turn diameters for the stomach and duodenum then terminates in a turn of quantitatively selectable diameter. The smallest final turn diameter that an afterloader can pass is recorded as the QA parameter. Conclusion: With this device and QA process, we have the ability to quantitatively evaluate and track our afterloader performance for a technically challenging ERCP brachytherapy procedure.« less

Preventive medicine for von Hippel-Lindau disease-associated pancreatic neuroendocrine tumors.

PubMed

Krauss, Tobias; Ferrara, Alfonso Massimiliano; Links, Thera P; Wellner, Ulrich; Bancos, Irina; Kvachenyuk, Andrey; Villar Gómez de Las Heras, Karina; Yukina, Marina; Petrov, Roman; Bullivant, Garrett; von Duecker, Laura; Jadhav, Swati S; Ploeckinger, Ursula; Welin, Staffan; Schalin-Jantti, Camilla; Gimm, Oliver; Pfeifer, Marija; Ngeow, Joanne; Hasse-Lazar, Kornelia; Sanso, Gabriela; Qi, Xiao-Ping; Ugurlu, Umit; Diaz, Rene Eduardo; Wohllk, Nelson; Peczkowska, Mariola; Aberle, Jens; Lourenço, Delmar Muniz; Pereira, Maria Adelaide; Fragoso, Maria Candida Barisson Villares; Hoff, Ana O; Almeida, Madson Queiroz; Violante, Alice H D; Quidute, Ana R P; Zhang, Zheiwei; Recasens, Monica; Robles Diaz, Luis; Kunavisarut, Tada; Wannachalee, Taweesak; Sirinvaravong, Sirinart; Jonasch, Eric; Grozinsky-Glasberg, Simona; Fraenkel, Merav; Beltsevich, Dmitry; Egorov, Viacheslav I; Bausch, Dirk; Schott, Matthias; Tiling, Nikolaus; Pennelli, Gianmaria; Zschiedrich, Stefan; Därr, Roland; Ruf, Juri; Denecke, Timm; Link, Karl-Heinrich; Zovato, Stefania; von Dobschuetz, Ernst; Yaremchuk, Svetlana; Amthauer, Holger; Makay, Ozer; Patocs, Attila; Walz, Martin K; Huber, Tobias B; Seufert, Jochen; Hellman, Per; Kim, Raymond H; Kuchinskaya, Ekaterina; Schiavi, Francesca; Malinoc, Angelica; Reisch, Nicole; Jarzab, Barbara; Barontini, Marta; Januszewicz, Andrzej; Shah, Nalini; Young, William; Opocher, Giuseppe; Eng, Charis; Neumann, Hartmut P H; Bausch, Birke

2018-05-10

Pancreatic neuroendocrine tumors (PanNETs) are rare in von Hippel-Lindau disease (VHL) but cause serious morbidity and mortality. Management guidelines for VHL-PanNETs continue to be based on limited evidence, and survival data to guide surgical management are lacking. We established the European-American-Asian-VHL-PanNET-Registry to assess data for risks for metastases, survival and long-term outcomes to provide best management recommendations. Of 2,330 VHL patients, 273 had a total of 484 PanNETs. Median age at diagnosis of PanNET was 35 years (range 10-75). Fifty-five (20%) patients had metastatic PanNETs. Metastatic PanNETs were significantly larger (median size 5 vs 2 cm; P<0.001) and tumor volume doubling time (TVDT) was faster (22 vs 126 months; P=0.001). All metastatic tumors were ≥2.8 cm. Codons 161 and 167 were hotspots for VHL germline mutations with enhanced risk for metastatic PanNETs. Multivariate prediction modeling disclosed maximum tumor diameter and TVDT as significant predictors for metastatic disease (positive and negative predictive values of 51% and 100% for diameter cutoff ≥2.8 cm, 44% and 91% for TVDT cutoff of ≤24 months). In 117/273 patients, PanNETs >1.5 cm in diameter were operated. Ten-year survival was significantly longer in operated vs non-operated patients, in particular for PanNETs <2.8cm vs ≥2.8 cm (94% vs 85% by 10 years; P=0.020; 80% vs 50% at 10 years; P=0.030). This study demonstrates that patients with PanNET approaching the cut-off diameter of 2.8 cm should be operated. Mutations in exon 3, especially of codons 161/167 are at enhanced risk for metastatic PanNETs. Survival is significantly longer in operated non-metastatic VHL-PanNETs.

Status of National Spherical Torus Experiment Liquid Lithium Divertor

NASA Astrophysics Data System (ADS)

Kugel, H. W.; Viola, M.; Ellis, R.; Bell, M.; Gerhardt, S.; Kaita, R.; Kallman, J.; Majeski, R.; Mansfield, D.; Roquemore, A. L.; Schneider, H.; Timberlake, J.; Zakharov, L.; Nygren, R. E.; Allain, J. P.; Maingi, R.; Soukhanovskii, V.

2009-11-01

Recent NSTX high power divertor experiments have shown significant and recurring benefits of solid lithium coatings on plasma facing components to the performance of divertor plasmas in both L- and H- mode confinement regimes heated by high-power neutral beams. The next step in this work is the 2009 installation of a Liquid Lithium Divertor (LLD). The 20 cm wide LLD located on the lower outer divertor, consists of four, 80 degree sections; each section is separated by a row of graphite diagnostic tiles. The temperature controlled LLD structure consists of a 0.01cm layer of vacuum flame-sprayed, 50 percent porous molybdenum, on top of 0.02 cm, 316-SS brazed to a 1.9 cm Cu base. The physics design of the LLD encompasses the desired plasma requirements, the experimental capabilities and conditions, power handling, radial location, pumping capability, operating temperature, lithium filling, MHD forces, and diagnostics for control and characterization.

Transverse Coefficient of Thermal Expansion Measurements of Carbon Fibers Using ESEM at High Temperatures

NASA Technical Reports Server (NTRS)

Ochoa, O.; Jiang, J.; Putnam, D.; Lo, Z.; Ellis, A.; Effinger, Michael

2003-01-01

The transverse coefficient of thermal expansion (CTE) of single IM7, T1000, and P55 carbon fibers are measured at elevated temperatures. The specimens are prepared by press-fitting fiber tows into 0.7mm-diameter cavity in a graphite disk of 5mm in diameter and 3mm high. The specimens are placed on a crucible in an ESEM, and images of the fiber cross section are taken as the fibers are heated up to 800 C. Holding time, heating and cool down cycles are also introduced. The geometrical changes are measured using a graphics tablet. The change in area/perimeter is calculated to determine the strain and transverse CTE for each fiber. In a complimentary computational effort, displacements and stresses are calculated with finite element models.

Phased Array Focusing for Acoustic Wireless Power Transfer.

PubMed

Tseng, Victor Farm-Guoo; Bedair, Sarah S; Lazarus, Nathan

2018-01-01

Wireless power transfer (WPT) through acoustic waves can achieve higher efficiencies than inductive coupling when the distance is above several times the transducer size. This paper demonstrates the use of ultrasonic phased arrays to focus power to receivers at arbitrary locations to increase the power transfer efficiency. Using a phased array consisting of 37 elements at a distance nearly 5 times the receiver transducer diameter, a factor of 2.6 increase in efficiency was achieved when compared to a case equivalent to a single large transducer with the same peak efficiency distance. The array has a total diameter of 7 cm, and transmits through air at 40 kHz to a 1.1-cm diameter receiver, achieving a peak overall efficiency of 4% at a distance of 5 cm. By adjusting the focal distance, the efficiency can also be maintained relatively constant at distances up to 9 cm. Numerical models were developed and shown to closely match the experimental energy transfer behavior; modeling results indicate that the efficiency can be further doubled by increasing the number of elements. For comparison, an inductive WPT system was also built with the diameters of the transmitting and receiving coils equivalent to the dimensions of the transmitting ultrasonic phased array and receiver transducer, and the acoustic WPT system achieved higher efficiencies than the inductive WPT system when the transmit-to-receive distance is above 5 cm. In addition, beam angle steering was demonstrated by using a simplified seven-element 1-D array, achieving power transfer less dependent on receiver placement.

High voltage electrochemical double layer capacitors using conductive carbons as additives

NASA Astrophysics Data System (ADS)

Michael, M. S.; Prabaharan, S. R. S.

We describe here an interesting approach towards electrochemical capacitors (ECCs) using graphite materials (as being used as conductive additives in rechargeable lithium-ion battery cathodes) in a Li + containing organic electrolyte. The important result is that we achieved a voltage window of >4 V, which is rather large, compared to the standard window of 2.5 V for ordinary electric double layer capacitors (DLCs). The capacitor performance was evaluated by cyclic voltammetry (CV) and galvanostatic charge/discharge techniques. From charge-discharge studies of the symmetrical device (for instance, SFG6 carbon electrode), a specific capacitance of up to 14.5 F/g was obtained at 16 mA/cm 2 current rate and at a low current rate (3 mA/cm 2), a higher value was obtained (63 F/g). The specific capacitance decreased about 25% after 1000 cycles compared to the initial discharge process. The performances of these graphites are discussed in the light of both double layer capacitance (DLC) and pseudocapacitance (battery-like behavior). The high capacitance obtained was not only derived from the current-transient capacitive behavior but is also attributed to pseudocapacitance associated with some kind of faradaic reaction, which could probably occur due to Li + intercalation/deintercalation reactions into graphitic layers of the carbons used. The ac impedance (electrochemical impedances spectroscopy, EIS) measurements were also carried out to evaluate the capacitor parameters such as equivalent series resistance (ESR) and frequency dependent capacitance ( Cfreq). Cyclic voltammetry measurements were also performed to evaluate the cycling behavior of the carbon electrodes and the non-rectangular shaped voltammograms revealed the non-zero time constant [ τ( RC)≠0] confirming that the current contains a transient as well as steady-state components.

Reactive template synthesis of nitrogen-doped graphene-like carbon nanosheets derived from hydroxypropyl methylcellulose and dicyandiamide as efficient oxygen reduction electrocatalysts

NASA Astrophysics Data System (ADS)

Hu, Chun; Zhou, Yao; Ma, Ruguang; Liu, Qian; Wang, Jiacheng

2017-03-01

Oxygen reduction reaction (ORR) plays a dominant role in proton exchange membrane fuel cells (PEMFCs). Thus, the design and preparation of efficient ORR electrocatalysts is of high importance. In this work, we successfully prepared a series of nitrogen-doped graphene-like carbon nanosheets (NCNSs) with large pore volumes of up to 1.244 cm3 g-1 and high level of N dopants (5.3-6.8 at%) via a one-step, in-situ reactive template strategy by co-pyrolysis of hydroxypropyl methylcellulose (HPMC) and dicyandiamide (DICY) as the precursors at 1000 °C. The DICY-derived graphitic carbon nitride (g-C3N4) nanosheets could act as the hard template for the confined growth of 2D carbon nanosheets, and the further increase in the pyrolysis temperature could directly remove off the g-C3N4 template by complete decomposition and simultaneously dope N atoms within the carbon nanosheets. The pyridinic and graphitic nitrogen groups are dominant among various N functional groups in the NCNSs. The NCNS_1:10 prepared with the HPMC/DICY mass ratio of 1/10 can be used as the metal-free ORR electrocatalysts with optimal activity (onset potential: -0.1 V vs. SCE; limiting current density: 4.8 mA cm-2) in O2-saturated 0.1 M KOH electrolyte among the NCNSs. Moreover, the NCNS_1:10 demonstrates a dominant four-electron reduction process, as well as excellent long-term operation stability and outstanding methanol crossover resistance. The excellent ORR activity of the NCNS_1:10 should be mainly owing to high contents of pyridinic and graphitic N dopants, large pore volume, hierarchical structures, and microstructural defects.

Management of the high-order mode content in large (40 microm) core photonic bandgap Bragg fiber laser.

PubMed

Gaponov, D A; Février, S; Devautour, M; Roy, P; Likhachev, M E; Aleshkina, S S; Salganskii, M Y; Yashkov, M V; Guryanov, A N

2010-07-01

Very large-mode-area Yb(3+)-doped single-mode photonic bandgap (PBG) Bragg fiber oscillators are considered. The transverse hole-burning effect is numerically modeled, which helps properly design the PBG cladding and the Yb(3+)-doped region for the high-order mode content to be carefully controlled. A ratio of the Yb(3+)-doped region diameter to the overall core diameter of 40% allows for single-mode emission, even for small spool diameters of 15 cm. Such a fiber was manufactured and subsequently used as the core element of a cw oscillator. Very good beam quality parameter M(2)=1.12 and slope efficiency of 80% were measured. Insensitivity to bending, exemplified by the absence of temporal drift of the beam, was demonstrated for curvature diameter as small as 15 cm.

Plasma-enhanced chemical vapor deposition of multiwalled carbon nanofibers.

PubMed

Matthews, Kristopher; Cruden, Brett A; Chen, Bin; Meyyappan, M; Delzeit, Lance

2002-10-01

Plasma-enhanced chemical vapor deposition is used to grow vertically aligned multiwalled carbon nanofibers (MWNFs). The graphite basal planes in these nanofibers are not parallel as in nanotubes; instead they exhibit a small angle resembling a stacked cone arrangement. A parametric study with varying process parameters such as growth temperature, feedstock composition, and substrate power has been conducted, and these parameters are found to influence the growth rate, diameter, and morphology. The well-aligned MWNFs are suitable for fabricating electrode systems in sensor and device development.

Plasma-enhanced chemical vapor deposition of multiwalled carbon nanofibers

NASA Technical Reports Server (NTRS)

Matthews, Kristopher; Cruden, Brett A.; Chen, Bin; Meyyappan, M.; Delzeit, Lance

2002-01-01

Plasma-enhanced chemical vapor deposition is used to grow vertically aligned multiwalled carbon nanofibers (MWNFs). The graphite basal planes in these nanofibers are not parallel as in nanotubes; instead they exhibit a small angle resembling a stacked cone arrangement. A parametric study with varying process parameters such as growth temperature, feedstock composition, and substrate power has been conducted, and these parameters are found to influence the growth rate, diameter, and morphology. The well-aligned MWNFs are suitable for fabricating electrode systems in sensor and device development.

The compressive failure of graphite/epoxy plates with circular holes

NASA Technical Reports Server (NTRS)

Knauss, J. F.; Starnes, J. H., Jr.; Henneke, E. G., II

1978-01-01

The behavior of fiber reinforced composite plates containing a circular cutout was characterized in terms of geometry (thickness, width, hole diameter), and material properties (bending/extensional stiffness). Results were incorporated in a data base for use by designers in determining the ultimate strength of such a structure. Two thicknesses, 24 plies and 48 plies were chosen to differentiate between buckling and strength failures due to the presence of a cutout. Consistent post-buckling strength was exhibited by both laminate configurations.

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)

The Physics and Chemistry of carbides, Nitrides and Borides. Volume 185

DTIC Science & Technology

1990-01-01

and C-B-C chains [15,17]. Clearly, the use of boron-rich solids as electronic materials will place new demands on the quality of materials. In this...first heated in a pyrolytic boron nitride (PBN) crucible ( Union Carbide Corp.) under high vacuum (< 50 mTorr) to 1900°C. This removed surface...contamination of the sample. The powders were loaded into a graphite die with a high-purity BN die liner ( Union Carbide Grade HBC) with inner diameter of 3/8

Elastic torsional buckling of thin-walled composite cylinders

NASA Technical Reports Server (NTRS)

Marlowe, D. E.; Sushinsky, G. F.; Dexter, H. B.

1974-01-01

The elastic torsional buckling strength has been determined experimentally for thin-walled cylinders fabricated with glass/epoxy, boron/epoxy, and graphite/epoxy composite materials and composite-reinforced aluminum and titanium. Cylinders have been tested with several unidirectional-ply orientations and several cross-ply layups. Specimens were designed with diameter-to-thickness ratios of approximately 150 and 300 and in two lengths of 10 in. and 20 in. The results of these tests were compared with the buckling strengths predicted by the torsional buckling analysis of Chao.

Criticality Safety Analysis on the Mixed Be, Nat-U, and C (Graphite) Reflectors in 55-Gallon Waste Drums and Their Equivalents for HWM Applications

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

Chou, P

The objective of this analysis is to develop and establish the technical basis on the criticality safety controls for the storage of mixed beryllium (Be), natural uranium (Nat-U), and carbon (C)/graphite reflectors in 55-gallon waste containers and/or their equivalents in Hazardous Waste Management (HWM) facilities. Based on the criticality safety limits and controls outlined in Section 3.0, the operations involving the use of mixed-reflector drums satisfy the double-contingency principle as required by DOE Order 420.1 and are therefore criticality safe. The mixed-reflector mass limit is 120 grams for each 55-gallon drum or its equivalent. a reflector waiver of 50 gramsmore » is allowed for Be, Nat-U, or C/graphite combined. The waived reflectors may be excluded from the reflector mass calculations when determining if a drum is compliant. The mixed-reflector drums are allowed to mix with the typical 55-gallon one-reflector drums with a Pu mass limit of 120 grams. The fissile mass limit for the mixed-reflector container is 65 grams of Pu equivalent each. The corresponding reflector mass limits are 300 grams of Be, and/or 100 kilograms of Nat-U, and/or 110 kilograms of C/graphite for each container. All other unaffected control parameters for the one-reflector containers remain in effect for the mixed-reflector drums. For instance, Superior moderators, such as TrimSol, Superla white mineral oil No. 9, paraffin, and polyethylene, are allowed in unlimited quantities. Hydrogenous materials with a hydrogen density greater than 0.133 gram/cc are not allowed. Also, an isolation separation of no less than 76.2 cm (30-inch) is required between a mixed array and any other array. Waste containers in the action of being transported are exempted from this 76.2-cm (30-inch) separation requirement. All deviations from the CS controls and mass limits listed in Section 3.0 will require individual criticality safety analyses on a case-by-case basis for each of them to confirm their criticality safety prior to their deployment and implementation.« less

DESIGN CHARACTERISTICS OF THE IDAHO NATIONAL LABORATORY HIGH-[TEMPERATURE GAS-COOLED TEST REACTOR

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

Sterbentz, James; Bayless, Paul; Strydom, Gerhard

A point design for a graphite-moderated, high-temperature, gas-cooled test reactor (HTG TR) has been developed by Idaho National Laboratory (INL) as part of a United States (U.S.) Department of Energy (DOE) initiative to explore and potentially expand the existing U.S. test reactor capabilities. This paper provides a summary of the design and its main attributes. The 200 MW HTG TR is a thermal-neutron spectrum reactor composed of hexagonal prismatic fuel and graphite reflector blocks. Twelve fuel columns (96 fuel blocks total and 6.34 m active core height) are arranged in two hexagonal rings to form a relatively compact, high-power density,more » annular core sandwiched between inner, outer, top, and bottom graphite reflectors. The HTG-TR is designed to operate at 7 MPa with a coolant inlet/outlet temperature of 325°C/650°C, and utilizes TRISO particle fuel from the DOE AGR Program with 425 ?m uranium oxycarbide (UCO) kernels and an enrichment of 15.5 wt% 235U. The primary mission of the HTG TR is material irradiation and therefore the core has been specifically designed and optimized to provide the highest possible thermal and fast neutron fluxes. The highest thermal neutron flux (3.90E+14 n/cm2s) occurs in the outer reflector, and the maximum fast flux levels (1.17E+14 n/cm2s) are produced in the central reflector column where most of the graphite has been removed. Due to high core temperatures under accident conditions, all the irradiation test facilities have been located in the inner and outer reflectors where fast flux levels decline. The core features a large number of irradiation positions with large test volumes and long test lengths, ideal for thermal neutron irradiation of large test articles. The total available test volume is more than 1100 liters. Up to four test loop facilities can be accommodated with pressure tube boundaries to isolate test articles and test fluids (e.g., liquid metal, liquid salt, light water) from the helium primary coolant system.« less

29 CFR 1926.57 - Ventilation.

Code of Federal Regulations, 2013 CFR

2013-07-01

... shall be cleaned up promptly. Aisles and walkways shall be kept clear of steel shot or similar abrasive... not more than one forty-eighth of their diameter for those up to, and including, 20 inches (50.8 cm) in diameter, and not more than one-sixtieth of their diameter for those larger than 20 inches (50.8...

[The penis prolongation and augmentation combined with autologous granular fat injection and silicone implantation].

PubMed

Xie, Yang-chun; Zhang, Yang; Fan, Jin-cai; Liu, Yuan-bo; Liu, Li-qiang; Wang, Qian

2007-07-01

To prevent the retraction of the penis after prolongation and augmentation. After all the superficial and part of the deep suspensory ligament amputation, we implanted the silicon sheet (the length 2.3-3.6 cm, the width 1.5-2.5 cm, the thickness 2-3 mm) and injected autologous granular fat (30-48 ml) into penis. 16 patients (age 22-63 years, averagely 38 years) underwent this kind operation, the prolongation length is 1.8-5.1 cm, the average was 2.91 cm, the increased diameter of penis was 0.6-1 cm, the average is 0.85 cm, the following period is 3 months to 2 years. The results are satisfactory with the penis retraction less than 8%, and less than 10% decrease in diameter. This method is an ideal way of the penis prolongation and augmentation, the implantation of the silicon sheet is effective way to prevent the retraction of the penis.

Design of ultrasonic attenuation sensor with focused transmitter for density measurements of a slurry in a large steel pipeline

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

Greenwood, Margaret Stautberg

2015-12-01

To design an ultrasonic sensor to measure the attenuation and density of a slurry carried by a large steel pipeline (diameter up to 70 cm) is the goal of this research. The pitch-catch attenuation sensor, placed in a small section of the pipeline, contains a send unit with a focused transducer that focuses the ultrasound to a small region of the receive unit on the opposite wall. The focused transducer consists of a section of a sphere (base ~12 cm) on the outer side of the send unit and a 500 kHz piezoelectric shell of PZT5A epoxied to it. Themore » Rayleigh surface integral is used to calculate the pressure in steel and in water (slurry). An incremental method to plot the paths of ultrasonic rays shows that the rays focus where expected. Further, there is a region where the parallel rays are perpendicular to the wall of the receive unit. Designs for pipeline diameters of 25 cm and 71 cm show that the pressure in water at the receive transducer is about 17 times that for a pitch-catch system using 5 cm diameter disk transducers. The enhanced signal increases the sensitivity of the measurements and improves the signal-to-noise ratio.« less

Body size and substrate type modulate movement by the western Pacific crown-of-thorns starfish, Acanthaster solaris.

PubMed

Pratchett, Morgan S; Cowan, Zara-Louise; Nadler, Lauren E; Caballes, Ciemon F; Hoey, Andrew S; Messmer, Vanessa; Fletcher, Cameron S; Westcott, David A; Ling, Scott D

2017-01-01

The movement capacity of the crown-of-thorns starfishes (Acanthaster spp.) is a primary determinant of both their distribution and impact on coral assemblages. We quantified individual movement rates for the Pacific crown-of-thorns starfish (Acanthaster solaris) ranging in size from 75-480 mm total diameter, across three different substrates (sand, flat consolidated pavement, and coral rubble) on the northern Great Barrier Reef. The mean (±SE) rate of movement for smaller (<150 mm total diameter) A. solaris was 23.99 ± 1.02 cm/ min and 33.41 ± 1.49 cm/ min for individuals >350 mm total diameter. Mean (±SE) rates of movement varied with substrate type, being much higher on sand (36.53 ± 1.31 cm/ min) compared to consolidated pavement (28.04 ± 1.15 cm/ min) and slowest across coral rubble (17.25 ± 0.63 cm/ min). If average rates of movement measured here can be sustained, in combination with strong directionality, displacement distances of adult A. solaris could range from 250-520 m/ day, depending on the prevailing substrate. Sustained movement of A. solaris is, however, likely to be highly constrained by habitat heterogeneity, energetic constraints, resource availability, and diurnal patterns of activity, thereby limiting their capacity to move between reefs or habitats.

Measurement of absorbed dose with a bone-equivalent extrapolation chamber.

PubMed

DeBlois, François; Abdel-Rahman, Wamied; Seuntjens, Jan P; Podgorsak, Ervin B

2002-03-01

A hybrid phantom-embedded extrapolation chamber (PEEC) made of Solid Water and bone-equivalent material was used for determining absorbed dose in a bone-equivalent phantom irradiated with clinical radiation beams (cobalt-60 gamma rays; 6 and 18 MV x rays; and 9 and 15 MeV electrons). The dose was determined with the Spencer-Attix cavity theory, using ionization gradient measurements and an indirect determination of the chamber air-mass through measurements of chamber capacitance. The collected charge was corrected for ionic recombination and diffusion in the chamber air volume following the standard two-voltage technique. Due to the hybrid chamber design, correction factors accounting for scatter deficit and electrode composition were determined and applied in the dose equation to obtain absorbed dose in bone for the equivalent homogeneous bone phantom. Correction factors for graphite electrodes were calculated with Monte Carlo techniques and the calculated results were verified through relative air cavity dose measurements for three different polarizing electrode materials: graphite, steel, and brass in conjunction with a graphite collecting electrode. Scatter deficit, due mainly to loss of lateral scatter in the hybrid chamber, reduces the dose to the air cavity in the hybrid PEEC in comparison with full bone PEEC by 0.7% to approximately 2% depending on beam quality and energy. In megavoltage photon and electron beams, graphite electrodes do not affect the dose measurement in the Solid Water PEEC but decrease the cavity dose by up to 5% in the bone-equivalent PEEC even for very thin graphite electrodes (<0.0025 cm). In conjunction with appropriate correction factors determined with Monte Carlo techniques, the uncalibrated hybrid PEEC can be used for measuring absorbed dose in bone material to within 2% for high-energy photon and electron beams.